Surface enhanced Raman spectroscopy(SERS) and confocal Raman microscopy are applied to investigate the structure and the molecular arrangement of sub-micron furosemide and polyvinylpyrrolidone(furosemide/PVP) particle...Surface enhanced Raman spectroscopy(SERS) and confocal Raman microscopy are applied to investigate the structure and the molecular arrangement of sub-micron furosemide and polyvinylpyrrolidone(furosemide/PVP) particles produced by spray flash evaporation(SFE). Morphology, size and crystallinity of furosemide/PVP particles are analyzed by scanning electron microscopy(SEM) and X-ray powder diffraction(XRPD). Far-field Raman spectra and confocal far-field Raman maps of furosemide/PVP particles are interpreted based on the far-field Raman spectra of pure furosemide and PVP precursors.Confocal far-field Raman microscopy shows that furosemide/PVP particles feature an intermixture of furosemide and PVP molecules at the sub-micron scale. SERS and surface-enhanced confocal Raman microscopy(SECo RM) are performed on furosemide, PVP and furosemide/PVP composite particles sputtered with silver(40 nm). SERS and SECo RM maps reveal that furosemide/PVP particle surfaces mainly consist of PVP molecules. The combination of surface and bulk sensitive analyses reveal that furosemide/PVP sub-micron particles are formed by the agglomeration of primary furosemide nanocrystals embedded in a thin PVP matrix. Interestingly, both far-field Raman microscopy and SECo RM provide molecular information on a statistically-relevant amount of sub-micron particles in a single microscopic map;this combination is thus an effective and time-saving tool for investigating organic sub-micron composites.展开更多
The microstructure of laser welds of sub-micron particulate-reinforced aluminum matrix composite Al_2O_(3p)/6061Al and the weldability of the material were studied. Experimental results indicated that because of the h...The microstructure of laser welds of sub-micron particulate-reinforced aluminum matrix composite Al_2O_(3p)/6061Al and the weldability of the material were studied. Experimental results indicated that because of the huge specific surface area of the reinforcement, the interfacial reaction between the matrix and the reinforcement was re- strained intenslvely at elevated temperature and pulsed laser beam. The main factor affecting the weldability of the com- posite was the reinforcement segregation in the weld resulting from the push of the liquid/solid interface during the soli- dification of the molten pool. The laser pulse frequency directly affected the reinforcement segregation and the reinfor- cement distribution in the weld, so that the weldability of the composite could be improved by increasing the laser pulse frequency. On the basis of this, a satisfactory welded joint of sub-micron paniculate-reinforced aluminum matrix com- posite Al_2O_(3p)/6061Al was obtained by using appopriate welding parameters.展开更多
The influence of different sintering processes, including vacuum sintering, vacuum sintering followed by HIP and sintering-HIP, on the microstructure and properties of sub-micron Ti(C,N) cermets with various binder co...The influence of different sintering processes, including vacuum sintering, vacuum sintering followed by HIP and sintering-HIP, on the microstructure and properties of sub-micron Ti(C,N) cermets with various binder contents was studied. Image analysis based on back-scattered electrons image observations was used to determine the morphologic and structural characteristics. Transverse rupture strength(TRS), hardness, fracture toughness were measured and TRS data were treated by Weibull statistics further. It is shown that a very significant improvement in TRS can be obtained by HIP or sintering-HIP treatment for the alloys with lower and middle binder content at the controlled cooling rate, but the effect is not obvious for the alloys with higher binder content. HIP is also helpful for improving the hardness of sub-micron Ti(C,N) cermets, however, but can lower the fracture toughness. The variation of these properties was interpreted in terms of the difference in morphologic and structural characteristics.展开更多
