Nucleation and crystal growth of PEEK on carbon fiber

The necleation and crystal growth of poly(ether ether ketone) (PEEK) on carbon fiber during isothermal crystallization were studied using optical microscopy. It was shown that the nucleation rate on the fiber is affected by the crystallization and melting temperatures. Transcrystallinity of PEEK was found to appear in the range 280–315°C after PEEK was melted at rather high temperature. Its linear growth rates at various temperatures were found to be similar to those of the spherulite in the bulk. Also, its thickness depends on the crystallization and melting temperatures. Variation of the molecular weight of PEEK within a small range has no obvious influence on its nucleation rate on the fiber, but affects the transcrystalline growth rate. © 1993 John Wiley & Sons, Inc.     

Efficiently activated carbon fiber derived from grafted novoloid fiber

Graft copolymerization of methyl methacrylate onto novoloid fiber was carried out by the electron beam mutual irradiation method. The characteristics of the grafted fiber were almost the same as those of the original novoloid fiber. The grafted fiber was carbonized and activated to yield an efficiently activated carbon fiber. The yield and the specific surface area of the activated carbon fiber, derived from the grafted novoloid fiber, were much greater than those derived from the original novoloid fiber. This is because grafted poly(methyl methacrylate) decomposes into monomer and gaseous products, forming pores on the surface and inside of the novoloid fiber on heating. © 1993 John Wiley & Sons, Inc.     

Circulating flow reactor for recycling of carbon fiber from carbon fiber reinforced epoxy composite

For the purpose of development of a chemical recycling process for carbon fiber from carbon fiber reinforced epoxy composite, a new chemical recycling system using nitric acid aqueous solution has been proposed. The recycling system is composed of hexahedral circulating flow reactor made of quartz, Teflon supporter, acid resistance pump and auxiliaries. Epoxy matrix in the composite was effectively decomposed by nitric acid aqueous solution in the circulating flow reactor and carbon fiber could be recycled without any tangle or disturbance. Optimum conditions for the recycling process have been experimentally established. Tensile strength loss of recycled carbon fiber and composition of liquid phase decomposition products were analyzed.     

A new carbon fiber from lignin

A new carbon fiber was prepared from the lignin (steam-exploded lignin), which was isolated from steam-exploded birch wood (Betula platyphylla). The lignin was modified to melt thermally on hydrogenolysis. The chloroform soluble and carbon disulfide insoluble fraction (HL) of the reaction products was heated at 300–350°C for 30 min, giving a molten viscous material (HHL). The HHL had a softening point of 110°C and melted at over 145°C to form viscous liquid. When HHL was subjected to a spinning test, according to a conventional fusion spinning method at a speed over 100 m/min, a fine filament could be continuously formed through a pinhole (diameter: 0.3 mm). After the filaments were heated in air at 1–2°C/min up to 210°C, by which time the filament was converted to have an infusible property, the filaments were carbonized by heating from a room temperature to 1000°C at a heating rate of 5°C/min in a stream of nitrogen. The typical properties of the lignin based carbon fiber were as follows: Fiber diameter = 7.6 ± 2.7μ Elongation = 1.63 ± 0.29% Tensile strength = 660 ± 230 MPa; Modulus of elasticity = 40.7 ± 6.3 GPa. The chemical structure of the precursor was remarkably changed from that of the original lignin, indicating the elimination of aliphatic functional groups implied originally in the starting material.     

Effect of electrochemical anodization and growth time on continuous growth of carbon nanotubes on carbon fiber surface

Carbon nanotubes (CNTs)/carbon fiber (CF) reinforcements were prepared by chemical vapor deposition after electrochemical anodization and catalyst impregnation. The results showed that after the electrochemical anodization, the CFs were oxidatively etched and the surface roughness increased, which is helpful to form a uniform catalyst coating on the surface of CF. Under the current of 0.4 A and 0.6 A, CNTs can grow evenly on the surface of CF. Within a certain range, with the increase of growth time, the density and length of CNTs are improved. The CNTs/CF reinforcement prepared at the current intensity of 0.4 A and the growth time of 8 min has the best comprehensive performances compared with other as-fabricated samples. The tensile strength of the sample can reach a high value of 4.56 GPa, and the wettability of resin has an effective improvement.     

Preparation of activated carbon dots from sugarcane bagasse for naphthalene removal from aqueous solutions

ABSTRACT

The synthesis of cheap and environmental friendly adsorbent from residual sugarcane bagasse was done for the removal of naphthalene from aqueous solution. The activated carbon dot was obtained by KOH chemical activation of carbon dots. The characteristics of carbon dots and activated carbon dots were determined using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and thermogravimetric analysis. A series of experiments were conducted in a batch system to assess the effect of the system variables, i.e., initial pH, initial naphthalene concentration, adsorbent dosage, and contact time. The kinetic data showed better fit to the pseudo-second-order model. The equilibrium data were better fitted to Freundlich and Temkin isotherms.     

