A novel two-step sintering for nano-hydroxyapatite scaffolds for bone tissue engineering

Abstract

In this study, nano-hydroxyapatite scaffolds with high mechanical strength and an interconnected porous structure were prepared using NTSS for the first time. The first step was performed using a laser characterized by the rapid heating to skip the surface diffusion and to obtain the driving force for grain boundary diffusion. Additionally, the interconnected porous structure was achieved by SLS. The second step consisted of isothermal heating in a furnace at a lower temperature (T2) than that of the laser beam to further increase the density and to suppress grain growth by exploiting the difference in kinetics between grain-boundary diffusion and grain-boundary migration. The results indicated that the mechanical properties first increased and then decreased as T2 was increased from 1050 to 1250°C. The optimal fracture toughness, compressive strength and stiffness were 1.69 MPam1/2, 18.68 MPa and 245.79 MPa, respectively. At the optimal point, the T2 was 1100°C, the grain size was 60 nm and the relative density was 97.6%. The decrease in mechanical properties was due to the growth of grains and the decomposition of HAP. The cytocompatibility test results indicated that cells adhered and spread well on the scaffolds. A bone-like apatite layer formed, indicating good bioactivity.

Two-Step Sintering of Ceramics

“…In addition, a modified two-step sintering profile is also reported with a cooling step (to room temperature) in between first and second step sintering [2,13,14]. Especially, this method used different sintering methods at first and second steps [2,14].…”

Microstructure and material properties of porous hydroxyapatite-zirconia nanocomposites using polymethyl methacrylate powders

“…However, its inherent poor mechanical properties have inhibited its applications in heavy load-bearing implants [7][8][9]. To improve the mechanical properties of this class of materials, several research groups have tried to make composites incorporating nano/micro-sized metallic or ceramic particles, such as Ag [10], ZrO 2 and Al 2 O 3 [11], Ti 3 SiC 2 [12] particles, into a ceramic matrix.…”

“…Different types of bio-implants have been widely used for artificial implants. However, the elastic moduli of the widely used bio-implant materials are much higher than that of the cortical bone (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) GPa) [15]. For instance, the moduli of 316L stainless steel [16], Co-Cr alloys [17], Ti alloys [18,19], Al 2 O 3 [15], ZrO 2 [15] and bioactive HAp [20] are about 200 GPa, 210 GPa, 110 GPa, 380 GPa, 200 GPa and 80 GPa, respectively.…”

Low-temperature densification of Mg-doped hydroxyapatite fine powders under hydrothermal hot processing conditions

“…In general, all of the vibrational bands found in the spectra correspond to the main functional groups of PO 4 3-and were assigned to the symmetric stretching mode of P-O (v 1 at 966 cm -wavenumber range of 3200-3600 cm -1 , corresponding to water molecules, formed during the HHP densification treatment. These water molecules were adsorbed on the surface of the packed MgHA particles inside the pellet [34]. No particular differences in the content of water adsorbed at different reaction temperatures was determined by the FT-IR analyses, indicating that the nominal water (10 wt%) kneaded with the MgHA powder reacted completely and a layer of solvated water molecules was produced on the surface of the packed particles under HHP conditions.…”