• Applied Microscopy
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• 제46권3호
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• pp.160-163
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• 2016

Effect of dealloying condition on the formation of nanoporous structure in melt-spun $Al_{60}Ge_{30}Mn_{10}$ alloy has been investigated in the present study. In as-melt-spun $Al_{60}Ge_{30}Mn_{10}$ alloy spinodal decomposition occurs in the undercooled liquid during cooling, leading to amorphous phase separation. By immersing the as-melt-spun $Al_{60}Ge_{30}Mn_{10}$ alloy in 5 wt% HCl solution, Al-rich amorphous region is leached out, resulting in an interconnected nano-porous $GeO_x$ with an amorphous structure. The dealloying temperature strongly affects the whole dealloying process. At higher dealloying temperature, dissolution kinetics and surface diffusion/agglomeration rate become higher, resulting in the accelerated dealloying kinetics, i.e., larger dealloying depth and coarser pore-ligament structure.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권12호
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• pp.593-598
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• 2001

Transient liquid phase processing was investigated to decrease processing temperatures while maintaining useful piezoelectric properties in the lead zirconate titanate (PZT) system. Niobium oxide$(Nb_2O_5)$ modified crystalline PZT (PZTN) powder was combined with lead silicate $(PS; PbO-SiO_2)$ glass powder and crystalline titania, zirconia, and niobia. Firing above the melting temperature of the lead silicate $(PS; Tm \risingdotseq\; 714^{\circk}C)$ resulted in liquid phase densification of the PZTN followed by dissolution of the titania, zirconia, and niobia into the liquid phase, and crystallization of additional PZTN. The addition of crystalline titania, zirconia, and niobia to react with the lead oxide from the lead silicate phase resulted in an increase in the dielectric and Piezoelectric properties.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.291-292
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• 2006

A steel/cemented carbide couple is selected to generate a tough/hard two layers material. Sintering temperature and composition are deduced from phase equilibria, and experimental studies are used to determine optimal conditions. Liquid migration from the hard layer to the tough one is observed. Microstructure evolution during sintering of the tough material (TEM, SEM, image analysis) evidences coupled mechanisms of pore reduction and WC dissolution. Liquid migration, as well as interface crack formation due to differential densification are limited by suitable temperature and time conditions.

• 한국염색가공학회지
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• 제2권2호
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• pp.1-6
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• 1990

In order to investigate the fine structural changes of poly (ethylene terephthalate) film by hydrazinolysis, PET was treated with hydrazine hydrate in methanol at $30^{\circ}C$ for various times. Initially apparent crystallite size and degree of orientation are increased and then, gradually decreased with hydrazinolysis. According to thermoluminescence measurement, trap site decreased by dissolution and then gradually increased with growth of defect in structure. Maximum peak temperature of tan and dynamic loss modulus E" upon hydrazinolysis shifted to the lower temperature in the progress of hydrazinolysis.ysis.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2001년도 정기총회 및 봄 학술발표회 초록집
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• pp.236-237
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• 2001

In this study, experiments were carried out to measure the variations in the corrosion potential and current density of polarization curves with amorphous $Fe_{70}Cr_5Si_{10}B_{15}$ and $Co_{70}Cr_5Si_{10}B_{15}$ alloy ribbon. The results were particularly examined to identify the influences of corrosion potential including various conditions such as hydrochloric acid, temperature, salt, pH, and oxygen. The optimum conditions were established with variations including temperature, salt, pH, oxygen, corrosion rate, and resistance of corrosion potential. The mass tranfer coefficient(${\alpha}$) value was determined with the Tafel's slope for the anodic dissolution based on the polarization effect with optimum conditions. The second anodic current density peak and maximum passive current density were designated as the critical corrosion sensitivity($I_{r}/I_{f}$).

