Mar and abrasion resistance were investigated by a progressive load scratch test and steel wool abrasion test, respectively. Two acrylic coating systems including trimethylolpropane triacrylate (TMPTA) and pentaerythr...Mar and abrasion resistance were investigated by a progressive load scratch test and steel wool abrasion test, respectively. Two acrylic coating systems including trimethylolpropane triacrylate (TMPTA) and pentaerythritol triacrylate (PETA) were prepared. A soft base layer was introduced as an intermediate layer between two different types of top layer and poly (methyl methacrylate) (PMMA) substrate to demonstrate the effect of soft base layer on mar and abrasion resistance. Abrasion damage on the coating surface was found to be less severe, when the soft base layer was incorporated into the coating systems. The reduction in scratch coefficient of friction (SCOF) and surface roughness was also observed. The results suggested that mar and abrasion resistance was greatly influenced by the presence of soft base layer, although different top layers were used. Moreover, it was found that abrasion resistance was further improved as the thicker soft base layer was applied.展开更多
Recent advances in two-dimensional layered systems have greatly enriched electronic transport studies, particularly in inter-layer Coulomb drag research. Here, systematic transport measurements were conducted in graph...Recent advances in two-dimensional layered systems have greatly enriched electronic transport studies, particularly in inter-layer Coulomb drag research. Here, systematic transport measurements were conducted in graphene-based electronic double-layer structures, revealing giant yet reproducible drag fluctuations at cryogenic temperatures. These fluctuations' characteristics, including amplitude and peak/valley spacing, are mainly determined by the drag layer's carrier dynamics rather than the drive layer's, resulting in violation of the Onsager reciprocity relation. Notably, the drag fluctuations remain observable up to 35 K, far exceeding universal conductance fluctuations within individual layers. This suggests enhanced phase coherence in inter-layer drag compared to single-layer transport, as further confirmed by quantitative analysis of auto-correlation fields of fluctuations under magnetic fields. Our findings provide new insights into quantum interference effects and their interplay with Coulomb interactions in solids. The observations of significant drag fluctuations could potentially help address chaotic signals between nearby components in nanoscale devices.展开更多
This paper proposed a precast concrete pavement structure with the composite base layer comprised of the concrete beam and the filling low strength materials(B-PCP).The mechanical responses of the B-PCP induced by mov...This paper proposed a precast concrete pavement structure with the composite base layer comprised of the concrete beam and the filling low strength materials(B-PCP).The mechanical responses of the B-PCP induced by moving wheel loads coupled with temperature loads were analysed using the finite element method.Then the optimal geometry of the concrete beam was determined based on the sensitivity analysis,considering the tensile stress of both the slab and the beam of the base layer,the slab curling,and the faulting.Furthermore,the performance evaluation of the B-PCP was conducted by the numerical analysis and the scale experiment testing,respectively.The results showed that the optical concrete beam was 0.81.0 m wide and 0.20.3 m thick.The numerical results showed that the optimal B-PCP structure had a good fatigue resistance performance,and the corresponding slab curling decreased by almost 40%compared with that of the traditional precast concrete pavement.Meanwhile,the scale experiment testing verified that the optimal B-PCP structure exhibited an excellent ability to resist the deformation.The results also showed that the bearing capacity of the optimal B-PCP structure was larger than 350kN,indicating a good bearing capacity.展开更多
After different heat treatment processes, the metal compound, the microstructure and the hardness of the C-Cr-W- Mo-V-RE Fe-based hardfacing layers are investigated by means of metallographic microscope, X-ray diffrac...After different heat treatment processes, the metal compound, the microstructure and the hardness of the C-Cr-W- Mo-V-RE Fe-based hardfacing layers are investigated by means of metallographic microscope, X-ray diffraction （ XRD ）, energy dispersive spectrum（ EDS ）, transmission electron microscope（TEM） and hardness tester. The results show that the hardfacing layers have higher tempering stability and secondary hardening property. After quenching at 820 ℃ ,the hardness value（ HRC37 ） and the microstructure of the layers are similar to that normalized at 820 - 1 000 ℃. The tempering stability and the hardness increases with increasing quench temperature, which is attributed to the amount of the alloy element in the matrix. These results are very helpful for improving the mechanical properties of the hardfacing layers.展开更多
