• Bulletin of the Korean Chemical Society
• /
• 제20권5호
• /
• pp.517-524
• /
• 1999

By heating the magnesiumsilicate (Mg2SiO4:forsterite) xerogel in carbon dioxide, carbonaceous component was intentionally introduced into the amorphous solid precursor. Carbon was introduced homogeneously as unidentate carbonate. Upon being heated at 800 。C in carbon dioxide, the xerogel which had homogeneously distributed carbonaceous component in it crystallized into a single phase product of a new crystalline material, which had approximate composition of Mg8Si4Ol8C. The powder X-ray diffraction pattern of the new crystalline material did not match with any known crystalline compound registered in the powder diffraction file. Crystallization from amorphous xeroget to the new crystalline phase occurred in a very narrow range of temperature, from 750 。C to 850 。C in carbon dioxide, or in dty oxygen. Upon being heated above 850 。C, carbonaceous component was expelled from the product, accompanied by irreversible transition from the new crystalline material to forsterite.

• 폴리머
• /
• 제24권2호
• /
• pp.211-219
• /
• 2000

액정성을 가지는 플로렌계 발광고분자에 비버정성 플로렌계 발광고분자를 첨가한 블렌드를 제조하여 에너지전달 효과와 흡광 및 발광 이방성에 대하여 고찰하였다. 비액정성 고분자를 액정성 고분자에 0.5wt% 첨가하고 360nm로 여기한 결과, 420nm에서 관찰되었던 액정성 고분자의 발광피크는 거의 사라졌으며 대신 비액정성 고분자에 의한 480nm에서의 새로운 발광피크가 관찰되었다. 블렌드 시료의 480nm 발광은 비액정성 고분자가 2.0wt% 첨가되었을때 가장 강했으며, 발광강도는 블렌딩 이전의 각 고분자보다 13배 증자하였다. 블렌드내의 분자들을 마찰 폴리이미드 기판상에서 가열-냉각시켜 배향시키면 시료의 발광 이방성과 order parameter는 각각 2.0 및 0.25를 나타내었다. 시간 상관 단광자 계수법 (TCSPC)에 의해 고찰한 결과, 마찰 폴리이미드 기판상에서의 배향에 의해 두 발광고분자간의 에너지전달에 필요한 시간은 93 ps만큼 단축되며 에너지전달 효율은 9% 증가함을 알 수 있었다.

• 한국초전도학회:학술대회논문집
• /
• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
• /
• pp.86-91
• /
• 2000

Ni tapes were textured by taking advantage of their secondary recrystallization. The obtained 18cm long tapes had textures of single crystalline qualities with their [001] axes tilted with respect to the surface and their [010] axes parallel to the rolling direction. YBCO/CeO$_2$/YSZ/CeO$_2$ films grown on the Ni tape had the same crystalline orientations. Magnetic field dependent I-V relations were measured on a 5cm section of the tape. Jc defined by 1mV criterion was 1.5 ${\times}$ 10$^5$A/cm$^2$ at 77K under zero field and was reduced by ${\sim}$50% under the applied magnetic field of 5T.

• Progress in Superconductivity
• /
• 제2권1호
• /
• pp.33-38
• /
• 2000

Ni tapes were textured by taking advantage of their secondary recrystallization. The obtained 18cm long tapes had textures of single crystalline qualities with their [001] axes tilted with respect to the surface and their [010] axes parallel to the rolling direction. The reproducibility of this texturing was checked by taking statistics on the crystal orientations of 24 Ni tapes. $YBCO/CeO_2/YSZ/CeO_2$ films grown on the Ni tape had the same crystalline orientations. Magnetic field dependent I-V relations were measured on a 5cm section of the tape. $J_c$ defined by $20{\mu}V/mm$ criterion was $1.5\times10^5A/cm^2$ at 77K under zero field and was reduced by $\sim$50% under the applied magnetic field of 5T.

