Aiming at serious catastrophic oxidation problem of super-austenitic stainless steel S32654,the influence of different rare earth elements on its oxidation behavior was comparatively investigated at 1200℃.The mechani...Aiming at serious catastrophic oxidation problem of super-austenitic stainless steel S32654,the influence of different rare earth elements on its oxidation behavior was comparatively investigated at 1200℃.The mechanism of Y significantly improving high-temperature oxidation resistance of S32654 was unveiled.The results demonstrated that Y played much better beneficial roles than Ce and La in the initial formation of oxide layer:(1)Y promoted Cr segregation to steel surface to combine with O;(2)its preferential oxidation provided nucleation cores for Cr_(2)O_(3).Both roles jointly promoted the selective oxidation of Cr and then the formation of protective Cr-rich oxide layer.This provided good prerequisites for inhibiting the formation and volatilization of MoO_(3).Additionally,Y cation segregation to oxide grain boundaries further promoted the selective oxidation of Cr and Si to form more protective oxide layer.These beneficial roles of Y essentially eliminated the synergistic effects of MoO_(3) volatilization and lamellar Cr_(2)N precipitation on catastrophic oxidation.Accordingly,the oxidation resistance of Y-bearing S32654 was improved by 22%–45%.展开更多
Influence mechanism of B segregation on the microstructure evolution and hot ductility of S32654 at850-1250℃was systematically investigated through experimental research and theoretical calculation.The results demons...Influence mechanism of B segregation on the microstructure evolution and hot ductility of S32654 at850-1250℃was systematically investigated through experimental research and theoretical calculation.The results demonstrated that the segregation of B at grain boundary(GB)played different roles in the microstructure evolution and hot ductility at various temperatures.At 850℃,B segregation inhibited Mo segregation at the GB and enhanced the GB cohesion.At 900-950℃,B segregation restricted the diffusion and segregation of Mo to the GB,inhibiting the precipitation ofσphase.At 1000-1050℃,B segregation accelerated the dislocation accumulation and limited the GB migration,promoting the nucleation and inhibiting the growth of DRX grains.At 1100-1150℃,B has little effect on the DRX due to sufficient energy supply by higher temperature.Under the above beneficial effects of B,the hot ductility of S32654 was improved to varying degrees at 850-1150℃.However,as the temperature increased to1200-1250℃,B segregation decreased the solidus temperature and enhanced the liquefaction cracking tendency,resulting in a deterioration of the hot ductility.展开更多
The state-of-the-art lithium-ion capacitors (LICs),consisting of high-capacity battery-type anode and high-rate capacitor-type cathode,can deliver high energy density and large power density when comparing with tradit...The state-of-the-art lithium-ion capacitors (LICs),consisting of high-capacity battery-type anode and high-rate capacitor-type cathode,can deliver high energy density and large power density when comparing with traditional supercapacitors and lithium-ion batteries,respectively.However,the ion kinetics mismatch between cathode and anode leads to unsatisfied cycling lifetime and anode degradation.Tremendous efforts have been devoted to solving the abovementioned issue.One promising strategy is altering high conductive hard carbon anode with excellent structural stability to match with activated carbon cathode,assembling dual-carbon LIC.In this contribution,one-pot in-situ expansion and heteroatom doping strategy was adopted to prepare sheet-like hard carbon,while activated carbon was obtained involving activation.Ammonium persulfate was used as expanding and doping agent simultaneously.While furfural residues (FR) were served as carbon precursor.The resulting hard carbon (FRNS-HC) and activated carbon (FRNS-AC)show excellent electrochemical performance as negative and positive electrodes in a lithium-ion battery (LIB).To be specific,374.2 m Ah g^(-1)and 123.1 m Ah g^(-1)can be achieved at 0.1 A g^(-1)and 5 A g^(-1)when FRNS-HC was tested as anode.When combined with a highly porous carbon cathode (S_(BET)=2961 m^(2)g^(-1)) synthesized from the same precursor,the LIC showed high specific energy of147.67 Wh kg^(-1)at approximately 199.93 W kg^(-1),and outstanding cycling life with negligible capacitance fading over 1000 cycles.This study could lead the way for the development of heteroatom-doped porous carbon nanomaterials applied to Li-based energy storage applications.展开更多
