Fabrication of carbon fibers with nanoporous morphologies from electrospun polyacrylonitrile/poly(L‐lactide) blends

Porous carbon nanofibers were prepared through electrospinning a blend solution of polyacrylonitrile and poly(L ‐lactide), followed by carbonization at different temperatures and in different atmospheres. Structural features of these porous carbon nanofibers were characterized using scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, X‐ray powder diffraction, and Raman spectroscopy. Surface area and pore structure were evaluated using the nitrogen adsorption technique. It was found that carbon fibers prepared by this scalable and relatively economical method exhibited a porous surface morphology with high specific surface area and large pore volume. The fiber diameter, surface area, pore volume, bulky crystalline structure, and surface crystalline structure of these carbon nanofibers showed a strong dependence on the polymer precursor composition and carbonization condition. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 493–503, 2009     

Kinetics of radiation-induced carbonization of poly(vinylidene fluoride) film surface

The kinetics of radiation-induced carbonization of PVDF surfaces aiming at carbyne (one-dimensional carbon allotrope) synthesis have been studied. A sample of poly(vinylidene fluoride) film was exposed to Mg Kα radiation (?ω = 1253.6 eV) in an ESCALAB Mk II spectrometer for 14 h with the aim of surface carbonization. Some 221 spectra of C 1s electrons were measured and expanded using 7 Gaussian curves to reveal and identify species being created on the film surface during its carbonization. A decrease in the content of CF₂ groups, the emergence of CF species in two different states, and growth of a number of fluorine-free carbon atoms have been detected. Simultaneous variations of CH/CH₂, CF and CF₂ peaks suggest elimination of H and F atoms as HF. A proposed model shows three probabilistic factors affecting the rate of degradation, one of which remains uncertain.     

稀土萃取分离废水制备高纯碳酸氢镁溶液过程中铁杂质的行为与影响

以稀土冶炼分离过程中产生的氯化镁废水和白云石为原料制备氢氧化镁,然后采用碳化法制备高纯碳酸氢镁溶液,研究了铁杂质离子的行为与影响。结果表明:碳酸氢镁溶液中的杂质铁是由于二价固态铁发生碳化反应而引入并以重碳酸亚铁(Fe(HCO3)2)形式存在,即碳化反应过程是除铁的核心工序,Mg(HCO3)2溶液经过除铁后沉淀稀土离子可以明显降低沉淀产物中铁杂质含量。本文为氯化镁废水-白云石碳化法制备碳酸氢镁溶液过程中铁杂质离子的去除提供切实可行的理论指导。     

Simultaneous determination of Fe, P, Ca, Mg, Zn, and Cu in whole blood by two-jet plasma atomic emission spectrometry

Availability of many biological samples in ample quantity for biomedical investigations sometimes is very restricted. Therefore, there is the need for the simple techniques allowing the analysis of small amount samples. In the present work the two-jet plasma atomic emission spectrometry techniques for the determination of Fe, P, Ca, Mg, Zn, and Cu in whole blood are proposed. The first technique is developed for direct analysis of freeze-dried blood. The sample preparation consisted in a dilution of blood powder (particle size 20 μm or less) with a spectroscopic buffer (graphite powder containing 15 wt.% NaCl). For the analysis of liquid whole blood, previous carbonization (not ashing) of blood evaporated on graphite powder was applied. Calibration samples based on graphite powder containing 15 wt.% NaCl were used. The validation of the techniques was confirmed by the use of different sample preparation procedures (wet acid digestion and dry carbonization), the analysis of IAEA A-13 reference material (freeze-dried bovine whole blood), and the comparison of the results obtained by the proposed technique with the results of the stripping voltammetry technique. Just 20-50 μL of whole blood is quite enough for all determinations. The proposed techniques were successfully applied for the simultaneous determination of Fe, P, Ca, Mg, Zn, and Cu in whole blood of living experimental rats and mice and human blood.     

采用碳化-沉淀法制备纤维状纳米Mg(OH)_2的研究

本文以轻烧白云石粉料为原料,用碳化法制备出碱式碳酸镁,酸化后以氨水为沉淀剂,用化学沉淀法制得Mg(OH)2,用乙二胺对制得的Mg(OH)2进行后处理,制得纤维状纳米Mg(OH)2。用SEM、XRD和TG-DTA对制得的Mg(OH)2进行表征。XRD结果表明重结晶温度180℃以上可以得到具有完整晶体结构的Mg(OH)2。SEM结果显示Mg(OH)2颗粒的尺寸随着乙二胺加入量的增大而增大。当Mg(OH)2的重结晶时间超过21 h后,可以得到直径20~30 nm,长度400~700 nm的纤维状Mg(OH)2。TG-DTA表明Mg(OH)2在318~416℃分解为MgO。     

