Density of intercalated graphite fibers

The density of Amoco P-55, P-75, P-100, and P-120 pitch-based graphite fibers and their intercalation compounds with bromine, iodine monochloride, and copper (II) chloride have been measured using a density gradient column. The distribution of densities within a fiber type is found to be a sensitive indicator of the quality of the intercalation reaction. In all cases the density was found to increase, indicating that the mass added to the graphite is dominant over fiber expansion. Density increases are small (less than 10 percent) giving credence to a model of the intercalated graphite fibers which have regions which are intercalated and regions which are not

Stability of bromine, iodine monochloride, copper (II) chloride, and nickel (II) chloride intercalated pitch-based graphite fibers

Four different grades of pitch-based graphite fibers (Amoco P-55, P-75, P-100. and P-120) were intercalated with each of four different intercalates: bromine (Br2), iodine monochloride (ICl), copper (II) chloride (CuCl2), and nickel (II) chloride (NiCl2). The P-55 fibers did not react with Br2 or NiCl2, and the P-75 did not react with NiCl2. The stability of the electrical resistance of the intercalated fibers was monitored over long periods of time in ambient, high humidity (100 percent at 60 C), vacuum (10 to the -6 torr), and high temperature (up to 400 C) conditions. Fibers with lower graphitization form graphite intercalation compounds (GIC's) which are more stable than those with higher graphitization (i.e., P-55 (most stable) greater than P-75 greater than P-100 greater than P-120 (least stable). Br2 formed the most stable GIC's followed in order of decreasing stability by ICl, CuCl2, and NiCl2. While Br2 GIC's had the most stability, ICl had the advantages of forming GIC's with slightly greater reduction in resistance (by about 10%) than Br2, and the ability to intercalate P-55 fiber. Transition metal chlorides are susceptible to water vapor and high temperature. The stability of fibers in composites differs

Effect of lightning strike on bromine intercalated graphite fiber/epoxy composites

Laminar composites were fabricated from pristine and bromine intercalated pitch based graphite fibers. It was found that laminar composites could be fabricated using either pristine or intercalated graphite fibers using standard fabrication techniques. The intercalated graphite fiber composites had electrical properties which were markedly improved over both the corresponding pitch based and polyacrylonitrile (PAN) based composites. Despite composites resistivities more than an order of magnitude lower for pitch based fiber composites, the lightning strike resistance was poorer than that of the Pan based fiber composites. This leads to the conclusion that the mechanical properties of the pitch fibers are more important than electrical or thermal properties in determining the lightning strike resistance. Based on indicated lightning strike tolerance for high elongation to failure materials, the use of vapor grown, rather than pitch based graphite fibers appears promising

Effect of Heat-Treatment Temperature of Vapor-Grown Graphite Fibers I. Properties of Their Bromine Intercalation Compounds

Vapor-grown graphite fibers, which have been heat treated to 2000, 2200, 2400 2600, 2800 or 3000 ^oC, are treated with bromine vapor at room temperature for two days. The fibers are characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), density and resistivity measurements. Fibers heat treated at any single temperature exhibit a wide range of properties. Bromination products of fibers that have been heat treated to 2600 ^oC and above exhibit a DSC peak near 100 ^oC, which is used as a signature of intercalation. The XRD, density and temperature dependence of the resistivity suggest fibers with regions of pristine graphite and regions of stage-two intercalation compounds. Fiber diameter is found to be an important variable, with fibers having a diameter greater than about 13 μm exhibiting low resistivities (50 μω cm or less) independent of their heat-treatment temperature. The temperature dependence of the resistivity suggests that 6 μω cm is the minimum resistivity of this system unless more uniform intercalation can be achieved

Effect of Heat-Treatment Temperature of Vapor-Grown Graphite Fibers I. Properties of Their Bromine Intercalation Compounds

Vapor-grown graphite fibers, which have been heat treated to 2000, 2200, 2400 2600, 2800 or 3000 ^oC, are treated with bromine vapor at room temperature for two days. The fibers are characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), density and resistivity measurements. Fibers heat treated at any single temperature exhibit a wide range of properties. Bromination products of fibers that have been heat treated to 2600 ^oC and above exhibit a DSC peak near 100 ^oC, which is used as a signature of intercalation. The XRD, density and temperature dependence of the resistivity suggest fibers with regions of pristine graphite and regions of stage-two intercalation compounds. Fiber diameter is found to be an important variable, with fibers having a diameter greater than about 13 μm exhibiting low resistivities (50 μω cm or less) independent of their heat-treatment temperature. The temperature dependence of the resistivity suggests that 6 μω cm is the minimum resistivity of this system unless more uniform intercalation can be achieved