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
제25권 제9호 (2015년 9월) 12건
1.
2015.09
구독 인증기관 무료, 개인회원 유료
Resistance switching memory cells were fabricated using atomically dispersed Pt-SiO2 thin film prepared via RF co-sputtering. The memory cell can switch between a low-resistance-state and a high-resistance-state reversibly and reproducibly through applying alternate voltage polarities. Percolated conducting paths are the origin of the low-resistance-state, while trapping electrons in the negative U-center in the Pt-SiO2 interface cause the high-resistance-state. Intermediate resistance-states are obtained through controlling the compliance current, which can be applied to multi-level operation for high memory density. It is found that the resistance value is related to the capacitance of the memory cell: a 265-fold increase in resistance induces a 2.68-fold increase in capacitance. The exponential growth model of the conducting paths can explain the quantitative relationship of resistance-capacitance. The model states that the conducting path generated in the early stage requires a larger area than that generated in the last stage, which results in a larger decrease in the capacitance.
4,000원
2.
2015.09
구독 인증기관 무료, 개인회원 유료
The γ/γ´ two-phases, commonly known as a eutectic structure, are observed in the γ interdendritic region of a Nibase superalloy. However, the growth behavior of the γ/γ´ two-phases, whether it is of eutectic or peritectic nature, has not been decidedly established. Directional solidifications were, thus, performed with the planar interface at a low growth rate of 0.5 μm/s in order to promote macro segregation. Directional solidification started with the γ planar interface and the γ´ phase nucleated on the γ planar interface at the solidification fraction of 0.75. The γ/γ´ two-phases showed the γ´ rod structure as major phase and the γ minor phase between γ´ rods, and the volume fraction of the γ phase changed continuously with an increasing solidification fraction. The two-phase γ/γ´ is seen as the coupled peritectic.
4,000원
3.
2015.09
구독 인증기관 무료, 개인회원 유료
The effects of coating parameters were investigated in wear resistance coatings of Diamalloy-406 on Inconel 718 to obtain an optimum coating condition by high velocity oxy-fuel spraying. The coating parameters, the flow rates of source gases (hydrogen and oxygen), the powder feed rate, and the spray distance, were designed by the Taguchi method. The optimal conditions were determined: oxygen flow rate 34 FRM, hydrogen flow rate 57 FRM, powder feed rate 35 g/min, and spray distance 7 inch. Friction coefficients of the coating and the substrate decreased with an increasing sliding surface temperature from 25 oC to 450 oC. The friction coefficient of Diamalloy-4006 coating decreased as the sliding surface temperature increased from 0.43 ± 0.01 at 25 oC to 0.29 ± 0.01 at 450 oC. The wear trace and wear depth of the coating were smaller than the substrate at all temperatures tested. The relationship between spray parameters and wear resistance was discussed extensively, based on the measured roughness, hardness, and porosity in each coating.
4,000원
4.
2015.09
구독 인증기관 무료, 개인회원 유료
A simulation method to estimate microstructure dependent material properties and their influence on performance for a honeycomb structured SiC heating element has been established. Electrical and thermal conductivities of a porous SiC sample were calculated by solving a current continuity equation. Then, the results were used as input parameters for a finite element analysis package to predict temperature distribution when the heating element was subjected to a DC bias. Based on the simulation results, a direction of material development for better heating efficiency was found. In addition, a modified metal electrode scheme to decelerate corrosion kinetics was proposed, by which the durability of the water heating system was greatly improved.
4,000원
5.
