• Title/Summary/Keyword: $MgB_4O_7$

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The evaluation of absorbed dose of rectum for the patient of intracavitary treatment $^{60}$ Co by MgB$_4$O$_{7}$ (Mn) TLD (MgB$_4$O$_{7}$ (Mn) TLD에 의한 $^{60}$ Co 강내 치료 환자의 직장의 흡수선량 평가)

  • 유명진;신병철;문창우;정태식;염하용;도시홍
    • Progress in Medical Physics
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    • v.5 no.2
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    • pp.21-26
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    • 1994
  • By measuring with TLD, absorbed dose of rectum will be determined more accurately than calculated value. MgB$_4$O$\sub$7/(Mn) TLD phosphor was prepared and its characteristic was studied. To measure the absorbed dose of rectum with TLD, 33 patients who had intracavitary treatment with $\^$60/Co from April 1994 to September 1994 at Kosin Medical center. There were 10-59% differecne in most cases between the calculation and the measurement for the absorbed dose of rectum. The difference was less the case with tandem and ovoid than the case with only ovoid.

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Preparation of FeB by SHS (Self Propagating High Temperature Synthesis) (자전연소합성법에 의한 FeB 분말의 제조)

  • Shin, Chang-Yun;Won, Chang-Whan
    • Journal of the Korean Ceramic Society
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    • v.45 no.7
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    • pp.418-422
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    • 2008
  • The preparation of FeB by SHS in $B_2O_3-Mg-Fe-Fe_3O_4$ system was investigated in this study. In the preparation of FeB, the effects of the initial pressure of inert gas in reactor, the content of Mg and $Fe_3O_4$ in mixture on the reactivity and reaction products was investigated. The minimum initial pressure of inert gas in reactor for SHS reaction in this system was 25 atm, and as the pressure increased, the concentration of unreacted Mg decreased and combustion temperature increased. At the initial inert gas pressure in reactor of 25 atm, the optimum composition for the preparation of pure FeB was $1.5B_2O_3$+3.43Mg+ 1.7Fe+$0.1Fe_3O_4$. The FeB synthesized in this condition had an irregular shape and the particle size of $5\;{\mu}m$.

Formation of the Fluorite Structure in the $\textrm{Y}_{0.8}\textrm{Ta}_{0.2}\textrm{O}_{1.7}$-MO(M=Ba, Sr, Ca and Mg) System ($\textrm{Y}_{0.8}\textrm{Ta}_{0.2}\textrm{O}_{1.7}$-MO(M=Ba, Sr, Ca 및 Mg)계에 있어서 형석구조의 생성)

  • Kim, Shin;Choi, Soon-Mok;Lee, Hong-Lim
    • Korean Journal of Materials Research
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    • v.7 no.1
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    • pp.57-61
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    • 1997
  • Formation of fluorite structure and other related crystal structures in the $Y_{0.8}Ta_{0.2}O_{1.7}$-MO(M=Ba, Sr, Ca and Mg) system has been studied $Ba_2YTaO_6,\;Sr_2YTaO_6$ of cubic perovskite type ordered structure anti $Y_2O_3$ of cubic structure were produced besides the defect fluorite structure when 4 moIob of BaO or SrO was added to $Y_{0.8}Ta_{0.2}O_{1.7}$ When CaO more than 8 nlol"/o was added to $Y_{0.8}Ta_{0.2}O_{1.7}$, monoclinic: $Ca_2YTaO$, and cubic $Y_2O_3$ were pri~tlucecl ;IS this sec:onci phases hesides the main fluorite truc,ture. Smglc phase of fluorite structure \vas 1)roduc:ciI when MgO was added up to 12 mol%, however, MgO appeared as the second phase besides the main fluorire structure when MgO was added more than lti moI0'. Consquently, it is considered rh;it the formation of tluorite structure is related with the formation of the cubic perovskite type ordered structure of $A_2(B'B")O_6$ as well as the cation radii of the additives.additives.

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Fabrication of $Li_2B_4O_7$ Series Single-Crystal TLDs and their TL properties ($Li_2B_4O_7$ 계열 단결정 TLD 소자의 제작과 특성)

  • Park, Myeong-Hwan;Park, Kang-Soo
    • Journal of radiological science and technology
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    • v.28 no.1
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    • pp.1-7
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    • 2005
  • High-quality single crystals of pure $Li_2B_4O_7$ as well as $Li_2B_4O_7$ doped with Cu, Mn and Mg impurities (1.0mol%, respectively) have been grown from the melt of $Li_2CO_3+2B_2O_3$ by Czochralski method in platinum crucibles. To study the thermoluminescent properties, $Li_2B_4O_7$ series single crystal TLDs were made by cutting in the size of $4{\times}5{\times}1\;mm^3$. The glow curves show two or three peaks which can be easily deconvoluted. It is observed that room temperature($20{\sim}30^{\circ}C$) fadings of the dosimetric peaks of $Li_2B_4O_7$ series single crystal TLDs were about 10 % for 30 days. The relative photon energy response for $Li_2B_4O_7$ series single crystal TLDs were about 85 % when the responses were normalized to that measured with $^{60}Co\;(1.25\;MeV)\;{\gamma}-rays$. The measured data are in a good agreement with theoretical ones. The $Li_2B_4O_7$ series single crystal TLDs fabricated in this work can be used for monitoring personal and environmental radioactivity.

