H. Mazurek

Low temperature x-ray diffraction study of stage 1 graphite-FeCl3

Abstract The temperature dependence of the (00l) X-ray reflections in graphite-FeCl3 is reported. The c-axis unit cell, Ic, shows a large expansion with increasing temperature, associated with a large relative expansion of the Fe-Cl interplanar distances and a smaller expansion of the graphite-intercalant interplanar distances. The expansion of the Fe-Cl interlayer distance in the stage 1 graphite-FeCl3 compound is in good agreement with that of pristine FeCl3. Within experimental accuracy, no changes in Ic were observed in the temperature range where magnetic transitions have been reported.

The nature of the initial transient in the rate of formation of nickel carbonyl

Abstract The transient in the rate of Ni(CO) 4 formation has been studied as a function of the gas used in the initial heat treatment of the nickel samples. Quantitatively similar transient effects were seen whether the samples were heated in reducing (H 2 , D 2 ) or neutral (He) atmospheres. A mechanism is proposed in which the heat treatment activates the surface; in particular a finite number of low coordination nickel sites are activated. These sites are energetically favored for Ni(CO) 4 formation and are responsible for the transient behavior.

Scanning transmission electron microscopy of multiphases in graphite-alkali metal intercalation compounds

Abstract Structural and micro-analytical evidence is presented for the presence of multiphase regions in graphite-Rb intercalation compounds for stages n ⩾ 2. The intercalate layers are composed of islands of alkali metal, ordered incommensurately with respect to the adjacent graphite layers and embedded in a background of disordered rubidium in the intercalate layer. The results confirm the non-integral stoichiometry of graphite alkali metal intercalation compounds for stages n ⩾ 2.

Multi-phase superlattices and phase transitions in graphite intercalation compounds with Rb, Cs, K, Li

Abstract Recent electron diffraction and real space imaging experiments for alkali metal donor compounds are discussed and are shown to yield strong evidence for the coexistence of multiple phases for the in-plane intercalate structure. Island formation indicates the presence of coexisting multiphases. X-ray fluorescence and dark-field imaging measurements using the scanning transmission electron microscope indicate that the dark islands have a higher alkali metal concentration than the lighter background and that the superlattice diffraction pattern is associated with the islands.

Raman Spectra of Ion Implanted Graphite

Raman spectroscopy is used in a variety of ways to monitor different aspects of the lattice damage caused by ion implantation into graphite. Particular attention is given to the use of Raman spectroscopy to monitor the restoration of lattice order by the annealing process, which depends critically on the annealing temperature and on the extent of the original lattice damage. At low fluences the highly disordered region is localized in the implanted region and relatively low annealing temperatures are required, compared with the implantation at high fluences where the highly disordered region extends all the way to the surface. At high fluences, annealing temperatures comparable to those required for the graphitization of carbons are necessary to fully restore lattice order.