In order to improve the polishing ability of polishing pads, a kind of polishing pad with the tin fixed abrasive blocks, which are arranged based on the phyllotaxis theory of biology, was designed and fabricated by th...In order to improve the polishing ability of polishing pads, a kind of polishing pad with the tin fixed abrasive blocks, which are arranged based on the phyllotaxis theory of biology, was designed and fabricated by the use of electroplating technology, and also its polishing ability for JGS-2 wafer was investigated by polishing experiments. The research results show that the phyllotactic parameters of the polishing pad influence the arrangement density of the tin fixed abrasive blocks, the polishing pad with phyllotactic pattern is feasibly fabricated by the use of electroplating technology, and the good polishing result can be obtained by using the polishing pad with phyllotactic pattern to polish a wafer when the diameter D of the tin fixed abrasive block is between Φ1.3 mm and Φ1.4 mm, and the phyllotactic coefficient k between 1.0 and 1.1,respectively.展开更多
Silicon nitride (Si 3N 4) has been the main material for balls in ceramic ball bearings, for its lower density, high strength, high hardness, fine thermal stability and anticorrosive, and is widely used in various fie...Silicon nitride (Si 3N 4) has been the main material for balls in ceramic ball bearings, for its lower density, high strength, high hardness, fine thermal stability and anticorrosive, and is widely used in various fields, such as high speed and high temperature areojet engines, precision machine tools and chemical engineer machines. Silicon nitride ceramics is a kind of brittle and hard material that is difficult to machining. In the traditional finishing process of silicon nitride balls, balls are lapped by expensive diamond abrasive. The machining is inefficiency and the cost is high, but also lots of pits, scratch subsurface micro crazes and dislocations will be caused on the surface of the balls, the performance of the ball bearings would be declined seriously. In these year, a kind of new technology known as chemical mechanical polishing is introduced in the ultraprecision machining process of ceramic balls. In this technology, abrasives such as ZrO 2, CeO 2 whose hardness is close to or lower than the work material (Si 3N 4) are used to polishing the balls. In special slurry, these abrasives can chemo-mechanically react with the work material and environment (air or water) to generate softer material (SiO 2). And the resultants will be removed easily at 0.1 nm level. So the surface defects can be minimized, very smooth surface (Ra=4 nm) and fine sphericity (0.15～0.25 μm ) can be obtained, and the machining efficiency is also improved. The action mechanism of the abrasives in the chemical mechanical polishing process in finishing of silicon nitride ball will be introduced in this paper.展开更多
In this paper, the manufacturing and testing procedures to make large off-axis aspherical mirrors are presented. The difficulties in polishing and testing for both circular aperture and rectangular aperture mirrors ar...In this paper, the manufacturing and testing procedures to make large off-axis aspherical mirrors are presented. The difficulties in polishing and testing for both circular aperture and rectangular aperture mirrors are previewed, and a possible solution is given. The two mirrors have been polished by means of CCOS, and the final accuracy is 25nm rms for 770mm×210mm rectangular mirror and 20nm rms for φ600mm circular mirror. These results just meet the optical tolerances specified by the designer, and the manufacturing and testing procedures presented here show good ability to make the large off-axis aspherical mirrors.展开更多
Three kinds of aggregates were polished by genuine pneumatic rubber tyres.The initial states of surface texture and dynamic friction coefficient were measured and their developments in polishing process were monitored...Three kinds of aggregates were polished by genuine pneumatic rubber tyres.The initial states of surface texture and dynamic friction coefficient were measured and their developments in polishing process were monitored.The characterizations of height distribution and power spectral density of aggregate surface texture were estimated.The changes of micro-texture were also investigated based on a fractal filtering method with sound theoretical backgrounds of rubber friction on rough surfaces.Global height reduction and differential removal of mineral component are observed in polishing process.It is concluded that the tyre-polishing action plays the critical roles in the micro-scale texture,and the evolution of friction of aggregate is governed by the micro-texture changes due to the differential removal of mineral component.展开更多
With an elastic negative pole being driven by ultra so nic vibration and being moved along the surface of work-piece compliantly by ro bot, a new kind of effective EDM, the compliant EDM, cuts the electrically condu c...With an elastic negative pole being driven by ultra so nic vibration and being moved along the surface of work-piece compliantly by ro bot, a new kind of effective EDM, the compliant EDM, cuts the electrically condu ctive materials away and polishes work-piece of free-form surface. The study o f the contact force between the end of polishing tool and the surface of work-p iece is the key for the compliant EDM to study its cutting mechanism and to make better use of it. This paper makes a model for the contact force and verifies i t by experiments and simulation based on the theory of elastic body kinetics and dynamic stress concentration. The research work shows that this contact force i s caused by both the electrical impulsion of EDM and the mechanical force of ult rasonic vibration, the discharge frequency of compliant EDM has a much more clos er connection with the vibration frequency of polishing tool rather than the fre quency of ultrasonic vibration.展开更多
