• 대한기계학회논문집A
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• 제35권9호
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• pp.999-1005
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• 2011

고무복합재료에 대해 변형에 의한 결정화(SIC)가 기계적 특성에 미치는 영향을 연신율(${\lambda}$) 및 다중벽 탄소나노튜브(CNT)와 카본블랙(CB)의 함유량을 함수로 하여 연구하였다. 시차 주사 열량(DSC) 분석을 통해 CB 및 CNT의 함유량에 따라 결정화 정도가 증가함을 확인 하였다. 또한 연신율이 증가함에 따라 복합재료의 유리전이온도(Tg)는 증가하였고, 결정화 잠열 값(LHc)은 ${\lambda}$=1.5에서 최대값을 보였다. CNT의 함유량 증가에 따라 기계적 특성과 LHc는 비례관계임을 확인하였다. 열 중량 분석(TGA)을 통해 기지의 소실율은 94.3%였고, 복합재료의 소실율은 보강재의 함유량 증가에 따라 감소하였다. 인장탄성율 비는 고무 내의 CNT 배향으로 인장강도 비보다 높게 나타났다.

• 대한화학회지
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• 제37권10호
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• pp.867-873
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• 1993

결정화 시간 및 반응 혼합물내의 $H_2O/Al_2O_3$의 비가 AlPO$_4$-5 분자체의 합성에 미치는 영향을 X-선 회절(XRD), 질소흡착실험, 전자현미경(SEM) 그리고 고체상 $^{27}$Al nuclear magnetic resonance(NMR)를 사용하여 조사하였다. 반응온도가 150$^{\circ}$C일 때 AlPO$_4$-5의 결정화 시간에 따른 결정성은 S자형 곡선을 보였으며, 유도기간(induction period)은 1시간 이내인 것으로 나타났다. 반응물에서 생성물, AlPO$_4$-5로의 전환을 명확히 관측할 수 있었으며 약 2시간의 결정화 전후 측정된 모든 물성은 큰 변화를 보였다. 반응물내의 $H_2O/Al_2O_3$의 비가 증가함에 따라 다결정의 AlPO$_4$-5는 육각기둥 모양의 단결정으로 변화하였으며 얻어진 결정의 길이/너비의 비는 증가하였다.

• 한국식품영양과학회지
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• 제31권3호
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• pp.475-481
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• 2002

분해성 천연 고분자인 PHB와 chitosan을 블렌드하여 필름을 제조한뒤 필름의 결정특성 및 물리적 성질을 측정한 결과 PHB/chitosan 필름의 X선 회절도 측정에서 상대 결정화도는 chitosan의 함량이 증가할수록 낮아졌으며 FT-lR 측정에서는 chitosan 비율이 증가할수록 PHB의 carbonyl기 의 피크가 작아졌다. DSC측정에 의한 필름의 열적 특성에서는chitosan의 첨가로 인해 열안정성과 결정성이 낮아지는 경향을 보였다. 시차주사현미경을 이용하여 관찰한 필름의 표면상태에서는 chitosan의 비율이 증가할수록 입자크기가 감소하는 것으로 나타났다. 필름의 물성은 PHB에 대한 chitosan의 함량이 증가할수록 인장강도와 신장률이 증가하여 chitosan 첨가로 인해 필름의 물성이 향상된 것을 알 수 있었다. PHB/chitosan필름의 색도 측정 결과 PHB에 chitosan의 함량이 증가할수록 L값과 b값은 낮아지고 필름의 투명도는 높아졌다.

• 한국군사과학기술학회지
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• 제23권5호
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• pp.523-531
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• 2020

Extraction and anti-solvent crystallization were proposed to recover octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) from pressed polymer bonded explosives(PBXs). DXC-57 and DXC-59, whose polymeric binders are Estane and HyTemp with dioctyl adipate plasticizer, respectively, were used as pressed PBX models. Estane of DXC-57 was removed by washing with tetrahydrofuran prior to extraction, which enabled the crystallization of HMX at a low degree of supersaturation, sufficient to obtain β-form HMX. Using dimethyl sulfoxide and ethanol as the extraction solvent and the anti-solvent for crystallization, respectively, HyTemp and dioctyl adipate in DXC-59 were separated from HMX. The purity of recovered β-form HMX was higher than 99 %.

• 한국응용과학기술학회지
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• 제25권2호
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• pp.130-136
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• 2008

$xTiO_2$-$ySiO_2$ system photocatalysts were developed by sol-gel method based on the change of production parameters, and their structure of crystallization and the specific surface area were measured. Considering the efficiency of the ethanol and phenol degradation using the catalyst, the conclusions were obtained as follows: By means of X-ray analysis of $xTiO_2$-$ySiO_2$ powder that is obtained from Titanium and Silicon alkoxide by sol-gel process, it is shown that crystal structure of anatase type is a dominating structure and, on the other hand, the structure of rutile also partly exists. The increase of $SiO_2$ contents causes the decrease of the degree of crystallization of the gel, whereas the specific surface area preferentially increases. It is shown that more than 90% of ethanol and phenol are degraded when reaction time is about three and an hours, and the maximum degradation rate of ethanol and phenol is shown in $60TiO_2$-$40SiO_2$ catalyst.

