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
제21권 제6호 (2011년 6월) 11건
1.
2011.06
구독 인증기관 무료, 개인회원 유료
ZnS:Mn, Dy yellow phosphors for White Light Emitting Diode were synthesized by a solid state reaction methodusing ZnS, MnSO4·5H2O, S and DyCl3·6H2O powders as starting materials. The mixed powder was sintered at 1000oC for 4h in an air atmosphere. The photoluminescence of the ZnS:Mn, Dy phosphors showed spectra extending from 480 to 700nm,peaking at 580nm. The photoluminescence of 580nm in the ZnS:Mn, Dy phosphors was associated with 4T1→6A1 transitionof Mn2+ ions. The highest photoluminescence intensity of the ZnS:Mn, Dy phosphors under 450nm excitation was observedat 4mol% Dy doping. The enhanced photoluminescence intensity of the ZnS:Mn, Dy phosphors was explained by energytransfer from Dy3+ to Mn2+. The CIE coordinate of the 4 mol% Dy doped ZnS:Mn, Dy was X=0.5221, Y=0.4763. Theoptimum mixing conditions for White Light Emitting Diode was obtained at the ratio of epoxy:yellow phosphor=1:2 formCIE coordinate.
3,000원
2.
2011.06
구독 인증기관 무료, 개인회원 유료
[ WO3 ]powders were ball-milled with an alumina ball for 0-72 hours. In2O3 doped WO3 was prepared by soaking ball-milled WO3 in an InCl3 solution. The mixed powder was annealed at 700˚C for 30 min in an air atmosphere. A paste for screen-printing the thick film was prepared by mixing the WO3:In2O3 powders with α-terpinol and glycerol. In2O3 doped WO3 thick films were fabricated into a gas sensor by a screen-printing method on alumina substrates. The structural properties of the WO3:InO3 thick films were a monoclinic phase with a (002) dominant orientation. The particle size of the WO3:InO3 decreased with the ball-milling time. The sensing characteristics of the In2O3 doped WO3 were investigated by measuring the electrical resistance of each sensor in the test-box. The highest sensitivity to 5 ppm CH4 gas and 5 ppm CH3CH2CH3 gas was observed in the ball-milled WO3:InO3 gas sensors at 48 hours. The response time of WO3:In2O3 gas sensors was 7 seconds and recovery time was 9 seconds for the methane gas.
3,000원
3.
2011.06
구독 인증기관 무료, 개인회원 유료
The effect of heat treatment on the micro-structures and the mechanical properties of 0.002% boron added low carbon steel was investigated. The tensile strength reached the peak at about 880-890˚C with the rising quenching temperature and then the hardness decreased sharply, but the tensile strength hardly decreased. The tensile and yield strength decreased and the total elongation increased with a rising tempering temperature, but the tensile and yield strength sharply fell and the total elongation prominently increased from above a 400-450˚C tempering temperature. Tempered martensite embrittlement (TME) was observed at tempering condition of 350-400˚C. In the condition of quenching at 890˚C and tempering at 350˚C, the boron precipitates were observed as Fe-C-B and BN together. The hardness decreased in proportion to the tempering temperature untill 350˚C and dropped sharply above 400˚C regardless of the quenching temperature.
4,000원
4.
2011.06
구독 인증기관 무료, 개인회원 유료
The power capacitors used as vehicle inverters must have a small size, high capacitance, high voltage, fast response and wide operating temperature. Our thin film capacitor was fabricated by alumina layers as a dielectric material and a metal electrode instead of a liquid electrolyte in an aluminum electrolytic capacitor. We analyzed the micro structures and the electrical properties of the thin film capacitors fabricated by nano-channel alumina and metal electrodes. The metal electrode was filled into the alumina nano-channel by electroless nickel plating with polyethylene glycol and a palladium catalyst. The spherical metals were formed inside the alumina nano pores. The breakdown voltage and leakage current increased by the chemical reaction of the alumina layer and PdCl2 solution. The thickness of the electroless plated nickel layer was 300 nm. We observed the nano pores in the interface between the alumina layer and the metal electrode. The alumina capacitors with nickel electrodes had a capacitance density of 100 nF/cm2, dielectric loss of 0.01, breakdown voltage of 0.7MV/cm and leakage current of 104μA.
4,000원
5.
