Phospho-olivine pristine LiMnPO4/C and yttrium-substituted LiMn1-xYxPO4/C(x=0,0.01,0.03,0.05)were synthesized by a solution combustion method.The effects of Y-doped on structure,morphology and electrochemical performa...Phospho-olivine pristine LiMnPO4/C and yttrium-substituted LiMn1-xYxPO4/C(x=0,0.01,0.03,0.05)were synthesized by a solution combustion method.The effects of Y-doped on structure,morphology and electrochemical performances were investigated.From powder X-ray diffraction pattern,all substituted materials adopt an identical structure to that of the LiMnPO4 olivine structure,suggesting that the yttrium ion was well inco rporated into the crystal lattice,without any changes in the host crystal structure.The electrochemical impedance spectroscopy provides clearly that yttrium-substituting reduces the charge transfer impedance and improves the lithium ion diffusion through the structure.When x=0.01,the material shows an excellent capacity and stability during charge/discharge process.The initial specific discharge capacity can reach up to 156.84 mAh/g at C/20,with a coulombic efficiency of about 96.11%,which is 14%higher than that of the pristine material.The results confirm that the cyclic stability and the electrochemical performances of LiMnPO4/C are highly improved by Y-doping.展开更多
With the continuous development of electronic industry, people’s demand for semiconductor materials is also increasing. How to prepare semiconductor materials with low cost, low energy consumption and high yield has ...With the continuous development of electronic industry, people’s demand for semiconductor materials is also increasing. How to prepare semiconductor materials with low cost, low energy consumption and high yield has become one of the hot spots of research. ZnTe is commonly used in the semiconductor industry due to its superior optoelectronic properties. Electrochemical deposition is one of the most frequently used methods to prepare ZnTe thin films. However,the traditional electrochemical deposition technology has many shortcomings, such as slow deposition rate and poor film quality. These hinder the large-scale promotion of zinc telluride electrochemical deposition technology. To solve the problems encountered in the preparation of semiconductor thin films by conventional electrochemical deposition, and based on the photoconductive properties of semiconductor materials themselves, the basic principles of photoelectrochemistry of semiconductor electrodes, and some characteristics of the electrochemical deposition process of semiconductor materials, the use of photoelectrochemical deposition method for the preparation of semiconductor materials was proposed. Firstly, the electrochemical behaviors(electrode reactions, nucleation growth and charge transport process) of the ZnTe electrodeposition under illumination and dark state conditions were studied. Then, the potentiostatic deposition of ZnTe was carried out under light and dark conditions. The phase structure, morphology and composition of the sediments were studied using X-ray diffractometer, scanning electron microscope and other testing methods. Finally, the photoelectrochemical deposition mechanisms were analyzed. Compared with conventional electrochemical deposition, photoelectrochemical deposition increases the current density during deposition and reduces the charge transfer impedance during ZnTe deposition process. In addition, since light illumination promotes the deposition of the difficult-to-deposit element Zn, the component ratio of ZnTe thin films prepared by photoelectrochemical deposition is closer to 1:1, making it a viable and reliable approach for ZnTe production.展开更多
A homologous series of heterocycles,6-methyl-2-（4-alkoxybenzylidenamino）benzothiazoles,were synthesized and characterized using FT-IR,^1H and ^（13）C NMR and mass spectrometric analysis.Enantiotropic nematic phase ...A homologous series of heterocycles,6-methyl-2-（4-alkoxybenzylidenamino）benzothiazoles,were synthesized and characterized using FT-IR,^1H and ^（13）C NMR and mass spectrometric analysis.Enantiotropic nematic phase was observed for shorter members.Smectic A phase only emerged from octyloxy derivative onwards.The terminal methyl group at the benzothiazole fragment and the Schiff base linkage influenced the mesomorphic behavior of the present series.展开更多
Ultra-thin hafnium-oxide gate dielectric films deposited by atomic layer deposition technique using HfCl4 and H2O precursor on a hydrogen-terminated Si substrate were investigated. X-ray photoelectron spectroscopy ind...Ultra-thin hafnium-oxide gate dielectric films deposited by atomic layer deposition technique using HfCl4 and H2O precursor on a hydrogen-terminated Si substrate were investigated. X-ray photoelectron spectroscopy indicates that the interface layer is Hf-silicate rather than phase separated Hf-silicide and silicon oxide structure. The Hf-silicate interfacial layer partially changes into SiOx after high temperature annealing, resulting in a complex HfO2-silicate-SiOx dielectric structure. Electrical measurements confirms that HfO2 on Si is stable up to 700 ℃ for 30 s under N2 ambient.展开更多
