HK1078930B

HK1078930B - Apparatus for analyzing mixtures of gases

Info

Publication number: HK1078930B
Application number: HK05110771.9A
Authority: HK
Inventors: Patricia A. Morris
Original assignee: E. I. Du Pont De Nemours And Company
Filing date: 2002-04-05
Publication date: 2009-12-18

Description

Gas mixture analysis device

Technical Field

The present invention is a method and apparatus for detecting and analyzing a specific gas, including NO, in a multi-component gas system using chemical sensors and chemical sensor arrays_xHydrocarbons, carbon monoxide and oxygen. The sensors and sensor arrays employ chemo/electro-active materials to detect the presence and/or calculate the concentration of a single gas in a multi-component gas system.

Background

The use of chemical sensing devices to detect certain gases is well known. Researchers have made many attempts to find materials that are selective and sensitive to specific gases. For example, US4535316 discloses a resistance sensor for measuring oxygen. See also H.Meixner et al, Sensors and actors, B33(1996), 198-. Obviously, different materials must be used to detect each gas. However, when a gas is part of a multicomponent system, it is difficult to detect a particular gas with a single material due to the cross-sensitivity of the material to the different gas components in the mixture.

An example of a multi-component gas system is a combustion exhaust gas that may include oxygen, carbon monoxide, and nitrogen oxidesHydrocarbon, CO₂，H₂S, sulfur dioxide, hydrogen, water vapor, halogen gas and ammonia gas. See H.Meixner et al, Fresenius' J.anal.chem., 348(1994) 536-541. In many combustion processes, it is desirable to determine whether the exhaust gas meets federal and state established air quality standards in different jurisdictions. A number of gas sensors have been developed to meet this need. See Friese et al, U.S. patent US 560920, which discloses an electrochemical oxygen sensor; U.S. patent No. 4770760 to Noda et al, which discloses sensors for measuring oxygen and nitrogen oxides; and US patent US4535316, which discloses a resistance sensor for measuring oxygen. It would be advantageous if two or more components of a mixture, such as gas produced by combustion, could be analyzed simultaneously to calculate concentration, e.g., based solely on data derived from direct contact of the gases in the mixture with a sensor, without the need to separate any of the gases in the mixture. The prior art methods do not meet this current need.

A large number of sensors have been used to measure gases generated from food and other relatively low temperature applications. See K.Albert et al, chem.Rev., 200(2000) 2595-2626. There are also a number of doped and undoped tin oxide sensor arrays disclosed for sensing various combustion gases up to 450 c. See C.Di Natale et al, Sensors and actors, B20 (1994) 217-224; getino et al, Sensors and actors, B33(1996) 128-133; and C.Di Natale et al, Sensors and promoters, B23 (1995) 187-191. However, in some high temperature and highly corrosive environments where chemical sensors are used to monitor combustion gases, operating temperatures can alter or compromise the performance of the sensor array. In this case, the high temperature environment requires that the materials used be both chemically and thermally stable and maintain a measurable response to the gas being measured. The effect of operating temperatures up to 450 ℃ on tin oxide based sensor arrays was investigated. See C.Di Natale et al, Sensors and actors, B23 (1995) 187-191. However, in addition to the materials known in the art, there remains a need for additional materials to provide a method and apparatus that can directly monitor the exhaust gas in a multi-component gas system at higher temperatures, such as the temperature at which a combustion gas system operates.

To meet this need, chemical sensors may be used to measure combustion emissions, such as automobile exhaust, and determine whether these emissions meet functional and mandatory requirements. In addition, it has been surprisingly found that the method and apparatus for analyzing high temperature gases, such as automobile emissions, of the present invention has the same effect when used for analyzing low temperature gases.

Summary of The Invention

The invention provides a method for directly measuring gas components in a multi-component gas system, which comprises the following steps: (i) a chemical sensor with an array of at least two chemo/electro-active materials is exposed to a multi-component gas system, the response is detected, and the response of each chemo/electro-active material is directly measured. Preferably, the chemo/electro-active material is a semiconductor material and the multi-component gas system is an emission from a combustion process. The measured response may be a measure of capacitance, voltage, current, ac impedance, or dc resistance.

The present invention also provides an apparatus for directly determining the presence of a gas component in a multi-component gas system, comprising: a substrate; an array of at least two chemo/electro-active materials on said substrate; and a means for determining a response from said chemo/electro-active material when exposed to said analyte gas constituent in said system. Preferably, the chemo/electro-active material is a semiconductor material and the multi-component gas system is an emission from a combustion process. The measured response may be an electrical property such as capacitance, voltage, current, ac impedance, or dc resistance. The device may also include a housing, means for measuring the detected response, and means for analyzing the measured response to determine the presence and/or concentration of the analyte gas constituent.

The present invention also provides a chemical sensor device for directly detecting the presence and/or concentration of one or more gas components in a multi-component gas system, comprising: a substrate; an array of at least two chemo/electro-active materials deposited on the substrate; a means for determining a change in an electrical property of said chemo/electro-active material when exposed to said multi-component gas; a means for analysing the results of the measured change in electrical property to determine the presence and/or concentration of said one or more analyte gas components; and a housing. The chemo/electro-active material may be a semiconductor material.

Another embodiment of the present invention is a gas sensitive device comprising an array of at least three chemo/electro-active materials, each chemo/electro-active material exhibiting a change in electrical resistance when exposed to a multi-component gas mixture, wherein at least one chemo/electro-active material (a) has a viscosity of about 1ohm-cm to about 10ohm-cm when exposed to a temperature of about 400 ℃ or greater⁶An electrical resistivity of ohm-cm, and (b) the material exhibits a change in electrical resistance of at least about 0.1% when exposed to the gas mixture as compared to before exposure to the gas mixture. Another embodiment of the invention is an apparatus for analyzing a multi-component gas mixture comprising an array as described above, and means for determining the electrical response of the chemo/electro-active material when the array is exposed to the gas mixture.

Another embodiment of the invention is a gas sensitive device comprising an array of at least two chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic when exposed to a multi-component gas mixture at a selected temperature than each other chemo/electro-active material, the electrical response characteristic of at least one material quantifiable to a value, wherein the response value of the material is constant or does not vary by more than about 20% over the course of exposure of the material to the gas mixture for at least about one minute at the selected temperature. Another embodiment of the invention is an apparatus for analyzing a multi-component gas mixture comprising an array as described above, and means for determining the electrical response of the chemo/electro-active material when the array is exposed to the gas mixture.

Another embodiment of the invention is an array of chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic when exposed to a multi-component gas mixture at a selected temperature than each other chemo/electro-active material, wherein at least one chemo/electro-active material is selected from the group consisting of: m¹O_X，M¹ _aM² _bO_XAnd M¹ _aM² _bM³ _cO_X(ii) a Wherein M is¹Selected from the group consisting of Ce, Co, Cu, Fe, Ga, Nb, Ni, Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr; m²And M³Each independently selected from the group consisting of: al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo, Na, Nb, Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn and Zr, but In M¹ _aM² _bM³ _cO_XIn, M²And M³Different; a. b and c are each from about 0.0005 to about 1; and X is a number sufficient to balance the oxygen present with the charge of the other elements in the compound. Another embodiment of the invention is an apparatus for analyzing a multi-component gas mixture comprising the aforementioned array, and means for determining the electrical response of the chemo/electro-active material when the array is exposed to the gas mixture.

Another embodiment of the invention is a gas sensitive device comprising an array of first and second chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic when exposed to a multi-component gas mixture than each other chemo/electro-active material, wherein the chemo/electro-active materials are selected from the group of pairs comprising:

(i) the first material being M¹O_XAnd the second material is M¹ _aM² _bO_X；

(ii) The first material being M¹O_XAnd the second material is M¹ _aM² _bM³ _cO_X；

(iii) The first material being M¹ _aM² _bO_XAnd the second material is M¹ _aM² _bM³ _cO_X；

(iv) The first material is a first M¹O_XAnd the second material is a second M¹O_X；

(v) The first material is a first M¹ _aM² _bO_XAnd the second material is a second M¹ _aM² _bO_X；

(vi) The first material is a first M¹ _aM² _bM³ _cO_XAnd the second material is a second M¹ _aM² _bM³ _cO_X；

Wherein M is¹Selected from the group consisting of Ce, Co, Cu, Fe, Ga, Nb, Ni, Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr; m²And M³Each independently selected from the group consisting of: al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo, Na, Nb, Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn and Zr; but at M¹ _aM² _bM³ _cO_XMiddle M²And M³Is different; and X is a number sufficient to balance the oxygen present with the charge of the other elements in the compound. Another embodiment of the invention is an apparatus for analyzing a multi-component gas mixtureAn array comprising the foregoing, and means for determining the electrical response of the chemo/electro-active material when the array is exposed to a gas mixture.

Another embodiment of the invention is an apparatus for analyzing a multi-component gas mixture, comprising (a) an array of at least two chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic when exposed to the multi-component gas mixture than each other chemo/electro-active material; and (b) means for determining the electrical response of each chemo/electro-active material individually when the array is exposed to a gas mixture. The apparatus may optionally further comprise means for measuring the temperature of the array, and means for digitizing the measured electrical response and temperature.

Another embodiment of the invention is an apparatus for calculating the concentration of at least two separate gaseous analyte components in a multi-component gas mixture, comprising (a) -an array of at least three chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic when exposed to the multi-component gas mixture than each other chemo/electro-active material; (b) means for determining the electrical response of each chemo/electro-active material when the array is exposed to only the unseparated components of the gas mixture; and (c) means for calculating the concentration of a single analyte gas component from the electrical response of the chemo/electro-active material.

Another embodiment of the invention is an apparatus for analyzing a multi-component gas mixture, comprising (a) -an array of at least three chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic when exposed to the multi-component gas mixture than each other chemo/electro-active material; (b) means for determining the electrical response of each chemo/electro-active material when the array is exposed to a gas mixture; and (c) means for (i) detecting the presence of a subgroup of gases in the mixture by a response of a first group comprising at least two chemo/electro-active materials, and (ii) detecting the presence of a single gas component in the mixture by a response of a second group comprising at least two chemo/electro-active materials.

Another embodiment of the invention is a method of analyzing a multi-component gas mixture, comprising the steps of:

(a) providing an array of at least two chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic when exposed to the multi-component gas mixture than each other chemo/electro-active material;

(b) exposing the array to a gas mixture;

(c) measuring the electrical response of each chemo/electro-active material when the array is exposed to the gas mixture;

(d) independently determining the temperature of the gas mixture while determining the electrical response of each chemo/electro-active material; and

(e) the measured electrical response and temperature measurements are digitized.

Another embodiment of the invention is a method of calculating the concentration of at least two individual gas analyte components in a multi-component gas mixture having a temperature of about 400 ℃ or greater, comprising the steps of:

(a) providing an array of at least three chemo/electro-active materials in the gas mixture, each chemo/electro-active material exhibiting a different electrical response characteristic when exposed to the gas mixture than each other chemo/electro-active material; wherein the at least one chemo/electro-active material (i) has a viscosity of about 1ohm-cm to about 10 when the temperature is about 400 ℃ or higher⁶An electrical resistivity of ohm-cm, and (ii) the material exhibits a change in resistance of at least about 0.1% when exposed to the gas mixture as compared to before exposure to the gas mixture;

(b) measuring the electrical response of each chemo/electro-active material when the array is exposed to the unseparated component of the gas mixture;

(c) the concentration of each individual analyte gas component is calculated from the measured electrical response of the chemo/electro-active material.

