阅读说明：本技术 一种低温脉冲加压制备碳化硼陶瓷的方法 (Method for preparing boron carbide ceramic by low-temperature pulse pressurization ) 是由 李瑞迪 袁铁锤 陈雨 周志辉 张梅 于 2020-06-12 设计创作，主要内容包括：本发明公开了一种低温脉冲加压制备碳化硼陶瓷的方法,包括以下步骤：1)将原料B<Sub>4</Sub>C粉末,经过干燥处理后,放入球磨机中,进行球磨,球磨完毕后,干燥过筛,得到微细粒的B<Sub>4</Sub>C粉末；2)将步骤1)中的B<Sub>4</Sub>C粉末装入加压烧结炉的加压装置的模具中,接着抽真空或通入惰性气体,然后开始加热升温,升温至100℃后,进行脉冲加压,直到温度到达1300～1500℃后,停止脉冲加压,再然后升温至烧结温度,在恒定的压力下进行烧结,烧结完毕并冷却后,得到致密度高的细晶碳化硼陶瓷材料。采用本发明的脉冲加压的方式,在不加入助剂的情况下可以减少了烧结时间,降低了烧结温度,实现碳化硼粉末的完全致密化(致密度达到98％以上),同时保持了细晶材料的特性。(The invention discloses a method for preparing boron carbide ceramic by low-temperature pulse pressurization, which comprises the following steps: 1) mixing the raw material B 4 C powder is dried and then put into a ball mill for ball milling, and after the ball milling is finished, the powder is dried and sieved to obtain micro-fine particle B 4 C, powder; 2) b in the step 1) 4 And C, filling the powder C into a mold of a pressurizing device of a pressurizing sintering furnace, vacuumizing or introducing inert gas, heating to raise the temperature, performing pulse pressurization after the temperature is raised to 100 ℃, stopping pulse pressurization after the temperature reaches 1300-1500 ℃, raising the temperature to the sintering temperature, sintering under constant pressure, and cooling after sintering to obtain the fine-grained boron carbide ceramic material with high density. By adopting the pulse pressurization mode of the invention, the situation that no auxiliary agent is added can be reducedThe sintering time reduces the sintering temperature, realizes the complete densification (the density reaches more than 98%) of the boron carbide powder, and simultaneously maintains the characteristics of the fine-grained material.)

1. A method for preparing boron carbide ceramic by low-temperature pulse pressurization comprises the following steps:

1) mixing the raw material B₄C powder is dried and then put into a ball mill for ball milling, and after the ball milling is finished, the powder is dried and sieved to obtain micro-fine particle B₄C, powder;

2) b in the step 1)₄Filling the powder C into a mold of a pressurizing device of a pressurizing sintering furnace, vacuumizing or introducing inert gas, heating to 100 ℃, performing pulse pressurization until the temperature reaches 1300-1500 ℃, stopping pulse pressurization, heating to the sintering temperature, sintering under constant pressure, and cooling to obtain the fine-grained boron carbide ceramic material with high density;

the pulse pressurization is to set a pressure value, then to increase the pressure value, to maintain the pressure for 5-10 min, and then to release the pressure, to complete a pulse pressurization cycle.

2. The method for preparing boron carbide ceramic by low-temperature pulse pressurization according to claim 1, wherein in the step 1), raw material B is used₄The granularity of the C powder is less than 30 mu m, the ball-material ratio of ball milling is (15-20): 1, the ball milling rotation speed is 300-500 r/min, the ball milling time is 40-80 h, the C powder is sieved to sequentially pass through 650, 800 and 900 mesh screens, and the B powder is controlled₄The average particle size of the C powder is 2-4 um, and the drying is vacuum drying.

3. The method for preparing boron carbide ceramic by low-temperature pulse pressurization according to claim 1, wherein in the step 2), the temperature rise rate is 5-15 ℃/min, the pressure value of the pulse pressurization is 30-50 MPa, the pressure increase and reduction rates are 5-15 MPa/min, the time of each period interval is 2-5 min, and the heating stage needs 5-12 periods of pulse pressurization.

