A visible light-induced, Cu-doped BiVO_4 photocatalyst was synthesized by a microwave hydrothermal method. The photocatalytic efficiency was investigated in the degradation of model water pollutants like Methylene Blu...A visible light-induced, Cu-doped BiVO_4 photocatalyst was synthesized by a microwave hydrothermal method. The photocatalytic efficiency was investigated in the degradation of model water pollutants like Methylene Blue(dye) and ibuprofen(pharmaceuticals), as well as the inactivation of Escherichia coli(bacteria). The Cu-doped BiVO4 samples showed better efficiency than undoped BiVO_4, and the 1 wt.% Cu-doped BiVO_4 sample showed the best efficiency. The degradation of Methylene Blue reached 95%, while the degradation of ibuprofen reached 75%, and the inactivation of E. coli reached 85% in irradiation with visible light. The appearance of additional absorption band shoulders and widening of the optical absorption in the visible range makes the prepared powder an efficient visible light-driven photocatalyst. Moreover, the formation of an in-gap energy state just above the valance band as determined by density functional theory(DFT) first principle calculation, facilitates the wider optical absorption range of the doped system. Similarly, this in-gap energy state also acts as an electron trap, which is favorable for the efficient separation and photoexcited charge carriers' transfer process. The formation of oxygen vacancies due to doping also improved the separation of the charge carrier, which promoted the trapping of electrons and inhibited electron hole recombination, thus increasing the photocatalytic activity. No decrease in the efficiency of the 1 wt.% Cu-doped BiVO_4 photocatalyst in the degradation of ibuprofen over three consecutive cycles revealed the stability of the photocatalyst towards photocorrosion. These findings highlight the multifunctional applications of Cu-doped BiVO_4 in wastewater containing multiple pollutants.展开更多
Ni—SiC—h/BN composite materials were prepared by electrodeposition technique with the dispersion of SiC（10 g/L） and h/BN nanosheets（10 g/L） in a nickel sulfamate electrolytic bath.Different ratio of sodium dodec...Ni—SiC—h/BN composite materials were prepared by electrodeposition technique with the dispersion of SiC（10 g/L） and h/BN nanosheets（10 g/L） in a nickel sulfamate electrolytic bath.Different ratio of sodium dodecyl sulfate（SDS） and cetyltrymethyl ammonium bromide（CTAB） surfactants were used to evaluate the effect of surfactants on the properties of the electrodeposited composite coatings.The coating samples were characterized by scanning electron microscopy,X-ray diffraction,Vickers microhardness test,scratch and tribology tests.The results revealed that the co-deposition of nanoparticles was significantly influenced by surfactants during electrodeposition process.Pyramidal or polyhedral nickel crystallites were observed at higher ratio of SDS/CTAB while smaller oval grains with refined surface morphologies were obtained at lower ratio of SDS/CTAB surfactants.In addition,wt%of particles co-deposition was increased,and Vickers microhardness,wear and coefficient of friction of the electrodeposited composite coatings were improved at increased CTAB and decreased SDS contents in the electrolyte during electrodeposition process.展开更多
The present work aims to study the influence of direct current and pulse current techniques as well as embedded SiC nanoparticles on the mechanical properties of the electrodeposited Ni-W coating.The electrodeposited ...The present work aims to study the influence of direct current and pulse current techniques as well as embedded SiC nanoparticles on the mechanical properties of the electrodeposited Ni-W coating.The electrodeposited coatings were studied for morphological,microstructural,mechanical,and scratch resistance properties using the surface roughness tester,scanning electron microscopy,energy-dispersive X-ray spectroscopy,X-ray diffraction,Vickers microhardness,and scratch tester.Application of pulse current exhibited relatively homogeneous and smooth surface of the coatings.A remarkable increment of microhardness was observed in both Ni-W and Ni-W-SiC coatings prepared under pulse current as compared to the direct current technique.Similarly,the scratch test revealed a considerable improvement in the scratch resistance behavior of the Ni-W alloy and the composite coatings from the pulsed current condition.Hence,the application of pulse current not only improved the surface-and microstructure-related properties but also enhanced the Vickers microhardness and scratch resistance properties of the coatings.In addition,the reduction in micro-cracks revealed the improvement in scratch resistance properties of the coatings due to the incorporated SiC nanoparticles into the Ni-W alloy matrix.展开更多