Structural properties of carbon materials from the electrochemical reduction of fluorinated naphthalene pitch

Synthesis of carbon materials from fluorinated naphthalene pitch has been carried out by means of electrochemical reduction. Structural and morphological properties of synthesized carbons were investigated using X-ray photoelectron spectrum (XPS), Raman scattering spectrum, X-ray diffraction measurements and scanning and transmission electron microscopy (SEM and TEM). Furthermore, a change in the structure of synthesized carbons with an electron beam irradiation was examined. The synthesized carbon has a disordered structure composed of fragments of the sp² hexagonal network, and also has lots of micro-voids. A carbyne-like structure was found only a little with the reduction of fluorinated naphthalene pitch by Raman spectra. A lot of ribbon-like graphite nanocrystal was formed by irradiation of an electron beam at a high temperature to the defluorinated carbon. Bending of a long ribbon-like crystal of graphite was often observed. Formation mechanism of graphite nanocrystals was discussed.     

Catalyst optimization and reduction condition of continuous growth of carbon nanotubes on carbon fiber surface

Carbon nanotubes (CNTs)/carbon fiber (CF) reinforcements were synthesized under different catalyst compositions and reduction conditions. The effects of the catalyst, reduction temperature and reduction time on the surface morphology, graphitization, and single filament tensile strength of the prepared CNTs/CF samples were investigated. When nickel was used as the catalyst and copper as the catalyst promoter, with the increase of copper concentration, the catalytic activity increased. Thus, the carbon source was consumed more completely, improving the abundance of CNTs with good graphitization. And the effect of repairing CF defects was more obvious, hence the single filament tensile strength accordingly increased. Besides, the increase of catalyst reduction temperature and reduction time intensified the etching of CF by catalyst, and decreased the single filament tensile strength of CF. With the deposition of CNTs, the tensile strength of CF was enhanced in varying degrees. When the concentration of cooper was 0.01 mol/L with the reduction time of 10 min and reduction temperature of 450 °C, CNTs/CF had the highest tensile strength, which can reach up to 4.51 GPa. We determined that bimetallic catalysts could adjust the catalytic activity of nickel. The change of reduction time and temperature would affect the quality of CNTs, which was helpful to obtain high quality CNTs on CF surface and improve the mechanical properties of CNTs/CF and its composites.     

The effect of halogens on the rate of absorption of carbon dioxide

The presence of small amounts of chlorine or bromine greatly accelerates the rate of absorption of CO₂ in aqueous buffer solutions. This is because the halogens are hydrolysed to OCl^? or OBr^?, which are powerful catalysts for the reaction between CO₂ and water. An approximate mathematical analysis is given, and agrees reasonably with the observations.     

浅析聚丙烯腈基碳纤维焦油形成的原因

根据聚丙烯腈基碳纤维生产工艺路线,从原丝、预氧化、碳化工艺及结构上分析了聚丙烯腈基碳纤维焦油形成的原因。其主要原因为碳化前纤维缺陷结构的遗传、碳化中分子键的热断裂和分子链的无规热裂解。     

Effect of carbon nanotubes growth topology on the mechanical behavior of hybrid carbon nanotube/carbon fiber polymer composites

In this study, carbon nanotubes (CNTs) were incorporated into carbon fiber‐reinforced polymer composites (CFRPs) by growing them on the surface of PAN‐based carbon fibers utilizing a relatively low temperature technique. The effect of various surface treatments of the carbon fibers on the in‐plane and out‐of‐plane mechanical performance of the hybrid CFRPs (e.g., exposure to or shielding against elevated temperatures, patterned vs. unpatterned growth of the CNTs over the carbon fibers) were investigated. The in‐plane quasi‐static mechanical properties and out‐of‐plane dynamic properties of the hybrid CFRPs were examined utilizing tension and dynamic impact tests, respectively. To study the progressive damage mechanism of the hybrid CFRPs, spherical punch tests as well as X‐ray radiography of the impact damaged hybrid CFRPs were carried out. The results revealed that the strength and impact energy dissipation of the CFRPs improved by 11% and 127%, respectively, utilizing patterned growth of CNTs on the surface of the carbon fibers. POLYM. COMPOS., 37:2639–2648, 2016. © 2015 Society of Plastics Engineers     

Fibers from polypropylene/nano carbon fiber composites

Fibers from polypropylene and polypropylene/vapor grown nano carbon fiber composite have been spun using conventional melt spinning equipment. At 5 wt% nano carbon fiber loading, modulus and compressive strength of polypropylene increased by 50 and 100%, respectively, and the nano carbon fibers exhibited good dispersion in the polypropylene matrix as observed by scanning electron microscopy.     

