• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.354-359
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• 2003

The microwave dielectric characteristics of (1-x)(Al$\_$$\frac{1}{2}$/Ta$\_$$\frac{1}{2}$/)O$_2$-x(Mg$\_$1/3/Ta$\_$2/3/)O$_2$ (0$\leq$x$\leq$1.0) ceramics were investigated by crystalstructure, variations of ionic polarizability, and microstructures. As x increased, (1-x)(Al$\_$$\frac{1}{2}$/Ta$\_$$\frac{1}{2}$/)O$_2$-x(Mg$\_$1/3/Ta$\_$2/3/)O$_2$ transformed to tetragonal structure. Because the ionic radius of (Mg$\_$1/3/Ta$\_$2/3/)$\^$4+/was slightly bigger than one of (Al$\_$$\frac{1}{2}$/Ta$\_$$\frac{1}{2}$/)$\^$4+/, the cell parameters increased with increase of (Mg$\_$1/3/Ta$\_$2/3/)O$_2$concentration and coincided with prediction of the molecular additivity rule. As x increased, the compositions revealed ordered phase and were of single phase above 60 mol%. The increase of the ordered phase and grain size enhanced the Q and when ordering was completed at x over 0.6, the grain size was major factor for the increase in the a. Though the grain size increased, however, the porosity deteriorated the q. Therefore, the a depended on the order/disorder, the porosity, and the grain size in regular order.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.220-221
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• 2003

Equiatomic FePt and CoPt alloy thin films have received considerable attention as possible magnetic and magneto-optic recording because of their high magnetic anisotropy energy and high coercivity. The high coercivity in these thin films is due to the presence of finely dispersed ordered FePt phase mixed with disordered FePt phase. However, a high temperature treatment, either substrate heating during deposition or post annealing, is needed to obtain the ordered L1$\_$0/ phase with high value of magneto crystalline anisotropy. Recent microstructural studies on these films suggest that the average grain size ranges from 10-50 nm and the grains are magnetically coupled between each other. On the other hand, the ultrahigh-density magnetic recording media with low media noise imposes the need of a material, which consists of magnetically isolated grains with size below 10 nm. The magnetic grain isolation can be controlled by the amount of additional non-magnetic element in the system which determines the interparticle separation and therefore the interparticle interactions. Recently, much research work has been done on various non-magnetic matrices. Preliminary studies showed that the samples prepared in B$_2$O$_3$ and Carbon matrices have shown strong perpendicular anisotropy and fine grain size down to 4nm, which suggest these nanocomposite films are very promising and may lead to the realization of a magnetic medium capable of recording densities beyond 1 Tb/in$^2$. So, in this work, the effect of Carbon doping on the magnetic properties of FePt nanoparticles were investigated.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.8.2-8.2
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• 2011

This talk demonstrates diverse patterned structures utilizing in-situ self-organization and phase separation of the materials into an ordered fashion. The patterned structures in this talk include electrospun nanofibers and electrosprayed microparticles embedding small particles. The positions of the small particles are in-situ controlled during the electrohydrodynamic process by the interaction with the polymer matrix. Another topic of the talk includes selective deposition of spin-coated materials on a corrugated surface that was prepared by buckling of polymer thin films. Solution are strong tendency to be positioned in the trench area of the surface, which facilitates the fabrication of micropatterns of diverse materials.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.537-537
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• 2012

We have studied a fabrication of vapor phase polymerized Poly(3,4-ethylenedioxythiophene) (PEDOT) nanowire arrays for the first time. The vapor-phase polymerization (VPP) technique is a bottom-up processing method that utilizes the organic arrangement of macromolecules to easily produce ordered aggregates, including on the nanoscale, or prepare thin films of self-assembled molecules, micropatterns, or modified microstructures of pure conducting polymers. Also, liquid-bridge-mediated nanotransfer molding (LB-nTM), which was reported as a new direct patterning method recently, is for the arrayed formation of two- or three-dimensional structures with feature sizes as small as tens of nanometers over large areas up to 4 inches across and is based on the direct transfer of various materials from a mould to a substrate through a liquid bridge between them. The PEDOT nanowires grown by VPP method and transferred on a substrate to use LB-nTM method have been fabricated to single crystal PEDOT nanowires investigated Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED), X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and electrical properties.

