금속 주조시 사용되는 탄소이형제를 카본블랙과 점증제 겸 알데하이드 화합물의 경화제로 사용될 수 있는 수용성 고분자인 잔탄검(X-gum), 카르복시메틸셀룰로오스(CMC)을 혼합하여 제조하였다. 이 때 카본블랙의 안정한 분산을 위하여 0.25 wt%의 X-gum 또는 1.0 wt%의 CMC가 적당하였다. 1.0 wt% 보다 낮은 농도의 CMC를 사용했을 경우 카본블랙이 매우 쉽게 층분리되었다. 유리판에 대한 부착력은 경화제와, 구르탈알데하이드 및 사슬연장제인 올리고당의 양에 비례하였으며. X-gum으로 제조된 탄소 이형제는 CMC를 이용해 제조된 것보다 유리에 대한 부착력이 우수하였다. 결과적으로 본 실험의 최적 조건에서 제조된 탄소이형제는 친환경적으로 주조시에 적용할 수 있을 것으로 판단된다.

The microstructure and tensile properties of Al-Mn/Al-Si hybrid aluminum alloys prepared by electromagnetic duocasting were investigated. Only the Al-Mn alloy showed the typical cast microstructure of columnar and equiaxed crystals. The primary dendrites and eutectic structure were clearly observed in the Al-Si alloy. There existed a macro-interface of Al-Mn/Al-Si alloys in the hybrid aluminum alloys. The macro-interface was well bonded, and the growth of primary dendrites in Al-Si alloy occurred from the macro-interface. The Al-Mn/Al-Si hybrid aluminum alloys with a well-bonded macro-interface showed excellent tensile strength and 0.2% proof stress, both of which are comparable to those values for binary Al-Mn alloy, indicating that the strength is preferentially dominated by the deformation of the Al-Mn alloy side. However, the degree of elongation was between that of binary Al-Mn and Al-Si alloys. The Al-Mn/Al-Si hybrid aluminum alloys were fractured on the Al-Mn alloy side. This was considered to have resulted from the limited deformation in the Al-Mn alloy side, which led to relatively low elongation compared to the binary Al-Mn alloy.

A Li2O-2SiO2 (LS2) glass was investigated as a lithium-ion conducting oxide glass, which is applicable to a fast ionic conductor even at low temperature due to its high mechanical strength and chemical stability. The Li2O-2SiO2 glass is likely to be broken into small pieces when quenched; thus, it is difficult to fabricate a specifically sized sample. The production of properly sized glass samples is necessary for device applications. In this study, we applied spark plasma sintering (SPS) to fabricate LS2 glass samples which have a particular size as well as high transparency. The sintered samples, 15mmφ×2mmT in size, (LS2-s) were produced by SPS between 480˚C and 500˚C at 45MPa for 3~5mim, after which the thermal and dielectric properties of the LS2-s samples were compared with those of quenched glass (LS2-q) samples. Thermal behavior, crystalline structure, and electrical conductivity of both samples were analyzed by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and an impedance/gain-phase analyzer, respectively. The results showed that the LS2-s had an amorphous structure, like the LS2-q sample, and that both samples took on the lithium disilicate structure after the heat treatment at 800˚C. We observed similar dielectric peaks in both of the samples between room temperature and 700˚C. The DC activation energies of the LS2-q and LS2-s samples were 0.48±0.05eV and 0.66±0.04eV, while the AC activation energies were 0.48±0.05eV and 0.68±0.04eV, respectively.

The purpose of this study was to determine the optimum amounts of vegetables to use for flavoring chicken head soup base. The effects of the amounts of ginger and onion on the sensory properties of chicken head soup base were examined, and the optimum amounts were determined using response surface methodology. Sensory properties that were evaluated were yellowness, turbidity, bloody flavor, chicken-brothiness, organ meat-like flavor, and sweet taste. The increased amounts of ginger and onion led to a decrease in bloody flavor and organ meat-like flavor. The optimum levels of ginger and onion were determined to be 40g and 50g, respectively. Chicken head soup base prepared with optimum amounts of vegetables contained more arginine, tryptophan, inosine monophosphate (IMP), and hypoxanthine than plain chicken head soup base. It also had less hexanal, which is related to fat rancidity.

