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Abstrak :
Die soldering adalah fenomena melengketnya produk cor dengan cetakan akibat reaksi interface antara aluminium cair dengan material cetakan. Akibat tingginya afinitas aluminium terhadap besi, unsur besi dari material cetakan berdifusi menuju aluminium cair membentuk lapisan intermetalik pada permukaan cetakan. Kemudian, sehingga aluminium cair menempel pada permukaan cetakan dan tertinggal setelah pelepasan hasil pengecoran. Fenomena ini mengakibatkan terjadinya kegagalan cetakan dan menurunnya kualitas permukaan hasil coran, sehingga mengarah kepada penurunan produktivitas dan peningkatan biaya produksi pengecoran. Untuk mencegah terjadinya die soldering, pembentukan lapisan intermetalik pada permukaan cetakan harus dihindari atau diminimalisir. Penelitian ini dilakukan untuk mempelajari morfologi dan karakteristik lapisan intermetalik AlxFeySiz yang terbentuk selama proses reaksi antar muka pada saat pencelupan. Sampel uji yang digunakan yaitu baja perkakas jenis H13 hasil temper, yang dicelup pada paduan Al-7%Si dan Al-12%Si yang telah ditambah 0,1%, 0,3%, 0,5%, dan 0,7% Mn pada temperatur tahan 6800C,7000,C , dan 7200,C dengan putaran 2500, 3000, 3500 rpm. Hasil penelitian menunjukkan dua lapisan intermetalik terbentuk pada permukaan baja perkakas H13 yakni compact intermetallic layer dan broken intermetalik layer dengan fasa intermetalik AlxFey, ketebalan lapisan broken layer rata-rata lebih tebal dibanding compact layer. Demikian pula kekerasan compact layer lebih tinggi dibandingkan broken layer. Penambahan 0.3 - 0.5 %Mn pada paduan Al-7%Si pada suhu 7200C, dan Al-12%Si dengan penambahan 0.7 %Mn dengan waktu kontak 30 menit pada suhu 7000C, menunjukkan hasil signifikan dalam menurunkan lapisan intermetalik, pada rentang kecepatan 2500 - 3000 rpm, pada penambahan 0.1 Mn. Pada suhu 7000C ketebalan lapisan intermetalik meningkat dengan meningkatnya kecepatan, dan kekerasan temper lebih tebal dibandingkan dengan kekerasan over temper. ...... Die soldering is the stickiness phenomenon of the mold to cast products due to the reaction between liquid aluminum interface with the mold material. The high degree of aluminum affinity toward iron led to the iron element of die material to diffuse into liquid aluminum and form an intermetallic layer on the die surface. Then, the liquid aluminum adheres on the die surface and left behind after the release of casting product. This phenomenon induce a failure in the die and decrease surface quality of the casting product, which lead to decrease in productivity and increase in casting production cost. To prevent die soldering, the forming of intermetallic layer on die surface must be avoided or minimized. This research was conducted to study about the morphology and characteristic of AlxFeySiz intermetallic layer, which formed during interface reaction process during of dipping process. The speciment used are tool steel type H13 that has been tempered, which dipped in Al- 7% and Al-12%Si alloy with the addition of Mn as much as 0.1%, 0.3%, 0.5%, and 0.7%, holding temperature on, 6800C, 7000 and 7200C, with rotational speed 2,500, 3,000, and 3,500 rpm. The research showed that two intermetallic layers was formed on the surface of H13 tool steel, namely compact intermetallic layer and broken intermetalik layer with AlxFey intermetallic phase. The thickness of broken layer is higher than compact layer but the hardness of compact layer is higher than broken layer. The addition of 0.3 - 0.5 Mn in the alloy Al-7% Si at a temperature of 7200 C, and Al-12% Si 0.7 Mn with the addition of 30 minutes of contact time at a temperature of 7000C significantly lower intermetallic layer, the speed range 2500-3000 rpm, the addition of 0.1 Mn , at a temperature of 7000C intermetallic layer thickness increases with increasing speed,. The Hardness of temper is higher than the hardness of over temper.

