Surface Of Carbon Particles Research Articles

Crystallization of Silicon Thin Films by Infrared Semiconductor Laser Irradiation Using Carbon Particles

*** We report the crystallization of 40-nm-thick hydrogenated amorphous silicon films using 940nm continuous wave infrared semiconductor laser with 200 nm diameter carbon particles as photo absorption. The laser beam was focused to 100 μm diameter at the surface of carbon particles. Laser irradiation at 25 W heated the carbon surface region to about 3430 K, which was estimated by analysis of spectra of light emission caused by laser irradiation when quartz substrates were placed on the surface of carbon particles. The silicon films coated with SiO2 films were crystallized by laser irradiation for 170 μs at 25 W. The crystallization volume ratio was 0.53. Crystallization over 1.1 mm area was also demonstrated by laser irradiation at 25 W.

Utilization of polymer degradation to modify electrical properties of poly( l-lactide)/poly(methyl methacrylate)/carbon filler composites

This research attempts to utilize polymer degradability in modifying electrical properties of poly( l-lactide) (PLLA)/poly(methyl methacrylate) (PMMA)/carbon fillers composites. Three kinds of carbon particles, i.e. carbon black, vapor-grown carbon fiber, and carbon nanotube, were compounded with PLLA/PMMA blend, followed by hydrolytic degradation of the composites, resulted in degradation of PLLA molecular chain from the surface of samples, with PMMA and carbon particles remained undegraded. By controlling degradation rate, it was possible to prepare samples with low surface resistivity, yet at the same time exhibited high value of volume resistivity. It was also found that final electrical properties of degraded composites depend on the size and the shape of the fillers.

Formation of Pt Clusters Covered with Carbon Layer and Origin of the Generation of Electricity

In order to prevent coalescence of platinum clusters on a carbon particle surface, new platinum catalysts covered with a thin carbon layer were proposed. The catalysts were produced by evaporation above the eutectic point between carbon and platinum. Most of the platinum core of 5 nm diameter was covered with a graphene layer of 1 nm thickness. The generation of electricity using this carbon coated platinum surface catalyst in a proton exchange membrane fuel cell has been demonstrated. The mechanism of the generation of electricity has been discussed on the basis of the idea of the contact potential. The electric dipole of water also has been discussed with regard to the generation of electricity.

Carbon–protein covalent conjugates in non-instrumental immunodiagnostic systems

An original technique for obtaining stable conjugates using colloid carbon particles as indicator labels has been developed. The reliability and stability of the diagnostic reagents obtained is provided by covalent binding of various affine compounds on the surface of carbon particles. The stability of the reagents has been studied under various storage conditions for 3–10 years. It was shown that even when storage conditions were outside the optimal range, some conjugates preserved their analytical characteristics for 10 years. A number of systems for analytical detection of various ligands have been designed based on the carbon–protein conjugates synthesized. The major characteristics of these systems are their high sensitivity and specificity, reliability, and reproducibility, simplicity in operation, and quick results.

Synthesis of nano-CaCo 3 composite particles and their application

Nano-calcium carbonate composite particles were synthesized by the soapless emulsion polymerization technique of double monomers. The composite particles formation mechanism was investigated. The effects of composite particles on the mechanical properties of nano-CaCO 3-ABS (acrylonitrile-butadiene-styrene copolymer) composite material were studied. It was validated that the composite particles are made up of the nano-calcium carbonate cores and the shells of alternating copolymers of buty1 acrylate (BA) and styrene (St). The shells are chemically grafted and physically wrapped on the surface of nano-calcium carbonate particles. When the composite particles were filled in ABS matrix, the CaCO 3 particles are homogeneously dispersed in the composite material as nanoscales. The impact strength of the composite material is obviously enhanced after filling appropriate amounts of composite particles. It can be concluded that the soapless emulsion polymerization of double monomers is an effective method for nano-CaCO 3 surface treatment.

