• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
• /
• pp.105-105
• /
• 2012

We have developed a photoemission-assisted plasma-enhanced chemical vapor deposition (PAPE-CVD) [1,2], in which photoelectrons emitting from the substrate surface irradiated with UV light ($h{\nu}$=7.2 eV) from a Xe excimer lamp are utilized as a trigger for generating DC discharge plasma as depicted in Fig. 1. As a result, photoemission-assisted plasma can appear just above the substrate surface with a limited interval between the substrate and the electrode (~10 mm), enabling us to suppress effectively the unintended deposition of soot on the chamber walls, to increase the deposition rate, and to decrease drastically the electric power consumption. In case of the deposition of DLC gate insulator films for the top-gate graphene channel FET, plasma discharge power is reduced down to as low as 0.01W, giving rise to decrease significantly the plasma-induced damage on the graphene channel [3]. In addition, DLC thickness can be precisely controlled in an atomic scale and dielectric constant is also changed from low ${\kappa}$ for the passivation layer to high ${\kappa}$ for the gate insulator. On the other hand, negative electron affinity (NEA) of a hydrogen-terminated diamond surface is attractive and of practical importance for PAPECVD, because the diamond surface under PAPE-CVD with H2-diluted (about 1%) CH4 gas is exposed to a lot of hydrogen radicals and therefore can perform as a high-efficiency electron emitter due to NEA. In fact, we observed a large change of discharge current between with and without hydrogen termination. It is noted that photoelectrons are emitted from the SiO2 (350 nm)/Si interface with 7.2-eV UV light, making it possible to grow few-layer graphene on the thick SiO2 surface with no transition layer of amorphous carbon by means of PAPE-CVD without any metal catalyst.

• 한국결정성장학회지
• /
• 제18권6호
• /
• pp.242-247
• /
• 2008

$Fe_2O_3$, ZnO 등이 주성분인 EAF dust를 $30{\sim}70\;wt%$ 첨가한 규산염계 유리 및 결정화유리를 제조하고, 시편내부에 생성된 상 및 미세구조와 물리적 특성과의 관계를 고찰하였다. 또한 제조된 유리와 결정화유리의 결정화 거동을 상분석 및 미세구조 관찰을 통하여 분석하였다. EAF dust가 30 wt% 첨가된 용융체의 경우 전형적인 비정질 XRD 패턴을 나타냈으며, 그 이상 첨가된 용융체에는 미용해 된 결정상이 일부 존재하였다. 모든 결정화유리에서는 franklinite, willemite 그리고 augite 결정상이 형성되었다. 결정화유리의 비중은 같은 조성의 유리에 비하여 높았고, EAF dust 함량에 따라 함께 증가하였다. 또한 결정화 유리의 열적 및 기계적 특성이 유리보다 우수하게 나타났다. 즉 유리는 EAF dust 첨가량과 함께 열팽창 계수가 증가하였으나 결정화유리에서는 반대로 감소하였다. 또한 EAF dust 첨가량에 따라 비커스 경도는 유리 및 결정화유리 모두 증가되었으며 같은 조성에서 결정화 유리의 경도값이 항상 더 높게 나타났다.

• E2M - 전기 전자와 첨단 소재
• /
• 제10권5호
• /
• pp.467-472
• /
• 1997

In this study, we investigated the thickness dependence of thermal bleaching(TB) effect as well as photo-induced scalar phenomena, such as photodrakening(PD) effect and photorefraction(PR) change, in chalcogenide A $s_{40}$ G $e_{10}$S $e_{15}$ $S_{35}$ thin films. We found that when these films were exposed for 15 minutes using blue-pass filtered Hg lamp(~4300$\AA$) after annealing for 30 minutes around the glass transition temperature Tg(20$0^{\circ}C$), the refractive index change ($\Delta$n) was varied up to 0.02~0.46 according to each thickness condition and the optical energy gap ($\Delta$ $E_{op}$ ) was shifted to a longer wavelength of approximately 0.67eV, especially for 1000$\AA$-thickness. Also, the TB PD effects have been understood by the results related to optical absorption characteristics. The TB effect could be estimated as increasing the stabilization of amorphous chalcogenide films since absorption slope of extended regions(U) was not changed by annealing. On the other hand, the PD effect could be understood as due to the enhancement of disorder since U and the slope of Urbachs tail(1/F) around an absorption edge were decreased by exposing.ing.n edge were decreased by exposing.

