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 제10호 (2016년 10월) 10건
1.
2016.10
구독 인증기관 무료, 개인회원 유료
The effect of NaOH concentration on the properties of electrolytic plasma processing (EPP) coating formed on AZ61A Mg alloy is studied. Various types of EPP were employed on magnesium alloy AZ61A in a silicate bath with different concentrations of NaOH additive. Analysis of the composition and structure of the coating layers was carried out using an Xray diffractometer (XRD) and a scanning electron microscope (SEM). The results showed that the oxide coating layer mainly consisted of MgO and Mg2SiO4; its porosity and thickness were highly dependent on the NaOH concentration. The Vickers hardness was over 900 HV for all the coatings. The oxide layer with 3 g/l of NaOH concentration exhibited the highest hardness value (1220 HV) and the lowest wear rate. Potentiodynamic testing of the 3 g/l NaOH concentration showed that this concentration had the highest corrosion resistance value of 2.04 × 105 Ωcm2; however, the corrosion current density value of 5.80 × 10−7 A/cm2 was the lowest such value.
4,000원
2.
2016.10
구독 인증기관 무료, 개인회원 유료
Geopolymers have many advantages over Portland cement, including energy efficiency, reduced greenhouse gas emissions, high strength at early age and improved thermal resistance. Alkali activated geopolymers made from waste materials such as fly ash or blast furnace slag are particularly advantageous because of their environmental sustainability and low cost. However, their durability and functionality remain subjects for further study. Geopolymer materials can be used in various applications such as fire and heat resistant fiber composites, sealants, concretes, ceramics, etc., depending on the chemical composition of the source materials and the activators. In this study, we investigated the thermal properties and microstructure of fly ash and blast furnace slag based geopolymers in order to develop eco-friendly construction materials with excellent energy efficiency, sound insulation properties and good heat resistance. With different curing times, specimens of various compositions were investigated in terms of compressive strength, X-ray diffraction, thermal property and microstructure. In addition, we investigated changes in X-ray diffraction and microstructure for geopolymers exposed to 1,000 oC heat.
4,000원
3.
2016.10
구독 인증기관 무료, 개인회원 유료
The aim of this paper is to consider the effect of the manufacturing processes on corrosion and centerline cracking of ancient bronze spoons. The ancient bronze spoons in question were made by several steps of forging, in reheated condition with cast ingots. The manufacturing method is similar to that of the modern spoons. The investigations include observations from light and scanning electron microscopes of the microstructure in terms of the crack propagation. Cracks in the centerline are caused by solute segregation in the center-line region; this solute is solidified in the final stage of bronze spoon manufacture. Centerline cracking is also caused by α phase segregation, accompanied by forged overlapping along the longitudinal direction of the spoons. A vertical stripe with cracks along the centerline of the spoon’s width is formed by folding in the wrought process. The overlapping area causes crack propagation with severe corrosion on the spoon surfaces over a period of a thousand years. The failure mechanisms of ancient bronze spoons may be similar to that of modern spoons, and the estimation of the failure mechanisms of ancient spoons can be appropriate to determine failure causes for such modern spoons.
4,000원
4.
2016.10
구독 인증기관 무료, 개인회원 유료
The present study deals with the effects of micro-alloying elements such as Ni, V, and Ti on the recrystallization behavior of carbon steels at different strain rates. Eight steel specimens were fabricated by varying the chemical composition and reheating temperature; then, a high-temperature compressive deformation test was conducted in order to investigate the relationship of the microstructure and the recrystallization behavior. The specimens containing micro-alloying elements had smaller prior austenite grain sizes than those of the other specimens, presumably due to the pinning effect of the formation of carbonitrides and AlN precipitates at the austenite grain boundaries. The high-temperature compressive deformation test results indicate that dynamic recrystallization behavior was suppressed in the specimens with micro-alloying elements, particularly at increased strain rate, because of the pinning effect of precipitates, grain boundary dragging and lattice misfit effects of solute atoms, although the strength increased with increasing strain rate.
4,000원
5.
2016.10
구독 인증기관 무료, 개인회원 유료
The influence of NiCrAlY bond coating on the adhesion properties of an Fe thermal coating sprayed on an Al substrate was investigated. By applying a bond coat, an adhesion strength of 21MPa was obtained, which was higher than the 15.5MPa strength of the coating without the bond coat. Formation of cracks at the interface of the bond coat and the Al substrate was suppressed by applying the bond coat. Microstructural analysis of the coating interface using EBSD and TEM indicated that the dominant bonding mechanism was mechanical interlocking. Mechanical interlocking without crack defects in the coating interface may improve the adhesion strength of the coating. In conclusion, the use of an NiCrAlY bond coat is an effective method of improving the adhesion properties of thermal sprayed Fe coatings on Al substrates.
