Abstract The metastable tantalum suboxides have been found to be a cause of complicated oxidation behaviour of fine tantalum particles when heated in air at moderate temperatures. Fine Ta 0.02–10 μm particles of bimodal size distribution with average volume maxima of 0.12 and 4 μm were prepared via electric explosion of thin Ta wire in Ar atmosphere. The oxidation reaction proceeded via several intermediate suboxides (Ta 6 O, Ta 4 O, Ta 2 O and TaO 2 ) in which chemical and structure transformations caused multistep kinetics of the oxidation process in a narrow temperature interval of 250–570 °C. Within the interval of 250–400 °C, the oxidation process occurred under diffusion control with an apparent activation energy E a,1 = 31.6 ± 1.2 kJ/mol and the main oxidation products were Ta(O) solid solutions and suboxides Ta 6 O and Ta 4 O. In the interval of 400–520 °C, oxidation was accompanied by a low-barrier martensite-like transformation of the lower suboxides resulting in reducing of diffusion limitations of the process ( E a,2 = 4.8 ± 1.2 kJ/mol). In the interval of 520–570 °C, oxidation of the larger Ta particles was completed to form Ta 2 O ( E a,3 = 64.7 ± 1.9 kJ/mol). An abrupt decay of Ta 2 O at temperatures greater than ~ 570 °C induced the high-rate oxidation of micron-sized Ta particles, resulting in self-heating of the sample. Graphic Abstract

中文翻译：

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细钽颗粒的氧化：亚稳态中间体和多步动力学

摘要 已发现亚稳态钽低氧化物是细钽颗粒在中等温度下在空气中加热时产生复杂氧化行为的原因。通过细钽丝在 Ar 气氛中的电爆炸制备了双峰尺寸分布的 0.02-10 μm 细 Ta 颗粒，平均体积最大值为 0.12 和 4 μm。氧化反应通过几种中间低价氧化物（Ta 6 O、Ta 4 O、Ta 2 O 和 TaO 2 ）进行，其中化学和结构转变在 250-570 °C 的狭窄温度区间内引起氧化过程的多步动力学。在250-400°C的区间内，氧化过程发生在扩散控制下，表观活化能E a,1 = 31.6 ± 1.2 kJ/mol，主要氧化产物为Ta(O)固溶体和低价氧化物Ta 6 O和Ta 4 O。在 400–520 °C 的区间内，氧化伴随着低价低价氧化物的低势垒马氏体状转变，导致该过程的扩散限制降低（E a,2 = 4.8 ± 1.2 kJ/mol）。在 520–570 °C 的区间内，较大的 Ta 颗粒完全氧化形成 Ta 2 O ( E a,3 = 64.7 ± 1.9 kJ/mol)。Ta 2 O 在高于 ~ 570 °C 的温度下突然衰变会引起微米级 Ta 颗粒的高速氧化，从而导致样品自热。图形摘要 9 kJ/mol)。Ta 2 O 在高于 ~ 570 °C 的温度下突然衰变会引起微米级 Ta 颗粒的高速氧化，从而导致样品自热。图形摘要 9 kJ/mol)。Ta 2 O 在高于 ~ 570 °C 的温度下突然衰变会引起微米级 Ta 颗粒的高速氧化，从而导致样品自热。图形摘要