纸上色层分离-重量法测定铝铌合金中铌

铝铌合金中铌的含量对铝铌合金的性能和应用有直接影响。使用纸上色层分离-重量法测定铌时,铌与其他元素的分离效果受层析剂配比和环境的影响较大。实验通过考察称样量、层析剂配比、层析时间、共存元素的影响等,最终确定了最佳的试验条件,实现了铝铌合金中铌含量的准确测定。试样经氢氟酸和硝酸溶解,将浓缩后的溶液涂在色层纸上,利用铌与铝及其他共存元素在特定的层析剂中迁移速率的不同,实现铌与其他共存元素的分离;将含有铌的色层纸在900℃马弗炉中灼烧至恒量。对于铌质量分数为50%~80%的铝铌合金,称样量选择0.10g,层析剂中4-甲基-2-戊酮、丁酮、氢氟酸、硝酸体积比为125∶42∶32∶7,层析时间为6h时分离效果最佳,试样中共存的铁、钼、硅、镍、铬等微量元素对测定结果无影响,若样品中钽的质量分数大于0.01%,需从粗氧化铌沉淀中减去氧化钽的质量。实验方法用于3种铝铌合金样品中铌的测定,结果的相对标准偏差(RSD,n=11)为0.18%~0.29%;加标回收率为98%~102%。选择4家实验室协同验证,经科克伦检验测试结果无明显差异。

Determination of niobium in aluminum-niobium alloy by paper chromatography separation-gravimetric method

The content of niobium in aluminum-niobium alloy has significant influence on the performance and application of aluminum-niobium alloy. During the determination of niobium by paper chromatography separation-gravimetric method, the separation effect of niobium from other elements is greatly affected by the chromatographic agent composition and environment. The effects of sample mass, chromatographic agent composition, chromatographic time and coexisting element were investigated in experiments. The optimal experimental conditions were finally obtained. The accurate determination of niobium content in aluminum-niobium alloy was realized. The sample was dissolved with hydrofluoric acid and nitric acid. The concentrated solution was coated on the colored paper. The separation of niobium from other coexisting elements was realized based on the different migration rates of niobium, aluminum and other coexisting elements in the specific chromatographic agent. The colored paper containing niobium was fired to constant mass in a muffle furnace at 900℃. For the aluminum-niobium alloy containing 50%-80% niobium (mass fraction), the separation effect was best under the following experimental conditions: the sample mass was 0.10g; the volume ratio of 4-methyl-2-pentanone, butanone, hydrofluoric acid and nitric acid in chromatographic agent was 125∶42∶32∶7; the chromatographic time was 6h. The coexisting microelements such as iron, molybdenum, silicon, nickel and chromium had no influence on the determination of niobium. If the mass fraction of tantalum in sample was higher than 0.01%, the mass of tantalum oxide should be subtracted from the crude niobium oxide precipitate. The proposed method was applied for the determination of niobium in three aluminum-niobium alloy samples. The relative standard deviations (RSD, n=11) of determination results were between 0.18%-0.29%. The spiked recoveries were between 98% and 102%. Four laboratories were selected for collaborative verification, and there was no significant difference in measurement results by the Cochran test.