Another embodiment of the invention is directed to a method of analyzing a multi-component gas mixture, comprising the steps of:

(a) providing an array of at least two chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic when exposed to the gas mixture at the selected temperature than each other chemo/electro-active material, the electrical response characteristic of at least one material being quantifiable to a value, wherein the response value of the material is constant or does not vary by more than about 20% over the course of exposure of the material to the gas mixture for at least about one minute at the selected temperature; and

(b) the electrical response of each chemo/electro-active material is measured when the array is exposed to a gas mixture.

Another embodiment of the invention is a method of analyzing a multi-component gas mixture by (a) providing an array of at least three chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic when exposed to the gas mixture than each other chemo/electro-active material; (b) measuring the electrical response of each chemo/electro-active material when the array is exposed to the gas mixture; (c) determining (i) the presence of a subgroup of gases in the mixture by responses of a first group comprising at least two chemo/electro-active materials, and (ii) the presence of a single gas component in the mixture by responses of a second group comprising at least two chemo/electro-active materials.

Drawings

Figure 1 depicts an array of chemo/electro-active materials.

Fig. 2 is a schematic of a nested electrode pattern coated with a dielectric coating to form 16 blank holes in an array of chemo/electro-active materials.

Fig. 3 depicts an electrode pattern, a dielectric pattern, and a sensor material pattern in an array of chemo/electro-active materials.

Detailed description of the invention

The present invention is a method and apparatus for directly determining one or more gas analytes in a multi-component gas system under variable temperature conditions. By "direct measurement" is meant that an array of gas sensitive materials is exposed to a gas mixture that forms a multi-component gas system, such as a flowing gas stream. The array may be placed in the gas mixture, more preferably in the source of the gas mixture, if desired. Furthermore, the array may be provided in a chamber to which the gas mixture is passed from a source at another location. When gas is passed to the chamber in which the array is placed, the gas mixture may be passed into and removed from the chamber by a line, pipe or any other suitable gas delivery means.

A response is obtained when the gas sensitive material is exposed to a multi-component gas mixture, and the response is a function of the concentration of one or more of the gas analytes in the gas mixture themselves. The sensor material is exposed to each of the gaseous analytes substantially simultaneously and the analyte gases need not be physically separated from the multi-component gas mixture in order to analyze the mixture and/or one or more components to be processed therein. The invention can be used, for example, to detect and/or determine the concentration of combustion gases, such as oxygen, carbon monoxide, nitrogen oxides, hydrocarbons such as butane, CO, in motor vehicle exhaust at various temperatures₂，H₂S, sulfur dioxide, halogen gas, hydrogen, water vapor and ammonia.

Thus, the present invention is useful at the higher temperatures of automotive exhaust systems, typically about 400 ℃ to 1000 ℃. In addition, the present invention can be used in a variety of other combustion processes, including diesel engines and home heating. These applications typically require the detection of gases such as nitrogen oxides, ammonia, carbon monoxide, hydrocarbons and oxygen at ppm to percent concentration levels in highly corrosive environments. The invention is also useful in determining gases in other gas systems, such as gases generated during production, waste gas streams, and environmental monitoring; or systems where odor detection is important and/or at low temperatures, such as in the medical, agricultural or food and beverage industries.

The present invention utilizes an array of sensing materials to analyze a gas mixture and/or components thereof, e.g., to detect and/or calculate the concentration of one or more individual analyte gas components in a system. "array" refers to at least two different materials that are spatially separated, as in the example illustrated in FIG. 1. For example, the array may include 3, 4, 5, 6, 8, 10, or 12 gas sensitive materials, or other desired greater or lesser numbers. Preferably, at least one sensor material is provided for each individual gas or subgroup in the mixture to be analyzed. However, it may be desirable to provide more than one sensor material that responds to a single gas and/or a particular subgroup in the mixture. For example, a set of at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 sensors may be used to determine the presence and/or calculate the concentration of one or more individual gas components and/or one or more subgroups of gases in a mixture. Different sets of sensors with or without common components may be used for this purpose. A subgroup of gases with a subgroup as analyte may or may not include as a component thereof a single gas, which is itself an analyte. Preferably, the mole percentage of the major component of each gas sensitive material is different from the other materials.

The sensing material used is a chemo/electro-active material. "chemo/electro-active material" refers to a material that has an electrical response to at least a single gas in a mixture. Some metal oxide semiconductor materials, mixtures thereof, or mixtures of metal oxide semiconductor materials with other inorganic compounds are chemically/electrically active and are particularly useful in the present invention. Each different chemo/electro-active material used herein preferably exhibits a different kind and/or degree of electrically detectable response when exposed to a mixture and/or a gaseous analyte than the other chemo/electro-active materials. Thus, arrays of appropriately selected chemo/electro-active materials can be used to analyze multi-component gas mixtures, for example, by interacting with an analyte gas, detecting the analyte gas, or determining the presence or concentration of one or more analyte gases in a mixture, regardless of the presence therein of an uninteresting interfering gas.

The present invention is useful for detecting gases that may be present in a gas stream. For example, during combustion, gases that may be present include oxygen, nitrogen oxides (e.g., NO)₂，N₂O or N₂O₄) Carbon monoxide, hydrocarbons (e.g. C)_nH_2n+2May be saturated or unsaturated, or may be optionally substituted with other heteroatoms; and cyclic or aromatic analogs thereof), ammonia or hydrogen sulfide, sulfur dioxide, CO₂Or methanol. Other gases of interest include: alcohol vapors, solvent vapors, hydrogen, water vapor, and gases derived from saturated and unsaturated hydrocarbons, ethers, ketones, aldehydes, carbonyl compounds, biomolecules, and microorganisms. The components of the multi-component gas mixture that are analytes of interest may be a single gas, such as carbon monoxide; or a subgroup of some, but not all, of the gases in the mixture, e.g. Nitrogen Oxides (NO)_x) (ii) a Or may be a combination of one or more individual gases and one or more subgroups. When a subgroup of gases is the analyte, the chemo/electro-active material will respond to the collective concentration of that subgroup of components within the multi-component gas mixture.

When these sensor materials are exposed to a mixture containing one or more analyte gases, information relating to the constituent content of the gas mixture, such as a measure of the gas concentration, may be obtained based on the change in electrical properties, such as AC impedance, of at least one of the materials, but preferably each and all of the materials. The gas mixture can also be analyzed for the degree of change in other electrical properties of the sensor material, such as capacitance, voltage, current, or ac or dc resistance. For example, the change in the direct current resistance is measured by measuring the change in temperature at a constant voltage. The change in one of the above exemplary properties of the sensor material is a function of the gas partial pressure of an analyte gas in the gas mixture, which in turn determines the concentration of the analyte gas molecules adsorbed to the sensor material surface, thereby affecting the electrical response characteristics of the material. By employing an array with chemo/electro-active materials, the respective response patterns exhibited by the materials when exposed to a mixture including one or more analyte gases can be used to simultaneously and directly determine the presence, and/or concentration, of at least one gas in a multi-component gas system. Thus, the present invention can be used to determine the composition of a gas system. The concept is schematically presented in fig. 1 and is exemplified below.

For ease of illustration, the following theoretical example exposes the sensor material to a mixture containing one analyte gas. When a response was obtained, the event was described as positive (+), and when no response was obtained, the event was described as negative (-). Material 1 responds to gas 1 and gas 2, but not to gas 3. Material 2 is responsive to gas 1 and gas 3 but not to gas 2, and material 3 is responsive to gas 2 and gas 3 but not to gas 1.

	Material 1	Material 2	Material 3
	Material 1	Material 2	Material 3	Gas 1	+	+	-
Gas 2	+	-	+	Gas 1	+	+	-
Gas 2	+	-	+	Gas 3	-	+	+

Thus, if an array comprising materials 1, 2 and 3, gives the following response to an unknown gas,

	material 1	Material 2	Material 3
	material 1	Material 2	Material 3	Unknown gas	+	-	+

Then the unknown gas may be identified as gas 2. The response of each sensor material is a function of the partial pressure, and thus the concentration, of the analyte gas or the collective concentration of the subgroup of analyte gases in the mixture; the response may be quantified or recorded as a processable value, such as a numerical value. In such a case, one or more response values may be used to obtain quantitative information about the concentration of one or more analyte gases in the mixture. In a multi-component gas system, the concentration of one or more analyte gases in the system mixture may be calculated using stoichiometry, neural networks, or other pattern recognition techniques.

The chemo/electro-active material can be any type of material, but particularly useful are semiconducting metal oxides, such as ZnO, TiO₂，WO₃And SnO₂. These particular materials have the advantage of chemical and thermal stability. The chemo/electro-active material may be a mixture of two or more semiconductor materials, or a mixture of one semiconductor material and one inorganic material, or a combination thereof. The semiconductor material of interest may be deposited on a suitable insulating solid substrate, such as, but not limited to, aluminum or silicon, and is stable under multicomponent gas mixture conditions. Thus, the array is in the form of sensor material deposited on the substrate. Other suitable sensor materials include: single crystal or polycrystalline semiconductors in bulk or thin film form, semiconductor materials in amorphous state, and semiconductor materials not composed of metal oxides.

In the present invention, the chemo/electro-active material as the sensor material may be, for example, a metal oxide having the following formula, including M¹O_X，M¹ _aM² _bO_XOr M¹ _aM² _bM³ _cO_XOr mixtures thereof, wherein

M¹，M²And M³Is a metal capable of forming a stable oxide when combusted in the presence of oxygen at above 500 ℃;

M¹elements selected from groups 2-15 of the periodic table and lanthanides;

M²and M³Are selected from elements of groups 1-15 of the periodic Table and lanthanides, respectively, but in M¹ _aM² _bM³ _cO_XMiddle M²And M³Are not identical;

a. b and c are each independently in the range of about 0.0005 to about 1; and

x is a number sufficient to balance the oxygen present with the charge of the other elements in the compound.

The metal oxide comprising more than one metal need not be a compound or solid solution, but may be a mixture of discrete metal oxides. They may exhibit compositional gradients and may be crystalline or amorphous. Suitable metal oxides have the following characteristics:

1) having a temperature of about 1ohm-cm to about 10 when the temperature is about 400 ℃ or higher⁶Resistivity of ohm-cm, preferably about 1ohm-cm to about 10⁵ohm-cm, more preferably from about 1ohm-cm to about 10⁴ohm-cm，

2) Exhibits a chemical/electrical response to at least one gas of interest, and

3) is stable and has mechanical integrity, i.e., capable of adhering to a substrate and not degrading at operating temperatures.

The metal oxide may also include trace amounts or traces of water as well as elements present in the precursor material.

In certain preferred embodiments, the metal oxide material may include:

M¹selected from the group consisting of Ce, Co, Cu, Fe, Ga, Nb, Ni, Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr; and/or

M²And M³Each independently selected from the group consisting of: al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo, Na, Nb, Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn and Zr; but at M¹ _aM² _bM³ _cO_XMiddle M²And M³Is different.

