Electrochemical impedance spectroscopy(EIS)is a widely used technique to monitor the electrical properties of a catalyst under electrocatalytic conditions.Although it is extensively used for research in electrocatalys...Electrochemical impedance spectroscopy(EIS)is a widely used technique to monitor the electrical properties of a catalyst under electrocatalytic conditions.Although it is extensively used for research in electrocatalysis,its effectiveness and power have not been fully harnessed to elucidate complex interfacial processes.Herein,we use the frequency dispersion parameter,n,which is extracted from EIS measurements(C_(s)=af^(n+1),-2<n<-1),to describe the dispersion characteristics of capacitance and interfacial properties of Co_(3)O_(4) before the onset of oxygen evolution reaction(OER)in alkaline conditions.We first prove that the n-value is sensitive to the interfacial electronic changes associated with Co redox processes and surface reconstruction.The n-value decreases by increasing the specific/active surface area of the catalysts.We further modify the interfacial properties by changing different components,i.e.,replacing the proton with deuterium,adding ethanol as a new oxidant,and changing the cation in the electrolyte.Intriguingly,the n-value can identify different influences on the interfacial process of proton transfer,the decrease and blocking of oxidized Co species,and the interfacial water structure.We demonstrate that the n-value extracted from EIS measurements is sensitive to the kinetic isotope effect,electrolyte cation,adsorbate surface coverage of oxidized Co species,and the interfacial water structure.Thus,it can be helpful to differentiate the multiple factors affecting the catalyst interface.These findings convey that the frequency dispersion of capacitance is a convenient and useful method to uncover the interfacial properties under electrocatalytic conditions,which helps to advance the understanding of the interfaceactivity relationship.展开更多
Vanadium nitride(VN)is a promising pseudocapacitive material due to the high theoretical capacity,rapid redox Faradaic kinetics,and appropriate potential window.Although VN shows large pseudocapacitance in alkaline el...Vanadium nitride(VN)is a promising pseudocapacitive material due to the high theoretical capacity,rapid redox Faradaic kinetics,and appropriate potential window.Although VN shows large pseudocapacitance in alkaline electrolytes,the electrochemical instability and capacity degradation of VN electrode materials present significant challenges for practical applications.Herein,the capacitance decay mechanism of VN is investigated and a simple strategy to improve cycling stability of VN supercapacitor electrodes is proposed by introducing VO_(4)^(3-)anion in KOH electrolytes.Our results show that the VN electrode is electrochemical stabilization between-1.0and-0.4 V(vs.Hg/Hg O reference electrode)in 1.0 MKOH electrolyte,but demonstrates irreversible oxidation and fast capacitance decay in the potential range of-0.4 to0 V.In situ electrochemical measurements reveal that the capacitance decay of VN from-0.4 to 0 V is ascribed to the irreversible oxidation of vanadium(V)of N–V–O species by oxygen(O)of OH^(-).The as-generated oxidization species are subsequently dissolved into KOH electrolytes,thereby undermining the electrochemical stability of VN.However,this irreversible oxidation process could be hindered by introducing VO_(4)^(3-)in KOH electrolytes.A high volumetric specific capacitance of671.9 F.cm^(-3)(1 A.cm^(-3))and excellent cycling stability(120.3%over 1000 cycles)are achieved for VN nanorod electrode in KOH electrolytes containing VO_(4)^(3-).This study not only elucidates the failure mechanism of VN supercapacitor electrodes in alkaline electrolytes,but also provides new insights into enhancing pseudocapacitive energy storage of VN-based electrode materials.展开更多
The development of high-performance,reproducible carbon(C)-based supercapacitors remains a significant challenge because of limited specific capacitance.Herein,we present a novel strategy for fabricating LaCoO_(x) and...The development of high-performance,reproducible carbon(C)-based supercapacitors remains a significant challenge because of limited specific capacitance.Herein,we present a novel strategy for fabricating LaCoO_(x) and cobalt(Co)-doped nanoporous C(LaCoO_(x)/Co@ZNC)through the carbonization of Co/Zn-zeolitic imidazolate framework(ZIF)crystals derived from a PVP-Co/Zn/La precursor.The unique ZIF structure effectively disrupted the graphitic C framework,preserved the Co active sites,and enhanced the electrical conductivity.The synergistic interaction between pyridinic nitrogen and Co ions further promoted redox reactions.In addition,the formation of a hierarchical pore structure through zinc sublimation facili-tated electrolyte diffusion.The resulting LaCoO_(x)/Co@ZNC exhibited exceptional electrochemical performance,delivering a remarkable specific capacitance of 2,789 F/g at 1 A/g and outstanding cycling stability with 92%capacitance retention after 3,750 cycles.Our findings provide the basis for a promising approach to advancing C-based energy storage technologies.展开更多
Noise is inevitable in electrical capacitance tomography(ECT)measurements.This paper describes the influence of noise on ECT performance for measuring gas-solids fluidized bed characteristics.The noise distribution is...Noise is inevitable in electrical capacitance tomography(ECT)measurements.This paper describes the influence of noise on ECT performance for measuring gas-solids fluidized bed characteristics.The noise distribution is approximated by the Gaussian distribution and added to experimental capacitance data with various intensities.The equivalent signal strength(Ф)that equals the signal-to-noise ratio of packed beds is used to evaluate noise levels.Results show that the Pearson correlation coefficient,which indicates the similarity of solids fraction distributions over pixels,increases with Ф,and reconstructed images are more deteriorated at lower Ф.Nevertheless,relative errors for average solids fraction and bubble size in each frame are less sensitive to noise,attributed to noise compromise caused by the process of pixel values.These findings provide useful guidance for assessing the accuracy of ECT measurements of multiphase flows.展开更多
