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Abstrak :
ABSTRAK Magnet permanen berperekat mulai memegang peran yang sangat vital dalam perkembangan Industri modern sejak ditemukannya material magnet Alloy magnet logam tanah jarang berbasis fasa Nd2Fe14B. Material magnet ini memiliki produk energi maksimum yang sangat tinggi sehingga memungkinkan untuk dibuat magnet berperekat dengan energi yang dapat divariasi menurut kebutuhan. Dari hasil fabrikasi magnet permanen hibrida berperekat Nd-Fe-B dan BaO.6(Fe203) dengan teknik cetakan kompresi menunjukkan penurunan port hingga <10% dengan bertambahnya fraksi perekat. Dari hasil evaluasi terhadap sifat-sifat magnetik untuk material magnet berperekat menunjukkan bahwa remanen magnetik adalah mendekati hasil teori dengan koersivitas ?300kA.m 1 dengan produk energi maksimum 12.3 -27.5 kJ.m-3. Hasil lebih rendah 47.9% - 59.4% terhadap nilai teori.

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ABSTRACT Bonded permanent magnets play a vital role in modem Industries since the discovery and development of Rare earth based alloys that have magnetic phase of Nd2Fe14B. The alloy has very high maximum energy product, (BH)max that could derive bonded magnets of various energy product. In this research, fabrication of bonded remanent magnets based on hybrid materials between Nd-Fe-B and Ferrite BaO.6(Fe203) has been made by compression molding. It was observed that fraction of porosity in magnets was reduced to a value of < 10% (in volume) as bonded material was increased. Evaluation of magnetic properties for the bonded magnet shown that permanence magnetization is almost equal to the theoretical value with coercivities -300kA.m'1 and corresponding maximum energy product in the range 12.3 - 27.5 kJ.m'3. However, these result is less to 47.9% - 59.4% from the theory.

Abstrak :
Ceramic magnets with the chemical composition of barium hexaferrite (BaFe12O19) were obtained through the synthesis of magnetite powder from iron sand taken from the Southern Coast of Yogyakarta in Indonesia. The iron sand was dissolved and then synthesized to produce magnetite powder. Subsequently, the magnetite powder was oxidized at temperatures of 700, 900, and 1100°C for five hours to produce hematite. The un-oxidized magnetite and the magnetite which was oxidized at the different temperatures were each mixed with barium carbonate, respectively. The mixtures were then calcined at 1100°C for two hours. The calcined products were compacted and then sintered at 1100°C for one hour to produce sintered ceramic magnets. X-ray diffraction (XRD), a vibrating sample magnetometer (VSM), a scanning electron microscope (SEM) with an energy dispersive X-ray spectroscope (EDS), and thermogravimetry analysis (TGA) were used to characterize the ceramic magnets. The results showed the magnetite that was directly calcined, compacted, and sintered had a BaFe12O19 phase and also had the presence of a Fe2O3 phase with a BH(max) of 0.26 MGOe, Hc of 1.27 kOe, and Ms of 31.421 emu/g. The sintered ceramic magnet which was initially oxidized at a temperature of 900°C had a BaFe12O19 phase with a BH(max) of 0.78 MGOe, Hc of 1.95 kOe, and Ms of 46.970 emu/g. These results indicate satisfactory results as a permanent magnet. Thus, the iron sand from the Southern Coast of Yogyakarta in Indonesia has potential for the production of ceramic permanent magnets.

