• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.9
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• pp.582-588
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• 2014

3 mol% Co-added $Ni(OH)_2$ fine powders, which showed ${\beta}$-phase, as positive electrode materials have been fabricated using $NiSO_4{\cdot}6H_2O$ aqueous solution by ultrasonic spray-chemical precipitation and subsequent hydrothermal method, and sheet-like Ni nanopowder was fabricated by mechano-chemical reduction method. The addition effects of the sheet-like Ni nanopowder on the electrochemical properties of the positive electrode in Ni-Zn Redox flow battery were investigated. Impedance spectroscopy revealed that the addition of the sheet-like Ni nanopowder resulted in decrease in the electrical resistivity; 10 wt.% addition reduced the electrical properties by a fifth. Cyclic voltammetry showed the addition of the sheet-like Ni nanopowder resulted in decrease in the potential difference of oxidation and reduction; this means the increase in the reversability for electrode reduction. Charge/discharge measurement confirmed that the addition of the sheet-like Ni nanopowder resulted in the increase in the discharge efficiency.

• Journal of the Korean Ceramic Society
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• v.54 no.3
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• pp.211-216
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• 2017

ZnO nanopowder was synthesized using a relatively facile and convenient glycol process. ZnO nanopowder was successfully synthesized at temperatures as low as $125^{\circ}C$ using zinc acetate as the Zn source and 1,4-butanediol as the solvent. Then, the effects of water content on the growth process and morphological evolution of ZnO powders were investigated using 1,4-butanediol and water as binary solvent mixtures. Using pure 1,4-butanediol at a temperature above $125^{\circ}C$, the prepared hexagonal ZnO nanopowder exhibited a quasi-spherical shape with average crystalline size of approximately 30 - 50 nm. It is also demonstrated that the morphology of ZnO powders can be controlled by the addition of various water content in 1,4-butanediol. With increasing water content, the morphologies of the ZnO powders changed sequentially from quasi-spherical to hexagonal plate and pyramid, and finally to hexagonal prismatic with a pyramidal tip. A sharp peak centered at 384 nm in the UV region and a weak broad peak in the visible region between 450 and 700 nm were shown in the room temperature PL spectra of the ZnO synthesized using the glycol process, regardless of the addition of water, suggesting that ZnO nanopowders with the best crystallinity were obtained under these conditions.

• Journal of the Korean Ceramic Society
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• v.55 no.2
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• pp.140-144
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• 2018

$ZnO/TiO_2$ nanocomposites were synthesized via a modified sol-gel technique by incorporating 30 and 70 wt% $TiO_2$ nanopowder into a ZnO sol-gel matrix. Zinc acetate dihydrate was used as the ZnO precursor and de-ionized water as the solvent, while titanium oxysulfate was employed for the synthesis of $TiO_2$ nanopowder. The synthesized $ZnO/TiO_2$ nanocomposites were characterized by x-ray diffraction, UV-vis spectroscopy, scanning electron microscopy, and transmission electron microscopy. The $ZnO/TiO_2$ nanocomposites showed both the ZnO (wurtzite) and $TiO_2$ (anatase) phases. The average ZnO crystallite size of the $ZnO/TiO_2$ nanocomposites was found to be about 26.3 nm. The TEM results confirmed that spherical $TiO_2$ particles were embedded in the ZnO matrix. $TiO_2$ particles attached onto the rod-like ZnO particles were also observed. The $ZnO/TiO_2$ nanocomposites exhibited optical absorption properties superior to those of pure ZnO and $TiO_2$.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.04a
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• pp.107.1-107
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• 2003

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.824-829
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• 2012

Zn wires have been electrically exploded in methanol or distilled water using the pulsed power technologies. The nanopowders produced by the explosions have been observed by using SEM and TEM, and analyzed its phase by using EDS and XRD. The nanopowders produced in distilled water showed ZnO phase only. On the other hands, the nanopowder produced in methanol showed mixed phases with Zn and ZnO. The HR-TEM images of the nanopowders produced in methanol showed that the some particles have been coated with carbon like materials. It is considered that the carbon coatings could be depended on the positions of the particles during the plasma state formed by explosion.

