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
제23권 제4호 (2013년 4월) 8건
1.
2013.04
구독 인증기관 무료, 개인회원 유료
The effects of a Ni coating on the sensing properties of nano ZnO:Ni based gas sensors were studied for CH4 and CH3CH2CH3 gases. Nano ZnO sensing materials were prepared by the hydrothermal reaction method. The Ni coatings on the nano ZnO surface were deposited by the hydrolysis of zinc chloride with NH4OH. The weight % of Ni coating on the ZnO surface ranged from 0 to 10 %. The nano ZnO:Ni gas sensors were fabricated by a screen printing method on alumina substrates. The structural and morphological properties of the nano ZnO : Ni sensing materials were investigated by XRD, EDS, and SEM. The XRD patterns showed that nano ZnO : Ni powders with a wurtzite structure were grown with (1 0 0), (0 0 2), and (1 0 1) dominant peaks. The particle size of nano ZnO powders was about 250 nm. The sensitivity of nano ZnO:Ni based sensors for 5 ppm CH4 gas and CH3CH2CH3 gas was measured at room temperature by comparing the resistance in air with that in target gases. The highest sensitivity of the ZnO:Ni sensor to CH4 gas and CH3CH2CH3 gas was observed at Ni 4 wt%. The response and recovery times of 4 wt% Ni coated ZnO:Ni gas sensors were 14 s and 15 s, respectively.
3,000원
2.
2013.04
구독 인증기관 무료, 개인회원 유료
Vanadium dioxide (VO2) is an attractive material for smart window applications where the transmittance of light can be automatically modulated from a transparent state to an opaque state at the critical temperature of ~68˚C. Meanwhile, F : SnO2 (F-doped SnO2, FTO) glass is a transparent conductive oxide material that is widely used in solar-energy-related applications because of its excellent optical and electrical properties. Relatively high transmittance and low emissivity have been obtained for FTO-coated glasses. Tunable transmittance corresponding to ambient temperature and low emissivity can be expected from VO2 films deposited onto FTO glasses. In this study, FTO glasses were applied for the deposition of VO2 thin films by pulsed DC magnetron sputtering. VO2 thin films were also deposited on a Pyrex substrate for comparison. To decrease the phase transition temperature of VO2, tungsten-doped VO2 films were also deposited onto FTO glasses. The visible transmittance of VO2/FTO was higher than that of VO2/pyrex due to the increased crystallinity of the VO2 thin film deposited on FTO and decreased interface reflection. Although the solar transmittance modulation of VO2/FTO was lower than that of VO2/pyrex, room temperature solar transmittance of VO2/FTO was lower than that of VO2/pyrex, which is advantageous for reflecting solar heat energy in summer.
3,000원
3.
2013.04
구독 인증기관 무료, 개인회원 유료
Activated magnetite (Fe3O4-δ) has the capability of decomposing CO2 proportional to the δ-value at comparativelylow temperature of 300oC. To enhance the CO2 decomposition capability of Fe3O4-δ, (Fe1-xCox)3O4-δ and (Fe1-xMnx)3O4-δ weresynthesized and then reacted with CO2. Fe1-xCoxC2O4·2H2O powders having Fe to Co mixing ratios of 9:1, 8:2, 7:3, 6:4, and5:5 were synthesized by co-precipitation of FeSO4·7H2O and CoSO4·7H2O solutions with a (NH4)2C2O4·H2O solution. The samemethod was used to synthesize Fe1-xMnxC2O4·2H2O powders having Fe to Mn mixing ratios of 9:1, 8:2, 7:3, 6:4, 5:5 with aMnSO4·4H2O solution. The thermal decomposition of synthesized Fe1-xCoxC2O4·2H2O and Fe1-xMnxC2O4·2H2O was analyzedin an Ar atmosphere with TG/DTA. The synthesized powders were heat-treated for 3 hours in an Ar atmosphere at 450oCto produce activated powders of (Fe1-xCox)3O4-δ and (Fe1-xMnx)3O4-δ. The activated powders were reacted with a mixed gas(Ar:85%, CO2:15%) at 300oC for 12 hours. The exhaust gas was analyzed for CO2 with a CO2 gas analyzer. The decom-position of CO2 was estimated by measuring CO2 content in the exhaust gas after the reaction with CO2. For (Fe1-xMnx)3O4-δ,the amount of Mn2+ oxidized to Mn3+ increased as x increased. The δ value and CO2 decomposition efficiency decreased asx increased. When the δ value was below 0.641, CO2 was not decomposed. For (Fe1-xCox)3O4-δ, the δ value and CO2decomposition efficiency increased as x increased. At a δ value of 0.857, an active state was maintained even after 12 hoursof reaction and the amount of decomposed CO2 was 52.844cm3 per 1g of (Fe0.5Co0.5)3O4-δ.
