• Title/Summary/Keyword: Heat Diffusion

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Thermal stability enhancement of silicide by kinetic modifications (Kinetics 수정에 의한 실리사이드의 열적 안정성 향상에 대한 연구)

  • Nam, Hyoung-Gin
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.8 no.5
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    • pp.1042-1046
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    • 2007
  • In this study, we investigated the mechanism responsible for the thermal stability of CoSi by addition of a foreign chemical element. Addition of W was found to increase the heat of formation of CoSi. This increase was claimed to inhibit the glass formation, which is preferred by silicide formation kinetics depicted by the maximum system energy degradation rate. In this case, there forms at the interface between CoSi and Si wafer a crystalline structure, the effective diffusion coefficient of which is much less than the self-diffusion rate provided by the glass. It was stated that the phase transition requires a higher thermal energy as the consequence, thereby enhancing the thermal stability of CoSi.

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Bond Strength of Steel honeycomb Structure (철강 하니콤구조의 접합강도)

  • Song, Keun;Hong, Young Hwan
    • Journal of the Korean Society for Heat Treatment
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    • v.16 no.4
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    • pp.197-204
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    • 2003
  • Honeycomb structure has been fabricated by brazing method using 0.1 wt%C and 1.0wt%C carbon steel core and STS304 stainless steel face sheet. Core shear strength ratio in W and L directions was 1:1.03 in 7 mm cell size, whereas 1:1.45 in 4 mm cell size. Flexural strength on face sheet was 166.4 MPa (0.1 wt%C, W direction), 171.1 MPa (0.1 wt%C, L direction), and 120.2 MPa (1.0 wt%C, W direction) in 7 mm cell size. And in 4mm cell size specimen, it was 169.2 MPa (0.1 wt%C, W direction), 224.2 MPa (0.1 wt%C, L direction). This means that flexural strength of 0.1 wt%C core material was higher than that of 1.0wt%C core material, which was contrary to expectation. SEM and EDS analysis represented that grain boundary diffusion had occurred in0.1 wt%C core, but no grain boundary diffusion in 1.0 wt%C core. And corrugated surface of 0.1 wt%C core was flat, whereas that of 1.0 wt%C core was not flat. As a result, contact area between two 1.0 wt%C cores was much less than that of 0.1 wt% cores, It is thought to be main reason for lower flexural strength of 1.0 wt%C core.

Siliconizing of Bonded Couple between Fe-5.8at.%Si and(Si Wafer or Fe-Si Alloy) (Fe-5.8 at.%Si과 (Si 웨이퍼 또는 Fe-Si합금)과의 접합에 의한 규소침투처리)

  • 이성열;정건영
    • Journal of Advanced Marine Engineering and Technology
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    • v.27 no.1
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    • pp.134-144
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    • 2003
  • Reactive diffusion couples between Fe-5.8at.%Si and (Si wafer, $FeSi_2$, or FeSi alloy) were heat-treated at 1423k. The only layer of $Fe_3Si$ phase was formed in each diffusion couple. The width of $Fe_3Si$ layer was proportional to square root of diffusion time in each kind of diffusion couple. Growth rate of $Fe_3Si$ layer was relied on the concentration of Si in the supplied source of Si atoms. Interdiffusion coefficient of $Fe_3Si$ has been determined from the derived relation between growth rate constant and interdiffusion coefficient in this work. It was shown that the behavior of Kirkendall's void in $Fe_3Si$ layer was not affected by the kind of Si source. But solid solution $\alpha$ was formed in the diffusion couple between Fe-5.8 at.%Si and $Fe_3Si$ alloy. Kirkendall's voids in diffusional $\alpha$ were neglectively smaller than the case of $Fe_3Si$ phase growth.

Low-temperature Sintering Behavior of TiO2 Activated with CuO

  • Paek, Yeong-Kyeun;Shin, Chang-Keun;Oh, Kyung-Sik;Chung, Tai-Joo;Cho, Hyoung Jin
    • Journal of the Korean Ceramic Society
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    • v.53 no.6
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    • pp.682-688
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    • 2016
  • In $TiO_2$-CuO systems, low-temperature sinterability was investigated by a conventional sintering method. Sintering temperatures were set at under $950^{\circ}C$, at which the volume diffusion is inactive. The temperatures are less than the melting point of Ag ($961^{\circ}C$), which is often used as an internal conductor in low-temperature co-fired ceramic technology. To optimize the amount of CuO dopant, various dopant contents were added. The optimum level for enhanced densification was 2 wt% CuO. Excess dopants were segregated to the grain boundaries. The segregated dopants supplied a high diffusion path, by which grain boundary diffusion improved. At lower temperatures in the solid state region, grain boundary diffusion was the principal mass transport mechanism for densification. The enhanced grain boundary diffusion, therefore, improved densification. In this regard, the results of this study prove that the sintering mechanism was the same as that of activated sintering.

A novel low resistivity copper diffusion joint for REBa2Cu3O7-δ tapes by thermocompression bonding in air

  • Wei, Ren;Zhen, Huang;Fangliang, Dong;Yue, Wu;Zhijian, Jin
    • Progress in Superconductivity and Cryogenics
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    • v.24 no.4
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    • pp.16-24
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    • 2022
  • Applications of REBa2Cu3O7-δ tapes require joints with a simple manufacturing process, low resistance and good mechanical properties. In the present study, we successfully developed a copper diffusion joint between Cu-stabilized REBa2Cu3O7-δ tapes that meets the above requirements without solder simply by applying flux, heat and pressurization. After a 3 min thermocompression process at approximately 150 δ and 336 MPa in air, two tapes were directly connected between Cu stabilizers by copper diffusion, which was proven by microstructure analysis. The specific resistivity of the copper diffusion joint reached 5.8 nΩ·cm2 (resistance of 0.4 nΩ for a 306 mm splicing length) at 77 K in the self-field. The axial tensile stress reached 200 N without critical current degradation. The results show promise for the preparation of copper diffusion joints to be used in coils, attached tapes, and wire/cable terminals.

