• Applied Chemistry for Engineering
• /
• v.9 no.7
• /
• pp.990-997
• /
• 1998

In this work, the $SiO_2$ films on the silicon substrate with different orientations were first prepared by the low temperature process using the ECR plasma diffusion as a function of microwave power and oxidation time. Before and after thermal treatment, the surface morphology, Si/O ratio from physicochemical properties, and the electrical properties of the oxide films were also investigated. The oxidation rate increased with microwave power, while surface morphology showed the nonuniform due to etching. The film quality, therefore, was lowered with increasing the defect by etching and the content of positive oxide ions in the oxide films from bulk by higher self-DC bias. The content of positive oxide ions in the oxide films with different Si orientations showed Si(100) < Si(111) < poly Si. The defects in $Si/SiO_2$ interface of $SiO_2$ film could be decreased by annealing, while $Q_{it}$ and $Q_f$ were independent of thermal treatment and the dependent on concentration of reactive oxide ions and self-DC bias of substrate. At microwave power of 300, and 400 W, the high quality $SiO_2$ film that had lower surface roughness and defect in $Si/SiO_2$ interface was obtained. The value of interface trap density, then, was ${\sim}9{\times}10^{10}cm^{-2}eV^{-1}$.

• Ceramist
• /
• v.3 no.1
• /
• pp.45-52
• /
• 2000

전자싸이클로트론공명플라즈마 화학기상증착법(ECR-PECVD)에 의한 Pt 및 $RuO_2$ 기판에서의 PZT 박막의 증착특성 및 전기적 특성을 조사하였다. $RuO_2$ 기판에서는 Pt 기판에 비하여 Pb-관련 이차상이 형성되기 쉬웠고, PZT 페로브스카이트 핵생성이 어려웠다. 하지만, $RuO_2$ 기판에서도 금속유기 원료기체의 정확한 유량조절(특히, $Pb(DPM)_2$ 유량)과 Ti-oxide 씨앗층의 도입을 통하여 $450^{\circ}C$의 비교적 낮은 증착온도에서 단일한페로브스카이트 박막 제조가 가능하였으며, $RuO_2$ 기판에서도 미세구조가 향상된 PZT 박막의 경우 $10^{-6}A/cm^2@100kV/cm$의 우수한 누설전류 특성을 나타내었다. 4 가지 전극배열의 PZT 커패시터들 중에서 $RuO_2//RuO_2$ 커패시터는 누설전류밀도가 $10^{-4}A/cm^2@100kV/cm$ 정도로 높았지만, 피로현상은 나타나지 않았다. 일방향 전계 (unipolar) 피로특성에서 나타난 polarization-shift 현상과 양방향 전계 (bipolar) 피로특성의 온도의존성 결과는 PZT 박막내 charged defect의 이동이 어려움을 나타내었다. Bipolar 신호에 의한 피로현상은 인가전계에 의한 분극반전 과정에서 Pt 계면에서 charged defect의 형성과 관련이 있는 것으로 판단되었다. 또한, 상하부 전극물질 이 다른 경우에는 상하부 계면의 charged defect 밀도에 차이가 생겨 내부전계가 형성되는 것으로 판단되었다.

• Polymer(Korea)
• /
• v.24 no.4
• /
• pp.556-563
• /
• 2000

In general, the development of thermoplastic composites has been confronted with difficult problems such as the weak bonding strength between fibers and matrix. However, now, such problems are being surmounted by the development of resins, the improvement of processes, and introduction of interphase. Especially, the introduction of interphase between fiber and matrix can help a dissipation of the impact energy and provide a good adhesion between fibers and matrix. In this study, polymeric interphase was introduced by electrodeposition, modified polypropylene was added to improve the weak bonding strength between interphase and polypropylene matrix. By evaluation of interlaminar shear strength and impact strength of the composites, it was found that composites with introduced composites showed higher mechanical properties than those of composites without interphase. Reactive polymers which have either anhydride or free acid functional group were used as interphase materials, and these polymers also behave as charge carrier in aqueous solution during the electrodeposition process. Weight gain on the carbon fibers was evaluated by changing process parameters such as concentration of solution, current density, and electrodeposition time.

• Journal of the Microelectronics and Packaging Society
• /
• v.10 no.2
• /
• pp.39-47
• /
• 2003

Cr thin films were deposited on photosensitive polyimide substrates by RF bias sputtering and DC sputtering and the interfaces between Cr thin film and polyimide were observed using TEM. When the polyimide surface was in-situ RF plasma cleaned at the RF power density of 0.13-2.12 $W/cm^2$, increasing of RF power density changed the morphology of polyimide surfaces from round dig to sharp shape, and surface roughness increased by anisotropic etching. The intermixed layer-like interfaces between Cr and polyimide were observed in the RF bias sputtered specimens. This interface seems to be formed due to the RF cleaning effect; the polyimide surface was RF plasma cleaned while RF power was increased to the setting point before Cr deposition.

