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
제30권 제5호 (2020년 5월) 8건
1.
2020.05
구독 인증기관 무료, 개인회원 유료
The design and fabrication of catalysts with low-cost and high electrocatalytic activity for the oxygen evolution reaction (OER) have remained challenging because of the sluggish kinetics of this reaction. The key to the pursuit of efficient electrocatalysts is to design them with high surface area and more active sites. In this work, we have successfully synthesized a highly stable and active NiCo2S4 nanowire array on a Ni-foam substrate (NiCo2S4 NW/NF) via a two-step hydrothermal synthesis approach. This NiCo2S4 NW/NF exhibits overpotential as low as 275 mV, delivering a current density of 20 mA cm-2 (versus reversible hydrogen electrode) with a low Tafel slope of 89 mV dec-1 and superior long-term stability for 20 h in 1M KOH electrolyte. The outstanding performance is ascribed to the inherent activity of the binder-free deposited, vertically aligned nanowire structure, which provides a large number of electrochemically active surface sites, accelerating electron transfer, and simultaneously enhancing the diffusion of electrolyte.
4,000원
2.
2020.05
구독 인증기관 무료, 개인회원 유료
As a case study on aspect ratio behavior, Kaolin, zeolite, TiO2, pozzolan and diatomaceous earth minerals are investigated using wet milling with 0.3 mm media. The grinding process using small media of 0.3 pai is suitable for current work processing applications. Primary particles with average particle size distribution D50, ~6 μm are shifted to submicron size, D50 ~0.6 μm after grinding. Grinding of particles is characterized by various size parameters such as sphericity as geometric shape, equivalent diameter, and average particle size distribution. Herein, we systematically provide an overview of factors affecting the primary particle size reduction. Energy consumption for grinding is determined using classical grinding laws, including Rittinger's and Kick's laws. Submicron size is obtained at maximum frictional shear stress. Alterations in properties of wettability, heat resistance, thermal conductivity, and adhesion increase with increasing particle surface area. In the comparison of the aspect ratio of the submicron powder, the air heat conductivity and the total heat release amount increase 68 % and 2 times, respectively.
4,000원
3.
2020.05
구독 인증기관 무료, 개인회원 유료
The composition of martensite transformation in NiAl alloy is determined using pure nickel and aluminum powder by vacuum hot press powder metallurgy, which is a composition of martensitic transformation, and the characteristics of martensitic transformation and microstructure of sintered NiAl alloys are investigated. The produced sintered alloys are presintered and hot pressed in vacuum; after homogenizing heat treatment at 1,273 K for 86.4 ks, they are water-cooled to produce NiAl sintered alloys having relative density of 99 % or more. As a result of observations of the microstructure of the sintered NiAl alloy specimens quenched in ice water after homogenization treatment at 1,273 K, it is found that specimens of all compositions consisted of two phases and voids. In addition, it is found that martensite transformation did not occur because surface fluctuation shapes did not appear inside the crystal grains with quenching at 1,273 K. As a result of examining the relationship between the density and composition after martensitic transformation of the sintered alloys, the density after transformation is found to have increased by about 1 % compared to before the transformation. As a result of examining the relationship between the hardness (Hv) at room temperature and the composition of the matrix phase and the martensite phase, the hardness of the martensite phase is found to be smaller than that of the matrix phase. As a result of examining the relationship between the temperature at which the shape recovery is completed by heating and the composition, the shape recovery temperature is found to decrease almost linearly as the Al concentration increases, and the gradient is about -160 K/ at% Al. After quenching the sintered NiAl alloys of the 37 at%Al into martensite, specimens fractured by three-point bending at room temperature are observed by SEM and, as a result, some grain boundary fractures are observed on the fracture surface, and mainly intergranular cleavage fractures.
4,000원
4.
2020.05
구독 인증기관 무료, 개인회원 유료
Synthesizing one-dimensional nanostructures of oxide semiconductors is a promising approach to fabricate highefficiency photoelectrodes for hydrogen production from photoelectrochemical (PEC) water splitting. In this work, vertically aligned zinc oxide (ZnO) nanorod arrays are successfully synthesized on fluorine-doped-tin-oxide (FTO) coated glass substrate via seed-mediated hydrothermal synthesis method with the use of a ZnO nanoparticle seed layer, which is formed by thermally oxidizing a sputtered Zn metal thin film. The structural, optical and PEC properties of the ZnO nanorod arrays synthesized at varying levels of Zn sputtering power are examined to reveal that the optimum ZnO nanorod array can be obtained at a sputtering power of 20W. The photocurrent density and the optimal photocurrent conversion efficiency obtained for the optimum ZnO nanorod array photoanode are 0.13 mA/cm2 and 0.49 %, respectively, at a potential of 0.85 V vs. RHE. These results provide a promising avenue to fabricating earth-abundant ZnO-based photoanodes for PEC water oxidation using facile hydrothermal synthesis.
