阅读说明：本技术 采用热压与热等静压制备硼酸铝晶须增强非金属基复合材料的方法 (Method for preparing aluminum borate whisker reinforced non-metal-based composite material by adopting hot pressing and hot isostatic pressing ) 是由 贾碧 施金良 江寒梅 王如转 万鑫 朱俊 王智远 吴慧明 吴春艳 张丹瑕 张文轩 于 2021-06-23 设计创作，主要内容包括：本发明公开了一种采用热压与热等静压制备硼酸铝晶须增强非金属基复合材料的方法,包括以下步骤：a.将硼酸铝晶须和非金属材料混合并球磨处理；b.将球磨后的混合料先进行真空热压烧结处理后再进行热等静压处理；经过前期的热压烧结后,复合材料已经达到了一定的相对密度,可制备出基本不含开口气孔的烧结体,再对其进行热等静压处理,主要是通过扩散蠕变机制来进一步提高相对密度,而扩散蠕变的速度与应力成正比,因此高的热等静压压力能够进一步消除体系内的气孔,愈合一些结构缺陷,从而提高材料的相对密度；而且由于热等静压是对试样施以各向同等的压力,因此烧结体的结构更加均匀。(The invention discloses a method for preparing an aluminum borate whisker reinforced nonmetal-based composite material by hot pressing and hot isostatic pressing, which comprises the following steps: a. mixing and ball-milling aluminum borate crystal whiskers and a non-metallic material; b. carrying out vacuum hot-pressing sintering treatment on the ball-milled mixture and then carrying out hot isostatic pressing treatment; after the composite material is subjected to the early hot pressing sintering, the composite material reaches a certain relative density, a sintered body basically not containing open pores can be prepared, and then hot isostatic pressing treatment is carried out on the sintered body, the relative density is further improved mainly through a diffusion creep mechanism, and the diffusion creep speed is in direct proportion to stress, so that the high hot isostatic pressing pressure can further eliminate the pores in a system and heal some structural defects, and the relative density of the material is improved; further, since hot isostatic pressing is performed by applying an equal pressure to the sample, the structure of the sintered body is more uniform.)

1. A method for preparing an aluminum borate whisker reinforced non-metal matrix composite material by hot pressing and hot isostatic pressing is characterized by comprising the following steps: the method comprises the following steps:

a. mixing and ball-milling aluminum borate crystal whiskers and a non-metallic material;

b. and carrying out vacuum hot-pressing sintering treatment on the ball-milled mixture, and then carrying out hot isostatic pressing treatment.

2. The method of preparing an aluminum borate whisker reinforced non-metal based composite material by hot pressing and hot isostatic pressing according to claim 1, wherein: in the step a, the non-metallic material is alumina ceramic.

3. The method of preparing an aluminum borate whisker reinforced non-metal based composite material by hot pressing and hot isostatic pressing according to claim 2, wherein: in the step a, the aluminum borate whisker accounts for 1-50% of the volume of the composite material.

4. The method of preparing an aluminum borate whisker reinforced non-metal based composite material by hot pressing and hot isostatic pressing according to claim 3, wherein: in the step a, the length of the aluminum borate whisker is 1-50 μm, and the diameter of the aluminum borate whisker is 0.05-1.0 μm.

5. The method of preparing an aluminum borate whisker reinforced non-metal based composite material by hot pressing and hot isostatic pressing according to claim 1, wherein: in the step b, the hot-pressing sintering temperature is 1300-1650 ℃, and the sintering pressure is 5-60 MPa.

6. The method of preparing an aluminum borate whisker reinforced non-metal based composite material by hot pressing and hot isostatic pressing according to claim 5, wherein: in the step b, the hot isostatic pressing temperature is 1300-1500 ℃, the pressure is 80-195 MPa, and the heat preservation time is 30-180 min.

7. The method of preparing an aluminum borate whisker reinforced non-metal based composite material by hot pressing and hot isostatic pressing according to claim 1, wherein: in the step a, adding the aluminum borate whisker, the non-metallic material and the zirconia grinding ball into a ball milling tank for ball milling.

8. The method for preparing the aluminum borate whisker reinforced non-metal based composite material according to claim 7, characterized in that: and (a) ball-milling until the particle size of the powder is less than 1.0 mu m.

Technical Field

The invention relates to the field of aluminum borate whisker reinforced non-metal-based composite materials, in particular to a method for preparing an aluminum borate whisker reinforced non-metal-based composite material by adopting hot pressing and hot isostatic pressing.

