• Journal of the Korean Magnetics Society
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• v.26 no.3
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• pp.76-80
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• 2016

CoSiB is the amorphous ferromagnetic material and multilayer consisting of CoSiB and Pd has perpendicular magnetic anisotropic property. PMA has strong advantages for STT-MRAM. Moreover, amorphous materials have two advantages more than crystalline materials: no grain boundary and good thermal stability. Therefore, we studied the magnetic properties of multilayers consisting of the $Co_{75}Si_{15}B_{10}$ with PMA. In this study, we investigated the magnetic property of the [CoSiB (3, 4, 5, and 6) ${\AA}$/Pd(11, 13, 15, 17, 19,and $24{\AA})]_5$ multilayers and found the annealing temperature dependence of the magnetic property. The annealing temperature range is from room temperature to $500^{\circ}C$. The coercivity and the saturation magnetization of the CoSiB/Pd multilayer system have a close association with the annealing temperature. Moreover, the coercivity especially shows a sudden increasing at the specific annealing temperature.

• Progress in Superconductivity
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• v.10 no.1
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• pp.35-39
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• 2008

By using the hybrid physical-chemical vapor deposition (HPCVD) technique, we have fabricated $MgB_2$ thick films on $Al_{2}O_3$ substrates with various impurity layers of Ni, Ti, and SiC. We have found a significant enhancement of the critical current density ($J_c$) for $MgB_2$ films grown on impurity layered substrates, indicating that additional impurity layers were provided as possible pinning sites by chemical doping in $MgB_2$ films. All samples doped by Ni, Ti, and SiC were observed to have high superconducting transition temperatures of 39 - 41 K. The $J_c$ of $MgB_2$ films grown on SiC impurity layered substrates showed three times higher than that of undoped films at high magnetic fields above 1 T.

• Journal of the Korean Magnetics Society
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• v.4 no.1
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• pp.12-19
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• 1994

The crystallization behavior of the amorphous $Fe_{73.5}Cu_{1}Nb_{3}Si_{16.5}B_{6}$ alloy with isothermal annealing at $552^{\circ}C$ was studied by $M\"{o}ssbauer$ spectroscopy. The amorphous phase was revealed to coexist together with $Do_{3}-FeSi$ nanocrystalline and Cu-duster in annealed alloys by $M\"{o}ssbauer$ spectrum analysis. At the early stage of crystallization, Si content of FeSi is high due to the creation of Cu-cluster, and decreases with annealing until 60 minutes, which results in the increase in the mean hyperfine field of FeSi, and thereafter keeps constant. After 60 minutes, the decrease in the mean hyperfine field of the residual armrphous, in spite of a slight change in the volume fraction of the FeSi and the residual armrphous, is caused by the increase in the content of Nb and B in residual amorphous phase. Both directions of the hyperfine field, those of the FeSi and the residual amorphous, become randomly oriented in about 60 minutes. For FeSi and Cu-duster, the Avrami exponents are 0.51 and O.65, the activation energies are 2.35 eV and 2.44 eV, and the incubation times are 2.4 minutes and 0.8 minutes respectively. Earlier formation of Cu-duster than that of FeSi is coincidence with the fact that Cu atom promotes the nucleation of the FeSi.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.291-294
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• 1989

The 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 microscpy. Amouphous $Fe_{78}B_{13}Si_9$ alloy was annealed isothermally for 5 to 1200 min. between $300^{\circ}C$ and $540^{\circ}C$. It has been found that close relation between relative resistivity and X-ray diffraction pattern showed. The crystalline peaks of ${\alpha}$-(Fe, Si) and $Fe_2B$ are detected by X-ray experiment. The crystalline phases observed by TEH show ${\alpha}$-(Fe, Si) and $Fe_2B$ 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.

• Journal of the Korean Ceramic Society
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• v.28 no.10
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• pp.767-776
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• 1991

Effects of the additions of SiB4 as burnable poison to UO2 on the green density, densification, interdependence between density-grain growth and microstructure of sintered UO2 were studied. UO2 pellets were sintered in flowing hydrogen, at temperature 1200, 1350, 1500, and 168$0^{\circ}C$ for 3 hours and at 168$0^{\circ}C$ for 0, 1, 3, and 10 hours, respectively. Green densities were in the range of about 4.5~5.4 g/㎤, and decreased as the amount of SiB4 increased when green pellets were made by with use of a double action press at 1000 kg/$\textrm{cm}^2$. The density of sintered UO2 pellets was around 92~94% of the theoretical density and did not change significantly as the amount of SiB2 addition increased. However, the density of sintered pellets decreased with the increase in SiB4. The grain growth could be characterized in terms of two stages: Grain growth occurred with the increasing density in the first stage, whereas the second stage was characterized by the grain growth without increasing of density. A liquid phase was observed at grain boundaries and grain edges in the microstructure of sintered UO2 pellets with 5000 ppm and 10,000 ppm SiB4. This liquid, possible formed at about 168$0^{\circ}C$, did not enhance the shrinkage, but appeared to accelarate the grain growth. It seems that the second stage grain growth was due to the presence of pressurized insoluble trapped gas in isolated pores.

