• Applied Chemistry for Engineering
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• v.4 no.2
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• pp.291-299
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• 1993

Hydrothermal synthesis of 1.13nm tobermorite was performed to obtain the mixing ratio of raw materials, the optimum reaction time and the effect of aluminum in two systems, $CaO-SiO_2-H_2O$ and cement sludge-$SiO_2-H_2O$. 1.13nm tobermorite($5CaO{\cdot}6SiO_2{\cdot}5H_2O:C_5S_6H_5$) was synthesized excellently from $CaO-SiO_2-H_2O$ system on each mole ratio (0.4, 0.8) of $CaO/SiO_2$ at $180^{\circ}C$. But a tobermorite crystals had a sign of crystal conversion after 6 hours of reaction times in the case of $CaO/SiO_2=0.4$ and 4 hours of reaction time in the case of $CaO/SiO_2=0.8$. However, a tobermorite synthesized from cement sludge wastes did not show the crystal conversion on each mole ratio(0.4, 0.8) of $CaO/SiO_2$ within 10 hours of reaction times. It is considered that aluminum ions dissolved from cement sludge wastes retarded the recrystallization of tobermorite. This role of aluminum ion was confirmed in $CaO-SiO_2-H_2O+Al$ powder system. According as added amount of Al powder was increased from 0.8% to 3.0%, the crystal had a highly flatter and larger shape. Recrvstallization was not detected within the same reaction times when aluminum was added.

• Korean Journal of Food Science and Technology
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• v.22 no.3
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• pp.272-277
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• 1990

Some additives were applied to improve Yukwa(Popped rice snack) quality and process modifications were tested for cutting down soaking time and application of rice flour. Addition of soaked soybean (3%, w/w) to dough showed higher expansion rate and better physical properties with more acceptable quality by sensory evaluation of Yukwa. Baking powder, modified starch and alcoholic liquor, Mackeali(rice wine, turbid). Soju(distilled liquor) and Yakju(rice wine, clear), were no positive effect on quality of Yukwa but alcoholic liquor gave more fine texture than others. High temprature soaking $(60^{\circ}C)$ of rice for 3 hours which is near gelatinization temperature of rice starch. gave same quality of Yukwa comparing with long time soaking (12 hours) at room temperature. Extention of high temperature soaking (12 hours) did not improve the quality of Yukwa. The 100 mesh of rice flour by dry milling method was better in expansion rate and hardness than 40 and 80mesh but it was worse than ordinary wet milling. It was notified that milling method and milling mechines for Yukwa preparation should be studied in more detail.

• Applied Biological Chemistry
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• v.20 no.1
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• pp.95-100
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• 1977

To get a basic information for improving Korean's pattern of comsuming red pepper and the possibility of its industrial production, consumer's ways of red pepper processing and his present dietary habits were surveyed and the results are follows; (1) Korean's daily consumption of red pepper was on the average 9.2 g on the basis of the whole dried red pepper. (2) The tendency of evading the home drying method was increased; 72.22% in urban community and 50.4% in rural community purchased the dried red pepper in the lump yearly. The household purchasing the fresh red pepper and using the home drying was 27.8% in urban community and 49.6% in rural community, so one third of urban household was still using the home drying method. The case of dependence on tine drying factory was no more than 2.6%. (3) Drying method was mainly sun drying which done on the poor circumstance like as the street side without the proper equipment of drying. Home process of red pepper by housewife was 70.8%, and the old, housekeeper were only 7.3% respectively. (4) The hygienic sense in the drying was rare; 68.8% was not washed and 51.9% of decayed red pepper was eaten. (5) Koreans prefered the strong pungency, deep red color and fine powder form. (6) While the 45.5% of seed was collected by second hand dealer and made use of as resources of edible oil, it was not used effectively due to complexity of its collection system. (7) While 40.1% desired the improvement of red pepper dietary life, 41.1% distrusted the present commercial red pepper powder on the market. From the results above, we conclude the fact many households have still hygienically poor red pepper processed at home, in spite of the red pepper is one of the most important spices in Korea. Considering the growing urban population, reduction of unemployed labor due to the increasing nuclear family and hygienic problems caused by the serious pollution, the improvement of red pepper processing method is urgently required. And it is believed that red pepper has a good prospect to be processed on the industrial scale in Korea.