• Transactions of Materials Processing
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• v.13 no.6 s.70
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• pp.522-527
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• 2004

Permalloys were successfully fabricated by melt drag casting in the present study, and their microstructure and consequent magnetic properties have been investigated as a function of Si content. In order to understand the relationship between magnetic properties and Si content, microstructure and texture were observed and phase analysis were performed by TEM. The effective permeability went through a maximum value at $2\%$ Si and then decreased with increasing Si content. Increasing Si content enlarged grain size, which resulted in improvement of permeability. However, over-added Si caused the formation of $Ni_3Fe$ order phase so that $5\%$ Si added permalloys had the smallest permeability.

• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.694-698
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• 2009

The $Co_{3}Ti$ phase hardens appreciably by the fine precipitation of disordered fcc Co-rich phase upon aging after quenching from solution annealing temperature. Transmission electron microscope (TEM) observations revealed that the precipitates are platelet in shape, lying nearly parallel to the {100} planes of the $Ll_{2}$-ordered matrix, and perfectly coherent with the matrix lattice at the beginning of aging. The high temperature strength increases appreciably with the fine precipitation of disordered Co-rich phase over the whole temperature range investigated. TEM observations of the under-aged and deformed alloys revealed that superdislocations are pinned by precipitates indicating an attractive interaction between dislocations and precipitates. In the over-aged state, thin twins are introduced in the fcc Co-rich precipitates during deformation.

• International conference on construction engineering and project management
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• 2005.10a
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• pp.1154-1157
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• 2005

This report is to do design management for constructability review of high quality exposed concrete, which is used increasingly in recent. To secure systematic management at design phase, we reviewed each definition and work at each design phase, we define high quality exposed concrete, a part of architectural concrete, as "an exposed concrete which has well ordered joint & is in pursuit of smooth surface." We reviewed requirements and influential factor to obtain High quality finishing surface and compared construction process of high quality exposed concrete with that of other finishing method. Management method at each design phase for constructability review to meet additional works and requirements is presented.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.168.2-168.2
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• 2015

We observed the temperature-dependent evolution and behavior of P3HT type-II phase during a real time annealing process from a cryo-cooled low temperature in the absence and presence of an Al electrode. A poly (3-hexylthiophene) (P3HT) Type-II phase in the P3HT:PCBM films started to form near at $-10^{\circ}C$, regardless of Al layer presence. In the absence of an Al layer, type-II phase was extinct at $30^{\circ}C$. However, the extinction temperature was extended to $50^{\circ}C$ in the presence of the Al layer. Simultaneously, combined with the type-II phase, a 1:3 ordered P3HT type-II (1/3,0,0) super-lattice peak evolved. These type-II domains tended to be formed near the Al electrode layer with higher aligned status than host P3HT crystals.

• Korean Journal of Optics and Photonics
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• v.7 no.3
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• pp.219-226
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• 1996

The wave-particle duality of light plays important role in quantum optics and it often produces a result different from that of classical wave theory. In this paper, we study the intensity and phase fluctuation of light which show certain change after light goes through a beam splitter, and show the difference between the classical and quantum theory. We show quantitatively that the uncertainty of phase increases at the output of a beam splitter due to the contribution of vacuum fluctuation, even though classical theory predicts no such change in phase fluctuation. The expectation values of normally ordered operators are introduced where the vacuum effect is naturally eliminated, and it is shown that the classical informations are recovered in this way. Analysis on the expectation values produces a distinction between measured phase and inferred phase values and they are related through the contribution of vacuum field.

• Korean Journal of Materials Research
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• v.21 no.3
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• pp.168-173
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• 2011

Precipitation of the ordered icosahedral quasicrystal in Mg-6wt%Zn-1wt%Y alloy has been characterized by transmission electron microscopy observations. The lamellar-type icosahedral qusicrystal phases (I-phase) with the face-centered icosahedral (FCI) structure are observed in alloy after solution treatment at $550^{\circ}C$. In the alloy annealed at $400^{\circ}C$, polygon-shaped I-phases are observed in the ${\alpha}$-Mg matrix. The interfaces of the I-phase with the matrix are facetted and the facets are on five-fold and two- fold plane of the I-phase. The orientation relationship of the I-phase with the matrix is determined to be $[I5]_I//[001]_{Mg}$, $(2f)_I//(2\overline{1}0)_{Mg}$ and $[I2]_I//[311]_{Mg}$, $(5f)_I//(0\overline{1}1)_{Mg}$. The icosahedral grains are occasionally found to be twinned with one of the five-fold axis as the twin axis. The twin boundaries appear to be fairly straight and perpendicular to the fivefold twin axis. The icosahedral twin can be expressed as a rotation of $63.4^{\circ}$ or $116.62^{\circ}$ around two fold zone axis.