• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4393-4411
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• 2022

In recent years, beryllium oxide has been widely utilized in multiple compact nuclear reactors as the neutron moderator, the neutron reflector or the matrix material with dispersed nuclear fuels due to its prominent properties. In the past 70 years, beryllium oxide has been studied extensively, but rarely been systematically organized. This article provides a systematic review of the application history, thermal properties, mechanical properties, corrosion behavior and fabrication methods of beryllium oxide. Data from previous literature are extracted and sorted out, and all of these original data are attached as the supplementary material, so that subsequent researchers can utilize this paper as a database for beryllium oxide research in reactor design or simulation analysis, etc. In addition, this review article also attempts to point out the insufficiency of research on beryllium oxide, and the possible key research areas about beryllium oxide in the future.

• Carbon letters
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• v.13 no.1
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• pp.39-43
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• 2012

The size and the physical properties of graphene oxide sheets were controlled by changing the oxidation temperature of graphite. Graphite oxide (GO) samples were prepared at different oxidation temperatures of $20^{\circ}C$, $27^{\circ}C$ and $35^{\circ}C$ using a modified Hummers' method. The carbon-to-oxygen (C/O) ratio and the average size of the GO sheets varied according to the oxidation temperature: 1.26 and 12.4 ${\mu}m$ at $20^{\circ}C$, 1.24 and 10.5 ${\mu}m$ at $27^{\circ}C$, and 1.18 and 8.5 ${\mu}m$ at $35^{\circ}C$. This indicates that the C/O ratio and the average size of the graphene oxide sheets respectively increase as the oxidation temperature decreases. Moreover, it was observed that the surface charge and optical properties of the graphene oxide sheets could be tuned by changing the temperature. This study demonstrates the tunability of the physical properties of graphene oxide sheets and shows that the properties depend on the functional groups generated during the oxidation process.

• Journal of the Korean Vacuum Society
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• v.1 no.1
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• pp.190-197
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• 1992

In this study we have investigated physical and electrical properties of high temperature oxide (HTO) thin film using dichlorosilane (DCS) gas. This film had low etch rate and excellent step coverage, and its characteristics of Si-O bond were similar to those of thermal oxide. I-V curves also showed similar electrical properties to those of thermally grown oxide (SiO2) while time dependent dielectric breakdown (TDDB) results revealed 1/4 value of thermal oxide. However, defect density was measured to be much lower value than that of thermal oxide.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.10
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• pp.896-901
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• 2005

The microstructure and electrical properties of praseodymium-based zinc oxide varistors were investigated at various cobalt oxide contents in the range of $0.5{\~}5.0 mol\%$. The ceramic density increased in the range of $5.25{\~}5.55 g/cm^3$ with increasing cobalt oxide content. The varistor doped with cobalt oxide of $1.0 mol\%$ exhibited the highest nonlinearity, with 66.6 in nonlinear exponent and 1.2 $\mu$A in leakage current. The donor concentration, density of interface states, and tamer height were in the range of $(1.06{\~}1.69){\times}10^{18}/cm^3$, $(3.11 {\~}3.56){\times}10^{12}/cm^2$, and 0.80${\~}$1.07 eV, respectively.

• Advances in concrete construction
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• v.3 no.2
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• pp.145-159
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• 2015

The evolution of nanotechnology provides materials with advance properties. It's a fast growing area of research to introduce the oxide nanoparticles into the cement pastes to improve their performance. The purpose of this paper is to review the effects of oxide nanoparticles (such as $SiO_2$, $TiO_2$, $Fe_2O_3$, $ZnO_2$, $Cr_2O_3$ and $Al_2O_3$) on both of hardened concrete properties (i.e., compressive strength, split tensile strength and flexural strength, water permeability, Abrasion resistance and pore structure of concrete) and fresh concrete properties (i.e., workability and setting time). Graphical representations of all these parameters were presented to facilitate the comparison of the effect of oxide nanoparticles on concrete processing. The paper also introduces some discussion about future work in this direction by identifying some open research area.

• Korean Journal of Materials Research
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• v.31 no.7
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• pp.420-426
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• 2021

Graphene, a new material with various advantageous properties, has been actively used in various fields in recent years. Applications of graphene oxide are increasing in combination with other materials due to the different properties of graphene oxide, depending on the number of single and multiple layers of graphene. In this study, single-layer graphene oxide and multi-layer graphene oxide are spray coated on polystyrene, and the physicochemical properties of the coated surfaces are characterized using SEM, Raman spectroscopy, AFM, UV-Vis spectrophotometry, and contact angle measurements. In single-layer graphene oxide, particles of 20 ㎛ are observed, whereas a 2D peak is less often observed, and the difference in surface height increases according to the amount of graphene oxide. Adhesion increases with an increase in graphene oxide up to 0.375 mg, but decreases at 0.75 mg. In multi-layer graphene oxide, particles of 5 ㎛ are observed, as well as a 2D peak. According to the amount of graphene oxide, the height difference of the surface increases and the adhesive strength decreases. Both materials are hydrophilic, but single-layer graphene oxide has a hydrophilicity higher than that of multi-layer graphene oxide. We believe that multi-layer graphene oxide and single-layer graphene oxide can be implemented based on the characteristics that make them suitable for application.

