阅读说明：本技术 一种碳化硼陶瓷的制备方法 (Preparation method of boron carbide ceramic ) 是由 刘汝强 王殿春 李晓明 吴思华 周清波 于 2020-07-02 设计创作，主要内容包括：本发明涉及一种碳化硼陶瓷的制备方法。该方法包括采用化学气相沉积,以氮气作为保护稀释气体,以甲烷和气态BCl<Sub>3</Sub>为反应气体,反应温度控制在1500～2000℃之间,压力控制在200～1000Pa之间,在基体模具上形成碳化硼陶瓷制品。本发明通过控制反应温度来获得对应密度的碳化硼材料,提高了材料性质的可控性。在较高温度下获得碳化硼密度可达2.5g/cm<Sup>3</Sup>。本发明碳化硼材料的纯度为99.95-99.99％。(The invention relates to a preparation method of boron carbide ceramic. The method comprises adopting chemical vapor deposition, using nitrogen as protective diluent gas, and using methane and gaseous BCl 3 The reaction temperature is controlled to be 1500-2000 ℃, the pressure is controlled to be 200-1000 Pa, and the boron carbide ceramic product is formed on the matrix mould. According to the invention, the boron carbide material with corresponding density is obtained by controlling the reaction temperature, so that the controllability of the material property is improved. The density of boron carbide obtained at higher temperature can reach 2.5g/cm 3 . The purity of the boron carbide material is 99.95-99.99%.)

1. Of boron carbide ceramicsThe preparation method comprises adopting chemical vapor deposition, taking nitrogen as protective diluent gas, and taking methane and gaseous BCl₃The reaction temperature is controlled to be 1500-2000 ℃, the pressure is controlled to be 200-1000 Pa, and the boron carbide ceramic product is formed on the matrix mould.

2. The method of preparing a boron carbide ceramic according to claim 1, comprising the steps of:

(1) after the substrate is arranged on a rotating device, the substrate is placed in a chemical vapor deposition reaction chamber, a furnace cover is closed, the temperature is increased and the vacuum is pumped, and when the temperature reaches 800-950 ℃, the temperature is kept for 30-60 min under the condition that the vacuum degree is 200-500 Pa;

(2) continuously introducing nitrogen as protective diluent gas according to BCl₃∶CH₄Mixing raw material methane and gaseous BCl in a volume ratio of (0.01-1): (0.5-50)₃Introducing the mixture into a reaction chamber, heating to 1500-2000 ℃, controlling the vacuum degree to be 200-1000 Pa, introducing raw material gas for reaction for 15-40h, and depositing on a matrix mold to form a boron carbide ceramic product; after the reaction is finished, closing a raw material gas source;

(3) and after cooling, taking down the boron carbide ceramic on the matrix mold to obtain the boron carbide ceramic product.

3. The method for preparing boron carbide ceramic according to claim 2, wherein in the step (1), the temperature is 900 ℃ and the vacuum degree is 300 to 400 Pa.

4. The method of producing a boron carbide ceramic according to claim 2, wherein in the step (2), when producing boron carbide, methane and gaseous BCl are used₃Volume ratio of BCl₃∶CH₄＝(0.02-0.05):(30-40)。

5. The method of producing a boron carbide ceramic according to claim 2, wherein in the step (2), the raw material gas CH₄And BCl₃The purity of the product is more than or equal to 99.99 percent.

6. The method according to claim 2, wherein the degree of vacuum in step (2) is 500-700 Pa.

7. The method according to claim 2, wherein in the step (2), the raw material gas is introduced for a reaction time of 20 to 30 hours.

8. The method for preparing boron carbide ceramic as claimed in claim 1 or 2, wherein the reaction temperature is controlled at 1500-³Boron carbide.

9. The method for preparing boron carbide ceramic as claimed in claim 1 or 2, wherein the reaction temperature is controlled at 1900-2000 ℃ to obtain a density of 2.45-2.50g/cm³The high-density boron carbide.

Technical Field

The invention relates to a preparation method of boron carbide ceramic, belonging to the technical field of hard ceramic materials.

Background

Boron carbide (B)₄C) Is an important superhard material with hardness second to that of diamond and cubic boron nitride in nature. It has the features of high melting point, high modulus, small specific weight, good self-lubricating property, wear resistance, acid and alkali corrosion resistance, radiation resistance, neutron absorption, etc. it is a comprehensive oneThe novel high-performance engineering ceramic material with outstanding performance has important application in the aspects of high-end liquid-gas sealing materials, aerospace engine nozzles, high-end ceramic bearings, high-end bulletproof armor materials, polishing of hard materials, fine abrasives and the like. In addition, the boron carbide ceramic has irreplaceable functions in the aspects of neutron absorption and shielding components of nuclear power reactors and the like.

The boron carbide ceramic has extremely strong covalent bond and large grain boundary resistance, is a ceramic material which is extremely difficult to sinter, the conventional normal pressure sintering method can only achieve about 80 percent of compactness, and the obtained boron carbide ceramic has poor performance. In order to improve the sintering density and performance of boron carbide ceramics, hot-pressing sintering method and liquid-phase sintering method are generally adopted. The hot pressing sintering method is to apply pressure of tens of megapascals in the sintering process to promote boron carbide sintering densification, for example, chinese patent documents CN1803714A, CN1541981A, and the like. The hot-pressing sintering method has low yield, high cost and simple product structure, and is difficult to produce in large scale.

