Solids in nano-scales hold the promise to exhibit extreme strength and elasticity due to the absence of interior defects and the designability of micro-arrangements.A nano-scaled bulk sample can be produced by diamond...Solids in nano-scales hold the promise to exhibit extreme strength and elasticity due to the absence of interior defects and the designability of micro-arrangements.A nano-scaled bulk sample can be produced by diamond,ice,metallic twins,high entropy alloy(HEA),or cubic boron nitride(cBN).A loading stage capable of 4-DoF movements was designed and built to achieve multi-axial mechanical loading inside a transmission electronic microscope chamber with sub-nanometer loading precision.For single crystal diamond in the shape of nano-needles,we were able to achieve an extreme bending strength of 125 GPa at the tensile side,approaching the theoretical strength of diamond.For ice fibers of sub-micron radius,an extreme elastic strain of 10.9%was acquired,far exceeding the previous record of 0.3%for the elastic strain achievable by ice.For metallic twin specimens made by nano-welding,a shear strain as large as 364%was recorded parallel to the twin boundary.Cyclic shear loading aligned with the twin boundary would drive an up-and-down sweeping movement of the low-angle grain boundary,as composed by an array of dislocations.The sweep of the grain boundary effectively cleanses the lattice defects and creates a feasible scenario of unlimited cyclic endurance.For a HEA dog-bone specimen in nano-scale,an extreme elastic strain of about 10%was achieved.At this level of mechanical straining,stretch-induced melting for crystalline metals,as envisaged by Lindemann a century ago,was realized.For cBN crystals,a fracture path inclined to the stacking hexagon planes would result in a new failure mechanism of layered decohesion,triggered by the extremely large elastic strain(>7%)along the edge of the submicron-scaled specimen.These results indicate ample room for upgrading the mechanical behaviour of solids in nano-scales.展开更多
[Objective] The aim was to observe the antibacterial effect of nano-scale Titanium dioxide on parasitic bacterium of Nanfeng Citrus in storage period.[Method] Nano-scale Titanium dioxide was prepared by dibutyl phthal...[Objective] The aim was to observe the antibacterial effect of nano-scale Titanium dioxide on parasitic bacterium of Nanfeng Citrus in storage period.[Method] Nano-scale Titanium dioxide was prepared by dibutyl phthalate through sol-gel method under anhydrous conditions,and orthogonal experiment was used to determine optimum conditions for nano-scale Titanium dioxide preparation,and structure characterization of nano-scale Titanium dioxide was carried out by X-Ray diffractometer.Oxford cup method was used to explore inhibition effect of nano-scale Titanium dioxide suspension on the activity of normal parasitic bacterium of Nanfeng Citrus.Simultaneously,the empirical preservation test was carried out.[Result] The average diameter of nano-scale Titanium dioxide powder attained to 14.6 nm,actual average yield could reach 90.83% with RSD（Relative Standard Deviation）of 0.86%.[Conclusion] Nano-scale Titanium dioxide had good antibacterial effect on the parasitic bacterium of Nanfeng Citrus in storage period.展开更多
There are two main trends in the development of unmanned aerial vehicle(UAV)technologies:miniaturization and intellectualization,in which realizing object tracking capabilities for a nano-scale UAV is one of the most ...There are two main trends in the development of unmanned aerial vehicle(UAV)technologies:miniaturization and intellectualization,in which realizing object tracking capabilities for a nano-scale UAV is one of the most challenging problems.In this paper,we present a visual object tracking and servoing control system utilizing a tailor-made 38 g nano-scale quadrotor.A lightweight visual module is integrated to enable object tracking capabilities,and a micro positioning deck is mounted to provide accurate pose estimation.In order to be robust against object appearance variations,a novel object tracking algorithm,denoted by RMCTer,is proposed,which integrates a powerful short-term tracking module and an efficient long-term processing module.In particular,the long-term processing module can provide additional object information and modify the short-term tracking model in a timely manner.Furthermore,a positionbased visual servoing control method is proposed for the quadrotor,where an adaptive tracking controller is designed by leveraging backstepping and adaptive techniques.Stable and accurate object tracking is achieved even under disturbances.Experimental results are presented to demonstrate the high accuracy and stability of the whole tracking system.展开更多