Recently,with the rapid development of chemical vapor deposition(CVD)technology,large area free-standing CVD diamond films have been produced successfully.However,the coarse grain size on the surface and the non-unifo...Recently,with the rapid development of chemical vapor deposition(CVD)technology,large area free-standing CVD diamond films have been produced successfully.However,the coarse grain size on the surface and the non-uniform thickness of unprocessed CVD diamond films make it difficult to meet the application requirement.The current study evaluates several existing polishing methods for CVD diamond films,including mechanical polishing,chemical mechanical polishing and tribochemical polishing technology.展开更多
Chemical mechanical polishing is used to polish large area free-standing CVD diamond films with diameters of 66 mm.The influence of polishing plates(iron plate,asphalt plate and soft cushion)and oxidizing agents(K_2S_...Chemical mechanical polishing is used to polish large area free-standing CVD diamond films with diameters of 66 mm.The influence of polishing plates(iron plate,asphalt plate and soft cushion)and oxidizing agents(K_2S_2O_8 and K_2FeO_4)on polishing results are investigated.Profilometer(tip radius 5μm),optical microscope and Raman spectroscopy are used to evaluate the polishing effects of the CVD diamond films.Results show that the material removal rate of iron plate is the highest,while the surface polished by soft cushion is the most uniform with roughness of 2nm.It is also found that the most effective oxidizing agent is K_2FeO_4.In conclusion,the optimum polishing conditions are soft cushion and K_2FeO_4.展开更多
The optimization of electrolytes and the material removal mechanisms for Cu electrochemical mechanical planarization(ECMP)at different pH values including 5-methyl-1H-benzotriazole(TTA),hydroxyethylidenediphosphoric a...The optimization of electrolytes and the material removal mechanisms for Cu electrochemical mechanical planarization(ECMP)at different pH values including 5-methyl-1H-benzotriazole(TTA),hydroxyethylidenediphosphoric acid(HEDP),and tribasic ammonium citrate(TAC)were investigated by electrochemical techniques,X-ray photoelectron spectrometer(XPS)analysis,nano-scratch tests,AFM measurements,and polishing of Cu-coated blanket wafers.The experimental results show that the planarization efficiency and the surface quality after ECMP obtained in alkali-based solutions are superior to that in acidic-based solutions,especially at pH=8.The optimal electrolyte compositions(mass fraction)are 6% HEDP,0.3% TTA and 3% TAC at pH=8.The main factor affecting the thickness of the oxide layer formed during ECMP process is the applied potential.The soft layer formation is a major mechanism for electrochemical enhanced mechanical abrasion.The surface topography evolution before and after electrochemical polishing(ECP)illustrates the mechanism of mechanical abrasion accelerating electrochemical dissolution,that is,the residual stress caused by the mechanical wear enhances the electrochemical dissolution rate.This understanding is beneficial for optimization of ECMP processes.展开更多
With Al2O3 and SiO2 as polishing medium, under different polishing conditions, e.g. with different polishing pressure, polishing time and polishing fluid, the influences of polishing treatment on the return loss of op...With Al2O3 and SiO2 as polishing medium, under different polishing conditions, e.g. with different polishing pressure, polishing time and polishing fluid, the influences of polishing treatment on the return loss of optical fiber connectors were investigated. The return loss of optical fiber connectors is 32CD*238dB before polishing. The results show that dry polishing（i.e. no polishing fluid） with Al2O3 has less influence on return loss of optical fiber connectors, while dry polishing with SiO2 reduces return loss to about 20dB because of the end-face of optical fiber contaminated. The wet polishing（i.e. using distilled water as polishing fluid） with Al2O3 or SiO2 can increase return loss to 45CD*250dB, but wet polishing with Al2O3 may produce optical fiber undercut depth of 80CD*2140nm. Wet polishing with SiO2 should be preferentially selected for optical fiber connectors and polishing time should be controlled within 20CD*230s.展开更多