2015.09
구독 인증기관 무료, 개인회원 유료
SnS-TiO2 nanocomposites are synthesized using simple, cheap, and less toxic SnCl2 as the tin (II) precursor. The prepared nanoparticles are characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-Vis diffuse reflectance spectra (DRS). The XRD and TEM results indicate that the prepared product has SnS nanoparticles and a grain diameter of 30 nm. The DRS demonstrate that SnS-TiO2 possesses the absorption profile across the entire visible light region. The generation of reactive oxygen species is detected through the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). It is found that the photocurrent density and photocatalytic effect increase with the modified SnS. Excellent catalytic degradation of Texbrite BA-L (TBA) solution is observed using the SnS-TiO2 composites under visible light irradiation. It is proposed that both the strong visible light absorption and the multiple exciton excitations contribute to the high visible light photocatalytic activity.
4,000원
6.
2015.09
구독 인증기관 무료, 개인회원 유료
Pellicle is defined as a thin transparent film stretched over an aluminum (Al) frame that is glued on one side of a photomask. As semiconductor devices are pursuing higher levels of integration and higher resolution patterns, the cleaning of the Al flame surface is becoming a critical step because the contaminants on the Al flame can cause lithography exposure defects on the wafers. In order to remove these contaminants from the Al frame, a highly concentrated nitric acid (HNO3) solution is used. However, it is difficult to fully remove them, which results in an increase in the Al surface roughness. In this paper, the pellicle frame cleaning is investigated using various cleaning solutions. When the mixture of sulfuric acid (H2SO4), hydrofluoric acid (HF), hydrogen peroxide (H2O2), and deionized water with ultrasonic is used, a high cleaning efficiency is achieved without HNO3. Thus, this cleaning process is suitable for Al frame cleaning and it can also reduce the use of chemicals.
4,000원
7.
2015.09
구독 인증기관 무료, 개인회원 유료
Evaluations of the microstructure and mechanical properties of age hardenable Cu-2.0wt%Be alloy are performed in order to determine whether it can be used as a welding electrode for projection welding. The microstructure examinations, hardness measurements, and tensile tests of selective aging conditions are conducted. The results indicate that the aging treatment with the fine-grained microstructure exhibits better hardness and high tensile properties than those of the coarsegrained microstructure. The highest hardness value and high tensile strength are obtained from the aged condition of 300 oC for 360 min due to the presence of the metastable γ. precipitates on the grain boundaries. The values of the highest hardness and tensile strength are measured as 374 Hv and 1236.2 MPa, respectively. The metastable γ. precipitates are transferred to the equilibrium γ precipitates due to the over-aged treatment. The presence of the γ precipitates appears as nodule-like precipitates decorated around the grain boundaries. The welding electrode with the best aging treated condition exhibits better welding performance for electrodes than those of electrodes used previously.
4,000원
8.
2015.09
구독 인증기관 무료, 개인회원 유료
YNbO4:Yb3+/Er3+ is synthesized using a solid-state reaction process with a LiCl flux. The effects of the Er/(Yb+Er) ratios (REr) on the up-conversion (UC) and down-conversion (DC) spectra are investigated. The XRD data confirm that the Yb3+ and Er3+ ions are fully substituted for the Y3+ sites. The UC emission spectra activated by 980 nm consists of green and red emission bands, which originate from the Er3+ ions through an energy transfer (ET) process from Yb3+ to Er3+. The UC emission intensity depends on the REr value, and the findings demonstrate that REr ≤ 0.14 is suitable for an effective UC process. The DC emission spectra under 269 nm radiation of the synthesized powders exhibits not only a strong blue emission assigned to the [NbO4]3− niobates, but also green peaks that originate from the Er3+ ions through an ET process between [NbO4]3− and Er3+.
4,000원
9.