To improve the coercivity and temperature stability of Nd-Fe-B sintered magnets for high-temperature applications,the eutectic Tb_(80)Fe_(20)(wt%)alloy powders were added into the Nd-Fe-B sintered magnets by intergran...To improve the coercivity and temperature stability of Nd-Fe-B sintered magnets for high-temperature applications,the eutectic Tb_(80)Fe_(20)(wt%)alloy powders were added into the Nd-Fe-B sintered magnets by intergranular method to enhance the coercivity(H_(cj))and thermal stability.The micro structure,magnetic properties and thermal stability of the Nd-Fe-B magnets with different Tb_(80)Fe_(20)contents were studied.The experimental results demonstrate that the coercivity(H_(cj))of the sintered Nd-Fe-B magnet is significantly enhanced from 14.12 to 27.78 kOe,and the remanence(Br)decreases not obviously by introducing 4 wt%Tb_(80)Fe_(20)alloy.Meanwhile,the reversible tempe rature coefficients of coercivity(β)and remanence(α)of the Nd-Fe-B magnets are increased from-0.5634%/℃to-0.4506%/℃and-0.1276%/℃to-0.1199%/℃at 20-170℃,respectively.The Curie temperature(TC)of the Nd-Fe-B magnet is slightly enhanced with the increase of Tb_(80)Fe_(20)content.Moreover,the irreversible flux magnetic loss(hirr)is obviously reduced as Tb80Fe20addition increases.Further analysis of the microstructure reveals that a modified microstructure,i.e.clear and continuous RE-rich grain boundary layer,is acquired in the sintered magnets by introducing Tb_(80)Fe_(20)alloy.The associated mechanisms on improved coercivity and thermal stability were comprehensively researched.展开更多
Thermal annealing and laser irradiation were used to study the activation rate of phosphorus in silicon after ion implantation.The activation rate refers to the ratio of activated impurity number to the total impurity...Thermal annealing and laser irradiation were used to study the activation rate of phosphorus in silicon after ion implantation.The activation rate refers to the ratio of activated impurity number to the total impurity number in the sample.After injecting phosphorus with the dose and energy(energy=55 keV,dose=3×10^(15) cm^(-2)),the samples were annealed at different temperatures,and laser irradiation experiments were performed after annealing.The experimental results showed that the activation rate of phosphorus was the highest at 850℃,and the highest activation rate was 67%.Upon femtosecond laser irradiation samples after thermal annealing,while keeping the crystalline silicon surface without damage,the activation rate was improved.When the energy-flux density of the femtosecond laser was 0.65 kJ/cm2,the activation rate was the highest,increasing from 67%to 74.81%.展开更多
CH4 dissociation on Co（0001） surfaces is an important step, which has been investigated at the level of density functional theory. It is found that CH4 is unfavorable to adsorb on Co（0001）, while CH4 favores to di...CH4 dissociation on Co（0001） surfaces is an important step, which has been investigated at the level of density functional theory. It is found that CH4 is unfavorable to adsorb on Co（0001）, while CH4 favores to dissociate to CH3, CH2 and CH on Co（0001） surface by sequential dehydrogenation. In the whole process of CH4 dehydrogenation, CH4 dissociate to CH3 and H is the rate-determining step. The calculated results show that CH2 and CH exist mainly on Co（0001） surface, while the dehydrogenation of CH into C and H is difficult.展开更多
The substitution/adsorption structures of Co on an anatase TiO2 （001）-（1 × 4） surface are investigated using the DFT/local density approximation （LDA） method. Theoretical calculation shows that the Co ion p...The substitution/adsorption structures of Co on an anatase TiO2 （001）-（1 × 4） surface are investigated using the DFT/local density approximation （LDA） method. Theoretical calculation shows that the Co ion prefers to be adsorbed on the surface of anatase TiO2. The density of states （DOS） analysis finds that the Co 3d is located mainly in the energy gap region. The Co 3d partial density of states （PDOS） indicates that there is a substantial degree of hybridization between O 2s and Co 3d in valence band （VB） regions in the substitution models. The conclusion is that the mode of substitution is more active when the catalyst is a higher-energy surface.展开更多
