Ultra-precision diamond cutting is a promising machining technique for realizing ultra-smooth surface of different kinds of materials.While fundamental understanding of the impact of workpiece material properties on c...Ultra-precision diamond cutting is a promising machining technique for realizing ultra-smooth surface of different kinds of materials.While fundamental understanding of the impact of workpiece material properties on cutting mechanisms is crucial for promoting the capability of the machining technique,numerical simulation methods at different length and time scales act as important supplements to experimental investigations.In this work,we present a compact review on recent advancements in the numerical simulations of material-oriented diamond cutting,in which representative machining phenomena are systematically summarized and discussed by multiscale simulations such as molecular dynamics simulation and finite element simulation:the anisotropy cutting behavior of polycrystalline material,the thermo-mechanical coupling tool-chip friction states,the synergetic cutting responses of individual phase in composite materials,and the impact of various external energetic fields on cutting processes.In particular,the novel physics-based numerical models,which involve the high precision constitutive law associated with heterogeneous deformation behavior,the thermo-mechanical coupling algorithm associated with tool-chip friction,the configurations of individual phases in line with real microstructural characteristics of composite materials,and the integration of external energetic fields into cutting models,are highlighted.Finally,insights into the future development of advanced numerical simulation techniques for diamond cutting of advanced structured materials are also provided.The aspects reported in this review present guidelines for the numerical simulations of ultra-precision mechanical machining responses for a variety of materials.展开更多
A specific revised HFCVD apparatus and a novel process combining HFCVD and polishing technique were presented to deposit the micro-and nano-crystalline multilayered ultra-smooth diamond（USCD） film on the interior-ho...A specific revised HFCVD apparatus and a novel process combining HFCVD and polishing technique were presented to deposit the micro-and nano-crystalline multilayered ultra-smooth diamond（USCD） film on the interior-hole surface of WC-Co drawing dies with aperture ranging from d1.0 mm to 60 mm.Characterization results indicate that the surface roughness values（Ra） in the entry zone,drawing zone and bearing zone of as-fabricated USCD coated drawing die were measured as low as 25.7,23.3 and 25.5 nm,respectively.Furthermore,the friction properties of USCD films were examined in both dry sliding and water-lubricating conditions,and the results show that the USCD film presents much superior friction properties.Its friction coefficients against ball-bearing steel,copper and silicon nitride balls（d4 mm）,is always lower than that of microcrystalline diamond（MCD） or WC-Co sample,regardless of the lubricating condition.Meanwhile,it still presents competitive wear resistance with the MCD films.Finally,the working lifetime and performance of as-fabricated USCD coated drawing dies were examined under producing low-carbon steel pipes in dry-sliding and water-lubricating conditions.Under the water-lubricating drawing condition,its production significantly increases by about 20 times compared with the conventional WC-Co drawing dies.展开更多
Molecular dynamics method is applied to study the machining mechanisms of polishing based on coupling vibrations of liquid. The physical phenomena of abrasive particles bombarding on silicon monocrystal surface are si...Molecular dynamics method is applied to study the machining mechanisms of polishing based on coupling vibrations of liquid. The physical phenomena of abrasive particles bombarding on silicon monocrystal surface are simulated using Tersoff potentials. The effects of vibration parameters, particle size, incident angle and particle material are analyzed and discussed. Material removal mechanisms are studied. Deformation and embedment phenomena are found in the simulations, Bombardment will destroy the crystal structures near the impact point, and adhesion effect is responsible for final removal of material.展开更多
The effects of impacting particles from a jet of liquid on the removal of a surface material(on the impacted workpiece)were investigated.Experimental observations show that the cross section of the material removed ch...The effects of impacting particles from a jet of liquid on the removal of a surface material(on the impacted workpiece)were investigated.Experimental observations show that the cross section of the material removed changed fromʹWʹ‐shaped toʹUʹ‐shaped as the size of abrasive particles was increased.Comparisons between removed material profiles and particle collision distributions indicate that the particle-surface collisions are the main reason for the material removal.The deduced number of atoms removed by a single collision implies that a transition occurs in the removal mode.For nanoscale particles,the polished surface is likely to be removed in an atom‐by‐atom manner,possibly due to the chemisorption of the impacting particles on the impacted surface.Contrarily,for the case of microscale particles,bulk material removal produced by particle bombardment is more likely to occur.The present mechanism of material removal for particle-surface collisions is further corroborated experimentally.展开更多
