Electrical and optical properties of an argon plasma jet were characterized. In particular, effects of an additive gas, namely nitrogen or oxygen, on these properties were studied in detail. The plasma jet was found t...Electrical and optical properties of an argon plasma jet were characterized. In particular, effects of an additive gas, namely nitrogen or oxygen, on these properties were studied in detail. The plasma jet was found to be of a glow-like discharge, which scarcely changed upon the injection of an additive gas, either directly or through a glass capillary. Optical emission spectroscopy characterization revealed that excited argon atoms were the predominant active species in this plasma jet. Metastable argon atoms were highly quenched, and N2（C3yIu） became the main energy carrier following nitrogen injection. When oxygen was added to the afterglow zone through a glass capillary, no significant quenching effect was observed and the number of oxygen atoms decreased with the increase in oxygen concentration. Finally, to demonstrate an application of this plasma jet, a high-density polyethylene surface was treated with argon, argon/nitrogen, and argon/oxygen plasmas.展开更多
The non-isothermal kinetics of CdO nanoparticles prepared from CdCO3 precursor using thermal decomposition method was investigated. A model-fitting Malek approach and a model-free advanced isoconversional method of Vy...The non-isothermal kinetics of CdO nanoparticles prepared from CdCO3 precursor using thermal decomposition method was investigated. A model-fitting Malek approach and a model-free advanced isoconversional method of Vyazovkin were applied to the analysis of the DSC and TGA data. The results showed that CdO nanoparticles prepared from CdCO3 followed an autocatalytic reaction. Sestak–Berggren model could favorably describe the studied reaction process. Moreover, the apparent activation energy of CdCO3 decomposition was calculated to be (119.19±9.97) kJ/mol and the explicit rate equation form of CdCO3 decomposition was established.展开更多
Molybdenum sulfide materials receive high attention as high-performance electrodes for electrochemical energy storage devices.In this study,we investigate the electrochemical energy storage properties of amorphous MoS...Molybdenum sulfide materials receive high attention as high-performance electrodes for electrochemical energy storage devices.In this study,we investigate the electrochemical energy storage properties of amorphous MoS_(3) and crystalline MoS_(2) materials(prepared via thermal decomposition of ammonium tetrathiomolybdate)using an organic liquid electrolyte.Physicochemical characterization using X-ray diffraction pattern and laser Raman analysis confirms the formation of amorphous MoS_(3) and crystalline MoS_(2),respectively.The energy storage properties of MoS_(3) and MoS_(2) based symmetric supercapacitor devices were comparatively studied using cyclic voltammetry,electrochemical impedance spectroscopy,and galvanostatic charge–discharge analysis.The cyclic voltammetry analysis reveals the mechanism of charge storage in MoS_(3) and MoS_(2) is due to the ion-intercalation/de-intercalation pseudocapacitance.Electrochemical impedance spectroscopy studies reveal the better capacitance and charge-transfer nature of the crystalline MoS_(2) symmetric supercapacitor compared to that of the amorphous MoS_(3) symmetric supercapacitor.The charge–discharge analysis suggests that the MoS_(2) symmetric supercapacitor device possesses better electrochemical energy storage properties with a high specific capacity of 20.81 mA h g^(−1)(24.98 F g^(−1))and energy density of about 20.69 W h kg^(−1) with the excellent cyclic stability of about 2000 cycles.The experimental results suggest that the crystalline MoS_(2) sheets might be a better choice than amorphous MoS_(3) as an electrode material for supercapacitors using an organic liquid electrolyte.展开更多
A novel hybrid of Cu_(2)MoS_(4) nanoparticles embedded on reduced graphene oxide(rGO)sheets was prepared via a one-pot hydrothermal method without any surfactants or templates.The electrochemical properties of the as-...A novel hybrid of Cu_(2)MoS_(4) nanoparticles embedded on reduced graphene oxide(rGO)sheets was prepared via a one-pot hydrothermal method without any surfactants or templates.The electrochemical properties of the as-prepared Cu_(2)MoS_(4)-rGO electrode were investigated as an advanced electrode for supercapacitor applications,and it exhibited higher specific capacitance(231.51 F g^(-1) at 5 mV s^(-1))compared to the pristine Cu_(2)MoS_(4) electrode(135.78 F g^(-1) at 5 mV s^(-1)).展开更多
This work shows that a soft,thin film comprising randomly aligned carbon nanotubes(CNTs)can reduce surface wear more effectively than a homogeneous thin film because of enhanced elastic recoverability and contact stre...This work shows that a soft,thin film comprising randomly aligned carbon nanotubes(CNTs)can reduce surface wear more effectively than a homogeneous thin film because of enhanced elastic recoverability and contact stress relief originating from its mesh structure.To investigate the wear characteristics of the mesh structure compared to those of the homogeneous thin film,multi-walled CNTs(MWCNTs)and diamond-like carbon(DLC)thin films were prepared to conduct nanoscale tribological experiments using the atomic force microscopy(AFM).The MWCNT thin film showed unmeasurably low wear compared with the DLC thin film under a certain range of normal load.To demonstrate the wear reduction mechanism of the MWCNT thin film,its indentation and frictional behaviors were assessed.The indentation behavior of the MWCNT thin film revealed repetitive elastic deformation with a wide strain range and a significantly lower elastic modulus than that of the DLC thin film.The permanent deformation of the MWCNT thin film was observed through frictional experiments under relatively high normal load conditions.These results are expected to provide insights into the design of highly wear-resistant surfaces using nanostructures.展开更多