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A Study on the Preparation of $MgB_4O_7$ Thermoluminescent Phosphors and X-ray Dosimetry ($MgB_4O_7$ 열형광체의 제작과 X선의 선량측정에 관한 연구)

  • Song, Jea-Heung;Noh, Kyung-Suk;Lee, Deog-Kyu;Koo, Hyo-Geun
    • Journal of radiological science and technology
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    • v.21 no.2
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    • pp.47-52
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    • 1998
  • Tissue-equivalent $MgB_4O_7$ TL phosphors were prepared and the effects of Lantanides series activators on TLD properties of the phosphors were studied. The glow curve of TLD increased TL intensity and the peak temperature is low that is, the heating rate is $10^{\circ}C/sec$. The activation energy of the main peak estimated by the peak shape method. By these methods, the estimated activation energies were $0.76{\sim}1.55eV$ respectively. The TL phosphors prepared in this work may be utilized to radiation sensor elements because of this high sensitivity to X-ray.

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Preparation and Characterization of Ordered Perovskite (CaLa) (MgMo) $_6$

  • Choy, Jin-Ho;Hong, Seung-Tae;Suh, Hyeong-Mi
    • Bulletin of the Korean Chemical Society
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    • v.9 no.6
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    • pp.345-349
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    • 1988
  • The polycrystalline powder of (CaLa) (MgMo)$O_6$ has been prepared at $1350^{\circ}C$ in $H_2/H_2O$ and $N_2$ flowing atmosphere. The powder X-ray diffraction pattern indicates that (CaLa) (MgMo)$O_6$ has a monoclinic perovskite structure with the lattice constants $a_0=b_0=7.901(1){\AA}$, $c =7.875(1){\AA}\;and\;{\gamma}=89^{\circ}$16'(1'), which can be reduced to orthorhombic unit cell, a = 5.551(1) ${\AA}$, b = 5.622(1) ${\AA}$ and c = 7.875(1) ${\AA}$. The infrared spectrum shows two strong absorption bands with their maxima at 590($ν_3$) and 380($ν_4$) cm, which are attributed to $2T_{1u}$ modes indicating the existence of highly charged molybdenum octahedron $MoO_6$ in the crystal lattice. According to the magnetic susceptibility measurement, the compound follows the Curie-Weiss law below room temperature with the effective magnetic moment 1.83(1)$_{{\mu}B}$, which is well consistent with that of spin only value (1.73 $_{\mu}_B$) for $Mo^{5+}$ with $4d^1$-electronic configuration within the limit of experimental error. From the thermogravimetric analysis, it has been confirmed that (CaLa) (MgMo)$O_6$ decomposes gradually into $CaMoO_4,\;MoO_3,\;MgO,\;La_2O_3$ and unidentified phases due to the oxidation of $Mo^{5+}$ to $Mo^{6+}$.

Characteristics of Groundwater Pollution and Contaminant Attenuation at Waste Disposal Sites (폐기물 매립지 주변의 지하수 오염과 오염물질의 지연 특성)

  • 오석영;전효택
    • Journal of the Korean Society of Groundwater Environment
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    • v.3 no.1
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    • pp.37-49
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    • 1996
  • The objectives of this study are to investigate the groundwater and surface water contamination, to interpret the attenuation mechanism of contaminant transport, and to find the appropriate contamination indicator. at the two big landfill sites : Nanjido Landfill and Hwasung Landfill. Leachate from the Nanjido, th, Hwasung and the Kimpo waste disposal sites is characterized by high temperature (31.7-40.1$^{\circ}C$), high electric conductivity (14,650-32,800 ${\mu}$S/cm), somewhat higher pH(7.58-8.45) and low Eh (-119.4-20.4 mV), and is enriched in both major (Na$^{+}$, K$^{+}$, Ca$^{2+}$, Mg$^{2+}$, HC $O_3$$^{-}$, Cl$^{-}$) and minor (Mn, Sr$^{2+}$, Ba$^{2+}$, Li$^{+}$, F$^{-}$, Br$^{-}$) ions. Municipal solid waste leachate and industrial waste leachate are effectively discriminated by the content of S $O_4$$^{2-}$, Fe, and heavy metals. The attenuation mechanism of each component was assessed using the chemical analysis. Cl-normalizing process, WATEQ4F simulation, and preceding flownet analysis. Based on the calculation of Contamination Factor, K, Na, Ca, Mg, B, Zn, HC $O_3$, Cl, F, Br and TOC are effective contamination indicators in the Nanjido landfill site, and K, Na, Ca, Mg, B, S $O_4$, HC $O_3$, Cl, F, Br and TOC in the Habsburg landfill site Particularly, TOC is the best contamination indicator in landfill sites influenced by sea water.

