WO2014168299A1 - Method for preparing β-eucryptite by mechanochemical activation and calcination, and β-eucryptite obtained thereby - Google Patents

Abstract

Disclosed are a method for preparing β-eucryptite by mechanochemical activation and calcination, and β-eucryptite obtained by the method. The method for preparing β-eucryptite by mechanochemical activation and calcination comprises the steps of: (A) preparing materials comprising pyrophyllite (Al₂O₃·4SiO₂·H₂O), gibbsite (Al₂O₃·3H₂O) and lithium carbonate (Li₂CO₃); (B) planetary milling the prepared materials and mixing the same; and (C) calcining the mixed materials. At this time, the materials can be amorphized. In addition, the planetary milling can be carried out for 90-120 minutes and the calcination can be carried out at 900-1,000℃ for 60-90 minutes.

Description

Method for producing beta-eucryptite by mechanochemical activation and calcination, and beta-eucryptite obtained by the method

The present invention relates to a method for producing beta (β) -eucryptite by mechanochemical activation and calcination, and to beta-eucryptite obtained by the method. It relates to a method for producing beta-eucryptite by activating the mixture mechanically and then calcining, and to beta-eucryptite by the method.

Since LAS-based ceramics as lithium aluminum silicate materials exhibit very low or even negative thermal expansion properties and chemically very stable properties, much research has been conducted on their preparation.

The LAS-based glass ceramic is used as a heat resistant material in a furnace, and is also used as a heat exchanger material of a gas turbine in which stability and thermal shock resistance are essential. Other applications include tableware, electronics, glass (glass) materials for telescope reflection mirror processing, ring laser gyroscopes, and other optically stable platforms.

The spokes dyumin _{(Li 2 O · Al 2 O} 3 · 4SiO 2) - -eucryptite _{(Li 2 O · Al 2 O} 3 · 2SiO 2) and a beta-beta (β) apparently important decision in the LAS-based glass ceramic Can be mentioned. In this case, the beta-eucryptite may be transparent or translucent, and exist in various colors including colorless.

Conventionally, these LAS type glass ceramics have obtained by recrystallizing the glass which carried out the solid state melting. However, according to the conventional method, during sintering, auxiliary materials such as TiO ₂ , F, ZrO ₂ , and P ₂ O ₅ had to be used. However, when using such a sintering auxiliary material, the problem that the thermal expansion coefficient becomes large has arisen.

Another problem required high temperatures of 1200 ° C to 1400 ° C when sintering the molten glass. Therefore, in order to lower the sintering temperature, it was necessary to add oxides such as ZnO, CaO, Na ₂ O, and K ₂ O. When these oxides are added, unwanted crystal phases are produced and thus have an undesirable effect on the coefficient of thermal expansion.

Furthermore, in order to suppress the formation of these undesired crystal phases, a more complicated manufacturing process had to be applied, and therefore it is very important to manufacture LAS-based glass ceramic powders of economically uniform composition.

The prior art related to the present invention is Republic of Korea Patent Publication No. 2002-0003502 (published on Jan. 12, 2002).

Therefore, the present invention is an economical and simple method, by using a lipite (Al ₂ O ₃ · 4 SiO ₂ · H ₂ O), gibbsite (Al ₂ O ₃ · 3H ₂ O), and lithium carbonate (Li ₂ CO ₃ ) It is an object of the present invention to provide a method for producing beta-eucryptite by mechanical chemical activation and calcination, and a beta-eucryptite obtained by this method.

The problem to be solved by the present invention is not limited to the problem (s) mentioned above, and other object (s) not mentioned are obvious to those skilled in the art from the following description. Can be understood.

In order to solve the above problems, according to a preferred embodiment of the present invention, the method for producing beta-eukryptite by mechanochemical activation and calcination, (A) feldspar (Al ₂ O ₃ · 4 SiO ₂ · H ₂ O) Preparing a powder of each of Gibbsite (Al ₂ O ₃ · 3H ₂ O), and lithium carbonate (Li ₂ CO ₃ ); (B) pulverizing and mixing the prepared material; And (C) calcining the mixed material.

Here, the step (B) is preferably carried out through the planetary ball mill apparatus.

In the step (B), the materials can be amorphous. In addition, the step (B) may be performed for 90 minutes to 120 minutes.

The step (C) may be performed at 900 ° C. to 1000 ° C., preferably 60 minutes to 90 minutes.

