• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.94-94
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• 2013

The Cr-Zr-N films have much improved mechanical properties and very smooth surface roughness. However, in spite of their outstanding properties, the Cr-Zr-N coatings revealed their mechanical properties deteriorated severely with increasing Zr content at $500^{\circ}C$ ecause of very rapid oxidation. Recently oxynitride films have been widely studied due to their excellent unique mechanical properties and oxidation resistance. In this work, CrZr-O-N films with various O contents were synthesized by unbalanced magnetron sputtering with Cr-Zr segment targets (Cr:Zr volume ratios is 1：1) and all films were prepared in a nitrogen rich mixture of N2 and O2. Characteristics such as crystalline structure, hardness and chemical composition as a function of the O content were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), microhardness testing system and energy dispersive spectroscopy (EDS). Results showed that the thin films had dense and compact microstructure as O content in the films increases. The microstructure of the thin films consisted of mainly crystalline Cr (Zr)N phase and Cr2O3 phase. The maximum hardness and elastic modulus of the films was measured to be approximately 33.2 GPa and 280.6 GPa from the films with low content of O elements. Detailed experimental results will be presented.

• 대한화학회지
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• 제42권6호
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• pp.679-695
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• 1998

A series of ${\alpha}{\omega}-bis[4-(4'-(S)-(+)-2-methylbutylbiphenyl-4-carboxy)phenoxy]alkanes$, were synthesized, and their thermal and liquid crystalline properties were studied. The chain length of the central polymethylene spacers, x, of the chiral twin compounds was varied from 3 to 12. These compounds were characterized by elemental analysis, IR and NMR spectroscopy, differential thermal analysis (DSC), and crosspolarized microscopy. All compounds were found to be enantiotropic liquid crystalline, and the values of melting $(T_m)$ and isotropization temperature $(T_i)$ as well as ${\delta}H_I$ and ${\delta}S_I$ decreased in a zig-zag fashion, revealing the so called odd-even effect as x increased. Their mesomorphic properties fell into four categories depending upon x; (a) compounds with x=3, 4 and 5 formed only a cholesteric phase on heating, while on cooling they went through two transitions of isotropic (I)-to-cholesteric (Ch) and Ch-to-smectic $A\;(S_A)$ phases before crystallization. (b) compounds with x=6, 8 and 10 exhibited only a cholesteric phase both on heating and on cooling. (c) compounds with x=7 and 9 went through three transitions of crystal $(C)-to-S_A,\;S_A-to-Ch,$ and Ch-to-I phases on heating while on cooling they went through four transitions of I-to-Ch, $Ch-to-S_A,\;S_A-to-Smectic\;C\;(S_C),\;and\;S_c-to-C$ phases in that order, and (d) compounds with x=11 and 12 went reversibly through four transitions of $C-to-S_C,\;S_C-to-S_A,\;S_A-to-Ch,$ and Ch-to-I phases.

• Composites Research
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• 제30권6호
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• pp.350-355
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• 2017

Phenylcyclohexyl (PCH) mesogen을 diglycidyl terephthalate의 2,5 위치에 치환시킨 새로운 액정성 에폭시 수지를 설계하였다. 이 물질의 액정성은 DSC(differential scanning calorimetry)와 POM(polarized optical microscopy)으로 분석하였다. 모든 액정성 에폭시 유도체는 가열 및 냉각 시에 모두 smectic상을 나타내는 enantiotropic한 성질을 나타내었다. 액정성 에폭시의 공융 혼합물을 통하여 액정 온도구간을 확장시켰다. 경화된 신규 액정성 에폭시는 $0.4W{\cdot}m^{-1}{\cdot}K^{-1}$의 높은 열전도도를 나타냈다. 높은 열전도도를 갖는 신규 액정성 에폭시는 전자 및 디스플레이용 복합소재로 이용될 것으로 기대된다.

