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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).

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