• 한국전기전자재료학회논문지
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• 제14권11호
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• pp.904-911
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• 2001

High-density lead zirconate titanate(Pb(Zr$\_$0.53/Ti$\_$0.47/)O$_3$, PZT) ceramics were fabricated by a new milling-precipitation(MP) process improved from the conventional solid state process. This process was progressed by a milling impregnation through mixing ZrO$_2$ and TiO$_2$ powders with lead nitrate(Pb(NO$_3$)$_2$) water solution in zirconia ball media, and then milling precipitation was induced from precipitation of PbC$_2$O$_4$ by adding ammonium of oxalate monohydrate((NH$_4$)$_2$C$_2$O$_4$$.$H$_2$O) as a precipitant. As a result of this process, single-phase perovskite structure was formed at the calcination temperature of 750$\^{C}$ for Pb(Zr$\_$0.53/Ti$\_$0.47/)O$_3$ powders. In addition, the highest density at the sintering temperature of 1100$\^{C}$ was obtained, because of the highly sinterable PZT Powders ground through the re-milling process. Piezoelectric and dielectric properties of sintered sample were improved by MP process.

• 한국식품저장유통학회지
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• 제31권1호
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• pp.46-63
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• 2024

This study evaluated the impact of storage temperature on the quality characteristics of texturized vegetable protein (TVP). TVP was prepared by mixing defatted Daewon soybean flour at 80℃, gluten, and corn starch in a 5:3:2 ratio, which was then extruded at a screw speed of 250 rpm and a barrel temperature of 190℃ with moisture addition at 9 rpm. Subsequently, the extruded TVP was vacuum-sealed in polyethylene packaging and stored at -20℃, 0℃, and 4℃ for 9 days. Texture analysis revealed that the curing rate followed 4℃ > 0℃ > -20℃ sequence. No significant color variation was observed across the storage conditions, although water content increased at all temperatures. Notable changes were detected in moisture absorption capacity (%) and solid leaching (%), following the order of -20℃ > 0℃ > 4℃. The turbidity of the solution released during cooking varied, with the highest to the lowest sequence being -20℃ > 4℃ > 0℃, while pH levels remained neutral. Regarding free amino acids, sweetness and textural quality improved with storage across all temperatures, whereas bitterness components diminished at 4℃. The study suggests that refrigerated storage at 4℃ is a viable method for distributing TVP, which was previously distributed only in a frozen and dry state.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.325-325
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• 2007

The perovskites in the $LaAlO_3-BaZrO_3$ system (i.e., $(1-x)LaAlO_3-xBaZrO_3$ were fabricated by a solid state reaction and their dielectric properties were investigated. For the compositions of x=0.1~0.9, the mixture of $LaAlO_3$ with a rhombohedral structure and $BaZrO_3$ with a cubic was observed when the sintering was conducted at $1500^{\circ}C$, indicating that the solubility of constituent elements was very low and a narrow solid solution region might exist. The large difference of ionic radii between $La^{3+}$ ion (0.136nm, C.N.=12) and $Ba^{2+}$ ion (0.161nm) or $Al^{3+}$ ion (0.0535nm, C.N.=6) and $Zr^{4+}$ ion (0.072nm) might hinder the mutual substitution. Within the compositions of x=0~0.7, the dielectric constant of the mixture increased with the amount of $BaZrO_3$, i.e., x value, which was in good agreement with the logarithmic mixing rule (In $_{r,i}={\Sigma}v_iln\;_{r,i}$). The increase in $BaZrO_3$ doping decreased $Q{\times}f$ value significantly due to the low $Q{\times}f$ value of $BaZrO_3$ itself, a poor microstructure of the mixture with an increased grain boundary area per volume, and defects in the cation and oxygen sub-lattices which were respectively caused by the evaporation of barium during the sintering process and the substitution of Ba on La-site or Al on Zr-site.

• 한국재료학회지
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• 제16권11호
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• pp.705-709
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• 2006

Nb was doped to Pb-free $(Bi_{0.5}Na_{0.5})TiO_3$ (BNT) by a solid state mixing process to form $(Bi_{0.5}Na_{0.5})Ti_{1-x}Nb_xO_3\;(x=0{\sim}0.05)$ (BNTNb) and its doping effects on ferroelectric and piezoelctric properties of BNT were investigated. The BNTNb solid solutions were formed up to x=0.01 with no apparent second phases while grain sizes decreased. As x increased, coercive field ($E_c$) and mechanical quality factor ($Q_m$) decreased but piezoelectric constant ($d_{33}$) increased, which indicates Nb acts as a donor for BNT.