Diamond is a promising material for the modern industry. It is widely used in different applications, such as cutting tools, optical windows, heat dissipation, and semiconductors.However, these application areas requi...Diamond is a promising material for the modern industry. It is widely used in different applications, such as cutting tools, optical windows, heat dissipation, and semiconductors.However, these application areas require exceptionally flattened and polished diamond surfaces.Unfortunately, due to the extreme hardness and chemical inertness of diamond, the polishing of diamond is challenging. Since the 1920s, various conventional and modern mechanical,chemical, and thermal polishing techniques have been proposed and developed for finishing diamond surfaces. Therefore, to impart proper guidance on selecting a good polishing technique for production practice, this paper presents an in-depth and informative literature survey of the current research and engineering developments regarding diamond polishing. At first, a brief review of the general developments and basic material removal principles is discussed. This review concludes with a detailed analysis of each techniques' polishing performance and critical challenges, and a discussion of the new insights and future applications of diamond polishing.展开更多
The modern optics industry demands rigorous surface quality with minimum defects,which presents challenges to optics machining technologies.There are always certain defects on the final surfaces of the compo-nents for...The modern optics industry demands rigorous surface quality with minimum defects,which presents challenges to optics machining technologies.There are always certain defects on the final surfaces of the compo-nents formed in conventional contacting machining proc-esses,such as micro-cracks,lattice disturbances,etc.It is especially serious for hard-brittle functional materials,such as crystals,glass and ceramics because of their special characteristics.To solve these problems,the atmospheric pressure plasma polishing(APPP)method is developed.It utilizes chemical reactions between reactive plasma and surface atoms to perform atom-scale material removal.Since the machining process is chemical in nature,APPP avoids the surface/subsurface defects mentioned above.As the key component,a capacitance coupled radio-fre-quency plasma torch is first introduced.In initial opera-tions,silicon wafers were machined as samples.Before applying operations,both the temperature distribution on the work-piece surface and the spatial gas diffusion in the machining process were studied qualitatively by finite element analysis.Then the following temperature measurement experiments demonstrate the formation of the temperature gradient on the wafer surface predicted by the theoretical analysis and indicated a peak temper-ature about 90uC in the center.By using commercialized form talysurf,the machined surface was detected and the result shows regular removal profile that corresponds well to the flow field model.Moreover,the removal profile also indicates a 32 mm^(3)/min removal rate.By using atomic force microscopy(AFM),the surface roughness was also measured and the result demonstrates an Ra 0.6 nm surface roughness.Then the element composition of the machined surface was detected and analyzed by X-ray photoelectron spectroscopy(XPS)technology.The results also demonstrate the occurrence of the anticipated main reactions.All the experiments have proved that this atmospheric pressure plasma polishing method has the potential to achieve the m展开更多
A New method,named atmospheric pressure plasma polishing,for the ultra-smooth machining of the silicon based materials is introduced.By inputting the CF4 gas into the atmospheric pressure plasma flame,high density rea...A New method,named atmospheric pressure plasma polishing,for the ultra-smooth machining of the silicon based materials is introduced.By inputting the CF4 gas into the atmospheric pressure plasma flame,high density reactive radicals will be generated,which will then react with the silicon based materials.The reaction product is the vaporization of the SiF4,which can be easily processed.In this way,the atomic scale material removal can be realized and the defect free ultra-smooth surface can be obtained.An experimental setup is built up,and the SiC polishing experiment is carried out.The AFM test result shows that the finished surface roughness (Ra) can be improved from 4.529 nm to 0.926 nm in 3 minutes.展开更多
CsPbI_(2)Br is an ideal inorganic perovskite material with a reasonable bandgap for solar cell applications because of its advantage of superior thermal and phase stability. However, the performance of CsPbI2Br based ...CsPbI_(2)Br is an ideal inorganic perovskite material with a reasonable bandgap for solar cell applications because of its advantage of superior thermal and phase stability. However, the performance of CsPbI2Br based solar cells highly relied on the perovskite crystallization process along with the interfacial contact engineering process between CsPbI_(2)Br perovskite and charge-transporting layers. In this work, a programmable crystallization method is developed to obtain ultra-smooth CsPbI_(2)Br perovskite film with a well-engineered contact interface in perovskite solar cells. This method combines a pre-stand-by process with a programmable gradient thermal engineering process, which mediates the crystal growth dynamics process of CsPbI2Br perovskite by controlling the release of dimethyl sulfoxide(DMSO) from its coordinates with the perovskite film, leading to high-quality CsPbI_(2)Br film with large-scale crystalline grains, reduced surface roughness, and low trap density. Fabricated perovskite devices based on CsPbI_(2)Br film obtained by this method deliver power conversion efficiency of 14.55 %;meanwhile, the encapsulated CsPbI_(2)Br perovskite device achieves a maximum efficiency of 15.07 %. This decent solar conversion efficiency demonstrates the effectiveness of the programmable crystallization method used in this work,which shows great potential as a universal approach in obtaining high-quality CsPbI_(2)Br perovskite films for fabricating high-efficiency inorganic perovskite solar cells.展开更多
