Anisotropy of skeleton structure of highly porous carbonized bamboo and yucca related to the pyrolysis temperature of the precursors

作者：Krzesinska Marta^*

来源：Journal of Analytical and Applied Pyrolysis, 2017, 123: 73-82.

DOI：10.1016/j.jaap.2016.12.024

• Pyrolysis
• Bamboo
• Biomorphous carbons
• Anisotropic structure
• Skeleton properties

In this work, anisotropic properties of skeleton of highly porous monolithic blocks of carbonized stems of bamboo and yucca are discussed in relation to temperature of pyrolysis ranging between 300 degrees C and 950 degrees C. Elastic moduli of skeleton, i.e. of continuous matrix of porous block were calculated using two models: the series model of two-component system and the Knudsen formula relating elastic modulus to bulk porosity. Two models of pore shape were assumed: cuboid and cylindrical. The experimental data of the physical properties previously presented: bulk porosity and dynamic elastic modulus were applied for calculations. The dependence of the skeleton elastic moduli on the temperature of pyrolysis exhibited wide minimum at temperatures similar to 300-400 degrees C. Sharp increase of skeleton stiffness found at temperature similar to 600 degrees C could be interpreted as the phase transition from disordered to ordered structure of pore wall.
Anisotropy of structure of carbonized plants studied was discussed on two levels: (i) macroscopic-description using physical parameters measured along basic directions of a block sample and (ii) microscopic-anisotropy of skeleton structure. Ultrasonic measurements supported an information similar to that obtained previously by means of different methods (XRD, EPR and optical microscopy): ordering of aromatic structures develops with increasing temperature of pyrolysis. However because of their random arrangement solid carbon skeleton is nearly isotropic -anisotropy of carbonized plant structure is mostly due to pore system.

• 出版日期2017-1