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 제4호 (2009년 4월) 10건
1.
2009.04
구독 인증기관 무료, 개인회원 유료
We fabricated thermally evaporated 30 nm-Ni/(20 nm or 60 nm)a-Si:H/Si films to investigate the energy-saving property of silicides formed by rapid thermal annealing (RTA) at temperatures of 350˚C, 450˚C, 550˚C, and 600˚C for 40 seconds. A transmission electron microscope (TEM) and a high resolution X-ray diffractometer (HRXRD) were used to determine the cross-sectional microstructure and phase changes. A UVVIS-NIR and FT-IR (Fourier transform infrared spectroscopy) were employed for near-IR and middle-IR absorbance. Through TEM and HRXRD analysis, for the nickel silicide formed at low temperatures below 450˚C, we confirmed columnar-shaped structures with thicknesses of 20~30 nm that had δ-Ni2Si phases. Regarding the nickel silicide formed at high temperatures above 550˚C, we confirmed that the nickel silicide had more than 50 nm-thick columnar-shaped structures with a Ni31Si12 phase. Through UV-VIS-NIR analysis, nickel silicide showed almost the same absorbance in the near IR region as well as ITO. However, in the middle IR region, the nickel silicides with low temperature showed similar absorbance to those from high temperature silicidation.
4,000원
2.
2009.04
구독 인증기관 무료, 개인회원 유료
Thermoelectric power and resistivity are measured for the perovskite LaNi1-xTixO3 (x≤0.5) in thetemperature range 77K−300K. The measured thermoelectric power of LaNi1-xTixO3 (x≤0.5) increases linearlywith temperature and is represented by A+BT. The x=0.1 sample showed metallic behavior, the x=0.3showed metal and insulating transition around 150K, and x=0.5 showed insulating behavior the over thewhole temperature range. The electrical resistivity of x=0.1 shows linear temperature dependence over thewhole temperature range and T2 dependence. On the other hand, the electrical resistivity of x=0.3 shows alinear relation between lnρ and T−1/4 (variable range hopping mechanism) in the range of 77K to 150K. Forx=0.5, the temperature dependence of resistivity is characteristic of insulating materials; the resistivity datawas fitted to an exponential law, such as ln(ρ/T) and T−1, which is usually attributed to a small polaronhopping mechanism. These experimental results are interpreted in terms of the spin polaron (x=0.1) andvariable range hopping (x=0.3) or small polaron hopping (x=0.5) of an almost localized Ni3+ 3d polaron.
4,000원
3.
2009.04
구독 인증기관 무료, 개인회원 유료
Carbon nanotubes (CNT) were used as a catalyst support where catalytically active Pd and Pt metalparticles decorated the outside of the external CNT walls. In this study, Pd and Pt nanoparticles supportedon HNO3-treated CNT were prepared by microwave-assisted heating of the polyol process using PdCl2 andH2PtCl6•6H2O precursors, respectively, and were then characterized by SEM, TEM, and Raman. Ramanspectroscopy showed that the acid treated CNT had a higher intensity ratio of ID/IG compared to that of non-treated CNT, indicating the formation of defects or functional groups on CNT after chemical oxidation.Microwave irradiation for total two minutes resulted in the formation of Pd and Pt nanoparticles on the acidtreated CNT. The sizes of Pd and Pt nanoparticles were found to be less than 10nm and 3nm, respectively.Furthermore, the SnO2 films doped with CNT decorated by Pd and Pt nanoparticles were prepared, and thenthe NO2 gas response of these sensor films was evaluated under 1~5ppm NO2 concentration at 200oC. It wasfound that the sensing property of the SnO2 film sensor on NO2 gas was greatly improved by the addition ofCNT-supported Pd and Pt nanoparticles.
4,000원
4.
