Mechanical,expansion and rheological properties of circulating fluidized bed fly ash based ecological cement:A critical review

Circulating fluidized bed fly ash(CFBFA)is a solid waste product from circulating fluidized bed(CFB)boilers in power plants,and the storage of CFBFA is increasingly become an environmental problem.Previous scholars have made contributions to improve the resource utilization of CFBFA.Especially,ecological cement is prepared by CFBFA,which is more conducive to its large-scale utilization.In recent years,a lot of effort has been paid to improve the properties of ecological cement containing CFBFA.In this work,the physicochemical properties of CFBFA are introduced,and recent research progress on the mechanical,expansion,and rheological properties of CFBFA based ecological cement(CEC)is extensively reviewed.The problem of over-expansion of f-CaO is summarized,which limits the scale application of CFBFA in ecological cement.Hence,the challenge for f-CaO in CFBFA to compensate for cement volume shrinkage is proposed,which is beneficial to the utilization of CFBFA in ecological cement,and the reduction of CO_(2) emissions from the cement industry.In addition,the environmental performance,durability,and economy of CEC should be valued in future research,especially the environmental performance,because the CFBFA contains heavy metals,such as Cr,As,which may pollute groundwater.

Polymer electrolytes for Li-S batteries:Polymeric fundamentals and performance optimization

Lithium-sulfur(Li-S) batteries have been considered as one of the most promising candidates to traditional lithium ion batteries due to its low cost,high theoretical specific capacity(1675 mAh g^(-1)) and energy density(2600 Wh kg^(-1)) of sulfur.Compared with traditional liquid electrolytes,polymer electrolytes(PEs) are ever-increasingly preferred due to their higher safety,superior compatibility,long cycling stability and so on.Despite some progresses on PEs,however,there remain lots of hurdles to be addressed prior to commercial applications.This review begins with native advantages for PEs to replace LEs,and then proposes the ideal requirements for PEs.Furthermore,a brief development history of typical PEs for Li-S batteries is presented to systematically summarize the recent achievements in Li-S batteries with PEs.Noted that the structure-performance relationships of polymer matrixes for PEs are highlighted.Finally,the challenges and opportunities on the future development of PEs are presented.We hold the view that composite polymer electrolytes in virtue of the high ionic conductivity and the compatible interfacial property will be promising solution for high performance Li-S batteries.

Interfacial stress characterization of GaN epitaxial layer with sapphire substrate by confocal Raman spectroscopy

As an important wide-bandgap semiconductor,gallium nitride(GaN)has attracted considerable attention.This paper describes the use of confocal Raman spectroscopy to characterize undoped GaN,n-type GaN,and p-type GaN through depth profiling using 405-,532-,and 638-nm wavelength lasers.The Raman signal intensity of the sapphire substrate at different focal depths is studied to analyze the depth resolution.Based on the shift of the E2 H mode of the GaN epitaxial layer,the interfacial stress for different types of GaN is characterized and calculated.The results show that the maximum interfacial stress appears approximately at the junction of the GaN and the sapphire substrate.Local interfacial stress analysis between the GaN epitaxial layer and the substrate will be very helpful in furthering the applications of GaN devices.

Optimization on transport of charge carriers in cathode of sulfide electrolyte-based solid-state lithium-sulfur batteries

Lithium-sulfur(Li-S)batteries are considered as promising candidates for novel energy storage technology that achieves energy density of 500 Wh·kg^(−1).However,poor cycle stability resulting from notorious shuttle effect and the safety concerns deriving from flammability of ether-based electrolyte hinder the practical application of Li-S batteries.Because of low solubility to polysulfide,high ionic conductivity,and safety property,sulfide-based electrolytes can fundamentally address above issues.It is widely known that the effective transports of both electrons and ions are basic requirement for redox reaction of active materials in cathode.Thereby,construction of fast and stable ionic and electronic transport paths in cathode is especially pivotal for cycle stability of solid-state Li-S batteries(SSLSBs).In this review,we provide research progresses on facilitating transport of charge carriers in composite cathode of SSLSBs.From perspective of materials,intrinsically conductivity of electrolyte and carbon shows dramatic effect on migration of charge carriers in cathode of SSLSBs,thereby the conductive additives are summarized in the manuscript.Additionally,the charge transport in cathode of SSLSBs fully depends on the physical contact between active materials and conductive additives,therefore we summarized the strategies optimizing interfacial contact and reducing interfacial resistance.Finally,potential future research directions and prospects for SSLSBs with improved energy density and cycle performance are also proposed.

Depositional Environments of the Upper Permian Quartzose Sandstone(Shandong Province, North China): Insight from Trace Element Geochemistry

The depositional environment of the Upper Permian quartzose sandstone （Kuishan sandstone in Shihezi Formation of Upper Permian） in the North China epicontinental basin is controversial. In order to test the previous hypotheses, we analyzed sedimentological characteristics of the Kuishan sandstones in outcrops and boreholes, and carried out trace element geochemical analysis by electron probe microanalyzer. Three lithofacies were recognized, including normal-graded conglomerate （Cng）, trough and planar cross-bedded coarse sandstone （CStpc）, and planar cross-bedded medium sandstone （MSpc）. Normal-graded conglomerate （Cng） formed in the meandering river or deltaic distributary channels. Trough and planar cross-bedded coarse sandstone （CStpc） formed in meandering river or distributary channels of near-source deltaic plain. Planar cross-bedded medium sandstone （MSpc） formed in the siliciclastic beach with highto moderate-energy conditions. By the petrology and trace elements analysis, three relatively large-scale transgressions were revealed. Each transgression was reflected by the lower content of Ba and ratios of Fe/Mn, and the high content of B and ratios of B/Ga. The ratios of Ni/Co of all samples are all lower than 2, suggesting oxygen-enriched shallower water en- vironment during deposition of the Kuishan sandstones.