• Advances in nano research
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• 제5권3호
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• pp.193-201
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• 2017

ZnO, ZnO: Cu, Ga, and ZnO: Cu, Ga, Ag thin films were obtained by oxidization of ZnS and ZnS: Cu, Ga films deposited onto glass substrates by electron-beam evaporation from ZnS and ZnS: Cu, Ga targets and from ZnS: Cu, Ga film additionally doped with Ag by the closed space sublimation technique at atmospheric pressure. The film thickness was about $1{\mu}m$. The oxidation was carried out at $600-650^{\circ}C$ in air or in an atmosphere containing water vapor. Structural characteristics were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). Photoluminescence (PL) spectra of the films were measured at 30-300 K using the excitation wavelengths of 337, 405 and 457.9 nm. As-deposited ZnS and ZnS: Cu, Ga films had cubic structure. The oxidation of the doped films in air or in water vapors led to complete ZnO phase transition. XRD and AFM studies showed that the grain sizes of oxidized films at wet annealing were larger than of the films after dry annealing. As-deposited doped and undoped ZnS thin films did not emit PL. Shape and intensity of the PL emission depended on doping and oxidation conditions. Emission intensity of the films annealed in water vapors was higher than of the films annealed in the air. PL of ZnO: Cu, Ga films excited by 337 nm wavelength exhibits UV (380 nm) and green emission (500 nm). PL spectra at 300 and 30 K excited by 457.9 and 405 nm wavelengths consisted of two bands - the green band at 500 nm and the red band at 650 nm. Location and intensities ratio depended on the preparation conditions.

• 한국전기전자재료학회논문지
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• 제18권9호
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• pp.815-820
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• 2005

ZnO varistor ceramics were fabricated with variation of addition of glass-frit amount and the sintering temperature was $1100^{\circ}C$. The average grain sizes were showed increased from $8.6{\mu}m\;to\;10{\mu}m$, and varistor voltages were decreased from 506V to 460V by added amount of glass-frit. Nonlinear coefficient $\alpha$, of all were with increasing the amount of glass-frit more than 70, in case of added on $0.03wt\%$ glass-frit was 83. And leakage current were less than $1{\mu}A$ with applied at $82\%$ of varistor voltage. The clamping voltage ratio of the specimens added $0.03wt\%$ glass-frit was 1.41 at applied 25A $[8/20\;{\mu}s]$. In the specimen added $0.03wt\%$ glass-frit, endurance of surge current and deviation of varistor voltage were $6200A/cm^2,\;\Delta-1.67\%$, respectively and clamping voltage ratio was 2.33. In the Specimen added $0.03wt\%$ glass-frit were superior to any other compositions on High Temperature Load Test(HTLT) for 1000 hr at $85^{\circ}C$, and deviation of the varistor voltage were $\Delta-1.29\%$.

• 대한본초학회지
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• 제30권4호
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• pp.65-69
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• 2015

Objectives : The root ofCyanchum wifordii(CW) had been used as herbal medicine, 'Baeksuo', in Korea. However, the root ofCynanchum auriculatum(CA) had also been mis-used as 'Baeksuo' in herbal markets, due to its morphological similarity with CW. This study aimed to compare discriminative features and establish the identification-keys between two herbal medicines using microscopic methods.Methods : Microscopic preparations including fixation, rapid dehydration, paraffin infiltration, paraffin embedding, sectioning, mounting, and staining, were performed and the microscopic features between CW and CA samples were compared.Results : The starch grain of parenchymal cells, the amounts of calcium oxalate crystals, cell sizes, and the shape of phloem were not different between CW and CA samples. However, the clusters of stone cells which were conglomerated at outer cortex were apparently observed in CA sample (4~8 layers of stone cells), but not in CW sample (2~4 layers of stone cells, or not). Xylem of CW consisted of several vessels and fiber bundles which were formed as linear shapes and discontinuous radial lines, while that of CA, in which radial lines was not observed, were shaped as a wedge and scattered near cambium with comparatively few fiber bundles enclosed vessels. Especially, in the xylem of CA, fiber bundles located towards cambium were relatively more developed than those located outward cambium.Conclusions : The identification-keys established in this study would be helpful to discriminate microscopic features between CW and CA.

