• 한국세라믹학회지
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• 제32권10호
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• pp.1194-1202
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• 1995

The influences of TiC additions to the α-SiC on microstructural, mechanical, and electrical properties were investigated. Electrical discharge machinability of SiC-TiC composites was also studied. Samples were prepared by adding 30, 45, 60 wt.% TiC particles as a second phase to a SiC matrix. Sintering of SiC-TiC composites was done by hot pressing under a vacuum atmospehre from 1000 to 2000℃ with a pressure of 32 MPa and held for 90 minutes at 2000℃. Samples obtained by hot pressing were fully dense with the relative densities over 99% except 60wt.% TiC samples. Flexural strength and fracture toughness of the samples were increased with the TiC content. In case of SiC samples containing 45 wt.% TiC, the fracture toughness showed 90% increase compared to that of monolithic SiC sample. The crack propagation and crack deflection were observed with a SEM for etched samples after Vicker's indentation. The electrical resistivities of SiC-TiC composites were measured utilizing the four-point probe. The electrical dischage machining of composites was also conducted to evaluate the machinability.

• 대한치과기공학회지
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• 제25권1호
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• pp.21-28
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• 2003

The purpose of this study was to process bio-active glass ceramic composite, reinforced with sapphire fibers, by hot press. Also to study the interface of the matrix and the sapphire fiber, and the mechanical properties. Glass raw materials melted in Pt crucible at 1300$^{\circ}C$ during 3.5 hours. The melt was crushed in ball mill and then crushed material, ground and sieved to $<40{\beta}{\mu}m$. Sapphire fibers cut (30mm) and aligned. Powder and fibers hot pressed. The micrographs show good bonding between the matrix and the fiber and no porosity in the glass matrix. This means ideal fracture phenomena. Glass is fractured before the fiber. This is indication of good fracture strength. EDXS showing aluminum rich phase and crystalline phase. Bright field image of the matrix showing crystalline phase. Also diffraction pattern of TEM showing the crystalline phase and more than one phase. Strength of the samples was determined by 3 point bend testing. Strength of the 10vol% sample was approximately 69MPa, while strength of the control sample is 35MPa. Conclusions through this study as follow: 1. Micrographs show no porosity in the glass matrix and the interface. 2. The interface between the fiber and the glass matrix show no gaps. 3. Fracture of the glass indicates characteristic fiber-matrix separation. 4. Presence of crystalline phase at high processing temperature. 5. Sapphire is compatible with bioactive glass.

• 한국세라믹학회지
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• 제37권11호
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• pp.1039-1043
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• 2000

$\alpha$-Si$_3$N$_4$가 20vol% 혼합된 SiC/Si$_3$N$_4$혼합물에서 $\alpha$-SiC의 일부를 SiC whisker로 치환하여 첨가한 후 180$0^{\circ}C$, 25MPa의 압력으로 hot pressing하여 SiC/Si$_3$N$_4$/SiCw 복합체를 제조하였다. SiC whisker의 첨가 함량이 증가할수록 상대밀도, 꺽임강도, 마모 저항성은 감소되었으나, 파괴인성은 크게 향상되었다. $\alpha$-SiC의 일부를 SiC whisker로의 치환은 치밀화를 억제하였으나 파괴인성의 증가는 마모 저항성을 향상시키지 않았다.

• 마이크로전자및패키징학회지
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• 제7권4호
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• pp.1-5
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• 2000

열전반도체 ($Pb_{1-x}Sn_{x}$)Te를 AC통전 가압법으로 제조하여 그물성에 대해서 연구하였다. 균질성 향상과 구성 성분의 휘발방지에 유효한 진동분쇄공정으로 기계적 합금화를 시켰다. Sn 함량이 증가함에 따라 합금화에 요구되는 기계적 합금화 시간이 증가되었다. AC 통전 hot press법으로 873-923 K에서 1~4분간 150 kgf/$\textrm{cm}^2$의 압력으로 소결하였다. 단시간의 소결은 Te의 증발을 억제할 수 있었다. ($Pb_{1-x}-Sn_{x}$)Te 밀도는 소결 시간보다 소결온도에 더 영향을 받았다. Sn첨가량이 10 mol% 이하일때 온도 상승에 따라 p-n전이 현상이 일어났으나 그 이상의 함량에서는 p-type반도성이 그대로 유지됨이 관찰되었다. 열기전력은 500 K, x=0.2일때 250 $\mu$V/K의 최대치론 나타내었다. Sn함량의 증가에 따라 최대치는 낮아졌으며, 그 온도는 고온측으로 이동하였으며, 전기전도도의 최대치는 온도가 상승함에 따라 저하되었다.

• 한국자기학회지
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• 제7권1호
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• pp.49-54
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• 1997

급속응고된 (N $d_{14.73}$F $e_{78.67}$ $B_{6.60}$)$_{100-x}$ $Co_{x}$(X = 0, 1, 2, 3)리본의 열처리 온도에 따른 자기적 특성, 상변화, 미세조직의 변화에 대해 연구하였다. Co의 첨가로 인해 N $d_{2}$F $e_{14}$B 상의 결정입도가 균일해졌으며, Nd-rich 상들이 입계에 잘 분포됨으로써 보자력($_{i}$ $H_{c}$)이 향상되어 X=2에서 최대 20.3 kOe를 얻었다. 이와 같은 미량의 Co에 의한 보자력 향상의 효과는 고온성형을 요하는 hot-press 및 die-upset에서도 동일하게 나타났으며 최대의 보자력은 X=2에서 hot press시에 16.9 kOe, die-upset 시에 15.12 kOe 이다.