Improved interlaminar shear properties of multiscale carbon fiber composites with bucky paper interleaves made from carbon nanofibers

The effects of bucky paper interleaves made from carbon nanofibers on interlaminar shear properties of carbon fiber reinforced composites (CFRPs) are studied. The study includes fabrication of bucky papers, resin impregnation by different techniques, i.e., soaking, hot-compression and vacuum filtration, followed by β-stage curing and the integration with carbon fiber prepregs to produce CFRP composites with bucky paper interleaves. The vacuum infiltration technique results in the best quality of polymer impregnation through bucky papers. Remarkable 31% and 104% improvements in interlaminar shear strength and mode-II shear interlaminar fracture toughness of the multiscale composites, respectively, are achieved with the incorporation of interleaves at failure-prone locations. The pertinent mechanisms responsible for the ameliorating effects of interleaves include improved interfacial adhesion and matrix shear strength for the interlaminar strengthening and crack-tip bridging and meandering for the toughening. The present technique can be used to incorporate carbon nanotubes (CNTs) or carbon nanofibers (CNFs) of high contents to strengthen/toughen at selective locations in FRP composites, which has not been possible previously because of the high viscosity caused by randomly-oriented CNTs/CNFs in a polymer resin.     

Structure of carbon fiber obtained from nanotube-reinforced mesophase pitch

Flow-induced orientation of discotic mesophase precursor typically leads to a center-origin, radial microstructure in the resulting carbon fibers. In the present study, we report the microstructure of carbon fibers that were derived from mesophase pitch that was modified using carbon multi-wall nanotubes (MWNTs). For an MWNT content as low as 0.1 wt.%, the microstructure was found to be fairly random (rather than radial).     

活性炭纤维吸附石化废水中苯酚的吸附平衡及动力学

以活性炭纤维(ACF)为吸附剂,研究了ACF对石化废水中苯酚的吸附平衡及动力学。在25、40、55及65℃下测定了吸附平衡等温线,采用Langmuir、Freundlich和Redlich-Peterson等温方程对吸附平衡数据进行了拟合,结果表明吸附平衡数据更符合Langmuir与Redlich-Peterson方程。体系温度从25、40、55升高到65℃时,ACF对模拟废水中苯酚的吸附能力随温度升高而降低,而ACF对石化废水中苯酚的吸附能力并不完全随温度升高而降低。ACF对石化废水与模拟废水中苯酚的吸附过程均符合拟二级动力学方程。颗粒内扩散模型对吸附动力学实验数据的拟合结果表明,吸附初期吸附速率主要受颗粒内扩散控制且石化废水中苯酚吸附的k_id随温度升高而增大,吸附中后期吸附速率除了受颗粒内扩散控制外还受到外扩散的影响。热力学分析表明,石化废水中ACF吸附苯酚过程的ΔG<0,由于石油类物质对苯酚吸附的影响,温度升高ΔG的数值变化不大。     

活性炭纤维吸附废水中酚的研究

通过静态和动态试验对活性炭纤维吸附废水中的酚进行了研究,测定了吸附等温线,考察了活性炭纤维的用量、苯酚浓度,以及过柱流速对吸附的影响.结果表明,活性炭纤维对苯酚的动态吸附容量为256 mg/g随着活性炭纤维用量的增加,处理水稳定时间延长;苯酚浓度越高,穿透时间越短;过柱流速越大,穿透时间越短;吸附饱和后的活性炭纤维再生后,吸附容量几乎不变.     

Selective synthesis of carbon nanotubes and nanocapsules using naphthalene pyrolysis assisted with ferrocene

Selective synthesis of well aligned multi-walled carbon nanotubes (MW-CNT) and multi-shelled carbon nanocapsule (MS-CNC) using pyrolysis of naphthalene with the presence of ferrocene was experimentally examined. With higher mole fraction of naphthalene to ferrocene, more MW-CNTs could be synthesized due to higher concentration of carbonaceous precursors emerging from the decomposed naphthalene. Based on kinetic analysis, at lower temperature, MW-CNTs could preferably be synthesized due to the controlled supply of carbonaceous clusters to get onto the surface of Fe clusters. On the other hand, at temperature higher than 900 °C the Fe clusters become more active to catalyze carbonaceous precursors to undergo self assembling process of MS-CNCs. With cheaper cost of naphthalene compared with other high-value hydrocarbons, usage of naphthalene would provide an advantage of reasonably economical synthesis of MW-CNT or MS-CNC.     

The kinetics of fiber growth from flowing solutions

Data are presented for the longitudinal and radial growth rates of polyethylene fibers grown from high molecular weight solutions using a seeding method in Poiseuille tube flow. Results indicate growth is a two-step process with the first step the formation of very thin untapered filaments ～25 μm in diameter which grow very rapidly the full length of the capillary tube. The second step involves radial thickening of the filament into a tapered shape, the kinetics of which have been measured. The discussion includes an analysis of the rapid longitudinal growth and a critical comparison to earlier experiments in both Poiseuille and Couette flow. A possible growth mechanism is suggested to explain the high growth rates found in these experiments as well as the unusual growth observed earlier for Couette rotor growth. A discussion of some kinetic data for the radial growth process is also given along with preliminary results which indicate thickening may only occur in flow of extensional kinematics.