간행물
한국재료학회지 KCI 등재 SCOPUS Korean Journal of Materials Research
- 발행기관 한국재료학회
- 자료유형 학술지
- 간기 월간
- ISSN 2799-8525 (Print)2799-8681 (Online)
- 수록기간 1991 ~ 2024
- 주제분류 공학 > 재료공학 공학 분류의 다른 간행물
- 십진분류KDC 530DDC 620
권호리스트/논문검색
제18권 제10호 (2008년 10월) 10건
1.
2008.10
구독 인증기관 무료, 개인회원 유료
We have synthesized Eu3+-doped YVO4 phosphors by using a hydrothermal method and investigatedtheir luminescent properties. Aqueous solutions of Y2O3, V2O5, Eu2O3, and nitric acid with various pH valueswere used as the precursors. The crystallinity, surface condition, and emission characteristics were examinedusing XRD, FT-IR, and photo-excited spectrometer. Eu3+ incorporation followed by the efficient red emissionstrongly depends on the acidity of solution media. The emission intensity becomes stronger as the pH valuesincrease to 7 and then gradually decreases. This phenomenon might be related to the hydroxyl quenchingeffect, which is induced by surface bound OH- groups.
3,000원
2.
2008.10
구독 인증기관 무료, 개인회원 유료
We fabricated 10 nm-TiO2 thin films for DSSC (dye sensitized solar cell) electrode application using ALD (atomic layer deposition) method at the low temperatures of 150˚ and 250˚. We characterized the crosssectional microstructure, phase, chemical binding energy, and absorption of the TiO2 using TEM, HRXRD, XPS, and UV-VIS-NIR, respectively. TEM analysis showed a 10 nm-thick flat and uniform TiO2 thin film regardless of the deposition temperatures. Through XPS analysis, it was found that the stoichiometric TiO2 phase was formed and confirmed by measuring main characteristic peaks of Ti 2p1, Ti 2p3, and O 1s indicating the binding energy status. Through UV-VIS-NIR analysis, ALD-TiO2 thin films were found to have a band gap of 3.4 eV resulting in the absorption edges at 360 nm, while the conventional TiO2 films had a band gap of 3.0 eV (rutile)~3.2 eV (anatase) with the absorption edges at 380 nm and 410 nm. Our results implied that the newly proposed nano-thick TiO2 film using an ALD process at 150˚ had almost the same properties as thsose of film at 250˚. Therefore, we confirmed that the ALD-processed TiO2 thin film with nano-thickness formed at low temperatures might be suitable for the electrode process of flexible devices.
4,000원
3.
2008.10
구독 인증기관 무료, 개인회원 유료
We present the structural, optical, and electrical properties of amorphous silicon suboxide (a-SiOx) films grown on indium tin oxide glass substrates with a radio frequency magnetron technique from a polycrystalline silicon oxide target using ambient Ar. For different substrate-target distances (d = 8 cm and 10 cm), the deposition temperature effects were systematically studied. For d = 8cm, oxygen content in a-SiOx decreased with dissociation of oxygen onto the silicon oxide matrix; temperature increased due to enlargement of kinetic energy. For d = 10 cm, however, the oxygen content had a minimum between 150˚ and 200˚. Using simple optical measurements, we can predict a preferred orientation of liquid crystal molecules on a-SiOx thin film. At higher oxygen content (x > 1.6), liquid crystal molecules on an inorganic liquid crystal alignment layer of a-SiOx showed homogeneous alignment; however, in the lower case (x< 1.6), liquid crystals showed homeotropic alignment.
4,000원
4.
2008.10
구독 인증기관 무료, 개인회원 유료
The hydrogen gas sensing properties of a zinc oxide nanowire structure were studied. Porous zinc oxide nanowire structures were fabricated by oxidizing zinc deposited on a single-wall carbon nanotube (SWNT) template. This revealed a porous ZnO-SWNT composite due to the porosity in the SWNT film. The gas sensing properties were compared with those of zinc oxide thin films deposited on SiO2/Si substrates in sensitivity and operating temperature. The composite structure showed higher sensitivity and lower operating temperature than the zinc oxide film. It showed a response even at room temperature while the film structure did not.
4,000원
5.
2008.10
구독 인증기관 무료, 개인회원 유료
Growth behavior of InGaN/GaN self-assembled quantum dots (QDs) was investigated with respect to different growth parameters in low pressure metalorganic chemical vapor deposition. Locally formed examples of three dimensional InGaN islands were confirmed from the surface observation image with increasing indium source ratio and growth time. The InGaN/GaN QDs were formed in Stranski-Krastanow (SK) growth mode by the continuous supply of metalorganic (MO) sources, whereas they were formed in the Volmer-Weber (V-W) growth mode by the periodic interruption of the MO sources. High density InGaN QDs with 1~2nm height and 40~50nm diameter were formed by the S-K growth mode. Dome shape InGaN dots with 200~400nm diameter were formed by the V-W growth mode. InN content in InGaN QDs was estimated to be reduced with the increase of growth temperature. A strong peak between 420-460 nm (2.96-2.70 eV) was observed for the InGaN QDs grown by S-K growth mode in photoluminescence spectrum together with the GaN buffer layer peak at 362.2 nm (3.41 eV).
4,000원
6.
