solidification

Topics: Electroplating, Coatings, Electric current Pages: 8 (1293 words) Published: March 26, 2014
ELECTRODEPOSITED NI-BASED
NANOCOMPOSITES

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.

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.

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.

• 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

.

• Ni–SiC composites have been commercialized for the protection of friction parts, combustion engines and casting moulds.

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.

CATHODE EFFICIENCY VS. CURRENT DENSITY
• This can be attributed to
polarization at surface of
cathode with increasing
current density
and temperature.

CATHODE EFFCIENCY VS. SIC CONC.
• When the SiC nanoparticulates collide at the
cathode surface, the conditions
for deposit formation are
established and so the
cathode efficiency increases.

WT.% SIC VS. SIC CONC.






where a higher particle
concentration in the electrolyte
increases the adsorption.
while the decrease in the weight
percent happens due to
agglomeration of SIC particles and
also due to poor wettability.
Due to high collision factor and
turbulent flow due to high stirring
rate that washed away SIC
particulates leads to decrease in
wt% of SIC.

WT.% SIC VS. CURRENT DENSITY




The process is controlled by the
adsorption of the SIC-particles
and the particle deposition is
dominant.
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.

WT.% SIC VS. TEMP.


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...
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