Fabrication of metal-containing carbon fibre based on modified polycarproamide fibre

Fabrication of elementary carbon fibre materials based on graft copolymers of polycaproamide and poly(dimethylaminoethyl methacrylate) was investigated. The possibility of complexation of the graft polymer with Cu²⁺ and VO²⁺ ions was demonstrated and the catalytic activity of the metal complexes obtained in thermooxidation and carbonization of modified PCA was established. It was found that thermooxidation of modified PCA fibre in the presence of copper- and vanadium-containing compounds results in a nonthermoplastic polymer in softer conditions (with respect to the duration of heat treatment) in comparison to the same process without the corresponding treatment of the fibre. The effect of copper- and vanadium-containing compounds on thermooxidation and carbonization of PCA-PDMAEMA graft copolymers results in a nonbrittle, elementary carbon fibre material with a yield of up to 24–28 wt. %, a 72–80 wt. % concentration of carbon, and 14–16% concentration of the metal. Moscow State Textile Academy. Translated fromKhimicheskie Volokna, No. 1, pp. 3–7, January–February, 1999.     

Surface modification of PEEK by UV irradiation for direct co-curing with carbon fibre reinforced epoxy prepregs

Adding a layer of thermoplastic resin on the surface of thermoset composites enables welding as a possible joining method for thermoset composites. Adhesion at the thermoset/thermoplastic interface was achieved by direct co-curing of an UV irradiation treated PEEK film with aerospace grade carbon/epoxy prepregs. The effectiveness of UV irradiation for surface modification of PEEK was characterized using Fourier-Transformed InfraRed (FTIR) spectroscopy and contact angle measurement. The adhesion quality at the thermoset/thermoplastic interface was evaluated using a double cantilever beam test and Atomic Force Microscopy (AFM). UV treatment was found to effectively modify the chemical structure of PEEK surface and improve the wettability, which enables the development of a thermoset/thermoplastic interface by direct co-curing.     

Fabrication of carbon fibre composites for gas separation

The fabrication of monolithic activated carbon fibre composites using isotropic pitch based carbon fibres, and phenolic resin as binder, is briefly described. The dimensional changes during drying, curing, baking and activation stages are presented and discussed. Data on other physical properties of the composites including their permeability and surface area are presented. With respect to gas separation, a technique developed to assess the potential of the composites to separate methane and carbon dioxide is described; the effects of some of the fabricating process variables on performance in CH₄/CO₂ separation is presented and discussed. In particular the effect of the extent of weight loss during activation on the final composite's properties is described.     

Fabrication of short carbon fibre reinforced SiC multilayer composites by tape casting

Silicon carbide multilayer composites containing short carbon fibres (C_sf/SiC) were prepared by tape casting and pressureless sintering. C fibres were dispersed in solvents and then mixed with SiC slurry to make green C_sf/SiC tape. Triton X-100 was found to be the best one for Toho Tenax HTC124 fibres (with water soluble coating) among BYK-163, BYK-410, BYK-2150, BYK-9076, BYK-9077 and Triton X-100 dispersants. C_sf/SiC multilayer composites containing 5 vol.% fibre (mean fibre length of 3, 4.5, and 6 mm) were obtained. Addition of short C fibres seems to worsen the densification process in the C_sf/SiC multilayer composites, whereas anisotropy shrinkage in C_sf/SiC was also observed. Open pores size was increased slightly after the addition of C fibre but it decreased with the mean fibre length. Mechanical properties were affected by high residual porosity. The addition of short C fibre has not changed the crack deflection at weak interfaces. C_sf/SiC multilayer composites containing longer fibres (4.5 and 6 mm) presented higher elastic modulus, bending strength and Vickers hardness as compared to shorter fibres (3 mm). Improved sintering performance and fibre content are necessary to improve mechanical properties.     

Fabrication of a weakly basic chemisorption fibre with aliphatic amino groups

The conditions for fabrication of an anion-exchange fibre with primary and secondary amine groups by preliminary treatment of Nitron fibre with an aqueous solution of hydroxylamine. The effect of the chemical nature of aminating reagents—hydrazine hydrate, ethylenediamine, and triethylenetetramine—on formation of aliphatic amine groups in Nitron fibre was investigated. It was hypothesized that the kinetics of amination is a function of the basicity of the aminating reagent. All-Russian Scientific-Research Institute of Polymer Fibres, Mytishchi. Translated fromKhimicheskie Volokna, No. 3, pp. 25–27, May–June, 1999.     