Background

Aluminum borate whiskers were first discovered by a japanese scientist study to have extremely high young's modulus, greater tensile strength and mohs hardness. The aluminum borate whisker has various varieties and the chemical general formula of the aluminum borate whisker is nAl₂O₃·B₂O₃Depending on the sintering temperature and the preparation method, 9Al is commonly used₂O₃·2B₂O₃、Al₂O₃·B₂O₃、2Al₂O₃·B₂O₃These three types. Wherein 9Al₂O₃·2B₂O₃Has a density of 2.93g cm^-3Melting point of about 1450 ℃, high hardness, high strength, insolubility in acid and alkaline solutions, best comprehensive performance, low price and suitability for large-scale production. Non-metallic materials, such as alumina ceramic materials, have excellent properties such as high hardness, high strength, high temperature resistance, wear resistance, corrosion resistance, and the like, and are widely used for structural ceramics and wear-resistant elements. Poor fracture toughness limits the industrial applicability of alumina ceramic materials due to their inherent brittleness. In the prior art, aluminum borate whisker reinforced and toughened non-metallic materials (including inorganic non-metallic materials and high polymer materials) are not adopted.

Disclosure of Invention

In view of the above, the present invention provides a method for preparing an aluminum borate whisker reinforced non-metal matrix composite material by hot pressing and hot isostatic pressing, so as to improve the properties of the composite material, such as bending strength, hardness, fracture toughness, and the like.

The method for preparing the aluminum borate whisker reinforced non-metal-based composite material by adopting hot pressing and hot isostatic pressing comprises the following steps of:

a. mixing and ball-milling aluminum borate crystal whiskers and a non-metallic material;

b. carrying out vacuum hot-pressing sintering treatment on the ball-milled mixture and then carrying out hot isostatic pressing treatment;

further, in the step a, the non-metal material is a special ceramic material containing alumina ceramic;

further, in the step a, the aluminum borate whisker accounts for 1-50% of the volume of the composite material;

further, in the step a, the length of the aluminum borate whisker is 1-50 μm, and the diameter of the aluminum borate whisker is 0.05-1.0 μm;

further, in the step b, the hot-pressing sintering temperature is 1300-1650 ℃, and the sintering pressure is 5-60 MPa;

further, in the step b, the hot isostatic pressing temperature is 1300-1500 ℃, the pressure is 80-195 MPa, and the heat preservation time is 30-180 min;

further, in the step a, adding the aluminum borate whisker, the non-metallic material and the zirconia grinding ball into a ball-milling tank for ball-milling;

further, in the step a, ball milling is carried out until the particle size of the powder is less than 1.0 μm.

The invention has the beneficial effects that: according to the method for preparing the aluminum borate whisker reinforced non-metal-based composite material by adopting hot pressing and hot isostatic pressing, after the composite material is subjected to hot pressing sintering in the early stage, a sintered body basically not containing open pores can be prepared, hot isostatic pressing treatment is carried out on the sintered body, the relative density is further improved mainly through a diffusion creep mechanism, and the diffusion creep speed is in direct proportion to stress, so that the pores in the system can be further eliminated by high hot isostatic pressing pressure, and some structural defects are healed, so that the relative density of the material is improved; moreover, since the hot isostatic pressing is performed on the sample with the same pressure, the structure of the sintered body is more uniform; in addition to the further enhancement of the solid solution strengthening effect, the three causes result in further improvement of the bending strength, the hardness and the fracture toughness of the composite material.

Drawings

The invention is further described below with reference to the following figures and examples:

FIG. 1 is an SEM image of a cross section of a sample: (a) hot pressing and sintering; (b) hot pressing sintering and hot isostatic pressing sintering;

FIG. 2 is an EDS diagram of an aluminum borate reinforced alumina ceramic under (a) hot press sintering (HP) and (b) hot isostatic pressing sintering (HIP);

FIG. 3 is a graph showing the content of B, O, Al and Ti in an aluminum borate-reinforced alumina ceramic without hot isostatic pressing sintering and hot isostatic pressing sintering.

Detailed Description

The method for preparing the aluminum borate whisker reinforced non-metal matrix composite material by adopting hot pressing and hot isostatic pressing comprises the following steps:

a. mixing and ball-milling aluminum borate crystal whiskers and a non-metallic material;

b. carrying out vacuum hot-pressing sintering treatment on the ball-milled mixture and then carrying out hot isostatic pressing treatment; after the composite material is subjected to the early hot pressing sintering, the composite material reaches a certain relative density, a sintered body basically not containing open pores can be prepared, and then hot isostatic pressing treatment is carried out on the sintered body, the relative density is further improved mainly through a diffusion creep mechanism, and the diffusion creep speed is in direct proportion to stress, so that the high hot isostatic pressing pressure can further eliminate the pores in a system and heal some structural defects, and the relative density of the material is improved; moreover, since the hot isostatic pressing is performed on the sample with the same pressure, the structure of the sintered body is more uniform; in addition to the further enhancement of the solid solution strengthening effect, the three causes result in further improvement of the bending strength, the hardness and the fracture toughness of the composite material.

