Microtexture of shock reaction products of niobium and silica mixtures
- PDF / 980,977 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 80 Downloads / 202 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Microtexture of shock reaction products of niobium and silica mixtures Reiko Murao, Masae Kikuchi, Kiyoto Fukuoka, Eiji Aoyagi, Toshiyuki Atou, and Yasuhiko Syono Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577 Japan (Received 14 October 1998; accepted 19 January 1999)
Shock compression experiments on powder mixtures of niobium metal and quartz were conducted for the pressure range of 30–40 GPa by a 25-mm single-stage propellant gun. Chemical reaction occurred above 35 GPa, and products were found to be mainly so-called “Cu3Au-type” Nb3Si, which contained a small amount of oxygen. Microtextures of the specimen were examined by scanning and transmission electron microscopy. A field-emission transmission electron microscope was used for energy-dispersive x-ray analysis of microtextures in small particles found in the SiO2 matrix, and various species with different Nb/Si ratio and oxygen content were shown to be produced through the nonequilibrium process of shock compression.
I. INTRODUCTION
II. EXPERIMENTAL
Shock waves traveling through solid materials are known to produce very reactive states, which lead to various chemical reactions during the short period of shock loading. Such fast chemical reactions have been used for the formation of refractory materials. Many kinds of intermetallic compounds such as Ni–Al, Ti–Si, and Nb–Si1–3 have been successfully synthesized by a shock compression technique. A redox reaction, in which oxidation and reduction in the mixtures of metal and metal oxide mixture simultaneously occur under shock compression, is one of the most interesting phenomena and has been studied for many systems such as Al + SiO2, Al + Fe2O3, and Fe(Cr, Ni) + GeO2 or V2O5.4–6 We have already reported shock-induced reactions between tantalum metal and quartz, which resulted in formation of silicon and Ta2O5 under a nonequilibrium process.7 It would be interesting to study similar shock-induced reactions between niobium, the same V group element as tantalum, and quartz. Because of the lower melting temperature of niobium, an oxidation-reduction reaction between niobium and quartz was expected to occur at lower pressures and temperatures than that between tantalum and quartz. However, in the course of our study, we found that a very complex reaction was induced by shock compression. Instead of the formation of niobium oxides, a niobium–silicon intermetallic compound interstitially containing oxygen was produced and various complex textures were observed. In this paper, we present the experimental results of x-ray powder diffraction analysis and scanning and transmission electron microscopic observation (SEM and TEM).
Powder mixtures were used for shock-loading experiments to increase the area of the reactive interface boundary. Niobium metal powder (Koch Chemicals, 99.9%, 45 m) and silicon dioxide powder with the quartz structure (High Purity Chemicals, 99.9%, 62 m) were blended mechanically in a 2/1 (mol/mol) pro
Data Loading...