In this study,a high-density polyethylene（HDPE,5-mm-thick,0.95 g/cm3） surface was treated using an RF capacitive atmospheric pressure cold Ar plasma jet.By using this Ar plasma jet,a hydrophilic HDPE surface was for...In this study,a high-density polyethylene（HDPE,5-mm-thick,0.95 g/cm3） surface was treated using an RF capacitive atmospheric pressure cold Ar plasma jet.By using this Ar plasma jet,a hydrophilic HDPE surface was formed during the plasma treatment.In particular, the effects of an additive gas（N;or O2） on the HDPE surface treatment were investigated in detail.It was shown that the addition of N2 or O2 gas had an important influence on the HDPE surface treatment.Compared to pure Ar plasma treatment,a lower value of water contact angle （WCA） was obtained when a trace of N2 or O2 gas was added.It was also found that besides the quantities of active species in the plasma jet,the treatment temperature played an important role in the HDPE surface treatment.This is because surface molecular motion is not negligible when the treatment temperature is close to the melting point of the polymer.展开更多
Accurate soil organic carbon storage(SOCS)estimation is crucial for sustaining ecosystem health and mitigating climate change impacts.This study investigated the accuracy and variability of SOCS predictions,focusing o...Accurate soil organic carbon storage(SOCS)estimation is crucial for sustaining ecosystem health and mitigating climate change impacts.This study investigated the accuracy and variability of SOCS predictions,focusing on the role of pedotransfer functions(PTFs)in estimating soil bulk density(BD).Utilizing a comprehensive dataset from the Korean Rural Development Administration(RDA database),which includes 516 soil horizons,we evaluated 36 widely-used BD PTFs,well-established formulas that estimate BD by considering soil properties,including soil organic carbon(SOC),soil organic matter(OM),sand,gravel,silt,and clay.These PTFs demonstrated varying levels of precision,with root mean squared errors(RMSE)ranging from 0.177 to 0.377 Mg m^(-3) and coefficients of determination(R^(2))from 0.176 to 0.658;hence,the PTFs have been classified into excellent,moderate,and poor-performing groups for predicting BD.Further,a novel PTF based on an exponential function of SOC was developed,showing superior predictive power(R^(2)=0.73)compared to existing PTFs,using an independent validation dataset.Our findings reveal significant differences in SOCS predictions and observations among the PTFs,with a p-value<0.05.The highest concentrations of SOCS were noted in forest soils,considerably above the national average,highlighting the importance of tailored soil management practices to enhance carbon sequestration.These findings are crucial for refining PTF precision to improve the accuracy of national SOCS estimates,supporting effective land management and climate change mitigation strategies.展开更多
In this work,a novel chalcopyrite(CuFeS_(2))platelet like open-pored micro-flower structured electrode material was synthesized via a one-step hydrothermal method and its electrochemical performance as an electrode ma...In this work,a novel chalcopyrite(CuFeS_(2))platelet like open-pored micro-flower structured electrode material was synthesized via a one-step hydrothermal method and its electrochemical performance as an electrode material for supercapacitors were investigated.First and foremost,the structural,morphological,vibrational,and chemical compositional characteristics of the as prepared CuFeS_(2)were investigated by X-ray diffraction(XRD),field emission scanning electron microscopy(FE-SEM)with elemental mapping,laser Raman spectroscopy,and X-ray photoelectron spectroscopy(XPS),respectively.Subsequently,the electrochemical properties of the CuFeS_(2)electrode were explored using cyclic voltammetry(CV),galvanostatic charge-discharge(CD),and electrochemical impedance spectroscopy(EIS)studies in 1 M LiOH electrolyte.Cyclic voltammetry and charge-discharge analysis reveal the pseudocapacitive nature of the CuFeS_(2)electrode by obtaining a maximum specific capacity of about 26.46 mA h g^(-1)(specific capacitance of about∼95.28 F g^(-1))at a scan rate of 5 mV s^(-1)with a cycling stability retention of 94.38%even after 2000 cycles at a discharge current rate of 5 mA.Furthermore,in view of practical application a symmetric supercapacitor device was fabricated using the CuFeS_(2)electrode which delivered a maximum specific capacitance of about 34.18 F g^(-1)at a current rate of 1 mA and a maximum energy density of about 4.74 W h kg^(-1)with excellent cycling stability.The acquired results confirmed that the CuFeS_(2)electrode could be a prospective and electrochemically active candidate for next generation supercapacitors.展开更多
文摘Electrical and optical properties of an argon plasma jet were characterized. In particular, effects of an additive gas, namely nitrogen or oxygen, on these properties were studied in detail. The plasma jet was found to be of a glow-like discharge, which scarcely changed upon the injection of an additive gas, either directly or through a glass capillary. Optical emission spectroscopy characterization revealed that excited argon atoms were the predominant active species in this plasma jet. Metastable argon atoms were highly quenched, and N2（C3yIu） became the main energy carrier following nitrogen injection. When oxygen was added to the afterglow zone through a glass capillary, no significant quenching effect was observed and the number of oxygen atoms decreased with the increase in oxygen concentration. Finally, to demonstrate an application of this plasma jet, a high-density polyethylene surface was treated with argon, argon/nitrogen, and argon/oxygen plasmas.
