CN1412150A - Self-lubricating ceramic composite material and its preparation process - Google Patents

Abstract

The invention discloses a self-lubricating ceramic composite material and a preparation process. The ceramic composite material prepared by the invention is composed of yttrium oxide, zirconium oxide and molybdenum disulfide. The process is to add MoS ₂ powder to the alcohol-water solution of yttrium nitrate and ZrOCl ₂ 8H ₂ O and heat it, and then prepare the yttria-stabilized tetragonal zirconia-coated molybdenum disulfide through filtration, washing, calcination and other processes. composite powder. A composite material of yttria-stabilized tetragonal zirconia and molybdenum disulfide was prepared by hot-pressing sintering process. The yttria-stabilized tetragonal zirconia and molybdenum disulfide composite powder prepared by the invention has the advantages of less agglomeration, high sintering activity, and good uniformity. Molybdenum ceramic materials have a small coefficient of friction and wear.

Description

Self-lubricating ceramic composite material and its preparation process

technical field

The invention relates to a ceramic composite material and a preparation process, in particular to a self-lubricating ceramic composite material and a preparation process.

Background technique

Due to its high melting point, high hardness, wear resistance, and stable chemical properties, precision ceramics are used as wear-resistant materials in non-lubricating media in the fields of petroleum, chemical industry, automobiles, and machinery industries, such as bearings, balls, linings, etc. , Piston rings, sealing rings, etc., so the tribological properties of ceramic materials are an important aspect to be considered. In the research, it was found that although ceramic materials have high hardness and shear strength, when paired with ceramic parts, their friction coefficient is generally 0.7 to 0.9, and severe wear and failure occur. In practical engineering applications restricted. Therefore, improving the tribological properties of ceramic materials is one of the key prerequisites for their successful application. One way to improve the tribological properties of ceramic friction pairs is to make the sliding surface of the material have self-lubricating properties, that is, to reduce the friction coefficient and wear coefficient to the required range under dry friction conditions. Another significance of realizing self-lubrication of materials is that: eliminating the lubrication system can reduce weight and volume, improve equipment reliability and prolong life (no need to consider the supplement of lubricant). Yttrium oxide (Y ₂ O ₃ ) stabilized tetragonal zirconia (ZrO ₂ ) ceramics (Y-TZP) are widely used in engineering because of their high strength and fracture toughness. Molybdenum disulfide is a compound with a metal layer structure, that is, a layer of Mo atoms is sandwiched between two layers of S atoms to form a sandwich structure. The S atomic layers of the other plate are adjacent to each other, and they are combined by weak van der Waals force. Six S atoms are arranged around Mo atoms in the layered structure, and they are bonded by strong covalent bonds. Due to the unique layered structure of molybdenum disulfide (MoS ₂ ), it has excellent self-lubrication. Therefore, molybdenum disulfide and zirconia can be combined to obtain self-lubricating composite materials with complementary properties.

The mechanical properties and tribological properties of materials are closely related to their microstructure and process; at the same time, when the composition of the material is constant, the process has a decisive effect on the microstructure of the material. However, the existing process for preparing self-lubricating ceramic composite materials is to directly mix ceramic powder and lubricating phase powder, and then prepare bulk materials through certain molding and sintering processes. It is difficult to ensure the uniform dispersion of ceramic powder and lubricating phase powder in the above process, which determines the inhomogeneity of the microstructure of the prepared self-lubricating ceramic material. Therefore, it is difficult to ensure the unity of lubricity and mechanical properties of the ceramic composite prepared by this process. Therefore, the synthesis of ceramic composite powders with uniform dispersion, less agglomeration and high activity is one of the key technologies for preparing high-performance self-lubricating ceramic composite materials, so as to ensure the preparation of ceramic composite materials with uniform microstructure and excellent macroscopic properties.

Contents of the invention

The object of the present invention is to provide a self-lubricating composite ceramic material and its preparation process. The prepared composite ceramic material has excellent mechanical properties and tribological properties.

A self-lubricating ceramic composite material is characterized in that the material consists of 2-8 parts by weight of yttrium oxide, 100 parts of zirconium oxide and 50-100 parts of molybdenum disulfide.

Because yttrium oxide (Y ₂ O ₃ ) stabilized tetragonal zirconia (ZrO ₂ ) ceramics (Y-TZP) have high strength and fracture toughness, and molybdenum disulfide (MoS ₂ ) materials have excellent self-lubrication, therefore, Through special process means, the composite powder of Y-TZP wrapped _MoS2 is prepared, and the composite ceramic material with special microstructure is prepared by high temperature hot pressing and sintering. The microstructural characteristics of the material are: Y-TZP is a continuous phase, and MoS ₂ self-lubricating phase is uniformly dispersed in Y-TZP. This microstructure can organically combine the high strength and fracture toughness of Y-TZP and the excellent self-lubricating properties of MoS ₂ , so the composite material has excellent mechanical properties and tribological properties. At the same time, MoS ₂ is wrapped by Y-TZP, which is beneficial to prevent the high-temperature oxidation of MoS ₂ , thereby increasing the use temperature of this composite material.