In certain other preferred embodiments, the metal oxide material may include:

M¹O_xis Ce_aO_x，CoO_x，CuO_x，FeO_x，GaO_x，NbO_x，NiO_x，PrO_x，RuO_x，SnO_x，Ta_aO_x，TiO_x，TmO_x，WO_x，YbO_x，ZnO_x，ZrO_xSnO added with Ag_xZnO doped with Ag_xTiO with added Pt_xZnOx with glaze, NiO with glaze_XSnO added with glaze_xOr WO with addition of glaze_xAnd/or

M¹ _aM² _bO_xIs Al_aCr_bO_X，Al_aFe_bO_x，Al_aMg_bO_x，Al_aNi_bO_x，Al_aTi_bO_X，Al_aV_bO_x，Ba_aCu_bO_x，Ba_aSn_bO_x，Ba_aZn_bO_x，Bi_aRu_bO_x，Bi_aSn_bO_x，Bi_aZn_bO_x，Ca_aSn_bO_x，Ca_aZn_bO_x，Cd_aSn_bO_x，Cd_aZn_bO_x，Ce_aFe_bO_x，Ce_aNb_bO_x，Ce_aTi_bO_x，Ce_aV_bO_x，Co_aCu_bO_x，Co_aGe_bO_x，Co_aLa_bO_x，Co_aMg_bO_x，Co_aNb_bO_x，Co_aPb_bO_x，Co_aSn_bO_x，Co_aV_bO_x，Co_aW_bO_x，Co_aZn_bO_x，Cr_aCu_bO_x，Cr_aLa_bO_x，Cr_aMn_bO_x，Cr_aNi_bO_x，Cr_aSi_bO_x，Cr_aTi_bO_x，Cr_aY_bO_x，Cr_aZn_bO_x，Cu_aFe_bO_x，Cu_dGa_bO_x，Cu_aLa_bO_x，Cu_aNa_bO_x，Cu_aNi_bO_x，Cu_aPb_bO_x，Cu_aSn_bO_x，Cu_aSr_bO_x，Cu_aTi_bO_x，Cu_aZn_bO_x，Cu_aZr_bO_x，Fe_aGa_bO_x，Fe_aLa_bO_x，Fe_aMo_bO_x，Fe_aNb_bO_x，Fe_aNi_bO_x，Fe_aSn_bO_x，Fe_aTi_bO_x，Fe_aW_bO_x，Fe_aZn_bO_x，Fe_aZr_bO_x，Ga_aLa_bO_x，Ga_aSn_bO_x，Ge_aNb_bO_x，Ge_aTi_bO_x，In_aSn_bO_x，K_aNb_bO_x，Mn_aN_bO_x，Mn_aSn_bO_x，Mn_aTi_bO_x，Mn_aY_bO_x，Mn_aZn_bO_x，Mo_aPb_bO_x，Mo_aRb_bO_x，Mo_aSn_bO_x，Mo_aTi_bO_x，Mo_aZn_bO_x，Nb_aNi_bO_x，Nb_aNi_bO_x，Nb_aSr_bO_x，Nb_aTi_bO_x，Nb_aW_bO_x，Nb_aZr_bO_x，Ni_aSi_bO_x，Ni_aSn_bO_x，Ni_aY_bO_x，Ni_aZn_bO_x，Ni_aZr_bO_x，Pb_aSn_bO_x，Pb_aZn_bO_x，Rb_aW_bO_x，Ru_aSn_bO_x，Ru_aW_bO_x，Ru_aZn_bO_x，Sb_aSn_bO_x，Sb_aZn_bO_x，Sc_aZr_bO_x，Si_aSn_bO_x，Si_aTi_bO_x，Si_aW_bO_x，Si_aZn_bO_x，Sn_aIa_bO_x，Sn_aTi_bO_x，Sn_aW_bO_x，Sn_aZn_bO_x，Sn_aZr_bO_x，Sr_aTi_bO_x，Ta_aTi_bO_x，Ta_aZn_bO_x，Ta_aZr_bO_x，Ti_aV_bO_x，Ti_aW_bOx，Ti_aZn_bO_x，Ti_aZr_bO_x，V_aZn_bO_x，V_aZr_bO_x，W_aZn_bO_x，W_aZr_bO_x，Y_aZr_bO_x，Zn_aZr_bO_xGlaze-added Al_aNi_bO_xCr with glaze added_aTi_bO_xFe with glaze added_aLa_bO_xFe with glaze added_aNi_bO_xFe with glaze added_aTi_bO_xNb with glaze added_aTi_bO_xNb with glaze added_aW_bO_xNi with glaze added_aZn_bO_xNi with glaze added_aZr_bO_xSb with glaze added_bSn_bO_xTa with added glaze_aTi_bO_xOr Ti with glaze added_aZn_bO_x(ii) a And/or

M¹ _aM² _bM³ _cO_xIs Al_aMg_bZn_cO_X，Al_aSi_bV_cO_x，Ba_aCu_bTi_cO_x，Ca_aCe_bZr_cO_x，Co_aNi_bTi_cO_x，Co_aNi_bZr_cO_x，Co_aPb_bSn_cO_x，Co_aPb_bZn_cO_x，Cr_aSr_bTi_cO_x，Cu_aFe_bMn_cO_x，Cu_aLa_bSr_cO_x，Fe_aNb_bTi_cO_x，Fe_aPb_bZn_cO_x，Fe_aSr_bTi_cO_x，Fe_aTa_bTi_cO_x，Fe_aW_bZr_cO_x，Ga_aTi_bZn_cO_x，La_aMn_bNa_cO_x，La_aMn_bSr_cO_x，Mn_aSr_bTi_cO_x，Mo_aPb_bZn_cO_x，Nb_aSr_bTi_cO_x，Nb_aSr_bW_cO_x，Nb_aTi_bZn_cO_x，Ni_aSr_bTi_cO_x，Sn_aW_bZn_cO_x，Sr_aTi_bV_cO_x，Sr_aTi_bZn_cO_x，

Or Ti_aW_bZr_cO_x。

In certain other preferred embodiments, the metal oxide material comprises an array of first and second chemo/electro-active materials, wherein the chemo/electro-active materials are selected from the group of pairs comprising:

Wherein M is¹Selected from the group consisting of Ce, Co, Cu, Fe, Ga, Nb, Ni, Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr; m²And M³Each independently selected from the group consisting of: al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo, Na, Nb, Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn and Zr; but at M¹ _aM² _bM³ _cO_XMiddle M²And M³Is different; and X is a number sufficient to balance the oxygen present with the charge of the other elements in the compound.

The sensor material may optionally include one or more additives to promote adhesion to the substrate, or to alter the conductivity, resistance, or selectivity of the sensor material. Examples of adhesion-promoting additives are glazes, which are ground fine glass or ground fine inorganic minerals that can be converted into glass or enamel upon heating. Examples of glazes include materials available from DuPont Technologies under the designations F2834, F3876, F2967, KH770, KH710 and KH 375. The amount of the above-mentioned substances in the composition making up the sensor material may be 30% (volume percent). Examples of additives that alter the conductivity, resistance or selectivity of the sensor material include Ag, Au, Pt and glaze.

If desired, the sensor material may also include additives, for example, to catalyze the oxidation of the gas of interest or to promote selectivity for a particular analyte gas; or contain one or more dopants that convert n-semiconductors to p-semiconductors or vice versa. The amount of these additives can be up to 30% by volume of the composition from which the sensor material is made. Any glaze or other additive used in the fabrication need not be uniformly or homogeneously distributed throughout the sensor material, but may be disposed on or near a particular surface, as desired. Each chemo/electro-active material may be covered with a porous dielectric capping layer, if desired. A suitable overlayer is QM44 from DuPont iTechologies.

Any method of depositing the chemo/electro-active material on the substrate is suitable. One deposition technique employed is to apply the semiconductor material on an aluminum substrate on which electrodes are screen printed. The semiconductor material may be deposited on top of the electrodes using hand-applied semiconductor material to the substrate, pipetted into the wells, thin film deposition or thick film printing techniques. Most processes are followed by a final firing to sinter the semiconductor material.

The process of screen printing the electrodes and chemo/electro-active material onto the substrate is illustrated in fig. 2-3. Fig. 2 depicts a method of forming a blank hole capable of depositing a chemo/electro-active material therein using a nested electrode stack on a dielectric material. Fig. 3 depicts an electrode printing pattern with an array of 6 materials printed on both sides of a substrate to form an array chip of 12 materials. The two electrodes are arranged in parallel so that each connects only 6 different materials. In the array shown in fig. 3, the top two materials are only simultaneously accessible, from top to bottom, by the bifurcated electrodes with which they are in common contact. Below this is a screen pattern of dielectric material screen printed on top of the electrodes on both sides of the substrate to avoid contamination of the material with gas mixtures, such as bituminous coal deposits which can cause short circuits. Below this is a screen pattern of the actual sensor material. The pattern is printed in a dielectric hole on top of the electrode. When more than one material is employed in the array, one material is printed at a time.

The electrical response of each chemo/electro-active material is measured when the array is exposed to the gas mixture, and the means for measuring the electrical response comprises conductors interconnected with the sensor material. The conductors are in turn connected to input and output circuitry, including data acquisition and processing means adapted to determine and record the response of the sensor material in the form of electrical signals. The response value, e.g. a measure for the resistance, may be indicated by the magnitude of the signal. The sensor array may generate one or more signals for each analyte component in the mixture, whether the analyte is one or more single gases and/or one or more subgroups of gases.

The electrical response of each chemo/electro-active material is detected independently of the electrical response of each other chemo/electro-active material. This can be accomplished by sequentially passing a current through each chemo/electro-active material, using a multiplexer to generate a signal that distinguishes one material from another, for example, in the time or frequency domain. Therefore, it is preferred that the chemo/electro-active material is not connected in series circuit with any other of the above-mentioned materials. However, the electrode through which the current reaches the chemo/electro-active material may be placed in contact with a variety of materials. An electrode may be in contact with all, less than all, of the chemo/electro-active materials in an array. For example, if there are 12 chemo/electro-active materials in an array, one electrode may be in contact with each composition of a set of 2, 3, 4, 5 or 6 (or, optionally, more in each instance) chemo/electro-active materials. The electrodes are preferably arranged such that an electric current can pass through them to each of the constituents of the above-mentioned group of chemo/electro-active materials in succession.

Conductors such as printed circuits may be used to connect a voltage source to the sensor material, which when a voltage is applied to the sensor material, produces a corresponding current through the material. Although the voltage may be ac or dc, the voltage value is generally kept constant. The current generated is proportional to the applied voltage and the resistance of the sensor material. The material response can be measured in the form of current, voltage or resistance, and the means for measuring include commercially available analog circuit components such as precision resistors, filter capacitors and operational amplifiers (e.g., OPA 4340). Each of the voltage, current and resistance is a known function of two other electrical characteristics, and a known value of one characteristic can be readily converted to a value of the other characteristic.

For example, the electrical response may be digitized to determine resistance. The means for digitizing the electrical response comprises a digital-to-analog converter (a/D) as is known in the art and may also comprise, for example, the electrical components and circuitry involved in the operation of the comparator. As previously described, an electrical response in the form of a voltage signal generated by applying a voltage to the sensor material can be used as an input to the comparator section (e.g., LM 339). The other input of the comparator is driven by a linear ramp voltage, which is obtained by charging a capacitor using an operational amplifier (e.g., LT1014) and an external transistor (e.g., PN2007a) as a constant current power supply. The ramp voltage is controlled and monitored by a microcomputer (T89C51CC 01). The second comparator section can also be driven with a ramp voltage but needs to be compared to an accurate reference voltage. The microcomputer captures the length of time from the start of the ramp voltage to the comparator start, thereby generating a signal based on the count time.

The resistance of the sensor material is then calculated, or quantified, by a microcomputer, from the ratio between the time signal resulting from the material output voltage and the time signal corresponding to a known reference voltage and ultimately to the resistance as a function of the reference voltage. A microprocessor chip may be used for this function, such as T89C51CC 01. The microprocessor chip may also serve as a means of determining the change in resistance of the sensor material by comparing the measured resistance with a predetermined resistance value.

For example, electrical characteristics such as impedance or capacitance are determined using circuit components such as impedance, capacitance or inductance meters.

The means for digitizing the temperature of the array of chemo/electro-active materials may comprise, for example, the aforementioned components that convert signals representative of a physical characteristic, state or condition of the thermometry device into a count time based.

