1. Boron Carbide Stoichiometry by Raman SpectroscopyWilliam G. Fahrenholtz, Missouri University of Science and Technology, DMR 0906584 Micro-Raman spectroscopy has been used to investigate compositional changes to boron carbide (B4C) during densification of zirconium diboride (ZrB2). Pioneering work at Missouri S&T showed that ZrB2 could be densified by solid state sintering, if reactive additives such as B4C were incorporated to react with and remove oxide impurities on the ZrB2 particle surfaces. Initial analysis assumed that B4C was a stoichiometric compound that reacted directly with the oxides by reactions such as: 5 B4C + 7 ZrO2 7 ZrB2 + 3 B2O3 + 5 COAnalysis by Raman spectroscopy has revealed that the “B4C” powder contained a mixture of carbon-rich B13C3 and nanocrystalline carbon. A study is underway to elucidate details of the mechanism(s) by which B4C and carbon promote densification of ZrB2 ceramics. Among the questions to be answered include: 1) Does carbon or boron carbide react preferentially with oxides during heating? and 2) Does the stoichiometry of the boron carbide change during densification? The blue pattern is a Raman spectrum of the “B4C” powder used as a sintering aid with ZrB2 showing the presence of nanocrystalline carbon (broad D1 and G lines) in addition to boron carbide. For comparison, the red pattern is a Raman spectrum for ZrB2 densified by adding phenolic resin as a carbon precursor. The broad G’ line indicates it crystallized to form graphite.

2. Outreach Activities at Missouri S&TWilliam G. Fahrenholtz, Missouri University of Science and Technology, DMR 0906584 Students in the high temperature materials group are active in outreach efforts such as ASM Materials Camp, which introduce high school students to education and career opportunities in the field of materials science. To the left, undergraduate Eric Neuman uses an oxy-acetylene torch to demonstrate the excellent thermal shock resistance of a ZrB2-based ultra-high temperature ceramic. Below, undergraduate David Shahin demonstrates superconductivity in ceramics to high school students. Both David and Eric performed research with our group as undergraduates.