Study Of Preparation And Performance Of A New Type Of SiC/Al Composite Materials

Porous ceramics have many features,including chemical inertness,thermal shock resistance,corrosion resistance,wear resistance,low density,high specific surface area,low dielectric constant,etc.they are being utilized in a broad range of applications in order to mitigate several environmental,biological,and transportation related issues society facing,such applications include for example the molten metal filter,heat insulation,catalyst carrier,diesel engine exhaust particle filter.According to the low mechanical performance of porous ceramics and the pore structure was difficult controlled,the effects of ceramic slurry,coating times,reprocessing and indirect 3D printing on the properties of porous foamed ceramics were studied in this paper.The main studies and results are listed as follow:（1）Silicon carbide porous ceramics were prepared by the polymer templates replica method,and the slurry rheological properties,mechanical properties and microscopic morphology were analyzed.The study shows that the good stability and fluidity of the slurry with the PAA-NH₄ as dispersing agent,pH value of 11 and the ratio of particle size of d₃=0.33D,a more appropriate dip coating and dip coating and yttrium sol reprocessing can increase the thickness of the ceramic slurry and filling pore in the porous frame.The mechanical properties of porous ceramics were enhanced by multiple dip coating and yttrium sol post-treatment process.The compressive strength of porous ceramics was gradually increased from 1.79 MPa to 2.28 MPa.（2）Silicon carbide reticulated porous ceramics with a regular shape were successfully prepared by combining three-dimensional（3D）printing,gelcasting and liquid drying.A 3D reticulated structured polyvinyl alcohol（PVA）mould was first fabricated by 3D printing,and then a slurry with a high-loading of SiC was gelcast into it.The PVA mould could be removed without any damage to form the gelled SiC structure by immersion in an aqueous solution,i.e.by liquid drying.The relative density of the porous ceramics prepared by the silicon carbide slurry（0.46 Pa·s）and high solid loading（57.5 vol%）was 97.6%,and the average compressive strength was 45 MPa.The present method shows good potential for fabricating porous and/or complex-shaped high-quality ceramics,and could also be applied in various kinds of advanced ceramics.（3）The two kinds SiC porous ceramics reinforced Al matrix composite were prepared by in-situ reaction pressure-free infiltration method.The relative density,phase composition,mechanical properties,thermal conductivity and microstructure were analyzed.The study shows that the metal melt has good fluidity and wettability when addition content of magnesium and silica powder was 8 wt%and 2 wt%,respectively.The suitable compound technology was thermal insulation temperature at 900℃,and thermal insulation time was 6 h.The relative density of the composite material formed using porous ceramics obtained by the organic foam replica method was 73.77%,the compressive strength and thermal conductivity was 685.8 MPa,112.36 W/m·K,respectively.The properties of indirect printed SiC porous ceramics reinforced Al matrix composites are better than that of polymer templates replica method.The relative density,compressive strength and thermal conductivity of composites was 92.3%,735.2 MPa and 112.36 W/m·K,respectively.