Nano-sized reinforcements improved the mechanical characteristics efficiently by promoting more implicit particle hardening mechanisms compared to micron-sized reinforcements.Nano-sized particles lessen the critical p...Nano-sized reinforcements improved the mechanical characteristics efficiently by promoting more implicit particle hardening mechanisms compared to micron-sized reinforcements.Nano-sized particles lessen the critical particle solidification velocity for swamp and thus offers better dispersal.In the present investigation,the friction stir processing(FSP)is utilized to produce AZ31/Al_(2)O_(3)nanocomposites at various tool rotation speeds(i.e.,900,1200,and 1500 rpm)with an optimized 1.5%volume alumina(Al_(2)O_(3))reinforcement ratio.The mechanical and corrosion behavior of AZ31/Al_(2)O_(3)-developed nanocomposites was investigated and compared with that of the AZ31 base alloy.The AZ31 alloy experienced a comprehensive dynamic recrystallization during FSP,causing substantial grain refinement.Grain-size strengthening is the primary factor contributed to the enhancement in the strength of the fabricated nanocomposite.Tensile strength and yield strength values were lower than those for the base metal matrix,although an upward trend in both values has been observed with an increase in tool rotation speed.An 19.72%increase in hardness along with superior corrosion resistance was achieved compared to the base alloy at a tool rotational speed of 1500 rpm.The corrosion currents(Jcorr)of all samples dropped with increase in the rotational speed,in contrast to the corrosion potentials(Ecorr),which increased.The values of Jcorr of AZ31/Al_(2)O_(3)were 42.3%,56.8%,and 65.5%lower than those of AZ31 alloy at the chosen rotating speeds of 900,1200,and 1500 rpm,respectively.The corrosion behavior of friction stir processed nanocomposites have been addressed in this manuscript which has not been given sufficient attention in the existing literature.Further,this work offers an effective choice for the quality assurance of the FSP process of AZ31/Al_(2)O_(3)nanocomposites.The obtained results are relevant to the development of lightweight automobile and aerospace structures and components.展开更多
Auxetic mechanical metamaterials are artificially architected materials that possess negative Poisson’s ratio,demonstrating transversal contracting deformation under external vertical compression loading.Their physic...Auxetic mechanical metamaterials are artificially architected materials that possess negative Poisson’s ratio,demonstrating transversal contracting deformation under external vertical compression loading.Their physical properties are mainly determined by spatial topological configurations.Traditionally,classical auxetic mechanical metamaterials exhibit relatively lower mechanical stiffness,compared to classic stretching dominated architectures.Nevertheless,in recent years,several novel auxetic mechanical metamaterials with high stiffness have been designed and proposed for energy absorption,load-bearing,and thermal-mechanical coupling applications.In this paper,mechanical design methods for designing auxetic structures with soft and stiff mechanical behavior are summarized and classified.For soft auxetic mechanical metamaterials,classic methods,such as using soft basic material,hierarchical design,tensile braided design,and curved ribs,are proposed.In comparison,for stiff auxetic mechanical metamaterials,design schemes,such as hard base material,hierarchical design,composite design,and adding additional load-bearing ribs,are proposed.Multi-functional applications of soft and stiff auxetic mechanical metamaterials are then reviewed.We hope this study could provide some guidelines for designing programmed auxetics with specified mechanical stiffness and deformation abilities according to demand.展开更多
A Chinese satellite gravity mission called SAGM (Space Advanced Gravity Measurements) is now taken into consideration.To meet its designed requirement,the measurement precision of the laser ranging system used to meas...A Chinese satellite gravity mission called SAGM (Space Advanced Gravity Measurements) is now taken into consideration.To meet its designed requirement,the measurement precision of the laser ranging system used to measure the inter-satellite distance change has to be better than l00nm/Hz1/2 within a broad bandwidth from 0.1mHz to 1Hz.An equal arm heterodyne Mach-Zehnder interferometer has been built on ground to demonstrate the measurement principle of a laser ranging system,which potentially can be used for both SAGM and future GW (gravitational wave) space antennas.Because of the equal arm length,the laser frequency noise has been significantly suppressed in the interferometer.Thus,the sensitivity better than 1nm/Hz1/2 in a frequency range of 0.15 mHz-0.375 Hz has been achieved.The result shows that the proposed methodology has very promising feasibility to meet the requirements of SAGM and of GW space antennas as well.展开更多
