The Effect of Sintering Temperature on the Microstructural and Mechanical Characteristics of Hydroxyapatite Macroporous Scaffolds Prepared via Freeze-Casting

Abstract

The most important characteristic of biomaterial as bone-repairing material, in addition to biocompatibility and appropriate porosity, is providing mechanical strength complying with injured tissue. In the present work, slurry with 15 vol% HA prepared from calcinated hydroxyapatite. The prepared slurry freeze casted unidirectionally with the cooling rate of 8°C/min from the ambient temperature. Then, green bodies freeze-dried for 72h following with sintering at different temperatures of 1250-1350°C with intervals of 25°C. The results showed that lamella space and porosity decreases with temperature while compressive strength and shrinkage goes up. Total porosity has a range of 75-83% while has a compressive strength of ~2-8 MPa. The sintered sample at 1350°C, with 75% porosity, which has a ~ 8 MPa compressive strength, chose to be the optimum. Also, some dendritic branch like structure and bridges can be seen on the internal walls of lamellae which can improve mechanical properties. These features may improve adhesion and growth of osseous cells.

A meta-analysis of the mechanical properties of ice-templated ceramics and metals

“…Color code: blue: no defects [26–31, 33, 36, 38, 40, 41, 43, 44, 46, 50–55, 61, 64, 65, 67, 68, 70, 71, 73, 77, 78, 85, 90, 91, 94, 98, 100, 103–110, 113, 115, 118, 124–127, 129, 130, 132, 134, 135, 143], yellow: defects [25, 52, 86, 91, 96], white: cannot tell from the published micrographs [37, 39, 49, 56, 91, 95, 96, 119]. …”

“…References for the data: water [8, 12, 26, 27, 31, 33–38, 43–49, 51, 52, 55–61, 68, 69, 72–76, 81, 84, 86–92, 94–101, 103, 104, 111, 113, 116, 119, 124, 128–132, 134, 135], camphene [9, 29, 30, 42, 50, 64–67, 70, 80, 85, 93, 102, 105–109, 114, 115, 117, 118, 120–123, 125–127, 136], TBA [10, 32, 39–41, 53, 62, 63, 71, 77, 78, 82, 83, 110, 137]. The marker size is proportional to the pore size.…”

Physicochemical and mechanical properties of freeze cast hydroxyapatite-gelatin scaffolds with dexamethasone loaded PLGA microspheres for hard tissue engineering applications

“…Moreover, 0.5% (w/w) glutaraldehyde-gelatin [6]was added to the solutions before freezing operation for cross linking reactions. In freeze casting technique, freezing operation done by home-made machine as described previously [3,4,6,18,[31][32][33][34].…”

“…There are several methods to fabricate tissue engineering scaffolds; such as freeze casting [3,4,6,18,[31][32][33][34], freeze drying [17,35,36], electrospinning [24,[37][38][39][40][41], gas foaming [42], and phase separation [43][44][45]. Freeze casting is a useful technique to produce unidirectional porous ceramic or/and polymeric constructs.…”

Effects of compressive ratio and sintering temperature on mechanical properties of biocompatible collagen/hydroxyapatite composite scaffolds fabricated for bone tissue engineering

“…It is well known that sintering temperature plays a key role in determining the mechanical and physical characteristics of scaffolds. It is also worth noting that porosity attenuation enhances the mechanical properties of scaffolds [31]. The phase stability of a scaffold is an important consideration in its selection for use in bone tissue regeneration.…”