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"Penelitian ini bertujuan mempelajari pembentukan nanopartikel strontium hexaferrite yang disubstitusi secara parsial ion Mn dan Ti. Sintesis material dilakukan melalui proses mechanical alloying menghasilkan partikel material fasa tunggal dengan komposisi SrFe9Mn1.5Ti1.5O19. Pembentukan nanopartikel dilakukan dengan menggunakan destruksi ultrasonik partikel yang telah mendapat perlakuan etching. Dalam hal ini, partikel kristalin yang diperoleh dari tahapan pemaduan mekanik direndam dalam larutan yang mengandung etching agent HF 48% (Hydroflouric Acid). Untuk mengetahui sejauh mana pengaruh etching terhadap efektivitas pembentukan nanopartikel selama proses destruksi ultrasonik, maka diberikan variasi perlakuan berupa etching agent konsentrasi berbeda yaitu 5%, 10%, 15%. Untuk setiap larutan waktu perendaman sampel ditetapkan selama 10, 20, dan 30 menit sebelum perlakuan destruksi ultrasonik diterapkan. Pengujian material menggunakan XRD (X-Ray Diffraction) untuk mengetahui pembentukan fasa dan distribusi ukuran kristalit, PSA (Particle Size Analyzer) untuk mengukur distribusi ukuran partikel, dan SEM (Scanning Electron Microscopy) untuk melihat morfologi partikel. Hasil identifikasi XRD memastikan tidak terjadi perubahan fase setelah proses destruksi ultrasonik dan etching. Berdasarkan hasil evaluasi PSA diketahui bahwa ukuran partikel material setelah tahapan sintesis adalah 732 nm. Sedangkan, hasil ukuran rata-rata partikel setelah proses destruksi ultrasonik pada material tanpa perlakuan etching adalah 150 nm. Ukuran rata-rata partikel pasca perendaman dalam larutan HF berkonsentrasi 5 % selama 10, 20, dan 30 menit masing-masing adalah 138 nm, 214 nm, 385 nm. Untuk konsentrasi 10% adalah 142 nm, 235 nm, 302 nm, dan untuk 15% adalah 162 nm, 269 nm, 368 nm. Sedangkan, pada kristalit tidak terjadi perubahan ukuran secara signifikan hanya berada dalam rentang 22-28 nm pada semua partikel pasca perendaman dan destruksi. Dapat disimpulkan bahwa partikel dari material dengan perlakuan etching HF memiliki kecenderungan terjadinya peningkatan ukuran terhadap durasi waktu etching yang semakin lama dibandingkan dengan ukuran partikel pada material tanpa etching. Sedangkan pada kristalit, proses etching tidak terlalu memberikan pengaruh pada perubahan ukuran.

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This research is aimed at studying the formation of substituted Mn and Ti strontium hexaferrite nanoparticles. Synthesis material was conducted by a mechanical alloying process which produced single phase material particles of SrFe9Mn1.5Ti1.5O19 composition. The formation of nanoparticles was done by means of ultrasonic destruction of particles which have been chemically treated. In this case, the crystalline particles obtained from mechanical alloying were immersed into a solution containing 48% HF etching agent (Hydrofluoric Acid). To what extent the influence of etching agent on the effectiveness of nanoparticle formation during the process of ultrasonic destruction, then three different solutions containing HF of respectively 5%, 10%, 15% were employed. For each solution the immersion time for particles was set for 10, 20, and 30 minutes before ultrasonic destruction started. As to the material characterization, the following tools were employed: XRD (X-Ray Diffraction) was used to determine the phase formation and distribution of crystallite sizes, PSA (Particle Size Analyzer) to measure the particle size distribution, and SEM (Scanning Electron Microscopy) to look at the morphology of the particles.

XRD results confirmed that there have no changed in materials phase after ultrasonic destruction and etching process. Based on results of PSA evaluation, the mean particle size of the material after the synthesis was 732 nm. The particles were refined to the mean size 150 nm after ultrasonic destruction process with no etching treatment given. However, the mean particle size after immersion in a solution containing HF of 5% for 10, 20, and 30 minutes respectively are 138 nm, 214 nm and 385 nm. While for those of 10% respectively are 142 nm, 235 nm, 302 nm, and for 15%, the mean particle size are respectively 162 nm, 269 nm and 368 nm. As to the crystallite sizes evaluation, results showed no significant changing in crystallite sizes. The mean crystallite sizes were in the range 22-28 nm obtained in all particles after immersion and destruction. It can be concluded that particles of material with longer HF etching treatment tend to increase the size when compared with that of no treatment. The etching process and ultrasonic destruction do not give ant significant effect to the crystallite sizes."

