阅读说明：本技术 一种可在超高温环境中使用的高强度氮化硼陶瓷的制备方法 (Preparation method of high-strength boron nitride ceramic capable of being used in ultrahigh-temperature environment ) 是由 吴赟 孙志远 温广武 李俐 侯永昭 张衡 李道谦 王鑫昊 李鑫 刘业青 仲诚 于 2020-08-04 设计创作，主要内容包括：本发明公开了一种可在超高温环境中使用的高强度氮化硼陶瓷的制备方法,包括如下步骤：1)将氮化硼粉料置于球磨罐中,并加入不同直径的氧化锆研磨球,然后将球磨罐抽真空或通入氮气,利用球磨设备对其进行粉磨使其粒度D<Sub>50</Sub>＜1μm,其中球磨方式可以采用干磨或湿磨,球磨过程中控制物料温度低于40℃；2)根据产品使用性能要求,在处理后的氮化硼粉料中加入质量分数为0~25%的二硼化锆,0~15%的硼粉,进行均匀混合后得到陶瓷原料。将陶瓷原料置于热压模具中,装模,预压。3)将装完料的模具置于真空热压炉内真空度＜10Pa,以3-15℃/min的速率升温到1800-2100℃后,开始对样品进行加压处理,压力为20-60MPa,保温10-120min后降温泄压,降温速率为3-15℃/min.即得所述的高强氮化硼陶瓷材料。这种方法提高了传统氮化硼陶瓷的强度,且物相中不含影响其高温性能的氧化硼,降低高强氮化硼陶瓷材料的生产成本。该方法对原料要求简单,且危险性小,对制备的环境要求比较低,可大量制备。(The invention discloses a preparation method of high-strength boron nitride ceramic capable of being used in an ultrahigh-temperature environment, which comprises the following steps: 1) placing boron nitride powder in a ball milling tank, adding zirconia grinding balls with different diameters, vacuumizing the ball milling tank or introducing nitrogen, and grinding the powder by using ball milling equipment to ensure that the particle size D of the powder is D 50 Less than 1 μm, wherein the ball milling mode can adopt dry milling or wet milling, and the temperature of the materials is controlled to be lower than 40 ℃ in the ball milling process; 2) according to the requirement of the service performance of the product, adding 0-25% of zirconium diboride and 0-15% of boron powder by mass into the treated boron nitride powder, and uniformly mixing to obtain the ceramic raw material. And (3) placing the ceramic raw material in a hot-pressing die, filling the die and prepressing. 3) Placing the mold in a vacuum hot-pressing furnace at a vacuum degree of less than 10Pa and a temperature of 3-15 deg.CHeating to 1800-. The method improves the strength of the traditional boron nitride ceramic, does not contain boron oxide which affects the high-temperature performance of the traditional boron nitride ceramic, and reduces the production cost of the high-strength boron nitride ceramic material. The method has the advantages of simple requirements on raw materials, low risk and low requirements on preparation environment, and can be used for mass preparation.)

1. A preparation method of high-strength boron nitride ceramics capable of being used in an ultrahigh-temperature environment is characterized by comprising the following steps:

(1) placing boron nitride powder in a ball milling tank, adding zirconia grinding balls with different diameters, vacuumizing the ball milling tank or introducing nitrogen, and grinding the powder by using ball milling equipment to ensure that the particle size D of the powder is D₅₀Less than 1 μm, wherein the ball milling mode can adopt dry milling or wet milling, and the temperature of the materials is controlled to be lower than 40 ℃ in the ball milling process;

(2) according to the requirement of the service performance of the product, adding boron powder with the volume fraction of 0-20% into the ball-milled boron nitride powder, and uniformly mixing to obtain a ceramic raw material; placing the ceramic raw material in a hot-pressing mould, filling the mould and prepressing;

(3) and (3) placing the mold filled with the material into a vacuum hot pressing furnace, wherein the vacuum degree in the furnace is less than 10Pa, heating to 1800 plus 2100 ℃ at the speed of 3-15 ℃/min, starting to pressurize the sample, keeping the pressure at 20-60MPa, keeping the temperature for 10-120min, cooling and releasing the pressure, and obtaining the high-strength boron nitride ceramic material, wherein the cooling speed is 3-15 ℃/min.