• 한국세라믹학회지
• /
• 제39권11호
• /
• pp.1113-1118
• /
• 2002

마이크로파 유전체용 $(Pb_{0.5}Ca_{0.5})(Fe_{0.5}Nb_{0.5})O_3$ (PCFN) 나노 분말을 metal-citrate 공정을 이용하여 합성하였다. 금속 이온들과 유기 조직의 결합으로 이루어진 고분자 전구체를 형성시키고 이를 열처리하여 화학양론적 조성과 균일한 크기 분포를 갖는 PCFN 분말을 성공적으로 합성하였다. 초기 비정질상 PCFN 분말은 약 $400{\circ}$에서부터 결정화가 시작되어 $700{\circ}$에서 완전한 결정화를 이루었고, $900{\circ}$ 이상에서는 PbO의 해리로 인한 pyrochlore상이 생성되었다. $700{\circ}$에서 열처리된 단일상의 perovskite PCFN 분말은 약 40 nm의 평균 크기와 균일한 형상으로 분포되어 있었다.

• The Korean Journal of Ceramics
• /
• 제3권2호
• /
• pp.116-123
• /
• 1997

A chemically stabilized $\beta$-cristobalite, which is stabilized by stuffing cations of $Ca^{2+}$ and $Al^{3+}$, was prepared by a solution-polymerization route employing Pechini resin or PVA solution as a polymeric carrier. The polymeric carrier affected the crystallization temperature, morphology of calicined powder, and particle size distribution. In case of the polyvinyl alcohol (PVA) solution process, a fine $\beta$-cristobalite powder with a narrow particle size distribution (average particle size : 0.3$\mu\textrm{m}$) and a BET specific surface area of 72 $\m^2$/g was prepared by an attrition-milling for 1 h after calcination at 110$0^{\circ}C$ for 1h. Wider particle size distribution and higher specific surface area were observed for the $\beta$-cristobalite powder derived from Pechini resin. The cubie(P1-to-tetraganalb) phase transformation in polynystalline $\beta$-cristobalite was induced at approximately 18$0^{\circ}C$. Like other materials showing transformation toughening, a critical size effect controlled the $\beta$-to-$\alpha$ transformation. Densifed cristobalite sample had some cracks in its internal texture after annealing. The cracks, occurred spontaneoulsy on cooling, were observed in the sample with an average grain sizes of 4.0 $\mu\textrm{m}$ or above. In case of the sintered cristobalite having a composition of CaO.$2Al_2O_3$.40SiO$_2$, small amount of amorphous phase and slow grain growth during annealing were observed. Shear stress-induced transformation was also observed in ground specimen. Cristobalite having a composition of CaO.2Al2O3.80SiO2 showed a more sensitive response to shear stress than the CaO.$2Al_2O_3$.40SiO$_2$ type cristobalite. Shear-induced transformation resulted in an increase of volume about 13% in $\alpha$-cristobalite phase on annealing for above 10 h in the case of the former composition.

• Journal of Periodontal and Implant Science
• /
• 제40권3호
• /
• pp.125-131
• /
• 2010

Purpose: Among available biomaterials, bioceramics have drawn special interest due to their bioactivity and the possibility of tailoring their composition. The degradation rate and formulation of bioceramics can be altered to mimic the compositions of the mineral phase of bone. The aim of this study was to investigate the bone formation effect of amorphous calcium phosphate glass cement (CPGC) synthesized by a melting and quenching process. Methods: In five male beagle dogs, $4{\times}4$ mm 1-wall intrabony defects were created bilaterally at the mesial or distal aspect of the mandibular second and fourth premolars. Each of the four defects was divided according to graft materials: CPGC with collagen membrane (CM), biphasic calcium phosphate (BCP) with CM, CM alone, or a surgical flap operation only. The dogs were sacrificed 8 weeks post-surgery, and block sections of the defects were collected for histologic and histometric analysis. Results: There were significant differences in bone formation and cementum regeneration between the experimental and control groups. In particular, the CPGC and BCP groups showed greater bone formation than the CM and control groups. Conclusions: In conclusion, CPGC was replaced rapidly with an abundant volume of new bone; CPGC also contributed slightly to regeneration of the periodontal apparatus.

• 대한세포병리학회지
• /
• 제9권1호
• /
• pp.105-110
• /
• 1998

유방에 발생한 선근상피종은 드문 양성 종양으로 세침흡인 세포학적 소견이 잘 알려져 있지 않다. 저자들은 조직소견상 관상 선근상피종으로 확진된 23세 여자의 좌측 유방종괴의 세침흡인 세포학적 특징과 전형적인 유방 섬유선종과 비교하여 감별점을 찾아보았다. 세침흡인 세포학적 소견상 흡인된 양이 많아 높은 세포학적 밀도를 보였으며, 배경에는 풍부한 나핵 세포와 점액성 물질이 관찰되었다. 상피세포의 군집의 크기는 작거나 중간 정도였으며, 느슨한 응집성을 보였고, 소수의 촘촘한 응집성을 보이기도 하였다. 상피 세포의 핵은 둥글고 비교적 균일하였으며, 작은 핵소체는 가끔 발견되었으나 핵의 비정형성이나 유사분열상은 관찰되지 않았다. 근상피세포들이 풍부하게 관찰되었으며 응집성이 좋은 상피세포 군집의 변연부를 따라 배열하기도 하였다. 기질 조직은 흡인된 양이 적었으며 섬유성 양상이었다. 전형적인 섬유선종과 구별되는 선근상피종의 세포학적 특징은 응집성이 덜한 상피세포 군집, 불분명한 군집의 변연부, 상피세포의 작은 덩어리가 미만성으로 관찰되는 점과 적은 양의 섬유조직성 기질조직이었다.

