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
제20권 제2호 (2010년 2월) 10건
1.
2010.02
구독 인증기관 무료, 개인회원 유료
Transparent conductive films of single wall carbon nanotube (SWCNT) were prepared by spray coating method. The effect of acid treatment on the SWCNT films was investigated. The field emission scanning electron microscope (FESEM) shows that acid treatment can remove dispersing agent. The electrical and optical properties of acid-treated films were enhanced compared with those of as deposited SWCNT films. Nitric acid (HNO3), sulfuric acid (H2SO4), nitric acid:sulfuric acid (3:1) were used for post treatment. Although all solutions reduced sheet resistance of CNT films, nitric acid can improve electrical characteristics efficiently. During acid treatment, transmittance was increased continuously with time. But the sheet resistance was decreased for the first 20 minutes and then increased again. Post-treated SWCNT films were transparent (85%) in the visible range with sheet resistance of about 162Ω/sq. In this paper we discuss simple fabrication, which is suitable for different types of large-scale substrates and simple processes to improve properties of SWCNT films.
3,000원
2.
2010.02
구독 인증기관 무료, 개인회원 유료
Na+ ion conductivity can be improved by the substitution of an Mg atom for an Al atom to form a nonstoichiometric Na+ β-alumina. We performed a first principles study to investigate the most stable substitution site of an Mg atom and the resulting structural change of the nonstoichiometric Na+ β-alumina. Al atoms were classified as four different layers in the spinel block that are separated by conduction planes in the nonstoichiometric Na+ β-alumina. The substitution of an Mg atom for an Al atom at a tetragonal site was more favorable than that at an octahedral site. The substitution in the spinel block was more favorable than that close to the conduction plane. This result was well explained by the volume changes of the polyhedrons, by the standard deviation of the Mg-O distance, and by the comparison with bulk MgO structure. Our result indicates that the most preferable site for the Mg atom was the tetrahedral site at the spinel block in the nonstoichiometric Na+ β-alumina.
4,000원
3.
2010.02
구독 인증기관 무료, 개인회원 유료
This study looked at high performance copper-based alloys as LED lead frame materials with higher electrical-conductivity and the maintenance of superior tensile strength. This study investigated the effects on the tensile strength, electrical conductivity, thermal softening, size and distribution of the precipitation phases when Cr was added in Cu-Fe alloy in order to satisfy characteristics for LED Lead Frame material. Strips of the alloys were produced by casting and then properly treated to achieve a thickness of 0.25 mm by hot-rolling, scalping, and cold-rolling; mechanical properties such as tensile strength, hardness and electrical-conductivity were determined and compared. To determine precipitates in alloy that affect hardness and electrical-conductivity, electron microscope testing was also performed. Cr showed the effect of precipitation hardened with a Cr3Si precipitation phase. As a result of this experiment, appropriate aging temperature and time have been determined and we have developed a copper-based alloy with high tensile strength and electrical-conductivity. This alloy has the possibility for use as a substitution material for the LED Lead Frame of Cu alloy.
4,000원
4.
2010.02
구독 인증기관 무료, 개인회원 유료
In this study, the effect of Sn and Mg on microstructure and mechanical properties of Cu-Fe-P alloy were investigated by using scanning electron microscope, transmission electron microscope, tensile strength, electrical conductivity, thermal softening, size and distribution of the precipitation phases in order to satisfy characteristic for lead frame material. It was observed that Cu-0.14wt%Fe-0.03wt%P-0.05wt%Si-0.1wt%Zn with Sn and Mg indicates increasing tensile strength compare with PMC90 since Sn restrained the growth of the Fe-P precipitation phase on the matrix. However, the electrical conductivity was decreased by adding addition of Sn and Mg because Sn was dispersed on the matrix and restrained the growth of the Fe-P precipitation. The size of 100 nm Mg3P2 precipitation phase was observed having lattice parameter a:12.01Å such that [111] zone axis. According to the results of the study, the tensile strength and the electrical conductivity satisfied the requirements of lead frame; so, there is the possibility of application as a substitution material for lead frame of Cu alloy.
4,000원
5.
2010.02
구독 인증기관 무료, 개인회원 유료
Glass-ceramics were fabricated by heat-treatment of glass obtained by melting a coal bottom ash with Li2O addition. The main crystal grown in the glass-ceramics, containing 10 wt% Li2O, was β-spodumene solid solution, while in Li2O 20 wt% specimen was mullite, identified using XRD. The activation energy and Avrami constant for crystallization were calculated and showed that bulk crystallization behavior will be predominant, and this expectation agreed with the microstructural observations. The crystal phase grown in Li2O 10 wt% glass-ceramics had a dendrite-like shaped whereas the shape was flake-like in the 20 wt% case. The thermal expansion coefficient of the Li2O 10 wt% glass-ceramics was lower than that of the glass having the same composition, owing to the formation of a β-spodumene phase. For example, the thermal expansion coefficient of Li2O 10 wt% glass-ceramics was 20×10-7, which is enough for application in various heat-resistance fields. But above 20 wt% Li2O, the thermal coefficient expansion of glass-ceramics, on the contrary, was higher than that of the same composition glass, due to formation of mullite.
4,000원
6.