본 연구에서는 고투과성을 가지는 기체분리막 제조를 위해 6FDA와 APAF를 이용하여 하이드록시 폴리이미드를 합성하였다. H-NMR과 FT-IR 분석을 통해서 HPI의 합성여부를 확인하였으며 열적특성을 알아보기 위해 Differential scanning calorimetry (DSC)와 thermogravimetric analyzer (TGA)를 측정하였다. 특히 합성된 HPI는 약 450℃에서 polybenzoxazole (PBO)로 변환이 됨을 확인 가능하였다. 고투과성 고분자 분리막의 제조를 위해 고분자, 용매 그리고 비용매-첨가제를 포함하는 3성분계의 시스템을 도입하였으며, 상전이법을 이용하여 HPI 비대칭 평막을 제조하였다. 최종적으로 각성분들에 따른 모폴로지 변화를 전계방출주사현미경(FE-SEM)을 통해 확인할 수 있었다.

H2S adsorption characteristics of adsorbent made by drinking water treatment sludge were investigated. For analyses of the manufactured adsorbent, various methods such as scanning electron microscope(SEM), measurements of BET surface area were adopted. As the major adsorption characteristic, breakthrough curve was measured by using a continuous fixed bed adsorption column for operating variables such as aspect ratio(L/D, 3∼9), gas flow rate(0.2∼1.0 liter/min) and type of samples. The experimental results showed that the breakthrough pint decreased with increasing gas flow rate, but increased with increasing aspect ratio. It was also found that the physical and chemical treatments of drinking water treatment sludge are very important for the improvement in H2S adsorption capacity due to property changes of the sludge.

다공성 La0.6Sr0.4Ti0.3Fe0.7O3-δ로 코팅된 Ba0.5Sr0.5Co0.8Fe0.2O3-δ 관형 분리막은 압출성형 및 dip coating 방법으로 제조 되었다. 코팅된 관형 분리막의 특성은 X-선 회절분석기(XRD)와 전자 주사 현미경(SEM)을 이용하여 분석하였으며, 분석결과 2mum의 다공성 코팅 층을 갖는 페롭스카이트 구조임을 알 수 있었다. 산소투과량 분석은 750~950℃ 범위에서 공급측과 투과 측을 대기 중 공기와 진공으로 하여 수행되었다. 다공성의 La0.6Sr0.4Ti0.3Fe0.7O3-δ로 코팅된 Ba0.5Sr0.5Co0.8Fe0.2O3-δ 관형 분리막의 산소투과량은 950℃에서 3.2mL/min·cm2로 코팅되지 않은 분리막보다 높게 나타났으며, 11일 동안의 장기 안정성 실험결과 코팅 층에 의해 안정성이 증가됨을 알 수 있었다.

The particle size of MgO was examined as a function of the Na content in Mg(OH)2 powders and the calcination temperature. Mg(OH)2 suspension was obtained by dropwise precipitation of Mg(NO3)2·6H2O and NaOH solutions. The suspension was diluted by varying the dilution volume ratio of distilled water to Mg(OH)2 suspension to change the Na salt concentration in the suspension. Mg(OH)2 slurry was filtered and dried at 60˚C under vacuum, and then its Mg(OH)2 powder was calcined to produce MgO with different amount of Na content at 500~900˚C under air. Investigation of the physical and chemical properties of the various MgO powders with dilution ratio and calcination temperature variation was done by X-ray diffraction, transmission electron microscopy, BET specific surface area and thermal gravimetric analysis. It was observed that MgO particle size could depend on the condition of calcination temperature and dilution ratio of the Mg(OH)2 suspension. The particle size of the MgO depends on the Na content remaining in the Mg(OH)2 powder, which powder was prepared by changing the dilution ratio of the Mg(OH)2 suspension. This change increased as the calcination temperature increased and decreased as the dilution ratio increased. The growth of MgO particle size according to the increase of temperature was more effective when there was a relatively high content of Na. The increase of Na content lowered the temperature at which decomposition of Mg(OH)2 to MgO took place, thereby promoting the crystal growth of MgO.