Derivatization and characterization of functionalized carbon powder via diazonium salt reduction

Chemical reduction of 4-chloro-2-nitrobenzenediazonium chloride salt in the presence of hypophosphorous acid and carbon powder results in functionalized carbon powder with chloronitrophenyl groups attached on carbon particle surface. This type of bulk derivatization protocol is very useful and most inexpensive compared to widely used electrochemically assisted derivatization protocol. The derivatized carbon powder has been characterized by studying its Fourier transform infrared spectroscopy (FTIR) and cyclic voltammetric studies. The surface functionalized moieties have been examined electrochemically by immobilizing them onto the surface of basal plane pyrolytic graphite electrode and studying its cyclic voltammetry. The effect of pH, scan rate (v), and the peak potentials (Ep) as a function of pH has revealed that the species are surface bound in nature and covalently attached on the carbon surface. The FTIR studies of the derivatized carbon powder have revealed that the modifying molecule is covalently attached on the carbon particle surface.

INFLUENCE OF SURFACE-MODIFICATION FOR CALCIUM CARBONATE ON THE INTERACTION BETWEEN THE FILLERS AND POLYDIMETHYLSILOXANE

The surface of calcium carbonate (CaCO3) particles was modified with stearic acid (SA) and the chemical structures of the product were characterized by FT-IR analysis. The interaction between polydimethylsiloxane (PDMS) and CaCO3 fillers with different surface character was investigated by means of dynamic rheological and bound rubber tests for uncured compounds and mechanical properties measurements for the corresponding vulcanites. The results of dynamic tests indicate that with the increase of SA mass fraction, the span of the linear viscoelastic region broadens and the height of the modulus plateau decreases. The reasons for these are ascribed to that the SA decreases the surface energy of filler particles and weakens their tendency to agglomerate. Moreover, the results of mechanical measurements reveal that the vulcanized compound filled with modified filler has a relative high tensile strength induced by a reinforced interaction between filler and polymer matrix, which is confirmed by the bound rubber tests and transmission electron microscopy (TEM) observations.

Electric Field Effect for Pt Particle on Carbon Particle

The electric field effect on Pt cluster-carbon particle nanosystem for the polymer electrolyte fuel (PEFC) cell has been directly demonstrated by two experimental methods. The Pt- C catalyst was flown to the plus plate about 830 V/cm2 electric field due to the electrostatic tension for the nanosystem. The Pt particle surface was covered with graphene layers. In order to make clear the electric field effect, the Pt-C system was put in the 1 volt field and the alteration of the system was directly observed by transmission electron microscopy. The alteration of Pt surface and structure of carbon particles have been discussed as the intense electric field action of the order of 1000 volt on the nanosystem.

Formation of carbon nanoparticles by the condensation of supersaturated atomic vapor obtained by the laser photolysis of C3O2

A new technique is suggested for obtaining nanoparticles from highly supersaturated vapor resulting from the laser photolysis of volatile compounds. The growth of carbon nanoparticles resulting from C3O2 photolysis has been studied in detail. Absorbing UV quanta (from an Ar-F excimer laser), C3O2 molecules decompose to yield atomic carbon vapor with precisely known and readily controllable parameters. This is followed by the condensation of supersaturated carbon vapor and the formation of carbon nanoparticles. These processes have been investigated by the laser extinction and laser-induced incandescence (LII) methods in wide ranges of experimental conditions (carbon vapor concentration, nature of the diluent gas, and gas pressure). The current and ultimate particle sizes and the kinetic parameters of particle growth have been determined. The characteristic time of particle growth ranges between 20 and 1000 μs, depending on photolysis conditions. The ultimate particle size determined by electron microscopy is 5–12 nm for all experimental conditions. It increases with increasing total gas pressure and carbon vapor partial pressure and depends on the diluent gas. The translational energy accommodation coefficients for the Ar, He, CO, and C3O2 molecules interacting with the carbon particle surface have been determined by comparing the LII and electron microscopic particle sizes. A simple model has been constructed to describe the condensation of carbon nanoparticles from supersaturated atomic vapor. According to this model, the main process in nanoparticle formation is surface growth through the addition of separate atoms to the nucleation cluster. The nucleus concentrations for various condensation parameters have been determined by comparing experimental and calculated data.

