Laser Heated Gradient NMR Studies of Ceramic Liquids R.F. Marzke, G.H. Wolf, Arizona State University, DMR0116361 Alumina fibers in a matrix of monazite (LaPO4) form non-brittle ceramic matrix composites (CMCs) with many uses. LaPO4 and Al2O 3 do not mix atomically when melted and cooled together, which contributes to maintaining the composites’ integrity at high temperatures. When CaO is added, however, electron micrographs often show glassy character (upper left – compare with crystalline samples at upper right), as do X-ray and Raman spectra (middle figure – note breadths of the Raman lines) This indicates not only atomic mixing of constituents but also formation of glasses of a new kind. Synthesis of alumina-calcia-monazite glasses has been attempted previously, but methods developed by Master’s student S. Boucher have produced the first examples. Shown at bottom is a structural model of a glassy sample having approximately 25% monazite content, composed of individual PO4 tetrahedra linked to one or possibly two 4- or 6-fold Al ions, with La and Ca in nearby positions. Since melting temperatures are relatively high (1300-1600 Celsius) such materials may be described as aluminate - orthophosphate glasses. Broader Impacts from this research program, funded by DMR0116361 R.F. Marzke and G.H. Wolf Arizona State University Students: Jeremy Piwowarczyk (Physics, M.A. 2000, ASU). Now at Freescale Semiconductor, Tempe, AZ Susan Boucher (Chemistry M.A. 2005). Currently teaching at South Mountain Community College, Phoenix, AZ. Ceramics: Novel study of Al’s bonding and motions (both via NMR), in a group of Al-bearing ceramic melts. Development of new high-temperature aluminate-phosphate glasses, in the alumina-calcia- monazite system.
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