Whiskerization of carbon beads by vapor phase growth of carbon fibers to obtain sea urchin-type particles

Whiskerization of sulfur-containing hard carbon beads with carbon fibers has been examined to prepare sea urchin-type particles. Propylene was used as a source material for the fiber growth and decomposed at 1000°C for 2 hr. Sulfur-catalyzed carbon fibers 4–6 μm in diameter and 90–120 μm long formed with a density of 400–550 per bead on the surfaces of carbon beads containing ≥ 2.5 wt% sulfur. These beads were prepared by carbonization of styrene/divinylbenzene copolymers sulfonated with fuming sulfuric acid. Very few, if any, fibers grew on beads from copolymers sulfonated with chlorosulfuric acid, probably because of lower sulfur contents (<2.5 wt%) and/or inhibition by residual chlorine.     

Carbon spheres prepared from zeolite Beta beads

Porous carbon beads were prepared from macroporous anion-exchange resin beads preliminary converted into resin-zeolite Beta composite or pure zeolite Beta spheres. Two synthesis procedures were used depending on the initial template employed. In a series of experiments, the resin from the resin-zeolite Beta composite was directly carbonized into carbon. In another series of experiments, the resin was removed by oxidation at 600 °C leaving behind self-bonded zeolite Beta beads, which were filled with carbon by chemical vapor deposition (CVD) of propylene. As a final step for both procedures, the zeolite was dissolved in hydrofluoric acid. All the carbons prepared inherited the macroscopic spherical shape of the template spheres as well as the morphology of the primary particles building up the beads. The synthesis procedure and the carbonization temperature or the temperature for CVD of carbon employed influenced the ordering and the pore structure of the produced carbons. The carbons prepared by direct carbonization showed relatively low surface areas, less than 1000 m² g⁻¹, and no zeolite structural regularity. The samples obtained via CVD maintained the zeolite ordering with a periodicity of 11.7 Å and had surface areas of over 2000 m² g⁻¹.     

Carbon aerogels for catalysis applications: An overview

Carbon aerogels are nanostructured carbons obtained from the carbonization of organic aerogels, which are prepared from the sol-gel polycondensation of certain organic monomers. These materials have a great versatility both at the nanoscopic level in terms of their pore texture and at the macroscopic level in terms of their form. Thus, the surface area, pore volume, and pore size distribution are tuneable surface properties related to the synthesis and processing conditions, which can produce a wide spectrum of materials with unique properties. In addition, carbon aerogels can be obtained in the form of monoliths, beads, powders or thin films. All these properties make them promising materials for application in adsorption and catalysis. Metal-doped monolithic organic aerogels can be easily prepared by following three main strategies: by addition of the metal precursor to the initial mixture, by ion-exchange or by deposition of the metal precursor on the organic or the carbon aerogel by one of various methods. These metal-doped carbon aerogels have been used as catalysts and as electrodes for electrical double-layer capacitors. This article shows the preparation of metal-doped carbon aerogels, their physico-chemical surface properties and their applications as catalysts in various reactions.     

Iron doped phenolic resin based activated carbon micro and nanoparticles by milling: Synthesis,characterization and application in arsenic removal

In this study, we have prepared iron-doped activated micro/nano carbon particles as efficient adsorbents for arsenic removal. Starting with phenolic resin monomers, polymeric spherical beads of size ～0.2–1 mm were first synthesized by suspension polymerization. Iron (Fe) was incorporated in an intermediate step during polymerization. The internal porous structure was developed in the Fe-doped polymeric beads by carbonization followed by physical activation using steam. Subsequent to activation, beads were milled to prepare the micro/nano particles in the size range of 100–500 nm. In an alternate route to preparing the adsorbents, the synthesized polymeric beads were first milled and then carbonized and activated. The absorbent particles thus prepared were applied in the removal of arsenic (III and V) present at low concentration levels (<20 mg/L) in water. The method in which milling was performed first produced a superior adsorbent. For both the ions, the equilibrium loading (～3–15 mg/g) in the adsorbate were found to be comparable to the adsorbates reported in literature. The simple and up-scalable methodology developed in this study has the potential for the preparation of a wide variety of similar metal impregnated porous (polymeric precursor based) adsorbents/catalysts in other environmental remediation applications.     