By means of dynamic plastic deformation （DPD） followed by thermal annealing, a mixed structure of micro-sized austenite grains embedded with nano-scale twin bundles （of about 20% in volume） has been synthesized in...By means of dynamic plastic deformation （DPD） followed by thermal annealing, a mixed structure of micro-sized austenite grains embedded with nano-scale twin bundles （of about 20% in volume） has been synthesized in a 316L stainless steel （SS）. Such a 316L SS sample exhibits a tensile strength as high as 1001 MPa and an elongation-to-failure of about 23%. The much elevated strength originates from the presence of a considerable number of strengthening nano-twin bundles, while the ductility from the recrystallized grains. The superior strength-ductility combination achieved in the nano-twins-strengthened austenite steel demonstrates a novel approach for optimizing the mechanical properties in engineering materials.展开更多
Ce-incorporated apatite（Ce-HA） nano-scale particles with different Ce percentage contents（atomic ratio of Ce to Ce ＋ Ca is 5%,10%and 20%,respectively） were synthesized via a simple wet chemical method in this stu...Ce-incorporated apatite（Ce-HA） nano-scale particles with different Ce percentage contents（atomic ratio of Ce to Ce ＋ Ca is 5%,10%and 20%,respectively） were synthesized via a simple wet chemical method in this study.The crystal structure,chemical groups,thermal stability,crystal morphologies and crystal sizes of the Ce-HA nano-particles were characterized by X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR）,and transmission electron microscopy（TEM）.The influences of reaction temperature,reaction time,pH value,and the atomic ratio of Ce to Ce ＋ Ca on the structure and performance of Ce-HA particles were studied.The results show that the lattice constants,particle sizes,crystallinity and thermal stability of Ce-HA vary with the doped Ce contents.With the increase of Ce content,the lattice constants of the Ce-HA nano-particles remarkably increase but the particle size,crystallinity and thermal stability gradually decrease.The reaction temperature as well as the reaction time has no significant effect on the properties of the final products,while the pH value has a direct relationship with their final chemical composition.The obtained Ce-HA nanosize particles possess potential application in preparing artificial bone implants,bone tissue engineering scaffold and other bioactive coatings.展开更多
Nano-scale Tb-incorporated apatite （nano-Tb-AP） particles with different Tb contents （Tb/（Tb＋Ca）） of 0%, 5%, 10% and 20% were synthesized through a simple wet chemical method in this study. The crystal structur...Nano-scale Tb-incorporated apatite （nano-Tb-AP） particles with different Tb contents （Tb/（Tb＋Ca）） of 0%, 5%, 10% and 20% were synthesized through a simple wet chemical method in this study. The crystal structure, thermal stabilities, chemical groups, crystal morphologies and crystal sizes of the nano--Tb-AP particles were characterized by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, and transmission electron microscopy （TEM）, respectively. It was found that lattice constants, particle sizes, crystalline and thermal stability varied with the doped Tb contents. With the increasing of Tb content, the lattice constants, particle size, length/diameter ratio, crystalline and thermal stability of nano-Tb-AP gradually decrease. Especially, almost all the 20%Tb-AP nano particles had been decomposed at 1200 ℃ while only a few of the decomposed products （β-TCP） were detected in the Tb-free nano apatite powders： This kind of nano-scale Tb-incorporated apatite exhibits an extremely potential clinic application because it integrates both the excellent biological functions of Tb element and apatite in human body.展开更多
The mechanical properties of nano-scale Cu/FeS composite were simulated by molecular dynamics （MD） simulation in this paper. Through the analysis on the stress-strain curves, the results of MD simulation were in goo...The mechanical properties of nano-scale Cu/FeS composite were simulated by molecular dynamics （MD） simulation in this paper. Through the analysis on the stress-strain curves, the results of MD simulation were in good agreement with mechanisms of macroscopic deformation. When the size of particles was smaller than a certain value, the relationship between yield strength and size, which was different from the large size crystals abided by the contrary Hall-Petch relationship. Based on the discussion of nano-scale Cu/FeS composite, some interesting conclusions were obtained. For example, the ＂S＂ type curves were discovered in stress-strain curves and the anisotropy of FeS was very evident when the exposures of reinforcing phase （FeS） were different and so on. The basic theories and calculations of the composite that contains nano-scale particles were discussed. At the same time, a new modeling building method of composites, which was close to actual experiences, were considered in this paper.展开更多