Based on Hartmann-Shack sensor technique, an online thin film stress measuring system was introduced to measure the film stresses of TiO2 and SiO2, and comparison was made between the film stresses prepared respective...Based on Hartmann-Shack sensor technique, an online thin film stress measuring system was introduced to measure the film stresses of TiO2 and SiO2, and comparison was made between the film stresses prepared respectively by the conventional process and the ion-beam assisted deposition. The effect of ion-beam assisted deposition on the film stresses of TiO2 and SiO2 was investigated in details, and the stress control methodologies using on-line adjustment and film doping were put forward. The results show that the film stress value of TiO2 prepared by ion-beam assisted deposition is 40 MPa lower than that prepared by conventional process, and the stress of TiO2 film changes gradually from tensile stress into compressive stress with increasing ion energy; while the film stress of SiO2 is a tensile stress under ion-beam assisted deposition because of the ion-beam sputtering effect, and the film refractive index decreases with increasing ion energy. A dynamic film stress control can be achieved through in-situ adjustment of the processing parameters based on the online film stress measuring technique, and the intrinsic stress of film can be effectively changed through film doping.展开更多
3D printing-based supercapacitors have been extensively explored,yet the rigid rheological requirement for corresponding ink preparation significantly limits the manufacturing of true 3D architecture in achieving supe...3D printing-based supercapacitors have been extensively explored,yet the rigid rheological requirement for corresponding ink preparation significantly limits the manufacturing of true 3D architecture in achieving superior energy storage.We proposed the stereolithographic technique to fabricate the metallic composite lattices with octet-truss arrangement by using electroless plating and engineering the 3D hierarchically porous graphene onto the scaffolds to build the hierarchically cellular lattices in quasi-solid supercapacitor application.The supercapacitor device that is composed of composite lattices span several pore size orders from nm to mm holds promising behavior on the areal capacitance(57.75 mF cm-2),rate capability(70% retention,2-40 mA cm-2),and long lifespan(96% after 5000 cycles),as well as superior energy density of 0.008 mWh cm-2,which are comparable to the state-of-the-art carbon-based supercapacitor.By synergistically combining this facile stereolithographic 3D printing technology with the hierarchically porous graphene architecture,we provide a novel route of manufacturing energy storage device as well as new insight into building other high-performance functional electronics.展开更多
Diamond,as an ultra-wide bandgap semiconductor,has become a promising candidate for next-generation microelec-tronics and optoelectronics due to its numerous advantages over conventional semiconductors,including ultra...Diamond,as an ultra-wide bandgap semiconductor,has become a promising candidate for next-generation microelec-tronics and optoelectronics due to its numerous advantages over conventional semiconductors,including ultrahigh carrier mo-bility and thermal conductivity,low thermal expansion coefficient,and ultra-high breakdown voltage,etc.Despite these ex-traordinary properties,diamond also faces various challenges before being practically used in the semiconductor industry.This review begins with a brief summary of previous efforts to model and construct diamond-based high-voltage switching diodes,high-power/high-frequency field-effect transistors,MEMS/NEMS,and devices operating at high temperatures.Following that,we will discuss recent developments to address scalable diamond device applications,emphasizing the synthesis of large-area,high-quality CVD diamond films and difficulties in diamond doping.Lastly,we show potential solutions to modulate diamond’s electronic properties by the“elastic strain engineering”strategy,which sheds light on the future development of diamond-based electronics,photonics and quantum systems.展开更多
