Page 79 - IJB-6-1
P. 79
Shuai, et al.
Schinhammer et al. introduced palladium (Pd) due to the rapid melting and solidification process
into Fe−Mn alloy and found that Pd accelerated Fe (with a cooling rate of 10 – 10 °C/s), as pointed
6
3
degradation through micro-galvanic corrosion . out by Yu et al. Moreover, Dadbakhsh et al.
[20]
[11]
Zhou et al. prepared silicon carbide (SiC) thin stated that selective laser melting possessed an
films on the Fe surface through sandblasting exceptional flexibility to manufacture composites
treatment . They found that surface morphology, with a uniform dispersion of secondary phase
[12]
surface composition, and surface area of Fe were due to laser-based and layer-by-layer natures,
changed, causing higher weight loss. Moravej et simultaneous powder metallurgy [21-23] . Besides,
al. fabricated Fe implants by electroforming and selective laser melting is well known for the
evaluated the degradation behavior in vitro . This capability of directly preparing 3D parts with
[13]
process increased structural defects of Fe, which precise shape [24-29] . This paper aimed to present a
was responsible for the fast corrosion. These Fe- systematic study that investigated the degradability
based implants exhibit a faster degradation rate than of selective laser melting derived Fe/Mg Si
2
Fe in the physiological environment. However, as composites based on their composition variation.
the degradation proceeds, corrosion products will The microstructure and mechanical properties of
gradually accumulate on the substrate, forming the composites were investigated for bone implant
dense protective layers due to their low solubility. applications. In addition, cytocompatibility was
This inevitably impedes or even insulates the also systematically evaluated. This study covered
contact between the solution and the matrix, processes of 3D printing technologies, property
resulting in a slow degradation at the later stage of evaluations of printed implants, interactions of
degradation . MG-63 cells, the composites, etc.
[12]
Magnesium silicide (Mg Si) is a common
2
biomaterial with favorable biocompatibility, 2 Materials and methods
and both of silicon (Si) and magnesium (Mg) 2.1 Materials
are essential elements in the human body,
as reported by Jiang et al. Due to the high Fe powder with a purity of 99.9% was purchased
[14]
chemical activity, Mg Si can rapidly react with from Wuxi Sairui metal powder manufacturing
2
H O, releasing expansive gases . This prompts Co., Ltd. (Jiangsu, China). The powder particle
[15]
2
us to contemplate that if Mg Si is introduced into size was characterized by laser particle analyzer
2
the Fe matrix, the rapid hydrolysis of Mg Si will (Malvern 3000, UK). Mg Si powder was obtained
2
2
expose more area of Fe matrix to the physiological from Shanghai Xianxin New Material Technology
environment. More importantly, the escaped gases Co., Ltd. The Mg Si powder was milled to get a
2
resulted from Mg Si hydrolysis may penetrate small particle size at a speed of 200 rpm for 3 h
2
the dense degradation product layers, which is in a planetary ball mill, and the stainless steel ball
expected to solve the above-mentioned problem to powder ratio was 1:1. Subsequently, Mg Si
2
induced by dense degradation product layers, powder with different mass ratio (0, 0.3, 0.6, 0.9,
thereby endowing the Fe-based implant a rapid and 1.2 wt.%) was mixed with Fe powder using
degradation throughout the degradation process. mechanical stirring followed by milling at a speed
In this work, hydrolyzable Mg Si was cleverly of 200 rpm for 60 min after optimization of the
2
exploited to accelerate Fe degradation. Fe/Mg Si main parameters of mixing time and rotation
2
composites were prepared through selective laser rate. These mixing parameters were beneficial for
melting process, which was also known as one kind relatively better powder mixing performance [30,31] .
of three-dimensional (3D) printing techniques [16,17] . 2.2 Sample preparation
Moving laser can irradiate powder bed with a
rapid solidification rate compared with traditional Fe/Mg Si composites were prepared by a selective
2
method [18,19] , which was beneficial for ensuring the laser melting system, which was composed of a
relative phase stability of samples, which may be laser melting platform, control system, and lifting
International Journal of Bioprinting (2020)–Volume 6, Issue 1 75