During oilfield development,a comprehensive model for assessing inter-well connectivity and connected volume within reservoirs is crucial.Traditional capacitance(TC)models,widely used in inter-well data analysis,face ...During oilfield development,a comprehensive model for assessing inter-well connectivity and connected volume within reservoirs is crucial.Traditional capacitance(TC)models,widely used in inter-well data analysis,face challenges when dealing with rapidly changing reservoir conditions over time.Additionally,TC models struggle with complex,random noise primarily caused by measurement errors in production and injection rates.To address these challenges,this study introduces a dynamic capacitance(SV-DC)model based on state variables.By integrating the extended Kalman filter(EKF)algorithm,the SV-DC model provides more flexible predictions of inter-well connectivity and time-lag efficiency compared to the TC model.The robustness of the SV-DC model is verified by comparing relative errors between preset and calculated values through Monte Carlo simulations.Sensitivity analysis was performed to compare the model performance with the benchmark,using the Qinhuangdao Oilfield as a case study.The results show that the SV-DC model accurately predicts water breakthrough times.Increases in the liquid production index and water cut in two typical wells indicate the development time of ineffective circulation channels,further confirming the accuracy and reliability of the model.The SV-DC model offers significant advantages in addressing complex,dynamic oilfield production scenarios and serves as a valuable tool for the efficient and precise planning and management of future oilfield developments.展开更多
Neodymium chromium oxide(NdCrO_(3))and NdCrO_(3)/graphene oxide(GO)nanocomposite were synthesized via sol-gel and co-precipitation techniques for being used in high-perfo rmance supercapacitors and for the possible ap...Neodymium chromium oxide(NdCrO_(3))and NdCrO_(3)/graphene oxide(GO)nanocomposite were synthesized via sol-gel and co-precipitation techniques for being used in high-perfo rmance supercapacitors and for the possible application in ultraviolet(UV)materials.Herein the systematic synthesis approach was adopted,which enhances the optical and electrical properties of the grown wide band-gap composite nanomaterial.Structural characterization of the grown materials was attempted using X-ray diffraction(XRD)and scanning electron microscopy(SEM).Most importantly the electrochemical analysis of the grown samples was carried out by employing a glassy carbon electrode and 3 mol/L KOH electrolyte,which demonstrates significant improvements in a specific capacitance of approximately360 F/g,an energy density of approximately 18 Wh/kg,and a maximum power density of approximately 257 W/kg,respectively.Moreover,NdCrO_(3)/GO nanocomposite maintains a cyclic stability of 97.6%after4000 cycles.Photoluminescence(PL)spectroscopy confirms the wide bandgap nature of the NdCrO_(3)and NdCrO_(3)/GO nanocomposite,indicating its potential application in UVC devices.These findings emphasize the potential of the NdCrO_(3)/GO nanocomposite in advancing efficient energy storage solutions and the possibility of being used in UVC technology.展开更多
Transient negative capacitance(NC),as an available dynamic charge effect achieved in resistor-ferroelectric capacitor(R-FEC)circuits,has triggered a series of theoretical and experimental works focusing on its physica...Transient negative capacitance(NC),as an available dynamic charge effect achieved in resistor-ferroelectric capacitor(R-FEC)circuits,has triggered a series of theoretical and experimental works focusing on its physical mechanism and device application.Here,we analytically derived the effects of different mechanical conditions on the transient NC behaviors in the R-FEC circuit based on the phenomenological model.It shows that the ferroelectric capacitor can exhibit either NC(i.e.,“single NC”and“double NC”)or positive capacitance,depending on the mechanical condition and temperature.Further numerical calculations show that the voltage drop caused by NC can be effectively controlled by temperature,applied stress,or strain.The relationship between NC voltage drop and system configurations including external resistance,dynamical coefficient of polarization,and input voltage are presented,showing diverse strategies to manipulate the NC effect.These results provide theoretical guidelines for rational design and efficient control of NC-related electronic devices.展开更多
The negative ion based neutral beam injector(NNBI)with a beam energy of 400 keV is one of the subsystems at the Comprehensive Research fAcility for Fusion Technology(CRAFT)in China.The distributed capacitance of the h...The negative ion based neutral beam injector(NNBI)with a beam energy of 400 keV is one of the subsystems at the Comprehensive Research fAcility for Fusion Technology(CRAFT)in China.The distributed capacitance of the high-voltage components is an important basis for the design of surge suppression devices at CRAFT NNBI.This study conducted calculations of distributed capacitance for the key components,including the high-voltage deck,transmission line and isolation transformer in the power supply system using the finite element method.The relationship between the high-voltage deck(HVD)distributed capacitance and the distance from the wall is discussed.The differences in distributed capacitance and energy storage between noncoaxial and coaxial transmission lines are also debated.Finally,the capacitance between the primary and secondary windings of the-400 kV isolation transformer,as well as between the secondary winding and the oil tank casing,was calculated.展开更多
Graphene-based frameworks suffer from a low quantum capacitance due to graphene’s Dirac point at the Fermi level.This theoretical study investigated the effect structural defects,nitrogen and boron doping,and surface...Graphene-based frameworks suffer from a low quantum capacitance due to graphene’s Dirac point at the Fermi level.This theoretical study investigated the effect structural defects,nitrogen and boron doping,and surface epoxy/hydroxy groups have on the electronic structure and capacitance of graphene.Density functional theory calculations reveal that the lowest energy configurations for nitrogen or boron substitutional doping occur when the dopant atoms are segregated.This elucidates why the magnetic transition for nitrogen doping is experimentally only observed at higher doping levels.We also highlight that the lowest energy configuration for a single vacancy defect is magnetic.Joint density functional theory calculations show that the fixed band approximation becomes increasingly inaccurate for electrolytes with lower dielectric constants.The introduction of structural defects rather than nitrogen or boron substitutional doping,or the introduction of adatoms leads to the largest increase in density of states and capacitance around graphene’s Dirac point.However,the presence of adatoms or substitutional doping leads to a larger shift of the potential of zero charge away from graphene’s Dirac point.展开更多
