• 제목/요약/키워드: hot-pressing temperature

검색결과 254건 처리시간 0.029초

Fabrication and Characteristics of Chitosan Non-woven Fabric developed using only water as plasticizer

  • Lee, Shin-Hee;Hsieh, You-Lo
    • 한국의류산업학회지
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    • 제16권2호
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    • pp.319-325
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    • 2014
  • This article describes a method for producing chitosan non-woven fabrics by just hot pressing without the use of a binder. A study has been made of the wet spinning of chitosan fiber. The fibers were rinsed thoroughly in running water and chopped wet into staples of with a length of approximately 5-10 mm. The chopped chitosan staples were dispersed uniformly in water and fabricated using a non-woven making machine. This study examined the formation and the characteristics of chitosan non-woven fabrics manufactured by hot pressing without the use of a binder. The effects of the non-woven fabrication conditions on the thermal, morphological, structural, and physical properties of chitosan non-woven fabric with and without water as a plasticizer were studied. The temperature of the exothermic peak, decomposition of chitosan fibers increased with increasing heating rate. Water in the chitosan fiber effectively plasticized the chitosan fiber. The thermal bonded structure of the wet chitosan fiber with water as a plasticizer was clearly found in many parts of the non-woven fabric at a fabrication temperature of $200^{\circ}C$. The intensity and profile of the (100) plane($2{\theta}=10.2^{\circ}$) and (040) plane($2{\theta}=20.9^{\circ}$) in the chitosan non-woven fabric decreases and became smooth in the non-woven fabric formation by melting.

극저온 기계화학적 밀링(Mechano-Chemical Milling)에 의해 제조된 ODS Fe 합금의 기계적 특성 (Mechanical Properties of ODS Fe Alloys Produced by Mechano-Chemical Cryogenic Milling)

  • 한성인;홍영환;황승준
    • 열처리공학회지
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    • 제25권3호
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    • pp.138-145
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    • 2012
  • An ${\alpha}$-Ferrite (Fe) powder dispersed with 4 vol.% of $Al_2O_3$ was successfully produced by a simple miling at 210 K with a mixture of $Fe_2O_3$, Fe and Al ingredient powders, followed by 2 step high temperature consolidation: Hot Pressing (HP) at 1323 K and then Hot Isostatic Pressing at 1423 K. The microstructure of the consolidated material was characterized by standard metallographic techniques such as XRD (X-ray Diffraction), TEM and STEM-EDS. The results of STEM-EDS analysis showed that the HIPed materials comprised a mixture of pure Fe matrix with a grain size of ~20 nm and $Al_2O_3$ with a bimodal size distribution of extremely fine (~5 nm) and medium size dispersoids (~20 nm). The mechanical properties of the consolidated materials were characterized by compressive test and micro Vickers hardness test at room temperature. The results showed that the yield strength of the ODS (Oxide Dispersion Strengthened) Fe alloy are as much as $674{\pm}39$ MPa and the improvement of the yield strength is attributed to the presence of the fine $Al_2O_3$ dispersoid.

Sintering and Oxidation of GdB4 Synthesized by B4C Reduction Method

  • Sonber, Jitendra Kumar;Murthy, Tammana Shri Ram Chandra;Sairam, Kannan;Kain, Vivekanand
    • 한국세라믹학회지
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    • 제54권2호
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    • pp.121-127
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    • 2017
  • Gadolinium tetraboride ($GdB_4$) was synthesized by reduction of $Gd_2O_3$ using boron carbide in presence of carbon. Effect of temperature on product quality was investigated. Pure $GdB_4$ powder was obtained in vacuum at $1500^{\circ}C$. Pressureless sintering experiments revealed that sintering takes place only above $1600^{\circ}C$. A maximum density of 77.1% of the theoretical value was obtained at $1800^{\circ}C$ by pressureless sintering. Hot pressing resulted in 95.5% of theoretical density at the lower temperature of $1700^{\circ}C$ under 35 MPa pressure. Hardness and fracture toughness of dense $GdB_4$ were measured and found to be 21.4 GPa and $2.3MPa{\cdot}m^{1/2}$, respectively. After exposure to air at $900^{\circ}C$, the formation of a porous and non-protective oxide layer was observed.