In this embodiment, in the step a, the non-metallic material is alumina ceramic; adopting aluminum borate crystal whisker to reinforce the non-metallic material; the fracture strength of a composite material is primarily dependent on the size of the largest grains or clusters in the microstructure of the material. The increase of the fracture toughness of the composite material is mainly caused by whisker toughening, the aluminum borate whisker liquefied in the sintering process is extruded by the crystal grains and recrystallized on the surface of the crystal grains to form the whisker similar to a needle shape, and meanwhile, the bridging phenomenon occurs among partial whiskers. Through the increase in fracture toughness of the composite material caused by bridging of the whiskers. Meanwhile, the fracture toughness of the material is further improved by crack deflection, bridging and the like caused by toughening of the whiskers. The aluminum borate whisker has various varieties and the chemical general formula of the aluminum borate whisker is nAl₂O₃·B₂O₃Depending on the sintering temperature and the preparation method, 9Al is commonly used₂O₃·2B₂O₃、Al₂O₃·B₂O₃、2Al₂O₃·B₂O₃These three types. Wherein 9Al₂O₃·2B₂O₃Has a density of 2.93g cm^-3Melting point of about 1450 ℃, high hardness, high strength, insolubility in acid and alkaline solutions, best comprehensive performance, low price and suitability for large-scale production. The wear resistance of ceramic materials is closely related to the hardness and toughness of the ceramic materials, and the greater the strength and toughness of the ceramic materials, the better the wear resistance of the ceramic materials. Non-woven fabricThe alumina ceramics containing aluminum borate added thereto have poor wear properties because of their low toughness, although they have high hardness. Adding aluminum borate whisker into an alumina ceramic raw material system, and sintering at a temperature higher than the melting point of the whisker to ensure that the whisker plays a role of a flux and realize a liquid phase sintering process.

In the embodiment, in the step a, the aluminum borate whisker accounts for 1-30% of the volume of the composite material; with the increase of the volume fraction of the aluminum borate whiskers, the bending strength and the hardness of the alumina ceramic matrix composite material tend to increase and then decrease, and the fracture toughness of the material gradually increases. The wear rate of the composite material shows a trend of first decreasing and then increasing along with the increase of the volume fraction of the aluminum borate whiskers.

In the embodiment, in the step a, the length of the aluminum borate whisker is 1 to 50 μm, and the diameter thereof is 0.05 to 1.0 μm.

In the embodiment, in the step b, the hot-pressing sintering temperature is 1300-1650 ℃, and the sintering pressure is 5-60 MPa; the hot isostatic pressing temperature is 1380-1480 ℃, the pressure is 80-195 MPa, and the heat preservation time is 30-180 min. The number of voids in the cross-section was also reduced after the samples were hiped, indicating that hiping aids in the expulsion of voids in the sintered body. In addition, it can be seen from the figure that the proportion of transgranular fracture in the sample after the hot isostatic pressing treatment is increased, which indicates that the bonding force at the grain boundary of the sample is further strengthened.

In the embodiment, in the step a, aluminum borate whiskers, a non-metallic material and zirconia grinding balls are added into a ball milling tank for ball milling;

in this embodiment, in step a, the powder is ball-milled until the particle size is smaller than 1.0 μm.

Example one

(group a) the method for preparing an aluminum borate whisker reinforced non-metal matrix composite material using hot pressing and hot isostatic pressing of this example comprises the steps of:

a. mixing aluminum borate whisker 9Al₂O₃·2B₂O₃(10% by volume) and Al₂O₃(72% by volume), TiB₂(18% volume percentage) and zirconia are added into a ball milling tank for ball milling until the granularity of the powder is less than 1.0 μm;

b. and (3) carrying out vacuum hot-pressing sintering on the ball-milled mixture, wherein the sintering pressure is 36MPa, and the sintering temperature is 1550 ℃ to obtain the compact.

Group B: step a is the same as above;

step b: and (3) carrying out vacuum hot-pressing sintering on the ball-milled mixture, wherein the sintering pressure is 36MPa, the sintering temperature is 1550 ℃ to obtain a compact, and then carrying out hot isostatic pressing treatment on the compact for 60 minutes in an environment with the pressure of 150MPa and the temperature of 1430 ℃.

