• Proceedings of the Korea Association of Crystal Growth Conference
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• 2000.06a
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• pp.195-214
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• 2000

The high-speed steel (shorten as HSS) consists of Fe and several kinds of transition metal carbides. The cutting tools or wear-resistant materials made from HSS experience relatively high thermal shock because a coolant such as water or oil is flowed over the surface of heated HSS. The purpose of this research is to increase the hardness, strength, fracture toughness and thermal shock resistance of HSS. A possible strategy is to incorporate a hard ceramic material with high strength in HSS matrix. This paper describes the processing, microstructure and mechanical properties of the oriented unidirectional mullite fiber/HSS composite. The unidirectional mullite fibers of 10${\mu}{\textrm}{m}$ diameter were dispersed by the ultrasonic irradiation of 38 kHz in an ethylenglycol suspension containing HSS powder of 11${\mu}{\textrm}{m}$ median size. The dried green composites with 4-68 vol% fibers were hot-pressed for 2h at 100$0^{\circ}C$ in Ar atmosphere under a pressure of 39 MPa. The higher density was achieved in the composite with a lower content of fibers. The oriented unidirectional fibers were well dispersed in the HSS matrix. The average distance between the center of fibers in the cross section was close to the value calculated from the fiber fraction. No reaction occurred at the interfaces between HSS and mullite fibers in the composites. The composite with 13.6 vol% fibers showed 100 MPa of four point flexural strength at room temperature. The thermal expansion of composite with heating was influenced by the orientation of mullite fibers.

• The Journal of the Korea Contents Association
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• v.16 no.8
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• pp.209-216
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• 2016

Latent fingerprint left on the adhesive sides of tapes can be easily found at a crime scene. Small Particle Reagents(SPR) based on iron oxide($Fe_3O_4$) is a technique for the detection of a latent fingerprint adhesive surface. In this study, found out that the causes affecting the quality of the fingerprints developed when used SPR based on iron oxide. To a suspension of 0.5g of iron oxide in 100ml of distilled water, 0.5ml or more surfactant were added can be developed latent fingerprints of good quality. In addition, using surfactants HLB(hydrophile-lipophile balance) value of 11~18 showed good contrast to the background and latent fingerprint.

• Journal of the Korea Convergence Society
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• v.8 no.2
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• pp.157-162
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• 2017

Inorganic stiffening agents were prepared by mixing paper sludge incineration ash, blast furnace slag fine powder quicklime, anhydrous gypsum and fly ash. The main components of the solidifying agent developed for sludge treatment were SiO, $Al_2O_3$, $TiO_2$, $Fe_2O_3$, $Mn_2O_3$, CaO, MgO, $Na_2O$, $K_2O$, $P_2O$, and $SO_3$. Unlike cement, the developed solidifying agent did not contain $Cr^{6+}$, which is known as a carcinogen. Heavy metals and oil contaminated soil were mixed with solidifying agent and cured for 7 days and the heavy metal content was below the environmental standard. Sewage sludge cake, food waste and solidifying agent were mixed with each other, and after 7 days curing, soil component test showed that the heavy metal content was below the environmental standard. After mixing the sludge, solidifying agent and additive mixture into the beaker, the ammonia concentration was measured to be 0 after 3 days.

• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.434-440
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• 2003

The powders of L $a_{0.8}$C $a_{0.2}$Mn $O_3$ Colossal Magnetoresistance (CMR) materials were synthesized by sol-gel process. Lanthanum(H), Calcium(II) and Manganese(III) 2,4-Pentanedionate were dissolved in a mixed binary solution consisted of propionic acid and methanol with PEG (15 wt%) aqueous solution. The progress of reactions was monitored by FT-IR spectroscopy. The Lao scao.2Mn03 gel powders were annealed at various temperatures. The structural changes were investigated by FT-IR, CP/MAS $^{ 13}$C solid state NMR spectroscopy and XRD. The thermochemical property, particle characterization, microstructure of sintered sample, and cation composition of gel powder were studied by TG/DTA, FE-SEM and ICP-AES. The magnetic characterizations were identified through measurement of magnetic moment by VSM.

• Polymer(Korea)
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• v.31 no.1
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• pp.74-79
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• 2007

Polypyrrole (PPy) was made by an emulsion polymerization using iron (III) chloride ($FeCl_3$) as an initiator and dodecyl benzene sulfuric acid (DBSA) as an emulsifier and dopant. Poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) was sulfonated by chlorosulfonic acid (CSA). The cathode was composed of $PPy^+DBS^-$ complex, conductor powder, and PPO or sulfonated poly (2,6-dimethyl-1,4-phenylene oxide) (SPPO) as a binder or dopant. The charge-discharge performance of $PPy^+DBS^-/SPPO$ cathode was increased as the extent of about 50%, than $PPy^+DBS^-/PPO$. This is because SPPO played a role as a binder as well as a dopant. In addition, sulfonation brings out the increase of miscibility between PPy and SPPO, and the increase of contact area between cathode and electrolyte.

• Current Photovoltaic Research
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• v.2 no.4
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• pp.177-181
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• 2014

$Cu_2ZnSn(S_xSe_{1-x})_4$ (CZTSSe) absorber thin films were prepared on Mo coated soda lime glass substrates by sulfo-selenization of sputtered stacked Zn-Sn-Cu precursor thin films. The Zn-Sn-Cu precursor thin films were sulfo-selenized inside a graphite box containing S and Se powder using rapid thermal processing furnace at $540^{\circ}C$ in Ar atmosphere with pre-treatment at $300^{\circ}C$. The effect of different S/Se ratio on the structural, compositional, morphological and electrical properties of the CZTSSe thin films were studied using XRD (X-ray diffraction), XRF (X-ray fluorescence analysis), FE-SEM (field-emission scanning electron microscopy), respectively. The XRD, FE-SEM, XRF results indicated that the properties of sulfo-selenized CZTSSe thin films were strongly related to the S/Se composition ratio. In particular, the CZTS thin film solar cells with S/(S+Se)=0.25 shows best conversion efficiency of 4.6% ($V_{oc}$ : 348 mV, $J_{sc}$ : $26.71mA/cm^2$, FF : 50%, and active area : $0.31cm^2$). Further detailed analysis and discussion for effect of S/Se composition ratio on the properties CZTSSe thin films will be discussed.