Study of Extraction of Co(II) Ions using the Synthesized Polyacrylonitrile-Manganese Dioxide Composite Beads

Extraction of cobalt ions from aqueous medium has been studied, using macroporous polyacrylonitrile-manganese dioxide composite beads. Polyacrylonitrile, synthesized by γ-radiation induced polymerization of saturated aqueous solution of acrylonitrile monomer, has been employed, to produce polyacrylonitrile-manganese dioxide composite beads. Results of the extraction study indicate efficient adsorption of cobalt ions from neutral, or slightly acidic, aqueous solutions. The cobalt ions, adsorbed on the composite beads, can be leached out with 0.1 M HNO₃ solution. The effect of various experimental parameters, such as concentration of cobalt ions, pH of the aqueous solution, etc., on the adsorption process and its kinetics has been studied. Further, adsorption capacity of the beads for cobalt ion, as well as their reusability for multiple adsorption-desorption of the cobalt ions, have also been evaluated. SEM and BET techniques have been used to determine the porous nature of the beads. IR spectroscopy has been used to understand the interaction of the polyacrylonitrile-manganese dioxide composite beads with cobalt ions.     

Particulate reinforcement of polyacrylate elastomers III. Swelling measurements

This paper presents and discusses results which have been obtained for the swelling in chlorobenzene of crosslinked polyethylacrylates containing various amounts of microscopic glass beads. The adhesion between the glass beads and the elastomer matrix was varied by subjecting the beads to different surface treatments. The swelling behaviour has been found to correlate very closely with the extent of adhesion as judged by peel force measurements and tensile stress-strain properties reported previously. In the case of beads showing pronounced adhesion to the matrix, restrictions on swelling have been interpreted in terms of an apparent enhancement of crosslink density by the reactive beads.     

Carbonization of petroleum binders. 2. Oils from carbonization of petroleum binders

Changes of composition, structure, and contents of some functional groups, of oils from petroleum binders, in relation to temperature of carbonization from about 710 K to 1200 K have been investigated. Oils from carbonization of petroleum binders are of hydrocarbon type, and their elemental compositions are almost independent of carbonization temperature. During the thermal decomposition of these binders, about 75–80 wt % of gaseous and vapour products are emitted. As carbonization temperature increases, molecular weights of the oils increase from about 250 to about 290; their density, index of refraction, and molar refraction increase. Structural analysis of the oils showed that they contained about 30% of cyclic hydrocarbons (aromatic and cycloalkane) as well as alkanes. The number of rings in the average structural unit of oil increases with increase of carbonization temperature, especially the number of aromatic rings. About 60–70 vol % distills before 633 K under atmospheric pressure; the distillate is paraffinic, while the residue after distillation is aromatic-alicyclic. Oils from carbonization of P-70 asphalt have similar compositions and chemical natures, but lower molecular weights, than oils from carbonization of residues after vacuum distillation of crude oil. Oils from carbonization of pitch are decidedly aromatic.     

Development of lignin carbon fibers: Evaluation of the carbonization process

The use of lignin as a renewable resource for the production of less‐expensive carbon fibers has in recent years attracted great interest. In order to develop the strength properties, the stabilization and carbonization processes have to be optimized. For this reason, the process parameters during carbonization have here been studied on stabilized lignin fibers in the temperature interval from 300 to 1300 °C. The effects of temperature, heating rate, and straining of fibers during carbonization on the strength properties of carbon fibers were investigated. The heating rate, in the range from 1 to 40 °C/min, was shown to have no effect on the property development of the fibers. During carbonization with no load applied to the fibers, a shrinkage of 20% was noted. Counteracting the shrinkage by imposing a load on the fibers during the carbonization resulted in fibers with a greater stiffness. The tensile strength was not, however, affected by this loading. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43965.     

