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# Waltraud M. Kriven <w-kriven@uiuc.edu>
# requesting 6 days, at minimum=3 days
# beamline 33BM, "In-situ, high-temperature phase transformations in tantala, mullite and calcium phosphatesM"
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# top:/home/www/beamtime-requests/req00394.txt
# UNICAT Member Beam Time Request  #394
# created Mon Mar 17 17:02:00 CST 2003
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beamline:
	33BM

collaboration:
	Yes

collaborator+Paul:
	on

contact:
	w-kriven@uiuc.edu

days:
	6

description:
	Phase transformations can have a wide spread application in ceramics. For example, toughening mechanisms in ceramics include transformation  (e.g., with zirconia, where the volume change is positive) and transformation weakening causing debonding of interphases (e.g., cristobalite, enstatite, where the volume change is negative). In addition, ceramic phase transformations can find applications as multifunctional actuators in "smart" or "intelligent" systems. Tantala, Ti-, Ga, Fe- doped mullites, and  calcium phosphates, are examples of model systems for academic understanding Theoretical predictions of the relationships between parent and product phases quantify the magnitude of macroscopic shape changes and describe the nature and relative amounts of lattice invariant shears of slip and/or twinning.  These will then be compared with experimental observations made as a function of temperature, using synchrotron radiation.  This basic crystallographic data will guide the design and processing of high temperature ceramic composites. the  Tantala appears to have a phase transformation resulting in five orders of magnitude change in dielectric properties, but little is known of the precise crystallographic structure changes involved. 
	       This work is important because it does basic research to find new phase transformations in oxide ceramics particularly at elevated temperatures. The crystallographic data measured by state of the art Rietveld technques from data collected in situ at high temperatures in air, will guide the design and fabrication of tough, strong ceramic matrix composites.  It will also guide the development of large force actuators and shape memory behavior in ceramics.

equipment+required:
	Water chiller

experiment:
	In-situ, high-temperature phase transformations in tantala, mullite and calcium phosphatesM

foreign+nationals:
	Professor Waltraud M. Kriven (Australian)
	Dr. Kerstin Jurckschat (German)
	Dr. Pankaj Sarin (Indian)

hazards:
	The experiment  uses a small, water-cooled, four-lamp furnace capable of 2,000 degrees C. There are no apparent hazards other than those normally assocaited with using high energy synchrotron radiation.  The samples are small, sintereed rods of dimensions of 300-400 microns in diameter, by 2.5 cm in height, which are mounted with high temperature alumina cement in the furnace, and through which the synchrotron rays penetrate. All of the samples are non-toxic.

minimumdays:
	3

name:
	Waltraud M. Kriven

new+request:
	on

nonmembers:
	Dr. Jason Hodges at ANL, IPNL

unacceptable+dates:
	None


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