Effects of Sr2+/Zn2+ co-substitution on crystal structure and properties of nano-β-tricalcium phosphate

The incorporation of therapeutic ions like Sr²⁺, Si⁴⁺, Zn²⁺ and Li⁺ into biomaterials has become a promising approach to promote bone regeneration. However, the effects of Sr²⁺ and Zn²⁺ co-substitution on the crystal structure and properties of β-tricalcium phosphate (β-TCP) have not been elucidated well. In this study, Sr²⁺/Zn²⁺ co-substituted β-tricalcium phosphate (SrZnTCP) nano-powders with different extents of substitution (0–4.8 mol%) were synthesized by poly(ethylene glycol)-assisted co-precipitation and subsequent heat treatment. The as-synthesized SrZnTCP nano-powders were characterized by x-ray diffraction, Fourier transform infrared spectroscopy, elemental analysis, Rietveld refinement and differential scanning calorimetry. The results showed that the conversion of calcium-deficient apatite to β-TCP was achieved after heat-treatment above 800 °C. The a-axis and c-axis lattice parameters gradually decreased with increasing level of Sr²⁺/Zn²⁺ co-substitution in β-TCP lattice. Sr²⁺ and Zn²⁺ preferentially occupied the ninefold coordinated Ca (4) sites and the sixfold coordinated Ca (5) sites, respectively. The co-substitution of Sr²⁺ and Zn²⁺ for Ca²⁺ significantly improved the thermal stability of β-TCP. The release rate of Zn²⁺ from SrZnTCP depended on Ca²⁺ concentration over 63-day immersion in PBS solution while that of Sr²⁺ was not affected by Ca²⁺ concentration. The amount of Sr²⁺ released increased with increasing Sr²⁺ content in SrZnTCP. Collectively, SrZnTCP showed great promise as a Sr²⁺/Zn²⁺-releasing biomaterial for bone repair, although no obvious mineralization was observed on β-TCP and SrZnTCP disc samples during 56 days of immersion in simulated body fluid.     

医用钕铁硼磁环的发展及应用现状

阐述了医用钕铁硼磁环的重要性及发展现状,并从制备钕铁硼磁环的两种不同方式,综述了钕铁硼磁环的成型机理和应用研究现状.介绍了医用钕铁硼磁环表面改性的发展现状和应用前景.     

FeCrAl纤维混合毡的吸声性能

通过分散机将3种不同丝径的FeCrAl纤维均匀分散后,由铺毡机铺制出混合毡,将该单层混合毡制成一定厚度的多孔纤维吸声材料。测定结果表明,不同材质、同一丝径的两种纤维多孔材料,具有相似的吸声性能;利用混合毡所制成的纤维多孔材料具有与其它纤维多孔材料一样的吸声性能变化规律;无论怎么样改变单层材料的内部结构,其吸声性能均差于正梯度结构的吸声性能。     

The preparation of oxygen-deficient ZnO nanorod arrays and their enhanced field emission

Vertical and uniform zinc oxide (ZnO) nanorod arrays (NRAs) with sharp tips were fabricated on Zn substrate by a straightforward hydrothermal method without the assistance of seed layer, template or surfactant. Whereafter, the as-synthesized ZnO NRAs were successfully doped with oxygen vacancies by sodium borohydride (NaBH₄) solution reduction, aiming to generate donor energy levels below the conduction band. More importantly, the doped concentration of oxygen vacancies could be effectively controlled by adjusting the reduction temperature, and we have ultimately achieved the purpose of controllable tailoring the energy band structure of ZnO NRAs. As with design, the oxygen-deficient ZnO NRAs present a lower turn-on field of 0.67 V/μm, higher field enhancement factor of 64601 and better field emission stability. Such excellent FE performance of the as-prepared emitter should originate from the optimization of geometry, the efficient electron transport, as well as the decreased work function.     

Glass coatings on stainless steels for high-temperature oxidation protection: Mechanisms

The oxidation behavior of a martensitic stainless steel with or without glass coating was investigated at 600–800 °C. The glass coating provided effective protection for the stainless steel against high-temperature oxidation. However, it follows different protection mechanisms depending on oxidation temperature. At 800 °C, glass coating acts as a barrier for oxygen diffusion, and oxidation of the glass coated steel follows linear law. At 700 or 600 °C, glass coating induces the formation of a (Cr, Fe)₂O₃/glass composite interlayer, through which the diffusion of Cr³⁺ or Fe³⁺ is dramatically limited. Oxidation follows parabolic law.     

FeAl系合金抗高温氧化性能研究进展

FeAl金属间化合物具有优异的力学性能和抗高温氧化、硫化腐蚀性能,被公认为是高温结构材料、高温气体除尘领域内具有重要应用价值的新材料,因而成了人们研究的重点课题之一。系统地讨论了铁铝金属间化合物的氧化过程、机理以及研究的进展情况。     

Enhanced photocatalytic H2 evolution and anti-photocorrosion of sulfide photocatalyst by improving surface reaction: A review

The photocatalytic evolution of hydrogen is a potential method for acquiring green hydrogen from nature. Unfortunately, this technique has limitations owing to a lack of knowledge of the reaction processes, despite the fact that in recent decades significant scientific adva`nces have been achieved regarding catalyst design and efficiency. Often neglected in favor of heterojunction engineering or band engineering, the chemical environment of catalysts has long been the subject of research. This article offers insight into the photocatalytic H₂ evolution from the surface reaction. It was underlined that reactant adsorption and surface charge extraction have a significant impact on the enhancement of photocatalytic H₂ evolution and anti-photocorrosion properties of the catalyst, which are also strongly connected to the catalyst's chemical environment. Specifically, this study emphasizes the significance of surface/interface condition, type and concentration of electrolytes, reaction solvents, and temperature, etc., during photocatalytic H₂ development, all of which play a crucial role in surface charge extraction of catalyst. In addition, the surface kinetics, adsorption and diffusion of reactants, the selectivity of intermediates, etc., are emphasized for designing highly efficient reaction systems in future applications of photocatalysis. It was shown that more comprehensive methodologies are urgently required for constructing efficient and stable photocatalytic reaction systems by merging catalyst design and reaction environment manipulation. This review may provide fresh ideas for the use of photocatalytic solar energy conversion.     

Research progress in the application of metal organic frameworks and its complex in microbial fuel cells: Present status,opportunities, future directions and prospects

Metal organic frameworks (MOFs) could greatly improve the power generation and degradation performance of microbial fuel cells (MFCs). MOFs and their compound derivatives played key role in cathode, anode and proton exchange membrane of MFCs, which greatly promoted the power generation of MFC and the degradation efficiency of various pollutants. However, MOFs were still possessed some defects, such as complex synthesis process, difficult regulation, instability, etc. Moreover, the application of MFC was limited in low power density, system internal resistance, microbial consumption, etc. Which further limited the degradation of pollutants by MFC. The existing problems and various improvement schemes of MOFs for MFCs were further summarized, which would provide references for promoting the application of MOFs materials in MFC system. It was expected to enhance the application of MOFs materials and promote the performance of MFC.