Multi-function,multiband,cost-effective,miniaturized reconfigurable radio frequency(RF)components are highly demanded in modern and future wireless communication systems.This paper discusses the needs and implementati...Multi-function,multiband,cost-effective,miniaturized reconfigurable radio frequency(RF)components are highly demanded in modern and future wireless communication systems.This paper discusses the needs and implementation of multiband reconfigurable RF components with microfabrication techniques and advanced materials.RF applications of fabrication methods such as surface and bulk micromachining techniques are reviewed,especially on the development of RF microelectromechanical systems(MEMS)and other tunable components.Works on the application of ferroelectric and ferromagnetic materials are investigated,which enables RF components with continuous tunability,reduced size,and enhanced performance.Methods and strategies with nano-patterning to improve high frequency characteristics of ferromagnetic thin film(e.g.,ferromagnetic resonance frequency and losses)and their applications on the development of fully electrically tunable RF components are fully demonstrated.展开更多
Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<φs<1), which involves the processing of alloys in the semi-solid state.Tooling has to be adapted to this particular process to b...Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<φs<1), which involves the processing of alloys in the semi-solid state.Tooling has to be adapted to this particular process to benefit shear thinning and thixotropic behaviour of such semi-solid material.Tooling parameters, such as the forming speed and tool temperature, have to be accurately controlled because of their influence on thermal exchanges between material flow and tool.These thermal exchanges influence the high-cracking tendency and the rheology of the semi-solid material during forming, which affects parts properties and therefore their quality.Extrusion tests show how thermal exchanges influence quality of thixoforged parts made of 7075 aluminium alloys at high solid fraction by modifying process parameters like forming speed, tool temperature and tool thermal protector.Thus an optimum in terms of thermal exchanges has to be found between surface quality and mechanical properties of the part.A direct application is the evaluation of surface quality of thixoforged thin wall parts made of 7075 aluminium alloy.展开更多
Friction stir processing（FSP） was utilized to produce surface composites by incorporating nano-sized cerium oxide（CeO2） and silicon carbide（SiC） particles individually and in combined form into the Al5083 alloy ...Friction stir processing（FSP） was utilized to produce surface composites by incorporating nano-sized cerium oxide（CeO2） and silicon carbide（SiC） particles individually and in combined form into the Al5083 alloy matrix. The study signified the role of these reinforcements on microstructure and wear behavior of the resultant surface composite layers. The wear characteristics of the resultant mono and hybrid surface composite layers were investigated using a pin-on-disc wear tester at room temperature. The microstructural observations of FSPed regions and the worn out surfaces were performed by optical and scanning electron microscopy. Considerable grain refinement and uniform distribution of reinforcement particles were achieved inside the nugget zone. All the composite samples showed higher hardness and wear resistance compared to the base metal. Among the composite samples, the hybrid composite（Al5083/CeO2/SiC） revealed the highest wear resistance and the lowest friction coefficient, whereas the Al5083/SiC composite exhibited the highest hardness, i.e., 1.5 times as hard as that of the Al5083 base metal. The enhancement in wear behavior of the hybrid composites was attributed to the solid lubrication effect provided by CeO2 particles. The predominant wear mechanism was identified as severe adhesive in non-composite samples, which changed to abrasive wear and delamination in the presence of reinforcing particles.展开更多
Ti Ni shape memory alloys（SMAs） have been normally used as the competent elements in large part of the industries due to outstanding properties, such as super elasticity and shape memory effects. However, traditiona...Ti Ni shape memory alloys（SMAs） have been normally used as the competent elements in large part of the industries due to outstanding properties, such as super elasticity and shape memory effects. However, traditional machining of SMAs is quite complex due to these properties. Hence, the wire electric discharge machining（WEDM） characteristics of Ti Ni SMA was studied. The experiments were planned as per L27 orthogonal array to minimize the experiments, each experiment was performed under different conditions of pulse duration, pulse off time, servo voltage, flushing pressure and wire speed. A multi-response optimization method using Taguchi design with utility concept has been proposed for simultaneous optimization. The analysis of means（ANOM） and analysis of variance（ANOVA） on signal to noise（S/N） ratio were performed for determining the optimal parameter levels. Taguchi analysis reveals that a combination of 1 μs pulse duration, 3.8 μs pulse off time, 40 V servo voltage, 1.8×105 Pa flushing pressure and 8 m/min wire speed is beneficial for simultaneously maximizing the material removal rate（MRR） and minimizing the surface roughness. The optimization results of WEDM of Ti Ni SMA also indicate that pulse duration significantly affects the material removal rate and surface roughness. The discharged craters, micro cracks and recast layer were observed on the machined surface at large pulse duration.展开更多
