Both fullerenes and single-walled carbon nanotubes (SWNTs) exhibit many advantageous properties. Despite the similarities between these two forms of carbon, there have been very few attempts to physically merge them. We have discovered a novel hybrid material that combines fullerenes and SWNTs into a single structure in which the fullerenes are covalently bonded to the outer surface of the SWNTs. These fullerene-functionalized SWNTs, which we have termed NanoBuds, were selectively synthesized in two different one-step continuous methods, during which fullerenes were formed on iron-catalyst particles together with SWNTs during CO disproportionation. The field-emission characteristics of NanoBuds suggest that they may possess advantageous properties compared with single-walled nanotubes or fullerenes alone, or in their non-bonded configurations.

No abstract

Graphite materials were prepared from two Spanish anthracites, AF and ATO, by heating at different temperatures within the range 2000−2800 °C. XRD and Raman spectroscopy were employed to characterize the degrees of crystallinity and crystal orientation of the materials. In addition to studying the evolution of typical crystal parameters such as interlayer spacing, d 002, and crystallite sizes, L a and L c , with temperature, this work aimed to evaluate the influence of elemental composition, texture (as measured by optical microscopy), and mineral matter of the raw anthracites on their ability to graphitize. Two temperature segments were discerned during the development of crystallinity. The first segment exhibited major improvements in crystal parameters, which afterward reached a plateau value. Raman parameters indicated that further improvement in crystal orientation could be obtained after heating at the highest temperature (2800 °C). The limiting temperature at which the materials showed their highest degree of structural order, i.e., the temperature at which the plateau was reached, was lower for the most graphitizable anthracite (AF). This anthracite was found to have higher hydrogen and mineral matter (specifically Al, Fe, K, and Si) contents. However, the textural anisotropy of this most graphitizable anthracite was lower than that of the other anthracite under study (ATO). Optical microscopy characterization of the carbonized materials showed that this trend changed after heating the anthracites at 1000 °C, i.e., the anisotropy of the texture in the carbonized AF was higher than that of the corresponding carbonized material prepared from ATO. It was concluded that the structural and textural changes of the anthracites during carbonization, which are related with both their microtexture and hydrogen content, influence the graphitization process.

Anthracites with different mineral matter content and composition but similar organic matter compositionand, therefore, microtexturewere obtained by consecutive immersion in mixtures of organic liquids of increasing density from an anthracite with a low degree of graphitizability, thus reducing the characteristics of the anthracite that affect the graphitization process to the mineral matter. Graphite materials were then prepared by heating the anthracites in the temperature interval of 2400−2600 °C for the purpose of studying the influence of the anthracite mineral matter (amount and composition) on their ability to graphitize. The interlayer spacing (d 002) and crystallite sizes (along the c-axis (L c) and along the a-axis (L a)), calculated from X-ray diffractometry (XRD), as well as the relative intensity of the Raman D-band (I D/I t), were used to assess the degree of structural order of the materials. A progressive increase in this degree of structural order with increasing mineral matter content of the anthracite was observed. The catalytic effect of the mineral matter on the graphitization of the anthracites relies mainly on promotion of the growth of the crystallites along the basal plane. Reasonably good linear correlations between the mineral matter content and the L a value of the material were attained. Among the different constituents of the mineral matter, the clay mineral illite and the iron carbonates ankerite and siderite were observed to be the main active catalyst compounds during the graphitization of anthracites. In addition to the amount and composition of the mineral matter, the distribution of the mineral matter also influences the graphitization process of the anthracite. A fine distribution in the organic matter, such as that in the case of the iron compounds, was observed to improve the catalytic effect of the mineral matter.

The purpose of this research was to study the influence of the temperature, treatment time, and initial coal particle size on the evolution of the structural order of graphite materials that have been prepared from an anthracite at temperatures >2273 K. Crystalline parameters such as the interlayer spacing and crystallite sizes were calculated from X-ray diffractometry measurements. The analysis of the first- and second-order Raman spectra allowed the assessment of the degree of orientation at the outermost layers of these materials. The graphitization of the anthracite happened in two different stages. The temperature of 2673 K seems to be the inflection point for the change in the graphitization rate of the anthracite. Highly crystalline materials were obtained at 2673 K. Temperatures of treatment >2673 K led to minor changes in the degree of structural order of the graphite materials obtained. The initial particle size of the anthracite affected the evolution of the graphitization process with temperature, because of differences in the ratio of particles that contain organic matter and mineral matter associations. The degree of graphitization achieved with this coal was comparable to that of other natural and synthetic graphites.