Silicon-based thin film was prepared at room temperature by an electrochemical deposition method and a feasibility study was conducted for its use as an anode material in a rechargeable lithium battery. The growth of the electrodeposits was mainly concentrated on the surface defects of the Cu substrate while that growth was trivial on the defect-free surface region. Intentional formation of random defects on the substrate by chemical etching led to uniform formation of deposits throughout the surface. The morphology of the electrodeposits reflected first the roughened surface of the substrate, but it became flattened as the deposition time increased, due primarily to the concentration of reduction current on the convex region of the deposits. The electrodeposits proved to be amorphous and to contain chlorine and carbon, together with silicon, indicating that the electrolyte is captured in the deposits during the fabrication process. The silicon in the deposits readily reacted with lithium, but thick deposits resulted in significant reaction overvoltage. The charge efficiency of oxidation (lithiation) to reduction (delithiation) was higher in the relatively thick deposit. This abnormal behavior needs to clarified in view of the thickness dependence of the internal residual stress and the relaxation tendency of the reaction-induced stress due to the porous structure of the deposits and the deposit components other than silicon.

Thin film electrode consisting purely of porous anodic tin oxide with well-defined nano-channeled structure was fabricated for the first time and its electrochemical properties were investigated for application to an anode in a rechargeable lithium battery. To prepare the thin film electrode, first, a bi-layer of porous anodic tin oxides with well-defined nano-channels and discrete nano-channels with lots of lateral micro-cracks was prepared by pulsed and continuous anodization processes, respectively. Subsequent to the Cu coating on the layer, well-defined nano-channeled tin oxide was mechanically separated from the specimen, leading to an electrode comprised of porous tin oxide and a Cu current collector. The porous tin oxide nearly maintained its initial nano-structured character in spite of there being a series of fabrication steps. The resulting tin oxide film electrode reacted reversibly with lithium as an anode in a rechargeable lithium battery. Moreover, the tin oxide showed far more enhanced cycling stability than that of powders obtained from anodic tin oxides, strongly indicating that this thin film electrode is mechanically more stable against cycling-induced internal stress. In spite of the enhanced cycling stability, however, the reduction in the initial irreversible capacity and additional improvement of cycling stability are still needed to allow for practical use.

Two-dimensional (2D) nano patterns including a two-dimensional Bravais lattice were fabricated by laser interference lithography using a two step exposure process. After the first exposure, the substrate itself was rotated by a certain angle, 90˚ for a square or rectangular lattice, 75˚ for an oblique lattice, and 60˚ for a hexagonal lattice, and the 90˚ and laser incident angle changed for rectangular and the 45˚ and laser incident angle changed for a centered rectangular; we then carried out a second exposure process to form 2D bravais lattices. The band structure of five different 2D nano patterns was simulated by a beam propagation program. The presence of the band-gap effect was shown in an oblique and hexagonal structure. The oblique latticed ZnO nano-photonic crystal array had a pseudo-bandgap at a frequency of 0.337-0.375, 0.575-0.596 and 0.858-0.870. The hexagonal latticed ZnO nano-crystallite array had a pseudo-bandgap at a frequency of 0.335-0.384 and 0.585-0.645. The ZnO nano structure with an oblique and hexagonal structure was grown through the patterned opening window area by a hydrothermal method. The morphology of 2D nano patterns and ZnO nano structures were investigated by atomic force microscopy and scanning electron microscopy. The diameter of the opening window was approximately 250 nm. The height and width of ZnO nano-photonic crystals were 380 nm and 250 nm, respectively.