Microbial electrochemical systems are a promising green and sustainable technology that can transform waste into electricity.Improving conversion efficiency and lowering system costs,particularly for elec-trodes,are t...Microbial electrochemical systems are a promising green and sustainable technology that can transform waste into electricity.Improving conversion efficiency and lowering system costs,particularly for elec-trodes,are the primary directions that promote practical application.Cellulose sponges made from wood pulp have been industrially mass-produced in various application scenarios due to their porosity and green sustainability.In this study,the three-dimensional(3D)porous cellulose sponges carbon(CSC)was obtained by directly carbonizing cellulose sponges at different temperatures(600,700,800,900,1000,and 1100℃).It has been successfully used as a high-performance anode in microbial fuel cells(MFCs).The carbonization temperature significantly impacted the materials’specific surface area,con-ductivity,and capacitance.The greater the anode material’s carbonization temperature,the lower the charge transfer resistance and the higher the maximum power density(CSC-1100,4.1±0.1 W m^(-2)).The CSC-700's maximum power density(3.62±0.11 W m^(-2))was the highest power density reported to date among lignocellulose-based anodes with relatively low energy consumption.The pleated multilayer porous surface promotes microbial adhesion and can build thicker biofilms with the highest biomass of 2661±117μg cm^(-2)(CSC-1100)and containing 86%electrogenic bacteria(Geobacter).To investigate the effect of conducting polymers on the material’s surface,we introduced polyaniline and polypyrrole.We found that the CSC-1000/PPy bioanodes produced a maximum power density(4.18±0.05 W m^(-2)),slightly higher than of without polypyrrole-modified(CSC-1000,3.99±0.06 W m^(-2)),indicating that the CSCs anode surface had excellent electron transfer efficiency and could achieve the same amount of energy as the polypyrrole surface.This study introduced a promising method for fabricating high-performance anodes using low-cost,industrialized,and sustainable materials.展开更多
Developing anode materials with high specific/volumetric capacities,high-rate capability,long-term cycles and low cost is significant for advanced sodium-ion storage.Herein,we report the hybrid TiO_(2)/graphite(TiO_(2...Developing anode materials with high specific/volumetric capacities,high-rate capability,long-term cycles and low cost is significant for advanced sodium-ion storage.Herein,we report the hybrid TiO_(2)/graphite(TiO_(2)/G)anodes for fast(dis)charging sodium-ion storage.Taking advantage of the rapid pseudocapacitive surface-redox on anatase TiO_(2)nanoparticles(NPs)and fast[Na(diglyme)_(x)]^(+)co-intercalation into graphite,the hybrid anodes display excellent rate capabilities.Additionally,the TiO_(2)NPs are able to fill into the interspaces among graphite flakes and the graphite provides continuous electron pathways,which largely boosts the volumetric capacities and rate performance.展开更多
Applications for quanta and space sensing both depend on efficient low-light imaging.To precisely optimize and design image sensor pixels for these applications,it is crucial to analyze the mechanisms behind dark curr...Applications for quanta and space sensing both depend on efficient low-light imaging.To precisely optimize and design image sensor pixels for these applications,it is crucial to analyze the mechanisms behind dark current generation,considering factors such as temperature,trap cross-section and trap concentration.The thresholds for these generating effects are computed using optoelectrical technology computer aided design(TCAD)simulations,and the ensuing changes in pinned photo-diode(PPD)dynamic capacitance are observed.Various generation models along with an interfacial trap model are used to compare PPD capacitance fluctuations during light and dark environments.With the use of this comparison study,current compact models of complementary metal oxide semiconductor(CMOS)image sensors can be modified to accurately capture the impacts of dark current in low-light conditions.The model developed through this study demonstrates a deviation of only 6.85%from the behavior observed in physical devices.These results not only enhance our understanding of dark current generation mechanisms but also offer practical applications by improving the performance and accuracy of image sensors.展开更多
In view of drastic possible changes in fuze environment tempera- ture,a kind of temperature autocompensated detecting circuit for the capaci- tance fuze is proposed.It provides a steady detected output when the envi- ...In view of drastic possible changes in fuze environment tempera- ture,a kind of temperature autocompensated detecting circuit for the capaci- tance fuze is proposed.It provides a steady detected output when the envi- ronment temperature varies from-50℃ to 65℃ and keeps a stable detecting sensitivity.Based on an analysis of the circuit,influence of the major param- eters of the oscillating circuit on the amplitude are explored.A few impor- tant controllable parameters affecting the circuit feature are found out.A parameter-control method is given in order to improve the circuit perfor- mance.展开更多
A distributed capacitance model for monolithic inductors is developed to predict the equivalently parasitical capacitances of the inductor.The ratio of the self-resonant frequency (f SR) of the differential-driven sym...A distributed capacitance model for monolithic inductors is developed to predict the equivalently parasitical capacitances of the inductor.The ratio of the self-resonant frequency (f SR) of the differential-driven symmetric inductor to the f SR of the single-ended driven inductor is firstly predicted and explained.Compared with a single-ended configuration,experimental data demonstrate that the differential inductor offers a 127% greater maximum quality factor and a broader range of operating frequencies.Two differential inductors with low parasitical capacitance are developed and validated.展开更多
Parasitic capacitances associated with overhangs of the T-shape-gate enhancement-mode(E-mode)GaN-based power device,were investigated by frequency/voltage-dependent capacitance-voltage and inductive-load switching mea...Parasitic capacitances associated with overhangs of the T-shape-gate enhancement-mode(E-mode)GaN-based power device,were investigated by frequency/voltage-dependent capacitance-voltage and inductive-load switching measurements.The overhang capacitances induce a pinch-off voltage distinguished from that of the E-mode channel capacitance in the gate capacitance and the gatedrain capacitance characteristic curves.Frequency-and voltage-dependent tests confirm the instability caused by the trapping of interface/bulk states in the LPCVD-SiNx passivation dielectric.Circuit-level double pulse measurement also reveals its impact on switching transition for power switching applications.展开更多
