• Title/Summary/Keyword: temperature cycles

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Evaluation of Hydrogenation Properties on Ti-Cr-Nb Alloys Manufactured by Arc Melting (아크용해법에 의한 Ti-Cr-Nb합금의 제조와 수소와 특성 평가)

  • Lee, Young-Geun;Hong, Tae-Whan
    • Transactions of the Korean hydrogen and new energy society
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    • v.19 no.6
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    • pp.482-489
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    • 2008
  • Ti-Cr alloys consist of BCC solid solution, C36, C14 and C15 Laves phase at high temperature. Among others, the BCC solid solution phase was reported to have a high hydrogen storage capacity. However, activation, wide range of hysteresis at hydrogenation/dehydrogenation, and degradation of hydrogen capacity due to hydriding/dehydriding cycles must be improved for its application. In this study, to improve such problems, we added a Nb. For attaining target materials, Ti-10Cr-xNb(x=1, 3, 5wt.%) specimens were prepared by arc melting. The arc melting process was carried out under argon atmosphere. As-received specimens were characterized using XRD(X-ray diffraction), SEM(Scanning Electron Microscopy) with EDX(Energy Dispersive X-ray) and TG/DSC(Thermo Gravimetric Analysis/Differential Scanning Calorimetry). In order to examine hydrogenation behavior, the PCI(pressure-Composition-Isotherm) was performed at 293, 323, 373 and 423K.

Separation and Purification of Fructo-oligosaccharides by an Ion-Exchange Resin Column (이온교환수지탑을 이용한 Fructo-oligosaccharides의 분리 및 정제)

  • 윤종원;송승구
    • KSBB Journal
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    • v.9 no.1
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    • pp.35-39
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    • 1994
  • Separation of pure fructo-oligosaccharides from the mixed solution of glucose, sucrose and fructo-oligosaccharides was studied using a cationic ion-exchange resin column. Optimum separation conditions, i.e., temperature, feeding rate and the ratio of column vs. diameter were evaluated, which were found to be $85^{\circ}C$, $0.25h^{-1}$ and 30, respectively. At the optimized separation conditions, high-purity fructo-oligosaccharides up to 96% were obtained and the total recovery yield was about 66% after four cycles. After the chromatographic separation, purification to remove the salts and color in pure fructo-oligosaccharides solution was successfully conducted using the mixed-bed of cationic and anionic ionexchange resin columns.

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Properties of $Sr_{0.8}Bi_{2.3}{(Ta_{1-x}Nb_{x})}_{2}O_{9+{\alpha}}$ Thin Films

  • Park, Sang-Jun;Jang, Gun-Eik
    • Transactions on Electrical and Electronic Materials
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    • v.1 no.1
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    • pp.22-25
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    • 2000
  • Polycrystalline SBTN layered ferroelectric thin film with various Nb mole ratios were prepared by sol-gel method Pt/ $SiO_2$/Si (100) substrates. The films were annealed at different temperature and characterized in terms of phase and microstructure. The films were crystallized with a high (105) diffraction intensity and had rodike structure, SBTN films fired at 800$^{circ}C$ revealed standard hysteresis loops with no fatigue for up to 10$^{10}$ cycles. At an applied voltage of 5V the dielectric constant($varepsilon$) , dissipation factor (tan $delta$), remanent polarization(ZPr) and coercive field(Ec) of typical S $r_{0.8}$B $i_{2.3}$(T $a_{1-x}$ N $b_{x}$) $O_{9+}$$alpha$/ thin film(x=0.1) prepared on Pt/ $SiO_2$/Si (100) were about 277.7, 0.042, 3.74$mu$C/$textrm{cm}^2$, and 24.8kv/cm respectively.ly.y. respectively.ly.y.y..