Abstrak :
Magnet permanen nanokomposit merupakan magnet yang memiliki sifat kemagnetan yang ditingkatkan melalui struktur komposit, terdiri dari dua atau lebih fasa magnetik. Fasa magnetik hadir dalam bentuk kristalit dalam ukuran nanometer. Bila terjadi kontak yang erat antar permukaan fasa magnetik, maka sifat kemagnetan terutama remanen (Mr) dan energi produk maksimum (BH)max menjadi meningkat. Pada penelitian ini, telah dilakukan evaluasi sifat kemagnetan dari sistem komposit BaFe12O19/CoxFe3-xO4 (x=0,5; 0,7; 1,0 dan 1,2). BaFe12O19 atau BHF dipersiapkan dengan teknik pemaduan mekanik, menghasilkan material magnet permanen dengan nilai Mr=0,185 T dan koersifitas Hc=176,7 kA/m merupakan nilai tipikal dari BHF. Demikian juga material CoxFe3-xO4 dipersiapkan dengan teknik yang sama. Hasil evaluasi sifat kemagnetan menunjukkan magnet dengan komposisi x=1,0 dan x=1,2 adalah yang terbaik untuk dijadikan komponen magnet nanokomposit. Magnet CoFe2O4 (x=1,0) menghasilkan nilai Mr, Magnetik total (Ms) dan (BH)max masing-masing adalah 0,28 T; 0,48 T dan 3,8 kJ/m3. Sedangkan magnet Co1,2Fe2,8O4 (x=1,2) memiliki nilai 0,22 T; 0,43 T dan 3,4 kJ/m3. Komposit kedua fasa magnetik dipersiapkan untuk empat komposisi berbeda. Adapun komponen kedua fasa magnetik, hadir dalam struktur komposit divariasikan sehingga diperoleh komposit yang terdiri dari komponen sistem multikristalit partikel atau komp-A dan komp-B; sistem multikristalit-monokristalit partikel atau komp-C; sistem monokristalit-multikristalit partikel atau komp-D dan sistem monokristalit partikel atau komp-E untuk mengoptimalkan peningkatan sifat kemagnetan melalui efek interaksi antar grain (grain exchanged interaction). Evaluasi sifat kemagnetan dari sistem komposit, keseluruhan magnet memperlihatkan terjadinya peningkatan sifat kemagnetan terutama nilai Mr dan (BH)max. Nilai (BH)max magnet komposit meningkat antara 25,5%-80% dibandingkan nilai (BH)max BHF. Sedangkan rasio Mr/Ms keseluruhan magnet komposit adalah 0,57-0,67 atau 14%-34% diatas nilai Mr/Ms = 0,5 ( isotropi). ...... The nanocomposite permanent magnet is a magnet with enhanced magnetic properties due to the composite structure, which consisting of two or more magnetic phases. The magnetic phases present in the form of crystallites in nanometer size. Subject to a close contact among surfaces of the magnetic phase, the magnetic properties especially remanence (Mr) and maximum energy product, (BH)max are increased. In this research, magnetic properties of composite BaFe12O19/CoxFe3-xO4 (x=0.5; 0.7; 1.0 and 1.2) permanent magnets have been evaluated. A component of BaFe12O19 (BHF) phase was prepared by a mechanical alloying technique, which yielded a permanent magnet with a value of Mr=0.185 T and the coercivity, Hc=176.7 kA/m, which are the typical values of BHF. Similarly, CoxFe3-xO4 materials were prepared through the same technique. Based on the magnetic property evaluation, it showed that magnets with x=1.0 and 1.2 compositions are the best for the second magnetic component in the composite magnets. It was found that the CoFe2O4 has values of Mr, total magnetization (Ms) and (BH)max respectively 0.28 T; 0.48 T and 3.8 kJ/m3. While those of Co1.2Fe2.8O4 are 0.22 T; 0.43 T and 3.4 kJ/m3. The two component of the magnetic phase, present in the composite structure were varied so as to obtain composites comprising components of the multicrystallite particle system or komp-A and komp-B; Multicrystallite-monocrystallite particle system or komp-C; Monocrystallite-multicrystalite particle system or komp-D; Monocrystallite particle system or komp-E to optimize magnetic properties enhancement through the effects of grain exchanged interaction. Evaluation of magnetic properties of the composite systems shows that the overall magnets have an increased in magnetic properties especially Mr and (BH)max values. The (BH)max for the composite magnets increased to 25.5%-80% compared with that of the BHF. While the Mr/Ms ratio for the overall composite magnets is 0.57-0.67 or 14%-34% above the value of Mr/Ms = 0.5 (isotropic).

