• 한국전기전자재료학회논문지
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• 제20권7호
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• pp.581-586
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• 2007

[ $(Ba_{0.57}Sr_{0.33}Ca_{0.10})TiO_3$ ] (BSCT) powders, prepared by sol-gel method, were mixed with organic vehicle and the BSCT thick films were fabricated by the screen printing method. The structural and dielectric properties were investigated as a function of the $Yb_2O_3$ doping contents. As a result of the TG-DTA, exothermic peak was observed at around $670^{\circ}C$ due to the formation of the polycrystalline perovskite phase. All BSCT thick films showed the typical XRD patterns of a cubic polycrystalline structure. The average thickness of all BSCT thick films was about $70{\mu}m$. The grain size of the BSCT thick film doped with 0.7 mol% $Yb_2O_3$ was approximately $6.2{\mu}m$. The Curie temperature and relative dielectric constant at room temperature decreased with increasing $Yb_2O_3$ amount. Relative dielectric constant and dielectric loss of the specimen doped with 0.1 mol% $Yb_2O_3$ were 4637 and 19 % at Curie temperature, respectively.

• Nuclear Engineering and Technology
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• 제31권5호
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• pp.455-464
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• 1999

The effect of TiO$_2$ on the sintering behavior of mixed UO$_2$-U$_3$O$_{8}$ Powder compacts has been investigated using the U$_{3}$O$_{8}$ powder made tv oxidation of defective UO$_{2}$ pellets. Without TiO$_2$, UO$_2$ pellet density is inversely proportional to U$_3$O$_{8}$ content and is below 94 %TD in the U$_3$O$_{8}$ range above 15 wt%. Using more than 0.1 wt % TiO$_2$, however, the density decreases slightly with U$_3$O$_{8}$ content and thus is higher than about 94% TD in the whole range of U$_3$O$_{8}$ content. The grain sizes of UO$_2$ pellets with more than 0.1 wt % TiO$_2$are larger than about 30${\mu}{\textrm}{m}$. Therefore, the U$_3$O$_{8}$ Powder can be reused without any restriction on its amount in UO$_2$ pellet fabrication by sintering the mixed UO$_2$-U$_3$O$_{8}$ compact with the aid of TiO$_2$. Mechanisms for densification and grain growth are proposed and discussed, based on a dilatometry study and an examination of microstructure. microstructure.

• Journal of the Korean Wood Science and Technology
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• 제40권1호
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• pp.1-9
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• 2012

바이오매스로부터의 고밀화연료는 북미와 유럽에서 신재생에너지로서 널리 이용되고 있다. 본 연구에서는 일본잎갈나무와 현사시나무를 피스톤 프레스를 이용하여 브리켓을 제조하였으며, 연료적 특성 및 고밀화 특성을 밝히고자 압력, 가압시간, 수종 및 목분 크기가 브리켓의 특성에 미치는 영향을 조사하였다. 상온에서 110~170 MPa의 압력을 가해 제조된 일본잎갈나무와 현사시나무 브리켓의 4주간 경과 후의 밀도는 0.66~0.94 g/$cm^3$이고, 적정 가압시간은 12초이며, 제조 압력이 증가하면 브리켓의 밀도는 직선적으로 증가하였다. 일본잎갈나무 브리켓이 현사시나무 브리켓보다 밀도가 컸으며, 목분의 크기가 클수록 브리켓의 밀도가 컸다.

• 펄프종이기술
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• 제44권4호
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• pp.85-90
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• 2012

Wet pressing process has great influence not only on the paper properties but also on the efficiency of total manufacturing process including energy efficiency. The slow drainage propensity of old corrugated container(OCC) might require more complicated control of wet pressing process. In this study, the change in press efficiency and in structure of wet sheet by the various condition of laboratory roll press simulator were evaluated to provide background information about wet pressing of OCC. The higher pressure and the slower machine speed resulted in higher efficiency of wet pressing but the change trends of dryness depending on the wet press pressure and machine speed were shown differently according to OCC treatment. The effects of water contents of felt on the wet press efficiency and sheet structure were also investigated. The higher contents of water in felt resulted in less removal of water generally and the crushed structure of wet sheet were appeared especially at higher pressure.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.358-358
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• 2010

Ion beam bombardment at low energy forms nanosize patterns such as ripples, dots or wrinkles on the surface of polymers in ambient temperature and pressure. It has been known that the ion beam can alter the polymer surface that induces skins stiffer or the density higher by higher compressive stress or strain energies associated with chain scissions and crosslinks of the polymer. Atomic scale structure evolution in polymers is essential to understand a stress generation mechanism during the ion beam bombardment, which governs the nanoscale surface structure evolution. In this work, Molecular Dynamics (MD) simulations are employed to characterize the phenomenon occurred in bombardment between the ion beam and polymers that forms nanosize patterns. We investigate the structure evolution of Low Density Polyethylene (LDPE) at 300 K as the polymer is bombarded with Argon ions having various kinetic energies ranging from 100 eV to 1 KeV with 50 eV intervals having the fluence of $1.45\;{\times}\;1014 #/cm2$. These simulations use the Reactive Force Field (ReaxFF), which can mimic chemical covalent bonds and includes van der Waals potentials for describing the intermolecular interactions. The results show the details of the structural evolution of LDPE by the low energy Ar ion bombardment. Analyses through kinetic and potential energy, number of crosslinks and chain scissions, level of local densification and motions of atoms support that the residual strain energies on the surface is strongly associated with the number of crosslinks or scissored chains. Also, we could find an optimal Ar ion beam energy to make crosslinks well.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.203.1-203.1
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• 2013