Abstrak :
Penelitian yang akan dikembangkan adalah material pelat bipolar polimer komposit berbasis karbon, terdiri dari epoksi resin dan hardener sebagai binder, sedangkan grafit, carbon black (CB) dan tabung nano berdinding banyak (multiwall carbon nanotube-MWCNT) sebagai penguat (reinforcement) dan pengisi (filler). Berbagai komposisi material serta variasi proses kompresi dilakukan untuk mendapatkan optimasi pelat bipolar yang memenuhi persyaratan, oleh karena itu penelitian ini dilakukan dalam beberapa tahapan. Pada tahapan awal penelitian, bertujuan untuk mengetahui apakah grafit limbah elektroda electric arc furnace (grafit EAF) dapat digunakan untuk menggantikan grafit sintetis sebagai reinforcement material dalam polimer karbon komposit. Pelat bipolar berbasis grafit EAF yang berukuran partikel < 44 µm dan pelat bipolar berbasis grafit sintetis berukuran partikel < 55 µm dicampur dengan carbon black (CB) pada interval komposisi dari (0; 2.5; 5; 7.5; 10; 12.5; 15; 17.5 dan 20) wt%. Proses kompresi dilakukan pada tekanan 30 MPa dan temperatur 70 0C. Sifat pelat bipolar dengan penguat (reinforcement) yang berasal dari grafit sintetis atau grafit EAF menunjukkan hasil yang relatif sama untuk ke empat jenis pengujian yaitu pengujian densitas, porositas, kekuatan fleksural dan konduktivitas listrik pada penambahan CB (5 dan 10) wt%. Hasil pengujian dengan penambahan polimer konduktif polianilin (PANI) pada rentang konsentrasi dari (0.027; 0.054; 0.081 dan 0.108) %wt memberikan konfirmasi dan justifikasi bahwa grafit EAF dapat digunakan sebagai reinforcement untuk menggantikan grafit sintetis. Penelitian pada tahapan lanjut hanya menggunakan grafit EAF dan CB yang berasal dari serabut kelapa hasil proses pirolisis pada temperatur 600 0C dalam lingkungan nitrogen. Variabel penelitian mencakup variasi tekanan dan temperatur kompresi, variasi ukuran partikel baik untuk grafit maupun CB. Kekuatan fleksural optimum dicapai pada tekanan kompresi 55 MPa dan temperatur kompresi 100 0C sebesar (48 ? 48.24) MPa, telah memenuhi persyaratan pelat bipolar DOE yaitu > 25 MPa. Nilai densitas seluruh hasil pengujian (1.69 ? 1.78) gr/cm3lebih kecil dari 5 gr/cm3, hal ini juga telah memenuhi persyaratan sebuah pelat bipolar yang ringan. Hasil pengujian untuk porositas berkisar antara (0.36-0.70) %. Pelat bipolar dengan komposisi CB 5 wt%, temperatur kompresi pada 100 0C serta tekanan kompresi pada 55 MPa memberikan hasil yang relatif lebih baik dibandingkan dengan komposisi CB 10 wt%. Penambahan MWCNT bertujuan untuk meningkatkan sifat mekanik dan listrik pada pelat bipolar yang dihasilkan dari penelitian sebelumnya. Nilai densitas terendah dan kekuatan fleksural tertinggi dihasilkan pada komposisi 90grafit EAF/5CB/5MWCNT yaitu sebesar 1.52 gr/cm3 untuk densitas dan 63.71 MPa untuk kekuatan fleksural. Nilai konduktivitas tertinggi dari seluruh tahapan penelitian diperoleh dari pelat bipolar dengan komposisi 95grafit EAF/2CB/3MWCNT yaitu sebesar 8.94 S/cm.

