Based on the development of a coupled thermo-mechanical plane strain large deformation orthogonal cutting model, the numerical simulation for elastic recovery process of ultra-precision machined surface of oxygen-free...Based on the development of a coupled thermo-mechanical plane strain large deformation orthogonal cutting model, the numerical simulation for elastic recovery process of ultra-precision machined surface of oxygen-free high-conductivity(OFHC) copper was performed. The simulation results indicate that the spring-back of machined surface is less than 10nm when the depth of cut reaches the same order of cutting edge radius. But with the decrement of cutting edge radius or depth of cut, the elastic recovery will reduce due to the decline of extrusion between diamond cutting tools edge and chip or machined surface.展开更多
Nanoindentation tests performed in a commercial atomic force microscope have been utilized to directly measure the elastic modulus and the hardness of single crystal copper thin films fabricated by the vacuum vapor de...Nanoindentation tests performed in a commercial atomic force microscope have been utilized to directly measure the elastic modulus and the hardness of single crystal copper thin films fabricated by the vacuum vapor deposition technique. Nanoindentation tests were conducted at various indentation depths to study the effect of indentation depths on the mechanical properties of thin films. The results were interpreted by using the Oliver-Pharr method with which direct observation and measurement of the contact area are not required. The elastic modulus of the single crystal copper film at various indentation depths was determined as (67.0±(6.9) GPa) on average which is in reasonable agreement with the results reported in literature. The indentation hardness constantly increases with decreasing indentation depth, indicating a strong size effect.展开更多
A new Precision Extrusion nozzle based ball screw transmission was developed. 3D hierarchical porous PLLA/nano-Hydroxyapatite（PLLA/nHA） scaffolds were fabricated by low-temperature deposition manufacturing. Scaffold...A new Precision Extrusion nozzle based ball screw transmission was developed. 3D hierarchical porous PLLA/nano-Hydroxyapatite（PLLA/nHA） scaffolds were fabricated by low-temperature deposition manufacturing. Scaffolds with macropores of 200-500 rtm and micropores about 10 pm were fabricated through a thorough study and control of the processing parameters, in which the processing path and speed of material extrusion determine the macropores and there is a suitable temperature zone for fabricating qualified macropores. Micropore morphology can be controlled by adjusting supercooling of solvent crystallization or adding water into the solvent system. The compressive modulus of the scaffolds in air and phosphate buffer solution was measured, which increased with HA addition. In-vitro cell culture results showed a ~ood biocomoatibilitv of PLLA/HA scaffolds with the ore-osteoblastic MC3T3-E1 cells.展开更多
In this paper torsional deformation of the carbon nanotubes is simulated by molecular dynamics method. The Brenner potential is used to set up the simulation system. Simulation results show that the carbon nanotubes c...In this paper torsional deformation of the carbon nanotubes is simulated by molecular dynamics method. The Brenner potential is used to set up the simulation system. Simulation results show that the carbon nanotubes can bear larger torsional deformation, for the armchair type （10,10） single wall carbon nanotubes, with a yielding phenomenon taking place when the torsional angle is up to 63°（1.1rad）. The influence of carbon nanotube helicity in torsional deformation is very small. The shear modulus of single wall carbon nanotubes should be several hundred GPa, not 1 GPa as others reports.展开更多
The nanomechanical behaviors of （110） and （111 ） CdZnTe crystals were investigated by nanoindentation. It was found that the indenter tip was adhered by the removed materials in scanning testing area although the ...The nanomechanical behaviors of （110） and （111 ） CdZnTe crystals were investigated by nanoindentation. It was found that the indenter tip was adhered by the removed materials in scanning testing area although the scanning force on the tested surface was very small （1000 nN）, which would affect the testing result of nanoindentation, so the indenter was clean before nanoindentation test. The experimemtal results showed that the hardness and Young＇s modulus decreased with the increase of indentation loads on the same plane. Because of the anisotropy of the CdZnTe crystal, the average hardness of （110） plane is 35% lower than that of （111） plane, and there are about 30% difference of the hardness along different crystallographic directions on the same plane. The hardness in 0° and 120° testing directions was the same due to the threefold symmetry of a Berkovich indenter. And the anisotropy affected the surface quality during machining of CdZnTe crystal.展开更多
An improved arc discharge method is developed to fabricate carbon nanotube probe of atomic force microscopy （AFM） here. First, silicon probe and carbon nanotube are manipulated under an optical microscope by two hig...An improved arc discharge method is developed to fabricate carbon nanotube probe of atomic force microscopy （AFM） here. First, silicon probe and carbon nanotube are manipulated under an optical microscope by two high precision microtranslators. When silicon probe and carbon nanotube are very close, several tens voltage is applied between them. And carbon nanotube is divided and attached to the end of silicon probe, which mainly due to the arc welding function. Comparing with the arc discharge method before, the new method here needs no coat silicon probe with metal film in advance, which can greatly reduce the fabrication＇s difficulty. The fabricated carbon nanotube probe shows good property of higher aspect ratio and can more accurately reflect the true topography of silicon grating than silicon probe. Under the same image drive force, carbon nanotube probe had less indentation depth on soft triblock copolymer sample than silicon probe. This showed that carbon nanotube probe has lower spring constant and less damage to the scan sample than silicon probe.展开更多