The alcohol-water solution heating method is a method for preparing ZrO ₂ powder with less agglomeration and high activity. The basic principle is: when ZrOCl ₂ 8H ₂ O is heated in alcohol-water solution, the dielectric constant of the solution drops rapidly, As a result, the solvation energy of the solution decreases, the solvency of the solvent decreases, and the solution reaches a saturated state, resulting in precipitation. Using this principle, _ZrO2 powder with good sintering performance can be prepared. And the present invention utilizes the above-mentioned principle, adds MoS ₂ powder in the alcohol-water solution of yttrium nitrate and ZrOCl ₂ 8H ₂ O, and heats, makes the Zr(OH) ₄ that ZrOCl ₂ 8H ₂ O forms on the surface of MoS ₂ particles Heterogeneous nucleation; when the pH value of the solution is adjusted to greater than 9, yttrium nitrate turns into Y(OH) ₃ and precipitates out of the solution, finally forming Y(OH) ₃ and Zr(OH) ₄ wrapped MoS ₂ powder particles , and then calcined under the protection of nitrogen to decompose Y(OH) ₃ and Zr(OH) ₄ and form Y-TZP. Through the above process, Y-TZP wrapped MoS ₂ powder particles with good sintering performance can be prepared. Sintering at a certain temperature and pressure, the yttria-stabilized tetragonal zirconia and molybdenum disulfide composite material with excellent tribological and mechanical properties is finally obtained.

The raw materials used in the present invention are industrial raw materials, yttrium nitrate, ZrOCl ₂ ·8H ₂ O, the purity of MoS ₂ is greater than 99%, wherein the particle size of MoS ₂ is 1-5 μm, the water content of ethanol is less than 1%, and the water is distilled water. The raw material composition of the yttria-stabilized tetragonal phase zirconia and molybdenum disulfide composite material is: 6-15 parts of yttrium nitrate, 100 parts of ZrOCl ₂ ·8H ₂ O, and 50-100 parts of MoS ₂ .

The preparation method of the yttrium oxide stabilized tetragonal phase zirconia and molybdenum disulfide composite material is carried out according to the following sequential steps:

(1) Add 6-15 parts of yttrium nitrate and 100 parts of ZrOCl ₂ ·8H ₂ O into the mixed solution of ethanol and water, and add 50-100 parts of MoS ₂ powder particles into the above solution under stirring conditions , until MoS ₂ is uniformly dispersed in the solution;

(2) Under stirring conditions, heat the mixed solution to 70-80°C, keep it warm for 4-8 hours, cool to room temperature, and adjust the pH value of the solution to be greater than 9;

(3) filtering the mixed solution, and washing, drying and calcining the filtered product;

(4) The prepared powder is molded with a pressure of 100-200 MPa, and the formed green body is put into a hot-press furnace for sintering.

In the preparation method of the present invention, the purity of yttrium nitrate, ZrOCl ₂ ·8H ₂ O and MoS ₂ is greater than 99%, wherein the particle size of MoS ₂ is 1-5 μm.

In the mixed solution of ethanol and water in the preparation method of the present invention, the volume concentration of ethanol is 20-95%.

In the preparation method of the present invention, the concentration of ZrOCl ₂ ·8H ₂ O in the mixed solution of ethanol and water is 0.1-0.5 mol/liter.

In the preparation method of the present invention, the dry product is calcined under the protection of nitrogen at a temperature of 700-900° C. and kept for 1-5 hours.

In the preparation method of the present invention, the sintering temperature of the composite material is 1200-1400° C., the pressure is 20-40 MPa, and the holding time is 0.5-2 hours.

The performance parameters of the yttria-stabilized tetragonal zirconia and molybdenum disulfide composite material prepared in Example 1: relative theoretical density 90-99% hardness 2～5GPa Coefficient of friction (the friction pair is zirconia) not greater than 0.25 Wear coefficient (friction pair is zirconia) Less than 1×10 ^-6 mm ³ /Nm

The yttria-stabilized tetragonal zirconia and molybdenum disulfide composite material prepared by the present invention has the following characteristics:

(1) The prepared yttria-stabilized tetragonal zirconia-coated molybdenum disulfide powder particles have the characteristics of less agglomeration, high sintering activity, and good uniformity;

(2) The particles of molybdenum disulfide are wrapped with yttria-stabilized tetragonal zirconia, which is beneficial to prevent the oxidation of molybdenum disulfide at high temperature, thereby increasing the high-temperature oxidation temperature of molybdenum disulfide;

(3) The surface of the particles of molybdenum disulfide is coated with yttria-stabilized tetragonal zirconia, and the yttria-stabilized tetragonal zirconia forms a continuous phase through high-temperature sintering, and the final prepared ceramic material has good mechanical properties;

(4) The self-lubricating phase of molybdenum disulfide exists in the composite material, which makes it have a small friction coefficient and wear coefficient, which can meet the requirements of solid lubricating materials.