Dye-sensitized solar cells （DSSCs） are one of the most promising next-generation solar cells due to their advantages over other counterparts. The photoanode of DSSCs has a great effect on the photovoltaic per- forma...Dye-sensitized solar cells （DSSCs） are one of the most promising next-generation solar cells due to their advantages over other counterparts. The photoanode of DSSCs has a great effect on the photovoltaic per- formance. Traditional photoanode includes a bottom nanoparticle layer and an upper scattering layer for better light capture in longer wavelength. Mesoporous nanostructures with size comparable to the wavelength of visible light are considered to be excellent light scattering centers by providing extra places for dye loading. Developing a green synthetic method is of great importance. Herein we report a facile and surfactant-free synthesis of mesoporous futile TiO2 submicrometer-sized spheres at temperature as low as 70 ℃. DSSCs based on photoanodes with an upper scattering layer composed of as-obtained mesoporous spheres on nanoparticle dense layer demonstrate an 18.0% improvement of power conver- sion efficiency. This simple approach may offer an energy-efficient and environmentally friendly alternative for DSSCs fabrication.展开更多
Scale-up synthesis of sub-micron ZSM-5 molecular sieve in a quasi-solid system was investigated. Compared with traditional hydrothermal synthesis, the synthesis in a quasi-solid system has the advantages of high yield...Scale-up synthesis of sub-micron ZSM-5 molecular sieve in a quasi-solid system was investigated. Compared with traditional hydrothermal synthesis, the synthesis in a quasi-solid system has the advantages of high yield, short crystallization time, low energy consumption as well as low emissions. However, the high solid content in the quasi-solid system can cause the mass and heat transfer problems and make scalable production difficult. In order to solve the problem, we have developed a method for the optimization of the mass and heat transfer. By this method one can vary the flow field in the reactor by changing the stirrer speed. Scale-up synthesis of the sub-micron ZSM-5 molecular sieve in a quasi-solid system was carried out in a 5 L reactor with double propeller-type agitators. The process was investigated with product characterization using X-ray diffraction （XRD） and scanning electron microscopy （SEM） and the flow field information was collected using laser Doppler velocimetry （LDV）. The results showed that the flow field patterns can be tuned by using different stirrer speeds, the morphology and size of assynthesized of ZSM-5 can be effectively controlled.展开更多
Ultralong titanyl phthalocyanine （TiOPc） sub-micron wires have been synthesized by a novel solution-based self- assembly method. By using different solvents, changing the mass concentration and the solvent vapor pre...Ultralong titanyl phthalocyanine （TiOPc） sub-micron wires have been synthesized by a novel solution-based self- assembly method. By using different solvents, changing the mass concentration and the solvent vapor pressure, the length and the shape of the wires can be adjusted. The mixed-phase properties of the TiOPc sub-micron wires were investigated by the ultraviolet-visible （UV-vis） absorption spectrum and X-ray diffraction. Organic transistors based on these wires were studied, which show the typical p-channel characteristics.展开更多
Pattem imprinting in deep sub-micron static random access memories （SRAMs） during total dose irradiation is inves- tigated in detail. As the dose accumulates, the data pattern of memory cells loading during irradiat...Pattem imprinting in deep sub-micron static random access memories （SRAMs） during total dose irradiation is inves- tigated in detail. As the dose accumulates, the data pattern of memory cells loading during irradiation is gradually imprinted on their background data pattern. We build a relationship between the memory cell＇s static noise margin （SNM） and the background data, and study the influence of irradiation on the probability density function of ASNM, which is the difference between two data sides＇ SNMs, to discuss the reason for pattern imprinting. Finally, we demonstrate that, for micron and deep sub-micron devices, the mechanism of pattern imprinting is the bias-dependent threshold shift of the transistor, but for a deep sub-micron device the shift results from charge trapping in the shallow trench isolation （STI） oxide rather than from the gate oxide of the micron-device.展开更多
Grooved gate structure Metal-Oxide-Semiconductor (MOS) device is consideredas the most promising candidate used in deep and super-deep sub-micron region, for it cansuppress hot carrier effect and short channel effect ...Grooved gate structure Metal-Oxide-Semiconductor (MOS) device is consideredas the most promising candidate used in deep and super-deep sub-micron region, for it cansuppress hot carrier effect and short channel effect deeply. Based on the hydrodynamic energytransport model, using two-dimensional device simulator Medici, the relation between structureparameters and hot carrier effect immunity for deep-sub-micron N-channel MOSFET's is studiedand compared with that of counterpart conventional planar device in this paper. The examinedstructure parameters include negative junction depth, concave corner and effective channel length.Simulation results show that grooved gate device can suppress hot carrier effect deeply even indeep sub-micron region. The studies also indicate that hot carrier effect is strongly influencedby the concave corner and channel length for grooved gate device. With the increase of concavecorner, the hot carrier effect in grooved gate MOSFET decreases sharply, and with the reducingof effective channel length, the hot carrier effect becomes large.展开更多
