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
제19권 제9호 (2009년 9월) 10건
1.
2009.09
구독 인증기관 무료, 개인회원 유료
Recently, metal molding has become essential not only for automobile parts, but also mass production, and has greatly influenced production costs as well as the quality of products. Its surface has been treated by carburizing, nitriding and induction hardening, but these existing treatments cause considerable deformation and increase the expense of postprocessing after treatment; furthermore, these treatments cannot be easily applied to parts that requiring the hardening of only a certain section. This is because the treatment cannot heat the material homogeneously, nor can it heat all of it. Laser surface treatment was developed to overcome these disadvantages, and, when the laser beam is irradiated on the surface and laser speed is appropriate, the laser focal position is rapidly heated and the thermal energy of surface penetrates the material after irradiation, finally imbuing it with a new mechanical characteristic by the process of self-quenching. This research estimates the material characteristic after efficient and functional surface treatment using HPDL, which is more efficient than the existing CW Nd:YAG laser heat source. To estimate this, microstructural changes and hardness characteristics of three parts (the surface treatment part, heat affect zone, and parental material) are observed with the change of laser beam speed and surface temperature. Moreover, the depth of the hardened area is observed with the change of the laser beam speed and temperature.
4,000원
2.
2009.09
구독 인증기관 무료, 개인회원 유료
The Charge Trap Flash (CTF) memory device is a replacement candidate for the NAND Flash device. In this study,Pt/Al2O3/La2O3/SiO2/Si multilayer structures with lanthanum oxide charge trap layers were fabricated for nonvolatile memorydevice applications. Aluminum oxide films were used as blocking oxides for low power consumption in program/erase operationsand reduced charge transports through blocking oxide layers. The thicknesses of SiO2 were from 30Å to 50Å. From the C-Vmeasurement, the largest memory window of 1.3V was obtained in the 40Å tunnel oxide specimen, and the 50Å tunnel oxidespecimen showed the smallest memory window. In the cycling test for reliability, the 30Å tunnel oxide sample showed an abruptmemory window reduction due to a high electric field of 9~10MV/cm through the tunnel oxide while the other samples showedless than a 10% loss of memory window for 104cycles of program/erase operation. The I-V measurement data of the capacitorstructures indicated leakage current values in the order of 10-4A/cm2 at 1V. These values are small enough to be used in non-volatile memory devices, and the sample with tunnel oxide formed at 850oC showed superior memory characteristics comparedto the sample with 750oC tunnel oxide due to higher concentration of trap sites at the interface region originating from the roughinterface.
4,000원
3.
2009.09
구독 인증기관 무료, 개인회원 유료
The silver nanofluids were synthesized by the pulsed wire evaporation (PWE) method in a liquid-gas mixture. The size and microstructure of nanoparticles in the deionized water were investigated by a particle size analyzer (PSA), transmission electron microscope (TEM), and scanning electron microscope (SEM). Also, the synthesized nanofluids were investigated in order to assess the stability of dispersion of nanofluid by the zetapotential analyzer and dispersion stability analyzer. The results showed that the spherical silver nanoparticle formed in the deionized water and mean particle size was about 50 nm. Also, when explosion times were in the range of 20~200 times, the absolute value of zeta potential was less than -27 mV and the dispersion stability characteristic of low concentration silver nanofluid was better than the high concentration silver nanofluid by turbiscan.
4,000원
4.
2009.09
구독 인증기관 무료, 개인회원 유료
In order to provide the mechanism of nozzle clogging, recovered nozzles for high strength steel grade were examined carefully after continuous casting. The thickness of clogged material in SEN is increased in the following order: from the bottom to the top of the nozzle, upper part of slag line, and the pouring hole. Nozzle clogging material begins to form due the adhesion of metal to nozzle wall, the decarburization, and reduction of oxide in the refractory by Al and Ti in the melt. The reduction of oxide in the refractory by Al and Ti improves the wettability of the melt on the refractory and forms a thin Al-Ti-O layer. Metal containing micro alumina inclusions is solidified on the Al-Ti-O layer, and the solid layer grows due to the heat evolution through the nozzle wall. Thermodynamic calculation has been made for the related reactions. The effect of superheat to the nozzle clogging is discussed on ultra low carbon steel and low carbon steel.
4,000원
5.
2009.09
구독 인증기관 무료, 개인회원 유료
The photocatalysts of Fe-ACF/TiO2 compositeswere prepared by the sol-gel method and characterizedby BET, XRD, SEM, and EDX. It showed that the BET surface area was related to adsorption capacity foreach composite. The SEM results showed that ferric compound and titanium dioxide were distributed on thesurfaces of ACF. The XRD results showed that Fe-ACF/TiO2 composite only contained an anatase structurewith a Fe mediated compound. EDX results showed the presence of C, O, and Ti with Fe peaks in Fe-ACF/TiO2 composites. From the photocataytic degradation effect, TiO2 on activated carbon fiber surface modifiedwith Fe (Fe-ACF/TiO2) could work in the photo-Fenton process. It was revealed that the photo-Fenton reactiongives considerable photocatalytic ability for the decomposition of methylene blue (MB) compared to non-treatedACF/TiO2, and the photo-Fenton reaction was improved by the addition of H2O2. It was proved that thedecomposition of MB under UV (365nm) irradiation in the presence of H2O2 predominantly accelerated theoxidation of Fe2+ to Fe3+ and produced a high concentration of OH. radicals.
4,000원
6.
