Materials for temperatures above 1500°C in oxidizing atmospheres. Part I: Basic considerations on materials selection

Oxidation of ZrB[sub 2]-Based Ceramics in Dry Air

“…In fact, the latter compound has an unusually low melting point, 450°C, 26 and a high vapor pressure ͑Fig. 20 Nonetheless, grain boundary siliconcontaining phases, although in very limited amounts as in material A, promote the formation of a borosilicate glass with higher melting point, and lower vapor pressure ͑Fig. The rapid increase in weight gain of a pure ZrB 2 material with 87% relative density ͑Fig.…”

“…The as-processed powder batches were hot-pressed under vacuum ͑ϳ0.5 mbar͒ using BN-lined graphite die. 20 The fabricated materials were subjected to two thermal treatments in flowing dry air ͑ϳ50 cm 3 /min͒ at ambient pressure, namely, ͑i͒ a nonisothermal run up to 1350°C, heating rate of 2°C/min, and free cooling; and (ii) an isothermal run at 1120°C ͑heating rate of 20°C/min͒ for 20 h and free cooling using a thermogravimetric analyzer ͑model STA409, NETZSCH Gerätebau GmbH, Germany͒. Detailed descriptions of the powder processing, microstructure, and mechanical properties of the three materials are reported elsewhere.…”

Materials for temperatures above 1500°C in oxidizing atmospheres. Part II: Experimental results on the oxidation of MoSi2 composites and coated RSiC

“…The concepts developed in part I of this publication [1] proved to be successful from an oxidation resistance point of view. The presence of Mo 5 Si 3 in MoSi 2 materials impairs the oxidation resistance at temperatures of 1500 8C and above in the first hours of oxidation until a dense SiO 2 scale is formed which prevents direct evaporation of MoO 3 .…”

“…Described in a previous paper [1] are the basic considerations of material selection for applications at temperatures of 1500 8C and above in oxidizing environments. A large amount of literature has been reviewed under the aspect of oxidation resistance and mechanical strength at these temperatures and we found that two promising alternatives exist for a materials system that can withstand temperatures above 1500 8C.…”

Short-term oxidation of a ternary composite in the system AlN–SiC–ZrB2

“…B 2 O 3 , liquid at these temperatures, is known to have a protective effect, while ZrO 2 is semiprotective due to its anion deficiency. 13 Thus, in this temperature range, the oxidation of the ternary composite resembles that of a ZrB 2 monolithic material, with nearly parabolic kinetic. The multiple linear regression fit, gives a negative linear term, which could be related to the release of volatile products from the reaction (3).…”