Page 12 - MSAM-3-1

Materials Science in Additive Manufacturing Preparation and modification of porous Ti

A B

C

Figure 4. Classification of the foaming method and the morphology of the prepared samples. (A) Classification of slurry foaming method. (B) Principle
of preparation of porous titanium alloy by foaming method. (C) Porous titanium with different porosity obtained by the slurry foaming method and its
microstructure. Copyright © 2009 Elsevier. Reprinted with permission from Elsevier.
44
surfactant (Hypermer KD-6) and poly(vinyl alcohol) was removed at 200°C, the porous titanium scaffold was
(PVA) to form TiH2 suspension, which was poured into prepared at 1000°C. After sintering, NaCl was removed by
a mold after creating a large number of bubbles inside the soaking the scaffold in warm water for 24 h, and the porosity
suspension by mechanical stirring, and sintered at 1400°C of the prepared scaffold was about 64%. Mechanical tests
for 2 h to obtain porous scaffolds with 83% porosity, with a showed that the strength of porous titanium with different
strength of 8.9 ± 1.6 MPa. pore shapes varied between 230 and 340 MPa, and the
The foaming process is simple, rapid, and low-cost. modulus was between 3.78 and 6.32 GPa. The results of
However, it is challenging to ensure a pore uniformity in the cell proliferation experiments in vitro showed that the
porous material prepared by this process, and the material roughness and high surface area provided by acute angle
is also prone to crack and fatigue damage. In addition, in Ti/NU and Ti/SC samples significantly improved the
if the material is used as a medical porous implant, the cell viability of the samples. Compared with titanium
residual blowing agent may enter and harm the human alloy, magnesium metal is degradable in the human
body, has better biocompatibility, and has a significant
body. Therefore, this method is predominantly used for the
preparation of porous structures of low-density materials difference in physical properties from titanium metal, so
such as polymer compounds. 47 it is also used as one of the pore-making materials. Luo
et al. used magnesium powder, magnesium particles,
49
3.1.3. Space holder technique and titanium powder as pore-making agents (Figure 5B),
mixed titanium powder with magnesium powder/particles
The space holder method mixes the metal powder and and ethanol adhesive, pressurized the sample to form at
pore-forming agent in proportion, prepares the precursor 400 MPa, heated the sample at 60°C to remove ethanol,
under certain conditions for sintering, and removes the and finally heated the sample slowly to 1150°C for 4 h
pore-forming agent in the sintering process to obtain to remove magnesium powder and complete sintering.
porous metal materials. Commonly used pore-forming Porous titanium with a 35 – 65% porosity was obtained,
agents include hydride, carbide, magnesium, and sodium as shown in Figure 5C. Mechanical experiments showed
chloride. 31 that its strength and Young’s modulus were 22 – 126 MPa
Pore-forming agents’ shape, content, and distribution and 0.063 – 1.18 GPa, respectively. In addition to organic
are the main factors affecting the pore characteristics. As substances and metals, CaCl in inorganic substances is
2
shown in Figure 5A, Haghjoo et al. used urea and cubic also one of the pore-making agents. Yang et al. mixed
50
48
sodium chloride (SC) of two different forms (NU and Ti O and calcium chloride powder with different contents
2
3
SU) as pore-making agents, which were mixed with TiH into cylindrical preforms. It was then transferred into
2
and compacted under a load of 120 MPa. After the urea the crucible, and the bottom was placed with metallic
Volume 3 Issue 1 (2024) 6 https://doi.org/10.36922/msam.2753