Diamond impregnated Cu-Fe-Co based saw-blade segments are directly processed by vacuum and pressure-assisted sintering at different temperature,with the purpose of reducing the cobalt content in diamond tools.Copper a...Diamond impregnated Cu-Fe-Co based saw-blade segments are directly processed by vacuum and pressure-assisted sintering at different temperature,with the purpose of reducing the cobalt content in diamond tools.Copper and iron are used as the bonding elements and co-balt-chrome pre-alloyed powder is used as the hardening phase.Effects of sintering temperature on microstructures and mechanical properties of the sintered matrix and diamond graphitization were investigated by X-ray diffraction analysis,electron probe micro-analyzer,universal testing machine,digital Rockwell hardness tester and Raman scattering analyzer.Results showed that microstructures of the sintered matrix were refined and porosities in the sintered matrix were closed to a more spherical-like shape with the increase of the sintering temperature.Densification,hardness and tensile strength of the matrix sintered at 820 ℃ were 12.75%,2.72% and 156.38% higher than that of the matrix sintered at 740 ℃,respectively.Diamond graphitization was not occurred at 820 ℃.The hardness and the tensile strength rose 32.8% and 13.5%,respectively,after 7.5 h ageing treatment.The matrix densification ascent and the dispersed distribution of Co-Cr pre-alloyed powders contributed a hardness improvement and a tensile strength improvement to the Cu-Fe based matrix.展开更多
The effective valuation of catalyst supports in the catalytic oxidation makes the contribution to understand the support effect of great interest.Here,the role of active substrate in the performance and stability of C...The effective valuation of catalyst supports in the catalytic oxidation makes the contribution to understand the support effect of great interest.Here,the role of active substrate in the performance and stability of CuFe-Co ternary oxides was studied towards the complete catalytic oxidation of CO.The Cu-Fe-Co oxide thin films were deposited on copper grid mesh(CUGM)using one-step pulsed-spray evaporation chemical vapor deposition method.Crystalline structure and morphology analyses revealed nano-crystallite sizes and do me-top-like morphology.Synergistic effects between Cu,Fe and Co,which affect the surface Cu^2+,Fe^3+,Co^3+and chemisorbed oxygen species(O2 and OH)of thin films over the active support and thus result in better reducibility.The thin film catalysts supported on CUGM exhibited attractive catalytic activity compared to the te rnary oxides supported on ine rt grid mesh at a high gas hourly space velocity.Moreove r,the stability in time-on-stream of the ternary oxides on CUGM was evaluated in the CO oxidation for 30 h.The ad opted deposition strategy ofternary oxides on CUGM presents an excessive amount of adsorbed active oxygen species that play an impo rtant role in the complete CO oxidation.The catalysts supported on CUGM showed better catalytic conve rsion than that on inert grid mesh and some literature-reported noble metal oxides as well as transition metal oxides counterparts,revealing the beneficial effect of the CUGM suppo rt in the improvement of the catalytic performance.展开更多
基金financially supported by Gansu Key Technology Project (No.090JKCA050)Gansu Outstanding Youth Foundation (No.201105)
文摘Diamond impregnated Cu-Fe-Co based saw-blade segments are directly processed by vacuum and pressure-assisted sintering at different temperature,with the purpose of reducing the cobalt content in diamond tools.Copper and iron are used as the bonding elements and co-balt-chrome pre-alloyed powder is used as the hardening phase.Effects of sintering temperature on microstructures and mechanical properties of the sintered matrix and diamond graphitization were investigated by X-ray diffraction analysis,electron probe micro-analyzer,universal testing machine,digital Rockwell hardness tester and Raman scattering analyzer.Results showed that microstructures of the sintered matrix were refined and porosities in the sintered matrix were closed to a more spherical-like shape with the increase of the sintering temperature.Densification,hardness and tensile strength of the matrix sintered at 820 ℃ were 12.75%,2.72% and 156.38% higher than that of the matrix sintered at 740 ℃,respectively.Diamond graphitization was not occurred at 820 ℃.The hardness and the tensile strength rose 32.8% and 13.5%,respectively,after 7.5 h ageing treatment.The matrix densification ascent and the dispersed distribution of Co-Cr pre-alloyed powders contributed a hardness improvement and a tensile strength improvement to the Cu-Fe based matrix.
基金financial support from the MOST(No.2017YFA0402800)the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China(No.51888103)。
文摘The effective valuation of catalyst supports in the catalytic oxidation makes the contribution to understand the support effect of great interest.Here,the role of active substrate in the performance and stability of CuFe-Co ternary oxides was studied towards the complete catalytic oxidation of CO.The Cu-Fe-Co oxide thin films were deposited on copper grid mesh(CUGM)using one-step pulsed-spray evaporation chemical vapor deposition method.Crystalline structure and morphology analyses revealed nano-crystallite sizes and do me-top-like morphology.Synergistic effects between Cu,Fe and Co,which affect the surface Cu^2+,Fe^3+,Co^3+and chemisorbed oxygen species(O2 and OH)of thin films over the active support and thus result in better reducibility.The thin film catalysts supported on CUGM exhibited attractive catalytic activity compared to the te rnary oxides supported on ine rt grid mesh at a high gas hourly space velocity.Moreove r,the stability in time-on-stream of the ternary oxides on CUGM was evaluated in the CO oxidation for 30 h.The ad opted deposition strategy ofternary oxides on CUGM presents an excessive amount of adsorbed active oxygen species that play an impo rtant role in the complete CO oxidation.The catalysts supported on CUGM showed better catalytic conve rsion than that on inert grid mesh and some literature-reported noble metal oxides as well as transition metal oxides counterparts,revealing the beneficial effect of the CUGM suppo rt in the improvement of the catalytic performance.