The liquid phase sintering method is to add proper amount of Y into boron carbide₂O₃、Al₂O₃、La₂O₃And (3) the low-melting-point substances are utilized to generate partial liquid phase to promote sintering in the sintering process. Such as chinese patent documents CN1552667A, CN1438201A, etc. The boron carbide ceramics prepared by the liquid phase sintering method have relatively poor performance, and the performance of the materials is rapidly deteriorated due to liquid phase precipitation when the boron carbide ceramics are used at high temperature.

The normal pressure sintered boron carbide ceramic has the outstanding advantages of low process cost, capability of preparing products with complex structures and suitability for large-scale production, but the density of the traditional normal pressure sintered boron carbide is generally 2.0-2.1g/cm³The density is about 80%, the purity is about 90%, and how to improve the density and the purity of the boron carbide ceramic becomes a key difficult problem to be broken through urgently.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a preparation method of boron carbide ceramic based on a chemical vapor deposition method, which can obviously improve the purity and density of boron carbide and has controllable density.

The technical scheme of the invention is as follows:

a process for preparing boron carbide ceramic includes chemical vapor deposition, nitrogen as protecting diluent gas, methane and gaseous BCl₃The reaction temperature is controlled to be 1500-2000 ℃, the pressure is controlled to be 200-1000 Pa, and the boron carbide ceramic product is formed on the matrix mould.

According to the invention, the reaction temperature is controlled at 1500-³Boron carbide of (2); the reaction temperature is controlled at 1900-2000 ℃ to obtain the density of 2.45-2.50g/cm³The high-density boron carbide.

In more detail, the preparation method of the boron carbide ceramic comprises the following steps:

(1) after the substrate is arranged on a rotating device, the substrate is placed in a chemical vapor deposition reaction chamber, a furnace cover is closed, the temperature is increased and the vacuum is pumped, and when the temperature reaches 800-950 ℃, the temperature is kept for 30-60 min under the condition that the vacuum degree is 200-500 Pa;

(2) continuously introducing nitrogen as protective diluent gas according to BCl₃∶CH₄Mixing raw material methane and gaseous BCl in a volume ratio of (0.01-1): (0.5-50)₃Introducing the mixture into a reaction chamber, heating to 1500-2000 ℃, controlling the vacuum degree to be 200-1000 Pa, introducing raw material gas for reaction for 15-40h, and depositing on a matrix mold to form a boron carbide ceramic product; after the reaction is finished, closing a raw material gas source;

(3) and after cooling, taking down the boron carbide ceramic on the matrix mold to obtain the boron carbide ceramic product.

According to the invention, in the step (1), the temperature is 900 ℃, and the vacuum degree is 300-400 Pa.

Preferably, in step (2), the boron carbide is prepared from methane and gaseous BCl₃Volume ratio of BCl₃∶CH₄＝(0.02-0.05):(30-40)。

According to the present invention, in the step (2), it is preferable that the raw material gas CH₄And BCl₃The purity of the product is more than or equal to 99.99 percent;

preferably, in step (2), the degree of vacuum is 500-700Pa when preparing boron carbide.

According to the invention, in the step (2), the raw material gas is preferably introduced for a reaction time of 20 to 30 hours. The time for introducing the raw material gas is selected according to the thickness of the boron carbide to be grown.

Preferably, according to the present invention, in step (2), when the reaction temperature is 1500-³Boron carbide of (2); when the reaction temperature is 1900-2000 ℃, the density of 2.45-2.50g/cm can be obtained³The high-density boron carbide.

According to the invention, the material of the matrix is preferably graphite material, and the shape of the matrix can be processed according to the use requirement.

The method is suitable for manufacturing nozzles for sand blasting machines, nozzles for high-pressure water cutting machines, sealing rings, ceramic tools and dies and the like.

The invention has the technical characteristics and beneficial effects that:

1. the invention can obtain the boron carbide material with corresponding density by controlling the reaction temperature, and improves the controllability of the material property compared with the traditional sintering preparation method.

2. The invention can obtain the boron carbide material with high density and high density at higher reaction temperature, and compared with the traditional sintering preparation method, the boron carbide material with higher performance can be obtained. The density can reach 2.5g/cm³。

3. The invention uses high-purity raw material CH₄And BCl₃Compared with the traditional sintering preparation method, the method for preparing the high-purity boron carbide does not need substances such as a catalyst and the like, reduces the introduction of impurities, improves the purity of the boron carbide material, and realizes the preparation of the high-purity boron carbide material with the purity of 99.95-99.99%.

4. The invention can obtain products with corresponding shapes by controlling the shapes of the molds, thereby improving the plasticity of the products.

Drawings

FIG. 1 is a photograph of a real object of boron carbide prepared in example 1.

FIG. 2 is a scanning electron micrograph of the product prepared in example 2.

FIG. 3 is a graph of the density of boron carbide produced at different reaction temperatures, with the abscissa being temperature (. degree. C.) and the ordinate being density (%).

Detailed Description

The present invention will be further described by way of examples, but not limited thereto, with reference to the accompanying drawings.