[
ABSTRAKFe-Cr adalah paduan yang memiliki ketahanan temperatur tinggi dan
potensial digunakan sebagai interkonektor pada sel bakar (SOFC=solid oxide fuel
cell). Sintesis paduan Fe-Cr terus dikembangkan untuk mendapatkan metode yang
efektif, dan efisien. Metode sintesis paduan Fe-Cr yang ada sekarang ini adalah
metode peleburan, metalurgi serbuk ataupun metode pemaduan mekanik. Metodemetode
tersebut memiliki kelemahan misalnya paduan yang tidak homogen,
terdapat oksida, proses panjang dan membutuhkan waktu lama. Untuk
meminimumkan permasalahan ini, adalah penting untuk menghasilkan paduan
mikro Fe-Cr yang memiliki kestabilan fasa dan sifat mekanis baik. Metode
ultrasonik dapat dimanfaatkan untuk sintesis paduan mikro homogen melalui
penggunaan gelombang suara ultrasonik. Gelombang suara ultrasonik
menghasilkan gelembung-gelembung kavitasi, setiap runtuhan kavitasi dapat
dianggap sebagai reaktor mikro yang mampu menghasilkan temperatur sekitar
4737 oC dan tekanan sekitar 1000 atm dan yang terbentuk dengan sangat cepat,
serta menghasilkan gelombang kejut. Dengan demikian metode ultrasonik dapat
dimanfaatkan dalam pembuatan paduan mikro Fe-Cr yang homogen serta tanpa
oksida dan diharapkan bisa mengatasi kelemahan metode pembuatan paduan
berbasis Fe saat ini. Pada penelitian ini telah dilakukan sintesis paduan mikro Fe-
Cr dengan metode ultrasonik pada frekuensi 20 kHz dalam cairan toluene.
Tahapan yang telah dilakukan adalah perlakuan ultrasonik sebagai variasi waktu
terhadap partikel prekursor (Fe, Cr), kemudian terhadap campuran partikel
precursor untuk mendapatkan paduan mikro Fe-Cr. Kemudian dilakukan
pembuatan bongkah paduan Fe-Cr dari partikel hasil perlakuan ultrasonik melalui
kompaksi tanpa lubrikan dan sintering dalam kapsul kaca kuarsa. Karakterisasi
yang dilakukan adalah menggunakan Scanning Electron Microscopy (SEM)
terhadap partikel precursor hasil rekayasa ultrasonic. Untuk partikel campuran
prekursor Fe-Cr hasil perlakuan ultrasonik karakterisasi dilakukan menggunakan
SEM-EDS (Energy Dispersive Spectroscopy), X-Ray Diffraction (XRD) disertai
analisis dengan metode Rietveld, Transmission Electron Microscopy-Selected
Area Electron Diffraction (TEM-SAED). Untuk bongkah Fe-Cr hasil konsolidasi
dengan menggunakan SEM-EDS, XRD disertai analisis dengan metode Rietveld,
pengukuran densitas sebenarnya, pengujian kekerasan Vickers. Efek perlakuan
ultrasonik terhadap partikel Fe adalah pengurangan ukuran, penyatuan, dan
aglomerasi. Setelah perlakuan ultrasonik 40 jam terjadi peningkatan ukuran
partikel Fe (>2μm). Terhadap partikel Cr memberikan efek erosi permukaan,
pengurangan ukuran dan pemecahan partikel aglomerasi. Partikel Cr aglomerasi
terurai sepenuhnya menjadi partikel Cr kecil (< 2 m) setelah 63 jam. Terhadap
campuran partikel Fe dan Cr dapat menyatukan partikel kohesif (Fe-Fe, Cr-Cr)
dan adhesif (Fe-Cr), terbentuk paduan mikro Fe-Cr seutuhnya (setelah 20 jam)
ataupun paduan mikro Fe-Cr sebagian (setelah 50 jam). Pembentukan paduan
mikro Fe-Cr diawali pada ukuran partikel Fe ataupun Cr < 2m. Bongkah paduan mikro Fe-Cr yang diperoleh adalah homogen dan tanpa oksida, dengan
karakteristik densitas melalui sintering dua tahap yaitu tipe O = 8.655 gr/cm3, tipe
B=8.179 gr/cm3, dan tipe A=8.196 gr/cm3, dan melalui proses sintering satu tahap
tipe O = 7.678 gr/cm3, tipe B=7.587gr/cm3, dan tipe A=7.092 gr/cm3. Kekerasan
bongkah Fe-Cr terbesar melalui sintering satu tahap yaitu 88 VHN adalah tipe B,
sementara terbesar dua tahap yaitu 81 VHN adalah tipe A. Proses perlakuan
ultrasonik memberikan dampak positif baik dari sisi waktu proses maupun
kualitas hasil paduan Fe-Cr. Dengan demikian metode ultrasonik bisa diandalkan
sebagai alternatif dalam pembuatan paduan berbasis Fe untuk mengatasi kendala
homogenisasi dan oksidasi yang dihadapi pada metode saat ini.;
ABSTRACTFe-Cr alloys have the potential for use as an interconnection material for
solid oxide fuel cell (SOFC) due to its being resistance to high temperatures.
