Page 80 - IJB-6-1
P. 80
Hydrolytic expansion accelerates Fe biodegradation
platform [32,33] . The specific laser melting procedure tests were carried out using micro-indentation
was as follows: (1) Fe/Mg Si powders were put on tester (Shanghai Taiming Optical Instrument Co.
2
the laser melting platform; (2) Fe/Mg Si powders Ltd., China) with a dwell time of 10 s. For each
2
was selectively melted by laser beam; (3) after group, at least four measurements were carried out
laser melting, a descending height was achieved to acquire accurate average values.
through the lifting platform; (4) the steps of (1) –
(3) were continually repeated until the Fe/Mg Si 2.5 Electrochemical tests
2
composites were completely prepared; and (5) an The electrochemical behaviors of Fe/Mg Si
2
air compressor was used for scrubbing samples and composites were tested by an IM6 electrochemical
removing residual powder. In this study, the laser workstation (Zahner, Germany) in simulated
scan rate of 24 mm/s, layer thickness of 100 μm, body fluid (SBF) at 37°C. The SBF with a pH
and laser power of 90 W were used as the melting of 7.4 contained 8.035 g·L NaCl, 0.225 g·L
−1
−1
parameters for good formality during experiments. KCl, 0.311 g·L MgCl ·6H O, 0.231 g·L
−1
−1
2
2
−1
2.3 Microstructural characterization K HPO ·3H O, 6.118 g·L (CH OH) CNH ,
4
2
3
2
2
2
0.355 g·L NaHCO , 0.292 g·L CaCl ,and 0.072
−1
−1
2
3
Fe/Mg Si composites were mechanically polished, g·L Na SO 4 [2,35] . The typical three-electrode
−1
2
2
thereafter ultrasonically cleaned in ethanol. After cell, containing the saturated calomel electrode
etching in 4% HNO alcohol solution for 40 s, (SCE, reference electrode), the sample (working
3
the metallographic microstructure of Fe/Mg Si electrode), and the platinum electrode (auxiliary
2
composites was observed using an Olympus electrode), was used to perform electrochemical
optical microscope (PMG-3, Japan). The surface tests. The potentiodynamic polarization curves
morphology was characterized by a XL-30FEG of samples were obtained at a rate of 0.25 mV/s
scanning electron microscopy (SEM, Philips, the (−1200 – 100 mV) in SBF. The corrosion current
Netherlands), and the elemental compositions were density (I ) of samples was calculated by tafel
corr
determined by energy-dispersive X-ray spectroscopy extrapolation of the anodic and cathodic part of
(EDS). The phase analysis of Fe/Mg Si composites the polarization curves. Afterward, the I corr was
2
was performed by a Siemens X-ray diffractometer converted into the electrochemical corrosion rates
(XRD, D5000, Germany) with a scanning speed of based on the ASTM G59 standard [36,37] . The surface
8/min from 20° to 90° of scattering angles. morphologies of the samples were examined
using a Wyko NT9100 optical profiler (VEECO,
2.4 Mechanical tests USA) and the surface roughness value (Ra) was
The mechanical properties of Fe/Mg Si simultaneously acquired by the average standard
2
composites were determined by compression, deviation of height values.
bending, and hardness tests. The compression tests 2.6 Immersion tests
were performed on a Zhongluchang Universal
Tester (Model WDW-10H, China) at a strain The immersion tests of Fe/Mg Si composites were
2
rate of 0.05 mm/s according to the ASTM E9-09 performed to study the degradation behavior,
standard . The prepared Fe/Mg Si samples were including corrosion rates, corrosion morphologies,
[34]
2
circular cylinder with a diameter of 8 mm and a and surface composition. The immersion tests were
height of 12 mm. As all the samples were ductile, carried out in SBF . According to the ASTM-
[38]
compression strength was determined by the stress G31-72, Fe/Mg Si samples with an exposed surface
2
at a strain of 30% . Three-point bending tests (cm ) to SBF (ml) ratio of 1:15 were separately
2
[34]
were performed at a speed of 0.05 mm/s on the immersed at 37°C [3,39] . After immersion for 21 days,
Zhongluchang Universal Tester (Model WDW- the samples were first rinsed with deionized water
10H, China). The span of the bending tests was and ethanol, and then dried in hot air. The cross-
12 mm between the two supporting points. Hardness sectional morphologies were observed using SEM.
76 International Journal of Bioprinting (2020)–Volume 6, Issue 1
