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VOLUME 11 NO. 2, AGUSTUS 2015 ANALISIS PROKSIMAT DAN NILAI KALOR BRIKET HIBRID (BROWN COAL – SEKAM PADI) DENGAN PEREKAT LIQUID VOLATILE MATTER (LVM) YANG DIPREPARASI DENGAN METODE PIROLISIS Rahmat ., H.M. Jahiding, E.S. Hasan PRODUKSI DAN KARAKTERISASI SENYAWA LIQUID VOLATILE MATTER AMPAS SAGU MENGGUNAKAN METODE PIROLISIS DAN GAS CHROMATOGRAPHY Muhammad Jahiding, W.O.S. Ilmawati, M. Burhan THEORETICAL ANALYSIS OF MICROWAVE SINTERING OF CERAMICS Muhammad Zamrun F PENGARUH TEMPERATUR KALSINASI TERHADAP KAPASITANSI SUPERKAPASITOR PADA KOMPOSIT TIO2-ARANG AKTIF KULIT BIJI METE Muhammad Anas, Hajjah Hunaidah PERCEPATAN REAKSI KIMIA DENGAN PEMANASAN MIKROWAVE I Nyoman Sudiana, Muhammad Zamrun Firihu Ponderomotive Force Generated by Microwaves During Sintering Muhammad Zamrun F, I Nyoman Sudiana
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Abstract Hasil-hasil ekperimen menunjukkan bahwa ada penambahan laju gerak ion maupun atom selama disintering dengan microwave dibandingkan dengan cara konvensional. Namun teori yang memadai belum ada yang bisa menjelaskan secara memuaskan. Pada tulisan ini model untuk nonthermal effect pada gerak ion selama sintering dengan microwave dianalisa. Diperoleh bahwa radiasi microwave couple pada osilasi kekisi frekuensi rendah yang menghasilkan distribusi nonthermal dari phonon. Hal ini memicu percepatan mobilitas ion dan juga lajunya. Model linear osilator yang digunakan menjelaskan kopling antara foton dan osilasi kekisi. Model ini mengindikasikan bahwa nonthermal effect dari microwave lebih kuat pada polycrystalline ketimbang bahan single crystal. Data eksperimen terdahulu digunakan untuk menganalisa hasil.
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JURNAL APLIKASI FISIKA VOLUME 11
NOMOR 2
AGUSTUS 2015
THEORETICAL ANALYSIS OF MICROWAVE SINTERING OF CERAMICS Muhammad Zamrun Firihu Jurusan Fisika, Fakultas Matematika dan Ilmu Pengetahuan Alam, Universitas Halu Oleo, Kendari, Sulawesi Tenggara, 93231 email :
[email protected] ABSTRAK Hasil-hasil ekperimen menunjukkan bahwa ada penambahan laju gerak ion maupun atom selama disintering dengan microwave dibandingkan dengan cara konvensional. Namun teori yang memadai belum ada yang bisa menjelaskan secara memuaskan. Pada tulisan ini model untuk nonthermal effect pada gerak ion selama sintering dengan microwave dianalisa. Diperoleh bahwa radiasi microwave couple pada osilasi kekisi frekuensi rendah yang menghasilkan distribusi nonthermal dari phonon. Hal ini memicu percepatan mobilitas ion dan juga lajunya. Model linear osilator yang digunakan menjelaskan kopling antara foton dan osilasi kekisi. Model ini mengindikasikan bahwa nonthermal effect dari microwave lebih kuat pada polycrystalline ketimbang bahan single crystal. Data eksperimen terdahulu digunakan untuk menganalisa hasil. Keywords: nonthermal effect, diffusi, mikrowave, polycristalline I INTRODUCTION Microwave
processing
of
conventional
sintering. For example,
ceramics have been studied by some
experiments with beta-alumina suggest
scholars in the last decade [1-7]. Some
an
evidences indicated as ‘microwave effects’
energy
were found.. The first remarkable results
sintering,when
of microwave sintering ceramic have
conventional sintering. Specifically, the
been reported by researchers Janney, et
inferred activation
al., at Oak Ridge National Laboratory [2].
conventional process was 575 kJ/mole,
Indeed, their observations go beyond
compared to an inferred activation
these bulk effects,
suggesting that
energy of 170 kJ/mole for the microwave
different microscopic mechanisms for the
process. In FIR Center, University of
motion of ions are responsible for the
Fukui, by using a very high frequency
differences
microwave sintering system of 300 GHz
between
microwave
and
22
apparent of
reduction in activation 70%
during
microwave
compared
with
energy for the
Theoritical analysis…………………………………………………………….. (Muhammad Zamrun Firihu)
calculated the activation energy of
Where j is flux, C is concentration, D is
alumina
the chemical diffusion coefficient,
of
196
kJ/mole.
