Abstracts:An ever-increasing energy demand has stimulated intense research into electrochemical technologies for both energy storage and conversion such as unitized regenerative fuel cells (URFCs). Due to its high efficiency, low cost, and low environmental impact, the URFC, which combines a polymer electrolyte membrane fuel cell (PEMFC) with a polymer electrolyte water electrolyzer (PEWE), has been regarded as an important energy technology that can offer new opportunities to not only further reduce investment costs but also to open doors to the mass production of domestic applications. Despite this, URFCs still have to be further improved and optimized to reach a level of maturity of both fuel cells and electrolyzers in terms of energy efficiency and long-term performance. Currently, the major challenge of URFC technology has been the insufficient performance of the bifunctional electrocatalyst. Based on the most recent research trends and progresses of bifunctional oxygen catalyst materials, this review will provide a systematic introduction and a comprehensive assessment of various bifunctional oxygen catalysts; their science and technology, including material selection, synthesis, and characterization, as well as their applications in URFCs. This review aims to correlate the physicochemical characteristics of URFCs with the catalytic activity/stability of these materials.

Abstracts:The crystallization of fresnoite from glasses enables to produce a wide variety of materials including piezoelectric glass-ceramics due to the aligned growth of these crystals in the amorphous matrix. The crystal structure of fresnoite leads to interesting pyroelectric, piezoelectric and non-linear optical properties and is one of the few known non-ferroelectrics which can be easily produced as polycrystalline but polar materials. This review provides a summary of the properties of fresnoite crystals as well glass-ceramics containing fresnoite crystals. A special focus is the preparation of oriented and polar glass-ceramics and the resulting properties. The literature concerning the complete process from the amorphous glass to crystal nucleation and the subsequent growth is reviewed.

Abstracts:The development of novel high-temperature structural and multifunctional thermal protection materials for harsh environment applications, such as high-temperature oxidation, severe thermal shock, ablation by combustion gas flow etc., is one of the urgent needs of the modern aerospace industry. Ceramic matrix composites such as Cf/(C, SiC, Si3N4), SiCf/ZrB2, SiCp/(Si3N4, HfB2) have received much attention in recent years. Coincidently, metastable silicoboron carbonitride (Si-B-C-N) ceramics and corresponding matrix composites stand out from all recent materials offering great potential at high temperatures due to their high microstructural stability and excellent high-temperature properties including resistance to oxidation, thermal shock and ablation.