砷对紫钨制备及碳化过程的影响
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摘要
砷(As)是白钨矿中常见的杂质元素,通常在冶金过程中需对其进行除杂处理,而As对后续钨产品的影响尚不清楚。以仲钨酸铵(APT)和As单质为原料制备As质量含量为1%的APT-As复合粉末,经煅烧和碳化,分别制备出含As的紫钨(W_(18)O_(49)-As)及碳化钨(WC-As)。采用X射线衍射仪、扫描电镜、高分辨透射电镜和差示扫描量热仪对W_(18)O_(49)-As及WC-As的形貌及结构进行分析。分析结果表明:As元素主要以W_2O_3(AsO_4)_2第二相的形式存在于棒条状W_(18)O_(49)-As的表面,易使棒条状W_(18)O_(49)-As发生断裂;W_(18)O_(49)-As还原和碳化反应起始温度比不含As的W_(18)O_(49)低;W_2O_3(AsO_4)_2第二相分布于W_(18)O_(49)之间,阻碍W_(18)O_(49)碳化过程中物质的迁移扩散,从而抑制细小WC颗粒的聚集长大,得到均匀性好的WC-As粉末。
Arsenic(As)is a common impurity element in scheelite,and needs to be removed in the metallurgical process.However,the effect of arsenic on the subsequent tungsten products is not clear.APT-As composite powders with As mass content of 1% was prepared by using ammonium tungstate and As element as raw materials.After the treatment of calcination and carbonization,violet tungsten oxide(W_(18)O_(49)-As)and tungsten carbide(WC-As)containing arsenic were obtained,respectively.X-ray diffractometer,scanning electron microscope,high-resolution transmission electron microscope and differential scanning calorimeter were used to analyse the morphology and structure of W_(18)O_(49)-As and WC-As.The results show that As element mainly exists in the surface of the bar W_(18)O_(49)-As in the form of W_2O_3(AsO_4)_2 phase,making bar W_(18)O_(49)-As easily break.The initial reaction temperatures of reduction and carbonization of W_(18)O_(49)-As are lower than those of W_(18)O_(49).The phase of W_2O_3(AsO_4)_2 is distributed between W_(18)O_(49) powders,hindering substance migration and diffusion in the process of W_(18)O_(49) carbonization and inhibiting aggregation and growth of fine WC particles,so the uniform WC-As powders are obtained.
Arsenic(As)is a common impurity element in scheelite,and needs to be removed in the metallurgical process.However,the effect of arsenic on the subsequent tungsten products is not clear.APT-As composite powders with As mass content of 1% was prepared by using ammonium tungstate and As element as raw materials.After the treatment of calcination and carbonization,violet tungsten oxide(W_(18)O_(49)-As)and tungsten carbide(WC-As)containing arsenic were obtained,respectively.X-ray diffractometer,scanning electron microscope,high-resolution transmission electron microscope and differential scanning calorimeter were used to analyse the morphology and structure of W_(18)O_(49)-As and WC-As.The results show that As element mainly exists in the surface of the bar W_(18)O_(49)-As in the form of W_2O_3(AsO_4)_2 phase,making bar W_(18)O_(49)-As easily break.The initial reaction temperatures of reduction and carbonization of W_(18)O_(49)-As are lower than those of W_(18)O_(49).The phase of W_2O_3(AsO_4)_2 is distributed between W_(18)O_(49) powders,hindering substance migration and diffusion in the process of W_(18)O_(49) carbonization and inhibiting aggregation and growth of fine WC particles,so the uniform WC-As powders are obtained.
引文
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[2]ZHAO Z,LI J,WANG S,et al.Extracting tungsten from scheelite concentrate with caustic soda by autoclaving process[J].Hydrometallurgy,2011,108(1):152-156.
[3]谭敦强,李亚蕾,杨欣,等.杂质元素对钨产品结构及性能的影响[J].材料导报,2013,27(17):98-100.
[4]李洪桂,孙培梅.选择性沉淀法从钨酸盐溶液中除钼、砷、锑、锡等杂质的研究[J].中国钨业,1998(4):17-19.
[5]ZHU H,TAN D,LI Y,et al.Refining mechanisms of arsenic in the hydrogen reduction process of tungsten oxide[J].Advanced Powder Technology,2015,26(3):1 013-1 020.
[6]WANG X,TAN D,ZHU H,et al.Effect mechanism of arsenic on the growth of ultrafine tungsten carbide powder[J].Advanced Powder Technology,2018,29(6):1 348-1 356.
[7]张湘.直接碳化技术制备碳化钨粉的研究[J].硬质合金,2013,30(2):73-78.
[8]张永会,傅声华,李飞.紫色氧化钨的制备及工艺研究[J].中国钨业,2011,26(3):47-49.
[9]秦明礼,陈鹏起,陈铮,等.一种制备纳米针状紫钨粉末的方法:CN104843792A[P].2015-08-19.
[10]王岗,李海华,黄忠伟,等.蓝钨与紫钨氢还原法生产超细钨粉的比较[J].稀有金属材料与工程,2009,38(S1):548-552.
[11]宋志华,郭亨群,吴冲浒,等.以紫钨为原料制备纳米钨粉体的研究[J].稀有金属材料与工程,2011,40(12):2 216-2 220.
[12]WU C.Preparation of ultrafine tungsten powders by insitu hydrogen reduction of nano-needle violet tungsten oxide[J].International Journal of Refractory Metals&Hard Materials,2011,29(6):686-691.
[13]张久兴,张国珍,张利平,等.氧化钨/碳SPS原位合成WC硬质合金的XPS研究[J].稀有金属材料与工程,2006,35(6):937-940.