阅读说明：本技术 一种B4C/h-BN高温复相陶瓷及其制备方法 (B4C/h-BN high-temperature complex-phase ceramic and preparation method thereof ) 是由 温广武 孙志远 王桢 于 2020-12-29 设计创作，主要内容包括：本发明涉及一种B4C/h-BN高温复相陶瓷及其制备方法,属于高温结构功能一体化陶瓷的技术领域,可适用于火箭燃烧室的内衬、高温热电偶保护套、高频高压焊接工具的高温绝缘部件、宇宙飞船的热屏蔽材料以及制造熔炼半导体的坩埚及冶金用高温容器等高温环境中。本发明提供的制备方法简单,制备环境要求较低,原料成本较低,可实现大规模产业化生产。本专利制备的h-BN复相陶瓷性能优于传统工艺制备的h-BN陶瓷,能够达到高新技术领域的严格要求,具有更为广泛的用途。(The invention relates to B4C/h-BN high-temperature complex-phase ceramic and a preparation method thereof, belonging to the technical field of high-temperature structural function integrated ceramic, and being applicable to high-temperature environments such as an inner liner of a rocket combustion chamber, a high-temperature thermocouple protective sleeve, a high-temperature insulating part of a high-frequency high-pressure welding tool, a heat shielding material of a spacecraft, a crucible for manufacturing a smelting semiconductor, a high-temperature container for metallurgy and the like. The preparation method provided by the invention is simple, has low requirements on preparation environment and low cost of raw materials, and can realize large-scale industrial production. The h-BN complex phase ceramic prepared by the method has better performance than the h-BN ceramic prepared by the traditional process, can meet the strict requirements of high and new technology fields, and has wider application.)

1. B₄The C/h-BN high-temperature complex-phase ceramic and the preparation method thereof comprise the following experimental steps:

a. mixing 10-70% of hexagonal boron nitride powder, 0-50% of boron carbide powder, 0-60% of boron powder, 0-50% of graphite powder, 0-30% of boric acid and 0-40% of melamine according to mass fraction to obtain a raw material; b. the raw materials are placed in a high-energy ball mill for ball milling, and after being uniformly mixed, the raw materials are dried to obtain mixed powder with the particle size of less than 5 mu m; c. placing the uniformly mixed powder into a mould, placing the mould into a heating furnace for sintering, wherein the vacuum degree in the furnace is about 1.0 multiplied by 10¹Pa, heating to 1500-2500 ℃ at the speed of 3-20 ℃/min, slowly increasing the pressure from 0 to 10-50MPa in the heating process along with the pressurizing process, cooling after heat preservation and pressure maintaining for 1-6h at the cooling speed of 3-10 ℃/min, releasing the pressure after cooling to 1000-1200 ℃, and cooling along with the furnace; d. taking out the mould, and taking out the sintered sample to obtain the product B₄C/h-BN high-temperature complex-phase ceramic material.

2. The preparation method according to claim 1, wherein the raw materials in step a comprise 10-70% of hexagonal boron nitride powder, 0-50% of boron carbide powder, 0-60% of boron powder, 0-50% of graphite powder, 0-30% of boric acid and 0-40% of melamine.

3. The method according to claim 1, wherein the pressure is slowly increased from 0 to 10 to 50MPa during the temperature increase in step c accompanied by the pressurization.

4. The method as claimed in claim 1, wherein the cooling rate in the step c is 3-10 ℃/min, and the pressure can be released after cooling to 1000-1200 ℃, and then the sample is cooled in a furnace.

Technical Field

The invention relates to a B which can be used for a long time in a high-temperature environment₄A preparation process of C/h-BN high-temperature complex-phase ceramic belongs to the technical field of high-temperature structure function integrated ceramic, and is applicable to high-temperature environments such as an inner liner of a rocket combustion chamber, a high-temperature thermocouple protective sleeve, a high-temperature insulating part of a high-frequency high-pressure welding tool, a heat shielding material of a spacecraft, a crucible for manufacturing a smelting semiconductor, a high-temperature container for metallurgy and the like.

Background

The hexagonal boron nitride (h-BN) ceramic has excellent chemical stability and can be used in an oxidation environment of 1173K or less and a nitrogen and inert atmosphere environment of 3073K or less. Because of its excellent physical and chemical properties, the h-BN ceramic has a very wide application range. However, poor sintering properties of h-BN ceramic lead to poor mechanical properties which limit its use in certain high temperature environments as well as erosion resistant environments.

In response to this phenomenon, researchers often improve the mechanical properties by introducing a second phase. The mechanical property of the h-BN material is improved by adding SiC particles by Dianthus hai teachers and the like: the grain growth of the SiC particles is inhibited because the BN wraps the SiC particles. In addition, the hard SiC crystal grains deflect the propagation path of the microcracks. The section teacher et al improved the h-BN material by adding the mullite phase: the mullite can provide an environment for atomic diffusion on one hand, and can fill gaps of a card house type structure formed by crossing h-BN grains on the other hand, so that sintering and densification of the material are promoted. SiO is added to the teachers and the like₂SiO and AlN to improve the mechanical property of h-BN material₂And AlN is introduced to generate SiAlON phase in the material, and the generated particles are dispersed and distributed in the matrix macroscopically, when the crack tip meets SiAlON crystal grains in the expansion process, the crack tip can deflect on the surfaces of the crystal grains and expand along the interior of the matrix with lower modulus, so that the particle strengthening effect is realized. The h-BN complex phase ceramic prepared by the research has higher density and mechanical property, but the added second phase has lower melting point, so that the material stability in a high-temperature environment is poor, and the application in the high-temperature environment is influenced.