• 한국세라믹학회지
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• 제48권1호
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• pp.80-85
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• 2011

The crystallization behavior and microstructural change of the glass-ceramics were analyzed as a function of concentration and etching time of the HF solution in order to enhance the degree of crystallinity induced by heterogeneous nucleation of glass of bottom ash containing 15 wt% $Li_2O$. The nucleation site seemed to be generated where the Si ion was eluted. The main crystal phases in the glass-ceramics fabricated in this study were $\beta$-spodumene and $Li_2SiO_3$. The specimens etched with HF of 0.5 vol% within 0~60 seconds showed increased crystalline peak intensities in XRD pattern with etching time compared to no-etched one. Also the crystal size and crystal occupancy in the glass matrix observed by SEM were increased with etching time. For the glass-ceramics etched with 1.0 and 2.0 vol% HF solution, the etching time over 10 s was not effective to increase the crystallinity. From this study, it was found that the glass-ceramics with the higher crystallinity could be obtained by HF-etching followed by heat treatment process, even though the nucleating agent or 2-stages thermal treatment process were not used.

• 한국재료학회지
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• 제12권8호
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• pp.595-599
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• 2002

A homogeneous and stable, amorphous-type, anorthite (CaO $Al_2$$O_3$ $2SiO_2$)powder was synthesized by an organic-inorganic steric entrapment route. Polyvinyl alcohol ( PVA) was used as an organic carrier for the precursor ceramic gel. The PVA content, its degree of polymerization and type of silica sol had a significant influence on the calcination and crystallization behavior of the precursors. For densifiction and crystallization at low temperature, porous and soft, amorphous-type anorthite powder was planetary milled for 20h. The milled powder crystallized to stable anorthite phase and densified to a relative density of 94% below $1000^{\circ}C$. In the development of crystalline phases of the planetary milled powder, omisteinbergite phase was unusually observed at $900^{\circ}C$, and then anorthite was observed at $950^{\circ}C$. The sintered anorthite had a thermal expansion coefficient of $4.6$\times$10^{-6}$ /$^{\circ}C$ and a dielectric constant of 7.5 at 1 MHz. Finally, the anorthite synthesized by the new process is expected to be an useful material for low-firing ceramic substrate.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.630-633
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• 2003

Integrating the driver circuitry directly onto the glass substrate would be one of the advantages of polycrystalline Si (poly-Si) TFT-(LCD). Low-temperature poly-Si TFT(LTPS) is well-suited for higher-definition display applications due to its intrinsically superior electrical characteristics. In order to improve LTPS electrical characteristics, currently the excimer laser-induced crystallization (ELC) processes and sequential lateral solidification method were developed. Grain size of the poly-Si is mainly affected by beam pitch and energy density. Key parameter for making a larger poly-Si using excimer laser annealing(ELA) and increasing a throughput is due to increase in beam pitch and energy density to a certain degree. Furthermore, thin $SiO_{2}$ capping is effective to suppress the protrusion of the poly-Si thin films and to reduce the interface state density. From the ELA process, we are able to control grain size by varying different parameters such as number of shots and energy density.

• 한국결정성장학회지
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• 제10권3호
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• pp.258-263
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• 2000

마이크로파 열처리공정이 여러 가지 CuO 조성을 가진 $Li_2O-2SiO_2$-xCuO 유리의 전기전도도와 결정화 거동에 미치는 영향을 조사하기 위하여 재래식 열처리 공정과 비교하였다. 각기 재래식과 마이크로파 가열법으로 열처리하였을 때, 시편들의 전기전도도는 CuO 함량이 증가할수록 증가하였고, 각 조성에서 마이크로파로 열처리된 시편이 재래식으로 열처리된 시편에 비하여 높은 전기전도도를 보였다. 또한 X-선 회절 실험 결과, 마이크로파 열처리는 $Li_2Si_2O_5$ , $Li_2Cu_5(Si_2O_7)_2$및 $Li_2Cu_O_3$상의 결정화 정도를 향상시켜주었다. $Li_2O-2SiO_2$-1.3CuO(30 mo1% CuO) 유리를 $500^{\circ}C$에서 30분 동안 재래식과 마이크로파로 열처리한 후 상온에서 측정한 시편들의 전기전도도는 각기 $0.11{\times}10^{-4}(\Omega \textrm {cm})^{-1}$과 $0.68{\times}10^{-4}(\Omega \textrm {cm})^{-1}$이었다. 마이크로파 에너지는 시편들의 결정화를 향상시키고, 전기전도도 값도 증가시킨다고 판단되었다.

• Elastomers and Composites
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• 제54권1호
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• pp.61-69
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• 2019

Poly(ethylene-co-vinyl acetate) (EVA) is a copolymer of ethylene and vinyl acetate (VA). It is important to determine the VA content of EVA, since the properties of EVA depend highly on the VA content. EVA copolymers have been used in a wide range of applications appropriate for the different VA contents. IR, NMR, and TGA are generally used for determination of the VA content of EVA copolymers. Of these, TGA is the most reliable method and can be applied to cured EVAs. Analytical methods for determination of the VA content and properties of EVA copolymers via TGA were herein reviewed. Thermal behaviors of EVA copolymers (glass transition temperature ($T_g$), melting point ($T_m$), and crystallization temperature ($T_c$)) determined by DSC were also reviewed. Analysis of the related literature revealed that the $T_g$, $T_m$, and $T_c$ decrease by about 0.46, 1.36, and $2.08^{\circ}C$, respectively, for every 1 wt% in VA content. A method for determining the degree of crosslinking of cured EVA copolymers was also reviewed, and the degree of crosslinking tends to increase with the decrease in the VA content.