• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.429-429
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• 2008

Li$[Ni_{1/2}Co_{1/2}]O_2$ powder were synthesized from co-precipitation spherical metal oxide, $[Ni_{1/2}Co_{1/2}](OH)_2$. The preparation of metal hydroxide was significantly dependent on synthetic conditions, such as pH, amount of chelating agent, stirring speed, etc. The optimized condition resulted in $[Ni_{1/2}Co_{1/2}](OH)_2$, of which the particle size distribution was uniform and the particle shape was spherical, as observed by scanning electron microscopy. Calcination of the uniform metal hydroxide with LiOH at higher temperature led to a well-ordered layer-structured Li$[Ni_{1/2}Co_{1/2}]O_2$, as confirmed by X-ray diffraction pattern. Also these materials have ${\alpha}-NaFeO_2$ ($R\bar{3}m$) structure. Due to the homogeneity of the metal hydroxide, $[Ni_{1/2}Co_{1/2}](OH)_2$, the final product, Li$[Ni_{1/2}Co_{1/2}]O_2$, was also significantly uniform, i.e., the average particle size was of about 10 to 15 ${\mu}m$ in diameter and the distribution was relatively narrow. As a result, the corresponding tap-density was also high approximately 2.41 $gcm^{-3}$, of which the value is comparable to that of commercialized $LiCoO_2$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.456-456
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• 2008

In the past few years, the deposition and characterization of cadmium sulfide semiconducting thin films has received a considerable amount of interest due to their potential application in the area of electronic and opto-electronic devices fabrications. Polycrystalline CdS thin films posses good optical transmittance, wide band-gap and electrical properties makes it as one of the ideal material for their application to solar cell fabrication. Cadmium sulfate thin films were deposited by the chemical bath deposition method using tartaric acid and triethanolamine as a complexing agent. Deposition parameters such as pH, temperature, deposition time and concentration of the reactant species were optimized so as to obtain reflecting, good adherent uniform thin films on the glass substrate. Reaction mechanism of the thin film formation is also reported. The crystallographic structure and the crystallite size were studied by the X-ray diffraction pattern. The optical band-gap of deposited film is identified by measuring the transmittance in the visible region. Temperature dependence of resistivity confirmed the semiconducting behavior of the film. Scanning electron micrographs (SEM) showed the presence of grain particles of size 50 nm.

• Journal of Energy Engineering
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• v.19 no.1
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• pp.16-20
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• 2010

In present work, tin-carbon mixtures by using carbon from pyrolyzed coffee seeds were synthesized. Synthesis methods includes simple mixing and chemical mixing. X-ray diffraction pattern indicated carbon and tin mixture peaks and scanning electron microscope images showed particles size of $12{\sim}85\;{\mu}m$ and shape. Charge discharge test were carried out. Tin-carbon mixture by chemical mixing indicated higher discharge capacity of 191 mAh/g than commercial carbon black(105 mAh/g) for 15cycles. Tin-carbon mixture by simple mixing indicated similar performance to carbon black.

• Journal of Korean Society on Water Environment
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• v.21 no.6
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• pp.637-642
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• 2005

The focus of this study was to examine the phosphorus removal characteristic by zirconium mesoporous structured material synthesized on various conditions. The zirconium sulfate-surfactant mesoporous structured material(ZS) was synthesized by hydro-thermal synthesis. The material has regular hexagonal array of surfactant micelles and sulfate ion ($HSO_4{^-}$). We confirmed that sulfate ion in zirconium mesoporous structured material can be ion-exchanged with phosphate ion ($H_2PO_4{^-}$) in phosphoric acid solution. On the X-ray diffraction (XRD) pattern of ZS, three peaks which shows the important characteristics of hexagonal crystal lattice were observed at (100), (110) and (200). The transmission electron micrograph (TEM) show high crystallization with pore size about $47{\AA}$. The maximum adsorption capacity of ZS was as great as 3.2 mmol-P/g-ZS. From the adsorption isotherm, correlation coefficients were higher for the Langmuir isotherm than the Freundlich isotherm. With the respect of chain length of surfactant, the adsorption capacity for phosphate synthesized with C12 was higher than C16 and C18. The highest amount of adsorbed phosphate on ZS was observed at the surfactant-to-zirconium molar ratio of 0.5 to 1.

• Journal of the Korean Vacuum Society
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• v.5 no.1
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• pp.14-24
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• 1996

We have investigated atomic and electronic structures of a clean Pd(111) surface using low energy electron diffraction (LEED) and angle-resolved photoemission spectroscopy (ARPES). A typical clean LEED pattern with a 3-fold symmetry has been observed, corresponding to that for an fcc (111) surface. ARPES measurements have been performed along the $\Gamma-M,\Gamma-K,\Gamma-M$TEX> symmetry lines, from which the experimental band structure of Pd(111) has been determined. The experimental band structure and work function of Pd(111) surface are found to agree well with the calculated band structure of bulk Pd and the calculated work function of Pd(111), respectively. However, the peak positions in the experimental band structure are located closer to the Fermi level than in the theoretical band structure by 0.1~0.8 eV, depending on the $\kappa$-points in the Brillouin zone. In additin, the experimental band widths are narrower than the theoretical band widths by about 0.5eV. The effects of the localized surface Pd 4d states and the Coulomb interaction between Pd 4d bulk electrons have been discussed as possible origins of such discrepancies between experiment and theory.

