• 한국표면공학회지
• /
• 제52권5호
• /
• pp.246-250
• /
• 2019

Nano-multilayered $Cr_{25.2}Al_{19.5}Si_{4.7}N_{50.5}$ films were deposited on the steel substrate by cathodic arc plasma deposition. They were corroded at $900^{\circ}C$ in $Ar/1%SO_2$ gas in order to study their corrosion behavior in sulfidizing/oxidizing environments. Despite the presence of sulfur in the gaseous environment, the corrosion was governed by oxidation, leading to formation of protective oxides such as $Cr_2O_3$ and ${\alpha}-Al_2O_3$, where Si was dissolved. Iron diffused outward from the substrate to the film surface, and oxidized to $Fe_2O_3$ and $Fe_3O_4$. The films were corrosion-resistant up to 150 h owing to the formation of thin ($Cr_2O_3$ and/or ${\alpha}-Al_2O_3$)-rich oxide layers. However, they failed when corroded at $900^{\circ}C$ for 300 h, resulting in the formation of layered oxide scales due to not only outward diffusion of Cr, Al, Si, Fe and N, but also inward movement of sulfur and oxygen.

• 자원리싸이클링
• /
• 제20권3호
• /
• pp.48-54
• /
• 2011

황산으로 탈황 폐촉매를 침출한 결과 황산농도 1 M, 반응시간 1 hr인 실험조건에서 Ni 및 V은 95% 이상, 그리고 Mo은 30%가 침출되었다. 탈황 폐촉매의 Mo matrix 특성으로 인하여 다른 금속에 비하여 Mo의 침출율이 낮았으며, 본 침출반응은 확산반응에 의하여 제어되는 것으로 판단된다. Mo을 완전히 침출하기 위하여 유황성분이 제거된 폐촉매로 침출실험을 실시하였다. 1M 황산으로 처리후 탄산나트륨으로 세척시 Ni, Mo 그리고 V의 침출율은 99% 이었다. Ni 2 g/L; V 9 g/L, Mo 0.6 g/L 조성의 침출액을 LIX 841로 용매추출한 조건에서 A:O 비 5:2, 2단계로 처리시 Mo은 98% 이상 추출되었으며 A:O 비 5:3, 2단계로 처리시 V은 82%가 추출되었다.

• Bulletin of the Korean Chemical Society
• /
• 제26권2호
• /
• pp.281-284
• /
• 2005

The Fe/MgO catalysts with different Fe loadings (1, 4, 6, 15 and 30 wt% Fe) were prepared by a wet impregnation with iron nitrate as precursor. All of the catalysts were characterized by BET surface analyzer, X-ray diffraction (XRD), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The maximum removal capacity of $H_2S$ was obtained with 15 wt% Fe/MgO catalyst which had the highest BET surface area among the measured catalysts. XRD of Fe/MgO catalysts showed that well dispersed Fe particles could be present on Fe/MgO with Fe loadings below 15 wt%. The crystallites of bulk $\alpha$-$Fe_2O_3$ became evident on 30 wt% Fe/MgO, which were confirmed by XRD. TPR profiles showed that the reducibility of Fe/MgO was strongly related to the loaded amounts of Fe on MgO support. Therefore, the highest removal efficiency of $H_2S$ in wet oxidation could be ascribed to a good dispersion and high reducibility of Fe/MgO catalyst. XPS studies indicated that the $H_2S$ oxidation with Fe/MgO could proceed via the redox mechanism ($Fe^{3+}\;{\leftrightarrow}\;Fe^{2+}$).

• 대한금속재료학회지
• /
• 제49권12호
• /
• pp.956-966
• /
• 2011

Bioleaching studies of metals from a spent catalyst were conducted using both adapted and unadapted bacterial cultures. The bacterium used in this experiment was Acidithiobacillus ferrooxidans. A comparison of the kinetics of leaching was made between the two cultures by varying the leaching parameters, including the pulp density, particle size and temperature. Both cultures showed similar effects with respect to the above parameters, but the leaching rates of all metals were higher with the adapted compared to the unadapted bacterial cultures. The leaching reactions were continued for 240 h in the case of the unadapted bacterial culture, but only for 40 h in the case of the adapted bacterial culture. The leaching reactions followed first order kinetics. In addition, the kinetics of leaching was concluded to be a diffusion control model; therefore, the product layers were impervious.

