A B4C-TiB2-SiC conductive composite ceramic and its preparation method

Abstract

The present invention discloses a B4C-TiB2-SiC conductive composite ceramic and its preparation method, belonging to the field of ceramic materials. This conductive composite ceramic has a microstructure of TiB2-SiC composite small grains encapsulating large B4C grains, wherein the volume content of TiB2 is 5–20%, and the molar ratio of TiB2 to SiC is 2:3. The conductive composite ceramic is prepared from B4C, TiC, and elemental Si powders. The preparation steps include: weighing the raw material powders according to the designed composition ratio; mixing them uniformly and then thoroughly drying them; and sintering them in a spark plasma sintering furnace in a vacuum atmosphere to prepare the composite ceramic. The present invention creates an encapsulated microstructure of TiB2-SiC composite small grains encapsulating large B4C grains. The introduction of SiC effectively inhibits the growth of TiB2 conductive phase grains and promotes the formation and improvement of the conductive network. Compared to ceramics without SiC, the composite ceramic prepared in this invention exhibits higher electrical conductivity at the same or lower TiB2 content. The preparation process of the present invention is simple and does not require any other special and complicated methods.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic materials, and in particular relates to a B4C-TiB2-SiC conductive composite ceramic and a preparation method thereof. Background Art

[0002] Superhard ceramics, as an advanced ceramic material with ultra-high hardness and high strength, are widely used as wear-resistant parts, and show advantages that are difficult to match with metal materials in extreme environments such as high temperature and corrosion. However, superhard ceramics have poor toughness and are difficult to be quickly and precisely processed using conventional mechanical processing methods, which seriously affects their application potential. Electrospark machining (EDM) technology uses the instantaneous high temperature generated by electric spark discharge between the electrode and the workpiece to etch away the material on the surface of the workpiece. When using EDM processing, the electrode and the workpiece are not in direct contact, and its processability has nothing to do with the mechanical properties of the material. Therefore, it is particularly suitable for ceramic materials with high hardness and poor toughness. EDM processing technology requires that the material has a certain electrical conductivity (≥1S / m), so making the ceramic conductive is a prerequisite for it to be processed using EDM.

[0003] B4C–TiB2 composite ceramics are a type of superhard conductive ceramic. Due to their high electrical conductivity, they can be processed using EDM technology, significantly improving machining efficiency and precision while reducing machining costs. According to EDM principles, high electrical conductivity and low thermal conductivity are beneficial to EDM performance. In B4C–TiB2 composite ceramics, the electrical conductivity of the material is primarily dependent on the content of the conductive phase TiB2. A higher TiB2 content indicates higher electrical conductivity. However, increasing the TiB2 content also increases the thermal conductivity of the composite ceramic. Therefore, reducing the TiB2 content while maintaining or increasing the material's electrical conductivity is key to improving the EDM performance of B4C–TiB2 composite ceramics. Patent ZL202210185924.X utilizes B4C, TiC, and elemental boron as raw materials. By constructing a coating-type microstructure, the material achieves improved electrical conductivity. However, the use of elemental boron in the raw materials is expensive. Summary of the Invention

[0004] To overcome the deficiencies of the prior art, the present invention provides a B4C–TiB2–SiC conductive composite ceramic and a preparation method thereof, in order to further improve the conductivity of the composite ceramic under the premise of reducing the TiB2 content, while also reducing the cost of raw materials.

[0005] The present invention is achieved through the following technical solutions.

[0006] The present invention discloses a B4C-TiB2-SiC conductive composite ceramic having an encapsulated microstructure, namely, small TiB2 and SiC grains encapsulate large B4C grains. The volume content of TiB2 in the conductive composite ceramic is 5-20%, and the molar ratio of TiB2 to SiC is 2:3.

[0007] The present invention also provides a method for preparing the above-mentioned B4C-TiB2-SiC conductive composite ceramic, which specifically comprises the following steps:

[0008] (1) Weigh B4C, TiC and elemental Si powders according to the composition design;

[0009] (2) Mix the weighed powders evenly and dry them thoroughly;

[0010] (3) The dried powder is placed into a graphite mold and placed in a spark plasma sintering furnace for sintering in a vacuum atmosphere.