Precipitation strengthening of nano-scale TiC is a promising method to improve mechanical properties of Fe–16Mn–9Al–0.8C(wt.%)low-density steel.This work attempted to introduce nano-scale TiC precipitates by adding...Precipitation strengthening of nano-scale TiC is a promising method to improve mechanical properties of Fe–16Mn–9Al–0.8C(wt.%)low-density steel.This work attempted to introduce nano-scale TiC precipitates by adding 1 wt.%Ti element.The experimental results show that these precipitates with the total fraction of about 2 vol.%were formed and no coarse precipitates were observed despite the high Ti addition.It was interesting that the polygonal and needle-shaped TiC precipitates were observed inγ-austenite andδ-ferrite,respectively.Ti addition also decreased the volume fraction ofγ-austenite significantly.Correspondingly,the yield strength was increased,but the elongation was significantly decreased due to the significant decrease ofγ-austenite.Comparing with the Ti-free steel,the formation of TiC precipitates was the main reason for the increase in yield strength of Ti-bearing steel,and TiC precipitates also led to a higher strain hardening index at the first deformation stage.TiC precipitates promoted the Orowan strengthening,resulting in a higher strain hardening capability than Ti-free steel reinforced by shearableκ-carbide.展开更多
To improve the comprehensive mechanical properties of Al-Si-Cu alloy,it was treated by a high-pressure torsion process,and the effect of the deformation degree on the microstructure and properties of the Al-Si-Cu allo...To improve the comprehensive mechanical properties of Al-Si-Cu alloy,it was treated by a high-pressure torsion process,and the effect of the deformation degree on the microstructure and properties of the Al-Si-Cu alloy was studied.The results show that the reinforcements(β-Si andθ-CuAl_(2)phases)of the Al-Si-Cu alloy are dispersed in theα-Al matrix phase with finer phase size after the treatment.The processed samples exhibit grain sizes in the submicron or even nanometer range,which effectively improves the mechanical properties of the material.The hardness and strength of the deformed alloy are both significantly raised to 268 HV and 390.04 MPa by 10 turns HPT process,and the fracture morphology shows that the material gradually transits from brittle to plastic before and after deformation.The elements interdiffusion at the interface between the phases has also been effectively enhanced.In addition,it is found that the severe plastic deformation at room temperature induces a ternary eutectic reaction,resulting in the formation of ternary Al+Si+CuAl_(2)eutectic.展开更多
By conducting experimental analyses, including thermal pyrolysis, micro-/nano-CT, argon-ion polishing field emission scanning electron microscopy (FE-SEM), confocal laser scanning microscopy (CLSM), and two-dimensiona...By conducting experimental analyses, including thermal pyrolysis, micro-/nano-CT, argon-ion polishing field emission scanning electron microscopy (FE-SEM), confocal laser scanning microscopy (CLSM), and two-dimensional nuclear magnetic resonance (2D NMR), the Gulong shale oil in the Songliao Basin was investigated with respect to formation model, pore structure and accumulation mechanism. First, in the Gulong shale, there are a large number of pico-algae, nano-algae and dinoflagellates, which were formed in brackish water environment and constituted the hydrogen-rich oil source materials of shale. Second, most of the oil-generating materials of the Qingshankou Formation shale exist in the form of organo-clay complex. During organic matter thermal evolution, clay minerals had double effects of suppression and catalytic hydrogenation, which expanded shale oil window and increased light hydrocarbon yield. Third, the formation of storage space in the Gulong Shale was related to dissolution and hydrocarbon generation. With the diagenesis, micro-/nano-pores increased, pore diameter decreased and more bedding fractures appeared, which jointly gave rise to the unique reservoir with dual media (i.e. nano-scale pores and micro-scale bedding fractures) in the Gulong shale. Fourth, the micro-/nano-scale oil storage unit in the Gulong shale exhibits independent oil/gas occurrence phase, and shows that all-size pores contain oils, which occur in condensate state in micropores or in oil-gas two phase (or liquid) state in macropores/mesopores. The understanding about Gulong shale oil formation and accumulation mechanism has theoretical and practical significance for advancing continental shale oil exploration in China.展开更多