• Journal of Pharmaceutical Investigation
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• 제27권4호
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• pp.253-263
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• 1997

To investigate the interaction of omeprazole (OMP) and meglumine (MEG), a complex was prepared by freeze-drying method in ammoniacal aqueous medium at room temperature and subjected to IR, DSC, and 1H NMR analysis. In addition, the stability of the complex was tested by accelerated stability analysis, and the dissolution rate of both powder and enteric coated was determined pellet by paddle method. The results are as follows; i) IR, DSC, and $^{1}H$ NMR studies indicate the formation of inclusion complex between OMP and MEG probably by electrostatic forces as $[OMP]\;[MEGH]^+$ form in a stoichiometric ratio (1:1) of OMP : MEG. ii) The dissolution rate of enteric coated OMP-MEG complex pellet in simulated enteric fluid was 90.6% in 10 minutes, which may satisfy the requirement for the regulation of dissolution. iii) OMP-MEG complex were decomposed according to pseudo 1st order kinetics: while the decomposition of OMP showed a rate constant $(k_{25^{\circ}C})$ of $5.13{\times}10^{-4}{\cdot}\;day^{-1}$, a half-life$(t_{1/2})$ of 1,350 days, a shelf-life$(T_{90%})$ 205 days and an activation energy of 23.53 kcal/mole. OMP-MEG complex inhibited a rate $(k_{25})$ of $2.92{\times}10^{-4}{\cdot}\;day^{-1}$, a half-life$(t_{1/2})$ of 2,373 days, a shelf-life $(T_{90%})$ of 306 days and an activation energy of 20.18 kcal/mole. iv) OMP was stabilized markedly by the formation of OMP-MEG complex between OMP and MEG, and the humidity increased the stability of OMP-MEG complex by decreasing the decomposition rate$(k_{50^{\circ}C})$ from $1.27{\times}10^{-2}{\cdot}\;day^{-1}$ at 31% R.H. to $2.54{\times}10^{-2}{\cdot}\;day^{-1}$ at 90% R.H.

• 방사성폐기물학회지
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• 제5권1호
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• pp.85-90
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• 2007

양이온교환수지인 IRN-77을 직접 분해 처리하기 위하여 Fonton시약을 적용하였으며, 분해반응의 특징으로써 반응의 효율 및 안전을 위해 수지를 먼저 건조시키고 $FeSO_4$ 용액을 수지에 완전히 흡수시킨 후 $H_2O_2$를 첨가하는 방법을 적용하였다. 수지 분해반응의 특성은 반응이 개시되기까지 반응유도시간이 필요하였으며, 반응유도시간은 $FeSO_4$의 농도가 낮을수록 또한 $H_2O_2$의 초기 첨가량이 적을수록 길었다. 단위량의 수지를 분해하는데 적절한 반응조건으로서 $FeSO_4$의 농도는 0.9 M 및 15% $H_2O_2$의 용액의 첨가량은 수지량에 대해 6-7배 비율로 나타났으며, 반응유도시간을 포함하여 1.5시간 이내에 완전 분해가 가능하였다. $H_2O_2$의 첨가방법은 반응 초기 및 반응개시 후로 나누어 첨가하므로서 $H_2O_2$의 분해효율 및 첨가량을 최소화하였다. 가열효과로서 분해반응 개시 전에 비교적 낮은 온도인 $50^{\circ}C$ 정도로 가열하면 반응유도시간이 5분 이내로 단축되었으며, 수지의 양을 5g 및 10g 으로 증가시킨 결과, $H_2O_2$의 첨가비율을 9-10배 정도로 증가시키면 완전분해가 가능하였다.

• Restorative Dentistry and Endodontics
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• 제19권1호
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• pp.1-26
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• 1994

