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
제26권 제7호 (2016년 7월) 8건
1.
2016.07
구독 인증기관 무료, 개인회원 유료
The hydrogen embrittlement of two austenitic high-manganese steels was investigated using tensile testing under high-pressure gaseous hydrogen. The test results were compared with those of different kinds of austenitic alloys containing Ni, Mn, and N in terms of stress and ductility. It was found that the ultimate tensile stress and ductility were more remarkably decreased under high-pressure gaseous hydrogen than under high-pressure gaseous argon, unlike the yield stress. In the specimens tested under high-pressure gaseous hydrogen, transgranular fractures were usually observed together with intergranular cracking near the fracture surface, whereas in those samples tested under high-pressure gaseous argon, ductile fractures mostly occurred. The austenitic high-manganese steels showed a relatively lower resistance to hydrogen embrittlement than did those with larger amounts of Ni because the formation of deformation twins or microbands in austenitic highmanganese steels probably promoted planar slip, which is associated with localized deformation due to gaseous hydrogen.
4,000원
2.
2016.07
구독 인증기관 무료, 개인회원 유료
Mineral filler is used for resin compounds, because it increases the stiffness and thermal stability of a resin compound, and it also cuts down the cost. Calcium carbonate, silica, magnesium oxide, and others are used as filler materials in general, and the type of filler material, the size, and content can affect the physical properties of compounds. Those factors also influence the viscosity of resin mixtures and the workability, and should be adjusted by changing the contents of the filler, which depends on the size. In this study, five kinds of ground calcium carbonate, which were different in size, were used to produce polyester compounds ; the physical properties were compared with the filler size and contents. The mechanical properties were measured by bending strength and tensile strength, and the heat deflection temperature was obtained for thermal stability.
3,000원
3.
2016.07
구독 인증기관 무료, 개인회원 유료
NaCaLa1-x(MoO4)3:Ho3+/Yb3+ ternary molybdates with proper doping concentrations of Ho3+ and Yb3+ (x = Ho3+ +Yb3+, Ho3+ = 0.05 and Yb3+ = 0.35, 0.40, 0.45 and 0.50) were successfully synthesized by microwave sol-gel method. Well-crystallized particles formed after heat-treatment at 900 oC for 16 h showed a fine and homogeneous morphology with particle sizes of 3-5 μm. Under excitation at 980 nm, the UC intensities of the doped samples exhibited strong yellow emissions based on the combination of strong emission bands at 520-nm and 630-nm emission bands in the green and red spectral regions, respectively. The optimal Yb3+:Ho3+ ratios were obtained at 9:1 and 10:1, as indicated by the compositiondependent quenching effect of the Ho3+ ions. The pump power dependence of the upconversion emission intensity and the Commission Internationale de L'Eclairage chromaticity coordinates of the phosphors were evaluated in detail.
4,000원
4.
2016.07
구독 인증기관 무료, 개인회원 유료
Tensile tests and creep tests were carried out at high temperatures on an Al-Al4C3 alloy prepared by mechanical alloying technique. The material contains about 2.0 % carbon and 0.9 % oxygen in mass percent, and the volume fractions of Al4C3 and Al2O3 particles are estimated at 7.4 and 1.4 %, respectively, from the chemical composition. Minimum creep rate decreased steeply near two critical stresses, σcl (the lower critical stress) and σcu (the upper critical stress), with decreasing applied stress at temperatures below 723 K. Instantaneous plastic strain was observed in creep tests above a critical stress, σci, at each test temperature. σcu and σci were fairly close to the 0.2% proof stress obtained by tensile tests at each test temperature. It is thought that σcl and σcu correspond to the microscopic yield stress and the macroscopic yield stress, respectively. The lower critical stress corresponds to the local yield stress needed for dislocations to move in the soft region within subgrains. The creep strain in the low stress range below 723 K arises mainly from the local deformation of the soft region. The upper critical stress is equivalent to the macroscopic yield stress necessary for dislocations within subgrains or in subboundaries; this stress can extensively move beyond subboundaries under a stress above the critical point to yield a macroscopic deformation. At higher temperatures above 773 K, the influence of the diffusional creep increases and the stress exponent of the creep rate decreases.
4,000원
5.