In
both
is
processes, equal bulk temperatures were
electrochemical potential (all of the i-th
maintained based on
species),
thermocouple
is Boltzmann's constant,
measurements. In similar experiments
and T is the temperature of the solid. As
with
sapphire,
with all phenomenological descriptions
microwave heating was observed to yield
of kinetic processes, Eq. (1) represents
enhanced tracer diffusion kinetics
for
the product of a driving force and a
Moreover, empirically
species mobility: the driving force is the
single
oxygen ions.
crystal
inferred activation energies for ion
gradient
diffusion based on a thermal process
potential; the mobility is contained in the
model were 20% lower for microwave
chemical diffusion coefficient.
versus
mobility involves the motion of point
conventional
heating.
No
in
electrochemical Ionic
fundamental physical mechanisms have
defects, and the chemical
yet
coefficient can be described as a function
been established to explain these
diffusion
phenomena. For oxide ceramics, a
of point defect
physical explanation must concentrate on
point defect mobility. In a thermal
the effect of long wavelength (i.e.,
process, the dependence
low-energy)
that is, one can write:
radiation
on
the
ionic
concentration and is separable;
diffusion that results in the densification of a powder compact. In sintering, the driving force for ionic motion is the decrease in
[defect concentration]·[defect mobility]
(2)
surface energy that occurs
as free surface area is replaced by
for diffusion driven by a Boltzmann
solid-solid
distribution of ionic energies. A corollary
interfaces (i.e., grain
boundaries) [8].
to Eq. (2) is that, for thermal diffusion,
The diffusion fluxes involved
the activation energy Q can be expressed
can be analyzed from a Fick-Einstein
as the sum of that for formation of point
perspective [9]
defects
and that for the mobility
of defects
[10-11]
(1)
(3) The plotting logarithms of microwave
23
Theoritical analysis…………………………………………………………….. (Muhammad Zamrun Firihu) J A F V11 o lN o 2. ( 2 05) 1 22-28 J A F V11 o lN o 2. ( 2 05) 1 22-28
sintering rates against bulk inverse
valid at temperature exceeds the Debye
temperatures
a
temperature for the solid compound. The
thermocouple yields lower slopes than
Debye temperatures for most of the
for
conventional sintering has been
material compounds of interest will
interpreted as a decrease in activation
typically be less than or equal to 300 K)
energy.
The microwave radiation
In addition,
generates
a
phonon
bound electron by an ideal spring. Each
in the (poly) crystalline
electron collectively represents an atomic
lattice and thereby enhances the mobility
electron cloud which can be displaced
of crystal lattice ions. This leads to
from the nucleus by an external electric
enhanced diffusion and to enhanced
field. To model the effect of the
sintering rates. It is also believed that
microwaves, we subject the charges (ion
similar
are
and electron masses) to a sinusoidal
responsible for unusual observations
external electric field. The simplified
reported in
microwave heating
model assumes that all of the ions in the
processes. In this paper, we analyze
lattice chain are identical. Allowing for
theoriticallythe results of a series of
the multiple ion species normally present
microwave
in a compound will quantitatively refine,
distribution
as
measured
nonthermal
nonthermal other
sintering
by
effects
experiments
of
ceramics.
each ion is coupled to a
but not qualitatively alter, the essence of our arguments. Mathematically the system can be described as following equations
II RESULTS AND DISCUSSION In this part, we will discuss models
[9-10],
of effect microwave on solid state oxide
(4)
materials by using previous experimental data [3-4, 6-7,12]. Generally, we are
(5)
looking for the most appropriate coupling formula
between
microwave
and
materials.
where
is the spring constant for
one ion-ion (ion-electron) bond, and
A. Linear coupling to elastic oscillations The model uses a simplified kinetic model for oscillations in a perfect one-dimensional crystal lattice where be
is the mass of a single ion (electron), oscillation
is
the
resonant
frequency for the single
spring connecting two ions, while
24
is
Theoritical analysis…………………………………………………………….. (Muhammad Zamrun Firihu)
the
resonant
frequency for a single
infrared photons, while the electron-ion
ion-electron pair. Strictly speaking, the
bound are characterized by resonant
linear
frequency approaching the optical regime.
force
model is valid only for
small displacements
of the ions (and
for
example,
the
resonant
restrahl
valence electron clouds) relative to their
frequency
equilibrium
ion masses is typically of the order
positions; ,
equilibrium
where
ion
modeling
i.e.,
of a single spring and two
is the
spacing.