After tempering treatment at different conditions, the tempering stability of Fe-base hardfacing layer containing RE and multiple alloying was investigated. The results show that after heat preservation at 560 ℃ and ...After tempering treatment at different conditions, the tempering stability of Fe-base hardfacing layer containing RE and multiple alloying was investigated. The results show that after heat preservation at 560 ℃ and tempering for 4 h the hardness value of Fe-base hardfacing layer containing RE and multiple alloying can reach HRC57; By repeatedly heating circle 700 ℃17 ℃ for 150 times, the hardness value of Fe-base hardfacing layer can reach HRC43, tempering stability is higher and causes the secondary hardening phenomenon. Reasons for higher tempering stability of Fe-base hardfacing layer were analyzed by means of metallographic, XRD, TEM and EDS.展开更多
Surface chemical properties of supports have an important influence on active sites and their catalytic behavio r.Here,we fabricated a series of cobalt-based catalysts supported by carbon layer-coated ordered mesoporo...Surface chemical properties of supports have an important influence on active sites and their catalytic behavio r.Here,we fabricated a series of cobalt-based catalysts supported by carbon layer-coated ordered mesoporous silica(OMS) composites for higher alcohol synthesis(HAS).The carbon layers were derived from different sources and uniformly coated on the porous surface of OMS.Combined with the characterization results of carbonized catalysts,it is demonstrated that the carbon layer-coated supports significantly enhanced the metal dispersion and increased the ratio of Co2+ to Co0 sites,which further increased the CO conversion and alcohols selectivity.Moreover,it is found that the catalytic activity changed in line with the amount of defects and surface oxygenic groups of carbon layers,which re sulted from the different carbon sources.The highest space time yield of C2+OH was 27.5 mmol gcat-1h-1)obtained by the catalyst coated with glucose-derived carbon layer.But the carbon source is not the key factor influencing the distribution of Co-Co2+ dual sites and shows little effect on selectivity in HAS.These results may guide for further design of carbon supported catalysts.展开更多
By laser multi-layer cladding using a pulsed Nd-YAG irradiation the thickness of the cladding zone Mg-based alloys(ZM2 and ZM5) can reach about 1.0 mm.The microstructure of the substrate and the cladding zone was stud...By laser multi-layer cladding using a pulsed Nd-YAG irradiation the thickness of the cladding zone Mg-based alloys(ZM2 and ZM5) can reach about 1.0 mm.The microstructure of the substrate and the cladding zone was studied using optical microscope, scanning electron microscopy(SEM), X-ray diffractometry(XRD) and micro hardness analysis. It is observed that constituent of ZM5 alloy is δ+Mg 17Al 12, that of ZM2 alloy is α+MgZn+Mg 9Ce. That of cladding layer ZM2 alloy(L-ZM2) is Mg+Mg 2Zn 11+MgCe; while that of the cladding layer ZM5 alloy(L-ZM5) is Mg+Mg 32(Al, Zn) 49. The hardness of the cladding area can be increased to values above HV127. Very fine uniform microstructure and the produced new phases of nanometer/sub-micrometer order were obtained. Now, many repaired Mg-based alloy components have been passed by flying test in outside field.展开更多
Objective In geo-marine science,the generalized bottom boundary layer（BBL）represents a layer between sediments and seawater.The BBL plays an important role in geological,geobiochemical,geophysical and geotechnical r...Objective In geo-marine science,the generalized bottom boundary layer（BBL）represents a layer between sediments and seawater.The BBL plays an important role in geological,geobiochemical,geophysical and geotechnical research because it is the connection region of hydrosphere,展开更多
The thermal fatigue property of Cr-W-Mo-Ni-Mn-RE ferric-base hardfacing layer was investigated. The results show that the generation and propagation of thermal fatigue cracks prefer the parts of oxidation and etching ...The thermal fatigue property of Cr-W-Mo-Ni-Mn-RE ferric-base hardfacing layer was investigated. The results show that the generation and propagation of thermal fatigue cracks prefer the parts of oxidation and etching of the grain boundary, the joint efforts of cycle stress and oxidation at high temperatures are the main factors in the generation and propagation of thermal fatigue cracks. When the temperatures is below 600 ℃, the Cr-W-Mo-Ni-Mn-RE ferric-base hardfacing layer has higher ability of thermal fatigue resistance. The function of the alloy and rare earth elements was discussed.展开更多
Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stre...Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stress within the surfacing welding layer. The results show that cracking in the surfacing welding layer is directly related to the producing of eutectic phase β' (NiAl) in the interdendritic region and high thermal stress within the surfacing welding layer. When the process of electric arc surfacing welding is changed from along straight line to along' Z' pattern, cracking in the surfacing welding layer of Ni3Al based alloy is prevented due to being reduced of both the cooling rate of liquid in the molten pool and the moving speed of the heat source. Reducing the melting volume of the substrate material by lowering the output power of electric arc welding would make the content of iron atoms in the molten pool decrease. and this also can reduce the trend of the eutectic reaction in the interdendfitic region and is helpful to Suppress cracking in the surfacing welding layer.展开更多