This paper investigates the formation process of surface pyramid and etching characteristics during the texturing process of mono-crystalline silicon wafers. It is found that there is an etch rate transition point in ...This paper investigates the formation process of surface pyramid and etching characteristics during the texturing process of mono-crystalline silicon wafers. It is found that there is an etch rate transition point in alkaline anisotropic etching when{100} plane-dominated etch turns to {111} plane-dominated etch, and the pyramid size has a strong linear correlation with the etch amount at the transition point. Several techniques were developed to control the pyramid size by monitoring and adjusting the etching amount. A wide range of average pyramid sizes were successfully achieved, from 0.5 to 12 μm. The experiments of the pyramid size on the light reflectance, the minority carrier lifetime(MCLT), and the performance of silicon heterojunction(SHJ)solar cells were carried out and analyzed. A desirable range of pyramid sizes was empirically determined by our investigation. In order to reduce the density states on the texturing surface, the wet-chemical smoothing treatment was also investigated. The smoothing treatment improves the passivation quality and the performance of the solar cells. Through pyramid size control and morphology treatment, together with the amorphous silicon(a-Si:H) deposition improvement, and electrode optimization, high performance of SHJ solar cells has been achieved, up to conversion efficiency 23.6%.展开更多
The gradient doping regions were employed in the emitter layer and the base layer of GaAs based laser power converters(LPCs).Silvaco TCAD was used to numerically simulate the linear gradient doping and exponential gra...The gradient doping regions were employed in the emitter layer and the base layer of GaAs based laser power converters(LPCs).Silvaco TCAD was used to numerically simulate the linear gradient doping and exponential gradient doping structure,and analyze the transport process of photogenerated carriers.Energy band adjustment via gradient doping improved the separation and transport efficiency of photogenerated carriers and reduced the total recombination rate of GaAs LPCs.Compared with traditional structure of LPCs,the photoelectric conversion efficiency of LPCs with linear and exponential gradient doping structure were improved from 52.7%to 57.2%and 57.7%,respectively,under 808 nm laser light at the power density of 1 W/cm^(2).展开更多
The role of cerium(Ce)in enhancing the hot ductility of super austenitic stainless steel S32654 at 850–1250℃was systematically unveiled through theoretical calculations and microstructure characterization.The result...The role of cerium(Ce)in enhancing the hot ductility of super austenitic stainless steel S32654 at 850–1250℃was systematically unveiled through theoretical calculations and microstructure characterization.The results indicated that Ce microalloying improved the hot ductility of S32654 throughout the entire deformation temperature range.Specifically,the addition of Ce greatly enhanced the hot ductility in the low(850–900℃)and high(1100–1250℃)temperature ranges,but only slightly increased that in the medium temperature range(900–1100℃).At 850–900℃,Ce addition not only reduced the sulfur(S)content and suppressed the S segregation at the grain boundary,but also promoted the formation of slip bands and deformation twins,apparently improving the hot ductility.At 900–1100℃,Ce addition promoted the nucleation of intergranularσphases and dynamic recrystallization(DRX)grains,which have adverse and beneficial effects on the hot ductility,respectively.As the temperature increased,the precipitation tendency presented a first increasing and then decreasing trend around 1000℃,while the DRX gradually increased.Accordingly,the improvement degree of Ce on the hot ductility first weakened and then enhanced.At 1100–1250℃,Ce significantly promoted the DRX to form more fine and uniform deformation structure,thereby remarkably increasing the cracking resistance and then the hot ductility.展开更多
First-principles calculations are carried out to examine the adsorption of acetylene over the Pd(111)surface.A hydrogen adsorption system is initially investigated to confirm the reliability of the selected calculatio...First-principles calculations are carried out to examine the adsorption of acetylene over the Pd(111)surface.A hydrogen adsorption system is initially investigated to confirm the reliability of the selected calculation method.Adsorption energies,Mulliken-populations,overlap populations,charge density,and projected density of states(PDOS)are then calculated in the optimised acetylene adsorption system.Results show that C_(2)H_(2) molecule tends to adsorb through the threefold parallel-bridge configuration that is computed to be the most stable.In this