For establishing the equation of the capacitive target detection accurately, the distributing characteristics of the charges on the bomb body with capacitance fuze were explored. Continuous charges were analyzed disp...For establishing the equation of the capacitive target detection accurately, the distributing characteristics of the charges on the bomb body with capacitance fuze were explored. Continuous charges were analyzed dispersively. Based on the Coulomb's law, the dynamic equilibrium equations of the inducing charges on the bomb body were set up. For the four cases of d 0/L (the ratio between the electrode distance and the bomb length), the curves of the charge's distribution were given. It was concluded that: ① the charge density decreases steadily from the end near the frontal electrode to the bomb tail; ② the declining rate of the density is governed by d 0/L , the larger the value of d 0/L ,the higher the declining rate, and vice versa.展开更多
For a detector in a capacitanee fuze working in an electrostatic field, the bomblength (effective length of the conductor part) is an important factor affecting the sensitivityof detection. For the two different kinds...For a detector in a capacitanee fuze working in an electrostatic field, the bomblength (effective length of the conductor part) is an important factor affecting the sensitivityof detection. For the two different kinds of detecting circuit models in general use (the frequency-sensitive and the amplitude-coupling ), mechanism of the effect of bomblength on the sensitvity of detection is analyzed. Through the analysis a conclusion in fullagreement with experimental results has been drawn, that is. the longer the bomb length,the higher the sensitivity, on the condition that the sizes and the sites of the detecting electrodes and bomb diameter remain unchanged.展开更多
The finite element method is first introduced into the design process of detecting electrodes of three electrode capacitance fuze, the mutual capacitance of the fuze and target is calculated by the finite element met...The finite element method is first introduced into the design process of detecting electrodes of three electrode capacitance fuze, the mutual capacitance of the fuze and target is calculated by the finite element method, which provides the parameters for simulation circuit and design of detecting electrode. The finite element method pierces the traditional method of designing detecting electrode-design, test and adjustment. The system capacitance can be calculated accurately and the performance can be predicted in the design period of the detecting electrode, which saves a lot of research fee. The capacitances of a mortar shell fuze above ground 2 m and lower are given. After putting the computing data into simulating circuit, the demodulation voltage can be obtained, its changing trend is in agreement with the tested result.展开更多
An improved method of extracting the coupling capacitances of quantum dot structure is reported. This method is based on measuring the charge transfer current in the silicon nanowire metal-oxide-semiconductor field-ef...An improved method of extracting the coupling capacitances of quantum dot structure is reported. This method is based on measuring the charge transfer current in the silicon nanowire metal-oxide-semiconductor field-effect transistor （MOSFET）, in which the channel closing and opening are controlled by applying alternating-current biases with a half period phase shift to the dual lower gates. The capacitances around the dot, including fringing capacitances and barrier capacitances, are obtained by analyzing the relation between the transfer current and the applied voltage. This technique could be used to extract the capacitance parameters not only from the bulk silicon devices, but also from the silicon-on-insulator （SOI） MOSFETs.展开更多
This paper reports that metal-oxide-semiconductor （MOS） capacitors with a single layer of Ni nanopartictes were successfully fabricated by using electron-beam evaporation and rapid thermal annealing for application ...This paper reports that metal-oxide-semiconductor （MOS） capacitors with a single layer of Ni nanopartictes were successfully fabricated by using electron-beam evaporation and rapid thermal annealing for application to nonvolatile memory. Experimental scanning electron microscopy images showed that Ni nanoparticles of about 5 nm in diameter were clearly embedded in the SiO2 layer on p-type Si （100）. Capacitance-voltage measurements of the MOS capacitor show large flat-band voltage shifts of 1.8 V, which indicate the presence of charge storage in the nickel nanoparticles. In addition, the charge-retention characteristics of MOS capacitors with Ni nanoparticles were investigated by using capacitance-time measurements. The results showed that there was a decay of the capacitance embedded with Ni nanoparticles for an electron charge after 104 s. But only a slight decay of the capacitance originating from hole charging was observed. The present results indicate that this technique is promising for the efficient formation or insertion of metal nanoparticles inside MOS structures.展开更多
基金Swiss National Science Foundation through its PRIM A grant(grant No.PR00P2_193111)the NCCR MARVEL,a National Centre of Competence in Researchfunded by the Swiss National Science Foundation。
文摘Electrochemical impedance spectroscopy(EIS)is a widely used technique to monitor the electrical properties of a catalyst under electrocatalytic conditions.Although it is extensively used for research in electrocatalysis,its effectiveness and power have not been fully harnessed to elucidate complex interfacial processes.Herein,we use the frequency dispersion parameter,n,which is extracted from EIS measurements(C_(s)=af^(n+1),-2<n<-1),to describe the dispersion characteristics of capacitance and interfacial properties of Co_(3)O_(4) before the onset of oxygen evolution reaction(OER)in alkaline conditions.We first prove that the n-value is sensitive to the interfacial electronic changes associated with Co redox processes and surface reconstruction.The n-value decreases by increasing the specific/active surface area of the catalysts.We further modify the interfacial properties by changing different components,i.e.,replacing the proton with deuterium,adding ethanol as a new oxidant,and changing the cation in the electrolyte.Intriguingly,the n-value can identify different influences on the interfacial process of proton transfer,the decrease and blocking of oxidized Co species,and the interfacial water structure.We demonstrate that the n-value extracted from EIS measurements is sensitive to the kinetic isotope effect,electrolyte cation,adsorbate surface coverage of oxidized Co species,and the interfacial water structure.Thus,it can be helpful to differentiate the multiple factors affecting the catalyst interface.These findings convey that the frequency dispersion of capacitance is a convenient and useful method to uncover the interfacial properties under electrocatalytic conditions,which helps to advance the understanding of the interfaceactivity relationship.