Sub-micron-structure machining on silicon substrate was studied by direct writing system of femtosecond laser with the central wavelength of 800 nm, pulse duration of 120 fs and repetition rate of 1 kHz. Three kinds o...Sub-micron-structure machining on silicon substrate was studied by direct writing system of femtosecond laser with the central wavelength of 800 nm, pulse duration of 120 fs and repetition rate of 1 kHz. Three kinds of experiments were conducted: 1) the effect of photoresist on silicon; 2) machinability of different orientations of silicon; and 3) the size of micro-structure and the cross-section shape. Photoresist SU8 was coated onto silicon substrates in thicknesses of 100 μm. SU8 remained on the silicon substrate while the silicon under the machined SU8 was removed after laser machining. Orientations of (100), (110), and (111) silicon substrates were machined with the laser power of 60 μW and the scanning speed of 3 mm/min. Spike morphologies were observed on all three orientations of silicon substrates without obvious directional difference of these spikes on different silicon substrates. In addition, the ablation threshold energies were also similar. In the consideration of ablation energy, one numerical model of the machining parameters has been proposed to simulate the cross-section of the micro-structure. The predicted shape by simulation can fit the profile of the cross-section shape well.展开更多
The analysis of gunshot residue(GSR) has played an integral role within the legal system in relation to shooting cases. With a characteristic elemental composition of lead, antimony, barium, and a typically discrimina...The analysis of gunshot residue(GSR) has played an integral role within the legal system in relation to shooting cases. With a characteristic elemental composition of lead, antimony, barium, and a typically discriminative spheroidal morphology, the presence and distribution of GSR can aid in firearm investigations. In this experiment, three shots of low velocity rim-fire ammunition were fired over polished silicon collection substrates placed at six intervals over a 100 cm range. The samples were analysed using a Field Emission Gun Scanning Electron Microscope(FEG-SEM) in conjunction with an X-flash Energy Dispersive X-ray(EDX) detector, allowing for GSR particle analyses of composition and structure at the sub-micron level. The results of this experiment indicate that although classic spheroidal particles are present consistently throughout the entire range of samples their sizes vary significantly, and at certain distances from the firearm particles with an irregular morphology were discerned, forming "impactdisrupted" GSR particles, henceforth colloquially referred to as "splats". Upon further analysis, trends with regards to the formation of these splat particles were distinguished. An increase in splat frequency was observed starting at 10 cm from the firearm, with 147 mm^(-2) splat density, reaching a maximal flux at 40 cm(451 mm^(-2)), followed by a gradual decrease to the maximum range sampled. Moreover, the structural morphology of the splats changes throughout the sampling range. At the distances closest to the firearm, molten-looking particles were formed, demonstrating the metallic residues were in a liquid state when their flight path was disrupted. However, at increased distances-primarily where the discharge plume was at maximum dispersion and moving away from the firearm, the residues have had time to cool in-fight resulting in semi-congealed and solid particles that subsequently disrupted upon impact, forming more structured as well as disaggregated splats. The relative compositions of the characteristic elements that are present in GSR also change in the different splat morphologies sampled,which may contribute to the particles' physical structures. Two distinct populations of splats were also observed: circular and elongated, which suggest the residues hit the substrate at different angles. The difference in the splat impact angle can be ascribed to the position of the residues within the firearm discharge plume; particles get caught up in the vortex that is created by the discharge gases behind the projectile as it leaves the barrel, thereby affecting their directionality and flight time. This reasoning could also justify the existence of both spheroidal and splat particles at certain distances. The novel sampling and analytical techniques used in this experiment have provided previously unknown information in relation to GSR structure and formation which could have greater implications to its current analysis amongst laboratories and law enforcement agencies worldwide.展开更多