Layered Co-based ceramics with a nominal composition Bi2-xLaxSr2Co2O8-δ (x=0.0, 0.4, 0.8, short by BLC-222) were prepared using conventional solid state reaction method. X-ray photoemission spectroscopy (XPS) was use...Layered Co-based ceramics with a nominal composition Bi2-xLaxSr2Co2O8-δ (x=0.0, 0.4, 0.8, short by BLC-222) were prepared using conventional solid state reaction method. X-ray photoemission spectroscopy (XPS) was used to investigate their electronic structures. The cobalt ions are highly mixed valences of Co3+ and Co4+. The fraction of Co4+ almost keeps unchanged with the increase of x. The O-1s photoemission spectra show that there are lattice oxygen and chemical absorbed oxygen in all the samples. The substitution of Bi3+ by La3+ results in a change from metallic-like behavior to semiconductor behavior. This abnormal phenomenon means that La3+ plays a key role in effecting the electrical transport property of BLC-222. The O-Co covalence bond is strengthened by the increase of La3+, which results in the decrease of conductivity.展开更多
The advantages of a blue InGaN-based light-emitting diode with a p-InGaN layer inserted in the GaN barriers is studied. The carrier concentration in the quantum well, radiative recombination rate in the active region,...The advantages of a blue InGaN-based light-emitting diode with a p-InGaN layer inserted in the GaN barriers is studied. The carrier concentration in the quantum well, radiative recombination rate in the active region, output power, and internal quantum efficiency are investigated. The simulation results show that the InGaN-based light-emitting diode with a p-InGaN layer inserted in the barriers has better performance over its conventional counterpart and the light emitting diode with p-GaN inserted in the barriers. The improvement is due to enhanced Mg acceptor activation and enhanced hole injection into the quantum wells.展开更多
We present a systematic analysis of the exciton-recombination zone within all-quantum-dot （QD） multilayer films using sensing QD layers in QD-based light-emitting diodes （QLEDs）, and demonstrate the a11-QD multila...We present a systematic analysis of the exciton-recombination zone within all-quantum-dot （QD） multilayer films using sensing QD layers in QD-based light-emitting diodes （QLEDs）, and demonstrate the a11-QD multilayer films with different sequences of layers prepared by inserting a sensing blue QD layer denoted as B at various positions within four red QD multilayers denoted as R. We also use different hole transporting layers （PVK, CBP as well as poly-TPD） to prevent the formation of leakage current and to improve the luminance. The results show that the total EL emission is mostly at the fourth （60%） and fifth （40%） QD monolayers, adjacent to ITO. This presents both decreasing current density and increasing brightness with different hole transporting layers, thus resulting in more efficient performance.展开更多
文摘Mar and abrasion resistance were investigated by a progressive load scratch test and steel wool abrasion test, respectively. Two acrylic coating systems including trimethylolpropane triacrylate (TMPTA) and pentaerythritol triacrylate (PETA) were prepared. A soft base layer was introduced as an intermediate layer between two different types of top layer and poly (methyl methacrylate) (PMMA) substrate to demonstrate the effect of soft base layer on mar and abrasion resistance. Abrasion damage on the coating surface was found to be less severe, when the soft base layer was incorporated into the coating systems. The reduction in scratch coefficient of friction (SCOF) and surface roughness was also observed. The results suggested that mar and abrasion resistance was greatly influenced by the presence of soft base layer, although different top layers were used. Moreover, it was found that abrasion resistance was further improved as the thicker soft base layer was applied.
基金supported by the National Natural Science Foundation of China (Grant Nos.12474051 and 92165201)the Chinese Academy of Sciences Project for Young Scientists in Basic Research (Grant No.YSBR-046)+1 种基金the National Key Research and Development Program of China (Grant No.2023YFA1406300)the Anhui Provincial Natural Science Foundation (Grant Nos.2308085J11 and2308085QA14)。
文摘Recent advances in two-dimensional layered systems have greatly enriched electronic transport studies, particularly in inter-layer Coulomb drag research. Here, systematic transport measurements were conducted in graphene-based electronic double-layer structures, revealing giant yet reproducible drag fluctuations at cryogenic temperatures. These fluctuations' characteristics, including amplitude and peak/valley spacing, are mainly determined by the drag layer's carrier dynamics rather than the drive layer's, resulting in violation of the Onsager reciprocity relation. Notably, the drag fluctuations remain observable up to 35 K, far exceeding universal conductance fluctuations within individual layers. This suggests enhanced phase coherence in inter-layer drag compared to single-layer transport, as further confirmed by quantitative analysis of auto-correlation fields of fluctuations under magnetic fields. Our findings provide new insights into quantum interference effects and their interplay with Coulomb interactions in solids. The observations of significant drag fluctuations could potentially help address chaotic signals between nearby components in nanoscale devices.
