• Polymer(Korea)
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• v.24 no.6
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• pp.737-743
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• 2000

Polyquinonediimines (PQDI) which have stable structure on heat and contains mono-azobenzene in the side chain were synthesized by means of condensation polymerization under TiCl$_4$. The synthesized monomers and polymers were identified by FT-IR, $^1$H-NMR, and elementary analysis. Especially, PQDI was comfirmed by the double-bonding peak of >C=N appeared near 1625 $cm^{-1}$ / by means of FT-IR spectrum. PQDI containing mono-azobenzene group in both side chains wat not soluble in non-polar solvents at all but partially soluble in the polar solvents having small dielectric constant, and dissolved in the strong acid such as sulfuric acid and $CH_3$SO$_3$H. Molecular weight distribution of PQDI measured by GPC showed 1.74. It was confirmed through X-ray diffraction analysis that the polymer was partially crystalline at the low angle region, but amorphous after heat treatment at 1$25^{\circ}C$. The glass transition temperature (T$_{g}$ ) of synthesized polymer was measured as 1$25^{\circ}C$ by differential scanning calorimetry. The SHG value for $\chi$$^{(2)}$ after poling at 1$25^{\circ}C$ was 8.6 pm/V (λ=1.542 ${\mu}{\textrm}{m}$). The SHG value slowly decreased with time from the start but appeared temporal stability after 100 hours.

• Journal of Sensor Science and Technology
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• v.6 no.4
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• pp.316-327
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• 1997

Polycrystalline $Sr_{2}Nb_{2}O_{7}$ and $La_{2}Ti_{2}O_{7}$ ceramics with very high Curie temperatures were synthesized by the chemical coprecipitation method (CCP). The powders synthesized were identified by XRD and their sintering behavior and physical properties were studied. The grain-orientation and electrical properties of sintered ceramics were investigated as a function of firing temperature. Single phase could be obtained by CCP method at temperature lower than that of the conventional method by 100 - $150^{\circ}C$. Strontium niobate, $Sr_{2}Nb_{2}O_{7}$, powder was Prepared by CCP method at temperatures as low as $800^{\circ}C$ via intermediate phase of $Sr_{5}Nb_{4}O_{15}$ formed at $700^{\circ}C$. The resulting CCP-derived powder was observed to have finer and more uniform particle size distribution than those obtained through the conventional or the molten salt synthesis method. Sintering of CCP-derived $Sr_{2}Nb_{2}O_{7}$ powder at $1500^{\circ}C$ yielded a highly dense ceramics with 97% theoretical density. Very high grain-orientation developed along the (0k0) direction was observed by SEM, which resulted in anisotropic dielectric properties of the sintered samples, with the dielectric constant values approaching those for single crystal.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.220-220
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• 2008

물 첨가 열화학기상증착을 이용하여 750도에서 길고 수직 성장한 다중벽 탄소나노튜브를 합성하였다. 사용된 기판으로는 우선 실리콘 웨이퍼에 열 증착기로 확산 방지층으로 Ti 50 nm를 입히고 그 위에 Al 15 nm를 입히고 난 후 촉매 층으로 Invar 36 (63 wt% Fe, 37 wt% Ni)을 1 nm 얇게 증착하였다. 탄소나노튜브의 성장에 사용된 가스는 Ar, $C_2H_2$ 이다. Ar은 분위기 가스로 사용되었고, $C_2H_2$는 탄소나노튜브의 성장에 관여하는 가스이다. 또한, 합성중에 약간의 물을 첨가함으로 기존의 탄소나노튜브 성장 길이보다 10배 가량 더 성장 하였다. 이것은 합성 중의 물 첨가로 인해 촉매 입자들의 활동성이 기존에 비해 더 증가했다는 것을 보여준다. 합성된 탄소나노튜브의 길이와 정렬도를 보기 위해 주사전자현미경 (scanning electron microscopy, SEM)을 이용하였고, 탄소나노튜브의 지름과 벽의 개수를 파악하기 위해 투과전자현미경 (transmission electron microscopy)을 이용하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.206-210
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• 1997

