• Journal of the Korean Ceramic Society
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• v.23 no.6
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• pp.45-51
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• 1986

$SrTiO_3$ reaction mechanism formed from $TiCl_4$ and $SrCl_2$ solution by direct-wet-process was studied. Through this study it is identified that crystalline $SrTiO_3$ is formed above pH 13.8 amorphous $SrTiO_3$ above pH7 and crystallization temperature of amorphous $SrTiO_3$ is at 37$0^{\circ}C$. the final products are composed of 60% crystalline $SrTiO_3$ and 40% amorphous $SrTiO_3$ The amorphous $SrTiO_3$ is identified with the IR absorption spectrum of Sr-Ti-O by FT-IR spectrometer. Under pH 7 gelationus metatitanate (H2TiO3) is formed from TiCl4 but above pH7 the activity by the formation of metatitnic acid ion $[TiO_3]^{2-}$ is so high that $SrTiO_3$is formed more easily through the reaction with $Sr^{2+}$.

• Journal of the Korean Ceramic Society
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• v.38 no.12
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• pp.1150-1154
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• 2001

Silicon oxynitride (SiON) thick films using the core layer of silica optical waveguide have been deposited on Si wafer by PECVD at low temperature (32$0^{\circ}C$) were obtained by decomposition of appropriate mixture of (SiH$_4$+$N_2$O+$N_2$) gaseous mixtures under RF power and SiH$_4$/($N_2$O+$N_2$) ratio deposition condition. Prism coupler measurements show that the refractive indices of SiON layers range from 1.4663 to 1.5496. A high SiH$_4$/($N_2$O+$N_2$) of 0.33 and deposition power of 150 W leads to deposition rates of up to 8.67 ${\mu}{\textrm}{m}$/h. With decreasing SiH$_4$/($N_2$O+$N_2$) ratio, the SiON layer become smooth from 41$\AA$ to 6$\AA$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.5
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• pp.211-216
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• 2018

The recovery of rare earth elements (REE) including La, Nd and Ce from spent batteries is important issues to reuse scarce resources. Herein, we present a simple recovery process to obtain lanthanum oxide ($La_2O_3$) from spent Ni-MH batteries, and demonstrate the conversion mechanism from $NaLa(SO_4)_2{\cdot}H_2O$ to $La_2O_3$. This strategy requires the initial preparation of $NaLa(SO_4)_2{\cdot}H_2O$ and subsequent metathesis reaction with $Na_2CO_3$ at $70^{\circ}C$. This metathesis reaction resulted in the crystalline lanthanum carbonate hydrate ($La_2(CO_3)_3{\cdot}xH_2O$) powder with plate-like morphology. On the basis of TGA result, the $La_2(CO_3)_3{\cdot}xH_2O$ powder was calcined in air at three different temperatures, that is, $300^{\circ}C$, $500^{\circ}C$, and $1000^{\circ}C$. As the calcination temperature increased, the morphology of powder was changed; prism-like ($NaLa(SO_4)_2{\cdot}H_2O$) ${\rightarrow}$ platelike ($La_2(CO_3)_3{\cdot}xH_2O$) ${\rightarrow}$ aggregated irregular shape ($La_2O_3$). Futhermore, XRD results indicated that the crystalline $La_2O_3$ could be synthesized after the metathesis reaction with $Na_2CO_3$, followed by heat-treatment at $1000^{\circ}C$, along with a change of crystallographic structures; $NaLa(SO_4)_2{\cdot}H_2O$ ${\rightarrow}$ $La_2(CO_3)_3{\cdot}xH_2O$ ${\rightarrow}$ $La_2O_3$.

• Journal of the Korean Ceramic Society
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• v.51 no.3
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• pp.197-200
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• 2014

We investigated the influence of blistering on $Al_2O_3$/SiON stacks and $Al_2O_3$/SiNx:H stacks passivation layers. $Al_2O_3$ film provides outstanding Si surface passivation quality. $Al_2O_3$ film as the rear passivation layer of a p-type Si solar cell is usually stacked with a capping layer, such as $SiO_2$, SiNx, and SiON films. These capping layers protect the thin $Al_2O_3$ layer from an Al electrode during the annealing process. We compared $Al_2O_3$/SiON stacks and $Al_2O_3$/SiNx:H stacks through surface morphology and minority carrier lifetime after annealing processes at $450^{\circ}C$ and $850^{\circ}C$. As a result, the $Al_2O_3$/SiON stacks were observed to produce less blister phenomenon than $Al_2O_3$/SiNx:H stacks. This can be explained by the differences in the H species content. In the process of depositing SiNx film, the rich H species in $NH_3$ source are diffused to the $Al_2O_3$ film. On the other hand, less hydrogen diffusion occurs in SiON film as it contains less H species than SiNx film. This blister phenomenon leads to an increase insurface defect density. Consequently, the $Al_2O_3$/SiON stacks had a higher minority carrier lifetime than the $Al_2O_3$/SiNx:H stacks.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.49.1-49.1
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• 2021