In this study, nano-sized tin oxide powder with an average particle size of below 50 nm is prepared by the spray pyrolysis process. The influence of air pressure on the properties of the generated powder is examined. Along with the rise of air pressure from 0.1kg/cm2 to 3kg/cm2, the average size of the droplet-shaped particles decreases, while the particle size distribution becomes more regular. When the air pressure increases from 0.1kg/cm2 to 1kg/cm2, the average size of the dropletshaped particles, which is around 30-50 nm, shows hardly any change. When the air pressure increases up to 3kg/cm2, the average size of the droplet-shaped particles decreases to 30 nm. For the independent generated particles, when the air pressure is at 0.1kg/cm2, the average particle size is approximately 100 nm; when the air pressure increases up to 0.5kg/m2, the average particle size becomes more than 100 nm, and the surface structure becomes more compact; when the air pressure increases up to 1kg/cm2, the surface structure is almost the same as in the case of 0.5kg/cm2, and the average particle size is around 80- 100 nm; when the air pressure increases up to 3kg/cm2, the surface structure becomes incompact compared to the cases of other air pressures, and the average particle size is around 80-100 nm. Along with the rise of air pressure from 0.1kg/cm2 to 0.5kg/cm2, the XRD peak intensity slightly decreases, and the specific surface area increases. When the air pressure increases up to 1kg/cm2 and 3kg/cm2, the XRD peak intensity increases, while the specific surface area also increases.

The goal of this investigation was to produce a zirconia-family black ceramics that has enhanced functionality andreliability. Color zirconia ceramics have been produced by adding pigments. Pigments cause structural defects within zirconiaand result in a drop in physical properties. Using environmentally friendly rice husk, we produced a black zirconia that is freeof structural defects. In optimal firing conditions for black zirconia the calcining temperatures of the molding product arechanged from 400oC to 1200oC, and the firing temperatures are changed from 1400oC to 1600oC. Color of testing the specimenswas analyzed using Ultraviolet (UV) spectroscopy. Scanning Electron Microscope (SEM), EDAX (EDX), and Fourier transforminfrared spectroscopy (FT-IR) analyses were carried out in order to examine impregnation properties and crystal phases.Universial Test Machine (UTM) was used to measure the flexual strength as well as the compressive strength. Fromexperimental results, it was found that in optimal firing conditions the sample was calcined from 1000oC to 1500oC. Commissioninternationalde I’Edairage (CIE) values of manufactured black zirconia color were L*=29.73, a*=0.23, b*=−2.68. Thebending strength was 918 MPa and the compressive strength was 2676 MPa. These strength values are similar to typicalstrength values of zirconia, which confirms that carbon impregnation did not influence physical properties.

One of the trace constituents included in cement clinker, chromium, has become prominent and highly noticed lately as a social issue both inside and outside of this country because it affects the human body negatively. The purpose of the present study was to investigate leaching properties of water-soluble hexavalent chromium by different manufacturing conditions of cement clinker. Raw materials were prepared to add different SiO2, Al2O3 and Fe2O3 sources. After the raw materials, such as limestone, sand and clay, iron ore was pulverized and mixed, and the raw meal was burnt at 1450˚C in a furnace with an oxidizing atmosphere. Leaching of soluble hexavalent chromium showed a tendency to decrease with an increasing LSF and IM. However, leaching of soluble hexavalent chromium increased with an increasing S.M. Alkali contents of iron source minerals is closely related to the leaching properties of soluble hexavalent chromium. Green sludge has the highest content of alkali added; leaching of water-soluble hexavalent chromium was mostly high. In order to reduce the water-soluble hexavalent chromium in cement, reducing the alkali content in raw materials is important.

The a-Si:H/c-Si hetero-junction (HJ) solar cells have a variety of advantages in efficiency and fabrication processes. It has already demonstrated about 23% in R&D scale and more than 20% in commercial production. In order to further reduce the fabrication cost of HJ solar cells, fabrication processes should be simplified more than conventional methods which accompany separate processes of front and rear sides of the cells. In this study, we propose a simultaneous deposition of intrinsic thin a-Si:H layers on both sides of a wafer by dual hot wire CVD (HWVCD). In this system, wafers are located between tantalum wires, and a-Si:H layers are simultaneously deposited on both sides of the wafer. By using this scheme, we can reduce the process steps and time and improve the efficiency of HJ solar cells by removing surface contamination of the wafers. We achieved about 16% efficiency in HJ solar cells incorporating intrinsic a-Si:H buffers by dual HWCVD and p/n layers by PECVD.