The characteristic of metallographic structure of the SnSb alloy moulds is that hard particles are distributed on the soft metal matrix. Great difference of the hard particles and the soft metal matrix’hardness makes...The characteristic of metallographic structure of the SnSb alloy moulds is that hard particles are distributed on the soft metal matrix. Great difference of the hard particles and the soft metal matrix’hardness makes moulds’polishing become difficult. When a rigid grindstone is used to polish the surface of the SnSb alloy mould, the hard abrasives fall off and are embed in the soft matrix of SnSb alloy and while the process, the grinding chips are able to block the gap on the grindstone surface and enable the grindstone to blunt, which brings about the polished area on the surface of the mould is seriously squeezed and deformed and the crystal lattice of SnSb alloys is seriously distorted, and the work hardening takes place. At the same time, the rigid grindstone is easy to scratch the surface of the SnSb alloy mould. Owing to the above reasons, it is difficult to reduce surface roughness and improve the surface quality of SnSb alloy moulds. Taking use of the CAD/CAM technique and the complex processing of combining electrolyzing polishing and mechanical polishing with the magnetic force, mould’s polishing automation is realized on the numerical control machine tool. This complex processing is finished under a comprehensive action as the following: 1. Electrolyzing polishing action Under the electric field, the electrolyte between the elastic grind wheel and the mould is ionized, which electrolyzes the metal of the mould’s surface. The electrolyzing speed of convex peak on the mould’s surface is faster than that of concave valley, which levels the mould’s surface. 2. Mechanical Polishing action During electrolyzing, a dense passive film of low hardness is formed on the mould’s surface. While polishing, soft grinding wheel scraps the passive film on the conven peak easily, and the new metal surface is exposed, then, a new passive film is formed again, going round and round, the conven peak on the mould’s surface is leveled quickly. 3. Magnetic force action The charged particles in electric field will be acted by the Lorentz force in magnetic field. The field plays a stirring part on electrolyte and reduces electrochemical polarization and concentration polarization, and accelerates the electrochemical reaction. The complex polishing process is not only of high efficiency, but also of good surface quality and provides a good effective method for the non-ferrous metal polishing. When the mould is polished, a speed-raising tool system is used and it can increase the grinding wheel spindle’s speed up to five times. This paper describes the SnSb alloy moulds’polishing steps, grinding wheel speed-raising tool system, polishing principle and the results.展开更多
Low dielectric constant materials/Cu interconnects integration technology provides the direction as well as the challenges in the fabrication of integrated circuits(IC) wafers during copper electrochemical-mechanical ...Low dielectric constant materials/Cu interconnects integration technology provides the direction as well as the challenges in the fabrication of integrated circuits(IC) wafers during copper electrochemical-mechanical polishing(ECMP). These challenges arise primarily from the mechanical fragility of such dielectrics, in which the undesirable scratches are prone to produce. To mitigate this problem, a new model is proposed to predict the initiation of scratching based on the mechanical properties of passive layer and copper substrate. In order to deduce the ratio of the passive layer yield strength to the substrate yield strength and the layer thickness, the limit analysis solution of surface scratch under Berkovich indenter is used to analyze the nano-scratch experimental measurements. The modulus of the passive layer can be calculated by the nano-indentation test combined with the FEM simulation. It is found that the film modulus is about 30% of the substrate modulus. Various regimes of scratching are delineated by FEM modeling and the results are verified by experimental data.展开更多
To determine mirror surface finishing conditions and efficient and economical superfinishing conditions for pure titanium and titanium alloys, an abrasive film is used when superfinishing is performed under varying co...To determine mirror surface finishing conditions and efficient and economical superfinishing conditions for pure titanium and titanium alloys, an abrasive film is used when superfinishing is performed under varying conditions. These conditions include the workpiece rotation speed, the oscillation speed, the contact pressure of the roller, the hardness of the roller, and the type of abrasive film. The superfinishing device is applied to polishing a thin and long cylindrical bar. A micro-finishing film and a lapping film were used as abrasive films. A1203 grains or SiC grains were used as abrasives. The surface roughness of a polished workpiece was measured using a stylus-type surface-roughness measuring instrument. As a result, the conditions to improve the polishing surface efficiently include high values for the workpiece rotation speed, oscillation speed and contact pressure. The roller hardness has no effect on the efficient polishing conditions. The mirror finish of a surface can be created using lapping film of 3 μm with Al2O3 grains after polishing to a steady surface roughness under the efficient polishing conditions.展开更多
The infrared conformal window is one of the most critical components in aircraft.Conformal windows with high performance bring low aberrations,high aerodynamic performance,reliability in extreme working environments,a...The infrared conformal window is one of the most critical components in aircraft.Conformal windows with high performance bring low aberrations,high aerodynamic performance,reliability in extreme working environments,and added value for aircraft.Through the past decades,remarkable advances have been achieved in manufacturing technologies for conformal windows,where the machining accuracy approaches the nanometer level,and the surface form becomes more complex.These advances are critical to aircraft development,and these manufacturing technologies also have significant reference values for other directions of the ultra-precision machining field.In this review,the infrared materials suitable for manufacturing conformal windows are introduced and compared with insights into their performances.The remarkable advances and concrete work accomplished by researchers are reviewed.The challenges in manufacturing conformal windows that should be faced in the future are discussed.展开更多
