electrodeposited

1. ELECTRODEPOSITED NI-BASED
NANOCOMPOSITES

2. ELECTRODEPOSITION
• Electroplating is often also called "electrodeposition“.
• It’s a process using electrical current to reduce cations of a desired
material from a solution and coat that material as a thin film onto a
conductive substrate surface.
• The overall process is also known as electrolysis.

3. OBJECTIVE
• To apply thin films of material to the surface of an object to change
its external properties such as to increase corrosion protection,
increase abrasion resistance, improve decorative quality or simply to
deposit a layer which is part of a more complicated device.
• MECHANICAL PROPERTIES: Mechanical properties of the
electrodeposited film depend to a considerable extent on the types
and amounts of growth-inhibiting substance at the cathode surfaces.
• ADHESION: It is desirable that the substrate and the deposited
metal interdiffuse with interlocking grains to give a continuous
interfacial region.

4. APPLICATIONS
• Decoration: Coating a more expensive metal onto a base metal
surface in order to improve the appearance. Applications are
jewellery , furniture fittings, builders’ hardware and tableware.
• Protection: Corrosion-resistant coatings such as chromium plating of
automobile parts and domestic appliances, zinc and cadmium
plating of nuts, screws and electrical components. Wear-resistant
coatings such as nickel or chromium plating of bearing surfaces and
worn shafts and journals.
• Electroforming: Manufacture of sieves, screens, dry shaver heads,
record stampers, moulds, and dies.
• Enhancement: coatings with improved electrical and thermal
conductivity, solderability, reflectivity etc.

5. • nano-composite coatings can give various properties, such as wear
resistance, high-temperature corrosion protection, oxidation
resistance and self-lubrication, to a plated surface.
• Research on electrodeposition of nano-composite coatings has
been attention directed towards the determination of optimum
conditions for their production, i.e. current density, temperature,
particle concentration and bath composition.

6. ELECTRODEPOSITION OF NI–SIC NANO-COMPOSITE
COATINGS
• EXPERIMENTAL DETAILS:-
• Cathodes, made of copper were positioned in vertical plane with
anode. A platinum plate was used as the anode.
• Analytical reagents and distilled water were used to prepare the
plating solution. Prior to plating, the SiC nano-particulates of a mean
diameter 50 nm with concentration of 1–20 g L−1 were dispersed in
the electrolyte in the presence of saccharine.

7. • Ni–SiC composites have been commercialized for the protection of
friction parts, combustion engines and casting moulds.
• The effects of the incorporated SiC on the cathodic efficiency of
bath, corrosion and wear resistance of the nanocomposite coatings
were analyzed.
• The dependence of SiC nano-particulates amount in the nano-composite
coatings was investigated in relation to the SiC
concentration in bath, cathode current density, stir rate and
temperature of plating bath and it is shown that these parameters
strongly affected the volume percentage of SiC nano-particulates.

9. • This can be attributed to
polarization at surface of
cathode with increasing
current density
and temperature.

10. • When the SiC nano-particulates
collide at the
cathode surface, the conditions
for deposit formation are
established and so the
cathode efficiency increases.

11. • where a higher particle
concentration in the electrolyte
increases the adsorption, thus
resulting in a higher weight
percent of SiC nano-particulates in
composite coatings, while the
decrease in the weight percent of
the SiC nano-particulates at a
concentration of SiC
nanoparticulates above 5 g/ L is
attributed to the agglomeration of
the SiC nano-particulates in the
electrolyte owing to their poor
wettability.

12. • Increasing the stirring rate up to 120 rpm causes to increase the
percent of SiC nano-particulates but when the stirring rate is too
high, the decreasing trend of the weight percent is principally caused
by the collision factor. At a high-stirring rate, because of turbulent
flow in bath, the SiC nano-particulates on the cathode surface are
washed away and thus the SiC nanoparticulates percent in
composite coating decreases.

13. • Before the maximum the increasing
percent of SiC nano-particulates can
be attributed to the increasing
tendency for adsorbed particles to
arrive in the cathode surface.The
process is controlled by the
adsorption of the particles and the
particle deposition is dominant.
• When current density is greater than
20 mA/cm2, the decreasing trend
can be explained by the fact that an
increase in current density results in
more rapid deposition of the metal
matrix and fewer particles are
embedded in the coating. Hence,
the metal deposition dominates the
deposition process.

