This application claims the benefit of priority from Chinese Patent Application No. 202210485924.X, filed on May 6, 2022. The content of the aforementioned application, including any intervening amendments thereto, is incorporated herein by reference in its entirety.
This application relates to ceramic materials, and more particularly to an electro-conductive B4C—TiB2 composite ceramic and a preparation method thereof.
B4C has been widely used in bulletproof armor, wear-resistant devices, aerospace and nuclear industries because of its high hardness, low density, good chemical stability, and large neutron-absorption cross section. Due to the presence of covalent bonds, B4C has poor sintering performance, which makes it difficult to achieve densification. Furthermore, the low fracture toughness of monolithic B4C ceramic leads to poor machining efficiency and accuracy and high cost, which limit the application of the monolithic B4C ceramic.
The introduction of a second phase TiB2 into the B4C matrix to form B4C—TiB2 composite ceramics can not only significantly improve the sintering performance and mechanical properties of B4C ceramics, but also greatly reduce the electrical resistivity thereby meeting the requirements of electrical discharge machining (EDM). Usually, a material with lower electrical resistivity is more suitable for the EDM processing. Therefore, a key to improving the EDM processing performance of B4C—TiB2 composite ceramics is reducing the electrical resistivity. The most effective way to reduce the electrical resistivity is increasing the conductive phase content in composite ceramics. However, the increased content of TiB2 conductive phase in the B4C—TiB2 composite ceramics will bring the following problems: (1) increasing the overall density of the composite ceramics (the density of TiB2 is about 1.8 times that of B4C); (2) reducing the hardness of composite ceramics (the hardness of TiB2 is lower than that of B4C); and (3) increasing the raw material cost. The above problems limit the application of B4C—TiB2 composite ceramic in lightweight armor. In conventional methods, a lower electrical resistivity of B4C—TiB2 composite ceramics is achieved mainly at the expense of other properties or cost.
In view of the deficiencies in the prior art, this application provides an electro-conductive B4C—TiB2 composite ceramic having a high electrical conductivity at low TiB2 content and a preparation method thereof In the microstructure of the B4C—TiB2 composite ceramic provided herein, the large B4C grains are coated by small TiB2 grains.
Technical solutions of this application are described as follows.
In a first aspect, this application provides an electro-conductive B4C—TiB2 composite ceramic, wherein the electro-conductive B4C—TiB2 composite ceramic has a microstructure in which B4C grains are coated by TiB2 grains; a grain size of the B4C grains is much larger than that of the TiB2 grains; and a TiB2 volume percentage in the electro-conductive B4C—TiB2 composite ceramic is 10˜30%;
wherein the electro-conductive B4C—TiB2 composite ceramic is prepared through steps of:
In a second aspect, this application further provides a method for preparing the electro-conductive B4C—TiB2 composite ceramic, including:
In an embodiment, the sintering is performed at 2000° C. and 50 MPa for 5˜20 min.
Compared to the prior art, this application has the following beneficial effects.
The patent or application file contains
The technical solutions of the present disclosure will be further described in detail below in conjunction with the accompanying drawings and embodiments, but the embodiments below are not intended to limit the disclosure.
5.03 g of B4C powder with a particle size of 10.3 μm, 1.83 g of TiC powder with a particle size of 0.05 and 2.19 g of amorphous B powder with a particle size of 0.9 μm were weighed, mixed uniformly, and dried to obtain a mixed powder. The mixed powder was loaded into a graphite mold, subjected to sintering in a spark plasma sintering furnace under vacuum at 2000° C. and 50 MPa for 16 min, and cooled naturally to obtain an electro-conductive B4C-15 vol % TiB2 composite ceramic. As demonstrated by the performance test, the prepared B4C-15 vol % TiB2 composite ceramic had a relative density of 98.7%, a three-point flexural strength of 676 MPa, a Vickers hardness of 29.0 GPa, a fracture toughness of 5.3 MPa·m1/2, and an electrical conductivity of 2.8×104 S/m.
A B4C-15 vol % TiB2 composite ceramic prepared from 10.3 μm B4C powder and 2.5 μm TiB2 powder through the same mixing and sintering process was used as comparison. As demonstrated by the performance test, the obtained B4C-15 vol % TiB2 composite ceramic had a relative density of 95.3%, a three-point flexural strength of 552 MPa, a Vickers hardness of 27.5 GPa, a fracture toughness of 4.4 MPa·m1/2, and an electrical conductivity of 4.3×103 S/m.
As shown in
5.99 g of B4C powder with a particle size of 3.1 μm, 1.22 g of TiC powder with a particle size of 0.8 μm, and 1.46 g of amorphous B powder with a particle size of 0.9 μm were weighed, mixed uniformly, and dried to obtain a mixed powder. The mixed powder was loaded into a graphite mold, subjected to sintering in a spark plasma sintering furnace under vacuum at 2000° C. and 50 MPa for 16 min, and cooled naturally to obtain an electro-conductive B4C-15 vol % TiB2 composite ceramic. As demonstrated by the performance test, the prepared B4C-15 vol % TiB2 composite ceramic had a relative density of 99.5%, a three-point flexural strength of 780 MPa, a Vickers hardness of 31.8 GPa, a fracture toughness of 5.8 MPa·m1/2, and an electrical conductivity of 3.3×103 S/m.
B4C-15 vol % TiB2 composite ceramic prepared from 3.1 μm B4C powder and 2.5 μm TiB2 powder through the same mixing and sintering method was used as comparison. As demonstrated by the performance test, the obtained B4C-15 vol % TiB2 composite ceramic had a relative density of 98.65%, a three-point flexural strength of 638 MPa, a Vickers hardness of 29.2 GPa, a fracture toughness of 4.9 MPa·m1/2, and an electrical conductivity of 2.1×103 S/m.
4.07 g of B4C powder with a particle size of 10.3 μm, 2.45 g of TiC powder with a particle size of 0.8 and 2.91 g of amorphous B powder with a particle size of 0.9 μm were weighed, mixed uniformly, and dried to obtain a mixed powder. The mixed powder was loaded into a graphite mold, subjected to sintering in a spark plasma sintering furnace under vacuum at 2000° C. and 50 MPa for 16 min, and cooled naturally to obtain an electro-conductive B4C-20 vol % TiB2 composite ceramics. As demonstrated by the performance test, the prepared B4C-20 vol % TiB2 composite ceramic had a relative density of 98.1%, a three-point flexural strength of 701 MPa, a Vickers hardness of 28.5 GPa, a fracture toughness of 6.2 MPa·m1/2, and an electrical conductivity of 6.9×104 S/m.
B4C-20 vol % TiB2 composite ceramic prepared from 10.3 μm B4C powder and 2.50 μm TiB2 powder by the same mixing and sintering method was used as comparison. As demonstrated by the performance test the obtained B4C-20 vol % TiB2 composite ceramic had a relative density of 93.5%, a three-point flexural strength of 587 MPa, a Vickers hardness of 27.6 GPa, a fracture toughness of 5.1 MPa·m1/2, and an electrical conductivity of 1.6×104 S/m.
Number | Date | Country | Kind |
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202210485924.X | May 2022 | CN | national |