Surface Nanostructuring of Metallic Materials …
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shape whereas those attached on SMAT TLM alloy are polygonal in shape, which
suggests the ability of the treated alloy to enhance spreading of the hFOB1.19 cells.
In addition, the number of hFOB1.19 cells attached on the surface of SMAT TLM
alloy is much higher than those attached to the untreated alloy. Cell adhesion and
cell proliferation involves four major steps, namely, protein adsorption, cell-material
interaction, cell attachment and spreading. Implants tend to absorb proteins and the
adsorbed protein layer improves implant-cell interactions, which in turn promotes
cell attachment and spreading. Since SMAT TLM alloy promotes adsorption of Fn
and Vn, it is promising that it is likely to improve interaction with the cells and
facilitate its attachment. The enhancement of adhesion and spreading of hFOB1.19
osteoblast cells on SMAT TLM alloy is due to the decrease in grain size, increase
in grain boundary density, higher degree of hydrophilicity and its ability to promote
adsorption of proteins.
Azadmanjiri et al. [57] have studied the viability of human adipose-derived stem
cells after 1 day and 4 days of cell culture on the surface of untreated Ti and those
subjected to SMAT using 3 mm Ø zirconia balls at 20 kHz. The cell density and total
coverage of the cells are much higher on SMAT Ti than the untreated Ti (Fig. 13).
The increase in R a and nanocrystallization of the surface could have exerted a beneficial influence on cell adhesion. The viability of MC3T3-E1 subclone 4 mouse
calvarial pre-osteoblasts cells on low modulus Ti-Nb-Ta-O alloy with two different
microstructures before and after SMAT is studied by Acharya et al. [54]. According
to them, the attachment and proliferation of MC3T3-E1 cells are not influenced by
SMAT of the Ti alloy. Impingement of 500 numbers of 4.75 mm Ø hardened steel
balls on the surface of the Ti alloy has increased the R a from 74 to 95 nm with no
significant change in water contact angle. Hence, it is evident that a higher degree of
hydrophilicity and higher surface energy is warranted to promote cell adhesion and
spreading.
CP-Ti and Ti6Al4V alloy are highly amenable for nanocrystallization by SMAT
unlike the β-phase Ti alloys wherein their microstructure seem to exert a strong
influence. The nanocrystallization of Ti-25Nb-3Mo-3Zr-2Sn (TLM) alloy consisting
of β phase (solution treated) and duplex α + β phases (aged) by SMAT using 2 mm
Ø zirconia balls at 50 Hz for 5 and 30 min, was evaluated by Huang et al. [56].
SMAT has enabled grain refinement resulting in the formation of a nanocrystalline
structure only for the aged TLM alloys consisting of both α and β phases. After
SMAT for 30 min, the average grain size is reduced to 36 ± 3, 30 ± 7 and 26 ± 4 nm
for TLM alloys aged at 450, 550 and 650 °C for 6 h, respectively. On the contrary,
nanostructuring of the surface could not be observed for the solution treated TLM
samples consisting of only the β phase. The much smaller unrecoverable strain is
considered to hinder grain refinement. Instead, a high density of dislocations and
deformation twins are observed at their surface.
The difference in nanocrystallization between the solution treated and aged TLM
alloys stems from the difference in their microstructure. The microstructure of TLM
alloy aged at 450 °C for 6 h reveals the presence of uniformly distributed nanosized α cobbles, which offers it higher strength. The microstructure of TLM alloys
aged at 550 and 650 °C for 6 h, reveals the presence of α needles with non-uniform
489
shape whereas those attached on SMAT TLM alloy are polygonal in shape, which
suggests the ability of the treated alloy to enhance spreading of the hFOB1.19 cells.
In addition, the number of hFOB1.19 cells attached on the surface of SMAT TLM
alloy is much higher than those attached to the untreated alloy. Cell adhesion and
cell proliferation involves four major steps, namely, protein adsorption, cell-material
interaction, cell attachment and spreading. Implants tend to absorb proteins and the
adsorbed protein layer improves implant-cell interactions, which in turn promotes
cell attachment and spreading. Since SMAT TLM alloy promotes adsorption of Fn
and Vn, it is promising that it is likely to improve interaction with the cells and
facilitate its attachment. The enhancement of adhesion and spreading of hFOB1.19
osteoblast cells on SMAT TLM alloy is due to the decrease in grain size, increase
in grain boundary density, higher degree of hydrophilicity and its ability to promote
adsorption of proteins.
Azadmanjiri et al. [57] have studied the viability of human adipose-derived stem
cells after 1 day and 4 days of cell culture on the surface of untreated Ti and those
subjected to SMAT using 3 mm Ø zirconia balls at 20 kHz. The cell density and total
coverage of the cells are much higher on SMAT Ti than the untreated Ti (Fig. 13).
The increase in R a and nanocrystallization of the surface could have exerted a beneficial influence on cell adhesion. The viability of MC3T3-E1 subclone 4 mouse
calvarial pre-osteoblasts cells on low modulus Ti-Nb-Ta-O alloy with two different
microstructures before and after SMAT is studied by Acharya et al. [54]. According
to them, the attachment and proliferation of MC3T3-E1 cells are not influenced by
SMAT of the Ti alloy. Impingement of 500 numbers of 4.75 mm Ø hardened steel
balls on the surface of the Ti alloy has increased the R a from 74 to 95 nm with no
significant change in water contact angle. Hence, it is evident that a higher degree of
hydrophilicity and higher surface energy is warranted to promote cell adhesion and
spreading.
CP-Ti and Ti6Al4V alloy are highly amenable for nanocrystallization by SMAT
unlike the β-phase Ti alloys wherein their microstructure seem to exert a strong
influence. The nanocrystallization of Ti-25Nb-3Mo-3Zr-2Sn (TLM) alloy consisting
of β phase (solution treated) and duplex α + β phases (aged) by SMAT using 2 mm
Ø zirconia balls at 50 Hz for 5 and 30 min, was evaluated by Huang et al. [56].
SMAT has enabled grain refinement resulting in the formation of a nanocrystalline
structure only for the aged TLM alloys consisting of both α and β phases. After
SMAT for 30 min, the average grain size is reduced to 36 ± 3, 30 ± 7 and 26 ± 4 nm
for TLM alloys aged at 450, 550 and 650 °C for 6 h, respectively. On the contrary,
nanostructuring of the surface could not be observed for the solution treated TLM
samples consisting of only the β phase. The much smaller unrecoverable strain is
considered to hinder grain refinement. Instead, a high density of dislocations and
deformation twins are observed at their surface.
The difference in nanocrystallization between the solution treated and aged TLM
alloys stems from the difference in their microstructure. The microstructure of TLM
alloy aged at 450 °C for 6 h reveals the presence of uniformly distributed nanosized α cobbles, which offers it higher strength. The microstructure of TLM alloys
aged at 550 and 650 °C for 6 h, reveals the presence of α needles with non-uniform