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Electric Properties of MFIS Capacitors using Pt/LiNbO3/AlN/Si(100) Structure (Pt/LiNbO3/AlN/Si(100) 구조를 이용한 MFIS 커패시터의 전기적 특성)

  • Jung, Soon-Won;Kim, Kwang-Ho
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.17 no.12
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    • pp.1283-1288
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    • 2004
  • Metal-ferroelectric-insulator-semiconductor(WFIS) capacitors using rapid thermal annealed LiNbO$_3$/AlN/Si(100) structure were fabricated and demonstrated nonvolatile memory operations. The capacitors on highly doped Si wafer showed hysteresis behavior like a butterfly shape due to the ferroelectric nature of the LiNbO$_3$ films. The typical dielectric constant value of LiNbO$_3$ film in the MFIS device was about 27, The gate leakage current density of the MFIS capacitor was 10$^{-9}$ A/cm$^2$ order at the electric field of 500 kV/cm. The typical measured remnant polarization(2P$_{r}$) and coercive filed(Ec) values were about 1.2 $\mu$C/cm$^2$ and 120 kV/cm, respectively The ferroelectric capacitors showed no polarization degradation up to 10$^{11}$ switching cycles when subjected to symmetric bipolar voltage pulses of 1 MHz. The switching charges degraded only by 10 % of their initial values after 4 days at room temperature.e.

Performance Tests and Development of the Cyclic Load Device Using a Bellows (벨로우즈를 이용한 반복 하중부과장치의 개발 및 성능시험)

  • Choi, Myoung-Hwan;Cho, Man-Soon;Park, Sung-Jae;Kim, Bong-Goo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.9
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    • pp.903-909
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    • 2007
  • A fatigue capsule is one of the special capsules to investigate the fatigue characteristics of the nuclear materials during an irradiation test in a research reactor, HANARO. In this study, the performance test and the preliminary fatigue test results by using a cyclic load device newly developed for a fatigue capsule are described. In order to obtain the characteristics such as a realization and a controllability of the periodic wave shape and the relationship between the pressure and the load, a spring and rigid bar specimens are used. The fatigue test for the 316L stainless steel specimen with 1.8mm in diameter and 12.5mm in gage length is also performed under the same conditions as the temperature($550^{\circ}C$) of the specimen during irradiation tests. As a result of the test, the fracture of the specimen occurs at a total of 70,120 cycles(about 12 days), and the displacement in this case is 2.02 mm. It is expected that these results will be used for determining test conditions and a comparison of the in-pile fatigue test results.

Three Dimensional Solidification Analysis in Automotive Cast Piston (자동차용 피스톤 주물의 3차원 응고해석)

  • Kim, Ji-Joon;Kim, Jin-Soo;Ryu, Gwan-Ho;Choi, Jeong-Kil;Lee, Zin-Hyoung;Hong, Chun-Pyo
    • Journal of Korea Foundry Society
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    • v.13 no.3
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    • pp.268-275
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    • 1993
  • In gravity die casting, die cooling systems are frequently employed with water cooling to remove the heat of the solidifying metal. Thermal modeling is an important technique in mold design for improving the productivity of the process. Computer simulation system which consists of pre-processor, main solidification simulator and post-processor has been developed for three dimensional solidification analysis of cyclic gravity die casting. The pre-processor is used for mesh generation in a PC system. The modified finite difference method is adopted for the main solidification simulation algorithm during all the casting cycles. The post-processor graphically presents the simulation results. Several experiments in automotive cast piston were carried out. The temperature variations in casting and mold with time are measured experimentally, and the results are compared with calculation results. The effects of cycle number on solidification pattern are also studied. Several experimental results for the prediction of shrinkage defects are compared with calculated results.

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TWO-STEP THERMOCHEMICAL CYCLES FOR HYDROGEN PRODUCTION WITH DISH TYPE SOLAR THERMAL SYSTEM and $CeO_2/NiFe_2O_4$ (접시형 태양열 집광 시스템과 산화세륨 및 페라이트산화물을 이용한 열화학 사이클의 수소생산)

  • Kwon, Hae-Sung;Oh, Sang-June;Seo, Tae-Beom
    • 한국태양에너지학회:학술대회논문집
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    • 2012.03a
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    • pp.113-119
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    • 2012
  • The two-step water splitting thermochemical cycle is composed of the T-R (Thermal Reduction) and W-D (Water Decomposition) steps. The mechanism of this cycle is oxidation-reduction, which produces hydrogen. The reaction temperature necessary for this thermochemical cycle can be achieved by a dish-type solar thermal collector (Inha University, Korea). The purpose of this study is to validate a water splitting device in the field. The device is studied and fabricated by Kodama et al (2010, 2011). The validation results show that the foam device, when loaded with $CeO_2$ powder, was successfully achieved hydrogen production under field conditions. Through this experiment, we can analyze the characteristics of the catalyst and able to determine which is more advantageous thing to produce hydrogen compared with previous experiment that used ferrite-device.

