CN102633504A - Zirconium diboride/silicon carbide composite material and method for preparing same by means of arc melting in-suit reaction - Google Patents

Abstract

The invention discloses a zirconium diboride/silicon carbide composite material and a method for preparing the same by means of an arc melting in-suit reaction. Raw materials for reaction comprise zirconium powder, carbon boride powder and silicon carbide powder; the dried mixed powder is melted by electric arcs under the protection of argon so that the mixed powder reacts; and then the target material can be formed through solidification and crystallization. The zirconium diboride/silicon carbide composite material prepared by the arc melting in-suit reaction method has a microhardness of 24.0+/-0.8 GPa and a breaking tenacity of 6.7+/-0.7 MPa m<1/2>; the obdurability of the composite material is obviously higher than that of the zirconium diboride/silicon carbide composite materials prepared by other methods. Furthermore, the melting solidification preparation method employed in the invention is capable of solving the problems of high requirements for initial materials, complex preparation method, low material density and mechanical performance, high cost and the like in the preparation of the ZrB2-based composite material through solid-state sintering.

Description

A zirconium diboride/silicon carbide composite material and its preparation method using arc melting in-situ reaction

technical field

The invention relates to the technical field of ceramic materials, and more specifically relates to a high-performance zirconium diboride/silicon carbide composite material and a preparation method thereof.

Background technique

Zirconium diboride (ZrB ₂ ) is a metalloid structure compound of hexagonal C32 structure. , Composite materials, refractory materials, electrode materials and nuclear control materials and other fields have been paid attention to and widely used. Many reports have shown that the addition of SiC can improve the oxidation resistance of materials and enhance their mechanical properties. Therefore, people have done a lot of research on the mechanical properties and high temperature properties of zirconium diboride/silicon carbide composites through traditional hot pressing (HP) and pressureless methods. The Chinese patent "a high-strength and high-toughness zirconium diboride-silicon carbide-zirconia ceramic matrix composite material and its preparation method" (application number 201010565353.8, application date 2010.11.30, application publication date: 2011.05.18) discloses the following Zirconium diboride powder, silicon carbide powder and silicon dioxide fiber are used as raw materials to prepare zirconium diboride-silicon carbide-zirconia ceramic matrix composite material and its preparation method through wet mixing, drying, grinding and hot pressing sintering. However, studies have shown that the application of solid-state sintering to prepare zirconium diboride/silicon carbide composites has the following limitations: 1. Due to the strong covalent bonds between ZrB ₂ and SiC, it is difficult to carry out the diffusion process in traditional sintering, and it is difficult to prepare dense Zirconium diboride/silicon carbide composite material with high strength and toughness; Second, in order to improve material properties, it is often necessary to select appropriate sintering aids (such as: CoB, Ni ₃ B ₄ , Y ₂ O ₃ , ZrO _{2 ,} etc.), This will adversely affect the performance of composite materials; 3. The traditional method has strict requirements on raw materials and process, which makes the preparation process complicated and inefficient, and increases the cost of preparation materials; therefore, it is necessary to choose an efficient and cheap method to prepare high High-performance high-temperature ceramic materials are an important way to solve the bottleneck restricting their large-scale application.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, solve the problems existing in the process of preparing zirconium diboride/silicon carbide composite materials by the solid-state sintering method, and provide a fast method for improving the mechanical properties of zirconium diboride/silicon carbide composite materials. Preparation.

The purpose of the present invention is achieved through the following technical solutions:

Zirconium diboride/silicon carbide composite materials are prepared by using zirconium powder, boron carbide powder and silicon carbide powder (common commercial medicines are enough) as raw materials for the reaction. By changing the components, it can be prepared by arc melting in situ reaction. A composite material with zirconium diboride/silicon carbide as the main phase is produced, and C, ZrC, and ZrSi ₂ phases are generated at the same time to realize the compounding of materials; the new phase structure synthesized by melting and reaction can not only make zirconium diboride/silicon carbide Composite materials have higher density, which can also improve their mechanical and high temperature properties.

