• The Journal of the Petrological Society of Korea
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• v.20 no.1
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• pp.61-75
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• 2011

Mantle-derived xenoliths, corresponding to spinel harzburgite and lherzolite in alkali basalts from Jeju Island, are metasomatized to various extents. They contain distinctive secondary orthopyroxene, forming corona or poikilitic textures. It clearly indicate that this secondary orthopyroxene has been produced at the expense of olivine along the grain boundaries and margins, suggesting silica-enriched metasomatic melt infiltrated through grain boundaries. Based on the geotectonic characteristics of Jeju Island and textural characteristics and major elements composition of mantle xenoliths, it is suggested that the silica-enriched melt/fluid could have derived from the ancient subducted slab, possibly in the mantle wedge, implying that the high $SiO_2$ activity in the lithospheric upper mantle beneath Jeju Island at that time.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.1
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• pp.31-35
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• 2002

Abstract Spinel powder having a particle size of 0.9$\mu$m was calcined for 30 min at $1300^{\circ}C$, followed by ball milling for 4h, to obtain the spinel particle size of 3.29$\mu$m. The die-pressed spinel was presintered at $1100^{\circ}C$ for 2h and then lanthanum aluminosilicate glass was infiltrated at $1080^{\circ}C$ for 0~2 h to investigate the penetration kinetics in glass-spinel composite. The infiltration distance is parabolic in time due to capillarity. The strength and the fracture toughness of glassspinel composites were 317 MPa and 3.56 MPa $m^{1/2}$ respectively and dual microstructure of column (needle) and polygonal shapes as a result of recrystallization was observed due to the high calcination temperature.

• Korean Journal of Crystallography
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• v.7 no.1
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• pp.81-87
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• 1996

The mechanism of silicon incorporation has been analyzed for the boat-grown GaAs crystals on the basis of phase equilibrium in the Ga and As system. Comparison was made between silicon concentrations calculated from the thermodynamics of incorporation reaction and carrier concentrations measured from van der Pauw method. For the 1-T HB(single temperature zone horizontal Bridgman) crystals, calculated concentrations were 5.3 ×10 15 (atoms/cm3), measured as 9.8 ×10 15(/cm3) at the seed part. They were calculated to be 1.1 ×10 16(atoms/cm3) and measured as 1.5 ×10 16(/cm3) for the 2-T(double temperature zone) HB crystals. On the other hand, it was found to be closer between the calculated and measured silicon concentrations for the VGF(vertical gradient freeze) crystals, which were grown within half the run time compared with 1-T or 2-T HB method.

• Journal of the Korean Magnetics Society
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• v.17 no.3
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• pp.141-146
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• 2007

A new class of LC-resonator for micro magnetic sensor device was invented and fabricated by means of MEMS technique. The micro LC-resonator consists of a solenoidal micro-inductor with a bundle of soft magnetic microwire cores and a capacitor connected in parallel to the micro-inductor. The core magnetic material is a tiny glass coated $Co_{83.2}B_{3.3}Si_{5.9}Mn_{7.6}$ microwire fabricated by a glasscoated melt spinning technique. The core materials were annealed at various temperatures $150^{\circ}C,\;200^{\circ}C\;,250^{\circ}C\;,$ and $300^{\circ}C$ for 1 hour in a vacuum to improve soft magnetic properties. The solenoidal micro-inductors fabricated by MEMS technique were $500{\sim}1,000{\mu}m$ in length with $10{\sim}20$ turns. The changes of inductance as a function of external magnetic field in micro-inductors with properly annealed microwire cores were varied as much as 370%. Since the permeability of ultra soft magnetic microwire is changing rapidly as a function of external magnetic field. The inductance ratio as well as magnetoimpedance ratio (MIR) in a LC-resonator was varied drastically as a function of external magnetic field. The MIR curves can be tuned very precisely to obtain maximum sensitivity. A prototype magnetic sensor device consisting of the developed microinductors with a multivibrator circuit was test successfully.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.4
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• pp.277-291
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• 2021

A mineral phase contained in a rock sample can be categorized into several crystal populations with distinct origins and crystal growth histories. A detailed textural and mineralogical investigation on a clinopyroxene megacryst-bearing porphyritic dike with glassy chilled margins (tachylyte) in the southeastern Ulleung Island was conducted to decipher its crystal populations. During this study, we have measured glass and mineral major element compositions using electron microprobe analyzer. Tachylyte has a homogeneous trachyandesitic composition without any significant alteration characteristics, suggesting that its composition may represent the original melt composition of the dike. Clinopyroxene and plagioclase larger than 0.5 mm are antecrysts equilibrated with a more primitive melt composition than trachyandesitic tachylyte. Meanwhile, clinopyroxene and plagioclase microlites (<0.5mm) are regarded as primocrysts crystallized in-situ. According to our results, all clinopyroxenes in the Stage I Dodong Basalt are sectored into basal and prismatic parts, whose compositional ranges systematically vary: [Mg+Si+Fe]_basal ↔ [Al+Ti+Na]_prism. Therefore, we suggest that the effect of the elemental partitioning caused by the clinopyroxene sector zonation in Stage I volcanism should be considered in the future works.