• Journal of Powder Materials
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• v.12 no.6 s.53
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• pp.399-405
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• 2005

Nanopowders of titanium dioxide $(TiO_2)$ incorporating the transition metal element(s) were synthesized by flame synthesis method. Single element among Fe(III), Cr(III), and Zn(II) was doped into the interior of $TiO_2$ crystal; bimetal doping of Fe and Zn was also made. The characteristics of transition-metal-doped $TiO_2$ nanopowders in the particle feature, crystallography and electronic structures were determined with various analytical tools. The chemical bond of Fe-O-Zn was confirmed to exist in the bimetal-doped $TiO_2$ nanopowders incorporating Fe-Zn. The transition element incorporated in the $TiO_2$ was attributed to affect both Ti 3d orbital and O 2p orbital by NEXAFS measurement. The bimetal-doped $TiO_2$ nanopowder showed light absorption over more wide wavelength range than the single-doped $TiO_2$ nanopowders.

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.163.2-163
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• 2002

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05b
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• pp.47-53
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• 2003

자발착화연소법과 분무열분해법을 동시에 적용한 초음파분무연소법을 이용하여 40~50nm 크기를 갖는 결정성 ZnO 분말을 합성하였다. 또한 바리스터로의 응용을 위해 Bi, Sb, Co, Mn을 초기출발원료인 Zn-nitrate에 첨가하여 복합조성의 ZnO계 바리스터 분말을 합성하였다. 합성된 바리스터의 분말을 성형 및 소결하여 전기적 특성을 관찰한 결과 Co를 첨가한 분말보다 Mn을 첨가한 분말에서 우수한 전기적 특성을 나타내었다.

• Korean Journal of Materials Research
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• v.30 no.5
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• pp.252-261
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• 2020

We prepare ZnO nanoparticles by environmentally friendly synthesis using Cyathea nilgiriensis leaf extract. Various phytochemical constituents are identified through the assessment of ethanolic extract of plant Cyathea nilgiriensis holttum by GC-MS analysis. The formation of ZnO nanoparticles is confirmed by FT-IR, XRD, SEM-EDX, TEM, SAED and PSA analysis. TEM observation reveals that the biosynthesized ZnO nanopowder has a hexagonal structure. The calculated average crystallite size from the high intense plane of (1 0 1) is 29.11 nm. The particle size, determined by TEM analysis, is in good agreement with that obtained by XRD analysis. We confirm the formation of biomolecules in plant extract by FT-IR analysis and propose a possible formation mechanism of ZnO nanoparticles. Disc diffusion method is used for the analyses of antimicrobial activity of ZnO nanoparticles. The synthesized ZnO nanoparticles exhibit antimicrobial effect in disc diffusion experiments. The biosynthesized ZnO nanoparticles display good antibacterial performance against B. subtilis (Gram-positive bacteria) and K. pneumonia (Gram-negative bacteria). Bio-synthesized nanoparticles using green method are found to possess good antimicrobial performance.

• The Journal of Advanced Prosthodontics
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• v.9 no.6
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• pp.482-485
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• 2017

PURPOSE. This laboratory study aimed to investigate the effect of doping an acrylic denture base resin material with nanoparticles of ZnO, CaO, and $TiO_2$ on biofilm formation. MATERIALS AND METHODS. Standardized specimens of a commercially available cold-curing acrylic denture base resin material were doped with 0.1, 0.2, 0.4, or 0.8 wt% commercially available ZnO, CaO, and $TiO_2$ nanopowder. Energy dispersive X-ray spectroscopy (EDX) was used to identify the availability of the nanoparticles on the surface of the modified specimens. Surface roughness was determined by employing a profilometric approach; biofilm formation was simulated using a monospecies Candida albicans biofilm model and a multispecies biofilm model including C. albicans, Actinomyces naeslundii, and Streptococcus gordonii. Relative viable biomass was determined after 20 hours and 44 hours using a MTT-based approach. RESULTS. No statistically significant disparities were identified among the various materials regarding surface roughness and relative viable biomass. CONCLUSION. The results indicate that doping denture base resin materials with commercially available ZnO, CaO, or $TiO_2$ nanopowders do not inhibit biofilm formation on their surface. Further studies might address the impact of varying particle sizes as well as increasing the fraction of nanoparticles mixed into the acrylic resin matrix.