Zinc oxide (ZnO) nanocrystalline thin films on various growth temperatures for active layer and different buffer layer thickness were grown by plasma-assisted molecular beam epitaxy (PA-MBE) on Si substrates. The ZnO active layer were grown with various growth temperature from 500 to $800^{\circ}C$ and the ZnO buffer layer were grown for different time from 5 to 40 minutes. To investigate the structural and optical properties of the ZnO thin films, scanning electron microscope (SEM), X-ray diffractometer (XRD), and photoluminescence (PL) spectroscopy were used, respectively. In the SEM images, the ZnO thin films have high densification of grains and good roughness and uniformity at $800^{\circ}C$ for active layer growth temperature and 20 minutes for buffer layer growth time, respectively. The PL spectra of ZnO buffer layers and active layers display sharp near band edge (NBE) emissions in UV range and broad deep level emissions (DLE) in visible range. The intensity of NBE peaks for the ZnO thin films significantly increase with increase in the active layer growth temperature. In addition, the NBE peak at 20 minutes for buffer layer growth time has the largest emission intensity and the intensity of DLE peaks decrease with increase in the growth time.

• 한국재료학회지
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• 제3권3호
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• pp.310-315
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• 1993

P-type(100)Si Wafer 위에 400$\AA$의 Ta를 증착하여 열산화법으로 ${Ta_2}{O_5}$박막을 형성시킴 후 RTA후처리를 통하여 절연파괴전장 특성 개선을 이루고자 하였다. 유전상수에 미치는 RTA후처리의 영향은 미약하지만 절연파괴전장을 나타내었으나 결정화 온도 이하의 RTA온도에서는 절연파괴전장이 5.4MV/cm로 RTA효과가 크게 나타났다. 이러한 RTA효과는 RTA온도 $575^{\circ}C$에서 flat band voltage shift가 RTA 시간에 따라 변화가 없는 것으로 미루어 보아 RTA효과는 계면 변화에 의한 것이 아님을 알 수 있었으며, RBS 분석을 통하여 ${Ta_2}{O_5}$1박막의 치밀화에 의한 것임을 확인할 수 있었다.

• 대한금속재료학회지
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• 제50권1호
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• pp.34-38
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• 2012

Titanium has good deformability, high hardness, high biocompatibility, excellent corrosion resistance and low density. Due to these attractive properties, it has been used in many industrial applications. Dense nanostructured Ti was sintered from mechanically activated Ti and $TiH_2$ powders by high frequency induction heating under pressure of 80 MPa. The advantage of this process is that it allows very quick densification to near theoretical density and inhibition of grain growth. $TiH_2$ powder was decomposed to Ti during sintering. The hardness of Ti increased and the average grain size of Ti decreased with increasing milling time. The average grain sizes of Ti samples sintered from Ti and $TiH_2$ powder milled for 5 hrs were about 26 nm, 44 nm, respectively. The hardness of Ti sintered from Ti and $TiH_2$ powder milled for 5 h was $504kg/mm^2$ and $567kg/mm^2$, respectively.

• 대한금속재료학회지
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• 제49권9호
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• pp.678-685
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• 2011

The aim of this study was to determine the effect of applied pressure and sintering temperature on the microstructure and mechanical properties for spark plasma sintering (SPS) from commercial pure titanium (CP-Ti) powders. Spark plasma sintering is a relatively new sintering technique in powder metallurgy which is capable of sintering metal and ceramic powers quickly to full density at a fairly low temperature due to its unique features. SPS of -200 mesh or -400 mesh CP-Ti powders was carried out in an $Ar+H_2$ mixed gas flowing atmosphere between $650^{\circ}C$ and $750^{\circ}C$ under 10 to 80 MPa pressure. When SPS was carried out at relatively low temperatures ($650^{\circ}C$ to $750^{\circ}C$), the high (>60 MPa) pressure had a marked effect on densification and grain growth suppression. The full density of titanium was achieved at temperatures and pressures above $700^{\circ}C$ and 60 MPa by spark plasma sintering. The crystalline phase and microstructure of titanium sintered up to $700^{\circ}C$ consisted of ${\alpha}$-Ti and equiaxed grains. Vickers hardness ranging from 293 to 362 Hv and strength ranging from 304 to 410 MPa were achieved for spark plasma sintered titanium.

• 대한금속재료학회지
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• 제50권11호
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• pp.817-822
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• 2012

Nano powders of $Al_2O_3$ and $TiO_2$ compounds made by high energy ball milling were pulsed current activated sintered for studying their sintering behaviors and mechanical properties. The advantage of this process is that it allows very quick densification to near theoretical density and inhibition of grain growth. Nano-structured $Al_2TiO_5$ with small amount of $Al_2O_3$ and$TiO_2$ was formed by sintering at $1300^{\circ}C$ for 5 minute, in which average grain size was about 96 nm. Hardness and fracture toughness of the nano-structured $Al_2TiO_5$ compound with a small amount of $Al_2O_3$ and$TiO_2$ were $602kg/mm^2$ and $2.6MPa{\cdot}m^{1/2}$, respectively.