The mechanism of ultrasonic vibration honing Nd-Fe-B has been briefly elaborated after the introduction of the strategic significance of processing Nd-Fe-B. Based on the formation principle of Scanning Electrtmic Micr...The mechanism of ultrasonic vibration honing Nd-Fe-B has been briefly elaborated after the introduction of the strategic significance of processing Nd-Fe-B. Based on the formation principle of Scanning Electrtmic Microscope （SEM）, and at the examination with the aid of SEM to the ultrasonic vibration honing Nd-Fe-B material＇s superficial microscopic topography, the paper discusses the new processing nechanism according to the SEM examination picture. The research indicates that as a result of supersonic high frequency vibration, the path of the abrasion extends at the same time, and the supersonic cavitation effect forms the intense shock-wave, knpacting Nd-Fe-B material＇s intemal surface, providing the supersonic energy for the superticial abrasive dust＇s dimination, which directly explain that the honing processing efficiency is enhanced, and the processing surface roughness is high.展开更多
The chemical mechanical polishing(CMP)technology has been widely used for surface modification of critical materials and components with high quality and efficiency.In a typical CMP process,the mechanical properties o...The chemical mechanical polishing(CMP)technology has been widely used for surface modification of critical materials and components with high quality and efficiency.In a typical CMP process,the mechanical properties of abrasives play a vital role in obtaining the ultra-precision and damage-free surface of wafers for improvement of their performances.In this work,a series of fine structured rod-shaped silica(RmSiO2)-based abrasives with controllable sizes and diverse ordered mesoporous structures were synthesized via a soft template approach,and successfully applied in the sustainable polishing slurry for improving the surface quality of cadmium zinc telluride(CZT)wafers.Compared with commercial silica gel,solid and mesoporous silica spheres,the RmSiO2 abrasives present superior elastic deformation capacity and surface precision machinability on account of their mesoporous structures and rod shapes.Especially,ultra-precision surface roughness and relatively effective material removal speed were achieved by the CMP process using the RmSiO2 abrasives with a length/diameter(L/d)ratio of 1.In addition,a potential CMP mechanism of the developed polishing slurry to CZT wafer was elucidated by analyzing X-ray photoelectron spectra and other characterizations.The proposed interfacial chemical and mechanical effects will provide a new strategy for improving abrasives’machinability and precision manufacture of hard-to-machine materials.展开更多
Porous materials such as metal-organic frameworks(MOFs)with high theoretical volumetric gas uptake capacity are promising materials for gas storage and separation,but the structuring for practical applications is chal...Porous materials such as metal-organic frameworks(MOFs)with high theoretical volumetric gas uptake capacity are promising materials for gas storage and separation,but the structuring for practical applications is challenging.Herein,we report a general and feasible strategy to combine electrospinning with a phase conversion method to decorate polyacrylonitrile nanofibers(PAN NFs)with CuMOF(HKUST-1).The strategy is based on the combination of surface pretreatment of the NFs with Cu(OH)_(2) and a subsequent phase conversion into HKUST-1 crystals(PCHKUST-1).A significant higher loading of HKUST-1 in the PAN NF matrix was achieved by the phase conversion method compared with direct electrospinning of MOF slurries or insitu growth of MOF crystals on NFs.As a result,the hierarchical structured PC(phase conversion)-HKUST-1 NFs revealed the highest gravimetric storage capacity of 86 cm^(3) g^(-1)(STP)at 3500 kPa and 298 K for methane(CH_(4)),which is higher than other HKUST-1 NFs reported previously.The improved CH_(4) uptake can be explained by the high loading of HKUST-1 due to the high availability of Cu-ions localized on the surface of the NFs during the phase conversion process,resulting in high surface area and excellent gas access of the phase converted HKUST-1.Thus,the developed strategy of structuring MOFs could be of interest for the fabrication of tailor-made MOF NF architectures for other energy and environmental applications.展开更多
基金Projects(1253929,1910853)supported by the National Natural Science Foundation of China。
文摘Multi-function,multiband,cost-effective,miniaturized reconfigurable radio frequency(RF)components are highly demanded in modern and future wireless communication systems.This paper discusses the needs and implementation of multiband reconfigurable RF components with microfabrication techniques and advanced materials.RF applications of fabrication methods such as surface and bulk micromachining techniques are reviewed,especially on the development of RF microelectromechanical systems(MEMS)and other tunable components.Works on the application of ferroelectric and ferromagnetic materials are investigated,which enables RF components with continuous tunability,reduced size,and enhanced performance.Methods and strategies with nano-patterning to improve high frequency characteristics of ferromagnetic thin film(e.g.,ferromagnetic resonance frequency and losses)and their applications on the development of fully electrically tunable RF components are fully demonstrated.