• 한국의류학회지
• /
• 제35권11호
• /
• pp.1297-1308
• /
• 2011

This research investigates the application of ZnO (zinc oxide) nanoparticles and $TiO_2$ (titanium dioxide) nanoparticles to polypropylene nonwoven fabrics via an electrospinning technique for the development of textile materials that can decompose harmful gases. To fabricate uniform ZnO nanocomposite fibers, two types of ZnO nanoparticles were applied. Colloidal $TiO_2$ nanoparticles were chosen to fabricate $TiO_2$ nano- composite fibers. ZnO/poly(vinyl alcohol) (PVA) and $TiO_2$/PVA nanocomposite fibers were electrospun under a variety of conditions that include various feed rates, electric voltages, and capillary diameters. The morphology of electrospun nanocomposite fibers was examined with a field-emission scanning electron micro- scope and a transmission electron microscope. Decomposition efficiency of gaseous materials (formaldehyde, ammonia, toluene, benzene, nitrogen dioxide, sulfur dioxide) by nanocomposite fiber webs with 3wt% nano-particles (ZnO or $TiO_2$) and 7$g/m^2$ web area density was assessed. This study shows that ZnO nanoparticles in colloid were more suitable for fabricating nanocomposite fibers in which nanoparticles are evenly dispersed than in powder. A heat treatment was applied to water-soluble PVA nanofiber webs in order to stabilize the electrospun nanocomposite fibrous structure against dissolution in water. ZnO/PVA and $TiO_2$/PVA nanofiber webs exhibited a range of degradation efficiency for different types of gases. For nitrogen dioxide, the degradation efficiency was 92.2% for ZnO nanocomposite fiber web and 87% for $TiO_2$ nanocomposite fiber web after 20 hours of UV light irradiation. The results indicate that ZnO/PVA and $TiO_2$/PVA nano- composite fiber webs have possible uses in functional textiles that can decompose harmful gases.

• 한국대기환경학회지
• /
• 제20권2호
• /
• pp.225-236
• /
• 2004

Diesel engines which emit a lot of PM and NOx have been known as a main air polluter. Especially, diesel particulate matters (OPM) including black smoke are hazardous air pollutants to human health and environment. The nations retaining advanced engine technologies have reinforced emission regulations. To meet these regulations diesel engine manufacturers have developed low-emission diesel engines, aftertreatment equipments, alternative fuel technologies and so on. In this study, particle number concentrations characteristics according to particle size and engine driving conditions were analyzed when these low-emission technologies were applied. There was a tendency of increasing particle number concentrations from heavy-duty diesel engines with increasing engine rpm and load rate. In the cases of COPF (Catalytic Diesel Particulate Filter), CNG (Compressed Natural Gas) engine and ULSD (Ultra Low Sulfur Diesel) more than 99% of particle number concentration were removed.

• 한국폐기물자원순환학회지
• /
• 제35권7호
• /
• pp.670-682
• /
• 2018

Engineered nanomaterials (ENMs) can be released to humans and the environment through the generation of waste containing engineered nanomaterials (WCNMs) and the use and disposal of nano-products. Nanoparticles can also be introduced intentionally or unintentionally into waste streams. This study examined WCNMs in domestic industries, and target nanomaterials, such as silicon dioxide, titanium oxide, zinc oxide, nano silver, and carbon nanotubes (CNTs), were selected. We tested 48 samples, such as dust, sludge, ash, and by-products from manufacturing facilities and waste treatment facilities. We analyzed leaching and content concentrations for heavy metals and hazardous constituents of the waste. Chemical compositions were also measured by XRD and XRF, and the unique properties of nano-waste were identified by using a particle size distribution analyzer and TEM. The dust and sludge generated from manufacturing facilities and the use of nanomaterials showed higher concentrations of metals such as lead, arsenic, chromium, barium, and zinc. Oiled cloths from facilities using nano silver revealed high concentrations of copper, and the leaching concentrations of copper and lead in fly ash were higher than those in bottom ash. In XRF measurements at the facilities, we detected compounds such as silicon dioxide, sulfur trioxide, calcium oxide, titanium dioxide, and zinc oxide. We found several chemicals such as calcium oxide and silicon dioxide in the bottom ash of waste incinerators.

