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 제2호 (2016년 2월) 8건
논 문
1.
2016.02
구독 인증기관 무료, 개인회원 유료
In order to fabricate porous mullite ceramics with controlled pore structure and improved mechanical strength, a freeze casting route has been processed using camphene mixed with tertiary-butyl alcohol (TBA) and coal fly ash/alumina as the solvent and the ceramic material, respectively. After sintering, the solidification characteristics of camphene and TBA solvent were evident in the pore morphology, i.e., dendritic and straight pore channels formed along the solidification directions of camphene and TBA ice, respectively, after sublimation. Also, the presence of microcracks was observed in the bodies sintered at 1500 oC, mainly due to the difference in solidification volume change between camphene and TBA. The compressive strength of the sintered bodies was found generally to be dependent, in an inverse manner, on the porosity, which was mainly determined by the processing conditions. After sintering at 1300~1500 oC with 30~50 wt% solid loading, the resulting mullite ceramics showed porosity and compressive strength values in ranges of 83.8~43.1% and 3.7~206.8 MPa, respectively.
4,000원
2.
2016.02
구독 인증기관 무료, 개인회원 유료
BaMoO4:Tb3+ phosphor powders were synthesized with different concentrations of Tb3+ ions using the solid-state reaction method. XRD patterns showed that all the phosphors, irrespective of the concentration of Tb3+ ions, had tetragonal systems with two main (112) and (004) diffraction peaks. The excitation spectra of the Tb3+-doped BaMoO4 phosphors consisted of an intense broad band centered at 290 nm in the range of 230-330 nm and two weak bands. The former broad band corresponded to the 4f8 →4f75d1 transition of Tb3+ ions; the latter two weak bands were ascribed to the 7F2→ 5D3 (471 nm) and 7F6→ 5D4 (492 nm) transitions of Tb3+. The main emission band, when excited at 290 nm, showed a strong green band at 550 nm arising from the 5D4→ 7F5 transition of Tb3+ ions. As the concentration of Tb3+ increased from 1 to 10 mol%, the intensities of all the emission lines gradually increased, approached maxima at 10 mol% of Tb3+ ions, and then showed a decreasing tendency with further increase in the Tb3+ ions due to the concentration quenching effect. The critical distance between neighboring Tb3+ ions for concentration quenching was calculated and found to be 12.3 Å, which indicates that dipoledipole interaction was the main mechanism for the concentration quenching of the 5D4→ 7F5 transition of Tb3+ in the BaMoO4:Tb3+ phosphors.
4,000원
3.
2016.02
구독 인증기관 무료, 개인회원 유료
TiO2 nanoparticles were synthesized by a sol-gel process using titanium tetra isopropoxide as a precursor at room temperature. Ag-doped TiO2 nanoparticles were prepared by photoreduction of AgNO3 on TiO2 under UV light irradiation and calcinated at 400 oC. Ag-doped TiO2 nanoparticles were characterized for their structural and morphological properties by Xray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The photocatalytic properties of the TiO2 and Ag-doped TiO2 nanoparticles were evaluated according to the degree of photocatalytic degradation of gaseous benzene under UV and visible light irradiation. To estimate the rate of photolysis under UV (λ = 365 nm) and visible (λ ≥ 410 nm) light, the residual concentration of benzene was monitored by gas chromatography (GC). Both undoped/doped nanoparticles showed about 80 % of photolysis of benzene under UV light. However, under visible light irradiation Ag-doped TiO2 nanoparticles exhibited a photocatalytic reaction toward the photodegradation of benzene more efficient than that of bare TiO2. The enhanced photocatalytic reaction of Ag-doped TiO2 nanoparticles is attributed to the decrease in the activation energy and to the existence of Ag in the TiO2 host lattice, which increases the absorption capacity in the visible region by acting as an electron trapper and promotes charge separation of the photoinduced electrons (e−) and holes (h+). The use of Ag-doped TiO2 nanoparticles preserved the option of an environmentally benign photocatalytic reaction using visible light; These particles can be applicable to environmental cleaning applications.
4,000원
4.