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Fabrication of $ZrB_2$ Ceramics for Thermocouple Protective Tubes by SHS Process (SHS 공정에 의한 열전대 보호관용 $ZrB_2$ 세라믹스의 제조)

  • 곽철상;김상배;이윤복;박홍채;오기동
    • Journal of the Korean Ceramic Society
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    • v.34 no.11
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    • pp.1165-1172
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    • 1997
  • ZrB2 powders were prepared from a mixture of ZrO2, B2O3 and Mg by self-propagating high temperature synthesis method. The combustion product was successfully obtained from a mixture of ZrO2:B2O3:Mg=1:2:8.5 molar ratio. By-product, MgO was effectively removed by leaching with 1M HCl solution at 9$0^{\circ}C$ for over 5hours. After leaching, the Mg content was 0.86~1.42 wt%, and the mean particle size was 4.72${\mu}{\textrm}{m}$. The addition of 7.5 wt%(14Ni:1.0C) as a sintering aid greatly densified ZrB2 bodies compared with that of only Ni. The ZrB2 sintered bodies containing 7.5 wt%(14Ni:1.0C) was 94.3% of the theoretical density. In this case, ZrB2 existed as a major phase and had a bend strength of 300 MPa and a vickers hardness of 2000 kg/$\textrm{mm}^2$.

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Determination of Thermoluminescence Properties of MgB4O7 Doped with Dy3+, La3+ and Ho3+ for a Light Tracer Application (비화공식 예광탄 응용을 위한 Dy3+, La3+ 그리고 Ho3+이 도핑된 MgB4O7의 열 발광 특성 분석)

  • Park, Jinu;Kim, Nakyung;Choi, Jiwoon;Koh, Jaehyuk;Chin, Hee Sik;Jung, Duck Hyeong;Shin, Byungha
    • Korean Journal of Materials Research
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    • v.32 no.1
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    • pp.9-13
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    • 2022
  • Bullets flying with a light from the back are called "tracers". Tracers are ignited by the combustion gas of the propellant and emit bright light that allows the shooter to visually trace the flight path. Therefore, tracers mark the firing point for allies to assist shooters to hit target quickly and accurately. Conventional tracers are constructed with a mixture of an oxidizing agent, raw metal, and organic fuel. Upon ignition, the inside of the gun can be easily contaminated by the by-products, which can lead to firearm failure during long-term shooting. Moreover, there is a fire risk such as forest fires due to residual flames at impact site. Therefore, it is necessary to develop non-combustion type luminous material; however, this material must still use the heat generated from the propellant, so-called "thermoluminescence (TL)". This study aims to compare the TL emission of Dy3+, La3+ and Ho3+ doped MgB4O7 phosphors prepared by solid state reaction. The crystal structures of samples were determined by X-ray diffraction and matched with the standard pattern of MgB4O7. Luminescence of various doses (200 ~ 15,000 Gy) of gamma irradiated Dy3+, La3+ and Ho3+ (at different concentrations of 5, 10, 15 and 20 %) doped MgB4O7 were recorded using a luminance/color meter. The intensity of TL yellowish (CIE x = 0.401 ~ 0.486, y = 0.410 ~ 0.488) emission became stronger as the temperature increased and the total gamma-ray dose increased.

Microstructural and Magnetic Properties of CoFeB/MgO/CoFeB Based Magnetic Tunnel Junction Depending on Capping Layer Materials (Capping층 재료에 따른 CoFeB/MgO/CoFeB 자기터널접합의 미세구조와 자기저항 특성)

  • Chung, Ha-Chang;Lee, Seong-Rae
    • Journal of the Korean Magnetics Society
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    • v.17 no.4
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    • pp.162-165
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    • 2007
  • We investigated the effects of the capping layer materials on the crystallization of the amorphous top-CoFeB (t-CoFeB) electrode and the magnetoresistance properties of the magnetic tunnel junctions (MTJs). When the hcp(002)-textured Ru capping layer was used, the amorphous t-CoFeB was crystallized to bcc-CoFe(110). The CoFe(110)/Ru(002) texture relation can be minimized the lattice mismatch down to 5.6%. However, when the fine polycrystalline but almost amorphous TiAl or amorphous ZrAl were used, the amorphous t-CoFeB was crystallized to bcc-CoFe(002). When the amorphous capping materials were used, the evolution of the t-CoFeB texture was affected mainly by the MgO(001) texture. Consequently, the M ratios of the annealed MTJ capped with the ZrAl and TiAl (72.7 and 71.8%) are relatively higher than that of the MTJ with Ru capping layer (46.7%). In conclusions, the texture evolution of the amorphous t-CoFeB during the post deposition annealing could be controlled by the crystallinity of the adjacent capping layer and in turn, it affects the TMR ratio of MTJs.