In the fields of the optics, precise machine, semiconductors, the micro-positioning actuators are required for the control of position in the submicron range. PNN-P2N-PZT ceramics were fabricated with various mole ratio of the PZT[Pb(Zr$_{1}$2//Ti$_{1}$2)O$_3$]. PNN (Pb(Ni$_{1}$3/Nb$_{2}$3/)O$_3$]and PZN[Pb(Zn$_{1}$3//Nb/sbu 2/3/)O$_3$] powders prepared by double calcination and PZT powders prepared by molten- salt synthesis method. The relative permittivity of specimen with PZT 0.3 mole ratio was shown 5,320 and appeared the relaxor ferroelectric feature. The maximum Piezoelectric coefficient d$_{31}$ to be used for evaluation the displacement of piezoceramics in PNN-PZN-PZT ceramics was 324$\times$10$^{-12}$ (C/V) at the vicinity of morphotropic phase boundary and was larger than that of solid PZT ceramics(120$\times$10$^{-12}$ C/V).

• Journal of the Korea Society of Computer and Information
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• v.17 no.1
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• pp.1-10
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• 2012

Improving operating frequency of processors is no longer today's issues; a multiprocessor technique which integrates many processors has received increasing attention. Currently, high-performance processors that integrate 64 or 128 cores are developing for large data processing over 2, 4, or 8 processor cores. This paper proposes an optimal many-core processor for synthesizing guitar sounds. Unlike the previous research in which a processing element (PE) was assigned to support one of guitar strings, this paper evaluates the impacts of mapping different numbers of PEs to one guitar string in terms of performance and both area and energy efficiencies using architectural and workload simulations. Experimental results show that the maximum area energy efficiencies were achieved at PEs=24 and 96, respectively, for synthesizing guitar sounds with sampling rate of 44.1kHz and 16-bit quantization. The synthesized sounds were very similar to original guitar sounds in their spectra. In addition, the proposed many-core processor was 1,235 and 22 times better than TI TMS320C6416 in area and energy efficiencies, respectively.

• Journal of Sensor Science and Technology
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• v.5 no.3
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• pp.93-100
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• 1996

Polycrystalline $Sr_{2}(Ta_{1-x}Nbx)_{2}O_{7}$ and $La_{2}Ti_{2}O_{7}$ ceramics having very high Curie temperatures were synthesized by the conventional oxide mixing method (CON) and the molten salt synthesis method (MSS). Physical characteristics and phase relationship of calcined powders, as well as the sintering behavior, the grain-orientation and dielectric properties of sintered ceramics were investigated as a function of composition and firing temperature. The single $A_{2}B_{2}O_{7}$ phase was synthesized by using the MSS method at 100 - $150^{\circ}C$ lower temperature compared to the CON method. As Nb content increased in $Sr_{2}(Ta_{1-x}Nbx)_{2}O_{7}$ ceramics, the Curie temperature and the dielectric constant at Curie temperature were raised, and the sintering behavior and the degree of grain-orientation were also improved at the same time. The use of MSS-derived powders made it possible to lower the sintering temperature and to improve the dielectric properties of the sintering samples. However, the piezoelectric properties as well as the grain-orientation were not improved any further by the MSS route.

• Polymer(Korea)
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• v.25 no.4
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• pp.496-502
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• 2001