2010.02
구독 인증기관 무료, 개인회원 유료
Surface modification of silica nanoparticles was investigated using an aerosol self assembly. Stearic acid was used as surface treating agent. A two-fluid jet nozzle was employed to generate an aerosol of the colloidal suspension, which contained 20 nm of silica nanoparticles, surface modifier, and ethyl alcohol. Powder properties such as morphology, specific surface area and pore size distribution were analyzed by SEM, BET and BJH methods, respectively. Surface properties of the silica power were analyzed by FT-IR. The OH bond of the SiO2 surface was converted to a C-H bond. It was revealed that the hydrophilic surface changed to a hydrophobic one due to the aerosol self assembly. Morphology of the surface treated powder was nanostructured with lots of pores having an average diameter of around 2 μm. Depending on the stearic acid concentration (0.25 to 1.0 wt%), the pore size distribution of the particles and the degree of hydrophobicity ranged from 1.5 nm to 180 nm and 29.6% to 50.2%, respectively.
3,000원
7.
2010.02
구독 인증기관 무료, 개인회원 유료
Benzotriazole (B.T.A) which has been mainly used for the stabilization processing method of excavated copper and bronze artifacts is vaporized within 2~3 years after the usage because it is unstable at the acid conditions and cannot protect the surface of artifacts. In this study, NaOH method which has been used for the steel artifacts was applied as a stabilization process for the method of copper and bronze artifacts to gush chlorine ion out. For the reproduction of excavated samples, copper and bronze plates were dipped in 0.1M HCl for 26 hrs to form CuCl, rusted at 70˚C with RH 75% for the formation of corrosion products, and desalted in 0.1 M NaOH solution. The concentration of chlorine ion was measured by using ionchromatography. During the desalting process, a large quantity of chlorine ions was gushed out in early period and corrosion products were not additionally generated through the re-corrosion experiment. This NaOH desalting process was found to be a method of stabilization process for copper and bronze artifacts from the formation of Tenorite (CuO) during desalting as a protection layer for corrosion.
4,000원
8.
2010.02
구독 인증기관 무료, 개인회원 유료
The recirculating electrochemical flow reactor developed at UCLA has been employed to fabricate nanostructured GMR multilayers. For comparison, Ni/Cu multilayers have been electrodeposited from a single bath, from dual baths and from the recirculating electrochemical flow reactor. For a magnetic field of 1.5 kOe, higher GMR (Max. -5%) Ni/Cu multilayers with low electrical resistivity (< 10 μΩ·cm) were achieved by the electrochemical flow reactor system than by the dual bath (Max. GMR = -4.2% and< 20 μΩ·cm) or the single bath (Max. GMR = -2.1% and< 90 μΩ·cm) techniques. Higher GMR effects have been obtained by producing smoother, contiguous layers at lower current densities and by the elimination of oxide film formation by conducting deposition under an inert gas environment. Our preliminary GMR measurements of Ni/Cu multilayers from the electrochemical flow reactor obtained at low magnetic field of 0.15 T, which may approach or exceed the highest reported results (-7% GMR) at magnetic fields > 5 kOe.
4,000원
9.
2010.02
구독 인증기관 무료, 개인회원 유료
In this study, a new, relatively simple fabrication method for forming a mesoporous Al(OH)3 film onAl substrates was demonstrated. This method, i.e., alkali surface modification, was simply comprised of dippingthe substrate in a 5×10-3M NaOH solution at 80oC for one minute and then immersing it in boiling waterfor 30 minutes. After alkali surface modification, a mesoporous Al(OH)3 film was formed on the Al substrate,and its chemical state and crystal structure were confirmed by XPS and TEM. According to the results of theXPS analysis, the flake-like morphology after the alkali surface modification was mainly composed of Al(OH)3,with a small amount of Al2O3. The mesoporous Al(OH)3 layer was composed of three regions: an amorphous-rich region, a region of mixed amorphous and crystal domains, and a crystalline-rich region near the Al(OH)3layer surface. It was confirmed that the stabilization process in the alkali surface modification stronglyinfluenced the crystallization of the mesoporous Al(OH)3 layer.
4,000원
10.
2010.02
구독 인증기관 무료, 개인회원 유료
The characteristics of all polymer composites containing carbon materials are determined by four factors: component properties, composition, structure and interfacial interactions. The most important filler characteristics are particle size, size distribution, specific surface area and particle shape. As a consequence, in this paper we discuss the aspects of the mechanical, electrical and thermal properties of composites with different fillers of carbon black, carbon nanotube (CNT), graphene and graphite and focus on the relationship between factors and properties, as mentioned above. Accordingly, we fabricate rubber composites that contain various carbon materials in carbon black-based and silica based-SBR matrixes with dual phase fillers and use scanning electron microscopy, Raman spectroscopy, a rhometer, an Instron tensile machine, and a thermal conductivity analyzer to evaluate composites' mechanical, fatigue, thermal, and electronic properties. In mechanical properties, hardness and 300%-modulus of graphene-composite are sharply increased in all cases due to the larger specific surface. Also, it has been found that the thermal conductivity of the CNT-composite is higher than that of any of the other composites and that the composite with graphene has the best electrical properties.
4,000원