This paper discusses some techniques for treating discontinuities of the right-hand functions of ordinary differential equations (ODEs) in real-time digital simulation (RTDS). The numericalexperiments show that these ...This paper discusses some techniques for treating discontinuities of the right-hand functions of ordinary differential equations (ODEs) in real-time digital simulation (RTDS). The numericalexperiments show that these techniques are effective.展开更多
Fabrication of the lightweight mirror is one of the key techniques for many large optical systems. CAD,CAM and CNC technologies are adopted in designing and manufacturing such mirrors in CIOMP. Better working efficien...Fabrication of the lightweight mirror is one of the key techniques for many large optical systems. CAD,CAM and CNC technologies are adopted in designing and manufacturing such mirrors in CIOMP. Better working efficiency and higher lightweight grade have been achieved. The results show that mirrors up to 70% weight reduction and 0.02λ(rms.) surface accuracy or better can be obtained.展开更多
Removal of brittle materials in the brittle or ductile mode inevitably causes damaged or strained surface layers containing cracks, scratches or dislocations. Within elastic deformation, the arrangement of each atom c...Removal of brittle materials in the brittle or ductile mode inevitably causes damaged or strained surface layers containing cracks, scratches or dislocations. Within elastic deformation, the arrangement of each atom can be recovered back to its original position without any defects introduced. Based on surface hydroxylation and chemisorption theory, material removal mechanism of quartz glass in the elastic mode is analyzed to obtain defect-free surface. Elastic contact condition between nanoparticle and quartz glass surface is confirmed from the Hertz contact theory model. Atoms on the quartz glass surface are removed by chemical bond generated by impact reaction in the elastic mode, so no defects are generated without mechanical process. Experiment was conducted on a numerically controlled system for nanoparticle jet polishing, and one flat quartz glass was polished in the elastic mode. Results show that scratches on the sample surface are completely removed away with no mechanical defects introduced, and microroughness(Ra) is decreased from 1.23 nm to 0.47 nm. Functional group Ce — O — Si on ceria nanoparticles after polishing was detected directly and indirectly by FTIR, XRD and XPS spectra analysis from which the chemical impact reaction is validated.展开更多
Ultrasonic treatment technology is utilized to fabricate RBSiC, and a new polishing technology-float polishing is developed to process RBSiC. SEM, XRD, AFM. Raman scattering and WYCO are applied to measure and analyze...Ultrasonic treatment technology is utilized to fabricate RBSiC, and a new polishing technology-float polishing is developed to process RBSiC. SEM, XRD, AFM. Raman scattering and WYCO are applied to measure and analyze the RBSiC and the polished surface. The results indicate that the ultrasonic treatment decreases the content of the free Si and makes RBSiC denser and more uniformity. The float polishing technology is suitable for polishing RBSiC effectively.展开更多
How to improve the finishing efficiency and surface roughness have been all along the objective of research in electrochemical polishing. However, the research activity, i.e. during electrochemical polishing, directly...How to improve the finishing efficiency and surface roughness have been all along the objective of research in electrochemical polishing. However, the research activity, i.e. during electrochemical polishing, directly introduce the magnetic field to study how the magnetic field influences on the finishing efficiency, quality and the electrochemical process in the field of finishing machining technology, is insufficient. When introducing additional magnetic field in the traditional electrochemical polishing, due to the co-action of Lorentz’ force and electric field force, the ions arriving the machined surface by way of a curvilinear motion result in the electric current density distribution on the surface even more non-uniform, then the dissolving velocity of the peak points or side faces and the diffusion velocity of the product are enhanced, and the forcible agitation is happened on the electrodes surface by magnetic field, the removal rate of peak points are still more greater, and efficiency is also still more higher. Compared with the electrochemical polishing, in the magnetic electrochemical finishing machining, the finishing speed at peak points is higher, but at valley points it is lower, therefore after machining, both the highness at peak points and finishing depth at valley points are smaller, the results are propitious to minish initial wear quantity caused by friction and wear when machined workpiece