Abstrak :
Telah dilakukan rekayasa struktur material magnet pemanen berbasis fasa Nd2Fe14B melalui subsitusi parsial atom neodymium (Nd) dalam sel satuan dengan atom dysprosium (Dy) sehingga membentuk fasa (Nd,Dy)2Fe14B untuk meningkatkan nilai koersifitas. Rekayasa struktur untuk peningkatan nilai koersifitas dimaksud juga dilakukan melalui pengecilan ukuran partikel fasa (Nd,Dy)2Fe14B dengan memperpanjang durasi waktu penghalusan pada proses penghalusan mekanik. Ingot material dengan tiga komposi berbeda Nd20-xDyxFe14B dengan x = 1, 3, 5 at.% dipersiapkan dengan mini arc melting furnace (AMF) dan dilanjutkan dengan perlakuan anil selama 24 jam untuk homogenisasi mikrostruktur. Sampel magnet untuk masing - masing komposisi diperoleh setelah tahapan-tahapan penghalusan mekanik dengan variasi durasi waktu penghalusan 5, 10, 15 dan 20 jam. Evaluasi nilai koersifitas sampel magnet memperlihatkan peningkatan tajam terjadi karena pembentukan mikrostruktur yang terdiri dari fasa utama (Nd,Dy)2Fe14B dan fasa yang kaya Nd (Nd-rich phase) paska perlakuan panas. ......A change of the cell structure of the permanent magnet materials based on the Nd2Fe14B phase has been carried out through partial substitution of the neodymium (Nd) atom with the dysprosium (Dy) to form (Nd, Dy)2Fe14B phase to increase the coercivity value. The increase in coercivity has also been achieved by refining the particle size of (Nd, Dy) by mechanical milling with varying times of time. Ingot of Nd20-xDyxFe14B with x = 1, 3, 5 at.% were prepared by mini arc melting furnace (AMF) and successively followed by annealing treatment for 24 hours in a sealed quartz tube for microstructure homogenization. As annealed magnetic ingots for for each composition was then mechanically refined for the duration of grinding times 5, 10, 15 and 20 hours and compacted in a cylindrical die of 12 mm diameter for magnetic sample preparation. The value of coercivity of all magnetic samples was evaluated from the hysteresis loop. It is found that the best improvement of coercivity occurred due to microstructural formation which consisting of the main phase (Nd, Dy)2Fe14B and the Nd rich phase (Nd rich phase) after heat treatment.

Abstrak :
Seiring dengan perkembangan zaman dan teknologi, tidak terlepas dari meningkatnya limbah elektronik yang terus meningkat setiap tahunnya. Limbah elektronik yang paling umum di daur ulang adalah papan elektronik atau PCB (Printed Circuit Board). Kategori limbah elektronik termasuk dalam limbah B3 yaitu limbah berbahaya dan beracun. Proses daur ulang diperlukan untuk mencegah pengerusakan lingkungan. Salah satu material yang terkandung didalam papan elektronik memiliki harga jual tinggi yaitu alumunium dan tembaga yang termasuk kedalam kategori logam nonferrous. Untuk mendaur kedua material ini, dibutuhkan proses pemisahan tersendiri karena terdapat banyak material lain seperti plastik. Separasi atau pemisahan dengan Eddy current dapat dilakukan khususnya untuk mendapatkan material berharga nonferrous seperti alumunium dan tembaga. Eddy current dihasilkan dari rotasi roll magnet yang terdiri dari magnet permanen. Susunan magnet permanen yang digunakan adalah alternating current dimana disetiap posisi magnet yang bergantian antara bagian utara dan bagian selatan. Prototip eddy current separator pada penelitian ini mampu memvalidasi data beberapa metode dengan error paling besar 26% dan paling kecil 1,515%. Adapun jarak lontar terjauh yang dihasilkan untuk material aluminium sebesar 17,5 cm dan material tembaga sebesar 14,5 cm. Rotasi roll magnet juga turut mempengaruhi jarak lontar yaitu sebesar 15 cm pada putaran 2600 rpm dan 13,5 cm pada putaran 1800 rpm pada aluminium dengan ukuran 30 mm x 30 mm ketebalan 1 mm. ......Along with the times and technology, it is inseparable from the increase in electronic waste which continues to increase every year. The most common electronic waste recycled is an electronic board or PCB (Printed Circuit Board). The category of electronic waste is included in B3 waste, namely hazardous and toxic waste. The recycling process is needed to prevent environmental damage. One of the materials contained in the electronic board has a high selling price, namely aluminum and copper which are included in the nonferrous metal category. To recycle these two materials, a separate separation process is needed because there are many other materials such as plastic. Eddy current separation or separation can be done especially to obtain nonferrous valuable materials such as aluminum and copper. Eddy current is generated by rotating a magnetic roll consisting of permanent magnets. The arrangement of the permanent magnets used is the alternating current in which each position of the magnet alternates between the north and the south. The eddy current separator prototype in this study was able to validate data from several methods with the biggest error of 26% and the smallest 1.515%. The farthest distance produced for aluminum material is 17.5 cm and copper material is 14.5 cm. The magnetic roll rotation also affects the ejection distance, which is 15 cm at 2600 rpm and 13.5 cm at 1800 rpm on aluminum with a size of 30 mm x 30 mm with a thickness of 1 mm.