4,000원
5.
2020.05
구독 인증기관 무료, 개인회원 유료
The annealing characteristics of cold-rolled Al-6.5Mg-1.5Zn-0.5Fe-0.5Mn alloy, newly designed as an automobile material, are investigated in detail, and compared with those of other aluminum alloys. Using multi-pass rolling at room temperature, the ingot aluminum alloy is cut to a thickness of 4 mm, width of 30 mm, and length of 100 mm to reduce the thickness to 1 mm (r = 75 %). Annealing after rolling is performed at various temperatures ranging from 200 to 500 oC for 1 hour. The specimens annealed at temperatures up to 300 oC show a deformation structure; however, from 350 oC they have a recrystallization structure consisting of almost equiaxed grains. The hardness distribution in the thickness direction of the annealed specimens is homogeneous at all annealing temperatures, and their average hardness decreases with increasing annealing temperature. The tensile strength of the as-rolled specimen shows a high value of 496 MPa; however, this value decreases with increasing annealing temperature and becomes 338MPa after annealing at 400 oC. These mechanical properties of the specimens are compared with those of other aluminum alloys, including commercial 5xxx system alloys.
4,000원
6.
2020.05
구독 인증기관 무료, 개인회원 유료
We prepare ZnO nanoparticles by environmentally friendly synthesis using Cyathea nilgiriensis leaf extract. Various phytochemical constituents are identified through the assessment of ethanolic extract of plant Cyathea nilgiriensis holttum by GC-MS analysis. The formation of ZnO nanoparticles is confirmed by FT-IR, XRD, SEM-EDX, TEM, SAED and PSA analysis. TEM observation reveals that the biosynthesized ZnO nanopowder has a hexagonal structure. The calculated average crystallite size from the high intense plane of (1 0 1) is 29.11 nm. The particle size, determined by TEM analysis, is in good agreement with that obtained by XRD analysis. We confirm the formation of biomolecules in plant extract by FT-IR analysis and propose a possible formation mechanism of ZnO nanoparticles. Disc diffusion method is used for the analyses of antimicrobial activity of ZnO nanoparticles. The synthesized ZnO nanoparticles exhibit antimicrobial effect in disc diffusion experiments. The biosynthesized ZnO nanoparticles display good antibacterial performance against B. subtilis (Gram-positive bacteria) and K. pneumonia (Gram-negative bacteria). Bio-synthesized nanoparticles using green method are found to possess good antimicrobial performance.
4,000원
7.
2020.05
구독 인증기관 무료, 개인회원 유료
In this paper, we investigated the effect of the passivation stack with Al2O3, hydrogenated silicon nitride (SiNx:H) stack and Al2O3, silicon oxynitride (SiONx) stack in the n type bifacial solar cell on monocrystalline silicon. SiNx:H and SiONx films were deposited by plasma enhanced chemical vapor deposition on the Al2O3 thin film deposited by thermal atomic layer deposition. We focus on passivation properties of the two stack structure after laser ablation process in order to improve bifaciality of the cell. Our results showed SiNx:H with Al2O3 stack is 10 mV higher in implied open circuit voltage and 60 μs higher in minority carrier lifetime than SiONx with Al2O3 stack at Ni silicide formation temperature for 1.8% open area ratio. This can be explained by hydrogen passivation at the Al2O3/Si interface and Al2O3 layer of laser damaged area during annealing.
4,000원
8.
2020.05
구독 인증기관 무료, 개인회원 유료
Cerium oxide (ceria, CeO2) is one of the most wide-spread oxide supporting materials for the precious metal nanoparticle class of heterogeneous catalysts. Because ceria can store and release oxygen ions, it is an essential catalytic component for various oxidation reactions such as CO oxidation (2CO + O2 2CO2). Moreover, reduced ceria is known to be reactive for water activation, which is a critical step for activation of water-gas shift reaction (CO + H2O → H2 + CO2). Here, we apply van der Waals-corrected density functional theory (DFT) calculations combined with U correction to study the mechanism of water chemisorption on CeO2(111) surfaces. A stoichiometric CeO2(111) and a defected CeO2(111) surface showed different water adsorption chemistry, suggesting that defected CeO2 surfaces with oxygen vacancies are responsible for water binding and activation. An appropriate level of water-ceria chemisorption energy is deduced by vdW-corrected non-local correlation coupled with the optB86b exchange functional, whereas the conventional PBE functional describes weaker water-ceria interactions, which are insufficient to stabilize (chemisorb) water on the ceria surfaces.
4,000원
