Some elements normally occur at trace levels while the majority of natural geological materials may be exceedingly enriched in some special cases, such as the Bayan Obo ore deposit where REE and Nb are extremely enric...Some elements normally occur at trace levels while the majority of natural geological materials may be exceedingly enriched in some special cases, such as the Bayan Obo ore deposit where REE and Nb are extremely enriched. These elements may not be removed completely during purification. Therefore, matrix effects will be caused during stable isotope ratio measurement in the MC-ICP-MS. Experiments have shown that the established methods of chromatographic separation of Cu, Fe, and Zn using AG MP-1 Anion Exchange Resin cannot make ef-fective separation of Nb, W, and Cu from Fe using 20 mL 6 M HCl. It is also observed that the elution curves of W and Cu overlap at working conditions and thus W is present in measurable amounts in some sample solutions. Matrix effects in the MC-ICP-MS induced by Nb, W, and Cu during Fe isotope ratio measurements and by W during Cu isotope ratio measurements were thus investigated by examining their changes in delta values between doped and undoped standards. The results show that the effects of the matrix elements Nb, W, or Cu on Fe isotope ratio measurements are minimal in the case of m(Nb)/m(Fe)<0.005, m(W)/m(Fe)<0.01, or m(Cu)/m(Fe)<0.6. This finding, combined with the extremely low levels of W and Cu, and the fact that nearly 90% of Nb can be removed during purification, demonstrates that the methods of chromatographic separation of Fe established before are suitable for Bayan Obo ore samples and that the methods can be simplified when Cu elution is unnecessary. The effects of the matrix element W on Cu isotope determinations are minimal in the case of m(W)/m(Cu)<0.7. Therefore, W exerts no significant effect on the measurements of Cu isotopes for the majority of natural geological materials.展开更多
W-25Cu alloys were microwave sintered in a 2.45 GHz multimode applicator.The densification,microstructure and their dependence on sintering mode and Fe addition were investigated in detail.Owing to the volumetric heat...W-25Cu alloys were microwave sintered in a 2.45 GHz multimode applicator.The densification,microstructure and their dependence on sintering mode and Fe addition were investigated in detail.Owing to the volumetric heating intrinsic in microwave processing,a microstructure with larger W grain size in center regions was observed as against larger grain size in edge regions for conventional sintering.Microwave sintering demonstrates its intrinsic advantages such as rapid heating rate,densification enhancement and microstructural homogeneity;but it undesirably promotes W grain growth.Under microwave sintering,the role of Fe addition on compact consolidation is not so substantial as under conventional sintering.Moreover Fe degrades the microstructural quality,generating worse uniformity and coarser W grains.展开更多
基金financially supported by the National Natural Science Foundation of China (Grant No. 40973037)the MLR Public Benefit Research Foundation of China (Grant No.200911043-14)
文摘Some elements normally occur at trace levels while the majority of natural geological materials may be exceedingly enriched in some special cases, such as the Bayan Obo ore deposit where REE and Nb are extremely enriched. These elements may not be removed completely during purification. Therefore, matrix effects will be caused during stable isotope ratio measurement in the MC-ICP-MS. Experiments have shown that the established methods of chromatographic separation of Cu, Fe, and Zn using AG MP-1 Anion Exchange Resin cannot make ef-fective separation of Nb, W, and Cu from Fe using 20 mL 6 M HCl. It is also observed that the elution curves of W and Cu overlap at working conditions and thus W is present in measurable amounts in some sample solutions. Matrix effects in the MC-ICP-MS induced by Nb, W, and Cu during Fe isotope ratio measurements and by W during Cu isotope ratio measurements were thus investigated by examining their changes in delta values between doped and undoped standards. The results show that the effects of the matrix elements Nb, W, or Cu on Fe isotope ratio measurements are minimal in the case of m(Nb)/m(Fe)<0.005, m(W)/m(Fe)<0.01, or m(Cu)/m(Fe)<0.6. This finding, combined with the extremely low levels of W and Cu, and the fact that nearly 90% of Nb can be removed during purification, demonstrates that the methods of chromatographic separation of Fe established before are suitable for Bayan Obo ore samples and that the methods can be simplified when Cu elution is unnecessary. The effects of the matrix element W on Cu isotope determinations are minimal in the case of m(W)/m(Cu)<0.7. Therefore, W exerts no significant effect on the measurements of Cu isotopes for the majority of natural geological materials.
基金Funded by China Postdoctoral Science Foundation (No. 20060400882) Postdoctoral Science Foundation of Central South University
文摘W-25Cu alloys were microwave sintered in a 2.45 GHz multimode applicator.The densification,microstructure and their dependence on sintering mode and Fe addition were investigated in detail.Owing to the volumetric heating intrinsic in microwave processing,a microstructure with larger W grain size in center regions was observed as against larger grain size in edge regions for conventional sintering.Microwave sintering demonstrates its intrinsic advantages such as rapid heating rate,densification enhancement and microstructural homogeneity;but it undesirably promotes W grain growth.Under microwave sintering,the role of Fe addition on compact consolidation is not so substantial as under conventional sintering.Moreover Fe degrades the microstructural quality,generating worse uniformity and coarser W grains.