Specific details of other embodiments are included in the detailed description and the accompanying drawings.

Advantages and / or features of the present invention and methods for achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the invention is defined only by the scope of the claims.

Throughout the specification, the same reference numerals refer to the same components, it should be understood that the size, position, coupling relationship, etc. of each component constituting the invention may be exaggerated for clarity of the specification.

According to the manufacturing method of beta-eucryptite by the mechanochemical activation and calcining according to the preferred embodiment of the present invention as described above, beta eukrite can be produced by an economical and simple method.

1 is a flow chart briefly illustrating a method for preparing beta-eucryptite by mechanochemically active and then calcining a mixture of leadstone, gibbsite, and lithium carbonate powder, according to a preferred embodiment of the present invention.

2 is a graph showing the XRD pattern of a mixture ground with a planetary ball mill under various time conditions, according to a preferred embodiment of the present invention.

3 is a graph showing the thermal analysis (TG-DTA) curve of a mixture ground with a planetary ball mill under various time conditions, according to a preferred embodiment of the present invention.

4 is a graph showing the XRD pattern of the calcined mixture under various temperature conditions, in accordance with a preferred embodiment of the present invention.

FIG. 5 is a graph showing the FT-IR spectra of the mixture which calcined the mixture which was not pulverized and the mixture ground by a planetary ball mill for 120 minutes in accordance with a preferred embodiment of the present invention at 950 ° C., respectively.

6 is a graph showing the coefficient of thermal expansion when the mixed specimen pulverized with a planetary ball mill according to a preferred embodiment of the present invention at 950 ℃.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention;

1 is a flow chart briefly illustrating a method for preparing beta-eucryptite by mechanochemically active and then calcining a mixture of leadstone, gibbsite, and lithium carbonate powder, according to a preferred embodiment of the present invention.

According to Figure 1, according to a preferred embodiment of the present invention, the method for producing beta-eucryptite by mechanical and chemical activation and calcination, the material preparation step (S100), the step of grinding the prepared material with a planetary ball mill (S120) ), And calcining the material pulverized with the planetary ball mill (S140), and may further include analyzing the generated beta-eucryptite (S160).

Material preparation

The material preparation step S100 is a step of preparing a material for use in a preferred embodiment of the present invention.

In this material preparation step (S100), each powder of leadstone (Al ₂ O ₃ · 4 SiO ₂ · H ₂ O), gibbsite (Al ₂ O ₃ · 3H ₂ O), and lithium carbonate (Li ₂ CO ₃ ) is removed. Prepare.

Herein, the amounts of the feldspar, gibbsite, and lithium carbonate are prepared so that the molar ratio of Li: Al: Si is 1: 1: 1 when they are mixed.

At this time, it is preferable that the three powder materials are accurately weighed and prepared to have a Li: Al: Si molar ratio of 1: 1: 1. The molar ratio is in consideration of the fact that the molar ratio of Li: Al: Si of eu cryptite is 1: 1: 1.

The feldspar was prepared by lumping ore collected from an aging mine in Korea, and then pulverizing the feldspar in a stainless steel stamp mill and filtering it through a 200 mesh (75 μm) sieve. As a result of preliminary XRD analysis, it was found that quartz is the main impurity in the pavement. Gibbsite is Korea's KC Co. Ltd. Prepared as a product, the gibbsite is characterized in that 95% less than 50 ㎛. Finally, lithium carbonate is reagent grade and is manufactured by Junsei Chemical Co. of Japan. Ltd. Prepared as a product.

Specific compositions will be described in the description of preferred embodiments of the present invention described below.

Planetary ball mill grinding

The planetary ball mill grinding step S120 is a step of mixing and grinding these prepared materials.

The planetary grinder used in this planetary ball mill grinding step (S120) is a Palverisette-7 model of Fritsch, Germany, and milled the prepared materials at about 650 rpm under atmospheric conditions. At this time, the amount of the mixed material was 5 g.

In order to find the optimum conditions according to the invention, grinding was carried out at different time conditions for 15 to 120 minutes. However, if the grinding time becomes longer, excessive temperature rise in the grinder may be caused. Thus, the grinding period is set for 15 minutes, and then a rest period of 10 minutes is set.

calcination

The calcining step (S140) is a step of calcining each mixture of the planetary ball mill milled. As in the oily grinding step (S120), each of the mixtures was calcined under atmospheric conditions at 750, 850, and 950 ° C. for 60 to 90 minutes to find the optimum calcination conditions of the present invention. The temperature rising condition at this time was 10 degreeC / min.