A method for preparing zirconium diboride/silicon carbide composite material by in-situ reaction by arc melting is carried out according to the following steps:

(1) Use 20-100 mesh zirconium powder (Zr; purity ≥992), boron carbide powder (B ₄ C; purity ≥95) and silicon carbide powder (SiC; purity ≥95) as raw materials for the reaction, according to the chemical reaction according to the substance The amount ratio of Zr: B ₄ C: SiC is 1.56～3:1:0.5～3 to prepare the powder; in the agate mortar, the mixed powder is mixed evenly, the grinding time is 15～60 minutes, and the volume ratio of the prepared water glass and water is The 1:1 solution is added to the mixed powder as a binder, the amount added is 3%-5% of the total mass of the mixed powder, and the wet powder is prefabricated on the graphite plate substrate and pressed into shape with a graphite mold;

(2) Dry the molded sample to remove the influence of moisture: place the sample at room temperature and dry it in the shade for 12 to 24 hours, then heat it to 350°C at a heating rate of 2°C/s in a drying oven. ~450°C and stay at the highest temperature for 0.5~1 hour to dry, during which you can choose to use air or inert gas atmosphere (such as argon, nitrogen, helium)

(3) Arc processing conditions: quickly melt the dried sample by arc (for example, place the sample on the cathode and use the arc for rapid melting), and the entire arc is in a flowing inert atmosphere (such as argon, nitrogen, helium protection Bottom), completed under the process conditions of DC current of 180-250A, voltage of 28-35V, protective gas flow rate of 10L/min and arc scanning speed of 1.00-3.00mm/s.

In the step (1), the purity of the zirconium powder is ≥99.2, the purity of the boron carbide powder is ≥95, and the purity of the silicon carbide powder is ≥95.

In the step (3), the DC current is preferably 200-250A, the voltage is preferably 30-35V, and the arc scanning speed is 1.5-2.5mm/s.

The invention provides a method for preparing zirconium diboride/silicon carbide composite material by means of electric arc melting in-situ reaction. Using ordinary commercial powder, through rapid melting and reaction to obtain materials with high density, controllable microstructure and good mechanical properties. In addition, the method has high preparation efficiency, low energy consumption, and low production cost, and greatly improves the processability of the material and the reliability of the product. It has good industrialization prospect.

The appearance of the zirconium diboride/silicon carbide composite material prepared by the present invention is composed of texture and polycrystalline structure, and the texture-like structure is mainly composed of _ZrB2 rod-like structures embedded in the SiC matrix and arranged neatly, with a well-bonded interface , wherein the width of ZrB ₂ rod-shaped grains is about 1 μm, the length range is 7-10 μm, and the average aspect ratio is 8.0. The growth of ZrB ₂ rod-shaped grains shows a certain direction; the formation of textured structure makes ZrB ₂ and The complex interface between the two phases of SiC increases the material density and crack growth resistance. The microhardness of the tested material is 24.0±0.8GPa, the fracture toughness is 6.7±0.7MPa m ^1/2 , and its strength and toughness are greatly improved compared with the properties of zirconium diboride/silicon carbide composite materials under other methods.

Description of drawings

Fig. 1 is the XRD diffraction pattern of embodiment 1 (XRD, D/Max-2500V Rigaku, Tokyo, Japan)

Fig. 2 is the scanning electron microscope microscopic image (SEM of the polished section of embodiment 1; Hitachi S-4800, Tokyo, Japan)

Fig. 3 is the XRD diffraction pattern of embodiment 4 (XRD, D/Max-2500V Rigaku, Tokyo, Japan)

Fig. 4 is the scanning electron microscope microscopic image (SEM of the polished section of embodiment 4; Hitachi S-4800, Tokyo, Japan)

Fig. 5 is the XRD diffraction pattern of embodiment 5 (XRD, D/Max-2500V Rigaku, Tokyo, Japan)

Fig. 6 is the scanning electron microscope microscopic image (SEM of the polished section of embodiment 5; Hitachi S-4800, Tokyo, Japan)

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with specific embodiments. The hardness test and fracture toughness test are carried out on the prepared materials, the hardness test standard is GB/T 16534-1996 Vickers hardness test method for engineering ceramics, the instrument used is the automatic turret Vickers hardness tester Wolpert Wilson Instruments 432SVD, and the industrial test instrument (Shanghai) Co., Ltd.; the fracture toughness test is based on "Testing Methods for Fracture Toughness of Fine Ceramics," Japanese Industrial Standard No. JIS R 1607, (1995).

