• Journal of the Korean Ceramic Society
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• v.31 no.8
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• pp.934-940
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• 1994

Fibers of ZrO2-SiO2 system were prepared from the hydrolysis and condensation of Si(OC2H5)4 and Zr(OnC3H7)4 with different H2O/alkoxide molar ratios. It was found that fibers could be drawn in the viscosity range of 1~100 poise from HCl catalyzed solutions with lower water contents of the mole ratio H2O/alkoxide, r 2. The fibrous gels were converted into the corresponding oxide glass fibers by heating at 80$0^{\circ}C$. Mechanical test was performed on E, A and 20ZrO2-80SiO2 glass fibers reinforced cement in order to investigate the flexural strength. The flexural strength value of 20ZrO2-80SiO2 glass fibers reinforced cement was greater than those of E and A. The chemical durability of the fibers in alkaline solutions increased with ZrO2 content. The weight loss due to the corrosion by 2N-NaOH solutions at $25^{\circ}C$ for 160 hours was about 0.31$\times$10-2 mg/dm2 for the 20ZrO2-80SiO2 glass fibers, which was superior to that of Vycor glass.

• Transactions on Electrical and Electronic Materials
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• v.15 no.2
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• pp.81-86
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• 2014

The process parameter in optimized KOH alkali activation of soft carbon series coke material in high purity was set with DOE experiments design. The activated carbon was produced by performing the activation process based on the set process parameters. The specific surface area was measured and pore size was analyzed by $N_2$ absorption method for the produced activated carbon. The surface functional group was analyzed by Boehm method and metal impurities were analyzed by XRF method. The specific surface area was increased over 2,000 $m^2/g$ as the mixing ratio of activation agent increased. The micro pores in $5{\sim}15{\AA}$ and surface functional group under 0.4 meq/g were obtained. The contents of the metal impurity in activated carbon which is the factor for reducing the electrochemical characteristics was reduced less than 100 ppm through the cleansing process optimization. The electrochemical characteristics of activated carbon in 38.5 F/g and 26.6 F/cc were checked through the impedance measuring with cyclic voltammetry scan rate in 50~300 mV/s and frequency in 10 mHz ~100 kHz. The activated carbon was made in the optimized activation process conditions of activation time in 40 minutes, mixing ratio of activation agent in 4.5 : 1.0 and heat treatment temperature over $650^{\circ}C$.

• KSBB Journal
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• v.24 no.1
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• pp.89-95
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• 2009

Biodiesel (fatty acid alkyl esters), which is produced from sustainable resources such as vegetable oil, animal fat and waste oils, have used to as substitutes for petro-diesel. In this study, we investigate the performance of 30 L and 300 L pilot-scale biodiesel production system using alkali-catalyst transesterification from soybean oil and rapeseed oil produced at Jeju island in Korea. The 30 L-scale biodiesel production was performed to in the condition of reaction temperature $65^{\circ}C$, catalyst amount 1% (w/w) and oil to methanol molar ratio 1 : 8. At that reaction condition, the fatty acid methyl ester contents of product are above 98% within reaction time 30 min. Also, the conversion yield of over 98% was obtained in 300 L-scale biodiesel production system using rapeseed oil and soybean oil. The quality of biodiesel produced from reaction system was satisfied to recommended quality standard of Korea. Our results may provide useful information with regard to the scale-up of more economic and efficient biodiesel production process.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.36.2-36.2
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• 2010

A small amount of Na incorporated in $CuInSe_2$ (CIS) absorption layer has become widely accepted as a requirement for efficient polycrystalline CIS solar cells. However, there is ongoing argument on the role of sodium incorporated in the absorber. In this paper, CIS absorption layers have been deposited using the three-stage co-evaporation process on Mo coated non-Alkali glass substrates. The NaF was evaporated during the second-stage with various fluxes. This paper is focusing on differences of micro-structure and composition ratio of the absorber realized with different Na contents and the variation of electrical properties of the cells with the corresponding absorbers. The analytical results of x-ray diffraction (XRD) patterns, field emission scanning electron microscope (FE-SEM), energy dispersive spectroscopy (EDS) and current-voltage characteristics will be discussed to investigate the effect of NaF flux on the CIS absorber formation and its cell performance.

• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.59-63
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• 2008

Poly (vinylchloride) (PVC) membrane electrodes based on neutral carrier, tetracycline was prepared as an active sensor for Hg(II) ion, and tested in different contents of the potassium tetrakis (4-chlorophenyl) borate (KTpClPB) as lipophilic salt. Bis (2-ethylhexyl) sebacate (DOS), bis(l-butylpentyl) adipate (BBPA), 2-nitrophenyl octyl ether (NPOE) and dibutyl phthalate (DBP) were used as diverse plasticizing solvent mediators. This electrode shows excellent potentiometric response characteristics and display good linearity with log $[Hg^{+2}]$ versus EMF response, over a range of concentrations between $10^{-7}$ and $10^{-3}M$. With 30.8mV/decade Nernstian slope, the detection limit was $6.9{\times}10^{-9}M$ and the response time was less than 20s. The proposed electrode yields very good selectivity for mercury (II) ion over many cations such as alkali, alkaline earth, transition and heavy metal ions. And it shows a very stable potential values in a wide pH range. This reliable electrode prepared was kept at least a month without considerable alteration in their response to Hg (II) ion.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.5
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• pp.85-90
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• 2015