The purpose of this study was to investigate the dissolution components during corrosion of amalgams and to identify surface corrosion products in the modified Fusayama artificial saliva. Four type of amalgam alloys were used: low copper lathe cut amalgam alloy (Cavex 68), low copper spherical amalgam alloy (Caulk Spherical Alloy), high copper admixed amalgam alloy (Dispersalloy) and high copper single composition amalgam alloy (Tytin). Each amalgam alloy and Hg were triturated according to the manufacturer's direction by means of mechanical amalgamator (Capmaster, S.S.White), and then the triturated mass was inserted into the cylindrical metal mold which was 10mm in diameter and 2.0mm in height and condensed with compression of 150kg/$cm^2$ using oil pressor. The specimens were removed from the mold and stored at room temperature for 7 days and cleansed with distiled water for 30 minutes in an ultrasonic cleaner. The specimens were immersed in the modified Fusayama artificial saliva for the periods of 1 month, 3 months and 6 months. The amounts of Hg, Cu, Sn and Zn dissolved from each amalgam specimen immersed in the artificial saliva for the periods of 1 month, 3 months and 6 months were measured using Inductivity Coupled Plasma Atomic Emission Spectrometry (ICPQ-1000, Shimadzu, Japan) and amount of Ag dissolved from amalgam specimen was measured using Atomic Absorption Spectrophotometry (Atomic Absorption/Flame emission spectrophotometer M-670, Shimadzu, Japan). A surface corrosion products of specimens were analysed using Electron Spectroscopy Chemical Analyser (ESCA PHI-558, PERKIN ELMER, U.S.A.). The secondary image and back scattered image of corroded surface of specimens was observed under the SEM, and the corroded surface of specimens was analysed with the EDX. The following results were obtained. 1. The dissolution amount of Cu was the most in high copper admixed amalgam(Dispersalloy) and the least in high copper single composition amalgam(Tytin). 2. Sn and Zn were dissolved during all the experiment periods, and dissolution amounts were decreased as the time elapsed. 3. Initial surface corrosion products were ZnO and SnO. 4. Corrosion of ${\gamma}$ and ${\gamma}_2$ phase in low copper amalgams was observed and Ag-Cu eutectic alloy phase was corroded in low copper spherical amalgam(Caulk Sperical Alloy). 5. Corrosion of ${\gamma}$ and $\eta$' phase in high copper amalgams was observed and Ag-Cu eutectic alloy phase was corroded in high copper admixed amalgam(Dispersalloy). 6. Sn-Cl was produced in the subsurface of low copper amalgams and high copper admixed amalgam.

• 자원리싸이클링
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• 제31권3호
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• pp.61-72
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• 2022

주요성분이 Sn(93.0 %)-Ag(3.26 %)-Cu(0.89 %)로 구성되는 SAC 폐무연솔더로부터 주석과 은을 회수하기 위한 전기화학적인 방법을 연구하였다. 폐무연솔더의 건식용해, 주조를 통해 제조한 작업전극을 사용하여 분극거동 조사와 정전류 전해용해를 실시하였다. 분극시험 시 활성화영역의 산화전류피크는 전해액의 황산 농도가 높아질수록 감소하였으며, 1 molL^-1 황산농도가 전해용해를 위해 가장 적절한 것으로 나타났다. 정전류 용해 시 전극표면의 부동태층인 양극슬라임이 두꺼워짐에 따라 전극전위가 지속적으로 높아졌으며, 10 mAcm^-2에서 25시간동안 지속적인 전해용해가 가능한 반면 50 mAcm^-2에서는 2.5 시간 이후부터 전극전위가 급상승하여 전해용해반응이 중단되었다. 정전류 전해용해 시 은은 양극슬라임에 농축되었으며, 전해액내 염소이온의 농도가 0.3 molL^-1인 경우 농축율이 미첨가 조건보다 12.7% 높은 94.3%를 나타내었다. 또한 염소이온의 첨가에 의해 전해액내 주석이온의 안정성을 높이고 주석의 전착전류효율을 향상시킬 수 있었다.

• 열처리공학회지
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• 제28권1호
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• pp.17-23
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• 2015

Hydroxyapatite coatings were fabricated by a room temperature spray method on zirconia substrates and the influence of heat-treatment on their microstructure was also investigated. Phase composition of coated hydroxyapatite films was similar to the starting powder, but the grain size of hydroxyapatite particles was reduced to the size of nano-scale about 100 nm. Grain size, particle compactness, and adhesiveness to zirconia of hydroxyapatite coatings were increased with heat-treatment temperature, but some of cracks by heat-treatment above $1100^{\circ}C$ were initiated between hydroxyapatite coatings and zirconia substrate. Heat-treated hydroxyapatite layers show the dissolution in SBF solution for 5 days. Hydroxyapatite-coated specimen heat-treated at $1100^{\circ}C$ for 1 h has a good biocompatibility, which specimen induced the nanocrystalline hydroxyapatite precipitates on the coating surface by the immersion in SBF solution for 5 days.