• Korean Journal of Optics and Photonics
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• v.3 no.4
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• pp.258-265
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• 1992

A low loss optical waveguide of $P_{2}O_{5}-SiO_{2}$on Si substrate is produced by using the chemical vapour deposition method of $SiO_2$ thin films used in Si technology. Propagation loss of the waveguide layer was 1.65 dB/cm as produced and reduced down to 0.1 dB/cm after heat treatment at $1100^{\circ}C$. By using laser lithography and reactive ion etching method $P_{2}O_{5}-SiO_{2}$ waveguide was produced and subsequently annealed at $1100^{\circ}C$.As a result of this annealing the shape of the waveguide core was changed from rectangular to semi-circular form, and the propagation loss was reduced as down to 0.03 dB/cm at 0.6328$\mu$m and 0.04dB/cm at 1.53$\mu$m. We think that the mechanism of the reduction in propagation loss during the heat treatment is the following: 1) The hydrogen bonding in waveguide layer, which causes absorption loss, is dissociated and diffused out. 2) The roughness of the interface and the micro-structure of the waveguide layer is removed. 3) The irregularities in the cross-sectional shape of the waveguide which was induced during the lithographic process were disappeared by flowing of the waveguide core.

• Journal of Korea Foundry Society
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• v.28 no.1
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• pp.25-30
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• 2008

To develop a functionally graded microstructure of cylindrical liner, effect of centrifugal casting parameters such as pouring temperature of hyper-eutectic Al-Si alloy melt, mold pre-heating temperature, and rotational frequency of mold on distribution of primary Si particles across wall thickness were investigated. Segregation tendency of Si particles toward inner side of cylindrical liner increased as the increase of rotational frequency of mold, pouring temperature of melt and mold pre-heating temperature. Especially, distribution density of primary Si particles within 1.5 mm from inner surface of cylindrical liner was above 35% under the centrifugal casting condition of $750^{\circ}C$ melt pouring temperature, $300^{\circ}C$ mold pre-heating temperature, and 2500 rpm mold rotational frequency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.67-70
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• 2002

The composites were fabricated 61vol% ${\beta}$-SiC and 39vol.% $TiB_2$ powders with the liquid forming additives of 8, 12, 16wt% $Al_2O_3+Y_2O_3$ by pressureless annealing at $1650^{\circ}C$ for 4 hours to form YAG. The result of phase analysis of composites by XRD revealed ${\alpha}$-SiC(6H), $TiB_2$, and YAG($Al_5Y_3O_{12}$) crystal phase. The relative density and the Young's modulus showed the highest value of 82.29% and 54.60 Gpa for composites added with 16wt% $Al_2O_3+Y_2O_3$ additives at room temperature.

• Composites Research
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• v.16 no.3
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• pp.25-31
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• 2003

In this work the effect of surface treated SiC on thermal stability and mechanical interfacial properties of carbon fiber/epoxy resin composites. The surface properties of the SiC were determined by acid/base values and contact angles. The thermal stabilities of carbon fiber/epoxy resin composites were investigated by TGA. The mechanical interfacial properties of the composites were studied in ILSS, critical stress intensity factor ($\textrm{K}_{IC}$), and critical strain energy release rate($\textrm{G}_{IC}$) measurements. As a result, the acidically treated SiC(A-SiC) had higher acid value than untreated SiC(V-SiC) or basically treated SiC(B-SiC). According to the contact angle measurements, it was observed that chemical treatments led to an increase of surface free energy of the SiC surfaces, mainly due to the increase of the specific(polar) component. The mechanical interfacial properties of the composites including ILSS, $\textrm{K}_{IC}$, and $\textrm{G}_{IC}$ had been improved in the specimens treated by chemical solutions. These results were explained that good wetting played an important role in improving the degree of adhesion at interfaces between SiC and epoxy resin matrix.

• Journal of the Korean Magnetics Society
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• v.2 no.3
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• pp.216-221
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• 1992

Annealing effects on the permeability aftereffect(disaccommodation) of liquid quenched single strip $Fe_{73.5}Cu_1Nb_3Si_{16}B_{6.5}$ alloys were investigated with pulse method. The initial susceptibility X, $B_{10},$ (the flux density at 10 Oe) and disaccommodation intensity D (D = [X(1 s)-X(64 s)]/X(1 s), where X(1 s) and X(64 s) are the susceptibility of 1 and 64 s of rest time after A. C. demagnetization) were about 800, 0.8 T and 16 %, respectively. The soft magnetic properties were improved with isothermal annealing for 1 hour at $300{\sim}600^{\circ}C.$ X, $B_{10},$ and D at $570^{\circ}C$ of optimum annealing temperature were 15000, 1.2 T and 1.1 %, respectively. The origin of the change of characteristics were examined with fine crystalline structure and magnetostriction.