碳纳米结构构建:十二烷基二甲基苄基氯化铵@氯化钠体系

碳纳米材料用途十分广泛,但其形貌的控制和制备方法的完善仍然是个研究热点和亟需攻克的难点。在此,基于阳离子表面活性剂十二烷基二甲基苄基氯化铵(DDBAC)@氯化钠(NaCl)体系成功制备了碳纳米结构（碳纳米管、纳米碳球、棒状和层状碳纳米结构）。以DDBAC为碳源。碳化过程中使用NaCl晶体分隔DDBAC的有序聚集体。结果表明,通过控制DDBAC浓度制备出不同形貌的碳纳米结构,在1倍临界胶束浓度（CMC）~5CMC下制备了球形、棒形碳纳米结构和碳纳米管,在10CMC下制备了矩形层状碳纳米结构。利用TEM、PL、Raman等手段对制备的碳纳米结构进行表征。通过TEM分析DDBAC @ NaCl体系结构的转变,建立了胶束结构的演变过程。表面活性剂浓度的增加最终使得碳纳米形态从球形碳纳米结构到层状碳纳米结构的变化。本实验结论表明了表面活性剂@盐体系是一种潜在的制备碳纳米结构的方法。     

木基炭微纳功能骨架

木基炭骨架能精准遗传木材经过长期进化所形成的层次分明、构造有序的天然多级结构,这种炭骨架由于特殊的层级结构特征,在生物模板、传感器、吸油材料和纳米材料制备基材等方面有巨大应用潜力。同时还可作为一类新型的骨架进行微纳功能修饰和结构二次调控,在海水淡化、污水清理、能源存储与转化等诸多领域具有极为广阔的应用空间。本文首先介绍了木材的基本结构,综述了木材热解过程中结构的变化,介绍了近年来木材炭化骨架作为新型功能材料的前沿应用,对应用过程中亟待解决的问题进行了剖析,并对木基炭骨架材料未来的研究方向进行了展望。本综述旨在重新对木材层级结构进行功能化开发,从而推动木材在功能材料领域的蓬勃发展。     

Functionalized ZrP nanosheet with free‐radical quenching capability and its synergism in intumescent flame‐retardant polypropylene

The combination of catalyzing carbonization and free‐radical quenching mechanism is proposed to be a promising strategy for the preparation of high‐efficiency flame‐retardant polypropylene (PP). Herein, a novel functionalized zirconium phosphate (RQZrP) nanosheet with free‐radical quenching capability was fabricated by decorating macromolecular N‐alkoxy hindered amine (MNOR) onto the surface of ZrP. It was combined with an intumescent flame retardant (IFR) to flame‐retard PP. The results showed that there was a good synergism between RQZrP and IFR, which effectively improved the fire safety of PP. When the content of RQZrP was 2 wt% and IFR was 23 wt%, the limiting oxygen index (LOI) of PP increased from 19.0% to 33.0%, and it achieved a UL‐94 V‐0 rating. Meanwhile, the peak heat release rate (PHRR), total heat release (THR), carbon monoxide production (COP), and carbon dioxide production (CO₂P) were significantly decreased. It revealed that nitroxyl radicals generated by RQZrP could capture alkyl radicals and peroxy radicals that produced during the degradation and combustion of PP. Meanwhile, RQZrP acted as a solid acid that catalyzed PP chains rapidly cross‐linking to form char on its surface, and it also played as a supporting skeleton to enhance the strength and compactness of the char layer, thus effectively preventing the transmission of heat, oxygen, and combustible gases.     

NUMERICAL SIMULATION FOR A PROCESS ANALYSIS OF A COKE OVEN

A computational fluid dynamic model is established for a coking process analysis of a coke oven using PHOENICS CFD package. The model simultaneously calculates the transient composition, temperatures of the gas and the solid phases, velocity of the gas phase and porosity and density of the semi-coke phase. Numerical simulation is illustrated in predicting the evolution of volatile gases, gas flow paths, profiles of density, porosity of the coke oven charge, profiles of temperatures of the coke oven gas and the semi-coke bed. On the basis of above modeling, the flow of coke oven gas （COG） blown from the bottom of the coke oven into the porous semi-coke bed is simulated to reveal whether or not and when the blown COG can uniformly flow through the porous semi-coke bed for the purpose of desulfurizing the semi-coke by recycling the COG. The simulation results show that the blown COG can uniformly flow through the semi-coke bed only after the temDerature at the center of the semi-coke bed has risen to above 900℃.