Fibrous Carbon Materials Research Articles

Electrochemical properties of fibrous and granulated carbon materials

The influence exerted by the porous structure of fibrous and granulated carbon materials on the nature of the charging process and depth of penetration of the electrochemical process was studied.

Heavy oil sorption and recovery by using carbon fiber felts

On fibrous carbon materials, including activated carbon fibers, sorption capacity for heavy oils, less viscous A-grade and more viscous C-grade, was determined. Sorption capacity depended strongly on their bulk density; the correlation was the same as that found previously on exfoliated graphite and carbonized fir fibers. On carbon fiber felts, excellent recycling performance was observed, though sorption capacity was not so high as on exfoliated graphite and carbonized fir fibers. By filtration under suction, about 90% of sorbed A-grade heavy oil could be recovered and no decrease in sorption capacity was detected even after eight cycles. By washing with solvents, n-hexane for A- and C-grade oils and A-grade oil for C-grade oil, almost 100% recovery with no marked reduction in sorption capacity was found for each cycle. For the felts of PAN-based carbon fibers, rather severe operations for oil recovery, centrifugation and squeezing with twisting, could be applied without pronounced decreases in sorption capacity and recovery ratio.

Stability of Fibrous Carbon Materials in Cathodic Polarization in Nitric Acid Solutions

Stability and electrical conductivity of graphitized and carbonized fibrous carbon materials are studied in cathodic polarization in nitric acid solutions.

窒素ガス吸着挙動から見たスギ樹皮熱分解物の特性

Japanese cedar (Cryptomeria japonica D. Don) bark was pyrolyzed in a stream of N2 at 573-1273K for 3-12h under atmospheric pressure. Fibers of the cedar bark that mainly comprise cellulose, hemicellulose and lignin shrunk during heat treatment. However breaking down of the fibers was not observed during the pyrolysis, leading to the formation of fibrous carbon materials from cedar bark. The development of micro porosity was observed for the materials pyrolyzed at temperatures above 773K. The increase in specific surface area and total pore volume was due to the selective formation of micro pores which were distributed sharply around 0.32 to 0.4nm in radius. Analysis of adsorption data by t-plot and αs-plot methods suggest that the properties of the surface of carbonaceous cedar bark pyrolyzed below 873K are quite different from those of typical carbon black, while those of cedar bark pyrolyzed at 1073-1273K are similar to that of carbon black. It is indicated that organic moiety and functional groups originated from cedar bark may affect the surface characteristics of pyrolyzed cedar bark under relatively mild conditions.

Morphology and texture of silica prepared by sol-gel synthesis on the surface of fibrous carbon materials

Silica materials are synthesized by the sol–gel method including the deposition of tetraethoxysilane on various micro- and nanocarbon fibers. The use of nanofibrous carbon as a template makes it possible to prepare thermally stable mesoporous SiO2 samples with unusually high surface areas (up to 1255 m2/g) and high porosity (up to 5.6 cm3/g). These silica materials and aerogels prepared by supercritical drying have comparable pore volumes. It is found by high-resolution electron microscopy that a thin-wall matrix permeated by channels is a prevailing structure of silica materials. When some catalytic fibrous carbons are used as templates, silica nanotubes can be prepared.

Carbon materials in the treatment of soft and hard tissue injuries.

Carbon-based implant materials are of interest because they are well accepted by the biological environment. Carbon fibrous materials developed in the Department of Special Ceramics of the University of Mining and Metallurgy in Cracow were tested in in vivo studies to determine their influence on the living body. For comparative purposes, different carbon fibers were prepared and subjected to different surface modifications. Carbon materials prepared in the form of braids were implanted in subcutaneous tissue of rabbits and into skeletal muscle of rats. Carbon fabrics were examined as scaffolds in reconstruction of bone defects. The present study examined the synthesis-structure-property relationships of fibrous carbon samples with respect to the tissue response. It was shown that the tissue response depends on the form of the material form, the degree of order of the crystallites, the surface state and microstructural parameters. Carbon fibers with higher crystallinity and a better-organized graphite structure were assimilated by the body with more difficulty and small particles coming from these materials were found in the regional lymph nodes. Low-carbonized carbon fibers (small crystallite size) underwent partial fragmentation and reacted with the biological environment by being gradually resorbed in the implantation site. The presence of acidic groups on the surface of the carbon fibers enhanced phagocytosis of the carbon material by macrophages. Depending on the surface state of carbon fibers different rates of bone wound healing were observed.