As a result of calcination, it was found that the calcination temperature is preferably between 900 ° C and 1000 ° C. If the calcining temperature is less than 900 ° C., there is a possibility that cristobalite and / or quartz, which will be described later, may remain, and if calcining temperature exceeds 1000 ° C., there is a high possibility of causing waste of time and energy.

In addition, a suitable time for calcination is also related to the pulverization time and calcination temperature, but if the calcination time is less than 60 minutes, impurities such as cristobalite and / or quartz may remain. In the case of a mixture, when calcining for at least one hour or more, a nearly constant eu kryptite crystal phase can be obtained, a suitable time for calcination may be one hour or more. However, considering the remaining impurities or waste of energy, the time required for calcination is preferably between 60 minutes and 90 minutes.

analysis

The analyzing step S160 is a step of performing various analyzes as follows.

Specifically, X-ray diffraction analysis (RINT-2000, manufactured by Rigaku, Japan) was performed on the crystal phase in each of the mixtures calcined and calcined above the planetary ball mill.

In addition, thermal analysis was performed using a TG-DTA analyzer (DTG-60H, Shimazu, Japan) to investigate the thermal decomposition characteristics of the planetary ball mill pulverized mixed powder.

Infrared spectroscopy (Nicolet iS10 from Thermo Scientific, USA) was also used to obtain an infrared spectrum of the calcined powder.

In order to measure the thermal expansion coefficient and the coefficient of thermal expansion of the calcined powder, the specimen was formed at a height of 5 mm and a diameter of 10 mm, and then the temperature was increased at a rate of 3 ° C./min under atmospheric conditions. Q20).

Example

Hereinafter, a beta-eucryptite production method according to the present invention and a beta-eucryptite by the method through a preferred embodiment of the present invention will be described. However, it should be noted that the present invention is presented as a preferred example of the present invention, and the present invention is not limited thereto by any means.

Contents not described herein may be sufficiently technically inferred by those of ordinary skill in the art, and thus descriptions thereof will be omitted.

1. Preparation of materials

Materials according to preferred embodiments of the present invention can be prepared according to the following Table 1. Table 1 prepares a molar ratio of Li: Al: Si so that the ratio of 1: 1: 1 may be obtained by mixing the chemical compositions of the materials in consideration of the chemical compositions of the materials.

Table 1

2. Planetary Ball Mill Grinding

As described above, in a preferred embodiment of the present invention, in order to find the optimum grinding conditions, each powder is put into the planetary ball mill apparatus, under different conditions of 15 minutes to 120 minutes, including a 10 minute rest period. Pulverized.

3. Calcination

As described above, in the preferred embodiment of the present invention, in order to find the optimum calcination condition, the pulverized mixture was calcined at 750, 850, and 950 ° C, respectively, while maintaining a temperature raising condition of 10 ° C / min. .

4. Grinding and Physical Property Test of Calcined Powder

For the powders subjected to the grinding and calcining step, as mentioned in the analysis step (S160), X-ray diffraction analysis, thermal analysis, infrared spectrum, thermal expansion coefficient and the like were evaluated.

2 is a graph showing the XRD pattern of a mixture ground with a planetary ball mill under various time conditions, according to a preferred embodiment of the present invention.

2, from bottom to top, (a) is not ground, (b) is 15 minutes, (c) is 30 minutes, (d) is 60 minutes, (e) is 90 minutes, and (f ) Represents the XRD pattern of the mixture ground for 120 minutes. In addition, P represents a feldspar, Q represents quartz, G represents gibbsite, and L represents lithium carbonate.

According to Figure 2, the peak value of the prepared material can be seen that the peak intensity gradually decreases as the grinding proceeds. In particular, except for quartz, it can be seen that amorphousness of other materials is more accelerated as grinding progresses.

Referring to the case of (e) of Figure 2, when the grinding is in progress for 90 minutes, the peak value of the mixture is very weak, in this case, it can be said that the lattice structure of the mixture is formed mostly irregular. That is, it should be understood that the amorphous phase during the planetary ball mill grinding is most preferable when the grinding is performed for about 90 minutes.