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Syngas and Hydrogen Production under concentrated solar radiation : Redox system of $ZrO_2$ nano-structure (고온 태양열을 이용한 합성가스 및 수소 생산 : $ZrO_2$ 나노 구조화에 따른 산화/환원 특성)

  • Jang, Jong-Tak;Lee, Jong-Min;Cho, Eun-Su;Yang, Seung-Chan;Yoon, Ki-June;Han, Gui-Young
    • 한국태양에너지학회:학술대회논문집
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    • 2012.03a
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    • pp.463-469
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    • 2012
  • Solar thermochemical syngas and hydrogen production process bv redox system of metal oxide was performed under direct irradiation of the metal oxide on the SiC ceramic foam device using solar simulator. $CeO_2/ZrO_2$ nanotube has been synthesized by anodic oxidation method. Syngas and hydrogen production process is one of the promising chemical pathway for storage and transportation of solar heat by converting solar energy to chemical energy. The produced syngas had the $H_2/CO$ ratio of 2, which was suitable for methanol synthesis or Fischer-Tropsch synthesis process. After ten cycles of redox reaction, $CeO_2$ was analyzed using XRD pattern and SEM image in order to characterize the physical and chemical change of metal oxide at the high temperature.

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The Deformation of Knitted Cotton Fabrics with/without Spandex During Laundering (스판덱스 혼합 면 편성물과 면 편성물의 세탁에 따른 변형 비교)

  • Chung, Haewon;Kim, Ku-Ja;Kim, Mikyung
    • Journal of the Korean Society of Clothing and Textiles
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    • v.30 no.2 s.150
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    • pp.296-305
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    • 2006
  • This study evaluate the effect of laundering on the deformation of knitted spandex/cotton fabrics compared with that of knitted cotton fabrics. Commercial knitted spandex/cotton and knitted cotton fabrics for T-shits were laundered in a drum-type washing machine and dried in a tumble dryer. Wale spirality, shrinkage, elastic recovery and surface contour of knitted fabrics were investigated under different laundering conditions: washing temperature, presoaking time and washing cycles. Knitted spandex/cotton fabrics had a lower angle of spirality than knitted cotton fabrics. After the first washing cycle, the angles of spirality of all the fabrics had decreased greatly. Knitted cotton fabric of low density deformed more than that of higher density. Knitted spandex/cotton. fabric of low density shrank less, because of the greater extension given during heat-set. Permanent elongation length at the 80$\%$ extension was longer than at the 50$\%$ extension, and the knitted spandex/cotton fabric which was expanded greatly during heat-set had a lower elastic recovery rate. The surface appearance of the knitted spandex/cotton fabrics was worsl~ than that of the knitted cotton fabrics before laundering and after repeated laundering, because of the much protruded cotton fibers from the yarns.

A Study on Change of Texture During Thermal Cycling in Cu-Zn-AI Shape Memory Alloy (Cu-Zn-AI 형상기억 합금의 열사이클에 따른 집합조직의 변화에 관한 연구)

  • Hong, D.W.;Park, Y.K.
    • Journal of the Korean Society for Heat Treatment
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    • v.5 no.3
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    • pp.179-185
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    • 1992
  • The shape memory effect results from the martensite transfomation of each individual grain. Thus it is necessary to study the texture and its variation. In this study the change of texture during thermal cycling and it's effect on shape memory ability are investigated. The major component of the rolling texture in the parent phase is identified (001) [110], and minor components are (112) [110], (111) [112], {hkl}<100> fiber texture is developed at $45^{\circ}$ from rolling direction. In the case of martensite phase, it is estimated that the major component is (011) [100] and the minor components are (105) [501], (010) [101] and (100) [001]. According to thermal cycling. severity of texture, especially (001) [110] component in parent phase and (011) [100] component in martensite phase are increased. The shape memory ability is increased with increase of thermal cycles and also increased as the direction of specimen approach to $45^{\circ}$ from rolling direction. After first thermal cycling the temperature of transformation can be define clearly and Ms and As are raised by thermal cycling.

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