• Journal of the Korean Vacuum Society
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• v.6 no.2
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• pp.172-176
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• 1997

The change of surface structures for the deposition of indium on clean Si(111) surface is investigated as a function of substrate temperature and surface coverage by RHEED. We find that at substrate temperature of $400^{\circ}C$, $\sqrt{3}\times\sqrt{3},\sqrt{31}\times\sqrt{31},4\times 1$ structures are formed at indium coverages of 0.2, 0.3 and 0.5 ML, respectively. We also find that for the substrate temperature of $300^{\circ}C$, 4$\times$1 structure starts to be forme by 0.2 ML of indium, and the mixed structure of 4$\times$1 and $\sqrt{3}\times\sqrt{3}$is observed for more than 1.0 ML. On the other hand, if the indium is deposited on the Si(111)-$\sqrt{3}\times\sqrt{3}$ structure at room temperature, $2\times2\; and\;\sqrt{7}\times\sqrt{3}$ structures are found to form at 0.2 and 0.4 ML, respectovely. From the desorption process, the desorption energy of indium in Si $\sqrt{7}\times\sqrt{3}$ structure is observed to be 2.84 eV.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.3
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• pp.197-203
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• 2004

New lithography techniques are employed for the patterning of arbitrary shapes in nanometer scale. When, in the photolithography, the electromagnetic waves such as UV and X-ray are incident on the mask patterned in nanometer scale, the diffraction effect is unavoidable and degrades images of the mask imprinted on wafer. Only a convex lens is well-known Fourier transformer. It is possible to make the mask Fourier-transformed with the convex lens, even though the size of pattern on the mask is very large compared to the wavelength of electromagnetic wave. If the mask, modified according to new technique described in this paper, was placed at the front of the lens and was illuminated with laser beam, the nanometer-size patterns are only formed on the plane called Fourier transform plane. The new method presented here is quite simple setup and comparable with present and next generation lithographies such as UV/EUV photolithograpy and electron projection lithography when compared in attainable minimum linewidth. In this paper, we showed our theoretical research work in the field of Fourier optics, . In the near future, we are going to verify this theoretical work by experiments.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.5
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• pp.550-555
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• 2007

The effective fracture toughness testing of materials intended for application in Micro Electro Mechanical Systems (MEMS) devices is required in order to improve understanding of how micro sized material used in device may be expected to perform upon the micro scale. ${\gamma}$-TiAl based materials are being considered for application in MEMS devices at elevated temperatures. Especially, in Alloy 4, both ${\alpha}_2$ and ${\gamma}$ lamellae were altered markedly in 3,000 h, $700^{\circ}C$ exposure. Parallel decomposition of coarse ${\alpha}_2$ into bunches of very fine (${\alpha}_2+{\gamma}$) lamellae. Parallel decomposition of coarse ${\alpha}_2$ into bunches of very fine (${\alpha}_2+{\gamma}$) lamellae. The materials were examined 2 types Alloy 4 on heat exposed specimen($700^{\circ}C$, 3,000 h) and no heat exposed one. Micro sized cantilever beams were prepared mechanical polishing on both side at $25{\sim}30{\mu}m$ and electro final stage polishing to observe lamellar orientation of same colony with EBSD (Electron Backscatter Diffraction Pattern). Through lamellar orientation as inter-lamellae or trans-lamellae, Cantilever beam was fabricated with Focused Ion Beam(FIB). The directional behavior of the lamellar structure was important property in single material, because of the effects of the different processing method and variations in properties according to lamellar orientation. In MEMS application, it is first necessary to have a reliable understanding of the manufacturing methods to be used to produce micro structure.

• Applied Biological Chemistry
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• v.34 no.2
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• pp.94-101
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• 1991

Physicochemical properties of waxy and non-waxy naked barley starches were investigated. The starch granules observed by photomicroscope, polarized-light microscope and scanning electron microscope were round. The starch showed a typical A type by X-ray diffraction pattern. Water binding capacity, swelling power and solubility of waxy naked barley starch were higher than non-waxy naked barley starch at the same temperature. Transmittance of 0.1% starch suspension was increased rapidly from $60^{\circ}C$ in case of waxy naked barley starch and from $65^{\circ}C$ in case of non-waxy naked barley starch. Amylogram revealed that the non-waxy naked barley starches had higher initial pasting temperature than waxy naked barley starch. Enthalpy for gelatinization of non-waxy and waxy naked barley starches were 1.12-1.58 and 0.85 cal/g, respectively.

• Journal of the Korean institute of surface engineering
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• v.42 no.2
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• pp.86-94
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• 2009

Various types of multilayer coatings including Al/$Al_2O_3$ structure have been prepared on Nd-Fe-B permanent magnet to modify the morphology of the coating and to enhance the corrosion resistance of the magnet. Magnetron sputtering has been employed to make the multilayer coatings. $Al_2O_3$sputtering conditions were optimized in reactive sputtering by varying the deposition parameters. The formation of $Al_2O_3$ film was confirmed from the binding energy shift measured by electron spectroscopy for chemical analysis. 3 types of coating structures were designed and prepared by magnetron sputtering. The coating structures consist of (1) single Al coating, (2) modified coatings having oxide or plasma treated layer in the middle of coating structure, and (3) Al/$Al_2O_3$ multilayer coatings. Surface and cross-sectional morphologies showed that Al/$Al_2O_3$ multilayer grew as a layered structure, and that very compact Zone 3 like structure were formed. X-ray diffraction peak showed that the crystal orientations of multilayer coatings were similar to that of the bulk powder pattern. Hardness increased drastically when the Al thickness was around 1im in the Al/$Al_2O_3$ multilayer. From the salt spray test and pressure cooker test, it has been shown that the multilayer coatings showed good corrosion resistance compared to Al single or modified layer coatings.