2008.10
구독 인증기관 무료, 개인회원 유료
BaTiO3/epoxy composites can be applied as the dielectric materials for embedded capacitors. The effects of the degree of BaTiO3 particle agglomeration on the dielectric properties of BaTiO3/epoxy composites were investigated in the present study. The degree of particle agglomeration was controlled by the milling of the agglomerated particles. The size and content of the agglomerated BaTiO3 particles decreased with an increase in the milling time. The dielectric constants and polarizations of BaTiO3/epoxy composites abruptly decreased with the increase of the milling time. It was concluded that the dielectric constants and polarizations of BaTiO3/epoxy composites decreased as the degree of particle agglomeration decreased. The degree of agglomeration of BaTiO3 particles turned out to be a very influential factor on the dielectric properties of BaTiO3/epoxy composites.
4,000원
7.
2008.10
구독 인증기관 무료, 개인회원 유료
Crack-free joining of Si3N4 and Al2O3 using 15 layers has been achieved by a unique approach introducing Sialon polytypoids as a functionally graded materials (FGMs) bonding layer. In the past, hot press sintering of multilayered FGMs with 20 layers of thickness 500μm each has been fabricated successfully. In this study, the number of layers for FGM was reduced to 15 layers from 20 layers for optimization. For fabrication, model was hot pressed at 38 MPa while heating up to 1700˚, and it was cooled at 2˚/min to minimize residual stress during sintering. Initially, FGM with 15 layers had cracks near 90 wt.% 12H / 10 wt.% Al2O3 and 90 wt.% 12H/10 wt.% Si3N4 layers. To solve this problem, FEM (finite element method) program based on the maximum tensile stress theory was applied to design optimized FGM layers of crack free joint. The sample is 3-dimensional cylindrical shape where this has been transformed to 2-dimensional axisymmetric mode. Based on the simulation, crack-free FGM sample was obtained by designing axial, hoop and radial stresses less than tensile strength values across all the layers of FGM. Therefore, we were able to predict and prevent the damage by calculating its thermal stress using its elastic modulus and coefficient of thermal expansion. Such analyses are especially useful for FGM samples where the residual stresses are very difficult to measure experimentally.
4,000원
8.
2008.10
구독 인증기관 무료, 개인회원 유료
Modified thermal annealing was applied to the activation of the polycrystalline silicon films doped as p-type through implantation of B2H6. The statistical design of experiments was successfully employed to investigate the effect of rapid thermal annealing on activation of polycrystalline Si doped as p-type. In this design, the input variables are furnace temperature, power of halogen lamps, and alternating magnetic field. The degree of ion activation was evaluated as a function of processing variables, using Hall effect measurements and Raman spectroscopy. The main effects were estimated to be furnace temperature and RTA power in increasing conductivity, explained by recrystallization of doped ions and change of an amorphous Si into a crystalline Si lattice. The ion activation using rapid thermal annealing is proven to be a highly efficient process in low temperature polycrystalline Si technology.
4,000원
9.
2008.10
구독 인증기관 무료, 개인회원 유료
TiAlN films were deposited on WC-5Co substrates with different buffer layers by D.C. magnetron sputtering. The films were evaluated by microstructural observations and measuring of preferred orientation, hardness value, and adhesion force. As a process variable, various buffer layers were used such as TiAlN single layer, TiAlN/TiAl, TiAlN/TiN and TiAlN/CrN. TiAlN coating layer showed columnar structures which grew up at a right angle to the substrates. The thickness of the TiAlN coating layer was about 1.8μm, which was formed for 200 minutes at 300˚. XRD analysis showed that the preferred orientation of TiAlN layer with TiN buffer layer was (111) and (200), and the specimens of TiAlN/TiAl, TiAlN/CrN, TiAlN single layer have preferred orientation of (111), respectively. TiAlN single layer and TiAlN/TiAl showed good adhesion properties, showing an over 80N adhesion force, while TiAlN/TiN film showed approximately 13N and the TiAlN/CrN was the worst case, in which the layer was destroyed because of high internal residual stress. The value of micro vickers hardness of the TiAlN single layer, TiAlN/TiAl and TiAlN/TiN layers were 2711, 2548 and 2461 Hv, respectively.
4,000원
10.
2008.10
구독 인증기관 무료, 개인회원 유료
Nanostructured carbon materials have been found to have applications in fuel cell electrodes, field emitters, electronic devices, sensors and electromagnetic absorbers, etc. Especially, the CNF (carbon nanofiber) can be expected to play an important role in catalyst supporters for fuel cell electrodes and chemical reactions. In this study, we synthesized CNF from a liquid phase carbon source by a solvothermal method. In addition, we studied the parameters for the preparation of CNF by controlling heating and cooling rates, synthesis temperature and time. We characterized the CNF by SEM/TEM, XRD, Raman spectroscopy and EDS. We found that the heating and cooling rate have strong effects on the CNF formation and growth. We were able to prepare the best CNF at the heating rate of 10˚/min, at 450˚ for 60 minutes, and at the cooling rate of 4˚/min. As a result of Raman spectra, we found that the sample showed two characteristic Raman bands at ~1350cm-1 (D band) and ~1600cm-1 (G band). The G band indicates the original graphite feature, but the D band has been explained as a disorder feature of the carbon structure. The diameter and length of the CNF was about 15~20nm, and over 1μ, respectively.
4,000원
