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1.
《International Journal of Hydrogen Energy》2022,47(12):7836-7845
Catalyst samples for CH4 decomposition were prepared from red mud (RM) by an acid-leaching neutralization precipitation approach. Water-washing the resultant precipitates multiple times, followed by drying at 105 °C and calcination at 500 °C, resulted in a threshold of residual Na2O, equivalent to 96% Na2O removal. Drying the precipitate at a higher temperature of 200 °C, followed by repeated water washing, provided a deeper Na2O removal of 99% and made the resultant samples more active for the targeted reaction. Subsequently, four catalyst samples with a simulated red mud composition and NaOH contents from 0 to 0.3 wt% were prepared and the catalytic test results revealed that the Na2O remaining in the RM-derived catalysts did not only inhibit their activation in CH4 but also lower their maximal activities for CH4 decomposition. Finally, two catalysts with the same simulated red mud composition and their Na impregnated respectively on Fe2O3 and a mixture support of Al2O3-SiO2-TiO2 were prepared and tested to explore the effect of Na distribution on the activation behavior of RM-derived catalysts for CH4 decomposition. The activity testing results showed that it was the Na residual dispersed on iron oxides in the RM-derived samples to significantly inhibit the activation of CH4 decomposition. 相似文献
2.
Qian Wu Xiangmei Liu Bo Li Lei Tan Yong Han Zhaoyang Li Yanqin Liang Zhenduo Cui Shengli Zhu Shuilin Wu Yufeng Zheng 《材料科学技术学报》2021,67(8):70-79
Pathogens pose a serious challenge to environmental sanitation and a threat to public health.The frequent use of chemicals for sterilization in recent years has not only caused secondary damage to the environment but also increased pathogen resistance to drugs,which further threatens public health.To address this issue,the use of non-chemical antibacterial means has become a new trend for environmental disinfection.In this study,we developed red phosphorus nanoparticles(RPNPs),a safe and degradable photosensitive material with good photocatalytic and photothermal properties.The red phosphorus nanoparticles were prepared using a template method and ultrasonication.Under the irradiation of simulated sunlight for 20 min,the RPNPs exhibited an efficiency of 99.98%in killing Staphylococcus aureus due to their excellent photocatalytic and photothermal abilities.Transmission electron microscopy and ultraviolet–visible spectroscopy revealed that the RPNPs exhibited degradability within eight weeks.Both the RPNPs and their degradation products were nontoxic to fibroblast cells.Therefore,such RPNPs are expected to be used as a new type of low-cost,efficient,degradable,biocompatible,and eco-friendly photosensitive material for environmental disinfection. 相似文献
3.
《International Journal of Hydrogen Energy》2022,47(59):25022-25033
Injecting hydrogen into the natural gas network to reduce CO2 emissions in the EU residential sector is considered a critical element of the zero CO2 emissions target for 2050. Burning natural gas and hydrogen mixtures has potential risks, the main one being the flame flashback phenomenon that could occur in home appliances using premixed laminar burners. In the present study, two-dimensional transient computations of laminar CH4 + air and CH4 + H2 + air flames are performed with the open-source CFD code OpenFOAM. A finite rate chemistry based solver is used to compute reaction rates and the laminar reacting flow. Starting from a flame stabilized at the rim of a cylindrical tube burner, the inlet bulk velocity of the premixture is gradually reduced to observe flashback. The results of the present work concern the effects of wall temperature and hydrogen addition on the flashback propensity of laminar premixed methane-hydrogen-air flames. Complete sequences of flame dynamics with gradual increases of premixture velocity are investigated. At the flame flashback velocities, strong oscillations at the flame leading edge emerge, causing broken flame symmetry and finally flame flashback. The numerical results reveal that flashback tendency increase with increasing wall temperature and hydrogen addition rate. 相似文献
4.
《Ceramics International》2022,48(13):18793-18802
The luminescence center energy transfer, crystal field strength, and covalency are limited by the crystal structure of the host and subsequently affect the luminescence efficiency, color, and intensity. Here, we report an excellent red phosphor BaLaLiWO6:0.40Eu3+ and the dependence between symmetry and luminous performance. A model for changing symmetry is drawn by analyzing the Coulomb potential and structure for the application of a double-perovskite phosphor BLLWO: Dy3+, Eu3+ in white light LEDs. The addition of Dy3+/Eu3+ makes the W-O bond formed by the B-site and oxygen ion longer and the Li-O bond shorter, and the difference between the eight octahedral around the A-site is reduced, increasing the symmetry of the A-site. Local symmetry was successfully modulated by changing the Eu3+ concentration to control the Y/B ratio of Dy3+ and the R/O ratio of Eu3+ and smoothly achieved (0.382, 0.373) warm white light color coordinate. The phosphor has excellent thermal stability and still has 92.3% intensity at 475 K. The above results show that the wavelength composition of the luminescence is tunable by changing the symmetry of the environment in which the doped ions are located. It applies to single hosts for the regulation of white light emission. 相似文献
5.
