• Journal of Sensor Science and Technology
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• v.19 no.5
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• pp.385-390
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• 2010

CO sensing thick film gas sensors using $Co_3O_4$ powders prepared by hydrothermal reaction method, were fabricated, and their structural, electrical and CO gas sensing properties were investigated. The specific surface area of the $Co_3O_4$ powders obtained from BET analysis was about 79.0 $m^2/g$. XRD and SEM results show that the thick films heat-treated at $500^{\circ}C$ for 30 min after screen printing had the preferred orientation of (311) direction and the crystalline size was calculated to 221 $\AA$. The maximum activation energy obtained from the temperature-resistance characteristics was 3.11 eV in the temperature range of $290^{\circ}C$ to $310^{\circ}C$. The sensitivity to 1,000 ppm CO was about 150 %. The specific surface area, crystalline size, and maximum activation energy were increased significantly and the sensitivity for CO gas was improved largely.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.10
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• pp.1028-1033
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• 2008

Sequential quick crushing and alkali hydrolysis(SeCAH), as a pretreatment for foodwaste, incorporating mechanical crushing and alkali hydrolysis was proposed and investigated in this study. Focuses were placed on the improvement of biodegradability of foodwaste and the estimation of potential inhibitors for anaerobic digestion. The solubility of the pretreated foodwaste by SeCAH was increased 2.5 times rather than mechanical crushing. Considering solubility improvement and energy consumption, 2,000 rpm of crushing strength and 5$\sim$10 sec of crushing time are recommended. After SeCAH, the fraction of large organic particles(>2.36 mm) of foodwaste was sharply decreased from 88.0% to 29.0%, otherwise the fraction of small particles(<75 $\mu$m) was greatly increased from 10.5% to 40.7%. Ammouinum, potassium and sulfate were estimated as potential inhibitors for anaerobic digestion and their concentrations in pig slurry were 3331.3 mg/L, 4256.5 mg/L and 1017.5 mg/L, respectively.

• Proceedings of the Materials Research Society of Korea Conference
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• 2005.05a
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• pp.202-202
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• 2005

• Korean Journal of Materials Research
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• v.20 no.8
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• pp.434-438
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• 2010

The selenization process has been a promising method for low-cost and large-scale production of high quality CIGS film. However, there is the problem that most Ga in the CIGS film segregates near the Mo back contact. So the solar cell behaves like a $CuInSe_2$ and lacks the increased open-circuit voltage. In this study we investigated the Ga distribution in CIGS films by using the $Ga_2Se_3$ layer. The $Ga_2Se_3$ layer was applied on the Cu-In-Ga metal layer to increase Ga content at the surface of CIGS films and to restrict Ga diffusion to the CIGS/Mo interface with Ga and Se bonding. The layer made by thermal evaporation was showed to an amorphous $Ga_2Se_3$ layer in the result of AES depth profile, XPS and XRD measurement. As the thickness of $Ga_2Se_3$ layer increased, a small-grained CIGS film was developed and phase seperation was showed using SEM and XRD respectively. Ga distributions in CIGS films were investigated by means of AES depth profile. As a result, the [Ga]/[In+Ga] ratio was 0.2 at the surface and 0.5 near the CIGS/Mo interface when the $Ga_2Se_3$ thickness was 220 nm, suggesting that the $Ga_2Se_3$ layer on the top of metal layer is one of the possible methods for Ga redistribution and open circuit voltage increase.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.3
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• pp.107-112
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• 2010

The Cu$(In_{1-x}Ga_x)Se_2$ is the absorber material for thin film solar cell with high absorption coefficient of $1{\times}10^5cm^{-1}$. In the case of CIGS, the movable energy band gap from $CuInSe_2$ (1.00 eV) to $CuGaSe_2$ (1.68 eV) can be acquired while controlling Ga contain ratio. Generally, the co-evaporator method have used for development and fabrication of the CIGS absorption layer. However, this method should need many steps and lengthy deposition time with high temperature. For these reasons, in this paper, a new growth method of CIGS layer was attempted to hydride vapor transport (HVT) method. The CIGS mixed-source material reacted for HCl gas in the source zone was deposited on the substrate after transporting to growth zone. c-plane $Al_2O_3$ and undoped GaN were used as substrates for growth. The characteristics of grown samples were measured from SEM and EDS.

• Macromolecular Research
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• v.12 no.6
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• pp.598-603
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• 2004

Cellulose nitrate (CN) composite membranes, containing cobalt porphyrin (CoP) complexes self-assembled within nanometer-sized rhenium clusters (ReCoP), have been prepared and their oxygen and nitrogen gas perme­abilities were analyzed. The solubility of ReCoP and the characteristics of the corresponding composite membranes were analyzed using a Cahn microbalance, FT-IR spectroscopy, wide-angle X-ray scattering, and differential scanning calorimetry. The nitrogen permeability through the CN composite membranes decreased upon addition of ReCoP and CoP, which implies that the presence of these oxygen carrier complexes affects the structure of the polymer matrix. The oxygen permeability through the composite membranes containing small quantities of ReCoP decreased, but it increased upon increasing the concentration. The oxygen gas transport was affected by the matrix at low ReCoP concentrations, but higher concentrations of ReCoP increased the oxygen permeability as a result of its reversible and specific interactions with oxygen, effectively realizing ReCoP carrier-mediated oxygen transport.

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.411-414
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• 2013

In order to enhance the photovoltaic property of the CdS/CdSe co-sensitized quantum dot sensitized solar cells (QDSSCs), the surface of nanoporous $TiO_2$ photoanode was modified by ultrathin $Al_2O_3$ layer before the deposition of quantum dots (QDs). The $Al_2O_3$ layer, dip-coated by 0.10 M Al precursor solution, exhibited the optimized performance in blocking the back-reaction of the photo-injected electrons from $TiO_2$ conduction band (CB) to polysulfide electrolyte. Transient photocurrent spectra revealed that the electron lifetime (${\tau}_e$) increased significantly by introducing the ultrathin $Al_2O_3$ layer on $TiO_2$ surface, whereas the electron diffusion coefficient ($D_e$) was not varied. As a result, the $V_{oc}$ increased from 0.487 to 0.545 V, without appreciable change in short circuit current ($J_{sc}$), thus inducing the enhancement of photovoltaic conversion efficiency (${\eta}$) from 3.01% to 3.38%.

• Journal of the Korean Institute of Gas
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• v.24 no.6
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• pp.77-82
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• 2020

In this paper, we developed a cooling system for the refrigeration truck using natural carbon dioxide refrigerant which is attracting attention as an environmentally-friendly refrigerant. We developed a high efficient environmentally-friendly refrigerated truck that converted the existing diesel vehicle into an LNG vehicle to improve emissions of truck and improved the efficiency of the cooling system by utilizing a heat of LNG vaporization. The COP of refrigerated truck system was increased 144%.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.10a
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• pp.16-19
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• 2009

Recently, CO2 geologic storage (geologic sequestration) has been concerned as one of methodologies for reducing greenhouse gas. We expect that geophysical approach plays an important role in the site selection, characterization, and monitoring during CO2 injection or post-injection. Especially we believe that monitoring and verification technologies such as surface and borehole geophysical methods are an important part of making CO2 geologic storage an acceptable method.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2007.10a
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• pp.73-74
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• 2007