AFM is used for forming silicon dioxide as a layer (mask) on the silicon wafer surface (100) during the cutting process in ambient atmosphere. The silicon dioxide is made through reaction of silicon and oxygen in the ...AFM is used for forming silicon dioxide as a layer (mask) on the silicon wafer surface (100) during the cutting process in ambient atmosphere. The silicon dioxide is made through reaction of silicon and oxygen in the atmosphere. As a result of the anisotropic behavior of single crystalline silicon, the etching rates in alkaline solution depend greatly on the various crystal orientations. The anisotropic etching behaviors in KOH solution and reasons of crystalline silicon are described. Effect of etching conditions such as etching temperature and KOH concentration of the alkaline solution on height of the micro-protuberances has been described.展开更多
An improved arc discharge method is developed to fabricate the carbon nanotube probe. In this method, the silicon probe and the carbon nanotube were manipulated under an optical microscope. When the silicon probe and ...An improved arc discharge method is developed to fabricate the carbon nanotube probe. In this method, the silicon probe and the carbon nanotube were manipulated under an optical microscope. When the silicon probe and the carbon nanotube were very close, 30-60 V dc or ae was applied between them, and the carbon nanotube was divided and attached to the end of the silicon probe. Comparing with the arc discharge method, the new method need not coat the silicon probe with metal in advance, which can greatly reduce the fabrication difficulty and cost. The fabricated carbon nanotube probe exhibits the good property of high aspect ratio and can reflect the true topography more accurately than the silicon probe.展开更多
Ordinary AFM probes'characters prevent the AFM' s application in various scopes. Carbon nanotubes represent ideal AFM probe materials for their higher aspect ratio, larger Young's modulus, unique chemical ...Ordinary AFM probes'characters prevent the AFM' s application in various scopes. Carbon nanotubes represent ideal AFM probe materials for their higher aspect ratio, larger Young's modulus, unique chemical structure, and well-defined electronic property. Carbon nanotube AFM probes are obtained by using a new method of attaching carbon nanotubes to the end of ordinary AFM probes, and are then used for doing AFM experiments. These experiments indicated that carbon nanotube probes have higher elastic deformation, higher resolution and higher durability. And it was also found that carbon nanotube probes ean accurately reflect the morphology of deep narrow gaps, while ordinary probes can not reflect.展开更多
文摘Based on the development of a coupled thermo-mechanical plane strain large deformation orthogonal cutting model, the numerical simulation for elastic recovery process of ultra-precision machined surface of oxygen-free high-conductivity(OFHC) copper was performed. The simulation results indicate that the spring-back of machined surface is less than 10nm when the depth of cut reaches the same order of cutting edge radius. But with the decrement of cutting edge radius or depth of cut, the elastic recovery will reduce due to the decline of extrusion between diamond cutting tools edge and chip or machined surface.
文摘Nanoindentation tests performed in a commercial atomic force microscope have been utilized to directly measure the elastic modulus and the hardness of single crystal copper thin films fabricated by the vacuum vapor deposition technique. Nanoindentation tests were conducted at various indentation depths to study the effect of indentation depths on the mechanical properties of thin films. The results were interpreted by using the Oliver-Pharr method with which direct observation and measurement of the contact area are not required. The elastic modulus of the single crystal copper film at various indentation depths was determined as (67.0±(6.9) GPa) on average which is in reasonable agreement with the results reported in literature. The indentation hardness constantly increases with decreasing indentation depth, indicating a strong size effect.
基金Funded by the Harbin Science and Technology Innovation Researchers Project(No.2007RFXXSO21)
文摘A new Precision Extrusion nozzle based ball screw transmission was developed. 3D hierarchical porous PLLA/nano-Hydroxyapatite（PLLA/nHA） scaffolds were fabricated by low-temperature deposition manufacturing. Scaffolds with macropores of 200-500 rtm and micropores about 10 pm were fabricated through a thorough study and control of the processing parameters, in which the processing path and speed of material extrusion determine the macropores and there is a suitable temperature zone for fabricating qualified macropores. Micropore morphology can be controlled by adjusting supercooling of solvent crystallization or adding water into the solvent system. The compressive modulus of the scaffolds in air and phosphate buffer solution was measured, which increased with HA addition. In-vitro cell culture results showed a ~ood biocomoatibilitv of PLLA/HA scaffolds with the ore-osteoblastic MC3T3-E1 cells.