基金sponsored by the National Natural Science Fund of China(ID:52008310).
文摘This paper proposed a precast concrete pavement structure with the composite base layer comprised of the concrete beam and the filling low strength materials(B-PCP).The mechanical responses of the B-PCP induced by moving wheel loads coupled with temperature loads were analysed using the finite element method.Then the optimal geometry of the concrete beam was determined based on the sensitivity analysis,considering the tensile stress of both the slab and the beam of the base layer,the slab curling,and the faulting.Furthermore,the performance evaluation of the B-PCP was conducted by the numerical analysis and the scale experiment testing,respectively.The results showed that the optical concrete beam was 0.81.0 m wide and 0.20.3 m thick.The numerical results showed that the optimal B-PCP structure had a good fatigue resistance performance,and the corresponding slab curling decreased by almost 40%compared with that of the traditional precast concrete pavement.Meanwhile,the scale experiment testing verified that the optimal B-PCP structure exhibited an excellent ability to resist the deformation.The results also showed that the bearing capacity of the optimal B-PCP structure was larger than 350kN,indicating a good bearing capacity.
文摘After different heat treatment processes, the metal compound, the microstructure and the hardness of the C-Cr-W- Mo-V-RE Fe-based hardfacing layers are investigated by means of metallographic microscope, X-ray diffraction （ XRD ）, energy dispersive spectrum（ EDS ）, transmission electron microscope（TEM） and hardness tester. The results show that the hardfacing layers have higher tempering stability and secondary hardening property. After quenching at 820 ℃ ,the hardness value（ HRC37 ） and the microstructure of the layers are similar to that normalized at 820 - 1 000 ℃. The tempering stability and the hardness increases with increasing quench temperature, which is attributed to the amount of the alloy element in the matrix. These results are very helpful for improving the mechanical properties of the hardfacing layers.
文摘After tempering treatment at different conditions, the tempering stability of Fe-base hardfacing layer containing RE and multiple alloying was investigated. The results show that after heat preservation at 560 ℃ and tempering for 4 h the hardness value of Fe-base hardfacing layer containing RE and multiple alloying can reach HRC57; By repeatedly heating circle 700 ℃17 ℃ for 150 times, the hardness value of Fe-base hardfacing layer can reach HRC43, tempering stability is higher and causes the secondary hardening phenomenon. Reasons for higher tempering stability of Fe-base hardfacing layer were analyzed by means of metallographic, XRD, TEM and EDS.
基金support from the National Natural Science Foundation of China(Nos.U1462204,21706184)the National Postdoctoral Program for Innovative Talents of China(No.BX20180221)。
文摘Surface chemical properties of supports have an important influence on active sites and their catalytic behavio r.Here,we fabricated a series of cobalt-based catalysts supported by carbon layer-coated ordered mesoporous silica(OMS) composites for higher alcohol synthesis(HAS).The carbon layers were derived from different sources and uniformly coated on the porous surface of OMS.Combined with the characterization results of carbonized catalysts,it is demonstrated that the carbon layer-coated supports significantly enhanced the metal dispersion and increased the ratio of Co2+ to Co0 sites,which further increased the CO conversion and alcohols selectivity.Moreover,it is found that the catalytic activity changed in line with the amount of defects and surface oxygenic groups of carbon layers,which re sulted from the different carbon sources.The highest space time yield of C2+OH was 27.5 mmol gcat-1h-1)obtained by the catalyst coated with glucose-derived carbon layer.But the carbon source is not the key factor influencing the distribution of Co-Co2+ dual sites and shows little effect on selectivity in HAS.These results may guide for further design of carbon supported catalysts.
文摘By laser multi-layer cladding using a pulsed Nd-YAG irradiation the thickness of the cladding zone Mg-based alloys(ZM2 and ZM5) can reach about 1.0 mm.The microstructure of the substrate and the cladding zone was studied using optical microscope, scanning electron microscopy(SEM), X-ray diffractometry(XRD) and micro hardness analysis. It is observed that constituent of ZM5 alloy is δ+Mg 17Al 12, that of ZM2 alloy is α+MgZn+Mg 9Ce. That of cladding layer ZM2 alloy(L-ZM2) is Mg+Mg 2Zn 11+MgCe; while that of the cladding layer ZM5 alloy(L-ZM5) is Mg+Mg 32(Al, Zn) 49. The hardness of the cladding area can be increased to values above HV127. Very fine uniform microstructure and the produced new phases of nanometer/sub-micrometer order were obtained. Now, many repaired Mg-based alloy components have been passed by flying test in outside field.
