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Abstrak :
Inokulasi dan penambahan elemen paduan umum digunakan dalam industry besi tuang (cast iron) untuk mendapatkan mikrostruktur tertentu. Silicon adalah salah satu elemen paduan yang paling penting dan sering ditambahkan dalam bentuk FeSi. Untuk menyelidik efek ini, potongan besi tuang dipotong menjadi ukuran yang lebih kecil dan dicairkan untuk dicelupkan sampel FeSi. Dalam eksperimen ini, temperature pencelupan yang dipilih adalah 1350 ̊C, 1420 ̊C dan 1490 ̊C. Analisa dari mikroskop optik dan scanning electron microscope (SEM) menunjukkan bahwa penambahan FeSi menghasilkan perbedaan kurva pendinginan dan pembentukan zona reaksi. Studi mikrostruktur menunjukkan bahwa penambahan FeSi menghasilkan pembentukan grafit.

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Inoculation and adding alloying elements are commonly used in cast iron industry in order to obtain certain microstructure. Silicon is one of the most important alloying elements and often added by FeSi. To investigate these effects, cast iron scraps were cut into smaller sizes and melted for the FeSi samples to be dipped into. The dipping temperatures chosen for the experiment are 1350 ̊C, 1420 ̊C and 1490 ̊C. Optical microscope and scanning electron microscope analysis does show that FeSi addition resulted in different cooling curves and formation of reaction zones. Microstructural studies show that FeSi addition resulted in graphite formation.

Abstrak :
Saat ini sudah banyak sekali produk-produk berbasis material polimer khususnya plastik. Namun, plastik sangat tidak ramah lingkungan karena sifatnya yang sulit untuk terdegradasi. Biokomposit yang mengandung matriks polimer dan serat alam merupakan salah satu alternatif dalam mereduksi penggunaan produk-produk plastik karena sifatnya yang mudah terdegradasi oleh alam. Serat alam yang memiliki potensi bagus untuk dijadikan sebagai penguat ialah serat sorgum. Selulosa dari serat sorgum diperlukan untuk menghasilkan penguat yang baik pada matriks polimer. Selulosa ini bisa didapatkan dengan mendefibrilasi serat sorgum sehingga kandungan non-selulosa seperti lignin dan hemiselulosa dapat berkurang. Proses defibrilasi dilakukan menggunakan teknik hidrotermal dengan metode rendam bertekanan dengan variasi waktu proses selama 5, 10, 15, 20, 25, 30, dan 60 menit. Hasil menunjukkan bahwa nilai optimum dalam mendefibrilasi serat sorgum terdapat pada proses hidrotermal rendam bertekanan selama 5 menit. Serat sorgum yang dihasilkan memiliki permukaan yang halus dan mengalami peningkatan kristalinitas, hidrofilisitas, dan kestabilan termal.

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Nowadays, we have a lot of polymer based products, especially plastic. However, the plastic is not very environmentally friendly because it is difficult to degrade. Biocomposites containing polymer matrix and natural fibers is an alternative in reducing the use of plastic products because of its ease biodegradable. Natural fiber that has good potential to be used as a reinforce is sorghum fiber. Cellulose from sorghum fiber is required to produce a good compatibility with polymer matrix. This cellulose can be obtained by defibrillate the sorghum fibers so that non cellulose content such as lignin and hemicellulose can be reduced. The defibrillation process was performed using hydrothermal technique with pressure soak method with variation of processing time for 5, 10, 15, 20, 25, 30, and 60 minutes. The results showed that the optimum value in the defibrillation of sorghum fiber was found in the hydrothermal pressurized soak process for 5 minutes. The resulting sorghum fiber has a smooth surface and increases in crystallinity, hydrophilicity, and thermal stability.

