• Title/Summary/Keyword: BeO

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Sapphire Enhancement with BeO Powder Source (BeO를 확산원으로 한 사파이어의 향상처리)

  • Song, Oh-Sung;Kim, Sang-Yeop
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.6 no.2
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    • pp.105-109
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    • 2005
  • We heat treated pure sapphire samples at $1800^{\circ}C{\sim}100$ hours in BeO-${Al_2}{O_3}$ powder by varying BeO contents of $5{\sim}50\;wt%$ in order to quantify the BeO diffusion enhancement for corundum gem stones. We investigated the heat treated samples with visual evaluation, color coordination analysis, and surface roughness measurement. We confirmed that $Be^{2+}$ ions did not lead to orange color but to dark gray. The lightness in CIE Lab index decreased while surface roughness increased rapidly as BeO contents increased. We propose that BeO yellow color enhancement may be feasible only for $Fe^{3+}$ rich blue sapphires and sub-5% BeO content be appropriate to shorten post re- cutting process.

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Geochemical Dispersion and Enrichment of Fluvial Sediments Depending on the Particla Size Distribution (입도분포에 따른 하상퇴적물의 지구화학적 분산 및 부화)

  • 이현구
    • Economic and Environmental Geology
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    • v.32 no.3
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    • pp.247-260
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    • 1999
  • Geochermical characteristics of the fluvial sediments deprnding on particle size distribution size were investigated in the respect of majir, minor and rare eath element chemisitry. Ratios of $Al_{2}O_{3}/Na_{2}O$ and $K_{2}O/Na_{2}O$ of the sediments show the homogeneous valus, and partly positive correlation with $SiO_{2}/Al_{2}O_{3}$, respecively. Characteristics of minor element ratios (V/Ni, Cr/V, Ni/Co and Zr/Hf)are within the lower and narrow range. Thesesuggested that sediment sources may be acidic to intermediate granitic rock, and may be explained by simple weathering and sedimentation. With increasing SiO2 contents, concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, CaO and MgO decreased, but those of $K_{2}O$ and $Na_{2}O$ increased, Concentrations of Ba, Be, Cs, Cu, Li, Ni, Sr, V and Zr show comparatively normal negative and some positive trends. Compared with the mean composition of granite, concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, MnO, CaO and MgO in the sediments of the study area were highly enriced. Among some minor and rare earth elements, concentrations of As, Cd, Cu, and V were enriched, but those of Be, Ce, Rb, Sc, Sr and Zn were depleted when compared with average composition of granite. By decreasing of particle size fractions, SiO2, Rb and Sr conterts decreased, but concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, CaO, MgO, $TiO_{2}$, MgO, $P_{2}O_{5}$, Be, Cu, Hf, Pb, V and Zr increased. From the correlations between particle size fractions and element concenreations, some elements of $Fe_{2}O_{3}$, CaO, MgO, $P_{2}O_{5}$, Cu, Ni, Zn and Zr showed typical trends in the secondary contramination sediments. These trends are typically shown under 100 mesh fractions. It indicates that the fraction of minus 100 mesh is the optimum size fraction for geochemical and environmental survey.

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Characterization and Acid Catalytic Properties of Beryllia-Silica Catalysts (베릴리아-실리카 촉매의 특성과 산촉매성질)

  • Sohn, Jong-Rack;Park, Eun-Hee;Jang, Hyang-Ja;Kim, Hae-Won
    • Applied Chemistry for Engineering
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    • v.7 no.2
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    • pp.245-251
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    • 1996
  • A series of $BeO-SiO_2$ catalysts were prepared by coprecipitation from the mixed solution of berylium chloride and sodium silicate. The addition of BeO to $SiO_2$ caused the increased of acidity, acid strength, specific surface area, and acid catalytic activity, giving a maximum at 20 mol% of BeO. On the basis of x-ray diffraction pattern, the catalysts calcined at $400{\sim}500^{\circ}C$ were found to be amorphous, having both $Br{\ddot{o}}nsted$ and Lewis acid sites. Catalytic activities for cumene dealkylation were closely correlated with the acidity of catalysts.

