A significant enhancement in solar hydrogen generation efficiency has been achieved by inductive coupled etching （ICP） surface roughening treatment using nano-sized nickel mask. As much as 7 times improvement of pho...A significant enhancement in solar hydrogen generation efficiency has been achieved by inductive coupled etching （ICP） surface roughening treatment using nano-sized nickel mask. As much as 7 times improvement of photocurrent is demonstrated in comparison with a planar one fabricated from the same parent wafer. Under identical illumination conditions in HBr solution, the incident photon conversion efficiency （IPCE） shows an enhancement with a factor of 3, which even exceed 54% at 400 nm wavelength. We believe the enhancement is attributed to several facts including improvement in absorption, reacting area, carder localization and carrier lifetime.展开更多
The morphology and lateral growth rate of isotactic polybutene-1(it-PB1)have been investigated for crystallization from the melt over a wide range of crystallization temperatures from 50 to 110℃.The morphology of it-...The morphology and lateral growth rate of isotactic polybutene-1(it-PB1)have been investigated for crystallization from the melt over a wide range of crystallization temperatures from 50 to 110℃.The morphology of it-PB1 crystals is a rounded shape at crystallization temperatures lower than 85℃,while lamellarsingle crystals possess faceted morphology at higher crystallization temperatures.The kinetic roughening transi-tion occurs around 85℃.The nucleation and growth mechanism for crystallization does not work below 85℃,since the growth face is rough.However,the growth rate shows the supercooling dependence derived from the nucleation and growth mechanism.The nucleation theory seems still to work even for rough surface growth.Possible mechanisms for the crystal growth of this polymer are discussed.展开更多
By using the wafer bonding technique and wet etching process,a wafer bonded thin film AlGaInP LED with wet etched n-AlGaInP surfaces was fabricated.The morphology of the etched surface exhibits a pyramid-like feature....By using the wafer bonding technique and wet etching process,a wafer bonded thin film AlGaInP LED with wet etched n-AlGaInP surfaces was fabricated.The morphology of the etched surface exhibits a pyramid-like feature.The wafer was cut into 270×270μm2 chips and then packaged into TO-18 without epoxy resin.With 20-mA current injection,the light intensity and output power of LED-Ⅰwith surface roughening respectively reach 315 mcd and 4.622 mW,which was 1.7 times higher than that of LED-Ⅱwithout surface roughening.The enhancement of output power in LED-Ⅰcan be attributed to the pyramid-like surface,which not only reduces the total internal reflection at the semiconductor-air interface but also effectively guides more photons into the escape angle for emission from the LED device.展开更多
Severe surface roughening during plastic deforming of aluminum alloy parts can produce ＂orange peel＂ defects. To analyze ＂orange peel＂ of 6063 aluminum alloy tube quantificationally, the tensile tests of trapezoid...Severe surface roughening during plastic deforming of aluminum alloy parts can produce ＂orange peel＂ defects. To analyze ＂orange peel＂ of 6063 aluminum alloy tube quantificationally, the tensile tests of trapezoidal specimens were carried out. The tubes with different grain sizes were obtained by spinning and subsequent annealing heat treatment. The macroscopical behavior of surface roughening was characterized by surface roughness Ra using a laser scanning confocal microscope. The corresponding microscopic behavior was reflected by microstructures of specimens and in-situ observation using electron back-scattered diffraction（EBSD）. The obtained results show that the surface roughness increased firstly with increasing strain and then decreased slightly. There was a critical strain for aluminum alloy tube, below which ＂orange peel＂ defect would not occur. For the tube with a mean grain size of 80, 105, 130 and 175 μm, the critical strains were 10.17%, 5.74%, 3.15% and 1.62%, respectively. Meanwhile, the surface roughening behavior was produced by serious inhomogeneous deformation between grains as strain increased, and was aggravated as the grain size increased due to the larger local deformation in larger grains.展开更多