基金supported by the National Natural Science Foundation of China (grants No.41427803 amd 41272316)
文摘Objective In geo-marine science,the generalized bottom boundary layer（BBL）represents a layer between sediments and seawater.The BBL plays an important role in geological,geobiochemical,geophysical and geotechnical research because it is the connection region of hydrosphere,
文摘The thermal fatigue property of Cr-W-Mo-Ni-Mn-RE ferric-base hardfacing layer was investigated. The results show that the generation and propagation of thermal fatigue cracks prefer the parts of oxidation and etching of the grain boundary, the joint efforts of cycle stress and oxidation at high temperatures are the main factors in the generation and propagation of thermal fatigue cracks. When the temperatures is below 600 ℃, the Cr-W-Mo-Ni-Mn-RE ferric-base hardfacing layer has higher ability of thermal fatigue resistance. The function of the alloy and rare earth elements was discussed.
文摘Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stress within the surfacing welding layer. The results show that cracking in the surfacing welding layer is directly related to the producing of eutectic phase β' (NiAl) in the interdendritic region and high thermal stress within the surfacing welding layer. When the process of electric arc surfacing welding is changed from along straight line to along' Z' pattern, cracking in the surfacing welding layer of Ni3Al based alloy is prevented due to being reduced of both the cooling rate of liquid in the molten pool and the moving speed of the heat source. Reducing the melting volume of the substrate material by lowering the output power of electric arc welding would make the content of iron atoms in the molten pool decrease. and this also can reduce the trend of the eutectic reaction in the interdendfitic region and is helpful to Suppress cracking in the surfacing welding layer.
基金the National Nature Science Foundation of China (20571019)the Project-sponsored by SRF for ROCS ,HLJ (LC06C13)+1 种基金Project-Sponsored by Program of Harbin Subject Chief Scientist (2006RFXXG001)Development Programfor Outstanding Young Teachers in Harbin Institute of Technology (HITQNJS.2006.028)
文摘Layered Co-based ceramics with a nominal composition Bi2-xLaxSr2Co2O8-δ (x=0.0, 0.4, 0.8, short by BLC-222) were prepared using conventional solid state reaction method. X-ray photoemission spectroscopy (XPS) was used to investigate their electronic structures. The cobalt ions are highly mixed valences of Co3+ and Co4+. The fraction of Co4+ almost keeps unchanged with the increase of x. The O-1s photoemission spectra show that there are lattice oxygen and chemical absorbed oxygen in all the samples. The substitution of Bi3+ by La3+ results in a change from metallic-like behavior to semiconductor behavior. This abnormal phenomenon means that La3+ plays a key role in effecting the electrical transport property of BLC-222. The O-Co covalence bond is strengthened by the increase of La3+, which results in the decrease of conductivity.
文摘The advantages of a blue InGaN-based light-emitting diode with a p-InGaN layer inserted in the GaN barriers is studied. The carrier concentration in the quantum well, radiative recombination rate in the active region, output power, and internal quantum efficiency are investigated. The simulation results show that the InGaN-based light-emitting diode with a p-InGaN layer inserted in the barriers has better performance over its conventional counterpart and the light emitting diode with p-GaN inserted in the barriers. The improvement is due to enhanced Mg acceptor activation and enhanced hole injection into the quantum wells.
基金Supported by the National High Technology Research and Development Program of China under Grant No 2013AA032205the National Natural Science Foundation of China under Grant Nos 11474018,51272022 and 61575019+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant Nos 20120009130005 and 20130009130001the Technological Development Contract under Grant No HETONG-150188-04E008
文摘We present a systematic analysis of the exciton-recombination zone within all-quantum-dot （QD） multilayer films using sensing QD layers in QD-based light-emitting diodes （QLEDs）, and demonstrate the a11-QD multilayer films with different sequences of layers prepared by inserting a sensing blue QD layer denoted as B at various positions within four red QD multilayers denoted as R. We also use different hole transporting layers （PVK, CBP as well as poly-TPD） to prevent the formation of leakage current and to improve the luminance. The results show that the total EL emission is mostly at the fourth （60%） and fifth （40%） QD monolayers, adjacent to ITO. This presents both decreasing current density and increasing brightness with different hole transporting layers, thus resulting in more efficient performance.