3 is a graph showing the TG-DTA curve of a mixture ground under various time conditions, according to a preferred embodiment of the present invention.

In Figure 3, going from top to bottom, (a) is not ground, (b) is 15 minutes, (c) is 30 minutes, (d) is 60 minutes, (e) is 90 minutes, and (f ) Shows the TG-DTA curve of the mixture ground for 120 minutes. Here, the solid line represents the endothermic and exothermic curve (DTA) due to the pyrolysis of the material, and the dotted line represents the thermal weight loss curve (TG), respectively.

It can be seen from FIG. 3 that the mixture in the non-pulverized state exhibits an endothermic peak at about 290 ° C, 600 ° C, and 700 ° C. At this time, each of the endothermic peaks corresponds to the dehydration temperature of Gibbsite (290 ° C), the dehydration temperature of leadstone (600 ° C), and the decomposition of lithium carbonate (700 ° C), respectively.

In addition, it can be seen that the endothermic peak at about 290 ° C. slightly shifted to the low temperature side when pulverized for 60 minutes. Continued grinding leads to a more extensive endothermic reaction at 200 ° C. or lower due to the deformation of the crystal structure associated with the water molecules in the gibbsite structure.

The endothermic peak at 600 ° C corresponds to the change in the formation of feldspar by decomposition of water molecules in the feldspar, that is, the formation of hydroxy feldspar, and it can be seen that the migrating to the low temperature side as the grinding proceeds. It is presumed that structural deformation of the material occurred as in the case of the site.

The exothermic peak at about 620 ° C. corresponding to the crystallization of beta-eucryptite increased in the curve for the mixture which had been pulverized for 90 minutes, and moved to about 670 ° C. when the oil was ground for 120 minutes. Can be.

In the case of the endothermic peak followed by the thermal weight loss curve, it can be seen that the weight loss gradually increases as the oil grinding is progressed. At this time, it can be seen that the weight loss is remarkably remarkable as the hydroxy group in the pavement is absorbed, which absorbs a considerable amount of water molecules from the atmosphere during grinding. It is assumed that this is due to a wide endothermic reaction at 500 ° C or lower.

4 is a graph showing the XRD pattern of the calcined mixture under various temperature conditions, in accordance with a preferred embodiment of the present invention.

4, from bottom to top, (a) is not ground, (b) is 15 minutes, (c) is 30 minutes, (d) is 60 minutes, (e) is 90 minutes, and (f ) Shows the XRD pattern which calcined the mixture ground for 120 minutes under various temperature conditions. Here, E represents beta-eucryptite, Q represents quartz, and C represents cristobalite, respectively.

From FIG. 4, from the results at 750 ° C. on the left, lithium silicate (Li ₂ SiO ₃ ), lithium aluminum silicate (Li ₂ Al ₂ Si ₃ O ₁₀ and Li (AlSi ₂ O ₆ )), and quartz were produced in the initial mixture. It can be seen that the main crystal phase. In addition, it can be seen that the peak gradually disappears as the grinding progresses, and the peak of beta-eucryptite increases.

The beta-eucryptite phase is formed as the main phase in the milled mixture. However, even when the planetary ball mill grinding is performed for 120 minutes, it can be seen that afterimages of other small bonding phases such as cristobalite and quartz still remain.

As shown in Figure 4, it can be seen that the beta-eucryptite was formed from the XRD pattern of the mixture heat-treated at different temperatures of 850 ℃ and 950 ℃. In this case, unlike the case at 750 ℃, it can be seen that the beta-eukrypite phase is significantly increased when the heat treatment temperature is raised to 850 ℃ ~ 950 ℃.

That is, most of the cristobalite and quartz remaining in the powder mixture at 750 ℃ and 850 ℃ disappeared almost, and it can be seen that the beta-eucryptite is formed in the mixture when pulverized at 950 ℃ for 120 minutes.

In order to investigate the structural deformations that occurred with the formation of the beta-eucryptite phase, the FT-IR spectra of the oil-free pulverized mixture and the oil-pulverized mixture calcined at 950 ° C. for 120 minutes were measured, and the result is the graph of FIG. 5. Shown in

In FIG. 5, (a) shows the FT-IR spectrum of the mixture that has not been oil milled and (b) has been oil milled for 120 minutes and calcined at 950 ° C.

