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Laser Heated Gradient NMR Studies of Ceramic Liquids by a74abaf35cd8e297


									      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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