Accurately
the
phonon
[11].
this is too
large for direct coupling from microwave photos
characterized
by
frequency
distribution, including the irreversible
. thus, in perfect
thermalization of microwave phonons,
single crystal compounds, should be only
would
slight
require
the
consideration
of
coupling
between
microwave
nonlinear effects. In this model coupled
energy and locally resonant perturbations
linear harmonic oscillators under the
of the ions. In case of polycrystalline
influence
oscillatory
compounds as have been used in our
i.e. the microwave
experimental research materials [3,4,6,7] ,
electric field. Since damping effects are
however, the possibility for weaker
neglected, the system dynamics may be
surface bond modes exists at the various
analyzed and understood in terms of the
microscopic surface and grain boundary
two normal modes of oscillations of the
interfaces. This is especially true for green
lattice driven by the microwave field as
bodies prior to sintering. Hence we can
follows [10,12]:
imagine the possibility of small scale or
Small-resonant coupling. In this approach
localize microwave phonon excitation
the assumption is microwave radiation to
through resonant coupling to weak surface
resonantly
bounds. similarly, in both polycrystalline
of
an
forcing function
external
drive
small-scale
elastic
oscillations, involving only a few ions on
and
a localized scale (such sites could serve as
presence of point defects (vacancies) can
localized
lead
sources
for
propagating phonons).
excitation
of
this is unlikely to
single-crystal to
compounds,
localized
restrahl frequency
ion-ion
effects can be observed.
are
characterized
by
at
frequency much lower than the typically
occur within a perfect crystal lattice, as bonds
resonances
the
resonant frequencies in the range of
25
. So that microwave
JAF Vol 11analysis…………………………………………………………….. No. 2 (2015) 22-28 Theoritical (Muhammad Zamrun Firihu)
Zero-frequency coupling. In this normal
dislocations. It creates localized excess
mode is a zero-frequency mode in which
charges
the center of mass of an aggregate of ions
polycrystalline compounds, the possibility
is displaced by the microwave field [15].
exists
An individual ion’s displacement
microwave-frequency
is
thus,
for
in
stimulating phonons
near
random thermal motions are sufficient to
the center-of-mass motion for
(6)
make substantial changes to ion jump
ions
probabilities and ion mobility [14]. A value of
electrons is determined by the
should
be considered a significant nonthermal
equation
effect, where
(7) where and
lattice;
microwave deviations of ion kinetics from
relative to the
center of mass:
and
the
extended lattice defects. A relative small
the sum of a center-of-mass displacement plus a displacement
in
is
is the equilibrium
lattice ion spacing,
the electric field strength
.
is the net charge on the ion (or
electron cloud). Eq. (7) implies that there
By using experimental data of
will be on coupling to this zero-frequency
sintering of oxide ceramics performed by
mode unless there exists some (local)
Sudiana et al, Aripin, et al, Bykov, et al.
charge imbalance in the chain of coupled
and
atoms-i.e.,
. Associating an
temperatures:
of
grain size: 50-500 nm, the average ion’s
effective
charge
atoms
of
(where
C, average
order
[3],.
microwave-induced
) leads to local displacement of every ion the chain
satisfying
according to :
significant
For
perturbations , which is
deviation
from
thermal
equilibrium. To get order-of-magnitude
(8) where
o
thermal motion involves fluctuations
with a chain of identical (i.e., regular)
Janney, et al., [2-7], i.e. sintering
estimates for the local charge imbalance
represent the fractional charge
concentrations needed to couple to a
imbalance,
zero-frequency mode, we also consider
Local charge will imbalance mostly in
the
free surfaces, grain boundaries, and
experiments
26
sintering
parameter
[3,13-14].
For
of
the
example,
Theoritical analysis…………………………………………………………….. (Muhammad Zamrun Firihu)
based on a measured microwave cavity Q
such as microwave absorption through
of
inverse Brillouin scattering may occurred
,. input power of
kW, volume of
, sample
[14-15].
dielectric constant
(alumina),
.