Example 1

According to the formula, the Zr: B ₄ C mass ratio is 72: 28, that is, the molar ratio is 1.56: 1 for batching, and the mass fraction of Zr and B ₄ C powder is 30% SiC (equivalent to B ₄ C: SiC molar ratio is 1: 1.5), placed in a mortar and ground for 15 minutes, then added 3wt% water glass solution (the volume ratio of water glass and water is 1: 1) as a binder, and the mixed powder was pressed with a graphite mold On the surface of the graphite substrate, place the sample at room temperature and dry it in the shade for 24 hours, then heat it to 450°C in a drying oven at a heating rate of 2°C/s and stay there for 1 hour, and place the dried sample on the cathode The arc is rapidly melted, and the entire arc is under the protection of flowing argon gas. It is completed under the condition of 250A DC, 35V voltage, 10L/min shielding gas flow rate and 1.67mm/s arc scanning speed. Finally, a zirconium diboride/silicon carbide composite block material with a length, width, and thickness of 50mm×10mm×3mm was prepared. The microhardness of the material was 24.0±0.8GPa, and the fracture toughness was 6.7±0.7MPa m ^1/2 . XRD analysis is as shown in the accompanying drawing.

Example 2

According to the formula, the Zr: B ₄ C mass ratio is 72: 28, that is, the molar ratio is 1.56: 1 for batching, and the mass fraction of Zr and B ₄ C powder is 30% SiC (equivalent to B ₄ C: SiC molar ratio is 1: 1.5), put it in a mortar and grind for 15 minutes, then add 5wt% water glass solution (the volume ratio of water glass and water is 1: 1) as a binder, and compress the mixed powder with a graphite mold With the surface of the graphite substrate, place the sample at room temperature and dry it in the shade for 12 hours, then heat it to 350°C in a drying furnace at a heating rate of 2°C/s and stay for 0.5 hours, and place the dried sample on the cathode The arc is rapidly melted, and the entire arc is under the protection of flowing argon gas. It is completed under 200A DC, 30V voltage, 10L/min shielding gas flow rate and 1.67mm/s arc scanning speed. Finally, the length, width and thickness are 50mm×10mm. ×3mm zirconium diboride/silicon carbide composite bulk material.

Example 3

The difference from Example 1 is that it is completed at an arc scanning speed of 2.5mm/s, and a zirconium diboride/silicon carbide composite block material is finally prepared.

Example 4

The difference from Example 1 is that according to the formula, Zr: B ₄ C mass ratio is 77: 23 and the ingredients are weighed, that is, the ingredients are weighed according to x: y=2: 1 in the chemical formula (1), 180A DC, 28V voltage, 10L/min shielding gas flow rate and 1mm/s arc scanning speed, the ZrB ₂ -ZrC-C-SiC composite bulk material with a size of 50mm×10mm×3mm was finally prepared. The microhardness of the material is 20.0±1.0GPa, the fracture toughness is 5.8±0.5MPa m ^1/2 , and its SEM and XRD analysis are shown in the accompanying drawings.

Example 5

The difference from Example 1 is: According to the formula, Zr: B ₄ C mass ratio is 83:17, and the ingredients are weighed according to x:y=3:1 in the chemical formula (1), 200A direct current, 30V voltage, The shielding gas flow rate of 10L/min and the arc scanning speed of 3mm/s finally prepared a ZrB ₂ -ZrC-ZrSi ₂ -SiC composite bulk material with a size of 50mm×10mm×3mm. The microhardness of the material is 16.0±0.9GPa, the fracture toughness is 4.9±0.4MPa m ^1/2 , and its SEM and XRD analysis are shown in the accompanying drawings.

Example 6

The difference from Example 1 is that the ZrB ₂ -SiC composite bulk material can be prepared by adding SiC with a mass fraction of 10%, that is, when the molar ratio of the reaction material Zr:B ₄ C:SiC=1.56:1:0.5.

Example 7

The difference from Example 1 is that when SiC with a mass fraction of 60% is added, that is, when the molar ratio of reaction materials Zr:B ₄ C:SiC=1.56:1:3, different ZrB ₂ -SiC composite blocks can be prepared Material.

In the above examples, different raw material ratios and process parameters were used for preparation, and the prepared composite block material was mainly composed of zirconium diboride/silicon carbide, and compared with the materials prepared in the prior art, the performance was significantly improved . During the preparation process, C, ZrSi ₂ , and ZrC phases will be generated according to the ratio of raw materials. When Zr:B ₄ C=1.56:1, B ₄ C will be in excess, and when Zr:B ₄ C=2:1 and Zr:B ₄ C=3:1, the reaction will proceed completely. However, in practice, B ₄ C will be lost, so when B ₄ C is required to be excessive in preparation, a relatively pure ZrB ₂ -SiC composite material can be obtained.

The present invention is not limited to the technology described in the example, its description is illustrative, not restrictive, the authority of the present invention is defined by the claims, based on methods such as changes, recombination, etc. that those skilled in the art can according to the present invention The obtained technologies related to the present invention are all within the protection scope of the present invention.