In one embodiment, when an electrical response, such as resistance, is generated in the manner previously described, analysis of the multi-component gas mixture is completed. Since the measure of the electrical resistance displayed by the sensor material is a function of the partial pressure of one or more gas components in the gas mixture when the sensor material is exposed to the gas mixture, the measured electrical resistance provides useful information about the composition of the gas mixture. For example, the information may indicate the presence or absence of a particular gas or subgroup of gases in the mixture. However, in another embodiment, it is preferred that the electrical response is processed or further processed to obtain information about the relative concentration of one or more specific gases or subgroups of gases in the mixture, or to calculate the actual concentration of one or more specific gases or subgroups of gases in the mixture.

The means for obtaining information about the relative concentration of one or more individual gases and/or one or more subgroups of gases in the mixture, or detecting the presence or calculating the actual concentration of one or more individual gases and/or subgroups in the mixture, may comprise a model algorithm incorporating signal pre-processing and output post-processing, the model algorithm incorporating a pls (projection on to last systems) model, a back-propagation neural network model, or a combination of both. Signal pre-processing includes, but is not limited to, operations such as principal component analysis, simple linear transformations and scaling, logarithmic and natural logarithmic transformations, differentiation of raw signal values (e.g., resistance), and differentiation of logarithmic values. The algorithm includes a model of the predetermined parameters that empirically models the relationship between the pre-processed input signal and information about the concentration of the gas of interest. Output post-processing includes, but is not limited to, all of the operations enumerated above and their inverse.

The model is constructed using equations in which constants, coefficients, or other factors are derived from predetermined values representing the accurately determined response of an individual sensor material to a particular individual gas or subgroup of gases that may be present as one of the components in the mixture to be analyzed. The equation may be constructed in any manner, with temperature as a value that is independent of the electrical response produced by the sensor material when exposed to the gas mixture. Each individual sensor material in the array responds differently to at least one constituent gas or subgroup in the mixture than the other sensors, and the different responses described above for each sensor are determined and used to construct the equations used in the model.

The analyte gas in the mixture to which the chemo/electro-active material is exposed may be a single gas, a subgroup of gases, or one or more gases or subgroups mixed with an inert gas such as nitrogen. The particular gases of interest are the donor and acceptor gases. These gases supply electrons to the semiconductor material, e.g. carbon monoxide, H₂S and hydrocarbons, or accepting electrons from semiconductor materials, e.g. O₂Nitrogen oxides (commonly described as NO)_x) And a halogen gas. When exposed to the donor gas, the resistance of the n-type semiconductor material decreases, the current increases, and due to I²R is heated and thus its temperature increases. When exposed to an acceptor gas, the resistance of the n-type semiconductor material increases, the current decreases, and due to I²R is heated and thus its temperature decreases. In p-type semiconductor materials, the opposite is true for each case.

The geometry of the sensor material built into the array, including features such as thickness, ofa compound or composition selected for use as a sensor, and voltage applied across the array, can be varied as required by sensitivity. The sensor material is preferably connected in parallel to a circuit that applies a voltage of about 1 to 20 volts, preferably about 1 to 12 volts, across the sensor material. When analyzing a multi-component gas mixture, it is preferred that each chemo/electro-active sensor material in the array exhibits a different electrical response characteristic when exposed to a mixture containing one or more analyte gases than the other chemo/electro-active materials in the array.

As previously mentioned, the types of electrical response characteristics that may be measured include AC impedance or resistance, capacitance, voltage, current, or DC impedance. Preferably, the electrical resistance is used as an electrical response characteristic of the sensor material, which is measured to analyze the gas mixture and/or the components thereof. For example, suitable sensor materials can have a resistivity of at least about 1ohm-cm, and preferably at least about 10ohm-cm, and not greater than about 10ohm-cm at temperatures of about 400 ℃ or higher⁶ohm-cm, preferably not higher than about 10⁵ohm-cm, more preferably not higher than about 10⁴ohm-cm. The sensor material may also be characterized by a change in resistance of at least about 0.1%, preferably at least about 1%, when exposed to a gas mixture, preferably when the temperature is about 400 ℃ or higher, as compared to the resistance when not exposed to the mixture.

For the purpose of analyzing the mixture and/or the gas component of interest therein, regardless of the type of response characteristic measured, it is preferable that the response characteristic quantification of the sensor material employed be stable over an extended period of time. When the sensor material is exposed to a mixture containing an analyte, the analyte concentration as a function of the composition of the particular gas mixture and the response value of the sensor material preferably remain constant, or vary only to a small extent, during prolonged exposure to the mixture at a constant temperature. For example, if varied, the response value may vary by no more than about 20%, preferably no more than about 10%, more preferably no more than about 5%, and most preferably no more than about 1% over a period of at least about one minute, or preferably over several hours, such as at least about 1 hour, preferably at least about 10 hours, more preferably at least about 100 hours, and most preferably at least about 1000 hours. One advantage of sensor materials of the type described above is that they are characterized by such response stability.

When used with gas mixtures having temperatures above about 400 c, the temperature of the sensor material and the array can be determined solely, and preferably separately, by the temperature of the gas mixture containing the gaseous analyte. Which is typically a variable temperature. When analyzing hot gases, it is desirable to provide a heat source to the array so that the sensor material quickly reaches a minimum temperature. However, once analysis is initiated, the heat source (if used) is typically turned off and no means is provided to maintain the sensor material at a preselected temperature. Thus, the temperature of the sensor material is raised or lowered to the same temperature as the surrounding environment. The temperature of the ambient environment, and hence the temperature of the sensor and array, is typically substantially dependent only on (or from) the temperature of the gas mixture to which the array is exposed.

When used with gas mixtures having temperatures below about 400 c, it may be preferable to maintain the temperature of the sensor material and the array at a predetermined temperature of about 400 c or higher. The preselected temperature may be substantially constant, or preferably constant. The preselected temperature may also be about 500 ℃ or greater, about 600 ℃ or greater, or about 700 ℃ or greater. Heaters may be incorporated into the array to conveniently achieve the above temperatures according to techniques well known in the art. The temperature of the gas mixture may also be less than about 300 deg.C, less than about 200 deg.C, or less than about 100 deg.C.

Changes in the temperature of the array may be indicated by changes in the quantified value of the electrical response characteristic of the sensor material, such as resistance. When the partial pressure of the gas of interest in the mixture is constant, the value of the electrical response characteristic of the sensor material may vary with the array temperature and thus the material temperature. In order to determine or measure the temperature change and thus the degree of change in the value, the change in the value of such an electrical response characteristic may be measured. Preferably, although not required, the temperature is measured independently of information about the compositional content of the gas mixture. Instead of using a sensor that provides compositional information for the additional purpose of determining temperature, the above-described purpose is achieved by selectively connecting the temperature measurement device and the sensor material in a parallel circuit, rather than in series. The means for measuring the temperature may comprise a thermocouple attached to the sensor array, or a pyrometer. If the temperature determining means is a thermistor of a material that is generally non-responsive to the analyte gas, the thermistor is preferably made of a material that is different from the material of any of the gas sensors. Regardless of the method used to determine the temperature or change in temperature, a quantitative change in temperature or value is a desirable input, preferably in digital form, so that the gas mixture and/or its components can be analyzed.

In the method and apparatus of the invention, unlike the various prior art techniques, there is no need to separate the individual gas components of the mixture for analysis purposes, such as by membranes or electrolytic cells. When the method of the invention is used for analysis, it is also not necessary to use a reference gas, for example for the purpose of returning the response or analysis result to a baseline value. In addition to the preliminary measurements during which the normalized response values assigned to each sensor material exposed to a single analyte gas are determined, the sensor material is only exposed to the mixture in which the analyte gas and/or the subgroup is contained. The sensor material is not exposed to any other gas to obtain a response value and is thus compared to the response value obtained by exposure to the analyte-containing mixture. Thus, analysis of the mixture is solely based on the electrical response obtained by exposing the chemo/electro-active material to the mixture containing the analyte. Exposing the sensor material to any other gas than the analyte contained in the mixture does not infer information about the analyte gas and/or subgroup.

The present invention thus provides a method and apparatus for directly detecting the presence and/or concentration of one or more gases in a multi-component gas system, comprising an array of at least two chemo/electro-active materials selected for detecting the gases in the multi-component gas stream. The multi-component gas system can be located at essentially any temperature as long as the temperature is not too high or too low resulting in degradation of the sensor material or failure of the sensor device. In one embodiment, the gas system may be at a lower temperature, such as room temperature (about 25℃.), or any temperature in the range of about 0℃. to at least about 100℃, while in another embodiment, the gas mixture may be at a higher temperature, such as in the range of about 400℃. to about 1000℃.

The invention is applicable to gas mixtures which can be at relatively high temperatures, for example in gas streams resulting from combustion, such as automobile exhaust or emissions, diesel engines or domestic heating systems. Moreover, the invention is also applicable to gas mixtures of other sources, such as production processes, exhaust gases and environmental monitoring; or systems where odor detection is important and/or systems at lower temperatures, such as in the medical, agricultural or food and beverage industries. The array of chemo/electro-active materials can be used, for example, to supplement or calibrate the results of a gas chromatograph. Thus, the gas mixture can have a temperature of about 100 ℃ or more, about 200 ℃ or more, about 300 ℃ or more, about 400 ℃ or more, about 500 ℃ or more, about 600 ℃ or more, about 700 ℃ or more, about 800 ℃ or more, yet less than about 1000 ℃, less than about 900 ℃, less than about 800 ℃, less than about 700 ℃, less than about 600 ℃, less than about 500 ℃, less than about 400 ℃, less than about 300 ℃, less than about 200 ℃, or less than about 100 ℃.

The present invention also provides a means of determining, measuring and recording the response exhibited by the chemo/electro-active materials present in the array when exposed to a gas mixture. For example, any tool capable of determining, measuring, and recording changes in electrical characteristics may be used. For example, the means may be a device capable of determining the change in the alternating current impedance of a material in response to the concentration of gas molecules adsorbed on its surface. Other means of determining the electrical property may be, for example, suitable devices for determining capacitance, voltage, current or DC resistance. Furthermore, the temperature change of the sensor material can also be measured and recorded. The chemical assay methods and devices may also provide a means of assaying or analyzing the mixture and/or the gas to be assayed so that the presence of the gas can be determined and their concentration measured. These tools may include, for example, instruments or devices capable of performing chemometrics, neural networks, or other pattern recognition techniques. The chemical sensor device further comprises a housing for the array of chemo/electro-active materials, detection means and analysis means.

The present invention also provides a chemical sensor for directly detecting the presence and/or concentration of one or more gases in a multi-component gas system, comprising a substrate, an array of at least two selected chemo/electro-active materials for detecting one or more predetermined gases in the multi-component gas stream, and a means for detecting a change in an electrical property of each chemo/electro-active material when exposed to the gas system.

An array with sensor material should be able to detect the analyte of interest despite competing reactions caused by the various other components present in the multi-component mixture. To this end, the present invention employs an array having a plurality of sensor materials, each material having a different sensitivity to at least one gas component in the mixture to be measured, as described herein. By selecting an appropriate material composition from which to make the sensor, a sensor is obtained that has the desired sensitivity and is operable to produce analytical assays and results of the type described above. The foregoing describes a variety of materials suitable for this purpose. The number of sensors in the array is typically greater than or equal to the number of individual gas components to be analyzed in the mixture.

The gas mixture to be analyzed may be the effluent of a process or the product of a chemical reaction delivered to the device. In this case, the device of the invention further comprises means for utilizing the electrical response of the array and optionally the temperature measurement in order to control the process or device.