30%Al2O3p/Al-Cu-2.0Mg composite and Al2O3p/Al-Cu-2.5Mg composite with 0.3μm-Al2O3 particles were fabricated. Age-hardening behaviors of two composites and the related matrix alloys were studied by means of Brinell-ha...30%Al2O3p/Al-Cu-2.0Mg composite and Al2O3p/Al-Cu-2.5Mg composite with 0.3μm-Al2O3 particles were fabricated. Age-hardening behaviors of two composites and the related matrix alloys were studied by means of Brinell-hardness measurement, DSC and TEM. The results show that the hardness of the composite is improved obviously because of the addition of sub-micron Al2O3 particles. But the hardness increment of Al2O3p/Al composite after aging is lower than that of the related matrix alloy. Moreover, the formation of GP region is suppressed by the addition of sub-micron Al2O3 particles, which broadens the exothermic peak of S' phase. The increment of Mg content has a different influence on accelerating the aging processes of aluminum alloys and the composites, and the hardness also increases.展开更多
A sub-micron structured film with a poly(3-methylthiophene) (P3MT)-modified CdTe/ZnO shell-core sub-micron tube array has been prepared by a series of electrodeposition processes, and a semiconductor-sensitized solar ...A sub-micron structured film with a poly(3-methylthiophene) (P3MT)-modified CdTe/ZnO shell-core sub-micron tube array has been prepared by a series of electrodeposition processes, and a semiconductor-sensitized solar cell based on this structure was also fabricated. Vertically oriented ZnO sub-micron tubes were obtained on an indium tin oxide (ITO) substrate, and then CdTe nanocrystals and a thin P3MT layer were electrodeposited sequentially onto the walls of the ZnO sub-micron tubes. A suitable thickness of CdTe and P3MT could improve the photovoltaic properties of the solar cell, which was attributed to the enhancement in the light absorption and the decrease in the recombination of photogenerated carriers. In addition, a p–n heterojunction formed between the interface of CdTe and P3MT played an important part in the efficient separation and fast transport of photogenerated carriers in the sub-micron structure. A power conversion efficiency of 1.20% was obtained with this type of solar cell.展开更多
A new sub-micron photolithography tool has been realized by utilizing the interference of surface plasmon waves(SPWs) on the near surface of a silver(Ag)-clad ultraviolet(UV) planar waveguide.A laser beam with a wavel...A new sub-micron photolithography tool has been realized by utilizing the interference of surface plasmon waves(SPWs) on the near surface of a silver(Ag)-clad ultraviolet(UV) planar waveguide.A laser beam with a wavelength of 325 nm was incident into the waveguide core,and suffered a series of total internal reflections on the interfaces between the waveguide core and the cladding layers.The incident light and the reflected light induced two beams of SPWs traveling in contrary directions,which interfered with each other and formed a standing wave as a sub-micron photolithography tool.A near-field scanning optical microscope(NSOM) was employed to measure the intensity distribution of the stationary wave field of the near surface of the Ag layer of the waveguide,anastomosed with theoretical values acquired by use of finite difference time domain(FDTD) simulations.And with this sub-micron photolithography tool a SMG with a period of 79.3 nm,in good agreement with the theoretical value of 80.1 nm,was inscribed on the surface of a self-processing hybrid SiO2/ZrO2 solgel film for the first time.展开更多
Strontium-substituted bioactive glass(Sr-BG)has shown superior performance in bone regeneration.Sr-BG-induced osteogenesis has been extensively studied;however,Sr-BG-mediated osteoclastogenesis and the underlying mole...Strontium-substituted bioactive glass(Sr-BG)has shown superior performance in bone regeneration.Sr-BG-induced osteogenesis has been extensively studied;however,Sr-BG-mediated osteoclastogenesis and the underlying molecular mechanism remain unclear.It is recognized that the balance of osteogenesis and osteoclastogenesis is closely related to bone repair,and the receptor activators of nuclear factor kappaB ligand(RANKL)signaling pathway plays a key role of in the regulation of osteoclastogenesis.Herein,we studied the