Synthesis methods of Fe-Cr alloy continue to be developed in order to obtain a
method that is both effective and efficient. Presently, the synthesis of Fe-Cr alloys
include the casting, the powder metallurgy, and the mechanical alloying method.
These methods have several drawbacks such as inhomogeneity in the resulting
products, oxidation, and require a very time-consuming process to accomplish. In
order to minimize this problem, it is important to produce Fe-Cr microalloys. Fe-
Cr microalloys exhibit phase stability and good mechanical properties. Ultrasonic
methods can be used in the synthesis of homogeneous microalloys by employing
the ultrasonic sound waves. Ultrasonic sound waves will generate cavitation
bubbles. Any cavitation collapse can be considered as a micro reactor in which a
temperature of about 4737 oC and a pressure of about 1000 atm a very rapidly
created, thereby generating a shock wave. Thus, the ultrasonic method can be
used in producing homogeneous and free-oxide Fe-Cr microalloys and can be
expected to overcome the limitations imposed by the current methods. In this
work the formation of Fe-Cr microalloys by ultrasonic treatment at a frequency of
20 kHz in toluene liquid is presented. In the synthesis procedure, the procedure
steps followed were: (1) the treatment of precursor particles (Fe, Cr) through
ultrasonic method with a time-variation, followed by (2) the same time-varying
ultrasonic treatment on the admixture of these specially prepared precursor
particles in order to obtain the Fe-Cr microalloys, and (3) finally, the lubricantless
compaction method was employed on these precursor particles admixture
followed by sintering process inside quartz tubes to obtain a bulk of Fe-Cr alloy.
Observations of the specially prepared precursor particles using ultrasonic
technique were carried out by scanning electron microscopy (SEM) method.
Observation of the precursor mixture of Fe-Cr particles mixture treated
ultrasonically was performed using a SEM-EDS (energy-dispersive spectroscopy)
apparatus, a X-Ray diffractometer and accompanied by the Rietveld analysis
method, and transmission electron microscopy (TEM)-selected area electron
diffraction (SAED) apparatus. The bulk of Fe-Cr alloy were observed using SEMEDS,
XRD accompanied by analysis by the Rietveld method, true density
measurement, and Vickers microhardness testing. Ultrasonic treatment has caused
Fe particles to form agglomerations, an interparticles neck formation, and a fusing
among the particles. The size of the Fe particles increased (>2μm) after 40 hours
treatment. The agglomerated Cr particles experienced fragmentation, surface
erosion, and reduction of particle size. The agglometrated Cr particles fully
disintegrated into Cr microparticles (<2μm) after 63 hours treatment. The mixture
of Fe-Cr forming cohesive (Fe-Fe, Cr-Cr) and adhesive (Fe-Cr) particles, forming
completely (after ultrasonic treatment for 20 hours) and partially (after ultrasonic
treatment for 50 hours) Fe-Cr microalloys. The complete formation of Fe-Cr microalloy was possible with an equal particle size of the precursor Fe and Cr
(approximately <2 μm). The bulk of Fe-Cr alloy results are homogenous and
oxide-free. For two-step sintering, its density (in gr/cm3 unit) is 8.655 for type O,
is 8.179 for type B, and is 8.196 for type A, and for one-step sintering its density
is 7.678 for type O, is 7.587 for type B, and is 7.092 for type A. The greatest
microhardness number of 88 VHN is of type B (one-step sintering), and of 81
VHN is of type A (two-step sintering). The ultrasonic treatment process has a
positive impact, with respect to both of quality and time-consumption to finish the
Fe-Cr alloying process. Therefore the ultrasonic method can be relied upon as an
alternative method in the production of Fe-based alloys to solve problems in
homogenization and oxidation encountered in current methods;Fe-Cr alloys have the potential for use as an interconnection material for
solid oxide fuel cell (SOFC) due to its being resistance to high temperatures.