Fabrication of fibre materials containing a polymeric antimicrobial

The possibility of obtaining fibre materials containing polyhexamethyleneguanidine hydrochloride fixed with glutaraldehyde was investigated. The resistance of the materials obtained to wet treatments simulating the conditions of laundering, which allows using them many times, was demonstrated. The fibre material fabricated on a viscose-Lavsan matrix has high resistance to water treatments. The amount of antimicrobial strongly bound in the fibre material is a function of the type and conditions of fabrication of the material and the molecular weight of the polyhexamethyleneguanidine. Moscow State Textile Academy. Translated fromKhimicheskie Volokna, No. 1, pp. 30–33, January–February, 1999.     

Compression behaviour of a fibre bundle with grafted carbon nanotubes

When carbon nanotubes (CNTs) are grown on carbon fibres, with the goal to increase toughness of a carbon fibre reinforced composite, the compressibility of the carbon fibre bundle or a fabric decreases significantly. The pressure, necessary to achieve the desired fibre volume fraction in a composite, should be increased by several bars. The paper proposes modelling approaches for calculation of the change of compression resistance of the CNT-grafted fibre bundle and fabric. The models use a previously developed algorithm for calculation of the compression resistance of a random assembly of CNTs. Two possible scenarios for the CNT-growth positioning are considered: a CNT assembly that homogeneously fills the free space between the fibres and a CNT assembly that is localised on the surface of the fibres. The model is validated against measurements of the compression resistance of carbon fibre bundles and fabrics with CNTs grown using the CVD method.     

Fabrication of porous carbon monoliths with a graphitic framework

Macro/mesoporous carbon monoliths with a graphitic framework were synthesized by carbonizing polymeric monoliths of poly(benzoxazine-co-resol). The overall synthesis process consists of the following steps: (a) the preparation of polymeric monoliths by co-polymerization of resorcinol and formaldehyde with a polyamine (tetraethylenepentamine), (b) doping the polymer with a metallic salt of Fe, Ni or Co, (c) carbonization and (d) the removal of inorganic nanoparticles. The metal nanoparticles (Fe, Ni or Co) formed during the carbonization step catalyse the conversion of a fraction of amorphous carbon into graphitic domains. The resulting carbon monoliths contain >50 wt.% of graphitic carbon, which considerably improves their electrical conductivity. The use of tetraethylenepentamine in the synthesis results in a nitrogen-containing framework. Textural characterization of these materials shows that they have a dual porosity made up of macropores and mesopores (∼2–10 nm), with a BET surface area in the 280–400 m² g⁻¹ range. We tested these materials as electrodes in organic electrolyte supercapacitors and found that no conductive additive is needed due to their high electrical conductivity. In addition, they show a specific capacitance of up to 35 F g⁻¹, excellent rate and cycling performance, delivering up to 10 kW kg⁻¹ at high current densities.     

Fabrication of nanoporous copper ribbons by dealloying of Al-Cu alloys

Nanoporous copper (NPC) ribbons were synthesized by free corrosion dealloying of Al-Cu alloy ribbons prepared by single-roller melt spinning processing equipment for precursor samples. The components and microstructures of NPC were characterized by utilizing X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray (EDS) analysis. The results show that, the microstructures of the NPC ribbons strongly depend upon the phase constitutions of the starting Al-Cu alloys. In dealloying, Al atoms in the ??-Al phase and Al₂Cu phase can be easily etched off, resulting in the formation of NPC with a homogeneous porous structure, while the AlCu phase can hardly be eroded. Moreover, etching solution and annealing process also have important effects on the dealloying process and morphology of the NPC ribbons.     

Fabrication of sorption-active carbon fibre materials in the presence of ammonium phosphate and its optimization

As a result of studying the adsorption and structural characteristics of carbon fibre materials (CFM), it was found that incorporation of a phosphorous-containing additive in CFM alters the activation process toward formation of a finer and more homogeneous pore structure with an effective pore radius of 0.50–0.88 nm. A method was developed for fabrication of a new variety of sorption-active carbon fibre materials. The method will predetermine original solutions for the entire technological process by ensuring an increase in the yield of final product, significantly expand the raw material base by allowing processing of CFM of different natures, and allow production of sorption-active CFM with improved or previously defined properties. Translated from Khimicheskie Volokna, No. 3, pp. 22–25, May–June, 1998.     

Nonwoven carbon materials from high-modulus viscose fibre waste

Conclusions The possibility of preparing nonwoven carbon materials from wastes in the manufacture of high-modulus viscose fibre has been demonstrated.The regulatable physicomechanical, physicochemical, and electrophysical characteristics of the materials prepared make it possible to use them in various branches of the national economy.Translated from Khimicheskie Volokna, No. 5, pp. 41–42, September–October, 1989.     

