K. Naskar et al. /Ceramics Intemational 35(2009)3073-3079 Table la zirconia-yttria matrix, showed m-and t-zro2 along with 8-and XRD results of matrix(M)materials calcined I h at different temperatures 8-Al2O3 up to 1200C. A mixture of t-and c-ZrO2 along with a Calcination temperature (C) Crystalline phases trace amount of a-Al2O3 and orthorhombic mullite phases each designation was obtained at 1400C MZY All the composites(CAZ, CAS and CA) prepared with alumina-zirconia, alumina-silica and alumina matrices respec- tively, showed a significant amount of 8-, 0-and Y-Al2O3 at c 800-1000C. The a-Al2O3 which appeared at 1200C became MAZ 8+y-+t prominent at 1400C. At 1200C, along with the other 8+y-+t polymorphs of alumina, t- and c-ZrO2 were found in CAZ and orthorhombic mullite was obtained in cas and CA a 1400C, the a-Al,O3 and mullite were obtained in CAS and MAS Y-+Sio2(amorphous) CA composites while CAz crystallized with a-Al,O3, t-,c- y-+ SiO2(amorphous) ZrO, and trace amount of mullite mmy The load displacement curves of the composites, CZY, CAZ, CAS and Ca sintered at 800-1400C each are shown in Fig. 5 It is evident from the features of the curves that all the samples heat treated at 800-1000C indicate some pseudo-ductile character showing steady falls of load elongation curves afte ote:c-, cubic ZrO2: t, tetragonal ZrO2: y, y-Al2O3 XRD results of fibre preform(FP)calcined I h at different temperatures Calcination designation temperature (C) 0-+0-+a-(trace)+mul(trace) P10 8-+0-+a-(trace)+mul (trace) 8-+0-+a-+mul(trace) FP14 c-(major)+ mul(minor) Note: B, BAl2O3. CAS substantial quantity of a-Al2O3 was found along with a small y入个 amount of mullite phase for 1400C-treated sample Crystallization behaviours of the CMCs(CZY, CAZ, CAs and CA, here C stands for composite) at different temperatures 0.250.35045 are depicted in Fig. 4. XRD of composite material CzY, with CAZ 1400 C+L+a(tr+mu a+t+c+mu(tr) a+mu a(maj)+mu(min 1+C+o+e(tr) 8+8+a+t+c 0+8+mu+ 8+日+a+mu 0050.150250350.45 m+t+8+08+0+tt)8+6+y+a(r)+b+0+y+atr 0.30 0+B+y+t(tr) 8+0+y+a(tr)+ &+e+r+a(tr) Sample ID No 0050.150.250.350.45 Fig. 4. Change in crystalline phases of the composites, CZY, CAZ, CAS and CA at different temperatures. m, monoclinic ZrO2: t, tetragonal ZrO,; c, cubic ZrO2: Fig. 5. Load displacement curves of the composites CZY, CAZ. CAS and CA y, yALO3: a, a-Al2O3: 8, 8-Al2O3: 0, 8-Al2O3; mu, orthorhombic mullin each sintered at(a)800°C,(b)1000°C,(c)1200°Cand(d)14substantial quantity of a-Al2O3 was found along with a small amount of mullite phase for 1400 8C-treated sample. Crystallization behaviours of the CMCs (CZY, CAZ, CAS and CA, here C stands for composite) at different temperatures are depicted in Fig. 4. XRD of composite material CZY, with zirconia–yttria matrix, showed m- and t-ZrO2 along with d- and u-Al2O3 up to 1200 8C. A mixture of t- and c-ZrO2 along with a trace amount of a-Al2O3 and orthorhombic mullite phases each was obtained at 1400 8C. All the composites (CAZ, CAS and CA) prepared with alumina–zirconia, alumina–silica and alumina matrices respec￾tively, showed a significant amount of d-, u- and g-Al2O3 at 800–1000 8C. The a-Al2O3 which appeared at 1200 8C became prominent at 1400 8C. At 1200 8C, along with the other polymorphs of alumina, t- and c-ZrO2 were found in CAZ and orthorhombic mullite was obtained in CAS and CA. At 1400 8C, the a-Al2O3 and mullite were obtained in CAS and CA composites while CAZ crystallized with a-Al2O3, t-, c￾ZrO2 and trace amount of mullite. The load displacement curves of the composites, CZY, CAZ, CAS and CA sintered at 800–1400 8C each are shown in Fig. 5. It is evident from the features of the curves that all the samples, heat treated at 800–1000 8C indicate some pseudo-ductile character showing steady falls of load elongation curves after Table 1a XRD results of matrix (M) materials calcined 1 h at different temperatures. Sample designation Calcination temperature (8C) Crystalline phases MZY 800 m- + t- 1000 m- + t- 1200 c- + t- 1400 c- + t￾MAZ 800 d- + g- + t- 1000 d- + g- + t- 1200 a- + t- + c- 1400 a- + t- + c￾MAS 800 g- + SiO2 (amorphous) 1000 g- + SiO2 (amorphous) 1200 mul 1400 mul MA 800 g- 1000 g- + d- 1200 a- 1400 a￾Note: c-, cubic ZrO2; t-, tetragonal ZrO2; g-, g-Al2O3; a-, a-Al2O3; d-, d-Al2O3; mul, orthorhombic mullite. Table 1b XRD results of fibre preform (FP) calcined 1 h at different temperatures. Sample designation Calcination temperature (8C) Crystalline phases FP8 800 d- + u- + a- (trace) + mul (trace) FP10 1000 d- + u- + a- (trace) + mul (trace) FP12 1200 d- + u- + a- + mul (trace) FP14 1400 a- (major) + mul (minor) Note: u-, u-Al2O3. Fig. 4. Change in crystalline phases of the composites, CZY, CAZ, CAS and CA at different temperatures. m, monoclinic ZrO2; t, tetragonal ZrO2; c, cubic ZrO2; g, g-Al2O3; a, a-Al2O3; d, d-Al2O3; u, u-Al2O3; mu, orthorhombic mullite. Fig. 5. Load displacement curves of the composites CZY, CAZ, CAS and CA each sintered at (a) 800 8C, (b) 1000 8C, (c) 1200 8C and (d) 1400 8C. 3076 M.K. Naskar et al. / Ceramics International 35 (2009) 3073–3079