Study On Preparation And Properties Of TiB₂ Based Super High Temperature Ceramics

TiB₂ ceramics have good physical and chemical properties,and their crystal structure bonds are mainly composed of strong covalent bonds and ionic bonds.They have high melting point,high hardness,excellent electrical conductivity and high temperature mechanical properties,and are widely used in nonferrous metal smelting.,wear-resistant structural components,cutting tools and protective materials.However,TiB₂ ceramics have low self-diffusion coefficient and poor sintering performance.As a result,single-phase TiB₂ceramics have lower oxidation resistance,thermal shock resistance and fracture toughness,and thus become the biggest drawback of this material,which limits its wide application.In order to improve the density and fracture toughness of TiB₂ ceramics,we use a variety of sintering methods in this paper,add different toughening phases to observe various properties of the obtained composite materials and study the oxidation behavior of TiB2-5vol.%SiC composites prepared by hot-pressing was investigated.The main research content of this paper is to use different sintering methods to prepare TiB2 matrix composites,and to study the properties of the resulting composites.The experimental methods included composition and microstructure analysis,physical properties testing and mechanical properties testing.TiB2 composites were prepared by reaction sintering,hot-pressing sintering and microwave sintering.The results show that the TiB2-SiC composites prepared by reaction sintering have vickers hardness of 18.6 GPa,bending strength of 635 MPa,fracture toughness of 5.17 MPa·m^1/2,and TiB₂-5vol.%SiC composites prepared by hot-pressing sintering.The Vickers hardness of the material is 21.2 GPa,the flexural strength is 721 MPa,and the fracture toughness is 4.3 MPa·m^1/2.Among them,the TiB2-carbon black composite material obtained by the hot casting method is prepared.The maximum Vickers hardness is 24.5 GPa,the maximum bending strength is 520.1 MPa,and the maximum fracture toughness is 6.8 MPa·m^1/2.The micro-hardness of TiB₂-carbon black composites prepared by microwave sintering is very low,and the bending strength is 350MPa.The fracture toughness is 7.8 MPa·m^1/2.Based on the comparison of microstructure analysis and performance analysis,the oxidation behavior of TiB2-5vol.%SiC composites prepared by hot-press sintering under hot-pressing sintering was studied in detail under different pressures.The results show that,under the pressure of 500 Pa,a large number of holes appear on the surface of the sample.The longer the oxidation time,the lower the thickness and density of the borosilicate glass layer.Under the pressure of 1500 Pa,the microscopic defects of the oxide layer on the surface of the sample are significantly reduced.The longer the oxidation time,the smaller the number,but the thickness of the borosilicate glass layer did not change significantly.The titanium element in the oxide layer was significantly increased compared to the pressure of 500 Pa,and the proportion of the borosilicate glass phase was significantly reduced;at 2500 Pa Under pressure,as the oxidation time prolonged,the number of surface microscopic defects increased significantly,and the thickness of the borosilicate glass layer did not change significantly.At 3500 Pa pressure,the number of microscopic defects on the surface increased significantly with the extension of oxidation time.Titanium boride?TiB₂?is the most stable compound of boron and titanium.It has excellent wear resistance,corrosion resistance,oxidation resistance,and high hardness.It has important applications in spacecraft and space nuclear power systems.With the continuous advancement of powder preparation technology,composite technology level and sintering technology,the application of TiB₂-based multiphase ceramics will become wider and wider in the future.