GaN-based light-emitting diodes （LEDs） with surface-textured indium tin oxide （ITO） as a transparent current spreading layer were fabricated. The ITO surface was textured by inductively coupled plasma （ICP） etch...GaN-based light-emitting diodes （LEDs） with surface-textured indium tin oxide （ITO） as a transparent current spreading layer were fabricated. The ITO surface was textured by inductively coupled plasma （ICP） etching technology using a monolayer of nickel （Ni） nanoparticles as the etching mask. The luminance intensity of ITO surface-textured GaN-based LEDs was enhanced by about 34% compared to that of conventional LED without textured ITO layer. In addition, the fabricated ITO surface-textured GaN-based LEDs would present a quite good performance in electrical characteristics. The results indicate that the scattering of photons emitted in the active layer was greatly enhanced via the textured ITO surface, and the ITO surface-textured technique could have a potential application in improving photoelectric characteristics for manufacturing GaN-based LEDs of higher brightness.展开更多
Solution crystallization of metallocene short chain branched polyethylene (SCBPE) was carried out and very nice single crystals were obtained. Compared with single crystals grown from linear polyethylene, SCBPE single...Solution crystallization of metallocene short chain branched polyethylene (SCBPE) was carried out and very nice single crystals were obtained. Compared with single crystals grown from linear polyethylene, SCBPE single crystals are dirty due to intermolecular heterogeneity The crystal morphology changes with crystallization temperatures. Lozenge, truncated lozenge, hexagonal, rounded and elongated crystal morphologies have been found at much lower crystallization temperature than in linear polyethylene. The electron diffraction shows there is a possibility that the single crystals may have hexagonal packing in a crystallization temperature range. The lateral habits of single crystal are discussed based on roughening theories.展开更多
This paper describes the pretreatment process for metal[ization of PZT ceramics surfaces by electrolytic Ni plating which includes cleaning, roughening, sensitization and activation. The experimental procedure, result...This paper describes the pretreatment process for metal[ization of PZT ceramics surfaces by electrolytic Ni plating which includes cleaning, roughening, sensitization and activation. The experimental procedure, results and influeneing factors for these processes are investigated and discussed.展开更多
Two methods used to grow adherent coatings, roughening of the surface for mechanical interlocking and the use of chemically compatible interlayers having intermediate thermal expansion coefficients are analyzed numeri...Two methods used to grow adherent coatings, roughening of the surface for mechanical interlocking and the use of chemically compatible interlayers having intermediate thermal expansion coefficients are analyzed numerically with the aid of phase diagram. Calculations indicate that more roughness and smaller periodicity of the substrate surface will increase the interfacial area and thus enhance the adherence strength of the coating. The phase diagram shows that an intermediate layer with a proper composition gradient from the substrate to the film will relax the thermal stress at the interface effectively.展开更多
This work is concerned with numerical simulations of surface roughening in a polycrystalline aluminum alloy. Using 3D finite difference model, high-resolution simulations are conducted. Effects of loading conditions a...This work is concerned with numerical simulations of surface roughening in a polycrystalline aluminum alloy. Using 3D finite difference model, high-resolution simulations are conducted. Effects of loading conditions and grain size on surface roughening and mesoscale deformation processes in AL6061-T3 aluminum alloy under quasistatic uniaxial tension are investigated.展开更多
Aluminum foils having thicknesses of 10-20 μm are commonly employed as current collectors for cathode electrodes in Li-ion batteries. The effects of the surface morphology of the foil on battery performance were inve...Aluminum foils having thicknesses of 10-20 μm are commonly employed as current collectors for cathode electrodes in Li-ion batteries. The effects of the surface morphology of the foil on battery performance were investigated by using a foil with roughened surface by chemical etching and a plain foil with smooth surface on both sides. For high-conductivity LiCoO2 active materials with large particle size, there are no significant differences in battery performance between the two types of foils. But for low-conductivity LiFePO4 active materials with small particle size, high-rate discharge properties are significantly different. The possibility shows that optimizing both the surface morphology of the aluminum foil and particle size of active material leads to improvement of the battery performance.展开更多
