• Proceedings of the Korean Vacuum Society Conference
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• 1997.02a
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• pp.128-128
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• 1997

• Proceedings of the Korean Vacuum Society Conference
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• 1996.02a
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• pp.56-56
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• 1996

• Proceedings of the Materials Research Society of Korea Conference
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• 1998.11a
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• pp.12-12
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• 1998

• Composites Research
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• v.33 no.3
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• pp.153-160
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• 2020

In this paper, hexagonal boron nitride (h-BN) particles were added between the sheets of prepreg, and the effect of on many properties of BN-embedded carbon fiber reinforced plastics was investigated. The amount of BN particles which corresponds with 0 to 15 wt% of total resin weight was used as an additive material. The tensile strength and the inter-laminar shear strength of BN-embedded CFRP samples were improved by maximally 13.6%, and 6.7%, respectively. The tendency changes of thermal, electrical conductivities and the morphology of cross-section of CFRPs were also observed. This study suggests the possibility of controlling the characteristics of carbon fiber-BN-epoxy composites to use for aerospace applications.

• Steel and Composite Structures
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• v.23 no.2
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• pp.153-160
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• 2017

It is extremely important to be aware of the ballistic performances of engineering materials in order to be able to choose the lightest armor providing full ballistic protection in civil and military applications. Therefore, ballistic tests are an important part of armor design process. In this study, ballistic performance of plates made of carbon steel and cold worked tool steel against 7.62 mm AP (armor-piercing) bullets was examined experimentally and numerically in accordance with NIJ standards. Samples in different sizes were prepared to demonstrate the effect of target thickness on ballistic performance. Some of these samples were coated with titanium nitride using physical vapor deposition (PVD) method. After examining all successful and unsuccessful samples at macro and micro levels, factors affecting ballistic performance were determined. Explicit non-linear analyses were made using Ls-Dyna software in order to confirm physical ballistic test results. It was observed that the ballistic features of steel plates used in simulations comply with actual physical test results.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3258-3264
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• 2012

Aluminum oxide ($Al_2O_3$) nanofibers were treated thermally under an ammonia ($NH_3$) gas stream balanced by nitrogen to form a thin aluminum nitride (AlN) layer on the nanofibers, resulting in the enhancement of thermal conductivity of $Al_2O_3$/epoxy nanocomposites. The micro-structural and morphological properties of the $NH_3$-assisted thermally-treated $Al_2O_3$ nanofibers were characterized by X-ray diffraction (XRD) and atomic force microscopy (AEM), respectively. The surface characteristics and pore structures were observed by X-ray photoelectron spectroscopy (XPS), Zeta-potential and $N_2$/77 K isothermal adsorptions. From the results, the formation of AlN on $Al_2O_3$ nanofibers was confirmed by XRD and XPS. The thermal conductivity (TC) of the modified $Al_2O_3$ nanofibers/epoxy composites increased with increasing treated temperatures. On the other hand, the severely treated $Al_2O_3$/epoxy composites showed a decrease in TC, resulting from a decrease in the probability of heat-transfer networks between the filler and matrix in this system due to the aggregation of nanofiber fillers.

• Journal of the Korean Ceramic Society
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• v.25 no.5
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• pp.561-569
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• 1988

Mixtures of very small amounts of additive, carbon and silica(about 0.46${\mu}{\textrm}{m}$) which synthesized by the hydrolysis of ethyl silicate, the molar ratio of SiO2/C was fixed to 1/10, was nitrided at 145$0^{\circ}C$. It was considered that the optimum amount of additive to promote the nitridation reaction was below 2.0wt%. By the addition of additive, the nitridation reaction was promoted and formation of $\beta$-Si3N4 was promoted at 145$0^{\circ}C$ for 1hour, but, the nitridation reaction was decreased and the ratio of $\alpha$/$\beta$ of Si3N4, was increased at 145$0^{\circ}C$ for 5 hours. The crystal phase was $\alpha$ phase and the nitridation reaction was promoted and the particle size of silicon nitride was become smaller by the addition of $\alpha$-Si3N4, but silicon nitride of whisker-like form was produced by the addition of transition elements. There was a difference in the lattice constants of $\alpha$-Si3N4, but no difference in its of $\beta$-Si3N4 according to kinds of added substance and reaction time.

• Journal of the Korean Vacuum Society
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• v.7 no.3
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• pp.242-247
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• 1998

Hydrogenated amorphous carbon nitride[a-C:H(N)] films were deposited on p-type Si(100) at room temperature with bias voltage of 200 V by DC saddle-field plasma-enhanced chemical vapor deposition. Effects of the ratio of $N_2$ to $CH_4$($N_2/CH_4$), in the range of 0 and 4 on such properties as optical properties, microstucture, relative fraction of nitrogen and carbon, etc. of the films have been investigated. The thickness of the a-C:H(N) film was abruptly decreased with the addition of nitrogen, but at $N_2/CH_4$>0.5, the thickness of the film gradually decreased with the increase of the $N_2/CH_4$. The ratio of N to C(N/C) of the films was saturated at 0.25 with the increase of $N_2CH_4$. N-H, C≡N bonds of the films increased but C-H bond decreased with the increase of $N_2CH_4$.Optical band gap energy of the film decreased from 2.53 eV at the ratio of $N_2CH_4$=4.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1579-1582
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• 2011

Alumina particles wrapped in few-layer graphene sheets were prepared by calcining aluminum nitride powders under a mixed gas flow of carbon monoxide and argon. The graphene sheets were characterized by powder X-ray diffraction (XRD), Raman spectroscopy, electron energy loss spectroscopy, and high-resolution transmission electron microscopy. The few-layer graphene sheets, which wrapped around the alumina particles, did not exhibit any diffraction peaks in the XRD patterns but did show three characteristic bands (D, G, and 2D bands) in the Raman spectra. The dye-sensitized solar cell (DSSC) with the alumina particles wrapped in few-layer graphene sheets exhibited significantly improved overall energy-conversion efficiency, compared to conventional DSSC, due to longer electron lifetime.

• Journal of the Korean Ceramic Society
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• v.24 no.2
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• pp.147-154
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• 1987

Silicon nitride powders were prepared by the simultaneous reduction and nitridation from powder mixtures of Kim cheon quartzite and carbon (graphite or carbon black) at1400$^{\circ}C$ for 10 hours in nitrogen atmosphere. The effects of the reaction variables on the yield of products and on the ${\alpha}$/${\beta}$ ratio were examined. The average particle size, density, and the ${\alpha}$/${\beta}$ ratio of the obtained si3N4 were 1.0$\mu\textrm{m}$, 3.10g/㎤ and 90/10, respectively. It was found that the Si3N4 powders obtained in this work were comparable to the foreign commercial products.