Use of facile mechanochemical method to functionalize carbon nanofibers with nanostructured polyaniline and their electrochemical capacitance

A facile approach to functionalize carbon nanofibers [CNFs] with nanostructured polyaniline was developed via in situ mechanochemical polymerization of polyaniline in the presence of chemically treated CNFs. The nanostructured polyaniline grafting on the CNF was mainly in a form of branched nanofibers as well as rough nanolayers. The good dispersibility and processability of the hybrid nanocomposite could be attributed to its overall nanostructure which enhanced its accessibility to the electrolyte. The mechanochemical oxidation polymerization was believed to be related to the strong Lewis acid characteristic of FeCl₃ and the Lewis base characteristic of aniline. The growth mechanism of the hierarchical structured nanofibers was also discussed. After functionalization with the nanostructured polyaniline, the hybrid polyaniline/CNF composite showed an enhanced specific capacitance, which might be related to its hierarchical nanostructure and the interaction between the aromatic polyaniline molecules and the CNFs.     

PVC/阻燃抑烟剂体系的力化学改性

研究了高能振磨作用对PVC／硼酸锌(ZB),PVC／三氧化二锑(Sb2O3)-三氧化钼(MoO3)以及PVC／Sb2O3-MoO3-ZB体系阻燃抑烟性能和力学性能的影响。结果表明,高能振磨可使PVC与ZB、Sb2O3或MoO3分子闯产生化学键合,增强了PVC基体与阻燃抑烟荆ZB,Sb2O3-MoO3,Sb2O3-MoO3-ZB之同的界面相互作用,促进了阻燃抑烟荆(FRs)在PVC中的分散,使PVC／FRs体系的烟密度(Dm)值降低,极限氧指数(LOI)值以及抗冲击强度,拉伸强度,断裂伸长率得到明显提高。     

Zirconium-boron reactive composite powders prepared by arrested reactive milling

ABSTRACT

Zirconium-boron composite powders with the stoichiometric bulk composition corresponding to ZrB₂ were prepared using high-energy milling in a shaker mill starting with elemental boron and zirconium. Milling times up to 3 hours were explored. The characterization of the prepared powders included measuring their particle size distribution, crystal structure, and assessment of particle structure and morphology. Reactions in the prepared powders were characterized using thermal analysis as well as custom ignition and combustion experiments. Composite powders consist of a Zr matrix with B inclusions mostly 100 nm or less in size. The homogeneity of mixing between boron and zirconium improves when the milling time increases from 1 to 2 hours; it is not affected by longer milling times. Boron and zirconium start reacting during milling; the degree of this reaction becomes appreciable when the milling time reaches 2 hours. In air, ignition of both pure zirconium and the prepared powders occurs in the same temperature range of ca. 400–700°C for the heating rates varied from 2000 to 20,000 °C/s. In fuel-rich conditions, ignition of the prepared powders is affected by the reaction between B and Zr, which occurs less readily for powders milled for 2 hours or longer. In air, particles of the prepared composite powders burn faster than either pure boron or zirconium. Flame temperatures for individual composite particles burning in air are reasonably close to those predicted as adiabatic flame temperatures for this composite-air system at stoichiometric and fuel-rich conditions. In combustion products of an air-acetylene flame, the burn rates of the prepared composites are lower than that of zirconium and are comparable to that of boron. Powders prepared by 1-hour milling burn faster than powders prepared using longer milling times.     