• Korean Journal of Environmental Agriculture
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• v.26 no.3
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• pp.259-266
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• 2007

Enormous amount of zeolite by-products as a fine powder have been produced while manufacturing commercial zeolite products. Granulation of the zeolite by-products is necessary in order for them to be recycled as soil conditioners or absorbent for various environmental contaminants due to the limitations inherent from their physical properties. We granulated the zeolite powders using Portland cement as a cementing agent and characterized the physical and chemical properties of the granulated zeolite product. The experimental natural zeolite had a Si/Al ratio of 4.8 and CEC of 68.1 $cmol_c\;kg^{-1}$. The X-ray diffractometry (XRD) revealed that clinoptilolite and mordenite were the major minerals of natural zeolite. Smectite, feldspar and quartz also existed as secondary minerals. Optimum conditions of granulated zeolite production occurred when natural zeolite was mixed with Portland cement at a 4:1 ratio and granulated using the extruder, left to harden for one month at $25^{\circ}C$ and treated at $400^{\circ}C$ for 3 hours. The wide spectra of XRD revealed that the granulated zeolite had amorphous oxide minerals. The alkali- or thermal-treated natural zeolite exhibited pH-dependent charge properties. The major minerals of the granulated zeolite were clinoptilolite, mordenite and tobermorite. The buffering capacity and charge density of the granulated zeolite were greater than those of natural zeolite.

• Journal of the Korean Chemical Society
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• v.50 no.4
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• pp.315-320
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• 2006

manganese oxides have been prepared by Chimie Douce redox reaction between permanganate and chalcogen element fine powder under acidic condition (pH = 1). According to powder X-ray diffraction analyses, the S- and Se-doped manganese oxides are crystallized with layered birnessite and tunnel-type -MnO2 structures, respectively. On the contrary, Te-doped compound was found to be X-ray amorphous. According to EDS analyses, these compounds contain chalcogen dopants with the ratio of chalcogen/manganese = 4-7%. We have investigated the chemical bonding character of these materials with X-ray absorption spectroscopic (XAS) analysis. Mn K-edge XAS results clearly demonstrated that the manganese ions are stabilized in octahedral symmetry with the mixed oxidation states of +3/+4. On the other hand, according to Se K- and Te L1-edge XAS results, selenium and tellurium elements have the high oxidation states of +6, which is surely due to the oxidation of neutral chalcogen element by the strong oxidant permanganate ion. Taking into account their crystal structures and Mn oxidation states, the obtained manganese oxides are expected to be applicable as electrode materials for lithium secondary batteries.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.4
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• pp.700-708
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• 2001

Traumatic injuries in young patients can result in the interruption of the development of the incompletely formed roots. In teeth with incomplete root-end formation and necrotic pulps, the root canals must be completely debrided. Because of a lack of an apical stop and the presence of thin and fragile walls in these teeth, it is imperative to perform apexification to obtain an adequate apical seal. Calcium hydroxide has become the material of choice for apexification. Despite its popularity for the apexification procedure, calcium hydroxide therapy has some inherent disadvantages that include variablility of treatment time, unpredictability of apical closure, difficulty in patient follow-up, and delayed treatment. An alternative treatment to long-term apexification procedure is the use of an artificial apical barrier that allows immediate obturation of the canal. MTA(Mineral Trioxide Aggregate) is a powder consisting of fine hydrophilic particles of tricalcium silicate, tricalcium aluminate, tricalcium oxide and silicate oxide. MTA has a pH of 12.5 after setting, similar to calcium hydroxide. This may impart some antimicrobial properties. MTA has low solubility and a radiopacity slightly eater than that of dentin. Also, MTA leaked significantly less than other materials and induced hard-tissue formation more than other materials.