Impingement heat transfer from the rib roughened surface within 2 dimensional arrays of circular jet has been experimentally investigated.This investigation is intended here to include the flow and the heat transfer c...Impingement heat transfer from the rib roughened surface within 2 dimensional arrays of circular jet has been experimentally investigated.This investigation is intended here to include the flow and the heat transfer characteristics of the jet impinging on the rib roughened surface with initial crossflow for simulating the impingement cooling midchord region of the gas turbine aerofoils in case where an initial crossflow is presented.The study covered the ranges of crossflow G_(c)/G_(j)=0~0.55 under the conditions of Re_(j)=8000~11000 and Z/d=1.5~3.0 for smooth and rib roughened surfaces.The test results show that the impingement heat transfer from the rib roughened surface is considerably affected by the initial crossflow rate.The existence of the initial crossflow will improve the efficiency of the impingement heat transfer from the rib roughened surface within arrays of circular jet compared with that from the smooth surface.展开更多
This study reports the controllable surface roughening of Au-Ag alloy nanoplates via the galvanic replacement reaction between single-crystalline triangular Ag nanoplates and HAuC14 in an aqueous medium. With a combin...This study reports the controllable surface roughening of Au-Ag alloy nanoplates via the galvanic replacement reaction between single-crystalline triangular Ag nanoplates and HAuC14 in an aqueous medium. With a combination of experimental evidence and finite element method （FEM） simulations, improved electromagnetic field （E-field） enhancement around the surface-roughened Au- Ag nanoplates and tunable light absorption in the near-infrared （NIR） region （-800-1,400 nm） are achieved by the synergistic effects of the localized surface plasmon resonance （LSPR） from the maintained triangular shape, the controllable Au-Ag alloy composition, and the increased surface roughness. The NIR light extinction enables an active photothermal effect as well as a high photothermal conversion efficiency （78.5%）. The well-maintained triangular shape, surface- roughened evolutions of both micro- and nanostructures, and tunable NIR surface plasmon resonance effect enable potential applications of the Au-Ag alloy nanoplates in surface-enhanced Raman spectroscopic detection of biomolecules through 785-nm laser excitation.展开更多
Low resistance and thermally stable n-type contacts to N-polar GaN are essentially important for vertical light emitting diodes （VLEDs）. The electrical characteristics of VLEDs with n-type contacts on a roughened an...Low resistance and thermally stable n-type contacts to N-polar GaN are essentially important for vertical light emitting diodes （VLEDs）. The electrical characteristics of VLEDs with n-type contacts on a roughened and flat N-polar surface have been compared. VLEDs with contacts deposited on a roughened surface exhibit lower leakage currents yet a higher operating voltage. Based on this, a new scheme by depositing metallization contacts on a selectively wet-etching roughened surface has been developed. Excellent electrical and optical characteristics have been achieved with this method. An aging test further confirmed its stability.展开更多
The behaviors of grain growth dominate the formation of the microstructure inside polycrystalline materials and thus strongly influence their practical performances.However,grain growth behaviors still remain ambiguou...The behaviors of grain growth dominate the formation of the microstructure inside polycrystalline materials and thus strongly influence their practical performances.However,grain growth behaviors still remain ambiguous and thus lack a mathematical formula to describe the general evolution despite decades of efforts.Here,we propose a new migration model of grain boundary(GB)and further derive a mathematical expression to depict the general evolution of grain growth in the cellular structures.The expression incorporates the variables influencing growth rate(e.g.GB features,grain size and local grain size distribution)and thus reveals how the normal,abnormal and stagnant behaviors of grain growth occur in polycrystalline systems.In addition,our model correlates quantitatively GB roughening transition with grain growth behavior.The general growth theory may provide new insights into the GB thermodynamics and kinetics during the cellular structure evolution.展开更多
The light beating technique (intensity correlation algorithm) was employed to analyze the Rayleigh scattering from the roughened Ag electrode in very dilute (10^(-4)M) pyrazine, pyridine and piperidine aqueous solutio...The light beating technique (intensity correlation algorithm) was employed to analyze the Rayleigh scattering from the roughened Ag electrode in very dilute (10^(-4)M) pyrazine, pyridine and piperidine aqueous solutions containing KCl (0.1 M). The relaxation time is longer when the applied voltages are between-0.4 V and-0.8 V(vs. SCE) where the Raman effect also shows greater surface enhancement. Also observed was that for the piperidine case the relaxation time reaches its maximum at the more negative applied voltage. The origin of the relaxation is attributed mainly to the desorp- tion process of the pyrazine. pyridine and piperidine molecules off the roughened Ag electrode. An. electrostatic model was also proposed for the interpretation of these experimental observations.展开更多
