TY - JOUR
T1 - Ceramics with the signature of wood
T2 - a mechanical insight
AU - Bigoni, D.
AU - Cavuoto, R.
AU - Misseroni, D.
AU - Paggi, M.
AU - Ruffini, A.
AU - Sprio, S.
AU - Tampieri, A.
N1 - Funding Information:
The authors are grateful to Mr. Flavio Vinante (University of Trento) for the invaluable help with the experiments. D.B. and R.C. acknowledge financial support from the PRIN 2015 ‘Multi-scale mechanical models for the design and optimization of micro-structured smart materials and metamaterials’ 2015LYYXA8-006. D.M. M.P. A.R. S.S. and A.T. acknowledge financial support from ERC-2013-ADG-340561-INSTABILITIES.
Publisher Copyright:
© 2019 The Author(s)
PY - 2020/1
Y1 - 2020/1
N2 - In an attempt to mimic the outstanding mechanical properties of wood and bone, a 3D heterogeneous chemistry approach has been used in a biomorphic transformation process (in which sintering is avoided) to fabricate ceramics from rattan wood, preserving its hierarchical fibrous microstructure. The resulting material (called biomorphic apatite [BA] henceforth) possesses a highly bioactive composition and is characterised by a multiscale hierarchical pore structure, based on nanotwinned hydroxyapatite lamellae, which is shown to display a lacunar fractal nature. The mechanical properties of BA are found to be exceptional (when compared with usual porous hydroxyapatite and other ceramics obtained from wood through sintering) and unique as they occupy a zone in the Ashby map previously free from ceramics, but not far from wood and bone. Mechanical tests show the following: (i) the strength in tension may exceed that in compression, (ii) failure in compression involves complex exfoliation patterns, thus resulting in high toughness, (iii) unlike in sintered porous hydroxyapatite, fracture does not occur ‘instantaneously,’ but its growth may be observed, and it exhibits tortuous patterns that follow the original fibrillar structure of wood, thus yielding outstanding toughness, (iv) the anisotropy of the elastic stiffness and strength show unprecedented values when situations of stresses parallel and orthogonal to the main channels are compared. Despite being a ceramic material, BA displays a mechanical behavior similar on the one hand to the ligneous material from which it was produced (therefore behaving as a ‘ceramic with the signature of wood’) and on the other hand to the cortical/spongy osseous complex constituting the structure of compact bone.
AB - In an attempt to mimic the outstanding mechanical properties of wood and bone, a 3D heterogeneous chemistry approach has been used in a biomorphic transformation process (in which sintering is avoided) to fabricate ceramics from rattan wood, preserving its hierarchical fibrous microstructure. The resulting material (called biomorphic apatite [BA] henceforth) possesses a highly bioactive composition and is characterised by a multiscale hierarchical pore structure, based on nanotwinned hydroxyapatite lamellae, which is shown to display a lacunar fractal nature. The mechanical properties of BA are found to be exceptional (when compared with usual porous hydroxyapatite and other ceramics obtained from wood through sintering) and unique as they occupy a zone in the Ashby map previously free from ceramics, but not far from wood and bone. Mechanical tests show the following: (i) the strength in tension may exceed that in compression, (ii) failure in compression involves complex exfoliation patterns, thus resulting in high toughness, (iii) unlike in sintered porous hydroxyapatite, fracture does not occur ‘instantaneously,’ but its growth may be observed, and it exhibits tortuous patterns that follow the original fibrillar structure of wood, thus yielding outstanding toughness, (iv) the anisotropy of the elastic stiffness and strength show unprecedented values when situations of stresses parallel and orthogonal to the main channels are compared. Despite being a ceramic material, BA displays a mechanical behavior similar on the one hand to the ligneous material from which it was produced (therefore behaving as a ‘ceramic with the signature of wood’) and on the other hand to the cortical/spongy osseous complex constituting the structure of compact bone.
KW - Fractal porosity
KW - Fracture
KW - Hydroxyapatite
KW - Mechanical properties
KW - Mechanical tests
KW - Strength
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U2 - 10.1016/j.mtbio.2019.100032
DO - 10.1016/j.mtbio.2019.100032
M3 - Article
C2 - 32211602
AN - SCOPUS:85078677505
SN - 2590-0064
VL - 5
SP - 100032
JO - Materials Today Bio
JF - Materials Today Bio
M1 - 100032
ER -