A dual-scale hybrid HfB_(2)/Cu-Hf composite with HfB_(2) microparticles and Cu_(5) Hf nanoprecipitates was designed and prepared.The contribution of the hybrid effect to the mechanical properties and high-temperature ...A dual-scale hybrid HfB_(2)/Cu-Hf composite with HfB_(2) microparticles and Cu_(5) Hf nanoprecipitates was designed and prepared.The contribution of the hybrid effect to the mechanical properties and high-temperature performances was studied from macro and micro perspectives,respectively.The hybrid of dual-scale particles can make the strain distribution of the composite at the early deformation stage more uniform and delay the strain concentration caused by the HfB_(2) particle.The dislocation pinning of HfB_(2) particles and the coherent strengthening of Cu_(5) Hf nanoprecipitates simultaneously play a strengthening role,but the strength of the hybrid composite is not a simple superposition of two strengthening mod-els.In addition,both Cu_(5) Hf nanoprecipitates and HfB_(2) microparticles contribute to the high-temperature performance of the composite,the growth and phase transition of nanoprecipitates at high temperature will reduce their contribution to strength,while the stable HfB_(2) particles can inhibit the coarsening of matrix grains and maintain the high-density geometrically necessary dislocations(GNDs)in the matrix,which ensures more excellent high-temperature resistance of the hybrid composite.As a result,the hy-brid structure can simultaneously possess the advantages of multiple reinforcements and make up for the shortcomings of each other.Finally,a copper matrix composite with high strength,high conductivity,and excellent high-temperature performance is displayed.展开更多
In this research, a series of wood-based panels were produced by using wood chips [beech (Fagus Sylvatica L.) and Scotch pine (Pinus sylvestris L.)] as wastes of wood-working workshops and acrylic fibers as wastes of ...In this research, a series of wood-based panels were produced by using wood chips [beech (Fagus Sylvatica L.) and Scotch pine (Pinus sylvestris L.)] as wastes of wood-working workshops and acrylic fibers as wastes of textiles factory. Four kinds of different panels (Eltapan I, II, III and IV) were obtained by mixing these components in different composition (0%, 25% and 50%). Some physical and mechanical properties of the samples taken from these panels were determined in accordance with ASTM D1037-12 and ASTM-C 1113. The values were compared to properties of industrially produced chipboard. As a result, the textile fibers used as additive material reduced density, thermal conductivity and bending resistance of wood panel and increased dimensional stability of wood panel.展开更多
Copper-based composites strengthened by ceria nanoparticles were processed by conventional powder metallurgy: mixing (30 min and 46 rpm), compaction (cold, uniaxial, 1080 MPa for 10 s) and sintering (800°C for 6 ...Copper-based composites strengthened by ceria nanoparticles were processed by conventional powder metallurgy: mixing (30 min and 46 rpm), compaction (cold, uniaxial, 1080 MPa for 10 s) and sintering (800°C for 6 h in vacuum atmosphere of 10−5 torr). It was studied the microstructure (optical microscopy, scanning electron microscopy), X-ray diffraction with Rietveld refinement and some properties (electrical conductivity, Vickers hardness and fracture analysis) of the compositions 92 wt% Cu - 8 wt% CeO2 and 80 wt% Cu - 20 wt% CeO2. The results showed uniform phase distribution, low porosity and ceria disperse inside copper grain. In despite of properties, the composites had electrical conductivity of 38% IACS and 15% IACS and hardness of 69 and 88 HV5, respectively. The results of 92 wt% Cu - 8 wt% CeO2 composites were promising, and they are in according with actual literature.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52127802,52271137,and 51834009).
文摘A dual-scale hybrid HfB_(2)/Cu-Hf composite with HfB_(2) microparticles and Cu_(5) Hf nanoprecipitates was designed and prepared.The contribution of the hybrid effect to the mechanical properties and high-temperature performances was studied from macro and micro perspectives,respectively.The hybrid of dual-scale particles can make the strain distribution of the composite at the early deformation stage more uniform and delay the strain concentration caused by the HfB_(2) particle.The dislocation pinning of HfB_(2) particles and the coherent strengthening of Cu_(5) Hf nanoprecipitates simultaneously play a strengthening role,but the strength of the hybrid composite is not a simple superposition of two strengthening mod-els.In addition,both Cu_(5) Hf nanoprecipitates and HfB_(2) microparticles contribute to the high-temperature performance of the composite,the growth and phase transition of nanoprecipitates at high temperature will reduce their contribution to strength,while the stable HfB_(2) particles can inhibit the coarsening of matrix grains and maintain the high-density geometrically necessary dislocations(GNDs)in the matrix,which ensures more excellent high-temperature resistance of the hybrid composite.As a result,the hy-brid structure can simultaneously possess the advantages of multiple reinforcements and make up for the shortcomings of each other.Finally,a copper matrix composite with high strength,high conductivity,and excellent high-temperature performance is displayed.
文摘In this research, a series of wood-based panels were produced by using wood chips [beech (Fagus Sylvatica L.) and Scotch pine (Pinus sylvestris L.)] as wastes of wood-working workshops and acrylic fibers as wastes of textiles factory. Four kinds of different panels (Eltapan I, II, III and IV) were obtained by mixing these components in different composition (0%, 25% and 50%). Some physical and mechanical properties of the samples taken from these panels were determined in accordance with ASTM D1037-12 and ASTM-C 1113. The values were compared to properties of industrially produced chipboard. As a result, the textile fibers used as additive material reduced density, thermal conductivity and bending resistance of wood panel and increased dimensional stability of wood panel.
文摘Copper-based composites strengthened by ceria nanoparticles were processed by conventional powder metallurgy: mixing (30 min and 46 rpm), compaction (cold, uniaxial, 1080 MPa for 10 s) and sintering (800°C for 6 h in vacuum atmosphere of 10−5 torr). It was studied the microstructure (optical microscopy, scanning electron microscopy), X-ray diffraction with Rietveld refinement and some properties (electrical conductivity, Vickers hardness and fracture analysis) of the compositions 92 wt% Cu - 8 wt% CeO2 and 80 wt% Cu - 20 wt% CeO2. The results showed uniform phase distribution, low porosity and ceria disperse inside copper grain. In despite of properties, the composites had electrical conductivity of 38% IACS and 15% IACS and hardness of 69 and 88 HV5, respectively. The results of 92 wt% Cu - 8 wt% CeO2 composites were promising, and they are in according with actual literature.
