A micron-sized honeycomb-like carbon material (MHC) is prepared in a facile way using nano-CaCO3 as a hard template. A novel electrode for lithium–oxygen batteries is fabricated and displays a superior discharge capacity as high as 5862 mA h g−1. The higher electrode space utilization is attributed to its hierarchical pore structure, with intrinsic mesopores in the MHC particles for Li2O2 depositions and macropores among them for oxygen transport.
Plastering mortar plays a protective role for building surface.Its mechanical properties are influenced by different factors.To improve the mechanical properties and solve the problems of mortar cracking and falling, this study proposed a method of studying the change in mechanical properties in accordance with the mesh number of quartz sand.The optimal mesh number of quartz sand was selected by measuring the water-cement ratio and consistency of fresh mortar, the compressive and flexural strength, and the water absorption rate of specimen.On the basis of the mesh number, an orthogonal test was designed using silica fume, calcium sulphoaluminate expansion agent, and polycarboxylate superplasticizer.The performance changes caused by the mesh number of quartz sand and the dosage of additives were analyzed, and plastering mortar with good mechanical properties was determined.Results demonstrate that the key to modification is to strengthen hydration reaction and compactness because cement mortar is porous and brittle.The mechanical properties of plastering mortar decrease with the increase in quartz sand mesh, and the effect is the best when 60-80 mesh quartz sand is used.When the additives are used for modification, the best effect can be obtained when mixing 3% silica fume, 5% calcium sulphoaluminate expansion agent, and 0.5% polycarboxylate superplasticizer.In this case, the compressive strength of the plastering mortar increases by about 22.8% and the water absorption decreases by about 2.4% compared with that before modification.The conclusions obtained in this study can provide an important reference for the modified application of plastering mortar.
By using records of frozen soil collected from 8 surface weather observation sites in Datong from 1961 to 2008,the date of Datong ground freezing and thawing,the number of freezing days,and the spatial and temporal distribution of maximum depth of frozen soil are analyzed.The results showed that in recent 40 years the freezing date has a delaying trend while the thawing date is ahead of the recorded.The number of ground freezing days has a corresponding decreasing trend and maximum depth of frozen soil decreases from northwest to southeast in successive years.The city's average maximum depth change of frozen soil over the years has the overall decreasing trend but after 2000,compared with 1960s to 1980s there is an increasing trend.
Abstract Bioabsorbable poly(4‐hydroxybutyrate) (P4HB) electrospun membrane has been widely used in various biomedical applications due to its biocompatibility and unique mechanical properties. When commercialization is envisaged, a sterilization procedure aiming to prevent bacterial contamination of biomedical devices is indispensable. Herein, P4HB membranes were sterilized by using different sterilization techniques. It's observed that ethylene oxide (EO), ultraviolet radiation (UV), and electron beam (E‐beam) irradiation do not influence the morphology of fiber membranes. Analysis of the data revealed that E‐beam irradiation sterilization can induce chain scission of P4HB. The EO sterilization process can increase the melting point of P4HB electrospun membranes. None of the sterilization methods showed a significant effect on the hemocompatibility of the P4HB membranes. Furthermore, the cytocompatibility experiment indicated that none of the P4HB membranes had any toxic effects on L929 cells. Taken together, selecting a suitable sterilization method that effectively sterilizes and does less damage during the sterilization process is critical to P4HB membranes for biomedical application.
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