• 한국분말재료학회지
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• 제30권5호
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• pp.409-414
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• 2023

YSZ (Y₂O₃-stabilized zirconia)-based ceramics have excellent mechanical properties, such as high strength and wear resistance. In the application, YSZ is utilized in the bead mill, a fine-grinding process. YSZ-based parts, such as the rotor and pin, can be easily damaged by continuous application with high rpm in the bead mill process. In that case, adding WC particles improves the tribological and mechanical properties. YSZ-30 vol.% WC composite ceramics are manufactured via hot pressing under different pressures (10/30/60 MPa). The hot-pressed composite ceramics measure the physical properties, such as porosity and bulk density values. In addition, the phase formation of these composite ceramics is analyzed and discussed with those of physical properties. For the increased applied pressure of hot pressing, the tetragonality of YSZ and the crystallinity of WC are enhanced. The mechanical properties indicate an improved tendency with the increase in the applied pressure of hot pressing.

• Journal of the Korean Wood Science and Technology
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• 제46권2호
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• pp.155-165
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• 2018

The objective of the research was to evaluate the effect of particle pre-treatment on physical, mechanical, and durability of jatropha fruit hulls (JFH) particleboard. The pre-treatments included were immersing in cold water, hot water, and acetic acid solution. After each treatment, the particles were dried up to 3% moisture content. Urea-formaldehyde (UF) resin was used to fabricate particleboards with board size, thickness and density target of 25 cm by 25 cm, 0.80 cm, and $0.70g/cm^3$, respectively. Board pressed at $130^{\circ}C$ for 10 minutes, and $25kg/cm^2$ pressure. The evaluation of particleboard followed the JIS A 5908-2003. Whilist their resistance to subterranean termite test (mass loss, mortality, antifeedant value and feeding rate) refers to the Indonesian standard (SNI 01.7207-2006). The physical and mechanical properties of particleboards showed that all pre-treatments decreased the pH of particles. Overall, all particle immersing treatments resulted of better physical and mechanical properties of particleboard than those of untreated ones. The acetic acid treatment resulted the best physical and mechanical properties of particleboard. Based on the mass loss of JFH particleboard, hot water and acetic acid treated particleboards were classified into weak resistance to subterranean attack. The other two treatments were classified into very weak resistance. Hot water treated particleboard provided the highest mortality and antifeedant as much as 87.40% and 34.20%, respectively. Based on antifeedant classification, hot water treated particleboards were classified into moderately strong resistance, while other treatments were categorized into weak resistance. The lowest feeding rate value ($45.30{\mu}g/termite/day$) was attained by hot water treatment.

• 한국분말재료학회지
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• 제12권5호
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• pp.357-361
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• 2005

Fe-doped skutterudite $CoSb_3$ with a nominal composition of $Fe_{x}Co_{4-x}Sb_{12}(0\;{\le}\;x\;{\le}\;2.5)$ has been synthesized by mechanical alloying (MA) of elemental powders, followed by hot pressing. Phase transformations during mechanical alloying and hot pressing were systematically investigated using XRD. Single phase skutterudite was successfully produced by vacuum hot pressing using as-milled powders without subsequent annealing. However, second phase in the form of marcasite structure $FeSb_2$ was found to exist in case of $x\;{\ge}\;2$, suggesting the solubility limit of Fe with Co in this system. Thermoelectric properties as functions of temperature and Fe contents were evaluated for the hot pressed specimens. Fe substitution up to x=1.5 with Co in $Fe_{x}Co_{4-x}Sb_{12}$ appeared to increase thermoelectric figure of merit (ZT) and the maximum ZT was found to be 0.78 at 525K in this study.

• Journal of Pharmaceutical Investigation
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• 제41권3호
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• pp.147-151
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• 2011

This paper demonstrates the development of a method for preparing micropatterned microdiscs in order to increase contact area with cells and to change the release pattern of drugs. The microdiscs were manufactured with hot embossing, where a polyurethane master structure was pressed onto both solid and porous microparticles made of polylactic-co-glycolic acid at various temperatures to form a micropattern on the microdiscs. Flat microdiscs were formed by hot embossing of porous microparticles; the porosity allowed space for flattening of the microdiscs. Three types of micro-grooves were patterned onto the flat microdiscs using prepared micropatterned molds: (1) 10 ${\mu}M$ deep, 5 ${\mu}M$ wide, and spaced 2 ${\mu}M$ apart; (2) 10 ${\mu}M$ deep, 9 ${\mu}M$ wide, and spaced 5 ${\mu}M$ apart; and (3) 10 ${\mu}M$ deep, 50 ${\mu}M$ wide, and spaced 50 ${\mu}M$ apart. This novel microdisc preparation method using hot embossing to create micropatterns on flattened porous microparticles provides the opportunity for low-cost, rapid manufacture of microdiscs that can be used to control cell adhesion and drug delivery rates.

• 문화기술의 융합
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• 제4권3호
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• pp.209-212
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• 2018

이방성 도전필름(ACF)을 사용한 본딩은 납땜이 용이하지 않은 이질적인 소재 간 미세 접합을 형성하는데 널리 사용되어진다. 성공적인 ACF 본딩 구현을 위한 3가지 제한조건이 존재한다. 본딩 접촉점은 설정된 작업 시간동안 적절한 압력과 온도를 유지한 헤드에 의해서 압착되어야 한다. 본 논문에서는 머신 비전을 기반으로 한 ACF 본딩기법을 제안하고 실험을 통해 검증한다. 시스템은 본딩 작업대 상의 PCB 위치 및 방향을 계산하고 헤드가 압착되어야 하는 최적의 접촉점을 결정한다. 제안한 시스템이 접촉면 상의 헤드 평탄도를 보장함으로써 접착력을 향상시킬 수 있음을 실험결과를 통해 보여준다.