J. Grune K. Sempert M. Kuznetsov T. Jordan 《International Journal of Hydrogen Energy》2021,46(23):12487-12496
This paper presents results of experimental investigations on spherical and cylindrical flame propagation in pre-mixed H2/air-mixtures in unconfined and semi-confined geometries. The experiments were performed in a facility consisting of two transparent solid walls with 1 m2 area and four weak side walls made from thin plastic film. The gap size between the solid walls was varied stepwise from thin layer geometry (6 mm) to cube geometry (1 m). A wide range of H2/air-mixtures with volumetric hydrogen concentrations from 10% to 45% H2 was ignited between the transparent solid walls. The propagating flame front and its structure was observed with a large scale high speed shadow system. Results of spherical and cylindrical flame propagation up to a radius of 0.5 m were analyzed. The presented spherical burning velocity model is used to discuss the self-acceleration phenomena in unconfined and unobstructed pre-mixed H2/air flames. 相似文献
6.
7.
Clay polyurethane nanocomposite (CPN) coating films were fabricated by uniformly dispersing nanoclay, organically modified with 25–30 wt.% octadecylamine in varying concentrations up to 5 wt.%, in a commercial two component, glossy, acrylic aliphatic polyurethane using ultrasonication. Organo-modified nanoclay was characterized by X-ray diffraction (XRD). The dispersion of the nanoclay into the matrix was investigated by scanning electron microscopy (SEM). CPN coating films were characterized by thermogravimetric analysis (TGA), and flame retardant, corrosion resistance and mechanical properties were also investigated. The XRD measurement indicated that, the organo-modified nanoclay particles were mainly constituted of montmorillonite with traces of quartz and calcite also found to be present. The SEM analysis showed that the nanoclay layers were dispersed and intercalated into the polyurethane coating. Thermogravimetric analysis showed that incorporating 5 wt.% organo-nanoclay into polyurethane considerably enhanced the thermal stability and increased the char residue to 14.11 wt.% relative to 4.58 for the sample without organo-nanoclay (blank polyurethane). The limiting oxygen index (LOI) test revealed that incorporation of organo-nanoclay led to a further increase in LOI values, which indicate an improvement in flame retardancy properties. The corrosion resistance also improved and this improvement increases with increase nanoclay wt.%. The mechanical resistance measurements demonstrated that the gloss of the CPN coating films slightly decreased, although hardness, adhesion and impact resistance of the CPN coating films improved with the incorporation of the organo-nanoclay. 相似文献
8.
《能源学会志》2020,93(6):2381-2387
To enhance the activity of catalysts for CO removal, the perovskite-type catalysts La1-xSrxCoO3 (x = 0, 0.2, 0.4, 0.6, and 0.8) with different Sr2+ doping amount were synthesized by flame spray synthesis (FSS) method. The perovskite-type catalyst synthesized by FSS has a much larger specific surface area (SSA) than that prepared by other conventional methods. The SSA of catalyst increases with the increase of Sr2+ doping amount and the SSA of La0.2Sr0.8CoO3 reaches 31.65 m2/g. Compared with other conventional methods, FSS method significantly improves the activity of catalyst and makes it close to the performances of catalysts with surface modification. The substitution of La3+ by Sr2+ promotes the generation of secondary phase Co3O4 and SrCO3. The catalytic activity of La1-xSrxCoO3 increases with the addition of Sr2+, which results from the increasing active sites and oxygen vacancies. Interestingly, La0.4Sr0.6CoO3 performs the highest activity for CO oxidation and the CO conversion reaches 50% at 148.6 °C and 90% at 165.9 °C. The oxidation of CO over La1-xSrxCoO3 catalyst may follow a combination of MvK and L-H mechanisms according to the experimental results of H2-TPR. Moreover, the catalyst exhibits good catalytic activity in consecutive oxidation cycles. In consecutive oxidation experiments with La0.4Sr0.6CoO3, the CO conversion reaches 50% at 168.8 °C and 90% at 197.8 °C in the eighth oxidation cycle. These results prove that FSS method can further improve the activity of catalysts and is suitable for the preparation of efficient catalysts. 相似文献
9.
The flame front deformation instability of low-velocity filtration combustion within an inert packed bed is studied based on the initial preheating non-uniformity. Based on the experimental phenomena, an initial thermal perturbation model is numerically proposed so as to predict the deformation behaviors of the flame front instabilities. The numerical prediction indicates that the assumption of an initial thermal perturbation is a feasible explanation as the cause of the flame front inclination instability. As the initial thermal perturbation increases, the phenomena of the flame front break and shrinking instabilities could easily occur at high filtration velocity or low equivalence ratio. Moreover, the evolutions of the flame front break rate and the shrinking rate are quantitatively analyzed. 相似文献
10.