Nanohairs, which can be found on the epidermis of Tokay gecko＇s toes, contribute to the adhesion by means of van der Waals force, capillary force, etc. This structure has inspired many researchers to fabricate the at...Nanohairs, which can be found on the epidermis of Tokay gecko＇s toes, contribute to the adhesion by means of van der Waals force, capillary force, etc. This structure has inspired many researchers to fabricate the attachable nano-scale structures. However, the efficiency of artificial nano-scale structures is not reliable sufficiently. Moreover, the mechanical parameters related to the nano-hair attachment are not yet revealed qualitatively. The mechanical parameters which have influence on the ability of adhesive nano-hairs were investigated through numerical simulation in which only van der Waals force was considered. For the numerical analysis, finite element method was utilized and van der Waals force, assumed as 12-6 Lennard-Jones potential, was implemented as the body force term in the finite element formulation.展开更多
基于系统级封装(System in a Package, SiP)技术的SRAM型FPGA微系统广泛应用于航天领域。由于微系统复杂的封装结构,限制了大多数传统失效分析设备与分析方式的应用。针对微系统器件的故障诊断困难、测试流程复杂等可靠性问题,开展了常...基于系统级封装(System in a Package, SiP)技术的SRAM型FPGA微系统广泛应用于航天领域。由于微系统复杂的封装结构,限制了大多数传统失效分析设备与分析方式的应用。针对微系统器件的故障诊断困难、测试流程复杂等可靠性问题,开展了常见故障分析研究。对SRAM配置固有缺陷和FPGA内部配置刷新电路异常等典型故障的产生机理进行了深入分析和总结。结合理论分析和问题现象,提出了配置位回读校验测试及比对、辅助电源VCC, AUX电流参数一致性控制等测试筛选方法,有效提升了测试覆盖性。利用相应测试手段和数据分析方法,可精准定位失效机理与失效部位,对后续宇航用SRAM型FPGA微系统应用及筛选有重要意义。展开更多
The aim of this article was to provide a systematic method to perform molecular dynamics simulotion or evaluation for nano-scale interfacial friction behavior between two kinds of materials in MEMS design. Friction is...The aim of this article was to provide a systematic method to perform molecular dynamics simulotion or evaluation for nano-scale interfacial friction behavior between two kinds of materials in MEMS design. Friction is an important factor affecting the performance and reliability of MEMS. The model of the nano-scale interracial friction behavior between two kinds of materials was presented based on the Newton＇ s equations of motion. The Morse potential function was selected for the model. The improved Verlet algorithm was employed to resolve the model, the atom trajectories and the law of the interfacial friction behavior. Comparisons with experimental data in other paper confirm the validity of the model. Using the model it is possible to simulate or evaluate the importance of different factors for designing of the nano-scale interfacial friction behavior between two kinds of materials in MEMS.展开更多
With the device size gradually approaching the physical limit, the small changes of the Si(001)/SiO 2 interface in silicon-based devices may have a great impact on the device characteristics. Based on this, the bridge...With the device size gradually approaching the physical limit, the small changes of the Si(001)/SiO 2 interface in silicon-based devices may have a great impact on the device characteristics. Based on this, the bridge-oxygen model is used to construct the interface of different sizes, and the finite size effect of the interface between fine electronic structure silicon and silicon dioxide is studied. Then, the influence of the finite size effect on the electrical properties of nanotransistors is calculated by using the first principle. Theoretical calculation results demonstrate that the bond length of Si-Si and Si-O shows a saturate tendency when the size increases, while the absorption capacity of visible light and the barrier of the interface increase with the decrease of size. Finally, the results of two tunneling current models show that the finite size effect of Si(001)/SiO 2 interface can lead to a larger change in the gate leakage current of nano-scale devices, and the transition region and image potential, which play an important role in the calculation of interface characteristics of large-scale devices, show different sensitivities to the finite size effect. Therefore, the finite size effect of the interface on the gate leakage current cannot be ignored in nano-scale devices.展开更多
This paper presents the development of a coarse-fine dual precision positioning stage to achieve long travel range and high accuracy.The fine stage is arranged in series with a coarse stage.The key in the fine stage d...This paper presents the development of a coarse-fine dual precision positioning stage to achieve long travel range and high accuracy.The fine stage is arranged in series with a coarse stage.The key in the fine stage design is the choice of a toggle mechanism for a tight mechanical loop with high stiffness and compactness.We designed the toggle mechanism for reduction of the displacement to suppress signal noises.The performance of the coarse and fine stages was verified with an optical encoder and capacitive sensor,respectively.The measurement results show that the dual mechanism has a travel range of 1 mm and resolution of 30 nm.展开更多
Nanomaterials fabricated via soft lithography has provided many useful tools for biology. The most commonly used material in soft lithography is poly(dimethylsiloxane) (PDMS).