2016.02
구독 인증기관 무료, 개인회원 유료
A commercial NiO (green nickel oxide, 86 wt% Ni) powder was reduced using a batch-type fluidized-bed reactor in a temperature range of 500 to 600 oC and in a residence time range of 5 to 90 min. The reduction rate increased with increases in temperature; however, agglomeration and sintering (sticking) of Ni particles noticeably took place at high temperatures above 600 oC. An increasing tendency toward sticking was also observed at long residence times. In order to reduce the oxygen content in the powder to a level below 1 % without any sticking problems, which can lead to defluidization, proper temperature and residence time for a stable fluidized-bed operation should be established. In this study, these values were found to be 550 oC and 60 min, respectively. Another important condition is the specific gas consumption rate, i.e. the volume amount (Nm3) of hydrogen gas used to reduce 1 ton of Green NiO ore. The optimum gas consumption rate was found to be 5,000 Nm3/ton-NiO for the complete reduction. The Avrami model was applied to this study; experimental data are most closely fitted with an exponent (m) of 0.6 ± 0.01 and with an overall rate constant (k) in the range of 0.35~0.45, depending on the temperature.
4,000원
5.
2016.02
구독 인증기관 무료, 개인회원 유료
We present the rectifying and nitrogen monoxide (NO) gas sensing properties of an oxide semiconductor heterostructure composed of n-type zinc oxide (ZnO) and p-type copper oxide thin layers. A CuO thin layer was first formed on an indium-tin-oxide-coated glass substrate by sol-gel spin coating method using copper acetate monohydrate and diethanolamine as precursors; then, to form a p-n oxide heterostructure, a ZnO thin layer was spin-coated on the CuO layer using copper zinc dihydrate and diethanolamine. The crystalline structures and microstructures of the heterojunction materials were examined using X-ray diffraction and scanning electron microscopy. The observed current-voltage characteristics of the p-n oxide heterostructure showed a non-linear diode-like rectifying behavior at various temperatures ranging from room temperature to 200 oC. When the spin-coated ZnO/CuO heterojunction was exposed to the acceptor gas NO in dry air, a significant increase in the forward diode current of the p-n junction was observed. It was found that the NO gas response of the ZnO/CuO heterostructure exhibited a maximum value at an operating temperature as low as 100 oC and increased gradually with increasing of the NO gas concentration up to 30 ppm. The experimental results indicate that the spin-coated ZnO/CuO heterojunction structure has significant potential applications for gas sensors and other oxide electronics.
4,000원
6.
2016.02
구독 인증기관 무료, 개인회원 유료
In this study, to increase the strength and enhance the sintering property of Al2O3, Y2O3 and La2O3 were added; the effects of these additions on the sintering characteristics of Al2O3 were observed. Adding 1 % of Y2O3 to Al2O3 repressed the development of abnormal particles and reduced the grain boundary migration of Al2O3, curbing pores to capture particles; as such, the material showed a fine microstructure. But, when over 2% of Y2O3 was added, the sintering property was reduced because of abnormal particle grain growth and pore formation in particles. Adding 1 % of Y2O3 and La2O3 to Al2O3 led to the development of abnormal particles and formed pores in the particles; when over 3% of La2O3 was added, the sintering property was reduced because the shape of the Al2O3 particles changed to angled plates.
4,000원
7.
2016.02
구독 인증기관 무료, 개인회원 유료
In this study, 5 um sized ZrSiO4 was ground to 1.9 um, 0.3 um, and 0.1 um sized powders by wet high energy milling process, and the sintering characteristics were observed. Pure ZrSiO4 itself can-not be sintered to these levels of theoretical density, but it was possible to sinter ZrSiO4 powder of nano-scale size of, −0.1 um to the theoretical density and to lower the sintering temperature for full density. Also, the decomposition of ZrSiO4 with a size in the micron range resulted in the formation of monoclinic ZrO2; however, in the nano sized range, the decomposition resulted in the tetragonal phase of ZrO2. So, it was possible to improve the sintering characteristics of nano-sized ZrSiO4 powders.
4,000원
기술보고서
8.
2016.02
구독 인증기관 무료, 개인회원 유료
Zinc Sulfide (ZnS) is one of the II-VI semiconducting materials, having novel fundamental properties and diverse areas of application such as light-emitting diodes (LEDs), electroluminescence, flat panel displays, infrared windows, catalyst, chemical sensors, biosensors, lasers and biodevices, etc. However, despite the remarkable versatility and prospective potential of ZnS, research and development (R&D) into its applications has not been performed in much detail relative to research into other inorganic semiconductors. In this study, based on global patent information, we analyzed recent technical trends and the current status of R&D into ZnS applications. Furthermore, we provided new technical insight into ZnS applicable fields using in-depth analysis. Especially, this report suggests that ZnS, due to its infrared-transmitting optical property, is a promising material in astronomy and military fields for lenses of infrared systems. The patent information analysis in this report will be utilized in the process of identifying the current positioning of technology and the direction of future R&D.
4,000원