potential impact and underling mechanism of strontium-substituted sub-micron bioactive glass(Sr-SBG)on RANKL-induced osteoclast activation and differentiation in vitro.As expected,Sr-SBG inhibited RANKL-mediated osteoclastogenesis significantly with the experimental performance of decreased mature osteoclasts formation and downregulation of osteoclastogenesis-related gene expression.Furthermore,it was found that Sr-SBG might suppress osteoclastogenesis by the combined effect of strontium and silicon released through inhibition of RANKL-induced activation of p38 and NF-κB pathway.These results elaborated the effect of Sr-SBG-based materials on osteoclastogenesis through RANKLinduced downstream pathway and might represent a significant guidance for designing better bone repair materials.展开更多
文摘Surface enhanced Raman spectroscopy(SERS) and confocal Raman microscopy are applied to investigate the structure and the molecular arrangement of sub-micron furosemide and polyvinylpyrrolidone(furosemide/PVP) particles produced by spray flash evaporation(SFE). Morphology, size and crystallinity of furosemide/PVP particles are analyzed by scanning electron microscopy(SEM) and X-ray powder diffraction(XRPD). Far-field Raman spectra and confocal far-field Raman maps of furosemide/PVP particles are interpreted based on the far-field Raman spectra of pure furosemide and PVP precursors.Confocal far-field Raman microscopy shows that furosemide/PVP particles feature an intermixture of furosemide and PVP molecules at the sub-micron scale. SERS and surface-enhanced confocal Raman microscopy(SECo RM) are performed on furosemide, PVP and furosemide/PVP composite particles sputtered with silver(40 nm). SERS and SECo RM maps reveal that furosemide/PVP particle surfaces mainly consist of PVP molecules. The combination of surface and bulk sensitive analyses reveal that furosemide/PVP sub-micron particles are formed by the agglomeration of primary furosemide nanocrystals embedded in a thin PVP matrix. Interestingly, both far-field Raman microscopy and SECo RM provide molecular information on a statistically-relevant amount of sub-micron particles in a single microscopic map;this combination is thus an effective and time-saving tool for investigating organic sub-micron composites.
基金This project is financially supported by the National Nature Science Fund (59785016) and the Opening Fund ([2000]002) of the N
文摘The microstructure of laser welds of sub-micron particulate-reinforced aluminum matrix composite Al_2O_(3p)/6061Al and the weldability of the material were studied. Experimental results indicated that because of the huge specific surface area of the reinforcement, the interfacial reaction between the matrix and the reinforcement was re- strained intenslvely at elevated temperature and pulsed laser beam. The main factor affecting the weldability of the com- posite was the reinforcement segregation in the weld resulting from the push of the liquid/solid interface during the soli- dification of the molten pool. The laser pulse frequency directly affected the reinforcement segregation and the reinfor- cement distribution in the weld, so that the weldability of the composite could be improved by increasing the laser pulse frequency. On the basis of this, a satisfactory welded joint of sub-micron paniculate-reinforced aluminum matrix com- posite Al_2O_(3p)/6061Al was obtained by using appopriate welding parameters.
基金Project(50074017)supported by the National Natural Science Foundation of China+2 种基金Project(992P0332)supported by the Key Science and Technology Development Foundation of Hubei Province,ChinaProject supported by the State Key Laboratory of Ad—vanced Technology for Materials Synthesis and Processing,China
文摘The influence of different sintering processes, including vacuum sintering, vacuum sintering followed by HIP and sintering-HIP, on the microstructure and properties of sub-micron Ti(C,N) cermets with various binder contents was studied. Image analysis based on back-scattered electrons image observations was used to determine the morphologic and structural characteristics. Transverse rupture strength(TRS), hardness, fracture toughness were measured and TRS data were treated by Weibull statistics further. It is shown that a very significant improvement in TRS can be obtained by HIP or sintering-HIP treatment for the alloys with lower and middle binder content at the controlled cooling rate, but the effect is not obvious for the alloys with higher binder content. HIP is also helpful for improving the hardness of sub-micron Ti(C,N) cermets, however, but can lower the fracture toughness. The variation of these properties was interpreted in terms of the difference in morphologic and structural characteristics.
