Catalytically grown graphite nanofibers (GNF) are molecularly engineered structures that are produced by the interaction of carbon-containing gases with small metal particles at temperatures around 600°C. The fibrous solids consist of minuscule graphene sheets stacked at various angles with respect to the fiber axis. This arrangement generates a material possessing unique chemical properties because unlike conventional graphite crystals, only edges are exposed. Such a conformation produces a material composed entirely of nanopores that can accommodate small-sized adsorbate molecules, such as hydrogen, in the most efficient manner. In addition, the nonrigid pore walls can expand to accommodate the gas in a multilayer conformation. GNF exhibit extraordinary behavior toward the sorption and retention of hydrogen at high pressures and abnormally high temperatures. In this paper we discuss some of the critical factors involved in the adsorption of molecular hydrogen and the influence that this process exerts on the structural characteristics of the material. In addition, the deleterious effect of water vapor on the performance of the GNF is highlighted.

The hydrogenation of ethylene, 1-butene, and 1,3-butadiene has been used as a probe reaction in an attempt to monitor any possible changes in catalytic behavior induced by supporting nickel on different types of graphite nanofiber support materials. This study is designed to compare the catalytic behavior of the metal particles when dispersed on three types of nanofibers, where the orientation of the graphite platelets within the structures is significantly different in each case. The metal crystallites are located in such a manner that the majority of particles are in direct contact with graphite edge regions. It should be emphasized, however, that there are subtle differences in the spacing between adjacent exposed carbon atoms in the various nanofiber structures. As a consequence, it is highly probable that the atomic arrangement of the surfaces of nickel particles that nucleate on these different graphite edges will be dictated to a large degree by the interaction with the atoms in nanofiber supports. Under such circumstances one might reasonably expect that different crystallographic faces of nickel will be exposed to the reactant gas depending on which type of nanofiber structure is used as the supporting medium. For comparison purposes, the same set of hydrogenation reactions were carried out under similar conditions over γ-alumina supported nickel particles.

Catalytically grown carbon nanofibers are a set of novel structures that are produced by the decomposition of selected carbon-containing gases over metal particles. These conformations consist of nanosized graphite platelets separated a distance of at least 0.34 nm and stacked in various orientations with respect to the fiber axis. Such an arrangement results in a unique structure that is composed of an infinite number of extremely short and narrow pores, suitable for the sequestering of small molecules. We have attempted to capitalize on this blend of properties by using such structures for the selective removal of organic contaminants from aqueous streams. Experimental results indicate that nanofibers possessing a structure in which the graphite platelets are aligned perpendicular to the fiber axis and possessing a high degree of structural perfection exhibit superior selective adsorption properties with respect to removal of alcohols from aqueous media over those displayed by active carbon. Adsorption was enhanced when the carbon nanofibers were initially subjected to a treatment in 1 M hydrochloric acid. In contrast, when this step was carried out in the presence of 1 M nitric acid, the beneficial properties of the nanofibers were effectively suppressed. An analogous series of experiments carried out with nanofibers possessing a structure in which the graphene layers were oriented at an angle with respect to the fiber axis did not result in the same degree of selective capture of the alcohols. A rationale is presented to account for this diverse pattern of behavior.

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We have used a variety of experimental techniques, including high-resolution transmission electron microscopy, X-ray diffraction, and adsorptive decomposition of N2O to examine the characteristics of copper particles dispersed on different types of graphite nanofiber supports. When copper was dispersed on the edge sites of graphite nanofibers the particles adopted a relatively thin faceted morphology; characteristics that are associated with the establishment of a strong metal−support interaction. This behavior is to be contrasted with that observed when the metal was supported on active carbon or the basal planes of graphite. In these cases, the particles tended to acquire a globular geometry typically encountered in systems were there are relatively weak interfacial forces between the metal and the support. Structural modeling of the arrangement of copper atoms on the prismatic and basal plane surfaces of graphite indicated that formation of preferred crystallite orientations occurred at certain support locations. It was found that the atomic arrangement of Cu(110) exhibited the closest match with the graphite “zigzag” face, whereas that of Cu(100) was in register with a section of the “armchair” face configuration. On the other hand, the atomic arrangement of Cu(111) provided a good fit with the graphite basal plane. The ramifications of these features on the impact of different types of graphite nanofiber supports on the catalytic performance of copper are discussed.

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In the current investigation we have used the hydrogenation of ethylene and crotonaldehyde as probe reactions in an attempt to follow any changes in catalytic behavior induced by supporting nickel on different types of graphite nanofiber support materials. The hydrogenation of the α,β-unsaturated aldehyde to the desired product, crotyl alcohol, is a particularly difficult task since there is a strong tendency to hydrogenate both the C=C and C=O in the reactant molecule. This study is designed to compare the catalytic behavior of the metal particles when dispersed on three types of nanofibers, where the orientation of the graphite platelets within the structures is significantly different in each case. The metal crystallites are located in such a manner that the majority of particles are in direct contact with graphite edge regions. For comparison purposes, the same set of hydrogenation reactions were carried out under similar conditions over γ-Al2O3 supported nickel particles.

AWV (OR =0.77, 95%CI =0.75, 0.80). Even after adjusting for all the covariates, women with a cancer history were significantly less likely to receive AWV (AOR = 0.71, 95% CI = 0.68, 0.74) compared to those without cancer history. In addition, those aged 66 to 79 years and with comorbidities were more likely to use AWV compared to their counterparts. Conclusions: In this first population-based study, one in 10 older women with a cancer history used AWV. Our study findings highlight the very lowuptake of AWV among older women with and without cancer during the initial years of ACA. Future studies need to explore barriers to AWV and develop targeted interventions to improve AWV rates among women diagnosed with cancer .