2009.04
구독 인증기관 무료, 개인회원 유료
For use in ultrasonic actuators, we investigated the structural and piezoelectric properties of (1 - x)Pb(Zr0.515Ti0.485)O3 - xPb(Sb1/2Nb1/2)O3 + 0.5 wt% MnO2 [(1 - x)PZT - xPSN + MnO2] ceramics with a variation of x (x = 0.02, 0.04, 0.06, 0.08). All the ceramics, which were sintered at 1250˚C for 2 h, showed a typical perovskite structure, implying that they were well synthesized. A homogeneous micro structure was also developed for the specimens, and their average grain size was slightly decreased to 1.3μm by increasing x to 0.8. Moreover, a second phase with a pyrochlore structure appeared when x was above 0.06, which resulted in the deterioration of their piezoelectric properties. However, the 0.96PZT-0.04PSN+MnO2 ceramics, which corresponds with a morphotropic phase boundary (MPB) composition in the (1 - x)PZT - xPSN + MnO2 system, exhibited good piezoelectric properties: a piezoelectric constant (d33) of 325 pC/N, an electromechanical coupling factor (kp) of 70.8%, and a mechanical quality factor (Qm) of 1779. The specimens with a relatively high curie temperature (Tc) of 305˚C also showed a significantly high dielectric constant (εr) value of 1109. Therefore, the 0.96PZT - 0.04PSN + MnO2 ceramics are suitable for use in ultrasonic vibrators.
4,000원
5.
2009.04
구독 인증기관 무료, 개인회원 유료
SnxSe100-X (15|X|30) alloys have been studied to explore their suitability as phase change materials for nonvolatile memory applications. The phase change characteristics of thin films prepared by a Radio Frequency (RF) magnetron co-sputtering system were analyzed by an X-ray diffractometer and 4-point probe measurement. A phase change static tester was also used to determine their crystallization under the pulsed laser irradiation. X-ray diffraction measurements show that the transition in sheet resistance is accompanied by crystallization. The amorphous state showed sheet resistances five orders of magnitude higher than that of the crystalline state in SnxSe100-X (x = 15, 20, 25, 30) films. In the optimum composition, the minimum time of SnxSe100-X alloys for crystallization was 160, 140, 150, and 30ns at 15mW, respectively. The crystallization temperature and the minimum time for crystallization of thin films were increased by increasing the amount of Sn, which is correlated with the activation energy for crystallization.
3,000원
6.
2009.04
구독 인증기관 무료, 개인회원 유료
In this study, we attempted to develop a convenient aluminizing process, using Al-Ti mixed slurry as an aluminum source, to control the Al content of the aluminized layer as a result of a one-step process and can be widely adopted for coating complex-shaped components. The aluminizing process was carried out by the heat treatment on disc and rod shaped S45C steel substrates with Al-Ti mixed slurries that were composed of various mixed ratios (wt%) of Al and Ti powders. The surface of the resultant aluminized layer was relatively smooth with no obvious cracks. The aluminized layers mainly contain an Fe-Al compound as the bulk phase. However, the Al concentration and the thickness of the aluminized layer gradually decrease as the Ti proportion among Al-Ti mixed slurries increases. It has also been shown that the Al-Ti compound layer, which formed on the substrate during heat treatment, easily separates from the substrate. In addition, the incorporation of Ti into the substrate surface during heat treatment was not observed.
4,000원
7.
2009.04
구독 인증기관 무료, 개인회원 유료
A study on the dry beneficiation of sericite occurring in the Daehyun Mine of the Republic of Korea region as performed by applying selective grinding and air classification techniques. Quartz and sericite occurred in the raw ore as major components. The results of liberation using a ball mill and an impact mill showed that the contents of R2O were increased while SiO2 was decreased in proportion to decreasing particle size. According to the XRD, XRF analysis and the EDS of SEM analysis, the ball mill gave a better grade product in R2O content than the impact mill when the particle size was the same. When the raw ore was ground by the impact mill with arotor speed 57.6 m/sec and then followed by 15,000rpm classification using an air classifier, the chemical composition of the over flowed product was 49.65wt% SiO2, 32.15wt% Al2O3, 0.13wt% Fe2O3, 10.37wt% K2O, and 0.14wt% Na2O. This result indicates that the R2O contents were increased by 49.5% compared to that of the raw ore. From these results described above, it is suggested that hard mineral such as Quartz little ground by selective grinding using impact mill whereas soft mineral such as sericite easily ground to small size. As a result of that hard minerals can be easily removed from the finely ground sericite by air classification and the R2O grade of thus obtained concentrate was improved to higher than 10wt% which can be used for ceramics raw materials.