We carried out simultaneous monitoring observations of five maser lines, H₂O (22 GHz), SiO 𝝊 =1, 2, J =1-0 (43.1, 42.8 GHz), and SiO 𝝊 =1, J=2-1, J =3-2 (86.2, 129.3 GHz), toward the Mira variable star WX Serpentis with the 21-m antennas of the Korean VLBI Network (KVN) in 2009-2021 (~12 years). Most spectra of the H₂O maser are well separated into two parts of two blue- and one redshifted features within ± 10 km s-1 of the stellar velocity. All detected SiO masers are generally concentrated within ± 5 km s-1 of the stellar velocity, and sometimes appear split into two components. Overall, the profiles of SiO and H₂O masers detected in WX Serpentis illustrate typical characteristics of the Mira variable. In addition, flux variations of both SiO and H₂O masers are well correlated with the optical light curve of the central star, showing a phase lag of ~ 0.1 for SiO masers and ~ 0.2 for H₂O maser. This phenomenon is considered to be the direct effect of propagating shock waves generated by the stellar pulsation, because SiO and H₂O masers are sequentially distributed at different positions with respect to the central star. In addition, we analyzed long-term trends and characteristics of maser velocities, maser ratio, and the velocity extents (the full width at zero power; FWZP). We also investigated a spectral energy distribution (SED) ranging from 1.2 to 240 ㎛ obtained using several infrared data: 2MASS, WISE, IRAS, ISO, COBE DIBRE, RAFGL, and AKARI (IRC and FIS). From the IRAS LRS and ISO SWS spectra of this star, we identified 9.7 and 12 ㎛ silicate emission features consistent with the SE6 spectrum model, corresponding to the typical AGB phase.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.447-447
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• 2012

최근 생물전자공학에서 의료 산업 환경 등 많은 분야에 응용 가능한 바이오센서의 연구가 활발해지고 있다. 그 중 의료 분야에서, 수소이온 ($H^+$)의 농도 감지는 인간의 질병을 예측하는데 중요한 지표가 되며 이러한 수소이온 ($H^+$) 농도의 변화를 실시간으로 감지하기 위해 반도체를 기반으로 한 다양한 pH 센서가 제안되었다. Ion sensitive field effect transistor (ISFET), electrolyte-insulator-semiconductor (EIS)는 대표적인 반도체 pH센서로, 작은 소자 크기, 견고한 구조, 빠른 응답속도와 CMOS 공정과의 호환성이 좋다는 장점이 있다. 특히, EIS는 제조공정이 간단하고 감지막의 감지 특성 평가가 용이하기 때문에 지속적으로 연구되고 있는 pH 센서이다. 센서의 감지 특성을 평가함에 있어 감지막의 감지감도와 안정성이 우수해야 하며 이를 위해 high-k 물질이 감지막으로 사용되고 있다. 추가적으로 high-k 물질은 기존의 $SiO_2$와 $Si_3N_4$를 대신하여 높은 유전상수로 인한 고성능, 고감도 센서제작을 가능케 한다. 본 연구에서는, high-k 물질인 $HfO_2$, $Ta_2O_5$, $ZrO_2$, $Al_2O_3$를 각각 $SiO_2$ 완충막에 적층한 이단 감지막을 제작하였고, 그 특성을 기존의 $SiO_2$, $Si_3N_4$ 감지막의 감지특성과 비교하였다. pH 감지 특성을 평가해 본 결과, 기존의 $SiO_2$, $Si_3N_4$ 감지막과 비교했을 때 high-k 물질의 감지막을 갖는 EIS pH 센서에서 감지감도와 안정성 모두 우수하게 나타났다. 특히, high-k 물질 중 $HfO_2$에서 감지감도가 다소 크게 평가되었으나, 화학적 용액에 대한 안정성은 떨어졌다. 반면에 $Al_2O_3$과 $Ta_2O_5$은 화학용액에 대한 안정성 측면에서 최적의 특성을 보임을 확인하였다. 결론적으로, high-k 물질에 대한 전반적인 평가를 통하여 높은 pH 감지감도뿐만 아니라 우수한 안정성의 EIS pH 센서를 제작 할 수 있었다.