2015.09
구독 인증기관 무료, 개인회원 유료
Pb1-xMoO4:Er3+/Yb3+ phosphors with various doping concentrations of Er3+ and Yb3+ (x = Er3++Yb3+, Er3+ = 0.05, 0.1, 0.2, and Yb3+ = 0.2, 0.45) are successfully synthesized using a microwave sol-gel method, and the up-conversion photoluminescence properties are investigated. Well-crystallized particles, which are formed after heat treatment at 900 oC for 16 h, exhibit a fine and homogeneous morphology with particle sizes of 2-5 μm. Under excitation at 980 nm, the Pb0.7MoO4: Er0.1Yb0.2 and Pb0.5MoO4:Er0.05Yb0.45 particles exhibit a strong 525 nm emission band, a weak 550 nm emission band in the green region, and a very weak 655 nm emission band in the red region. The Raman spectra of the doped particles indicate the presence of strong peaks at higher and lower frequencies induced by the disordered structures of Pb1-xMoO4 through the incorporation of the Er3+ and Yb3+ ions into the crystal lattice, which results in the unit cell shrinkage accompanying the new phase formation of the MoO4-x group.
4,000원
10.
2015.09
구독 인증기관 무료, 개인회원 유료
In photovoltaic power generation where minority carrier generation via light absorption is competing against minority carrier recombination, the substrate thickness and material quality are interdependent, and appropriate combination of the two variables is important in obtaining the maximum output power generation. Medici, a two-dimensional semiconductor device simulation tool, is used to investigate the interdependency in relation to the maximum power output in front-lit Si solar cells. Qualitatively, the results indicate that a high quality substrate must be thick and that a low quality substrate must be thin in order to achieve the maximum power generation in the respective materials. The dividing point is 70 μm/5 × 10−6 sec. That is, for materials with a minority carrier recombination lifetime longer than 5 × 10−6 sec, the substrate must be thicker than 70 μm, while for materials with a lifetime shorter than 5 × 10−6 sec, the substrate must be thinner than 70 μm. In substrate fabrication, the thinner the wafer, the lower the cost of material, but the higher the cost of wafer fabrication. Thus, the optimum thickness/lifetime combinations are defined in this study along with the substrate cost considerations as part of the factors to be considered in material selection.
4,000원
11.
2015.09
구독 인증기관 무료, 개인회원 유료
Hydroxyapatite (HA), which is an important calcium phosphate mineral, has been applied in orthopedics, dentistry, and many other fields depending upon its morphology. HA can be synthesized with different morphologies through controlling the synthesis method and several parameters. Here, we synthesize various morphologies of HA using two simple methods: hydrothermal combustion and solution combustion. The phase purity of the synthesized HA is confirmed using X-ray diffractometry. It demonstrates that pure phased hydroxyapatite can be synthesized using both methods. The morphology of the synthesized powder is examined using scanning electron microscopy. The effects of pH and temperature on the final powder are also investigated. At 140 oC, using the hydrothermal method, nano-micro HA rods with a hexagonal crystal structure can be synthesized, whereas using solution combustion method at 600 oC, a dense cubic morphology can be synthesized, which exhibits monoclinic crystal structures.
4,000원
12.
2015.09
구독 인증기관 무료, 개인회원 유료
The hardenability of boron steel specimens with different molybdenum and chromium contents was investigated using dilatometry and microstructural observations, and then was quantitatively measured at a critical cooling rate corresponding to 90 % martensite hardness obtained from a hardness distribution plotted as a function of cooling rate. Based on the results, the effect of an austenitizing temperature on the hardenability and tensile properties was discussed in terms of segregation and precipitation behavior of boron atoms at austenite grain boundaries. The molybdenum addition completely suppressed the formation of pro-eutectoid ferrite even at the slowest cooling rate of 0.2 oC/s, while the chromium addition did at the cooling rates above 3 oC/s. On the other hand, the hardenability of the molybdenum-added boron steel specimens decreased with an increasing austenitizing temperature. This is associated with the preferred precipitation of boron atoms since a considerable number of boron atoms could be concentrated along austenite grain boundaries by a non-equilibrium segregation mechanism. The secondary ion mass spectroscopy results showed that boron atoms were mostly segregated at austenite grain boundaries without noticeable precipitation at higher austenitization temperatures, while they formed as precipitates at lower austenitization temperatures, particularly in the molybdenum-added boron steel specimens.
4,000원