Boron carbide (B)₄C) Has a plurality of excellent performances such as low density, high melting point, high hardness, high neutron absorptivity, chemical stability and the like, and is widely applied to the fields of mechanical equipment, grinding tool abrasive, catalytic carriers and the like. This patent is through adding high temperature resistant B₄The density of the h-BN ceramic is improved by the C powder, and further the mechanical property of the ceramic and the stability of the material in a high-temperature environment are improved.

This patent is based on the presence of ultrafine B as hard particles₄The C powder further reduces the size of the h-BN grains by cutting the h-BN grains in the high-energy ball milling process, and generates h-BN and B with smaller grain sizes through high-temperature reaction in the high-temperature sintering process₄And C, preparing the high-strength h-BN complex phase ceramic. The preparation method provided by the patent is simple and has lower requirements on preparation environmentThe cost of raw materials is low, and large-scale industrial production can be realized. The h-BN complex phase ceramic prepared by the method has better performance than the h-BN ceramic prepared by the traditional process, can meet the strict requirements of high and new technology fields, and has wider application.

Disclosure of Invention

The method aims to solve the problems of poor sintering performance of the h-BN ceramic material and obtain the h-BN ceramic with high density, high strength and good high-temperature stability. The method generates the h-BN and the B with smaller grains by refining the h-BN grains and carrying out high-temperature solid-phase reaction₄The method C provides an efficient and simple method for preparing the high-strength h-BN ceramic. The method has simple requirements on raw materials, low cost and low risk, and can be used for mass preparation. The method takes boron powder, boron carbide, carbon powder, boron nitride, boric acid, melamine and the like as raw materials, and prepares the high-strength boron nitride ceramic material by refining h-BN grains and carrying out high-temperature solid-phase reaction.

The technical scheme adopted by the invention is as follows: b₄The C/h-BN high-temperature complex-phase ceramic and the preparation method thereof comprise the following steps:

1) mixing 10-70% of hexagonal boron nitride powder, 0-50% of boron carbide powder, 0-60% of boron powder, 0-50% of graphite powder, 0-30% of boric acid and 0-40% of melamine according to mass fraction to obtain a raw material;

2) placing the raw materials in a high-energy ball mill for ball milling, and drying after uniformly mixing to obtain mixed powder with the particle size of less than 5 mu m;

3) placing the uniformly mixed powder into a mould, placing the mould into a heating furnace for sintering, wherein the vacuum degree in the furnace is about 1.0 multiplied by 10¹Pa, heating to 1500-2500 ℃ at the speed of 3-20 ℃/min, slowly increasing the pressure from 0 to 10-50MPa in the heating process along with the pressurizing process, cooling after heat preservation and pressure maintaining for 1-6h at the cooling speed of 3-10 ℃/min, releasing the pressure after cooling to 1000-1200 ℃, and cooling along with the furnace;

4) taking out the mould, and taking out the sintered sample to obtain the product B₄C/h-BN high-temperature complex-phase ceramic material.

Further, the raw materials in the step 1) comprise 10-70% of hexagonal boron nitride powder, 0-50% of boron carbide powder, 0-60% of boron powder, 0-50% of graphite powder, 0-30% of boric acid and 0-40% of melamine.

Further, the temperature rise process in the step 3) is accompanied with the pressurization process, and the pressure is slowly increased from 0 to 10-50 MPa.

Further, the cooling speed in the temperature reduction process of the step 3) is 3-10 ℃/min, the pressure can be released after the temperature is reduced to 1000-1200 ℃, and then the sample is cooled along with the furnace.

The invention has the beneficial effects that: solves the problem of poor sintering performance of the h-BN ceramic material, and obtains the h-BN ceramic with high density, high strength and better high-temperature stability. The invention generates the h-BN and B with smaller crystal grains by refining the h-BN crystal grains and carrying out high-temperature solid phase reaction₄The method C provides an efficient and simple method for preparing the high-strength h-BN ceramic. The method has simple requirements on raw materials, low cost and low risk, and can be used for mass preparation. The method takes boron powder, boron carbide, carbon powder, boron nitride, boric acid, melamine and the like as raw materials, and prepares the high-strength boron nitride ceramic material through grain refinement and high-temperature solid-phase reaction. The preparation process provided by the invention is simple, low in raw material cost, high in safety and easy to control, and can be used for industrial production.

Drawings

FIG. 1: the XRD pattern of the h-BN ceramic in example 1.

FIG. 2: data for h-BN complex phase ceramic in example 1.

FIG. 3: b is₄SEM image of raw material C.