4. The method for preparing the boron carbide ceramic through low-temperature pulse pressurization according to claim 3, wherein the temperature rise rate is 10 ℃/min, the pressure value of the pulse pressurization is 40MPa, the pressure rise rate is 10MPa/min, and 7-8 periods of pulse pressurization are required in the heating stage.

5. The method for preparing boron carbide ceramic by low-temperature pulse pressurization according to claim 1, wherein in the step 2), the sintering temperature is 1800-2000 ℃, the constant pressure is 30-50 Mpa, and the sintering time is 5-60 min.

6. The method for preparing boron carbide ceramic by low-temperature pulse pressurization according to claim 1, wherein in the step 2), B is₄An isolating layer is arranged between the powder C and a mould of the pressurizing device, and the isolating layer is graphite paper.

7. The method for preparing the boron carbide ceramic through low-temperature pulse pressurization according to claim 1, wherein in the step 2), the pulse pressurization is axial pulse pressurization.

8. The fine-grained boron carbide ceramic material with high density prepared by the preparation method according to any one of claims 1 to 8.

9. The high-density fine-grained boron carbide ceramic material according to claim 8, wherein the average grain size of the boron carbide ceramic material is less than 1 μm, the density is more than 98%, the Vickers hardness is more than 40GPa, and the fracture toughness is 5.1MPa.m^1/2The above.

Technical Field

The invention belongs to the technical field of processing and preparation of boron carbide ceramic materials, and particularly relates to a method for preparing boron carbide ceramic through low-temperature pulse pressurization.

Background

Boron carbide consists of two elements of carbon and boron, and the stoichiometric formula of the boron carbide is B₄C, the unit cell is hexagonal polyhedral structure, and boron carbide has many homomorphic isomers, such as B with rhombohedral structure₁₃C₂、B₁₂C₃And B close to it₁₃C₃In addition, the boron carbide has excellent physical properties due to the complex crystal structure and various allotropic isomers of the boron carbide. The boron carbide ceramic is used as a stable material with high hardness, high melting point, good abrasion resistance and corrosion resistance, and excellent self-lubricating and self-polishing performances, and is widely applied to the fields of industrial materials, aerospace, automobiles, mechanical parts and the like.

The traditional hot-pressing sintering method for preparing boron carbide ceramic has a series of problems of long sintering period, high sintering temperature, low product densification degree and the like, and meanwhile, the sintering densification process is completed at a high temperature stage, so that part of boron carbide ceramic grains grow abnormally, the performance of a boron carbide material is obviously reduced, and the density of the prepared boron carbide material is difficult to exceed 95%. At present, the main means for reducing the sintering temperature of boron carbide ceramic and improving the densification degree of the material are as follows: addition of a sintering aid, and strengthening by second-phase dispersion, and the like. However, the addition of the sintering aid and the introduction of the second phase reduce the sintering temperature to a certain extent and improve the compactness, but also destroy the lightweight property of the boron carbide ceramic, thereby adversely affecting the performance of the prepared product. Therefore, how to prepare the fine-grained boron carbide ceramic material with high densification degree and excellent physical properties at a lower temperature becomes the current research hotspot.

Disclosure of Invention

The invention aims to provide a method for preparing boron carbide ceramic by low-temperature pulse pressurization, which has high densification degree and excellent physical properties.

The method for preparing the boron carbide ceramic by low-temperature pulse pressurization comprises the following steps:

1) mixing the raw material B₄C powder is dried and then put into a ball mill for ball milling, and after the ball milling is finished, the powder is dried and sieved to obtain micro-fine particle B₄C, powder;

2) b in the step 1)₄Filling the powder C into a mold of a pressurizing device of a pressurizing sintering furnace, vacuumizing or introducing inert gas, heating to 100 ℃, performing pulse pressurization until the temperature reaches 1300-1500 ℃, stopping pulse pressurization, heating to the sintering temperature, sintering under constant pressure, and cooling to obtain the fine-grained boron carbide ceramic material with high density;

the pulse pressurization is to set a pressure value, then to increase the pressure value, to maintain the pressure for 5-10 min, and then to release the pressure, to complete a pulse pressurization cycle.

