• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06b
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• pp.271-278
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• 2006

We used polymers of alternating cationic and anionic nature to build up shells on fiber surfaces, strengthen the worn-out fibers and improve paper properties made from such fibers. OCC and ONP pulps were either dipped or salted out in the cationic polyallylamine, polyacrylamide and starch solutions. After centrifugal drying, these were followed by treatments in anionic polyacrylic acid, poly-acrylamide, and starch solutions, respectively. The shell-enhanced fibers were formed into handsheets and their physical properties evaluated. The results show that building multiple shells on worn-out fiber surfaces can strengthen the fibers and paper. The simpler and more practical impregnation-centrifuging treatment provided the desired effects, whereas salting out the polymers produced somewhat superior fibers. The latter process, were impractical, however. The first pair of polymeric shells imparted marked strength improvement, whereas later layers had diminishing efficacies. Overall, the methods can improve fiber quality, attaining paper strength requirements without resorting to expensive measures. Alternate cationic polymer and filler powders were also deposited on fiber surface based on the micriparticle system in an anticipation of stiffness gains. Platy minerals, such as montmorillonite, bentonite, sericite, clay and talc were added following cationic PAM. After dewatering of polymer-pigment shelled fiber of one to 3 pairs of layers, handsheets either calendered or uncalendered were evaluated. The results indicate that regardless of calendaring, stiffness of the handsheets did not improve appreciably while certain other strength properties showed gains. We also attempted the novel starch gel filler addition method wherein tapioca starch and filers (PCC, sericite or clay) were mixed at high solids content of 50% and cooked until gelatinized. The filled handsheets were dried under various conditions and then tested for their properties. Improvements in strengths of modified filled paper were observed.

• Journal of Sensor Science and Technology
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• v.11 no.6
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• pp.327-334
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• 2002

Fine particles of $SnO_2$ were fabricated by the sol-gel powder processing using tine(II) chloride dihydrate($SnCl_2{\cdot}2H_2O$) and ethanol($C_2H_5OH$) as raw materials. The powders were investigated about the properties and electrical sensing. Gel powders were fabricated by drying of sol at $120^{\circ}C$ after aging 72hrs and 168hrs. The amount of $SnO_2$ phase was increased below $600^{\circ}C$ due to the elimination of volatile components, and the $SnO_2$ phase was almost completed by the heat treatment at $700^{\circ}C$ for 30min. The grain sizes were about 30nm below $700^{\circ}C$, and it showed the narrow distribution of the grain sizes. The specimens to measure electrical properties were fabricated by the thick film screen printing technique on the alumina substrates. The conductance of $SnO_2$ was showed the intrinsic behaviour of semiconducting ceramics above at $450^{\circ}C$. The constant conductance was observed in the temperature range of $200{\sim}450^{\circ}C$. The sensing properties of response time, recovery, and sensitivity of CO were improved with aging time.

• Journal of the Mineralogical Society of Korea
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• v.20 no.2 s.52
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• pp.135-145
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• 2007

The needs for the ultra fine particles have been increased in preparation field of raw powders such as fine ceramics and high functional products. In this study, a series of wet grinding experiments were carried out on inorganic powders such as calcite, pyrophyllite and talc by a stirred ball mill. The particle size distribution of ground products of each test material fur a given grinding time was found to be expressed by the grinding rate (selection function) which was obtained from the grinding kinetics analysis. The median diameter decreased from 6.49 to $0.47{\mu}m$ in calcite, and decreased from 3.91 to $1.14{\mu}m$ in pyrophyllite. However, in talc, median diameter was decreased a little bit from 10.30 to $6.67{\mu}m$. The grinding rate changing on calcite and pyriphyllite were similar at the same conditions. However, in the case of talc, it was observed that the grinding rate was not increased compared to other samples.

• Korean journal of food and cookery science
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• v.31 no.5
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• pp.551-556
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• 2015

Iksan370 is a long-spike wheat developed by the Rural Development Administration yielding excellent features components such as cold resistance, disease resistance, and viviparous germination. The physicochemical and material properties of the raw wheat and milled flour of Iksan370 were analyzed to derive its appropriate uses. The raw wheat of Iksan370 showed high contents of ash and proteins at 1.71% and 13.7%, respectively. Its test weight of 763.0 g/L was similar to those of other varieties and its 1,000 kernel weight was high at 45.38 g. The milled flour of Iksan370 had an ash content of 0.45%, which corresponds with a class 1 flour, and its protein content is 12.18%, corresponding with strong flour. The damaged starch was 5.41%, which was lower than that of other varieties. The average grain size was $70.67{\mu}m$ and the grain distribution was at the level of a typical hard wheat. In the farinogram, the water absorption was 58.63%, which corresponded to the level of medium flour. The development time was 7.00 minutes, which was significantly lower than those of Jokyung and Keumkang. The degree of softening was 67.00 BU, similar to those of Yunbaek and Baekjoong. Among the physico-chemical characteristics, the high protein content and typical hard wheat grain distribution of Iksan370 were similar to those of strong wheat, usually used for bread making. However, in the farinogram, the dough development time was short and the degree of softening was high. As a result, Iksan370 was expected to have poor breadmaking properties and a small volume of the final bread product due to insufficient dough durability. On the other hand, Iksan370 showed the highest maximum gelatinization viscosity at 864.00 BU. Therefore, Iksan370 is expected to show glutinous texture when used for noodles and its flour appears to be appropriate for frying powders as well.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.82-89
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• 2009

