• Journal of the Korean Magnetics Society
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• v.18 no.6
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• pp.227-231
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• 2008

Magnetic and structural properties of CoFeZr alloy films as a function of Zr concentration and magnetoresistive properties of spin valves incorporated with amorphous CoFeZr alloy films have been studied. Magnetization and coercivity of CoFeZr alloy films decreased as the Zr content increased. A single amorphous CoFeZr phase was formed when the Zr content is about above 18 at%. Magnetoresistance ratio and exchange coupling field of spin valves with amorphous CoFeZr were reduced slightly as compared with spin valves with CoFe because the resistance of amophous CoFeZr is higher than that of crystalline CoFe. However, the ${\Delta}{\rho}$ of spin valves with amorphous CoFeZr was improved due to reduction of current shunting.

• Polymer(Korea)
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• v.36 no.6
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• pp.677-684
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• 2012

Injection molding process is a popular polymer processing involving plasticizing and enforcing the material flow into the mold. A polymer material shrinks according to temperature variations during the shaping process, and subsequently molding shrinkage developed. Developed deflections or warpages after molding process in part are caused by residual stress relaxation contained in the part. Adding inorganic materials or fibers such as glass and carbon to control shrinkage and enhance warpage resistance are common. In this study, warpages according to part design have been investigated through experiment. Warpages for molding conditions and mold designs such as gate locations were measured. Warpages along flow direction and perpendicular to the flow direction were also measured. Warpages near gate and far from gate were compared. Glass fiber reinforced crystalline polymers, PP and PA66 have been used in this experiment. Glass fiber reinforced crystalline polymers showed large warpage compared with glass reinforced amorphous polymers. Warpages in crystalline polymers were less influenced by molding conditions compared with amorphous polymers, however warpages of crystalline polymers significantly depend on part design.

• Economic and Environmental Geology
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• v.36 no.3
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• pp.177-189
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• 2003

The main purposes of this study are to utilize mineralogical studies such as optical microscope, XRD and SEM/EDS analyses to characterize the oxidation of sulfide minerals and the mechanisms controlling the movement of dissolved metals from waste rocks at the abandoned Seobo mine. Mineralogical research of the waste rocks confirms the presence of anglesite, covellite, goethite, native sulfur and nsutite as secondary minerals, suggesting that these phases control the dissolved concentrations of As, Cu, Fe, Mn, Pb and Zn. The dissolved metals are precipitated, adsorbed and/or coprecipitated with(or within) Fe(Mn)-hydroxides and Mn(Fe)-hydroxides. The main phases of secondary mineral, Fe-hydroxide, can be classified as amorphous or poorly crystalline and more crystallized phases(e.g. goethite) by crystallinity. Amorphous or poorly crystalline Fe-hydroxide has relatively high As contents(9-24 wt.%). This poorly crystalline Fe-hydroxide changes toward more crystallized phase(e.g. goethite) which contains relatively low As(0.6-7.7 wt.%). These results are mainly due to the progressive release of As with the crystallization evolution of the As-trapping poorly crystalline Fe-hydroxides. It is also attributed to the differences of specific surface areas between the poorly crystalline Fe-hydroxides and well crystallized phases. The dissolved metals from waste rocks at Seobo mine area are naturally attenuated by a series of precipitation(as Fe, Mn, Cu, Pb), coprecipitation(Fe, Mn) and adsorption(As, Cu, Pb, An) reactions. The results of mineralogical researches permit to assess the environmental impacts of mine waste rocks in the areas, and can be used as a useful data to lay available mine restoration plan.

• Current Photovoltaic Research
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• v.3 no.4
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• pp.107-111
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• 2015

Current characteristic curve of an illuminated solar cell was used to determine its reverse saturation current density ($J_0$), ideality factor (n) and resistances, by using numerical diode simulation. High efficiency amorphous silicon, heterojunction crystalline Si (HIT), plastic and organic-inorganic halide perovskite solar cell shows n=3.27 for a-Si and n=2.14 for improved HIT cell as high and low n respectively, while the perovskite and plastic cells show n=2.56 and 2.57 respectively. The $J_0$ of these cells remain within $7.1{\times}10^{-7}$ and $1.79{\times}10^{-8}A/cm^2$ for poorer HIT and improved perovskite solar cell respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1988.10a
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• pp.5-7
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• 1988

