Thermogravi metric Study of the Oxidation of ZrB[sub 2] in the Temperature Range of 800° to 1500°C

Abstract

A thermogravimetric system is described for the determination of the total oxygen consumption, sample weight‐change, and vaporization rate during the oxidation of ZrBr2 . The results show an increasing deviation from parabolic kinetics with increasing temperature at 250 mm oxygen pressure. The following equation is used to describe the total oxygen consumption in the temperature range of 800°–1500°C normalΔnO2A)(normalmoles O2cm2=5.41×10−4exp)(−25,0002RTt½+2.86exp)(−47,000RTt Because ZrBr2 is oxidized stoichiometrically, this result can be converted to the recession of ZrBr2 as follows δ)(normalcm=4.06×10−3exp)(−25,0002RT t½+2.10×101exp)(−47,000RT t

Mechanical, Thermal, and Oxidation Properties of Refractory Hafnium and zirconium Compounds

“…Hafnium hydride (HfH 2 ) was added to all starting mixtures to decrease processing temperatures. The non-stoichiometric HfC 0Á67 ceramics were prepared according to the reaction: 67rfg 33rfr 2 3 100rfg 0Á67 33r 2 The ZrB 2 /ZrC/SiC ceramics were synthesized from the starting mixtures consisting of Zr (Cerac, 99 . 7% purity, À325 mesh) or ZrC (Cerac, 99 .…”

Ultra high temperature ceramics for hypersonic vehicle applications.

“…The kinetics of high temperature oxidation of ZrB 2 were studied by Kuriakose and Margrave 37 and Tripp, et al 38 High temperature oxidation of zone melted HfB 2 and ZrB 2 was investigated by Berkowitz-Mattuck 8 . Tripp, et al 14 studied the role of added SiC in the formation of an oxygen diffusion barrier on ZrB 2 between 800°and 1500°C.…”

“…Tripp and Grahm 38 found an increasing deviation of oxidation of ZrB 2 (hot-pressed billet from Manlabs Incorporated) from parabolic kinetics with increase in temperature at an oxygen partial pressure of 250 mm. They showed that the rate of oxygen consumption was controlled by oxygen diffusion through the B 2 O 3 and that a paralinear equation could be derived for rate of oxygen consumption within their range of measurements.…”

Thermochemical and Mechanical Stabilities of the Oxide Scale of ZrB2+SiC and Oxygen Transport Mechanisms

“…Introduction R EFRACTORY diborides (HfB 2 , ZrB 2 ) with 20-30 vol% SiC additive are prominent ultrahigh-temperature ceramics withstanding temperatures 2000 K and above. 1,2 During operation in air its surface is oxidized, giving rise to a crystalline oxide skeleton (HfO 2 , ZrO 2 ) and a silica-rich borosilicate liquid that wets it, [3][4][5][6][7][8][9][10] produced by the reactions:…”