Carbon-fibrous-material-supported base catalysts of ozone decomposition

It has been found that a carbon fibrous material characterized by the developed porous structure and predominance of basic surface groups, being a catalyst of low-temperature ozone decomposition, is also a suitable support for liquid-phase base (X −) catalysts (X −=OH −, Br − and I −). The data obtained in the reaction kinetics study at an initial ozone concentration ranging from 3.1×10 −8 to 3.1×10 −7 mol/l show that the support raises considerably the activity of the base catalysts. The catalytic activity decreases in the following series: I −>Br −>OH −.

XPS and TEM study of new carbon material: N-containing catalytic filamentous carbon

N-containing fibrous carbon material prepared by decomposition of CH 4/H 2/pyridine mixtures over Ni–Cu catalysts has been studied by X-Ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM). The essential effect of the decomposition temperature (in the range of 820–1020 K) and reaction mixture composition on the nitrogen content, its chemical state and the texture of produced carbon filaments was found.

Catalysts for sanitary air cleaning from ozone

The results of the kinetic study of ozone decomposition over carbon fibrous materials and metal complex compounds (CuCl 2) supported on them at ozone concentrations in the 3.1 × 10 –8–3.1 × 10 –5 mol/l range are presented. Ozone decomposition occurs mainly in a catalytic way with the steady-state regime attainment depending on CFM physico-chemical as well as structural characteristics and macrokinetic factors of the process. Copper (II) catalyzes decomposition of ozone microconcentrations only. The data obtained can be a base for the development of sanitary air cleaning units and respirators (protective gas-masks).

Electrochemical activity of rhodium complexes supported on fibrous-carbon material

The redox properties of heterogenized RhI, RhII, and RhIII complexes with different, particularly organophosphorus, ligands were studied by cyclic voltammetry (CVA). The support is a carbon-paste electrode based on a fibrous-carbon material and activated carbon. The electrochemical reduction of RhIII produces Rh metal, which further catalyzes hydrogen evolution. After the reduction of water-soluble binuclear RhII complexes, the CVA curves exhibit peaks of electrocatalytic hydrogen evolution and irreversible RhI→RhII oxidation. The RhII complexes with organophosphorus ligands are characterized only by the peak of RhI→RhII oxidation. After reduction, the RhI complexes behave as a pseudo-reverse Rh0/RhI pair. The electron-donating properties of the ligand determine the reversibility of the system. The degree of structurization of the carbon matrix and the presence of phosphorus(v) atoms in it affect the electrochemical activity of the RhII and RhI complexes.

A biomaterial‐based carbon fiber

AbstractAn attempt to convert natural sisal fiber into low cost carbon fibrous materials was made. The pretreatment, pyrolysis and carbonization processes of raw sisal fiber as well as structure and properties of the resultant product were investigated. It was found that the sisal‐based carbon fiber with moderate mechanical performance can be manufactured under the conditions applied. In addition, the application of the obtained sisal‐based carbon fiber serving as functional material is presented.