According to the great city development and the rapid growth of redevelopment project, waste concrete emission has been increased. Waste concrete powder is one of the by-product originated from the recycling of the waste concrete. The more making high quality recycled aggregate to use aggregate for concrete, the more waste concrete powder is producted relatively. Therefore, to realize the total recycling of waste concrete, development of recycling technology for waste concrete powder need very much. This technical note present the discharged process and the various properties of waste concrete powder. As the results, on the average, the maximum particle-size of waste concrete powder is less than $600{\mu}m$, and oven-dry density is less than $2.5g/cm^3$. And waste concrete powder contains more than 50% of $SiO_2$, 30% of CaO and 10% of $Al_2O_3$. Thus qualities of waste concrete powder is lower than those of high quality raw material for concrete. However, if it is processed by grading to the purpose, it will be used as resource of raw materials for construction field.

• Resources Recycling
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• v.24 no.3
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• pp.59-65
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• 2015

Recycling of vulcanized rubber products is a serious problem in the world. A quantity of generated waste tires becomes much more and more because of increasing demands on automobiles, resulted in the cause of serious secondary pollution by sulfur component that is crosslinked to incineration or landfill. In addition, crosslinked surfur is used to interfere with the binding of the raw material rubber. In this study, we analyzed the degree of devulcanization by the chemical devulcanization. Devulcanization ratio of the samples were systematically analysed by variables such as time and temperature. In addition, the effect of swelling method as a pre-treatment process was also measured. A rubber specimen was deepened in a organic 2-buthanol solutions during various times of 1 ~ 5 hrs at 100, 150, $200^{\circ}C$ respectively, then to calculate the crosslink density and the number average molecular weight by using a parallel expansion process, which showed devulcanization degree of analyzed samples quantitatively. Also, the mechanical properties were measured with the samples prepared by using a hot press.

• Clean Technology
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• v.25 no.2
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• pp.101-106
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• 2019

The aim of this study is to investigate the feasibility of an Ni-SA catalyst, which was prepared from nickel, kieselguhr, and alumina, for the hydrogenation of triglyceride in a bench-scale reactor. Ni-SA powders were prepared by precipitating nickel precursors on a silica and alumina support. The powder was reduced in a hydrogen flow, mixed with a saturated palm oil, and then cooled to prepare an Ni-SA catalyst tablet. The sizes of NiO crystals of a commercial Pricat catalyst and the Ni-SA catalyst prepared in this study were $35{\AA}$ and $38{\AA}$, respectively. The pore volume and pore size of the Ni-SA catalyst was much larger than the pore volume and pore size of the Pricat catalyst. In addition, the average particle size of the Ni-SA catalyst was much smaller than that of the Pricat catalyst. The triglyceride hydrogenation reaction was carried out in a semi-batch reactor using catalysts impregnated with oil and molded into tablets. It was found that the Ni-SA catalyst was superior to the commercial Pricat catalyst in triglyceride hydrogenation, which could be ascribed to the raw material and the products being less influenced by the diffusion resistance in the pores of the Ni-SA catalyst. The Ni-SA catalyst prepared in this study has the potential to replace the Pricat catalyst as a catalyst for use in the commercial process for hydrogenation of triglyceride.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.6
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• pp.276-281
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• 2021

In order to manufacture a semiconductor circuit, etching, cleaning, and deposition processes are repeated. During these processes, the inside of the processing chamber is exposed to corrosive plasma. Therefore, the coating of the inner wall of the semiconductor equipment with a plasma-resistant material has been attempted to minimize the etching of the coating and particle contaminant generation. In this study, we synthesized yttrium oxyfluoride (YOF) powder by a solid-state reaction using Y₂O₃ and YF₃ as raw materials. Mixing ratio of the Y₂O₃ and YF₃ was varied from 1.0:1.0 to 1.0:1.6. Effects of the mixing ratio on crystal structure and microstructure of the synthesized YOF powder were investigated using XRD and FE-SEM. The synthesized YOF powder was successfully applied to plasma spray coating process on Al substrate.