In this study, porous silicon was prepared by coating SiO2 on the Mg2Si surface under controlled solvent conditions, followed by magnesiothermic reduction and etching as a high-capacity anode material for lithium-ion batteries. Porous silicon prepared using mixed solvents(ethanol/distilled water) formed a uniform porous structure with large pores. Porous silicon synthesized using distilled water exhibited a core-shell structure composed of the inner core with large pores and the shell layer with small pores. To improve the electrochemical performance, porous silicon composites were synthesized by the electrostatic assembly with MXene nanosheets and polydopamine-derived carbon coating. The W-Mg(0.1)-Si(2.6) with core-shell structure prepared using distilled water showed initial discharge capacity of 3614.6 mAh/g and high capacity of 1053.9 mAh/g at 4 C. The E-Mg(0.1)-Si(2.6)@MN(1:5) and E-Mg(0.1)-Si(2.6)@PDA(1:3) anode composites prepared by MXene nanosheets and polydopamine-derived carbon coating exhibited initial discharge capacities of 4531.6 and 3915.8 mAh/g and showed capacities of 1276.5 and 1193.1 mAh/g at 4 C.
This study investigated the effects of pretreatment conditions on the properties of kenaf/polypropylene (PP) biocomposites. Kenaf fibers were treated under alkaline conditions with moderate severity (NaOH 2-6 wt.%, Hfactor approximate to 800) and acidic conditions. The chemical composition changes were quantitatively analyzed using NREL standard methods, ensuring the reliability of the data, while the thermal and mechanical properties of the biocomposites were evaluated by thermogravimetric analysis (TGA) and tensile testing, respectively. The results showed that alkali pretreatment effectively reduced lignin and hemicellulose contents, leading to improved interfacial bonding between the fibers and the PP matrix. The tensile strength increased significantly with fiber loading up to 30 wt.%, while a decrease in the enhancement rate was observed at 40 wt.%, which could be explained by the theoretical rule of mixtures and fiber agglomeration. Thermal analysis revealed that pretreatment influenced the thermal degradation behavior of kenaf components, whereas the thermal stability of the PP matrix was largely maintained.
It is impractical to experimentally characterize hydrodynamics of molten-metal bubble columns (MMBCs) operated at high temperatures due to intrinsic opacity. This study investigated hydrodynamics of MMBCs with tertiary NiBiSe alloys and CH4 gas using a computational fluid dynamics (CFD) model based on level-set volume-of-fluid (LS-VOF), changing surface tension (sigma) and contact angle (theta). sigma of NiBiSe alloys containing 0, 1, and 5 mol% Selenium (Se) was 0.389, 0.317, and 0.31 N/m, respectively, while q was set to 120 degrees and 150 degrees. The six simulation cases were conducted in a rectangular MMBC with a centrally located bottom nozzle (diameter: 3.18 mm) at a superficial gas velocity of 0.39 mm/s under the bubbling flow regime. The time-averaged gas holdup ((alpha(G) )) overbar ranged 0.29-0.33%, the time- and volume-averaged bubble size ((d(32))) over bar was 6.54-8.05 mm, and the interfacial area ((a(s))) over bar was 1.70-2.09 m(2)/m(3). The ratio (gamma) of density to sigma was strongly related to d(32), and the minimum d(32) was observed in a Ni27Bi72Se1 MMBC exhibiting the highest gamma. Since the volume of initial bubbles formed at the column bottom increased with increasing theta, larger theta resulted in larger d(32). This study offers theoretical hydrodynamic foundation for hydrogen production in MMBCs via methane pyrolysis.
In this study, the CO2 capture characteristics of water-lean absorbents composed of 2-(ethylamino)ethanol (EAE), diethylene glycol monobutyl ether (DEGMBE), and water were investigated using a laboratory-scale packed absorption column at 40 degrees C. The effects of EAE (2-5 M) and DEGMBE (0-40 wt%) concentration on solvent viscosity, CO2 loading, absorption rate, and overall mass transfer coefficient were systematically examined. The viscosity of the solvent increased after CO2 absorption and with increasing DEGMBE content; however, the viscosity remained within the operable range for packed column operation. The rich CO2 loading increased with increasing EAE concentration due to the higher availability of reactive amine groups, whereas it decreased with increasing DEGMBE content as a result of reduced solvent polarity. The cyclic CO2 loading increased with EAE concentration, while the decrease with increasing DEGMBE content was relatively moderate. The CO2 absorption rate and overall mass transfer coefficient decreased with increasing lean CO2 loading because of the reduction in free amine concentration and the increase in liquid-phase and potential for reducing regeneration energy in CO2 capture processes.
We investigated effects of the precious metal and CeO2 loading on the performance of Pd-Rh-CeO2 based monolithic three-way catalysts. To explore the impact of aging, hydrothermal aging was also conducted at 1050 degrees C for 30 h. Under stoichiometric condition (lambda = 1.00), the performance with simulated automotive exhaust at 100-500 degrees C revealed that increase in CeO2 loading enhanced the NO and C3H8 removal. In contrast, under rich and lean conditions (lambda = 0.99 and 1.01, respectively), the overall performance was more strongly governed by precious metal loading than by CeO2 loading. In particular, excessive CeO2 loading tended to suppress C3H8 oxidation under conditions where NO2 formation or steam reforming was not favored, although the effect depended on PGM loading and A/F ratio. Simultaneously, N2O was more formed under NO reduction with lower CeO2 loading, but NH3 was more formed at higher CeO2 loading. Finally, after hydrothermal aging treatment, the deactivation of catalysts significantly occurred with increasing CeO2 loading, and the aging performance appeared similar regardless of the CeO2 content.
