Preparation of pitch-based activated carbon fibers with high specific surface area and excellent adsorption properties

Research on Chemical Intermediates - Activated carbon fibers (ACFs), as the third generation of activated carbon materials, are promising adsorbents due to their rich surface functional groups,...     

Mercury-coated carbon fiber microelectrodes : Preparation and some properties

Carbon fibre microelectrodes were made by sealing the fibres into glass and by using heat-shrinkable tubing. The electrodes can be coated with mercury by deposition at ?0.9 V vs. SCE from 0.1 M thiocyanate containing 0.05 mM mercury(II) at pH 2.5. Coulometric measurements and square-wave voltammetry were used to establish the properties of the deposit. Conditions for the deposition and stripping of cadmium are outlined.     

Gas permeation properties of asymmetric carbon hollow fiber membranes prepared from asymmetric polyimide hollow fiber

Asymmetric carbon hollow fiber membranes were prepared by pyrolysis of an asymmetric polyimide hollow fiber membrane, and their mechanical and permeation properties were investigated. The carbon membrane had higher elastic modulus and lower breaking elongation than the polyimide membrane. Permeation experiments were performed for single gases such as H₂, CO₂, and CH₄, and for mixed gases such as H₂/CH₄ at high feed pressure ranging from 1 to 5 MPa with or without toluene vapor. The permeation properties of the carbon membranes and the polyimide membrane were compared. There was little change in the properties of the carbon membranes with a passage of time. The properties were hardly affected by the feed pressure, whether the feed was accompanied with the toluene vapor or not, because the carbon membranes were not affected by compaction and plasticization.     

Preparation and properties of polyimide/chopped carbon fiber composite foams

In this study, a series of reinforced polyimide (PI)/carbon fiber (CF) composite foams were fabricated through thermal foaming of polyester ammonium salt (PEAS) precursor powders. The PEAS precursor powders containing different contents of chopped CF were synthesized from benzophenone‐3,3′,4,4′‐tetracarboxylic dianhydride (BTDA) and 4,4′‐diaminodiphenyl ether (ODA). The effects of different CF loadings on foaming behavior of PEAS/CF composite precursor powders, final cellular morphology, and physical properties of PI composite foams were investigated. The results revealed that the chopped CF acted as nucleation agent in the foaming process. The dispersion of CF can be evaluated using digital microscope. It is interesting to find that the chopped CF were highly oriented along the direction of cell arrises. As a result, the mechanical properties of PI foams were significantly enhanced owing to the incorporation of chopped CF. Furthermore, the thermal stability of PI composite foams were also slightly improved owing to fine dispersion of CF. In addition, the PI/CF composite foam shows uniform cell size distribution and the best comprehensive physical properties as chopped CF loading at around 6 wt%. Copyright © 2016 John Wiley & Sons, Ltd.     

中温煤沥青基碳量子点的制备与结构解析

以中温煤沥青为碳源，采用HNO₃预处理结合球磨过程及双氧水氧化刻蚀的方法制备沥青基荧光碳量子点，以CQDs的收率和荧光量子产率为目标，获得最优制备条件：反应时间6 h、H₂O₂加入量100 mL （c-CQDs），此时，CQDs收率和荧光量子产率分别为6.3%和11.2%，且尺寸均匀、粒径分布在4-14 nm。延长反应时间至8 h （a-CQDs），碳量子点团聚；H₂O₂用量增加至120 mL （b-CQDs）则导致碳量子点氧化过度，颗粒小且杂乱无章。对不同条件下所制备的CQDs进行XPS、红外光谱、热重、¹³C NMR、Raman和晶相分析，探究反应条件对CQDs结构的影响规律。结果表明，就碳含量而言，a-CQDs > b-CQDs > c-CQDs，氧元素含量则为b-CQDs > c-CQDs > a-CQDs。各CQDs结构中C主要以芳碳形式存在，c-CQDs的C=O、O-C=O含量最高，而b-CQDs的C-O含量最高，¹³C NMR分析发现CQDs中表征平均芳环尺寸大小的X_b约为0.5，相应地，其平均芳环数约为3。     

