Abstract Novel electrode coating materials are needed for coal-fired magnetohydrodynamic (MHD) direct-current extraction power plants. Addition of potassium salt to increase the conductivity of coal plasma combined with high temperature render the service conditions extremely arduous. Therefore, the electrode coating materials must possess certain properties including high-temperature corrosion resistance, high-temperature oxidation resistance, and adequate electrical conductivity. In this work, those very properties of three different compositions of transition metal diboride solid solutions of HfB2-ZrB2 are studied. Two main approaches of oxidation mitigation methods were employed: adding chemical dopants, such as Hf and La, and performing pre-anodization on the samples to create a protective oxide coating. Thermogravimetric experiments were run at different partial pressures of oxygen to determine the high-temperature oxidation resistance of these boride ceramics. In addition, two different salt coatings (KCl and K2SO4) were applied to the surface of the samples to test their hot corrosion resistance. High-temperature polarization resistance tests were also conducted to measure the electrical resistivity. The addition of lanthanum aided in long term oxidation and corrosion protection, with a parabolic rate constant, Kp = 1.33 × 10−5 kg2/m4 s, a 40% improvement over the sample without the addition of lanthanum under the same conditions. Anodization, however, proved disadvantageous when combined with either lanthanum or a corrosive environment.

中文翻译：

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ZrB 2 -HfB 2 固溶体在 KCl 和 K 2 SO 4 中的热腐蚀行为在 1500 °C

摘要 燃煤磁流体动力（MHD）直流提取发电厂需要新型电极涂层材料。添加钾盐以提高煤等离子体的电导率，加上高温使得使用条件极其艰苦。因此，电极涂层材料必须具备一定的性能，包括耐高温腐蚀性能、高温抗氧化性和足够的导电性。在这项工作中，研究了 HfB2-ZrB2 的三种不同过渡金属二硼化物固溶体组成的那些特性。采用了两种主要的抗氧化方法：添加化学掺杂剂，如 Hf 和 La，并对样品进行预阳极氧化以形成保护性氧化物涂层。在不同的氧分压下进行热重实验以确定这些硼化物陶瓷的高温抗氧化性。此外，将两种不同的盐涂层（KCl 和 K2SO4）涂在样品表面以测试其抗热腐蚀性能。还进行了高温极化电阻测试以测量电阻率。添加镧有助于长期氧化和腐蚀保护，抛物线速率常数 Kp = 1.33 × 10−5 kg2/m4 s，在相同条件下比未添加镧的样品提高了 40%。然而，当与镧或腐蚀性环境结合时，阳极氧化被证明是不利的。