In the step 1), the raw material B₄The granularity of the C powder is less than 30 mu m, the ball-material ratio of ball milling is (15-20): 1, the ball milling rotation speed is 300-500 r/min, the ball milling time is 40-80 h, the C powder is sieved to sequentially pass through 650, 800 and 900 mesh screens, and the B powder is controlled₄The average particle size of the C powder is 2-4 um, and the drying is vacuum drying.

In the step 2), the temperature rising rate is 5-15 ℃/min, the pressure value of pulse pressurization is 30-50 MPa, the pressure rising rate and the pressure reduction rate are 5-15 MPa/min, the time of each period interval is 2-5 min, and 5-12 periods of pulse pressurization are needed in the heating stage.

Preferably, the heating rate is 10 ℃/min, the pressure value of pulse pressurization is 40MPa, the pressure increasing rate is 10MPa/min, and 7-8 periods of pulse pressurization are required in the heating stage.

In the step 2), the sintering temperature is 1800-2000 ℃, the constant pressure is 30-50 Mpa, and the sintering time is 5-60 min.

In the step 2), B₄An isolating layer is arranged between the powder C and a mould of the pressurizing device, and the isolating layer is graphite paper.

In the step 2), the pulse pressurization is axial pulse pressurization.

The fine-grained boron carbide ceramic material with high density is prepared according to the preparation method.

The high-density fine-grain boron carbide ceramic material has the average size of less than 1 mu m, the density of more than 98 percent, the Vickers hardness of more than 40GPa and the fracture toughness of 5.1MPa^1/2The above.

The principle of the invention is as follows: the invention applies pulse-shaped pressure in the heating stage, promotes the sliding rearrangement of powder particles in the sintering process, enhances the plastic flow of the powder body, reduces the formation of defects such as air holes, agglomeration and the like in the boron carbide product, is beneficial to the densification of a sintered body, and improves the density of a sintered sample. After pulse pressurization is carried out, the time for constant pressure sintering of the sample can be shortened, and the generation of defects and abnormal growth of crystal grains of the sample under the condition of low-temperature and low-pressure sintering are reduced; a large number of researches show that the density of a sample is continuously increased along with the increase of sintering pressure, but the density is not greatly changed along with the continuous increase of the pressure. The sintering pressure is controlled in an optimal range, unnecessary energy consumption is reduced, and the densification process of the boron carbide sample can be realized in a short time. Meanwhile, the traditional pressurizing process is changed into pulse pressurizing, which is beneficial to releasing the internal stress of a sintered sample, so that a boron carbide product with more excellent performance is prepared.

The invention has the beneficial effects that: 1. by adopting the pulse pressurization mode, the invention can reduce the sintering time and the sintering temperature without adding an auxiliary agent, realize the complete densification (the density reaches more than 98%) of the boron carbide powder and simultaneously keep the characteristics of the fine-grained material. 2. The invention also strictly controls the grain size of the raw material powder, and has certain promotion effect on preparing the boron carbide ceramic with fine grains. 3. The preparation method has the advantages of simple preparation process and high efficiency, reduces energy loss in the production preparation process to the great extent, and is favorable for realizing industrial batch production; the prepared boron carbide has the excellent characteristics of fine grains, high compactness and the like.

Drawings

FIG. 1 is a schematic diagram of pulsed pressurization.

FIG. 2 SEM image of boron carbide powder after ball milling treatment.

FIG. 3 is a gold phase diagram of boron carbide ceramics prepared in examples 1 to 5, wherein 1 to 5 correspond to a to e, respectively.

FIG. 4 is a gold phase diagram of the boron carbide ceramic prepared in comparative example 1.

Detailed Description