| Structural and Mechanical Behavior of Mechanochemically
Synthesized Nanocrystalline Hydroxyapatite from
Mercenaria Clam Shells |
Anindya Pal,a Avijit Kumar Metya,b Amit Roy Chowdhuryc and Arijit Sinhaa
Pages : 175-181
DOI : 10.1080/0371750X.2020.1792806 |
| Abstract |
| The aim of the present investigation is to develop mechanochemically
synthesized nano-crystalline hydroxyapatite (nHAp) bioceramics using clam
seashells and phosphoric acid by varying the CaO:H3PO4 acid at different
wt% ratios, i.e. 1:0.75, 1:1.0, 1:1.25, 1:1.5 and 1:1.75. The synthesized powders
were characterized using X-ray diffraction (XRD), scanning electron
microscope and high resolution transmission electron microscopy. XRD
results showed that the average crystallite size of the powder varies from
54 to 69 nm with enhancement in its crystallinity from 85 to 96%. An attempt
was laid to access the mechanical behavior of nHAp through indentation at
the micron scale. Microindentation derived properties, viz. microhardness,
fracture toughness, brittleness index and fracture energy showed significant
variation with CaO:H3PO4 mixing ratio due to the evolution of HAp and other
calcium phosphate based phase(s). The fracture behavior illustrated a
considerable improvement with the variation in CaO:H3PO4 mixing ratio.
[Keywords: Clam shells, Mechanochemical, Hydroxyapatite, Microindentation,
Fracture toughness]
Introduction
Hydroxyapatite (HAp, Ca10[PO4]6[OH]2), the main
inorganic component of human hard tissues and bone,
for its excellent bioactivity and compatibility has been
applied widely in the biomedical engineering field.1 HAp
can be successfully prepared from synthetic calcium as
well as different biogenic materials, like coral, seashell
and eggshell using various chemical synthetic routes.2–6
Shells generally consist of three distinct layers and are
mostly composed of calcium carbonate with only a trace
amount of protein. Among different biogenic resources,
seashells have been found to be an attractive candidate
as it contains 95-99% CaCO3 with trace amounts of rear
oxides (SiO2, MgO, Al2O3, SrO, P2O5, Na2O, SO3),
nanoscale arrangement of crystals and high compressive
strength than common mineral crystal.4 Many researchers
had studied the synthesis of HAp powder from seashells
using different methods, viz. ball milling,7–9 wet chemical
synthesis,5, 8, 10, 11 hydrothermal,12 precipitation,13 etc.
Varieties of sea or water based shells, viz. mediterranean
mussel shells,14 sputnik |
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