Developing flexible sensors with high working performance holds intense interest for diverse applications in leveraging the Internet-of-things(IoT)infrastructures.For flexible piezoresistive sensors,traditionally most...Developing flexible sensors with high working performance holds intense interest for diverse applications in leveraging the Internet-of-things(IoT)infrastructures.For flexible piezoresistive sensors,traditionally most efforts are focused on tailoring the sensing materials to enhance the contact resistance variation for improving the sensitivity and working range,and it,however,remains challenging to simultaneously achieve flexible sensor with a linear working range over a high-pressure region(>100 kPa)and keep a reliable sensitivity.Herein,we devised a laserengraved silver-coated fabric as"soft"sensor electrode material to markedly advance the flexible sensor's linear working range to a level of 800 kPa with a high sensitivity of 6.4 kPa^-1 yet a fast response time of only 4 ms as well as long-time durability,which was rarely reported before.The integrated sensor successfully routed the wireless signal of pulse rate to the portable smartphone,further demonstrating its potential as a reliable electronic.Along with the rationally building the electrode instead of merely focusing on sensing materials capable of significantly improving the sensor's performance,we expect that this design concept and sensor system could potentially pave the way for developing more advanced wearable electronics in the future.展开更多
The extinction cross sections of a system containing two particles are calculated by the T-matrix method, and the results are compared with those of two single particles with single-scattering approximation. The neces...The extinction cross sections of a system containing two particles are calculated by the T-matrix method, and the results are compared with those of two single particles with single-scattering approximation. The necessity of the correction of the refractive indices of water and polystyrene for different incident wavelengths is particularly addressed in the calculation. By this means, the volume fractions allowed for certain accuracy requirements of single-scattering approximation in the light scattering experiment can be evaluated. The volume fractions calculated with corrected refractive indices are compared with those obtained with fixed refractive indices which have been rather commonly used, showing that fixed refractive indices may cause significant error in evaluating multiple scattering effect. The results also give a simple criterion for selecting the incident wavelength and particle size to avoid the 'blind zone' in the turbidity measurement, where the turbidity change is insensitive to aggregation of two particles.展开更多
The method of density matching between the solid and liquid phases is often adopted to effectively eliminate the effect of sedimentation of suspensions in studies on dynamic behaviour of a colloidal system. However, t...The method of density matching between the solid and liquid phases is often adopted to effectively eliminate the effect of sedimentation of suspensions in studies on dynamic behaviour of a colloidal system. However, the associated changes in the solvent composition may bring side effects to the properties investigated and therefore might lead to a faulty conclusion if the relevant correction is not made. To illustrate the importance of this side effect, we present an example of the sedimentation influence on the coagulation rate of suspensions of 2μm (diameter) polystyrene. The liquid mixtures, in the proper proportions of water (H2O), deuterium oxide (D2O) and methanol (MeOH) as the liquid phase, density-matched and unmatched experiments are performed. Besides the influence of viscosity, the presence of methanol in solvent media, used to enhance the sedimentation effect, causes significant changes (reduction) in rapid coagulation rates compared to that in pure water. Without the relevant corrections for those non-gravitational factors it seems that gravitational sedimentation would retard the coagulation. The magnitude of the contribution from the non-gravitational factor is quantitatively determined, making the relevant correction possible. After necessary the influence of the sedimentation on coagulation rates at corrections for all factors, our experiments show that the initial stage of the coagulation is not observable.展开更多
