• Corrosion Science and Technology
• /
• v.12 no.6
• /
• pp.295-303
• /
• 2013

Silane surface treatments have been developed as an alternative for toxic and carcinogenic chromate-based treatments for years. It is consistently observed that ultra-thin films offer excellent corrosion protection as well as paint adhesion to metals. The silane performance is comparable to, or in some cases better than, that of chromate layers. Based on the tetra-ethylorthosilicate(TEOS) and methlyl trieethoxysilane(MTES), inorganic sol was synthesized and formed hybrid networks with $SiO_2$ nano particle and polypropylene glycol(PPG) on Zn alloyed steel surface. According to SST results, addition of 10nm and 50nm $SiO_2$ nanoparticle in synthesized solution improved anti-corrosion property by its shear stress relaxation effect during curing process. Also, SST results were shown that anti-corrosive property was affected by the amounts of organic compounds.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.03a
• /
• pp.295-304
• /
• 2010

Performance of a landfill liner is evaluated based on leakage rate and mass flux. In this study, the recently utilized double composite liner system, which consists of a geomembrane (GM), a geosynthetic clay liner (GCL), a GM, and a compacted clay layer (61 or 91.5 cm) is compared with other popular composite liners including the single GCL system, the Subtitle D liner system, and the Wisconsin NR500 liner system. The leakage rate through circular and long defects in the GM of the landfill liners is analyzed using numerical models. For the mass flux criterion, the analyses of inorganic contaminant transport through defects in the GM component of liner systems and diffusion of organic compounds through intact landfill liners are conducted using three- and one-dimensional numerical models, respectively. Cadmium and toluene are used in the analyses as a typical inorganic and organic substance, respectively, which will be chemical species encountered during landfill operation. The comparison shows that the double composite liner systems are superior to the other liner systems according to the performance-based evaluation.

• Journal of Korean Society on Water Environment
• /
• v.31 no.5
• /
• pp.533-542
• /
• 2015

In order to investigate the effect of internal loading from sediment on algal blooming at Chusori area in Daechung Reservoir, the amount and contamination level of sediment and the release rate of total phosphorus were analyzed. The sedimentary layer was consisted with two layers, and the average depth of upper and lower ones were 0.35 and 1.44 m, respectively. The fraction of inorganic phosphorus in the sediment was higher than that of organic phosphorus, and the fractions of phosphorus which responsible for internal loading were very high as in the range of 72.7 and 80.2% of inorganic phosphorus. The C/N ratio of sediment taken with core sampler indicated the organic compounds are originated from settled algae from water body. The average release rate of total phosphorus from sediment was $6.74({\pm}0.50)mg/m^2/day$. These results indicated that the internal loading from sediment contributes the excessive algal growth at Churosi area, and the countermeasures to improve the quality of sediments are required to manage algal blooming in Daechung Reservoir.

• Microbiology and Biotechnology Letters
• /
• v.24 no.4
• /
• pp.507-511
• /
• 1996

Medium optimization for xylitol production from xylose by Candida parapsilosis ATCC 22019 mutant was performed. Effect of various nitrogen sources on xylitol production was investigatied. Of inorganic nitrogenous compounds, ammonium sulfate was effective for xylitol production and yeast extract was the most suitable orangic nitrogen nutrient for enhancement of xylitol production. Effect of inorganic salts such as KH$_{2}$PO$_{4}$ and MgSO$_{4}$-7H$_{2}$0 on xylitol production was also studied. Optimal medium was selected as xylose of 50 g/l, yeast extract of 5 g/l, (NH4$_{4}$)$_{2}$SO$_{4}$ of 5 g/l, KH$_{2}$PO$_{4}$ of 5 g/l, MgSO$_{4}$-7H$_{2}$O of 0.2 g/l. In a fermentor by using the optimal medium, a final xylitol concentration of 37 g/l could be obtained from 50 g/l of xylose with a xylitol yield of 74% and a xylitol productivity of 0.58 g/1-hr. At 300 g/l xylose, fermentation was also carried out and then a final xylitol concentration of 242 g/l was obtained at 272 hours. It was corresponding to xylitol yield of 80.7% and xylitol productivity of 0.58 g/1-hr.