Despite advancements in silicon-based anodes for high-capacity lithium-ion batteries,their widespread commercial adoption is still hindered by significant volume expansion during cycling,especially at high active mass...Despite advancements in silicon-based anodes for high-capacity lithium-ion batteries,their widespread commercial adoption is still hindered by significant volume expansion during cycling,especially at high active mass loadings crucial for practical use.The root of these challenges lies in the mechanical instability of the material,which subsequently leads to the structural failure of the electrode.Here,we present a novel synthesis of a composite combining expanded graphite and silicon nanoparticles.This composite features a unique interlayer-bonded graphite structure,achieved through the application of a modified spark plasma sintering method.Notably,this innovative structure not only facilitates efficient ion and electron transport but also provides exceptional mechanical strength(Vickers hardness:up to658 MPa,Young's modulus:11.6 GPa).This strength effectively accommodates silicon expansion,resulting in an impressive areal capacity of 2.9 mA h cm^(-2)(736 mA h g^(-1)) and a steady cycle life(93% after 100cycles).Such outsta nding performance is paired with features appropriate for large-scale industrial production of silicon batteries,such as active mass loading of at least 3.9 mg cm^(-2),a high-tap density electrode material of 1.68 g cm^(-3)(secondary clusters:1.12 g cm^(-3)),and a production yield of up to 1 kg per day.展开更多
The simultaneous optimization of the bulk and surface characteristics of photoelectrodes is essential to maximize their photoelectrochemical(PEC)performance.We report a novel one-pot hydrothermal synthesis of textured...The simultaneous optimization of the bulk and surface characteristics of photoelectrodes is essential to maximize their photoelectrochemical(PEC)performance.We report a novel one-pot hydrothermal synthesis of textured and surface-reconstructed BiVO_(4)photoanodes(ts-BVO),achieving significant improvements in PEC water splitting.By controlling precursor molarity and ethylene glycol(EG)addition,we developed a stepwise dual reaction(SDR)mechanism,which enables simultaneous bulk texture development and surface reconstruction.The optimized CoBi/ts-BVO photoanode exhibited a photocurrent density of 4.3 mA∙cm^(−2)at 1.23 V vs.reversible hydrogen electrode(RHE)with a high Faradaic efficiency of 98%under one sun illumination.Compared with nontextured BiVO_(4),the charge transport efficiency increased from 8%to 70%,whereas the surface charge transfer efficiency improved from 9%to 85%.These results underscore the critical role of both bulk and surface engineering in enhancing PEC performance.Our findings offer a streamlined approach for improving the intrinsic properties of photoanodes in solar water splitting.展开更多
The thermal conductivity of nanofluids is an important property that influences the heat transfer capabilities of nanofluids.Researchers rely on experimental investigations to explore nanofluid properties,as it is a n...The thermal conductivity of nanofluids is an important property that influences the heat transfer capabilities of nanofluids.Researchers rely on experimental investigations to explore nanofluid properties,as it is a necessary step before their practical application.As these investigations are time and resource-consuming undertakings,an effective prediction model can significantly improve the efficiency of research operations.In this work,an Artificial Neural Network(ANN)model is developed to predict the thermal conductivity of metal oxide water-based nanofluid.For this,a comprehensive set of 691 data points was collected from the literature.This dataset is split into training(70%),validation(15%),and testing(15%)and used to train the ANN model.The developed model is a backpropagation artificial neural network with a 4–12–1 architecture.The performance of the developed model shows high accuracy with R values above 0.90 and rapid convergence.It shows that the developed ANN model accurately predicts the thermal conductivity of nanofluids.展开更多