employing in practice, and increase contact stiffness of workpiece, and from the viewpoint of microcosmic theory, this phenomenon is also of advantage to reduce damage to substrate. It can also be seen from the equation presented in the paper that the track of ionic movement relates to the electrodes gap, potential and magnetic induction intensity and furthermore; under the given conditions, the movement also relate to the electrolyte. it can be inferred that there must be an optimum value in respect of the magnetic induction intensity influencing the efficiency of finishing machining, and at the same time, the rational matching among the interelectrodes voltage, gap sizes and magnetic induction intensity can raise the efficiency and quality as well as improve the surface roughness to the maximum. In short, the co-action of the Lorentz’ force and electric field force change the motion track of anions and make more uneven distribution of the electric current density on the anodes surface, thus the dissolving velocity and product diffusion velocity of the peak points or side faces of the anode are raised. All those and the forced agitation of magnetic field towards the electrode surface are the principal mechanism for surface finishing. This point has been proved from the experimental results in this paper.展开更多
基金Sponsored by the National Nature Science Foundation of China (50875179)
文摘In order to improve the polishing ability of polishing pads, a kind of polishing pad with the tin fixed abrasive blocks, which are arranged based on the phyllotaxis theory of biology, was designed and fabricated by the use of electroplating technology, and also its polishing ability for JGS-2 wafer was investigated by polishing experiments. The research results show that the phyllotactic parameters of the polishing pad influence the arrangement density of the tin fixed abrasive blocks, the polishing pad with phyllotactic pattern is feasibly fabricated by the use of electroplating technology, and the good polishing result can be obtained by using the polishing pad with phyllotactic pattern to polish a wafer when the diameter D of the tin fixed abrasive block is between Φ1.3 mm and Φ1.4 mm, and the phyllotactic coefficient k between 1.0 and 1.1,respectively.
文摘Silicon nitride (Si 3N 4) has been the main material for balls in ceramic ball bearings, for its lower density, high strength, high hardness, fine thermal stability and anticorrosive, and is widely used in various fields, such as high speed and high temperature areojet engines, precision machine tools and chemical engineer machines. Silicon nitride ceramics is a kind of brittle and hard material that is difficult to machining. In the traditional finishing process of silicon nitride balls, balls are lapped by expensive diamond abrasive. The machining is inefficiency and the cost is high, but also lots of pits, scratch subsurface micro crazes and dislocations will be caused on the surface of the balls, the performance of the ball bearings would be declined seriously. In these year, a kind of new technology known as chemical mechanical polishing is introduced in the ultraprecision machining process of ceramic balls. In this technology, abrasives such as ZrO 2, CeO 2 whose hardness is close to or lower than the work material (Si 3N 4) are used to polishing the balls. In special slurry, these abrasives can chemo-mechanically react with the work material and environment (air or water) to generate softer material (SiO 2). And the resultants will be removed easily at 0.1 nm level. So the surface defects can be minimized, very smooth surface (Ra=4 nm) and fine sphericity (0.15～0.25 μm ) can be obtained, and the machining efficiency is also improved. The action mechanism of the abrasives in the chemical mechanical polishing process in finishing of silicon nitride ball will be introduced in this paper.
文摘In this paper, the manufacturing and testing procedures to make large off-axis aspherical mirrors are presented. The difficulties in polishing and testing for both circular aperture and rectangular aperture mirrors are previewed, and a possible solution is given. The two mirrors have been polished by means of CCOS, and the final accuracy is 25nm rms for 770mm×210mm rectangular mirror and 20nm rms for φ600mm circular mirror. These results just meet the optical tolerances specified by the designer, and the manufacturing and testing procedures presented here show good ability to make the large off-axis aspherical mirrors.
基金Project(50809053) supported by the National Natural Science Foundation of ChinaProject(FE 04.208/2007/CRB) funded by Federal Highway Research Institute (Bast),Germany
文摘Three kinds of aggregates were polished by genuine pneumatic rubber tyres.The initial states of surface texture and dynamic friction coefficient were measured and their developments in polishing process were monitored.The characterizations of height distribution and power spectral density of aggregate surface texture were estimated.The changes of micro-texture were also investigated based on a fractal filtering method with sound theoretical backgrounds of rubber friction on rough surfaces.Global height reduction and differential removal of mineral component are observed in polishing process.It is concluded that the tyre-polishing action plays the critical roles in the micro-scale texture,and the evolution of friction of aggregate is governed by the micro-texture changes due to the differential removal of mineral component.