• Applied Science and Convergence Technology
• /
• 제24권6호
• /
• pp.268-272
• /
• 2015

We report the systematic study to reduce extrinsic doping in graphene grown by chemical vapor deposition (CVD). To investigate the effect of crystallinity of graphene on the extent of the extrinsic doping, graphene samples with different levels of crystal quality: poly-crystalline and single-crystalline graphene (PCG and SCG), are employed. The graphene suspended in air is almost undoped regardless of its crystallinity, whereas graphene placed on an $SiO_2/Si$ substrate is spontaneously p-doped. The extent of p-doping from the $SiO_2$ substrate in SCG is slightly lower than that in PCG, implying that the defects in graphene play roles in charge transfer. However, after annealing treatment, both PCG and SCG are heavily p-doped due to increased interaction with the underlying substrate. Extrinsic doping dramatically decreases after annealing treatment when PCG and SCG are placed on the top of hexagonal boron nitride (h-BN) substrate, confirming that h-BN is the ideal substrate for reducing extrinsic doping in CVD graphene.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2010년도 제39회 하계학술대회 초록집
• /
• pp.219-219
• /
• 2010

Silicides have been commonly used in the Si technology due to the compatibility with Si. Recently the silicide has been applied in solar cells [1] and nanoscale interconnects [2]. The modulation of Ni silicide phase is an important issue to satisfy the needs. The excellent electric-conductive nickel monosilicide (NiSi) nanowire has proven the low resistive nanoscale interconnects. Otherwise the Ni disilicide (NiSi2) provides a template to grow a crystalline Si film above it by the little lattice mismatch of 0.4% between Si and NiSi2. We present the formation of Ni silicide phases performed by the single deposition and the co-deposition methods. The co-deposition of Ni and Si provides a stable Ni silicide phase at a reduced processing temperature comparing to the single deposition method. It also discusses the Schottky contact formation between the Ni silicide and the grown crystalline Si film for the solar cell application.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2000년도 하계학술대회 논문집 D
• /
• pp.2796-2798
• /
• 2000

It is a quite quality concerning to control temperature of single crystalline growth as it does when you get most of heat treating products. It is also important factor to control temperature when you make the $Al_{2}O_3$(single crystalline) used to artificial jewels. glass of watches. heat resistant transparent glasses. Thus. it is a major interest to get the proper temperature in accordance with the time process while you are making mixture of oxygen and hydrogen to have the right temperature. In this paper. we will study of electrical valve positioning system for the gas mixture to improve the quality of products.

• 한국결정성장학회지
• /
• 제18권4호
• /
• pp.155-159
• /
• 2008

본 연구에서는 금속 Zn 팰렛을 원료 물질로 이용하여 열화학기상증착법으로 마이크로 크기의 프리스탠딩 ZnO/Zn 코어셀 다면체 구조물을 합성하였다. 마이크로 크기로 성장된 ZnO/Zn 코어셀 다면체의 형태와 구조적인 특성을 분석하기 위해서 주사전자현미경과 투과전자현미경을 이용하였다. 성장된 마이크로 크기의 다면체는 단결정 ZnO 나노막대 배열에 의해 둘러싸인 단결정 금속 Zn로 구성되어 있음을 확인할 수 있었다. 마이크로 크기의 단결정 Zn는 육방정 결정구조로 이루어져 있으며, 표면을 구성하고 있는 c-축 배향된 ZnO 나노막대가 10 nm와 100 nm 이하의 직경과 높이를 각각 가지며 육방정 결정구조의 단결정임을 확인하였다.

• 지질공학
• /
• 제1권1호
• /
• pp.68-84
• /
• 1991

A numerical analysis using Universal Distinct Element Code program for the nuclear waste disposal cavern has been performed for a typical Korean crystalline rock condition with same geometry of Swedish low and intermediate nuclear waste disposal repository(S.F.R). The stress concentration, displacement and safety factor for the typical single cross section of cavern, 5 caverns and a silo are analyzed.

• 한국결정성장학회:학술대회논문집
• /
• 한국결정성장학회 1999년도 PROCEEDINGS OF 99 INTERNATIONAL CONFERENCE OF THE KACG AND 6TH KOREA·JAPAN EMG SYMPOSIUM (ELECTRONIC MATERIALS GROWTH SYMPOSIUM), HANYANG UNIVERSITY, SEOUL, 06월 09일 JUNE 1999
• /
• pp.371-387
• /
• 1999

La2-xSrxCuO4 single-crystalline films were prepared on bulk single crystals of Zn-doped La2CuO4 as the substrates by LPE technique using tow deferent methods. When prepared using an alumina crucible in normal electrical furnace, the La2-xSrxCuO4 films were contaminated with less than 3 at% aluminum from the alumina crucibles. Aluminum contamination either reduced or completely destroyed the superconductivity of the La2-xSrxCuO4 films. For LPE growthby modified TSFZ method using an infrared heating furnace without crucibles, the La2-xSrxCuO4 films of x=0.11 showed superconducting with Tconset 36 K, which is 10 K higher than that in the La2-xSrxCuO4 bulk single crystals.