All-polymer solar cells(all-PSCs)have attracted significant research attention in recent years,primarily due to their advantages of outstanding photo-thermal stability and excellent mechanical flexibility.However,all-...All-polymer solar cells(all-PSCs)have attracted significant research attention in recent years,primarily due to their advantages of outstanding photo-thermal stability and excellent mechanical flexibility.However,all-PSCs typically exhibit complex morphologies during the film formation of blend films,primarily due to the tendency to become en-tangled in polymer chains,negatively impacting their fill fac-tor(FF)and morphology stability.Therefore,the optimization of the morphology of the co-mingled heterojunction is crucial for improving device performance.Recent studies reveal that solid additives(SAs)can realize the excellent regulation of the molecular aggregation state,molecular packing,and domain size of the active layer,which not only improves the exciton dissociation,charge transport and collection process of the device but also ultimately realizes the enhancement of the device efficiency.Therefore,this review provides an in-depth insight into the different mechanisms of solid additives in all-PSCs,offering a comprehensive discussion on the research progress in optimizing the morphology and enhancing mor-phology stability.Finally,we present an outlook for the fur-ther structural modification strategies of solid additives towards better bulk morphology and stability of all-PSCs,paving the way for achieving excellent photo-thermal stability,superior mechanical flexibility,and high-efficiency all-PSCs.展开更多
Magnetism in recently discovered van der Waals materials has opened several avenues in the study of fundamental spin interactions in truly two-dimensions.A paramount question is what effect higher-order interactions b...Magnetism in recently discovered van der Waals materials has opened several avenues in the study of fundamental spin interactions in truly two-dimensions.A paramount question is what effect higher-order interactions beyond bilinear Heisenberg exchange have on the magnetic properties of few-atom thick compounds.Here we demonstrate that biquadratic exchange interactions,which is the simplest and most natural form of non-Heisenberg coupling,assume a key role in the magnetic properties of layered magnets.Using a combination of nonperturbative analytical techniques,non-collinear first-principles methods and classical Monte Carlo calculations that incorporate higher-order exchange,we show that several quantities including magnetic anisotropies,spin-wave gaps and topological spin-excitations are intrinsically renormalized leading to further thermal stability of the layers.展开更多
Within this work,it is studied the photo-thermionic and photocurrent behavior of two kinds of carbon nanotube arrays,grown by chemical vapor deposition.One kind is fabricated by using a co-catalyst bilayer approach an...Within this work,it is studied the photo-thermionic and photocurrent behavior of two kinds of carbon nanotube arrays,grown by chemical vapor deposition.One kind is fabricated by using a co-catalyst bilayer approach and other by a catalyst-free route by using a porous alumina membrane as a template.The carbon nanotubes fabricated by both approaches exhibit low crystallinity.To compute the thermal properties of the nanomaterials,a photothermal experiment was measured at 1064 nm wavelength,and numerical simulations were conducted to analyze the photo-thermionic emission dynamics.The high absorbance of the carbon nanotubes leads to reach temperatures above 1500 K,with time response in the millisecond order and emission currents in the nanoampere range.On the other hand,the photodetector behavior was confirmed by a single pulse experiment that induces fast photocurrent recognition associated to a photodiode.Our results highlighted the coexistence of stable states related to high-power and high-speed electronic conversion energy dependent on the growth mechanism of carbon nanotubes.展开更多
文摘Phospho-olivine pristine LiMnPO4/C and yttrium-substituted LiMn1-xYxPO4/C(x=0,0.01,0.03,0.05)were synthesized by a solution combustion method.The effects of Y-doped on structure,morphology and electrochemical performances were investigated.From powder X-ray diffraction pattern,all substituted materials adopt an identical structure to that of the LiMnPO4 olivine structure,suggesting that the yttrium ion was well inco rporated into the crystal lattice,without any changes in the host crystal structure.The electrochemical impedance spectroscopy provides clearly that yttrium-substituting reduces the charge transfer impedance and improves the lithium ion diffusion through the structure.When x=0.01,the material shows an excellent capacity and stability during charge/discharge process.The initial specific discharge capacity can reach up to 156.84 mAh/g at C/20,with a coulombic efficiency of about 96.11%,which is 14%higher than that of the pristine material.The results confirm that the cyclic stability and the electrochemical performances of LiMnPO4/C are highly improved by Y-doping.