• Korean Journal of Materials Research
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• v.9 no.6
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• pp.577-582
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• 1999

In order to make the electroconductive $Si_3N_4$-TiN composities, the Si-Ti(N) compacts were nitrided at $1450^{\circ}C$ for 20hours, and then they were post-sintered by a gas-pressure-sintering technique at 1TEX>$1950^{\circ}C$ for 3.5 hours. As starting powders, commercial si powder of about $10\mu\textrm{m}$, two types of Ti powders of 100 and 325 mesh, and fine-sized TiN of $2.5\mu\textrm{m}$ powders were used. In the $Si_3N_4$-TiN sintered bodies used Ti powders, the relative density and fracture strength and electrical conductivity are low due to the existence of large amounts of coarse pores. However, in the $Si_3N_4$-TiN composite used TiN powder, the fracture toughness, fracture strength and electrical resistivity were $5.0MPa{\cdot}m^{1/2}$, 624MPa and $1400{\omega}cm$, respectively. The dispersion of TiN particles in the composite inhibited the growth of $Si_3N_4$ in the shape of rod and made strong strain field contrasts at the $Si_3N_4$-TiNinterfaces. It was recognized that microstructural control is required to improve the electrical conductivity and mechanical properties of $Si_3N_4$-TiN composites by dispersing TiN particles homogeneously.

• Korean Journal of Materials Research
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• v.10 no.10
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• pp.671-676
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• 2000

$BaTiO_3$-based ceramics with partially oxidized Ti powders were prepared by sintering at $1350^{\circ}C$ for 1 h in v vacuum, and then heated in air. In this study, the effect of partially oxidized Ti powders on electrical properties and microstructures of $BaTiO_3$-based ceramics was investigated. It was found out that the semiconductive $BaTiO_3$-based ceramics beζame to show excellent PTCR (more than $10^5$) characteristic by adding 5~7 vol% of partially oxidized Ti powder. Also, it was found out that the sintered compact had extremely porous and fine-grained microstructure. The relative density and grain size of sintered compact with 5 vol% of partially oxidized Ti powders were 54% and $1.3\;{\mu\textrm{m}}$, respectively. The mechanism for the development of PTCR characteristic in $BaTiO_3$-based ceramics with partially oxidized Ti powders due to the adsorption of oxygen at grain boundaries, and could be explained, based on Heywang model.

• Current Research on Agriculture and Life Sciences
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• v.31 no.3
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• pp.193-199
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• 2013

This study dyed rayon fabric using loess as a natural colorant. To obtain the optimal dyeing conditions, various dyeing conditions were examined (temperature, pH, time, and concentration). The color fastness was evaluated using standard washing and rubbing fastness tests. The results were as follows: The loess powder particle size ranged from 0.4 to $1.7{\mu}m$ with a distribution range of 1.1 to $1.4{\mu}m$, representing a fine and uniform manufactured loess powder. The loess component analysis showed a large amount of silicon dioxide and aluminum oxide. TheFT-IR spectra showed that the ammonium group in the rayon fabric produced N-H banding at $1,540cm^{-1}$. The highest K/S value for the rayon fabric was obtained when the pH was 8.0, and this value increased rapidly with a longer dyeing time and when increasing the loess concentration to 30% (w/v). Pre-treatment with a soybean solution produced the highest K/S value for the rayon fabric with a loess concentration of 30% (w/v). The SEM analysis showed a higher amount of loess adhered to the rayon fabric surface when increasing the loess concentration. However, pre-treatment with a cationic agent and soybean solution resulted in a much higher attachment of loess to the fabric surface. Thus, the experimental results showed that using a cationized fabric and pre-treatment with a soybean solution are more effective when dyeing rayon fabric with loess than when using only loess.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.5
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• pp.649-653
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• 1999

A magnetic fluid separation technology was confirmed to be very effective to remove the suspended solids (SS) from aquacultural recirculating water, In this study, the effects of operating variables on the characteristics of SS removal were investigated through the test runs using magnetite of 2 $\mu$m mean diameter as magnetic powder. Magnetic flocculation here formed by adsorbing fine magnetites on the surface of suspended solid was observed. The strength of magnet was of significance in determining the SS removal efficiency as well as the capacity of the equipment. In addition, the SS removal efficiency decreased with an increase in the superficial liquid velocity, but the effect became negligible when the mass ratio of magnetite to the suspended solids was higher than 1.0.