For controlling a process or a device, the means for utilizing the electrical response of the sensor material and optionally the temperature measurement comprise a decision procedure for controlling, for example, the combustion chemical reaction taking place inside the internal combustion engine, or controlling the engine itself, or the elements or devices associated therewith.

Combustion is a chemical reaction process that occurs in the oxidation of hydrocarbon fuel in the engine cylinder. An engine is a device that delivers the results of a chemical reaction, the result being the force generated by the combustion reaction necessary to propel a piston in a cylinder to work. Another example of a process for discharging a multi-component mixed gas is a chemical reaction that occurs in a fuel cell, and another example of delivering the product of the chemical reaction to a device is a boiler, such as a boiler used in a furnace or for power generation, or a scrubber that delivers the exhaust gas to a stack for pollution abatement treatment.

In the case of an engine, various decision-making routines regarding various parameters of the combustion process or engine operating characteristics are executed by a microcomputer (e.g., T89C51CC01) in order to control the combustion process or the operation of the engine itself. The microcomputer collects information about the compositional content of the engine exhaust and performs a decision-making routine by obtaining an array response of chemo/electro-active materials exposed to the exhaust stream, and optionally obtaining a temperature measurement. The information is temporarily stored in a random access memory, and then the microcomputer applies one or more decision-making programs to the information.

The decision-making routine processes the acquired information using one or more algorithms and/or mathematical operations to produce a decision in the form of a value that is equivalent to an ideal state or condition that the process-specific parameter or operating characteristic of the plant should have. Based on the results of the decision-making routine, the microcomputer issues or controls instructions to correct the parameters of the process or the states or conditions of the operating characteristics of the device. For processes embodied by chemical reactions of combustion, the process may be controlled by adjusting parameters of the reaction, such as the relative amounts of reactants fed to the reaction. For example, fuel or air flow into the cylinder may be increased or decreased. Control of the engine itself, as the means for communicating the results of the combustion reaction, may be achieved by adjusting an operating characteristic of the engine, such as torque or engine speed.

The following non-limiting examples are intended to illustrate the invention, but not to limit it in any way. In the embodiments given below, a "chip" is used to describe an aluminum substrate that includes electrodes and sensing material, and, if a dielectric is employed, a dielectric on the substrate. The symbol "X% A: MO" represents another inorganic compound (A) added to the Metal Oxide (MO) at a specific concentration (X% on an atomic basis). The term "glaze" is used to describe a mixture of inorganic compounds that typically form glass at certain temperatures.

Examples

The following description is an exemplary technique that may be used to prepare the sensor material and determine the signal using Infrared (IR) thermography and ac resistance techniques.

IR thermographic samples and assays

The change in the impedance of the sensor material when exposed to a gas or gas mixture can be determined by measuring the change in temperature of a sample of the material using, for example, thermographic imaging techniques.

A. Array chip fabrication

A blank array chip was prepared by screen printing a pattern of interdigitated electrodes on an alumina substrate (from Coors Tek, 96% alumina, 1 '. times.0.75 '. times.0.025 '), as shown in FIG. 2. A semi-automatic screen printer (EPT Electro-digital, Series L-400) was used. Electrode coatings are commercially available from DuPont iTechnologies, product # 5715. The electrode screen (available from Microcircuit engineering corporation) used had a latex thickness of 0.5 mil. After screen printing, the parts were dried in a convection oven at 120 ℃ for 10 minutes and then sintered. A10-zone Lindberg furnace was used in air and fired for 10 minutes at a maximum temperature of 850 ℃ for 30 minutes as a cycle time. As shown in FIG. 2, when the electrode was sintered on the substrate, a dielectric (Dupont i technologies, product #5704) pattern was screen printed on the electrode with a screen (Microcircuit Engineering Corporation) having a latex thickness of 0.9 mil. The part was then fired at 120 ℃ for 10 minutes using the same cycle as described previously.

B. Preparation of semiconductor metal oxide and application of semiconductor metal oxide on array chip

Approximately 175mg of semiconductive metal oxide powder, or a mixture of semiconductive metal oxide and a suitable glass frit (Dupont I technologies, products # F2889 or # F3876), or a mixture of semiconductive metal oxide powder and other inorganic compounds, together with approximately 75mg of a suitable medium (Dupont I technologies, products # M2619) and 1mg of a suitable surfactant (Dupont I technologies, product # R0546) are weighed out and placed on a glass slide. The medium and surfactant are mixed and the metal oxide powder or mixture is gradually added to the medium and surfactant to ensure wetting. If desired, a suitable solvent (Dupont iTechnologies, product # R4553) may be added at this point to reduce its viscosity. The paste was then transferred to an agate mortar and ground with a pestle for more thorough mixing. Very small amounts of paste were applied to one well of the array chip using a precision wooden tip applicator. This process is repeated for each metal oxide powder or mixture until each well of the array chip is filled with the paste. Once each well of the array chip is filled with the paste, the array chip can be placed in a closed chamber and a low flow of nitrogen gas is flowed over the chip. The array chip was then dried at 120 ℃ for 10 minutes. Firing was carried out using a Fisher programmed box furnace with a ramp rate of 1 c/min to 650 c, held at this temperature for 30 minutes. Cool to room temperature at a rate of 5 ℃/min.

C. Array chip wiring

The wire was prepared using about 0.005 "of platinum wire 1.5". One end of the lead is exposed, and the other end of the lead is connected with the negative RS232 binding post. The exposed ends of the platinum wires were connected to open conductive pads on the array chip using a conductive paste (Pelco product # 16023). In the same manner, the second wires are connected to other open conductive pads on the array chip. The chips were then dried at 120 ℃ for at least 4 hours.

D.ir thermographic detection assay

The detection chamber included a 2.75 "tube with gas flow input and output control valves, a 1" MgF window, two thermocouple feeds and two electrical feeds. The electrical feedthroughs were connected to sample heaters (Advanced Ceramics, Boralectric heater # HT-42) and a voltage/current measuring cell (Keithley Instruments model # 236). The gas flow was regulated using a multiple gas controller (MKS model # 647B). The sample heater was controlled using an element (70VAC/700W phase angle) from Hampton Controls. During the assay, an infrared camera (infrastratrics pm390) was focused on the front surface of the array chip using a 100 μm close-up lens.

Prior to the assay, the sample is placed on a sample heater in the detection chamber. The cathode pin connected to the lead is then connected to an electrical feedthrough connected to a voltage/current measuring element. The chamber is closed and placed in the visual path of the IR camera. Next, during the sample heating process, a gas (100sccm N) is introduced₂，25sccm O₂) Flows into the detection chamber. The sample was then heated (approximately 10 c/min) to the desired temperature and held constant before the voltage source measuring element was turned on and voltage applied. The voltage is typically adjusted to allow a current between 10-20mA to flow through the array.

The IR thermal phase image of the array material was taken after 20 minutes of each change of the following gas flow: n is a radical of₂，O₂And the following gas mixtures: 1% CO/99% N₂，1％NO₂/99％N₂And 1% of C₄H₁₀/99％N₂. All gas mixtures described below are present in volume percent unless otherwise indicated. In this example, the material is used at 2% O₂/98％N₂Minus their temperature in the other gas mixture to determine the temperature signal. Temperature subtraction was performed using a 95Pro (Thermoteknix Systems, Ltd.) thermal detector version 1.61. When exposed to a donor gas, the resistivity of the n-type semiconductor material will decrease and the current will increase accordingly, therebyIn I²The heating effect of R will show an increase in temperature. When exposed to a receptor gas, the resistivity of the n-type semiconductor material will increase and the current correspondingly decreases due to I²The heating of R will indicate a temperature drop. The opposite is true in p-type semiconductor materials.

AC impedance samples and measurements

A. Preparation of semiconductor metal oxide paste

Approximately 2-3 grams of semiconductive metal oxide powder, or a mixture of semiconductive metal oxide with a suitable glass frit (Dupont i technologies, product # F2889 or # F3876), or a mixture of semiconductive metal oxide with other inorganic compounds, is weighed, and an appropriate medium (Dupont i technologies, product # M2619) is weighed in an amount sufficient to provide approximately 40-70% solids by weight. These materials were then transferred to a grinding wheel (Hoover automated grinding wheel model # M5) and mixed with a spatula until no dry powder was present. If desired, a suitable surfactant is added to reduce tackiness, such as Dupont iTechnies product # R0546. A further 500 gram weight grinding wheel was used to grind approximately 6 times at 25 revolutions per pass. The final paste is then transferred to a container for use.

B. Preparation of Individual Sensors

Some detection chips are made of a single material rather than an array of detection materials. The electrodes with embedded electrode patterns were screen printed on an alumina substrate to prepare a single test sample chip, with electrodes 0.4 "long and 0.008" (Coors Tek, 96% alumina, 1 "× 0.025") on the alumina substrate. A semi-automatic screen printer (EPTElectron-dial, series L-400) was used. Electrode pastes were purchased from duponti technologies. The latex thickness of the electrode mesh (Microcircuit Engineering corporation) was 0.5 mil. After printing, the parts were dried in a convection oven at 120 ℃ for 10 minutes and then sintered. A10-zone Lindberg furnace (Lindberg) was used, and firing was carried out for 10 minutes at a maximum temperature of 850 ℃ with 30-minute cycles. Next, the sensor material was screen printed onto the substrate using a screen (Microcircuit engineering corporation) having an effective screen area of 0.5 "by 0.5". The latex thickness of this screen was 1 mil. After printing the sensor material, the part was fired in a convection oven at 120 ℃ for 10 minutes. The parts were then sintered in air using a Lindberg tube furnace for 10-45 minutes to 850 ℃.

C. Preparation of sensor arrays

A variety of electrode and sensor configurations may be employed for obtaining ac impedance data for the sensor array. The preparation of an array of 12 materials is described below.

The sensor array chip was obtained by screen printing an electrode pattern on an alumina substrate (Coors Tek, 96% alumina, 2.5 "x 0.75" x 0.040 "). A semi-automatic screen printer (EPTElectron-dial, series L-400) was used. Electrode pastes (#4597 products) were purchased from DuPont i technologies. The latex thickness of the electrode mesh (Microcircuit Engineering corporation) was 0.4 mil. Note that in fig. 3, the two sensor plates are parallel, so that only 6 unique sensor material measurements can be made from the electrode configuration. After printing, the parts were dried in a convection oven at 130 ℃ for 10 minutes and then sintered. A10-zone Lindberg furnace (Lindberg) was used in the air, and the firing was carried out for 10 minutes at a maximum temperature of 850 ℃ with 30-minute cycles. After the electrode was sintered to the substrate, a dielectric (DuPonti technologies, product # QM44) pattern was printed on top of the electrode using a 1mil latex screen (Microcircuit Engineering Corporation) as shown in FIG. 3. The part was dried in a convection oven at 130 c for 10 minutes and fired using the same firing cycle as previously described. At this time, as shown in fig. 3, each sensor material has been printed in holes with a dielectric on a substrate using a screen (Microcircuit Engineering Corporation). The latex thickness of the screen was 1.0 mil. After each sensor material was printed, the parts were dried in a convection oven at 130 ℃ for 10 minutes. After all of the sensor materials (6) were applied to that side of the sensor, firing was carried out using the same firing cycle as previously described. After this firing step, 6 additional sensor materials were added to the array chip on the back side of the substrate, and the printing, drying and sintering steps described above were repeated.

D. AC impedance measurement

For a single sensor material sample, a 1.2 "platinum wire was attached to each electrode on the sample using stainless steel screws. The end of the platinum wire was then connected to a 0.127 "diameter inconel wire extending outside the detection chamber. The entire inconel wire is encased in alumina and grounded inconel tube to reduce interference from electromagnetic fields present in the furnace. The Inconel tube was welded into a stainless steel flange placed on one end of a4 "long 24" fused silica reactor closed at one end. The quartz reactor is surrounded by a grounded stainless steel screen, which also serves to reduce the electromagnetic interference present in the furnace. The entire chamber assembly was placed in the chamber of a hinged Lindberg tube furnace and the furnace was closed.