Projection micro stereolithography(PμSL)has emerged as a powerful three-dimensional(3D)printing technique for manufacturing polymer structures with micron-scale high resolution at high printing speed,which enables th...Projection micro stereolithography(PμSL)has emerged as a powerful three-dimensional(3D)printing technique for manufacturing polymer structures with micron-scale high resolution at high printing speed,which enables the production of customized 3D microlattices with feature sizes down to several microns.However,the mechanical properties of as-printed polymers were not systemically studied at the relevant length scales,especially when the feature sizes step into micron/sub-micron level,limiting its reliable performance prediction in micro/nanolattice and other metamaterial applications.In this work,we demonstrate that PμSL-printed microfibers could become stronger and significantly more ductile with reduced size ranging from 20μm to 60μm,showing an obvious size-dependent mechanical behavior,in which the size decreases to 20μm with a fracture strain up to~100%and fracture strength up to~100 MPa.Such size effect enables the tailoring of the material strength and stiffness of PμSL-printed microlattices over a broad range,allowing to fabricate the microlattice metamaterials with desired/tunable mechanical properties for various structural and functional applications.展开更多
Incorporating high-entropy alloys(HEAs) in composite microlattice structures yields superior mechanical performance and desirable functional properties compared to conventional metallic lattices. However, the modulus ...Incorporating high-entropy alloys(HEAs) in composite microlattice structures yields superior mechanical performance and desirable functional properties compared to conventional metallic lattices. However, the modulus mismatch and relatively poor adhesion between the soft polymer core and stiff metallic film coating often results in film delamination and brittle strut fracture at relatively low strain levels(typically below 10%). In this work, we demonstrate that optimizing the HEA film thickness of a CoCrNiFe-coated microlattice completely suppresses delamination,significantly delays the onset of strut fracture(~100% increase in compressive strain),and increases the specific strength by up to 50%. This work presents an efficient strategy to improve the properties of metal-composite mechanical metamaterials for structural applications.展开更多
Amorphous/nanocrystalline dual-phase structures have recently emerged as an effective way for over-coming the strength-ductility trade-offand breaking the limitation of the reverse Hall-Petch effect.Here,we proposed a...Amorphous/nanocrystalline dual-phase structures have recently emerged as an effective way for over-coming the strength-ductility trade-offand breaking the limitation of the reverse Hall-Petch effect.Here,we proposed a new strategy to develop a hierarchical and interconnected amorphous-crystalline nanocomposite arising from the nanoscale elemental interdiffusion and oxygen adsorption behavior dur-ing thermal treatment processes.The nanocomposite consisted of a three-dimensional(3D)hierarchical network structure where the crystalline phase(Cr-Co-Ni-Al)was embedded into the Al-O-based amor-phous phase network with critical feature sizes encompassing three orders of magnitude(from microm-eter to nanometer scale).It can achieve ultrahigh compression yield strength of-3.6 GPa with large homogeneous deformation of over 50%strain.The massive interstitial atoms induced lattice distortion and hierarchical amorphous phase boundary contributed to the strength improvement.in situ Uniaxial compression inside a transmission electron microscope(TEM)revealed that the exceptional deformability of the nanocomposites resulted from the homogenous plastic flow of nano-sized amorphous phase and the plastic co-deformation behavior restricted by the nano-architected dual-phase interface.The proposed dual-phase synthesis approach can outperform conventional nanolaminates design strategies in terms of the mechanical properties achievable while providing a pathway to easily tune the microstructure of these nanolaminates.展开更多
Plate-based cellular materials exhibit greater stiffness and strength than conventional cellular materials formed by struts.In this study,we designed and fabricated a plate-based auxetic cylinder metamaterial using hi...Plate-based cellular materials exhibit greater stiffness and strength than conventional cellular materials formed by struts.In this study,we designed and fabricated a plate-based auxetic cylinder metamaterial using high-resolution projection micro-stereolithography three-dimensional printing technique.Experiment and modeling results validated the auxetic behavior of the plate-based cylinder.The normalized Young’s modulus and yield strength of a four-layer auxetic cylinder are increased by 141%and 32%,respectively,compared with the conventional auxetic honeycomb.This study presents a universal strategy for fabricating plate-based auxetic metamaterials with appropriate mechanical performance for various structural applications.展开更多