基金supported by the Special Funds for Major State Basic Research Project of China(Grant Nos.2011CB301900,2012CB619304,and 2010CB327504)the Hi-tech Research Project of China(Grant No.2011AA03A103)+4 种基金the National Nature Science Foundation of China(Grant Nos.60990311,61274003,60936004,and 61176063)the Program for New Century Excellent Talents in University of China(Grant No.NCET-11-0229)the Natural Science Foundation of Jiangsu Province of China(Grant No.BK2011010)the Funds of Key Laboratory of China(Grant No.9140C140102120C14)the Research Funds from NJU-Yangzhou Institute of Opto-electronics of China
文摘A significant enhancement in solar hydrogen generation efficiency has been achieved by inductive coupled etching （ICP） surface roughening treatment using nano-sized nickel mask. As much as 7 times improvement of photocurrent is demonstrated in comparison with a planar one fabricated from the same parent wafer. Under identical illumination conditions in HBr solution, the incident photon conversion efficiency （IPCE） shows an enhancement with a factor of 3, which even exceed 54% at 400 nm wavelength. We believe the enhancement is attributed to several facts including improvement in absorption, reacting area, carder localization and carrier lifetime.
文摘The morphology and lateral growth rate of isotactic polybutene-1(it-PB1)have been investigated for crystallization from the melt over a wide range of crystallization temperatures from 50 to 110℃.The morphology of it-PB1 crystals is a rounded shape at crystallization temperatures lower than 85℃,while lamellarsingle crystals possess faceted morphology at higher crystallization temperatures.The kinetic roughening transi-tion occurs around 85℃.The nucleation and growth mechanism for crystallization does not work below 85℃,since the growth face is rough.However,the growth rate shows the supercooling dependence derived from the nucleation and growth mechanism.The nucleation theory seems still to work even for rough surface growth.Possible mechanisms for the crystal growth of this polymer are discussed.
基金Project supported by the Natural Science Foundation of Beijing,China(No.4092007)the National High Technology Research and Development Program of China(No.2008AA03Z402)+1 种基金the Doctoral Program Foundation of Beijing,China(No.X0002013200801)the Eighth BJUT Technology Fund for Postgraduate Students,China
文摘By using the wafer bonding technique and wet etching process,a wafer bonded thin film AlGaInP LED with wet etched n-AlGaInP surfaces was fabricated.The morphology of the etched surface exhibits a pyramid-like feature.The wafer was cut into 270×270μm2 chips and then packaged into TO-18 without epoxy resin.With 20-mA current injection,the light intensity and output power of LED-Ⅰwith surface roughening respectively reach 315 mcd and 4.622 mW,which was 1.7 times higher than that of LED-Ⅱwithout surface roughening.The enhancement of output power in LED-Ⅰcan be attributed to the pyramid-like surface,which not only reduces the total internal reflection at the semiconductor-air interface but also effectively guides more photons into the escape angle for emission from the LED device.
基金Project(IRT1229)supported by Program for Chang-jiang Scholars and Innovative Research Team in University,China
文摘Severe surface roughening during plastic deforming of aluminum alloy parts can produce ＂orange peel＂ defects. To analyze ＂orange peel＂ of 6063 aluminum alloy tube quantificationally, the tensile tests of trapezoidal specimens were carried out. The tubes with different grain sizes were obtained by spinning and subsequent annealing heat treatment. The macroscopical behavior of surface roughening was characterized by surface roughness Ra using a laser scanning confocal microscope. The corresponding microscopic behavior was reflected by microstructures of specimens and in-situ observation using electron back-scattered diffraction（EBSD）. The obtained results show that the surface roughness increased firstly with increasing strain and then decreased slightly. There was a critical strain for aluminum alloy tube, below which ＂orange peel＂ defect would not occur. For the tube with a mean grain size of 80, 105, 130 and 175 μm, the critical strains were 10.17%, 5.74%, 3.15% and 1.62%, respectively. Meanwhile, the surface roughening behavior was produced by serious inhomogeneous deformation between grains as strain increased, and was aggravated as the grain size increased due to the larger local deformation in larger grains.