基金University of Liège,Walloon Region (First Europe Program Convention n°"NEP" 415824,THIXALU Project and MAGAL Project) and the COST 541 for their financial support
文摘Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<φs<1), which involves the processing of alloys in the semi-solid state.Tooling has to be adapted to this particular process to benefit shear thinning and thixotropic behaviour of such semi-solid material.Tooling parameters, such as the forming speed and tool temperature, have to be accurately controlled because of their influence on thermal exchanges between material flow and tool.These thermal exchanges influence the high-cracking tendency and the rheology of the semi-solid material during forming, which affects parts properties and therefore their quality.Extrusion tests show how thermal exchanges influence quality of thixoforged parts made of 7075 aluminium alloys at high solid fraction by modifying process parameters like forming speed, tool temperature and tool thermal protector.Thus an optimum in terms of thermal exchanges has to be found between surface quality and mechanical properties of the part.A direct application is the evaluation of surface quality of thixoforged thin wall parts made of 7075 aluminium alloy.
基金financial support provided by Shahid Chamran University of Ahvaz, Iran
文摘Friction stir processing（FSP） was utilized to produce surface composites by incorporating nano-sized cerium oxide（CeO2） and silicon carbide（SiC） particles individually and in combined form into the Al5083 alloy matrix. The study signified the role of these reinforcements on microstructure and wear behavior of the resultant surface composite layers. The wear characteristics of the resultant mono and hybrid surface composite layers were investigated using a pin-on-disc wear tester at room temperature. The microstructural observations of FSPed regions and the worn out surfaces were performed by optical and scanning electron microscopy. Considerable grain refinement and uniform distribution of reinforcement particles were achieved inside the nugget zone. All the composite samples showed higher hardness and wear resistance compared to the base metal. Among the composite samples, the hybrid composite（Al5083/CeO2/SiC） revealed the highest wear resistance and the lowest friction coefficient, whereas the Al5083/SiC composite exhibited the highest hardness, i.e., 1.5 times as hard as that of the Al5083 base metal. The enhancement in wear behavior of the hybrid composites was attributed to the solid lubrication effect provided by CeO2 particles. The predominant wear mechanism was identified as severe adhesive in non-composite samples, which changed to abrasive wear and delamination in the presence of reinforcing particles.
文摘Ti Ni shape memory alloys（SMAs） have been normally used as the competent elements in large part of the industries due to outstanding properties, such as super elasticity and shape memory effects. However, traditional machining of SMAs is quite complex due to these properties. Hence, the wire electric discharge machining（WEDM） characteristics of Ti Ni SMA was studied. The experiments were planned as per L27 orthogonal array to minimize the experiments, each experiment was performed under different conditions of pulse duration, pulse off time, servo voltage, flushing pressure and wire speed. A multi-response optimization method using Taguchi design with utility concept has been proposed for simultaneous optimization. The analysis of means（ANOM） and analysis of variance（ANOVA） on signal to noise（S/N） ratio were performed for determining the optimal parameter levels. Taguchi analysis reveals that a combination of 1 μs pulse duration, 3.8 μs pulse off time, 40 V servo voltage, 1.8×105 Pa flushing pressure and 8 m/min wire speed is beneficial for simultaneously maximizing the material removal rate（MRR） and minimizing the surface roughness. The optimization results of WEDM of Ti Ni SMA also indicate that pulse duration significantly affects the material removal rate and surface roughness. The discharged craters, micro cracks and recast layer were observed on the machined surface at large pulse duration.