文摘Nano-sized reinforcements improved the mechanical characteristics efficiently by promoting more implicit particle hardening mechanisms compared to micron-sized reinforcements.Nano-sized particles lessen the critical particle solidification velocity for swamp and thus offers better dispersal.In the present investigation,the friction stir processing(FSP)is utilized to produce AZ31/Al_(2)O_(3)nanocomposites at various tool rotation speeds(i.e.,900,1200,and 1500 rpm)with an optimized 1.5%volume alumina(Al_(2)O_(3))reinforcement ratio.The mechanical and corrosion behavior of AZ31/Al_(2)O_(3)-developed nanocomposites was investigated and compared with that of the AZ31 base alloy.The AZ31 alloy experienced a comprehensive dynamic recrystallization during FSP,causing substantial grain refinement.Grain-size strengthening is the primary factor contributed to the enhancement in the strength of the fabricated nanocomposite.Tensile strength and yield strength values were lower than those for the base metal matrix,although an upward trend in both values has been observed with an increase in tool rotation speed.An 19.72%increase in hardness along with superior corrosion resistance was achieved compared to the base alloy at a tool rotational speed of 1500 rpm.The corrosion currents(Jcorr)of all samples dropped with increase in the rotational speed,in contrast to the corrosion potentials(Ecorr),which increased.The values of Jcorr of AZ31/Al_(2)O_(3)were 42.3%,56.8%,and 65.5%lower than those of AZ31 alloy at the chosen rotating speeds of 900,1200,and 1500 rpm,respectively.The corrosion behavior of friction stir processed nanocomposites have been addressed in this manuscript which has not been given sufficient attention in the existing literature.Further,this work offers an effective choice for the quality assurance of the FSP process of AZ31/Al_(2)O_(3)nanocomposites.The obtained results are relevant to the development of lightweight automobile and aerospace structures and components.
基金support from the National Natural Science Foundation of China(Grant No.12102193)Shenzhen-Hong KongMacao Science and Technology Program(Category C)(SGDX2020110309300301)+1 种基金Key R&D Program from the Science and Technology Department of Sichuan Province(Key Science&Technology Project)(No.2022YFSY0001)Changsha Municipal Science and Technology Bureau under the Grant kh2201035.
文摘Auxetic mechanical metamaterials are artificially architected materials that possess negative Poisson’s ratio,demonstrating transversal contracting deformation under external vertical compression loading.Their physical properties are mainly determined by spatial topological configurations.Traditionally,classical auxetic mechanical metamaterials exhibit relatively lower mechanical stiffness,compared to classic stretching dominated architectures.Nevertheless,in recent years,several novel auxetic mechanical metamaterials with high stiffness have been designed and proposed for energy absorption,load-bearing,and thermal-mechanical coupling applications.In this paper,mechanical design methods for designing auxetic structures with soft and stiff mechanical behavior are summarized and classified.For soft auxetic mechanical metamaterials,classic methods,such as using soft basic material,hierarchical design,tensile braided design,and curved ribs,are proposed.In comparison,for stiff auxetic mechanical metamaterials,design schemes,such as hard base material,hierarchical design,composite design,and adding additional load-bearing ribs,are proposed.Multi-functional applications of soft and stiff auxetic mechanical metamaterials are then reviewed.We hope this study could provide some guidelines for designing programmed auxetics with specified mechanical stiffness and deformation abilities according to demand.
基金Supported by the Space Science Research Projects in Advance,Chinese Academy of Sciences.
文摘A Chinese satellite gravity mission called SAGM (Space Advanced Gravity Measurements) is now taken into consideration.To meet its designed requirement,the measurement precision of the laser ranging system used to measure the inter-satellite distance change has to be better than l00nm/Hz1/2 within a broad bandwidth from 0.1mHz to 1Hz.An equal arm heterodyne Mach-Zehnder interferometer has been built on ground to demonstrate the measurement principle of a laser ranging system,which potentially can be used for both SAGM and future GW (gravitational wave) space antennas.Because of the equal arm length,the laser frequency noise has been significantly suppressed in the interferometer.Thus,the sensitivity better than 1nm/Hz1/2 in a frequency range of 0.15 mHz-0.375 Hz has been achieved.The result shows that the proposed methodology has very promising feasibility to meet the requirements of SAGM and of GW space antennas as well.