文摘With an elastic negative pole being driven by ultra so nic vibration and being moved along the surface of work-piece compliantly by ro bot, a new kind of effective EDM, the compliant EDM, cuts the electrically condu ctive materials away and polishes work-piece of free-form surface. The study o f the contact force between the end of polishing tool and the surface of work-p iece is the key for the compliant EDM to study its cutting mechanism and to make better use of it. This paper makes a model for the contact force and verifies i t by experiments and simulation based on the theory of elastic body kinetics and dynamic stress concentration. The research work shows that this contact force i s caused by both the electrical impulsion of EDM and the mechanical force of ult rasonic vibration, the discharge frequency of compliant EDM has a much more clos er connection with the vibration frequency of polishing tool rather than the fre quency of ultrasonic vibration.
基金Science and technology plan project of Hebei Academy of Sciences(No.191408)Natural Science Foundation of Hebei Province(E2019302005)
文摘Recently,with the rapid development of chemical vapor deposition(CVD)technology,large area free-standing CVD diamond films have been produced successfully.However,the coarse grain size on the surface and the non-uniform thickness of unprocessed CVD diamond films make it difficult to meet the application requirement.The current study evaluates several existing polishing methods for CVD diamond films,including mechanical polishing,chemical mechanical polishing and tribochemical polishing technology.
文摘Chemical mechanical polishing is used to polish large area free-standing CVD diamond films with diameters of 66 mm.The influence of polishing plates(iron plate,asphalt plate and soft cushion)and oxidizing agents(K_2S_2O_8 and K_2FeO_4)on polishing results are investigated.Profilometer(tip radius 5μm),optical microscope and Raman spectroscopy are used to evaluate the polishing effects of the CVD diamond films.Results show that the material removal rate of iron plate is the highest,while the surface polished by soft cushion is the most uniform with roughness of 2nm.It is also found that the most effective oxidizing agent is K_2FeO_4.In conclusion,the optimum polishing conditions are soft cushion and K_2FeO_4.
基金Project(50975058)supported by the National Science Foundation of China
文摘The optimization of electrolytes and the material removal mechanisms for Cu electrochemical mechanical planarization(ECMP)at different pH values including 5-methyl-1H-benzotriazole(TTA),hydroxyethylidenediphosphoric acid(HEDP),and tribasic ammonium citrate(TAC)were investigated by electrochemical techniques,X-ray photoelectron spectrometer(XPS)analysis,nano-scratch tests,AFM measurements,and polishing of Cu-coated blanket wafers.The experimental results show that the planarization efficiency and the surface quality after ECMP obtained in alkali-based solutions are superior to that in acidic-based solutions,especially at pH=8.The optimal electrolyte compositions(mass fraction)are 6% HEDP,0.3% TTA and 3% TAC at pH=8.The main factor affecting the thickness of the oxide layer formed during ECMP process is the applied potential.The soft layer formation is a major mechanism for electrochemical enhanced mechanical abrasion.The surface topography evolution before and after electrochemical polishing(ECP)illustrates the mechanism of mechanical abrasion accelerating electrochemical dissolution,that is,the residual stress caused by the mechanical wear enhances the electrochemical dissolution rate.This understanding is beneficial for optimization of ECMP processes.
文摘With Al2O3 and SiO2 as polishing medium, under different polishing conditions, e.g. with different polishing pressure, polishing time and polishing fluid, the influences of polishing treatment on the return loss of optical fiber connectors were investigated. The return loss of optical fiber connectors is 32CD*238dB before polishing. The results show that dry polishing（i.e. no polishing fluid） with Al2O3 has less influence on return loss of optical fiber connectors, while dry polishing with SiO2 reduces return loss to about 20dB because of the end-face of optical fiber contaminated. The wet polishing（i.e. using distilled water as polishing fluid） with Al2O3 or SiO2 can increase return loss to 45CD*250dB, but wet polishing with Al2O3 may produce optical fiber undercut depth of 80CD*2140nm. Wet polishing with SiO2 should be preferentially selected for optical fiber connectors and polishing time should be controlled within 20CD*230s.