4,000원
4.
2013.04
구독 인증기관 무료, 개인회원 유료
Al-based alloys have recently attracted considerable interest as structural materials and light weight materials due to their excellent physical and mechanical properties. For the investigation of the potential of Al-based alloys, a surface porous Al88Cu6Si6 eutectic alloy has been fabricated through a chemical leaching process. The formation and microstructure of the surface porous Al88Cu6Si6 eutectic alloy have been investigated using X-ray diffraction and scanning electron microscopy. The Al88Cu6Si6 eutectic alloy is composed of an α-Al dendrite phase and a single eutectic phase of Al2Cu and α-Al. We intended to remove only the α-Al phase and then the Al2Cu phase would form a porous structure on the surface with open pores. Both acidic and alkaline aqueous chemical solutions were used with various concentrations to modify the influence on the microstructure and the overall chemical reaction was carried out for 24 hr. A homogeneous open porous structure on the surface was revealed via selective chemical leaching with a H2SO4 solution. Only the α-Al phase was successfully leached while the morphology of the Al2Cu phase was maintained. The pore size was in a range of 1~5μm and the dealloying depth was nearly 3μm. However, under an alkaline NaOH, aqueous solution, an inhomogeneous porous structure on the surface was formed with a 5 wt% NaOH solution and the morphology of the Al2Cu phase was not preserved. In addition, the sample that was leached by using a 7 wt% NaOH solution crumbled. Al extracted from the Al2Cu phase as α-Al phase was dealloyed, and increasing concentration of NaOH strongly influenced the morphology of the Al2Cu phase and sample statement.
4,000원
5.
2013.04
구독 인증기관 무료, 개인회원 유료
We collected Seokganju minerals (regions in Gyeryong Mountain, Sangsin-ri, Banpo-myeon, GongjuChungcheongnam-province), which were used as natural color pigments for grayish-blue during the 15th~16th centuries of theJoseon era, and investigated their crystallographic features to develop a black pigment having a spinel structure. By a Ramananalysis, the color of Seokganju under transparent glaze as a pigment for painting was black because hematite (Fe2O3) inSeokganju was converted to magnetite (Fe3O4) However, Seokganju into the transparent glaze as a pigment was brown becauseof hematite (Fe2O3) and small amounts of maghemite (γ-Fe2O3) in Seokganju minerals. Only Seokganju mineral is used, it isnot suitable for black pigment into the transparent glaze. This study tried to develop a spinel crystal black pigment stabilizedby Seokganju with CoO, Cr2O3, NiO, and MnO2 at 1280oC. A Raman spectroscopy analysis was performed to verify thepresence of Mn The results showed that it existed as spinel, and two crystal phases CoFe2O4 and MnFe2O4 were mixed.CoFe2O4 spinel has a dark grayish black color and Mn2O4 spinel has a greenish black color, and these two appeared as black.The color of a specimen calcined by adding 6wt% of pigment mixed with 5wt% of MnO2 added to lime glaze was analyzedwith a UV spectrophotometer. When applying the color pigment, it appeared black stabilized with L*24.23, a* 0.12, b* −2.29at 1260oC oxidative calcination, With 1240oC reduction firing, it is appeared black stabilized with low brightness of L* 23.13,a* −1.12, b* 0.54.