Claims (10)

1. A zirconium diboride/silicon carbide composite material, selects zirconium powder, boron carbide powder and silicon carbide powder as reaction raw materials, takes zirconium diboride/silicon carbide as the main phase, and proceeds according to the following steps: (1) Use zirconium powder, boron carbide powder and silicon carbide powder as reaction raw materials, according to the chemical reaction, according to the material ratio Zr: B ₄ C: SiC is 1.56 ~ 3: 1: 0.5 ~ 3 to prepare powder, mix evenly, add Mix 3%-5% of the binder in the total mass of the powder, prefabricate the wet powder on the graphite plate substrate and press it with a graphite mold; (2) Dry the molded sample to remove the influence of moisture (3) Arc processing conditions: quickly melt the dried sample with an arc, the entire arc is in a flowing inert atmosphere, the DC current is 180-250A, the voltage is 28-35V, the flow rate of the protective gas is 10L/min and the arc The scanning speed is completed under the process conditions of 1.00-3.00mm/s. 2. A kind of zirconium diboride/silicon carbide composite material according to claim 1, characterized in that, in the step (1), the purity of zirconium powder is ≥992, the purity of boron carbide powder is ≥95, and the purity of silicon carbide powder is ≥95. The purity of the powder is ≥95, and the mesh number of the powder is 20-100. 3. A kind of zirconium diboride/silicon carbide composite material according to claim 1, characterized in that, in the step (1), the mixed powder is mixed evenly in an agate mortar, and the grinding time is 15 to 60 minutes; the binder is a solution of water glass and water with a volume ratio of 1:1. 4. A zirconium diboride/silicon carbide composite material according to claim 1, characterized in that, in the drying step of said step (2), after the sample is placed in room temperature and dried in the shade for 12 to 24 hours Heat to 350-450°C at a heating rate of 2°C/s in the drying furnace and stay at the highest temperature for 0.5-1 hour. During this period, air or inert gas atmosphere can be used, such as argon, nitrogen, and helium. 5. A zirconium diboride/silicon carbide composite material according to claim 1, characterized in that, in the step (3), the DC current is preferably 200-250A, the voltage is preferably 30-35V, and the arc scanning speed is 1.5-2.5mm/s, the inert atmosphere is argon, nitrogen or helium. 6. A method for preparing zirconium diboride/silicon carbide composite material by in-situ reaction by arc melting, characterized in that, it is carried out according to the following steps: (1) Use zirconium powder, boron carbide powder and silicon carbide powder as reaction raw materials, according to the chemical reaction, according to the material ratio Zr: B ₄ C: SiC is 1.56 ~ 3: 1: 0.5 ~ 3 to prepare powder, mix evenly, add Mix 3%-5% of the binder in the total mass of the powder, prefabricate the wet powder on the graphite plate substrate and press it with a graphite mold; (2) Dry the molded sample to remove the influence of moisture (3) Arc processing conditions: quickly melt the dried sample with an arc, the entire arc is in a flowing inert atmosphere, the DC current is 180-250A, the voltage is 28-35V, the flow rate of the protective gas is 10L/min and the arc The scanning speed is completed under the process conditions of 1.00-3.00mm/s. 7. The method for preparing zirconium diboride/silicon carbide composite material by in-situ reaction of a kind of arc melting according to claim 6, characterized in that, in the step (1), the purity of the zirconium powder is ≥99.2, and the boron carbide The purity of the powder is ≥95, the purity of the silicon carbide powder is ≥95, and the mesh number of the powder is 20-100. 8. a kind of arc melting in-situ reaction according to claim 6 prepares the method for zirconium diboride/silicon carbide composite material, it is characterized in that, in described step (1), in agate mortar, mixed powder is mixed uniform, and the grinding time is 15-60 minutes; the binder is a solution of water glass and water with a volume ratio of 1:1. 9. the method for preparing zirconium diboride/silicon carbide composite material according to a kind of arc melting in-situ reaction according to claim 6, it is characterized in that, in the drying step of described step (2), the sample is placed at room temperature After drying in the environment for 12-24 hours, heat in a drying oven at a heating rate of 2°C/s to 350-450°C and stay at the highest temperature for 0.5-1 hour. During this period, you can choose to use air or an inert gas atmosphere, such as Argon, Nitrogen, Helium. 10. A method for preparing zirconium diboride/silicon carbide composite material by arc melting in-situ reaction according to claim 6, characterized in that, in the step (3), the direct current is preferably 200-250A, and the voltage is preferably 30-35V, the arc scanning speed is 1.5-2.5mm/s, and the inert atmosphere is argon, nitrogen or helium.

Images