• 한국결정성장학회지
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• 제31권4호
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• pp.154-158
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• 2021

550 nm 파장대에서 O₂/Ar+O₂ 혼합기체 농도비가 0에서 7.9 %로 변화 시 Mn 도핑된 SnO₂ 투명전도막의 투과율은 80.9에서 85.4 %로 밴드갭 에너지는 3.0에서 3.6 eV로 증가하였다. 비저항은 O₂/Ar+O₂ 혼합기체 농도비가 0에서 2.7 %까지 증가 시 3.21 Ω·cm에서 0.03 Ω·cm으로 감소하다 이후 7.9 %로 증가 시에는, 52.0 Ω·cm으로 급격하게 상승하였다. XPS 분석결과 혼합기체 O₂/Ar+O₂에서 O₂ 농도의 증가로 Sn_3d5/2의 결합에너지가 486.40에서 486.58 eV로, O_1s의 결합에너지도 530.20에서 530.34 eV로 조금 변화하였다. 따라서 스파터링 방법으로 제조한 Mn 도핑된 SnO₂ 투명전도막에서 O₂ 농도변화에 따라 SnO와 SnO₂ 2개의 상이 공존하는 것을 확인하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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• pp.54-59
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• 2007

In a view of capturing $CO_2$ as a greenhouse gas, an experimental study was conducted on the combustion characteristics of pulverized coal in $O_2$/$CO_2$ environment using TGA/DSC and DTF facilities. The effects of gas composition and concentration on the processes of devolatilization and char burning experienced by coal particles in combustion furnace and on the concentration of products such as $CO_2$, CO and $NO_x$ were observed using TGA/DSC and DTF respectively. As results, it were found that the rate of devolitilation is nearly independent on the $O_2$ concentration if it is over 20% but the char burning rate is a sensitive function of $O_2$ percent, and the two rates can be controlled by $O_2$ concentration in order to be similar with those of air combustion case. It was also found that high concentration $CO_2$ can be captured by oxy-coal combustion and high concentration of CO and low value of $NO_x$ are exhausted in that case. Additionally, NO reducing reaction by CO with char as catalyst was observed and a meaningful results were obtained.

• 한국세라믹학회지
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• 제28권10호
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• pp.831-837
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• 1991

Spherical TiO2 particles are prepared from TiCl4 aqueous solution by the spray pyrolysis method using ultrasonic atomization technique. The formation mechanism of TiO2 particles from atomized droplets it studied by varying the concentration of the source solution, reaction temperature, and the solvent. spherical TiO2 powders with almost the same normalized particle size distribution can be made reproducibly by changing the concentration of the source solution, and their mean sizes are in the range of 0.2~1.4${\mu}{\textrm}{m}$.

• 센서학회지
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• 제31권2호
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• pp.125-130
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• 2022

We describe the importance of zinc oxide nanoparticle (ZnO NP) concentration in the enhancement of electrical properties in a lead sulfide quantum dot (PbS QD)-based shortwave infrared (SWIR) photodetector. ZnO NPs were synthesized using the sol-gel method. The concentration of the ZnO NPs was controlled as 20, 30 and 40 mg/mL in this study. Note that the ZnO NPs layer is commonly used as an electron transport layer in PbS QDs SWIR photodetectors. The photo-to-dark ratio, which is an important parameter of a photodetector, was intensively examined to evaluate the electrical performance. The 20 mg/mL condition of ZnO NPs exhibited the highest photo-to-dark ratio value of 5 at -1 V, compared with 1.8 and 0.4 for 30 mg/mL and 40 mg/mL, respectively. This resulted because the electron mobility decreased when the concentration of ZnO NPs was higher than the optimized value. Based on our results, the concentration of ZnO NPs was observed to play an important role in the electrical performance of the PbS QDs SWIR photodetector.

• 한국세라믹학회지
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• 제48권1호
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• pp.99-105
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• 2011

Lead titanate ($PbTiO_3$) powder was prepared from lead nitrate ($Pb(NO_3)_2$) and titania ($TiO_2$) by hydrothermal route. Phase formation process was investigated by observing the phases formed in various experimental conditions like different KOH concentration, reaction temperature and time. $PbTiO_3$ powder was fabricated when the KOH concentration was 0.8M or higher. An intermediate compound, $PbTi_{0.8}O_{2.6}$, was formed at first by a reaction between PbO and $TiO_2$ and changed into $PbTiO_3$ powder with a perovskite crystal structure. A $PbTiO_3$ phase was formed in a shorter time when a KOH concentration was increased from 0.8M to 8M because a driving force for a $PbTiO_3$ formation was increased due to an increase in a degree of supersaturation. And $TiO_2$ (rutile) and $3PbO{\cdot}H_2O$ were observed at room temperature in a 0.8M KOH solution and $TiO_2$(rutile) and PbO (litharge) in a 8M KOH. A $PbTiO_3$phase was also formed in a shorter time at a higher reaction temperature as a reaction temperature influenced the rates for a dissolution and a precipitation.