• 공업화학
• /
• 제7권5호
• /
• pp.813-822
• /
• 1996

온실효과에 주요한 기여를 하는 이산화탄소를 줄이기 위하여 새로운 형태의 고분자인 폴리(알킬렌 카보네이트)가 합성되어졌다. 이산화탄소와 여러 가지 에폭시드로부터 칼복시산의 아연염을 촉매로 하여 교대 공중합체가 만들어졌다. 중합체의 수 평균 분자량은 50,000 정도이면 중합 분산도는 5~10 정도로 비교적 넓은 분포를 갖는다. 이 중합체는 비 결정성이고, 투명한 물질로써 열분해가 쉽게 일어난다. 높은 온도와 불활성 분위기 하에서도 완벽한 분해가 일어나 탄소 잔류물을 남기지 않는 것으로 알려졌다. 간단한 에폭시드와의 공중합체의 물리적인 성질을 개선하기 위하여 입체 장애가 큰 에폭시드와의 삼원 공중합체도 만들 수 있다. 이러한 분해성을 이용하여 세라믹, 금속, 전자 산업용 바인더나 lost-foam casting에 활용이 검토되었다. 또한 포장용 필름이나 가소제로의 활용도 연구될 수 있을 것으로 기대된다.

• Korea-Australia Rheology Journal
• /
• 제19권4호
• /
• pp.191-199
• /
• 2007

Precision injection molding process is of great importance since precision optical products such as CD, DVD and various lens are manufactured by those process. In such products, birefringence affects the optical performance while residual stress that determines the geometric precision level. Therefore, it is needed to study residual stress and birefringence that affect deformation and optical quality, respectively in precision optical product. In the present study, we tried to predict residual stress, final shrinkage and birefringence in injection molded parts in a systematic way, and compared numerical results with the corresponding experimental data. Residual stress and birefringence can be divided into two parts, namely flow induced and thermally induced portions. Flow induced birefringence is dominant during the flow, whereas thermally induced stress is much higher than flow induced one when amorphous polymer undergoes rapid cooling across the glass transition region. A numerical system that is able to predict birefringence, residual stress and final shrinkage in injection molding process has been developed using hybrid finite element-difference method for a general three dimensional thin part geometry. The present modeling attempts to integrate the analysis of the entire process consistently by assuming polymeric materials as nonlinear viscoelastic fluids above a no-flow temperature and as linear viscoelastic solids below the no-flow temperature, while calculating residual stress, shrinkage and birefringence accordingly. Thus, for flow induced ones, the Leonov model and stress-optical law are adopted, while the linear viscoelastic model, photoviscoelastic model and free volume theory taking into account the density relaxation phenomena are employed to predict thermally induced ones. Special cares are taken of the modeling of the lateral boundary condition which can consider product geometry, histories of pressure and residual stress. Deformations at and after ejection have been considered using thin shell viscoelastic finite element method. There were good correspondences between numerical results and experimental data if final shrinkage, residual stress and birefringence were compared.

• 에너지공학
• /
• 제13권1호
• /
• pp.82-91
• /
• 2004

석탄 및 하수슬러지 내에 함유된 무기물질을 환경적 측면에서 안정적인 물질로 재활용하기 위해서는 회재의 형태가 아닌 슬랙의 형태로 발생시키는 것이 한 방법이다. 가스화 반응에서 생성된 석탄 슬랙과 소각ㆍ용융과정에서 생성된 하수슬러지 슬랙의 특성을 분석하여, 재활용 측면에서 살펴보았다. 급냉을 시킨 슬랙들은 잘게 쪼개진 수 mm크기로 발생되었고, 함유된 미연탄소분은 모두 0.15% 이하였으며 슬랙의 구조는 대부분 무결정형인 특징을 보여주고 있었다. 분석 결과를 보면, 석탄 슬랙과 하수슬러지 슬랙 모두 중금속 성분이 용출되는 양은 국내기준치의 10배나 엄격한 일본기준보다도 훨씬 낮아서 재활용 물질로 활용하는 데에 문제가 없음을 알 수 있었다. 슬랙 내에 함유된 중금속 농도에서는 큰 차이가 있었는데, 향후 중금속 함량규제가 도입될 경우에는 두 슬랙 원료의 혼합 활용을 통해 중금속 함량 조절도 가능할 것이다.