文摘The characteristic of metallographic structure of the SnSb alloy moulds is that hard particles are distributed on the soft metal matrix. Great difference of the hard particles and the soft metal matrix’hardness makes moulds’polishing become difficult. When a rigid grindstone is used to polish the surface of the SnSb alloy mould, the hard abrasives fall off and are embed in the soft matrix of SnSb alloy and while the process, the grinding chips are able to block the gap on the grindstone surface and enable the grindstone to blunt, which brings about the polished area on the surface of the mould is seriously squeezed and deformed and the crystal lattice of SnSb alloys is seriously distorted, and the work hardening takes place. At the same time, the rigid grindstone is easy to scratch the surface of the SnSb alloy mould. Owing to the above reasons, it is difficult to reduce surface roughness and improve the surface quality of SnSb alloy moulds. Taking use of the CAD/CAM technique and the complex processing of combining electrolyzing polishing and mechanical polishing with the magnetic force, mould’s polishing automation is realized on the numerical control machine tool. This complex processing is finished under a comprehensive action as the following: 1. Electrolyzing polishing action Under the electric field, the electrolyte between the elastic grind wheel and the mould is ionized, which electrolyzes the metal of the mould’s surface. The electrolyzing speed of convex peak on the mould’s surface is faster than that of concave valley, which levels the mould’s surface. 2. Mechanical Polishing action During electrolyzing, a dense passive film of low hardness is formed on the mould’s surface. While polishing, soft grinding wheel scraps the passive film on the conven peak easily, and the new metal surface is exposed, then, a new passive film is formed again, going round and round, the conven peak on the mould’s surface is leveled quickly. 3. Magnetic force action The charged particles in electric field will be acted by the Lorentz force in magnetic field. The field plays a stirring part on electrolyte and reduces electrochemical polarization and concentration polarization, and accelerates the electrochemical reaction. The complex polishing process is not only of high efficiency, but also of good surface quality and provides a good effective method for the non-ferrous metal polishing. When the mould is polished, a speed-raising tool system is used and it can increase the grinding wheel spindle’s speed up to five times. This paper describes the SnSb alloy moulds’polishing steps, grinding wheel speed-raising tool system, polishing principle and the results.
基金Project(50975058) supported by the National Natural Science Foundation of China
文摘Low dielectric constant materials/Cu interconnects integration technology provides the direction as well as the challenges in the fabrication of integrated circuits(IC) wafers during copper electrochemical-mechanical polishing(ECMP). These challenges arise primarily from the mechanical fragility of such dielectrics, in which the undesirable scratches are prone to produce. To mitigate this problem, a new model is proposed to predict the initiation of scratching based on the mechanical properties of passive layer and copper substrate. In order to deduce the ratio of the passive layer yield strength to the substrate yield strength and the layer thickness, the limit analysis solution of surface scratch under Berkovich indenter is used to analyze the nano-scratch experimental measurements. The modulus of the passive layer can be calculated by the nano-indentation test combined with the FEM simulation. It is found that the film modulus is about 30% of the substrate modulus. Various regimes of scratching are delineated by FEM modeling and the results are verified by experimental data.
基金work supported by the Second Stage of Brain Korea 21 Projects of Korea
文摘To determine mirror surface finishing conditions and efficient and economical superfinishing conditions for pure titanium and titanium alloys, an abrasive film is used when superfinishing is performed under varying conditions. These conditions include the workpiece rotation speed, the oscillation speed, the contact pressure of the roller, the hardness of the roller, and the type of abrasive film. The superfinishing device is applied to polishing a thin and long cylindrical bar. A micro-finishing film and a lapping film were used as abrasive films. A1203 grains or SiC grains were used as abrasives. The surface roughness of a polished workpiece was measured using a stylus-type surface-roughness measuring instrument. As a result, the conditions to improve the polishing surface efficiently include high values for the workpiece rotation speed, oscillation speed and contact pressure. The roller hardness has no effect on the efficient polishing conditions. The mirror finish of a surface can be created using lapping film of 3 μm with Al2O3 grains after polishing to a steady surface roughness under the efficient polishing conditions.
基金the support from the National Key Research and Development Program of China[2018YFA0703400].
文摘The infrared conformal window is one of the most critical components in aircraft.Conformal windows with high performance bring low aberrations,high aerodynamic performance,reliability in extreme working environments,and added value for aircraft.Through the past decades,remarkable advances have been achieved in manufacturing technologies for conformal windows,where the machining accuracy approaches the nanometer level,and the surface form becomes more complex.These advances are critical to aircraft development,and these manufacturing technologies also have significant reference values for other directions of the ultra-precision machining field.In this review,the infrared materials suitable for manufacturing conformal windows are introduced and compared with insights into their performances.The remarkable advances and concrete work accomplished by researchers are reviewed.The challenges in manufacturing conformal windows that should be faced in the future are discussed.
