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•The activity of Co-BEA for O3-induced lean CH4 oxidation was examined.•The CH4 conversion initiated at ∼40 °C, reaching 98% at 125 °C.•Co-BEA showed better O3-LMO activity than ...Pd-BEA and Fe-BEA.•The isolated mononuclear Co ions are the dominant active species.•O3 oxidizes CH4 over the Co sites to methoxy, formate species and then CO2.
As the ‘Global Methane Pledge’ was launched at the UN COP26 climate conference in Glasgow, there is a growing need to develop efficient methods to remove lean methane emission or methane slip at low temperatures. In order to enhance the lean methane oxidation at temperatures lower than 200 °C, it can be effective to use ozone as an oxidant while applying an appropriate catalyst. In this study, we examined the activity of cobalt ion-exchanged BEA catalyst for ozone-induced lean methane oxidation under dry reaction conditions. The cobalt ion-exchanged BEA catalyst was more active than palladium and iron ion-exchanged BEA catalysts. It could initiate methane oxidation at ∼40 °C and reaches the highest methane conversion of 98% at 125 °C, maintaining the conversion higher than 50% in the temperatures from 55 to 185 °C. The most active cobalt species was the isolated mononuclear cobalt ions coordinated to BEA framework. Finally, we proposed the reaction mechanism based on the intermediate species identified by the Fourier transform infrared spectroscopy.
In this study, we demonstrated that graphene could selectively absorb/desorb NO
x
molecules at room temperature. Chemical doping with NO
2 molecules changed the conductivity of the graphene layers, ...which was quantified by monitoring the current–voltage characteristics at various NO
2 gas concentrations. The adsorption rate was found to be more rapid than the desorption rate, which can be attributed to the reaction occurred on the surface of the graphene layer. The sensitivity was 9% when an ambient of 100
ppm NO
2 was used. Graphene-based gas sensors showed fast response, good reversibility, selectivity and high sensitivity. Optimization of the sensor design and integration with UV-LEDs and Silicon microelectronics will open the door for the development of nano-sized gas sensors that are extremely sensitive.
Liquid organic hydrogen carrier (LOHC) materials have been under the spotlight for the storage, transport and extraction of hydrogen. In particular, the catalytic process for extracting hydrogen from ...LOHC requires a fairly high level of catalytic technology due to several important issues, such as saving energy consumption due to endothermic reaction, minimizing consumption of LOHC for recycle, and high purity of hydrogen produced. This study focused on the development of La-doped Pt/Al
2
O
3
catalyst with high activity for the dehydrogenation of perhydrodibenzyltoluene (H
18
-DBT), which is well-known as a LOHC compound. The dehydrogenation performance of the La-doped Pt/Al
2
O
3
catalyst was different depending on the La content it contained. A variety of characterization techniques are used to identify the performance differences of the catalysts. As revealed by the analyses of chemisorption, TEM and XPS, the number of lanthanum oxide particles on the surface of the catalyst increases and block the active sites of platinum, as the amount of La doped in the catalyst increases. However, by donating electrons from lanthanum oxide to platinum, the activity per unit active site of Pt increases. The Pt/La-Al
2
O
3
catalyst doped with 1 wt% La showed much higher activity than that of the Pt/Al
2
O
3
, and showed the best performance among the catalysts doped with various amounts of La. In addition, it was found through spin-lattice relaxation analysis that La doping by solution-deficient method did not have a positive effect on the Pt dispersion by creating Al
3+
penta
sites inside the alumina particle rather than on the surface.
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The α-Fe2O3@nitrogen doped carbon (as donated α-Fe2O3@NC) composites derived from green microalgae was synthesized using one-pot spray pyrolysis, which showed a high discharge ...capacity of 1281.5mAhg−1 at 100mAg−1 as anode materials for lithium ion storage. They also provided good rate performance in a range of 200mAg−1–1000mAg−1, and maintained a capacity of 92% after 100 cycles at 200mAg−1. It demonstrated not only improved electrical conductivity but also effective prevention of the volume expansion of iron oxide during battery charge/discharge by uniformly forming iron oxide nanoparticles on microalgae via spray pyrolysis.
본 연구에서는 망간강을 소재로 하는 부품의 수명향상을 위해 망간강에 Ti의 첨가량을 변화하여 망간강을 주조하였으며, 주조한 소재의 특성을 확인하기 위하여 인장 및 표면 특성 그리고 베어링률 등 가공특성에 대해 조사하였다. 고망간강에 Ti 첨가 시 0.5%를 초과 시 결정립 미세화로 인한 합금의 강도가 향상되었으며 내부에 미세 탄화물이 형성시킴으로써 Mn만 ...첨가된 합금에 비해 표면의 마모에 대한 저항성을 높이는 결과를 나타냄을 확인하였다. 망간강에서 Ti의 함유량이 증가함으로 인해 인장강도가 증가함에는 큰 차이가 없었으나 마모성의 부분에서는 Ti이 Mn에 비해 마모성에는 미량이지만 더 큰 영향을 끼치며 Ti의 함량에 따라 탄화물의 크기 및 분포가 조대하고 균일하게 분포하였다. 망간강을 소재로 하는 부품의 수명향상을 위해 망간강에 Ti 첨가함으로써 강도 및 표면특성을 향상시킬수 있음을 확인하였다. Ti이 수지상정 결정립의 미세화로 인한 내마모성이 우수한 재질을 개발하는데 효과있음을 알 수 있었다. Ti가 첨가된 샘플에서 탄화물은 표면 거칠기에 대한 내성을 증가시키는 것으로 나타났으며 Mn강의 특성상 표면경화가 일어나기 시작하여 수명이 연장되는 것으로 보인다.
In this study, in order to improve the lifespan of parts made of manganese steel, manganese steel was cast by varying the amount of Ti added to the steel. In order to confirm the characteristics of the cast material, processing characteristics including tensile and surface characteristics and bearing ratio were investigated. It was confirmed that when the amount of Ti added to high manganese steel exceeds 0.5%, the strength of the alloy is improved due to grain refinement, and fine carbides are formed inside the steel. This results in increased resistance to surface wear compared to the alloy with only Mn added. There was no significant difference in the increase in tensile strength as the Ti content in manganese steel was increased. However, inclusion of Ti showed a small but greater effect on wear resistance compared to Mn, and the size and the distribution of carbides become coarse depending on the Ti content. and was evenly distributed. It was confirmed that the strength and surface properties of manganese steel can be improved by the addition of Ti to improve the lifespan of parts made with this steel. It was found that Ti is effective in developing materials with excellent wear resistance due to refinement of dendrite crystal grains. In the samples where Ti was added, the carbide appears to increase the resistance to surface roughness, and due to the nature of Mn steel, surface hardening begins to occur, which appears to extend the life.
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