The sample was connected to a dielectric interface (Solartron 1296) and a frequency response analyzer (Solartron 1260) using 10 pairs of coaxial cables extending from inconel wire on the furnace outside the switch (Keithley 7001 with two Keithley7062 high frequency cards) and 1 pair of coaxial cables from the switch to the interface and analyzer. The switch, dielectric interface and frequency analyzer are all computer controlled.

The gas flow into the quartz chamber was controlled using a computer control system comprising 4 independent flow meters (MKS product #1179) and a multiple gas controller (MKS product # 647B). The temperature of the furnace was measured using a computer controlled fuzzy logic controller (Fuji PYX).

After the sample was loaded into the furnace, the quartz reactor was purged with the synthesis gas mixture during heating of the furnace. After the furnace reached equilibrium at the measured temperature, the gas concentration (N) was measured₂，O₂1% CO/99%, and 1% NO₂/99％N₂. ) Set to a desired value and allow the air in the reactor sufficient timeEquilibrium is reached. At this time, the AC impedance value (1Hz to 1MHz) of each sample was measured sequentially. The gas concentration is then typically set to a new value, the gas reaches equilibrium, and another measurement cycle is performed. This process is repeated until the sample is assayed in all of the desired gases at the selected temperature. At this point, the temperature is changed, and then the process is repeated. After all measurements were performed, the furnace was cooled to room temperature and the samples were removed.

For this array chip, an assay system similar to that described above was used. The only difference is that a conductive paste (Pelco product #16023) must be used to connect the platinum wires connected to the inconel wires on the oven to the electrode pads on the array chip. The number of connectors between the sample and the switch depends on the number of sensors on the array.

Example 1

This example shows the change in electrical properties of 20 metal oxide materials in 4 combustion gas mixtures at 450 ℃. The signals listed in table 1 below are from the infrared thermal imaging techniques described previously. These signals show that when a material is exposed to one of the 4 gas mixtures, it is relatively exposed to 2% O as a reference gas₂/98％N₂And reflects the change in resistance of the semiconductor material. Unless otherwise stated, all signals were generated at a voltage of 10V across the material. The blank spaces indicate that no detectable signal is produced when the gas mixture is in contact with the material. Unless otherwise stated, the gas measured is at N₂The concentration in (A) was 2000 ppm.

TABLE 1

Temperature (. degree. C.) Change

	ZnO	SnO	NiFeO	WO	1％Nb:TiO	PrO	SrNbO
	ZnO	SnO	NiFeO	WO	1％Nb:TiO	PrO	SrNbO	Containing NON of (A)	-38.1	-35.4	-27.4	-16.4	-2.7	-5.6	-2.8
Containing NO2% of O/98％N	-35.2	-32.5	-13.7	-13.5	-2.7	-	-	Containing NON of (A)	-38.1	-35.4	-27.4	-16.4	-2.7	-5.6	-2.8
Containing NO2% of O/98％N	-35.2	-32.5	-13.7	-13.5	-2.7	-	-	N containing CO	27.2	8.2	14	13.7	-	-	8.3
NReference to	16.9	9.6	11.2	5.6	12.4	-	-	N containing CO	27.2	8.2	14	13.7	-	-	8.3

	NiO	CuO	CuO	MnTiO	BaCuO	AlVO	CuMnFeO
	NiO	CuO	CuO	MnTiO	BaCuO	AlVO	CuMnFeO	Containing NON of (A)	5.5	8.2	8.2	5.6	6.6	-	-
Containing NO2% of O/98％N	5.5	5.6	5.5	-	2.6	-2.7	2.6	Containing NON of (A)	5.5	8.2	8.2	5.6	6.6	-	-
Containing NO2% of O/98％N	5.5	5.6	5.5	-	2.6	-2.7	2.6	N containing CO	-	-5.5	-13.8	-	-2.7	11.3	-
NReference to	-2.8	-5.6	-2.8	-	-2.7	8.3	-	N containing CO	-	-5.5	-13.8	-	-2.7	11.3	-

	LaFeO	CuGaO	CuFeO	ZnTiO	LaCuO	SrCuO
	LaFeO	CuGaO	CuFeO	ZnTiO	LaCuO	SrCuO	Containing NON of (A)	-	-2.8	-5.5	-5.7	4.2	-
Containing NO2% of O/98％N	-	-	2.5	-	-	2.6	Containing NON of (A)	-	-2.8	-5.5	-5.7	4.2	-
Containing NO2% of O/98％N	-	-	2.5	-	-	2.6	N containing CO	-2.8	-	-	7.3	-	-
NReference to	-	-	-	-	-	-	N containing CO	-2.8	-	-	7.3	-	-

The following measurements were made using voltages other than 10V. Measurement of Pr with 1V Voltage₆O₁₁(ii) a BaCuO measurement Using a 16V Voltage₂₅，CuMnFeO₄，CuGaO₂And CuFe₂O₄(ii) a Zn determination with a voltage of 20V₄TiO₆(ii) a LaCuO measurement with a 12V voltage₄And SrCu₂O₂。

Example 2

This example shows the change in electrical properties of 8 metal oxide semiconductor materials in 5 combustion gas mixtures at 450 ℃. The signals listed in table 2 below are from infrared thermal imaging technology. These signals show that when a material is exposed to the indicated gas mixture, the relative exposure is 2% O of the comparative gas₂/98％N₂Temperature (. degree. C.) of (A). Unless otherwise stated, all signals are generated at a voltage of 10V flowing through the semiconductor material. The blank spaces indicate that no detectable signal is produced when the gas mixture is in contact with the material. Unless otherwise stated, the gas measured is at N₂The concentration in (A) was 2000 ppm.

TABLE 2

Temperature (. degree. C.) Change

	ZnO	SnO	WO	SrNbO	NiO	CuO	CuO	AlVO
	ZnO	SnO	WO	SrNbO	NiO	CuO	CuO	AlVO	Containing NON of (A)	-38.1	-35.4	-16.4	-2.8	5.5	8.2	8.2	-
Containing NO2% of O/98％N	-35.2	-32.5	-13.5	-	5.5	5.6	5.5	-2.7	Containing NON of (A)	-38.1	-35.4	-16.4	-2.8	5.5	8.2	8.2	-
Containing NO2% of O/98％N	-35.2	-32.5	-13.5	-	5.5	5.6	5.5	-2.7	N containing CO	27.2	8.2	13.7	8.3	-	-5.5	-13.8	11.3
NReference to	16.9	9.6	5.6	-	-2.8	-5.6	-2.8	8.3	N containing CO	27.2	8.2	13.7	8.3	-	-5.5	-13.8	11.3
NReference to	16.9	9.6	5.6	-	-2.8	-5.6	-2.8	8.3	1％CH/99％N	38	28	22	-	-6	-7	-11	11

Example 3

This example shows the change in electrical properties of 26 metal oxide semiconductor materials in 4 combustion gas mixtures at 600 ℃. The signals listed in table 3 below are from infrared thermal imaging technology. These signals show that when a material is exposed to a gas mixture, it is exposed to 2% O relative to the gas used as a comparison₂/8％N₂Temperature (. degree. C.) of (A). Unless otherwise stated, all signals were generated at a voltage of 10V across the material. The blank spaces indicate that no detectable signal is produced when the gas mixture is in contact with the material. Unless otherwise stated, the gas measured is at N₂The concentration in (A) was 2000 ppm.

TABLE 3

Temperature (. degree. C.) Change

	ZnO	SnO	NiFeO	1％Nb:TiO	WO	FeTiO	SrTiO	NiO
	ZnO	SnO	NiFeO	1％Nb:TiO	WO	FeTiO	SrTiO	NiO	Containing NON of (A)	-54.4	-48.3	-36.3	-24.2	-18.1	-6.1	3	6
Containing NO2% of O/98％N	-48.3	-48.3	-30.2	-12.1	-18.1	-6.1	6	6	Containing NON of (A)	-54.4	-48.3	-36.3	-24.2	-18.1	-6.1	3	6
Containing NO2% of O/98％N	-48.3	-48.3	-30.2	-12.1	-18.1	-6.1	6	6	N containing CO	28.5	18.1	18.5	42.3	24.1	-	-	-6
N	30.2	24.1	15.1	24.1	6	3	-	-9.1	N containing CO	28.5	18.1	18.5	42.3	24.1	-	-	-6

	AlVO	CuO	CuO	LaFeO	BaCuO	FeO	SrNbO	ZnO+2.5％F2889
	AlVO	CuO	CuO	LaFeO	BaCuO	FeO	SrNbO	ZnO+2.5％F2889	Containing NON of (A)	-	-	-	-	-	-	-	-24
Containing NO2% of O/98％N	-6.1	6	6	-	-	-	-	-18	Containing NON of (A)	-	-	-	-	-	-	-	-24
Containing NO2% of O/98％N	-6.1	6	6	-	-	-	-	-18	N containing CO	18.1	-6	-12.1	-3	-6	72.5	28.5	18
N	18.1	-3	-	-	-6	-	18.1	21	N containing CO	18.1	-6	-12.1	-3	-6	72.5	28.5	18

	ZnO+10％F3876	SnO+5％F2889	WO+10％F3876	CuFeO	ZnTiO	ZnTiO	TmO	YbO
	ZnO+10％F3876	SnO+5％F2889	WO+10％F3876	CuFeO	ZnTiO	ZnTiO	TmO	YbO	Containing NON of (A)	-42	-6	-15	-6	-12	-6	-6	-6
Containing NO2% of O/98％N	-24	-6	-18	-6	-	-	-	-	Containing NON of (A)	-42	-6	-15	-6	-12	-6	-6	-6
Containing NO2% of O/98％N	-24	-6	-18	-6	-	-	-	-	N containing CO	12	24	6	-	6	-	-	-
N	27	9	18	-	6	-	-	-	N containing CO	12	24	6	-	6	-	-	-

	Fe:ZrO	MnCrO
	Fe:ZrO	MnCrO	Containing NON of (A)	-6	-
Containing NO2% of O/98％N	-	-	Containing NON of (A)	-6	-
Containing NO2% of O/98％N	-	-	N containing CO	6	24
N	-	-	N containing CO	6	24

Except that BaCuO was measured using a 4V voltage₂₅(ii) a Determination of Fe with a Voltage of 1V₂O₃(ii) a ZnO + 2.5% F2889, ZnO + 10% F3876, SnO were measured by using a voltage of 5V₂+5％F2889、Tm₂O₃、Yb₂O₃、Fe:ZrO₂And MnCrO₃(ii) a Measurement of the Voltage with 2V WO₃+ 10% F3876; CuFe measurement with a 6V Voltage₂O₄(ii) a And measuring Zn with a voltage of 20V₄TiO₆And ZnTiO₃In addition, all the other above measurements were carried out using a voltage of 10V.

Example 4

This example illustrates that 4 metal oxide materials in example 3 can distinguish the 4 gas mixtures shown at 600 c using infrared thermal imaging techniques. The results are shown in Table 4. These signals show that when a material is exposed to a gas mixture, it is relatively exposed to 2% O as a comparative gas₂/98％N₂Temperature (. degree. C.) of (A). Unless otherwise stated, all signals were generated at a voltage of 10V across the material. The blank spaces indicate that no detectable signal is produced when the gas mixture is in contact with the material. Unless otherwise stated, the gas measured is at N₂The concentration in (A) was 2000 ppm.

