In the grinding of high quality fused silica parts with complex surface or structure using ball-headed metal bonded diamond wheel with small diameter,the existing dressing methods are not suitable to dress the ball-he...In the grinding of high quality fused silica parts with complex surface or structure using ball-headed metal bonded diamond wheel with small diameter,the existing dressing methods are not suitable to dress the ball-headed diamond wheel precisely due to that they are either on-line in process dressing which may causes collision problem or without consideration for the effects of the tool setting error and electrode wear.An on-machine precision preparation and dressing method is proposed for ball-headed diamond wheel based on electrical discharge machining.By using this method the cylindrical diamond wheel with small diameter is manufactured to hemispherical-headed form.The obtained ball-headed diamond wheel is dressed after several grinding passes to recover geometrical accuracy and sharpness which is lost due to the wheel wear.A tool setting method based on high precision optical system is presented to reduce the wheel center setting error and dimension error.The effect of electrode tool wear is investigated by electrical dressing experiments,and the electrode tool wear compensation model is established based on the experimental results which show that the value of wear ratio coefficient K’ tends to be constant with the increasing of the feed length of electrode and the mean value of K’ is 0.156.Grinding experiments of fused silica are carried out on a test bench to evaluate the performance of the preparation and dressing method.The experimental results show that the surface roughness of the finished workpiece is 0.03 μm.The effect of the grinding parameter and dressing frequency on the surface roughness is investigated based on the measurement results of the surface roughness.This research provides an on-machine preparation and dressing method for ball-headed metal bonded diamond wheel used in the grinding of fused silica,which provides a solution to the tool setting method and the effect of electrode tool wear.展开更多
Owing to the high working voltage and energy-storage density and excellent cycling stability,Na_(3)V_(2)(PO_(4))_(2)O_(2)F(NVPOF)has been recognized as a promising cathode material for sodium ion batteries(SIBs).Usual...Owing to the high working voltage and energy-storage density and excellent cycling stability,Na_(3)V_(2)(PO_(4))_(2)O_(2)F(NVPOF)has been recognized as a promising cathode material for sodium ion batteries(SIBs).Usually,NVPOF is prepared by a high-temperature solid-state method,which easily leads to many deficiencies including large particle size,irregular morphology and poor high-rate capability.In order to avoid these deficiencies,the present study reveals a simple hydrothermal method to effectively regulate the morphology and size uniformity of the NVPOF particles and optimize the electrochemical properties by precisely adjusting the key preparation parameters including pH and temperature.It is disclosed that the optimized NVPOF prepared at pH=7.00±0.05 and 170℃ can achieve outstanding electrochemical properties in terms of high specific capacity of 123.2 mA h g^(−1) at 0.1 C,superior high-rate capability of 85.9 mA h g^(−1) at 20 C and long cycling stability(e.g.,a capacity retention up to 94.8%at 1 C after 500 cycles).All of the properties are obviously better than those of the controls obtained at other preparation parameters.The much enhanced performance should be beneficial from the short and fast Na+transport pathways because of the high uniformity and nanometer size of the NVPOF particles,making them a promising cathode material for high-performance SIBs.展开更多
Emerging monolayer molecular crystals(MMCs)have become prosperous in recent decades due to their numerous advantages.First,downsizing the active layer thickness to monolayer in organic field-effect transistors(OFETs)i...Emerging monolayer molecular crystals(MMCs)have become prosperous in recent decades due to their numerous advantages.First,downsizing the active layer thickness to monolayer in organic field-effect transistors(OFETs)is beneficial to elucidate the intrinsic charge-transport behavior.Next,the ultrathin conducting channel can reduce bulk injection resistance to extract mobility accurately.Then,direct exposure of the conducting channel can enhance the sensing performance.Finally,MMCs combine the merits of ultrathin thickness and high crystallization,which will improve the optoelectronic performance and realize complex device architectures for future advanced optoelectronic applications.In this Review,recent research progress in precise preparations and advanced applications of solution-processed MMCs are summarized.We present the current challenges related to MMCs with specific structures and desired performances,and an outlook regarding their application in next-generation integrated organic optoelectronics is provided.展开更多