文摘The non-isothermal kinetics of CdO nanoparticles prepared from CdCO3 precursor using thermal decomposition method was investigated. A model-fitting Malek approach and a model-free advanced isoconversional method of Vyazovkin were applied to the analysis of the DSC and TGA data. The results showed that CdO nanoparticles prepared from CdCO3 followed an autocatalytic reaction. Sestak–Berggren model could favorably describe the studied reaction process. Moreover, the apparent activation energy of CdCO3 decomposition was calculated to be (119.19±9.97) kJ/mol and the explicit rate equation form of CdCO3 decomposition was established.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(2018R1A4A1025998 and 2019R1A2C3009747).
文摘Molybdenum sulfide materials receive high attention as high-performance electrodes for electrochemical energy storage devices.In this study,we investigate the electrochemical energy storage properties of amorphous MoS_(3) and crystalline MoS_(2) materials(prepared via thermal decomposition of ammonium tetrathiomolybdate)using an organic liquid electrolyte.Physicochemical characterization using X-ray diffraction pattern and laser Raman analysis confirms the formation of amorphous MoS_(3) and crystalline MoS_(2),respectively.The energy storage properties of MoS_(3) and MoS_(2) based symmetric supercapacitor devices were comparatively studied using cyclic voltammetry,electrochemical impedance spectroscopy,and galvanostatic charge–discharge analysis.The cyclic voltammetry analysis reveals the mechanism of charge storage in MoS_(3) and MoS_(2) is due to the ion-intercalation/de-intercalation pseudocapacitance.Electrochemical impedance spectroscopy studies reveal the better capacitance and charge-transfer nature of the crystalline MoS_(2) symmetric supercapacitor compared to that of the amorphous MoS_(3) symmetric supercapacitor.The charge–discharge analysis suggests that the MoS_(2) symmetric supercapacitor device possesses better electrochemical energy storage properties with a high specific capacity of 20.81 mA h g^(−1)(24.98 F g^(−1))and energy density of about 20.69 W h kg^(−1) with the excellent cyclic stability of about 2000 cycles.The experimental results suggest that the crystalline MoS_(2) sheets might be a better choice than amorphous MoS_(3) as an electrode material for supercapacitors using an organic liquid electrolyte.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(2018R1A4A1025998,2019R1A2C3009747).
文摘A novel hybrid of Cu_(2)MoS_(4) nanoparticles embedded on reduced graphene oxide(rGO)sheets was prepared via a one-pot hydrothermal method without any surfactants or templates.The electrochemical properties of the as-prepared Cu_(2)MoS_(4)-rGO electrode were investigated as an advanced electrode for supercapacitor applications,and it exhibited higher specific capacitance(231.51 F g^(-1) at 5 mV s^(-1))compared to the pristine Cu_(2)MoS_(4) electrode(135.78 F g^(-1) at 5 mV s^(-1)).
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(No.2020R1A2C2004714)supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.2021R1I1A3060608).