14. • Below 50 ◦C, the activity of
particulates increases with
increasing the temperature of
bath. However, as the temperature
of bath is higher than 50 ◦C, the
thermodynamic movement of the
ions is greatly enhanced, which
results in increasing the kinetic
energy of particulates. increasing
the temperature leads to the
decrease in the adsorpability of
the particulates and hence to
decrease the overpotential of the
cathode and the electric field,
which makes it harder for the
particulates to be embedded in the
matrix and subsequently leads to
a decrease in the weight percent
of the SiC nano-particulates in the
composite coating.

15. SEM morphology of
nickel coating.
SEM morphology of
Ni–SiC nano-composite
coating.

16. • The figure reveals that the pure nickel deposit has exhibited
irregular polyhedral crystals. The incorporation of SiC nano-particulates
has modified the surface to particulate like
crystals. The change in the morphology can be associated to
the change from preferred orientation to random oriented
composite deposits.
• EDX analysis revealed the uniform distribution of SiC in the
composite. In addition, many nodular agglomerated grains are
seen on the nano-composite coating surface (Fig. 7c).
• It is supposed that the SiC nano-particulates of a uniform
distribution and agglomeration to some extent may contribute
to increase the wear resistance of the Ni–SiC nano-composite
coating.

18. • Fig. shows the variation in the microhardness and wear rate of the
Ni–SiC nano-composite coatings with the content of SiC nano-particulates.
It is seen that the Ni–5% SiC nano-composite coating
has a maximum hardness and minimum wear rate.
• The microhardness of the nano-composite coatings increases with
increasing weight percent of the SiC nano-particulate.Since the SiC
nano-particulates deposited in the nickel matrix could restrain the
growth of the nickel grains and the plastic deformation of the matrix
under a loading, by way of grain fining and dispersive strengthening
effects. The grain fining and dispersive strengthening effects
become stronger with increasing SiC nano-particulates content, thus
the microhardness and wear resistance of the Ni–SiC nano-composite
coatings increase with increasing SiC nanoparticulates
content.

19. Electrodeposition and mechanical properties of Ni–carbon
nanotube nanocomposite coatings
• EXPERIMENTAL PROCEDURE
• Ni–CNT nanocomposite coatings were electrodeposited in a sulfate
Watts bath of the following composition: 260 g/L nickel sulfate
(NiSO4 6H2O), 45 g/L nickel chloride (NiCl2 6H2O), 15 g/L boric
acid (H3BO3), and 0.5 g/L saccharine. To improve MWCNT
dispersion, SDS and HPC were added into the electrodeposition
solutions by varying the amounts of SDS and HPC from 0 to 10 g/L.
• The total amount of SDS and HPC was always kept as10 g/L.
MWCNTs of 10–15 nm diameter, produced by CVD, were used to
form the Ni–CNT electrodeposition solutions.
• Ni–CNT nanocomposites of 50 mm thickness were electrodeposited
on Cu substrates of 2 cm2 cm size at a current density of 40
mA/cm2. During electrodeposition of a Ni–CNT nanocomposite, the
bath was maintained at 40C with mechanical stirring at 500 rpm.

20. FESEM micrographs of the Ni–CNT nanocomposite electrodeposited in a bath containing
dispersion additive of (a) 10 g/L SDS, (b) 7.5 g/L SDS and 2.5 g/L HPC, (c) 5 g/L SDS and 5

21. • Fig. 1 illustrates surface morphologies of the Ni–CNT nanocomposites
electrodeposited in solutions with different amounts of SDS and HPC as
dispersion additives. The MWCNT concentration of the electrodeposition
solutions was maintained as 10 g/L and the total amount of SDS and HPC
was also kept as 10 g/L. Comparing Fig. 1(a) with Fig. 1(e) indicates that
SDS is more effective for MWCNT dispersion than HPC. As shown in Fig.
1(b) and (c), however, incorporation of MWCNTs into Ni matrix was greatly
enhanced by using SDS–HPC mixture with the SDS–HPC weight ratios of
3:1 and 1:1. Such SDS–HPC mixture might modify the surface chemistry of
MWCNTs more suitable for uniform dispersion in the electrolytic bath,
resulting in great increase in the MWCNT content of the Ni–CNT
nanocomposite. SDS–HPC mixture additive affected not only the MWCNT
dispersion characteristics but also the properties of Ni matrix itself. While
the hardness of a Ni coating electrodeposited without MWCNTs in a Watt
bath containing SDS of 10 g/L was 430 Hv, the value of one processed in a
solution with the SDS–HPC mixture of the 3:1 weight ratio increased to 527
Hv.

