Vital role of hydroxyapatite particle shape in regulating the porosity and mechanical properties of the sintered scaffolds

doi:10.1016/j.jmst.2017.01.008

Abstract

Abstract:

The effect of particle shape on the porosity and compressive strength of porous hydroxyapatite (HA) scaffolds was investigated by sintering the mixture of rod-shaped HA (r-HA) and spherical HA (s-HA) with polyacrylamide used as the sacrificial template. It was found, for the first time, that addition of r-HA into s-HA could exponentially decrease the porosity of sintered HA scaffolds and enhance their compressive strength with the increase of r-HA content. The mechanism, according to the results from scanning electron microscopy and X-ray diffraction, lies in the restriction of s-HA to the grain formation and growth of r-HA during sintering and results in the fusion of r-HA with s-HA. These findings suggest that mixture of r-HA and s-HA might provide a new and facile way to improve the compressive strength of porous HA scaffolds.

Key words: Spherical/rod-shaped hydroxyapatite, Bioceramics, Porous materials, Sintering, Compressive strength

Jinchuan Wu, Changshun Ruan, Yufei Ma, Yuanliang Wang, Yanfeng Luo. Vital role of hydroxyapatite particle shape in regulating the porosity and mechanical properties of the sintered scaffolds[J]. J. Mater. Sci. Technol., 2018, 34(3): 503-507.

Figures/Tables 8

Fig. 1. TEM images and size distribution of r-HA and s-HA particles.

Fig. 2. Preparation process of HA ceramic precursors: (A): ceramic slurry stirred at high speed, (B) formed in cylindrical molds, (C) ceramic precursors.

Table 1 Effect of r-HA/s-HA ratios on the total porosity and compressive strength of HA scaffolds.

PAM/HA in weight	r-HA/s-HA in weight
	100/0		60/40		50/50		40/60		0/100
	Porosity (%)	σ (MPa)	Porosity (%)	σ (MPa)	Porosity (%)	σ (MPa)	Porosity (%)	σ (MPa)	Porosity (%)	σ (MPa)
40/60	37.7 ± 2.0	5.94 ± 0.24	86.0 ± 1.4	1.16 ± 0.07	88.2 ± 0.4	0.33± 0.03	90.0 ± 1.9	0.19 ± 0.01	91.4 ± 0.2	0.08 ± 0.02
33/67	35.6 ± 1.1	7.36 ± 0.32	79.6 ± 2.0	1.72 ± 0.17	82.2 ± 1.2	1.54 ± 0.11	86.6 ± 1.6	0.80 ± 0.02	89.5 ± 1.1	0.10 ± 0.03
29/71	34.5 ± 0.8	9.06 ± 1.34	75.3 ± 2.9	3.60 ± 0.38	77.3 ± 2.0	1.96 ± 0.21	80.1 ± 0.6	1.35 ± 0.09	88.4 ± 0.5	0.14 ± 0.02

Fig. 3. Compressive strength of the porous HA scaffolds as a function of the r-HA content.

Fig. 4. Porosity of the porous HA scaffolds as a function of the r-HA content.

Table 2 Summarized compressive strength for HA scaffolds with different r-HA/s-HA ratios yet identical porosities.

Porosity (%)	r-HA/s-HA in weight
	100/0	60/40	50/50	40/60	0/100
～88	-	-	0.33 ± 0.03	-	0.14 ± 0.02
～86	-	1.16 ± 0.07	-	0.80 ± 0.02	-
～80	-	1.72 ± 0.17	-	1.35 ± 0.09	-

Fig. 5. SEM images of various HA scaffolds sintered from pure r-HA (A, a), mixture of r-HA and s-HA with r-HA/s-HA as 60/40 (B, b), 50/50 (C, c) and 40/60 (D, d), and pure s-HA (E, e). Lower case letters represent the zoom-in images of the corresponding capital letter-labeled scaffold. The PAM/HA ratios are all 33/67.

Fig. 6. XRD curves of various HA scaffolds. The PAM/HA ratios are all 33/67.

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