基金Project supported by the National Natural Science Foundation of China （Grant No 50405011） and the Natural Science Foundation of Heilongjiang Province of China （Grant No E0218）.
文摘In this paper torsional deformation of the carbon nanotubes is simulated by molecular dynamics method. The Brenner potential is used to set up the simulation system. Simulation results show that the carbon nanotubes can bear larger torsional deformation, for the armchair type （10,10） single wall carbon nanotubes, with a yielding phenomenon taking place when the torsional angle is up to 63°（1.1rad）. The influence of carbon nanotube helicity in torsional deformation is very small. The shear modulus of single wall carbon nanotubes should be several hundred GPa, not 1 GPa as others reports.
基金supported by the Key Project of National Natural Science Foundation of China (No.50535020)
文摘The nanomechanical behaviors of （110） and （111 ） CdZnTe crystals were investigated by nanoindentation. It was found that the indenter tip was adhered by the removed materials in scanning testing area although the scanning force on the tested surface was very small （1000 nN）, which would affect the testing result of nanoindentation, so the indenter was clean before nanoindentation test. The experimemtal results showed that the hardness and Young＇s modulus decreased with the increase of indentation loads on the same plane. Because of the anisotropy of the CdZnTe crystal, the average hardness of （110） plane is 35% lower than that of （111） plane, and there are about 30% difference of the hardness along different crystallographic directions on the same plane. The hardness in 0° and 120° testing directions was the same due to the threefold symmetry of a Berkovich indenter. And the anisotropy affected the surface quality during machining of CdZnTe crystal.
基金This project is supported by National Natural Science Foundation of China (No.50205006).
文摘An improved arc discharge method is developed to fabricate carbon nanotube probe of atomic force microscopy （AFM） here. First, silicon probe and carbon nanotube are manipulated under an optical microscope by two high precision microtranslators. When silicon probe and carbon nanotube are very close, several tens voltage is applied between them. And carbon nanotube is divided and attached to the end of silicon probe, which mainly due to the arc welding function. Comparing with the arc discharge method before, the new method here needs no coat silicon probe with metal film in advance, which can greatly reduce the fabrication＇s difficulty. The fabricated carbon nanotube probe shows good property of higher aspect ratio and can more accurately reflect the true topography of silicon grating than silicon probe. Under the same image drive force, carbon nanotube probe had less indentation depth on soft triblock copolymer sample than silicon probe. This showed that carbon nanotube probe has lower spring constant and less damage to the scan sample than silicon probe.
基金Sponsored by the Natural Science Foundation of China (Grant No.20271019), the Natural Science Foundation of Heilongjiang Province (Grant No.B200504) and the Education Department Foundation of Heilongjiang Province (Grant No.11511270).
文摘AFM is used for forming silicon dioxide as a layer (mask) on the silicon wafer surface (100) during the cutting process in ambient atmosphere. The silicon dioxide is made through reaction of silicon and oxygen in the atmosphere. As a result of the anisotropic behavior of single crystalline silicon, the etching rates in alkaline solution depend greatly on the various crystal orientations. The anisotropic etching behaviors in KOH solution and reasons of crystalline silicon are described. Effect of etching conditions such as etching temperature and KOH concentration of the alkaline solution on height of the micro-protuberances has been described.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50205006)
文摘An improved arc discharge method is developed to fabricate the carbon nanotube probe. In this method, the silicon probe and the carbon nanotube were manipulated under an optical microscope. When the silicon probe and the carbon nanotube were very close, 30-60 V dc or ae was applied between them, and the carbon nanotube was divided and attached to the end of the silicon probe. Comparing with the arc discharge method, the new method need not coat the silicon probe with metal in advance, which can greatly reduce the fabrication difficulty and cost. The fabricated carbon nanotube probe exhibits the good property of high aspect ratio and can reflect the true topography more accurately than the silicon probe.
基金Sponsored by the National Natural Science Foundation of China (Grant No. 50202006)the Multidisciline Scientific Research Foundation of Harbin Institute of Technology (Grant No. HIT. MD. 2001.04)
文摘Ordinary AFM probes'characters prevent the AFM' s application in various scopes. Carbon nanotubes represent ideal AFM probe materials for their higher aspect ratio, larger Young's modulus, unique chemical structure, and well-defined electronic property. Carbon nanotube AFM probes are obtained by using a new method of attaching carbon nanotubes to the end of ordinary AFM probes, and are then used for doing AFM experiments. These experiments indicated that carbon nanotube probes have higher elastic deformation, higher resolution and higher durability. And it was also found that carbon nanotube probes ean accurately reflect the morphology of deep narrow gaps, while ordinary probes can not reflect.