Synthesis and gas-sensing properties of phenylhydrazine-functionalized single wall carbon nanotubes in polymer matrix

Gas sensor material was prepared by encapsulation of functionalized single-walled carbon nanotubes (SWCNT) into a gas-permeable polymer poly(1-trimethylsilyl-1-propyne) (PTMSP). A phenylhydrazino group was used for the functionalization of SWCNTs to improve their solubility and compatibility with polymers. Syntheses were carried out in aqueous surfactant solutions and in pure phenylhydrazine without surfactant. Two different temperatures (24 and 50°C) and two surfactants (sodium dodecyl sulfate and tricaprylmethylammonium chloride — Aliquat®336) were compared. Functionalized SWCNTs were characterized by X-ray photoelectron (XPS), Raman and Fourier transform infrared (FTIR) spectroscopy. Analyses showed that the synthesis at higher temperature in pure phenylhydrazine resulted in the highest functionalization yield. Phenylhydrazine itself proved to be a good solvent for SWCNTs. The functionalized nanotubes were soluble in organic solvents that under the same conditions were appropriate solvents for polymers. The sensitivity of functionalized SWCNT-PTMSP thin film composite to NO₂ gas at room temperature was significantly higher than that of the similar sensor material containing the pristine SWCNTs.      

Preparation of macroporous carbon foam using emulsion templating method

A macroporous carbon foam (MCF) possessing three-dimensionally interconnected porous structure, that was composed of macropores, mesopores and micropores, could be synthesized by the oil-in-water (o/w) emulsion templating method using ultrasound. For the preparation of the o/w emulsion as a template of the macropores formed in the MCF, a resorcinol-formaldehyde (RF) solution and cyclohexane were used as an aqueous phase and an oil phase, respectively. We examined the effects of the viscosity of the RF solution, the mass ratio of cyclohexane with the RF solution as well as the concentration of a hydrophilic surfactant (Tween80) contained in the RF solution on the size distribution of the macropores. Consequently, the suitable viscosity of the RF solution to obtain a MCF with a narrow size distribution of the macropores was determined. It was revealed that the size of the macropores increased with the increase in the mass ratio of cyclohexane with the RF solution or with the decrease in the concentration of Tween80. It was possible to increase the porosity of the prepared MCF larger than 90% using a concentrated o/w emulsion as the template of the macropores.     

Electrochemical properties of diamond-like carbon electrodes prepared by the pulsed laser deposition method

Diamond-like carbon electrodes (DLCEs) have been synthesized by the pulsed laser deposition method. The surface structure of the DLCEs has been studied by atomic force microscopy and the root-mean-square roughness has been established as R _ms≥81 ?. Electrochemical impedance spectroscopy and cyclic voltammetry data show that DLCEs are nearly ideally polarizable in the potential region –0.4<E<1.1 V (vs. Ag|AgCl|sat. KCl in H₂O) in 0.1 M NaF+H₂O solution. Various equivalent circuits have been used for fitting the complex plane and Bode plots. A very good agreement between experimental and calculated Nyquist curves has been established if the charge transfer and double layer charging at the surface, intercalation of the H⁺ and (or) Na⁺ ions and solid phase diffusion inside the nanoparticle, as well as the effect of an insulating film at the surface (i.e. surrounding the nanoparticles), are taken into account.     

Sol-Gel法制备钙钛矿型复合氧化物YFeO~3气敏材料

用溶胶-凝胶法制备了YFeO~3气敏材料,并对其制备条件,导电行为和气敏效应作了系统研究,结果表明：铁钇物质的量之比n(Fe^3^+):n(Y^3^+)=1:1,800℃下热处理2h可得纯相钙钛矿型复合氧化物YFeO~3;电导测量显示,该材料呈p型半导体导电行为。2h预烧凝胶粉在800℃下热处理3h所得微粉制作的元件的电导突变温度为400℃,对乙醇有较高的灵敏度和良好的选择性,有望开发为一类新型酒敏传感器。     