• 대한화학회지
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• 제37권7호
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• pp.635-641
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• 1993

고체 전해질의 특성을 조사하기 위해 전기화학전지, $Pt|ar(PO_2=5.3{\times}10^{-3}atm)|Zr_{0.85}Ca_{0.15}O_{1.85}|air(PO_2=0.21atm)|Pt$을 제작하고 600~1000${\circ}$C의 온도구간에서 기전력의 온도 의존성을 측정하였다. 고체 전해질은 산소 음이온에 의한 순수한 이온성 전기전도도를 나타낸다. Fe-FexO, Co-CoO, Ni-NiO, 및 $Cu_2_O-CuO$전극들은 금속과 금속산화물을 1:1 몰비로 혼합한 후 800${\circ}$C에서 6h 동안 열처리하여 제조하였다. 전기 화학전지 Pt|M(s), $MO(s)|Zr_P{0.85}Ca_{0.15}O_{1.85}|air(PO_2=0.21atm)|Pt$을 제작하고 같은 온도 구간에서 기전력의 온도 의존성을 측정하였다 .그 전지들의 기전력과 기전력의 온도 의존성을 사용하여 금속산화물의 생성에 대한 열역학적 상태함수 변화들을 계산한다. 그 함수 변화들로 이들 산화물계의 물성을 논의하였다.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1996년도 춘계학술대회
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• pp.273-273
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• 1996

Recently a novel in vivo approach in dogs, using a regional segmental intestinal perfusion technique, has been developed. The perfusion tube consists of a highly sophisticated multichannel tube with two inflatable occluding balloons, which are placed in 10cm apart. The tube was introduced orally from the stomach through the upper jejunum under the guidance of solid-state pH meter. In the present study, four healthy dogs were infused in the proximal jejunum on two periods. The two perfusion experiments used the same flow rate, 2 $m\ell$/min, and the same perfusion solution to determine the intrasubject variability. The mean (${\pm}$ S. E.) fractions of ranitidine absorbed calculated from the perfusion data were 21.32${\pm}$2.01% (n=3) (1st period), 27.88 ${\pm}$ 17.54% (n=4) (2nd period), respectively. The effective permeabilities (Peffs${\times}$10$\^$4/) of ranitidine were 1.51${\pm}$0.47cm/sec (n=3) (1st period), 1.50 ${\pm}$ 0.31 cm/sec (n=4) (2nd period), respectively. The pH and osmolarity of perfusion solution were 7.50 ${\pm}$ 0.03 and 300 ${\pm}$ 0.06 mOsm/L, There was no significant intrasubject variation. Mixing equilibrium (steady-state) was reached at about 50 min. l-Phenylalanine was absorbed almost completely. Intrinsic intestinal wall permeability of ranitidine showed low permeable characteristics, suggesting permeability-limited absorption. The absorption of 1-phenylalanine, an actively transported nutrient, was not inhibited by ranitidine. The low intestinal membrane permeability is one of the important factors responsible for the variable oral absorption of ranitidine. Supported by FDA Grant FD01462-04 and KOSEF Grant.

• 한국세라믹학회지
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• 제39권3호
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• pp.272-277
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• 2002

전구체로 ($NH_4)[Al(ethylenediaminetetraacetate)]{\cdot}2H_2O$ 착물을 이용한 수정된 열탄소환원질화법으로 질화알루미늄(AlN) 분말과 휘스커를 합성하였다. 이 분말은 질소분위기에서 별도의 환원용 탄소를 혼합하지 않고 1200$^{\circ}$C에서 1500$^{\circ}$C까지의 온도에서 하소시킨 다름 잔류탄소를 태워 버림으로써 얻어졌다. 이 질화과정을 Al-27 마법각 스핀 핵자기공명, 적외선 분광법 및 X-선 회절법으로 연구했다. 전구체 착물은 열분해되어 ${\rho}$-알루미나와 ${\gamma}$-알루미나로 되었다가 ${\gamma}-{\alpha}$알루미나 전이없이 AlN으로 바뀌었다. ${\gamma}$-알루미나가 AlN으로 바뀌면서 분말의 형상이 유지되는 것으로 보아 이 변환과정에서의 중간체는 알루미늄이나 aluminum suboxides와 같은 기체상이 아니고, 고체상의 $AlO_xN_y$임을 알 수 있다. (0001) 사파이어를 이용하면 AlN 휘스커를 합성할 수 있다.

