Mechanical, chemical, and physical properties of wood and perennial grass biochars for possible composite application

Abstract

Miscanthus, switchgrass, and softwood chip biochars, produced by slow pyrolysis, were characterized to evaluate their properties in light of potential alternative and novel applications. This work investigated specific physical and chemical properties of biochars that have not been previously reported. Atomic force microscopy (AFM), moisture absorption, and electrical and thermal analysis were conducted to demonstrate the mechanical, physical, and chemical properties of biochars. In addition, elemental analysis, specific surface area, Fourier transform infrared in the attenuated total reflectance (FTIR-ATR), and X-ray diffraction were performed. The state-of-art quantitative nano-mechanical measurement yielded a modulus of elasticity of approximately 10 GPa for the wood chip biochar, while the grass-based samples exhibited a comparatively lower modulus of approximately 5 GPa. In addition, the pore blocking phenomenon by water molecules was identified as a cause for atypical behavior of the biochars' moisture absorptions, resulting in wood chip biochar having the lowest equilibrium moisture content of 6.2 wt.%. Results from electrical and thermal conductivity measurements demonstrated relatively lower values in comparison to carbonized biomass.