Combined with an excellent drapability as well as high tensile strength, they are a suitable electrode material e. Carbon fibers are mutable. Thus, we can offer nonwovens with adjusted surface properties and porosity: From pores in the range of micrometers to meso- and micro pores, as closed or open porosity. Many variations are possible, which increase the specific surface area and enable optimization for applications in electrochemistry, catalysis or acoustics.
Carbon fiber textiles are an optimal electrode material for bioelectrochemical technologies. They are biocompatible, offer a high surface area and a good electric conductivity and are highly drapable.
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Furthermore, their surface morphology and chemistry can be modified depending on the needs. We are partner of the MIDES project on research and scale up of microbial desalination for low energy drinking water. SGL Carbon covers the entire value chain of carbon fiber manufacturing. Thus, we can optimize fibers specifically for your needs.
Possible parameters are:. Contact DE EN. Contact 0 Scroll Top. Quick navigation. Reinforced nonwovens for filtration. PDF, KB. Nonwovens reinforced with carbon fiber grid. Woven fabrics as electrode material and catalyst support. Innovative nonwovens as electrode material and catalyst support. Tubular carbon fiber textiles. Seamless carbon fiber cylinder for insulation. PDF, 97 KB. Carbon electrodes for low energy desalination. PDF, 2 MB. Synthetic pitch prepared from the polymerization of naphthalene and its derivatives has attracted much attention recently.
Water was added to remove the residual catalyst in the pitch to achieve high purity. A stable water-in-oil emulsion could be formed while stirring. The optimum viscosity while water was added was 10— centipoise.
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Mochida et al. The existence of methyl groups lowered the softening point and improved the spinnability and stabilization reactivity.
Mitsubishi Gas Chemical Co. Mesophase synthetic pitch can be produced following processes similar to those used for natural pitch. Compared with natural pitch, synthetic pitch has a lower softening point. Therefore, it can be extruded at a lower temperature to avoid the molecular decomposition and the formation of solid particles in spinning. Stabilization must be performed at a lower temperature, but can be at a significantly faster rate at a given temperature compared with anisotropic-isotropic mixtures of natural pitch.
These could significantly reduce the processing cost. Compared with natural mesophase pitch, synthetic naphthalene pitch shows similar molecular weight distributions for anisotropic and isotropic fractions [ , ]. Thus a stable spinning can be achieved more easily. Isotropic pitch containing smaller mesophase spheres was believed to give smaller domains of random orientation in the fiber transverse direction, which could result in higher fiber mechanical properties [ , ]. Kamatsu et al. The resulting carbon fibers from the pitch with finer spheres showed smaller microdomains and thinner fibrils, and exhibited a higher compressive strength of MPa [ ].
The authors did not report the fiber tensile properties. As mentioned earlier, mesophase pitch can be melt spun into precursor fibers. Compared with isotropic pitch spinning, this process needs a higher spinning temperature due to the higher anisotropic content and higher molecular weights. The spinneret needs to be vented to avoid gas bubble formation during spinning. The viscosities of both isotropic and mesophase pitches heavily depend on the temperature and the shear rates [ 1 ].
Compared with synthetic melt spinnable polymers, this high dependency on temperature creates a significantly higher tensile stress in spinning filaments [ 1 ]. The extruded filaments solidify in a very short distance below spinneret, which creates a large velocity gradient in the axial direction. Thus, tension can be formed on the filaments. Some variations, such as temperature gradient across the spinneret face and quenching air speed and temperature, can make the spinning more difficult. An accurate control on the spinning conditions is required to melt spin pitch precursors, which increases the processing cost.
This is because the MP precursor fibers with relatively large diameters are preferred to avoid fiber breakage during spinning. In another investigation, the spinning of mesophase pitch was modified by spinning the pitch upward [ 5 , ]. Due to the density difference, pitch fibers moved upward in the liquid and were dehydrogenated in the higher-temperature liquid layer. Inert atmosphere was on the top of the liquid for carbonization. This process could remove the oxidation step, but no data on extrusion speed and fiber properties has been reported.
A high speed melt blown process has also been investigated to produce carbon fibers [ , ].
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Airflow normal to the direction of the filaments is used to attenuate the fibers. The authors believed that this process could produce low-cost carbon fibers due to the relatively low-cost mesophase pitch, the high carbon yield of the pitch, and the high speed fiber spinning method [ , ]. In order to reduce fiber sticking or fusion and prevent fiber breakage or fluff, silicone oils or fine solid particles including graphite, carbon black, calcium carbonate, oxides, carbides etc.
Similar to PAN precursor fibers, the pitch fibers are infusibilized or oxidized in air at elevated temperatures before being exposed to the final high temperature carbonization treatment. The oxidization temperature should be below the fiber softening point to keep the orientated structure. There is no consent on the function of fiber stretching in this step.
The oxidized pitch molecules contain ketone, carbonyl, and carboxyl groups that lead to the formation of a stronger hydrogen bonding between adjacent molecules.
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The introduction of oxygen containing groups and the formation of hydrogen bonding between molecules facilitate the three-dimensional crosslinking, but hinder the growth of crystallites [ 5 ]. Iodine has been used to reduce the stabilization time and increase the carbon yield for carbon fibers from natural pitch [ , ]. In a patent by Sasaki and Sawaki [ ], the pitch fiber was soaked in a methanol solution of iodine till at least 0.
The fiber was then heated under an oxidizing atmosphere for infusibilization. The infusibilization time was affected by the amount of imbibed iodine but generally could be finished within approximately 10 min. Stabilized fibers are then carbonized and graphitized. The greatest weight loss takes place in the early stages of carbonization. In order to avoid the defects created by the excessive release of volatiles, the fibers are preferred to be pre-carbonized for a brief period of 0. Barr et al. Although graphite layers are aligned along the fiber axis, the transverse structures of a carbon fiber can be different.
Velocity gradients orient the layers radially, circumferentially or randomly.
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It has been reported that a radial crack can form in mesophase carbon fibers with layer planes distributed radially [ 4 ]. The alignments in the precursor fiber are retained in the resultant carbon fiber. Therefore, carbon fiber strength could be improved by adjusting the microstructure in the precursor fiber.
Research has shown that the flaw sensitivity of MP carbon fibers is reduced by varying the microstructure of the pitch precursor fibers [ ]. The microstructure can be modified by changing flow profiles during melting spinning [ 1 ]. A radial cross-section is usually formed through the laminar flow of the pitch melt [ 5 ].
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Petoca Oil Company has used a technique of agitation in the spinneret to impart a randomized distribution for the folded graphene layer planes in the transverse direction [ 22 , , ]. The agitation created a turbulent flow and the produced carbon fibers showed increased tensile strength.
The turbulent flow can also be obtained by different die designs since the flow behavior heavily depends on the shape of the spinneret [ , ]. Spinnerets containing sections with different diameters have shown to be able to change the fiber microstructure [ ]. Since melt flow is dependent on melt viscosity, the change in microstructure can also be obtained simply by changing the spinning temperature. The application of cellulosic fibers including cotton, flax, sisal, and linen, and regenerated continuous fibers as carbon fiber precursors has been studied.
Among them, rayon has been used commercially and investigated most extensively. Rayon is produced from the least expensive cellulose, wood pulp by solution spinning.
The xanthated cellulose is spun into fibers and recovered from the coagulation bath. The research has mostly been focused on modifying the degradation mechanism to increase the carbon yield.