Sn substitution endows NaTi2(PO4)3/C with remarkable sodium storage performances

The further development of clean energy requires the use of more stable and reliable energy storage system. In addition to lithium ion battery power supplies, sodium ion batteries also have prospects for application and development thanks to the low cost and abundant resource. NaTi₂(PO₄)₃ has attracted much attention due to its three-dimensional channels for sodium ion transfer. In order to meliorate sodium storage properties of NaTi₂(PO₄)₃ electrode, a facile strategy of Sn substitution at Ti sites was employed, and a series of electrodes were successfully synthesized through sol-gel route. The electrochemical performances of Sn substituted composites are significantly improved compared with bare NaTi₂(PO₄)₃/C. And it was found that NaSn_0.2Ti_1.8(PO₄)₃ (NTP/C-Sn-2) delivers the largest capacity, and it also demonstrates the outstanding cycling performances. NTP/C-Sn-2 has discharge capacity of 131.1 mAh g⁻¹ at 4 A g⁻¹ in rate test and 121.4 mAh g⁻¹ at 1 A g⁻¹ after 1000 cycles in cycling test. The experimental results show that NaTi₂(PO₄)₃/C with Sn substitution with proper content exhibits the great potential in anode for sodium ion batteries, and can further provide reference for next generation electrode materials and battery systems.     

微孔发泡高分子材料的应用研究

以美国麻省理工学院N.P.Suh教授等研制开发的微孔发泡塑料为主线,简述了微孔发泡高分子材料优异的力学性能、热性能及加工性能,较详细地介绍了该材料在工业生产中的应用现状,并指出了微孔发泡高分子材料发展的方向。     

Uniform nitrogen and sulfur co-doped carbon nanospheres as catalysts for the oxygen reduction reaction

Uniform nitrogen and sulfur co-doped carbon nanospheres with an average diameter of approximately 200 nm were prepared using sulfur and polyacrylonitrile as precursors. The materials were characterized using scanning electron microscopy, transmission electron microscopy, elemental analysis, and X-ray photoelectron spectroscopy. The characterization results suggest the as-prepared materials had uniform, porous, nanospherical morphologies and high surface areas. For the typical sample containing 9.5% sulfur, the surface area is up to 653 m² g⁻¹. The catalysts exhibited enhanced catalytic activity, outstanding long-term stability, and excellent methanol tolerance in an alkaline medium. Significantly, the sulfur addition was found to be vital in improving materials’ catalytic performance through preventing aggregation of the nanospheres, constructing porous structures, increasing the surface area, and participating in the formation of active sites.     

An optimization method to find the thermodynamic limit on enhancement of solar thermal decomposition of methane

An optimization approach to enhancing the solar thermal decomposition of methane (TDM) reaction process based on the fluid flow pattern reconstruction is proposed. The sum of entropy generations due to TDM reaction and heat convection in the process is shown to tend to its maximum when the performance of the reaction is enhanced, and thus, is used as the criterial to optimize the velocity field of the fluid. This optimization problem is solved by the calculus of variations method. The obtained flow pattern is shown to be able to give the conditions to achieve the optimally enhanced TDM process. As the sum of the entropy generations tends to its extremum, the solution found by the optimization can be known as the thermodynamic limit for the TDM process enhancement. The obtained flow pattern can then be used to inspire the design of internal structures of the solar TDM reactor.     

Effect of introducing a steam pipe to n-dodecane decomposition by in-liquid plasma for hydrogen production

A method has been developed to improve the hydrogen production efficiency (HPE) by in-liquid plasma n-dodecane decomposition. A thin steam pipe is placed over the plasma electrode to recover the thermal energy emitted from the plasma to its surroundings. The steam generated by this energy is supplied to the vaporized n-dodecane around the edge of the plasma to cause a steam reforming reaction (SRR). Water pyrolysis is suppressed by not supplying the steam directly to the plasma. A large amount of CO and a small amount of CO₂ were detected in the produced gas. This indicates that a strong SRR has occurred. The HPE obtained by this method is 0.28 Nm³/kWh, which is two times greater than those obtained by previous methods, and similar to or greater than the yield of water electrolysis. This result is a major advance in the field of plasma heavy hydrocarbon decomposition aimed at hydrogen production. HPE is expected to be further improved by simply increasing the input power, due to synergy between the heat recovery effect of the steam pipe and the bubble stabilization effect. This indicates that this method has a high potential.     