Abstrak :
Baja tahan karat 316L merupakan baja yang memiliki ketahanan korosi yang baik namun masih rentan terhadap kerusakan korosi sumuran. Salah satu cara untuk mencegah fenomena ini adalah dengan menerapkan lapisan Aluminium pada baja tahan karat. Pada Penelitian ini menggunakan metode semprot panas busur listrik untuk mendepositkan material Aluminium. Dalam metode semprot panas, jarak penyemprotan adalah salah satu faktor penting untuk mendapatkan hasil semprot berkualitas tinggi. Karya ilmiah ini meneliti jarak penyemprotan yang efektif untuk mencapai lapisan aluminium berkualitas tinggi pada substrat stainless steel 316L menggunakan metode semprot busur listrik dengan bahan pelapis 99.5 Al. Permukaan baja tahan karat dipersiapkan dengan metode pembersihan menggunakan larutan thinner, pemanasan sekitar 80-90oC dan blasting menggunakan Al2O3. Jarak penyemprotan yang digunakan dalam penelitian ini adalah 10cm, 20cm, 30cm. Uji sembur garam dan metode uji pull-off diterapkan untuk mengamati ketahanan korosi dan kekuatan ikatan lapisan. Hasil uji sembur garam menunjukkan pada setiap jarak penyemprotan menambah ketahanan korosi namun tidak menunjukkan perbedaan yang signifikan pada permukaan hasil uji. Hasil uji pull-off menunjukkan jarak semprot 20cm memiliki kekuatan adhesi tertinggi dengan nilai 12,5 MPa. ......Stainless Steel 316L is a steel with high corrosion resistance, however, it is still susceptible to pitting corrosion damage. One way to prevent this phenomenon is by applying aluminium coating on stainless steel using electric arc thermal spray method. In the thermal spray method, the spraying distance is one of the important factors to obtain high quality spray results. This paper investigates the effective spraying distance to achieve high quality aluminium coating on stainless steel 316L substrate with 99.5 Al as coat by using the electric arc spray method. The spray distances employed in this research were of 10cm, 20cm, 30cm. Stainless steel 316L is prepared by cleaning with thinner, preheating about 80 90oC, and blasting with Al2O3. The salt spray test and pull off test method were applied to observe the corrosion resistance and the bonding strength of the coating. The salt spray test results show that at each spraying distance increase corrosion resistance but does not show significant differences on the surface of the test results. The pull off test results show 20cm spray distance has the highest adhesion strength with 12,5 MPa value.

Abstrak :
Karet alam merupakan salah satu komoditas terbesar yang ada di Indonesia. Kondisi tersebut mendorong perkembangan pesat industri karet. Namun rendahnya modulus kekakuan karet alam menjadi kelemahan dari produk karet alam contohnya ban kendaraan dimana akan menghasilkan sifat yang buruk sehingga berpengaruh kepada umur pakai ban tersebut. Untuk mengkompensasi modulus kekakuannya yang rendah, biasaya karet alam ditambahkan penguat yaitu silica atau carbon black. Tetapi kedua bahan tersebut memiliki kelemahan dimana harganya yang mahal. Alternatif yang dapat digunakan adalah dengan menggunakan penguat berupa serat sorgum. Permasalah kompatibilitas antara karet alam dan sorgum yang memiliki sifat permukaan berbeda menjadi hambatan dalam modifikasi ini. Permasalahan kompatibiltas tersebut dapat diatasi dengan penggunaan coupling agent yang dibuat dari hibrida lateks-pati. Coupling agent merupakan senyawa yang digunakan untuk meningkatkan adhesivitas antara dua material yang berbeda. Pengamatan terhadap perilaku alir vulkaniasi dan kompatibilitas karet alam berpenguat serat sorgum dengan penambahan coupling agent berbasis pati dilakukan untuk dapat mengamati kinetika vulkanisasi. Hasil perilaku alir menunjukkan kenaikan torsi maksimum (MH) dan torsi minimum (ML) serta penurunan waktu pematangan optimum (t90) dan waktu scorch (ts2) dengan adanya penambahan coupling agent berbasis pati. Didapat pula optimasi vulkanisasi pada komposisi coupling agent sebesar 3 phr dan temperatur 150oC. Penambahan coupling agent berbasi pati juga berpengaruh kepada kenaikan nilai laju reaksi dan penurunan energi aktivasi dalam proses vulkanisasi. Hasil karakterisasi menunjukan penambahan coupling agent meningkatkan absorpsi ikatan hidrogen O-H serta menurunkan fiber pull-out dan meningkatkan dispersi yang mengindikasikan kompatibilitas karet alam dengan sorgum meningkat.