基金support from the National Natural Science Foundation(Nos.51422206,51372159,11304217)the 1000 Youth Talents Plan,the National Program on Key Basic Research Project of China (973 Program,No. 2015CB358600)+2 种基金the Jiangsu Shuangchuang Planthe Project Supported by Jiangsu Science and Technology Committee for Distinguished Young Scholars (BK20140009)funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘Dye-sensitized solar cells （DSSCs） are one of the most promising next-generation solar cells due to their advantages over other counterparts. The photoanode of DSSCs has a great effect on the photovoltaic per- formance. Traditional photoanode includes a bottom nanoparticle layer and an upper scattering layer for better light capture in longer wavelength. Mesoporous nanostructures with size comparable to the wavelength of visible light are considered to be excellent light scattering centers by providing extra places for dye loading. Developing a green synthetic method is of great importance. Herein we report a facile and surfactant-free synthesis of mesoporous futile TiO2 submicrometer-sized spheres at temperature as low as 70 ℃. DSSCs based on photoanodes with an upper scattering layer composed of as-obtained mesoporous spheres on nanoparticle dense layer demonstrate an 18.0% improvement of power conver- sion efficiency. This simple approach may offer an energy-efficient and environmentally friendly alternative for DSSCs fabrication.
文摘Scale-up synthesis of sub-micron ZSM-5 molecular sieve in a quasi-solid system was investigated. Compared with traditional hydrothermal synthesis, the synthesis in a quasi-solid system has the advantages of high yield, short crystallization time, low energy consumption as well as low emissions. However, the high solid content in the quasi-solid system can cause the mass and heat transfer problems and make scalable production difficult. In order to solve the problem, we have developed a method for the optimization of the mass and heat transfer. By this method one can vary the flow field in the reactor by changing the stirrer speed. Scale-up synthesis of the sub-micron ZSM-5 molecular sieve in a quasi-solid system was carried out in a 5 L reactor with double propeller-type agitators. The process was investigated with product characterization using X-ray diffraction （XRD） and scanning electron microscopy （SEM） and the flow field information was collected using laser Doppler velocimetry （LDV）. The results showed that the flow field patterns can be tuned by using different stirrer speeds, the morphology and size of assynthesized of ZSM-5 can be effectively controlled.
基金supported by the National Natural Science Foundation of China(Grant No.61176021)the Innovation Group Project from Shanghai EducationCommission,China
文摘Ultralong titanyl phthalocyanine （TiOPc） sub-micron wires have been synthesized by a novel solution-based self- assembly method. By using different solvents, changing the mass concentration and the solvent vapor pressure, the length and the shape of the wires can be adjusted. The mixed-phase properties of the TiOPc sub-micron wires were investigated by the ultraviolet-visible （UV-vis） absorption spectrum and X-ray diffraction. Organic transistors based on these wires were studied, which show the typical p-channel characteristics.
文摘Pattem imprinting in deep sub-micron static random access memories （SRAMs） during total dose irradiation is inves- tigated in detail. As the dose accumulates, the data pattern of memory cells loading during irradiation is gradually imprinted on their background data pattern. We build a relationship between the memory cell＇s static noise margin （SNM） and the background data, and study the influence of irradiation on the probability density function of ASNM, which is the difference between two data sides＇ SNMs, to discuss the reason for pattern imprinting. Finally, we demonstrate that, for micron and deep sub-micron devices, the mechanism of pattern imprinting is the bias-dependent threshold shift of the transistor, but for a deep sub-micron device the shift results from charge trapping in the shallow trench isolation （STI） oxide rather than from the gate oxide of the micron-device.
基金Supported by the National Defense Preresearch Fund Program(No.99J8.1.1.DZD132)
文摘Grooved gate structure Metal-Oxide-Semiconductor (MOS) device is consideredas the most promising candidate used in deep and super-deep sub-micron region, for it cansuppress hot carrier effect and short channel effect deeply. Based on the hydrodynamic energytransport model, using two-dimensional device simulator Medici, the relation between structureparameters and hot carrier effect immunity for deep-sub-micron N-channel MOSFET's is studiedand compared with that of counterpart conventional planar device in this paper. The examinedstructure parameters include negative junction depth, concave corner and effective channel length.Simulation results show that grooved gate device can suppress hot carrier effect deeply even indeep sub-micron region. The studies also indicate that hot carrier effect is strongly influencedby the concave corner and channel length for grooved gate device. With the increase of concavecorner, the hot carrier effect in grooved gate MOSFET decreases sharply, and with the reducingof effective channel length, the hot carrier effect becomes large.