Experimental study the collapse failure mechanism of cemented casing under non-uniform load

Under non-uniform in-situ stress, the casing collapse failure often happens easily, and especially in soft rock the problem is more serious. In addition, only the few scholars do some studies about failure mechanism of cemented casing under non-uniform in-situ stress which has a strong effect on collapse properties of cemented casing, especially testing investigation. Hence, the collapsing test was performed for cemented casing under non-uniform load (NFL) by adopting self-developed testing equipment, by which the radial deformation of cemented casing and damage rules of cement sheath have been measured and the stress-strain laws of cemented casing are obtained during the testing process by the electrical method. The initial yield load and plastic limit load of cemented casing as well as the subsequent yield load have been obtained. By analyzing testing data, the stress-hardening rate and strain-hardening rate after hardening have been determined. The effects of cement sheath on collapse properties of P110SS casing and strain and deformation laws of P110SS casing after hardening have been obtained. The hardening character and failure mechanism of cemented casing have been figured out under NFL.     

Dynamic simulation of a cryogenic batch distillation process for hydrogen isotopes separation

The operational flexibility of cryogenic batch distillation may propel its application in the Isotope Separation System of the fusion reactor. The batch distillation, unlike continuous distillation, is not a steady-state process. In order to obtain improved separation efficiency, a reasonable dynamic model of batch distillation should be developed. In this paper, dynamic simulations of the batch distillation separation process of a hydrogen-deuterium mixture were performed utilizing Aspen Plus and Aspen Dynamics. The validity of the established simulation model was firstly verified by our experimental results. Following that, two dynamic control structures, i.e., composition control and temperature control, were added to improve the recovery efficiency of batch distillation light component products. In comparison with the distillation without dynamic control structure, the distillation with composition control and temperature control can improve the H₂ recovery ratio by 5.45% and 5.09%, respectively.     

Effect of friction stir processing conditions on fatigue behavior and texture development in A356-T6 cast aluminum alloy

Friction stir processing (FSP) was applied to A356-T6 cast aluminum alloy to modify the microstructure and to eliminate casting defects under two different tool rotational speeds. Plane bending fatigue tests had been conducted, revealing that FSP could enhance the fatigue strength where the lower rotational speed condition gave better results. The enhancement of fatigue strength was attributed to the elimination of casting defects. Crystallographic analysis by EBSD revealed that the texture induced by FSP had detrimental effect on growth resistance. The lower rotational speed condition resulted in the weaker texture, and consequently, further increase of fatigue strength was achieved compared with the higher rotational speed condition.     

Microstructure and oxidation behaviour of Ir-rich Ir–Al binary alloys

In the current study, alloys of Ir–11Al, Ir–23Al, Ir–30Al, Ir–41Al and Ir–45Al (at.%) were prepared to investigate the microstructure and oxidation behaviour of Ir-rich Ir–Al alloys. Ir(Al)_ss and/or β-IrAl intermetallic phases were found to exist in the prepared alloys. During isothermal oxidation at 1100 °C, the Ir(Al)_ss and β-IrAl individually changed to porous and dense Al₂O₃. The microstructure of the oxide scale formed on Ir–23Al was similar to that of its former alloy which possessed a dendrite-like configuration. It was found that the mass change of Ir–45Al followed a parabolic law, showing the best oxidation resistance among the Ir–Al alloys.     

Triblock copolymer-assisted synthesis of hierarchical ZIF-67 in the presence of 1,3,5-trimenthylbenzene

A hierarchically porous ZIF-67 was successfully synthesized by using non-ionic block copolymers P123 as a supramolecular templating surfactant and 1,3,5-trimethylbenzene (TMB) as a swelling agent. It was noted that TMB was an effective swelling agent to expand the pore size. Pore size distribution analyses reveal that the as-synthesized hierarchical ZIF-67 has a typical trimodal pore size distribution showing simultaneous micro-, meso- and macropore channel systems. Due to the effect of TMB and P123, the diameter of ZIF-67 nanoparticles was about twice of that synthesized with P123 only and larger pores were formed among the enlarged nanoparticles. This strategy is expected to be a facile and efficient method for the preparation of hierarchical ZIF-67.