Theoretical X-ray scattering intensity of carbons with turbostratic stacking and AB stacking structures

Order–Disorder in Clay Mineral Structures

We address the problem of the quantitative de- scription of X-ray powder pattern of turbostratically disor- dered layer compounds. The Debye formula is used, which allows the aperiodic description of any arrangement of atoms. With the extension of Yang and Frindt (1996) for the ideal turbostratic case, these calculations are used to gener- ate reference data that are subsequently treated by the Riet- veld method. We are able to show that the case of uncorre- lated turbostratic disorder can be modelled equally well in a periodic supercell approach with a single layer in the super- cell that is suitable for the Rietveld technique. A brief intro- duction of this new model was given as an oral contribution at EUROCLAY 2003 (Ufer et al., 2003). The fundamental principles are described in this article because of its com- plexity. The applicability of this approach to real systems is demonstrated for smectite and corundum mixtures.

Description of X-ray powder pattern of turbostratically disordered layer structures with a Rietveld compatible approach

The production of carbon fibers based on lignin reduces the cost and the environmental impact associated with carbon fiber manufacturing. However, the melt processing of lignin as a carbon fiber precursor is challenging due to its brittleness and limited thermoplastic behavior. For this reason we produce biopolymer blends based on Alcell organosolv hardwood lignin, hydroxypropyl modified Kraft hardwood, and a thermoplastic elastomer polyurethane (TPU). Samples with TPU content greater than 30% showed excellent melt processability and carbonization yield (35% carbon yield for the samples containing 30% of TPU). The thermal properties were analyzed by differential scanning calorimetry, rheology and thermogravimetric analysis. Fourier infrared measurements were utilized to explain the lignin/TPU interactions which governed the thermal and rheological behavior of the blends. SEM analysis showed that the blends produce a homogeneous structure which was void free after carbonization. These structurally compleme...

/pdf/biobased-structurally-compatible-polymer-blends-based-on-edv9y7grgc.pdf

B. E. Warren

Papers

The shape of two‐dimensional carbon black reflections