CN104529456A - A kind of preparation method of B4C-HfB2 high temperature eutectic self-generated composite ceramics - Google Patents

Abstract

The invention discloses a method for preparing B ₄ C-HfB ₂ high-temperature eutectic self-generated composite ceramics. By changing the ratio between the boron carbide and the hafnium boride, the composite ceramic can prepare a uniformly distributed eutectic structure, wherein the molar content of the hafnium boride is 10%-50%. The specific preparation method is to mix boron carbide powder and hafnium boride powder evenly, then cold isostatically press the mixed powder into a sheet with a diameter of 10mm at room temperature, and prepare B ₄ C- _HfB2 eutectic composites. Compared with the traditional solid phase sintering method, the invention has simple preparation method and short preparation period, and the prepared B ₄ C-HfB ₂ composite ceramic material has high density and better high temperature performance. In addition, the material has both the performance advantages of HfB ₂ and B ₄ C, and can be used as an ultra-high temperature ceramic material.

Description

A kind of preparation method of B4C-HfB2 high temperature eutectic self-generated composite ceramics

technical field

The invention relates to the technical field of ultra-high temperature ceramic materials and its preparation, in particular to a B ₄ C-HfB ₂ binary eutectic self-generated composite ceramic and a preparation method thereof.

Background technique

HfB ₂ belongs to transition metal borides. As an ultra-high temperature ceramic material, it has the characteristics of high melting point (3250°C), high hardness, good electrical and thermal conductivity, relatively good high-temperature oxidation resistance and impact resistance. These excellent properties make It can be used as a high-temperature structural material, such as: high-temperature electrodes, furnace components, rocket engines, and thermal protection systems for supersonic vehicles. However, a single hafnium boride material is difficult to sinter densely, and its own strength and toughness are relatively low, which limits its application in harsh environments.

At present, in order to improve this situation, B ₄ C can be used as a sintering aid to improve its density through the traditional solid-state sintering method. Harlan J.Brown-Shaklee et al. reported that because B ₄ C can be oxidized with transition metals Compounds react at high temperature to form metal borides, reduce the oxide impurities on the particle surface, and improve the density of hafnium boride materials, and study the effect of B/C atomic ratio on the density of hot-pressed sintered HfB ₂ -B _x C ceramics and thermal performance effects.

In addition, Frederic Monteverde et al. believe that B ₄ C can not only act as a sintering aid, but also inhibit the growth of hafnium boride grains and obtain a finer grain structure.

However, the traditional solid-state sintering method requires a higher sintering temperature and a longer preparation period. More importantly, the B ₄ C-HfB ₂ eutectic ceramics prepared by the arc melting method, compared with the traditional method, the connection interface between the phases is formed by the self-generation of the melt, and the phase-interface compatibility is good , very clean, high bonding strength, fine eutectic structure, and an interlaced three-dimensional network structure, making B ₄ C-HfB ₂ eutectic ceramics obtain more excellent high temperature performance.

Contents of the invention

The technical problem to be solved by the present invention is to provide a simple preparation method with a short preparation period and can effectively improve its The density method makes the performance of the prepared B ₄ C-HfB ₂ high-temperature eutectic self-generated composite ceramics approach or exceed that of products produced by traditional methods.

The present invention solves its technical problem and adopts the following technical solutions:

The preparation method of the B ₄ C-HfB ₂ high-temperature eutectic self-generated composite ceramics provided by the present invention specifically comprises: mixing boron carbide powder and hafnium boride powder with a molar content of 50%-90% and 10%-50% respectively, The ingredients are uniformly mixed by ball milling, and then cold isostatically pressed into flakes at room temperature, and then the sample is rapidly melted in an argon environment by electric arc melting furnace discharge, and then rapidly cooled with the copper plate in the arc melting furnace to obtain B ₄ C -HfB ₂ high temperature eutectic autogenous composite ceramics.

The purity of the boron carbide powder is 98%, and the particle size is 1-10 μm.

The purity of the hafnium boride powder is 99%.

The ball mill mixing process adopts a polyethylene ball mill pot and zirconia balls, and ball mills for 1 hour.

The sheet is cold isostatically pressed at room temperature into a cylindrical shape with a diameter of 10 mm and a height of 5 mm.

The argon pressure in the electric arc melting furnace is controlled at 60kPa, the output power during rapid melting is 20%-40%, and the current is 120-250A.

The cooling process is carried out on a copper plate in an electric arc melting furnace, and the water pressure during rapid cooling is 0.06-0.07 MPa.

The invention provides the B ₄ C-HfB ₂ high-temperature eutectic self-generated composite ceramic prepared by the above method, and its application in making ultra-high-temperature ceramic products.

Compared with the traditional solid phase sintering method, the present invention has the following main advantages:

1. The preparation method is simple and the required preparation cycle is short.

2. The connection interface between the phases of the prepared B ₄ C-HfB ₂ eutectic composite ceramics is formed by the self-generated fusion of the melt, the phase interface is well compatible, the phase interface is very clean, and the bonding strength is high.

