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C. Reynaud et al. International Journal of Refractory Metals d Hard Materials 19(2001)425-435 Table 5 Pores characteristics, measured by image analysis, of the monolithic laminates and of the laminar composites. Nearly 1500 pores have been taken Into account PFA Content Laminar composites (vo%) Equivalent diameter(um) Aspect ratIo Equivalent diameter(um) Corn starch 9±1.5 7.5±1.5 PA-C 12.8±1.5 l17±1 l1.3±1.5 8.9±1.5 PA-A 3.8±1.5 5±1.5 秘论没学叫 验就染静感 Fig. 13. Microstructure of symmetric multilayered sayers containing PA-A;(c)dense layer; (d)porous layer with equiaxed grains(bar =10 um)for licon carbide materials:(a) laminar composite with 45 vol% of corn starch incorporated in the a laminar composite containing 45 vol/ of corn starch. (iii)Pores: Porous layers exhibit the same pore fea- 4. Conclusion ures(identical mean values); i.e. pore characteris- tics are unaltered by the position (core or shell) Laminar silicon carbide composites have been elab- of the layer in the laminar composite. Moreover, orated by the tape casting- liquid phase sintering the pore characteristics are the same as those (YAG-alumina eutectic) processing. Porosity was in obtained for corresponding monolithic blocks (see troduced by the incorporation of PFAs(5-50 vol%,re- Table 5) ferred to the theoretical volume of the dry tapes)in the'+ 6 1 * ' +# * ' + 3 ' + 5 * - & '(%)* + , * % ' - ! . * + "> 6 ' + , $ . # ' + %*%# '+ # ' + , & 1 ' "! + $ . ? " !! 3 % '.+ 5 9& ' + % 9& ' + % C " " 7 " " 7 %* $! " 8 " " A ""7 " "A ""> " "A 8C " "A %*% $ >8 " "A " "A$ > " "A >C " "A "+ 1 % 2 3 "3+ 4 5 67 869 ':' $>>