• Journal of Powder Materials
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• v.24 no.2
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• pp.87-95
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• 2017

Lithium silicate, a lithium-ion conducting ceramic, is coated on a layer-structured lithium nickel manganese oxide ($LiNi_{0.7}Mn_{0.3}O_2$). Residual lithium compounds ($Li_2CO_3$ and LiOH) on the surface of the cathode material and $SiO_2$ derived from tetraethylorthosilicate are used as lithium and silicon sources, respectively. Powder X-ray diffraction and scanning electron microscopy with energy-dispersive spectroscopy analyses show that lithium silicate is coated uniformly on the cathode particles. Charge and discharge tests of the samples show that the coating can enhance the rate capability and cycle life performance. The improvements are attributed to the reduced interfacial resistance originating from suppression of solid-electrolyte interface (SEI) formation and dissolution of Ni and Mn due to the coating. An X-ray photoelectron spectroscopy study of the cycled electrodes shows that nickel oxide and manganese oxide particles are formed on the surface of the electrode and that greater decomposition of the electrolyte occurs for the bare sample, which confirms the assumption that SEI formation and Ni and Mn dissolution can be reduced using the coating process.

• Journal of the Korean Ceramic Society
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• v.49 no.3
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• pp.241-246
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• 2012

Physical properties of plasma electrolytic oxidized layers of 8 different kinds of Al alloys, A-1100, A-2024, A-5052, A-6061, A-6063, A-7075, ACD-7B and ACD-12 were investigated. The electrolyte for plasma electrolytic oxidation was mixture of distilled water, $Na_2P_2O_7$, KOH and some metal salts. Growth rate of oxide layer was slower in $Na_2P_2O_7$ electrolyte system than in $Na_2SiO_3$ system, and Ra50 surface roughness of oxidized layer was below $1.2{\mu}m$. Surface hardness in $Na_2P_2O_7$ electrolyte system is higher than in $Na_2SiO_3$ system, and roughness was lower in $Na_2P_2O_7$ electrolyte system than in $Na_2SiO_3$ system.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.247-253
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• 2010

The characteristics of selective oxidation prior to hot-dip galvanizing with the annealing atmosphere dew point and chemical composition in dual-phase steels and their effect on the inhibition layer formation relevant to coating adhesion have been studied using a combination of electron microscopic and surface analytical techniques. The annealed and also galvanized samples of 3 kinds of Si/Mn ratios with varied amounts of Si addition were prepared by galvanizing simulator. The dew point was controlled at soaking temperature $800^{\circ}C$ in 15%$H_2$ -85%$N_2$ atmosphere. It was shown that good adhesion factors were mainly uniformity of oxide particle distribution of low number density and low Si/Mn ratio prior to hot-dip galvanizing. Their effect was the greatly reduced coating bare spots and the formation of uniform inhibition layer leading to good adhesion of Zn overlay. The mechanism of good adhesion is suggested by two processes: the formation of inhibition layer on the oxide free surface uncovered with no $SiO_2$-containing particles in particular, and the inhibition layer bridging of oxide particles. The growth of inhibition layer was enhanced markedly by the delayed reaction of Fe and Al with the increase of Si/Mn ratio.

• Journal of Power System Engineering
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• v.12 no.3
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• pp.60-65
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• 2008

This study aims at investigating the wear properties of thermally sprayed $Al/Al_2O_3$ metal matrix composite(MMC) coating against different counterparts. $Al/Al_2O_3$ MMC coatings were fabricated using a flame spray system on an Al 6061 substrate. Dry sliding wear tests were performed using the sliding speeds of 0.2m/s and the applied loads of 1 and 2 N. AISI 52100, $Al_2O_3$, $Si_3N_4\;and\;ZrO_2$ balls(diameter: 8mm) were used as counterpart materials. Wear properties of $Al/Al_2O_3$ MMC coatings were analyzed using a scanning electron microscope(SEM) and energy dispersive X-ray spectroscopy (EDX). It was revealed that wear properties of $Al/Al_2O_3$ composite coatings were much influenced by counterpart materials. In the case of AISI 52100 used as counterparts, the wear rate of composites coating layer increased according to the increase of the applied load. On the contrary, in the case of ceramics used as counterparts, the wear rate of composites coating layer decreased according to the increase of the applied load.