基金supported by National Natural Science Foundation of China(Grant No.50935003)National Numerical Control Major Projects of China(Grant No.2013ZX04001000-215)
文摘In the grinding of high quality fused silica parts with complex surface or structure using ball-headed metal bonded diamond wheel with small diameter,the existing dressing methods are not suitable to dress the ball-headed diamond wheel precisely due to that they are either on-line in process dressing which may causes collision problem or without consideration for the effects of the tool setting error and electrode wear.An on-machine precision preparation and dressing method is proposed for ball-headed diamond wheel based on electrical discharge machining.By using this method the cylindrical diamond wheel with small diameter is manufactured to hemispherical-headed form.The obtained ball-headed diamond wheel is dressed after several grinding passes to recover geometrical accuracy and sharpness which is lost due to the wheel wear.A tool setting method based on high precision optical system is presented to reduce the wheel center setting error and dimension error.The effect of electrode tool wear is investigated by electrical dressing experiments,and the electrode tool wear compensation model is established based on the experimental results which show that the value of wear ratio coefficient K’ tends to be constant with the increasing of the feed length of electrode and the mean value of K’ is 0.156.Grinding experiments of fused silica are carried out on a test bench to evaluate the performance of the preparation and dressing method.The experimental results show that the surface roughness of the finished workpiece is 0.03 μm.The effect of the grinding parameter and dressing frequency on the surface roughness is investigated based on the measurement results of the surface roughness.This research provides an on-machine preparation and dressing method for ball-headed metal bonded diamond wheel used in the grinding of fused silica,which provides a solution to the tool setting method and the effect of electrode tool wear.
基金financial support from the National Natural Science Foundation of China(51602048)the Fundamental Research Funds for the Central Universities(2412017FZ013).
文摘Owing to the high working voltage and energy-storage density and excellent cycling stability,Na_(3)V_(2)(PO_(4))_(2)O_(2)F(NVPOF)has been recognized as a promising cathode material for sodium ion batteries(SIBs).Usually,NVPOF is prepared by a high-temperature solid-state method,which easily leads to many deficiencies including large particle size,irregular morphology and poor high-rate capability.In order to avoid these deficiencies,the present study reveals a simple hydrothermal method to effectively regulate the morphology and size uniformity of the NVPOF particles and optimize the electrochemical properties by precisely adjusting the key preparation parameters including pH and temperature.It is disclosed that the optimized NVPOF prepared at pH=7.00±0.05 and 170℃ can achieve outstanding electrochemical properties in terms of high specific capacity of 123.2 mA h g^(−1) at 0.1 C,superior high-rate capability of 85.9 mA h g^(−1) at 20 C and long cycling stability(e.g.,a capacity retention up to 94.8%at 1 C after 500 cycles).All of the properties are obviously better than those of the controls obtained at other preparation parameters.The much enhanced performance should be beneficial from the short and fast Na+transport pathways because of the high uniformity and nanometer size of the NVPOF particles,making them a promising cathode material for high-performance SIBs.
基金supported by the National Key R&D Plan of China(2022YFB3603800 and 2020YFB0204802)the National Natural Science Foundation of China(T2225028 and 22075295)+2 种基金Chinese Academy of Sciences(Hundred Talents PlanYouth Innovation Promotion Association,Young Scientists in Basic Research(YSBR-053))the Strategic Priority Research Program of Science(XDB0520201).
文摘Emerging monolayer molecular crystals(MMCs)have become prosperous in recent decades due to their numerous advantages.First,downsizing the active layer thickness to monolayer in organic field-effect transistors(OFETs)is beneficial to elucidate the intrinsic charge-transport behavior.Next,the ultrathin conducting channel can reduce bulk injection resistance to extract mobility accurately.Then,direct exposure of the conducting channel can enhance the sensing performance.Finally,MMCs combine the merits of ultrathin thickness and high crystallization,which will improve the optoelectronic performance and realize complex device architectures for future advanced optoelectronic applications.In this Review,recent research progress in precise preparations and advanced applications of solution-processed MMCs are summarized.We present the current challenges related to MMCs with specific structures and desired performances,and an outlook regarding their application in next-generation integrated organic optoelectronics is provided.