文摘Solids in nano-scales hold the promise to exhibit extreme strength and elasticity due to the absence of interior defects and the designability of micro-arrangements.A nano-scaled bulk sample can be produced by diamond,ice,metallic twins,high entropy alloy(HEA),or cubic boron nitride(cBN).A loading stage capable of 4-DoF movements was designed and built to achieve multi-axial mechanical loading inside a transmission electronic microscope chamber with sub-nanometer loading precision.For single crystal diamond in the shape of nano-needles,we were able to achieve an extreme bending strength of 125 GPa at the tensile side,approaching the theoretical strength of diamond.For ice fibers of sub-micron radius,an extreme elastic strain of 10.9%was acquired,far exceeding the previous record of 0.3%for the elastic strain achievable by ice.For metallic twin specimens made by nano-welding,a shear strain as large as 364%was recorded parallel to the twin boundary.Cyclic shear loading aligned with the twin boundary would drive an up-and-down sweeping movement of the low-angle grain boundary,as composed by an array of dislocations.The sweep of the grain boundary effectively cleanses the lattice defects and creates a feasible scenario of unlimited cyclic endurance.For a HEA dog-bone specimen in nano-scale,an extreme elastic strain of about 10%was achieved.At this level of mechanical straining,stretch-induced melting for crystalline metals,as envisaged by Lindemann a century ago,was realized.For cBN crystals,a fracture path inclined to the stacking hexagon planes would result in a new failure mechanism of layered decohesion,triggered by the extremely large elastic strain(>7%)along the edge of the submicron-scaled specimen.These results indicate ample room for upgrading the mechanical behaviour of solids in nano-scales.
文摘[Objective] The aim was to observe the antibacterial effect of nano-scale Titanium dioxide on parasitic bacterium of Nanfeng Citrus in storage period.[Method] Nano-scale Titanium dioxide was prepared by dibutyl phthalate through sol-gel method under anhydrous conditions,and orthogonal experiment was used to determine optimum conditions for nano-scale Titanium dioxide preparation,and structure characterization of nano-scale Titanium dioxide was carried out by X-Ray diffractometer.Oxford cup method was used to explore inhibition effect of nano-scale Titanium dioxide suspension on the activity of normal parasitic bacterium of Nanfeng Citrus.Simultaneously,the empirical preservation test was carried out.[Result] The average diameter of nano-scale Titanium dioxide powder attained to 14.6 nm,actual average yield could reach 90.83% with RSD（Relative Standard Deviation）of 0.86%.[Conclusion] Nano-scale Titanium dioxide had good antibacterial effect on the parasitic bacterium of Nanfeng Citrus in storage period.
基金supported in part by the Institute for Guo Qiang of Tsinghua University(2019GQG1023)in part by Graduate Education and Teaching Reform Project of Tsinghua University(202007J007)+1 种基金in part by National Natural Science Foundation of China(U19B2029,62073028,61803222)in part by the Independent Research Program of Tsinghua University(2018Z05JDX002)。
文摘There are two main trends in the development of unmanned aerial vehicle(UAV)technologies:miniaturization and intellectualization,in which realizing object tracking capabilities for a nano-scale UAV is one of the most challenging problems.In this paper,we present a visual object tracking and servoing control system utilizing a tailor-made 38 g nano-scale quadrotor.A lightweight visual module is integrated to enable object tracking capabilities,and a micro positioning deck is mounted to provide accurate pose estimation.In order to be robust against object appearance variations,a novel object tracking algorithm,denoted by RMCTer,is proposed,which integrates a powerful short-term tracking module and an efficient long-term processing module.In particular,the long-term processing module can provide additional object information and modify the short-term tracking model in a timely manner.Furthermore,a positionbased visual servoing control method is proposed for the quadrotor,where an adaptive tracking controller is designed by leveraging backstepping and adaptive techniques.Stable and accurate object tracking is achieved even under disturbances.Experimental results are presented to demonstrate the high accuracy and stability of the whole tracking system.
