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International Journal of Mechanical Engineering and Technology (IJMET)
Volume 9, Issue 11, November 2018, pp. 1579–1589, Article ID: IJMET_09_11_163
Available online at http://iaeme.com/Home/issue/IJMET?Volume=9&Issue=11
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication Scopus Indexed
OPTIMIZATION OF MILLING PARAMETERS OF PLANETARY BALL
MILL FOR SYNTHESIZING NANO PARTICLES
Subrahmanyam Vasamsetti
Research Scholar, Jawaharlal Nehru Technological University Kakinada and
HOD of Automobile Engineering, Godavari Institute of Engineering & Technology (A),
Rajahmundry, India
Lingaraju Dumpala
Assistant Professor, Department of Mechanical Engineering,
Jawaharlal Nehru Technological University Kakinada, India
V.V. Subbarao
Professor, Department of Mechanical Engineering, Jawaharlal Nehru Technological University
Kakinada, India
ABSTRACT
In this paper an effort is made to find optimum parameters for synthesizing
nanopowders with ball milling. Vertical planetary mill with tungsten carbide (WC)
grinding jar and WC balls were selected for performing milling operation. Rice husk ash
(RHA) prepared in the laboratory by using muffle furnace was taken for milling. Very
important grinding parameters such as milling speed, time of milling and ball to powder
ratio were selected as factors and in each three levels were taken to design the
experimentation. Different mill speeds 250, 375 and 500 rpms as three grinding speeds,
10, 20 and 30 hours as milling time and 5:1, 10:1 and 15:1 grinding balls to powder
rations were chosen as factors of milling. Design of experimentation is done on Taguchi
L9 orthogonal array. The nine results were taken as responses and analyzed using
Taguchi technique and found a predicted value and verified by doing confirmation test
and found close result. The results shown that both increase in milling speed and the time
of milling decreased particle size of the material considerably, but the weight ratio of
grinding ball to powder had shown effect up to10:1 and not shown much effect after that.
Analysis Of Variance (ANOVA) shown error with in allowable limits and proved that the
results were satisfactory.
Keywords: Planetary ball milling, Mechanical attrition, Synthesis of Nano powders,
Optimization of Milling parameters, Taguchi, ANOVA.
Cite this Article: Subrahmanyam Vasamsetti Lingaraju Dumpala and V.V. Subbarao,
Optimization of Milling Parameters of Planetary Ball Mill for Synthesizing Nano Particles,
International Journal of Mechanical Engineering and Technology, 9(11), 2018, pp. 1579–
1589.
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Subrahmanyam Vasamsetti Lingaraju Dumpala and V.V. Subbarao
1. INTRODUCTION
Metal Matrix Composites are widely using in various industries such as Automobile,
Aeronautics, Aerospace etc. The percentage of material utilization in Automobiles, Aeroplanes
and rockets are increasing day-by-day. If the reinforcing elements are in nano size the composites
are called as nanocomposites. Nanomaterials are the future materials [1-6]. Nano materials deal
with the study of properties of much smaller size elements with any one of the dimensions less
than 100 nanometer, their manufacturing, testing, performance and applications at appropriate
areas. Reducing the solid particles less than 100 nanometer size is called Attrition. There are
mainly two approaches of nanomaterial synthesis. 1. Bottom up approach and 2. Top down
approach. As the name indicates in bottom up approach the material is brought down to basic
units (atomic level) and then allowed to combine to nanoscale stable structures called
nanostructures. The techniques such as hydrothermal synthesis, solvothermal method, Chemical
vapor deposition (CVD), thermal decomposition and pulsed laser ablation are the widely
followed bottom up techniques. Though these fabrication methods are quicker, these are much
expensive and needs huge amount of heat. In top down approach initially larger structures are
reduced to nanostructures by mechanical means. Ball milling, etching through mask, X-ray
lithographic cutting, electron beam cutting, photo ion beam cutting and by the application of
severe plastic deformation are the widely used methods in top down approach. These methods
are cheaper than bottom up methods. Though these methods are comparatively slow, widely used
for commercial and research purpose.
Out of all the above methods, ball milling is the widely used nanomaterial synthesis method
due to its simplicity and applicability to wide range of materials preparation [7-15]. Using ball
milling, metallic and ceramic nanostructures are fabricated by mechanical attrition. In this
method kinetic energy from grinding balls is used to reduce the material size. Several types of
ball mills are available in the market. The machines may be attrition mills, vibration mills, pin
mills, vertical axis mills, horizontal mills or rolling mills. In attrition mills the bowl is kept
stationary and the material with grinding balls is rotated with impeller [16-18].