Electrochemical performance of nano-Pt-supported carbon anode for lithium ion batteries

A nano-Pt-supported carbon anode was prepared by supporting Pt nanoparticles onto carbon powder. Ultrafine Pt nanoparticles could be well distributed on the surface of carbon particles. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), cyclic voltammetry (CV), FTIR, and impedance spectroscopy were used to study on the electrode structure and electrochemical performance. Nano-Pt-supported carbon anode enhanced the Li discharge reaction and suppressed the solvent decomposition reaction, which are favorable for lithium batteries.

Voltammetric Characterization of 2-Methoxy-4-Nitrophenyl Derivatized Carbon Powder

Carbon powder has been functionalized with 2-methoxy-4-nitrophenyl groups by the reduction of 2-methoxy-4-nitrobenzenediazonium-1,5-naphthalenedisulfonate salt in presence of hypophosporous acid as a reducing agent. This provides an easy and inexpensive methodology to modify the carbon particle surface. This derivatization is carried out in the presence of 2-methoxy-4-nitrobenzenediazonium 1,5-naphthalenedisulfonate salt along with the carbon powder and hypophosporous acid. The electrochemical behavior of the resulting 2-methoxy-4-nitrophenyl functionalized carbon powder was characterized by immobilizing it onto basal plane pyrolytic graphite (bppg) electrode and studying its voltammetric behavior. The surface morphology of derivatized carbon powder has been examined by SEM studies which revealed that the size of the functionalized carbon particles are larger than bare carbon particles The effect of pH on peak potentials, scan rate and stability of the functionalized carbon particles has revealed that they are surface bound species.

In situ preparation of hydrophobic CaCO3 in the presence of sodium oleate

Hydrophobic CaCO3 particles were directly prepared via carbonation of Ca(OH)2 slurry in the presence of sodium oleate at room temperature. Sodium oleate was used to modify the surface property of CaCO3 particles. The measurement of relative contact angle and active ratio indicated that CaCO3 samples were hydrophobic. DTG, FT-IR and TEM analysis of the obtained product indicated that the hydrophobic property was attributed to the deposition of calcium oleate, produced in the reaction mixture, onto the surface of calcium carbonate particles. They were covered on the CaCO3 crystals surface and modified their surface property; at the same time they own CC bonds and could be polymerized or copolymerized later to give a polymeric monolayer.

Surface-modified calcium carbonate particles by admicellar polymerization to be used as filler for isotactic polypropylene

Admicellar polymerization was used to produce a thin layer of polypropylene (PP) on the surface of calcium carbonate (CaCO 3) particles using sodium dodecyl sulfate (SDS) as the surfactant template and sodium persulfate (Na 2S 2O 8) as the thermal initiator. The admicellar-treated CaCO 3 particles were characterized by Fourier-transformed infrared spectroscopy (FT-IR), gravimetric analysis, and particle size analysis. FT-IR analysis suggested successful coating of atactic polypropylene (aPP) on the surface of the particles. The behavior of these coated particles in an isotactic polypropylene (iPP) matrix was compared to that of uncoated and stearic acid-coated ones. Non-isothermal crystallization studies indicated that surface treatment of CaCO 3 particles reduced the ability for CaCO 3 particles to nucleate the iPP matrix. Compared to composites made from the uncoated material, composites made with stearic acid-coated and admicellar-treated CaCO 3 particles had lower tensile strength, Young's modulus, and flexural strength, but higher impact strength. Observation of the fractured surfaces of the composites by scanning electron microscopy (SEM) revealed an improvement in the dispersion and distribution of the CaCO 3 particles within the iPP matrix as a result of the surface treatment.