The test specimens obtained in example one and the test specimens of comparative example were subjected to the test: group A: the average grain size is 1.2 mu m, and the section has more pores; group B: the average grain size is 2.3 μm, and the cross-sectional pores are small. As shown in FIG. 1, the average grain size of the samples after hot isostatic pressing at 150MPa grew from 1.2 μm to 2.3. mu.m. The hot isostatic pressing treatment is carried out, which is equivalent to prolonging the sintering time, and although the temperature is lower and is only 1430 ℃, the sintering pressure of 140 MPa improves the migration and diffusion rate and the grain boundary moving rate of various substances in the material system, thereby causing the growth of grains. It can also be seen that the number of voids in the cross-section is also reduced after the sample is hiped, indicating that hiping aids in the venting of the voids in the sintered body. In addition, it can be seen from the figure that the proportion of transgranular fracture in the sample after the hot isostatic pressing treatment is increased, which indicates that the bonding force at the grain boundary of the sample is further strengthened.

FIG. 2 is an EDS diagram of an aluminum borate reinforced alumina ceramic under hot press sintering (HP) and (b) hot isostatic pressing sintering (HIP); FIG. 3 is a graph showing the content of B, O, Al and Ti in an aluminum borate-reinforced alumina ceramic without hot isostatic pressing sintering and hot isostatic pressing sintering; as can be seen from fig. 2 and 3, the amount of titanium element dissolved in the binder phase aluminum borate increases after the hot isostatic pressing treatment. This indicates that the hot isostatic pressing treatment enhances the solid solution strengthening effect of the aluminum borate phase.

Properties of hot pressed and hot isostatic pressed sintered specimens:

as can be seen from the table above, the relative density of the ceramic increased from 98.76% to 99.81% after the hiping. After the material is subjected to the hot pressing sintering in the early stage, the material reaches a certain relative density, the hot isostatic pressing treatment is carried out on the material, the relative density is further improved mainly through a diffusion creep mechanism, and the diffusion creep speed is in direct proportion to the stress, so that the high hot isostatic pressing pressure can further eliminate air holes in a system and heal some structural defects, and the relative density of the material is improved; moreover, since the hot isostatic pressing is performed on the sample with the same pressure, the structure of the sintered body is more uniform; in addition, the solid solution strengthening effect is further enhanced, and the bending strength, the hardness and the fracture toughness of the material are improved due to the three reasons.

Example two

The method for preparing the aluminum borate whisker reinforced non-metal matrix composite material by adopting hot pressing and hot isostatic pressing comprises the following steps:

a. mixing aluminum borate whisker 9Al₂O₃·2B₂O₃(20% by volume) and Al₂O₃(67% by volume), TiB₂(13% volume ratio) and zirconia are added into a ball milling tank for ball milling until the particle size of the powder is less than 1.0 μm; the length of the aluminum borate whisker is 5 μm, and the diameter of the aluminum borate whisker is 0.4 μm;

b. and (3) carrying out vacuum hot-pressing sintering on the ball-milled mixture, wherein the sintering pressure is 5MPa, the sintering temperature is 1300 ℃ to obtain a compact, and then carrying out hot isostatic pressing treatment on the compact for 60 minutes under the environment of the pressure of 80MPa and the temperature of 1380 ℃.

EXAMPLE III

The method for preparing the aluminum borate whisker reinforced non-metal matrix composite material by adopting hot pressing and hot isostatic pressing comprises the following steps:

a. mixing aluminum borate whisker 9Al₂O₃·2B₂O₃(10% by volume) and Al₂O₃(80% by volume))，TiB₂Adding the powder (10% by volume) and zirconia into a ball milling tank for ball milling until the particle size of the powder is less than 1.0 μm; the length of the aluminum borate whisker is 10 mu m, and the diameter of the aluminum borate whisker is 0.8 mu m;

b. and (3) carrying out vacuum hot-pressing sintering on the ball-milled mixture at 60MPa and 1650 ℃ to obtain a compact, and carrying out hot isostatic pressing on the compact for 30 minutes in an environment with 195MPa and 1480 ℃.

Example four

The method for preparing the aluminum borate whisker reinforced non-metal matrix composite material by adopting hot pressing and hot isostatic pressing comprises the following steps:

a. mixing aluminum borate whisker 9Al₂O₃·2B₂O₃(30% by volume) and Al₂O₃(50% by volume), TiB₂Adding the powder (20% by volume) and zirconia into a ball milling tank, and ball milling until the particle size of the powder is less than 1.0 μm; the length of the aluminum borate whisker is 50 μm, and the diameter of the aluminum borate whisker is 1.0 μm;

b. and (3) carrying out vacuum hot-pressing sintering on the ball-milled mixture, wherein the sintering pressure is 36MPa, the sintering temperature is 1550 ℃ to obtain a compact, and then carrying out hot isostatic pressing treatment on the compact for 180 minutes in an environment with the pressure of 170MPa and the temperature of 1450 ℃.

Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.