含锂矿物机械化学强化提锂工艺

采用机械化学活化方法,在机械活化过程中用K2SO4为活化添加剂,强化锂云母中惰性Li?O配位结构活化转型,通过温和稀酸浸出高效分离锂,考察了活化过程添加剂用量、球磨时间和球料比及浸出条件如酸浓度、液固比、搅拌速度、温度和时间等对锂回收率的影响,确定了最佳工艺条件,讨论了反应过程机理。结果表明,机械化学活化强化破坏云母片层结构中的Si?O?K结构,降低了Si?O配位结构对Li?O配位结构的牵制力,导致Li?O键强减弱,反应活性增加。在最优条件下(精矿与K2SO4质量比5:1,球磨机转速500 r/min,球料质量比20:1,球磨时间3 h,硫酸浓度15vol%、液固比4 L/g、反应温度80℃、浸出搅拌速率200 r/min),锂浸出率可达99.1%。     

高岭土干粉磨过程的机械力化学变化

本文较全面系统地介绍了高岭土干粉磨过程中发生的机械力化学变化。采用粒度分析、SEM、XRD、IR、DTA和TG、反气相色谱(IGC)和BET多层吸附等测试方法对干粉磨高岭土进行分析测定。结合高岭石晶体结构特点,从机械力化学角度阐述了在高岭土干粉磨过程中发生的晶格无序化,脱羟基反应、表面性质改变以及团聚作用的机理。     

机械化学法合成羟基磷灰石过程中的"爆炸式"反应

应用机械化学原理,研究了在振动磨样机中由磷酸二氢钙(MCPM)和氢氧化钙合成羟基磷灰石(HAP)过程的动力学机制,并建立了相应的动力学模型.结果表明,合成过程为生成中间产物二水磷酸氢钙(DCPD)的两步式反应,其中第二步反应在第一步反应结束后才开始,并且在很短的时间内(＜30s)迅速完成,即发生了"爆炸式"反应,反应过程可用类Avrami方程进行表征.探讨了发生"爆炸式"反应的可能机理.     

STIDU ON MACHANOCHEMIAL EFFECT OF POWDERY QUARTZ IN DRY AND WET GRINDING

Powdery quartz with average particle size of10. 4 μm which is a natural weathered quartz were ground inplanetary ball mill. Variations of particle size distribution,specific surface area, crystal structure,facial amorphous andthermal character in dry grinding and wet grindding wereexamined against grinding time. The results displayed thatthe fine grinding causes the structural disorder,facial amor-phism and the facial activity enhancing accompained by par-ticle size reduction as grinding proceeds,and the wet grind-ing lowered notably “Grinding Limit”of the powdery quartzwith this planetary ball mill.     

Mechanochemistry of Solids: Past, Present, and Prospects

A historical retrospective is presented beginning from the early observations by alchemists to the establishment of mechanochemistry as a branch of science. The changes in structure and chemical properties of solids under three-axes loading and by combined action of pressure and shift are demonstrated. The peculiarities of the phenomena taking place upon stressing of particle assemblies in various types of energy-intensive grinding mills are discussed. Based on the contemporary concepts, the mechanism of stress field formation and relaxation is analyzed. Among decisive factors influencing the mechanochemical synthesis, the formation and renewal of contact area between reacting compounds, the explosive evolution of heat, and the feedback phenomenon are emphasized. The perspective directions of practical application in the area known as mechanical alloying, as well as in preparation of functional ceramics and catalysts, and in pharmacy are discussed. The main directions for improving research, construction of milling devices, training of specialists, and exchange of knowledge are proposed.     

含能材料机械化学研究进展

概述了机械化学的起源、特点及其在含能材料研究领域中的应用与发展状况。含能材料机械化学可分为实验研究与理论研究。本文重点汇集和评述了国内外在含能材料机械化学理论研究领域的进展,分析了含能材料的爆炸始发机制、结构与性能的关系以及感度性能理论预测等方面的研究成果,展望了机械化学在含能材料领域的发展前景。附参考文献70篇。     

非金属矿物粉体机械力化学研究进展

在球磨过程中,机械力化学使颗粒和晶粒细化产生裂纹,比表面积增大,晶格缺陷增多,晶格发生畸变和结晶程度降低,甚至诱发低温化学反应,可以制备出高活性矿物粉体和性能优异的材料。本文介绍了机械力化学在非金属矿物粉体研究中的最新进展,并对其未来发展进行了展望。