#################################################### # Kriven # requesting 6 days, at minimum=3 days # beamline 33BM, "Martensitic Phase Transformaitons in Yttrium Niobate and Dysprosium Titanate" #################################################### # top:/home/www/beamtime-requests/req00333.txt # UNICAT Member Beam Time Request #333 # created Mon Dec 09 21:14:01 CST 2002 #################################################### beamline: 33BM collaboration: No contact: w-kriven@uiuc.edu days: 6 description: Toughening mechanisms in ceramics include: transformation toughening (e.g., with zirconia, delta V = positive) and transformation weakening causing debonding of interphases (e.g. cristobalite, enstatite, delta V = negative). It is proposed to study potentially new martensitic phase transformations in yttrium niobate and dysprosium titanate, as examples of model systems for academic understanding as well as potentially technologically useful ceramics for aerospace applications at 1600 degress C. Theoretical predictions of the martensitic transformation mechanisms will indicate the orientation relationships between parent and product phases, quantify the magnitute 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 and pressure, using synchrotron radiation. This basic crystallographic data will guide the design and processing of high temperature, transformation toughened, ceramic composites. Preliminary work in a previous thesis by Lay Foong Siah indicates that the high temperature cubic phase (discovered in our experiments) occurs above 1800 degrees C, but more precise information is needed, before this material can be applied as a high temperature, transformation toughener in an oxide system. The nature of the sequence of four phase transformations in dysprosium titanate is not known, since there are a choice of 3 space group symmetries fo each of the HT cubic, hexagonal, orthorhombic and RT cubic phases present. equipment+required: Huber four circle diffractometer, water chiller, precision sensitive detector experiment: Martensitic Phase Transformaitons in Yttrium Niobate and Dysprosium Titanate foreign+nationals: Dr. Kersten Jurkschat (German citizen) Dr. Pankaj Sarin (Indian citizen) Professor Waltraud Kriven (Australian citizen) hazards: There appear to be no extra hazards as compared to the normal acquisition of polycrystalline powder diffractometry plots by synchrotron data. Common sense procedures apply, e.g., not to touch the furnace when it is heating the specimen, and to look at the intense light only with double sheets of pyrometry glass which are provided. Care should be taken to ensure that the water chiller is always operating when the furnace is operating. minimumdays: 3 name: Kriven nonmembers: unacceptable+dates: None #REMOTE_HOST: mach-pc243.mse.uiuc.edu #REMOTE_ADDR: 128.174.229.243 #CONTENT_LENGTH: 2626 #HTTP_REFERER: http://www.uni.aps.anl.gov/unireq.htm #HTTP_USER_AGENT: Mozilla/4.0 (compatible; MSIE 5.0; Mac_PowerPC)