TABLE 4

Temperature (. degree. C.) Change

	SrTiO	CuO	FeO	SrNbO
	SrTiO	CuO	FeO	SrNbO	Containing NON of (A)	3	-	-	-
Containing NO2% of O/98％N	6	6	-	-	Containing NON of (A)	3	-	-	-
Containing NO2% of O/98％N	6	6	-	-	N containing CO	-	-12.1	72.5	28.5
N	-	-	-	18.1	N containing CO	-	-12.1	72.5	28.5

Example 5

This example illustrates that the 4 metal oxide materials of example 3 can distinguish between 4 gas mixtures at 600 c using infrared thermal imaging techniques. The results are shown in Table 5. These signals show that when a material is exposed to a gas mixture, it is relatively exposed to 2% O as a comparative gas₂/98％N₂Temperature (. degree. C.) of (A). Unless otherwise stated, all signals were generated at a voltage of 10V across the material. The blank spaces indicate that no detectable signal is produced when the gas mixture is in contact with the material. Unless otherwise stated, the gas measured is at N₂The concentration in (A) was 2000 ppm.

TABLE 5

Temperature (. degree. C.) Change

	ZnO	AlVO	LaFeO	BaCuO
	ZnO	AlVO	LaFeO	BaCuO	Containing NON of (A)	-54.4	-	-	-
Containing NO2% of O/98％N	-48.3	-6.1	-	-	Containing NON of (A)	-54.4	-	-	-
Containing NO2% of O/98％N	-48.3	-6.1	-	-	N containing CO	28.5	18.1	-3	-6
N	30.2	18.1	-	-6	N containing CO	28.5	18.1	-3	-6

Comparative example A

This comparative example illustrates that 6 metal oxide materials in example 3 cannot be used to distinguish 2 gas mixtures at 600 c using infrared thermal imaging techniques, and illustrates the importance of proper material selection. The results are shown in table 5A below. These signals show thatRelative exposure to 2% O as a comparative gas when the material was exposed to the gas mixture₂/98％N₂Temperature (. degree. C.) of (A). Unless otherwise stated, all signals were generated at a voltage of 10V across the material. The blank spaces indicate that no detectable signal is produced when the gas mixture is in contact with the material. Unless otherwise stated, the gas measured is at N₂The concentration in (A) was 2000 ppm.

TABLE 5A

Temperature (. degree. C.) Change

	SnO	WO	FeTiO	NiO	SnO+5％F2889	CuFeO
	SnO	WO	FeTiO	NiO	SnO+5％F2889	CuFeO	Containing NON of (A)	--48.3	-18.1	-6.1	6	-6	-6
Containing NO2% of O/98％N	-48.3	-18.1	-6.1	6	-6	-6	Containing NON of (A)	--48.3	-18.1	-6.1	6	-6	-6

Comparative example B

This comparative example illustrates that 3 metal oxide materials in example 3 cannot be used to distinguish 2 gas mixtures at 600 c using infrared thermal imaging techniques, and illustrates the importance of proper material selection. The results are shown in table 5B below. These signals show that when a material is exposed to a gas mixture, it is relatively exposed to 2% O as a comparative gas₂/98％N₂Temperature (. degree. C.) of (A). Unless otherwise stated, all signals were generated at a voltage of 10V across the material. The blank spaces indicate that no detectable signal is produced when the gas mixture is in contact with the material. Unless otherwise stated, the gas measured is at N₂The concentration in (A) was 2000 ppm.

TABLE 5B

Temperature (. degree. C.) Change

	AlVO	BaCuO	ZnTiO
	AlVO	BaCuO	ZnTiO	N containing CO	18.1	-6	6
N	18.1	-6	6	N containing CO	18.1	-6	6

Example 6

This example illustrates the measurement of the response of 19 metal oxide semiconductor materials in 4 gas mixtures at 400 c using ac impedance techniques. The data set forth in Table 6 below show the impedance values of the materials when exposed to the indicated gas mixtures versus the materials at a concentration of 10000ppmO₂N of (A)₂The ratio of the impedance values in (a). The gas used was a gas containing 200ppm NO₂N of (A)₂Containing 200ppmNO₂And 10000ppmO₂N of (A)₂N containing 1000ppm of mCO₂And N₂。

TABLE 6

	MgAlO	1％Zn:MgAlO	ZnO	WO	NiFeO	SnO	TiO
	MgAlO	1％Zn:MgAlO	ZnO	WO	NiFeO	SnO	TiO	Containing NON of (A)	0.6245	0.5544	55.85	8.772	5.008	9.243	1.536
Containing NOO of (A) to (B)/N	0.7680	0.6787	47.38	9.468	12.93	10.56	1.585	Containing NON of (A)	0.6245	0.5544	55.85	8.772	5.008	9.243	1.536
Containing NOO of (A) to (B)/N	0.7680	0.6787	47.38	9.468	12.93	10.56	1.585	N containing CO	1.531	1.459	0.1235	0.1865	1.248	0.0051	0.0116
N	0.8242	0.9219	4.1290	1.716	1.327	0.3208	1.055	N containing CO	1.531	1.459	0.1235	0.1865	1.248	0.0051	0.0116

	MnTiO	NiO	SrNbO	CeVO	1％Nb:TiO	FeTiO	PrO
	MnTiO	NiO	SrNbO	CeVO	1％Nb:TiO	FeTiO	PrO	Containing NON of (A)	0.8643	0.5692	1.217	0.9847	1.937	1.299	0.5475
Containing NOO of (A) to (B)/N	0.8475	0.9662	1.228	0.9977	1.674	1.034	0.5452	Containing NON of (A)	0.8643	0.5692	1.217	0.9847	1.937	1.299	0.5475
Containing NOO of (A) to (B)/N	0.8475	0.9662	1.228	0.9977	1.674	1.034	0.5452	N containing CO	37.35	9.679	0.6501	1.045	0.0112	0.6009	1.184
N	1.264	1.257	1.011	1.001	0.8811	1.028	1.103	N containing CO	37.35	9.679	0.6501	1.045	0.0112	0.6009	1.184

	SrTiO	BaCuO	CuMnFeO	LaFeO	ZnVO
	SrTiO	BaCuO	CuMnFeO	LaFeO	ZnVO	Containing NON of (A)	0.6524	0.7869	0.9559	0.8401	1.209
Containing NOO of (A) to (B)/N	0.7596	0.7834	0.9399	0.8506	1.114	Containing NON of (A)	0.6524	0.7869	0.9559	0.8401	1.209
Containing NOO of (A) to (B)/N	0.7596	0.7834	0.9399	0.8506	1.114	N containing CO	0.0178	0.7603	0.6089	2037	0.8529
N	1.061	1.063	1.136	1.756	0.9900	N containing CO	0.0178	0.7603	0.6089	2037	0.8529

Example 7

This example illustrates the measurement of the response of 19 metal oxide semiconductor materials in 4 gas mixtures at 550 c using ac impedance techniques. The data set forth in the table below was obtained according to the ac impedance technique. The signal is the impedance of the material when exposed to the indicated gas mixture and the material contained 10000ppmO₂N of (A)₂The ratio of the impedance values in (a). The gas used was a gas containing 200ppm NO₂N of (A)₂Containing 200ppmNO₂And 10000ppmO₂N of (A)₂N containing 1000ppm of mCO₂And N₂。

TABLE 7

	MgAlO	1％Zn:MgAlO	ZnO	WO	NiFeO	SnO
	MgAlO	1％Zn:MgAlO	ZnO	WO	NiFeO	SnO	Containing NON of (A)	0.9894	0.9583	3.866	2.335	3.025	1.655
Containing NOO of (A) to (B)/N	0.8937	0.8984	5.272	2.006	3.553	3.390	Containing NON of (A)	0.9894	0.9583	3.866	2.335	3.025	1.655
Containing NOO of (A) to (B)/N	0.8937	0.8984	5.272	2.006	3.553	3.390	N containing CO	1.046	0.9697	0.0133	0.2034	0.2506	0.0069
N	1.067	1.060	0.7285	0.9526	1.208	0.2666	N containing CO	1.046	0.9697	0.0133	0.2034	0.2506	0.0069

	TiO	MnTiO	NiO	SrNbO	CeVO	1％Nb:TiO	FeTiO
	TiO	MnTiO	NiO	SrNbO	CeVO	1％Nb:TiO	FeTiO	Containing NON of (A)	1.135	1.010	0.9483	1.006	1.003	1.271	1.193
Containing NOO of (A) to (B)/N	1.314	0.014	0.5207	1.044	0.9975	1.302	1.073	Containing NON of (A)	1.135	1.010	0.9483	1.006	1.003	1.271	1.193
Containing NOO of (A) to (B)/N	1.314	0.014	0.5207	1.044	0.9975	1.302	1.073	N containing CO	0.0017	44.00	1.194	0.2814	1.104	0.0021	0.6743
N	0.7263	1.280	1.341	0.9830	1.024	0.477	1.054	N containing CO	0.0017	44.00	1.194	0.2814	1.104	0.0021	0.6743

	PrO	SrTiO	BaCuO	CuMnFeO	LaFeO	ZnVO
	PrO	SrTiO	BaCuO	CuMnFeO	LaFeO	ZnVO	Containing NON of (A)	1.223	0.9055	0.7071	1.148	1.302	1.199
Containing NOO of (A) to (B)/N	0.9656	0.9881	0.3812	0.9891	0.9429	1.086	Containing NON of (A)	1.223	0.9055	0.7071	1.148	1.302	1.199
Containing NOO of (A) to (B)/N	0.9656	0.9881	0.3812	0.9891	0.9429	1.086	N containing CO	62.76	0.0029	3.0892	2.557	123.3	0.4726
N	1.495	1.210	1.333	1.681	1.789	0.9034	N containing CO	62.76	0.0029	3.0892	2.557	123.3	0.4726

Example 8

This example illustrates the measurement of the response of 23 metal oxide semiconductor materials in 4 gas mixtures at 650 deg.C to 700 deg.C using AC impedance techniques. The data set forth in the table below was obtained according to the ac impedance technique. The signal is the impedance of the material when exposed to the indicated gas mixture and the material contained 10000ppmO₂N of (A)₂The ratio of the medium impedance values. The gas used was a gas containing 200ppm NO₂N of (A)₂Containing 200ppmNO₂And 10000ppmO₂N of (A)₂Containing 1000ppN of mCO₂And N₂。

TABLE 8

	MgAlO	1％Zn:MgAlO	ZnO	WO	NiFeO	SnO	TiO
	MgAlO	1％Zn:MgAlO	ZnO	WO	NiFeO	SnO	TiO	Containing NON of (A)	0.9450	1.022	0.4876	0.7151	0.5807	0.5419	0.5617
Containing NOO of (A) to (B)/N	0.6412	0.8310	1.235	1.281	1.105	0.8265	1.030	Containing NON of (A)	0.9450	1.022	0.4876	0.7151	0.5807	0.5419	0.5617
Containing NOO of (A) to (B)/N	0.6412	0.8310	1.235	1.281	1.105	0.8265	1.030	N containing CO	0.9074	0.9684	0.0348	0.2693	0.0408	0.0238	0.0015
N	1.056	1.100	0.2753	0.6332	0.4421	0.3521	0.3957	N containing CO	0.9074	0.9684	0.0348	0.2693	0.0408	0.0238	0.0015