基金Project supported by the Production and Research Program of Guangdong Province and Ministry of Education (Grant No.2009B090300338)Guangdong Natural Science Foundation of China (Grant No.8251063101000007)+1 种基金Guangdong Science and Technology Plan of China (Grant No.2008B010200004)the Student Research Project of South China Normal University (Grant No.09XXKC03)
文摘GaN-based light-emitting diodes （LEDs） with surface-textured indium tin oxide （ITO） as a transparent current spreading layer were fabricated. The ITO surface was textured by inductively coupled plasma （ICP） etching technology using a monolayer of nickel （Ni） nanoparticles as the etching mask. The luminance intensity of ITO surface-textured GaN-based LEDs was enhanced by about 34% compared to that of conventional LED without textured ITO layer. In addition, the fabricated ITO surface-textured GaN-based LEDs would present a quite good performance in electrical characteristics. The results indicate that the scattering of photons emitted in the active layer was greatly enhanced via the textured ITO surface, and the ITO surface-textured technique could have a potential application in improving photoelectric characteristics for manufacturing GaN-based LEDs of higher brightness.
基金This work was jointly supported by National Natural Science Foundation of China and a Grant-in-Aid for Scientific Research from the Ministry of Education of China.
文摘Solution crystallization of metallocene short chain branched polyethylene (SCBPE) was carried out and very nice single crystals were obtained. Compared with single crystals grown from linear polyethylene, SCBPE single crystals are dirty due to intermolecular heterogeneity The crystal morphology changes with crystallization temperatures. Lozenge, truncated lozenge, hexagonal, rounded and elongated crystal morphologies have been found at much lower crystallization temperature than in linear polyethylene. The electron diffraction shows there is a possibility that the single crystals may have hexagonal packing in a crystallization temperature range. The lateral habits of single crystal are discussed based on roughening theories.
文摘This paper describes the pretreatment process for metal[ization of PZT ceramics surfaces by electrolytic Ni plating which includes cleaning, roughening, sensitization and activation. The experimental procedure, results and influeneing factors for these processes are investigated and discussed.
文摘Two methods used to grow adherent coatings, roughening of the surface for mechanical interlocking and the use of chemically compatible interlayers having intermediate thermal expansion coefficients are analyzed numerically with the aid of phase diagram. Calculations indicate that more roughness and smaller periodicity of the substrate surface will increase the interfacial area and thus enhance the adherence strength of the coating. The phase diagram shows that an intermediate layer with a proper composition gradient from the substrate to the film will relax the thermal stress at the interface effectively.
文摘This work is concerned with numerical simulations of surface roughening in a polycrystalline aluminum alloy. Using 3D finite difference model, high-resolution simulations are conducted. Effects of loading conditions and grain size on surface roughening and mesoscale deformation processes in AL6061-T3 aluminum alloy under quasistatic uniaxial tension are investigated.
文摘Aluminum foils having thicknesses of 10-20 μm are commonly employed as current collectors for cathode electrodes in Li-ion batteries. The effects of the surface morphology of the foil on battery performance were investigated by using a foil with roughened surface by chemical etching and a plain foil with smooth surface on both sides. For high-conductivity LiCoO2 active materials with large particle size, there are no significant differences in battery performance between the two types of foils. But for low-conductivity LiFePO4 active materials with small particle size, high-rate discharge properties are significantly different. The possibility shows that optimizing both the surface morphology of the aluminum foil and particle size of active material leads to improvement of the battery performance.