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Natural rubber is one of the largest commodities in Indonesia. This condition encouraged the rapid development of the rubber industry. However, the low modulus of natural rubber has become a weakness of natural rubber products, for example vehicle tires which will produce bad properties which affect the life of the tire. To compensate for the low modulus of stiffness, reinforcement is usually used, which are silica or carbon black. But both of these materials have weaknesses where the price is expensive. The alternative is to use sorghum fiber as a reinforced. Problems of compatibility between natural rubber and sorghum which have different surface properties are obstacles in binding. The compatibility problems can be overcome by using a coupling agent made from a hybrid of latex-starch. Coupling agent is a compound used to increase adhesivity between two different materials. Observations on the behavior of vulcanization and compatibility of natural rubber reinforced with sorghum fibers with the addition of starch-based coupling agents were carried out to be able to observe vulcanization kinetics. The results of the flow behavior show the increase in maximum torque (MH) and minimum torque (ML) and decrease in optimum ripening time (t90) and scorch time (ts2) with the addition of starch-based coupling agents. Optimization of vulcanization was also obtained on the composition of coupling agent by 3 phr and temperature of 150oC. Addition of starch-based coupling agent also influences the increase in reaction rate and decrease in activation energy in the vulcanization process. The characterization results show that the addition of coupling agents increases the absorption of O-H hydrogen bonds and decreases fiber pull-out and increases the dispersion which indicates the compatibility of natural rubber with sorghum increases.

Abstrak :
Peningkatan perhatian global mengenai masalah lingkungan dan sustainability terkait dengan pelestarian sumber daya alam tak terbarukan telah mendorong upaya untuk mengembangkan bahan dan produk ramah lingkungan baru berdasarkan sumber daya alam yang terbarukan. Serat sorgum memiliki potensi untuk dijadikan penguat komposit karena memiliki sifat mekanis yang baik, ramah lingkungan, murah. Pada studi ini komposit polipropilen-sorgum dibuat dengan rheomix pada temperatur 160Oc, kecepatan 50 rpm dengan variasi komposisi serat 5%, 10%, 15% serta variasi waktu pencampuran 5 menit, 7.5 menit, dan 10 menit. Sifat mekanis komposit polipropilen-sorgum dipengaruhi mechanical interlockpada interfaceserat dengan matriks polipropilen. Modifikasi alkalinasi-termal dengan NaOH 5% dan waktu kukus bertekanan selama 3 menit dilakukan untuk mengubah hidrofobisitas serat sorgum dan memperbaiki ikatan antara matriks polipropilen dengan serat sorgum. Diperoleh bahwa modulus young komposit polipropilen-sorgum menaik dengan penambahan serat dan penambahan waktu pencampuran, Ultimate Tensile Strength komposit polipropilen-sorgum menurun setelah melewati batas optimum komposisi serat dan menaik dengan penambahan waktu pencampuran. Sifat elastisitas komposit polipropilen-sorgum berkurang seiring penambahan komposisi serat dan penambahan waktu pencampuran. Hubungan antara variasi komposisi serat dan waktu pencampuran dianalisa untuk mengevaluasi pengaruhnya pada performa penguatan komposit polipropilen oleh serat sorgum. Tujuan penelitian adalah untuk mendapatkan variabel komposisiserat dan waktu pencampuran yang optimum untuk memperoleh sifat mekanis terbaik.