structure,the distance of the C-H bond is calculated to be 1.09 Å,and the C-C-H bond angle is 128°.The distance of the C-C bond in acetylene is 1.36 Å,increasing from 1.21 Å in the gas phase.Moreover,the C-C bond overlap population decreases from 1.98 to 1.38,revealing that the carbon configuration in C2H2 rehybridises from sp to sp^(2) and beyond.The obtained results are compared with available experimental studies on acetylene hydrogenation on single-metal surfaces.The PDOS study indicates that a carbonaceous layer may generate on the metal surface during acetylene adsorption.The carbonaceous layer can affect the adsorption and reaction of acetylene,thereby inactivating the metal surface.Our experiments also show that Pd exhibits high catalytic activity.展开更多
The inhibition of Mo segregation and phase precipitation is vital for improving the hot workability and corrosion resistance of superaustentic stainless steels(SASS).The boron non-equilibrium segregation of S31254 SAS...The inhibition of Mo segregation and phase precipitation is vital for improving the hot workability and corrosion resistance of superaustentic stainless steels(SASS).The boron non-equilibrium segregation of S31254 SASS was implemented through solid solution,air cooling,and diffusion at low-temperature treatment(SADT).The precipitation process and intergranular corrosion(IGC)of S31254 SASS with various boron distributions were researched at a sensitive temperature.The second phases were observed and identified by SEM and TEM.IGC susceptibility was evaluated by double-loop potentiodynamic reactivation(DL-EPR)measurements.The SADT treatment promoted more segregation of B at the grain boundary,leading to lower amounts of grain boundary precipitation before aging for 6 h.The decrease of σ phases in B-regulated samples enhances the IGC resistance,compared with the samples without B addition specimens.展开更多
A hot spot is a reliability problem in photovoltaic(PV) modules where a mismatched or shaded cell heats up significantly and degrades the PV module output power performance. High PV cell temperature due to a hot spot ...A hot spot is a reliability problem in photovoltaic(PV) modules where a mismatched or shaded cell heats up significantly and degrades the PV module output power performance. High PV cell temperature due to a hot spot can damage the cell encapsulate and lead to second breakdown, which both cause permanent damage to the PV module. In present systems, bypass diodes are used to mitigate the hot spot problem. In this work, five commercial polysilicon P V modules configured with different numbers of bypass diodes are used to study the influence of bypass diodes on the reverse bias voltage of a shaded cell and the resulting hot spot phenomenon. The reverse bias voltage of the shaded cell, and the hot spot probability and severity decrease as the number of bypass diodes increases. Negative terminal voltage of a shaded cell accompanied by a switched-off bypass diode are the necessary condition for hot spot generation. In an extreme case where each cell has an individual bypass diode in a P V module, it still cannot avoid the hazards of a hot spot under the shading areas of 5-7 cm2, but the probability of a hot spot is reduced to a minimum of 0.41%.展开更多
The influence of a combined process,involving air cooling and heat treatment at 300℃,on precipitation behavior and corrosion resistance of a S31254-Ce steel was explored through scanning electron microscopy(SEM),ener...The influence of a combined process,involving air cooling and heat treatment at 300℃,on precipitation behavior and corrosion resistance of a S31254-Ce steel was explored through scanning electron microscopy(SEM),energy dispersive X-ray spectrometry(EDS),electron backscatter diffraction(EBSD)and electrochemical analysis.After air cooling and heat treatment at 300℃,the S31254-Ce steel was conducive to the enrichment of Ce along the grain boundary and the content of Σ3 twins in aged samples increased.The composite heat treatment process is beneficial to inhibit the precipitation of precipitates in the aging process and improve the corrosion resistance of S31254-Ce steel.展开更多
基金the National Natural Science Foundation of China(Nos.U1860204 and 52004061)the Talent Project of Revitalizing Liaoning(No.XLYC1802101)+2 种基金the China Postdoctoral Science Foundation(No.2020M670777)the Northeastern University Postdoctoral Funds(No.20200321)the Fundamental Research Funds for the Central Universities(No.N2125017)。