Microstructure and Hardness of Al-Cu Alloy Coating on Monel 400 by Hot Dipping (액상 침적에 의한 Monel 400기지상에 형성된 Al-Cu 합금 코팅층의 조직 및 경도)

  • 조선욱;이임렬
    • Journal of the Korean institute of surface engineering
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    • v.29 no.4
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    • pp.278-285
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    • 1996
  • The structure of coating layer formed by hot dip Al-Cu alloy coating on Monel 1400 metal was studied. The coating layer consists of alloyed layer adjacent to the Monel 400 substrate and Al-Cu alloy. It was found that the hardness of coating increased with dipping time and heat treatment associated with the diffusion and the formation of intermetallic compound at the interface. However the thickness of coating layer was decreased at high dipping temperature due to tile higher viscosity of liquid coating alloy. Diffusion heat treatment at $600^{\circ}C$ after coating resulted in the disappearence of adhered Al(Cu) and $CuAl_2$ phases, and then they transformed into the new phases of CuAl and Al7Cu4Ni at coating layer.

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A Study on the Combustion Characteristic and Soot Distribution of a Common Rail Type D.I.Diesel Visualized Engine with Pilot Injection (파일럿 분사시의 커먼레일식 직분식 가시화 디젤엔진의 연소 및 Soot분포 특성에 관한 연구)

  • 이재용;한용택;이기형;이창식
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.6
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    • pp.37-43
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    • 2003
  • The objective of this work is to investigate the effect of swirl, injection pressure and pilot injection on D.I. diesel combustion by using a transparent engine system. The test engine is equipped with common rail injection system to obtain high pressure and to control injection timing and duration. In this study, the combustion analysis and steady flow test were conducted to estimate the heat release rate from in-cylinder pressure. Soot distribution in diffusion flame according to swirl ratio, injection pressure and pilot injection was investigated by using LII technique. As the results, high injection pressure was found to shorten ignition delay as well as enhance peak pressure and heat release rate was greatly affected by injection timing and pilot injection. In addition, the results showed that the period of soot formation corresponded to the diffusion flame.

Hydrogen Supplying System using Metal Hydride (금속 수소화물을 이용한 수소공급시스템)

  • Bae, Sang-Chul;Katsuta, Masafumi
    • 한국신재생에너지학회:학술대회논문집
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    • 2007.06a
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    • pp.13-19
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    • 2007
  • To find out the optimum design of hydrogen storage and supply tank using Metal Hydride (briefly MH) and to make clear the performance characteristics under various conditions are our research purpose. In order to use the low-temperature exhaust heat, $LaNi_{4.7}Al_{0.3}$ which operates under the low pressure of 1 MPa is chosen, and we measure the basic properties, namely density, specific heat, PCT(Pressure-Concentration-Temperature) characteristics, and effective thermal conductivity. Then, a numerical calculation model of hydrogen storage using MH alloy is suggested and this thermal diffusion equation of model is solved by the backward difference method. This calculation results are compared with the experimental results of the systems which installed 1kg MH alloy and, it is found out that our calculation model can well predict the experimental results. By the experimental using MH alloy, it is recognized that the hydrogen flow rate can control by the step adjustment of brine temperature.

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Numerical Analysis on the Die Pad/Epoxy Molding Compound(EMC) Interface Delamination in Plastic Packages under Thermal and Vapor Pressure Loadings

  • Jin Yu
    • Journal of the Microelectronics and Packaging Society
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    • v.5 no.2
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    • pp.37-48
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    • 1998
  • The popcorn cracking phenomena in plastic IC packages during reflow soldering are investigated by considering the heat transfer and moisture diffusion through the epoxy molding compound(EMC) along with the mechanics of interface delamination. Heat transfer and moisture diffusion through EMC under die pad are analyzed by finite difference method (FDM)during the pre-conditioning and subsequent reflow soldiering pro-cess and the amounts of moisture mass and vapor pressure at delaminated die pad/ EMC interface are calculated as a function of the reflow soldering time. The energy release rate stress intensity factor and phase angle were obtained under various loading conditions which are thermal crack face vapor pressure and mixed loadings. It was shown that thermal loading was the main driving force for the crack propagation for small crack lengths but vapor pressure loading played more significant role as crack grew.

The Apparent Mass Capacity Method for Transient Diffusion Problems with Change of Phase

  • Kim, Yongsoo;Wonmok Jae;D. R. Olander
    • Proceedings of the Korean Nuclear Society Conference
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    • 1995.05b
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    • pp.643-650
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    • 1995
  • A numerical method for treating transient diffusion Involving change of phase is presented. In other methods of dealing with this class of problems, the mass flux balance at the moving phase boundary requires explicit treatment of two distinct phases. The technique, originating from the apparent heat capacity method in transient heat conduction with the phase change, avoids the difficulty by transferring the concentration discontinuity at the boundary to smoothed physical property variations near the moving front. This technique accomodates the nonlinearities which preclude use of analytical solutions. It was tested against known analytical solutions for simple cases and turned out to be quite accurate.

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