• Journal of Surface Science and Engineering
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• v.45 no.5
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• pp.206-211
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• 2012

Process analysis was carried out during deposition of MgO by inductively coupled plasma assisted reactive magnetron sputtering in Ar and $O_2$ ambient. At the initiation of Mg sputtering with bipolar pulsed dc power in Ar ambient, total pressure showed sharp increase and then slow fall. To analyse partial pressure change, QMS was used in downstream region, where the total pressure was maintained as low as $10^{-5}$ Torr during plasma processing, good for ion source and quadrupole operation. At base pressure, the major impurity was $H_2O$ and the second major impurity was $CO/N_2$ about 10%. During sputtering of Mg in Ar, $H_2$ soared up to 10.7% of Ar and remained as the major impurity during all the later process time. When $O_2$ was mixed with Ar, the partial pressure of Ar decreased in proportion to $O_2$ flow rate and that of $H_2$ dropped down to 2%. It was understood as Mg target surface was oxidized to stop $H_2$ emission by Ar ion sputtering. With ICP turned on, the major impurity $H_2$ was converted into $H_2O$ consuming $O_2$ and C was also oxidized to evolve CO and $CO_2$.

• Resources Recycling
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• v.15 no.4 s.72
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• pp.27-35
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• 2006

In order to use alunite as an activator of blast furnace slag, we studied the hydration characteristics of the calcined alunite and the ground blast furnace slag. The alunite calcined at $650{\cire}C$ consists of KAl($KAl(SO_{4})_{2}$ and $Al_{2}O_{3}$. The calcined alunite reacts with $Ca(OH)_{2}$ and gypsum to form etrringite ($3CaO{\cdot}Al_{2}O_{3}{\cdot}3CaSO_{4}{\cdot}32H_{2}O$) as fellows:$2KAl(SO_{4})_{2}+2Al_{2}O_{3}+13Ca(OH)_{2}+5CaSO_{4}{\cdot}2H_{2}O+73H_{2}O{\rightarrow}3(3CaO{\cdot}Al_{2}O_{3}{\cdot}3CaSO_{4}{\cdot}32H_{2}O)+2KOH$. The $SO_{4}^{2-}$ ions from calcined alunite reacts with CaO in blast furnace slag to from gypsum, which reacts with CaO and $Al_{2}O_{3}$ to from ettringite in calcined alunite-blast furnace slag system. Therefore blast furnace slag can be activated by calcined alunite.

• Food Science of Animal Resources
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• v.32 no.1
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• pp.62-67
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• 2012

This study calculated kinetic parameters of Escherichia coli O157:H7 and developed a probabilistic model to estimate growth probabilities of E. coli O157:H7 on polyethylene cutting boards as a function of temperature and time. The surfaces of polyethylene coupons ($3{\times}5$ cm) were inoculated with E. coli O157:H7 NCCP11142 at 4 Log $CFU/cm^2$. The coupons were stored at 13 to $35^{\circ}C$ for 12 h, and cell counts of E. coli O157:H7 were enumerated on McConkey II with sorbitol agar every 2 h. Kinetic parameters (maximum specific growth rate, Log $CFU/cm^2/h$; lag phase duration, h; lower asymptote, Log $CFU/cm^2$; upper asymptote, Log $CFU/cm^2$) were calculated with the modified Gompertz model. Of 56 combinations (temperature${\times}$time), the combinations that had ${\geq}$0.5 Log $CFU/cm^2$ of bacterial growth were designated with the value of 1, and the combinations that had increases of <0.5 Log $CFU/cm^2$ were given the value 0. These growth response data were fitted to the logistic regression to develop the model predicting probabilities of E. coli O157:H7 growth. Specific growth rate and growth data showed that E. coli O157:H7 cells were grown at $28-35^{\circ}C$, but there were no obvious growth of the pathogen below $25^{\circ}C$. Moreover, the developed probabilistic model showed acceptable performance to calculate growth probability of E. coli O157:H7. Therefore, the results should be useful in determining upper limits of working temperature and time, inhibiting E. coli O157:H7 growth on polyethylene cutting board.

• Journal of the Korean Ceramic Society
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• v.23 no.3
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• pp.27-34
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• 1986

The hydration of flyash-$Ca(OH)_2-CaSO_4$.$2H_2O$ system was stuedied with varing mixing ratio of flyahs $Ca(OH)_2$ and caSO4.2H2O The samples were steam-cured for 1-7 days at 9$0^{\circ}C$. The optimum mixing composition was flyash : Ca (OH)2=65:35 with 15% $CaSO_4$.42H_2O$ added which produced the hardened material having the best compressive strength (300kg/$cm^2$) Also the low specific gravity(1, 2) of the hardened paste suggests the possibility that it can be used as a light-weight building material. The added $CaSO_4$.42H_2O$ constituted calcium-sulfo-aluminate hydrates which activates the formation of C-S-H hy-drates. Both hydrates developed the strength of hardened paste. The amount of calcium-sulfo-aluminate hydrates was increased when the $CaSO_4$.42H_2O$ was added over 15% however the increased amount did not help the development of strength because of the individually grown calcium-sulfo-aluminate hydrates.