• Journal of Powder Materials
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• v.28 no.4
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• pp.293-300
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• 2021

We investigate the effect of phosphorous content on the microstructure and magnetic properties of Fe_83.2Si_5.33-0.33xB_10.67-0.67xP_xCu_0.8 (x = 1-4 at.%) nanocrystalline soft magnetic alloys. The simultaneous addition of Cu and P to nanocrystalline alloys reportedly decreases the nanocrystalline size significantly, to 10-20 nm. In the P-containing nanocrystalline alloy, P atoms are distributed in an amorphous residual matrix, which suppresses grain growth, increases permeability, and decreases coercivity. In this study, nanocrystalline ribbons with a composition of Fe_83.2Si_5.33-0.33xB_10.67-0.67xP_xCu_0.8 (x = 1-4 at.%) are fabricated by rapid quenching melt-spinning and thermal annealing. It is demonstrated that the addition of a small amount of P to the alloy improves the glass-forming ability and increases the resistance to undesirable Fe_x(B,P) crystallization. Among the alloys investigated in this work, an Fe_83.2Si₅B₁₀P₁Cu_0.8 nanocrystalline ribbon annealed at 460℃ exhibits excellent soft-magnetic properties including low coercivity, low core loss, and high saturation magnetization. The uniform nanocrystallization of the Fe_83.2Si₅B₁₀P₁Cu_0.8 alloy is confirmed by high-resolution transmission electron microscopy analysis.

• Korean Journal of Materials Research
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• v.33 no.12
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• pp.525-529
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• 2023

β-Ga₂O₃ has become the focus of considerable attention as an ultra-wide bandgap semiconductor following the successful development of bulk single crystals using the melt growth method. Accordingly, homoepitaxy studies, where the interface between the substrate and the epilayer is not problematic, have become mainstream and many results have been published. However, because the cost of homo-substrates is high, research is still mainly at the laboratory level and has not yet been scaled up to commercialization. To overcome this problem, many researchers are trying to grow high quality Ga₂O₃ epilayers on hetero-substrates. We used diluted SiH4 gas to control the doping concentration during the heteroepitaxial growth of β-Ga₂O₃ on c-plane sapphire using metal organic chemical vapor deposition (MOCVD). Despite the high level of defect density inside the grown β-Ga₂O₃ epilayer due to the aggregation of random rotated domains, the carrier concentration could be controlled from 1 × 10¹⁹ to 1 × 10¹⁶ cm^-3 by diluting the SiH4 gas concentration. This study indicates that β-Ga₂O₃ hetero-epitaxy has similar potential to homo-epitaxy and is expected to accelerate the commercialization of β-Ga₂O₃ applications with the advantage of low substrate cost.

• Journal of the Korean Ceramic Society
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• v.41 no.12 s.271
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• pp.939-945
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• 2004

Glasses of $SiO_2-B_{2}O_3-Al_{2}O_3-CaO-La_{2}O_3$ with various amounts of $La_{2}O_3$ were infiltrated into a porous alumina to make an alumina-glass composite. The infiltration characterization and bending strength of the composite were examined in terms of glass composition. $La_{2}O_3$ in the glass decreased the high temperature viscosity and this enhanced the wetting behaviour of this glass to alumina, and made glass infiltration easier. The infiltrated glass dissolved the alumina skeleton, and $Al_{2}O_3$ component in the glass melt reprecipitated on the alumina. The grain growth occurred to a specific crystal direction. The glass containing $20mole\%$ of $La_{2}O_3$ was crystallized after infiltration, and this enhanced the bending strength of the composite.

• Polymer(Korea)
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• v.30 no.4
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• pp.318-325
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• 2006

Polypropylene-clay nanocomposites were studied by the modification of clay with amino silanes to introduce covalent bonds in nanocomposites, and prepared by melt-compounding with polypropylene, clay modified with amino silanes and maleic anhydride grafted polypropylene. The . .structure and surface properties of modified clay were determined by x-ray diffraction, infrared spectrum, and solid-state $^{29}Si$ nuclear magnetic resonance spectrum. The modification of clay with aminosilanes led to the increase of the silicate interlayers to about $19.8{\AA}$, the weakening effects of hydroxy group at $3650cm^{-1}$ and the signal of amine groups at -69 ppm proved that the modification had taken place.

• Resources Recycling
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• v.17 no.2
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• pp.46-54
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• 2008

It is well known that PCB (Printed Circuit Board) is a complex mixture of various metals. In this study, pyro-metallurgical process was investigated to extract valuable metallic components from the PCB scrap. PCB scrap was shredded and oxidized to remove plastic materials, and then, quantitative analysis were made. 15 mass %$Al_2O_3-45$ mass %CaO-40 mass %$SiO_2$ and 32 mass %$SiO_2-20$ mass %$Al_2O_3-38$ mass %CaO-10 mass %MgO, were chosen as basic slag compositions which are determined based on the quantitative analysis of PCB scrap. During experiments a super kanthal rotating furnace was used to melt and separate metallic components. Moreover the revolution effect on was the recovery of valuable metals from PCB scrap also investigated.