• 한국진공학회지
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• 제2권4호
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• pp.439-454
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• 1993

The phase sequence of codeposited Co-Si alloy and Co/si multilayer thin film was investigated by differential scanning calormetry(DSC) and X-ray diffraction (XRD) analysis, The phase sequence in codeposition and codeposited amorphous Co-Si alloy thin film were CoSilongrightarrow Co2Si and those in Co/Si multilayer thin film were CoSilongrightarrowCo2Silongrightarrow and CoSilongrightarrowCo2Si longrightarrowCoSilongrightarrowCoSi2 with the atomic concentration ration of Co to Si layer being 2:1 and 1:2 respectively. The observed phase sequence was analyzed by the effectvie heat of formatin . The phase determining factor (PDF) considering structural facotr in addition to the effectvie heat of formation was used to explain the difference in the first crystalline phase between codeposition, codeposited amorphous Co-Si alloy thin film and Co/Si multilayer thin film. The crystallinity of Co-silicide deposited by multitarget bias cosputter deposition (MBCD) wasinvestigated as a funcion of deposition temperature and substrate bias voltage by transmission electron microscopy (TEM) and epitaxial CoSi2 layer was grown at $200^{\circ}C$ . Parameters, Ear, $\alpha$(As), were calculate dto quantitatively explain the low temperature epitaxial grpwth of CoSi2 layer. The phase sequence and crystallinity had a stronger dependence on the substrate bias voltage than on the deposition temperature due to the collisional daxcade mixing, in-situ cleannin g, and increase in the number of nucleation sites by ion bombardment of growing surface.

• Korea-Australia Rheology Journal
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• 제11권3호
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• pp.255-263
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• 1999

Blends of two thermotropic liquid crystalline polymers, HX2000 and Vectra A950, were prepared by melt blending. Effects of transesterification on these blends are investigated by comparing properties of the blends with and without the addition of an inhibitor, in terms of blend miscibility and rheology. Both the uninhibited and inhibited blends are found to be largely immiscible with very limited miscibility in HX2000-rich phase. No strong evidence indicates the occurrence of transesterification in the blends in the solid state. Dynamic rheological behaviour, such as shear storage modulus (G') and shear loss modulus (G") as a function of frequency, of the blends are interpreted by a three-zone model. HX2000 shows terminal-zone and plateau-zone behaviour, whilst Vectra A950 shows plateau-zone and transition-zone behaviour. The un- inhibited blends show plateau-zone behaviour up to 50% Vectra A950 content and the inhibited blends show plateau-zone behaviour up to 60% Vectra A950 content. Compositional dependence of the complex viscosities of the uninhibited and inhibited blends displayed positive deviations from additivity, which is a characteristic feature for the immiscible thermoplastic blends. When under steady shear, both the uninhibited and inhibited blends show shear thinning behaviour and their viscosities decrease monotonically with the addition of Vectra A950. Compositional dependence of the steady shear viscosities of the two sets of blends displayed negative deviations from additivity and the uninhibited blends were more viscous than the inhibited blends for the full composition range. Although limited agreement with the Cox-Merz rule is found for the inhibited blends, these two sets of blends, in general, do not follow the rule due to their liquid crystalline order and two-phase morphology. Despite being immiscible blends, transesterification, such as polymerization, in the blends might occur during the rheological characterization, supported by the facts that uninhibited blends show HX2000-dominant behaviour at lower Vectra A950 content and are more viscous than the inhibited blends. The addition of transesterification inhibitor in such blends is advised if only physical mixing is desired.ired.

• 한국세라믹학회지
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• 제49권6호
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• pp.586-591
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• 2012

$Zr_2WP_2O_{12}$ powder, which has a negative thermal expansion coefficient, was synthesized by a solid-state reaction with $ZrO_2$, $WO_3$ and $NH_4H_2PO_4$ as the starting materials. The synthesis behavior was dependent on the solvent media used in the wet mixing process. The $Zr_2WP_2O_{12}$ powder prepared with a solvent consisting of D. I. water was fully crystallized at $1200^{\circ}C$, showing a sub-micron particle size. According to the results obtained from a thermal analysis, a $ZrP_2O_7$ was synthesized at a low temperature of $310^{\circ}C$, after which it was reacted with $WO_3$ at $1200^{\circ}C$. A new sintering additive, $Al(OH)_3$, was applied for the densification of the $Zr_2WP_2O_{12}$ powders. The cold isostatically pressed samples were densified with 1 wt% $Al(OH)_3$ additive or more at $1200^{\circ}C$ for 4 h. The main densification mechanism was liquid-phase sintering due to the liquid which resulted from the reaction with amorphous or unstable $Al_2O_3$ and $WO_3$. The densified $Zr_2WP_2O_{12}$ ceramics showed a relative density of 90% and a negative thermal expansion coefficient of $-3.4{\times}10^{-6}/^{\circ}C$. When using ${\alpha}-Al_2O_3$ as the sintering agent, densification was not observed at $1200^{\circ}C$.