2011.06
구독 인증기관 무료, 개인회원 유료
Melt foaming method is one of cost-effective methods to make metal foam and it has been successfully applied to fabricate Mg foams. In this research, AZ31 Mg alloy ingot was used as a metal matrix, using AlCa granular as thickening agent and CaCO3 powder as foaming agent, AZ31 Mg alloy foams were fabricated by melt-foaming method at different foaming temperatures. The porosity was above 41.2%~73.3%, pore size was between 0.38~1.52 mm, and homogenous pore structures were obtained. Microstructure and mechanical properties of the AZ31 Mg alloy foams were investigated by optical microscopy, SEM and UTM. The results showed that pore structure and pore distribution were much better than those fabricated at lower temperatures. The compression behavior of the AZ31 Mg alloy foam behaved as typical porous materials. As the foaming temperature increased from 660˚C to 750˚C, the compressed strength also increased. The AZ31 Mg alloy foam with a foaming temperature of 720˚C had the best energy absorption. The energy absorption value of Mg foam was 15.52 MJ/m3 at a densification strain of 52%. Furthermore, the high energy absorption efficiencies of the AZ31 Mg alloy foam kept at about 0.85 in the plastic plateau region, which indicates that composite foam possess a high energy absorption characteristic, and the Vickers hardness of AZ31 Mg alloy foam decreased as the foaming temperature increased.
4,000원
6.
2011.06
구독 인증기관 무료, 개인회원 유료
Flat rolling of wire is an industrial process used to manufacture electrical flat wire, medical catheters, springs, piston segments and automobile parts, among other products. In a multi-step wire flat rolling process, a wire with a circular crosssection is rolled at room temperature between two flat rolls in several passes to achieve the desired thickness to width ratio. To manufacture a flat wire with a homogeneous microstructure, mechanical and metallurgical properties with an appropriate pass schedule, this study investigated the effect of each pass schedule (1stand ~ 4stand) on the microstructures, mechanical properties and widths of cold rolled high carbon steel wires using four-pass flat rolling process. The evolutions of the microstructures and mechanical properties of the widths of cold rolled wires during three different pass schedules of the flat rolling process of high carbon wires were investigated, and the results were compared with those for a conventional eight-pass schedule. In the width of cold rolled wires, three different pass schedules are clearly distinguished and discussed. The experimental conditions were the same rolling speed, rolling force, roll size, tensile strength of the material and friction coefficient. The experimental results showed that the four-pass flat cold rolling process was feasible for production of designed wire without cracks when appropriate pass schedules were applied.
4,000원
7.
2011.06
구독 인증기관 무료, 개인회원 유료
Nanostructured cobalt materials have recently attracted considerable attention due to their potential applications in high-density data storage, magnetic separation and heterogeneous catalysts. The size as well as the morphology at the nano scale strongly influences the physical and chemical properties of cobalt nano materials. In this study, cobalt nano particles synthesized by a a polyol process, which is a liquid-phase reduction method, were investigated. Cobalt hydroxide (Co(OH)2), as an intermediate reaction product, was synthesized by the reaction between cobalt sulphate heptahydrate (CoSO4·7H2O) used as a precursor and sodium hydroxide (NaOH) dissolved in DI water. As-synthesized Co(OH)2 was washed and filtered several times with DI water, because intermediate reaction products had not only Co(OH)2 but also sodium sulphate (Na2SO4), as an impurity. Then the cobalt powder was synthesized by diethylene glycol (DEG), as a reduction agent, with various temperatures and times. Polyvinylpyrrolidone (PVP), as a capping agent, was also added to control agglomeration and dispersion of the cobalt nano particles. The optimized synthesis condition was achieved at 220˚C for 4 hours with 0.6 of the PVP/Co(OH)2 molar ratio. Consequently, it was confirmed that the synthesized nano sized cobalt particles had a face centered cubic (fcc) structure and with a size range of 100-200 nm.
4,000원
8.
2011.06
구독 인증기관 무료, 개인회원 유료
Saw wires have been widely used in industries to slice silicon (Si) ingots into thin wafers for semiconductor fabrication. This study investigated the microstructural and mechanical properties, such as abrasive wear and tensile properties, of a saw wire sample of 0.84 wt.% carbon steel with a 120 μM diameter. The samples were subjected to heat treatment at different linear velocities of the wire during the patenting process and two different wear tests were performed, 2-body abrasive wear (grinding) and 3-body abrasive wear (rolling wear) tests. With an increasing linear velocity of the wire, the tensile strength and microhardness of the samples increased, whereas the interlamellar spacing in a pearlite structure decreased. The wear properties from the grinding and rolling wear tests exhibited an opposite tendency. The weight loss resulting from grinding was mainly affected by the tensile strength and microhardness, while the diameter loss obtained from rolling wear was affected by elongation or ductility of the samples. This result demonstrates that the wear mechanism in the 3-body wear test is much different from that for the 2-body abrasive wear test. The ultra-high tensile strength of the saw wire produced by the drawing process was attributed to the pearlite microstructure with very small interlamellar spacing as well as the high density of dislocation.