文摘Aiming at serious catastrophic oxidation problem of super-austenitic stainless steel S32654,the influence of different rare earth elements on its oxidation behavior was comparatively investigated at 1200℃.The mechanism of Y significantly improving high-temperature oxidation resistance of S32654 was unveiled.The results demonstrated that Y played much better beneficial roles than Ce and La in the initial formation of oxide layer:(1)Y promoted Cr segregation to steel surface to combine with O;(2)its preferential oxidation provided nucleation cores for Cr_(2)O_(3).Both roles jointly promoted the selective oxidation of Cr and then the formation of protective Cr-rich oxide layer.This provided good prerequisites for inhibiting the formation and volatilization of MoO_(3).Additionally,Y cation segregation to oxide grain boundaries further promoted the selective oxidation of Cr and Si to form more protective oxide layer.These beneficial roles of Y essentially eliminated the synergistic effects of MoO_(3) volatilization and lamellar Cr_(2)N precipitation on catastrophic oxidation.Accordingly,the oxidation resistance of Y-bearing S32654 was improved by 22%–45%.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.U1860204,52004061)the Talent Project of Revitalizing Liaoning(Grant No.XLYC1802101)+4 种基金by China Postdoctoral Science Foundation(Grant Nos.2020M670777,2021T140100)the Northeastern University Postdoctoral Funds(Grant No.20200321)the Fundamental Research Funds for the Central Universities(Grant No.N2125017)the Elite Program of Southern Taihu Lakethe instrumental and data analysis from Analytical and Testing Center,Northeastern University。
文摘Influence mechanism of B segregation on the microstructure evolution and hot ductility of S32654 at850-1250℃was systematically investigated through experimental research and theoretical calculation.The results demonstrated that the segregation of B at grain boundary(GB)played different roles in the microstructure evolution and hot ductility at various temperatures.At 850℃,B segregation inhibited Mo segregation at the GB and enhanced the GB cohesion.At 900-950℃,B segregation restricted the diffusion and segregation of Mo to the GB,inhibiting the precipitation ofσphase.At 1000-1050℃,B segregation accelerated the dislocation accumulation and limited the GB migration,promoting the nucleation and inhibiting the growth of DRX grains.At 1100-1150℃,B has little effect on the DRX due to sufficient energy supply by higher temperature.Under the above beneficial effects of B,the hot ductility of S32654 was improved to varying degrees at 850-1150℃.However,as the temperature increased to1200-1250℃,B segregation decreased the solidus temperature and enhanced the liquefaction cracking tendency,resulting in a deterioration of the hot ductility.
基金financially supported by the National Natural Science Foundation of China (22075308, 22209197)Natural Science Foundation of Shanxi Province (20210302 1224439, 202203021211002)Shanxi Province Science Foundation for Youths (No: SQ2019001)。
文摘The state-of-the-art lithium-ion capacitors (LICs),consisting of high-capacity battery-type anode and high-rate capacitor-type cathode,can deliver high energy density and large power density when comparing with traditional supercapacitors and lithium-ion batteries,respectively.However,the ion kinetics mismatch between cathode and anode leads to unsatisfied cycling lifetime and anode degradation.Tremendous efforts have been devoted to solving the abovementioned issue.One promising strategy is altering high conductive hard carbon anode with excellent structural stability to match with activated carbon cathode,assembling dual-carbon LIC.In this contribution,one-pot in-situ expansion and heteroatom doping strategy was adopted to prepare sheet-like hard carbon,while activated carbon was obtained involving activation.Ammonium persulfate was used as expanding and doping agent simultaneously.While furfural residues (FR) were served as carbon precursor.The resulting hard carbon (FRNS-HC) and activated carbon (FRNS-AC)show excellent electrochemical performance as negative and positive electrodes in a lithium-ion battery (LIB).To be specific,374.2 m Ah g^(-1)and 123.1 m Ah g^(-1)can be achieved at 0.1 A g^(-1)and 5 A g^(-1)when FRNS-HC was tested as anode.When combined with a highly porous carbon cathode (S_(BET)=2961 m^(2)g^(-1)) synthesized from the same precursor,the LIC showed high specific energy of147.67 Wh kg^(-1)at approximately 199.93 W kg^(-1),and outstanding cycling life with negligible capacitance fading over 1000 cycles.This study could lead the way for the development of heteroatom-doped porous carbon nanomaterials applied to Li-based energy storage applications.