基金supported by The Natural Science Foundation of China(50975265)The Natural Science Foundation of Shanxi Province of China(2007011071)Program for the Top Young Academic Leaders of Higher Learning Institutions of Shanxi(20080205ZX)
文摘The mechanism of ultrasonic vibration honing Nd-Fe-B has been briefly elaborated after the introduction of the strategic significance of processing Nd-Fe-B. Based on the formation principle of Scanning Electrtmic Microscope （SEM）, and at the examination with the aid of SEM to the ultrasonic vibration honing Nd-Fe-B material＇s superficial microscopic topography, the paper discusses the new processing nechanism according to the SEM examination picture. The research indicates that as a result of supersonic high frequency vibration, the path of the abrasion extends at the same time, and the supersonic cavitation effect forms the intense shock-wave, knpacting Nd-Fe-B material＇s intemal surface, providing the supersonic energy for the superticial abrasive dust＇s dimination, which directly explain that the honing processing efficiency is enhanced, and the processing surface roughness is high.
基金the National Key R&D Program of China(2018YFA0703400)the Xinghai Science Funds for Distinguished Young Scholars+1 种基金Thousand Youth Talents at Dalian University of Technology,the Collaborative Innovation Center of Major Machine Manufacturing in Liaoning,Liaoning BaiQianWan Talents ProgramDalian National Laboratory for Clean Energy(DNL),DNL Cooperation Fund,Chinese Academy of Sciences(DNL180402)。
文摘The chemical mechanical polishing(CMP)technology has been widely used for surface modification of critical materials and components with high quality and efficiency.In a typical CMP process,the mechanical properties of abrasives play a vital role in obtaining the ultra-precision and damage-free surface of wafers for improvement of their performances.In this work,a series of fine structured rod-shaped silica(RmSiO2)-based abrasives with controllable sizes and diverse ordered mesoporous structures were synthesized via a soft template approach,and successfully applied in the sustainable polishing slurry for improving the surface quality of cadmium zinc telluride(CZT)wafers.Compared with commercial silica gel,solid and mesoporous silica spheres,the RmSiO2 abrasives present superior elastic deformation capacity and surface precision machinability on account of their mesoporous structures and rod shapes.Especially,ultra-precision surface roughness and relatively effective material removal speed were achieved by the CMP process using the RmSiO2 abrasives with a length/diameter(L/d)ratio of 1.In addition,a potential CMP mechanism of the developed polishing slurry to CZT wafer was elucidated by analyzing X-ray photoelectron spectra and other characterizations.The proposed interfacial chemical and mechanical effects will provide a new strategy for improving abrasives’machinability and precision manufacture of hard-to-machine materials.
基金supported by the Grande Solution Project“HiGradeGas”(48279)Innovation Fund Denmark,exploring NFs-based adsorbents for biogas upgrading and storage+1 种基金the Danish Research Council to provide funding to support fundamental research on electrospinning(8022-00237B)for investigating NFs structures for enzyme immobilization(6111-00232B)。
文摘Porous materials such as metal-organic frameworks(MOFs)with high theoretical volumetric gas uptake capacity are promising materials for gas storage and separation,but the structuring for practical applications is challenging.Herein,we report a general and feasible strategy to combine electrospinning with a phase conversion method to decorate polyacrylonitrile nanofibers(PAN NFs)with CuMOF(HKUST-1).The strategy is based on the combination of surface pretreatment of the NFs with Cu(OH)_(2) and a subsequent phase conversion into HKUST-1 crystals(PCHKUST-1).A significant higher loading of HKUST-1 in the PAN NF matrix was achieved by the phase conversion method compared with direct electrospinning of MOF slurries or insitu growth of MOF crystals on NFs.As a result,the hierarchical structured PC(phase conversion)-HKUST-1 NFs revealed the highest gravimetric storage capacity of 86 cm^(3) g^(-1)(STP)at 3500 kPa and 298 K for methane(CH_(4)),which is higher than other HKUST-1 NFs reported previously.The improved CH_(4) uptake can be explained by the high loading of HKUST-1 due to the high availability of Cu-ions localized on the surface of the NFs during the phase conversion process,resulting in high surface area and excellent gas access of the phase converted HKUST-1.Thus,the developed strategy of structuring MOFs could be of interest for the fabrication of tailor-made MOF NF architectures for other energy and environmental applications.
