• Journal of Electrochemical Science and Technology
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• v.10 no.2
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• pp.159-169
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• 2019

The activated carbon materials were prepared from waste biomass by ultrasonic assisted chemical activation method (UCA), ultrasonic assisted physical activation method (UPA) and Manganese nitrogen doped carbon (Mn/N-C). The XRD result shows the turbostatic (fully disordered) structure. The cyclic voltammetry test was done at 50 mV/s using 1M sodium sulfate and the values of specific capacitance were found to be 93, 100 and 115 F/g for UCA, UPA and Mn/N-C respectively. The power density values for the samples UCA, UPA and Mn/N-C were found to be 46.04, 87.97 and 131.42 W/kg respectively. The electrochemical impedance spectroscopy was done at low frequency between 1 to 10 kHz. The Nyquist plot gives the resistant characteristics of the materials due to diffusional resistance at the electrode-electrolyte interface. The Energy Dispersive X-Ray Spectroscopyanalysis (EDAX) analysis showed that the percentage doping of nitrogen and manganese were 3.53 wt% and 9.44 wt% respectively. It is observed from the experiment Mn/N-C doped carbon show good physical and electrochemical properties.

• Tribology and Lubricants
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• v.37 no.5
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• pp.179-188
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• 2021

Reputed for their low friction coefficient and wear protection effect, diamond-like carbon (DLC) materials are considered amongst the most important lubricant coatings for tribological applications. In this framework, this investigation aims to elucidate the effect of a few operating parameters, such as applied stress and sliding amplitude on the friction lifetime of DLC coatings. Fretting wear tests are conducted using a 12.7 mm radius counterpart of 52100 steel balls slid against a substrate of the same material coated with a 2 ㎛ thickness DLC. Approximately, 5 to 57 N force is applied, generating a maximum Hertzian contact pressure of 430 to 662 MPa, corresponding to the applied force. The coefficient of friction (CoF) generates three regimes, first a running-in period regime, followed by a steady-state evolution regime, and finally a progressive increase of the CoF reaching the steel CoF value, as an indicator of reaching the substrate. To track the wear scenario, interrupted tests are performed with analysis combining scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), 3D profilometer and micro-Raman spectroscopy. The results show two endurance values: one characterizing the coating failure (Nc₁), and the other (Nc₂) indicating the friction failure which is situated where the CoF reaches a threshold value of μ_th = 0.3 in the third regime. The Archard energy density factor is used to determine the two endurance values (Nc₁, Nc₂). Based on this approach, a master curve is established delimitating both the coating and the friction endurances.

• Korean Journal of Materials Research
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• v.32 no.5
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• pp.249-257
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• 2022

Transparent thin films of pure and nickel-doped ZrO₂ are grown successfully by sol-gel dip-coating technique. The structural and optical properties according to the different annealing temperatures (300 ℃, 400 ℃ and 500 ℃) are investigated. Analysis of crystallographic properties through X-ray diffraction pattern reveals an increase in crystallite size due to increase in crystallinity with temperature. All fabricated thin films are highly-oriented along (101) planes, which enhances the increase in nickel doping. Scanning electron microscopy and energy dispersive spectroscopy are employed to confirm the homogeneity in surface morphology as well as the doping configuration of films. The extinction coefficient is found to be on the order of 10^-2, showing the surface smoothness of deposited thin films. UV-visible spectroscopy reveals a decrease in the optical band gap with the increase in annealing temperature due to the increase in crystallite size. The variation in Urbach energy and defect density with doping and the change in annealing temperature are also studied.

• Journal of Hydrogen and New Energy
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• v.35 no.2
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• pp.185-194
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• 2024

Fe-Ni nanocatalysts loaded on carbon black were prepared via spontaneous reduction reaction of iron (II) acetylacetonate and nickel (II) acetylacetonate in dry process. Their morphology and elemental analysis were characterized by scanning electron microscopy, transmission electron microscopy (TEM), and energy dispersive X-ray analyzer. The loading weight of the nanocatalysts was measured by thermogravimetric analyze and the surface area was measured by BET analysis. TEM observation showed that Fe and Ni nanoparticles was well dispersed on the carbon black and their average particle size was 4.82 nm. The loading weight of Fe-Ni nanocatalysts on the carbon black was 6.83-7.32 wt%, and the value increased with increasing iron (II) acetylacetonate content. As the Fe-Ni loading weight increased, the specific surface area decreased significantly by more than 50%, because Fe-Ni nanoparticles block the micropores of carbon black. I-V characteristics showed that water electrolysis performance increased with increasing Ni nanocatalyst content.