5, the absorption band at a wave number near 1000 cm ⁻¹ may mean that Al and Si are substituted in a tetrahedral lattice of SiO ₄ . In addition, the absorption band around 758 cm ⁻¹ shown in the oil-pulverized mixture for 120 minutes showed vibrations peculiar to the covalent bonding of Al-O in the tetrahedral lattice of AlO _{4 in} the beta-eucryptite. Absorption bands near 669 and 654 cm ⁻¹ also exhibit beta-eucryptite specific absorption bands.

Here, it should be noted that this FT-IR analysis is an analysis that confirms the formation of eu cryptite in the same manner as the XRD result described above.

Next, Figure 6 is a graph showing the coefficient of thermal expansion when the pulverized mixed specimens are calcined at 950 ℃ according to a preferred embodiment of the present invention.

In Figure 6, going from the top to the bottom, (a) for 15 minutes, (b) for 30 minutes, (c) for 60 minutes, (d) for 90 minutes, (e) for 120 minutes pulverized mixed specimen 950 The thermal expansion rate of the mixture calcined at 占 폚 is shown. Here, ΔL / L ₀ may be represented as (L − L ₀ ) / L ₀ , where L is the length of the mixture specimen at a specific temperature and L ₀ represents the initial length of the specimen at room temperature.

The measurement result of FIG. 6 was put together in Table 2 which shows the average value of Thermal Expansion Coefficient (TEC) in different temperature range.

TABLE 2

6 and Table 2 show that the mixed specimen pulverized for 15 minutes showed a negative thermal expansion rate at room temperature, but a positive thermal expansion rate as the temperature rose to 150 ° C.

In addition, in the case of a mixture specimen pulverized for 30 minutes, the coefficient of thermal expansion shows a complicated aspect. Specifically, when the temperature is changed from room temperature to 800 ° C., there is shown a decrease in the coefficient of thermal expansion over several steps.

In addition, the coefficient of thermal expansion of the mixture specimen pulverized for 60 minutes is different from the above-described aspect. The thermal expansion curve at this time shows a mode in which the thermal expansion rate gradually decreases as the temperature increases from 400 ° C to 800 ° C.

On the other hand, similar thermal expansion curves can be obtained for the mixture specimens pulverized for 90 minutes and 120 minutes, respectively, with two steps of reduction in thermal expansion rates over the temperature range from room temperature to 120 ° C and 300 ° C to 500 ° C. Indicates.

Although the present invention has been described by the embodiments and drawings as described above, the present invention is not limited to the above-described embodiments, which are those skilled in the art to which the present invention pertains. You will know well that this is possible. Therefore, the spirit of the present invention should not be limited to the embodiments included in the above description, but should be understood only by the claims which follow, and all modifications equivalent to or equivalent to the claims are within the scope of the spirit of the present invention. Will belong to.

According to the manufacturing method of beta-eucryptite by the mechanochemical activation and calcining according to the preferred embodiment of the present invention as described above, beta eukrite can be produced by an economical and simple method.

Claims (7)

(A) preparing each powder of paurite (Al ₂ O ₃ · 4SiO ₂ · H ₂ O), gibbsite (Al ₂ O ₃ · 3H ₂ O), and lithium carbonate (Li ₂ CO ₃ ) as a material; (B) pulverizing and mixing the prepared material by planetary ball mill; And (C) calcining the mixed material; Process for the preparation of beta-eucryptite by mechanochemical activation and calcination. The method of claim 1, Step (B) is characterized in that is carried out through the planetary ball mill device, Process for the preparation of beta-eucryptite by mechanochemical activation and calcination. The method of claim 1, In the step (B), characterized in that the materials are amorphous Process for the preparation of beta-eucryptite by mechanochemical activation and calcination. The method of claim 1, Step (B), characterized in that performed for 90 minutes to 120 minutes, Process for the preparation of beta-eucryptite by mechanochemical activation and calcination. The method of claim 1, Step (C) is characterized in that it is carried out at 900 ℃ ~ 1000 ℃, Process for the preparation of beta-eucryptite by mechanochemical activation and calcination. The method of claim 5, Step (C) is characterized in that it is carried out 60 to 90 minutes, Process for the preparation of beta-eucryptite by mechanochemical activation and calcination. Claim 1 to 6, characterized in that obtained from a powder material having a molar ratio of Li: Al: Si = 1: 1: 1, Beta-eucryptite obtained by mechanochemical activation and calcination.

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