Preparation and characterization of interpenetrating network beads of poly(vinyl alcohol)‐grafted‐poly(acrylamide) with sodium alginate and their controlled release characteristics for cypermethrin pesticide

Interpenetrating network polymeric beads of poly(vinyl alcohol)‐grafted‐acrylamide with sodium alginate have been prepared by crosslinking with glutaraldehyde. Cypermethrin, a widely used pesticide, was loaded with 80% efficiency in these hydrogel beads. The beads were characterized by Fourier transform infrared spectroscopy to confirm the grafting. Scanning electron microscopy was used to know the morphology of the beads. Equilibrium swelling experiments indicated that swelling of the beads decreased with an increase in crosslinking. The in vitro release studies were performed under static conditions and the release data have been fitted to an empirical relation to estimate the transport parameters. The diffusion coefficients have been calculated for the transport of pesticide through the polymeric beads using the initial time approximation method. These values showed decrease with increasing crosslinking as well as increasing pesticide loading. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 552–560, 2002; DOI 10.1002/app.10306     

Effects of Carbonization Temperature and Time during Carbon Riveting Process on the Stability of Pt/C Catalyst

Effects of carbonization temperature and time during carbon riveting process on the stability of Pt/C catalysts have been investigated systematically. X‐ray diffraction, transmission electron microscopy, cyclic voltammograms, and accelerated potential cycling tests have been performed to characterize the catalysts. The experimental results show that the activity of the riveted Pt/C catalyst decreases with the increasing of the heat‐treated temperature and the extension of heat‐treated time due to sintering of Pt nanoparticles. The stability of the carbon riveted Pt/C catalysts exhibits the increasing trend with the increase of the carbonization time and temperature. Considering both of the activity and stability of the riveted Pt/C catalysts, the optimized carbonization temperature and time are 400 °C and 60 min for a Pt/VulcanXC‐72 catalyst with starting particle size before carbonization of 2.2 nm and 20 wt% platinum loading, respectively.     

Particulate reinforcement of polyacrylate elastomers. II. Mechanical properties

This paper presents and discusses results which have been obtained for the mechanical properties of crosslinked polyethylacrylates containing various amounts of microscopic glass beads. The adhesion between the glass beads and the elastomer matrix was varied by subjecting the beads to different surface treatments. That the adhesion is affected by surface treatment has been demonstrated in two ways: (i) Unfilled elastomer sheets have been cast in contact with glasses surfaces which had been treated with the same reagents as were used to treat the beads. The force required to peel the elastomer from the glass was then measured and found to depend strongly upon the surface treatment, (ii) Scanning electron micrographs of the ruptured surfaces of used tensile test-pieces cut from filled elastomer sheets confirm that surface treatment has a profound effect upon the adhesion between bead and matrix. Results are presented for the hardness and tensile stress-strain properties of elastomers containing various amounts of beads. In all cases, the stiffening effect of the beads increases as the adhesion between beads and matrix is improved. Beads which had been treated in such a way as to minimise the, adhesion to the matrix were found to cause an apparent softening of the material as revealed by the tensile stress-strain curve. It has been shown that this effect can be satisfactorily explained if it is assumed that in this case the beads merely serve to increase the void content of the material.     