基金Project partly supported by the Natural Science Foundation of Shanxi Province,China(201801D121100)the Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi(OIT)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(STIP)(201802033)。
文摘To improve the coercivity and temperature stability of Nd-Fe-B sintered magnets for high-temperature applications,the eutectic Tb_(80)Fe_(20)(wt%)alloy powders were added into the Nd-Fe-B sintered magnets by intergranular method to enhance the coercivity(H_(cj))and thermal stability.The micro structure,magnetic properties and thermal stability of the Nd-Fe-B magnets with different Tb_(80)Fe_(20)contents were studied.The experimental results demonstrate that the coercivity(H_(cj))of the sintered Nd-Fe-B magnet is significantly enhanced from 14.12 to 27.78 kOe,and the remanence(Br)decreases not obviously by introducing 4 wt%Tb_(80)Fe_(20)alloy.Meanwhile,the reversible tempe rature coefficients of coercivity(β)and remanence(α)of the Nd-Fe-B magnets are increased from-0.5634%/℃to-0.4506%/℃and-0.1276%/℃to-0.1199%/℃at 20-170℃,respectively.The Curie temperature(TC)of the Nd-Fe-B magnet is slightly enhanced with the increase of Tb_(80)Fe_(20)content.Moreover,the irreversible flux magnetic loss(hirr)is obviously reduced as Tb80Fe20addition increases.Further analysis of the microstructure reveals that a modified microstructure,i.e.clear and continuous RE-rich grain boundary layer,is acquired in the sintered magnets by introducing Tb_(80)Fe_(20)alloy.The associated mechanisms on improved coercivity and thermal stability were comprehensively researched.
基金supported by National Key R&D Program of China (No. 2018YFB1500500).
文摘Thermal annealing and laser irradiation were used to study the activation rate of phosphorus in silicon after ion implantation.The activation rate refers to the ratio of activated impurity number to the total impurity number in the sample.After injecting phosphorus with the dose and energy(energy=55 keV,dose=3×10^(15) cm^(-2)),the samples were annealed at different temperatures,and laser irradiation experiments were performed after annealing.The experimental results showed that the activation rate of phosphorus was the highest at 850℃,and the highest activation rate was 67%.Upon femtosecond laser irradiation samples after thermal annealing,while keeping the crystalline silicon surface without damage,the activation rate was improved.When the energy-flux density of the femtosecond laser was 0.65 kJ/cm2,the activation rate was the highest,increasing from 67%to 74.81%.
文摘CH4 dissociation on Co（0001） surfaces is an important step, which has been investigated at the level of density functional theory. It is found that CH4 is unfavorable to adsorb on Co（0001）, while CH4 favores to dissociate to CH3, CH2 and CH on Co（0001） surface by sequential dehydrogenation. In the whole process of CH4 dehydrogenation, CH4 dissociate to CH3 and H is the rate-determining step. The calculated results show that CH2 and CH exist mainly on Co（0001） surface, while the dehydrogenation of CH into C and H is difficult.