4,000원
6.
2016.10
구독 인증기관 무료, 개인회원 유료
We have investigated a glass-forming region of V2O5- P2O5-ZnO glass and the effects of the addition of modifier oxides (B2O3) to the glass systems as a sealing material to improve the adhesion between the glass frits and a soda lime substrate. Thermal properties and coefficient of thermal expansion were measured using a differential scanning calorimetry, a dilatometer and a hot stage microscopy. Structural changes and interfacial reactions between the glass substrate and the glass frit after sintering (at 400 oC for 1 h) were measured by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscope. The results showed that the adhesion strength increases as the content of B2O3 at 5 mol% increases because of changes in the structural properties. It seems that the glass structures change with B2O3, and the Si4+ ions from the substrate are diffused to the sealing glass. From these results, we could understand the mechanism of strengthening of the adhesion of soda lime silica substrate by ion-diffusion from the substrate to the glass.
4,000원
7.
2016.10
구독 인증기관 무료, 개인회원 유료
Using current-voltage (I-V) and capacitance-voltage (C-V) measurements, the electrical properties of Au and Cu Schottky contacts to n-Ge were comparatively investigated. Lower values of barrier height, ideality factor and series resistance were obtained for the Au contact as compared to the Cu contact. The values of capacitance showed strong dependence on the bias voltage and the frequency. The presence of an inversion layer at the interface might reduce the intercept voltage at the voltage axis, lowering the barrier height for C-V measurements, especially at lower frequencies. In addition, a higher interface state density was observed for the Au contact. The generation of sputter deposition-induced defects might occur more severely for the Au contact; these defects affected both the I-V and C-V characteristics.
4,000원
8.
2016.10
구독 인증기관 무료, 개인회원 유료
SrAl2O4: Eu2+ and Dy3+ phosphorescent phosphors were synthesized using the polymerized complex method. Generally, phosphorescent phosphors synthesized by conventional solid state reaction show a micro-sized particle diameter; thus, this process is restricted to applications such as phosphorescent ink and paint. However, it is possible to synthesize homogeneous multi-component powders with fine particle diameter by wet process such as the polymerized complex method. The characteristics of SrAl2O4: Eu2+ and Dy3+ powders prepared by polymerized complex method with one and two step calcination processes were comparatively analyzed. Temperatures of organic material removal and crystallization were observed through TG-DTA analysis. The crystalline phase and crystallite size of the SrAl2O4: Eu2+ and Dy3+ phosphorescent phosphors were analyzed by XRD. Microstructures and afterglow characteristics of the SrAl2O4: Eu2+ and Dy3+ phosphors were measured by SEM and spectrofluorometry, respectively.
4,000원
9.
2016.10
구독 인증기관 무료, 개인회원 유료
Using the ultrasonic pyrolysis method, spherical SiO2 powders were synthesized from aqueous SiO2 sol as a starting material. The effects of pyrolysis conditions such as reaction temperature, SiO2 sol concentration, and physical properties of precursor were investigated for the morphologies of the resulting SiO2 powders. The particle size, shape, and crystallite size of the synthesized SiO2 powders were demonstrated according to the pyrolysis conditions. Generally, the synthesized SiO2 particles were amorphous phase and showed spherical morphology with a smooth surface. It was revealed that increased crystallite size and decreased spherical SiO2 particle size were obtained with increases of the pyrolysis reaction temperature. Also, quantity of spherical SiO2 particles decreased with the decrease in the concentration and surface tension of the precursor.
4,000원
10.
2016.10
구독 인증기관 무료, 개인회원 유료
Dy3+ and Eu3+-codoped SrWO4 phosphor thin films were deposited on sapphire substrates by radio frequency magnetron sputtering by changing the growth and thermal annealing temperatures. The results show that the structural and optical properties of the phosphor thin films depended on the growth and thermal annealing temperatures. All the phosphor thin films, irrespective of the growth or the thermal annealing temperatures, exhibited tetragonal structures with a dominant (112) diffraction peak. The thin films deposited at a growth temperature of 100 oC and a thermal annealing temperature of 650 oC showed average transmittances of 87.5% and 88.4% in the wavelength range of 500-1100 nm and band gap energy values of 4.00 and 4.20 eV, respectively. The excitation spectra of the phosphor thin films showed a broad charge transfer band that peaked at 234 nm, which is in the range of 200-270 nm. The emission spectra under ultraviolet excitation at 234 nm showed an intense emission peak at 572 nm and several weaker bands at 479, 612, 660, and 758 nm. These results suggest that the SrWO4: Dy3+, Eu3+ thin films can be used as white light emitting materials suitable for applications in display and solid-state lighting.
4,000원