Abstrak :
Material stronsium heksaferit memiliki karakteristik yang unik, diantaranya nilai temperature curie Tc sebesar 737K/463°C, nilai konstanta magnetokristain anisotropi K = 3,6 × 102 erg.cm-3, nilai koersivitas JHc = 444,5 kA/m, nilai magnetisasi remanen Mr sebesar 0,245 T dan nilai saturasi magnetisasinya Ms = 0,475 T. Investigasi terbaru pada SrFe11.9In0.1O19 telah menunjukkan nilai ratio antara magnetisasi remanen dan magnetisasi saturasi yang lebih besar dari 0,5, dimana penggunaannnya tepat untuk magnet permanen isotropik. Dalam penelitian ini, material SrFe12-xInxO19 (x = 0,05; 0,10; 0,20; dan 0,50) dengan nilai magnetisasi remanen tertinggi dimodifikasi dengan substitusi Fe+3 terhadap material SrFe11.9In0.1O19 dengan ion Mn dan Ti untuk mengurangi nilai koersivitasnya sehingga tepat untuk digunakan sebagai material absorber. Material magnetik dengan komposisi SrFe11,9-yMny/2Tiy/2In0,1O19 (y = 0; 0,30; 0,60; 1,00 dan 1,20) telah dibuat dengan proses mechanical alloying. Loop histeresis untuk sampel SrFe11,9-yMny/2Tiy/2In0,1O19 menunjukkan bahwa koersivitas berkurang secara progresif dari 292,6 kA/m untuk y = 0 menjadi 90,23 kA/m untuk y = 1,2 dengan nilai magnetisasi remanen yag cenderung konstan. Nilai reflection loss (RL) material penyerap ini terus bertambah besar seiring dengan meningkatnya fraksi ion subsitusi Mn+2 dan Ti+4 hingga mencapai nilai RL tertinggi didapatkan pada y = 1,20 yaitu sebesar 40,23 dB pada frekuensi 11,162 GHz. Dengan nilai RL tersebut gelombang elektromagnetik yang masuk kedalam material dapat diserap hingga mencapai lebih dari 99 % dan hanya kurang dari 1 % intensitas gelombang yang datang direfleksikan kembali. ......Strontium hexaferrite has attracted much attentions due to its unique properties with a large value of curie temperature Tc = 737K, a large magnetocrystalline anisotropy constant K = 3.6 x 106 erg.cm-3, a high coercivity value JHc = 444,5 kA/m, high remanent (Mr) and saturation magnetization (Ms) of 0,245 T and 0.475 T respectively. A recent investigation on In substituted SrFe11.9In0.1O19 has shown excellent remanence to the saturation magnetization ratio value of much greater than 0.5 which most suitable for isotropic permanent magnets. In this work, SrFe12-xInxO19 (x = 0.05; 0.10; 0.20; and 0.50) with the highest value of remanent magnetization was modified by the co-substitution of Fe+3 in SrFe11.9In0.1O19 with Mn+2 and Ti+4 ions to reduce the coercivity which is suitable for radar absorbing applications. A series of magnetic material with SrFe11.9-yMny/2Tiy/2In0,1O19 (y = 0; 0.30; 0.60; 1.00 and 1.20) compositions were prepared by mechanical alloying process. The hysteresis loop for SrFe11.9-yMny/2Tiy/2In0.1O19 samples showed that the coercivity was progressively reduced from 292.6 kA/m for y = 0 to 90.23 kA/m for y = 1.2 with the remanence remained significantly un-changed. The reflection loss (RL) value of such materials continues to increase along with the increase of Mn+2 and Ti+4 fraction until the highest RL value of 40.23 dB at a frequency of 11.162 GHz was obtained at y = 1.20. With this RL value, the electromagnetic waves that enter the material can be absorbed up to more than 99% and only less than 1% of the intensity of the incoming waves is reflected.