喷雾干燥-氢还原制备W-50Cu纳米复合粉末过程中的相转变

Phase Transformation during Synthesis of W-50Cu Nanocomposite Powder by Spray-Drying and Hydrogen Reduction Process

采用溶胶-喷雾干燥、煅烧和氢还原工艺制备了纳米级W-50%Cu(质量分数,下同)复合粉末,采用扫描电镜(SEM)和X射线衍射分析(XRD)研究了粉末制备过程中的相演变。非晶态喷雾干燥前驱体经煅烧形成复合氧化物粉末,其形貌和相结构随煅烧温度而变化。煅烧后的复合氧化物粉末在还原过程中经过了一系列复杂的相转变,其相转变过程分为3个阶段:在350℃,粉末主要由Cu、Cu2O、WO3、W相组成;在450℃还原后粉末由Cu、Cu2O、WO3和WO2相组成;在550℃以上还原时,铜的氧化物全部变成Cu相,WO3和WO2渐渐变成W相,其中WO2一直在750℃仍保持稳定。一系列的XRD分析结果表明,还原后的W-Cu纳米复合粉末由W(Cu)超饱和固溶体新相和Cu相组成,其晶粒尺寸分别为33nm和63nm。

SEM and XRD characterized the phase evolution during synthesis of W-50wt%Cu nanocomposite powder prepared by sol-spray drying, calcination, and subsequent reduction process. The spray dried composite salt precursors changed into composite oxides after calcination, whose morphology and phase structure varied with the calcined temperature. The reduction of the calcined composite oxides go through a series of complicated phase transformation, which could be departed into three stages： Powder consisted of Cu, Cu2O, WO3, W phases below 350 ℃, Cu, Cu2O, WO3 and WO2 phase at temperature of 450 ℃, copper oxides changed into Cu phase completely at temperature above 550 ℃. WO3 and WO2 were gradually reduced, the WO2 phase kept stable up to 750 ℃. A series of XRD analysis implied that composite powder after reduction is composed of W（Cu） phase supersaturated solid-solution with grain size of 33 nm and Cu phase with 63 nm respectively.