• International Journal of Advanced Culture Technology
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• v.3 no.1
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• pp.13-20
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• 2015

The self-cleaning properties of nano-zinc oxide on cotton fabrics have been investigated. The cotton fabric has been prepared by pad-dry method. The nano-zinc oxide was encapsulated in the polystyrene particle by mini-emulsion process prior used. The loading amount of zinc oxide particles into the mini-emulsion were various from 1% wt to 40%wt. The particles sizes of ZnO-encapsulated polystyrene mini-emulsion were determined using dynamic light scattering. It was showed that the particle size of the mini-emulsion was in the range of 124-205 nm. The topography and morphology of ZnO-encapsulated polystyrene which coated on cotton fabrics was observed using scanning electron microscopy. The crystal structure of ZnO-coated on cotton fabrics was explored by X-ray diffraction spectroscopy. The photocatalytic activities of zinc oxide were present through the self-cleaning properties. The presents of the zinc oxide on cotton fabrics significantly showed the improving of the self-cleaning properties under UV radiation.

• Elastomers and Composites
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• v.49 no.3
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• pp.191-198
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• 2014

We synthesized thermoplastic polyurethane elastomer(TPU) with acid group and nano zinc oxide, and characterized their mechanical properties, thermal properties, contact angle and grip property. The effects of the zinc oxide content and size on the physical property of TPU were investigated. When the nano zinc oxide was introduced in TPU with acid group, it had excellent mechanical properties and grip by formation of hydrogen and ionic bonding. The wet slip of TPU with zinc oxide was increased continuously as ionization rate increased due to increase of hydrophilicity and ionic interaction, and mechanical properties were increased with increasing ionization rate up to 50%.

• Korean Journal of Materials Research
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• v.29 no.10
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• pp.609-616
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• 2019

Oxide coatings are formed on die-cast AZ91D Mg alloy through an environmentally friendly plasma electrolytic oxidation(PEO) process using an electrolytic solution of $NaAlO_2$, KOH, and KF. The effects of PEO condition with different duty cycles (10 %, 20 %, and 40 %) and frequencies(500 Hz, 1,000 Hz, and 2,000 Hz) on the crystal phase, composition, microstructure, and micro-hardness properties of the oxide coatings are investigated. The oxide coatings on die-cast AZ91D Mg alloy mainly consist of MgO and $MgAl_2O_4$ phases. The proportion of each crystalline phase depends on various electrical parameters, such as duty cycle and frequency. The surfaces of oxide coatings exhibit as craters of pancake-shaped oxide melting and solidification particles. The pore size and surface roughness of the oxide coating increase considerably with increase in the number of duty cycles, while the densification and thickness of oxide coatings increase progressively. Differences in the growth mechanism may be attributed to differences in oxide growth during PEO treatment that occur because the applied operating voltage is insufficient to reach breakdown voltage at higher frequencies. PEO treatment also results in the oxide coating having strong adhesion properties on the Mg alloy. The micro-hardness at the cross-section of oxide coatings is much higher not only compared to that on the surface but also compared to that of the conventional anodizing oxide coatings. The oxide coatings are found to improve the micro-hardness with the increase in the number of duty cycles, which suggests that various electrical parameters, such as duty cycle and frequency, are among the key factors controlling the structural and physical properties of the oxide coating.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.634-637
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• 1999

The amorphous vanadium oxide as a cathode material is very preferable for fabricating high performance micro-battery. The amorphous vanadium oxide cathode is preferred over the crystalline form because three times more lithium ions can be inserted into the amorphous cathode, thus making a battery that has a higher capacity. The electrochemical properties of sputtered films are strongly dependent on the oxygen partial pressure in the sputtering gas. The effect of different oxygen partial pressure on the electrochemical properties of vanadium oxide thin films formed by r.f. reactive sputtering deposition were investigated. The stoichiometry of the as-deposited films were investigated by Auger electro spectroscopy. X-ray diffraction and atomic force microscopy measurements were carried out to investigate structural properties and surface morphology, respectively. For high oxygen partial pressure(>30% ), the films were polycrystalline V$_2$O$_{5}$ while an amorphous vanadium oxide was obtained at the lower oxygen partial pressure(< 15%). Half-cell tests were conducted to investigate the electrochemical properties of the vanadium oxide film cathode. The cell capacity was about 60 $\mu$ Ah/$\textrm{cm}^2$ m after 200 cycle when oxygen partial pressure was 20%. These results suggested that the capacity of the thin film battery based on vanadium oxide cathode was strongly depends on crystallinity.y.