基金This work was supported by the National Natural Science Foundation of China (Grant No.20676087) the National Basic Research Program of China(Grant No 2005CB221204)
文摘The substitution/adsorption structures of Co on an anatase TiO2 （001）-（1 × 4） surface are investigated using the DFT/local density approximation （LDA） method. Theoretical calculation shows that the Co ion prefers to be adsorbed on the surface of anatase TiO2. The density of states （DOS） analysis finds that the Co 3d is located mainly in the energy gap region. The Co 3d partial density of states （PDOS） indicates that there is a substantial degree of hybridization between O 2s and Co 3d in valence band （VB） regions in the substitution models. The conclusion is that the mode of substitution is more active when the catalyst is a higher-energy surface.
文摘This paper investigates the formation process of surface pyramid and etching characteristics during the texturing process of mono-crystalline silicon wafers. It is found that there is an etch rate transition point in alkaline anisotropic etching when{100} plane-dominated etch turns to {111} plane-dominated etch, and the pyramid size has a strong linear correlation with the etch amount at the transition point. Several techniques were developed to control the pyramid size by monitoring and adjusting the etching amount. A wide range of average pyramid sizes were successfully achieved, from 0.5 to 12 μm. The experiments of the pyramid size on the light reflectance, the minority carrier lifetime(MCLT), and the performance of silicon heterojunction(SHJ)solar cells were carried out and analyzed. A desirable range of pyramid sizes was empirically determined by our investigation. In order to reduce the density states on the texturing surface, the wet-chemical smoothing treatment was also investigated. The smoothing treatment improves the passivation quality and the performance of the solar cells. Through pyramid size control and morphology treatment, together with the amorphous silicon(a-Si:H) deposition improvement, and electrode optimization, high performance of SHJ solar cells has been achieved, up to conversion efficiency 23.6%.
基金This work was supported by the National Key R&D Program of China(No.2018YFB1500500)also supported by Ally Fund of Chinese Academy of Sciences(No.Y072051002).
文摘The gradient doping regions were employed in the emitter layer and the base layer of GaAs based laser power converters(LPCs).Silvaco TCAD was used to numerically simulate the linear gradient doping and exponential gradient doping structure,and analyze the transport process of photogenerated carriers.Energy band adjustment via gradient doping improved the separation and transport efficiency of photogenerated carriers and reduced the total recombination rate of GaAs LPCs.Compared with traditional structure of LPCs,the photoelectric conversion efficiency of LPCs with linear and exponential gradient doping structure were improved from 52.7%to 57.2%and 57.7%,respectively,under 808 nm laser light at the power density of 1 W/cm^(2).
基金financially supported by National Natural Science Foundation of China(grant nos.52325406,52374334,and U1860204)Joint Program of Science and Technology Plans in Liaoning Province(grant nos.2023JH2/101700244 and 2023JH2/101800045)+1 种基金Fundamental Research Funds for the Central Universities(grant no.N2430002)Program of Introducing Talents of Discipline to Universities(grant no.B21001).
文摘The role of cerium(Ce)in enhancing the hot ductility of super austenitic stainless steel S32654 at 850–1250℃was systematically unveiled through theoretical calculations and microstructure characterization.The results indicated that Ce microalloying improved the hot ductility of S32654 throughout the entire deformation temperature range.Specifically,the addition of Ce greatly enhanced the hot ductility in the low(850–900℃)and high(1100–1250℃)temperature ranges,but only slightly increased that in the medium temperature range(900–1100℃).At 850–900℃,Ce addition not only reduced the sulfur(S)content and suppressed the S segregation at the grain boundary,but also promoted the formation of slip bands and deformation twins,apparently improving the hot ductility.At 900–1100℃,Ce addition promoted the nucleation of intergranularσphases and dynamic recrystallization(DRX)grains,which have adverse and beneficial effects on the hot ductility,respectively.As the temperature increased,the precipitation tendency presented a first increasing and then decreasing trend around 1000℃,while the DRX gradually increased.Accordingly,the improvement degree of Ce on the hot ductility first weakened and then enhanced.At 1100–1250℃,Ce significantly promoted the DRX to form more fine and uniform deformation structure,thereby remarkably increasing the cracking resistance and then the hot ductility.
基金the National Natural Science Foundation of China and Shenhua Group Corp(No.U1261103)the National Natural Science Foundation of China(Nos.20771080)the Open Fund of State Key Laboratory of Coal Conversion,Institute of Coal Chemistry,Chinese Academy of Sciences,(No.J12-13-913).