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Increasing global concern to environmental issues and sustainability related to preservation of non-renewable natural resources has encouraged research to development environmentally friendly materials and products based on renewable natural resources. Sorghum fiber has the potential to be a composite reinforcement because it has good mechanical properties, is environmentally friendly, inexpensive. In this study polypropylene-sorghum composites were made with Rheomix at a temperature of 160Oc, speed of 50 rpm with variations in fiber fraction of 5%, 10%, 15% and variations in mixing time of 5 minutes, 7.5 minutes, and 10 minutes. The mechanical properties of polypropylene-sorghum composites are determined by mechanical interlocks on fiber interfaces with the polypropylene matrix. Alkalination-thermal modification with 5% NaOH and pressurized steam for 3 minutes was carried out to change the hydrophobicity of sorghum fibers and improve the bond between the polypropylene matrix and sorghum fiber. It was found that the young modulus of polypropylene-sorghum composite increased with the addition of fiber and the addition of mixing time, the Ultimate Tensile Strength polypropylene-sorghum composite decreased after crossing the optimum fiber fraction boundary and increasing with the addition of mixing time. The elasticity of polypropylene-sorghum composites decreases with the addition of fiber fraction and the addition of mixing time. The relationship between variations in fiber fraction and mixing time was analyzed to evaluate their effect on the performance of composite reinforcement of polypropylene by sorghum fibers. The aim of the study was to obtain the optimal fiber fraction and mixing time to obtain the best mechanical properties.

Abstrak :
Ekstrak areca flower telah diteliti sebagai inhibitor korosi pada baja API 5L Gr. B pada lingkungan 1 M HCl dengan menggunakan pengujian Linear Polarisasi dan Electrochemical Impedance Spectroscopy EIS. Penambahan konsentrasi inhibitor 4 ml, 8 ml, 12 ml, 16 ml, dan 20 ml dapat meningkatkan efisiensi inhibitor. Efisiensi inhibitor optimum terjadi pada saat penambahan konsentrasi inhibitor 20 ml sebesar 96.6 pada pengujian Electrochemical Impedance Spectroscopy EIS. Senyawa polifenol dan flavonoid yang terkandung dalam areca flower dapat menginhibisi korosi secara adsorpsi fisika yang membentuk lapisan monolayer yang dapat menghambat terjadinya korosi. Adsorpsi terjadi secara spontan sesuai dengan adsorpsi isotermal Langmuir. Sesuai hasil pengujian polarisasi menunjukkan ekstrak areca flower memiliki tipe inhibisi campuran mixed-type . Nilai energi bebas adsorpsi -7.026 kJ/mol menunjukkan bahwa adsorpsi molekul inhibitor adalah adsorpsi fisika. ......Areca flower has been investigated as green corrosion inhibitor on API 5L Gr B in solution 1 M HCl acidic using Linear polarization and Electrochemical Impedance Spectroscopy EIS . Addition of 4 ml, 8 ml, 12 ml, 16 ml, and 20 ml inhibitor corrosion increase efficiency of the inhibitor. Optimum inhibition efficiency occurs at addition at concentration 20 ml is 96.6 on Electrochemical Impedance Spectroscopy EIS testing. Polyphenolic and flavanoid compounds contained in the areca flower inhibit corrosion by physical adsorption, to form a monolayer which can inhibit corrosion. Adsorption occurs spontaneously in accordance with Langmuir isothermal adsorption. The polarization showed that the areca flower extract acts through mixed ndash type inhibition. The value of the free energy 7.026 kJ mol of adsorption indicated that the adsorption of inhibitor molecules was typical of physical adsorption.

