Communications of the American Ceramic Sociery Vol 86. No. 1I interphases had bending strengths of 154, 155, and 184 MP respectively. Some typical load versus displacement curves three-point bending tests of the three different composites presented in the Fig. 4. All the composites showed"stepped versus displacement curves. Mullite IV. Conelusions The amorphous and crystalline forms of AlPO4 powders which AlPO4 ific surface area of 13 I-h attrition milling, were entrapment method. AlPO4 was chemically stable and did not disproportionate at high temperatures. Mullite and aluminum phosphate were compatible with each other without the formation of a third phase, after sintering at 1600.C/(10 h). The aluminum a three-point bending strength of 1.5 MPa after sintering at 500 microns 1600C/(10 h). The tape-casting formulations for the mullite and AlPO4, using 25 1 vol% powder loading, worked well for making Fig. 3. SEM micrograph showing crack deflection along the AlPO a laminated composite. The aluminum phosphate functioned as a terphase in the 3AlO, 2SiO2/AlPO4 laminated composite porous and weak interphase material in laminated configurations As the amount of mullite in the interphase increased from 0 to 10 to 30 vol%, the strength of the composite changed from 154 to 155 to 184 MPa, respectively. References 0.14 0% mullite 10% mullite 如Bm知mr址m: 30% mullite 2A. J. Leadbetter and T. W. Smith,"The a-B Transition in the Cristobalite Phase of SiOz and AlPO4, L. X-ray Studies, Philos Mag, 33 [1 105-12(1976). 4J. V. Bothe Jr. and P. W. Brown, "Low-Temperature Formation of Aluminum Orthophosphate, " J Am Ceram Soc., 76[2]362-68(1993 w. H. Gitzen, L. D. Hart, and G. Maczura, "Phosphate-Bonded Alumina Castables: Some Properties and Applications, "Am. Ceram. Soc. Bull, 35[6]217-23 P. E. Stone, E. P. Egan Jr, and J.R. Lehr,"Phase Relationships in the System Cao-Al O3-P2Os," J.A. Ceram. Soc., 39 [3]89-98(1956). O. Prakash, P, Sakar, and P S Nicholson, "Crack Deflection in Ceramic/Ceramic Lamin 0.1 P E. D Morgan and D B Mars Ceramic Composites of Monazite an m D. H Kuo and W. M. Riven, "A Strong and Damage-Tolerant Oxide Laminate J.Am. Ceram.Soc,8092421-24(1997) Fig. 4. Load versus displacement curve for the 3AL20, 2SIO2/AlPOA ow. M. Kriven, S. J. Lee, M. A. Gulgun, M. H. Nguyen, and D. K,Kim interphase composition of pure AlPO4 and 10 ""Synthesis of Oxide Powders via Polymeric Steric Entrapment"(invited review aper pp 99-110 in Ceramic Transacti and 30 vol% mullite added, respectively. nthesis of Ceramics, Glasses, Composites Ill. Edited by J. P. Singh, N. P. Ansel, th of the interphase material, 10 and 30 dded to the alPOa interphase. The com J. D. Cawley and W.E. Lee, "Oxide Ceramics"; Pp. 47-117 in Materials Science d Technology, Vol. 11, Structure and Properties of Ceramics. Edited by M. Swai O CH, New York, 1994To increase the strength of the interphase material, 10 and 30 vol% of mullite were added to the AlPO4 interphase. The com￾posites with pure AlPO4 and 10 and 30 vol% mullite-added interphases had bending strengths of 154, 155, and 184 MPa, respectively. Some typical load versus displacement curves for three-point bending tests of the three different composites are presented in the Fig. 4. All the composites showed “stepped” load versus displacement curves. IV. Conclusions The