文摘First-principles calculations are carried out to examine the adsorption of acetylene over the Pd(111)surface.A hydrogen adsorption system is initially investigated to confirm the reliability of the selected calculation method.Adsorption energies,Mulliken-populations,overlap populations,charge density,and projected density of states(PDOS)are then calculated in the optimised acetylene adsorption system.Results show that C_(2)H_(2) molecule tends to adsorb through the threefold parallel-bridge configuration that is computed to be the most stable.In this structure,the distance of the C-H bond is calculated to be 1.09 Å,and the C-C-H bond angle is 128°.The distance of the C-C bond in acetylene is 1.36 Å,increasing from 1.21 Å in the gas phase.Moreover,the C-C bond overlap population decreases from 1.98 to 1.38,revealing that the carbon configuration in C2H2 rehybridises from sp to sp^(2) and beyond.The obtained results are compared with available experimental studies on acetylene hydrogenation on single-metal surfaces.The PDOS study indicates that a carbonaceous layer may generate on the metal surface during acetylene adsorption.The carbonaceous layer can affect the adsorption and reaction of acetylene,thereby inactivating the metal surface.Our experiments also show that Pd exhibits high catalytic activity.
基金financially supported by the National Natural Science Foundation of China(52104338,U1860204 and 51871159)China Scholarship Council(202006935035)
文摘The inhibition of Mo segregation and phase precipitation is vital for improving the hot workability and corrosion resistance of superaustentic stainless steels(SASS).The boron non-equilibrium segregation of S31254 SASS was implemented through solid solution,air cooling,and diffusion at low-temperature treatment(SADT).The precipitation process and intergranular corrosion(IGC)of S31254 SASS with various boron distributions were researched at a sensitive temperature.The second phases were observed and identified by SEM and TEM.IGC susceptibility was evaluated by double-loop potentiodynamic reactivation(DL-EPR)measurements.The SADT treatment promoted more segregation of B at the grain boundary,leading to lower amounts of grain boundary precipitation before aging for 6 h.The decrease of σ phases in B-regulated samples enhances the IGC resistance,compared with the samples without B addition specimens.
基金Project supported by the National Natural Science Foundation of China(No.61504139,61275040)Chinese Academy of Sciences(No.Y072051002)
文摘A hot spot is a reliability problem in photovoltaic(PV) modules where a mismatched or shaded cell heats up significantly and degrades the PV module output power performance. High PV cell temperature due to a hot spot can damage the cell encapsulate and lead to second breakdown, which both cause permanent damage to the PV module. In present systems, bypass diodes are used to mitigate the hot spot problem. In this work, five commercial polysilicon P V modules configured with different numbers of bypass diodes are used to study the influence of bypass diodes on the reverse bias voltage of a shaded cell and the resulting hot spot phenomenon. The reverse bias voltage of the shaded cell, and the hot spot probability and severity decrease as the number of bypass diodes increases. Negative terminal voltage of a shaded cell accompanied by a switched-off bypass diode are the necessary condition for hot spot generation. In an extreme case where each cell has an individual bypass diode in a P V module, it still cannot avoid the hazards of a hot spot under the shading areas of 5-7 cm2, but the probability of a hot spot is reduced to a minimum of 0.41%.
基金financially supported by the National Natural Science Foundation of China(Nos.U1860204 and 51871159)
文摘The influence of a combined process,involving air cooling and heat treatment at 300℃,on precipitation behavior and corrosion resistance of a S31254-Ce steel was explored through scanning electron microscopy(SEM),energy dispersive X-ray spectrometry(EDS),electron backscatter diffraction(EBSD)and electrochemical analysis.After air cooling and heat treatment at 300℃,the S31254-Ce steel was conducive to the enrichment of Ce along the grain boundary and the content of Σ3 twins in aged samples increased.The composite heat treatment process is beneficial to inhibit the precipitation of precipitates in the aging process and improve the corrosion resistance of S31254-Ce steel.
