A boron-11 NMR study of the stability of the alkaline aqueous solution of sodium borohydride that is both an indirect fuel and a direct fuel for low-temperature fuel cells

Alkaline aqueous solution of sodium borohydride NaBH₄ (denoted SB-fuel) is an indirect fuel when it is used to generate H₂ by hydrolysis, with the as-generated H₂ feeding a fuel cell, and it is a direct fuel when it is an anodic fuel of a direct fuel cell. However, SB-fuel suffers from a major drawback: NaBH₄ spontaneously hydrolyzes. Our study falls within this context. We studied the instability, at the NMR scale and over 12 weeks, of a series of SB-fuels (initial NaBH₄ concentration from 3.65 to 31.22 wt%, NaOH concentration from 1 to 16 M, and temperature between ?15 and 60 °C) to find the conditions at which SB-fuel can be stored for weeks in relative safety. We found that SB-fuel with a NaOH concentration of ≥8 M is relatively stable under cold conditions (?15 and 4 °C). In these conditions, NaBH₄ is not prevented from hydrolyzing, but the reaction is significantly mitigated. Otherwise, our study highlights the gaps in our understanding of the SB-fuel, emphasizes SB-fuel is a new concept of fuel (it should not be seen as any current fuel), and points out the challenges for attaining higher technology readiness levels.     

Thermodynamic properties of sodium hexatitanate (Na2Ti6O13) at high temperature (298.15–1573 K)

Sodium hexatitanate (Na₂Ti₆O₁₃) was reported as an anode side material for Sodium ion batteries owing to low material cost, high energy efficiency, good thermal stability and long cycle life. Therefore, studies pertaining to the thermodynamic properties of Na₂Ti₆O₁₃ are indispensable for improving its service performance. However, a significant number of literature reviews concerning thermodynamic properties indicated that heat capacity of Na₂Ti₆O₁₃ at high temperatures should be confirmed. In this study, the 99.5% purity of Na₂Ti₆O₁₃ sample was successfully prepared via solid-state reaction using TiO₂ and Na₂CO₃ as initial materials. Heat capacity of the as-synthesized samples in the temperature range of 573–1523 K was measured using a multi-high temperature calorimeter 96 line. Heat capacity, Cp, from 298.15 to 1573 K was modeled as a polynomial formula with a prediction error of 3%: Cp = 474.08143 + 0.06286T-8.04068 × 10⁶ T⁻² (J⋅mol⁻¹⋅K⁻¹). In combination with the low-temperature data, heat capacity of Na₂Ti₆O₁₃ from 0 to 1573 K was given in present study. Values of changes in enthalpy, Gibbs free energy and entropy in the temperature range of 298.15–1573 K were calculated based on the temperature dependence of heat capacity.     

碱铝硅酸盐玻璃化学强化关键影响因素概述

化学强化是一种玻璃机械强度增强方法,适用于异型、超薄、高碱、高膨胀玻璃增强,因新型超薄显示产品的屏幕保护玻璃发展需要,化学强化技术重新在碱铝硅酸盐玻璃品种掀起研究热潮。本文对化学强化本质及铝硅酸盐玻璃在屏幕保护玻璃应用进行了回顾,基于玻璃化学强化的高CS、DOL和低CT诉求,归纳总结了关键影响因素,第1,碱铝硅酸盐玻璃的成分及结构是基础,氧化铝有利玻璃网络孔隙增大创造交换通道,氧化钠或氧化锂是离子交换关键物质;第2,对于玻璃组成和结构设计,要求玻璃网络键合度R=O/Si或O/(Si+Al)满足2.15~2.40,碱金属氧化物质量分数大于13%且膨胀系数大于6×10^-6/℃;第3,在化学强化工艺方面,化学强化温度决定离子扩散系数,化学强化时间决定DOL,一步法仅能获得相对较大的CS,而DOL不很理想,只有两种离子参与交换的二步法才有利于CS和DOL同步提高。     

Layered Birnessite Cathode with a Displacement/Intercalation Mechanism for High-Performance Aqueous Zinc-Ion Batteries

Mn-based rechargeable aqueous zinc-ion batteries(ZIBs)are highly promising because of their high operating voltages,attractive energy densities,and eco-friendliness.However,the electrochemical performances of Mn-based cathodes usually suffer from their serious structure transformation upon charge/discharge cycling.Herein,we report a layered sodium-ion/crystal water co-intercalated Birnessite cathode with the formula of Na0.55Mn2O4·0.57H2O(NMOH)for high-performance aqueous ZIBs.A displacement/intercalation electrochemical mechanism was confirmed in the Mn-based cathode for the first time.Na+and crystal water enlarge the interlayer distance to enhance the insertion of Zn^2+,and some sodium ions are replaced with Zn^2+ in the first cycle to further stabilize the layered structure for subsequent reversible Zn^2+/H^+ insertion/extraction,resulting in exceptional specific capacities and satisfactory structural stabilities.Additionally,a pseudo-capacitance derived from the surface-adsorbed Na^+ also contributes to the electrochemical performances.The NMOH cathode not only delivers high reversible capacities of 389.8 and 87.1 mA h g^−1 at current densities of 200 and 1500 mA g^−1,respectively,but also maintains a good long-cycling performance of 201.6 mA h g^−1 at a high current density of 500 mA g^−1 after 400 cycles,which makes the NMOH cathode competitive for practical applications.     

