Simple Method for the Preparation of Composites Based on PA6 and Partially Exfoliated Graphite

In the present work, the preparation of composite systems based on polyamide 6 (PA6) and exfoliated graphite was attempted by applying a simple procedure, which consists of a preliminary dispersion/exfoliation of graphite in the monomer, namely, ε- caprolactam (CL), and a subsequent polymerization of the above system. Atomic force microscopy (AFM) demonstrated specific interactions between CL and graphite surface. The dispersion of graphite in the monomer and polymer was assessed by scanning (SEM) and transmission (TEM) electron microscopy, while mechanical tests allowed to evaluate the influence of graphite on the polymer properties

Expandable Graphite/Polyamide-6 Nanocomposites

Polyamide-6 (PA-6)/graphite nanocomposites were prepared by melt blending, using a variety of graphites, including virgin graphite, expandable graphites and expanded graphite. The resulting nanocomposites were characterized by X-ray diffraction, thermogravimetric analysis, cone calorimetry, and tensile mechanical analysis. Nanocomposite formation does occur, as denoted by the nanometre dispersion of graphite layers in the polymer matrix, and the dispersion depends on the graphite treatment. The material properties of the resulting composites are improved relative to the virgin/unfilled polymer; in particular, there is an enhancement of the thermal stability without any significant deterioration of the mechanical properties

First-principles modeling of the interactions of iron impurities with graphene and graphite

Results of first principles modelling of interactions graphene and graphite with iron impurities predict the colossal difference between these two carbon allotropes. Insertion of the iron atoms between the planes of graphite is much more energetically favourable than adsorption of the iron adatom at graphite or graphene surface. High mobility of iron adatom over graphite surface and within bulk graphite is reported. Calculated values of formation energies for the substitutional iron impurities suggest that iron is more destructive for graphite than for graphene. This effect caused formation of uniform carbon environment of the iron atom inside the multilayer system. In contrast to graphene segregation of the substitutional iron impurities in graphite at the ambient conditions is not energetically favourable. Enhancement of interlayer bonding in contaminated graphite and purity of graphene from iron impurities are also reported.Comment: 14 pages, 3 figures, to appear in phis. stat. solidi (b

Sensing disks for slug-type calorimeters have higher temperature stability

Graphite sensing disk for slug-type radiation calorimeters exhibits better performance at high temperatures than copper and nickel disks. The graphite is heat-soaked to stabilize its emittance and the thermocouple is protected from the graphite so repeated temperature cycling does not change its sensitivity

Utilization of multiple graphene layers in fuel cells. 1. An improved technique for the exfoliation of graphene-based nanosheets from graphite

An improved, safer and mild method was proposed for the exfoliation of graphene like sheets from graphite to be used in fuel cells. The major aim in the proposed method is to reduce the number of layers in the graphite material and to produce large quantities of graphene bundles to be used as catalyst support in polymer electrolyte membrane fuel cells. Graphite oxide was prepared using potassium dichromate/sulfuric acid as oxidant and acetic anhydride as intercalating agent. The oxidation process seemed to create expanded and leafy structures of graphite oxide layers. Heat treatment of samples led to the thermal decomposition of acetic anhydride into carbondioxide and water vapor which further swelled the layered graphitic structure. Sonication of graphite oxide samples created more separated structures. Morphology of the sonicated graphite oxide samples exhibited expanded the layer structures and formed some tullelike translucent and crumpled graphite oxide sheets. The mild procedure applied was capable of reducing the average number of graphene sheets from 86 in the raw graphite to nine in graphene-based nanosheets. Raman spectroscopy analysis showed the significant reduction in size of the in-plane sp2 domains of graphene nanosheets obtained after the reduction of graphite oxide

Graphite ionization vacuum gauge

Triode gauge with electron source, electron collector, and positive ion collector made from either graphite or carbon material extends low-pressure ranges of existing gauges by changing only materials used in construction. Advantages of graphite gauge stem from physical properties of graphite (or carbon)

Understanding the negative thermal expansion in planar graphite–metal composites

The addition of graphitic fibers and flakes as fillers is commonly used to control the thermal expansion of metals. Sintered metal matrix composites with a planar distribution of graphite flakes show a low or negative thermal expansion coefficient perpendicular to the orientation plane of the graphite (z-CTE). Since the metal matrix has a positive isotropic expansion and graphite has a high z-CTE, this effect cannot be explained by a simple model of stapled metal–graphite layers. Instead, a mechanical interaction between graphite and matrix must be considered. With neutron scattering measurements, we show that there is little or no strain of the graphite flakes caused by the matrix, which can be explained by the high modulus of graphite. Instead, we suggest that a macroscopic crumpling of the flakes is responsible for the low z-CTE of the composite. The crumpled flakes are thicker at low temperature and get stretched and flattened by the expanding matrix at high temperature, explaining the reduction in the thermal expansion across the orientation plane

Transition from glass to graphite in manufacture of composite aircraft structure

The transition from fiberglass reinforced plastic composites to graphite reinforced plastic composites is described. Structural fiberglass design and manufacturing background are summarized. How this experience provides a technology base for moving into graphite composite secondary structure and then to composite primary structure is considered. The technical requirements that must be fulfilled in the transition from glass to graphite composite structure are also included