基金financially supported by the National Natural Science Foundation of China(No.U2004210)Application Foundation Frontier Project of Wuhan Science and Technology Program(No.2020010601012199)City University of Hong Kong Strategic Research Grant,Hong Kong,China(No.7005505)。
文摘Vanadium nitride(VN)is a promising pseudocapacitive material due to the high theoretical capacity,rapid redox Faradaic kinetics,and appropriate potential window.Although VN shows large pseudocapacitance in alkaline electrolytes,the electrochemical instability and capacity degradation of VN electrode materials present significant challenges for practical applications.Herein,the capacitance decay mechanism of VN is investigated and a simple strategy to improve cycling stability of VN supercapacitor electrodes is proposed by introducing VO_(4)^(3-)anion in KOH electrolytes.Our results show that the VN electrode is electrochemical stabilization between-1.0and-0.4 V(vs.Hg/Hg O reference electrode)in 1.0 MKOH electrolyte,but demonstrates irreversible oxidation and fast capacitance decay in the potential range of-0.4 to0 V.In situ electrochemical measurements reveal that the capacitance decay of VN from-0.4 to 0 V is ascribed to the irreversible oxidation of vanadium(V)of N–V–O species by oxygen(O)of OH^(-).The as-generated oxidization species are subsequently dissolved into KOH electrolytes,thereby undermining the electrochemical stability of VN.However,this irreversible oxidation process could be hindered by introducing VO_(4)^(3-)in KOH electrolytes.A high volumetric specific capacitance of671.9 F.cm^(-3)(1 A.cm^(-3))and excellent cycling stability(120.3%over 1000 cycles)are achieved for VN nanorod electrode in KOH electrolytes containing VO_(4)^(3-).This study not only elucidates the failure mechanism of VN supercapacitor electrodes in alkaline electrolytes,but also provides new insights into enhancing pseudocapacitive energy storage of VN-based electrode materials.
基金supported financially by National Natural Science Foundation of China(NSFC)(Nos.22478115,22075083)the Programme of Introducing Talents of Discipline to Universities(No.B16017).
文摘The development of high-performance,reproducible carbon(C)-based supercapacitors remains a significant challenge because of limited specific capacitance.Herein,we present a novel strategy for fabricating LaCoO_(x) and cobalt(Co)-doped nanoporous C(LaCoO_(x)/Co@ZNC)through the carbonization of Co/Zn-zeolitic imidazolate framework(ZIF)crystals derived from a PVP-Co/Zn/La precursor.The unique ZIF structure effectively disrupted the graphitic C framework,preserved the Co active sites,and enhanced the electrical conductivity.The synergistic interaction between pyridinic nitrogen and Co ions further promoted redox reactions.In addition,the formation of a hierarchical pore structure through zinc sublimation facili-tated electrolyte diffusion.The resulting LaCoO_(x)/Co@ZNC exhibited exceptional electrochemical performance,delivering a remarkable specific capacitance of 2,789 F/g at 1 A/g and outstanding cycling stability with 92%capacitance retention after 3,750 cycles.Our findings provide the basis for a promising approach to advancing C-based energy storage technologies.
基金National Key Research and Development Program of China(2021YFA1501302)the National Natural Science Foundation of China(22121004,22122808)+1 种基金the Haihe Laboratory of Sustainable Chemical Transformations and the Program of Introducing Talents of Discipline to Universities(BP0618007)for financial supportsupported by the XPLORER PRIZE.
文摘Noise is inevitable in electrical capacitance tomography(ECT)measurements.This paper describes the influence of noise on ECT performance for measuring gas-solids fluidized bed characteristics.The noise distribution is approximated by the Gaussian distribution and added to experimental capacitance data with various intensities.The equivalent signal strength(Ф)that equals the signal-to-noise ratio of packed beds is used to evaluate noise levels.Results show that the Pearson correlation coefficient,which indicates the similarity of solids fraction distributions over pixels,increases with Ф,and reconstructed images are more deteriorated at lower Ф.Nevertheless,relative errors for average solids fraction and bubble size in each frame are less sensitive to noise,attributed to noise compromise caused by the process of pixel values.These findings provide useful guidance for assessing the accuracy of ECT measurements of multiphase flows.