• 천문학회지
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• 제24권1호
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• pp.55-70
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• 1991

Infrared emission maps are constructed at 12.5, 25, 60, and $100{\mu}m$ for dark globules B5, B34, B133, B134, B361, L134 and L1523 by using Infrared Astronomical Satellite data base. These clouds are selected on the basis of their appearance in Palomar print as dark obscuring objects with angular sizes in the range of 3 to 30 arcminutes. The short wavelength(12.5 and $25{\mu}m$) maps show the embedded infrared sources. We found many such sources only in B5, B361 and B34 regions, Diffuse component at 12.5 and $25{\mu}m$, possibly arising from the stochastically heated very small dust grains(a < $0.01{\mu}m$) by interstellar radiation field, is found in B361 and L1523 regions. Such emission is characterized by the limb brightening, and it is confirmed in L1523 and in B361. Infrared emissions at the long wavelengths(60 and $100{\mu}m$) are due to colder dusts with temperature less than 20 K. The distribution of color index determined by the ratio 60 to $100{\mu}m$ intensities shows monotonic decrease of dust temperature toward the center. The black body temperature determined from these ratios is found to lie between 16 and 23 K. Such temperature is possible for small(i.e., $a\;{\lesssim}\;0.01{\mu}m$) graphite grains if the grains are mainly heated by interstellar radiation field. Thus IRAS 100 and $60{\mu}m$ emissions are arising mainly from small grains in the colud. The distribution of such dust grains implied from the emissivity distributions at 100 and $60{\mu}m$ resembles that of isothermal sphere. This contrasts to earlier findings of much steeper distribution of dusts contributing visible extinction. These dust grains are mainly larger ones(i.e., $a{\simeq}0.1{\mu}m$). Therefore we conclude that the average grain size increase, toward the cloud center.

• E2M - 전기 전자와 첨단 소재
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• 제9권6호
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• pp.605-615
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• 1996

In this paper, the effect of alkaline oxide addition such as Li$_{2}$O and Na$_{2}$O on the microstructure and humidity sensitivity of V$_{2}$O$_{5}$(2 mol%)-doped TiO$_{2}$(98 mol%) was investigated as a function of amount (0, 1, 2, 5, 10 mol%) of Li$_{2}$O and Na$_{2}$O additives. The pores in the alkaline free sample were distributed mostly in the range between 0.16 and 1.0.mu.m in diameter and its porosity was 23.29%. Li$_{2}$O caused grain overgrowth and reduced the porosity with a narrow distribution of the pore size, leading to poor humidity sensitivity. Na$_{2}$O helped to enlarge the distribution of the pore size through the formation of small soluble phases. The pore sizes of the sample containing Na$_{2}$O 2mol% were distributed mostly in the range between 1.0 and 2.5.mu.m in diameter and its porosity and intrusion volume of mercury were 31.13 % and 0.1155 mL/g respectively, which consequently improved the humidity sensing characteristics such as the sensitivity and temperature-stability. Especially, the addition of 2mol% of Na$_{2}$O improved the humidity-sensing characteristics such as sensitivity and linearity in the whole range between 30 and 90 %RH (Percentage Relative Humidity)y)

• 한국양식학회지
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• 제20권2호
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• pp.127-131
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• 2007

인공종묘 생산된 살조개, Protothaca jedoensis 치패를 대상으로 치패크기에 따른 잠입율, 저질선택성 및 생존율을 조사하였다. 살조개 치패의 저질별 잠입율을 조사한 결과 약 10분 후 살조개 치패는 점차 수관을 내고 호흡하였으며, 몇몇 개체는 패각을 뒤틀며 잠입하는 형태를 나타내었다. 실험 개시후 72시간째 중립실트에서 90.0%, 세립사 76.7%, 중립사 61.7%, 극조립사 85.0%의 잠입율을 나타내었다. 또한 살조개 치패의 생존율은 중립실트에서 90.0%, 세립사 98.3%, 중립사 86.7%, 극조립사 93.3%의 생존율을 나타내었다. 대조구인 저질이 없는 실험구에서 75.0%의 생존율을 보였다. 각장 크기에 따른 잠입능력은 각장이 증가할수록 잠입시간은 길어지며, 잠입율도 증가하였다.