4,000원
9.
2011.06
구독 인증기관 무료, 개인회원 유료
In this study, we inserted a Zn buffer layer into a AZO/p-type a-si:H layer interface in order to lower the contact resistance of the interface. For the Zn layer, the deposition was conducted at 5 nm, 7 nm and 10 nm using the rf-magnetron sputtering method. The results were compared to that of the AZO film to discuss the possibility of the Zn layer being used as a transparent conductive oxide thin film for application in the silicon heterojunction solar cell. We used the rf-magnetron sputtering method to fabricate Al 2 wt.% of Al-doped ZnO (AZO) film as a transparent conductive oxide (TCO). We analyzed the electro-optical properties of the ZnO as well as the interface properties of the AZO/p-type a-Si:H layer. After inserting a buffer layer into the AZO/p-type a-Si:H layers to enhance the interface properties, we measured the contact resistance of the layers using a CTLM (circular transmission line model) pattern, the depth profile of the layers using AES (auger electron spectroscopy), and the changes in the properties of the AZO thin film through heat treatment. We investigated the effects of the interface properties of the AZO/p-type a-Si:H layer on the characteristics of silicon heterojunction solar cells and the way to improve the interface properties. When depositing AZO thin film on a-Si layer, oxygen atoms are diffused from the AZO thin film towards the a-Si layer. Thus, the characteristics of the solar cells deteriorate due to the created oxide film. While a diffusion of Zn occurs toward the a-Si in the case of AZO used as TCO, the diffusion of In occurs toward a-Si in the case of ITO used as TCO.
4,000원
10.
2011.06
구독 인증기관 무료, 개인회원 유료
Degradation Behavior of Hydroxyapatite with Different Crystallinity in Simulated Body Fluid Solution
Hydroxyapatite (HAp) powders with different crystallinities were synthesized at various calcination temperatures through the co-precipitation of Ca(OH)2 and H3PO4. The degradation behavior of these HAp powders with different crystallinities was assessed in a simulated body fluid solution (SBF) for 8 weeks. Below 800˚C, the powders were nonstochiometric HAp, and the single HAp phase was successfully synthesized at 800˚C. The degree of crystallinity of the HAp powders increased with an increasing calcination temperature and varied in a range from 39.6% to 92.5%. In the low crystallinity HAp powders, the Ca and P ion concentrations of the SBF solution increased with an increasing soaking time, which indicated that the low crystallinity HAp degraded in the SBF solution. The mass of the HAp powders linearly decreased with respect to the soaking time, and the mass loss was higher at lower crystallinities. The mass loss ranged from 0.8% to 13.2% after 8 weeks. The crystallinity of the HAp powders increased with an increasing soaking time up to 4 weeks and then decreased because of HAp degradation. The pH of the SBF solution did not change much throughout the course of these experiments. These results suggested that the crystallinity of HAp can be used to control the degradation.
4,000원
11.
2011.06
구독 인증기관 무료, 개인회원 유료
[ Zn2(1-x)MnxSiO4 ]0.07≤x≤0.15) green phosphor was prepared by solid state reaction. The first heating was at 900˚C-1250˚C in air for 3 hours and the second heating was at 900˚C in N2/H2(95%/5%) for 2 hours. The size effect of SiO2 in forming Zn2SiO4 was investigated. The temperature for obtaining single phase Zn2SiO4 was lowered from 1100˚C to 1000˚C by decreasing the SiO2 particle size from micro size to submicro size. The effect of the activators for the Photoluminescence (PL) intensity of Zn2SiO4:Mn2+ was also investigated. The PL intensity properties of the phosphors were investigated under vacuum ultraviolet excitation (147 nm). The emission spectrum peak was between 520 nm and 530 nm, which was involved in green emission area. MnCl2·4H2O, the activator source, was more effective in providing high emission intensity than MnCO3. The optimum conditions for the best optical properties of Zn2SiO4:Mn2+ were at x = 0.11 and 1100˚C. In these conditions, the phosphor particle shape was well dispersed spherical and its size was 200 nm.
4,000원