FIG. 4: SEM image of h-BN complex phase ceramic in example 1.

Detailed Description

Example pair B₄The preparation method of the C/h-BN high-temperature complex-phase ceramic is described in detail.

Example 1

B₄The C/h-BN high-temperature complex-phase ceramic and the preparation method thereof comprise the following steps:

1) uniformly mixing 8.5g of carbon powder, 5.6g of boron carbide, 8.5g of boron powder and 41g of hexagonal boron nitride powder according to volume fraction to obtain a raw material;

2) putting the raw materials into a high-energy ball mill, adding zirconia balls according to the mass ratio of 1:5 of the raw materials to the zirconia balls, adding an organic solvent n-hexane, performing wet ball milling for 6 hours, and drying to obtain mixed powder with the average particle size of less than 5 microns;

3) placing the treated powder into a graphite mold, and placing the graphite mold into a hot pressing furnace for calcination, wherein the calcination system is as follows: heating from room temperature to 500 ℃ at a heating rate of 10 ℃/min; then heating to 1400 ℃ at the heating rate of 7 ℃/min; then heating to 2000 ℃ at the heating rate of 5 ℃/min; slowly pressurizing when the temperature is increased to 1200 ℃, pressurizing to 30MPa at 2000 ℃, and keeping the temperature and the pressure for 60 min; cooling at 5 deg.C/min, cooling to 1000 deg.C, removing pressure, and cooling with the furnace. To obtain B₄C/h-BN high-temperature complex-phase ceramic material.

Example 2

B₄The C/h-BN high-temperature complex-phase ceramic and the preparation method thereof comprise the following steps:

1) according to the mass ratio of the graphite powder, the boron powder and the boron nitride, the mass ratio of the graphite powder, the boron powder and the boron nitride is 1: 4: 5, uniformly mixing the powder to obtain a raw material;

2) putting the raw materials into a ball mill, adding corundum balls according to the mass ratio of 1:3 of the raw materials to the corundum balls, performing wet ball milling for 2.5 hours, and drying to obtain mixed powder with the particle size of less than 5 microns;

3) placing the sample into a mold, placing the mold into a vacuum heating furnace, and calcining according to the following steps: heating from room temperature to 500 ℃ at a heating rate of 15 ℃/min; then heating to 1400 ℃ at the heating rate of 7 ℃/min; then heating to 1900 ℃ at the heating rate of 5 ℃/min; keeping the temperature and the pressure for 30min under the pressure of 30 MPa; cooling along with the furnace; to obtain B₄C/h-BN high-temperature complex-phase ceramic material.

Example 3

B₄The C/h-BN high-temperature complex-phase ceramic and the preparation method thereof comprise the following steps:

1) according to the quantity ratio of substances, the quantity ratio of carbon black, boric acid and melamine substances is 1: 8:2 to obtain a raw material;

2) putting the raw materials into a ball mill, adding corundum balls according to the mass ratio of 1:8 of the raw materials to the corundum balls, and drying after carrying out wet ball milling for 2 hours to obtain mixed powder with the particle size of less than 5 microns;

3) placing the sample into a rubber mold, forming under 50MPa cold isostatic pressing, and demolding to obtain a blank;

4) placing the blank in a vacuum heating furnace, wherein the calcination system is as follows: heating from room temperature to 500 ℃ at a heating rate of 10 ℃/min; then heating to 1400 ℃ at the heating rate of 7 ℃/min; then heating to 1800 ℃ at the heating rate of 5 ℃/min; preserving the temperature for 180 min; cooling along with the furnace; to obtain B₄C/h-BN high-temperature complex-phase ceramic material.

In conclusion, this patent discloses a process for preparing B₄The method for preparing the C/h-BN high-temperature complex-phase ceramic material comprises the following steps: 1) mixing 10-70% of hexagonal boron nitride powder, 0-50% of boron carbide powder, 0-60% of boron powder, 0-50% of graphite powder, 0-30% of boric acid and 0-40% of melamine according to mass fraction to obtain a raw material; 2) placing the raw materials in a high-energy ball mill for ball milling, and drying after uniformly mixing to obtain mixed powder with the particle size of less than 5 mu m; 3) placing the uniformly mixed powder into a mould, placing the mould into a heating furnace for sintering, wherein the vacuum degree in the furnace is about 1.0 multiplied by 10¹Pa, heating to 2500 ℃ at the speed of 3-20 ℃/min, increasing the pressure from 0 to 10-50MPa in the heating process along with the pressurizing process, cooling at the cooling speed of 3-10 ℃/min after keeping the temperature and the pressure for 1-6h, releasing the pressure after cooling to 1200 ℃ along with the furnace cooling. 4) Taking out the mould, and taking out the sintered sample to obtain the product B₄C/h-BN high-temperature complex-phase ceramic material. The h-BN complex phase ceramic material prepared by the patent has the advantages of simple method, lower raw material price and large-scale preparation.

Although the preferred embodiments of the present invention have been described, the present invention is not limited to the above-mentioned embodiments, which are only illustrative and not restrictive, and those skilled in the art can make many modifications without departing from the spirit and scope of the present invention as claimed in the appended claims.