• Bulletin of the Korean Chemical Society
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• 제35권7호
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• pp.1985-1988
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• 2014

$Cu_2ZnSnSe_4$ (CZTSe) thin films were synthesized on transparent conducting oxide glass substrates via a simple, non-toxic, and low-cost process using a precursor solution paste. A three-step heating process (oxidation, sulfurization, and selenization) was employed to synthesize a CZTSe thin film as an absorber layer for use in thin-film solar cells. In particular, we focused on the effects of sulfurization conditions on CZTSe film formation. We found that sulfurization at $400^{\circ}C$ involves the formation of secondary phases such as $CuSe_2$ and $Cu_2SnSe_3$, but they gradually disappeared when the temperature was increased. The formed CZTSe thin films showed homogenous and good crystallinity with grain sizes of approximately 600 nm. A solar cell device was tentatively fabricated and showed a power conversion efficiency of 2.2% on an active area of 0.44 $cm^2$ with an open circuit voltage of 365 mV, a short current density of 20.6 $mA/cm^2$, and a fill factor of 28.7%.

• 한국자기학회지
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• 제3권2호
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• pp.143-148
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• 1993

열 분해법으로 $Bi_{x}Dy_{3-x}Al_{1}Fe_{4}O_{12}$(x=1, 1.2, 1.5) 자기 가넷 박막을 유리기판 위에 제조하였다. Bi 치환량을 증가시켰을 때 $M_{s}$ 값은 5 emu/cc에서 12 emu/cc로 증가하였고, 제조된 모든 박막이 수직 자기 이방성을 나타내었다. Bi 양의 증가에 따라 파장 780 nm의 광원을 사용했을 때 패러디 회전각이 $0.11^{\circ}/\mu\textrm{m}$에서 $0.20^{\circ}/\mu\textrm{m}$로 증가 하였으며 가넷 결정화 온도는 $660^{\circ}C$에서 $630^{\circ}C$로 감소하였다. 또한 보자력은 1200 Oe에서 600 Oe로 감소하였으며 결정립의 크기가 증가하였다. 박막의 두께를 $2000\;{\AA}$에서 $4000\;{\AA}$으로 증가시킴에 따라 $H_{c}$가 1750 Oe에서 1200 Oe로 감소했으며 ${\theta}_F$는 반사광의 간섭 효과에 의해 증가하였다.

• Journal of Magnetics
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• 제20권3호
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• pp.211-214
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• 2015

$Cr_2O_3$ nanoparticles were prepared via one-step reactive laser ablation of Cr in oxygen. The metastable $CrO_2$ phase was obtained through the subsequent oxidation of $Cr_2O_3$ nanoparticles under $O_2$ with gas pressures of up to 40 MPa. The as-prepared $Cr_2O_3$ nanoparticles are spherical or rectangular in shape with sizes ranging from 20 nm to 50 nm. High oxygen pressure annealing is effective in producing meta-stable $CrO_2$ from as-dried $Cr_2O_3$ nanoparticles, and the $Cr_2O_3$ nanoparticles exhibit a weak ferromagnetic behavior with an exchange bias of up to 11 mT that can be ascribed to the interfacial exchange coupling between uncompensated surface spins and the antiferromagnetic core. The $Cr_2O_3/CrO_2$ nanoparticles exhibit an enhanced saturation magnetization and a reduced exchange bias with an increasing faction of $CrO_2$ due to the elimination of uncompensated surface spins over the $Cr_2O_3$ nanoparticles when exposed to a high pressure of $O_2$ and/or possible phase segregation that results in a smaller grain size for both $Cr_2O_3$ and $CrO_2$.

• 한국지하수토양환경학회지:지하수토양환경
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• 제15권6호
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• pp.91-98
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• 2010

The effective thermal conductivity of porous materials is usually determined by porosity, water content, and the conductivity of the matrix. In addition, it is also affected by the internal structure of the materials such as the size, arrangement, and connectivity of the matrix-forming grains. Based on the structural models for multi-phase materials, thermal conductivities of soils and sands measured with varying the water content were analyzed. Thermal conductivities of dry samples were likely to fall in the region between the Maxwell-Eucken model with air as the continuous phase and the matrix as the dispersed phase ($ME_{air}$) and the co-continuous (CC) model. However, water-saturated samples moved down to the region between the $ME_{wat}$ model and the series model. The predictive inconsistency of the structural models for dry and water-saturated samples may be caused by the increase of porosity for water-saturated samples, which leads to decrease of connectivity among the grains of matrix. In cases of variably saturated samples with a uniform grain size, the thermal conductivity showed progressive changes of the structural models from the $ME_{air}$ model to the $ME_{wat}$ model depending on the water content. Especially, an abrupt increase found in 0-20% of the water content, showing transition from the $ME_{air}$ model to the CC model, can be attributed to change of water from the dispersed to continuous phase. On the contrary, the undisturbed soil samples with various sizes of grains showed a gradual increase of conductivity during the transition from the $ME_{air}$ model to the CC model.