• 한국재료학회지
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• 제8권10호
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• pp.898-904
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• 1998

10-50wt% 범위의 W을 함유하는 Ni-W 합금을 전기도금에 의해 제조하였다. 합금 중의 W 량은 전류밀도가 증가함에 따라 증가하였다. 전류밀도가 50mA/${cm}^2$이하인 경우 Ni-W합금은 미세한 결정립을 갖는 Ni의 고용체이었으며, 전류밀도가 50mA/${cm}^2$이상인 경우 비정질상으로 변화하였다. 이들의 결정질$\longrightarrow$비정질 천이는 W량이 40-46wt%인 구간에서 일어났으며 반각폭이 3배이상으로 증가하였다. 결정질 합금의 격자상수는 평형상태도 상의 W의 고용한계(약 30wt%)를 초과하는 40wt%까지 연속적으로 증가하는 것으로 나타나 Ni이 W을 과고용하고 있는 상태인 것으로 밝혀졌다. 비정질 Ni-W 합금은 $400^{\circ}C$이상의 온도에서 열처리하면 강한 [111]방향성을 가지며 재결정하였으며, $800^{\circ}C$이상의 온도에서는 과고용된 W이 석출하였다. 합금조성 및 결정구조의 전류밀도 의존성을 이용하여 Ni-30%W과 Ni-50%W 합금층이 반복되는 결정질/비정질의 다층도금을 제조하였다.

• 한국재료학회지
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• 제8권8호
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• pp.678-684
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• 1998

정압분자동역학 시뮬레이션에 의하여 주기경계조건을 지닌 L-J 입자들로 구성된 계의 액체-유리-결정 전이를 연구하였다. 원자체적과 엔탈피는 가열 및 냉각과정에서 온도의 함수로 계산되었다. 반경분포함수로부터 유도된 Wendt-Abraham비와 단거리규칙도를 나타내는 각도분포함수를 분석하여 액체, 유리 및 결정상태를 구분하였다. 초기 fcc 결정을 가열하여 얻은 액체상은 급냉시에 비정질화하나 서냉시엔 결정화하였다. 급냉으로 생긴 유리는 다시 서서히 가열하면 fcc로 결정화하였다. 자유표면을 지닌결정은 표면에서부터 용해가 시작되어 벌크에 비하여 낮은 온도에서 녹고 냉각시에는 빠른 냉각속도에서도 결정화가 쉽게 일어나는 경향을 보였다.

• Corrosion Science and Technology
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• 제18권5호
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• pp.206-211
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• 2019

Silicon carbide (SiC) thin films become superhard when they have microstructures of nanocolumnar crystalline grains (NCCG) with an intergranular amorphous SiC matrix. We investigated the role of ion bombardment and deposition temperature in forming the NCCG in SiC thin films. A direct-current (DC) unbalanced magnetron sputtering method was used with pure Ar as sputtering gas to deposit the SiC thin films at fixed target power of 200 W and chamber pressure of 0.4 Pa. The Ar ion bombardment of the deposited films was conducted by applying a negative DC bias voltage 0-100 V to the substrate during deposition. The deposition temperature was varied between room temperature and $450^{\circ}C$. Above a critical bias voltage of -80 V, the NCCG formed, whereas, below it, the SiC films were amorphous. Additionally, a minimum thermal energy (corresponding to a deposition temperature of $450^{\circ}C$ in this study) was required for the NCCG formation. Transmission electron microscopy, Raman spectroscopy, and glancing angle X-ray diffraction analysis (GAXRD) were conducted to probe the samples' structural characteristics. Of those methods, Raman spectroscopy was a particularly efficient non-destructive tool to analyze the formation of the SiC NCCG in the film, whereas GAXRD was insufficiently sensitive.

• 한국전기전자재료학회논문지
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• 제22권5호
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• pp.397-404
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• 2009

Effects of ceramic filler types and dose on the low temperature sintering and dielectric properties of ceramic/$CaO-Al_2O_3-SiO_2$ (CAS) glass composites were investigated. All of the specimens were sintered at $850{\sim}900^{\circ}C$ for 2 h, which conditions are required by the low-temperature co-firing ceramic (LTCC) technology. Ceramic fillers of $CaCO_3$, $Al_2O_3$, $CaCO_3-Al_2O_3$ mixture, and $CaCO_3-Al_2O_3$ compound ($CaAl_2O_4$), respectively, were used. The addition of $Al_2O_3$ yielded the crystalline phase of alumina, which was associated with the inhibition of sintering, while, $CaCO_3$ resulted in no apparent crystalline phase but the swelling was significant. The additions of $CaCO_3-Al_2O_3$ mixture and $CaAl_2O_4$, respectively, yielded the crystalline phases of alumina and anorthite, and the sintering properties of both composites increased with the increase of filler addition and the sintering temperature. In addition, the $CaAl_2O_4$/CAS glass composite, sintered at $900^{\circ}C$, demonstrated good microwave dielectric properties. In overall, all the investigated fillers of 10 wt% addition, except $CaCO_3$, yielded reasonable sintering (relative density, over 93 %) and low dielectric constant (less than 5.5), demonstrating the feasibility of the investigated composites for the application of the LTCC substrate materials.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.52-52
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• 2009

