High-temperature oxidation of borides of the group IV metals
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A study was made of the oxidation of dense ZrB2 and HfB2 specimens over the temperature range 500–1600°C.
It is shown that the dissolution of oxygen (nitrogen) in the lattices of these borides depends on the protective properties of the scale layers forming on them. Its extent decreases with rise in temperature owing to the formation of borates (900–1200°C) and the sintering of the scale (1300–1600°C).
It has been established that the good oxidation resistance of ZrB2 and HfB2 is due to the formation of borates at certain temperatures (900–1200°C) and to the sintering of the scale at higher temperatures. The latter phenomenon accounts for the absence under these conditions of the nitride phases ZrN and HfN at the inner interfacial boundaries.
KeywordsOxidation Oxygen Nitrogen Nitride Borate
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