Preparation By Hot-press Sintering And Connection Of H-BN/Si₃N₄Composites

The objective of this thesis on three areas: adding different sintering AIDS tostudy the sintering process of h-BN/Si3N4composite ceramics, add the differentcontent of h-BN to research on microstructure and properties of h-BN/Si3N4composite ceramic effects, Connecting h-BN/Si3N4composite ceramic with Thediffusion bonding processApplying cold isostatic pressing-pressureless sintering process, by studying thetypes of sintering additives and sintering temperature to find out the effects formicrostructure and properties of h-BN/Si3N4composite ceramic.The results showedthat the sintering additives can make different effect on mechanical and dielectricproperties of h-BN/Si3N4composite ceramic. Adding different sintering AIDS, thethe Highest of composite material density up to61.84%, but the lowest is54.86%;the Highest of bending strength reach to146.8Mpa, the lowest down to74.7MPa; thethe Highest of Dielectric constant up to4.36, the lowest down to3.70; the sinteringtemperature can make different effects on the phase transition and densification ofcomposite ceramic materials,-Si3N4can be fully converted to β-Si3N4at1800°Ctemperatures.through changing the addition of h-BN were compared and we found thatadding30vol.%h-BN density of39.9%, bending strength obtained of159.2MPa,dielectric constant of4.45, adding60vol.%h-BN density of58.8%, bending strengthobtained of19.5MPa, dielectric constant of2.85, The material properties and thecorresponding porosity had a good relationship to porosity.Adding the addition ofh-BN improved thermal shock resistance of materials, the materials have bettertemperature stability.We can find out from the four kinds of joint interface microstructure that thereis porous structure of joints and the middle layer generates Si2N2O with theSNSandSNS(B).we can find the micro-cracks between the base metal andmiddle-tier. But there is a layer of dense phase of MAS and there is no cracks found.The max-shear strength is37.4MPa, while the lowest is9.38MPa; the joint strengthfell sharply after the introduction of h-BN; Adding the addition of h-BN improvedthermal shock resistance of materials, the materials have better temperature stability.