The self-assembled silicon substrate. The resultant contact angle meter and atomic method was introduced to successfully obtain film was characterized by means of X-ray rare earth（RE） nanofilm on a single-crystal ph...The self-assembled silicon substrate. The resultant contact angle meter and atomic method was introduced to successfully obtain film was characterized by means of X-ray rare earth（RE） nanofilm on a single-crystal photoelectron spectroscopy （XPS）, ellipsometer, force microscopy （AFM）. The scratch experiment was performed for interfacial adhesion measurement of the RE film. The friction and wear behavior of RE nanofilm was examined on a DF-PM reciprocating friction and wear tester. The results indicate the RE nanofilm is of low coefficient of friction （COF） and high wear resistance. These desirable characteristics of RE nanofilm together with its nanometer thickness, strong bonding to the substrate and low surface energy make it a promising choice as a solid lubricant film in micro electromechanical system （MEMS） devices.展开更多
Repetitive bending fatigue tests were performed using five types of single-crystal silicon specimens with different crystal orientations fabricated from{100}and{110}wafers.Fatigue lifetimes in a wide range between 100...Repetitive bending fatigue tests were performed using five types of single-crystal silicon specimens with different crystal orientations fabricated from{100}and{110}wafers.Fatigue lifetimes in a wide range between 100 and 1010 were obtained using fan-shaped resonator test devices.Fracture surface observation via scanning electron microscope(SEM)revealed that the{111}plane was the primary fracture plane.The crack propagation exponent n was estimated to be 27,which was independent of the crystal orientation and dopant concentration;however,it was dependent on the surface conditions of the etched sidewall.The fatigue strengths relative to the deflection angle were orientation dependent,and the ratios of the factors obtained ranged from 0.86 to 1.25.The strength factors were compared with those obtained from finite element method stress analyses.The calculated stress distributions showed strong orientation dependence,which was well-explained by the elastic anisotropy.The comparison of the strength factors suggested that the first principal stress was a good criterion for fatigue fracture.We include comparisons with specimens tested in our previous report and address the tensile strength,initial crack length,volume effect,and effects of surface roughness such as scallops.展开更多
Ultra-precision machining causes materials to undergo a greatly strained deformation process in a short period of time.The effect of shear strain rates on machining quality, in particular on surface anisotropy, is a t...Ultra-precision machining causes materials to undergo a greatly strained deformation process in a short period of time.The effect of shear strain rates on machining quality, in particular on surface anisotropy, is a topic deserving of research that has thus far been overlooked.This study analyzes the impact of the strain rate during the ultra-precision turning of single-crystal silicon on the anisotropy of surface roughness.Focusing on the establishment of cutting models considering the tool rake angle and the edge radius, this is the first research that takes into account the strain rate dislocation emission criteria in studying the effects of the edge radius, the cutting speed, and the cutting thickness on the plastic deformation of single-crystal silicon.The results of this study show that the uses of a smaller edge radius, faster cutting speeds, and a reduced cutting thickness can result in optimally uniform surface roughness, while the use of a very sharp cutting tool is essential when operating with smaller cutting thicknesses.A further finding is that insufficient plastic deformation is the major cause of increased surface roughness in the ultra-precision turning of brittle materials.On this basis, we propose that the capacity of single-crystal silicon to emit dislocations be improved as much as possible before brittle fracture occurs, thereby promoting plastic deformation and minimizing the anisotropy of surface roughness in the machined workpiece.展开更多
文摘The self-assembled silicon substrate. The resultant contact angle meter and atomic method was introduced to successfully obtain film was characterized by means of X-ray rare earth（RE） nanofilm on a single-crystal photoelectron spectroscopy （XPS）, ellipsometer, force microscopy （AFM）. The scratch experiment was performed for interfacial adhesion measurement of the RE film. The friction and wear behavior of RE nanofilm was examined on a DF-PM reciprocating friction and wear tester. The results indicate the RE nanofilm is of low coefficient of friction （COF） and high wear resistance. These desirable characteristics of RE nanofilm together with its nanometer thickness, strong bonding to the substrate and low surface energy make it a promising choice as a solid lubricant film in micro electromechanical system （MEMS） devices.
文摘Repetitive bending fatigue tests were performed using five types of single-crystal silicon specimens with different crystal orientations fabricated from{100}and{110}wafers.Fatigue lifetimes in a wide range between 100 and 1010 were obtained using fan-shaped resonator test devices.Fracture surface observation via scanning electron microscope(SEM)revealed that the{111}plane was the primary fracture plane.The crack propagation exponent n was estimated to be 27,which was independent of the crystal orientation and dopant concentration;however,it was dependent on the surface conditions of the etched sidewall.The fatigue strengths relative to the deflection angle were orientation dependent,and the ratios of the factors obtained ranged from 0.86 to 1.25.The strength factors were compared with those obtained from finite element method stress analyses.The calculated stress distributions showed strong orientation dependence,which was well-explained by the elastic anisotropy.The comparison of the strength factors suggested that the first principal stress was a good criterion for fatigue fracture.We include comparisons with specimens tested in our previous report and address the tensile strength,initial crack length,volume effect,and effects of surface roughness such as scallops.
基金supported by the National Defence Scientific Research of China (A3520133004)
文摘Ultra-precision machining causes materials to undergo a greatly strained deformation process in a short period of time.The effect of shear strain rates on machining quality, in particular on surface anisotropy, is a topic deserving of research that has thus far been overlooked.This study analyzes the impact of the strain rate during the ultra-precision turning of single-crystal silicon on the anisotropy of surface roughness.Focusing on the establishment of cutting models considering the tool rake angle and the edge radius, this is the first research that takes into account the strain rate dislocation emission criteria in studying the effects of the edge radius, the cutting speed, and the cutting thickness on the plastic deformation of single-crystal silicon.The results of this study show that the uses of a smaller edge radius, faster cutting speeds, and a reduced cutting thickness can result in optimally uniform surface roughness, while the use of a very sharp cutting tool is essential when operating with smaller cutting thicknesses.A further finding is that insufficient plastic deformation is the major cause of increased surface roughness in the ultra-precision turning of brittle materials.On this basis, we propose that the capacity of single-crystal silicon to emit dislocations be improved as much as possible before brittle fracture occurs, thereby promoting plastic deformation and minimizing the anisotropy of surface roughness in the machined workpiece.