Adsorption properties of iodine-doped activated carbon fiber

Iodine-doped activated carbon fibers (ACFs) were prepared by the iodine immersion method on pitch-based ACF. Then iodine-doped ACFs were heated in argon at 523 K for 4 h and at 673 K for 2 h. The iodine structure of the resultant iodine-doped ACFs was examined using X-ray photoelectron spectroscopy. The micropore structures were determined by N(2) adsorption at 77 K. The surface area and micropore volume of iodine-doped ACFs are less than those of pristine ACFs. However, the pore width does not change with the iodine doping. The effects of iodine doping on adsorption properties of ACFs for H(2)O and NO at 303 K were examined. The iodine doping affected remarkably the adsorptivities of ACFs for H(2)O and NO. In particular, iodine-doped ACFs treated at 673 K show enhanced adsorptivities for H(2)O and NO. This result suggests that iodine molecules doped on the micropores should be charged by heat treatment at 673 K.     

Preparation and characterization of scandia-doped tungsten powders prepared by a spray-drying method

Scandium oxide-doped tungsten powders were prepared by a new method of spray drying combined with two-step hydrogen reduction. The particle size of doped tungsten, powder morphology, and distribution of doped scandium oxide were characterized by scanning electron microscopy, X-ray diffraction, and laser diffraction particle size analysis. Experimental results indicated that the predecessor powders prepared by spray drying were spherical in shape. Two compounds, WO₃ and Sc₂W₃O₁₂, in the raw powder calcined at 600???C were transformed into metallic tungsten and scandia after reduction at 850???C by hydrogen for 1?h. The scandia-doped tungsten powders obtained had an average size of 950?nm and scandium oxide was distributed evenly throughout the tungsten powder. The mechanism of reduction of the doped tungsten oxide is discussed in this paper.     

硅灰石纤维增强聚甲醛复合材料的制备与性能研究

采用经硅烷偶联剂处理的无机矿物硅灰石纤维(WF)填充改性聚甲醛(POM),通过熔融共混制备POM/WF复合材料,并讨论了纤维含量对复合材料的力学性能及热稳定性的影响.研究结果表明:当硅灰石纤维的添加量为1%(质量分数)时,复合材料的断裂伸长率、缺口冲击强度、洛氏硬度最大,分别为44.8%、6.5kJ/m~2、86.1,较纯POM基体分别提升19.5%、7.1%和4.1%.此外,硅灰石的加入能够有效提高复合材料的热稳定性.当硅灰石纤维含量为10%(质量分数)时,复合材料的起始分解温度较纯POM提高了11℃.     

Preparation and thermal properties of chemically prepared nanoporous silica aerogels

This work focuses on the dependence preparation conditions—structure—physical properties of hydrophobic silica aerogels, all of them prepared under subcritical drying conditions (70 °C and 0.4 atm.), thus aiming at potential application as case insulation filling in heat pumps. The so prepared, millimeter scaled nano-porous hydrophobic silica aerogel granules were analyzed with standard electron microscope and atomic force microscopy, IR spectroscopy, UV/Vis spectroscopy, differential scanning calorimetry and thermal conductivity measurements. The physical properties of the aerogels were compared with commercial aerogel granules. A method for contact angle measurement of micro-droplets situated on the silica granules was proposed to quantify the level of their hydrophobicity.     

Improved interfacial properties of carbon fiber/UHMWPE composites through surface coating on carbon fiber surface

Carbon fibers were coated in an attempt to improve the interfacial properties between carbon fibers and ultra‐high molecular weight polyethylene resin matrix. Atomic force microscopy, scanning electron microscopy, and X‐ray photoelectron spectroscopy were performed to characterize the changes of carbon fiber surface. Atomic force microscopy results show that the coating of carbon fiber significantly increased the carbon fiber surface roughness. X‐ray photoelectron spectroscopy indicates that silicon containing functional groups obviously increased after modification. Interlaminar shear strength was used to characterize the interfacial properties of the composites.     