Comparative studies on physico-chemical characterization of yeast cells entrapped with alginate and hybrid beads

Natural polymers used as carrier materials in immobilization technology have the advantage of being non-toxic, biocompatible and biodegradable. In the present investigation, immobilization of yeast cells using different polymers has been carried out and the properties such as morphological, hardening, thermal stability and characterization of functional groups of alginate and hybrid beads (alginate–carrageenan and alginate–xanthan gum) have been studied by different techniques such as scanning electron microscope, texture analyzer, differential scanning calorimetry, and Fourier transfer infrared spectroscopy. The swelling behavior in terms of pH variation as well as flow properties of alginate and hybrid beads has also been examined. The hybrid beads prepared from alginate and carrageenan were found to be the best in terms of strength, cell holding capacity, pH and thermal stability. The reusability of beads was also studied in terms of enzyme activity of the entrapped yeast cells. The beads prepared by alginate–carrageenan were found to be more stable than alginate and alginate–xanthan beads. The yeast cells entrapped in alginate–carrageenan beads showed no significant decrease in enzyme activity up to seven batches. Thus, alginate–carrageenan beads can be used as a polymeric carrier/support to develop a stable and long-term immobilized cell system, which indicates its high potential for commercial applications in food and pharmaceutical sector.     

Study of the Formation of Nano-Networks in Colloidal Particles

The authors studied the formation of a wafer-scale network of connected colloidal beads by reactive ion etching. The dimensions of the connections have been studied as a function of etching time for colloidal beads of different sizes, and could be well controlled. The authors have found that the nano-network forms and disappears for the same time of etching independent of the diameter of the polystyrene beads. With recent interest of connected colloidal networks in various optical sensing applications, such as photonic crystals, as surface-enhanced Raman scattering substrates, the studies have potential uses in the development of wafer-scale nanophotonic sensors.     

Investigation of retrogressive reactions leading to the carbonization of solvent-refined coal

The carbonization of solvent-refined coal (SRC) samples produced by the liquefaction of an HVc bituminous coal has been studied. Carbonization conditions were 450 °C, 34.4 MPa, for 1 and 5 h hold times. The original SRCs and pyridine-insoluble fractions of the carbonization products have been characterized by Fourier-transform infrared spectroscopy. Spectral changes demonstrate that the formation of larger molecules during carbonization involve the joining together of aromatic molecules that were originally present, without increasing their size significantly. This is accomplished by the elimination of methylene units and condensation of phenolic functional groups originally present on the aromatic groups in the SRCs.     

弯拉荷载和碳化耦合作用下氯离子扩散试验研究

为了解决盐雾区弯拉荷载和碳化耦合作用下氯离子在混凝土中的传输问题,设计了荷载对氯离子、碳化对氯离子扩散影响的试验,由于荷载作用会对碳化有所影响,进而再次影响氯离子的扩散作用,因此设计了荷载对碳化深度影响的试验.以Fick第二定律为基准模型,通过对以上三个实验数据的整理并结合已有的研究成果逐步建立了荷载碳化耦合作用下对氯离子扩散的影响关系,该模型对盐雾区受拉构件使用寿命的估算具有一定的指导意义.通过理论公式的计算结果与实验数据进行对比,误差低于5%,从而进一步说明了这样分步建立模型方法的正确性.     

生物质炭化原料选择及需热量分析

从生物质原料的工业分析结果和木质素含量两个角度出发,分析了二者对生物质炭化的影响.对生物质炭化原料进行选择,认为木材类生物质适合作为生物质炭化的原料,可加强对树木枝条、锯末及薪炭林的炭化;为实现生物质炭化的工业化,还应设计利用烟气余热等热源来热解生物质的换热器,这项设计需知道生物质热解需热量.运用热重-差示扫描(TG-DSC)同步热分析仪对选用的木屑进行热解实验并利用DSC曲线对木屑炭化需热量进行分析.结果表明,木屑炭化终温为500℃时(初始温度为40℃),需热量为491kJ/kg.提出DSC曲线在工业用热解换热器传热设计和校核中的应用方法.     