Abstrak :
Teknologi semprot panas merupakan suatu teknologi pelapisan yang sekarang banyak digunakan pada industri pabrik, minyak dan gas ataupun power plant. Pada penelitian ini telah dilakukan dua jenis teknik pelapisan semprot panas yaitu metode pelapisan High Velocity Oxygen Fuel dan metode Electric Arc Spray. Kedua metode ini memiliki jenis pelapisan logam yang berbeda.Tujuannya untuk mempelajari hasil lapisan molibdenum dan lapisan aluminium pada substrat baja tahan karat 316L. Pelapisan molibdenum dengan metode High Velocity Oxygen Fuel dilakukan dengan menggunakan serbuk molibdenum, sedangkan pelapisan aluminium dengan metode Electric Arc Spray menggunakan kawat aluminium.Adapun ketebalan pelapisan molibdenum pada substrat dengan kisaran 15-20 m dan ketebalan pelapisan aluminium pada substrat dengan kisaran 90-100 m.Sebelum proses pelapisan dilakukan pemanasan sampel untuk menghilangkan kontaminasi yang menempel.Selanjutnya dilakukan pengkasaran permukaan subsrat dengan tingkat kekasaran 10-20 m menggunakan grit blasting abrasive Brown Aluminium Oxide.Karakteristik hasil pelapisan dilakukan dengan uji Positive Material Identification PMI merk Niton XL2-800 model X-Ray Fluorescent, pengujian SEM/EDX, pengujian metalografi mikroskop optik, pengujian kekerasan, pengujian keausan dan pengujian ketahanan korosi dengan sembur garam Salt Spray. Pengujian dengan alat Positive Material Identification PMI memperlihatkan bahwa terjadi suatu ikatan mekanis pelapis dengan permukaan substrat. Pada pengamatan mikro dengan mikroskop optik perbesaran 100x terlihat bahwa ikatan pelapis molibdenum terhadap permukaan substrat lebih kuat dibandingkan dengan pelapis aluminium terhadap permukaan substrat. Pada pengamatan dengan uji SEM/EDX terlihat bagian antarmuka lapisan pelapis membentuk suatu ikatan mekanis dengan permukaan substrat, dimana untuk lapisan molibdenum lebih baik ikatannya dengan permukaan substrat dibandingkan dengan lapisan aluminium. Pengamatan dengan pengujian hardness dan uji keausan, terlihat bahwa untuk pelapisan aluminium pada substrat menghasilkan nilai hardness yang lebih rendah dibandingkan substrat yang dilapisi molibdenum sedangkan untuk uji keausan,nilai pelebaran celah substrat yang dilapisi aluminium b= 0,545 mm lebih besar dibandingkan dengan substrat yang dilapisi molibdenum b = 0,375 mm sehingga tingkat keausan lebih baik untuk nilai yang lebih kecil.Pengamatan substrat dengan uji sembur garam, kedua lapisan tidak mempengaruhi daerah penggoresan namun terlihat perubahan warna secara signifikan yang terlihat adanya pembentukan korosi secara merata.

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The technology of Thermal Spray is a coating technology is now widely used in the industries of oil and gas, factory or power plant. This research has been conducted on two types of coating technique of thermal spray coating method of High Velocity Oxygen Fuel and method of Electric Arc Spray. This different method to compare of this type coating metal on 316L stainless steel substrates. Molybdenum Coating with the method of High Velocity Oxygen Fuel using powder molybdenum and Aluminium Coating with the method Electric Arc Spray wire with 99.5 aluminium composition. The thickness of the coating on substrates with molybdenum with range 15 20 m and the thickness of the aluminum coating on substrates with the range of 90 100 m. Proceedings before the coating is carried out first warming to eliminate contamination.And then surface to be rough using grit blasting abrasive Brown Aluminum Oxide with range 10 20 m.Observations of the substrate after coating will identified with Positive Material Identification PMI Niton XL2 800 model Fluorescent X ray testing, SEM EDX, testing metalografi optical microscopy, hardness test,wear testing,testing corrosion resistant with Salt Spray.The result of testing with Positive Material Identification PMI shown coating had been a mechanical bond with substrate layer. On the observation with SEM EDX test shown bond of molibdenum's coating is better than aluminium's coating on substrate. Observations with the hardness testing and wear test related both, aluminum coating on substrate produces a lower hardness values than substrate coated molybdenum. The value of wear test results are aluminium coated substrates b 0.545 mm is greater than with molybdenum coated substrates b 0.375 mm . It means that the lower value will be more wear resistance.For observations of the substrate with salt spray test, both of looks discoloration significantly and visible presence of formation of corrosion.