• Journal of the Korean Wood Science and Technology
• /
• v.48 no.1
• /
• pp.86-94
• /
• 2020

This study serves as basic research for the development of a new wood-based building finishing material that improved the weakness of inorganic materials such as gypsum board and magnesium board widely used as interior finishing materials and brought out the strength of the wood. The results of evaluating the physical and mechanical properties and the environmental effect related to hazardous substance discharge having manufactured a wood-magnesium laminated composite are as follows. The thermal conductivity and thermal resistance of WML board was improved by about 28~109 percent over magnesium board due to the low thermal conductivity of wood. The adhesive strength of WML board showed a similar result to that of plywood as it exceeds 0.7N/㎟, the adhesive standard of wood veneer which is presented by KS F 3101. Bending strength and screw holding strength were more improved by manufacturing WML board than magnesium board. The WML board manufactured in this study satisfied the criteria for emissions of hazardous substances prescribed in the Indoor Air Quality Control Act, and confirmed the possibility of development as a new wood-based composite material that can replace existing inorganic materials.

• Macromolecular Research
• /
• v.17 no.11
• /
• pp.894-900
• /
• 2009

This study examined the charge carrier photogeneration and hole transport properties of blends of poly (9-vinylcarbazole) (PVK), $\pi$-conjugated polymer, with different weight proportions (0~29.4 wt%) of (PEA)$VOPO_4{\cdot}H_2O$ (PEA: phenethylammonium cation), a novel organic-inorganic hybrid material, using IR, UV-Vis, and energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), steady state photocurrent (SSPC) measurement, and atomic force microscopy (AFM). The SSPC measurements showed that the photocurrent of PVK was reduced by approximately three orders of magnitude by the incorporation of a small amount (~12.5 wt%) of (PEA) $VOPO_4{\cdot}H_2O$, suggesting that hole transport occurred through the PVK carbazole groups, whereas a reverse trend was observed at high proportions (>12.5 wt%) of (PEA)$VOPO_4{\cdot}H_2O$, suggesting that transport occurred via (PEA)$VOPO_4{\cdot}H_2O$ molecules. The transition to a trap-controlled hopping mechanism was explained by the difference in ionization potential and electron affinity of the two compounds as well as the formation of charge percolation threshold pathways.

• Korean Journal of Materials Research
• /
• v.28 no.12
• /
• pp.748-757
• /
• 2018

Inorganic semiconductor compounds, e.g., CIGS and CZTS, are promising materials for thin film solar cells because of their high light absorption coefficient and stability. Research on thin film solar cells using this compound has made remarkable progress in the last two decades. Vacuum-based processes, e.g., co-evaporation and sputtering, are well established to obtain high-efficiency CIGS and/or CZTS thin film solar cells with over 20 % of power conversion. However, because the vacuum-based processes need high cost equipment, they pose technological barriers to producing low-cost and large area photovoltaic cells. Recently, non-vacuum based processes, for example the solution/nanoparticle precursor process, the electrodeposition method, or the polymer-capped precursors process, have been intensively studied to reduce capital expenditure. Lately, over 17 % of energy conversion efficiency has been reported by solution precursors methods in CIGS solar cells. This article reviews the status of non-vacuum techniques that are used to fabricate CIGS and CZTS thin films solar cells.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.24 no.3
• /
• pp.141-148
• /
• 2018

Photo-oxidation is one of the main causes of food deterioration of great variety of foods, such as dairy products, nuts, meat products, and wine. It causes a loss of both nutritional value and sensorial quality of products and may even leads to the formation of toxic compounds. Active packaging for food and beverages has been investigated and developed with embedding light absorbers or blocking materials into the plastics. In recent years, several novel light barrier materials have been proposed as an alternative option for different applications. This article reviews the up-to-date technology in light absorber and blocking material with special emphasis on chemical compound and mechanism. Inorganic, organic, hybrid organic-inorganic, and natural light absorbers were scoped. The challenges and future perspectives of light barrier materials are also discussed.