Thermally stable polyquinonediimines(PQDI) containing di-azobenzene in the side chain were synthesized by means of condensation polymerization under $TiCl_4$. The synthesized monomers and polymers were identified by FT-IR, $^1H-NMR$, and elemental analysis. Especially, the polymerization of PQDI was confirmed by the double-bonding peak of >C=N appearing near 1625cm$^{-1}$ in FT-IR spectrum. PQDI with di-azobenzene group in one side chain was insoluble in methanol, acetone and non-polar solvents having big dielectric constant, but had good solubility in polar solvents having small dielectric constant. Molecular weight distribution of PQDI measured by GPC was 1.38. It was confirmed to be amorphous polymer through X-ray diffraction by the appearance of the halo in case of PQDI containing di-azobenzene in the side chain. The glass transition temperature ($_g$) of synthesized polymer was measured to be 116$^{\circ}C$ by differential scanning calorimetry. The SHG value for ${\chi}^{(2)}$ was 1.2 pm/V (${\lambda}$ = 1.542 ${\mu}$m). The SHG value slightly decreased in an early stage but showed temporal stability after 20 hours.

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.19-19
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• 2002

Perovskite-type titanate dielectrics have attracted much attention in memory devices such as DRAMs or FeRAMs due to their high dielectric constants. However, low volatility of the Ba, Sr, Pb or Zr precursors with only thd ligands has limitations in obtaining high quality thin films by liquid source metal organic chemical vapor deposition (LS-MOCVD) processes. To improve the volatility of these precursors, many attempts have been made such as adding polyether ligands to satisfy the coordinative saturation. We report the synthesis of new precursors Ba(thd)₂(tmeea) and Sr(thd)₂(tmeea), where tmeea = tris[2-(2-methoxyethoxy)ethyl]amino, and LS-MOCVD of barium strontium titanate (BSTO) thin films using these precursors. Due to increased basicity of amines compared with ethers, it is expected that the nitrogen-donor ligand will make a strong bond to a metal than an analogous oxygen-donor ligand, consequently improving the volatility and thermal behavior of these precursors. Thin films of BSTO were grown on Pt(111)/SiO₂/Si(100) substrates by LS-MOCVD using a cocktail source consisting of the conventional Ti precursor Ti(thd)₂(O/sup i/Pr), and these new Ba and Sr precursors. As-grown films were characterized by XPS, SEM, XRD, XRF, and C-V and I-V measurements. BSTO films grown at 420℃ were stoichiometric barium strontium titanate with very smooth surface morphology and their dielectric constants were found to be as targe as 450. Dependence of the composition, microstructure and the electrical properties of the BSTO films on the growth temperature, annealing temperature, working pressure, and the composition of the cocktail source will be discussed.

• Applied Chemistry for Engineering
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• v.8 no.3
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• pp.446-453
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• 1997

The initial product was prepared by heating for 3 hrs at $1000^{\circ}C$ using a mixture of the rutile sand and industral $K_2CO_3$ in the molar ratio 2.0. And the intermediate product, fibrous potassium tetratitanate of layer structure, was obtained by the boiling water treatment of 10hrs for initial product using the calcination method. Also $KHTi_4O_9{\cdot}1.1H_2O$ was synthesized by ion exchange reaction through the acid treatment for 30 min at 0.005M HCl solution and then $K_2Ti_8O_{17}$ whisker of $length=10{\mu}m$, $diameter=0.2{\mu}m$ was synthesized by heat treatment at temperature range of $400{\sim}600^{\circ}C$.

• Journal of Powder Materials
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• v.22 no.4
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• pp.229-233
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• 2015

Porous metallic glass compact (PMGC) are developed by electro-discharge sintering (EDS) process of gas atomized $Zr_{41.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ metallic glass powder under of 0.2 kJ generated by a $450{\mu}F$ capacitor being charged to 0.94 kV. Functional iron-oxides are formed and growth on the surface of PMGCs via hydrothermal synthesis. It is carried out at $150^{\circ}C$ for 48hr with distilled water of 100 mL containing Fe ions of 0.18 g/L. Consequently, two types of iron oxides with different morphology which are disc-shaped $Fe_2O_3$ and needle-shaped $Fe_3O_4$ are successfully formed on the surface of the PMGCs. This finding suggests that PMGC witih hydrothermal technique can be attractive for the practical technology as a new area of structural and functional materials. And they provide a promising road map for using the metallic glasses as a potential functional application.