The rupture behavior of electron beam physical vapour deposition（EBPVD） Ni/Ni3Al microlaminates composites subjected to tensile load were studied through the numerical method of finite element. 2D model and 3D model...The rupture behavior of electron beam physical vapour deposition（EBPVD） Ni/Ni3Al microlaminates composites subjected to tensile load were studied through the numerical method of finite element. 2D model and 3D model of EBPVD Ni/Ni3Al microlaminates with a centre crack were built respectively. A new scheme for building 3D crack point models was proposed and different types of elements were used. And stress intensity factors around the tip of the crack were obtained correspondingly. The results indicate that the key of the stress intensity factor for 2D model is presumably the average of the keys for 3D model in thickness and the key at the interface is the biggest, which suggests the propagation of the crack greatly likely happen at the interface.展开更多
Wurtzite structure gallium nitride, GaN,a direct bandgap semiconductor(3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ting diodes(LED),laser diodes(LD),and high power integra...Wurtzite structure gallium nitride, GaN,a direct bandgap semiconductor(3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ting diodes(LED),laser diodes(LD),and high power integrated circuits.When used a s the material for LEDs and LDs,GaN has high transforming efficiencies and its d evice s have a long using lifetime of up to 10000 hours,several decuple times longer t han that of conventional light emitting diodes.As a semiconductor material for b lue/green light sources,GaN is non replaceable.It will have important applications in li g ht emitting devices,optical communication systems,compact disk(CD)players,full c olor copying devices,full color printers,high distinguishing laser printers,gr ea t screen full color displaying devices,and super thin TV displaying devices etc . In recent years,GaN has been the focus and hotspot of semiconductor industries,a nd its devices have a shining place in light emitting and laser industries. We synthesized GaN nanowires by a chemical vapor deposition (CVD)method.The nano wires have diameters from 20 nm to 60 nm,and the maximum length is up to 100 μ m .Following figure is the scanning electron microscopy (SEM)image of the as synt hesized GaN nanowires.展开更多
Wurtzite strcture gallium nitride, GaN,a direct bandgap semiconductor (3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ti ng diodes, laser diodes,and high power integrated cir...Wurtzite strcture gallium nitride, GaN,a direct bandgap semiconductor (3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ti ng diodes, laser diodes,and high power integrated circuits.Recent progress in th in film crystal technique has realized the output of blue semiconductor lasers w i th a lifetime of over 10000 hours under continuous wave operation at room tempe r ature.So far GaN and its ternary indium and aluminum alloys are grown almost uni v ersally on foreign substrates with varying lattice mismatches.The mismatch undou btedly results in a significant dislocation density in the grown films.Hence it is necessary to grow single crystal GaN to be used as substrates for improvement of laser diodes.On the other hand,low dimensional GaN materials such as nanocry stalline powder,nanocrystal assembled bulk(nanophase) and nano wires are very u seful in both fundamental mesoscopic research and future development of GaN nano devices.Here we report our main recent progresses on the crystal growth of GaN a nd the preparation of its low dimensional materials.展开更多
文摘The rupture behavior of electron beam physical vapour deposition（EBPVD） Ni/Ni3Al microlaminates composites subjected to tensile load were studied through the numerical method of finite element. 2D model and 3D model of EBPVD Ni/Ni3Al microlaminates with a centre crack were built respectively. A new scheme for building 3D crack point models was proposed and different types of elements were used. And stress intensity factors around the tip of the crack were obtained correspondingly. The results indicate that the key of the stress intensity factor for 2D model is presumably the average of the keys for 3D model in thickness and the key at the interface is the biggest, which suggests the propagation of the crack greatly likely happen at the interface.
文摘Wurtzite structure gallium nitride, GaN,a direct bandgap semiconductor(3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ting diodes(LED),laser diodes(LD),and high power integrated circuits.When used a s the material for LEDs and LDs,GaN has high transforming efficiencies and its d evice s have a long using lifetime of up to 10000 hours,several decuple times longer t han that of conventional light emitting diodes.As a semiconductor material for b lue/green light sources,GaN is non replaceable.It will have important applications in li g ht emitting devices,optical communication systems,compact disk(CD)players,full c olor copying devices,full color printers,high distinguishing laser printers,gr ea t screen full color displaying devices,and super thin TV displaying devices etc . In recent years,GaN has been the focus and hotspot of semiconductor industries,a nd its devices have a shining place in light emitting and laser industries. We synthesized GaN nanowires by a chemical vapor deposition (CVD)method.The nano wires have diameters from 20 nm to 60 nm,and the maximum length is up to 100 μ m .Following figure is the scanning electron microscopy (SEM)image of the as synt hesized GaN nanowires.
文摘Wurtzite strcture gallium nitride, GaN,a direct bandgap semiconductor (3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ti ng diodes, laser diodes,and high power integrated circuits.Recent progress in th in film crystal technique has realized the output of blue semiconductor lasers w i th a lifetime of over 10000 hours under continuous wave operation at room tempe r ature.So far GaN and its ternary indium and aluminum alloys are grown almost uni v ersally on foreign substrates with varying lattice mismatches.The mismatch undou btedly results in a significant dislocation density in the grown films.Hence it is necessary to grow single crystal GaN to be used as substrates for improvement of laser diodes.On the other hand,low dimensional GaN materials such as nanocry stalline powder,nanocrystal assembled bulk(nanophase) and nano wires are very u seful in both fundamental mesoscopic research and future development of GaN nano devices.Here we report our main recent progresses on the crystal growth of GaN a nd the preparation of its low dimensional materials.