Description of drawings

Figure 1 is the X-ray diffraction pattern of the calcined powder in Example 1 under the protection of nitrogen. From the X-ray diffraction pattern of the powder, it can be seen that the composite powder prepared by the present invention only contains two phases of tetragonal zirconia (t-ZrO ₂ ) and MoS ₂ .

Fig. 2 is a scanning electron micrograph of a section of the yttria-stabilized tetragonal zirconia and molybdenum disulfide composite material in Example 1. From the cross-sectional scanning electron microscope photos of the composite material, it can be observed that the yttria-stabilized tetragonal zirconia is a continuous phase, wrapped around the flake-shaped molybdenum disulfide particles, and the molybdenum disulfide is oriented due to pressure, and its slip surface perpendicular to the direction of pressure.

Detailed ways

Example 1

2 grams of yttrium nitrate and 26 grams of ZrOCl ₂ ·8H ₂ O are added to the mixed solution of ethanol and water with a volume ratio of 10-6:1, the solution concentration of ZrOCl ₂ ·8H ₂ O is 0.1-0.3 mol/liter, Stir well. Under stirring conditions, 11.82 g of MoS ₂ powder particles were added into the above solution until MoS ₂ was uniformly dispersed in the solution. Under the condition of stirring, the mixed solution is heated to 70-80° C., kept for 2-4 hours, cooled naturally to room temperature, and the pH value of the solution is adjusted to be greater than 9. The mixture was filtered, washed and dried. The dried product is calcined under the protection of nitrogen at a temperature of 700-900° C., kept for 1-4 hours, and cooled naturally. The prepared powder is molded with a pressure of 200 MPa, and put into a hot-press furnace for sintering. The sintering temperature is 1200-1300°C, and the holding time is 1 hour.

Example 2

3 grams of yttrium nitrate and 52 grams of ZrOCl ₂ 8H ₂ O are added to the mixed solution of ethanol and water, and under stirring conditions, 20 grams of MoS ₂ powder particles are mixed in the solution, prepared according to the process of Example 1 Yttria stabilized tetragonal zirconia and molybdenum disulfide composites.

Claims (8)

1. A self-lubricating ceramic composite material, characterized in that the parts by weight of the material are composed of 2 to 8 parts of yttrium oxide, 100 parts of zirconia, and 50 to 100 parts of molybdenum disulfide. 2. A self-lubricating ceramic composite material, characterized in that the microstructure of the material: the yttria-stabilized tetragonal zirconia is the continuous phase, and the molybdenum disulfide self-lubricating phase is dispersed in the yttria-stabilized tetragonal zirconia. 3. the preparation technology of material as claimed in claim 1, this technology is carried out in the following sequential steps: (1) Add 6-15 parts of yttrium nitrate and 100 parts of ZrOCl ₂ ·8H ₂ O into the mixed solution of ethanol and water, and add 50-100 parts of MoS ₂ powder particles into the above solution under stirring conditions within until the MoS ₂ is uniformly dispersed in the solution; (2) Under stirring conditions, heat the mixed solution to 70-80°C, keep it warm for 4-8 hours, cool to room temperature, and adjust the pH value of the solution to be greater than 9; (3) filtering the mixed solution, and washing, drying and calcining the filtered product; (4) The prepared powder is molded with a pressure of 100-200 MPa, and the formed green body is put into a hot-press furnace for sintering. 4. The preparation process according to claim 3, characterized in that the purity of yttrium nitrate, ZrOCl ₂ ·8H ₂ O, and MoS ₂ is greater than 99%, and the particle size of MoS ₂ is 1-5 μm. 5. The preparation process according to claim 3, characterized in that in the mixed solution of ethanol and water, the volume concentration of ethanol is 20-95%. 6. The preparation process according to claim 3, characterized in that the concentration of ZrOCl ₂ ·8H ₂ O in the mixture of ethanol and water is 0.1-0.5 mol/liter. 7. The preparation process according to claim 3, characterized in that the dried product is calcined under the protection of nitrogen at a temperature of 700-900° C. and kept for 1-5 hours. 8. The preparation process according to claim 3, characterized in that the sintering temperature of the composite material is 1200-1400° C., the pressure is 20-40 MPa, and the holding time is 0.5-2 hours.

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