• Korean Journal of Materials Research
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• v.21 no.10
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• pp.563-567
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• 2011

We report the structural characterization of $Bi_xZn_{1-x}O$ thin films grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. By increasing the Bi flux during the growth process, $Bi_xZn_{1-x}O$ thin films with various Bi contents (x = 0~13.17 atomic %) were prepared. X-ray diffraction (XRD) measurements revealed the formation of Bi-oxide phase in (Bi)ZnO after increasing the Bi content. However, it was impossible to determine whether the formed Bi-oxide phase was the monoclinic structure ${\alpha}-Bi_2O_3$ or the tetragonal structure ${\beta}-Bi_2O_3$ by means of XRD ${\theta}-2{\theta}$ measurements, as the observed diffraction peaks of the $2{\theta}$ value at ~28 were very close to reflection of the (012) plane for the monoclinic structure ${\alpha}-Bi_2O_3$ at 28.064 and the reflection of the (201) plane for the tetragonal structure ${\beta}-Bi_2O_3$ at 27.946. By means of transmission electron microscopy (TEM) using a diffraction pattern analysis and a high-resolution lattice image, it was finally determined as the monoclinic structure ${\alpha}-Bi_2O_3$ phase. To investigate the distribution of the Bi and Bi-oxide phases in BiZnO films, elemental mapping using energy dispersive spectroscopy equipped with TEM was performed. Considering both the XRD and the elemental mapping results, it was concluded that hexagonal-structure wurtzite $Bi_xZn_{1-x}O$ thin films were grown at a low Bi content (x = ~2.37 atomic %) without the formation of ${\alpha}-Bi_2O_3$. However, the increased Bi content (x = 4.63~13.17 atomic %) resulted in the formation of the ${\alpha}-Bi_2O_3$ phase in the wurtzite (Bi)ZnO matrix.

• Tribology and Lubricants
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• v.26 no.6
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• pp.317-321
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• 2010

Thin films of tin sulphide (SnS) have been formed by a novel 2-stage process where-in D.C. magnetron sputtering was used to deposit to thin films of tin (Sn) and the layers then sulphidised using 5% hydrogen sulphide ($H_2S$) gas in Argon. Although it was not found possible to deposit high quality thin films of tin directly onto glass substrates, excellent layers of tin were produced by using molybdenum (Mo) coated glass as the substrate material. The chemical and physical properties of the SnS layers formed were determined using scanning electron microscopy, energy dispersive x-ray analysis, x-ray diffraction studies and using reflectance versus wavelength measurements and these related to the conditions of synthesis. The data shows that it should be possible to produce conventional "substrate structure" devices based on the use of this technology.

• Applied Chemistry for Engineering
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• v.28 no.2
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• pp.245-251
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• 2017

In this study, ZnO, which is widely known as a non $TiO_2$ photocatalyst, was synthesized using coprecipitation method and Ag was added in order to improve the catalytic performance. The physicochemical characteristics of the synthesized ZnO and Ag/ZnO particles were checked using X-ray diffraction (XRD), UV-visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL), and photocurrent measurements. The performance of catalysts was tested by $H_2$ production using the photolysis of $H_2O$ with MeOH. By adding Ag which plays a role as an electron capture on the ZnO catalyst, the performance increased due to the recombination of excited electrons and holes. In particular, $8.60{\mu}mol\;g^{-1}$ $H_2$ was produced after 10 h reaction over the 0.50 mol% Ag/ZnO.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.153-153
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• 2017

