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Publikācija: Amorphous Calcium Phosphate Offers Improved Crack Resistance: A Design Feature from Nature?

Publication Type Scientific article indexed in SCOPUS or WOS database
Funding for basic activity Unknown
Defending: ,
Publication language English (en)
Title in original language Amorphous Calcium Phosphate Offers Improved Crack Resistance: A Design Feature from Nature?
Field of research 2. Engineering and technology
Sub-field of research 2.5 Materials engineering
Authors Saeed Saber Samandari
Kārlis-Agris Gross
Keywords Amorphous calcium phosphate, Hydroxyapatite, Fracture toughness, Crack initiation, Biomineralization
Abstract Amorphous calcium phosphate (ACP) is found in biological organisms and coated implants, used in calcium phosphate cements, and has been recently confirmed as a precursor in mineralized tissue; however, nothing is known about crack initiation in ACP or its fracture toughness. The objective of this study was to determine the crack resistance of ACP to help understand its role in biological organisms and assist in the design of calcium-phosphate-based implants. ACP was manufactured by quenching droplets to form a bulk sample and individual splats. Testing of Berkovich and cube-corner indenter types revealed that the Berkovich indenter was more suitable, providing ease of crack detection. Nanoindentation was performed on polished ACP and hydroxyapatite (HAp), and cracks were identified with scanning electron microscopy. Additional nanoindentation was done on splats to assess the suitability for testing microarrays used in high throughput discovery of new bioceramics. ACP required about three times more force to initiate a crack compared to sintered HAp, but about nine times more than a single crystal. Crack initiation resistance decreased with increasing grain size. The fracture toughness of ACP was comparable to a single crystal, but higher for nanograined HAp. The crack initiation load can be potentially used for evaluating microsized samples. ACP prevents crack formation, but requires the presence of nanograins to provide a greater toughness. The implications of the higher crack initiation load in ACP are discussed for biological organisms and thermally processed biomaterials such as thermally sprayed and sintered HAp.
DOI: 10.1016/j.actbio.2011.06.048
Hyperlink: http://www.sciencedirect.com/science/article/pii/S1742706111002947 
Reference Saber Samandari, S., Gross, K. Amorphous Calcium Phosphate Offers Improved Crack Resistance: A Design Feature from Nature? Acta Biomaterialia, 2011, Vol. 7, Iss.12, pp.4235-4241. ISSN 1742-7061. Available from: doi:10.1016/j.actbio.2011.06.048
ID 14912