"Single phased SrO.6Fe2-xMnx/2Tix/2O3 (x = 0.0; 0.5; and 1.0) nanoparticles, whose mean size was comparable with the crystallite size, were successfully fabricated through mechanical alloying and a subsequent ultrasonic destruction processes. The ultrasonic destruction process employed a transducer operated under amplitudes of 35, 45, and 55 ?m. Results indicated that the mean particle size was not determined by the transducer amplitude, but the mechanical properties of the materials, as well as the initial size of the particles. After ultrasonic destruction, the mean sizes of the particles decreased to the range of 87–194 nm with a narrow distribution width. The mean particle sizes were about 1 to 3 times larger than the respective crystallite sizes. Such fine particles were aimed to decrease the coercivity, as was seen in the sample with x = 0, which showed a decrease in coercivity from 474 kA.m-1 to 24 kA.m-1 and 15 kA.m-1. A further reduction in the coercivity was observed in Mn-Ti substituted strontium hexaferrite."

"Hasil-hasil tentang pengaruh destruksi ultrasonik terhadap pembentukan nanopartikel material SrO.6Fe2-xMnx/2Tix/2O3 (x = 0.0; 0.5; dan 1.0) dibicarakan dalam skripsi ini. Seluruh material dipersiapkan melalui teknik pemaduan mekanik dimana semua prekursor yang diperlukan dipadukan bersama dalam alat planetary ball mill menghasilkan serbuk halus. Serbuk kemudian dikonsolidasi dalam bentuk bakalan muda dan menjalani tahapan sintering pada temperatur 1200°C selama 3 jam menghasilkan sampel kristalin berfasa tunggal. Serbuk material kristalin didapat melalui penghalusan kembali secara mekanik sampel kristalin selama 10 jam. Hasil evaluasi ukuran partikel menunjukkan ketiga sampel dengan komposisi berbeda memiliki ukuran rata-rata partikel berbeda masing-masing ~ 723 nm untuk x = 0.0, 293 nm untuk x = 1.0 dan 192 nm untuk x = 0.5. Partikel-partikel ini kemudian menjalani tahapan destruksi ultrasonik menggunakan transduser yang dioperasikan pada amplitudo 35, 45 dan 55 μm selama 5 jam. Ternyata, ukuran-ukuran partikel dapat berkurang secara efektif dengan bertambahnya daya transduser. Partikel-partikel material x = 0.0 awalnya memiliki ukuran sampai ~ 1500 nm menjadi mengecil sampai dibawah ukuran 300 nm pada penggunaan transduser dengan amplitudo 35 mikron. Ukuran partikel ini menjadi lebih halus lagi pada penggunaan transduser dengan amplitudo 55 mikron. Namun, hal ini berbeda dengan hasil evaluasi ukuran kristalit dimana tidak ditemukan pengaruh yang berarti pada proses destruksi ultrasonik. Pada partikel material x = 0.0, awalnya memiliki ukuran kristalit 143 nm hanya mengecil menjadi 85 nm paska destruksi ultrasonik mengunakan transduser dengan amplitudo 55 mikron. Hasil penelitian ini menyimpulkan bahwa teknik destruksi mekanik yang dilanjutkan dengan destruksi ultrasonik terhadap partikel dapat menjadi salah satu cara untuk pembuatan partikel-partikel berukuran nanometer. Dari hasil penelitian ini telah diperoleh partikel yang tersusun oleh 1 sampai dengan 3 buah kristalit material SrO.6Fe2-xMnx/2Tix/2O3 (x = 0.0; 0.5; dan 1.0).

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Results on effects of ultrasonic destruction to nanoparticles formation of SrO.6Fe2-xMnx/2Tix/2O3 (x = 0.0; 0.5; and 1.0) materials are reported. Materials were prepared through a mechanical alloying technique in which all precursors were co-milled into fine particles in a planetary ball mill. Sintering of 1200°C for 3 hours was introduced to the green compact which resulting in a single phase crystalline material. Crystalline particles were then obtained after re-milling the sintered samples for 10 hours. Particle size evaluations showed that the three compositions have different value of mean particle sizes respectively ~ 723 nm for x = 0.0, 293 nm for x = 1.0 and 192 nm for x = 0.5. These particles were then subjected to further refining by means of ultrasonic destruction employing 3 different amplitudes respectively 35, 45, and 55 μm for 5 hours each. It was found that the particle sizes were reduced effectively as the amplitude of transducer hence the transducer power increased. For material with x = 0.0, the particles with size up to ~ 1500 nm were reduced significantly to below 300 nm after ultrasonic destruction by a 35 μm transducer and reduced further to 100 nm by a 55 μm transducer. However, for Mn and Ti containing particles, the particle sizes were larger in which for x =1.0, the particles with sizes up to 300 nm were only obtained after ultrasonic destruction by 55 μm transducer. Referring to results of crystallite sizes evaluation for the particles, there is no significant effect to the reduction of crystallite sizes. The mean crystallite size of particles for x = 0.0 was initially 143 nm reduced to only 85 nm after ultrasonic destruction by a 55 μm transducer. It is concluded that the mechanical alloying assisted with ultrasonic destruction has proven to be an alternative route for nanoparticles fabrication. Particles containing up to 3 nano crystallites can be obtained in Mn and Ti substituted Strontium Hexaferrites."