Sorption of cesium, strontium, lead, and cadmium ions by fibrous carbon sorbents

Medical sorbents are used for reducing the negative effects on humans and animals of radionuclides, toxic metals, pesticides and other technological pollutants, particularly at the site of the Chernobyl accident. Sorbents based on fibrous carbon materials have a special place, especially the enterosorbent (Vaulen) and its modified forms prepared using cellulose hydrate materials. These agents differ from granular sorbents in having more homogeneous composition and structure; they have high internal and external surface areas and good kinetic characteristics for sorption. This property of fibrous carbon sorbents, along with their highly developed and regular porosity, results in rapid contact of the entire surface of the sorbent with the medium, which is important, for example, for the first aid of patients in serious states. Thanks to a complex of valuable properties, fibrous carbon hemo- and enterosorbents are of interest as therapeutic and prophylactic agents for reducing the risk of diseases in unfavorable radioecological conditions. Previous studies have demonstrated that fibrous active carbon (FAC) and fibrous carbon ionites (FCI) have better toxin- and metabolic-sorption and better kinetic characteristics than granular active carbons, which are widely used in clinical practice and are characterized by their selectivity for plasma proteins. In the present report, wemore » compare the properties of the enterosorbent {open_quotes}Vaulen{close_quotes} and its modified forms in terms of sorption of Cs, Sr, Pb, and Cd ions from dilute aqueous solutions of the appropriate salts. 10 refs., 1 fig., 3 tabs.« less

Fibrous carbon materials having a protective oxidation resistant coating

-- A gas-phase method of depositing one- or multiple-component carbide coatings on CFM of various textile structures has been developed. With preservation of the strength and elastic characteristics of the CFM, the thermo-oxidative resistance of the material is increased, plus the temperature range for the decomposition is shifted into the higher temperature region — by 150–250°C as compared with the starting material.

Fibrous carbon materials based on hydrocellulose fibres

Fibrous carbon materials based on hydrocellulose fibres

Investigation of the functional groups on the surface of modified fibrous carbon materials by the potentiometric titration method

-- In the investigated series of specimens of carbon fibre materials of various assortments, properties, and methods of modification, basically carbonyl groups were detected on the surface of the fibres.

Some properties of trypsin on the surface of fibrous carbon materials

-- It has been found that the conditions for preparing carbon fibres, their structure, and the chemical nature of the surface exert an important effect on the process of enzyme adsorption and on its catalytic activity.

Adsorption of methyl iodide and n-hexane on fibrous carbon materials

Adsorption isotherms of n-hexane and methyl iodide on fibrous carbon material (FCM), both uncoated and coated with 5% w/w triethylene diamine (TEDA), were determined in the temperature span from 303 to 318 K using gas-chromatographic technique. The isotherms obtained are of the BET IV type, suggesting multilayer adsorption. Monolayer capacities were determined for unmodified adsorbents only. Due to the mixed adsorption mechanism acting on the modified FCM, the monolayer capacity of this solid has not been possible to evaluate. It was shown that the adsorption of methyl iodide is greater than for n-hexane. Methyl iodide, in addition, has almost four times larger adsorption on FCM-TEDA compared to the bare solid presumably due to the specific reaction between the adsorbate and TEDA. Isosteric heat of adsorption of the two adsorbates exhibits a maximum in the vicinity of the corresponding monolayer surface capacity, approaching the limiting value of the heat of liquefaction at higher surface loadings.

Application of carbon materials in traumatology and orthopedics

Carbon fibrous materials of the “Ural” type, prepared from hydrocellulose fibre, satisfy all the medical and technical requirements for use in medical practice. They have optimum physicomechanical characteristics, do not become torn off by the organism, and do not require a repeated operation for removal.

Catalytic activity of platinum applied on fibrous carbon materials during hydrogenation of carbon monoxide

1. Platinum applied on cloth made of carbon fibers exhibits activity in hydrogenation of carbon monoxide; the activity of the samples is a function of the concentration of platinum in the sample. 2. The amount of platinum applied on the carbon fibers is a function of the acidic-basic properties of the surface of the carbon fibers.

Electric resistance alloying the surface of steel components with a fibrous carbon material

Electric resistance alloying the surface of steel components with a fibrous carbon material