**4. Conclusions**

where th experim For coat presents point on The loga plotted a the slope

he slope is g ental data. T tings produ s a series of n the � �axis arithm of sl against ��� e of this line

giving as �� This ratio is uced with f straight lin s i.e., � � � �

� � � � �. The s obtained in different c nes. The sele

ratio � � of th

n the follow urrent den ected � � ratio

he slope can wing way: nsities, the o must conv

n be pre‐det

termined fo

or fitting the

� against � rds the same

ee), 

� �� versus � quation (5) ected one. 

�������� �� lines towar

��������� ording to E l to the sele

**of Ni‐Al co**

**o‐deposition**

**n**

t 

eof 

presented. I ch converge �� point o adsorption

*<sup>K</sup>* point of

nst �� � . The the � � value

*A*

have been p lines, whic nes, the��� obtain the

plotted again ly equal to

plot of �� verge these 

graph of � ht line. Acc uld be equa

d from the on a straig

 ratio shou

**perimental d**

**deductions**

ual to 0.24, h of straight of these lin ossible to 

*<sup>A</sup>* ratio equal to 0.24, have been presented.

��� �� is p ue is exactl

*A* ratio is 0.24. This value is exactly equal to the *<sup>B</sup>*

 ratio equ on a series apolation o makes it po

ht lines ��� 4. This valu

� �

� �

�� obtained us ��� � lies he obtained

 

 **tion of exp**

idering the well‐fitted o From extra .62. This m

nee**Figure 5.** Graphical representation of experimental deductions of Ni-Al co-deposition system

intersection with *C-*axis is equal to −0.62. This makes it possible to obtain the adsorption

In Fig. 5(b), the logarithm of the slopes of the straight lines lg(tan*φ*) is plotted against lg*J* .

value considered previously for initial curve fitting. Hence, the co-deposition behavior of Ni

Composite electroplating is a two-step process according to Guglielmi's model. At first, solid particles during electro-deposition are surrounded with cloud of adsorbed ions, which are weakly adsorbed at cathode surface by van der waals forces. In the second step, the loosely adsorbed particles become strongly adsorbed onto cathode surface by Coulomb force and consequently entrapped within metal matrix. The main drawback of this model is absence of mass transfer effect during electro-deposition process such as the adsorption of ionic species on the particle surface, the nature of particle, the ions to be reduced, the bath components, and

Bonino et., al. in their model uses statistical approach that Gugliemi neglected [35]. The model describes the amount of particles that are likely to be incorporated at a given current density. Mass transport of particles is proportional to the mass transport of ions on the working electrode. Volume ratio of particles in the metal deposit will increase under charge transfer

A widely accepted model is developed by Kurozaki, which includes the transport of solid particles from the solution to the cathode surface by agitation. This model is developed in the

**•** Uniform dispersed particles are transported to the electric double layer via mechanical

**•** Charged particles are transported to the cathode surface by electrophoresis.

It is clear that experimental data can be well-fitted on a series of straight lines, which converge

�� �� � nes ������ � �� ��versu o�� � � � �. Th

lopes of lin �**,** i.e., ����� e is equal to

 

**Graphical**

**representat**

results cons ta can be w the �‐axis. qual to −0

toward the same point on the *C* -axis. From extrapolation of these lines, the <sup>−</sup> <sup>1</sup>

he slopes of so the � � r

19

f the straigh atio is 0.24

erimental r imental dat point on t *‐*axis is eq

In Fig. 5(a), the experimental results considering the *<sup>B</sup>*

arithm of th s 0.76 and 

−Al system is in good agreement with the Guglielmi's model.

K. 

control and decrease under mass transport control.

The slope of this line is 0.76 and so the *<sup>B</sup>*

the hydrodynamic conditions.

following steps:

agitation.

 

52 Electrodeposition of Composite Materials

**Figure 5 system**

**5a and 5b:**

(a), the exp that experi the same tion with *C* nt value of (b), the log f this line i

In Fig. 5( is clear toward intersect coefficie In Fig. 5 slope of

coefficient value of K.

The rate of embedding nanoparticles in matrix solution onto metal deposit depends on the applied current density, hydrodynamics and characteristics of the particles. High incorpora‐ tion rates have been confirmed by using:


Various electro-deposition techniques (direct current, pulsed direct current, and pulsed reverse current) have been employed to incorporate nano-sized particles into metal deposits. These techniques have enabled the fabrication of composite coatings with diverse properties not available with pure metal or alloy coatings. It has been established that pulse current deposition technique compared to direct current deposition for the production of nanocomposite showed more refined surface microstructure and increased incorporation rate into the metal deposit.

Inorganic (inert) nanoparticles are used as second phase in composite coating. They possess good chemical stability, high micro-hardness and good wear resistance and enhance corrosion resistance in the composite coating. They modify crystal growth to form a nano-crystalline metal deposit and also cause a shift in the reduction potential of a metal ion.

Agglomeration of nanoparticles occurs under condition of greater attraction energy. The adverse effect can be reduced or eliminated by controlled application of ultrasonic agitation, surfactants, and pulse reverse direct current.