基金Project(51774341) supported by the National Natural Science Foundation of ChinaProject(2018GK4001) supported by the Science and Technology Tackling and Transformation of Major Scientific and Technological Achievements Project of Hunan Province,China。
文摘With the continuous development of electronic industry, people’s demand for semiconductor materials is also increasing. How to prepare semiconductor materials with low cost, low energy consumption and high yield has become one of the hot spots of research. ZnTe is commonly used in the semiconductor industry due to its superior optoelectronic properties. Electrochemical deposition is one of the most frequently used methods to prepare ZnTe thin films. However,the traditional electrochemical deposition technology has many shortcomings, such as slow deposition rate and poor film quality. These hinder the large-scale promotion of zinc telluride electrochemical deposition technology. To solve the problems encountered in the preparation of semiconductor thin films by conventional electrochemical deposition, and based on the photoconductive properties of semiconductor materials themselves, the basic principles of photoelectrochemistry of semiconductor electrodes, and some characteristics of the electrochemical deposition process of semiconductor materials, the use of photoelectrochemical deposition method for the preparation of semiconductor materials was proposed. Firstly, the electrochemical behaviors(electrode reactions, nucleation growth and charge transport process) of the ZnTe electrodeposition under illumination and dark state conditions were studied. Then, the potentiostatic deposition of ZnTe was carried out under light and dark conditions. The phase structure, morphology and composition of the sediments were studied using X-ray diffractometer, scanning electron microscope and other testing methods. Finally, the photoelectrochemical deposition mechanisms were analyzed. Compared with conventional electrochemical deposition, photoelectrochemical deposition increases the current density during deposition and reduces the charge transfer impedance during ZnTe deposition process. In addition, since light illumination promotes the deposition of the difficult-to-deposit element Zn, the component ratio of ZnTe thin films prepared by photoelectrochemical deposition is closer to 1:1, making it a viable and reliable approach for ZnTe production.
基金Universiti Tunku Abdul Rahman and Ministry of Higher Education (MOHE) for the financial supports via LRGS(No.LR003-2011A)and research facilities
文摘A homologous series of heterocycles,6-methyl-2-（4-alkoxybenzylidenamino）benzothiazoles,were synthesized and characterized using FT-IR,^1H and ^（13）C NMR and mass spectrometric analysis.Enantiotropic nematic phase was observed for shorter members.Smectic A phase only emerged from octyloxy derivative onwards.The terminal methyl group at the benzothiazole fragment and the Schiff base linkage influenced the mesomorphic behavior of the present series.
文摘Ultra-thin hafnium-oxide gate dielectric films deposited by atomic layer deposition technique using HfCl4 and H2O precursor on a hydrogen-terminated Si substrate were investigated. X-ray photoelectron spectroscopy indicates that the interface layer is Hf-silicate rather than phase separated Hf-silicide and silicon oxide structure. The Hf-silicate interfacial layer partially changes into SiOx after high temperature annealing, resulting in a complex HfO2-silicate-SiOx dielectric structure. Electrical measurements confirms that HfO2 on Si is stable up to 700 ℃ for 30 s under N2 ambient.