文摘Based on Hartmann-Shack sensor technique, an online thin film stress measuring system was introduced to measure the film stresses of TiO2 and SiO2, and comparison was made between the film stresses prepared respectively by the conventional process and the ion-beam assisted deposition. The effect of ion-beam assisted deposition on the film stresses of TiO2 and SiO2 was investigated in details, and the stress control methodologies using on-line adjustment and film doping were put forward. The results show that the film stress value of TiO2 prepared by ion-beam assisted deposition is 40 MPa lower than that prepared by conventional process, and the stress of TiO2 film changes gradually from tensile stress into compressive stress with increasing ion energy; while the film stress of SiO2 is a tensile stress under ion-beam assisted deposition because of the ion-beam sputtering effect, and the film refractive index decreases with increasing ion energy. A dynamic film stress control can be achieved through in-situ adjustment of the processing parameters based on the online film stress measuring technique, and the intrinsic stress of film can be effectively changed through film doping.
基金the Research Grants Council of the Hong Kong Special Administrative Region of China (GRF No. CityU11216515)City University of Hong Kong (Nos. 7005070 and 9667153)+1 种基金Shenzhen Science and Technology Innovation Committee under the grant JCYJ20170818103206501the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2017JM5003)
文摘3D printing-based supercapacitors have been extensively explored,yet the rigid rheological requirement for corresponding ink preparation significantly limits the manufacturing of true 3D architecture in achieving superior energy storage.We proposed the stereolithographic technique to fabricate the metallic composite lattices with octet-truss arrangement by using electroless plating and engineering the 3D hierarchically porous graphene onto the scaffolds to build the hierarchically cellular lattices in quasi-solid supercapacitor application.The supercapacitor device that is composed of composite lattices span several pore size orders from nm to mm holds promising behavior on the areal capacitance(57.75 mF cm-2),rate capability(70% retention,2-40 mA cm-2),and long lifespan(96% after 5000 cycles),as well as superior energy density of 0.008 mWh cm-2,which are comparable to the state-of-the-art carbon-based supercapacitor.By synergistically combining this facile stereolithographic 3D printing technology with the hierarchically porous graphene architecture,we provide a novel route of manufacturing energy storage device as well as new insight into building other high-performance functional electronics.
基金the support from the Research Grants Council of the Hong Kong Special Administrative Region,China(Grant RFS2021-1S05)the National Natural Science Foundation of China(Grant 11922215)+1 种基金the funding from the National Natural Science Foundation of China(Grant 11902200)the Science and Technology Commission of Shanghai Municipality(Grant19YF1433600)。
文摘Diamond,as an ultra-wide bandgap semiconductor,has become a promising candidate for next-generation microelec-tronics and optoelectronics due to its numerous advantages over conventional semiconductors,including ultrahigh carrier mo-bility and thermal conductivity,low thermal expansion coefficient,and ultra-high breakdown voltage,etc.Despite these ex-traordinary properties,diamond also faces various challenges before being practically used in the semiconductor industry.This review begins with a brief summary of previous efforts to model and construct diamond-based high-voltage switching diodes,high-power/high-frequency field-effect transistors,MEMS/NEMS,and devices operating at high temperatures.Following that,we will discuss recent developments to address scalable diamond device applications,emphasizing the synthesis of large-area,high-quality CVD diamond films and difficulties in diamond doping.Lastly,we show potential solutions to modulate diamond’s electronic properties by the“elastic strain engineering”strategy,which sheds light on the future development of diamond-based electronics,photonics and quantum systems.