2016.07
구독 인증기관 무료, 개인회원 유료
For the development of a low-melting point filler metal for brazing aluminum alloy, we analyzed change of melting point and wettability with addition of Sn into Al-20Cu-10Si filler metal. DSC results showed that the addition of 5 wt% Sn into the Al-20Cu-10Si filler metal caused its liquidus temperature to decrease by about 30 oC. In the wettability test, spread area of melted Al-Cu-Si-Sn alloy is increased through the addition of Sn from 1 to 5 wt%. For the measuring of the mechanical properties of the joint region, Al 3003 plate is brazed by Al-20Cu-10Si-5Sn filler metal and the mechanical property is measured by tensile test. The results showed that the tensile strength of the joint region is higher than the tensile strength of Al 3003. Thus, failure occurred in the Al 3003 plate.
4,000원
6.
2016.07
구독 인증기관 무료, 개인회원 유료
Gas hydrates are crystalline solids in which gas molecules (guests) are trapped in water cavities (hosts) that are composed of hydrogen-bonded water molecules. During the formation of gas hydrates in seawater, the equilibria and kinetics are then affected by salinity. In this study, the effects of salinity on the equilibria of CO2 and R134-a gas hydrates has been investigated by tracing the changes of operating temperature and pressure. Increasing the salinity by 1.75% led to a drop in the equilibrium temperature of about 2 oC for CO2 gas hydrate and 0.38 oC for R-134a gas hydrate at constant equilibrium pressure; in other words, there were rises in the equilibrium pressure of about 1 bar and 0.25 bar at constant equilibrium temperature, respectively. The kinetics of gas hydrate formation have also been investigated by time-resolved in-situ Raman spectroscopy; the results demonstrate that the increase of salinity delayed the formation of both CO2 and R134-a gas hydrates. Therefore, various ions in seawater can play roles of inhibitors for gas hydrate formation in terms of both equilibrium and kinetics.
4,000원
7.
2016.07
구독 인증기관 무료, 개인회원 유료
A cold roll-bonding process was applied to fabricate an AA1050/AA6061/AA1050 laminate complex sheet. Two AA1050 and one AA6061 sheets of 2 mm thickness, 40 mm width and 300 mm length were stacked up after surface treatment that included degreasing and wire brushing; material was then reduced to a thickness of 3 mm by one-pass cold rolling. The laminate sheet bonded by the rolling was further reduced to 1.2 mm in thickness by conventional rolling. The rolling was performed at ambient temperature without lubricant using a 2-high mill with a roll diameter of 210 mm. The rolling speed was 5.0 m/sec. The AA1050/AA6061/AA1050 laminate complex sheet fabricated by roll bonding was then hardened by natural aging T4) and artificial aging (T6) treatments. The microstructures of the as-roll bonded and the age hardened Al complex sheets were revealed by optical microscope observation; the mechanical properties were investigated by tensile testing and hardness testing. The strength of the as-roll bonded complex sheet was found to increase by 2.9 times compared to that value of the starting material. In addition, the hardness of the complex sheets increased with cold rolling for AA1050 and age-hardening treatment for AA6061, respectively. After heat treatment, both AA1050 and AA6061 showed typical recrystallization structures in which the grains were equiaxed; however, the grain size was smaller in AA6061 than in AA1050.
4,000원
8.
2016.07
구독 인증기관 무료, 개인회원 유료
Flower-like nickel oxide (NiO) catalysts were coated on NiCrAl alloy foam using a hydrothermal method. The structural, morphological, and chemical bonding properties of the NiO catalysts coated on the NiCrAl alloy foam were investigated by field-emission scanning electron microscopy, scanning electron microscopy-energy dispersive spectroscopy, Xray diffraction, and X-ray photoelectron spectroscopy, respectively. To obtain flower-like morphology of NiO catalysts on the NiCrAl alloy foam, we prepared three different levels of pH of the hydrothermal solution: pH-7.0, pH-10.0, and pH-11.5. The NiO morphology of the pH-7.0 and pH-10.0 samples exhibited a large size plate owing to the slow reaction of the hydroxide (OH−) and nickel ions (Ni+) in lower pH than pH-11.5. Flower-like NiO catalysts (~4.7 μm-6.6 μm) were formed owing to the fast reaction of OH− and Ni2+ by increased OH− concentration at high pH. Thus, the flower-like morphology of NiO catalysts on NiCrAl alloy foam depends strongly on the pH of the hydrothermal solution.
4,000원