Synthesis methods of Fe-Cr alloy continue to be developed in order to obtain a
method that is both effective and efficient. Presently, the synthesis of Fe-Cr alloys
include the casting, the powder metallurgy, and the mechanical alloying method.
These methods have several drawbacks such as inhomogeneity in the resulting
products, oxidation, and require a very time-consuming process to accomplish. In
order to minimize this problem, it is important to produce Fe-Cr microalloys. Fe-
Cr microalloys exhibit phase stability and good mechanical properties. Ultrasonic
methods can be used in the synthesis of homogeneous microalloys by employing
the ultrasonic sound waves. Ultrasonic sound waves will generate cavitation
bubbles. Any cavitation collapse can be considered as a micro reactor in which a
temperature of about 4737 oC and a pressure of about 1000 atm a very rapidly
created, thereby generating a shock wave. Thus, the ultrasonic method can be
used in producing homogeneous and free-oxide Fe-Cr microalloys and can be
expected to overcome the limitations imposed by the current methods. In this
work the formation of Fe-Cr microalloys by ultrasonic treatment at a frequency of
20 kHz in toluene liquid is presented. In the synthesis procedure, the procedure
steps followed were: (1) the treatment of precursor particles (Fe, Cr) through
ultrasonic method with a time-variation, followed by (2) the same time-varying
ultrasonic treatment on the admixture of these specially prepared precursor
particles in order to obtain the Fe-Cr microalloys, and (3) finally, the lubricantless
compaction method was employed on these precursor particles admixture
followed by sintering process inside quartz tubes to obtain a bulk of Fe-Cr alloy.
Observations of the specially prepared precursor particles using ultrasonic
technique were carried out by scanning electron microscopy (SEM) method.
Observation of the precursor mixture of Fe-Cr particles mixture treated
ultrasonically was performed using a SEM-EDS (energy-dispersive spectroscopy)
apparatus, a X-Ray diffractometer and accompanied by the Rietveld analysis
method, and transmission electron microscopy (TEM)-selected area electron
diffraction (SAED) apparatus. The bulk of Fe-Cr alloy were observed using SEMEDS,
XRD accompanied by analysis by the Rietveld method, true density
measurement, and Vickers microhardness testing. Ultrasonic treatment has caused
Fe particles to form agglomerations, an interparticles neck formation, and a fusing
among the particles. The size of the Fe particles increased (>2μm) after 40 hours
treatment. The agglomerated Cr particles experienced fragmentation, surface
erosion, and reduction of particle size. The agglometrated Cr particles fully
disintegrated into Cr microparticles (<2μm) after 63 hours treatment. The mixture
of Fe-Cr forming cohesive (Fe-Fe, Cr-Cr) and adhesive (Fe-Cr) particles, forming
completely (after ultrasonic treatment for 20 hours) and partially (after ultrasonic
treatment for 50 hours) Fe-Cr microalloys. The complete formation of Fe-Cr microalloy was possible with an equal particle size of the precursor Fe and Cr
(approximately <2 μm). The bulk of Fe-Cr alloy results are homogenous and
oxide-free. For two-step sintering, its density (in gr/cm3 unit) is 8.655 for type O,
is 8.179 for type B, and is 8.196 for type A, and for one-step sintering its density
is 7.678 for type O, is 7.587 for type B, and is 7.092 for type A. The greatest
microhardness number of 88 VHN is of type B (one-step sintering), and of 81
VHN is of type A (two-step sintering). The ultrasonic treatment process has a
positive impact, with respect to both of quality and time-consumption to finish the
Fe-Cr alloying process. Therefore the ultrasonic method can be relied upon as an
alternative method in the production of Fe-based alloys to solve problems in
homogenization and oxidation encountered in current methods, Fe-Cr alloys have the potential for use as an interconnection material for
solid oxide fuel cell (SOFC) due to its being resistance to high temperatures.
