• Title/Summary/Keyword: neutron diffraction

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Effect of Conductive Additives on the Structural and Electrochemical Properties of Li4Ti5O12 Spinel

  • Park, Jae-Hwan;Lee, Seongsu;Kim, Sung-Soo;Kim, Jong-Huy
    • Bulletin of the Korean Chemical Society
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    • v.33 no.12
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    • pp.4059-4062
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    • 2012
  • The effect of a conductive agent on the structural and electrochemical properties of $Li_4Ti_5O_{12}$(LTO) spinel was investigated through neutron diffraction during Li intercalation and electrochemical measurements. The charging process of LTO is known as transformation of the white $(Li_3)_{8a}[LiTi_5]_{16d}O_{12}$ into a dark-colored $(Li_{3-X})_{8a}[Li_{X+Y}]_{16c}[LiTi_5]_{16d}O_{12}$ by incorporating the inserted Li into octahedral 16c sites, and the Li in tetrahedral 8a sites shifted to 16c sites. The occupancy of the tetrahedral 8a site varied with the existence of carbon in the electrode. Without carbon, the lattice parameter and cell volume of LTO decreased more notably than in the carbon-containing LTO electrode during Li insertion process. These phenomena might be attributed that the Li occupancy of the tetrahedral 8a of the LTO electrode without carbon was less than that of the carbon-containing LTO electrode.

A Study on Embrittlement of Fast Neutron-irradiated Nuclear Reactor Pressure Vessel Steels at Room- and Liquid Nitrogen-temperature (상온 및 액체질소 온도에서 고속 중성자 조사된 원자로 압력 용기의 취화 현상에 관한 연구)

  • Kim, H.B.;Kim, H.S.;Kim, S.K.;Shin, D.H.;Yu, Y.B.;Ko, J.D.
    • Journal of the Korean Magnetics Society
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    • v.15 no.2
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    • pp.142-147
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    • 2005
  • The embrittlement of fast neutron-irradiated reactor pressure vessel (RPV) steels was investigated by X-ray diffraction patterns at room temperature and $M\ddot{o}ssbauer$ spectroscopy at room- and liquid nitrogen-temperature. Neutron fluence on the samples were $10^{12},\;10^{13},\;10^{14},\;10^{15},\;10^{16},\;10^{17},\;10^{18}\;n/cm^2$. The X-ray diffraction patterns showed that the structure of the neutron unirradiated sample was bcc type, where as but the neutron irradiated samples with the fluence higher than $10^{17}\;n/{\cal}cm^2$ were so severely damaged, that bcc type structure disappeared. The $M\ddot{o}ssbauer$ spectra of all samples showed superposition of two or more sextets. In this paper all $M\ddot{o}ssbauer$ spectra were fitted by three set of sextet. The isomer shift and quadrupole splitting values were found around zero. At liquid nitrogen temperature, magnetic hyperfine field and absorption area increase rapidly S 1 sextet in the samples of $10^{17}\~10^{18}\;n/{\cal}cm^2$ neutron fluences. And at room temperature, magnetic hyperfine field and absorption increased rapidly at SI sextet in the samples of $10^{17}\~10^{18}\;n/{\cal}cm^2$ neutron fluences. This rapid increase of magnetic hyperfine field and absorption area were inferred to be caused by the change of $^{56}Fe,\;^{55}Mn$ into $^{57}Fe$ due to by neutron irradiation.

A Study of Characteristic of Electrical-magnetic and Neutron Diffraction of Long-wire High-superconductor for Reducing Energy Losses

  • Jang, Mi-Hye
    • Transactions on Electrical and Electronic Materials
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    • v.9 no.6
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    • pp.265-272
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    • 2008
  • In this paper, AC losses of long wire Bi-2223 tapes with different twist pitch of superconducting core were fabricated, measured and analyzed. These samples produced by a powder-in-tube method are multi-filamentary tape with Ag matrix. Also, it's produced by non-twist. The critical current measurement was carried out under the environment in Liquid nitrogen and in zero field by 4-prob method. And the Magnetic measurement was carried out under the environment of applied time-varying transport current by transport method. From experiment, the susceptibility measurements were conducted while cooling in a magnetic field. Flux loss measurements were conducted as a function of ramping rate, frequency and field direction. The AC flux loss increases as the twist-pitch of the tapes decreased, in agreement with the Norris Equation. Neutron-diffraction measurements have been carried out investigate the crystal structure, magnetic structures, and magnetic phase transitions in Bi-2223([Bi, Pb]:Sr:Ca:Cu:O).

Analysis of Residual Stresses for the Multipass Welds of 316L Stainless Steel Pipe by Neutron Diffraction Method (중성자 회절법에 의한 316L 스테인리스강 배관 다층용접부의 잔류응력 해석)

  • 김석훈;이재한
    • Journal of Welding and Joining
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    • v.21 no.6
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    • pp.64-70
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    • 2003
  • Multipass welds of the 316L stainless steel have been widely employed in the pipes of Liquid Metal Reactor. Owing to localized heating and subsequent rapid cooling by the welding process, the residual stress arises in the weld of the pipe. In this study, the residual stresses in the 316L stainless steel pipe welds were calculated by the finite element method using ANSYS code. Also, the residual stresses both on the surface and in the interior of the thickness were measured by HRPD(High Resolution Powder Diffractometer) instrumented in HANARO Reactor. The experimental data and the calculated results were compared and the characteristics of the distribution of the residual stress discussed.