Capacity Fading Mechanisms on Cycling a High-Capacity Secondary Sulfur Cathode

The cycle life and capacity fading mechanisms of secondary sulfur electrodes prepared by two different electrode fabrication methods were studied in an effort to improve the energy density of the cathode. Cycle life improved substantially when the uniformity of carbon distribution around the sulfur particles improved and electrode density increased, improving the overall structural integrity of the carbon matrix. Capacity fading in a high-energy-density cathode is mainly due to structural failure by physical crack propagations of the electrode structure and subsequent formation of the electrochemically irreversible layer at cracked surfaces of carbon particles or masses. The capacity fading due to these mechanisms appears to be reduced substantially and significantly by improved structural integrity with uniform pore structure of the carbon matrix. A Li/S cell containing a cathode fabricated by the improved technique cycled over 400 cycles without any severe structural damage of the electrode structure. © 2004 The Electrochemical Society. All rights reserved.

Film‐surface diffusion during the adsorption of acid dyes onto activated carbon

AbstractA mass transport model has been developed and applied to the adsorption of three acid dyes onto activated carbon in three single component systems. The mass transfer model is based on two rate controlling mass transfer steps, namely external film mass transfer and homogeneous solid‐phase surface diffusion (HSD). Almost all previous film‐HSD models have been based on numerical solutions to the diffusion equation using orthogonal collocation or Crank–Nicolson finite difference solutions. However, in the present model a semi‐analytical solution to the solid surface diffusion equation is presented, yielding a sophisticated solution of the differential equations. The solutions provide a good correlation between the experimental concentration–time decay curves by incorporating the Langmuir equilibrium isotherm to describe the solid phase surface dye concentrations. However, the surface diffusivities show a dependence on the carbon particle surface coverage and these diffusivities have been correlated using a Darken relationship. Copyright © 2004 Society of Chemical Industry

Influence of filler–rubber interactions on the viscoelastic properties of carbon‐black‐filled rubber compounds

AbstractThe specific role of filler–rubber interactions in dynamic properties was investigated. Natural rubber compounds, filled with N330 carbon black, were used, and the filler surface was modified through a gas treatment in the solid phase. The effects of this filler surface treatment on the dynamic properties were systematically studied at equal filler dispersion levels. The dynamic properties were assessed for both uncured and vulcanized compounds, and a number of advanced investigative techniques were used to characterize not only the modification of the carbon particle surface by an oxidative treatment but also the structure of the filled rubber compounds. Particular attention was paid to techniques that gave access to the segmental mobility to explain the benefit observed with modified carbon black. A molecular interpretation, based on NMR measurements, was considered that took into account physicochemical parameters. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 577–588, 2004

Nano‐Alloy Anode for Lithium‐Ion Batteries

AbstractFor Abstract see ChemInform Abstract in Full Text.

Nano-alloy anode for lithium ion batteries

The features related to nano-alloy anode for Li ion batteries are summarized in this paper mainly based on our recent studies on nano-SnSb. Electrochemical agglomeration, irreversible trapping of inserted ions by host lattice, and unstable solid electrolyte interphase (SEI) film are highlighted. A strategy that pinning nano-alloy particles on the surface of micrometer-sized carbon particles is introduced, in which all components are active for Li storage.

Chemical Reactions of Nitrogen Oxides on the Surface of Oxide, Carbonate, Soot, and Mineral Dust Particles: Implications for the Chemical Balance of the Troposphere

Particles present in the Earth's atmosphere provide reactive surfaces for potentially important chemistry. The role of heterogeneous reactions of trace atmospheric gases on solid aerosol surfaces p...

Phase transformations of nanometer size carbon particles in shocked hydrocarbons and explosives

Estimates for the displacement of the phase equilibrium lines for small carbon particles containing from several hundred to several tens of thousands of atoms are made, and an error analysis of the uncertainties in these estimates is derived and evaluated using available experimental data. Hugoniot calculations for methane, benzene, polyethylene, and polybutene, based on a carbon particle surface energy adjusted equation of state, are in better agreement with shock pressure-volume and temperature data than those obtained with a bulk carbon equation of state. The results suggest that carbon particles, of order 103–104 atoms, can exist in the liquid state at lower temperatures than bulk carbon.