Mechanical Activation Reinforced Porous Calcium Phosphate Cement

doi:10.15541/jim20140618

Abstract

Abstract:

Calcium phosphate cement (CPC) powder was activated by ball milling to improve the mechanical properties of porous CPC scaffolds. The mechanical activation mechanism was investigated by specific surface analyses, X-ray diffraction (XRD) and scanning electron microscopy (SEM). After ball milling, the average particle sizes of BCPC powder decreased while the specific surface area, apparent density, bulk density, and compact density increased when compared with non-activated CPC powder. The porosity and compressive strength of porous CPC scaffolds prepared from ball-milled powders (BCPC-S) were (77.98 ± 0.58)% and (4.11 ± 0.46) MPa, both significantly higher than those non-activated CPC powders (CPC-S), whose porosity and compressive strength were (64.23 ± 2.32)% and (1.99 ± 0.43) MPa, respectively. SEM revealed that there were two types of pores in the BCPC-S: one ranged a few microns in size and the other ranged several hundred microns. XRD indicated that grain sizes and crystallinities of dicalcium phosphate dehydrate (DCPD), α-tricalcium phosphate (α-TCP), calcium carbonate (CaCO₃) and hydroxyapatite (HA) in BCPC powder decreased, due to the mechanical activation compared to those of the non-activated CPC powders. In addition, the mechanical activation resulted in the conversion of DCPD to dicalcium phosphate anhydrous (DCPA), which promoted the hydration of CPC and the precipitation of HA, and improved the compressive strength of BCPC-S finally. This study provided a potential approach to improve the mechanical properties of porous CaP based scaffold to meet the clinic requirement.

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Key words: calcium phosphate cement, ball milling, mechanical activation, porous scaffold, compression strength

CLC Number:

HUANG Ping, LI Peng, ZHAO Jun-Sheng, QU Shu-Xin, FENG Bo, WENG Jie. Mechanical Activation Reinforced Porous Calcium Phosphate Cement[J]. Journal of Inorganic Materials, 2015, 30(4): 432-438.

Figures/Tables 9

Table 1 The optimal parameter combinations of orthogonal test for CPC-S, BCPC-S and Control-S

Samples	(L/P ratio)/ (mL·g^-1)	C_H2O2/%	pH	T/℃
BCPC-S	1.0	25	8.0	60
CPC-S	0.4	25	8.0	60
Control-S	1.0	0	8.0	60

Fig. 1 Variation of particle size with ball billing time

Table. 2 Apparent densities, bulk densities, compact densities and specific surface areas of BCPC-P and CPC-P(n=6)

Samples	d/(g·cm^-3)	d_B/(g·cm^-3)	d_C/(g·cm^-3)	SSA/(m²·g^-1)
BCPC	2.430 ± 0.138^a	0.498 ± 0.098^b	1.937 ± 0.106^c	15.100
CPC	2.871 ± 0.112^a	0.891 ± 0.127^b	2.135 ± 0.114^c	8.616

Fig. 2 XRD patterns of BCPC-P and CPC-P (a) and XRD patterns of DCPD with different treatments (b) DCPD: Drying at 37℃; DCPD-80℃: Drying at 80℃; DCPD + ethanol - 80℃: Drying at 80℃ after adding 50 mL ethanol; Ball milling DCPD-80℃: Drying at 80℃ after ball milling

Table 3 Grain sizes of different calcium phosphates of BCPC-P and CPC-P

Grain size/nm	DCPD	α-TCP	CaCO₃	HA
BCPC-P	59.42	29.48	33.16	42.59
CPC-P	74.26	51.65	51.85	47.15

Fig. 3 Compression strengths of the CPC-S, BCPC-S and Control-S (a), and typical stress-strain curves (b)

Fig. 4 XRD patterns of CPC-S, BCPC-S and Control-S after hydration for 24 h (a) and relative quantity of α-TCP and HA in BCPC-S, CPC-S and Control-S (b)

Fig. 5 Ptotal and Pmacro of BCPC-S and CPC-S *p<0.05, **p<0.01

Fig. 6 SEM images of cross-section of BCPC-S (a1, a2), CPC-S (b1, b2) and Control-S (c1, c2)

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