• Nuclear Engineering and Technology
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• v.52 no.11
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• pp.2613-2619
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• 2020

This work investigated the gamma-ray shielding performance, and the physical and mechanical properties of poly (methyl methacrylate) (PMMA) composites embedded with 0-44.0 wt% bismuth trioxide (Bi₂O₃) fabricated by the fast ultraviolet (UV) curing method. The results showed that the addition of Bi₂O₃ had significantly improved the gamma shielding ability of PMMA composites. Mass attenuation coefficient and half-value layer were examined using five gamma sources (Cs-137, Ba-133, Cd-109, Co-57, and Co-60). The high loading of Bi₂O₃ in the PMMA samples improved the micro-hardness to nearly seven times that of the pure PMMA. With these enhancements, it was demonstrated that PMMA/Bi₂O₃ composites are promising gamma shielding materials. Furthermore, the fast UV curing exerts its great potential in significantly shortening the production cycle of shielding material to enable rapid manufacturing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.284-284
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• 2007

In this study, the microwave dielectric property variations of (1-x)$BiNbO_4-(x)ZnNb_2O_6$ composites (x=0.3, 0.5 and 0.7) with 10wt% zinc borosilicate(ZBS) glass was investigated as a function of the substitution of $ZnNb_2O_6$ with a view to applying thes system to LTCC technology. The all composition addition of 10wt% ZBS glass ensured a successful sintering below $900^{\circ}C$. In addition, a small amount of $Bi_2SiO_5$ as the secondary phase was observed in the all composition. The substitution of $ZnNb_2O_6$ on the $BiNbO_4$ composites increased the $Q{\times}f$ values, but it decreased the sinterability and dielectric constant due to the high sintering temperature and low dielectric constant of $ZnNb_2O_6\;than\;BiNbO_4$ ceramics. The increasing of $ZnNb_2O_6$ content from 0.3 to 0.7 in the (1-x)$BiNbO_4-(x)ZnNb_2O_6$ composites with 10wt% ZBS glass sintered at $900^{\circ}C$ demonstrated 28.1~15.6 in the dielectric constant$({\varepsilon}_r)$, 5,500~8,700GHz in the $Q{\times}f$ value.

• Nuclear Engineering and Technology
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• v.54 no.9
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• pp.3459-3469
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• 2022

Matrix composites of n-WO₃/n-Bi₂O₃/PVA with different loadings of n-WO₃/n-Bi₂O₃ mixtures (0-15 wt%) and starch (0 and 3 wt%) were fabricated by using melt-mixing method. The X-ray attenuation capability were evaluated based on mass attenuation coefficient (μ/⍴) using a general diagnostic X-ray machine at 40-100 kVp. The effect of starch addition on the dispersion of the fillers in the PVA matrix were observed by using FESEM through morphological analysis. The fabricated samples have shrunken and caused their thickness to be decreased (0.35 mm-0.55 mm) after the drying process even though fixed thickness (2.0 mm) was set initially. The density and HVL values of the samples with 3 wt% starch was seen lower than samples without starch (0 wt%), however the former have provided improvement in filler dispersion and better X-ray attenuation capability compared to the latter. As conclusion, the matrix composite of n-WO₃/n-Bi₂O₃/PVA with 15 wt% of n-Bi₂O₃, 8 wt% of n-WO₃ and 3 wt% starch can be selected as the best promising candidate for X-ray shielding materials.

• Journal of the Korean Ceramic Society
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• v.51 no.3
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• pp.162-169
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• 2014

This paper introduces a microwave-assisted synthesis method to prepare hybrid $Bi_2Se_3-GR/TiO_2$ nanocomposites, which exhibit superior properties over single component materials. The as-prepared composites were characterized by XRD, UV-vis absorbance spectra, SEM,TEM, EDX, and BET analyses, revealing uniform covering of the graphene nanosheet with $Bi_2Se_3$ and $TiO_2$ nanocrystals. For visible light photocatalysis of Rh.B, a significant enhancement in the reaction rate was consequently observed with $Bi_2Se_3-GR/TiO_2$ composites. The degradation rate($k_{app}$) obtained for sonophotocatalysis was $6.8{\times}10^{-3}min^{-1}$, roughly 2.2 times better than that of VL photocatalysis under higher concentrations of Rh.B. The sonophotocatalysis was faster due to greater formation of reactive radicals as well as an increase of the active surface area of the $Bi_2Se_3-GR/TiO_2$ composites. The high activity is attributed to the synergetic effects of high charge mobility and red shift of the absorption edge of $Bi_2Se_3-GR/TiO_2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.1
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• pp.19-24
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• 2007

The effects of $B_2O_3-SiO_2-R(R;CaO,\;BaO,\;ZnO,\;Bi_2O_3)$ borosilicate glass system on the sintering behavior and microwave dielectric properties of ceramic/glass composites were investigated as functions of modifier, glass addition ($30{\sim}50\;vol%$) and sintering temperature ($500{\sim}900^{\circ}C$ for 2 hrs). The addition of 50 and 45 vol% glass ensured successful sintering below $900^{\circ}C$. Sintering characteristics of the composites were well described in terms of modifier. Borosilicate glass enhanced the reaction with $Al_{2}O_{3}$ to form pores, second phases and liquid phases, which was responsible to component of modifier. Dielectric constant (${\varepsilon}_{r},\;Q{\times}f_{o}$) and temperature coefficient of resonant frequency (${\tau}_{f}$) of the composite with 50 and 45 vol% glass contents($B_{2}O_{3}:SiO_{2}:R=25:10:65$) demonstrated A-CaBS(7.8, 2,560 GHz, -81ppm/$^{\circ}C$), A-BaBs(5.8, 3.130 GHz, -64 ppm/$^{\circ}C$), A-ZnBS(5.7, 17,800 GHz, -21 ppm/$^{\circ}C$), A-BiBs(45 vol% glass in total)(8.3, 2,700 GHz, -45 ppm/$^{\circ}C$) which is applicable to substrate requiring an low dielectric properties.