Residual Stress Measurements at HANARO Reactor (하나로 원자로를 이용한 잔류 응력의 측정)

  • Moon, Myung-Kook;Em, Vyacheslav T.;Shin, Eun-Joo;Lee, Chang-Hee;Kim, Huhn-Jun
    • Proceedings of the KSME Conference
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    • 2000.11a
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    • pp.298-303
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    • 2000
  • Principles of residual stress measurements by neutron diffraction and the residual stress instrument installed at 30MWt HANARO reactor in KAERI are considered. In-depth residual stress distribution was measured in aluminum VAMAS round robin sample and welded stainless steel plate, which showed high ability of the instrument for the stress measurements in components.

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Neutron Diffraction Analysis of Tungsten-Molybdenum-Disilicide Powders Formed by Self-propagating High Temperature Synthesis

  • Choi, Y.;Kim, Y.S.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09b
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    • pp.1325-1326
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    • 2006
  • Tungsten-molydiside $W_xMo_{1-x}Si_2$ was synthesized by self-propagating high temperature synthesis (SHS). The SHS product with the initial composition of (0.5Mo+0.5W+2Si) contains 23.9% $MoSi_2$, 40.89% $WSi_2$ with remaining 9.11% Mo, 9.16% Si and 16.94%W. Lattice parameters of the $MoSi_2$ and $WSi_2$ determined by Rietvelt analysis were a=0.3206 nm, c=0.7841 nm and a=0.3212 nm, c=0.7822 nm, respectively.

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Mechanical Alloying Effect in Immiscible Cu-Based Alloy Systems.

  • Lee, Chung-Hyo;Lee, Seong-Hee;Kim, Ji-Soon;Kwon, Young-Soon
    • Journal of Powder Materials
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    • v.10 no.3
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    • pp.164-167
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    • 2003
  • The mechanical alloying effect has been studied on the three Cu-based alloy systems with a positive heat of mixing. The extended bcc solid solution has been formed in the Cu-V system and an amorphous phase in the Cu-Ta system. However, it is round that a mixture of nanocrystalline Cu and Mo Is formed in the Cu-Mo system. The neutron diffraction has been employed at a main tool to characterize the detailed amorphization process. The formation of an amorphous phase in Cu-Ta system can be understood by assuming that the smaller Cu atoms preferentially enter into the bcc Ta lattice during ball milling.

A study on neutron diffraction of amorphous Ni-Ta and Cu-Ta alloy powders prepared by mechanical alloying (기계적 합금화법으로 제조한 비정질 Ni-Ta 및 Cu-Ta 합금분말의 중성자회절에 관한 연구)

  • Lee, Chung-Hyo;Lee, Jin
    • Electrical & Electronic Materials
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    • v.8 no.6
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    • pp.715-720
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    • 1995
  • 기계적 합금화법에 의한 비정질화 과정을 Ni-Ta계 및 Cu-Ta계에 대하여 조사하였다. Ni-Ta합금계는 혼합엔탈피가 음이나, Cu-Ta계는 혼합엔탈피가 양인 열역학적으로 대조적인 합금계이다. 볼밀 중 발생하는 원자구조 변화를 중성자회절법을 이용하여 관찰하였다. 두 합금게에 있어서 기계적 합금화에 의한 비정질상이 생성되었다. 비정질 Cu-Ta합금의 local원자구조를 혼합엔탈피가 크게 음인 Ni-Ta계의 결과와 비교하였다. 그 결과, 대조적 특성을 가진 두 합금계임에도 불구하고 원자크기가 작은 Ni 및 Cu가 bcc Ta의 결정격자 속으로 우선적으로 침입함으로써 비정질화가 진행됨을 알 수 있었다.

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Residual Stress Measurement on T-type Welded Specimen by Neutron Diffraction

  • Jang, D.Y.;Park, M.J.;Choi, H.D.;Kim, J.P.
    • International Journal of Korean Welding Society
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    • v.1 no.2
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    • pp.45-50
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    • 2001
  • This paper presents application of neutron diffraction technique to the measurement of residual stresses in the T-type 20 m thick welded stainless steel plates(100$\times$50 $mm^2$ and 50$\times$50 $mm^2$). The High Resolution Powder Diffractormeter of the Korea Atomic Research Institute was utilized in the measurement. The power of nuclear reactor was 24 MWt and the measured reflection in the 220 plane (2$\theta$)was $92.66^{\circ}$. Poisson ratio of 0.265 and elastic constant of 211 GPa were applied to the calculation of stresses and strains. Three directional components such as normal, transverse, and longitudinal stresses were measured. The results showed that three components were tensile and became compressive along the y axis in the zone away from the welded center. The compressive stresses became tensile in the zone away from the center line of x axis. This may be due to the balance effect caused by the net stress to keep the specimen shape flat.

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Determination of Non-stoichiometry of Tubular Titanium Carbide Formed by Self-Propagating High Temperature Synthesis

  • Choi, Y.;Cho, N.I.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09b
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    • pp.782-783
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    • 2006
  • Titinium carbide $(TiC_x)$ was produced by self-propagating high temperature synthesis (SHS) method. The morphology and non-stoichiometric number of the SHS product were observed by scanning electron microscopy and neutron diffractometry, respectively. Tubular titanium carbide with hole inside was formed with different non-stoichiometric number (x), which value increased with combustion temperature.

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