니켈 실리사이드 화합물의 소결특성 (Sintering Characteristics of Nickel Silicide Alloy)

  • 변창섭;이상호
    • 한국재료학회지
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    • 제16권6호
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    • pp.341-345
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    • 2006
  • [ $Ni_2Si$ ] mixed powders were mechanically alloyed by a ball mill and then processed by hot isostatic pressing (HIP) and spark plasma sintering (SPS). In the powder that was mechanically alloyed for 15minutes(MA 15 min), only Ni and Si were observed but in the powder that was mechanically alloyed for 30minutes(MA 30 min), $Ni_2Si$, Ni and Si were mixed together. Some of the MA 15 min powder and MA 30 min powder were processed by HIP under pressure of 150MPa at the temperature of $1000^{\circ}C$ for two hours and some of them were processed by SPS under pressure of 60 MPa at the temperature of $1000^{\circ}C$ for 60 seconds. Both methods completely compounded the powders to $Ni_2Si$. The maximum density of sintered lumps by HIP method was 99.5% and the maximum density of the sintered lump by SPS method was 99.3%. with the hardness of HRc 66 with the hardness of HRc 63. Therefore, the SPS method that can sinter in short time at low cost is considered to be more economical that the HIP method that requires complicated sintering conditions and high cost and the sintering can produce target materials in desired sizes and shapes to be used for thin film.

$Y_{0.1}$(Si, Al)$_12$(N, O)$_16$의 조성을 갖는 부분안정화 $\alpha$-Sialon 열간가압소결체의 고온강도 (High-Temperature Strength of the Hot-Pressed Partially Stabilized $\alpha$-Sialon Ceramics Having the Composition of Y0.1(Si, Al)12(N, O)16)

  • 조덕호;이형복
    • 한국세라믹학회지
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    • 제29권5호
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    • pp.410-418
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    • 1992
  • Si3N4, AlN and Y2O3 powder mixtures of the Y0.1(Si, Al)12(N, O)16 composition were hot-pressed at 1900℃ for 0 to 60 min under 30 MPa in order to fabricate the partially-stabilized α-Sialon ceramics (X=0.1). Room and high temperature flexural strengths of the specimens were compared with those of Si3N4-5 wt%Y2O3, Si3N4-5 wt%Y2O3-2 wt%Al2O3, and β-Sialon (Z=0.5) ceramics. The flexural strength of the α-Sialon ceramics which was hot-pressed for 15 min showed the highest value of 820 MPa at 1400℃ that is relatively higher temperature. It is guessed that a little amount of glassy phase existed in grain boundary because Y2O3 and AlN components were incoperated in Si3N4 grains, or transient liquid phase sintering, and microstructure with the smaller grain size and the interlocked grains of α'-and β-Si3N4 was obtained by the hot-pressing at high temperature of 1900℃ for the short time (15 min).

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Permanent disposal of Cs ions in the form of dense pollucite ceramics having low thermal expansion coefficient

  • Omerasevic, Mia;Lukic, Miodrag;Savic-Bisercic, Marjetka;Savic, Andrija;Matovic, Ljiljana;Bascarevic, Zvezdana;Bucevac, Dusan
    • Nuclear Engineering and Technology
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    • 제52권1호
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    • pp.115-122
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    • 2020
  • A promising method for removal of Cs ions from water and their incorporation into stable crystal structure ready for safe and permanent disposal was described. Cs-exchanged X zeolite was hot-pressed at temperature ranging from 800 to 950 ℃ to fabricate dense pollucite ceramics. It was found that the application of external pressure reduced the pollucite formation temperature. The effect of sintering temperature on density, phase composition and mechanical properties was investigated. The highest density of 92.5 %TD and the highest compressive strength of 79 MPa were measured in pollucite hot-pressed at 950 ℃ for 3 h. Heterogeneity of samples obtained at 950 ℃ was determined using scanning electron microscopy. The pollucite hot-pressed at 950 ℃ had low linear thermal expansion coefficient of ~4.67 × 10-6 K-1 in the temperature range from 100 to 1000 ℃.

