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The oxidation behavior of 0.8%La_2O_3-Mo_5Si_3/MoSi_2 composites at 1200 ℃ in air was investigated. The results reveal that the oxidation resistance of the material with 0.8% La_2O_3 and Mo_5Si_3 is impaired. The oxidation resistance is decreased with increasing Mo_5Si_3 content. The mass loss follows a linear law in the initial oxidation. With oxidation time prolonging, a continuous and dense oxidation scale prevents oxygen from diffusing and leads to mass change a little increasing when the Mo_5Si_3 content is less than 30%. However, the composite shows “PEST” with the addition of 40% Mo_5Si_3. With increasing Mo_5Si_3 content, the oxidation resistance of 0.8%La_2O_3-Mo_5Si_3/MoSi_2 decreases. This attributes to the poor oxidation resistance of Mo_5Si_3 and the relative density decreasing of 0.8% La_2O_3-Mo_5Si_3/MoSi_2 composite. In addition, the addition of rare earths and Mo_5Si_3 to MoSi_2 reduces the average grain size, which increases the grain boundary area. The reduction in the grain size is generally accompanied by acceleration of diffusion speed of oxygen and promotion of material oxidation.
The results show that the oxidation resistance of the material with 0.8% La_2O_3 and Mo_5Si_3 is impaired. The oxidation resistance of decreased with increasing Mo_5Si_3 content. The oxidation behavior of 0.8% La_2O_3-Mo_5Si_3 / MoSi_2 composites at 1200 ℃ in air was investigated. mass loss follows a linear law in the initial oxidation. With oxidation time prolonging, a continuous and dense oxidation scale prevents oxygen from diffusing and leads to mass change a little increasing when the Mo_5Si_3 content is less than 30%. However, the composite shows “ PEST ”with the addition of 40% Mo_5Si_3. With increasing Mo_5Si_3 content, the oxidation resistance of 0.8% La_2O_3-Mo_5Si_3 / MoSi_2 decreases. This attributes to the poor oxidation resistance of Mo_5Si_3 and the relative density decreasing of 0.8% La_2O_3-Mo_5Si_3 / MoSi_2 composite. In addition, the addition of rare earths and Mo_5Si_3 to MoSi_2 reduces the average grain size, which increases the grain boundary area. The reductio n in the grain size is generally accompanied by acceleration of diffusion speed of oxygen and promotion of material oxidation.