电热还原法一步制备V-Ti-Cr-Ni系储氢合金及其杂质控制机制研究

The V-Ti based BCC solid solutions have attracted much attention due to their large amount of theoretical hydrogen storage capacity and good performance of desorption hydrogen near room temperature. However, these alloys nearly can not be used to practical applications for their high preparation cost. In this study, the V-Ti based alloys were prepared with a electrothermal reduction method, and the metal oxides were used as the raw materials. During the process of preparation, the metallothermic reduction reactions first occurred. In order to diminish the aluminum and the non-metallic inclusions of the alloy, the smelting furnace was electrified in the later reaction phase, and some refining agents were injected in the alloy melt by a powder-spraying device. After a period of standing, the alloy melt was transferred to a vacuum induction furnace, and the secondary refining process was followed carried out, expecting to reduce the contents of oxygen. The study will research the temperature and the heat discharging of the reactions by DSC, and calculate the kinetic parameters of the reactions. Through analyzing compositions, phases, morphologies and performances of the alloys, this study will make clear the affection factors of the smelting process, understand the sources, occurrences and change laws of the impurities, illuminate the influence of impurity elements on alloy structures and properties, furthermore, reveal the impurities removal mechanism. Through optimizing the refining process parameters, this study will obtain high quality hydrogen alloy. This study will provide theoretical basis and technical support to the work of low preparation costs of V-Ti based hydrogen alloys.

钒钛基固溶体储氢合金储氢容量高、室温放氢动力学性能好，但因为其制备原料金属纯钒价格昂贵，加之熔点过高，限制了它的实际应用。为降低该类合金的制备成本，本研究以较廉价的钒、钛等金属氧化物为原料，采用电热还原法进行合金制备。制备开始时先进行金属热反应，反应后期电弧炉通电加热，并采用氩气负载方式向熔池内部吹入精炼渣，以脱除合金中的铝及氧化物夹杂，之后将液态合金转到真空感应炉内进行深度脱氧，制得最终合金。研究通过DSC测试技术，确定各热反应的发生温度及放热情况，计算各反应的动力学参数；通过分析不同工序时合金的成分、物相、形貌和储氢性能，明确熔渣组成和原料配比等因素对合金冶炼效果的影响规律，认识合金中各杂质的来源、赋存状态及变化规律，阐明杂质元素对合金结构及性能的影响方式，并揭示其去除机理；通过优化精炼工艺参数，制备出储氢性能优异的合金。该研究将为低成本制备钒钛基储氢合金工作提供理论依据和技术支持。

本研究以价格较低廉的V2O5为原料，采用电热还原法进行了V-Ti基储氢合金制备。.对反应的动力学研究表明，Al与TiO2反应的活化能明显高于Al与V2O5反应的活化能，反应速率受温度的影响更大。原料中添加一定CaO，可降低Al与TiO2反应的活化能。.熔渣性能测试表明，渣中添加一定MgO可起到助熔作用。MgO含量为8wt%时，初晶温度可降到1366℃，黏度小于0.83Pa•s。熔炼过程表明，m(CaO)/m(Al)为0.9、m(Al-Ca)/m(Al)为0.5时的熔炼效果较好。还原剂粒度不宜过细，3mm以内较适宜。合金中的Al杂质主要来自还原剂，有固溶和夹杂两种存在方式，Si主要来自耐火材料，以聚集形式存在合金中，而O主要与氧化物的脱O不彻底有关。.采用吹氩造渣对合金进行精炼，可较有效去除合金中的Al杂质，并能起到一定的预脱O作用。合适的条件为：渣量为合金量的35wt%，氩气流量5-9 L/min，精炼时间15min。精炼后合金中的Al由4.51wt%降到了1.53wt%，O由1.18wt%降到了0.8wt%。.采用熔盐电解脱氧可将合金的氧含量降到0.2wt%左右。以Ce为脱氧剂，采用真空精炼，可将O含量降到0.05wt%。Ce添加还具有降低合金的成分偏析、和提升合金储氢容量的作用，合金的有效放氢量可达到1.85wt%。.针对Ti28V33Cr9Ni30合金的电化学性能测试表明，Ce添加可提升电极的放电容量但不宜过多，添加5wt%时，电极放电容量最高可达228mAh.g-1，而添加11wt%时，只有198mAh.g-1。合金的循环稳定性也随Ce用量的增加呈现先增后降的变化趋势，用量为5wt%和7wt%时，C100/Cmax值可达到93%左右。合金的电化学反应的表观活化能为49.18kJ•mol-1，要高于LaNi5系合金。.本研究可为钒氧化物制备V基合金提供理论依据和技术支持。