• Elastomers and Composites
• /
• 제44권1호
• /
• pp.41-46
• /
• 2009

천연고무의 일정하중 영구압축률에 온도와 가교시스템이 미치는 영향을 고찰하였다. 다양한 가교시스템과 가교밀도의 고무시편을 만들기 위해 여러 가지 함량의 황과 dicumyl peroxide(DCP)를 사용하여 배합하였으며, 가교된 천연고무의 일정변위 조건에서 측정된 영구압축률과 일정하중에서 측정된 영구압축률의 차이를 비교하였다. 일정하중 영구압축률은 일정변위 영구압축률에 비해 가교밀도의 변화에 따라 상대적으로 큰 차이를 보였으며, 이는 영구압축률 측정 시 공급된 변형에너지가 다르기 때문이다. 또한 일정하중 영구압축률 측정에서 황으로 가교시킨 시편의 경우 하중과 온도증가에 따라 영구압축률이 크게 증가하였고, 이에 반해 DCP로 가교시킨 시편의 경우 하중과 온도증가에 큰 영향을 받지 않았다.

• 접착 및 계면
• /
• 제13권1호
• /
• pp.1-8
• /
• 2012

EPDM에 카르복시산을 포함하는 아크릴 단량체인 methacrylic acid (MA)가 도입된 grafted EPDM을 합성하여 MA의 grafting ratio가 탄성체의 물성과 다른 고무와의 접착특성에 미치는 영향을 연구하였다. Grafted EPDM의 storage modulus는 특정온도까지는 sulfur로 가교한 EPDM vulcanizate보다 높게 유지되다가 온도가 더 높아지면 2차 결합력이 약해지면서 급격하게 감소되는 것이 관찰되었다. EPDM에 수소결합을 유도할 수 있는 반응기를 도입했을 때 grafted EPDM 분자들 간의 aggregate 형성과 그라프트된 MA의 결정성으로 인해 우수한 기계적 물성을 나타내었다. EPDM 자체는 극성이 낮고 다른 종류의 고무와 분자간 결합력이 약해서 접착이 제대로 이루어지지 않았으며 그라프트된 MA의 함량이 증가할수록 접착강도가 더 높아졌으며 MA의 grafting ratio가 10% 이상일 때에는 접착평가 시 고무시편이 부분적으로 파괴될 정도로 접착력이 우수하였다.

• Transactions on Electrical and Electronic Materials
• /
• 제4권6호
• /
• pp.13-16
• /
• 2003

Mn-doped $ZnGa_{2}O_{4}$:$Mn^{2+}$ (M=S, Se) thin film phosphors have been grown using a pulsed laser deposition technique under various growth conditions. The structural characterization carr~ed out on a series of $ZnGa_{2}O_{4}$:$Mn^{2+}$ (M=S, Se) films grown on MgO(l00) substrates usmg Zn-rich ceramic targets. Oxygen pressure was varied from 50 to 200 mTorr and Zn/Ga ratio was the function of oxygen pressure. XRD patterns showed that the lattice constants of the $ZnGa_{2}O_{4}$:$Mn^{2+}$ (M=S, Se) thin film decrease with the substitution of sulfur and selenium for the oxygen in the $ZnGa_2O_4$. Measurements of photoluminescence (PL) properties of $ZnGa_{2}O_{4}$:$Mn^{2+}$ (M=S, Se) thin films have indicated that MgO(100) is one of the most promised substrates for the growth of high quality $ZnGa_2O_{4-x}M_{x}$:$Mn^{2+}$ (M=S, Se) thin films. In particular, the incorporation of Sulfur or Selenium into $ZnGa_2O_4$ lattice could induce a remarkable increase in the intensity of PL. The increasing of green emission intensity was observed with $ZnGa_2O_{3.925}Se_{0.075}:$Mn^{2+}$ and $ZnGa_2O_{3.925}S_{0.05}$:$Mn^{2+}$ films, whose brightness was increased by a factor of 3.1 and 1.4 in comparison with that of $ZnGa_{2}O_{4}$:$Mn^{2+}$ films, respectively. These phosphors may promise for application to the flat panel displays.