• Journal of the Korean Ceramic Society
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• v.17 no.4
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• pp.213-216
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• 1980

A glass-ceramics material of composition %SiO_2$: 38.50, $Al_2O_3$: 26.00, $Na_2O$: 18.00, CaO: 6.00, MgO: 4.00, $TiO_2$: 7.50 was strengthened by coating a series of glazes$(SiO_2-B_2O_3-Al_2O_3-CaO-PbO-Na_2O-)$, which has lower thermal expansion coefficient than that of the glass-ceramics. The thermal expansion coefficient of the glazes ranges $80~90{\times}10^{-7}$cm/cm/$^{\circ}C$, whereas that of the glass-ceramics is $115{\times}10^{-7}$cm/cm/$^{\circ}C$. The glass-ceramics was identified to be composed of nepheline, carnegieite low form, and meta sodium silicate crystal by X-ray diffraction phase analysis. The glaze, having lower melting point and appropriate thermal expansion coefficient, was tried to be stable and good at secondary heat treatment.

• Journal of Magnetics
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• v.12 no.1
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• pp.21-26
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• 2007

Si-based electromagnetic noise suppressors on coplanar waveguide transmission lines incorporated with a $SiO_2$ dielectric layer and a nanogranular Co-Fe-Al-O magnetic thin film are reported. Unlike glass-based devices, large signal attenuation is observed even in the bare structure without coating the magnetic thin film. Much larger signal attenuation is achieved in fully integrated devices. The transmission scattering parameter ($S_{21}$) is as small as -90 dB at 20 GHz at the following device dimensions; the thicknesses of the $SiO_2$ and Co-Fe-Al-O thin films are 0.1 $\mu$m and 1 $\mu$m, respectively, the length of the transmission line is 15 mm, and the width of the magnetic thin film is 2000 $\mu$m. In all cases, the reflection scattering parameter ($S_{11}$) is below -10 dB over the whole frequency band. Additional distributed capacitance formed by the Cu transmission line/$SiO_2$/Si substrate is responsible for these characteristics. It is considered that the present noise suppressors based on the Si substrate are a first important step to the realization of MMIC noise suppressors.

• Corrosion Science and Technology
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• v.23 no.3
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• pp.179-194
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• 2024

A layer-by-layer coating was produced using electrophoretic deposition for a HA/Al₂O₃ coating layer and a bioglass coating layer on Co-Cr-Mo alloy with a roughness of 0.5 ㎛ (400 emery paper SiC). The corrosion behaviour was analyzed by assessing the coating layers' exceptional corrosion resistance, which outperformed the substrate. Cr ion release test using AAS was carried out, indicating that factional graded coating inhibited ion release from the uncoated substrate to coated sample. The porosity was expressed as a percentage, representing the extent of imperfections on the surface of all coatings. These imperfections fell within an acceptable range of 1% to 3%. The roughness of the coated surface was measured using atomic force microscopy, which revealed an excellent roughness value of 3.32 nm. Tape test technique for adhesion revealed that the removal area of the substrate coating layer varied by 11.92%. X-ray diffraction analysis confirmed the presence of all coating material peaks and verified phases of the deposited coating layers. These findings provided evidence that the coating composition remains unaffected by the electrophoretic deposition process. The bioactivity was assessed by immersion in a simulated bodily fluid, which revealed the formation of HCA during a period of 5 days.