Ni-W-TiC composite coatings were prepared via electrodeposition technique by dispersing the different amount of TiC particles into the plating bath.The Ni-W and Ni-W-TiC composite coatings containing different concent...Ni-W-TiC composite coatings were prepared via electrodeposition technique by dispersing the different amount of TiC particles into the plating bath.The Ni-W and Ni-W-TiC composite coatings containing different concentrations of TiC particles were characterized by using the scanning electron microscope,X-ray diffraction technique,Vickers microhardness test,surface roughness test,and tribology test.The results show that the Ni-W coatings containing reinforced TiC particles have shown a typical FCC Ni-W crystal structure with significantly higher Vickers microhardness.The amount of dispersed TiC particles into the plating bath considerably affected codeposition weight percent of TiC into the Ni-W matrix,as revealed by the EDS analysis.Ni-W-TiC samples demonstrated the decreased abrasive wear as compared to Ni-W coating and no characteristic features observed for the adhesive wear.Similarly,an improvement in coefficient of friction was observed in Ni-W-TiC composite coating as compared to Ni-W coating.展开更多
Optical properties of hot pressed Sialon ceramics doped with different rare earth oxides（REOs） i.e. Eu2O3, Gd2O3, and Pr2O3 were investigated. The α-Sialon phase was the main phase obtained after sintering as obser...Optical properties of hot pressed Sialon ceramics doped with different rare earth oxides（REOs） i.e. Eu2O3, Gd2O3, and Pr2O3 were investigated. The α-Sialon phase was the main phase obtained after sintering as observed by X-ray diffraction（XRD）. The transparency of different samples of varying thickness measured from UV to IR region revealed that the samples were translucent in the visible region while transparent in IR region. The thin samples of 150 μm thickness had transmittance as high as 30% in the visible region. The luminescence was observed in transmittance mode to investigate the effect of sample thickness on luminescence intensity. We observed blue, yellow and red emissions in Sialon doped with Gd2O3, Eu2O3, and Pr2O3, respectively. The excitation wavelength for Gd2O3 and Pr2O3 doped samples were in UV region i.e. 280 and 270 nm, respectively, whereas, for Eu2O3 doped samples was in the blue region（460 nm）. The Eu2O3 doped Sialon having 300 μm thickness showed better white light extraction as coupled with blue LED. Moreover, the fabricated phosphor samples exhibited high hardness around 20 GPa and fracture toughness above 5 MPa·m1/2.展开更多
基金supported by the Global Research Laboratory Program of the National Research Foundation of Korea (NRF)funded by the Ministry of Education,Science and Technology (MEST) of Korea (No.2010-00339)
文摘A visible light-induced, Cu-doped BiVO_4 photocatalyst was synthesized by a microwave hydrothermal method. The photocatalytic efficiency was investigated in the degradation of model water pollutants like Methylene Blue(dye) and ibuprofen(pharmaceuticals), as well as the inactivation of Escherichia coli(bacteria). The Cu-doped BiVO4 samples showed better efficiency than undoped BiVO_4, and the 1 wt.% Cu-doped BiVO_4 sample showed the best efficiency. The degradation of Methylene Blue reached 95%, while the degradation of ibuprofen reached 75%, and the inactivation of E. coli reached 85% in irradiation with visible light. The appearance of additional absorption band shoulders and widening of the optical absorption in the visible range makes the prepared powder an efficient visible light-driven photocatalyst. Moreover, the formation of an in-gap energy state just above the valance band as determined by density functional theory(DFT) first principle calculation, facilitates the wider optical absorption range of the doped system. Similarly, this in-gap energy state also acts as an electron trap, which is favorable for the efficient separation and photoexcited charge carriers' transfer process. The formation of oxygen vacancies due to doping also improved the separation of the charge carrier, which promoted the trapping of electrons and inhibited electron hole recombination, thus increasing the photocatalytic activity. No decrease in the efficiency of the 1 wt.% Cu-doped BiVO_4 photocatalyst in the degradation of ibuprofen over three consecutive cycles revealed the stability of the photocatalyst towards photocorrosion. These findings highlight the multifunctional applications of Cu-doped BiVO_4 in wastewater containing multiple pollutants.
