Improved processing and oxidation-resistance of ZrB2 ultra-high temperature ceramics containing SiC nanodispersoids

ZrB2 belongs to a class of ceramics defined ultra-high-temperature ceramics with extremely high melting temperatures, but ZrB2 ceramics is difficultly sintered and easily oxidized. To make ZrB2 ceramics possess the high relative density and the better oxidation resistance. The effects of adding phase on the sintering and oxidation resistance mechanism of ZrB2 based high-temperature multi-phase ceramics were investigated. YAG and Al2O3 help for the densification of ZrB2 based ceramics. The oxidation layer thickness of sintered ceramics adding YAG or YAG-Al2O3 phase is thinner than that of sintered pure ZrB2 ceramics under the same oxidation condition, the oxidation layer thickness of sintered ceramics adding YAG-Al2O3 phase is thinner than that of sintered ceramics adding YAG phase, the oxidation layer thickness of sintered ceramics is decreased with an increased Al2O3 content.

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Processing and Characterization of Zr-, Hf- and Ta-Based Ultra High Temperature Ceramics

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.65.118 ◽

2010 ◽

Vol 65 ◽

pp. 118-123

Author(s):

Roberta Licheri ◽

Roberto Orrù ◽

Clara Musa ◽

Giacomo Cao

Keyword(s):

High Temperature ◽

Oxidation Resistance ◽

Point Of View ◽

Ultra High Temperature Ceramics ◽

Plasma Sintering ◽

High Temperature Synthesis ◽

Spark Plasma ◽

Energy Consuming ◽

Ultra High Temperature

The fabrication of MB2-SiC and MB2-MC-SiC (M=Zr, Hf, Ta) Ultra High Temperature Ceramics (UHTCs) is investigated in this work by combining Self-propagating High-temperature Synthesis (SHS) and Spark Plasma Sintering (SPS). Zr, Hf or Ta, B4C, Si, and graphite powders are first reacted by SHS to successfully form in-situ the desired composites. For the case of the Tabased systems, a 20 min ball milling treatment is also required to mechanically activate the SHS reactions. The resulting powders are subsequently consolidated by SPS at 1800 °C and P=20 MPa, thus obtaining products with densities greater than 96% within 30 min of total processing time. Hardness, fracture toughness, and oxidation resistance of the resulting dense UHTCs are among the best when compared to the corresponding values reported in the literature relative to analogous products synthesized by alternative, more energy-consuming and less rapid methods. Thermogravimetric analysis results evidenced the beneficial effect of SiC on the oxidation resistance of the composite materials, while the presence of transition metal carbides appears to be inconvenient from this point of view. This is because, they rapidly oxidize at high temperature to form MxOy and carbon oxides which lead to an increase in sample porosity thus enhancing product oxidation.

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Characteristics and Mechanisms of Dynamic Oxidation for ZrB2-SiC Based UHTC

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.368-372.1722 ◽

2008 ◽

Vol 368-372 ◽

pp. 1722-1726 ◽

Cited By ~ 4

Author(s):

Jie Cai Han ◽

Ping Hu ◽

Xing Hong Zhang ◽

Song He Meng

Keyword(s):

High Temperature ◽

Oxidation Resistance ◽

Experimental Results ◽

Thermodynamic Calculations ◽

Second Phase ◽

Future Directions ◽

Ultra High Temperature Ceramics ◽

Mechanism Of Oxidation ◽

Dynamic Oxidation ◽

Ultra High Temperature

The present study focuses on the dynamic oxidation resistance of five representative ZrB2-SiC based ultra-high temperature ceramics (UHTCs): ZrB2-SiC, ZrB2-SiC-Si3N4, ZrB2-SiC-TiB2, ZrB2-SiCHfB2 and ZrB2-SiC-ZrC using oxyacetylene torch and arc jet testing. The effects of second phase incorporation (Si3N4, TiB2, HfB2, ZrC) on oxidation resistance were compared and analyzed. The mechanism of oxidation based on experimental results and thermodynamic calculations were explored. Some approaches to improvement of oxidation resistance and future directions of UHTC are also presented.

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