The ball mills can be classified into two categories according to the axis of rotation of the
bowl. 1. Vertical axis and 2. Horizontal axis.
Figure 1 Direction of rotations of drums in (a) Vertical and (b) Horizontal axis ball mills
In Vertical axis ball mill, the drum with material to be ground and grinding balls rotates about
its own axis and revolves about disc or table’s vertical axis, where as in case of horizontal axis
ball mill, the drum rotates about horizontal axis as shown in fig. 1.
Several researchers employed ball milling successfully for synthesizing nanostructures of
different materials or to study the structural changes in the materials during ball milling [19-28].
Wen-Tien et al developed mesoporosity in eggshell and characterized by milling with planetary
ball mill [29]. Hui Li et al studied characteristics of fly ash on ball milling [30]. Hiroshi Mio et
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Optimization of Milling Parameters of Planetary Ball Mill for Synthesizing Nano Particles
al simulated balls specific impact energy with Discrete Element Method (DEM) and also
simulated ball mill computationally using scale-up method [31, 32]. Jin-Hua Dong et al studied
dynamic simulation of small planetary ball mill using virtual prototype technology ADAMS
(Automatic Dynamic Analysis of Mechanical System) [33]. Lu Sheng-Yong et al simulated ball
motion and also estimated conditions for standard operation to get better energy transfer [34]. L.
Guzman et al applied PFC a 3D software tool for simulating planetary ball mill [35]. F.J. Gotor
et al found various parameters influencing milling with planetary mill [36]. M. Broseghini et al
simulated the jar shape effect on efficiency of planetary ball mill [37, 387]. P.P. Chattopadhyay
et al mathematically analyzed mechanics of planetary ball milling [39, 40]. Y.T. Feng et al
simulated the dynamics of planetary ball milling using DEM [41]. A. Yazdani et al estimated
temperature, energy and particle size in planetary ball mill [42]. M. Abdellaoui et al modeled
planetary ball mill kinematically and studied mechanical alloying in planetary ball mill [43].
2. EXPERIMENTAL PROCEDURE
2.1. Methodology
Vertical axis ball mill is also called as planetary ball mill which is widely used in laboratories. A
generalized planetary ball mill which is used in laboratories is as shown in fig. 2.
Figure 2 a. Planetary ball mill, b. Bowl charged with material and grinding balls and c. Bowl locked in
position
The ball mill consists of a bowl or also called grinding jar, made with hard material such as
stainless steel or tungsten carbide (WC). The bowl consists of a cap with same material that can
be firmly locked in position by locking mechanism. Hard metal grinding balls similar to jar
material i.e. stainless steel or WC are kept in bowl with the material to be ground. The bowl is
mounted at the end of a rotating disc or also called table, and is allowed to revolve with the disc
and also rotates about its own axis but in opposite direction as shown in fig. 3. That is if the disc
rotates in clock wise direction, then the bowl rotates in anti-clock wise direction. Due to two
different motions the vertical milling machine is also called as planetary ball mill. There may be
more than one bowl for increasing output.
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Subrahmanyam Vasamsetti Lingaraju Dumpala and V.V. Subbarao
Figure 3 Directions of rotation of bowl and disc
The principle involved in ball milling is that the material which is taken in bowl is subjected
to high energy collisions. So these ball mills are called High Energy Mills (HEM). During ball
milling the material is subjected to severe plastic deformation, fracture and cold welding. The
particle deformation causes change in particle size and fracture breaks particle into smaller size.
Cold welding causes rejoining of particles and increase in size. Due to two opposite directions of
motions of disc and bowl, like and unlike centrifugal forces act on the grinding balls alternatively.
The grinding balls roll over the wall due to like centrifugal forces. The grinding balls impact
among themselves and also against the bowl wall due to unlike centrifugal forces. The material
is subjected to plastic deformation and fractures due to crushing between the grinding balls and
also between the grinding balls and walls of the bowl as shown in fig. 4.
Crushing material
Balls
Figure 4 Crushing of material between grinding balls and wall of bowl and also between the grinding
balls
A large number of process variables affect the performance of ball milling such as milling
time, powder to ball weight ratio, speed of milling, eccentricity of the bowl on the disc, volume
of the material to be grounded, medium, type of mill, jar dimensions, milling temperature, milling
environment etc [44].
2.2. Materials
Rice husk is an industrial waste which is the outer cover of the rice. Since oxidation of rice husk
is exothermic in nature, a huge amount of heat is liberated while burning. So rice husk can be
used as fuel in mini power plants and small scale to medium scale industries such as rice mills,
sugar industries, edible oil industries etc. Rice Husk Ash (RHA) is formed after combustion of
rice husk. RHA is an industrial waste and is used for preparation of bricks for civil constructions.
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