Synthesis and properties of calcium hydroxyapatite/carbon fiber composites

Composites comprising micrometer-sized carbon fibers (CFs) and biocompatible nanocrystalline calcium hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ (HA, NCHA), containing 1.0, 2.0, and 5.0 wt % CFs, have been synthesized in the course of precipitation from aqueous solutions in the Ca(OH)₂–H₃PO₄–CF–H₂O system. Some physicochemical characteristics of the precursor CFs and synthesis products have been determined using chemical, X-ray diffraction, and thermal analyses, IR spectroscopy, and scanning and transmission electron microscopy. An analysis of composition–synthesis conditions–structure–particle size–property correlations indicates that the presence of CFs in HA/CF composites strongly decreases the sizes and modifies the habit of NCHA. A rise of CF content in the HA/CF composite is accompanied by a decrease in particle size and a rise in solubility of NCHA.     

The recent progress of pitch-based carbon anodes in sodium-ion batteries

Sodium-ion batteries(SIBs)have attracted significant attentions as promising alternatives to lithium-ion batteries for large-scale energy storage applications.Here carbon materials are considered as the most competitive anodes for SIBs based on their low-cost,abundant availability and excellent structural stability.Pitch,with high carbon content and low cost,is an ideal raw precursor to prepare carbon materials for large-scale applications.Nevertheless,the microstructures of pitch-based carbon are highly ordered with smaller interlayer distances,which are unfavorable for Na ion storage.Many efforts have been made to improve the sodium storage performance of pitch-based carbon materials.This review summarizes the recent progress about the application of pitch-based carbons for SIBs anodes in the context of carbon’s morphology and structure regulation strategies,including morphology adjustment,heteroatoms doping,fabricating heterostructures,and the increase of the degree of disorder.Besides,the advantages,present challenges,and possible solutions to current issues in pitch-based carbon anode are discussed,with the highlight of future research directions.This review will provide a deep insight into the development of low-cost and high-performance pitch-based carbon anode for SIBs.     

Effects of carbon contents on morphology and electrical properties of Li2MnSiO4/C prepared by a vacuum solid-state method

To improve the electrochemical performance of Li₂MnSiO₄ with low electric conductivity, the Li₂MnSiO₄/C composite are synthesized by a vacuum solid-state reaction of a mixture of SiO₂, LiCH₃COO, Mn(CH₃COO)₂ and designed mass of C₆H₁₂O₆ · H₂O as carbon sources. The crystalline structure and morphology of products are analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser scattering technology (LS) respectively. The tested results show that carbon doping decrease the crystallite sizes of products, but keep the aggregation of the particles and made the impurity increased instead. The results of constant current charge-discharge prove that the mixed carbon improve Li⁺ transmission performance and decrease inner polatization resistance of Li₂MnSiO₄ materials, but can not prevent the collapse of Li₂MnSiO₄ crystal structure. While the galvanostatic intermittent titration technique (GITT) results demonstrate that the primary reason for the improved electrochemical performance can be attributed to increased Li-ion diffusion coefficient $(D_{Li^ + } )$ as a result from carbon doping.     

Preparation and evaluation of solid dispersions of nitrendipine prepared with fine silica particles using the melt-mixing method

Solid dispersions (SD) of nitrendipine (NTD), a poorly water-soluble drug, were prepared using the melt-mixing method with hydrophilic silica particles (Aerosil and Sylysia) with different particle size and specific surface areas as carriers. Powder X-ray diffraction and differential scanning calorimetry evaluation showed that NTD in the SDs treated with the melt-mixing method was dispersed in the amorphous state. FT-IR spectroscopy obtained with the SDs indicated the presence of hydrogen bonding between the secondary amine groups of NTD and silanol groups of silica particles. The dissolution property of NTD in the SDs was remarkably improved regardless of the grade of silica. At the end of the dissolution test (60 min) the concentrations of NTD for the SDs with Aerosil 200 and Sylysia 350 were 8.88 and 10.09 microg/ml, corresponding to 28 and 31 times that of the original NTD crystals, respectively. The specific surface area and the adsorbed water amount of the SDs were also significantly improved. The rapid dissolution rate from the SDs was attributed to the amorphization of drug, improved specific surface area and wettability than the original drug crystals. In the stability test, powder X-ray diffraction pattern indicated that amorphous NTD in the SD with Aerosil 200 was stable for at least 1 month under the humid conditions (40 degrees C/75% RH).