An ultrafine grained complex aluminum alloy was fabricated by an accumulative roll-bonding (ARB) process using dissimilar aluminum alloys of AA1050 and AA5052 and subsequently annealed. A two-layer stack ARB process was performed up to six cycles without lubricant at an ambient temperature. In the ARB process, the dissimilar aluminum alloys, AA1050 and AA5052, with the same dimensions were stacked on each other after surface treatment, rolled to the thickness reduction of 50%, and then cut in half length by a shearing machine. The same procedure was repeated up to six cycles. A sound complex aluminum alloy sheet was fabricated by the ARB process, and then subsequently annealed for 0.5h at various temperatures ranging from 100 to 350˚C. The tensile strength decreased largely with an increasing annealing temperature, especially at temperatures of 150 to 250˚C. However, above 250˚C it hardly decreased even when the annealing temperature was increased. On the other hand, the total elongation increased greatly above 250˚C. The hardness exhibited inhomogeneous distribution in the thickness direction of the specimens annealed at relatively low temperatures, however it had a homogeneous distribution in specimens annealed at high temperatures.

본 연구는 유기액비 재료가 유기액비 제조시 화학적 특성 변화에 미치는 영향을 구명코자 충청북도농업기술원 플라스틱하우스에서 수행하였다. 계분, 대두박, 쌀겨 등 3처리를 하였다. 본 시험에서 얻어진 결과를 다음과 같이 요약할 수 있다. 액비 원료의 총 질소 함량은 대두박이 55 mg·kg−1으로 가장많았으며, 인산과 칼륨 함량은 계분에서 가장 많았다. 계분의pH는 중성에 가까웠으며, 대두박과 쌀겨는 강산성을 띠었다. 계분 액비의 EC는 발효기간이 증가할수록 증가하였고, 대두박과 쌀겨 액비는 발효기간 중 증가하다가 감소, 증가하는 경향이었다. 계분 액비의 황화수소 발생량은 발효 후 2주차에는3,200 mg·L−1이었으나, 발효 12주차에는 1,600 mg·L−1으로 감소하였고, 대두박과 쌀겨 액비는 발효 과정중 황화수소 가스가 발생하지 않았거나 거의 발생하지 않았다. 질소와 칼슘 함량은 계분 액비와 대두박 액비에서 가장 많았다. 인산, 마그네슘의 함량은 쌀겨 액비에서 각각 5.6 g·kg−1, 1.5 g·kg−1으로 가장 높았다. 칼륨은 처리에 따라 4.3-4.4g·kg-1으로 차이가 없었다.

Cereals are the main raw material for sunsik manufacture. As the fundamental processing step, it is very important to confirm the level of the microorganism contamination in the cereals. This study was carried out a micrbiological screening of cereal samples for sunsik from 19 companies located in South Korea. Ten kinds of cereals which were glutinous rice, barley, brownrice, blackbean, blackrice, blacksesame, sorghum, millet, perilla seed, and adlay were investigated. As the results, the contaminations of general bacterial were 3.1~8.6 log(CFU/g). The results of Escherichia coli were 1.0~3.4 log(CFU/g). There was no contamination of Salmonella. spp in any cereal samples except black sesame and mold was detected in barley. The experiment for microbiological contamination during sunsik processing was also investigated in this study. The results of general bacteria were detected as 5.1~8.5, 4.4~7.5,1.0~2.3, 2.4~4.2, 1.0~4.0, 3.4~4.2, 4.3~5.2, and 3.3~5.5 log(CFU/g) during environment of warehousing, washing,steaming, 1st cooling, drying, 2nd cooling, grinding, and packaging process, respectively. The results of coliform were 1.0~2.0 log(CFU/g) during warehousing respectively. Mold was found in warehousing. In case of the instruments, the contaminations of general bacterial were 4.2~7.5, 0.1~2.0, 0.1~3.2, 3.7~4.0, 2.5~3.0, and 3.8~5.2 log(CFU/g) in cereals tanks, washing machines, grinding machines, packaging machines, and workrooms. The results of coliform were 2.4~4.0, 0.0~4.1 log(CFU/g) in cereals tanks and grinding machines, respectively. Mold were only found in cereals tanks, grinding machines, and workings. Therefore, the risk of hazard microorganisms contmination might be decrased as the exhaustive management is applied to the whole sunsik process.

