• Title/Summary/Keyword: SHS method

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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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Preparation of TaC Powder from the Waste of Ta powder Fabrication Process for Capacitor (Capacitor용 Ta분말 제조공정 Waste Ta를 이용한 TaC분말 제조)

  • Park Je-Shin;Suh Chang-Youl;Yaon Jae-Sik;Bae In-Sung;Park Hyeoung-Ho
    • Resources Recycling
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    • v.12 no.4
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    • pp.51-57
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    • 2003
  • Using the wastes of Ta powder fabrication process for capacitor, TaC powder was synthesized by SHS method. In previous to synthesis, the waste Ta was needed of milling and deoxidization treatments for active reaction and prevention of oxidation. In SHS reaction, it was found that the TaC single phase was obtained in composition of 5~6wt.%C. The reaction temperature was affected by the compaction pressure of the specimens, exhibiting the maximum values at 1600psi, respectively.

Heat Transfer analysis for Self-propagating High Temperature Synthesis of $MoSi_{2}$ (고온자전 반응에 의한 $MoSi_{2}$ 합성법의 열전달 해석)

  • 채수원;조해규;김용석
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1994.10a
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    • pp.303-308
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    • 1994
  • The finite element method has been used to model and analyze the heat transfer phenomena during manufacturing process of MoSi $_{2}$ by SHS. For this urpose nonlinear transient heat transfer analyses by using ANSYS have been performed to compute the temperature distributiuon and the peak temperature in the test specimen. The effects of manufacturing process parameters such as a pre-heating temperature, the velocity of reaction zone have also been investigated. The results of the analysis have been compared with the experimental results.

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A Study on the Synthesis of Titanium Carbonitride by SHS(Self-propagating High-temperature Synthesis) Method (자체반응열 고온합성법을 이용한 Titanium Carbonitride의 합성에 관한 연구)

  • Ha, Ho;Hwang, Gyu-Min;Lee, Hee-Cheol
    • Journal of the Korean Ceramic Society
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    • v.31 no.6
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    • pp.637-642
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    • 1994
  • Using SHS(Self-propagating High-temperature Synthesis) method, the optimum synthetic condition of titanium carbonitride was established by controlling the parameters such as relative density of mixture (Ti+C), nitrogen pressure, additive amounts of titanium hydride(TiH1.924) and protecting heat loss. Under 1 atm nitrogen pressure, nitridation ratio with changing relative density of the sample compacts has a maximum (87.2%) at about 55%, and in the case of enveloping the pellet with a quartz tube, the highest nitridation ratio of 90% was obtained at about 68%. At relative density of 55%, nitridation ratio with the nitrogen pressure has a miximum (87.3%) at 7 atm. As the amounts of additive titanium hydride increased, nitridation ratio decreased at below 7 atm nitrogen pressure and, increased at above this pressure until percent of addition percent reached 15 wt% and decreased abruptly upon futher increases in titanium hydride. In the synthesis of TiCxNy by combustion reaction, heat transfer from combustion zone to preheating zone and nitrogen gas penetration into the compact were found to be important factors affecting the TiCxNy formation. It was difficult to obtain high nitridation ratio when the conbustion temperature was either too high or too low, and it seems that the retention of high temperature after a combustion wave sweeped through the reactant mixture pellet is critical to obtain a satisfactory nitridation ratio.

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Oxidation behavior of (Mo1-xWx)Si2 high-temperature heating elements (초고온용 발열체 (Mo1-xWx)Si2의 산화거동에 대한 연구)

  • Lee, Sung-Chul;Myung, Jae-ha;Kim, Yong-Nam;Jeon, Minseok;Lee, Dong-won;Oh, Jong-Min;Kim, Bae-Yeon
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.30 no.5
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    • pp.200-207
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    • 2020
  • MoSi2, (Mo1/2W1/2)Si2, and WSi2 powders were synthesized by self-propagating high-temperature synthesis (SHS) method. The synthesized powders were heat-treated at 500, 1,000, 1,200, 1,300, 1,400, 1,500 and 1,600℃ in ambient atmosphere. Oxidation of Mo-W silicide powder was found at low temperature of 500℃. XRD structure analysis and DTA/TG data showed that MoO3 was formed with 500℃ heat treatment for 1 hour, and that it was α-cristobalite phase that was formed with 1200℃ heat treatment, not α-quartz phase which is commonly found and stable at room temperature. Existence of W accelerated decomposition at both low and high temperature. Fully sintered MoSi2 and (Mo1/2W1/2)Si2 specimen did not show decomposition or weight loss by oxidation, with 1 hour heat treatment at either low or high temperature. Notably, it was difficult to sinter WSi2 because of oxidation reaction at low temperature.

Effect of Diluent Size on Aluminum Nitride Prepared by Using Self-Propagating High-Temperature Synthesis Process (희석제 입도가 고온자전연소법에 의한 질화알루미늄 합성에 미치는 영향)

  • Lee, Jae-Ryeong;Lee, Ik-Kyu;Shin, Hee-Young;Chung, Hun-Saeng
    • Journal of the Korean Ceramic Society
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    • v.42 no.1
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    • pp.69-75
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    • 2005
  • To investigate the morphological effect on synthesis of aluminum nitride by SHS Process, two type of Al Powder (granular and flacky shape) with the mean size of 34 $\mu$m and the diluent AIN powders of four different mean sizes.0.12, 9.7, 39.3, 50.5 $\mu$m, were used to prepare green compact. The packing density was fixed to $35 TD\%. The initial pressure of $N_{2}$ and diluent fraction was varied in the range of $1\~10 MPa,\;0.4\~0.7$, respectively. AlN with high purity of $98\% or over and large particle size of about several tens fm can be synthesized by SHS reaction as a consequence of adjusting particle size of AlN dilutent similarly to that of Al reactant. This may be caused by improvement of $N_{2}$ gas permeation to compact after passing the propagation wave. In the case of flaky-shape aluminum used as reactant, instead of granular Al-powder, unstable combustion would be occurred. As the result, irregular propagation of combustion wave and falling-off of maximum temperature would be observed during the reaction.