基金Prof.Hai-Lung TSAI (Mechanical Engineering,Missouri University of Science and Technology,USA) for his laser system and the National Science Council for supporting the research project under the contract No. NSC-97-2622-E-007-004-CC3
文摘Sub-micron-structure machining on silicon substrate was studied by direct writing system of femtosecond laser with the central wavelength of 800 nm, pulse duration of 120 fs and repetition rate of 1 kHz. Three kinds of experiments were conducted: 1) the effect of photoresist on silicon; 2) machinability of different orientations of silicon; and 3) the size of micro-structure and the cross-section shape. Photoresist SU8 was coated onto silicon substrates in thicknesses of 100 μm. SU8 remained on the silicon substrate while the silicon under the machined SU8 was removed after laser machining. Orientations of (100), (110), and (111) silicon substrates were machined with the laser power of 60 μW and the scanning speed of 3 mm/min. Spike morphologies were observed on all three orientations of silicon substrates without obvious directional difference of these spikes on different silicon substrates. In addition, the ablation threshold energies were also similar. In the consideration of ablation energy, one numerical model of the machining parameters has been proposed to simulate the cross-section of the micro-structure. The predicted shape by simulation can fit the profile of the cross-section shape well.
文摘The analysis of gunshot residue(GSR) has played an integral role within the legal system in relation to shooting cases. With a characteristic elemental composition of lead, antimony, barium, and a typically discriminative spheroidal morphology, the presence and distribution of GSR can aid in firearm investigations. In this experiment, three shots of low velocity rim-fire ammunition were fired over polished silicon collection substrates placed at six intervals over a 100 cm range. The samples were analysed using a Field Emission Gun Scanning Electron Microscope(FEG-SEM) in conjunction with an X-flash Energy Dispersive X-ray(EDX) detector, allowing for GSR particle analyses of composition and structure at the sub-micron level. The results of this experiment indicate that although classic spheroidal particles are present consistently throughout the entire range of samples their sizes vary significantly, and at certain distances from the firearm particles with an irregular morphology were discerned, forming "impactdisrupted" GSR particles, henceforth colloquially referred to as "splats". Upon further analysis, trends with regards to the formation of these splat particles were distinguished. An increase in splat frequency was observed starting at 10 cm from the firearm, with 147 mm^(-2) splat density, reaching a maximal flux at 40 cm(451 mm^(-2)), followed by a gradual decrease to the maximum range sampled. Moreover, the structural morphology of the splats changes throughout the sampling range. At the distances closest to the firearm, molten-looking particles were formed, demonstrating the metallic residues were in a liquid state when their flight path was disrupted. However, at increased distances-primarily where the discharge plume was at maximum dispersion and moving away from the firearm, the residues have had time to cool in-fight resulting in semi-congealed and solid particles that subsequently disrupted upon impact, forming more structured as well as disaggregated splats. The relative compositions of the characteristic elements that are present in GSR also change in the different splat morphologies sampled,which may contribute to the particles' physical structures. Two distinct populations of splats were also observed: circular and elongated, which suggest the residues hit the substrate at different angles. The difference in the splat impact angle can be ascribed to the position of the residues within the firearm discharge plume; particles get caught up in the vortex that is created by the discharge gases behind the projectile as it leaves the barrel, thereby affecting their directionality and flight time. This reasoning could also justify the existence of both spheroidal and splat particles at certain distances. The novel sampling and analytical techniques used in this experiment have provided previously unknown information in relation to GSR structure and formation which could have greater implications to its current analysis amongst laboratories and law enforcement agencies worldwide.
基金Project(50071019) supported by the National Natural Science Foundation of ChinaProject(HIT2002.34) supported by the Science Research Foundation of Harbin Institute of Technology, China
文摘30%Al2O3p/Al-Cu-2.0Mg composite and Al2O3p/Al-Cu-2.5Mg composite with 0.3μm-Al2O3 particles were fabricated. Age-hardening behaviors of two composites and the related matrix alloys were studied by means of Brinell-hardness measurement, DSC and TEM. The results show that the hardness of the composite is improved obviously because of the addition of sub-micron Al2O3 particles. But the hardness increment of Al2O3p/Al composite after aging is lower than that of the related matrix alloy. Moreover, the formation of GP region is suppressed by the addition of sub-micron Al2O3 particles, which broadens the exothermic peak of S' phase. The increment of Mg content has a different influence on accelerating the aging processes of aluminum alloys and the composites, and the hardness also increases.