基金the National Natural Science Foundation of China(Grant No.52374051)the Joint Fund for Enterprise Innovation and Development of NSFC(Grant No.U24B2037).
文摘During oilfield development,a comprehensive model for assessing inter-well connectivity and connected volume within reservoirs is crucial.Traditional capacitance(TC)models,widely used in inter-well data analysis,face challenges when dealing with rapidly changing reservoir conditions over time.Additionally,TC models struggle with complex,random noise primarily caused by measurement errors in production and injection rates.To address these challenges,this study introduces a dynamic capacitance(SV-DC)model based on state variables.By integrating the extended Kalman filter(EKF)algorithm,the SV-DC model provides more flexible predictions of inter-well connectivity and time-lag efficiency compared to the TC model.The robustness of the SV-DC model is verified by comparing relative errors between preset and calculated values through Monte Carlo simulations.Sensitivity analysis was performed to compare the model performance with the benchmark,using the Qinhuangdao Oilfield as a case study.The results show that the SV-DC model accurately predicts water breakthrough times.Increases in the liquid production index and water cut in two typical wells indicate the development time of ineffective circulation channels,further confirming the accuracy and reliability of the model.The SV-DC model offers significant advantages in addressing complex,dynamic oilfield production scenarios and serves as a valuable tool for the efficient and precise planning and management of future oilfield developments.
基金support from the Deanship of Scientific Research at King Khalid University,Saudi Arabia(RGP2/505/45)。
文摘Neodymium chromium oxide(NdCrO_(3))and NdCrO_(3)/graphene oxide(GO)nanocomposite were synthesized via sol-gel and co-precipitation techniques for being used in high-perfo rmance supercapacitors and for the possible application in ultraviolet(UV)materials.Herein the systematic synthesis approach was adopted,which enhances the optical and electrical properties of the grown wide band-gap composite nanomaterial.Structural characterization of the grown materials was attempted using X-ray diffraction(XRD)and scanning electron microscopy(SEM).Most importantly the electrochemical analysis of the grown samples was carried out by employing a glassy carbon electrode and 3 mol/L KOH electrolyte,which demonstrates significant improvements in a specific capacitance of approximately360 F/g,an energy density of approximately 18 Wh/kg,and a maximum power density of approximately 257 W/kg,respectively.Moreover,NdCrO_(3)/GO nanocomposite maintains a cyclic stability of 97.6%after4000 cycles.Photoluminescence(PL)spectroscopy confirms the wide bandgap nature of the NdCrO_(3)and NdCrO_(3)/GO nanocomposite,indicating its potential application in UVC devices.These findings emphasize the potential of the NdCrO_(3)/GO nanocomposite in advancing efficient energy storage solutions and the possibility of being used in UVC technology.
基金This work was supported by the National Natural Science Foundation of China(Grants Nos.12222214,12132020,12002400,and 12172386)by Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(Grant No.2022B1212010008)+1 种基金by the National Natural Science Foundation of Guangdong Province(Grant No.2021B1515020021)by the Shenzhen Science and Techonlogy Program(Grant Nos.202206193000001 and 20220818181805001).
文摘Transient negative capacitance(NC),as an available dynamic charge effect achieved in resistor-ferroelectric capacitor(R-FEC)circuits,has triggered a series of theoretical and experimental works focusing on its physical mechanism and device application.Here,we analytically derived the effects of different mechanical conditions on the transient NC behaviors in the R-FEC circuit based on the phenomenological model.It shows that the ferroelectric capacitor can exhibit either NC(i.e.,“single NC”and“double NC”)or positive capacitance,depending on the mechanical condition and temperature.Further numerical calculations show that the voltage drop caused by NC can be effectively controlled by temperature,applied stress,or strain.The relationship between NC voltage drop and system configurations including external resistance,dynamical coefficient of polarization,and input voltage are presented,showing diverse strategies to manipulate the NC effect.These results provide theoretical guidelines for rational design and efficient control of NC-related electronic devices.
基金supported by the Comprehensive Research Facility for Fusion Technology Program of China(No.2018000052-73-01-001228)National Natural Science Foundation of China(No.11975263)Postgraduate Research and Practice Innovation Program of NUAA(No.xcxjh20231501)。
文摘The negative ion based neutral beam injector(NNBI)with a beam energy of 400 keV is one of the subsystems at the Comprehensive Research fAcility for Fusion Technology(CRAFT)in China.The distributed capacitance of the high-voltage components is an important basis for the design of surge suppression devices at CRAFT NNBI.This study conducted calculations of distributed capacitance for the key components,including the high-voltage deck,transmission line and isolation transformer in the power supply system using the finite element method.The relationship between the high-voltage deck(HVD)distributed capacitance and the distance from the wall is discussed.The differences in distributed capacitance and energy storage between noncoaxial and coaxial transmission lines are also debated.Finally,the capacitance between the primary and secondary windings of the-400 kV isolation transformer,as well as between the secondary winding and the oil tank casing,was calculated.
基金supported partially by JST SICORP(Grant No.JPMJSC2112)JST Adaptable and Seamless Technology Transfer Program through Target-driven R&D(A-STEP)(Grant No.JPMJTR22T6),and JSPS KAKENHI(Grant No.22K14757)+1 种基金Calculations were performed using the U.K.National Supercomputing Facility ARCHER2(http://www.archer2.ac.uk)via our membership of the U.K.’s HEC Materials Chemistry Consortium,which is funded by the EPSRC(Grant Nos.EP/L000202 and EP/R029431)the Molecular Modelling Hub for computational resources,MMM Hub,which is partially funded by EPSRC(Grant No.EP/P020194/1).This research has also utilized Queen Mary’s Apocrita HPC facility,supported by QMUL Research-IT.