	MnTiO	NiO	SrNbO	CeVO	1％Nb:TiO	FeTiO	PrO
	MnTiO	NiO	SrNbO	CeVO	1％Nb:TiO	FeTiO	PrO	Containing NON of (A)	1.445	1.379	0.8852	1.050	0.5711	0.9072	1.516
Containing NOO of (A) to (B)/N	0.9561	0.8127	0.9862	1.135	0.8263	0.9524	0.9814	Containing NON of (A)	1.445	1.379	0.8852	1.050	0.5711	0.9072	1.516
Containing NOO of (A) to (B)/N	0.9561	0.8127	0.9862	1.135	0.8263	0.9524	0.9814	N containing CO	113.3	1.782	0.0301	1.565	0.0035	0.4346	8005
N	1.877	1.409	0.8788	1.080	0.2802	0.8050	1.962	N containing CO	113.3	1.782	0.0301	1.565	0.0035	0.4346	8005

	SrTiO	BaCuO	CuMnFeO	LaFeO	ZnVO
	SrTiO	BaCuO	CuMnFeO	LaFeO	ZnVO	Containing NON of (A)	1.051	0.5615	3.401	1.331	0.8631
Containing NOO of (A) to (B)/N	0.9320	0.9703	1.001	1.013	0.9459	Containing NON of (A)	1.051	0.5615	3.401	1.331	0.8631
Containing NOO of (A) to (B)/N	0.9320	0.9703	1.001	1.013	0.9459	N containing CO	0.0020	381.3	2.198	43.11	0.4672
N	1.076	1.308	4.250	1.673	0.6574	N containing CO	0.0020	381.3	2.198	43.11	0.4672

	ZnO+2.5％F2889	ZnO+10％F3876	SnO+5％F2889	ZnO+10％F3876
	ZnO+2.5％F2889	ZnO+10％F3876	SnO+5％F2889	ZnO+10％F3876	Containing NON of (A)	0.5810	0.7944	0.6270	0.6055
Containing NOO of (A) to (B)/N	1.141	1.176	0.8927	1.284	Containing NON of (A)	0.5810	0.7944	0.6270	0.6055
Containing NOO of (A) to (B)/N	1.141	1.176	0.8927	1.284	N containing CO	0.0020	0.0016	0.0043	0.0122
N	0.1054	0.1338	0.2780	0.4862	N containing CO	0.0020	0.0016	0.0043	0.0122

Example 9

This example illustrates the measurement of the response of 16 metal oxide semiconductor materials in 4 gas mixtures at 800 c using ac impedance techniques. The data set forth in the table below was obtained according to the ac impedance technique. The signal is the impedance of the material when exposed to the indicated gas mixture and the material contained 10000ppmO₂N of (A)₂The ratio of the impedance values in (a). The gas used was a gas containing 200ppm NO₂N of (A)₂Containing 200ppm of O₂And 10000ppmO₂N of (A)₂N containing 1000ppm of mCO₂And N₂。

TABLE 9

	ZnO	WO	NiFeO	SnO	TiO	MnTiO	NiO	ArNbO
	ZnO	WO	NiFeO	SnO	TiO	MnTiO	NiO	ArNbO	Containing NON of (A)	0.3980	0.5737	0.6710	0.4050	0.4859	1.981	1.917	0.7555
Containing NOO of (A) to (B)/N	1.594	1.117	4.795	6.456	1.052	1.497	0.8529	0.9928	Containing NON of (A)	0.3980	0.5737	0.6710	0.4050	0.4859	1.981	1.917	0.7555
Containing NOO of (A) to (B)/N	1.594	1.117	4.795	6.456	1.052	1.497	0.8529	0.9928	N containing CO	0.688	0.2610	0.0642	0.2349	0.0014	123.2	5.129	0.0144
N	0.3070	0.5103	0.5339	0.2852	0.3093	2.882	2.124	0.5176	N containing CO	0.688	0.2610	0.0642	0.2349	0.0014	123.2	5.129	0.0144

	CeVO	1％Nb:TiO	FeTiO	PrO	SrTiO	BaCuO	CuMnFeO	LaFeO
	CeVO	1％Nb:TiO	FeTiO	PrO	SrTiO	BaCuO	CuMnFeO	LaFeO	Containing NON of (A)	1.013	0.3280	0.6799	1.569	0.0049	4.061	2.869	1.252
Containing NOO of (A) to (B)/N	1.058	1.006	0.9982	1.010	0.0260	0.9811	0.9389	1.326	Containing NON of (A)	1.013	0.3280	0.6799	1.569	0.0049	4.061	2.869	1.252
Containing NOO of (A) to (B)/N	1.058	1.006	0.9982	1.010	0.0260	0.9811	0.9389	1.326	N containing CO	2.165	0.0047	0.2831	3530	1.004	216.0	0.8810	63.36
N	1.075	0.1960	0.5600	2.999	1.048	7.445	3.413	1.612	N containing CO	2.165	0.0047	0.2831	3530	1.004	216.0	0.8810	63.36

Claims

1. An apparatus for analyzing at least one single gas component in a multi-component gas mixture, comprising:

(a) an array having first and second chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic when exposed to a gaseous analyte at a selected temperature than each other chemo/electro-active material, wherein the chemo/electro-active materials are selected from the group of pairs comprising:

(v) The first material is a first M¹ _aM² _bO_XAnd the second material is a second M¹ _aM² _bO_X(ii) a And

Wherein M is¹Selected from Ce, Cu, Fe, Ga, Nb, Ni, Pr, Sn, Ti, W, Zn, and Zr; m²And M³Each independently selected from: al, Ca, Cr, Cu, Fe, Ga, Mg, Mn, Nb, Ni, Sb, Sn, Sr, Ta, Ti, V, W, Zn and Zr, but in M¹ _aM² _bM³ _cO_XMiddle M²And M³Is different; a. b and c are each independently 0.0005 to 1; and X is a number sufficient to balance the oxygen present with the charge of the other elements in the compound;

(b) means for determining the electrical response of each chemo/electro-active material when the array is exposed to a gas mixture; and

(c) means for analyzing the gas analyte from the electrical response.

2. The apparatus of claim 1, wherein:

(a)M¹O_xselected from: ce_aO_x、CuO_x、FeO_x、NbO_x、NiO_x、PrO_x、SnO_x、TiO_x、TmO_x、WO_x、YbO_x、ZnO_x、ZrO_xAg-added SnO_xAnd Ag-added ZnO_xTiO with added Pt_xAnd ZnO added with glaze_xNiO with glaze added_XSnO with added glaze_xOr WO with glaze added_x；

(b)M¹ _aM² _bO_xSelected from: al (Al)_aCr_bO_X、Al_aFe_bO_x、Al_aMg_bO_x、Al_aNi_bO_X、Al_aTi_bO_X、Al_aV_bO_x、Ba_aCu_bO_x、Ba_aSn_bO_x、Ba_aZn_bO_x、Ce_aFe_bO_x、Ce_aNb_bO_x、Ce_aTi_bO_x、Ce_aV_bO_x、Cr_aMn_bO_x、Cr_aNi_bO_x、Cr_aTi_bO_x、Cr_aZn_bO_x、Cu_aFe_bO_x、Cu_aGa_bO_x、Cu_aNi_bO_x、Cu_aSn_bO_x、Cu_aSr_bO_x、Cu_aTi_bO_x、Cu_aZn_bO_x、Cu_aZr_bO_x、Fe_aGa_bO_x、Fe_aNb_bO_x、Fe_aNi_bO_x、Fe_aSn_bO_x、Fe_aTi_bO_x、Fe_aW_bO_x、Fe_aZn_bO_x、Fe_aZr_bO_x、Ga_aSn_bO_x、Mn_aNb_bO_x、Mn_aSn_bO_x、Mn_aTi_bO_x、Mn_aZn_bO_x、Nb_aNi_bO_x、Nb_aSr_bO_x、Nb_aTi_bO_x、Nb_aW_bO_x、Nb_aZr_bO_x、Ni_aSn_bO_x、Ni_aZn_bO_x、Ni_aZr_bO_x、Sb_aSn_bO_x、Sb_aZn_bO_x、Sn_aTa_bO_x、Sn_aTi_bO_x、Sn_aW_bO_x、Sn_aZn_bO_x、Sn_aZr_bO_x、Sr_aTi_bO_x、Ta_aTi_bO_x、Ta_aZn_bO_x、Ta_aZr_bO_x、Ti_aV_bO_x、Ti_aW_bO_x、Ti_aZn_bO_x、Ti_aZr_bO_x、W_aZn_bO_x、W_aZr_bO_x、Zn_aZr_bO_xGlaze-added Al_aNi_bO_xGlaze-added Cr_aTi_bO_xGlaze-added Fe_aNi_bO_xGlaze-added Fe_aTi_bO_xAnd Nb with glaze added_aTi_bO_xAnd Nb with glaze added_aW_bO_xAnd glaze-added Ni_aZn_bO_xAnd glaze-added Ni_aZr_bO_xOr Ta with glaze added_aTi_bO_x(ii) a And/or

(c)M¹ _aM² _bM³ _cO_xSelected from: al (Al)_aMg_bZn_cO_X、Ba_aCu_bTi_cO_x、Cr_aSr_bTi_cO_x、Cu_aFe_bMn_cO_x、Fe_aNb_bTi_cO_x、Fe_aSr_bTi_cO_x、Fe_aTa_bTi_cO_x、Fe_aW_bZr_cO_x、Ga_aTi_bZn_cO_x、Mn_aSr_bTi_cO_x、Nb_aSr_bTi_cO_x、Nb_aSr_bW_cO_x、Nb_aTi_bZn_cO_x、Ni_aSr_bTi_cO_x、Sn_aW_bZn_cO_x、Sr_aTi_bV_cO_x、Sr_aTi_bZn_cO_xOr Ti_aW_bZr_cO_x。

3. The apparatus of claim 1, wherein: the electrical response characteristic of at least one material is quantifiable to a value when exposed to the gas mixture at the selected temperature, and the response value of the material is constant or does not vary by more than 20% during exposure of the material to the gas mixture at the selected temperature for at least one minute.

4. The apparatus of claim 1, wherein: the electrical response is selected from resistance, impedance, capacitance, voltage or current.

5. The apparatus of claim 1, wherein: the array is placed in a gas mixture and the temperature of the gas mixture is 400 ℃ or higher.

6. The apparatus of claim 1, wherein: the temperature of the gas mixture is below 400 ℃.

7. The apparatus of claim 1, wherein: the constituent gases in the gas mixture are not separated.

8. The apparatus of claim 1, wherein: the electrical response of the chemo/electro-active material is determined when exposed to the multi-component gas mixture alone.

9. The apparatus of claim 1, wherein the gas mixture comprises one or more of the group consisting of: oxygen, carbon monoxide, nitrogen oxides, hydrocarbons, CO₂Hydrogen sulfide, sulfur dioxide, halogen gases, hydrogen, water vapor, ammonia, alcohol vapors, ethers, carbonyl compounds, and microorganisms.

10. The apparatus of claim 1, wherein the gas mixture comprises one or more of the group consisting of: oxygen, carbon monoxide, nitrogen oxides, hydrocarbons, CO₂Hydrogen sulfide, sulfur dioxide, halogen gases, hydrogen, water vapor, ammonia, alcohol vapors, ethers, ketones, aldehydes, and microorganisms.

11. The apparatus of claim 1, wherein the gas mixture comprises one or more of the group consisting of nitrogen oxides and ammonia.

12. The apparatus of claim 1, wherein the gas mixture comprises one or more of the group consisting of oxygen and hydrocarbons.

13. The apparatus of claim 1, wherein the gas mixture is an effluent of a combustion process, or is produced by a production process, a waste stream, environmental monitoring, or a medical, agricultural, food or beverage industry process.

14. The apparatus of claim 1, wherein the multi-component gas mixture is an effluent of a process or a chemical reaction product that is delivered to a device, and wherein the apparatus further comprises means for controlling the process or device using the electrical response.