文摘This paper discusses some techniques for treating discontinuities of the right-hand functions of ordinary differential equations (ODEs) in real-time digital simulation (RTDS). The numericalexperiments show that these techniques are effective.
文摘Fabrication of the lightweight mirror is one of the key techniques for many large optical systems. CAD,CAM and CNC technologies are adopted in designing and manufacturing such mirrors in CIOMP. Better working efficiency and higher lightweight grade have been achieved. The results show that mirrors up to 70% weight reduction and 0.02λ(rms.) surface accuracy or better can be obtained.
基金Projects(51305450,51275521)supported by the National Natural Science Foundation of China
文摘Removal of brittle materials in the brittle or ductile mode inevitably causes damaged or strained surface layers containing cracks, scratches or dislocations. Within elastic deformation, the arrangement of each atom can be recovered back to its original position without any defects introduced. Based on surface hydroxylation and chemisorption theory, material removal mechanism of quartz glass in the elastic mode is analyzed to obtain defect-free surface. Elastic contact condition between nanoparticle and quartz glass surface is confirmed from the Hertz contact theory model. Atoms on the quartz glass surface are removed by chemical bond generated by impact reaction in the elastic mode, so no defects are generated without mechanical process. Experiment was conducted on a numerically controlled system for nanoparticle jet polishing, and one flat quartz glass was polished in the elastic mode. Results show that scratches on the sample surface are completely removed away with no mechanical defects introduced, and microroughness(Ra) is decreased from 1.23 nm to 0.47 nm. Functional group Ce — O — Si on ceria nanoparticles after polishing was detected directly and indirectly by FTIR, XRD and XPS spectra analysis from which the chemical impact reaction is validated.
文摘Ultrasonic treatment technology is utilized to fabricate RBSiC, and a new polishing technology-float polishing is developed to process RBSiC. SEM, XRD, AFM. Raman scattering and WYCO are applied to measure and analyze the RBSiC and the polished surface. The results indicate that the ultrasonic treatment decreases the content of the free Si and makes RBSiC denser and more uniformity. The float polishing technology is suitable for polishing RBSiC effectively.
文摘How to improve the finishing efficiency and surface roughness have been all along the objective of research in electrochemical polishing. However, the research activity, i.e. during electrochemical polishing, directly introduce the magnetic field to study how the magnetic field influences on the finishing efficiency, quality and the electrochemical process in the field of finishing machining technology, is insufficient. When introducing additional magnetic field in the traditional electrochemical polishing, due to the co-action of Lorentz’ force and electric field force, the ions arriving the machined surface by way of a curvilinear motion result in the electric current density distribution on the surface even more non-uniform, then the dissolving velocity of the peak points or side faces and the diffusion velocity of the product are enhanced, and the forcible agitation is happened on the electrodes surface by magnetic field, the removal rate of peak points are still more greater, and efficiency is also still more higher. Compared with the electrochemical polishing, in the magnetic electrochemical finishing machining, the finishing speed at peak points is higher, but at valley points it is lower, therefore after machining, both the highness at peak points and finishing depth at valley points are smaller, the results are propitious to minish initial wear quantity caused by friction and wear when machined workpiece employing in practice, and increase contact stiffness of workpiece, and from the viewpoint of microcosmic theory, this phenomenon is also of advantage to reduce damage to substrate. It can also be seen from the equation presented in the paper that the track of ionic movement relates to the electrodes gap, potential and magnetic induction intensity and furthermore; under the given conditions, the movement also relate to the electrolyte. it can be inferred that there must be an optimum value in respect of the magnetic induction intensity influencing the efficiency of finishing machining, and at the same time, the rational matching among the interelectrodes voltage, gap sizes and magnetic induction intensity can raise the efficiency and quality as well as improve the surface roughness to the maximum. In short, the co-action of the Lorentz’ force and electric field force change the motion track of anions and make more uneven distribution of the electric current density on the anodes surface, thus the dissolving velocity and product diffusion velocity of the peak points or side faces of the anode are raised. All those and the forced agitation of magnetic field towards the electrode surface are the principal mechanism for surface finishing. This point has been proved from the experimental results in this paper.