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This research will examine the utilization of an alternative material to obtain bipolar plates that are light, affordable, and can be mass produced. The research that will be developed is to create carbon-based composite bipolar plate material consisting of epoxy resin and hardener as a binder, graphite, carbon black (CB) and multiwall carbon nano-tube (MWCNT) as a reinforcement or filler material. Various material compositions and variations made to get the compression molding process optimization of bipolar plates that meet requirements that can be obtained by several stages. We investigated whether graphite electrode waste from electric arc furnace (EAF) can subtitute graphite synthetic as a reinforcement material for polymer carbon composite. Bipolar plate based on graphite EAF has particle size < 44 micron, and bipolar plate based on graphite synthetic with particle size of < 55 micron mixing with carbon black (CB) from 0-20% w/w at intervals of 2.5% w/w. The materials are molded using compression hot press machine (30 MPa, 70oC). Samples are tested for: density, porosity, flexural, and electric conductivity, indicated the bipolar plate characteristics with graphite synthetic or graphite EAF showed the same results relatively. Further research showed that the characteristics of synthetic graphite-based bipolar plates and graphite EAF were influenced by the addition of conductive polymers such as polyaniline at interval concentration from 0,027 w/w; 0,054w/w; 0,081 w/w and 0,108 w/w. These results provide confirmation and justification that graphite is used subsequently derived from EAF graphite as reinforcement and the CB additions at (5 and 10) w/w used as a filler material bipolar plates. We then used graphite EAF and CB resulting from pyrolysis process of coconut husk at 600 0C for 10 hours in nitrogen environment. Research variable covered of variety of pressure and temperature compression, variety of particle sizes of graphite EAF or CB. Flexural strength was recorded to be optimum at 48.24 MPa (at 45 MPa, 100 0C), which fulfilled the requirement of bipolar plate > 25 MPa. Density test for all EAF graphite based bipolar plates less than 5 g/cm3. In addition, the porosity for all samples were under 2% (0.36 %-1.92%). Properties of bipolar plates with CB 5 w/w (at 55 MPa, 100 0C and pyrolysis temperature at 900 0C) showed relatively better results compared with CB 10 w/w. The effect of MWCNT improved mechanical and electrical properties. The lowest density value and the highest flexural strength achieved at composition of 90graphite EAF/5CB/5MWCNT of 1.53 g/cm3 for density and 63.71 MPa for flexural strength. The highest conductiviy value from of all research stages achieved from composition of 95graphite EAF/2CB/3MWCNT of 8.94 S.cm-1.

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]

Abstrak :
Disertasi ini membahas pengaruh batubara pada bijih besi tipe lateritik dalam bentuk pelet komposit. Tiga sampel R, C dan CTR digunakan dalam penelitian ini. R merupakan sampel yang berasal dari lokasi tambang, C merupakan bijih besi R yang telah dicuci dengan classifyer, dan CTR merupakan sampel C yang telah dilewatkan pada pemisah magnetik. Ketiganya berbeda dalam jumlah goethit, hematit dan magnetit. Sampel C hanya digunakan untuk reduksi diatas 1000 °C. Batubara yang digunakan sebagai reduktor merupakan batubara dengan kadar karbon rendah. Ketiga sampel digunakan berukuran lebih kecil dari 140 mesh. Sampel ditambahkan batubara dengan jumlah yang bervariasi, dibuat pelet dan dikeringkan. Pelet komposit kemudian direduksi. Reduksi diatas 1000 °C dilakukan dengan tungku tabung. Kecepatan pemanasan tungku 10 °C/menit hingga temperatur yang diinginkan, temperatur ditahan selama 10 menit dan kemudian diturunkan hingga temperatur kamar. Variasi jumlah batubara adalah 20 % berat dan 29 % untuk R dan C serta 31 % untuk CTR. Jumlah batubara yang terakhir tersebut berhubungan dengan komposisi stoekiometri Fet dan C. Variasi temperatur adalah 1100 °C, 1200 °C, 1300 °C dan 1350 °C. Analisis dilakukan dengan XRD untuk mengetahui fasa-fasa yang terbentuk dan diikuti dengan kuantifikasi fasa dengan metode Rietvield. Densitas pelet diukur untuk mengetahui perubahannya terhadap perubahan fasa. Mikrostruktur pelet diamati dengan SEM untuk mengetahui perbedaan dari pelet R dan CTR. Reduksi dibawah 1000 °C dilakukan dengan alat Simultaneous Thermal Analysis dan tungku tabung. Reduksi dengan alat STA dilakukan dengan kecepatan 10. ......The dissertation discusses the reduction process of lateritic iron ore-coal composite pellet. Three samples have been used, called R, C and CTR. R is lateritic iron ore from mining, C is washed lateritic iron ore and CTR is lateritic iron ore which has been washed folllowed by magnetic separation. The three samples have different quantity of goethite, hematite and magnetite phases. C has been used only for direct reduction above 1000 °C. The used coal has low fixed carbon. The R, C and CTR are smaller than 140 mesh. The composite pellets are made of mixture of coal and ore. Reduction above 1000 °C is carried out in tube furnace. Heating rate is 10 °C/minute. The temperature is fixed and maintained for 10 minutes. Then, temperature is decreased by turning off the electricity to room temperature. The composite of R and C are made of 20 % and 29 % of total weight whereas the composite of CTR are made of 20 % and 31 % of total weight. The temperatures are fixed at 1100 °C, 1200 °C, 1300 °C and 1350 °C. X-Ray Diffraction is used for analysing the phases present after heating and followed by quantification using Rietveld Method. Density of composite pellet are measured. Microstructure of pellets are also investigated using SEM. Reduction below 1000 °C is carried out using Simoultaneous Thermal Analysis and tube furnace. Heating rate is 10 °C/minute. Nitrogen is flowed 20 mL/minute. Obtained thermal graphs are analysed. Reduced samples are analysed using X-Ray Diffraction. During reduction, released gases are analysed using gas analyser.