[0011] As an optimization, in step (1), the particle size of the B4C powder is 10.0–30.0 μm, the particle size of the TiC powder is 0.05–3.0 μm, and the particle size of the elemental Si powder is 0.05–10.0 μm.

[0012] As a further optimization, in step (1), the particle size of the B4C powder is 10.3 μm, the particle size of the TiC powder is 0.05 μm, and the particle size of the elemental Si powder is 0.05 μm.

[0013] As an optimization, in step (3), in the spark plasma sintering furnace: the sintering temperature is 1900-2000°C, the pressure is 30-60 MPa, and the holding time is 5-20 min.

[0014] As a further optimization, in step (3), in the spark plasma sintering furnace: the sintering temperature is 2000° C., the pressure is 50 MPa, and the holding time is 16 min.

[0015] The principle of the present invention is as follows: the raw materials B4C, TiC and Si undergo an in-situ chemical reaction (B4C+TiC+3Si=2TiB2+3SiC) during the sintering process to generate TiB2-SiC ultrafine composite grains; the surface layer of the raw material B4C large particles is consumed by the reaction, and the generated TiB2-SiC composite small grains are distributed around the unreacted B4C grains, forming a coating-type microstructure.

[0016] Compared with the prior art, the present invention has the following technical effects:

[0017] 1. This invention utilizes a specific raw material formulation and optimized particle size to introduce a TiB2–SiC composite phase during the sintering process via an in-situ reaction. This simultaneously creates a microstructure in which small TiB2–SiC composite grains encapsulate large B4C grains. This effectively inhibits TiB2 grain growth during sintering and promotes the formation of a conductive network. Compared to ceramics without SiC, the composite ceramics produced by this invention exhibit higher electrical conductivity at the same or lower TiB2 content.

[0018] 2. The preparation process of the present invention is simple and does not require any other special and complicated methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a microstructure diagram of the fracture surface of the B4C–TiB2–SiC composite ceramic prepared in Example 1 of the present invention;

[0020] The black area is the B4C phase, the gray area is the SiC phase, and the white area is the TiB2 phase. It can be seen that the TiB2 grain size is small due to the pinning effect of the SiC grains; the TiB2–SiC composite grains are distributed around the large B4C grains, forming a good conductive network. DETAILED DESCRIPTION

[0021] In order to further understand the technical content of the present invention, the present invention is described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments.

[0022] Example 1

[0023] 5.64 g of B4C powder with a particle size of 10.3 μm, 1.69 g of TiC powder with a particle size of 0.05 μm, and 1.19 g of elemental Si powder with a particle size of 0.05 μm were weighed respectively. The weighed powders were mixed evenly and dried thoroughly. The dried powders were loaded into a graphite mold and placed in a spark plasma sintering furnace for sintering in a vacuum atmosphere at a sintering temperature of 2000 ° C, a pressure of 50 MPa, and a holding time of 16 min. After natural cooling, B4C–15 vol% TiB2–18.2 vol% SiC conductive composite ceramics were obtained. The test showed that the conductivity of the prepared B4C–TiB2–SiC composite ceramics was 8.5×10 4 S / m.

[0024] As a comparison, 10.3 μm B4C powder, 0.05 μm TiC powder and 0.9 μm amorphous B powder were used as raw materials and the B4C–15 vol% TiB2 composite ceramics were prepared by the same mixing and sintering method. The electrical conductivity of the composite ceramics was 2.8×10 4It can be seen that when using the same B4C and TiC powders, by replacing the simple B powder with simple Si powder, and at the same TiB2 content, the composite ceramics prepared by the present invention have higher electrical conductivity.