amorphous and crystalline forms of AlPO4 powders which have specific surface area of 137 and 87 cm2 /g, respectively, after 1-h attrition milling, were synthesized by an organic, steric entrapment method. AlPO4 was chemically stable and did not disproportionate at high temperatures. Mullite and aluminum phosphate were compatible with each other without the formation of a third phase, after sintering at 1600°C/(10 h). The aluminum phosphate had a density of 61% of the theoretical density and had a three-point bending strength of 1.5 MPa after sintering at 1600°C/(10 h). The tape-casting formulations for the mullite and AlPO4, using 25.1 vol% powder loading, worked well for making a laminated composite. The aluminum phosphate functioned as a porous and weak interphase material in laminated configurations. As the amount of mullite in the interphase increased from 0 to 10 to 30 vol%, the strength of the composite changed from 154 to 155 to 184 MPa, respectively. References 1 W. R. Beck, “Crystallographic Inversions of the Aluminum Phosphate Poly￾morphs and Their Relations to Those of Silica,” J. Am. Ceram. Soc., 32 [4] 147–51 (1949). 2 A. J. Leadbetter and T. W. Smith, “The
– Transition in the Cristobalite Phase of SiO2 and AlPO4, I. X-ray Studies,” Philos. Mag., 33 [1] 105–12 (1976). 3 D. E. C. Corbridge, Phosphorus: An Outline of Its Chemistry, Biochemistry and Technology; p. 141. Elsevier, New York, 1985. 4 J. V. Bothe Jr. and P. W. Brown, “Low-Temperature Formation of Aluminum Orthophosphate,” J. Am. Ceram. Soc., 76 [2] 362–68 (1993). 5 W. H. Gitzen, L. D. Hart, and G. Maczura, “Phosphate-Bonded Alumina Castables: Some Properties and Applications,” Am. Ceram. Soc. Bull., 35 [6] 217–23 (1956). 6 P. E. Stone, E. P. Egan Jr., and J. R. Lehr, “Phase Relationships in the System CaO–Al2O3–P2O5,” J. Am. Ceram. Soc., 39 [3] 89–98 (1956). 7 O. Prakash, P. Sakar, and P. S. Nicholson, “Crack Deflection in Ceramic/Ceramic Laminates with Strong Interfaces,” J. Am. Ceram. Soc., 78 [4] 1125–27 (1995). 8 P. E. D. Morgan and D. B. Marshall, “Ceramic Composites of Monazite and Alumina,” J. Am. Ceram. Soc., 78 [6] 1553–63 (1995). 9 D. H. Kuo and W. M. Kriven, “A Strong and Damage-Tolerant Oxide Laminate,” J. Am. Ceram. Soc., 80 [9] 2421–24 (1997). 10W. M. Kriven, S. J. Lee, M. A. Gu¨lgu¨n, M. H. Nguyen, and D. K. Kim, “Synthesis of Oxide Powders via Polymeric Steric Entrapment” (invited review paper); pp. 99–110 in Ceramic Transactions, Vol. 108, Innovative Processing and Synthesis of Ceramics, Glasses, Composites III. Edited by J. P. Singh, N. P. Bansel, and K. Niihara. American Ceramic Society, Westerville, OH, 1999. 11M. A. Gu¨lgu¨n, W. M. Kriven, and M. H. Nguyen, “Processes for Preparing Mixed-Oxide Powders,” U.S. Pat. No. 6 482 387, November 19, 2002. 12J. D. Cawley and W. E. Lee, “Oxide Ceramics”; pp. 47–117 in Materials Science and Technology, Vol. 11, Structure and Properties of Ceramics. Edited by M. Swain. VCH, New York, 1994. Fig. 3. SEM micrograph showing crack deflection along the AlPO4 interphase in the 3Al2O3
2SiO2/AlPO4 laminated composite. Fig. 4. Load versus displacement curve for the 3Al2O3
2SiO2/AlPO4 laminated composite with an interphase composition of pure AlPO4 and 10 and 30 vol% mullite added, respectively. 1964 Communications of the American Ceramic Society Vol. 86, No. 11