基金the financial support of the project from the National Natural Science Foundation of China(No.61904141)the funding of Natural Science Foundation of Shaanxi Province(No.2020JQ-295)+3 种基金the Key Research and Development Program of Shaanxi(Program No.2020GY-252)National Key Laboratory of Science and Technology on Vacuum Technology and Physics(HTKJ2019KL510007)City University of Hong Kong(Project Nos.7005070 and 9667153)Shenzhen Science and Technology Innovation Committee under the Grant JCYJ20170818103206501。
文摘Developing flexible sensors with high working performance holds intense interest for diverse applications in leveraging the Internet-of-things(IoT)infrastructures.For flexible piezoresistive sensors,traditionally most efforts are focused on tailoring the sensing materials to enhance the contact resistance variation for improving the sensitivity and working range,and it,however,remains challenging to simultaneously achieve flexible sensor with a linear working range over a high-pressure region(>100 kPa)and keep a reliable sensitivity.Herein,we devised a laserengraved silver-coated fabric as"soft"sensor electrode material to markedly advance the flexible sensor's linear working range to a level of 800 kPa with a high sensitivity of 6.4 kPa^-1 yet a fast response time of only 4 ms as well as long-time durability,which was rarely reported before.The integrated sensor successfully routed the wireless signal of pulse rate to the portable smartphone,further demonstrating its potential as a reliable electronic.Along with the rationally building the electrode instead of merely focusing on sensing materials capable of significantly improving the sensor's performance,we expect that this design concept and sensor system could potentially pave the way for developing more advanced wearable electronics in the future.
基金Supported by the National Natural Science Foundation of China under Grand Nos 10672173 and 10332050, and the China Postdoctoral Science Foundation.
文摘The extinction cross sections of a system containing two particles are calculated by the T-matrix method, and the results are compared with those of two single particles with single-scattering approximation. The necessity of the correction of the refractive indices of water and polystyrene for different incident wavelengths is particularly addressed in the calculation. By this means, the volume fractions allowed for certain accuracy requirements of single-scattering approximation in the light scattering experiment can be evaluated. The volume fractions calculated with corrected refractive indices are compared with those obtained with fixed refractive indices which have been rather commonly used, showing that fixed refractive indices may cause significant error in evaluating multiple scattering effect. The results also give a simple criterion for selecting the incident wavelength and particle size to avoid the 'blind zone' in the turbidity measurement, where the turbidity change is insensitive to aggregation of two particles.
基金Supported by the National Natural Science Foundation of China under Grant Nos 20473108 and 10332050, and the Knowledge Innovation Program of Chinese Academy of Sciences.
文摘The method of density matching between the solid and liquid phases is often adopted to effectively eliminate the effect of sedimentation of suspensions in studies on dynamic behaviour of a colloidal system. However, the associated changes in the solvent composition may bring side effects to the properties investigated and therefore might lead to a faulty conclusion if the relevant correction is not made. To illustrate the importance of this side effect, we present an example of the sedimentation influence on the coagulation rate of suspensions of 2μm (diameter) polystyrene. The liquid mixtures, in the proper proportions of water (H2O), deuterium oxide (D2O) and methanol (MeOH) as the liquid phase, density-matched and unmatched experiments are performed. Besides the influence of viscosity, the presence of methanol in solvent media, used to enhance the sedimentation effect, causes significant changes (reduction) in rapid coagulation rates compared to that in pure water. Without the relevant corrections for those non-gravitational factors it seems that gravitational sedimentation would retard the coagulation. The magnitude of the contribution from the non-gravitational factor is quantitatively determined, making the relevant correction possible. After necessary the influence of the sedimentation on coagulation rates at corrections for all factors, our experiments show that the initial stage of the coagulation is not observable.
基金the financial support from Shenzhen Science and Technology Innovation Committee under the Grant Nos. JCYJ20170818103206501, Type C 202011033000145Changsha Municipal Science and Technology Bureau Project kh2201035supported by the City University of Hong Kong under the Grant No. 9667226
文摘Projection micro stereolithography(PμSL)has emerged as a powerful three-dimensional(3D)printing technique for manufacturing polymer structures with micron-scale high resolution at high printing speed,which enables the production of customized 3D microlattices with feature sizes down to several microns.However,the mechanical properties of as-printed polymers were not systemically studied at the relevant length scales,especially when the feature sizes step into micron/sub-micron level,limiting its reliable performance prediction in micro/nanolattice and other metamaterial applications.In this work,we demonstrate that PμSL-printed microfibers could become stronger and significantly more ductile with reduced size ranging from 20μm to 60μm,showing an obvious size-dependent mechanical behavior,in which the size decreases to 20μm with a fracture strain up to~100%and fracture strength up to~100 MPa.Such size effect enables the tailoring of the material strength and stiffness of PμSL-printed microlattices over a broad range,allowing to fabricate the microlattice metamaterials with desired/tunable mechanical properties for various structural and functional applications.