3. The eutectic structure of the prepared B ₄ C-HfB ₂ eutectic composite ceramics is fine, and presents an interlaced three-dimensional network structure with a uniform structure.

4. The prepared B ₄ C-HfB ₂ eutectic composite ceramic has high density, and has more excellent mechanical properties and thermal stability.

Description of drawings

Fig. 1 is the XRD spectrum of the sample prepared by cold isostatic pressing of B ₄ C powder and HfB ₂ powder of the present invention after being uniformly mixed in a ball mill at room temperature into flakes, and then rapidly melted and cooled in an electric arc melting furnace .

Fig. 2 shows that the B ₄ C powder of the present invention and 50 (mol%) HfB ₂ powder are uniformly mixed through a ball mill, and the powder is cold isostatically pressed into a sheet at room temperature, and then rapidly melted and cooled in an electric arc melting furnace. The BSE spectrum of the sample.

Fig. 3 shows that the B ₄ C powder of the present invention and 35 (mol%) HfB ₂ powder are uniformly mixed through a ball mill, and the powder is cold isostatically pressed into a sheet at room temperature, and then rapidly melted and cooled in an electric arc melting furnace. The BSE spectrum of the sample.

Fig. 4 shows that the B ₄ C powder of the present invention and 22 (mol%) HfB ₂ powder are uniformly mixed through a ball mill, and the powder is cold isostatically pressed into a sheet at room temperature, and then rapidly melted and cooled in an electric arc melting furnace. The BSE spectrum of the sample.

Fig. 5 shows that the B ₄ C powder of the present invention and 10 (mol%) HfB ₂ powder are uniformly mixed through a ball mill, and the powder is cold isostatically pressed into a sheet at room temperature, and then rapidly melted and cooled in an electric arc melting furnace. The BSE spectrum of the sample.

Detailed ways

The present invention will be further described below in conjunction with specific implementation examples and accompanying drawings, but the present invention is not limited.

Example 1

This implementation case is a method for preparing B ₄ C-HfB ₂ high-temperature eutectic self-generated composite ceramics.

The method is: using commercially available high-purity B ₄ C and HfB ₂ powders, according to the molar ratio, wherein the molar content of B ₄ C powder is 50%, and the molar content of HfB ₂ is 50%, using a polyethylene ball mill tank , the zirconia balls are milled on a high-energy ball mill at a speed of 300 rpm for 1 hour to obtain the required powder, and then the powder after ball milling is mixed uniformly and cold isostatically pressed at room temperature into a ball with a diameter of 10 mm and a height of about 5 mm. Sheet shape, put it into the arc melting furnace, under 60kPa argon environment, through arc discharge, the sample is melted rapidly, the output power is 20-40%, the current is 120-250A, and then the copper plate in the arc melting furnace Rapidly cool to room temperature, the water pressure is 0.06-0.07MPa.

After testing, see Figure 1 and Figure 2, the XRD pattern of the B ₄ C-HfB ₂ high-temperature eutectic authigenic composite ceramic shows only the diffraction peaks of B ₄ C and HfB ₂ , and no other substances are formed. The backscattering diagram also shows that there are only two phases, that is, the black phase is B ₄ C and the white phase is HfB ₂ . In addition to the evenly distributed binary eutectic structure, there are also a large number of long rod-shaped HfB ₂ phase structures.

Example 2

This implementation case is a method for preparing B ₄ C-HfB ₂ high-temperature eutectic self-generated composite ceramics.

The method is: using commercially available high-purity B ₄ C and HfB ₂ powders, according to the molar ratio, wherein the molar content of B ₄ C powder is 65%, and the molar content of HfB ₂ is 35%, using a polyethylene ball mill tank , the zirconia balls are milled on a high-energy ball mill at a speed of 300 rpm for 1 hour to obtain the required powder, and then the powder after ball milling is mixed uniformly and cold isostatically pressed at room temperature into a ball with a diameter of 10 mm and a height of about 5 mm. Sheet shape, put it into the arc melting furnace, under 60kPa argon environment, through arc discharge, the sample is melted rapidly, the output power is 20-40%, the current is 120-250A, and then the copper plate in the arc melting furnace Rapidly cool to room temperature, the water pressure is 0.06-0.07MPa.

After testing, see Figure 1 and Figure 3, the XRD pattern of the B ₄ C-HfB ₂ high-temperature eutectic autogenous composite ceramic shows only the diffraction peaks of B ₄ C and HfB ₂ , and no other substances are formed. The backscattering diagram also shows that there are only two phases, that is, the black phase is B ₄ C and the white phase is HfB ₂ . In addition to the evenly distributed binary eutectic structure, there is also a small amount of long rod-shaped HfB ₂ phase structure.

Example 3

This example is a method for preparing a B ₄ C-HfB ₂ high temperature eutectic autogenous composite ceramic.