Properties of carbon nanofibers prepared from electrospun polyimide

A solution of a polyimide (PI, Matrimid® 5218) in dimethylacetamide was electrospun, and carbonization of the electrospun nonwoven fabrics produced carbon nanofiber fabrics. The effects of iron(III) acetylacetonate (AAI) on carbonization and the resulting morphology were also investigated. The carbonization behavior of the nonwoven fabrics was examined by X‐ray diffraction and Raman spectroscopy. AAI promoted carbonization of the nonwoven fabrics and increased the carbon yield. Addition of 3 wt % AAI increased the crystal dimension of electrospun PI nanofibers from 1.06 to 4.18 nm and decreased the integrated intensity ratio from 3.37 to 1.83 when heat treated at 1200°C. Scanning electron microscopy images of the carbonized nonwoven fabrics showed that AAI remained as particles within the fibers after carbonization. In addition, transmission electron microscopy observations revealed that turbostratic‐oriented graphite layers were observed around the particles even at 1200°C, which have been reported only on carbonization of rigid‐chain solvent insoluble PI materials under tension. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97:165–170, 2005     

Top-down strategy for bamboo lignocellulose-derived carbon heterostructure with enhanced electromagnetic wave dissipation

Biomass-derived residue carbonization has been an important issue for “carbon fixation” and “zero emission”, and the carbonized products have multiple application potentials. However, there have been no specific research to study the differences in macro- and micro-morphology, electrical properties and many other aspects of the products obtained from carbonization of pure cellulose, pure lignin or their complex, lignocellulose. In this work, lignocellulose with cellulose to lignin mass ratio of 10:1 is obtained using p-toluenesulfonic acid hydrolysis followed by homogenization process at a controlled condition. Then, carbon heterostructure with fibers and sheets (CH-10) are obtained by pyrolysis at 1500 ℃. Detailed results imply that the fiber-like carbon structure possesses high crystallinity and low defect density, coming from carbonization of the cellulose content in lignocellulose (LC) nanofibers. Correspondingly, the graphite-like carbon sheet with high defect density and low crystallinity comes from carbonization of the lignin content in LCs. Further investigation indicates CH-10 possesses enhanced polarization and moderate impedance matching which makes it an ideal candidate for electromagnetic wave (EMW) absorption. CH-10 exhibits an excellent EMW absorption performance with a minimum RL value of -50.05 dB and a broadest absorption bandwidth of 4.16 GHz at a coating thickness as thin as 1.3 mm.     

Swelling and drug release behavior of calcium alginate/poly (sodium acrylate) hydrogel beads

In the present work calcium alginate/poly (sodium acrylate) composite beads have been prepared by in situ formation of cross-linked poly (sodium acrylate) network, within the calcium alginate (CA) beads. The CA/poly (SA) beads have been found to be stable for more than 48 h, in the physiological fluid (PF) of pH 7.4, while the plain alginate beads disintegrated within a couple of hours. The water uptake of beads was investigated under various composition parameters such as the amount of alginate, concentration of ionic cross-linker Ca⁺⁺ ions, monomer sodium acrylate (SA) contents, and degree of cross-linking. The beads also exhibited fair stability in the media of varying pH. Finally the release of model drug methylene blue (MB) was investigated. It was found that plain CA and CA/poly (SA) composite beads exhibited different release mechanisms.     

Particulate reinforcement of polyacrylate elastomers. I. Introduction and Preparation of Materials

The series of papers, of which this is the first, aims to demonstrate the importance of chemical reactions between filler particles and elastomer matrix in determining the physical properties of filled elastomers. A model system comprising small glass beads as the filler and crosslinked polyethylacrylate as the elastomer has been used. The beads themselves are inert towards the matrix during polymerisation, but the reactivity of the surfaces of the beads can be varied by suitable treatments. This paper describes techniques for fractionating the beads to give narrow particle-size distribution, for preparing unfilled and filled elastomer sheets, and for preparing composites in which an elastomer sheet is polymerised in contact with a glass plate which may or may not have been previously subjected to surface treatment.