基金funding for this work from Shenzhen Science and Technology Innovation Committee under the Grant JCYJ20170413141157573Part of this project was supported by City University of Hong Kong (Project Nos. 9667164)。
文摘Incorporating high-entropy alloys(HEAs) in composite microlattice structures yields superior mechanical performance and desirable functional properties compared to conventional metallic lattices. However, the modulus mismatch and relatively poor adhesion between the soft polymer core and stiff metallic film coating often results in film delamination and brittle strut fracture at relatively low strain levels(typically below 10%). In this work, we demonstrate that optimizing the HEA film thickness of a CoCrNiFe-coated microlattice completely suppresses delamination,significantly delays the onset of strut fracture(~100% increase in compressive strain),and increases the specific strength by up to 50%. This work presents an efficient strategy to improve the properties of metal-composite mechanical metamaterials for structural applications.
基金supported by Shenzhen-Hong Kong-Macao Science and Technology Program(Category C)(No.SGDX2020110309300301)Key R&D Program from the Science and Technology Department of Sichuan Province(Key Science&Technology Project)(No.2022YFSY0001)+1 种基金Changsha Municipal Science and Technology Bureau(No.kh2201035)the Innovation and Technology Commission of Hong Kong(No.GHP/221/21GD).
文摘Amorphous/nanocrystalline dual-phase structures have recently emerged as an effective way for over-coming the strength-ductility trade-offand breaking the limitation of the reverse Hall-Petch effect.Here,we proposed a new strategy to develop a hierarchical and interconnected amorphous-crystalline nanocomposite arising from the nanoscale elemental interdiffusion and oxygen adsorption behavior dur-ing thermal treatment processes.The nanocomposite consisted of a three-dimensional(3D)hierarchical network structure where the crystalline phase(Cr-Co-Ni-Al)was embedded into the Al-O-based amor-phous phase network with critical feature sizes encompassing three orders of magnitude(from microm-eter to nanometer scale).It can achieve ultrahigh compression yield strength of-3.6 GPa with large homogeneous deformation of over 50%strain.The massive interstitial atoms induced lattice distortion and hierarchical amorphous phase boundary contributed to the strength improvement.in situ Uniaxial compression inside a transmission electron microscope(TEM)revealed that the exceptional deformability of the nanocomposites resulted from the homogenous plastic flow of nano-sized amorphous phase and the plastic co-deformation behavior restricted by the nano-architected dual-phase interface.The proposed dual-phase synthesis approach can outperform conventional nanolaminates design strategies in terms of the mechanical properties achievable while providing a pathway to easily tune the microstructure of these nanolaminates.
基金supported by the Shenzhen Science and Technology Innovation Commission(Grant Nos.SGDX2020110309300301 and JCYJ20170818103206501)the City University of Hong Kong(Grant Nos.9667226 and 9610461)。
文摘Plate-based cellular materials exhibit greater stiffness and strength than conventional cellular materials formed by struts.In this study,we designed and fabricated a plate-based auxetic cylinder metamaterial using high-resolution projection micro-stereolithography three-dimensional printing technique.Experiment and modeling results validated the auxetic behavior of the plate-based cylinder.The normalized Young’s modulus and yield strength of a four-layer auxetic cylinder are increased by 141%and 32%,respectively,compared with the conventional auxetic honeycomb.This study presents a universal strategy for fabricating plate-based auxetic metamaterials with appropriate mechanical performance for various structural applications.