• Title/Summary/Keyword: high temperature

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High-temperature drying of Pinus densiflora and Pinus rigida dimension lumber (소나무와 리기다소나무 평소각재(平小角材)의 고온건조(高溫乾燥))

  • Park, Moon-Jae;Jung, Hee-Suk
    • Journal of the Korean Wood Science and Technology
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    • v.15 no.2
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    • pp.53-66
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    • 1987
  • Korean red pine (Pinus densiflora S. et. Z.) and pitch pine(Pinus rigida Mill) $5{\times}10cm$ dimension lumber were dried in a kiln providing a cross-circulation velocity of 5 m/sec at dry-and wet-bulb temperatures of 116 and $71^{\circ}C$, followed by 3 hours at 91 and $85^{\circ}C$. Compared to dimension lumber dried lumber were as follows. 1. To dry to 10 percent moisture content, the high-temperatures schedule of Korean red pine and pitch pine lumber took less than one seventh the time required by the conventional kiln drying schedule. 2. High-temperature drying rate and conventional drying rate to 10 percent moisture content of Korean red pine lumber were 2.75 and 0.35%/hr, and those of pitch pine lumber were 3.38 and 0.46%/hr respectively. 3. Compared to lumber of both species on conventional schedule, moisture gradient of high-temperature lumber was greater. 4. Compared to lumber on conventional schedule, maximum surface checking of high-temperature lumber of both species was severer, and maximum end checking of high-temperature lumber of both species was similar to that of lumber on conventional schedule. 5. Compard to lumber on conventional schedule, Korean red pine lumber dried at high temperature showed more honeycombing, but pitch pine lumber dried at high-temperature showed significantly slighter honeycombing. 6. Compared to lumber on conventional schedule, the high-temperature lumber showed less warping lumber of both species. 7. Collapse and casehardening of Korean red pine and pitch pine lumber on both scheules were slight.

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Thermal Evolution of BaO-CuO Flux as Sintering Aid for Proton Conducting Ceramic Fuel Cells

  • Biswas, Mridula;Hong, Jongsup;Kim, Hyoungchul;Son, Ji-Won;Lee, Jong-Ho;Kim, Byung-Kook;Lee, Hae-Weon;Yoon, Kyung Joong
    • Journal of the Korean Ceramic Society
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    • v.53 no.5
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    • pp.506-510
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    • 2016
  • The eutectic melt of BaO-CuO flux is known to be a potential sintering aid for $Ba(Zr,Y)O_3$ (BZY) electrolyte for proton-conducting ceramic fuel cells (PCFCs). A density of BZY higher than 97% of theoretical density can be achieved via sintering at $1300^{\circ}C$ for 2 h using a flux composed of 28 mol% BaO and 72 mol% CuO. In the present study, chemical and structural evolution of BaO-CuO flux throughout the sintering process was investigated. An intermediate holding step at $1100^{\circ}C$ leads to formation of various impurity compounds such as $BaCuO_{1.977}$, $Ba_{0.92}Cu_{1.06}O_{2.28}$ and $Cu_{16}O_{14.15}$, which exhibit significantly larger unit cell volumes than the matrix. The presence of such secondary compounds with large lattice mismatch can potentially lead to mechanical failure. On the other hand, direct heating to the final sintering temperature produced CuO and $Cu_2O$ as secondary phases, whose unit cell volumes are close to that of the matrix. Therefore, the final composition of the flux is strongly affected by the thermal history, and a proper sintering schedule should be used to obtain the desired properties of the final product.

Microscopic Analysis of High Lithium-Ion Conducting Glass-Ceramic Sulfides

  • Park, Mansoo;Jung, Wo Dum;Choi, Sungjun;Son, Kihyun;Jung, Hun-Gi;Kim, Byung-Kook;Lee, Hae-Weon;Lee, Jong-Ho;Kim, Hyoungchul
    • Journal of the Korean Ceramic Society
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    • v.53 no.5
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    • pp.568-573
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    • 2016
  • We explore the crystalline structure and phase transition of lithium thiophosphate ($Li_7P_3S_{11}$) solid electrolyte using electron microscopy and X-ray diffraction. The glass-like $Li_7P_3S_{11}$ powder is prepared by the high-energy mechanical milling process. According to the energy dispersive X-ray spectroscopy (EDS) and selected area diffraction (SAD) analysis, the glass powder shows chemical homogeneity without noticeable contrast variation at any specific spot in the specimen and amorphous SAD ring patterns. Upon heating up to $260^{\circ}C$ the glass $Li_7P_3S_{11}$ powder becomes crystallized, clearly representing crystal plane diffraction contrast in the high-resolution transmission electron microscopy image. We further confirm that each diffraction spot precisely corresponds to the diffraction from a particular $Li_7P_3S_{11}$ crystallographic structure, which is also in good agreement with the previous X-ray diffraction results. We expect that the microscopic analysis with EDS and SAD patterns would permit a new approach to study in the atomic scale of other lithium ion conducting sulfides.

The Effect of Temperature on Tensile Properties in Conventionally Cast Ni-based Superalloy CM247LC (다결정 니켈기 초내열 합금 CM247LC의 온도에 따른 인장특성 변화)

  • Choi, Baig-Gyu;Kim, In Soo;Do, Jeonghyeon;Jung, Joong Eun;Seok, Woo-Young;Lee, Yu-Hwa
    • Journal of Korea Foundry Society
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    • v.40 no.4
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    • pp.118-127
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    • 2020
  • Microstructural evolution during a heat treatment and high-temperature tensile properties have been investigated in conventionally cast CM247LC. In as-cast specimens, MC carbides with high amounts of Ta, Ti, Hf, and W were found to exist in the interdendritic regions, and γ' was observed in the form of cubes and octocubes prior to decomposition into cubes. In the heat-treated condition, some portion of eutectic γ-γ' remained, and uniform cubic γ' was observed in both interdendritic regions and dendrite core. Three types of carbides with different stoichiometries and compositions were found at the grain boundaries. MC carbides with high Hf contents were observed in the vicinity of eutectic γ-γ'. The highest tensile strength value was found at 750℃, whereas the greatest ductility appeared at 649℃. The effect of the temperature on the tensile properties was closely related to the dislocation structure. With increase in the test temperature, the density of dislocations inside γ' decreased, whereas that in the γ matrix increased. Stacking faults generated in γ' at 750℃ had a strengthening effect, whereas thermally activated dislocation motion at a high temperature was considered to have the opposite effect.