基金supported by the National Natural Science Foundation of China (NSFC, Grant nos. 21173065, 20573031)the Ministry of Science and Technology of China (MSTC, Grant no. 2011CB808702)the Natural Science Foundation of Hebei Province of China (Grant no.B2010000856)
文摘A sub-micron structured film with a poly(3-methylthiophene) (P3MT)-modified CdTe/ZnO shell-core sub-micron tube array has been prepared by a series of electrodeposition processes, and a semiconductor-sensitized solar cell based on this structure was also fabricated. Vertically oriented ZnO sub-micron tubes were obtained on an indium tin oxide (ITO) substrate, and then CdTe nanocrystals and a thin P3MT layer were electrodeposited sequentially onto the walls of the ZnO sub-micron tubes. A suitable thickness of CdTe and P3MT could improve the photovoltaic properties of the solar cell, which was attributed to the enhancement in the light absorption and the decrease in the recombination of photogenerated carriers. In addition, a p–n heterojunction formed between the interface of CdTe and P3MT played an important part in the efficient separation and fast transport of photogenerated carriers in the sub-micron structure. A power conversion efficiency of 1.20% was obtained with this type of solar cell.
基金supported by the Natural Science Foundation of Guangdong Province, China (Grant Nos.8251063101000007, 10151063101000009,and 9451063101002082)the Scientific and Technological Plan of Guangdong Province (Grant Nos.2008B010200004, 2010B010600030, and 2009B011100003)the National Natural Science Foundation of China (Grant Nos.61078046 and 60977048)
文摘A new sub-micron photolithography tool has been realized by utilizing the interference of surface plasmon waves(SPWs) on the near surface of a silver(Ag)-clad ultraviolet(UV) planar waveguide.A laser beam with a wavelength of 325 nm was incident into the waveguide core,and suffered a series of total internal reflections on the interfaces between the waveguide core and the cladding layers.The incident light and the reflected light induced two beams of SPWs traveling in contrary directions,which interfered with each other and formed a standing wave as a sub-micron photolithography tool.A near-field scanning optical microscope(NSOM) was employed to measure the intensity distribution of the stationary wave field of the near surface of the Ag layer of the waveguide,anastomosed with theoretical values acquired by use of finite difference time domain(FDTD) simulations.And with this sub-micron photolithography tool a SMG with a period of 79.3 nm,in good agreement with the theoretical value of 80.1 nm,was inscribed on the surface of a self-processing hybrid SiO2/ZrO2 solgel film for the first time.
基金supported by Natural Science Foundation of Guangdong Province of China(No.2019A1515010365)National Natural Science Foundation of China(Grant Nos U1501245 and 51672088)+1 种基金China Postdoctoral Science Foundation(2018M633065)Scientific Research Cultivation Fund for Young Teachers of South China Normal University(18KJ16).
文摘Strontium-substituted bioactive glass(Sr-BG)has shown superior performance in bone regeneration.Sr-BG-induced osteogenesis has been extensively studied;however,Sr-BG-mediated osteoclastogenesis and the underlying molecular mechanism remain unclear.It is recognized that the balance of osteogenesis and osteoclastogenesis is closely related to bone repair,and the receptor activators of nuclear factor kappaB ligand(RANKL)signaling pathway plays a key role of in the regulation of osteoclastogenesis.Herein,we studied the potential impact and underling mechanism of strontium-substituted sub-micron bioactive glass(Sr-SBG)on RANKL-induced osteoclast activation and differentiation in vitro.As expected,Sr-SBG inhibited RANKL-mediated osteoclastogenesis significantly with the experimental performance of decreased mature osteoclasts formation and downregulation of osteoclastogenesis-related gene expression.Furthermore,it was found that Sr-SBG might suppress osteoclastogenesis by the combined effect of strontium and silicon released through inhibition of RANKL-induced activation of p38 and NF-κB pathway.These results elaborated the effect of Sr-SBG-based materials on osteoclastogenesis through RANKLinduced downstream pathway and might represent a significant guidance for designing better bone repair materials.