Abstrak :
Alginat adalah salah satu polisakarida alami yang dapat ditemukan pada sejumlah aplikasi biomedis. Hal ini didukung oleh sifatnya, yaitu biokompatibel, rendah kadar toksisitas, kelimpahan ketersediaannya, dan kemudahan proses gelasinya. Untuk meningkatkan sifat biodegradasi dan kemampuan interaksinya dengan sel tubuh, maka diperlukan modifikasi lanjut untuk senyawa alginat. Pada penelitian ini ditelaah metoda konjugasi alginat dengan reaksi oksidasi periodat dan reduksi aminasi. Penelitian diawali dengan pemetaan potensi protein dari sejumlah koleksi alga Indonesia. Kemudian dilanjutkan dengan konjugasi alginat dengan benzilamina dan ?-lisin. Kondisi reaksi optimal konjugasi dipelajari dengan menelaah pengaruh rasio substrat dengan oksidator dan reduktor. Alginat yang dikonjugasikan dengan benzilamina, mampu bertindak sebagai surfaktan karena membentuk misel pada pH asam, sedangkan dari senyawa alginat terkonjugasi ?-lisin, diperoleh produk berupa hidrogel dengan metoda pembentukan ikatan silang basa Schiff menggunakan gelatin. Hidrogel ini memiliki keunggulan karena ikatan yang terbentuk berupa pseudokovalen, menghasilkan hidrogel sifat self-healing. Dengan menggunakan kondisi konjugasi optimal, maka metoda modifikasi selanjutnya digunakan untuk membentuk alginat terkonjugasi lektin wheat germ aggulitinin (WGA). Mikropartikel dari alginat terkonjugasi WGA disintesis dengan metoda emulsifikasi dan ikatan silang ionik. Mikropartikel kemudian dimuat dengan kurkumin, pola pelepasan, hemakompatabilitas dan sitotoksisitinya diamati. Hasil penelitian menunjukkan enkapsulasi kurkumin dengan mikropartikel menghasilkan model pelepasan yang diperpanjang, dan pada konsentrasi rendah mikropartikel menunjukkan sifat hemakompatibel. ......Alginates are one of the natural polysaccharides that are found in numerous applications in biomedical science and engineering. This is due to the favorable properties of alginates, including biocompatibility, low toxicity, abundant availability, and ease of gelation. Chemical functionalization is one way to generate alginate derivatives with low molecular weight and high cell interactions. In this research conjugation method via periodate oxidation and reductive amination was studied. The research began with algae protein’s potential mapping from a few of Indonesian algae collection. The second part of the research was to conjugate the alginate with benzylamine and ?-lysine. We studied the effect of substrates against oxidation and reduction agents towards reaction yields. The benzylamine conjugated alginate was producing micelle on acidic pH, makes it suitable to acts as surfactant. From the ?-lysine conjugated alginate, we produced hydrogel by using gelatin to form Schiff base crosslinking. This hydrogel was linked by pseudocovalent linker which generates its self-healing properties. With conjugation optimum condition, alginate was conjugated with WGA lectin. Microparticles from alginate conjugated WGA were prepared through emulsification and ionic crosslinking. The microparticle was loaded with curcumin. The released pattern, hemacompatability and cytotoxicity of microparticle were investigated. The results show that encapsulation of curcumin with microparticle was released in prolonged manner and at low concentration, microparticle was hemocompatible.