• Clean Technology
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• v.19 no.1
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• pp.44-50
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• 2013

Tin-based materials for lithium ion battery have been proposed as new anode candidates owing to their higher specific capacity and relatively high lithium insertion potential. Tin-based materials have been extensively studied as possible replacements for carbon anodes in lithium ion batteries. However, the large volume expansion results in severe particle cracking with loss of electrical contact, giving irreversible capacity losses which prevent the widespread use of tin-based materials in lithium batteries. So remaining studies of tin-based materials are alleviating volume expansion and improving cycle performance. In this work, $SnO_2-SiO_2$ composites were manufactured with sol-gel method to overcome their volume expansion. Carbon was coated with 10 vol% propylene gas. The characteristics of active material and the effect of heat treatment were investigated with TG/DTA, XRD, SEM and FT-IR. Electrochemical characteristics of these composites were measured with CR2032 type coin cells. Carbon coated $SnO_2-SiO_2$at $300^{\circ}C$ heat treatment showed the best electrochemical performance.

• Korean Journal of Materials Research
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• v.23 no.1
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• pp.53-58
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• 2013

Superhydrophobic $SiO_2$ layers with a micro-nano hierarchical surface structure were prepared. $SiO_2$ layers deposited via an electrospray method combined with a sol-gel chemical route were rough on the microscale. Au particles were decorated on the surface of the microscale-rough $SiO_2$ layers by use of the photo-reduction process with different intensities ($0.11-1.9mW/cm^2$) and illumination times (60-240 sec) of ultraviolet light. With the aid of nanoscale Au nanoparticles, this consequently resulted in a micro-nano hierarchical surface structure. Subsequent fluorination treatment with a solution containing trichloro(1H,2H,2H,2H-perfluorooctyl)silane fluorinated the hierarchical $SiO_2$ layers. The change in surface roughness factor was in good agreement with that observed for the water contact angle, where the surface roughness factor developed as a measure needed to evaluate the degree of surface roughness. The resulting $SiO_2$ layers revealed excellent repellency toward various liquid droplets with different surface tensions ranging from 46 to 72.3 mN/m. Especially, the micro-nano hierarchical surface created at an illumination intensity of $0.11mW/cm^2$ and illumination time of 60 sec showed the largest water contact angle of $170^{\circ}$. Based on the Cassie-Baxter and Young-Dupre equations, the surface fraction and work of adhesion for the micronano hierarchical $SiO_2$ layers were evaluated. The work of adhesion was estimated to be less than $3{\times}10^{-3}N/m$ for all the liquid droplets. This exceptionally small work of adhesion is likely to be responsible for the strong repellency of the liquids to the micro-nano hierarchical $SiO_2$ layers.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.41.1-41.1
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• 2009

Aerosol Deposition (AD) is anovel way to fabricate bioactive ceramic coatings in biomedical implants and prostheses applications. In the present work, silicon-substituted hydroxyapatite (HA) coatings on commercially pure titanium were prepared by aerosol deposition using Si-HA powders. The incorporation of silicon in the HA lattice is known to improve the bioactivity of the HA, makingsilicon-substitute HA an attractive alternative to pure HA in biomedical applications. Si-HA powders with the chemical formula $Ca_{10}(PO_4)_6-x(SiO_4)x(OH)_2-x$, having silicon contents up to x=0.5 (1.4 wt%), were synthesized by solid-state reaction of $Ca_2P_2O_7$, $CaCO_3$, and $SiO_2$. The Si-HA powders were characterized by X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), and Fourier transform infrared spectroscopy(FT-IR). The corresponding coatings were also analyzed by XRD, scanning electron microscopy (SEM), and electron probe microanalyzer (EPMA). The results revealed that a single-phase Si-HA was obtained without any secondary phases such as $\alpha$- or $\beta$-tricalcium phosphate (TCP) for both the powders and the coatings.The Si-HA coating was about $5\;{\mu}m$ thick, had a densemicrostructure with no cracks or pores. In addition, the proliferation and alkaline phosphatase (ALP) activity of MC3T3-E1 preosteoblast cells grown on the Si-HA coatings were significantly higher than those on the bare Ti and pure HA coating. These results revealed the stimulatory effects induced by siliconsubstitution on the cellular response to the HA coating.