To date, chalcogenide alloy such as $Ge_2Sb_2Te_5$(GST) have not only been rigorously studied for use in Phase Change Random Access Memory(PRAM) applications, but also temperature gap to make different states is not enough to apply to device between amorphous and crystalline state. In this study, we have investigated a new system of phase change media based on the In-Sb-Te(IST) ternary alloys for PRAM. IST chalcogenide thin films were prepared in trench structure (aspect ratio 5:1 of length=500nm, width=100nm) using Tri methyl Indium $(In(CH_3)_4$), $Sb(iPr)_3$ $(Sb(C_3H_7)_3)$ and $Te(iPr)_2(Te(C_3H_7)_2)$ precursors. MOCVD process is very powerful system to deposit in ultra integrated device like 100nm scaled trench structure. And IST materials for PRAM can be grown at low deposition temperature below $200^{\circ}C$ in comparison with GST materials. Although Melting temperature of 1ST materials was $\sim 630^{\circ}C$ like GST, Crystalline temperature of them was ~$290^{\circ}C$; one of GST were $130^{\circ}C$. In-Sb-Te materials will be good candidate materials for PRAM applications. And MOCVD system is powerful for applying ultra scale integration cell.

• 한국산학기술학회논문지
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• 제11권10호
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• pp.4041-4046
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• 2010

유연한 알콕시 곁사슬을 갖는 전방향족 폴리에스터가 direct polycondensation에 의하여 합성되었으며, 합성된 중합체들은 $^1H$-NMR, FT-IR, DSC, TGA, 편광현미경 및 X-ray 분석기에 의하여 조사되었다. 1,1,2,2-테트라클로로에탄(TCE)을 용매로 사용하여 측정된 중합체의 고유점성도(${\eta}_{inh}$)는 0.46~2.41 dL/g의 값을 나타내었다. 곁사슬을 갖는 중합체들은 두 개의 용융전이 즉, 고체상-sanidic 액정상으로의 전이 ($T_{m1}$)와 sanidic 액정상-nematic 액정상으로의 전이 ($T_{m2}$)를 나타내었으며, 알콕시 곁사슬의 길이가 증가함에 따라 상전이온도들은 감소하고, 유기용매에 의한 용해도는 증가하는 경향을 나타내었다. X-ray 분석에서, $2{\theta}\;{\simeq}5$와 $2{\theta}\;{\simeq}20$ 피이크는 각각 중합체 주사슬과 긴 곁사슬의 결정화에 의한 것으로 나타났다.

• E2M - 전기 전자와 첨단 소재
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• 제8권4호
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• pp.478-486
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• 1995

Cu/NbTi multilayer thin films and superconducting wires were fabricated and heat treated with conventional annealing and analyzed by differential scanning calorimetry (DSC) as a basic study for the enhancement of Jc. Interfacial reactions of Cu/NbTi multilayer thin films and superconducting wires were investigated with optical microscope, SEM, and XRD. According to the effective heat of formation (EHF) model, CU$\_$3/Ti was predicted as a first phase. However, considering the crystalline structure and thermodynamics, CuTi was predicted as a first phase. According to the results of DSC and XRD, CU$\_$2/Ti was found to be the first phase, followed by the formation Of CU$\_$4/Ti. The difference in first crystalline phase between the experimental result and the predicted one was discussed. In case of Cu/NbTi superconducting wires, the compounds formed at the Cu/NbTi interface grew with annealing time and the amount of compounds formed in Nb-47wt%Ti alloy was larger than that in Nb-50wt%Ti alloy. It seemed that the incubation time for the formation of compounds in Nb-50wt%Ti alloy was longer than that formed in Nb-47wt%Ti alloy. Also, the diffusion was the rate controlling step for the growth of compounds in all specimens. These compounds were formed at 500-600.deg. C for I hour annealing and, thus, the drawing time below I hour must be required to minimize the growth of compounds for the enhancement of Jc.