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Beryllium oxide utilized in nuclear reactors: Part II, A systematic review of the neutron irradiation effects

  • Ming-dong Hou;Xiang-wen Zhou;Bing Liu
    • Nuclear Engineering and Technology
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    • v.55 no.2
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    • pp.408-420
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    • 2023
  • Beryllium oxide (BeO) is being re-emphasized and utilized in Micro Modular Reactors (MMR) because of its prominent nuclear and high temperature properties in recent years. The implications of the research about effects of neutron irradiation on the microstructure and properties of BeO are significant. This article comprehensively reviews the effects of neutron irradiation on BeO and proposes the maximum permissible neutron doses at different temperatures for BeO without cracks in appearance according to the data in the previous literature. This maximum permissible neutron dose value has important reference significance for the experimental study of BeO. The effects of neutron irradiation on the thermal conductivity and flexural strength of BeO are also discussed. In addition, microstructure evolution of irradiated BeO during post-irradiation annealing is summarized. This review article has important implications for the application of BeO in MMR.

Properties of the System $ZrO_2$+3m/o $Y_2O_3$ Powder Prepared by Co-Precipitation Method(II) Effects of $Al_2O3$$Cr_2O_3$Addition on Mechanical Properties and Microstructures of Y-TZP (공침법으로 제조한 $ZrO_2$+3m/o $Y_2O_3$계 분체의 특성(II) : Y-TZP의 기계적 성질 및 미세구조에 미치는 $Al_2O3$$Cr_2O_3$의 첨가영향)

  • 이홍림;최동근;홍기곤;신현곤
    • Journal of the Korean Ceramic Society
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    • v.27 no.4
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    • pp.465-472
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    • 1990
  • The effects of Al2O3 and Cr2O3 addition on the mechanical properties and microstructures of Y-TZP ceramics obtained by co-precipitation method of ZrO2+3m/o Y2O3, following pressureless sintering at 150$0^{\circ}C$ for 2h were investigated. The addition of Al2O3 and Cr2O3 improved the Y-TZP sinterability and the Al2O3 addition showed the better effect on Y-TZP sintering than that of the Cr2O3 addition. The density and microstructure had the better effect on the bending strength of specimen more than stressinduced phase transformation (SIPT) of ZrO2 from tetragonal to monoclinic phase. The hardness of the specimens was found to be depend on the relative density and the fracture toughness of Y-TZP was found to rely on the amount of SIPT. The grian size of Cr2O3-doped Y-TZP was observed to be relatively smaller and had a narrower distribution than that of Al2O3-doped Y-TZP. If decomposition reaction of Cr2O3 can be controlled at high temperatures, it is anticipated that the mechanical properties of Y-TZP can be much improved by the Cr2O3 addition.

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A Study on the Properties of Substituted Ferrite (Fe-Al-Ga-Si) (치환형 Ferrite (Fe-Al-Ga-Si)의 특성 연구)

  • Choi, Seung-Han
    • Korean Journal of Materials Research
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    • v.21 no.8
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    • pp.439-443
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    • 2011
  • The crystal structure and magnetic properties of a new solid solution type ferrite $(Fe_2O_3)_5-(Al_2O_3)_{3.4}-(Ga_2O_3)_{0.6}-SiO$ were investigated using X-ray diffraction and M$\"{o}$ssbauer spectroscopy. The results of the X-ray diffraction pattern indicated that the crystal structure of the sample appears to be a cubic spinel type structure. The lattice constant (a = 8.317 ${\AA}$) decreases slightly with the substitution of $Ga_2O_3$ even though the ionic radii of the Ga ions are larger than that of the Al ions. The results can be attributed to a higher degree of covalency in the Ga-O bonds than in the Al-O and Fe-O bonds, which can also be explained using the observed M$\"{o}$ssbauer parameters, which are the magnetic hyperfine field, isomer shift, and quadrupole splitting. The drastic change in the magnetic structure according to the Ga ion substitution in the $ (Fe_2O_3)_5(Al_2O_3)_{4-x}(Ga_2O_3)_xSiO$ system and the low temperature variation have been studied through a M$\"{o}$ssbauer spectroscopy. The M$\"{o}$ssbauer spectrum at room temperature shows the superpositions of two Zeeman patterns and a strong doublet. It shows significant departures from the prototypical ferrite and is comparable with the diluted ferrite. The doublet of spectrum at room temperature appears to originate from superparamagnetic clusters and also the asymmetry of the doublet appears to be caused by the preferred orientation of the crystallites. The M$\"{o}$ssbauer spectra below room temperature show various complicated patterns, which can be explained by the freezing of the superparamagnetic clusters. On cooling, the magnetic states of the sample were various and multi critical.

