Page 138 - Zmist-n4-2015

Materials are characterized by a grain size or particulate size of up to about 100 nm.
These materials exhibit enhanced mechanical, magnetic, elevated temperature, optical,
and excellent catalytic properties [7]. It was reported that the high-energy ball milling
has been used to improve particle distribution throughout the matrix [8]. The micro-
structure analysis of Al–Al 2O 3 composite produced by mechanical alloying method
was studied in [9]. In [10] the authors synthesized high volume fraction Al–Al 2O 3 nano
composite powders by high-energy milling and studied the characteristics of the milled
powders. X-ray diffraction is a convenient method for determining the mean size of
crystallites in crystalline bulk materials. The first scientist, Paul Scherrer, published his
results in a paper that included what became known as the Scherrer equation in 1981.
This can be attributed to the fact that “crystallite size” is not synonymous with “particle
size”, while X-Ray diffraction is sensitive to the crystallite size inside the particles.
The aim of present work is to prepare aluminium hybrid composite powders that
consist of TiO 2 and Gr by using ball milling process. An attempt was made to calculate
the grain size, lattice strain, stress, lattice space, lattice constant, dislocation density
and unit cell volume of mechanically milled powders. The grain size was calculated by
using Williamson-Hall and Scherrer equations. Microstructure analysis was carried out
to reveal the presence of reinforcement particles during ball milling.
Experimental details. Atomized aluminium (Al) powder size of –325 mesh and
purity of 99.7% supplied by Kemphasol, Mumbai, India was used for the matrix mate-
rial and rutile phase of titanium-di-oxide (TiO 2) and graphite powders supplied by the
Acechemie (India) were used as the reinforcement material. Natural Graphite is a mi-
neral consisting of graphitic carbon. It varies considerably in crystallinity. Natural
graphite is an excellent conductor of heat and electricity. It is stable over a wide range
of temperatures. Graphite is a highly refractory material with a high melting point
(3650°C). The required mass of Al, TiO 2 and Gr were accurately weighed in an electro-
nic weighing machine. The powders were milled for 20 h in a ball mill with a speed of
100 r/min. The vial of the ball mill is made up of high hardened stainless steel material.
Hardened high speed steel balls with a diameter of 10 mm were used and the ball-to-
powder ratio was 1:1. X-ray diffraction analysis was carried out using PANalyti-
calX’Pert X-ray diffractometer CuK α target, (λ = 1.5418 Å) to determine the lattice
space, lattice constant, grain size, lattice strain, stress, dislocation density and unit cell
volume of the milled composite powders by the following equations [11].
The grain size was calculated using Williamson-Hall equation:
 kl
( 2 sine
b cos q =   + ) q, (1)
 t 
where k is the shape factor (0.94); λ is the wavelength of the X-ray used (λ = 1.5406 Å);
θ is the Bragg diffraction angle and β is the FWHM in radian; t is the effective
crystallite size; e is the strain value.
The Scherrer Equation is given by
0.94l
D = . (2)
b cos q

The strain value (e) can be evaluated by using the following relation:
 l   b 
e =     , (3)
-
 D sinq  tan q 
where D is the grain size.
The dislocation density (δ) has been calculated by using the formula:
15e
d = , (4)
aD
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