基金support from the National Natural Science Foundation of China(52275416 and 51905194)National Key Research and Development Program(2021YFC2202303)Science Challenge Project(No.TZ2018006-0201-02)。
文摘Ultra-precision diamond cutting is a promising machining technique for realizing ultra-smooth surface of different kinds of materials.While fundamental understanding of the impact of workpiece material properties on cutting mechanisms is crucial for promoting the capability of the machining technique,numerical simulation methods at different length and time scales act as important supplements to experimental investigations.In this work,we present a compact review on recent advancements in the numerical simulations of material-oriented diamond cutting,in which representative machining phenomena are systematically summarized and discussed by multiscale simulations such as molecular dynamics simulation and finite element simulation:the anisotropy cutting behavior of polycrystalline material,the thermo-mechanical coupling tool-chip friction states,the synergetic cutting responses of individual phase in composite materials,and the impact of various external energetic fields on cutting processes.In particular,the novel physics-based numerical models,which involve the high precision constitutive law associated with heterogeneous deformation behavior,the thermo-mechanical coupling algorithm associated with tool-chip friction,the configurations of individual phases in line with real microstructural characteristics of composite materials,and the integration of external energetic fields into cutting models,are highlighted.Finally,insights into the future development of advanced numerical simulation techniques for diamond cutting of advanced structured materials are also provided.The aspects reported in this review present guidelines for the numerical simulations of ultra-precision mechanical machining responses for a variety of materials.
基金Project(51005154) supported by the National Natural Science Foundation of ChinaProject(12CG11) supported by the Chenguang Program of Shanghai Municipal Education Commission,ChinaProject(201104271) supported by the China Postdoctoral Science Foundation Special Funded Project
文摘A specific revised HFCVD apparatus and a novel process combining HFCVD and polishing technique were presented to deposit the micro-and nano-crystalline multilayered ultra-smooth diamond（USCD） film on the interior-hole surface of WC-Co drawing dies with aperture ranging from d1.0 mm to 60 mm.Characterization results indicate that the surface roughness values（Ra） in the entry zone,drawing zone and bearing zone of as-fabricated USCD coated drawing die were measured as low as 25.7,23.3 and 25.5 nm,respectively.Furthermore,the friction properties of USCD films were examined in both dry sliding and water-lubricating conditions,and the results show that the USCD film presents much superior friction properties.Its friction coefficients against ball-bearing steel,copper and silicon nitride balls（d4 mm）,is always lower than that of microcrystalline diamond（MCD） or WC-Co sample,regardless of the lubricating condition.Meanwhile,it still presents competitive wear resistance with the MCD films.Finally,the working lifetime and performance of as-fabricated USCD coated drawing dies were examined under producing low-carbon steel pipes in dry-sliding and water-lubricating conditions.Under the water-lubricating drawing condition,its production significantly increases by about 20 times compared with the conventional WC-Co drawing dies.
基金This project is supported by National Natural Science Foundation of China (No.50375029)Provincial Natural Science Foundation of Guangdong,China(No.4009486).
文摘Molecular dynamics method is applied to study the machining mechanisms of polishing based on coupling vibrations of liquid. The physical phenomena of abrasive particles bombarding on silicon monocrystal surface are simulated using Tersoff potentials. The effects of vibration parameters, particle size, incident angle and particle material are analyzed and discussed. Material removal mechanisms are studied. Deformation and embedment phenomena are found in the simulations, Bombardment will destroy the crystal structures near the impact point, and adhesion effect is responsible for final removal of material.
基金The work is financially supported by the National Natural Science Foundation of China(Nos.51575054 and 51527901)the Fundamental Research Funds for the Central Universities(No.YX2013‐02).
文摘The effects of impacting particles from a jet of liquid on the removal of a surface material(on the impacted workpiece)were investigated.Experimental observations show that the cross section of the material removed changed fromʹWʹ‐shaped toʹUʹ‐shaped as the size of abrasive particles was increased.Comparisons between removed material profiles and particle collision distributions indicate that the particle-surface collisions are the main reason for the material removal.The deduced number of atoms removed by a single collision implies that a transition occurs in the removal mode.For nanoscale particles,the polished surface is likely to be removed in an atom‐by‐atom manner,possibly due to the chemisorption of the impacting particles on the impacted surface.Contrarily,for the case of microscale particles,bulk material removal produced by particle bombardment is more likely to occur.The present mechanism of material removal for particle-surface collisions is further corroborated experimentally.