• 한국결정성장학회지
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• 제14권3호
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• pp.123-128
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• 2004

융제(flux)로서 $B_2O_3$의 농도를 0-10 wt%까지 변화시킨 $SrAl_2O_4$ : $Eu^{+2}$, $Dy^{+3}$계 장잔광 형광체를 고상반응법으로 합성한 후, $B_2O_3$의 첨가량에 따른 결정특성과 장잔광 축광재료로서 가장 중요한 발광 및 장잔광 특성을 조사하였다. $SrAl_2O_4$ : Eu$^{+2}$, $Dy^{+3}$계 형광체는 $B_2O_3$의 농도에 관계없이 520nm 파장을 최대 발광파장으로 하는 발광스펙트럼을 나타내었고, 3wt%의 $B_2O_3$ 농도에서 최대 발광강도를 나타내었다. 그리고 $SrAl_2O_4$ : Eu$^{+2}$, $Dy^{+3}$ 형광체의 잔광강도 역시 $B_2O_3$의 농도에 무관하게 시간에 따라 모든 시료에서 지수 함수적으로 감소하였으나, $B_2O_3$의 농도가 3wt%인 경우에 발광의 감쇠속도가 작은 뛰어난 장잔광특성을 나타내었다.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 14TH KACG TECHNICAL MEETING AND THE 5TH KOREA-JAPAN EMGS (ELECTRONIC MATERIALS GROWTH SYMPOSIUM)
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• pp.65-70
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• 1998

The Spray-ICP technique uses the ICP(Inductively Coupled Plasma) of ultra-high temperature which is produced by r.f power. The ICP is well-kwown as a clean heat source for the preparation of pure ceramic particles because the ICP is a electrodeless-thermal plasma without contamination. In this study,{{{{ { SnO}_{2 } }}}} particles were sythesized from metal salt solution by Spray-ICP technique. The effects of concentration of solution, collecting location of powders were investicated. The prepared {{{{ { SnO}_{2 } }}}} particles from each concentration of solution had same crystalline phase(tetragonal {{{{ { SnO}_{2 } }}}}) a nd the mean size decreased in proportion to the increase of solution concentration. Each {{{{ { SnO}_{2 } }}}} p owders collector in reactor and electrostatic collector had same crystalline phase and morphologies. The mean size of {{{{ { SnO}_{2 } }}}} p articles prepared by Spray-ICP technique was below 30nm.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.424-425
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• 2006

The effects of reaction temperature and precursor concentration on the microstructure and magnetic properties of ${\gamma}-Fe_2O_3$ nanoparticles synthesized as final products of iron acetylacetonate in chemical vapor condensation (CVC) were investigated. Pure ${\gamma}-Fe_2O_3$ phase was obtained at temperature above $900^{\circ}C$ and crystallite size of ${\gamma}-Fe_2O_3$ nanoparticles decreased with lowering precursor concentration. Also, the coercivity decreases with decreasing crystallite size of nanopowder. The lowest coercivity was 7.8 Oe, which was obtained from the ${\gamma}-Fe_2O_3$ nanopowder sample synthesized at precursor concentration of 0.3M. Then, the crystallite size of ${\gamma}-Fe_2O_3$ nanoparticles was 8.8 nm.

• Journal of Electrochemical Science and Technology
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• 제8권3호
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• pp.197-205
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• 2017

Lead dioxide thin films were electrodeposited on nickel substrate from acidic lead nitrate solution. Current efficiency and thickness measurements, cyclic voltammetry, AFM, SEM, and X-ray diffraction experiments were conducted on $PbO_2$ surface to elucidate the effect of lead nitrate concentration, current density, temperature on the morphology, chemical behavior, and crystal structure. Experimental results showed that deposition efficiency was affected by the current density and solution concentration. The film thickness was independent of current density when deposition from high $Pb(NO_3)_2$ concentration, while it decreased for low concentration and high current density deposition. On the other hand, deposition temperature had negative effect on current efficiency more for lower current density deposition. Cyclic voltammetric study revealed that comparatively more ${\beta}-PbO_2$ produced compact deposits when deposition was carried out from high $Pb(NO_3)_2$ concentration. Such compact films gave lower charge discharge current density during cycling. SEM and AFM studies showed that deposition of regular-size sharp-edge grains occurred for all deposition conditions. The grain size for high temperature and low concentration $Pb(NO_3)_2$ deposition was bigger than from low temperature and high concentration deposition conditions. While cycling converted all grains into loosely adhered flappy deposit with numerous pores. X-ray diffraction measurement indicates that high concentration, high temperature, and high current density favored ${\beta}-PbO_2$ deposition while ${\alpha}-PbO_2$ converted to ${\beta}-PbO_2$ together with some unconverted $PbSO_4$ during cycling in $H_2SO_4$.

• Corrosion Science and Technology
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• 제16권5호
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• pp.247-256
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• 2017

The feasibility of using hydrazine for inhibiting pitting corrosion in copper sprinkler tubes was investigated by examining microscopical and structural evolution of corrosion by-products with SEM, EDS, and XRD. Hydrazine removed dissolved oxygen and reduced CuO and $Cu_2O$ as well. The stable phase was changed from CuO to $Cu_2O$ or Cu depending on hydrazine concentration. Hydrazine concentration of 500 ppm could convert all CuO corrosion by-products to $Cu_2O$. In a tightly sealed acryl tube filled with aqueous solution of 500 ppm hydrazine, octahedral $Cu_2O$ particles were formed while plate-like structures with high concentration of Cu, O, N and C were formed near a corrosion pit. The inside structure of a corrosion pit was not altered by hydrazine aqueous solution. Uniform corrosion of copper was almost completely stopped in aqueous solution of 500 ppm hydrazine. Corrosion potential of a copper plate was linearly dependent on log (hydrazine concentration). The concept of stopping pitting corrosion reaction by suppressing oxygen reduction reaction could be verified by applying this method to a reasonable number of real sprinkler systems before full-scale application.