• Journal of the Korean Ceramic Society
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• v.53 no.1
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• pp.56-62
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• 2016

A heterogeneous $Bi_2S_3/TiO_2$ composite catalyst was synthesized via a green ultrasonic-assisted method and characterized by XRD, SEM, EDX, TEM analysis. The results clearly show that the $TiO_2$ particles were homogenously coated with $Bi_2S_3$ particles, indicating that $Bi_2S_3$ particle agglomeration was effectively inhibited after the introduction of anatase $TiO_2$. The Texbrite BA-L (TBA) degradation rate constant for $Bi_2S_3/TiO_2$ composites reached $8.27{\times}10^{-3}min^{-1}$ under visible light, much higher than the corresponding value of $1.04{\times}10^{-3}min^{-1}$ for $TiO_2$. The quantities of generated hydroxyl radicals can be analyzed by DPCI degradation, which shows that under visible light irradiation, more electron-hole pairs can be generated. Finally, the possible mechanism for the generation of reactive oxygen species under visible-light irradiation was proposed as well. Our result shows the significant potential of $Bi_2S_3$-semiconductor-based $TiO_2$ hybrid materials as catalysts under visible light for the degradation of industry dye effluent substances.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.342-342
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• 2008

The low temperature sintering and microwave dielectric properties of ceramic/glass composites which were composed of ceramics in the $Bi_2(Zn_{1/3}Nb_{2/3})_2O_7$ and zinc borosilicate glass/bismuth-zinc borosilicate glass were investigated with a view to applying the microwave dielectrics to low temperature co-fired ceramics. The $Bi_2(Zn_{1/3}Nb_{2/3})_2O_7$ addition of 5 wt% ZBS and BZBS glass ensured a successful sintering below $900^{\circ}C$. In addition, pyrochlore phase was observed in the all composition. $Bi_2(Zn_{1/3}Nb_{2/3})_2O_7$ with 5 wt% BZBS glasss demonstrated 70 as the dielectric constant ($\varepsilon_r$), 2,500 GHz as the Q$\times$f value, and -40 ppm/$^{\circ}C$ as TCF.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.4
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• pp.433-438
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• 2024

Piezoelectric ceramics play an important role in various electronic applications. However, traditional ceramics are difficult to be used in some complicated structures, due to their low flexibility and high brittleness. To solve this problem, this study prepared and investigated ceramic/polymer composites that can utilize a good flexibility of polymers. Polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) and 0.77(Bi_1/2Na_1/2)TiO₃-0.23SrTiO₃ (BNST23) ceramics were selected to fabricate the composites. Ceramic/polymer composites were prepared using various volume fractions of BNST23 ceramics. The distribution of piezoceramic particles in BNST23/PVDF-TrFE composites was investigated using optical microscopy (OM) and scanning electron microscopy (SEM). The dielectric and piezoelectric properties of the composites were significantly influenced by the volume fraction of the piezoelectric ceramics. As a result, the highest piezoelectric constant (d₃₃) of 56 pC/N was obtained in a composites with 70% volume fraction of BNST23 ceramics. Accordingly, it is expected that BNST23/PVDF-TrFE composites can be applied to various sensor applications.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.146.2-146
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• 2000

• Journal of Powder Materials
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• v.14 no.6
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• pp.354-361
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• 2007

The bi-materials with Al-Mg alloy and its composites reinforced with SiC and $Al_2O_3$ particles were prepared by conventional powder metallurgy method. The A1-5 wt%Mg and composite mixtures were compacted under $150{\sim}450\;MPa$, and then the mixtures compacted under 400 MPa were sintered at $773{\sim}1173K$ for 5h. The obtained bi-materials with Al-Mg/SiCp composite showed the higher relative density than those with $Al-Mg/Al_2O_3$ composite after compaction and sintering. Based on the results, the bi-materials compacted under 400 MPa and sintered at 873K for 5h were used for mechanical tests. In the composite side of bi-materials, the SiC particles were densely distributed compared to the $Al_2O_3$ particles. The bi-materials with Al-Mg/SiC composite showed the higher micro-hardness than those with $Al-Mg/Al_2O_3$ composite. The mechanical properties were evaluated by the compressive test. The bi-materials revealed almost the same value of 0.2% proof stress with Al-Mg alloy. Their compressive strength was lower than that of Al-Mg alloy. Moreover, impact absorbed energy of bi-materials was smaller than that of composite. However, the bi-materials with Al-Mg/SiCp composite particularly showed almost similar impact absorbed energy to $Al-Mg/Al_2O_3$ composite. From the observation of microstructure, it was deduced that the bi-materials was preferentially fractured through micro-interface between matrix and composite in the vicinity of macro-interface.