基金supported by the National Research Foundation, Prime Minister’s Office, Singapore, under its Competitive Research Programme (CRP award number NRF-CRP22-2019-008)Medium-Sized Centre Programme (CA2DM)+1 种基金the Ministry of Education of Singapore, under its Research Centre of Excellence award to the Institute for Functional Intelligent Materials (I-FIM, Project No. EDUNC-33-18-279-V12)by the EDB Singapore, under its Space Technology Development Programme (S2219013-STDP)。
文摘Despite advancements in silicon-based anodes for high-capacity lithium-ion batteries,their widespread commercial adoption is still hindered by significant volume expansion during cycling,especially at high active mass loadings crucial for practical use.The root of these challenges lies in the mechanical instability of the material,which subsequently leads to the structural failure of the electrode.Here,we present a novel synthesis of a composite combining expanded graphite and silicon nanoparticles.This composite features a unique interlayer-bonded graphite structure,achieved through the application of a modified spark plasma sintering method.Notably,this innovative structure not only facilitates efficient ion and electron transport but also provides exceptional mechanical strength(Vickers hardness:up to658 MPa,Young's modulus:11.6 GPa).This strength effectively accommodates silicon expansion,resulting in an impressive areal capacity of 2.9 mA h cm^(-2)(736 mA h g^(-1)) and a steady cycle life(93% after 100cycles).Such outsta nding performance is paired with features appropriate for large-scale industrial production of silicon batteries,such as active mass loading of at least 3.9 mg cm^(-2),a high-tap density electrode material of 1.68 g cm^(-3)(secondary clusters:1.12 g cm^(-3)),and a production yield of up to 1 kg per day.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(No.RS-2024-00335976)supported by the Korea Institute of Energy Technology Evaluation Planning(KETEP)from the Ministry of Trade,Industry,Energy(No.20214000000680).
文摘The simultaneous optimization of the bulk and surface characteristics of photoelectrodes is essential to maximize their photoelectrochemical(PEC)performance.We report a novel one-pot hydrothermal synthesis of textured and surface-reconstructed BiVO_(4)photoanodes(ts-BVO),achieving significant improvements in PEC water splitting.By controlling precursor molarity and ethylene glycol(EG)addition,we developed a stepwise dual reaction(SDR)mechanism,which enables simultaneous bulk texture development and surface reconstruction.The optimized CoBi/ts-BVO photoanode exhibited a photocurrent density of 4.3 mA∙cm^(−2)at 1.23 V vs.reversible hydrogen electrode(RHE)with a high Faradaic efficiency of 98%under one sun illumination.Compared with nontextured BiVO_(4),the charge transport efficiency increased from 8%to 70%,whereas the surface charge transfer efficiency improved from 9%to 85%.These results underscore the critical role of both bulk and surface engineering in enhancing PEC performance.Our findings offer a streamlined approach for improving the intrinsic properties of photoanodes in solar water splitting.
基金supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(2021R1A6A1A10044950).
文摘The thermal conductivity of nanofluids is an important property that influences the heat transfer capabilities of nanofluids.Researchers rely on experimental investigations to explore nanofluid properties,as it is a necessary step before their practical application.As these investigations are time and resource-consuming undertakings,an effective prediction model can significantly improve the efficiency of research operations.In this work,an Artificial Neural Network(ANN)model is developed to predict the thermal conductivity of metal oxide water-based nanofluid.For this,a comprehensive set of 691 data points was collected from the literature.This dataset is split into training(70%),validation(15%),and testing(15%)and used to train the ANN model.The developed model is a backpropagation artificial neural network with a 4–12–1 architecture.The performance of the developed model shows high accuracy with R values above 0.90 and rapid convergence.It shows that the developed ANN model accurately predicts the thermal conductivity of nanofluids.
