| Most metal-silicides and metal-silicon-carbides have not only good electrical and thermal conductivity of metal materials,but also high melting point,high hardness and oxidation resistance of ceramic materials.It has attractive application in areas of electric heating materials,bulletproof materials,wear-resistant materials,etc.In addition to systematic research on Ti3SiC2,seldom literature reported on other materials.In this paper,Mo4.8Si3C0.6,Al4SiC4,Cr5-xSi3-zCx+z,CrSi2 and TiSi2 were prepared by solid-state reaction using Mo,Al,Cr,Ti,Si and C powders as raw materials,the effects of the ratio of reactants,reaction temperature,holding time,and the type of carbon source on the composition and microstructure of each powder were studied.The reaction mechanism of Mo4.sSi3C0.6 and CrSi2 were discussed by thermodynamic calculations.Using the prepared powders as raw materials,Mo4.8Si3C0.6,Al4SiC4,Cr5-xSi3-zCx+z,CrSi2 and TiSi2 bulk materials were prepared by sintering process,the effect of sintering process on mechanical properties,thermal conductivity and conductive properties of each block material were also investigated.The main results are as follows:1 High-purity Mo4.8Si3C0.6 was prepared by solid-state reaction under Ar atmosphere at 1550? for 1.5h,the Mo4.8Si3C0.6 particle size is 0.52 ?m and the particles are petaloid,grains on the surface of the particles are regular polygonal sheet structures,the thickness of flake grain is about 50-80nm.Based on the phase composition and thermodynamics of the powders prepared at different reaction temperatures from 1100? to 1550?,the reaction mechanism of Mo4.8Si3C0.6 was calculated.With the increasing of temperature,the main product is gradually converted from Mo2C and Mo5Si3 to Mo4.8Si3C0.6,higher purity Mo4.8Si3C0.6 is obtained at 1550?.The volume density of Mo4.8Si3C0.6 bulk material sintered at 1700? for 1.5 h was 7.64 g·cm-3,the apparent porosity was 0.96%,and the volume resistivity was 0.1834 m?·cm.In the range of 25-1300?,the thermal conductivity of Mo4.8Si3C0.6 increases with the increaseing of temperature,and the thermal conductivity is reach to 34.3W·m-1·K-1.The failure mode of Mo4.8Si3C0.6 material is brittle fracture,with an average bending strength of 207±13 MPa,an elastic modulus of 131±11 GPa.2 High-purity Al4SiC4 was prepared by solid-state reaction at 1600? for 1.5h,the Al4SiC4 particle size is about 1.15 ?m,grains on the surface of the particles are regular polygonal sheet structures.The reaction mechanism of Al4SiC4 was analyzed based on the phase composition of the powders prepared at different reaction temperatures from 1300? to 1600?.With increasing temperature,the main product is gradually converted from Al4C3 and SiC to Al4SiC4,obtained higher purity Al4SiC4 at 1600?.The volume density of Al4SiC4 bulk material sintered at 1700? for 1.5 h was the highest,which was 2.87 g·cm-3,the apparent porosity was 1.71%,and the volume resistivity was 6.13 m?·cm.3 High-purity Cr5-xSi3-zCx+z was prepared by solid-state reaction at 1650? for 1.5h,the Cr5-xSi3-zCx+z particle size is about 1.3 ?m,grains on the surface of the particles are regular polygonal sheet structures.The reaction mechanism of Cr5-xSi3-zCx+z was analyzed based on the phase composition of the powders prepared at different reaction temperatures from 1450? to 1650?.With increasing temperature,the main product is gradually converted from CrSi25 CrSi and CrsSi3 to Cr5-xSi3-zCx+z,obtained higher purity Cr5-xSi3-zCx+z at 1650?.The volume density of Cr5-xSi3-zCx+z bulk material sintered at 1700? for 1.5 h was the highest,which was 4.71 g·cm-3,the apparent porosity was 9.68%,and the volume resistivity was 51.85 m?·cm.4 High-purity CrSi2 was prepared by solid-state reaction at 1250? for 1.5h,the CrSi2 particle size is about 1.3 ?m,grains growth tends to have a layered structure.The reaction mechanism of CrSi2 was calculated based on the phase composition and thermodynamics of the powders prepared at different reaction temperatures from 950?to 1250?.With increasing temperature,the main product is gradually converted from CrSi and Cr5Si3 to CrSi2,obtained higher purity CrSi2 at 1250?.The volume density of CrSi2 bulk material sintered at 1400? for 1.5 h was the highest,which was 4.66 g·cm-3;the apparent porosity was 3.44%,and the volume resistivity was 16.91 m?·cm.5 High-purity TiSi2 was prepared by solid-state reaction at 1350? for 1.5h,the TiSi2 particle size is about 1.15 ?m,grains growth tends to have a layered structure.The reaction mechanism of TiSi2 was analyzed based on the phase composition of the powders prepared at different reaction temperatures from 1050? to 1350?.With increasing temperature,the main product is gradually converted from Ti5Si3 to TiSi2,obtained higher purity TiSi2 at 1350?.The volume density of TiSi2 bulk material sintered at 1500? for 1.5 h was the highest,which was 3.76 g·cm-3,the apparent porosity was 2.02%,and the volume resistivity was 11.34 m?·cm. |
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