GHz, it can be
Whether the three approximations
estimated that the electric field strength
discussed above is relevant to the our
was of the order of
experimental parameters. First, it is
and frequency of
V/m
during these sintering experiments. From
expected
(8) for a typical lattice ion spacing of
the overmoded cavity as well the
, significant nonthermal phonon
that
ceramic
scattering within
sample
will
yield
an
k-spectrum
that
is
effects from microwave heating requires
electromagnetic
local
essentially isotropic.
effective
bound-charge
as within
Second,
it
has
. This is
already been established that due to the
consistent with the level of impurities
large cavity Q with high microwave
expected in even the highest commercial
frequency of 300 GHz., the electric field
grades of ceramic powders and compact
strengths within
(e.g., 99.8% for alumina and 97.5 % for
very
silica). Again, it is expected that this
microwave sources can be expected to
effect is more likely to exist locally near
produce a finite spectral bandwidth of
grain boundaries and microscopic surfaces
order
(where impurities concentrate) within
appears feasible
polycrystalline samples than within high
thus nonthermal) transfer of microwave
purity single crystal samples.
energy
concentrations of
occur
Microwave frequencies one can find bulk
phonon
modes
which
the
are
high. Third, most high power
. Hence, that
it
resonant (and
to crystal lattice phonons can between
two
electromagnetic
satisfy
cavity
high
waves
intensity
to
a
low
frequency elastic wave under
the
electromagnetic phase velocities greater
conditions
our
several orders than elastic wave phase
experiments. Recent other theory of
velocity. Thus direct linear coupling
nonthermal effect of microwave radiation
between microwave and elastic wave is
proposed by Rybakov and Semenov
unreasonable. Hence, nonlinear coupling
[15-16].
frequency
matching.
However,
the
should be considered. Nonlinear process
27
present
during
the
Theoritical (Muhammad Zamrun Firihu) JAF Vol 11analysis…………………………………………………………….. No. 2 (2015) 22-28
III CONCLUSION The enhancements in material processing and reductions in apparent activation energy for microwave versus conventional sintering are due to nonthermal phonon distributions excited by the microwave field. These mechanism favor polycrystalline over single crystal where consistent with reported experimental results. The higher temperature condition would enhance the probabilities these mechanisms. The experimental data were used to confirm the theory. REFERENCES [1] Brosnan, K. H. G. L. Messing, D. K. Agrawal, , J. of the Am. Cer. Soc. 86 (2003) 1307–1312. [2] M.A. Janney, H.D. Kimrey, Materials Research Society Proceeding.189 (1990),215 -228. [3] I. N. Sudiana, R. Ito, S. Inagaki, K. Kuwayama, K. Sako, S. Mitsudo, Int. J. of Infrared, Millimeter, and Terahertz Waves. 34 (2013) 627-638. [4] H. Aripin, S. Mitsudo, E.S. Prima, I.N. Sudiana, H. Kikuchi, Y. Fujii, T. Saito, T. Idehara, S. Sano, S. Sabchevski, Ceramics International, 41,pp.6488–6497(2015). [5] Bykov, H Y. V, O. I Get’man, V. V Panichkina, I. V Plotnikov, V. V Skorokhod, V. V Kholoptsev, Powder Metallurgy and Metal Ceramic, 40, 112 – 120 (2001). [6] Muhammad Zamrun Firihu, I Nyoman Sudiana, Contemporary Engineering Sciences, Vol. 9, 2016, 5, 237 – 247 [7] I.N. Sudiana, S. Mitsudo, T. Nishiwaki, P. E. Susilowati, L. Lestari, M. Z. Firihu, H. Aripin, Contemporary Engineering Sciences, Vol. 8 No. 34, (2015), 1607-1615.
28
[8] R. M. German, Sintering Theory and Practice, John Wiley, New York (1996). [9] Robert H. Doremus, J. Applied Physics, 100, 101301 (2006). [10] J.H. Booske, R.F. Cooper, L. McCaughan, S.A. Freeman, B. Meng, Microwave Processing of Material III, Matls. Res. Soc. Proc., 269, Ed. by R.L. Beattty, W.H. Sutton, and M.F. Iskander, p.185(1992). [11] J.H. Booske, R.F. Cooper, I. Dobson, L. McCaughan, ,Microwaves: Theory and Application in Material processing, Cer. Trans. 21, Am. Cer. Soc., Ed. by D.E Clark, F.D. Gac, and W.H. Sutton , p.137(1991). [12] Patterson, J., B. Bailey, Solid-State Physics: Introduction to the Theory, Springer, 2010. [13] Goldstein, H., Classical Mechanics, Addison Wesley, 1980. [14] Aripin, S. Mitsudo, E. S. Prima, I. N. Sudiana, H. Kikuchi, S. Sano, S. Sabchevski, Materials Science Forum ,737 (2013), 110-118 [15] Rybakov,K.I. and V.E.Semenov, Physical Review B , 52[ 5], 3030 (1995). [16] Semenov,V.E. and K.I. Rybakov, Proc. MAPEES`04, 111-117(2004).