Abstract

This work is devoted to the preparation of powders of Ti₂AlC and Ti₃AlC₂ MAX phases by self-propagating high-temperature synthesis (SHS) using the magnesium-thermal reduction from oxide feedstock. Oxide TiO₂ is used as the titanium source, and magnesium is used as the reducing agent. Purification with the removal of magnesium oxide is performed in diluted hydrochloric acid at a temperature of 70°C and concentration of 1 : 3. The target product yield with the magnesium-thermal reduction is 35–40%. It is revealed that the synthesis product with the stoichiometric component ratio after chemical leaching in hydrochloric acid consists of Ti₂AlC, MgAl₂O₄, and TiC. The formation of spinel MgAl₂O₄ is associated with the deficiency of the magnesium reducing agent in the charge; herewith, aluminum partially enters the reduction reaction of titanium from its oxide with the formation of Al₂O₃. This leads to the formation of spinel MgO ⋅ Al₂O₃. An increase in the content of excess magnesium in the charge from 20 to 30 wt % conditions the complete reduction of titanium from its oxide by magnesium with the formation of the Ti₂AlC MAX phase and titanium carbide. A decrease of 10 wt % in the carbon content causes a decrease in the titanium carbide fraction to 4%. The product, containing Ti₃AlC₂ and Ti₂AlC MAX phases, as well as TiC, is formed at an excess soot content from 20 to 35%, and the Ti₃AlC₂ weight fraction increases from 86 to 89%, respectively. These powders comprise agglomerates (87% of them are smaller than 65 μm) consisting of thin plates of MAX phases 70–100 nm in thickness.

中文翻译：

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还原阶段自蔓延高温合成制备Ti 2 AlC和Ti 3 AlC 2 MAX相

摘要

这项工作致力于通过使用镁原料从氧化物原料中进行热还原自蔓延高温合成（SHS）来制备Ti ₂ AlC和Ti ₃ AlC ₂ MAX相的粉末。氧化物TiO ₂被用作钛源，而镁被用作还原剂。除去氧化镁的纯化过程是在稀盐酸中，温度为70°C，浓度为1：3的情况下进行的。经镁热还原的目标产物收率为35-40％。结果表明，在盐酸中化学浸出后，化学计量比高的合成产物由Ti ₂ AlC，MgAl ₂ O _4组成。和TiC。尖晶石MgAl ₂ O ₄的形成与装料中镁还原剂的缺乏有关。因此，铝部分地从其氧化物进入钛的还原反应并形成Al ₂ O ₃。这导致形成尖晶石MgO·Al ₂ O ₃。装料中过量镁的含量从20wt％增加到30wt％，使得形成钛₂ AlC MAX相和碳化钛的情况下，钛被氧化物完全还原。碳含量降低10重量％导致碳化钛分数降低至4％。含Ti ₃的产品形成的AlC ₂和Ti ₂ AlC MAX相以及TiC的烟灰含量从20％增至35％，Ti ₃ AlC _2的重量分数分别从86％增至89％。这些粉末包含附聚物（其中的87％小于65μm），由厚度为70–100 nm的MAX相薄板组成。