基金the National Natural Science Foundation of China (Grants Nos. 50971122, 50431010,50621091 and 50890171)the Ministry of Science and Technology of China (2005CB623604) are acknowledged
文摘By means of dynamic plastic deformation （DPD） followed by thermal annealing, a mixed structure of micro-sized austenite grains embedded with nano-scale twin bundles （of about 20% in volume） has been synthesized in a 316L stainless steel （SS）. Such a 316L SS sample exhibits a tensile strength as high as 1001 MPa and an elongation-to-failure of about 23%. The much elevated strength originates from the presence of a considerable number of strengthening nano-twin bundles, while the ductility from the recrystallized grains. The superior strength-ductility combination achieved in the nano-twins-strengthened austenite steel demonstrates a novel approach for optimizing the mechanical properties in engineering materials.
基金supported by the National Natural Science Foundation of China(Nos.51072159 and 51273159)the Fundamental Research Funds for the Central University and Program for New Century Excellent Talents in Universities(Chinese Ministry of Education,NCET-08-0444(2301G107aaa))
文摘Ce-incorporated apatite（Ce-HA） nano-scale particles with different Ce percentage contents（atomic ratio of Ce to Ce ＋ Ca is 5%,10%and 20%,respectively） were synthesized via a simple wet chemical method in this study.The crystal structure,chemical groups,thermal stability,crystal morphologies and crystal sizes of the Ce-HA nano-particles were characterized by X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR）,and transmission electron microscopy（TEM）.The influences of reaction temperature,reaction time,pH value,and the atomic ratio of Ce to Ce ＋ Ca on the structure and performance of Ce-HA particles were studied.The results show that the lattice constants,particle sizes,crystallinity and thermal stability of Ce-HA vary with the doped Ce contents.With the increase of Ce content,the lattice constants of the Ce-HA nano-particles remarkably increase but the particle size,crystallinity and thermal stability gradually decrease.The reaction temperature as well as the reaction time has no significant effect on the properties of the final products,while the pH value has a direct relationship with their final chemical composition.The obtained Ce-HA nanosize particles possess potential application in preparing artificial bone implants,bone tissue engineering scaffold and other bioactive coatings.
基金supported by the Fundamental Research Funds for the Central Universitythe National Natural Science Foundation of China (No. 51072159+1 种基金51273159)Program for New Century Excellent Talents in Universities (Chinese Ministry of Education,NCET-08-0444)
文摘Nano-scale Tb-incorporated apatite （nano-Tb-AP） particles with different Tb contents （Tb/（Tb＋Ca）） of 0%, 5%, 10% and 20% were synthesized through a simple wet chemical method in this study. The crystal structure, thermal stabilities, chemical groups, crystal morphologies and crystal sizes of the nano--Tb-AP particles were characterized by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, and transmission electron microscopy （TEM）, respectively. It was found that lattice constants, particle sizes, crystalline and thermal stability varied with the doped Tb contents. With the increasing of Tb content, the lattice constants, particle size, length/diameter ratio, crystalline and thermal stability of nano-Tb-AP gradually decrease. Especially, almost all the 20%Tb-AP nano particles had been decomposed at 1200 ℃ while only a few of the decomposed products （β-TCP） were detected in the Tb-free nano apatite powders： This kind of nano-scale Tb-incorporated apatite exhibits an extremely potential clinic application because it integrates both the excellent biological functions of Tb element and apatite in human body.
基金supported by the National Basic Research Program of China (973 Program) under Grant No. 2008CB617609the National Key Project of Scientific and Technical Supporting Programs Funded by Ministry of Science & Technology of China under Grant No.2007BAE23B02
文摘The mechanical properties of nano-scale Cu/FeS composite were simulated by molecular dynamics （MD） simulation in this paper. Through the analysis on the stress-strain curves, the results of MD simulation were in good agreement with mechanisms of macroscopic deformation. When the size of particles was smaller than a certain value, the relationship between yield strength and size, which was different from the large size crystals abided by the contrary Hall-Petch relationship. Based on the discussion of nano-scale Cu/FeS composite, some interesting conclusions were obtained. For example, the ＂S＂ type curves were discovered in stress-strain curves and the anisotropy of FeS was very evident when the exposures of reinforcing phase （FeS） were different and so on. The basic theories and calculations of the composite that contains nano-scale particles were discussed. At the same time, a new modeling building method of composites, which was close to actual experiences, were considered in this paper.