Effect of isothermal aging on the crystallization of $Fe_{78}B_{13}Si_{9}$ metallic glass has been investigated by electrical resistivity, X-ray measurements, bending test, thermal analysis and transmission electron microscopy. Amorphous $Fe_{78}B_{13}Si_{9}$ alloy was annealed isothermally for 5 to 1200 mon. between 300 C and 540 C. It has been found that close relation between relative resistivity and X-ray diffraction pattern showed. The crystalline peak of $\alpha$-(Fe, Si) and Fe$_2$B are detected by X-ray experiment. The crystalline phases observed by TEM show $\alpha$-(Fe, Si) and Fe$_3$B with dendritic and cylindrical morphology, respectively. It has been also found that the embrittleness of aged samples rapidly increased with the crystallization and was shown before the crystallization.th the crystallization and was shown before the crystallization.

• Journal of Electrochemical Science and Technology
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• v.10 no.1
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• pp.82-88
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• 2019

Here, we report on nanocrystalline Si-Al-M (M = Fe, Cu, Ni, Zr) alloys for use as an anode for lithium-ion batteries, which were fabricated via a melt-spinning method. Based on the XRD and TEM analyses, it was found that the Si-Al-M alloys consist of nanocrystalline Si grains surrounded by an amorphous matrix phase. Among the Si-Al-M alloys with different metal composition, Ni-incorporated Si-Al-M alloy electrode retained the high discharge capacity of 2492 mAh/g and exhibited improved cyclability. The superior $Li^+$ storage performance of Si-Al-M alloy with Ni component is mainly responsible for the incorporated Ni, which induces the formation of ductile and conductive inactive matrix with crystalline Al phase, in addition to the grain size reduction of active Si phase.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.521-526
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• 2007

Density functional calculations have been performed for the reactions of perfluoroalkylsilane and alkylsilane with silica surfaces. The (100) and (111) surfaces of ${\beta}-cristobalite$ are used as two possible models of the hydroxylated amorphous silica surface. This is the crystalline phase of silica with density and refractive index closest to those of amorphous silica. Moreover, two ${\beta}-cristobalite$ surfaces have the two types of silanol groups, namely the single silanols and the geminal silanols. We investigate the possible adsorption structure and formation energy of perfluoroalkylsilane and alkylsilane molecules with two type of silanol groups. The results will be compared with cluster and slab model.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.3
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• pp.294-301
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• 1988

A study on the lattice damages and impurity depth profiles have been performed with BF2 ion implanted silicon materials. Electrical measurement, SIMS and TEM analysis techniques were used in order to identify the reverse annealing phenomena, impurity depth profiles and lattice damages. A typical reverse annealing phenomena were shown at the dose of 1x10**15/cm\ulcorner and non-reverse annealing at the dose of 5x10**15/cm\ulcorner This was explained with the formation of the amorphous region at BF2+ ion implantation with high dose. That is, the amorphous reigons were recrystallized centrated at certain regions were measured by SIMS technique. The dislocation loops-like crystalline defects were observed with TEM cross sections, which were formed at the lattice damaged region during annealing process.

• Journal of Sensor Science and Technology
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• v.21 no.5
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• pp.385-388
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• 2012

This paper describes the synthesis and characterization of graphene by RTA process. Amorphous 3C-SiC were deposited using APCVD for carbon source and Ni layer were employed for transition layer. Various parameters of the ramping speed, the annealing time and the cooling speed are evaluated for the optimized combination allowed for the reproducible fabrication of graphene using 3C-SiC thin film. For analysis of crystalline Raman spectra was employed. Transferred graphene shows a high IG/ID ratio of 2.73. SEM and TEM images show the optical transparency and 6 carbon network, respectively. Au electrode deposited on the transferred graphene shows linear I-V curve and its resistance is 358 ${\Omega}$.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 1979.10a
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• pp.243.3-244
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• 1979

Low molecular weight endo-glucanase fraction of cellulase from Trichoderma reesei was purified using Sephadex G-100 and concanavalin A-Sepha-rose 4B affinity chromatography. Its biochemical characteristics including pH profile, temperature profile and kinetic behavior were studied. The optimum conditions for enzymatic reaction were pH 6.0 and $5^{\circ}C.$ The activation energy for CMC (carboxymethylcellulose) was 10,800 cal/mole. Its adsorption to amorhous and crystalline cellulose was observed. Adsorption to amorphous cellulose was more rapid and greater than that of crystalline cellulose. Reconstitution study was performed. Significance of low molecular weight endo-glucanase on cellulose hydrolysis will be further discussed.