• Journal of Powder Materials
• /
• v.31 no.4
• /
• pp.293-301
• /
• 2024

All-solid-state lithium batteries (ASSLBs) are receiving attention as a prospective next-generation secondary battery technology that can reduce the risk of commercial lithium-ion batteries by replacing flammable organic liquid electrolytes with non-flammable solid electrolytes. The practical application of ASSLBs requires developing robust solid electrolytes that possess ionic conductivity at room temperature on a par with that of organic liquids. These solid electrolytes must also be thermally and chemically stable, as well as compatible with electrode materials. Inorganic solid electrolytes, including oxide and sulfide-based compounds, are being studied as promising future candidates for ASSLBs due to their higher ionic conductivity and thermal stability than polymer electrolytes. Here, we present the challenges currently facing the development of oxide and sulfide-based solid electrolytes, as well as the research efforts underway aiming to resolve these challenges.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.34 no.2
• /
• pp.166-178
• /
• 2024

Objectives: The 12 occupational exposure limits(OELs) for chromium and its compounds in Korea were set by applying the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLVs). However, this is significantly different from the TLVs after the existing TLVs were integrated and withdrawn in 2018, so it is necessary to review the revision. Methods: Various documents related to chromium OELs were reviewed, including the ACGIH TLV Documentations for chromium and its compounds. A field survey was conducted targeting workplaces handling chromium and its compounds. Based on this, a revised OELs were proposed and a socio-economic evaluation was conducted. Results: The OELs for chromium compounds in Korea was first enacted in 2002, and in 2007, the OELs for chromium (hexavalent) compounds (insoluble) was lowered from 0.05 mg/m³ to 0.01 mg/m³. In 2008, the OELs for strontium chromate was newly established as 0.0005 mg/m³, and in 2018, the OELs for calcium chromate was newly established as 0.001 mg/m³. Total chromium and hexavalent chromium were measured for each of 6 samples at 2 welding sites, 4 plating sites, and 2 spray coating sites. When omparing the average of the results measured by ICP, a total chromium analysis method, and the analysis results by IC, a hexavalent chromium analysis method, only workplace 4 was the same, and total chromium was evaluated more, and total chromium was evaluated at 0.0004 to 0.0027 mg/m³. And hexavalent chromium was evaluated as non-detection ~ 0.0014 mg/m³. Amendment ①: The exposure standard for hexavalent chromium is not divided into water soluble, insoluble, chromium ore processing, and other hexavalent chromium compounds, and is integrated into 0.01 mg/m³, which is the level of chromium (hexavalent) compound (insoluble)., OELs for chromium (metal) and chromium (trivalent) compounds are integrated into chromium (trivalent) compounds, and the exposure level is maintained. Amendment ②: As in the amendment ①, the OELs are integrated, but the level is lowered to 0.005 mg/m³, which is the OELs of OSHA, and there is a grace period of 4 years. Amendment ③: As in the amendment ①, the OELs are integrated, but the level is lowered to 0.0002 mg/m³, which is the exposure standard of ACGIH, and there is a grace period of 5 years. Conclusions: Amendment ①: The change in the OELs is insignificant, so the cost required is small, and the benefit/cost ratio is greater than 1, so there is no problem in applying the amendment. Amendment ②: In all scenarios except chromium 6(insoluble), the benefit/cost ratio is greater than 1, so it is thought that there will be no major problem in applying the amendment. Amendment ③: Since the benefit/cost ratio is less than 1 in all scenarios, it is thought that the total social benefit that can be obtained when applying the amendment is not large.