工业氧化钨相状态的Rietveld分析

Rietveld Analysis of Phase State of Industrial Tungsten Oxide

氧化钨是工业上制取钨粉的重要原料。除了常规粉末物理性能检测,现行物相检测方法通常为K值法或外标法,但主要是从表观颜色“黄蓝紫”及氧指数等化学组成上进行区分,对于生产工艺指导仍存在不足。本文尝试采用Rietveld法对工业氧化钨从物相结构上进行表征,通过结构模型假设及拟合条件限定以弱化氧化钨相分析难点的影响。系列工艺实验样的结果表明,方法的前提假设可行,适用于不同生产阶段的工业氧化钨的相分析。特定工艺下,黄钨向蓝钨的转变过程中,WO3三斜相减少较快,单斜相也减少,但速度相对较慢,斜方相则增加;蓝钨向紫钨的转变过程中,WO3单斜相和三斜相先消失,斜方相逐渐减少,先生成WO2.90单斜相,再生成WO2.90四方相,再进一步生成WO2.72单斜相。当被测相的质量分数大于5%,RSD均小于5%。

Tungsten oxide is an important raw material for the industrial production of tungsten powder.In addition to conventional physical performance testing of powder,the current phase detection methods are usually the K-value method or external standard method,but they mainly distinguish from the chemical composition such as the apparent yellow,blue,and purpleand oxygen index.There are still shortcomings in guiding the production process.This article attempts to use the Rietveld method to characterize the phase structure of industrial tungsten oxide and weaken the influence of difficulties in tungsten oxide phase analysis through structural model assumptions and fitting conditions.The results of a series of process experimental samples indicate that the premise assumption of the method is feasible and suitable for phase analysis of industrial tungsten oxide at different production stages.Under specific processes,during the transition from yellow tungsten to blue tungsten,the anorthic phase of WO3 decreases rapidly,and the monoclinic phase decreases,but the speed is relatively slow,while the orthorhombic phase increases.During the transition from blue tungsten to purple tungsten,the monoclinic and anorthic phases of WO3 first disappear,while the orthorhombic phase gradually decreases,forming WO2.90 monoclinic phase,followed by WO2.90 tetragonal phase,and further generating WO2.72 monoclinic phase.When the mass fraction of measured phase is more than 5%,the relative standard deviation can be less than 5%.