镓锗铜萃余液综合利用研究与应用

本文针对镓锗铜综合回收系统产出的萃余液,设计通过中和氧化除杂、锌粉置换除铜镉、有机试剂除钴镍、纯碱法生产碱式碳酸锌、高温煅烧生产活性氧化锌和一步法生产元明粉的生产工艺流程,有效的将镓锗铜萃余液分类分离富集,产出具有价值的富集渣和工业产品,进一步提升综合回收经济效益。     

Mg-bearing quartz solid solutions as structural intermediates between low and high quartz

Glass powder samples of cordierite composition (doped with 8 mol% TiO₂) were heat-treated to produce a series of increasingly SiO₂-enriched Mg-bearing quartz solid solutions (Qss). The obtained materials were then analyzed by X-ray diffraction: Rietveld structural refinements revealed that Mg-bearing Qss phases possess trigonal symmetry and a compositionally dependent intermediate structural arrangement between those of low and high quartz. High-temperature diffraction measurements were performed up to 700°C to characterize the thermal expansion behavior of the crystals. At SiO₂-rich compositions, a reversible high-to-intermediate inversion of the quartz structure is observed, which shifts with increasing stuffing to lower temperatures than the conventional 573°C for pure quartz. Similarities and differences to the better-established Li-bearing Qss are discussed in the text.     

Generation-IV reactors and nuclear hydrogen production

There are dozens of hydrogen production methods and techniques from many sources such as fossil fuels, renewable energy sources and nuclear energy in the literature. Thermo-chemical methods are more efficient at higher temperatures to produce large quantities of hydrogen. In this study, a comparative overview of Generation VI nuclear reactor types for major hydrogen production methods have been researched in the literature and suggestions have been carried out.This research work is addressing that both electric power cycle and hydrogen production based on nuclear technologies need to be developed. Generation IV nuclear reactors can provide hydrogen for a worldwide hydrogen economy. Both thermo-chemical and electrolysis (hybrid) processes in hydrogen production have a promising future, especially when integrated with Generation IV nuclear power plants. Efficient heat transfer is required for both high temperature thermodynamic cycles and the high temperature steam electrolysis. Hence, highly efficient heat exchanger designs are one of the key technologies for that purpose.     

Exploration of amorphous hollow FeOOH@C nanosphere on energy storage for sodium ion batteries

Sodium ion batteries (SIBs) have enjoyed a high profile in recent years and gradually been commercialized to supplement the lithium-ion batteries system. However, the large volume expansion of anode materials within discharging and low electrical conductivity hinder the application of SIBs. In this work, a FeOOH@C composite was synthesized with the use of hydrothermal method and pyrolyzing of polydopamine. The amorphous FeOOH exhibits a hollow spherical structure to offer free space for buffering the volumetric variation. Furthermore, the outer carbon served as a protective shell could maintain the sphere integrity and enhance the electrical conductivity. Hence, benefiting from the achieved synergy of the hollow architecture, amorphous structure and carbon shell, the composite presented a long cycle life (316 mA h g^?1 after 500 cycles at a current density of 100 mA g^?1 and 234.5 mA h g^?1 after 400 cycles at 2 A g^?1) and high-rate performance (180 mA h g^?1 at 5 A g^?1), revealing a potential to be a promising candidate for electrode material of SIBs.     

Potassium ions stabilized hollow Mn-based prussian blue analogue nanocubes as cathode for high performance sodium ions battery

Mn-based Prussian blue analogue is regarded as one of the promising cathodes for sodium ions battery owing to its high theoretical capacity and low cost. However, the unstable structure during charging/discharging process and the poor cycle life hinder its commercial application. In this work, potassium ions stabilized hollow Mn-based Prussian blue analogue is synthesized through a simple sodium citrate assisted method using for cathode of sodium-ions batteries. Although unique hollow structure could suffer volume variation during charging/discharging process, the K⁺ is introduced to further stabilize its structure. The PBAs cathode exhibits a high reversible specific capacity of 128 mA h g^?1 at 50 mA and superior rate performance of 72 mA h g^?1 at a high current density of 3200 mA g^?1, which is attributed to its stable structure and enhanced sodium ions transport kinetics. Ex-situ XRD/Raman tests and electrochemical measurements further prove the synergistic effect of various alkali ions (K⁺/Na⁺) and unique hollow structure. They work together to improve the structural stability and promote sodium ions diffusion rate of Mn-based PBAs.