文摘Graphene-based frameworks suffer from a low quantum capacitance due to graphene’s Dirac point at the Fermi level.This theoretical study investigated the effect structural defects,nitrogen and boron doping,and surface epoxy/hydroxy groups have on the electronic structure and capacitance of graphene.Density functional theory calculations reveal that the lowest energy configurations for nitrogen or boron substitutional doping occur when the dopant atoms are segregated.This elucidates why the magnetic transition for nitrogen doping is experimentally only observed at higher doping levels.We also highlight that the lowest energy configuration for a single vacancy defect is magnetic.Joint density functional theory calculations show that the fixed band approximation becomes increasingly inaccurate for electrolytes with lower dielectric constants.The introduction of structural defects rather than nitrogen or boron substitutional doping,or the introduction of adatoms leads to the largest increase in density of states and capacitance around graphene’s Dirac point.However,the presence of adatoms or substitutional doping leads to a larger shift of the potential of zero charge away from graphene’s Dirac point.
基金supported by the National Key Research and Development Program of China(No.2018YFA0901300)the Natural Science Foundation of Heilongjiang Province-Outstanding Youth Foundation(YQ2022E033)+3 种基金the State Key Laboratory of Urban Water Resource and Environment(Harbin Institute of Technology)(No.2022DS07,ES202224 andES202310)supported by the National Natural Science Foundation Youth Fund(No.51908403)the Fundamental Research Funds for the Central Universities(No.RFCU5710010122)the Youth Fund of Tianjin Science and Technology Project(No.20JCQNJC01640).
文摘Microbial electrochemical systems are a promising green and sustainable technology that can transform waste into electricity.Improving conversion efficiency and lowering system costs,particularly for elec-trodes,are the primary directions that promote practical application.Cellulose sponges made from wood pulp have been industrially mass-produced in various application scenarios due to their porosity and green sustainability.In this study,the three-dimensional(3D)porous cellulose sponges carbon(CSC)was obtained by directly carbonizing cellulose sponges at different temperatures(600,700,800,900,1000,and 1100℃).It has been successfully used as a high-performance anode in microbial fuel cells(MFCs).The carbonization temperature significantly impacted the materials’specific surface area,con-ductivity,and capacitance.The greater the anode material’s carbonization temperature,the lower the charge transfer resistance and the higher the maximum power density(CSC-1100,4.1±0.1 W m^(-2)).The CSC-700's maximum power density(3.62±0.11 W m^(-2))was the highest power density reported to date among lignocellulose-based anodes with relatively low energy consumption.The pleated multilayer porous surface promotes microbial adhesion and can build thicker biofilms with the highest biomass of 2661±117μg cm^(-2)(CSC-1100)and containing 86%electrogenic bacteria(Geobacter).To investigate the effect of conducting polymers on the material’s surface,we introduced polyaniline and polypyrrole.We found that the CSC-1000/PPy bioanodes produced a maximum power density(4.18±0.05 W m^(-2)),slightly higher than of without polypyrrole-modified(CSC-1000,3.99±0.06 W m^(-2)),indicating that the CSCs anode surface had excellent electron transfer efficiency and could achieve the same amount of energy as the polypyrrole surface.This study introduced a promising method for fabricating high-performance anodes using low-cost,industrialized,and sustainable materials.
基金financially supported by the National Natural Science Foundation of China(No.22179113)the Fundamental Research Funds for the Central Universities(Nos.20720230028 and 20720210045)+1 种基金the Science and Technology Projects of Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province(IKKEM)(No.HRTP-2022-19)the XMU Training Program of Innovation and Entrepreneurship for Undergraduates(No.2021Y1089)。
文摘Developing anode materials with high specific/volumetric capacities,high-rate capability,long-term cycles and low cost is significant for advanced sodium-ion storage.Herein,we report the hybrid TiO_(2)/graphite(TiO_(2)/G)anodes for fast(dis)charging sodium-ion storage.Taking advantage of the rapid pseudocapacitive surface-redox on anatase TiO_(2)nanoparticles(NPs)and fast[Na(diglyme)_(x)]^(+)co-intercalation into graphite,the hybrid anodes display excellent rate capabilities.Additionally,the TiO_(2)NPs are able to fill into the interspaces among graphite flakes and the graphite provides continuous electron pathways,which largely boosts the volumetric capacities and rate performance.
文摘Applications for quanta and space sensing both depend on efficient low-light imaging.To precisely optimize and design image sensor pixels for these applications,it is crucial to analyze the mechanisms behind dark current generation,considering factors such as temperature,trap cross-section and trap concentration.The thresholds for these generating effects are computed using optoelectrical technology computer aided design(TCAD)simulations,and the ensuing changes in pinned photo-diode(PPD)dynamic capacitance are observed.Various generation models along with an interfacial trap model are used to compare PPD capacitance fluctuations during light and dark environments.With the use of this comparison study,current compact models of complementary metal oxide semiconductor(CMOS)image sensors can be modified to accurately capture the impacts of dark current in low-light conditions.The model developed through this study demonstrates a deviation of only 6.85%from the behavior observed in physical devices.These results not only enhance our understanding of dark current generation mechanisms but also offer practical applications by improving the performance and accuracy of image sensors.
文摘In view of drastic possible changes in fuze environment tempera- ture,a kind of temperature autocompensated detecting circuit for the capaci- tance fuze is proposed.It provides a steady detected output when the envi- ronment temperature varies from-50℃ to 65℃ and keeps a stable detecting sensitivity.Based on an analysis of the circuit,influence of the major param- eters of the oscillating circuit on the amplitude are explored.A few impor- tant controllable parameters affecting the circuit feature are found out.A parameter-control method is given in order to improve the circuit perfor- mance.