2009.09
구독 인증기관 무료, 개인회원 유료
Thin films of single-wall carbon nanotubes (SWNT) with various thicknesses were fabricated, and their optical andelectrical properties were investigated. The SWNTs of various thicknesses were directly coated in the arc-discharge chamberduring the synthesis and then thermally and chemically purified. The crystalline quality of the SWNTs was improved by thepurification processes as determined by Raman spectroscopy measurements. The resistance of the film is the lowest for thechemically purified SWNTs. The resistance vs. thickness measurements reveal the percolation thickness of the SWNT film tobe ~50nm. Optical absorption coefficient due to Beer-Lambert is estimated to be 7.1×10-2nm-1. The film thickness for 80%transparency is about 32nm, and the sheet resistance is 242Ω/sq. The authors also confirmed the relation between electricalconductance and optical conductance with very good reliability by measuring the resistance and transparency measurements.
4,000원
7.
2009.09
구독 인증기관 무료, 개인회원 유료
Thermoluminescent Properties by the Cooling Temperature and Grain Size in the LiYSiO4 : La Phosphors
The thermoluminescent phosphors of LiYSiO4 containing rare earth metal(La) dopants of 1 wt.%5 wt.% were prepared, and their TL characteristics have been investigated as a function of parameters such as the doping level and the heating rate. The grain size and cooling temperature of the highly sensitive LiYSiO4: La phosphors have been investigated. The glow curve of LiYSiO4: La has two peaks (P1, P2), and the peak height ratio of the two peaks is called P2/P1; here, the main peak is P2. Experimental results indicate that the peak height ratios of the glow curve for LiYSiO4: La are clearly correlated with the grain size and cooling temperature. The maximum P2/P1 ratio 3.25, the maximum sensitivity was observed for a grain size between 100-150 μm. The intensity of the TL peak of the phosphors was linearly proportion to the dose of X-rays.
4,000원
8.
2009.09
구독 인증기관 무료, 개인회원 유료
Transparent ITO films were deposited on a polycarbonate substrate with RF magnetron sputtering in a pure argon(Ar) and oxygen (O2) gas atmosphere, and then post deposition electro annealed for 20 minutes in a 4×10-1Pa vacuum. Electronbombardment with an accelerating voltage of 100V increased the substrate temperature to 120oC. XRD analysis of the depositedITO films did not show any diffraction peaks, while electro annealed films indicated the growth of crystallites on the (211), (222),and (400) planes. The sheet resistance of ITO films decreased from 103 to 82Ω/□. The optical transmittance of ITO films inthe visible wavelength region increased from 85 to 87%. Observation of the work function demonstrated that the electro-annealingincreased the work function of ITO films from 4.4 to 4.6eV. The electro annealed films demonstrated a larger figure of meritof 3.0×10-3Ω-1 than that of as deposited films. Therefore, the electro annealed films had better optoelectrical performances thanas deposited ITO films.
4,000원
9.
2009.09
구독 인증기관 무료, 개인회원 유료
The Zr-based bulk metallic glass matrix composites of a mixture of gas-atomized metallic glass powders and Fe-based nanostructured powders were fabricated by spark plasma sintering. The Fe-based nanostructured powders adopted for the enhancement of plasticity were well distributed in the matrix after consolidation, and the matrix remains as a fully amorphous phase. The successful consolidation of metallic glass matrix composite with high density was attributed to viscous flow in the supercooled liquid state during spark plasma sintering. Unlike other amorphous matrix composites, in which improved ductility could be obtained at the expense of their strength, the developed composite exhibited improvement both in strength and ductility. The ductility improvement in the composite was considered to be due to the formation of multiple shear bands under the presence of the Fe-based nanostructured particles.
4,000원
10.
2009.09
구독 인증기관 무료, 개인회원 유료
The compound of 2,6-Bis[(9-phenylcarbazolyl)ethenyl]naphthalene (BPCEN-1), 2-[6-1-Cyano-2-(9-phenylcarbazoly)vinylnaphthyl]-3-(9-phenylcarbazolyl)acrylonitrile (BPCEN-2), 2,6-Bis[4-(1-naphthy l)phenylamino styrenyl] naphthalene (BNPASN-1), 2-[6-1-Cyano-2-(naphthylphenylaminophenyl) vinylnaphthyl]-3-(naphthylphenylaminophenyl)acrylonitrile (BNPASN-2) was analyzed electrochemically and spectroscopically and can be obtained by bonding phenylcarbazolyl, naphthylphenylaminophenyl and -CN ligands to 2,7-naphthalene. The electrochemical and spectroscopic study resulted in the P-type (BPCEN-1, BNPASN-1) being changed to N-type (BPCEN-2, BNPASN-2) according to -CN bonding despite having the same structure. The value of band gap(Eg) was revealed to be small as HOMO had shifted higher and LUMO lower. The Eg value for naphthylphenylaminophenyl ligand was reduced because it has a smaller HOMO/LUMO value than that of phenylcarbazolyl from a structural perspective. The electrochemical HOMO/LUMO values for BPCEN-1, BPCEN-2, BNPASN-1, BNPASN-2 were measured to be 5.55eV / 2.83eV, 5.73eV / 3.06eV, 5.48eV / 2.78eV, and 5.53eV / 2.98eV, respectively. By -CN ligand, the UV max, Eg and PL max were shifted to longer wavelength in their spectra and the luminescence band could be also confirmed to be broad in the photoluminescence (PL) spectrum.
4,000원