The application of the coating supports the mechanical characteristics of the implant, and various materials and coatings are currently being used in the implant in a way to accelerate adhesion. Especially, plasma electrolytic oxidation (PEO) coating has been proposed continually with good surface treatment of titanium alloys. Also, the PEO process can incorporate Ca and P ions on the titanium surface through variables varied factor. PEO process for bioactive surface has carried out in electrolytes containing Ca and P ions. Natural bone is composed of mineral elements such as Mg, Si, Zn, Sr, and Mn, etc. Especially, Mg and Si of these elements play role in bone formation and growth after clinical implantation of bio-implants. In this study, corrosion charateristics of PEO-treated Ti-6Al-4V alloy in solution containing Si and Mg ions has been investigated using several experimental techniques. The PEO-treated surfaces were identified by X-ray diffraction, using a diffractometer (XRD, Philips X' pert PRO, Netherlands) with Cu $K{\alpha}$ radiation. The morphology was observed by field-emission scanning electron microscopy (FE-SEM, Hitachi 4800, Japan) and energy-dispersive X-ray spectroscopy (EDX, Oxford ISIS 310, England). The potentiodynamic polarization and AC impedance tests for electrochemical degradations were carried out in 0.9% NaCl solution at similar body temperature using a potentiostat with a scan rate of 1.67mV/s and potential range from -1500mV to + 2000mV.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.389-389
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• 2012

Molybdenum is one of the most important materials used as a back ohmic contact for $Cu(In,Ga)(Se,S)_2$ (CIGS) solar cells because it has good electrical properties as an inert and mechanically durable substrate during the absorber film growth. Sputter deposition is the common deposition process for Mo thin films. Molybdenum thin films were deposited on soda lime glass (SLG) substrates using direct-current planar magnetron sputtering technique. The outdiffusion of Na from the SLG through the Mo film to the CIGS based solar cell, also plays an important role in enhancing the device electrical properties and its performance. The structure, surface morphology and electrical characteristics of Mo thin films are generally dependent on deposition parameters such as DC power, pressure, distance between target and substrate, and deposition temperature. The aim of the present study is to show the resistivity of Mo layers, their crystallinity and morphologies, which are influenced by the substrate temperature. The thickness of Mo films is measured by Tencor-P1 profiler. The crystal structures are analyzed using X-ray diffraction (XRD: X'Pert MPD PRO / Philips). The resistivity of Mo thin films was measured by Hall effect measurement system (HMS-3000/0.55T). The surface morphology and grain shape of the films were examined by field emission scanning electron microscopy (FESEM: Hitachi S-4300). The chemical composition of the films was obtained by the energy dispersive X-ray spectroscopy (EDX). Finally the optimum substrate temperature as well as deposition conditions for Mo thin films will be developed.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.74-74
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• 2018

Ti-6Al-4V alloys have been widely used as orthopedic materials because of their excellent corrosion resistance and mechanical properties. However, it does not bind directly to the bone, so it requires a surface modification. This problem can be solved by nanotube and micropore formation. Plasma electrolytic oxidation (PEO) treatment for micropore, which combines high-voltage spark and electrochemical oxidation, is a new way of forming a ceramic coating on light metals such as titanium and its alloys. This method has excellent reproducibility and can easily control the shape and size of the Ti alloy. In this study, formation of bioactive surface by PEO-treatment after $2^{nd}$ ATO technique of Ti-6Al-4V alloy was invesgated by various instrument. Nanotube oxide surface structure was formed on the surface by anodic oxidation treatment in 0.8 wt.% NaF and 1M $H_3PO_4$ electrolytes. After nanotube formation, nanotube layer was removed by ultrasonic cleaning. PEO-treatment was carried out at 280V for 3 minutes in the electrolytic solution containing the bioactive substance (Mg, Zn, Mn, Sr, and Si). The surface of Ti-6Al-4V alloy was observed by field emission scanning electron microscopy (FE-SEM, S-4800 Hitachi, Japan). An energy dispersive X-ray spectrometer (EDS, Inca program, Oxford, UK) was used to analyze the spectra of physiologically active Si, Mn, Mg, Zn, and Sr ions. The PEO film formed on the Ti-6Al-4V alloy surface was characterized using an X-ray diffractometer (TF-XRD, X'pert Philips, Netherlands). It is confirmed that bioactive ions play an essential role in the normal bone growth and metabolism of the human skeletal tissues.