基金the National Natural Science Foundation of China(No.51974184)National MCF Energy R&D Program of China(No.2018YFE0306102)Independent Research Project of State Key Laboratory of Advanced Special Steel and Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University.
文摘Precipitation strengthening of nano-scale TiC is a promising method to improve mechanical properties of Fe–16Mn–9Al–0.8C(wt.%)low-density steel.This work attempted to introduce nano-scale TiC precipitates by adding 1 wt.%Ti element.The experimental results show that these precipitates with the total fraction of about 2 vol.%were formed and no coarse precipitates were observed despite the high Ti addition.It was interesting that the polygonal and needle-shaped TiC precipitates were observed inγ-austenite andδ-ferrite,respectively.Ti addition also decreased the volume fraction ofγ-austenite significantly.Correspondingly,the yield strength was increased,but the elongation was significantly decreased due to the significant decrease ofγ-austenite.Comparing with the Ti-free steel,the formation of TiC precipitates was the main reason for the increase in yield strength of Ti-bearing steel,and TiC precipitates also led to a higher strain hardening index at the first deformation stage.TiC precipitates promoted the Orowan strengthening,resulting in a higher strain hardening capability than Ti-free steel reinforced by shearableκ-carbide.
基金Funded by the National Natural Science Foundation of China(No.51905215)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.SJCX23_1233)+1 种基金Major Scientific and Technological Innovation Project of Shandong Province of China(No.2019JZZY020111)the National College Students Innovation and Entrepreneurship Training Program of China(No.CX2022415)。
文摘To improve the comprehensive mechanical properties of Al-Si-Cu alloy,it was treated by a high-pressure torsion process,and the effect of the deformation degree on the microstructure and properties of the Al-Si-Cu alloy was studied.The results show that the reinforcements(β-Si andθ-CuAl_(2)phases)of the Al-Si-Cu alloy are dispersed in theα-Al matrix phase with finer phase size after the treatment.The processed samples exhibit grain sizes in the submicron or even nanometer range,which effectively improves the mechanical properties of the material.The hardness and strength of the deformed alloy are both significantly raised to 268 HV and 390.04 MPa by 10 turns HPT process,and the fracture morphology shows that the material gradually transits from brittle to plastic before and after deformation.The elements interdiffusion at the interface between the phases has also been effectively enhanced.In addition,it is found that the severe plastic deformation at room temperature induces a ternary eutectic reaction,resulting in the formation of ternary Al+Si+CuAl_(2)eutectic.
基金Supported by the Central Guiding Local Science and Technology Development Special Project(ZY20B13)。
文摘By conducting experimental analyses, including thermal pyrolysis, micro-/nano-CT, argon-ion polishing field emission scanning electron microscopy (FE-SEM), confocal laser scanning microscopy (CLSM), and two-dimensional nuclear magnetic resonance (2D NMR), the Gulong shale oil in the Songliao Basin was investigated with respect to formation model, pore structure and accumulation mechanism. First, in the Gulong shale, there are a large number of pico-algae, nano-algae and dinoflagellates, which were formed in brackish water environment and constituted the hydrogen-rich oil source materials of shale. Second, most of the oil-generating materials of the Qingshankou Formation shale exist in the form of organo-clay complex. During organic matter thermal evolution, clay minerals had double effects of suppression and catalytic hydrogenation, which expanded shale oil window and increased light hydrocarbon yield. Third, the formation of storage space in the Gulong Shale was related to dissolution and hydrocarbon generation. With the diagenesis, micro-/nano-pores increased, pore diameter decreased and more bedding fractures appeared, which jointly gave rise to the unique reservoir with dual media (i.e. nano-scale pores and micro-scale bedding fractures) in the Gulong shale. Fourth, the micro-/nano-scale oil storage unit in the Gulong shale exhibits independent oil/gas occurrence phase, and shows that all-size pores contain oils, which occur in condensate state in micropores or in oil-gas two phase (or liquid) state in macropores/mesopores. The understanding about Gulong shale oil formation and accumulation mechanism has theoretical and practical significance for advancing continental shale oil exploration in China.