基金financial support for this work from the Guangdong Basic and Applied Basic Research Foundation (2019A1515111133)the National Natural Science Foundation of China (Grant Nos. 52035009, 52005243)the research fund for International Cooperation (GJHZ20180928155412525) from the Science and Technology Innovation Committee of Shenzhen Municipality, Shenzhen, China。
文摘Diamond is a promising material for the modern industry. It is widely used in different applications, such as cutting tools, optical windows, heat dissipation, and semiconductors.However, these application areas require exceptionally flattened and polished diamond surfaces.Unfortunately, due to the extreme hardness and chemical inertness of diamond, the polishing of diamond is challenging. Since the 1920s, various conventional and modern mechanical,chemical, and thermal polishing techniques have been proposed and developed for finishing diamond surfaces. Therefore, to impart proper guidance on selecting a good polishing technique for production practice, this paper presents an in-depth and informative literature survey of the current research and engineering developments regarding diamond polishing. At first, a brief review of the general developments and basic material removal principles is discussed. This review concludes with a detailed analysis of each techniques' polishing performance and critical challenges, and a discussion of the new insights and future applications of diamond polishing.
基金supported by the National Natural Science Foundation of China(Grant Nos.50535020,50775055)the Defense Advanced Research Foundation(No.9140A180202–06HT0132)the Natural Science Foundation of Heilongjiang Province(No.E200622).
文摘The modern optics industry demands rigorous surface quality with minimum defects,which presents challenges to optics machining technologies.There are always certain defects on the final surfaces of the compo-nents formed in conventional contacting machining proc-esses,such as micro-cracks,lattice disturbances,etc.It is especially serious for hard-brittle functional materials,such as crystals,glass and ceramics because of their special characteristics.To solve these problems,the atmospheric pressure plasma polishing(APPP)method is developed.It utilizes chemical reactions between reactive plasma and surface atoms to perform atom-scale material removal.Since the machining process is chemical in nature,APPP avoids the surface/subsurface defects mentioned above.As the key component,a capacitance coupled radio-fre-quency plasma torch is first introduced.In initial opera-tions,silicon wafers were machined as samples.Before applying operations,both the temperature distribution on the work-piece surface and the spatial gas diffusion in the machining process were studied qualitatively by finite element analysis.Then the following temperature measurement experiments demonstrate the formation of the temperature gradient on the wafer surface predicted by the theoretical analysis and indicated a peak temper-ature about 90uC in the center.By using commercialized form talysurf,the machined surface was detected and the result shows regular removal profile that corresponds well to the flow field model.Moreover,the removal profile also indicates a 32 mm^(3)/min removal rate.By using atomic force microscopy(AFM),the surface roughness was also measured and the result demonstrates an Ra 0.6 nm surface roughness.Then the element composition of the machined surface was detected and analyzed by X-ray photoelectron spectroscopy(XPS)technology.The results also demonstrate the occurrence of the anticipated main reactions.All the experiments have proved that this atmospheric pressure plasma polishing method has the potential to achieve the m
文摘A New method,named atmospheric pressure plasma polishing,for the ultra-smooth machining of the silicon based materials is introduced.By inputting the CF4 gas into the atmospheric pressure plasma flame,high density reactive radicals will be generated,which will then react with the silicon based materials.The reaction product is the vaporization of the SiF4,which can be easily processed.In this way,the atomic scale material removal can be realized and the defect free ultra-smooth surface can be obtained.An experimental setup is built up,and the SiC polishing experiment is carried out.The AFM test result shows that the finished surface roughness (Ra) can be improved from 4.529 nm to 0.926 nm in 3 minutes.
基金scientific research starting the project of SWPU (X151528)。
文摘CsPbI_(2)Br is an ideal inorganic perovskite material with a reasonable bandgap for solar cell applications because of its advantage of superior thermal and phase stability. However, the performance of CsPbI2Br based solar cells highly relied on the perovskite crystallization process along with the interfacial contact engineering process between CsPbI_(2)Br perovskite and charge-transporting layers. In this work, a programmable crystallization method is developed to obtain ultra-smooth CsPbI_(2)Br perovskite film with a well-engineered contact interface in perovskite solar cells. This method combines a pre-stand-by process with a programmable gradient thermal engineering process, which mediates the crystal growth dynamics process of CsPbI2Br perovskite by controlling the release of dimethyl sulfoxide(DMSO) from its coordinates with the perovskite film, leading to high-quality CsPbI_(2)Br film with large-scale crystalline grains, reduced surface roughness, and low trap density. Fabricated perovskite devices based on CsPbI_(2)Br film obtained by this method deliver power conversion efficiency of 14.55 %;meanwhile, the encapsulated CsPbI_(2)Br perovskite device achieves a maximum efficiency of 15.07 %. This decent solar conversion efficiency demonstrates the effectiveness of the programmable crystallization method used in this work,which shows great potential as a universal approach in obtaining high-quality CsPbI_(2)Br perovskite films for fabricating high-efficiency inorganic perovskite solar cells.