• Polymer(Korea)
• /
• v.26 no.2
• /
• pp.185-192
• /
• 2002

Rigid polyurethane foams (PUFs) were prepared from polymeric 4.4'-diphenyl-methane diisocyanate (PMDI), polyether polyol, 1,4-butane diol, silicone surfactant, and distilled water. The density of the PUF was decreased from 173.7 to 41.7 kg/㎥ with an increase in distilled water from 0.5 to 3.0 php (parts per hundred polyol by weight), respectively, at the 0 php butane diol. The cell size of the PUF increased from 115 to 258 $mu extrm{m}$ with an increase in the amount of distilled water from 0.5 to 3.0 php, respectively, at the 10 php butane diol. It was found that the compressive strength of the PUF increased with the content of distilled water, at the same density. Out of the study for the surfactant effect on the properties of the PUF, it was observed that the cell site of the PUF decreased from 360 to 146 $mu extrm{m}$ with an increase in the amount of the surfactant from 0 to 0.33 php, respectively, but the tell size did not change significantly when the amount of the surfactant exceeded 0.33 php.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2012.05a
• /
• pp.105.1-105.1
• /
• 2012

고온가압소결으로 제조된 SiCf/SiC 복합체는 부식과 침식에 강하고 우수한 열적 성질과 고온에서의 높은 기계적 강도를 유지하는 장점을 가진 복합체다. 복합체의 파괴인성은 섬유와 기지 사이에 존재하는 열분해탄소 (PyC) 계면층에 의해 큰 영향을 받는데, 고온가압소결중 첨가되는 소결조제 ($Y_2O_3$, MgO, $Al_2O_3$)와 반응하여 계면이 손상되어 복합체의 기계적 특성치가 낮아지는 결과를 보였다. 본 연구에서는 계면의 손상을 보호하고자 PyC 계면상 위에 SiC 층을 증착하였는데 계면층과 SiC 층의 증착은 화학기상 증착법(CVD)을, 기지채움 공정은 전기영동법(EPD)과 고온가압소결방법(Hot Pressing)을 이용하여 복합체를 제조하였다. Tyranno-SA 섬유에 소스가스인 메탄을 열분해 하여 200nm 두께로 PyC 계면상을 증착하고, 두께를 달리하여 보호층으로써의 SiC 층을 single 과 double layer로 증착하였다. SiC 나노분말과 소결 첨가제인 $Y_2O_3$, $Al_2O_3$, MgO를 첨가한 슬러리를 전기영동법(EPD)을 이용하여 섬유내부에 슬러리를 함침시켰고, 이러한 프리폼을 $1750^{\circ}C$/20MPa의 조건으로 고온 가압소결 하여 $SiC_f$/SiC 복합체를 제조하였다. 이렇게 single layer와 double layer로 제조된 $SiC_f$/SiC 복합체에 대해 밀도와 미세구조를 관찰하였고, 기계적 특성을 비교하여 보호층으로써의 SiC 증착효과를 고찰하고자 하였다.

• Journal of Adhesion and Interface
• /
• v.20 no.3
• /
• pp.96-101
• /
• 2019

In this study, the flame retardant and physical properties of the expandable graphite/polyurethane foam composites were considered by the addition of expandable graphite. The tensile strength of expandable graphite/polyurethane foam composites decreased with the content of the expandable graphite and the analysis of cell shape by SEM has shown that as the expandable graphite content increases, the cell becomes uneven and collapses. As the results of the compressive strength, density and air permeability tests, it was found that density and as the content of the expandable graphite increased, the compressive strength of the composites increased but air permeability decreased. When the amount of expandable graphite was added at 10 phr or higher, the foam has excellent flame retardation performance. Analysis of the degree of diffraction by X-ray diffraction (XRD) showed that as the content of the expandable graphite increased, the crystal peak of the graphite appeared near $2{\theta}=26^{\circ}$.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.49 no.3
• /
• pp.225-230
• /
• 2023

In this study, the porous structure inside the hair were observed using an optical microscope without damaging the hair, and the porosity inside the hair was quantitatively expressed using the results. Experiments were conducted on the effect of the decrease in density inside the hair on the bending and tensile properties of the hair, and experiments on endogenous and extrinsic factors were conducted to find out the causes of the decrease in density inside the hair. As for the endogenous factor, the porosity of gray hair, one of the representative symptoms of aging, was compared with normal hair. As for extrinsic factors, it was observed that the internal density of hair decreased by surfactant and heat, which are factors that can cause hair damage in daily life. In addition, we confirmed whether it is possible to increase the internal density and luster of the hair by using an amino acids and material that can prevent hair lipid predisposition.

• Korean Journal of Materials Research
• /
• v.7 no.11
• /
• pp.986-990
• /
• 1997

LED와 LD의 수명과 효율은 결정에 존재하는 결함의 밀도에 반비례하며, 이러한 결함의 밀도는 적당한 기판을 사용하거나, 기판의 표면을 적절하게 제어함으로써 줄일 수 있다. GaN성장시 원자 단위의 매끄러운 표면은 완충충 성장이나 질화처리를 함으로써 얻어질 수 있다. 이렇게 얻어진 원자 단위의 매끄러운 표면에 의해 기판과 박막상이의 계면 자유에너지가 감소하기 때문에 2D성장이 촉진된다. 사파이어(AI$_{2}$O$_{3}$(0001))기판을 사용한 GaN 왕충충성장과 진화처리에 대한 최적조건은 AFM(Atomic Force Microscope)측정 결과에 의해 결정되었다. AFM에 의해 얻어진 표면 평활도의 개념은 사파이어 기판을 사용한 GaN박막성장의 최적조건을 결정하는 데 있어서 높은 신뢰도를 가질 수 있다.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.5 no.4
• /
• pp.378-385
• /
• 1995

The growth processes of improved methods for MBE, LPE and $\mu$ - PD methods are discussed taking the oxide materials, especially those of Bi - Sr - Ca - Cu family $LiNbO_3$ and $K_3Li_2Nb_5O_{15}$ family as examples. It is suggested that the crystal growth far from equilibr iu m including composition homogeneity has been achieved to satisfy in understanding and controlling the atomic interfaces.