文摘Nanohairs, which can be found on the epidermis of Tokay gecko＇s toes, contribute to the adhesion by means of van der Waals force, capillary force, etc. This structure has inspired many researchers to fabricate the attachable nano-scale structures. However, the efficiency of artificial nano-scale structures is not reliable sufficiently. Moreover, the mechanical parameters related to the nano-hair attachment are not yet revealed qualitatively. The mechanical parameters which have influence on the ability of adhesive nano-hairs were investigated through numerical simulation in which only van der Waals force was considered. For the numerical analysis, finite element method was utilized and van der Waals force, assumed as 12-6 Lennard-Jones potential, was implemented as the body force term in the finite element formulation.
文摘基于系统级封装(System in a Package, SiP)技术的SRAM型FPGA微系统广泛应用于航天领域。由于微系统复杂的封装结构,限制了大多数传统失效分析设备与分析方式的应用。针对微系统器件的故障诊断困难、测试流程复杂等可靠性问题,开展了常见故障分析研究。对SRAM配置固有缺陷和FPGA内部配置刷新电路异常等典型故障的产生机理进行了深入分析和总结。结合理论分析和问题现象,提出了配置位回读校验测试及比对、辅助电源VCC, AUX电流参数一致性控制等测试筛选方法,有效提升了测试覆盖性。利用相应测试手段和数据分析方法,可精准定位失效机理与失效部位,对后续宇航用SRAM型FPGA微系统应用及筛选有重要意义。
基金Funded by Natural Science Foundation of Guangxi Province ofChina (No.0339037) ,the Support Programfor Young and Middle-aged Disciplinary Leaders in Guangxi Higher Education Institution,the Science Foundationfor Qualified Personnel of Jiangsu University(04JDG027) ,andthe Innovative Science Foundation of Jiangsu Uni-versity
文摘The aim of this article was to provide a systematic method to perform molecular dynamics simulotion or evaluation for nano-scale interfacial friction behavior between two kinds of materials in MEMS design. Friction is an important factor affecting the performance and reliability of MEMS. The model of the nano-scale interracial friction behavior between two kinds of materials was presented based on the Newton＇ s equations of motion. The Morse potential function was selected for the model. The improved Verlet algorithm was employed to resolve the model, the atom trajectories and the law of the interfacial friction behavior. Comparisons with experimental data in other paper confirm the validity of the model. Using the model it is possible to simulate or evaluate the importance of different factors for designing of the nano-scale interfacial friction behavior between two kinds of materials in MEMS.
基金The National Natural Science Foundation of China(No.61774014)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYZZ15_0331)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.19KJB510060)
文摘With the device size gradually approaching the physical limit, the small changes of the Si(001)/SiO 2 interface in silicon-based devices may have a great impact on the device characteristics. Based on this, the bridge-oxygen model is used to construct the interface of different sizes, and the finite size effect of the interface between fine electronic structure silicon and silicon dioxide is studied. Then, the influence of the finite size effect on the electrical properties of nanotransistors is calculated by using the first principle. Theoretical calculation results demonstrate that the bond length of Si-Si and Si-O shows a saturate tendency when the size increases, while the absorption capacity of visible light and the barrier of the interface increase with the decrease of size. Finally, the results of two tunneling current models show that the finite size effect of Si(001)/SiO 2 interface can lead to a larger change in the gate leakage current of nano-scale devices, and the transition region and image potential, which play an important role in the calculation of interface characteristics of large-scale devices, show different sensitivities to the finite size effect. Therefore, the finite size effect of the interface on the gate leakage current cannot be ignored in nano-scale devices.
基金supported by the National Science Council (No.NSC-96-2628-E002-199)
文摘This paper presents the development of a coarse-fine dual precision positioning stage to achieve long travel range and high accuracy.The fine stage is arranged in series with a coarse stage.The key in the fine stage design is the choice of a toggle mechanism for a tight mechanical loop with high stiffness and compactness.We designed the toggle mechanism for reduction of the displacement to suppress signal noises.The performance of the coarse and fine stages was verified with an optical encoder and capacitive sensor,respectively.The measurement results show that the dual mechanism has a travel range of 1 mm and resolution of 30 nm.
文摘Nanomaterials fabricated via soft lithography has provided many useful tools for biology. The most commonly used material in soft lithography is poly(dimethylsiloxane) (PDMS).