• Korean journal of food and cookery science
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• v.13 no.5
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• pp.639-647
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• 1997

The hypoglycemic effects of five Korean wild vegetables, Aralia continentalis (A. con.), Castanea crenata (C. cre.), Xanthium strumarium (K, str.), Alisma canaliculatum (A. can,) and Eupatorium chinense var. simplicifolium for tripartium (E. tri) which have been utilized for the traditional remedies were investigated in this study. Diabetes mellitus was induced in male Sprague-Dawley rats by injections of streptozotocin (STZ) into the tail veins at a dose of 45 mg/kg. Five groups of STZ-induced diabetic rats were fed one of each experimental diet containing 10% of the Korean wild vegetable powder and normal and STZ-control rats were fed the control diet for five weeks. The body weight change, feed efficiency ratio (FER) and organ weights were compared. The plasma levels of glucose, protein, cholesterol, HDL-cholesterol, triglyceride, free fatty acid, and aminotransferase activity were determined. Mineral (Ca, K, Mg, Na, Cu, Fe, Mn and Zn) contents of the Korean wild vegetables were analyzed. The body weight gain was higher in normal, C. cre., A. can. and E. tri. groups than in the diabetic control group. The FER of C. cre., A. can. and E. tri. groups was significantly higher (p.＜0.05) than that of diabetic control group. Liver weight was heavier in A. con., X. str. and A. can. groups compared with the diabetic control group. The weights of kidney were lighter in all five Korean wild vegetable groups than in the diabetic control group. After five weeks, the plasma glucose level tends to be decreased in A. con., A. can. and E. tri. groups. Plasma cholesterol level was decreased the Korean wild vegetables except for X. str. group. Plasma HDL- cholesterol level was significantly higher in A. con., A. can. and E. tri. groups compared with the diabetic control group. Plasma triglyceride and free fatty acid levels were significantly higher in X. str. group compared with the diabetic control group. Mineral contents were higher in E. tri. (Ca, K, Na and Fe). The results suggest that the intakes of A. con., A. can. and E. tri. have a hypoglycemic effect in diabetic rats showing the possibility as the valuable food resources for the prevention of diabetic mellitus.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.2
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• pp.23-33
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• 1991

Mn - Zn Ferrite has the natural characteristics of incongruent melting and the zinc oxide evaporation while the crystal is being grown. As a result of these, it comes into existence to be a non-uniform distribution of cations along the crystal growth axis and also Pt particles are usually precipitated into the crystals in Bridgman method since the melt zone is maintained for a long time in the crucible. These have bad effects on the magnetic properties of ferrites. But, to overcome these faults and then acquire the better single crystals. new modified growth method was developed and the growth factors were investigated as following: melt height in the crucible, surface tension and density of melt, the behavior of melt at interface, the shapes of crucible and solid -liquid interface, powder feeding rate, and the crystal growing speed. In additon, when we analyzed the compositional fluctuations of grown crystals, they were supressed within 1.5 mol% $Fe_20_3$, 2 mol% MnO, ZnO respectively with comparing to initial composition of crystal and the microstructures of crystals on the(110) plane were observed by optical microscope through the chemical etching technique and the magnetic properties were determined.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.6
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• pp.303-308
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• 2017

The $FeCl_3$ waste solution used to etch various metals contains valuable metal such as nickel. In this study, we recovered as high purity nickel carbonate crystalline powders from nickel-containing etching waste solution after regeneration of iron chloride. Firstly we eliminated about of the iron impurities under the condition of pH 4 using 5 % NaOH aqueous solution and then removed the remaining impurities such as Ca, Mn and Zn etc. by using solvent extractant D2EHPA (Di-(2-ethylhexyl) phosphoric acid). Thereafter, nickel carbonate powder having a purity of 99.9 % or more was obtained through reaction with sodium carbonate in a nickel chloride solution.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.2
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• pp.236-242
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• 1989

In order to investigate the effects of hot corrosion on the creep rupture properties and creep life of 304 stainless steel being used as tube materials of heavy oil fired boiler, the creep rupture tests were carried out at temperature 630.deg.C, 690.deg.C and 750.deg.C in static air for the specimens with or without coating of double layer corrosives according to the new hot corrosion test method simulating the situation commonly observed on superheater tubes of the actual boiler. The double layer corrosives are 85% V$_{2}$O$_{5}$ + 10% Na$_{2}$So$_{4}$ + 5% Fe$_{2}$O$_{3}$ as the inner layer corrosive being once melted at 900.deg. C and crushed to powder, and 10% V$_{2}$O$_{5}$ + 85% Na$_{2}$SO$_{4}$ +5% Fe$_{2}$O$_{3}$ as the outer layer corrosive. As results, in the specimen coated with the double layer corrosives, the rupture strength was extremely lowered and showed a large difference each other. The rupture ductility also lowered remarkably as a result of the brittle fracture mode due to hot corrosion. These results indicate that hot corrosion could essentially alter the creep fracture mechanism. From the metallographic observation, it was clarified that the rupture life of 304 stainless steel subjected to hot corrosion was chiefly determined by the behavior of the aggressive intergranular penetration of sulfides.des.