Structural investigation in the TiB2-(Na2O•B2O3•Al2O3) system

Composites in the TiB2-Na2O center dot B2O3 center dot Al2O3 systems, TiB2-MBA (MB stands for sodium metaborate and A is Al2O3), were prepared by self-propagating high-temperature synthesis (SHS), in simultaneous mode. Selection of these compositions was ruled by the interesting properties of both TiB2 and double borates of alkali metal and aluminum. The structure of the obtained materials was evaluated by micro-Raman spectroscopy, from room temperature up to 600 degrees C, and X-ray photoelectron spectroscopy (XPS). Formation of the TiB2 and TiO2-xBx, phases along with TiO2 as rutile were identified as titanium speciation in the grain phase embedded in a sodium aluminum borate matrix. Integration of the Raman spectra of the grain phases revealed a TiB2 content of 16.99% and 23.32% for the two composite investigated 2TiB(2)center dot 2MBA and 3TiB(2)center dot 5MBA. A constrained-width model for the spectral deconvolution of the high-frequency Raman band was forwarded to calculate the proportion of tetrahedral boron atoms (7.424%) in the blank borate matrix Na2B2O4 center dot Al2O3 in solid phase. (C) 2010 Elsevier Inc. All rights reserved.