Synthesis methods of Fe-Cr alloy continue to be developed in order to obtain a
method that is both effective and efficient. Presently, the synthesis of Fe-Cr alloys
include the casting, the powder metallurgy, and the mechanical alloying method.
These methods have several drawbacks such as inhomogeneity in the resulting
products, oxidation, and require a very time-consuming process to accomplish. In
order to minimize this problem, it is important to produce Fe-Cr microalloys. Fe-
Cr microalloys exhibit phase stability and good mechanical properties. Ultrasonic
methods can be used in the synthesis of homogeneous microalloys by employing
the ultrasonic sound waves. Ultrasonic sound waves will generate cavitation
bubbles. Any cavitation collapse can be considered as a micro reactor in which a
temperature of about 4737 oC and a pressure of about 1000 atm a very rapidly
created, thereby generating a shock wave. Thus, the ultrasonic method can be
used in producing homogeneous and free-oxide Fe-Cr microalloys and can be
expected to overcome the limitations imposed by the current methods. In this
work the formation of Fe-Cr microalloys by ultrasonic treatment at a frequency of
20 kHz in toluene liquid is presented. In the synthesis procedure, the procedure
steps followed were: (1) the treatment of precursor particles (Fe, Cr) through
ultrasonic method with a time-variation, followed by (2) the same time-varying
ultrasonic treatment on the admixture of these specially prepared precursor
particles in order to obtain the Fe-Cr microalloys, and (3) finally, the lubricantless
compaction method was employed on these precursor particles admixture
followed by sintering process inside quartz tubes to obtain a bulk of Fe-Cr alloy.
Observations of the specially prepared precursor particles using ultrasonic
technique were carried out by scanning electron microscopy (SEM) method.
Observation of the precursor mixture of Fe-Cr particles mixture treated
ultrasonically was performed using a SEM-EDS (energy-dispersive spectroscopy)
apparatus, a X-Ray diffractometer and accompanied by the Rietveld analysis
method, and transmission electron microscopy (TEM)-selected area electron
diffraction (SAED) apparatus. The bulk of Fe-Cr alloy were observed using SEMEDS,
XRD accompanied by analysis by the Rietveld method, true density
measurement, and Vickers microhardness testing. Ultrasonic treatment has caused
Fe particles to form agglomerations, an interparticles neck formation, and a fusing
among the particles. The size of the Fe particles increased (>2μm) after 40 hours
treatment. The agglomerated Cr particles experienced fragmentation, surface
erosion, and reduction of particle size. The agglometrated Cr particles fully
disintegrated into Cr microparticles (<2μm) after 63 hours treatment. The mixture
of Fe-Cr forming cohesive (Fe-Fe, Cr-Cr) and adhesive (Fe-Cr) particles, forming
completely (after ultrasonic treatment for 20 hours) and partially (after ultrasonic
treatment for 50 hours) Fe-Cr microalloys. The complete formation of Fe-Cr microalloy was possible with an equal particle size of the precursor Fe and Cr
(approximately <2 μm). The bulk of Fe-Cr alloy results are homogenous and
oxide-free. For two-step sintering, its density (in gr/cm3 unit) is 8.655 for type O,
is 8.179 for type B, and is 8.196 for type A, and for one-step sintering its density
is 7.678 for type O, is 7.587 for type B, and is 7.092 for type A. The greatest
microhardness number of 88 VHN is of type B (one-step sintering), and of 81
VHN is of type A (two-step sintering). The ultrasonic treatment process has a
positive impact, with respect to both of quality and time-consumption to finish the
Fe-Cr alloying process. Therefore the ultrasonic method can be relied upon as an
alternative method in the production of Fe-based alloys to solve problems in
homogenization and oxidation encountered in current methods]
D2072-Marzuki Silalahi.pdf :: Unduh