基金supported by the Pioneer Research Program through the National Research Foundation of Korea funded by the Ministry of Education,Science and Technology(No.20100019473)
文摘Ni—SiC—h/BN composite materials were prepared by electrodeposition technique with the dispersion of SiC（10 g/L） and h/BN nanosheets（10 g/L） in a nickel sulfamate electrolytic bath.Different ratio of sodium dodecyl sulfate（SDS） and cetyltrymethyl ammonium bromide（CTAB） surfactants were used to evaluate the effect of surfactants on the properties of the electrodeposited composite coatings.The coating samples were characterized by scanning electron microscopy,X-ray diffraction,Vickers microhardness test,scratch and tribology tests.The results revealed that the co-deposition of nanoparticles was significantly influenced by surfactants during electrodeposition process.Pyramidal or polyhedral nickel crystallites were observed at higher ratio of SDS/CTAB while smaller oval grains with refined surface morphologies were obtained at lower ratio of SDS/CTAB surfactants.In addition,wt%of particles co-deposition was increased,and Vickers microhardness,wear and coefficient of friction of the electrodeposited composite coatings were improved at increased CTAB and decreased SDS contents in the electrolyte during electrodeposition process.
基金financially supported by the PhD full funding scholarship from the National Institute for International Education(NIIED),Republic of Korea.
文摘The present work aims to study the influence of direct current and pulse current techniques as well as embedded SiC nanoparticles on the mechanical properties of the electrodeposited Ni-W coating.The electrodeposited coatings were studied for morphological,microstructural,mechanical,and scratch resistance properties using the surface roughness tester,scanning electron microscopy,energy-dispersive X-ray spectroscopy,X-ray diffraction,Vickers microhardness,and scratch tester.Application of pulse current exhibited relatively homogeneous and smooth surface of the coatings.A remarkable increment of microhardness was observed in both Ni-W and Ni-W-SiC coatings prepared under pulse current as compared to the direct current technique.Similarly,the scratch test revealed a considerable improvement in the scratch resistance behavior of the Ni-W alloy and the composite coatings from the pulsed current condition.Hence,the application of pulse current not only improved the surface-and microstructure-related properties but also enhanced the Vickers microhardness and scratch resistance properties of the coatings.In addition,the reduction in micro-cracks revealed the improvement in scratch resistance properties of the coatings due to the incorporated SiC nanoparticles into the Ni-W alloy matrix.
基金This research was supported by the“International standardization of nickel-phosphorous ceramics electroless composite plating for industrial use”program through the “Korea Evaluation Institute of Industrial Technology”of Korea funded by the Ministry of Science,ICT and Future planning(Grant No.10080067)。
文摘Ni-W-TiC composite coatings were prepared via electrodeposition technique by dispersing the different amount of TiC particles into the plating bath.The Ni-W and Ni-W-TiC composite coatings containing different concentrations of TiC particles were characterized by using the scanning electron microscope,X-ray diffraction technique,Vickers microhardness test,surface roughness test,and tribology test.The results show that the Ni-W coatings containing reinforced TiC particles have shown a typical FCC Ni-W crystal structure with significantly higher Vickers microhardness.The amount of dispersed TiC particles into the plating bath considerably affected codeposition weight percent of TiC into the Ni-W matrix,as revealed by the EDS analysis.Ni-W-TiC samples demonstrated the decreased abrasive wear as compared to Ni-W coating and no characteristic features observed for the adhesive wear.Similarly,an improvement in coefficient of friction was observed in Ni-W-TiC composite coating as compared to Ni-W coating.
基金supported by Global Research Laboratory(GRL)Program of the National Research Foundation of Korea(NRF)funded by Ministry of Education,Science and Technology(MEST),Republic of Korea(2010-00339)
文摘Optical properties of hot pressed Sialon ceramics doped with different rare earth oxides（REOs） i.e. Eu2O3, Gd2O3, and Pr2O3 were investigated. The α-Sialon phase was the main phase obtained after sintering as observed by X-ray diffraction（XRD）. The transparency of different samples of varying thickness measured from UV to IR region revealed that the samples were translucent in the visible region while transparent in IR region. The thin samples of 150 μm thickness had transmittance as high as 30% in the visible region. The luminescence was observed in transmittance mode to investigate the effect of sample thickness on luminescence intensity. We observed blue, yellow and red emissions in Sialon doped with Gd2O3, Eu2O3, and Pr2O3, respectively. The excitation wavelength for Gd2O3 and Pr2O3 doped samples were in UV region i.e. 280 and 270 nm, respectively, whereas, for Eu2O3 doped samples was in the blue region（460 nm）. The Eu2O3 doped Sialon having 300 μm thickness showed better white light extraction as coupled with blue LED. Moreover, the fabricated phosphor samples exhibited high hardness around 20 GPa and fracture toughness above 5 MPa·m1/2.