Properties of Hot Pressed Alumina-Titanium Diboride Particulate Composites

  • Park, Dong-Soo;Han, Byung-Dong
    • The Korean Journal of Ceramics
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    • 제4권3호
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    • pp.227-230
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    • 1998
  • Alumina($Al_2O_3$)-Titanium Diboride($TiB_2) particulate composites were fabricated by hot pressing of the powder mixture that was prepared from Self-propagating High Temperature Synthesis (SHS) product and commercial powders. Their propeties were examined in order to find feasibility of using SHS for making the high performance ceramic composite. $TiB_2 particles obtained by grinding the SHS product were finer than the commercial powders. Hot pressed sample containing the SHS products exhibited higher strength than the one prepared from the commercial powders.

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SHS법에 의한 $\textrm{Al}_2\textrm{O}_3$-SiC 복합분말 제조 및 소결특성 (Characteristics of $\textrm{Al}_2\textrm{O}_3$-SiC Composite Powder Prepared by SHS Process and its Sintering Behavior)

  • 안창영;윤기석;정중채;원창완
    • 한국재료학회지
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    • 제9권8호
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    • pp.817-824
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    • 1999
  • $Al_2$$O_3$-SiC 화합물 분말이 $SiO_2$, A1 그리고 C 분말들을 원료분말로 하여 SHS(self-propagating High-temperature Synthesis)법에 의해 제조되었다. 원료 분말에서의 몰비, 성형압력, 반응물의 초기온도의 영향이 생성물과 연소과정에 대해 연구되었다. $SiO_2$/A1/C계의 자전연소합성은 낮은 연소온도 때문에 $400^{\circ}C$ 이상으로 예열되어야 한다. 연소반응의 결과로서 최종생성물의 순도는 반응물의 순도보다 높았다. 이 계에서 $SiO_2$:Al:C의 적당한 몰비는 3.0:4.0:6.0이었고, free carbon은 30min 동안 $650^{\circ}C$에서 배소함으로써 제거되었다. 본 연구에서 상압소결은 $1700^{\circ}C$에서 powder bed를 사용한 표본의 분해를 제어하고 치밀한 소결체를 얻는데 매우 효과적이었다. hot-pressing으로 생성된 소결체는 이론비교밀도의 약 98%이었다.

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소결분위기 제어에 의한 Al2O3/Fe-Ni 나노복합재료의 제조 및 특성 (Fabrication of Al2O3/Fe-Ni Nanocomposites by Atmosphere-controlled Sintering and their Properties)

  • 이홍재;정영근;오승탁;이재성
    • 한국세라믹학회지
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    • 제39권2호
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    • pp.199-203
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    • 2002
  • 소결 분위기가 금속입자분산 세라믹스기 복합체의 미세 조직 및 물성에 미치는 영향에 대하여 조사하고자 화학적 방법으로 합성한 $Al_2O_3$/Fe-Ni 나노복합분말을 수소 및 아르곤 가스 분위기, 또한 소결온도 등으로 제어하여 열간가압 소결하였다. 수소분위기에서 소결한 복합체는 아르곤분위기의 경우보다 반응상 $FeAl_2O_4$의 형성이 억제되었으며, 증가된 파괴강도 및 인성 값을 나타내었다. 또한, 소결 온도를 낮추었을 경우 기지상 및 금속 분산상의 미세화와 향상된 기계적 성질을 얻을 수 있었다. 소결 조건에 따른 기계적 특성의 변화는 주로 반응상의 형성과 관련된 미세조직 특성에 의존하는 것으로 해석하였다.

Effect of Post Deformation on the Structure and Properties of Sintered Al-Cu-SiC Composites

  • Chung, Hyung-Sik;Heo, Ryun-Min;Kim, Moon-Tae;Ahn, Jae-Hwan
    • 한국분말야금학회:학술대회논문집
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    • 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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    • pp.1301-1302
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    • 2006
  • Sintered composites of Al-8wt%Cu-10vol%SiCp were deformed by repressing or equal channel angular pressing(ECAP) at room temperature, $500^{\circ}C$ and $600^{\circ}C$. Repressing produced more densification than ECAP but resulted in much lower transverse rupture strengths. In both cases, deformation at room temperature and $500^{\circ}C$, resulted in much lower strengths than deformation at $600^{\circ}C$, and also caused the fracturing of some SiC particles. The higher bend strengths and less SiC fracturing at $600^{\circ}C$ are attributable to the presence of an Al-Cu liquid phase during deformation. The employment of copper coated SiC instead of bare SiC particles for preparing the composites was found not improving the properties.

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