The removal amount of pesticide residue which were remained in baechu (Chinese cabbage) and perilla leaf were measured during the preparation process of kimchi. The amounts of diazinon, procymidone and endosulfan applied to chinese cabbage were 9.18 ± 0.03 mg/kg, 22.27 ± 0.22 mg/kg and 10.46 ± 0.02 mg/kg respectively. When chinese cabbage was brined with 10% salt solution for 12 hours, the removal rates of three pesticides were 22.5%, 25.3% and 0.6% for diazinon, procymidone and endosulfan, respectively. When chinese cabbage was brined and rinsed 3 times with water, the removal rates of three pesticides were 69.9%, 85.6% and 11.2% for diazinon,procymidone and endosulfan, respectively. When kimchi was prepared and fermented for 28 days at 4oC, the removal rates of three pesticides were 79.4%, 94.4% and 21.0% for diazinon, procymidone and endosulfan, respectively. The relative percentages of removal dose of pesticides during brining were 28.4%, 26.9% and 3.2% for diazinon, procymidone and endosulfan, respectively and which were 59.7%, 63.8% and 50.4% during rinsing and which were 11.9%,9.3% and 46.4% during fermentation, respectively. The amounts of diazinon, procymidone and endosulfan applied to perilla leaf were 18.11 ± 0.62 mg/kg, 31.80 ± 0.33 mg/kg and 12.01 ± 0.01 mg/kg, respectively. When perilla leaf was rinsed 3 times with water, the removal rates of three pesticides were 60.5%, 52.0% and 23.7% for diazinon, procymidone and endosulfan, respectively. When perilla leaf was rinsed and brined with 10% salt solution for 14 days, the removal rates of three pesticides were 93.9%, 92.4% and 49.6% for diazinon, procymidone and endosulfan, respectively. The relative percentages of removal dose of pesticides during rinsing were 64.5%, 56.3% and 47.8% for diazinon,procymidone and endosulfan, respectively, and which during brining were 35.5%, 43.7% and 52.2% for diazinon, procymidone and endosulfan, respectively.

To evaluate the indoor air quality of food manufacturing plants, the presence of viable bacteria and fungi was assessed in the indoor air of the facilities at which 9 food items were manufactured. Air samples were collected from the general zone, low clean zone and clean zone of each factory with an air sampler, in combination with plate counts agar using for bacteria, and dichloran-glycerol agar for fungi. The samples were incubated at 25℃for 4 to 7 days. After culture, the colony forming units (CFU) on each plate were counted and corrected with a positive hole conversion table. The average concentration of bacteria was 2.2 × 10³ CFU/㎥ in the general zone, 1.2 ×10³ CFU/㎥ in the low clean zone and 7.3 × 10² CFU/㎥ in the clean zone. The average concentration of fungal microbes was 2.5 × 10³ CFU/㎥ in the general zone, 2.6 × 10³ CFU/㎥ in the low clean zone, and 2.0 × 10² CFU/㎥in the clean zone. No meaningful differences were detected between the general zone and the low clean zone, but the clean zone had significantly lower concentrations than the other zones. Additionally, the identification of the fungi was performed according to morphological method using a giant culture and slide culture. The fungi were identified as belonging to 18 genera, and the genera Cladosporium(33%), Penicillium(29%) and Aspergillus(26%), predominated. Aspergillus isolates were identified to species level, and A. ochraceus, a mycotoxigenic species, was identified. As part of the effort to control the quality of the indoor air of food manufacturing plants, our results show that continued studies are clearly warranted.