4,000원
6.
2013.04
구독 인증기관 무료, 개인회원 유료
Electrochemical surface treatment is commonly used to form a thin, rough, and porous oxidation layer on the surface of titanium. The purpose of this study was to investigate the formation of nanotubular titanium oxide arrays during short anodization processing. The specimen used in this study was 99.9% pure cp-Ti (ASTM Grade II) in the form of a disc with diameter of 15 mm and a thickness of 1 mm. A DC power supplier was used with the anodizing apparatus, and the titanium specimen and the platinum plate (3mm×4mm×0.1mm) were connected to an anode and cathode, respectively. The progressive formation of TiO2 nanotubes was observed with FE-SEM (Field Emission Scanning Electron Microscopy). Highly ordered TiO2 nanotubes were formed at a potential of 20 V in a solution of 1M H3PO4 + 1.5 wt.% HF for 10 minutes, corresponding with steady state processing. The diameters and the closed ends of TiO2 nanotubes measured at a value of 50 cumulative percent were 100 nm and 120 nm, respectively. The TiO2 nanotubes had lengths of 500 nm. As the anodization processing reached 10 minutes, the frequency distribution for the diameters and the closed ends of the TiO2 nanotubes was gradually reduced. Short anodization processing for TiO2 nanotubes of within 10 minutes was established.
4,000원
7.
2013.04
구독 인증기관 무료, 개인회원 유료
Nano-sized β-SiC nanoparticles were synthesized combined with a sol-gel process and a carbothermal process. TEOS and carbon black were used as starting materials for the silicon source and carbon source, respectively. SiO2 nanoparticles were synthesized using a sol-gel technique (Stober process) combined with hydrolysis and condensation. The size of the particles could be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of tetraethyl orthosilicate (TEOS) within the micro-emulsion. The average particle size and morphology of synthesized silicon dioxide was about 100nm and spherical, respectively. The average particles size and morphology of the used carbon black powders was about 20nm and spherical, respectively. The molar ratio of silicon dioxide and carbon black was fixed to 1:3 in the preparation of each combination. SiO2 and carbon black powders were mixed in ethanol and ball-milled for 12 h. After mixing, the slurries were dried at 80˚C in an oven. The dried powder mixtures were placed in alumina crucibles and synthesized in a tube furnace at 1400~1500˚C for 4 h with a heating rate of 10˚C/min under flowing Ar gas (160 cc/min) and furnace cooling down to room temperature. SiC nanoparticles were characterized by XRD, TEM, and SAED. The XRD results showed that high purity beta silicon carbide with excellent crystallinity was synthesized. TEM revealed that the powders are spherical shape nanoparticles with diameters ranging from 15 to 30 nm with a narrow distribution.
3,000원
8.
2013.04
구독 인증기관 무료, 개인회원 유료
In order to increase the toughness of ZTA(zirconia toughened alumina) ceramics, the present study focused on rearrangement and densification of particles according to the particle size of the parent material. When rough alumina was used for production of ZTA, densification behavior was observed in the specimen sintered at a temperature over 1550˚C. However, it was found that the densification behavior was occurred in the specimen sintered at 1450˚C when fine alumina powder was used. High relative density exceeding 98% was obtained when fine alumina powder was mixed with 15 wt% of 3Y-TZP and sintered at 1600˚C. Also, a hardness of 1820.2 Hv was obtained when a specimen containing 10 wt% of 3Y-TZP was sintered at 1600˚C. In the case of 3Y-TZP containing rough alumina powder that had been sintered the hardness value was around 1720.3 Hv. It was predicted that an improved toughening effect in ZTA could be achieved by using finer alumina powder as the parent material.
4,000원