Abstrak :
Pada masa ini penelitian mengenai busa poliuretan dipusatkan pada usaha peningkatan karakteristik kekakuan busa dengan pemilihan bahan baku dan proses yang bersifat terbarukan. Bio-coating kitosan adalah polisakarida linear yang merupakan produk turunan dari chitin, yaitu zat penyusun rangka terluar dari hewan antropoda seperti udang, kepiting, dan serangga. Hubung silang antara busa poliuretan dengan kitosan dibuktikan dari hasil pengamatan SEM dimana terbentuknya lapisan pada permukan dan pori pori busa. Kemudian pengujian FTIR yang menunjukkan fenomena curing terjadi pada bilangan gelombang 1374 cm-1, yaitu ikatan hubung sialng antara kitosan-STPP pada busa poliuretan. Dari hasil penelitian ini disimpulkan bahwa pada variasi waktu curing 75 menit dan suhu 135 C merupakan kondisi yang optimum untuk proses curing. Hal ini dibuktikan dengan meningkatnya kekuatan tarik sebesar 4.2 serta nilai resiliansi sebesar 2.5, juga disertai dengan menurunya nilai elongasi sebesar 24 dan nilai kekedapan udara sebesar 26. Nilai stabilitas termalnya juga meningkat dimana dibuktikan dengan meningkatknya persen berat sampel tersisa yaitu 13 dengan suhu degradasi yang lebih rendah yaitu 360 C.

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At this time research on polyurethane foam is centered on efforts to improve the characteristics of foam stiffness by selecting raw materials and renewable processes. Chitosan bio-coating is a linear polysaccharide which is a derivative product of chitin, the outermost constituent of anthropoid animals such as shrimp, crabs, and insects. The cross linking between polyurethane foam and chitosan is proven from SEM observations where the formation of layers on the surface and pores of the foam pores. Then the FTIR test which shows the curing phenomenon occurs at wave number 1374 cm-1, namely the bonding relationship between chitosan-STPP on polyurethane foam. From the results of this study concluded that the variation of 75 minutes curing time and 135 C temperature is the optimum condition for the curing process. This is evidenced by an increase in tensile strength of 4.2 and a resilience value of 2.5, also accompanied by a decline in the elongation value of 24 and an airtight value of 26. The thermal stability value also increases which is evidenced by the increase in the remaining percent weight of the sample by 13 with a lower degradation temperature of 360.

Abstrak :
ABSTRAK
Selama lebih dari 100 tahun, steel core digunakan sebagai konduktor pada kabel untuk memberikan ketahanan terhadap kekuatan tarik, mengurangi defleksi ke ground (sag) serta mampu mengakomodir rentang antar tiang yang cukup panjang. Dalam perkembangannya, seiring dengan permintaan akan kebutuhan peningkatan effisiensi dan kapasitas, telah ditemukan beberapa type dari konduktor dalam beberapa dekade terakhir. Type dari konduktor yang telah dikembangkan tersebut diklaim mampu, meningkatkan electrical capacity pada temperatur operasi yang tinggi dengan tingkat losses yang rendah. Konduktor ini diistilahkan dengan ACCC (Aluminum Conductor Composite Core) yang memiliki ketahanan terhadap temperatur tinggi. Pada penelitian ini sifat mekanik dari composite core ini diukur pada range temperatur 100 - 300°C selama 120 menit untuk tiap sampel dengan kenaikan temperatur tiap 50°C. Di atas temperatur 150°C, terjadi penurunan sifat mekanik dari composite core akibat perubahan struktur mikro dan berkurangnya sifat adhesive pada bagian interface. Sifat mekanik dari composite core ini menjadi bagian yang menentukan dalam aplikasinya untuk mendapatkan konduktor yang tahan terhadap temperatur tinggi dengan defleksi yang cukup kecil.

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ABSTRACT
For over one hundred years steel core strands have been used to increase the tensile strength and reduce thermal sag of bare overhead conductors to accommodate longer spans between fewer or shorter structures. As demand for electricity continues to grow, increasing the capacity and efficiency of existing or proposed transmission lines is becoming increasingly important. A new type of conductor that have been developed are claimed to be capable, increasing the electrical capacity at a high operating temperature with the loss rate is low. The conductor is designated ACCC (Aluminum Conductor Composite Core) which is resistant to high temperature. In this research, the high temperature strength of the conductor is assessed. The strength of the composite core measured at 100°C to 300°C within 120 minutes by 50°C increment. Above 150°C, the strength dropped due to the phase change in the matrix which degraded the elastic properties and decrease interface adhesion. The mechanical properties of the composite core highlight the potential for the use of composite materials to produce overhead conductors with low sag at high temperatures

Abstrak :
[ABSTRAK
Fe-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 < 2m. 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.;

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ABSTRACT
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, 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]