Effect of short carbon fibre concentration on microstructure and mechanical properties of TiCN-based cermets

Short carbon fibre (C_f) reinforced TiCN-based cermets (C_f/TiCN composites) were produced by powder metallurgy method with pressureless sintering technology. The phase evolution, microstructure and fracture morphology of C_f/TiCN composites were investigated. The results showed that TiC, TiN, WC, Cr₃C₂ and Mo phases disappeared gradually and diffused into core and rim phases by dissolution–reprecipitation process, finally formed new hard TiCN core phases and complex compound (Cr, W, Mo, Ti)(CN) rim phases, with the sintering temperature increasing. The added C_f did not change the ‘core–rim’ microstructure but improved the mechanical properties of TiCN-based cermets. The C_f/TiCN composite containing 3?wt-% C_f achieved the best comprehensive mechanical properties, with fracture toughness and bending strength increasing by about 14.4% and 30.8%, respectively, when compared with the composite without C_f. Toughening and strengthening mechanisms of C_f/TiCN composite were concluded as crack deflection and branch, as well as the pull-out, fracture and bridging of carbon fibres.     

Heterogeneity of carbon fibre

A range of polyacrylonitrile (PAN) and pitch based carbon fibre types (high, standard and intermediate modulus fibres) have been characterised using both physical and chemical techniques, the results highlighting the heterogeneity of the fibre. Nano-indentation showed variation in stiffness between different fibres of the same type as well as variation along a 20 μm length of a single fibre. Tensile tests showed variance of approximately 25% in tenacity for three different carbon fibre types but less variability in modulus with values from 8% to 19%. Raman spectroscopy showed variation in the graphitic content both between fibres of different origin as well as variation, with 0.5 μm spatial resolution, along the length of a single fibre. Inverse gas chromatography surface energy measurements of larger samples of fibres were carried out using the novel approach of incremental surface coverage by varying the probe molecule concentration and revealed different levels of energetic heterogeneity for PAN based fibres collected at different stages of carbon fibre production. The heterogeneity of the unoxidised fibres (collected after carbonisation) was restricted to about 15% of the fibre surface whereas the surface oxidised fibre sample (collected after the electrolytic oxidation bath) was heterogeneous over more than 30% and the sized fibres were shown to be quite homogeneous.     

Low temperature growth of carbon nanotubes on carbon fibre to create a highly networked fuzzy fibre reinforced composite with superior electrical conductivity

We report a method for the growth of carbon nanotubes on carbon fibre using a low temperature growth technique which is infused using a standard industrial process, to create a fuzzy fibre composite with enhanced electrical characteristics. Conductivity tests reveal improvements of 510% in the out-of-plane and 330% in the in-plane direction for the nanocomposite compared to the reference composite. Further analysis of current–voltage (I–V) curves confirm a transformation in the electron transport mechanism from charge – hopping in the conventional material, to an Ohmic diffusive mechanism for the carbon nanotube modified composite. Single fibre tensile tests reveal a tensile performance decrease of only 9.7% after subjecting it to our low temperature carbon nanotube growth process, which is significantly smaller than previous reports. Our low-temperature growth process uses substrate water-cooling to maintain the bulk of the fibre material at lower temperatures, whilst the catalyst on the surface of the carbon fibre is at optimally higher temperatures required for carbon nanotube growth. The process is large-area production compatible with bulk-manufacturing of carbon fibre polymer composites.     

Natural gas storage in activated carbon pellets without a binder

Activated carbon pellets without a binder from cellulose microcrystals as a raw material were investigated. After compression of the raw materials, the thus obtained raw material pellets were slowly carbonized to 1073 K under nitrogen. To activate them, the carbon pellets were heated to 1173 K under carbon dioxide. The activated carbon pellet shape, after heat treatment, was columnar by using the previous employed compression of the raw material. The total surface area, pore volume, and average pore diameter for all the samples were evaluated from the analysis of N₂ adsorption isotherm data. The total surface area and the pore volume were decreased with an increase in compression pressure under the same heat treatment conditions. On the contrary, the bulk densities of the activated carbon pellets were increased. However, these properties can be easily controlled by changing the sintering temperature and time. The bulk density of sample pellet was 0.56 g/cm³. It is 2.3 times higher than activated carbon powder, which was made without the compression process. The total methane storage capacity at 298 K reached 164 cm³ in 1 cm³ volume of activated carbon pellets at 3.5 MPa.