Characteristics of BaFe12O19 Particles Extracted from Amorphous Ba-Ferrite (비정질 Ba-Ferrite로부터 추출한 BaFe12O19 입자의 특성)

  • 김태옥;오영우;박효열;강원호
    • Journal of the Korean Ceramic Society
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    • v.24 no.6
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    • pp.553-560
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    • 1987
  • Amorphous ferrites with composition B2O3-mBaO-nFe2O3 were prepared by an ultra rapidquenching technique. X-ray patterns and SEM reveal the products to be amrophous at room temperature. BaFe12O19 fine particles extracted from amorphous Ba-ferrites which additived Al2O3, SiO2, TiO2 and CoO have narrow size distribution, average 0.2$\mu\textrm{m}$, and coercive force, average 1400 Oe, increased with increasing TiO2 amounts. The obtained BeFe12O19 fine particles would be appreciated as perpendicular magnetic recording media.

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Mechanical and Electrical Characteristics of $Al_2O_3-ZrO_2/A_2O_3$-TZP Structural Ceramics ($Al_2O_3-ZrO_2/A_2O_3$-TZP 세라믹스의 제조 및 기계적.전기적 특성)

  • 박재성;남효덕;이희영
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1999.11a
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    • pp.335-338
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    • 1999
  • The effect of monoclinic $ZrO_2$(pure) and tetragonal $ZrO_2$ containing 5.35wt% $Y_2$$O_3$(Y-TZP) addition on the mechanical properties and thermal shock resistance of $Al_2$$O_3$ ceramic were investigated. The addition of $ZrO_2$(m) and Y-TZP increased sintering density of $Al_2$$O_3$. The vickers hardness increased with increasing the volume fraction of Y-TZP going through a maximum at 20wt%. The hardness of the specimens was found to be depend on the sintering density. With increasing the volume fraction of $ZrO_2$(m) and Y-TZP, the fracture toughness of the composite is increased. This result may be taken as evidence that toughening of ${Al_2}{O_3}$ can also be achieved by the transformation toughening and microcrack toughening of $ZrO_2$. The property of the& shock for ${Al_2}{O_3}$-$ZrO_2$ composites was improved by increasing the volume fraction of monoclinic $ZrO_2$(pure).Grain size increased with increasing the volume fraction of $ZrO_2$.

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Ionic Conductivity of Solid Solution Ceramics in The System of Stabilized ZrO2 Prepared by Self-Propagating High-Temperature Synthesis

  • Soh, Deawha;Korobova, N.
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.15 no.4
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    • pp.349-355
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    • 2002
  • The ionic conductivity of cubic solid solutions in the systems of CaO-$ZrO_2$, $Y_2O_3-ZrO_2$ prepared by SHS was examined. The higher conductivity appears to be related to a lower activation energy rather than to the number of oxygen vacancies dictated by composition. Conductivity-temperature data was obtained at 1000 $^{\circ}C$ in atmosphere of low oxygen partial pressure (~$10^{-40}$ atm) for $Y_2O_3-ZrO_2$ cubic solid solutions. The data indicated that these materials could be reduced, and the decree of reduction would be related with the measuring electric field.

Electric Properties of NTC Thermistor with $Mn_{3}O_{4}-NiO-Fe_{2}O_{3}$ system for Mobile Communication Telephone (이동통신 단말기용 $Mn_{3}O_{4}-NiO-Fe_{2}O_{3}$계 NTC 써미스터의 전기적 특성)

  • Yoon, Joong-Rak;Kim, Jee-Gyun;Lee, Heon-Yong;Lee, Seok-Won
    • Proceedings of the KIEE Conference
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    • 2000.11c
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    • pp.506-508
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    • 2000
  • Oxide of the form $Mn_{3}O_{4}-NiO-Fe_{2}O_{3}$ present properties that make them useful as multilayer chip NTC thermistor for mobile phone NTC thermistor electric properties of $Mn_{3}O_{4}-NiO-Fe_{2}O_{3}$ system has been measured as a function of temperature and composition. In $Mn_{3}O_{4}-NiO-Fe_{2}O_{3}$ composition, it can be seen that resistivity and B-constant were increased as the ratio of $Mn_{3}O_{4}/F_{2}O_{3}$ and $Mn_{3}O_{4}$/NiO was increased. In particular, resistance change ratio (${\Delta}R$), the important factor for reliability varied within ${\pm}1%$, indicating the compositions of these products could be available for mobile phone.

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