三元脂肪酸/膨胀石墨复合相变材料的制备、包覆定形及热性能

采用癸酸、 月桂酸和棕榈酸的三元共晶混合物作为相变材料, 以膨胀石墨为基体, 通过膨胀石墨多孔结构的毛细吸附和复合涂饰剂的包覆定形, 将多元相变材料固定在膨胀石墨的孔道结构中, 制备出结构稳定、 密封性能优异、 热稳定性好和高导热的新型三元脂肪酸/膨胀石墨复合定形相变材料. 膨胀石墨具有膨胀疏松的多孔结构和良好的吸附性能; 其熔融潜热为95.6 J/g, 结晶焓为82.8 J/g, 说明其具有很好的相变蓄热特性和热循环稳定性; 材料的导热性能可增加至0.738 W/(m·K), 与脂肪酸相比得到大幅度提高.     

对钠与浓硫酸铜溶液反应发生着火原因的探究

正钠遇到浓的硫酸铜溶液时会迅速发生着火(并伴有爆炸),着火的原因主要有以下3个方面:(1)着火是由于硫酸铜溶液呈酸性引起的;(2)着火是由于浓的硫酸铜溶液黏度比较大引起的;(3)着火是由于生成的氢氧化铜沉淀引起的。那么究竟是什么呢?笔者进行了实验探究。1钠的着火是否是由酸性引起的硫酸铜溶液水解呈酸性,经测试常温下饱和硫酸铜溶液的pH约为3。为了研究钠的着火是否是由酸性引起的,我们选取了不产生沉淀且酸性更强的溶液进行实验。【实验1】向2个烧杯(规格125mL)中,分     

Direct electrochemistry and electrocatalysis of cytochrome c immobilized on gold nanoparticles-chitosan-carbon nanotubes-modified electrode

A robust and effective nanohybrid film based on gold nanoparticles (GNPs)/chitosan (Chit)/multi-walled carbon nanotubes (MWNTs) was prepared by a layer-by-layer self-assembly technique. Cytochrome c (Cyt c) was successfully immobilized on the nanohybrid film modified glassy carbon (GC) electrode by cyclic voltammetry. The direct electron transfer between Cyt c and the modified electrode was investigated in detail. Cyt c shows a couple of quasi-reversible and well-defined cyclic voltammetry peaks with a formal potential (E^0′) of −0.16 V (versus Ag/AgCl) in pH 7.0 phosphate buffer solution (PBS). The Cyt c/GNPs/Chit/MWNTs modified GC electrode gives an improved electrocatalytic activity towards the reduction of hydrogen peroxide (H₂O₂). The sensitivity is 92.21 μA mM⁻¹ cm⁻² and the calculated apparent Michaelis-Menten constant () is 0.791 mM, indicating a high-catalytic activity of Cyt c. The catalysis currents increase linearly to the H₂O₂ concentration in a wide range of 1.5 × 10⁻⁶ to 5.1 × 10⁻⁴ M with a correlation coefficient 0.999. The detection limit is 9.0 × 10⁻⁷ M (at the ratio of signal to noise, S/N = 3). Moreover, the modified electrode displays rapid response (5 s) to H₂O₂, and possesses good stability and reproducibility.     

Al-LiBH4复合材料的制备与产氢性能

采用机械球磨法制备了Al-LiBH4系列铝基复合材料.该材料的产氢性能和X射线衍射(XRD)分析结果表明,反应温度升高有利于金属铝和LiBH4之间的相互促进作用,提高材料的氢气产量及产率.常温下该复合材料与水反应迅速,氢气产量高.球料比30∶1、球磨5 h制备的Al-25%LiBH4复合材料30 min内每克材料可以产生720 mL氢气;当反应温度升高至90℃时,在30 min内的氢气产量高达2026 mL/g,氢气产率达95%;而在90℃反应时Al-30%LiBH4材料的氢气产量为2211 mL/g,氢气产率在96%以上.