基金the sponsorship of the Lee Shau-Kee Chair Professor (Materials Science)the support from the APRC Grant of the City University of Hong Kong (9380086, 9610419, 9610492, 9610508)+10 种基金the TCFS Grant (GHP/018/20SZ)MRP Grant (MRP/040/21X) from the Innovation and Technology Commission of Hong Kongthe Green Tech Fund (202020164) from the Environment and Ecology Bureau of Hong Kongthe GRF Grant (11307621, 11316422) from the Research Grants Council of Hong Kongthe CRF Grant (C6023-19GF) from the Research Grants Council of Hong Kongthe Shenzhen Science and Technology Program (SGDX20201103095412040)the Guangzhou Huangpu Technology Bureau (2022GH02)the Guangdong Major Project of Basic and Applied Basic Research (2019B030302007)the financial support of Hong Kong Scholar Program (XJ2021-038)the Young Talent Fund of Xi′an Association for Science and Technology (959202313080)the financial support of the Postgraduate Innovation and Practical Ability Training Program of Xi′an Shiyou University (YCS23212024)。
文摘All-polymer solar cells(all-PSCs)have attracted significant research attention in recent years,primarily due to their advantages of outstanding photo-thermal stability and excellent mechanical flexibility.However,all-PSCs typically exhibit complex morphologies during the film formation of blend films,primarily due to the tendency to become en-tangled in polymer chains,negatively impacting their fill fac-tor(FF)and morphology stability.Therefore,the optimization of the morphology of the co-mingled heterojunction is crucial for improving device performance.Recent studies reveal that solid additives(SAs)can realize the excellent regulation of the molecular aggregation state,molecular packing,and domain size of the active layer,which not only improves the exciton dissociation,charge transport and collection process of the device but also ultimately realizes the enhancement of the device efficiency.Therefore,this review provides an in-depth insight into the different mechanisms of solid additives in all-PSCs,offering a comprehensive discussion on the research progress in optimizing the morphology and enhancing mor-phology stability.Finally,we present an outlook for the fur-ther structural modification strategies of solid additives towards better bulk morphology and stability of all-PSCs,paving the way for achieving excellent photo-thermal stability,superior mechanical flexibility,and high-efficiency all-PSCs.
基金EJGS acknowledges computational resources through the UK Materials and Molecular Modelling Hub for access to THOMAS supercluster,which is partially funded by EPSRC(EP/P020194/1)CIRRUS Tier-2 HPC Service(ec131 Cirrus Project)at http://www.cirrus.ac.uk EPCC funded by the University of Edinburgh and EPSRC(EP/P020267/1)+2 种基金ARCHER UK National Supercomputing Service(http://www.archer.ac.uk)via Project d429EJGS acknowledges the EPSRC Early Career Fellowship(EP/T021578/1)the University of Edinburgh for funding support.
文摘Magnetism in recently discovered van der Waals materials has opened several avenues in the study of fundamental spin interactions in truly two-dimensions.A paramount question is what effect higher-order interactions beyond bilinear Heisenberg exchange have on the magnetic properties of few-atom thick compounds.Here we demonstrate that biquadratic exchange interactions,which is the simplest and most natural form of non-Heisenberg coupling,assume a key role in the magnetic properties of layered magnets.Using a combination of nonperturbative analytical techniques,non-collinear first-principles methods and classical Monte Carlo calculations that incorporate higher-order exchange,we show that several quantities including magnetic anisotropies,spin-wave gaps and topological spin-excitations are intrinsically renormalized leading to further thermal stability of the layers.
基金CONICYT-ANID for FONDECYT grants 3190552(JAGM),and 3201030(RV)National Doctoral Scholarship 1201589(LFI),and FONDEQUIP projects EQM150101 and EQM140142 for partial financial support.Alsothe support of the Chilean Ministry of Economy through the Millennium Nucleus MULTIMAT e ICM/MINECOM.
文摘Within this work,it is studied the photo-thermionic and photocurrent behavior of two kinds of carbon nanotube arrays,grown by chemical vapor deposition.One kind is fabricated by using a co-catalyst bilayer approach and other by a catalyst-free route by using a porous alumina membrane as a template.The carbon nanotubes fabricated by both approaches exhibit low crystallinity.To compute the thermal properties of the nanomaterials,a photothermal experiment was measured at 1064 nm wavelength,and numerical simulations were conducted to analyze the photo-thermionic emission dynamics.The high absorbance of the carbon nanotubes leads to reach temperatures above 1500 K,with time response in the millisecond order and emission currents in the nanoampere range.On the other hand,the photodetector behavior was confirmed by a single pulse experiment that induces fast photocurrent recognition associated to a photodiode.Our results highlighted the coexistence of stable states related to high-power and high-speed electronic conversion energy dependent on the growth mechanism of carbon nanotubes.