The method is: using commercially available high-purity B ₄ C and HfB ₂ powders, according to the molar ratio, wherein the molar content of B ₄ C powder is 78%, and the molar content of HfB ₂ is 22%, using a polyethylene ball mill tank , the zirconia balls are milled on a high-energy ball mill at a speed of 300 rpm for 1 hour to obtain the required powder, and then the powder after ball milling is mixed uniformly and cold isostatically pressed at room temperature into a ball with a diameter of 10 mm and a height of about 5 mm. Sheet shape, put it into the arc melting furnace, under 60kPa argon environment, through arc discharge, the sample is melted rapidly, the output power is 20-40%, the current is 120-250A, and then the copper plate in the arc melting furnace Rapidly cool to room temperature, the water pressure is 0.06-0.07MPa.

After testing, see Figure 1 and Figure 4, the XRD pattern of the B ₄ C-HfB ₂ high-temperature eutectic autogenous composite ceramic shows only the diffraction peaks of B ₄ C and HfB ₂ , and no other substances are formed. The backscattering diagram also shows that there are only two phases, that is, the black phase is B ₄ C, and the white phase is HfB ₂ , and a binary eutectic structure with a relatively uniform distribution can be observed.

Example 4

This implementation case is a method for preparing B ₄ C-HfB ₂ high-temperature eutectic self-generated composite ceramics.

The method is: using commercially available high-purity B ₄ C and HfB ₂ powders, according to the molar ratio, wherein the molar content of B ₄ C powder is 90%, and the molar content of HfB ₂ is 10%, using a polyethylene ball mill tank , the zirconia balls are milled on a high-energy ball mill at a speed of 300 rpm for 1 hour to obtain the required powder, and then the powder after ball milling is mixed uniformly and cold isostatically pressed at room temperature into a ball with a diameter of 10 mm and a height of about 5 mm. Sheet shape, put it into the arc melting furnace, under 60kPa argon environment, through arc discharge, the sample is melted rapidly, the output power is 20-40%, the current is 120-250A, and then the copper plate in the arc melting furnace Rapidly cool to room temperature, the water pressure is 0.06-0.07MPa.

After testing, see Figure 1 and Figure 5, the XRD pattern of the B ₄ C-HfB ₂ high-temperature eutectic autogenous composite ceramic shows only the diffraction peaks of B ₄ C and HfB ₂ , and no other substances are formed. The backscatter diagram also shows that there are only two phases, that is, the black phase is B ₄ C and the white phase is HfB ₂ . In addition to the evenly distributed binary eutectic structure, there are also a large amount of B ₄ C phase structure.

The high-energy ball mill mentioned in the above-mentioned embodiment can adopt Retsch PM100.

Claims (8)

1. A method for preparing B ₄ C-HfB ₂ high-temperature eutectic self-generated composite ceramics, characterized in that the molar content of boron carbide powder and hafnium boride powder is respectively 50%-90% and 10%-50% batching, The ingredients are uniformly mixed by ball milling, and then cold isostatically pressed into flakes at room temperature, and then the sample is rapidly melted in an argon environment by electric arc melting furnace discharge, and then rapidly cooled with the copper plate in the arc melting furnace to obtain B ₄ C -HfB ₂ high temperature eutectic autogenous composite ceramics. 2. The method for preparing B ₄ C-HfB ₂ high-temperature eutectic autogenous composite ceramics according to claim 1, characterized in that the boron carbide powder has a purity of 98% and a particle size of 1-10 μm. 3. The method for preparing B ₄ C-HfB ₂ high temperature eutectic autogenous composite ceramics according to claim 1, characterized in that the purity of the hafnium boride powder is 99%. 4. B ₄ C-HfB according to claim ₁ The preparation method of high-temperature eutectic self-generated composite ceramics is characterized in that the ball mill mixing process adopts a polyethylene ball mill jar and zirconia balls, and ball mills for 1h . 5. The preparation method of B ₄ C-HfB ₂ high-temperature eutectic autogenous composite ceramics according to claim 1, characterized in that the sheet is cold isostatically pressed at room temperature into a cylinder with a diameter of 10 mm and a height of 5 mm shape. 6. The preparation method of B ₄ C-HfB ₂ high-temperature eutectic autogenous composite ceramics according to claim 1, characterized in that the argon pressure is controlled at 60kPa in the electric arc melting furnace, and the output power during rapid melting is 20%-40 %, the current is 120-250A. 7. B ₄ C-HfB according to claim ₁ The preparation method of high-temperature eutectic self-generated composite ceramics is characterized in that the cooling process is carried out on a copper plate in an electric arc melting furnace, and the water pressure during rapid cooling is 0.06 -0.07MPa. 8. The B ₄ C-HfB ₂ high-temperature eutectic autogenous composite ceramic prepared by the method according to any one of claims 1 to 7, and its application in making ultra-high-temperature ceramic products.