4,000원
8.
2009.04
구독 인증기관 무료, 개인회원 유료
Lithium dihydrogen phosphate (LiH2PO4) powder was purchased from Aldrich Chemical Co. Fromthe scanning electron microscope (SEM) observation, these polycrystals have dimensions in the range of 25-250µm. The electrical conductivity was measured at a measuring frequency of 1 kHz on heating polycrystallinelithium dihydrogen phosphate (LiH2PO4) from room temperature to 493 K. Two anomalies appeared at 451K (Tp1) and 469 K (Tp2). The electrical conductivity reached the magnitude of the superprotonic phases: 3×10-2Ω-1cm-1 at 451 K (Tp1) and 1.2×10Ω-1cm-1 at 469 K (Tp2). It is uncertain whether the superprotonic phasetransformations are due to polymorphic transitions in the bulk, surface transitions, or chemical reactions(thermal decomposition) at the surface. Considering several previous thermal studies (differential scanningcalorimetry and thermogravimetry), our experimental results seem to be related to the last case: chemicalreactions (thermal decomposition) at the surface with the progressive solid-state polymerization.
3,000원
9.
2009.04
구독 인증기관 무료, 개인회원 유료
Nanofabrication is an essential process throughout industry. Technologies that produce general nanofabrication, such as e-beam lithography, dip-pen lithography, DUV lithography, immersion lithography, and laser interference lithography, have drawbacks including complicated processes, low throughput, and high costs, whereas nano-transfer printing (nTP) is inexpensive, simple, and can produce patterns on non-plane substrates and multilayer structures. In general nTP, the coherency of gold-deposited stamps is strengthened by using SAM treatment on substrates, so the gold patterns are transferred from stamps to substrates. However, it is hard to apply to transfer other metallic materials, and the existing nTP process requires a complicated surface treatment. Therefore, it is necessary to simplify the nTP technology to obtain an easy and simple method for fabricating metal patterns. In this paper, asnTP process with poly vinyl alcohol (PVA) mold was proposed without any chemical treatment. At first, a PVA mold was duplicated from the master mold. Then, a Mo layer, with a thickness of 20 nm, was deposited on the PVA mold. The Mo deposited PVA mold was put on the Si wafer substrate, and nTP process progressed. After the nTP process, the PVA mold was removed using DI water, and transferred Mo nano patterns were characterized by a Scanning electron micrograph (SEM) and Energy Dispersive spectroscopy (EDS).
3,000원
10.
2009.04
구독 인증기관 무료, 개인회원 유료
Phase transition in ferroelectric polymer is very interesting behavior and has been widely studiedfor real device applications, such as actuators and sensors. Through the phase transition, there is structuralchange resulting in the change of electrical and optical properties. In this study, we fabricated the Febry-Perotinterferometer with the thin film of ferroelectric P(VDF-TrFE) 50/50mol% copolymer, and thermo-opticalproperties were investigated. The effective thermo-optical coefficient of P(VDF-TrFE) was obtained as 2.3~3.8×10-4/K in the ferroelectric temperature region (45oC~65oC) and 6.0×10-4/K in the phase transition temperatureregion (65oC~85oC), which is a larger than optical silica-fiber and PMMA. The resonance transmission peakof P(VDF-TrFE) with the variation of temperature showed hysteretic variation and the phase transitiontemperature of the polymer in heating condition was higher than in the cooling condition. The elimination ofthe hysteretic phase transition of P(VDF-TrFE) is necessary for practical applications of optical devices.
3,000원