[0025] Example 2

[0026] 5.64 g of B4C powder with a particle size of 10.3 μm, 1.69 g of TiC powder with a particle size of 0.05 μm, and 1.19 g of elemental Si powder with a particle size of 2.0 μm were weighed respectively. The weighed powders were mixed evenly and dried thoroughly. The dried powders were loaded into a graphite mold and placed in a spark plasma sintering furnace for sintering in a vacuum atmosphere at a sintering temperature of 2000 ° C, a pressure of 50 MPa, and a holding time of 16 min. After natural cooling, B4C–15 vol% TiB2–18.2 vol% SiC conductive composite ceramics were obtained. The test showed that the conductivity of the prepared B4C–TiB2–SiC composite ceramics was 7.2×10 4 S / m.

[0027] As a comparison, 10.3 μm B4C powder, 0.05 μm TiC powder and 0.9 μm amorphous B powder were used as raw materials and the B4C–15 vol% TiB2 composite ceramics were prepared by the same mixing and sintering method. The electrical conductivity of the composite ceramics was 2.8×10 5 It can be seen that when using the same B4C and TiC powders, by replacing the simple B powder with simple Si powder, and at the same TiB2 content, the composite ceramics prepared by the present invention have higher electrical conductivity.

[0028] Example 3

[0029] 5.97 g of B4C powder with a particle size of 10.3 μm, 1.35 g of TiC powder with a particle size of 0.05 μm, and 0.95 g of elemental Si powder with a particle size of 0.05 μm were weighed respectively. The weighed powders were mixed evenly and dried thoroughly. The dried powders were loaded into a graphite mold and placed in a spark plasma sintering furnace for sintering in a vacuum atmosphere at a sintering temperature of 2000 ° C, a pressure of 50 MPa, and a holding time of 16 min. After natural cooling, B4C–12 vol% TiB2–14.6 vol% SiC conductive composite ceramics were obtained. The test showed that the electrical conductivity of the prepared B4C–TiB2–SiC composite ceramics was 2.8×10 4 S / m.

[0030] As a comparison, 10.3 μm B4C powder, 0.05 μm TiC powder and 0.9 μm amorphous B powder were used as raw materials and the B4C–15 vol% TiB2 composite ceramics were prepared by the same mixing and sintering method. The electrical conductivity of the composite ceramics was 2.8×104 It can be seen that when using the same B4C and TiC powders, the composite ceramics prepared by the present invention can still achieve the same electrical conductivity by replacing the elemental B powder with elemental Si powder and reducing the TiB2 content.

Claims

1. A B4C-TiB2-SiC conductive composite ceramic, characterized in that: The conductive composite ceramic has an encapsulated microstructure, i.e., small TiB2-SiC composite grains are encapsulated around large B4C grains; the volume content of TiB2 in the conductive composite ceramic is 5-20%, and the molar ratio of TiB2 to SiC is 2:3; The preparation method of the B4C-TiB2-SiC conductive composite ceramic comprises the following steps: (1) According to the composition design, B4C, TiC and elemental Si powders are weighed respectively; the particle size of the B4C powder is 10.0-30.0 μm, the particle size of the TiC powder is 0.05-3.0 μm, and the particle size of the elemental Si powder is 0.05-10.0 μm; (2) Mix the powder weighed in step (1) evenly and dry thoroughly; (3) The powder dried in step (2) is placed into a graphite mold and placed in a spark plasma sintering furnace for sintering in a vacuum atmosphere.

2. The B4C-TiB2-SiC conductive composite ceramic according to claim 1, characterized in that: In step (1), the particle size of the B4C powder is 10.3 μm, the particle size of the TiC powder is 0.05 μm, and the particle size of the elemental Si powder is 0.05 μm.

3. The B4C-TiB2-SiC conductive composite ceramic according to claim 1, characterized in that: In step (3), in the spark plasma sintering furnace, the sintering temperature is 1900–2000 °C, the pressure is 30–60 MPa, and the holding time is 5–20 min.

4. The B4C-TiB2-SiC conductive composite ceramic according to claim 3, characterized in that In step (3), in the spark plasma sintering furnace, the sintering temperature is 2000 °C, the pressure is 50 MPa, and the holding time is 16 min.

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