MECHANICAL PROPERTIES, PHYSICS OF STRENGTH, AND PLASTICITY StructureMediated Transition in the Behavior of Elastic and Inelastic Properties of Beach Tree BioCarbon

Microstructural characteristics and amplitude dependences of the Young modulus E and of inter� nal friction (logarithmic decrement δ) of biocarbon matrices prepared from beech tree wood at different car� bonization temperatures Tcarb ranging from 600 to 1600°C have been studied. The dependences E(Tcarb) and δ(Tcarb) thus obtained revealed two linear regions of increase of the Young modulus and of decrease of the dec� rement with increasing carbonization temperature, namely, ΔE ~ AΔTcarb and Δδ ~ BΔTcarb, with A ≈ 13.4 MPa/K and B ≈ -2.2 × 10 -6 K -1 for T carb 1000°C. The transition observed in the behavior of E(Tcarb) and δ(Tcarb) at Tcarb = 900-1000°C can be assigned to a change of sample microstructure, more specifically, a change in the ratio of the fractions of the amorphous matrix and of the nanocrystalline phase. For Tcarb 1000°C the nanocrystalline phase plays the dominant part. The structurally induced transition in the behavior of the elastic and microplastic character� istics at a temperature close to 1000°C correlates with the variation of the physical properties, such as elec� trical conductivity, thermal conductivity, and thermopower, reported in the literature.