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Role of surfactants on particle deposition, wear, and corrosion behavior of TaC particle incorporated electroless nickel-phosphorus coating

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Progress in Natural Science:Materials International 2022年第5期32卷 655-663页

作者： Jin-Hyuk Choi Dhani Ram Dhakal yuwaraj k.kshetri Bina Chaudhary Bhupendra Joshi Soo Wohn Lee Tae-Ho kim Research Center for Advance Green Materials Sun Moon University Department of Fusion Science and Technology Sun Moon University

The coatings prepared by incorporating submicron-sized TaC particles while depositing Ni and P atoms on the steel substrate via electroless method showed mixed results of surface finishing, microstructural properties,mechanical, tribological, and corrosion behavior with the addition of various surfactants during the coating process. The surfactant sodium dodecyl sulfate(SDS) enhanced the microhardness when added during the coating process of Ni–P–TaC composite, whereas the cetyltrimethyl ammonium bromide(CTAB) lowered the microhardness as compared to the surfactant-free coating. Moreover, the TaC particle incorporation was hindered by the surfactants CTAB and Triton X-100. An excellent wear resistance behavior has been observed in the surfactantfree Ni–P–TaC coating in comparison to particle-free Ni–P coating. The Ni–P–TaC coatings showed the dependency of wear behavior on the material properties of the counter sliding surface although this dependency has not been observed in Ni–P coatings. The wear damage in Ni–P coating is immense irrespective of the properties of counter-sliding materials. Various surfactant-used Ni–P–TaC coating surfaces deteriorated much more due to corrosion than surfactant-free Ni–P–TaC coating. Among the various surfactants, the CTAB used Ni–P–TaC coating showed weak corrosion resistance.

关键词： Electroless coating NiP-based coating Tantalum carbide Wear Corrosion

Surface modification of blue TiO2 with silane coupling agent for NOx abatement

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Progress in Natural Science:Materials International 2021年第2期31卷 230-238页

作者： Adriana Martinez-Oviedo yuwaraj k.kshetri Bhupendra Joshi Soo Wohn Lee Department of Environmental and Bio-Chemical Engineering Sun Moon University Research Center for Eco Multifunctional Nanomaterials Sun Moon University Department of Fusion Science and Technology Sun Moon University

The role of hydroxyl-functionalization of reduced TiO2(Blue TiO2) for the photocatalytic oxidation of toxic NOx was systematically explored in the present study. A hydrogenation technique was used to reduce the rutile phase in P25 TiO2giving rise to a Magneli phase. Then, the process was followed by the surface functionalization of the Blue TiO2with Trimethoxy(Propyl) Silane(TPS). The fabricated nanoparticles were structurally characterized,and photocatalytically tested for NOx abatement. OH-functionalized Blue TiO2showed strong photo-oxidation of NOx with NOx removal efficiency of 80.2%. The broad-band light absorption(UV and visible) and the formation of a higher number of radicals on the surface of OH-functionalized Blue TiO2made the material more efficient than other samples. In addition, the lowest NO2selectivity of 2.7% proved the effective suppression of toxic NO2and formation of nitrate ions. The reusability test was carried out for five cycles of 1 h and had 10% loss in NOx removal efficiency. The role of surface OH groups for the oxidation of NO and NO2has been discussed in this manuscript. A possible mechanism for NOx photo-oxidation is proposed based on FTIR, ESR, and ion chromatography test.

关键词： Blue TiO 2 OH-Functionalization NOx Photo-oxidation Hydroxyl radicals

Spectroscopic properties of Er3+/Ho3+/Tm3+ doped α-SiAlON ceramics under 793 nm excitation

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Progress in Natural Science:Materials International 2021年第6期31卷 891-897页

作者： Bina Chaudhary Dhani Ram Dhakal Tae-Ho kim Soo Wohn Lee yuwaraj k.kshetri Department of Fusion Science and Technology Sun Moon University Research Center for Eco-Multifunctional Nano Materials Sun Moon University Department of Environment and Bio-Chemical Engineering Sun Moon University

This paper reports the first demonstration of super broadband infrared downshifting emission extending from1640 nm to 2200 nm with the full width at half maximum of ～ 417 nm in lanthanides(Er3+, Ho3+, and Tm3+)-doped α-SiAlON ceramics upon 793 nm excitation. Using α-Si3N4ceramic as a precursor the lanthanides-dopedα-SiAlON ceramics were synthesized by the hot-press method. The lanthanides induced no significant secondary phases in the sintered α-SiAlON ceramics. Strong two-photon upconversion emission bands centered at 547,671 and 694 nm have also been observed upon 793 nm excitation. The time-resolved measurements of the upconversion emissions confirm that the efficient energy transfer among the Er3+, Ho3+and Tm3+ions as well as the ground state absorption in Er3+and Tm3+are responsible for the observed spectroscopic properties.

关键词： α-SiAlON Upconversion Downshifting 793 nm excitation

Understanding the multifunctionality in Cu-doped BiVO_4 semiconductor photocatalyst

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Journal of Environmental Sciences 2019年第1期31卷 84-97页

作者： Chhabilal Regmi yuwaraj k.kshetri Ramesh Prasad PANDey Tae-Ho kim Gobinda Gyawali Soo Wohn Lee Department of Environmental and Biochemical Engineering Sun Moon University Department of Advanced Materials Engineering Sun Moon University Institute of Biomolecule Reconstruction Department of BT-Convergent Pharmaceutical Engineering Sun Moon University Division of Mechanics and ICT Convergence Engineering Sun Moon University

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.

关键词： BiVO4 Photocatalyst Methylene Blue Ibuprofen Escherichia coli First principle calculation

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Microstructure investigation and multicolor upconversion in Yb3+/Ln3+(Ln=Er/Tm/Ho) ions doped α-Sialon

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Progress in Natural Science:Materials International 2019年第5期29卷 549-555页

作者： Sang Hoon Jeong yuwaraj k.kshetri Seung Ho kim Sung Hun Cho Soo W.Lee Department of Environment and Bio-Chemical Engineering Sun Moon University Research Center for Eco Multi-Functional Nano Materials Sun Moon University The Institute of Scientific and Industrial Research (ISIR) Osaka University

Yb3+/Ln3+(Ln=Er/Tm/Ho)-α-sialon ceramics were fabricated by hot press sintering *** microstructure and luminescent properties were studied by XRD,EDS,HRTEM and photoluminescence *** results showed that the sintered ceramics consisted ofα-Sialon with a trace amount ofβ-Sialon *** frequency upconversion and downconversion properties of Yb3+/Ln3+(Ln=Er/Tm/Ho)-α-Sialon ceramics were investigated under 980 nm low-power *** different concentrations of Yb3+/Ln3+(Ln=Er/Tm/Ho)produced multicolor emissions characteristics of each Ln3+ion as a result of the energy transfer from Yb3+to Er3+,Tm3+and Ho3+*** EDS spectra measurements and mappings showed that the Ln3+ions were well incorporated in theα-Sialon *** evolution of the emission decay behavior has been investigated to understand the energy transfer mechanism.

关键词： α-Sialon Hot press sintering Upconversion Energy transfer