文摘This work shows that a soft,thin film comprising randomly aligned carbon nanotubes(CNTs)can reduce surface wear more effectively than a homogeneous thin film because of enhanced elastic recoverability and contact stress relief originating from its mesh structure.To investigate the wear characteristics of the mesh structure compared to those of the homogeneous thin film,multi-walled CNTs(MWCNTs)and diamond-like carbon(DLC)thin films were prepared to conduct nanoscale tribological experiments using the atomic force microscopy(AFM).The MWCNT thin film showed unmeasurably low wear compared with the DLC thin film under a certain range of normal load.To demonstrate the wear reduction mechanism of the MWCNT thin film,its indentation and frictional behaviors were assessed.The indentation behavior of the MWCNT thin film revealed repetitive elastic deformation with a wide strain range and a significantly lower elastic modulus than that of the DLC thin film.The permanent deformation of the MWCNT thin film was observed through frictional experiments under relatively high normal load conditions.These results are expected to provide insights into the design of highly wear-resistant surfaces using nanostructures.
文摘In this study,a high-density polyethylene（HDPE,5-mm-thick,0.95 g/cm3） surface was treated using an RF capacitive atmospheric pressure cold Ar plasma jet.By using this Ar plasma jet,a hydrophilic HDPE surface was formed during the plasma treatment.In particular, the effects of an additive gas（N;or O2） on the HDPE surface treatment were investigated in detail.It was shown that the addition of N2 or O2 gas had an important influence on the HDPE surface treatment.Compared to pure Ar plasma treatment,a lower value of water contact angle （WCA） was obtained when a trace of N2 or O2 gas was added.It was also found that besides the quantities of active species in the plasma jet,the treatment temperature played an important role in the HDPE surface treatment.This is because surface molecular motion is not negligible when the treatment temperature is close to the melting point of the polymer.
基金supported by Korea Environmental Industry&Technology Institute(KEITI)through R&D Program for Innovative Flood Protection Technologies against Climate Crisis Project,funded by Korea Ministry of Environment(MOE)[2022003460002].
文摘Accurate soil organic carbon storage(SOCS)estimation is crucial for sustaining ecosystem health and mitigating climate change impacts.This study investigated the accuracy and variability of SOCS predictions,focusing on the role of pedotransfer functions(PTFs)in estimating soil bulk density(BD).Utilizing a comprehensive dataset from the Korean Rural Development Administration(RDA database),which includes 516 soil horizons,we evaluated 36 widely-used BD PTFs,well-established formulas that estimate BD by considering soil properties,including soil organic carbon(SOC),soil organic matter(OM),sand,gravel,silt,and clay.These PTFs demonstrated varying levels of precision,with root mean squared errors(RMSE)ranging from 0.177 to 0.377 Mg m^(-3) and coefficients of determination(R^(2))from 0.176 to 0.658;hence,the PTFs have been classified into excellent,moderate,and poor-performing groups for predicting BD.Further,a novel PTF based on an exponential function of SOC was developed,showing superior predictive power(R^(2)=0.73)compared to existing PTFs,using an independent validation dataset.Our findings reveal significant differences in SOCS predictions and observations among the PTFs,with a p-value<0.05.The highest concentrations of SOCS were noted in forest soils,considerably above the national average,highlighting the importance of tailored soil management practices to enhance carbon sequestration.These findings are crucial for refining PTF precision to improve the accuracy of national SOCS estimates,supporting effective land management and climate change mitigation strategies.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(2017R1C1B2012700,2018R1A4A1025998,and 2019R1A2C3009747).
文摘In this work,a novel chalcopyrite(CuFeS_(2))platelet like open-pored micro-flower structured electrode material was synthesized via a one-step hydrothermal method and its electrochemical performance as an electrode material for supercapacitors were investigated.First and foremost,the structural,morphological,vibrational,and chemical compositional characteristics of the as prepared CuFeS_(2)were investigated by X-ray diffraction(XRD),field emission scanning electron microscopy(FE-SEM)with elemental mapping,laser Raman spectroscopy,and X-ray photoelectron spectroscopy(XPS),respectively.Subsequently,the electrochemical properties of the CuFeS_(2)electrode were explored using cyclic voltammetry(CV),galvanostatic charge-discharge(CD),and electrochemical impedance spectroscopy(EIS)studies in 1 M LiOH electrolyte.Cyclic voltammetry and charge-discharge analysis reveal the pseudocapacitive nature of the CuFeS_(2)electrode by obtaining a maximum specific capacity of about 26.46 mA h g^(-1)(specific capacitance of about∼95.28 F g^(-1))at a scan rate of 5 mV s^(-1)with a cycling stability retention of 94.38%even after 2000 cycles at a discharge current rate of 5 mA.Furthermore,in view of practical application a symmetric supercapacitor device was fabricated using the CuFeS_(2)electrode which delivered a maximum specific capacitance of about 34.18 F g^(-1)at a current rate of 1 mA and a maximum energy density of about 4.74 W h kg^(-1)with excellent cycling stability.The acquired results confirmed that the CuFeS_(2)electrode could be a prospective and electrochemically active candidate for next generation supercapacitors.