2. The method of claim 1, wherein: the boron nitride raw material is hexagonal boron nitride, the content of Boron Nitride (BN) is more than or equal to 99.0 percent, and the granularity D₅₀＜3μm。

3. The method of claim 1, wherein: adding zirconia balls with different diameters in the raw material ball milling process in the step 1), and mixing according to a certain proportion for use.

4. The method of claim 1, wherein: the ball milling mode of the raw materials in the step 1) is divided into a dry milling mode and a wet milling mode, wherein the ball milling medium for the wet milling is an organic solvent.

5. The method of claim 1, wherein: the ball milling time in the step 1) is 1-5 h.

6. The method of claim 1, wherein: the temperature rise process of the step 3) is divided into three steps, wherein the temperature is raised from room temperature to 1200-1400 ℃ at the speed of 10-15 ℃/min in the first step, the temperature is raised to 1500-1700 ℃ at the speed of 6-10 ℃/min in the second step, and the temperature is raised to 1800-2100 ℃ at the speed of 5-8 ℃/min in the third step.

7. The method of claim 1, wherein: the pressurizing mode of the step 3) is to perform pre-pressing at the temperature of 1000-1300 ℃ for about 10 MPa, and pressurize at the temperature of 1800-2100 ℃ to 20-60 MPa; the pressurizing mode is slow pressurizing.

Technical Field

The invention belongs to the technical field of high-temperature structure function integrated ceramics, and relates to a preparation method of high-strength boron nitride ceramics capable of being used in an ultrahigh-temperature environment.

Background

Hexagonal boron nitride (h-BN) ceramic is a high-temperature structural ceramic material with great development potential. h-BN is a new material with a layered structure similar to graphite knots, is ivory white, is commonly called white graphite, has no obvious melting point, does not soften at high temperature, and resists corrosion of strong acid and strong alkali. h-BN is excellent in heat resistance and can be used in an oxidizing atmosphere of 900 ℃ or lower and in a nitrogen or inert atmosphere of 2800 ℃ or lower. Compared with other ceramic materials, the h-BN ceramic has a series of characteristics of high temperature resistance, high thermal conductivity, low expansion coefficient, thermal shock resistance and the like, is a high-temperature structural ceramic material with excellent performance, and is widely applied to various fields. Some problems also exist with the current hexagonal boron nitride ceramics: the h-BN powder has the properties of looseness, easy moisture absorption and the like, the hot-pressed sintered ceramic has low density, lower mechanical strength, more obvious anisotropy and poorer stability in oxygen atmosphere, and the use temperature is below 900 ℃ 1, 2.

Other patents have incorporated secondary phases to enhance the properties of boron nitride based ceramics [3, 4 ]. The invention researches a preparation method of high-strength boron nitride ceramic capable of being used in an ultrahigh-temperature environment, improves the mechanical property of the traditional boron nitride ceramic while ensuring the high-temperature property of the boron nitride ceramic, solves the contradiction between the thinning of boron nitride powder and the deliquescence and oxidation, and reduces the production cost of the high-strength boron nitride ceramic material.

Reference to the literature

[1] Leaf phenazine, once irradiated, hudaqing, etc., the main obstacle to densification of BN-based composite ceramics [ J ], modern technology ceramics, 1998, 19 (1): 7-10;

[2] chen guangle, pengzhen, fangshik, etc., hot-pressed sintering of high-purity h-BN ceramic materials and compactness studies [ J ], silicate notification, 2010, 29 (2): 436-;

[3] strictly, Xue 23839, a high-strength high-oxidation resistance BN ceramic and a preparation method thereof [ P ], Zhejiang: CN103420677A, 2013-12-04;

[4] jia dechang, Liang bin, Yangzhua, Wang Shengjin, Hupegang, Xiaoming, Zhouyu, a lamellar BN (C) crystal grain toughened Si # B # C # N ceramic preparation method [ P ], Heilongjiang: CN106518075A, 2017-03-22.

Disclosure of Invention

The invention researches a preparation method of high-strength boron nitride ceramic capable of being used in an ultrahigh-temperature environment, improves the mechanical property of the traditional boron nitride ceramic while ensuring the high-temperature property of the boron nitride ceramic, solves the contradiction between the thinning of boron nitride powder and the deliquescence and oxidation, and reduces the production cost of the high-strength boron nitride ceramic material. The invention adopts ball milling medium grading, ball milling environment control and parameter optimization to ball mill boron nitride powder to nano level, then zirconium diboride powder or boron powder is added into the boron nitride according to the performance requirement of the material, then the raw material is put into a mould for hot-pressing sintering, and the heating and cooling rate of the hot-pressing sintering is controlled. The method has simple requirements on raw materials, no pollutant emission in the preparation process, lower requirements on the preparation environment and equipment, and is beneficial to industrial large-scale preparation.