Development and Characterization of Ultrasonic transducers for High Temperature Contact Measurement (고온 접촉식 탐상용 초음파 탐촉자 개발 및 평가)

  • Kim, Ki-Bok;Kim, Byoung-Geuk;Lee, Seung-Seok;Yoon, Nam-Won;Yoon, Dong-Jin;Ahn, Yoon-Kook
    • Journal of the Korean Society for Nondestructive Testing
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    • v.23 no.1
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    • pp.14-20
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    • 2003
  • Piezoelectric ultrasonic transducers for high temperature contact measurement were developed. These high temperature ultrasonic transducers (HTUT) consisted of bismuth titanate piezoceramic element whose Curie temperature is higher than $600^{\circ}C$, a backing material of the mixture of tungsten powder and inorganic binder, an inner alumina tube, a wear Plate and a housing. The operational frequencies or the HTUT were 1.04 and 2.08 MHz, respectively. Various commercially available couplants for high temperature were evaluated and compared. As a couplant for high temperature ultrasonic testing between HTUT and test specimen, gold epoxy was selected. The peak amplitude of pulse-echo signals from steel test specimen decreased with increasing temperature. The operational temperature of the HTUT reached up to $500^{\circ}C$ at which the continuous contact measurement was possible.

Aluminium Based Brazing Fillers for High Temperature Electronic Packaging Applications

  • Sharma, Ashutosh;Jung, Jae-Pil
    • Journal of the Microelectronics and Packaging Society
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    • v.22 no.4
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    • pp.1-5
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    • 2015
  • In high temperature aircraft electronics, aluminium based brazing filler is the prime choice today. Aluminium and its alloys have compatible properties like weight minimization, thermal conductivity, heat dissipation, high temperature precipitation hardening etc. suitable for the aerospace industry. However, the selection of brazing filler for high temperature electronics requires high temperature joint strength properties which is crucial for the aerospace. Thus the selection of proper brazing alloy material, the composition and brazing method play an important role in deciding the final reliability of aircraft electronic components. The composition of these aluminium alloys dependent on the addition of the various elements in the aluminium matrix. The complex shapes of aluminium structures like enclosures, heat dissipaters, chassis for electronic circuitry, in avionics are designed from numerous individual components and joined thereafter. In various aircraft applications, the poor strength caused by the casting and shrinkage defects is undesirable. In this report the effect of various additional elements on Al based alloys and brazing fillers have been discussed.

Study for multi-filament drawing of Bi2223 high-temperature superconductivity wire by FE method (유한요소법에 의한 Bi2223 고온 초전도 선재의 다심 인발에 대한 연구)

  • 박동인;김병민;오상수
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.273-276
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    • 2003
  • High-temperature superconduction materials(Bi2223) possess electrical/electronic and magnetic properties. Because high-temperature superconduction materials is a ceramic powder, that can not be produced singlehandedly. So Ag sheathed Bi-2223 wire was produced by drawing process using powder-in-tube(PIT) method. This superconductor has many difficulties to produce. The main difficulty is that the mechanical properties of the ceramic powder are very different from those of the Ag sheath. Bi2223 high-temperature superconductivity have a single filament drawing process, and multi-filament drawing process. This study analysed multi-filament drawing process by FEM, a defects during multi-filament drawing was studied by FEM.

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A Study on the Shot Peening on the High Temperature Fatigue Crack Propagation (쇼트피이닝 가공된 스프링강의 고온 피로균열진전 평가)

  • 박경동;정찬기;하경준
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • pp.264-268
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    • 2001
  • In this study, CT specimens were prepared from spring steel(SUP9) processed shot peening which was room temperature, low temperature and high temperature experiment. And we got the following characteristics from fatigue crack growth test carried out in the environment of room, and high temperature at $25^{\circ}C,\; 50^{\circ}C, \;100^{\circ}C,\; 150^{\circ}C,\; and\; 180^{\circ}C$ in the range of stress ratio of 0.05 by means of opening mode displacement. The threshold stress intensity factor range $\DeltaK_{th}$ in the early stage of fatigue crack growth (Region I ) and stress intensity factor range $\Delta$K in the stable of fatigue crack growth (Region II) was decreased in proportion to descend temperature. It assumed that the fatigue resistance characteristics and fracture strength at low temperature and high temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region.

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A Study on the High Temperature Fatigue Behavior of Hot Forging Die STD61 Steel (STD61 열간 금형강의 고온피로거동에 관한 연구)

  • 여은구;이태문;이용신
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.711-714
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    • 2002
  • Although recent research of metallic materials in high temperature fatigue have been much accomplished, many studies about brittle material as a die steel in high temperature fatigue does not have been reported. Especially, the study on the fatigue behavior over the transformation temperature is not studied sufficiently because of its difficult analysis and experiment. Therefore, reliable results of brittle material in high temperature fatigue behavior are needed. In this paper, stress-strain curves and stress-life curves in die STD61 steel at 700 and 900 are carefully examined, as the basic experimental data are used to predict from fatigue life over 700.

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