SiO2 Behavior of MoSi2 Powders Containing SiO2 Synthesized by SHS Method (자전연소합성법으로 제조된 SiO2 첨가된 MoSi2 분말 내에서의 SiO2의 거동 연구)

  • Rha, Sa-Kyun;Jeon, Min-Seok;Song, Jun-Kwang;Han, Dong-Bin;Jeong, Cheol-Weon;Kim, Sung-Soo;Lee, Youn-Seoung
    • Journal of the Korean Ceramic Society
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    • v.48 no.6
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    • pp.559-564
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    • 2011
  • In order to investigate the behavior of $SiO_2$ in the molybdenum silicide powders, crystal structure of these powders was measured by XRD, in addition, surface composition and surface phase (or chemical states) and microstructure were analysed by XPS and TEM, respectively. Mo-silicide powders containing $SiO_2$ were synthesized by SHS (Self-Propagating High-Temperature Synthesis) technique. In XRD result, according to increase of $SiO_2$ contents, the crystal structure for synthesized $MoSi_2$ powders was still typical $MoSi_2$ bct without any other phases. By XPS analysis, the surface of Mo and Si source powders was covered with $MoO_3$ and $SiO_2$, respectively, and the surface of synthesized $MoSi_2$ powder was also covered with $MoO_3$ and $SiO_2$, which were stable oxides at room temperature. However, according to increase of $SiO_2$ addition, $MoSi_2$ phase in XPS spectra decreased and $SiO_2$ phase increased relatively in synthesized $MoSi_2$ powders. From the results by XPS and XRD, we found that the existent $SiO_2$ has amorphous structure. In the microstructure, the small particulates of the synthesized products added $SiO_2$ agglomerated together to form larger clusters (from ~10 nm to ~1 ${\mu}m$). From TEM, XPS, and XRD results, we found that the out layer of agglomeration of synthesized $MoSi_2$ powder is surrounded by amorphous $SiO_2$.

The Longitudinal Effect of Leisure on Happiness and Health in Midlife (중년기 여가생활이 행복과 건강에 미치는 영향에 대한 종단 연구)

  • Seungah Ryu ;Kyoungmi Kim ;Incheol Choi
    • Korean Journal of Culture and Social Issue
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    • v.17 no.4
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    • pp.415-434
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    • 2011
  • Leisure is an important role on happiness and health in midlife. Nevertheless, there has been little research using a longitudinal method in Korea to identify the influence of leisure on happiness and health. Current study examined the effect of leisure satisfaction and time for leisure activities on happiness(SHS) and health-related variables(psychological symptoms, physical symptoms, and quality of sleep) in middle aged adults(40-65 years) by longitudinal data. Two surveys were conducted with 10 months' interval and total 145 respondents(M=49.45) participated in both surveys. Hierarchical regression analysis was employed to investigate that both leisure satisfaction and time for leisure activities in the first time have an effect on happiness and health-related variables in the second time after controlling for each happiness and health variables in the first time as well as demographic variables. We found that leisure satisfaction influenced beneficially on happiness(SHS), psychological symptoms, and quality of sleep after 10-month. Similarly, time for leisure activities had effect on happiness(SHS), psychological symptoms, and physical symptoms after 10-month. The implication for study were discussed.

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Study on Sintering Properties of $TiB_2-TiC$ Composite by Self-Propagating High Temperature Synthesis Method (SHS법에 의한 $TiB_2-TiC$ 복합체의 소결특성에 관한 연구)

  • 이형복;조덕호;장준원
    • Journal of the Korean Ceramic Society
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    • v.29 no.7
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    • pp.577-585
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    • 1992
  • TiB2 and TiC were prepared from the mixture of metal titanium, boron and graphite powders in Argon atmosphere by Self-propagating High-temperature Synthesis method. The sintered properties of TiB2-TiC composite as a function of TiC content and sintering temperature were investigated in TiB2 matrix. The sintered properties were the most excellent at 10 wt% TiC content in TiB2-TiC composite. The relative density, M.O.R strength, hardness and fracture toughness of TiB2-10 wt% TiC composite sintered at 190$0^{\circ}C$ for 90 min by hot-pressing under the pressure of 30 MPa were 98.6%, 634 MPa, 2128.1 kg/$\textrm{mm}^2$ and 4.09 MN/m3/2, respectively.

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Synthesis of nanometric tungsten powders by solid state combustion method (고상연소반응법에 의한 나노텅스텐분말의 합성)

  • H.H. Nersisyan
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2003.11a
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    • pp.93-93
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    • 2003
  • Tungsten and tungsten heavy alloys have widespread application as radiation shielding devices and heavy duty electrical contacts. High density and good room temperature mechanical properties have generated interest in evaluating tungsten and tungsten alloys as kinetic energy penetrators against armor. Nowdays ultra fine-grained tungsten powders are in great interest because higly dense structures can be obtained at low temperature, pressure and lower sintering time. Several physical md chemical methods are available for the synthesis of nanometric metal Powders: ball milling, laser abalation, vapor condensation, chemical precipitation, metallic wire explosion i.e. However production rates of the above mentioned methods are low and further efforts are needed to find out large-scale synthesis methods. From this point of view solid state combustion method ( known as SHS) represents undoubted interest.

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