文摘Impingement heat transfer from the rib roughened surface within 2 dimensional arrays of circular jet has been experimentally investigated.This investigation is intended here to include the flow and the heat transfer characteristics of the jet impinging on the rib roughened surface with initial crossflow for simulating the impingement cooling midchord region of the gas turbine aerofoils in case where an initial crossflow is presented.The study covered the ranges of crossflow G_(c)/G_(j)=0~0.55 under the conditions of Re_(j)=8000~11000 and Z/d=1.5~3.0 for smooth and rib roughened surfaces.The test results show that the impingement heat transfer from the rib roughened surface is considerably affected by the initial crossflow rate.The existence of the initial crossflow will improve the efficiency of the impingement heat transfer from the rib roughened surface within arrays of circular jet compared with that from the smooth surface.
基金This work was supported by the National Natural Science Foundation of China （Nos. 91323301, 21322105, and 51372025）, the Research Fund for the Doctoral Program of Higher Education of China （No. 2011101120016） and Program for New Century Excellent Talents in University （No. NCET-11-0793）. The authors would like to thank Prof. Chen Wang and Prof. Yanjun Guo of National Center for Nanoscience and Technology, China for AFM and SERS measure- ments and helpful discussions, respectively Dr. Haiwei Li for help on BET tests and helpful discussions.
文摘This study reports the controllable surface roughening of Au-Ag alloy nanoplates via the galvanic replacement reaction between single-crystalline triangular Ag nanoplates and HAuC14 in an aqueous medium. With a combination of experimental evidence and finite element method （FEM） simulations, improved electromagnetic field （E-field） enhancement around the surface-roughened Au- Ag nanoplates and tunable light absorption in the near-infrared （NIR） region （-800-1,400 nm） are achieved by the synergistic effects of the localized surface plasmon resonance （LSPR） from the maintained triangular shape, the controllable Au-Ag alloy composition, and the increased surface roughness. The NIR light extinction enables an active photothermal effect as well as a high photothermal conversion efficiency （78.5%）. The well-maintained triangular shape, surface- roughened evolutions of both micro- and nanostructures, and tunable NIR surface plasmon resonance effect enable potential applications of the Au-Ag alloy nanoplates in surface-enhanced Raman spectroscopic detection of biomolecules through 785-nm laser excitation.
基金Project supported by the Knowledge Innovation Program of ISCAS(No.08S4060000)
文摘Low resistance and thermally stable n-type contacts to N-polar GaN are essentially important for vertical light emitting diodes （VLEDs）. The electrical characteristics of VLEDs with n-type contacts on a roughened and flat N-polar surface have been compared. VLEDs with contacts deposited on a roughened surface exhibit lower leakage currents yet a higher operating voltage. Based on this, a new scheme by depositing metallization contacts on a selectively wet-etching roughened surface has been developed. Excellent electrical and optical characteristics have been achieved with this method. An aging test further confirmed its stability.
文摘The behaviors of grain growth dominate the formation of the microstructure inside polycrystalline materials and thus strongly influence their practical performances.However,grain growth behaviors still remain ambiguous and thus lack a mathematical formula to describe the general evolution despite decades of efforts.Here,we propose a new migration model of grain boundary(GB)and further derive a mathematical expression to depict the general evolution of grain growth in the cellular structures.The expression incorporates the variables influencing growth rate(e.g.GB features,grain size and local grain size distribution)and thus reveals how the normal,abnormal and stagnant behaviors of grain growth occur in polycrystalline systems.In addition,our model correlates quantitatively GB roughening transition with grain growth behavior.The general growth theory may provide new insights into the GB thermodynamics and kinetics during the cellular structure evolution.
基金This work was supported by the National Natural Science Foundation of ChinaNational Laboratory for Structural Chemistry of Dynamical and Stable Species.
文摘The light beating technique (intensity correlation algorithm) was employed to analyze the Rayleigh scattering from the roughened Ag electrode in very dilute (10^(-4)M) pyrazine, pyridine and piperidine aqueous solutions containing KCl (0.1 M). The relaxation time is longer when the applied voltages are between-0.4 V and-0.8 V(vs. SCE) where the Raman effect also shows greater surface enhancement. Also observed was that for the piperidine case the relaxation time reaches its maximum at the more negative applied voltage. The origin of the relaxation is attributed mainly to the desorp- tion process of the pyrazine. pyridine and piperidine molecules off the roughened Ag electrode. An. electrostatic model was also proposed for the interpretation of these experimental observations.