To use the African tulip tree (Spathodea campanulata) as raw material for chemical pulping, soda and soda-AQ pulping was investigated. In chemical compositional analysis, lignin contents of African tulip (33.1%) was higher than other hardwood such as Yellow poplar (17.5%), Acacia (27.1%), or Eucalyptus (24.2%). Soda or soda-AQ pulping with African tulip tree resulted in yield at 43.4-44.8% with 29.5-34.5 Kappa number, pulping condition with 20-22% active alkali. Kappa number of African tulip tree pulp was quite higher than other tropical hardwood (Eucalyptus or Accacia) with less yield due to higher lignin content in wood. Fiber length and width of pulp from African tulip tree was similar to Accacia pulp and shorter than eucalyptus pulp.

• Advances in nano research
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• v.4 no.3
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• pp.181-195
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• 2016

Addition of nano-$SiO_2$ (NS) to geopolymer composites has been studied through measurement of compressive strengths, FTIR and XRD analysis. Alumino-silicate materials are coarse aggregate included waste concrete and demolished walls with its cementing binder, cement kiln dust (CKD) used and can possess a pronouncing activation for the geopolymer reaction resulting from the high alkali contents within. Materials prepared at water/binder ratios in a range of 0.30: 0.40 under curing of $40^{\circ}C$ and 100% Relative Humidity (R.H.), while the used activator is sodium hydroxide in the ratio of 2 wt. %. First, CKD is added in the ratio from 10 up to 50 wt., %, and the demolished walls was varied depending on the used CKD content, while using constant ratio of waste concrete (40 wt., %). Second step, depending on the optimum CKD ratio resulted from the first one (40 wt. %), so the control geopolymer mix composed of cement kiln dust, demolished walls and waste concrete in the ratio (40:20:40, wt %). Nano-silica partially replaced waste concrete by 1 up to 8%. Results indicated that, compressive strengths of geopolymer mixes incorporating nano-silica were obviously higher than those control one, especially at early ages and specially with 3%NS.

• The Journal of the Petrological Society of Korea
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• v.14 no.1
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• pp.45-60
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• 2005

This study was intended to elucidate the petrography and geochemical characteristics of the Someori Basalt in the Udo monogenetic volcano, eastern Jeju Island. The Someori basalts consist of plagioclase, olivine, orthopyroxene, clinopyroxene and ilmenite. The Someori basalts are plotted into subalkali rock series on the TAS diagram, and belong to tholeiitic basalts in the diagram of alkali index against to Al₂O₃ contents. The basalts belong to tholeiitic rock series, having normative quartz (less than 3.9%) + hypersthene + diopside.

• Journal of Magnetics
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• v.14 no.2
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• pp.80-85
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• 2009

The mineral dissolution sensor system using GMR-SV and glass/Mg(200 nm) was prepared and characterized. The magnetic field sensitivity of GMR-SV to microscopic magnetic variation was about 0.8%/Oe. The change that occurs when Mg-film dissolves in water, the solubility of water, which is one of the basic properties of mineral water, was sensed by measuring the subtle variation of an electric current. In the case of edible water with Mg mineral added, bubbles were generated on the surface of the Mg film in the first 45 minutes, and the number of drops that were dissolved more rapidly than with the tap and DI waters later reduced to zero. For the edible water samples that each had different mineral Mg concentrations, the Mg solubility speed significantly differed. After injecting Mg film into the edible water, the magnetoresistance of the output GMR-SV signal decreased from a maximum of $45.4\;{\Omega}$ to a minimum of $43.6\;{\Omega}$. The measurement time was within 1 min, giving the rate of change ${\Delta}R/{\Delta}t=0.18\;{\Omega}/s$. This measurement system can be applied to develop a mineral Mg solubility GMR-SV sensor that can be used to sense the change from edible water to reduced alkali.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.5
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• pp.581-593
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• 2010

The objectives of this study were to investigate the effects of raw water pH and basicity of coagulants on turbidity removal with several raw waters having different level of turbidity, alkalinity and pH. Raw waters were sampled from M, S and B water treatment plants(WTP) located at Miryang, Nakdong, Han river, respectively. Six coagulants which have different levels of basicity and aluminum contents were used for this evaluation. High basicity of the coagulant helped to properly control coagulation processes for treating turbid and low alkali raw water. It was difficult for operators to determine optimum coagulant dose for high basicity coagulants, since residual turbidity tended to decrease continuously as coagulant dose increased. Turbidity removal efficiencies with high basicity coagulants(E and F) were higher than the other coagulants at ambient pH for the M WTP. Turbidity removal efficiencies, however, at adjusted pH 7.0 showed similar among six coagulants. Residual turbidity kept low at excess dosages with high basicity coagulants. Optimum coagulant dosages at adjusted pH 7.0 showed higher than those at ambient pH in M WTP. On the contrary in B WTP, optimum coagulant dosage at ambient pH were higher than that at adjusted pH 7.0.