Research On Preparation Of ZrB₂-MoSi₂Ultra-high Temperature Ceram

ZrB2is a kind of good high temperature ceramic material. It has the characteristicsof low density, high melting point. It is the material of space needed, often used forsurface of spacecraft, the spacecraft against flight and atmospheric friction generated inthe process of high temperature, and has high hardness and fracture toughness. But theharder requirements monomer preparation of ceramics. MoSi2has high melting point,good conductivity and thermal conductivity. It were found after nickel base alloy as acompetitive superior high temperature material, especially good oxidation resistance athigh temperature is particularly noteworthy.This experiment USES the different components of ZrB2-MoSi2powder, afterforming, respectively by discharge plasma, no pressure and hot pressing sintering, andthe using X-ray diffraction (XRD), analysis of the diffraction pattern of the ceramic,analyzing the composition of the material composition and so on, using SEM and backscattering technology to the ceramic microstructure was analyzed, and compared to thesame materials with different composition and different sintering conditions ofcomposition and organization structure.Discharge plasma sintering preparation, sintering temperature of1750℃under thebest pressure holding time and sintering is10min and50mpa, respectively. In theoptimization process, the preparation of SPS ZrB2-MoSi2ceramic apparent densityincreased with the increase of MoSi2roughly, MoSi2is greater than15vol.%apparentdensity can be over99%, after more than35vol.%after apparent density almost nogrowth. Main phase grain for about5-9mu m, compared with the initial powder is notgood. Bending strength increased at first and lowered later with MoSi2highest ZrB2-30vol.%of MoSi2ceramic porcelain441.29MPa; Hardness increased at first and loweredlater with MoSi2most high ZrB2-25vol.%17.62GPa of MoSi2ceramics; Fracturetoughness is a small rise, with the increase of MoSi2first decreases after a maximum ofZrB2-15vol.%of MoSi2ceramics MPam15.76/2. Low temperature, short time, low consumption of SPS technology is the preparation of high density ZrB2-MoSi2ceramic parts the most cost-effective method.Pressureless sintering temperature, the tallest, longest, at1760℃under theprotection of argon heat preservation of the preparation of30min ZrB2-MoSi2ceramicgrain grew up, about8to12microns, MoSi2also grew up obviously, lowestpressureless sintering properties of the ceramic. Pressureless sintering ceramics allalong with the increase of MoSi2performance increase, so the ZrB2-40vol.%MoSi2ceramics has the highest apparent density (98.23%), the highest bending strength(280.81MPa), hardness (13.25GPa). This method can be used for the preparation ofcomplex, large ZrB2-MoSi2ceramics.Hot-pressing sintering preparation, its apparent density and comprehensiveperformance is slightly higher than that of SPS and ceramic, the highest bendingstrength is465.94MPa, hardness up to18.30GPa, fracture toughness is highest4.74MPam1/2, despite the long preparation period, hot-pressing sintering is the preparation oflarge size, simple shapes, ZrB2-the best way to MoSi2ceramics.