文摘A distributed capacitance model for monolithic inductors is developed to predict the equivalently parasitical capacitances of the inductor.The ratio of the self-resonant frequency (f SR) of the differential-driven symmetric inductor to the f SR of the single-ended driven inductor is firstly predicted and explained.Compared with a single-ended configuration,experimental data demonstrate that the differential inductor offers a 127% greater maximum quality factor and a broader range of operating frequencies.Two differential inductors with low parasitical capacitance are developed and validated.
基金the National Natural Science Foundation of China under Grant 61822407,Grant 61527816,Grant 11634002,Grant 61631021,Grant 62074161,Grant 62004213,and Grant U20A20208in part by the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(CAS)under Grant QYZDB-SSW-JSC012+2 种基金in part by the Youth Innovation Promotion Association of CASin part by the University of CASthe Opening Project of Key Laboratory of Microelectronic Devices&Integrated Technology,Institute of Microelectronics,CAS.
文摘Parasitic capacitances associated with overhangs of the T-shape-gate enhancement-mode(E-mode)GaN-based power device,were investigated by frequency/voltage-dependent capacitance-voltage and inductive-load switching measurements.The overhang capacitances induce a pinch-off voltage distinguished from that of the E-mode channel capacitance in the gate capacitance and the gatedrain capacitance characteristic curves.Frequency-and voltage-dependent tests confirm the instability caused by the trapping of interface/bulk states in the LPCVD-SiNx passivation dielectric.Circuit-level double pulse measurement also reveals its impact on switching transition for power switching applications.
文摘For establishing the equation of the capacitive target detection accurately, the distributing characteristics of the charges on the bomb body with capacitance fuze were explored. Continuous charges were analyzed dispersively. Based on the Coulomb's law, the dynamic equilibrium equations of the inducing charges on the bomb body were set up. For the four cases of d 0/L (the ratio between the electrode distance and the bomb length), the curves of the charge's distribution were given. It was concluded that: ① the charge density decreases steadily from the end near the frontal electrode to the bomb tail; ② the declining rate of the density is governed by d 0/L , the larger the value of d 0/L ,the higher the declining rate, and vice versa.
文摘For a detector in a capacitanee fuze working in an electrostatic field, the bomblength (effective length of the conductor part) is an important factor affecting the sensitivityof detection. For the two different kinds of detecting circuit models in general use (the frequency-sensitive and the amplitude-coupling ), mechanism of the effect of bomblength on the sensitvity of detection is analyzed. Through the analysis a conclusion in fullagreement with experimental results has been drawn, that is. the longer the bomb length,the higher the sensitivity, on the condition that the sizes and the sites of the detecting electrodes and bomb diameter remain unchanged.
文摘The finite element method is first introduced into the design process of detecting electrodes of three electrode capacitance fuze, the mutual capacitance of the fuze and target is calculated by the finite element method, which provides the parameters for simulation circuit and design of detecting electrode. The finite element method pierces the traditional method of designing detecting electrode-design, test and adjustment. The system capacitance can be calculated accurately and the performance can be predicted in the design period of the detecting electrode, which saves a lot of research fee. The capacitances of a mortar shell fuze above ground 2 m and lower are given. After putting the computing data into simulating circuit, the demodulation voltage can be obtained, its changing trend is in agreement with the tested result.
基金Project supported by the National Natural Science Foundation of China(Grant No.61474041)
文摘An improved method of extracting the coupling capacitances of quantum dot structure is reported. This method is based on measuring the charge transfer current in the silicon nanowire metal-oxide-semiconductor field-effect transistor （MOSFET）, in which the channel closing and opening are controlled by applying alternating-current biases with a half period phase shift to the dual lower gates. The capacitances around the dot, including fringing capacitances and barrier capacitances, are obtained by analyzing the relation between the transfer current and the applied voltage. This technique could be used to extract the capacitance parameters not only from the bulk silicon devices, but also from the silicon-on-insulator （SOI） MOSFETs.
基金Project supported by National Natural Science Foundation of China(Grant Nos.10874070,60976001,and 50872051)Natural Science Foundation of Jiangsu Province of China(Grant No.BK2008253)+2 种基金State Key Program for Basic Research of China(Grant Nos.2007CB935401 and 2010CB934402)Natural Science Foundation of Jiangsu Province for Universities(Grant No.09KJB510014)Nanjing University of Posts and Telecommunications Research Fund(Grant No.NY208057 and JG03309JX37)
文摘This paper reports that metal-oxide-semiconductor （MOS） capacitors with a single layer of Ni nanopartictes were successfully fabricated by using electron-beam evaporation and rapid thermal annealing for application to nonvolatile memory. Experimental scanning electron microscopy images showed that Ni nanoparticles of about 5 nm in diameter were clearly embedded in the SiO2 layer on p-type Si （100）. Capacitance-voltage measurements of the MOS capacitor show large flat-band voltage shifts of 1.8 V, which indicate the presence of charge storage in the nickel nanoparticles. In addition, the charge-retention characteristics of MOS capacitors with Ni nanoparticles were investigated by using capacitance-time measurements. The results showed that there was a decay of the capacitance embedded with Ni nanoparticles for an electron charge after 104 s. But only a slight decay of the capacitance originating from hole charging was observed. The present results indicate that this technique is promising for the efficient formation or insertion of metal nanoparticles inside MOS structures.
