Barrera, Enrique V.2009-06-042009-06-041997Chen, Jinmin. "A structural analysis of Al(3)Ti and Al(3)Ti-Nb titanium trialuminides by XRD and EXAFS." (1997) Master’s Thesis, Rice University. <a href="https://hdl.handle.net/1911/17070">https://hdl.handle.net/1911/17070</a>.https://hdl.handle.net/1911/17070In an effort to expand the composition range over which Al$\sb3$Ti is stable, various amounts of niobium were substituted for titanium and processed by melt-spinning. In order to characterize $\rm Al\sb3Ti\sb{x}Nb\sb{y},$ where x + y = 1 and y = 0.0, 0.1, 0.2, and 0.4 intermetallics, XRD and EXAFS were employed. Several samples were annealed both at 600$\sp\circ$C and 1000$\sp\circ$C. XRD showed that for all the samples the only structure present was the tetragonal DO$\sb{22}$ structure. The DO$\sb{22}$ structure was stable even after high temperatures heat treatments. Niobium atoms were observed to occupy titanium sites in DO$\sb{22}$ by EXAFS. Furthermore, in the unannealed samples, increasing wheel speed of the melt spinning process or the niobium concentration tended to distort the crystal structure. It was observed that Ti EXAFS had different results from the Nb EXAFS beyond their occupying similar sites. The samples were found to experience an order-disorder-order process with change of the annealing temperatures.76 p.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.Condensed matter physicsEngineeringMaterials scienceThesisTHESIS M.E. 1997 CHEN