22. FESEM micrographs of the Ni–CNT nanocomposite electrodeposited in
a bath containing an MWCNT concentration of (a) 1 g/L, (b) 2 g/L, (c)
5 g/L, and (d) 10 g/L.

23. • shows SEM micrographs of the Ni–CNT nanocomposites
processed in the electrodeposition solutions with the
MWCNT concentrations of 0–10 g/L and the 10 g/L SDS–
HPC mixture of the weight ratio of 3:1.
• The Ni–CNT nanocomposites were etched in nitric acid
to remove the surface layer for observation of the internal
morphology. With increasing the MWCNT concentration
in the electrodeposition bath up to 5 g/L, more MWCNTs
were incorporated into Ni matrix. However, microstructure
of the Ni–CNT composite became porous with increasing
the MWCNT concentration in the bath beyond 2 g/L.

25. • The MWCNT content in the Ni–CNT
• nanocomposite became larger and reached a maximum of
• 22.5 vol% with increasing the MWCNT concentration in
• the bath up to 5 g/L. However, the MWCNT content in the
• composite decreased with further increasing the MWCNT
• concentration in the bath beyond 5 g/L, which could be due
• to the agglomeration of MWCNTs in the bath containing
• MWCNTs above the saturation concentration [4]. As the
• MWCNT content decreased and the microstructure
• became substantially porous for the nanocomposite
• processed in the bath containing MWCNTs of 10 g/L,
• mechanical characterization was not conducted for this
• specimen.

26. • With increasing the MWCNT
content of the Ni–CNT
composite to 14.6 vol%, the
fracture stress was improved
from 607 to 780MPa. However,
the fracture stress dropped
drastically to 534MPa for the
specimen with the MWCNT
content of 22.5 vol% as
fabricated in the bath of the
MWCNT concentration of 5
g/L. This might be due to the
porous microstructure ofthe
nanocomposite with MWCNT
content of 22.5 vol%.

27. The morphology of electrodeposited pure nickel and Ni–CeO2 nanocomposite.
(a) Pure nickel; (b) Ni–CeO2 nanocomposites

28. • A pyramid structure as shown in Fig. 1(a) is observed at the surface
of the pure nickel. Whereas, with the addition of CeO2
nanoparticles, the grain size is reduced and the morphology is
changed to the hemispherical grain structure, as shown in Fig. 1(b).
• In the electrocodeposition process, CeO2 particles adsorb cations in
the bath under the high potential gradient. They will then be
transported to the cathode surface by electrophoresis, and will be
further adsorbed onto the cathode surface. This phenomenon
results in: (a) an increase in electrocrystalline potential because the
incorporated nanoparticles decrease the electrical cathode surface;
and (b) the occurrence of new nuclei because the adsorbed
nanoparticles limit the growth of the original crystal grains . It is
considered that both of the factors are favorable for fine grains, and
good surface morphology of the composite.

29. • The microhardness of pure nickel
is about 282.7 Hv. With an
addition of 30 g/L CeO2
nanoparticles, the microhardness
of the deposit increased
significantly to 446.2 Hv.
• The wear height loss of the
composite was 18 micron as
compared to 43 micron for pure
nickel.
• It is known that the microstructure
of the electrodeposit is refined
when nanoparticles are
embedded. It will increase the
load carrying capacity and
improve the resistance for plastic
deformation.

31. • shows the corrosion potential and corrosion current
• obtained from an immersion test with a 3.5 wt.% NaCl
• solution. The results indicate that the nanocomposite
• obtained from the bath containing 30 g l1 CeO2 nanoparticles
• and at the current density of 1 Adm2 exhibits the
• best corrosion resistance. Balathandan et al. reported that
• the corrosion potential and corrosion current of Ni matrix
• reinforced with micron CeO2 particles were 550 mV and
• 4 lA cm2, respectively, which are superior to Ni–ZrO2,
• Ni–PSZ, and pure Ni coatings [9]. In the present experiments,
• the corrosion potential and corrosion current of
• the nanocomposite were found to be 195.458 mV and
• 1.020 lA cm2, respectively, illustrating a significant
• improvement in corrosion resistance over the composite
• with micro-sized particles. It is considered that when
• CeO2 nanosized particles are embedded in the nickel
• matrix, the corrosion path is more seriously distorted as
• compared to micro-sized particles, which is favorable for
• corrosion resistance. In fact, the fine grain structure arising
• from the co-electrodeposition of CeO2 nanoparticles also
• promotes good corrosion resistance as compared to coarse
• grain structure [13,14].