Therefore, the technical scheme of the invention is as follows:

a preparation method of high-strength boron nitride ceramics used in an ultrahigh-temperature environment comprises the following steps:

(1) placing boron nitride powder in a ball milling tank, adding zirconia grinding balls with different diameters, vacuumizing the ball milling tank or introducing nitrogen, and grinding the powder by using ball milling equipment to ensure that the particle size D of the powder is D₅₀Less than 1 μm, wherein the ball milling mode can adopt dry milling or wet milling, and the temperature of the materials is controlled to be lower than 40 ℃ in the ball milling process;

(2) according to the requirement of the service performance of the product, adding boron powder with the volume fraction of 0-20% into the treated boron nitride powder, and uniformly mixing to obtain the ceramic raw material. Placing the ceramic raw material in a hot-pressing mould, filling the mould and prepressing;

(3) and (3) placing the mold filled with the material into a vacuum hot pressing furnace, wherein the vacuum degree in the furnace is less than 10Pa, heating to 1800 plus 2100 ℃ at the speed of 3-15 ℃/min, starting to pressurize the sample, keeping the pressure at 20-60MPa, keeping the temperature for 10-120min, cooling and releasing the pressure, and obtaining the high-strength boron nitride ceramic material, wherein the cooling speed is 3-15 ℃/min.

Preferably, the boron nitride raw material in the step (1) is hexagonal boron nitride, the content of Boron Nitride (BN) is more than or equal to 99.0 percent, and the granularity D is₅₀＜3μm；

Preferably, zirconia balls with different diameters are added into the raw materials in the step (1) in the ball milling process and are mixed according to a certain proportion for use;

preferably, the ball milling mode of the raw materials in the step (1) is divided into a dry milling mode and a wet milling mode, wherein the ball milling medium for the wet milling is an organic solvent;

preferably, the ball milling time in the step (1) is 1-5 h;

preferably, the temperature rise process in the step (3) is divided into three steps, wherein in the first step, the temperature is raised from room temperature to 1200-1400 ℃ at the speed of 10-15 ℃/min, in the second step, the temperature is raised to 1500-1700 ℃ at the speed of 6-10 ℃/min, and in the third step, the temperature is raised to 1800-2100 ℃ at the speed of 5-8 ℃/min;

preferably, the pressurizing manner in step (3) is to perform pre-pressing at 1000-1300 ℃ for about 10 MPa, and to pressurize at 1800-2100 ℃ to 20-60 MPa. The pressurizing mode is slow pressurizing.

The invention adopts ball milling medium grading, ball milling environment control and parameter optimization to ball mill the boron nitride powder to nano level. Adding zirconium diboride or boron powder into the treated boron nitride powder according to the use performance requirements of the product. By utilizing the hot-pressing sintering process, the heating rate, the heat preservation time, the hot-pressing temperature and the cooling rate are well controlled, and the growth of boron nitride grains is controlled, so that the novel high-strength boron nitride material with the strength and the electrical property higher than those of the existing boron nitride material is obtained, and the phase does not contain boron oxide which influences the high-temperature property of the boron nitride material. The invention provides a new technology, can improve the physical property of boron nitride, has lower preparation cost and is beneficial to industrial production and preparation.

Drawings

FIG. 1 is a comparison of the particle size of boron nitride powder dry and wet milling. The test results are shown in the figure: the effect of dry milling is more pronounced than that of wet milling in the same time.

FIG. 2 is an XRD spectrum of boron nitride powder and boron nitride ceramic after ball milling.

FIG. 3 is a SEM photograph of a refined raw material (a: raw material; b: dry ball milling for 210 min).

FIG. 4 is an SEM picture of fracture morphology of boron nitride ceramics.

FIG. 5 is an SEM photograph of a cross section of the boron nitride-boron powder composite ceramic (a: hot pressed sintered ceramic; b: ceramic after 2h of hot exposure to flowing argon at 2000 ℃).

FIG. 6 shows physical properties of boron nitride-based ceramics.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION