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Abstrak :
[ABSTRAK
Penggunaan gelombang mikro dalam beberapa tahun terakhir ini mengalami peningkatan yang sangat pesat seiring berkembangnya teknologi komunikasi dan informasi. Hal ini menimbulkan masalah baru yakni terjadinya polusi gelombang mikro. Untuk mengimbangi dampak negatif polusi interferensi gelombang elektromagnetik, para peneliti mencoba mengembangkan material penyerap gelombang elektromagnetik. Salah satu material yang menjadi kandidat potensial untuk aplikasi penyerap gelombang mikro adalah material berbasis lantanum manganat. Pada penelitian ini dipelajari rekayasa struktur material berbasis lantanum manganat dengan sistem La0,67Ba0,33Mn1-xNix/2Tix/2O3 (x = 0; 0,02; 0,04 dan 0,06). Fasa tunggal senyawa La0.67Ba0.33Mn1-xNix/2Tix/2O3 berhasil dibuat melalui proses pemaduan mekanik menggunakan prekusor-prekusor La2O3, MnCO3, BaCO3, TiO2, dan NiO dengan tingkat kemurnian tinggi. Selanjutnya serbuk hasil pemaduan mekanik menjalani perlakuan pemanasan pada suhu 1200oC selama 10 jam. Material yang telah dipanaskan kemudian dihaluskan kembali selama 20 jam. Hasil refinement pola difraksi sinar X menunjukkan bahwa senyawa La0,67Ba0,33Mn1-xNix/2Tix/2O3 memiliki strukstur kristal monoklinik untuk seluruh variasi x. Kurva histerisis sampel menunjukkan bahwa material ini termasuk magnet lunak. Hasil evaluasi distribusi ukuran partikel material dengan komposisi terbaik yakni La0,67Ba0,33Mn0,06Ni0,03Ti0,03O3 adalah 82,4 nm. Hasil pengujian sifat serapan gelombang mikro pada rentang 8-12,4 GHz menunjukkan material mampu mereduksi gelombang mikro hingga 94 % pada frekuensi 11,4 GHz. Dengan demikian senyawa La0,67Ba0,33Mn1-xNix/2Tix/2O3 dapat dijadikan sebagai material penyerap gelombang mikro.;

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ABSTRACT
In recent years, application of microwaves has been increased along with the development of communication and information technology and highly produces electromagnetic wave interference. To solve this problem, scientist tries to develop a new material that could absorb electromagnetic waves. One of potential candidates for absorbing materials is lanthanum manganese-based system. In this research, La0.67Ba0.33Mn1-xNix/2Tix/2O3 (x = 0, 0.02, 0.04, and 0.06) compound were studied as a microwaves absorber materials. Single phase of La0.67Ba0.33Mn1-xNix/2Tix/2O3 were successfully synthesized by mechanical alloying method. The mixture of all precursors were first mechanically milled for 20 hours and then sintered at a temperature of 1200oC for 10 h in which a fully crystalline material is ensured. The sintered materials were then re-milled for 20 hours to obtain powder-based nanoparticle. X-ray diffraction refinement shows that the samples have monoclinic structure at all x compositions. The hysteresis curve evaluation showed that the sample materials is soft magnetic. The best composition of La0.67Ba0.33Mn1-xNix/2Tix/2O3 with x = 0.06 has been evaluated. The compound has 82.4 nm particle size distributions and it is able to absorb up to 94% microwaves at 11.4 GHz. The study concluded the material of La0.67Ba0.33Mn1-xNix/2Tix/2O3 have a good potential to be a candidate of microwaves absorbing materials. ;In recent years, application of microwaves has been increased along with the development of communication and information technology and highly produces electromagnetic wave interference. To solve this problem, scientist tries to develop a new material that could absorb electromagnetic waves. One of potential candidates for absorbing materials is lanthanum manganese-based system. In this research, La0.67Ba0.33Mn1-xNix/2Tix/2O3 (x = 0, 0.02, 0.04, and 0.06) compound were studied as a microwaves absorber materials. Single phase of La0.67Ba0.33Mn1-xNix/2Tix/2O3 were successfully synthesized by mechanical alloying method. The mixture of all precursors were first mechanically milled for 20 hours and then sintered at a temperature of 1200oC for 10 h in which a fully crystalline material is ensured. The sintered materials were then re-milled for 20 hours to obtain powder-based nanoparticle. X-ray diffraction refinement shows that the samples have monoclinic structure at all x compositions. The hysteresis curve evaluation showed that the sample materials is soft magnetic. The best composition of La0.67Ba0.33Mn1-xNix/2Tix/2O3 with x = 0.06 has been evaluated. The compound has 82.4 nm particle size distributions and it is able to absorb up to 94% microwaves at 11.4 GHz. The study concluded the material of La0.67Ba0.33Mn1-xNix/2Tix/2O3 have a good potential to be a candidate of microwaves absorbing materials. , In recent years, application of microwaves has been increased along with the development of communication and information technology and highly produces electromagnetic wave interference. To solve this problem, scientist tries to develop a new material that could absorb electromagnetic waves. One of potential candidates for absorbing materials is lanthanum manganese-based system. In this research, La0.67Ba0.33Mn1-xNix/2Tix/2O3 (x = 0, 0.02, 0.04, and 0.06) compound were studied as a microwaves absorber materials. Single phase of La0.67Ba0.33Mn1-xNix/2Tix/2O3 were successfully synthesized by mechanical alloying method. The mixture of all precursors were first mechanically milled for 20 hours and then sintered at a temperature of 1200oC for 10 h in which a fully crystalline material is ensured. The sintered materials were then re-milled for 20 hours to obtain powder-based nanoparticle. X-ray diffraction refinement shows that the samples have monoclinic structure at all x compositions. The hysteresis curve evaluation showed that the sample materials is soft magnetic. The best composition of La0.67Ba0.33Mn1-xNix/2Tix/2O3 with x = 0.06 has been evaluated. The compound has 82.4 nm particle size distributions and it is able to absorb up to 94% microwaves at 11.4 GHz. The study concluded the material of La0.67Ba0.33Mn1-xNix/2Tix/2O3 have a good potential to be a candidate of microwaves absorbing materials. ]

Abstrak :
Material SBA-15 merupakan salah satu material mesopori dengan ukuran pori antara 2-50 nm. Material ini dapat diaplikasikan dalam berbagai penggunaan seperti dalam proses adsorpsi, katalis, filtrasi dan membran. Proses sintesis material SBA-15 dilakukan melalui jalur sol-gel. Bahan dasar yang digunakan ialah tetraethylorthosilicate (TEOS, Si(OC2H5)4) sebagai prekursor (sumber atom Si), surfaktan kopolimer triblok Pluronik P123 (EO20PO20EO20) sabagai cetakan/template dan air yang nanti akan bereaksi dengan TEOS. Kemudian ditambahkan juga bahan aditif yaitu etanol sebagi pelarut antara air dan TEOS dan HCI sebagai katalis. Penelitian ini bertujuan untuk mengetahui pengaruh peningkatan konsentrasi surfaktan terhadap karakteristik pori material mesopori SBA-15, serta memprediksi luas spesifik permukaan material SBA-15 sehlngga bisa diketahui nilai optimum penambahan konsentrasi sulfaktan terhadap luas spesifik permukaan. Variasi peningkatan konsentrasi surfaktan mulai dari 0,007 M hingga 0,066 M, sedangkan konsentrasi TEOS, air, etanol dan HCI dibuat tetap. Proses sintesis material SBA-15 terjadi dalam dua tahap yaitu proses pembentukan gel dan kemudian dilanjutkan dengan proses kalsinasi (400°C). Material SBA-15 kemudian dikarakterisasi dengan particle size; picnometer; SAXD, Adsorpsi-Desorpsi N2, SEM EDS, AFM, FESEM dan TEM. Hasil penelitian menunjukkan bahwa konsentrasi surfaktan tidak mempengaruhi struktur Kristal SBA-15, tetapi semakin tinggi konsentrasi surfaktan akan menurunkan derajat kristalisasi dari struktur heksagonal seperti terlihat dari hasil SAXD. Hasil pengujian luas spesifk permukan dengan adsorpsi-desorpsi N2 memperlihatkan peningkatan luas spesifik permukaan dari 482,20 m²/g menjadi 746,70 m²/g, dengan persentase kenaikan sebesar 54%. Peningkatan luas spesifik permukaan tersebut secara umum disebabkan oleh terbentuknya pori utama. Dengan metode perhitungan luas spesifik permukaan teoritis, diprediksi bahwa konsentrasi surfaktan optimum adalah sebesar 0,054 M, dimana nilai eksperimental luas spesifik permukaannya memiliki kesesuaian dengan nilai teoritis. Pada konsentrasi ini diperkirakan sebagai kontribusi maksimum dari pori utama. Pada konsentrasi surfaktan sebesar 0, 060 M dan 0,066 M dengan persentase kenaikan 11,11% dan 22,20% dari konsentrasi surfaktan 0,054 M akan lerjadi peningkatan luas spesifik permukaan dari 598,50 m²/g menjadi 702,10 m²/g dan 746,70 m²/g dengan persentase kenaikan 17,30% dan 24, 76%. Peningkatan luas spesifik permukaan ini bukan Iagi disebabkan oleh terbentuknya pori utama, melainkan pori antar dinding (intrawall pores). Pori intrawall tersebut terbentuk akibat kecenderungan kemampuan self assembly dari surfaktan pada daerah di antara pori-pori utama.

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SBA-15 belongs to mesoporous material having pore size ranging from 2 to 50 nm. This material can be applied in many application such as in adsoption process, catalist, filtration and membrane. SBA-15 was synthesized via sol-gel technique from tetraethylorthosilicate (TEOS, Si(OC2H5)4) as Si source/precursor surfactant triblok copolimer Pluronik P123 (EO20PO70EO20) and water which will react with TEOS. To enhance dissolution of TEOS in water; ethanol and HCl catalyst were added. This study was focused on the effect of surfactant concentration on the pore characteristics and optimization of the specific surface area of SBA-15. Surfactant concentration was varied from 0.007 to 0.066 M while TEOS, water, ethanol and HCl concentration were held constant. The synthesis was divided into two stage i.e gel formation and calcination at 400°C. Characterization of the product was performed using particle sizer; picnometer, SAXD, N2 adsorption-desorption, SEM, EDS, AFM, FESEM and TEM. The SAXD result shows that surfactant concentration can not effect crystal formation, but it will decrease the degree of hexagonal crystal formation. Measurement of specific surface area using N2 adsorption-desorption technique indicates an increase from 482.20 m²/g became 746.70 m²/g which in percentage was 54%. This increasing of specific surface area were mainly caused by main pore formation. It was theoritically calculated that optimum surfactant concentration was 0,054 M where the experimental value of specific surface area was close to its theoritical one. This concentration is considered the maximum specific surface area which is contributed by the main pores. In surfactant concentration 0.060 M and 0.066 M where in percentage are 11.11% and 22.20% from surfactant concentration 0.064 M, the specific surface area from 598.50 m²/g will increase became 702.10 m²/g and 746.70 m²/g, which are 17.30% and 24, 76% respectively. This increasing of specific surface area are not caused by main pore formation, but it was contribution of intrawall pores. These intrawall pores were formed as a result of surfactant tendency for self assembly in areas between the main pores.

Abstrak :
Lantanum manganat LaMnO3 (LMO) adalah material yang sedang menjadi perhatian banyak peneliti sampai saat ini karena memiliki potensi untuk diterapkan pada berbagai aplikasi terutama pada bidang magnetik-elektrik. Modifikasi struktur kristal senyawa LMO melalui subsitusi parsial ion La dan Mn dapat menginduksi sifat elektrik-magnetik seperti giant magneto resistance (GMR) atau colossal magneto resistance (CMR). Berdasarkan telusuran literatur, diketahui bahwa substitusi parsial ion La oleh ion Sr dan ion Mn oleh ion Fe dapat menimbulkan sifat baru, selain GMR atau CMR, juga memiliki kemampuan menyerap gelombang elektromagnetik, khususnya dalam rentang frekwensi ultra-tinggi (GHz). Dengan demikian senyawa LMO termodifikasi adalah merupakan salah satu radar absorbing materials (RAM) yaitu suatu material berkemampuan menyerap gelombang radar. Pada penelitian ini, dipelajari rekayasa struktur senyawa LMO dengan komposisi (La1-xSrx) (Mn0,25Fe0,5Ti0,25)O3 dimana x =0,25; 0,5; 0,75 dan 1,0. Pada tahapan sintesis material diperkenalkan teknik penggabungan antara pemaduan mekanik (mechanical alloying) dan destruksi sonikasi daya tinggi untuk menghasilkan ukuran rata-rata partikel skala nanometer. Karakterisasi material mencakup observasi struktur mikro, identifikasi fasa, sifat magnetik dan sifat absorbsi. Hasil penelitian menunjukkan bahwa material hasil pemaduan mekanik memiliki distribusi ukuran rata-rata partikel bimodal dengan waktu penghalusan relatif panjang (puluhan sampai ratusan jam) untuk memperoleh ukuran partikel rata-rata terendah. Bila sintesis melibatkan destruksi ultrasonik, distribusi ukuran partikel bersifat monomodal dengan ukuran partikel rata-rata mencapai <100 nm dalam waktu kurang dari 10 jam. Pola difraksi sinar X material memperlihatkan bahwa keseluruhan komposisi memiliki fasa tunggal dikarenakan jari-jari ion La dan Sr setara, demikian juga ion Fe dan Mn. Hasil evaluasi karakteristik serapan gelombang mikro material berdasarkan pengujian Vector Network Analyzer (VNA) memastikan bahwa keseluruhan material bersifat penyerap gelombang mikro dalam jangkau frekwensi 8 - 15 GHz. Serapan tertinggi terjadi pada frekwensi 14,8 GHz dengan nilai Reflection Loss ~ 1 dB atau 10 % gelombang yang datang diserap oleh material. Efek ukuran partikel dengan nilai rata-rata 90 nm meningkatkan kemampuan penyerapan hingga mencapai lebih dari 60 %. Penggabungan material ini dengan senyawa magnetik hexaferrite pada jaringan komposit memperlihatkan dua serapan setara pada dua frekwensi yang berbeda (10 dan 14,8 Ghz). Pengaruh komposisi pada sistem komposit memberikan efek pelebaran terhadap kedua puncak serapan hingga terbentuk sebuah serapan dengan jangkau frekwensi yang lebar (8-15 GHz). Kesimpulan pada penelitian ini adalah sintesis material penyerap gelombang mikro senyawa (La1-xSrx) (Mn0,25Fe0,5Ti0,25)O3 dengan ukuran rata-rata kristal berskala nanometer diperoleh secara efektif melalui penggabungan teknik pemaduan mekanik dan destruksi ultrasonik. Efek ukuran partikel adalah meningkatkan daya serap material. Penggabungan material ini dengan material magnetik hexaferrite dalam sistem komposit menghasilkan suatu material penyerap gelombang mikro dalam rentang frekwensi serapan yang lebar.

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Lanthanum manganites, LMO especially those doped LaMnO3, have attracted attentions of many researchers, due to their significant potential for applications in the field of magnetic electronic functional materials. Structural modification either through doping of La with Ca, Sr, and Ba or Mn with Fe, Cu, and Ti has been reported to induce electromagnetic properties such as giant magneto resistance (GMR) or colossal magneto resistance (CMR). A partial substitution of La with Sr or Mn with Fe gives rise to new properties, in addition to the GMR or CMR, in which the substituted LMO has the ability to absorb electromagnetic waves, especially in the ultra-high frequency range (GHz). Thus, doped LaMnO3 can be considered as one of radar-absorbing materials (RAM). In this study, structural modification of LMO with designated compositions (La1-xSrx) (Mn0.25Fe0.50Ti0.25)O3 where as x = 0.25; 0.50; 0.75 and 1.0 is reported. The materials were prepared by mechanical alloying assisted with high-power sonication to produce particles with mean size in a nanometer scale. Material characterization includes the observation of microstructures, identification oh phase materials, magnetic properties and microwave absorption characteristics. It was found that mechanically alloyed of doped LMO have a bimodal particle size distribution and required a relatively long milling time (tens to hundreds of hours) to obtain the lowest average particle size. It was also found that when sintered mechanically alloyed powders were further treated under the application of a high power sonicator, a monomodal particle size distribution with mean particle size of less than 100 nm was obtained within less than 10 hrs. X-ray diffraction traces indicated that synthesized materials are single phase due to ionic radii of La and Sr ions are almost similar. This is also applicable to Fe and Mn ions. Results of microwave absorption characteristics as evaluated by Vector Network Analyzer ensure that the entire materials have capability to absorb the microwaves in the frequency range 8-15 GHz. The highest absorption was occurred at 14.8 GHz with a Reflection Loss ~ 1 dB. It means that only 10% of the incident wave energy was absorbed by the material. However, materials with the average particle size ~ 90 nm increased the absorption up to 60%. Incorporation the doped LMO with hexaferrite particles in a composite structure has resulted two similar absorption peaks at two different frequencies (10 and 14.8 GHz). Furthermore, variation in composition of composite system was widening the absorption peak into a single peak with a wide range frequency (8-15 GHz). It is concluded that mechanical alloying coupled with ultra sonication can be an alternative route for the preparation of fine and homogeneous powder materials leading to nanoparticle-based materials. Effect of fine particles in the materials is to increase the microwave absorbing properties. Where as the composite structure is to affect the frequency absorption width.

Abstrak :
Lantanum manganat LaMnO3 (LMO) adalah material yang sedang menjadi perhatian banyak peneliti sampai saat ini karena memiliki potensi untuk diterapkan pada berbagai aplikasi terutama pada bidang magnetik-elektrik. Modifikasi struktur kristal senyawa LMO melalui subsitusi parsial ion La dan Mn dapat menginduksi sifat elektrik-magnetik seperti giant magneto resistance (GMR) atau colossal magneto resistance (CMR). Berdasarkan telusuran literatur, diketahui bahwa substitusi parsial ion La oleh ion Sr dan ion Mn oleh ion Fe dapat menimbulkan sifat baru, selain GMR atau CMR, juga memiliki kemampuan menyerap gelombang elektromagnetik, khususnya dalam rentang frekwensi ultra-tinggi (GHz). Dengan demikian senyawa LMO termodifikasi adalah merupakan salah satu radar absorbing materials (RAM) yaitu suatu material berkemampuan menyerap gelombang radar. Pada penelitian ini, dipelajari rekayasa struktur senyawa LMO dengan komposisi (La1-xSrx) (Mn0,25Fe0,5Ti0,25)O3 dimana x =0,25; 0,5; 0,75 dan 1,0. Pada tahapan sintesis material diperkenalkan teknik penggabungan antara pemaduan mekanik (mechanical alloying) dan destruksi sonikasi daya tinggi untuk menghasilkan ukuran rata-rata partikel skala nanometer. Karakterisasi material mencakup observasi struktur mikro, identifikasi fasa, sifat magnetik dan sifat absorbsi. Hasil penelitian menunjukkan bahwa material hasil pemaduan mekanik memiliki distribusi ukuran rata-rata partikel bimodal dengan waktu penghalusan relatif panjang (puluhan sampai ratusan jam) untuk memperoleh ukuran partikel rata-rata terendah. Bila sintesis melibatkan destruksi ultrasonik, distribusi ukuran partikel bersifat monomodal dengan ukuran partikel rata-rata mencapai <100 nm dalam waktu kurang dari 10 jam. Pola difraksi sinar X material memperlihatkan bahwa keseluruhan komposisi memiliki fasa tunggal dikarenakan jari-jari ion La dan Sr setara, demikian juga ion Fe dan Mn. Hasil evaluasi karakteristik serapan gelombang mikro material berdasarkan pengujian Vector Network Analyzer (VNA) memastikan bahwa keseluruhan material bersifat penyerap gelombang mikro dalam jangkau frekwensi 8 ? 15 GHz. Serapan tertinggi terjadi pada frekwensi 14,8 GHz dengan nilai Reflection Loss ~ 1 dB atau 10 % gelombang yang datang diserap oleh material. Efek ukuran partikel dengan nilai rata-rata 90 nm meningkatkan kemampuan penyerapan hingga mencapai lebih dari 60 %. Penggabungan material ini dengan senyawa magnetik hexaferrite pada jaringan komposit memperlihatkan dua serapan setara pada dua frekwensi yang berbeda (10 dan 14,8 Ghz). Pengaruh komposisi pada sistem komposit memberikan efek pelebaran terhadap kedua puncak serapan hingga terbentuk sebuah serapan dengan jangkau frekwensi yang lebar (8-15 GHz). Kesimpulan pada penelitian ini adalah sintesis material penyerap gelombang mikro senyawa (La1-xSrx) (Mn0,25Fe0,5Ti0,25)O3 dengan ukuran rata-rata kristal berskala nanometer diperoleh secara efektif melalui penggabungan teknik pemaduan mekanik dan destruksi ultrasonik. Efek ukuran partikel adalah meningkatkan daya serap material. Penggabungan material ini dengan material magnetik hexaferrite dalam sistem komposit menghasilkan suatu material penyerap gelombang mikro dalam rentang frekwensi serapan yang lebar.

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Lanthanum manganites, LMO especially those doped LaMnO3, have attracted attentions of many researchers, due to their significant potential for applications in the field of magnetic electronic functional materials. Structural modification either through doping of La with Ca, Sr, and Ba or Mn with Fe, Cu, and Ti has been reported to induce electromagnetic properties such as giant magneto resistance (GMR) or colossal magneto resistance (CMR). A partial substitution of La with Sr or Mn with Fe gives rise to new properties, in addition to the GMR or CMR, in which the substituted LMO has the ability to absorb electromagnetic waves, especially in the ultra-high frequency range (GHz). Thus, doped LaMnO3 can be considered as one of radar-absorbing materials (RAM). In this study, structural modification of LMO with designated compositions (La1-xSrx) (Mn0.25Fe0.50Ti0.25)O3 where as x = 0.25; 0.50; 0.75 and 1.0 is reported. The materials were prepared by mechanical alloying assisted with high-power sonication to produce particles with mean size in a nanometer scale. Material characterization includes the observation of microstructures, identification oh phase materials, magnetic properties and microwave absorption characteristics. It was found that mechanically alloyed of doped LMO have a bimodal particle size distribution and required a relatively long milling time (tens to hundreds of hours) to obtain the lowest average particle size. It was also found that when sintered mechanically alloyed powders were further treated under the application of a high power sonicator, a monomodal particle size distribution with mean particle size of less than 100 nm was obtained within less than 10 hrs. X-ray diffraction traces indicated that synthesized materials are single phase due to ionic radii of La and Sr ions are almost similar. This is also applicable to Fe and Mn ions. Results of microwave absorption characteristics as evaluated by Vector Network Analyzer ensure that the entire materials have capability to absorb the microwaves in the frequency range 8-15 GHz. The highest absorption was occurred at 14.8 GHz with a Reflection Loss ~ 1 dB. It means that only 10% of the incident wave energy was absorbed by the material. However, materials with the average particle size ~ 90 nm increased the absorption up to 60%. Incorporation the doped LMO with hexaferrite particles in a composite structure has resulted two similar absorption peaks at two different frequencies (10 and 14.8 GHz). Furthermore, variation in composition of composite system was widening the absorption peak into a single peak with a wide range frequency (8-15 GHz). It is concluded that mechanical alloying coupled with ultra sonication can be an alternative route for the preparation of fine and homogeneous powder materials leading to nanoparticle-based materials. Effect of fine particles in the materials is to increase the microwave absorbing properties. Where as the composite structure is to affect the frequency absorption width.

Abstrak :
[ABSTRAK
Pada penelitian Disertasi ini telah dilakukan rekayasa material untuk pembuatan nano komposit magnetoelectric yang merupakan material multifungsi dengan menggabungkan antara material berfasa ferromagnetik dan material berfasa ferroelektrik Rekayasa material dilakukan dengan menggunakan metoda mechanical alloying yang dilanjutkan dengan penghalusan secara mekanik dan destruksi ultrasonik daya tinggi untuk mendapatkan ukuran partikel dalam skala nanometer Material nanokomposit dipersiapkan dalam bentuk pellet Komponen komponen komposit baik itu Ba0 7Sr0 3O 6 Fe2O3 B7S3HF dan Ba0 7Sr0 3TiO3 B7S3T mengunakan material nanopartikel yang merupakan hasil subsitusi parsial ion Ba dengan Sr pada senyawa BHF dan BT sehingga meningkatkan volume sel satuan Hasil pengujian X Ray Diffraction XRD menunjukan bahwa sampel yang dihasilkan merupakan material fasa tunggal untuk senyawa Ba0 7Sr0 3O 6 Fe2O3 BSHF dan Ba0 7Sr0 3TiO3 BST Pengujian kemagnetan material dilakukan dengan Permagraph sedangkan sifat elektrik material dilakukan dengan electrometer Hasil pengujian ini menaikkan nilai magnetisasi remanen untuk BSHF dari BHF masing masing adalah 0 180 T dan dan 0 16 T menurunkan nilai koersivitas masing masing adalah 275 54 kA m 1 dan 322 14 kA m 1 Nilai ini sesuai dengan nilai yang dipublikasikan dalam berbagai literatur dan dengan demikian sintesis material berbasis BSHF dan BHF dengan metode yang diterapkan dipastikan menghasilkan material berfasa tungal Demikian juga halnya dengan hasil karakterisasi material BST dengan electrometer diperoleh nilai polarisasi total untuk BaTiO3 dan Ba0 7Sr0 3TiO3 masing masing adalah 42 8 C cm 2 dan 40 7 C cm 2 Hasil pengujian dengan menggunakan Particle Size Analyzer PSA terhadap material komponen komposit menunjukkan ukuran rata rata partikel Ba0 7Sr0 3TiO3 atau B7S3T adalah 78 nm dan Ba0 7Sr0 3O 6 Fe2O3 atau B7S3HF adalah 44 nm yang diperoleh pasca penghalusan mekanik yang dilanjutkan dengan destruksi ultrasonik selama 12 jam Sedangkan sifat kemagnetan material B7S3HF adalah 0 180 T untuk magnetisasi remanen dan 275 54 kA m 1 untuk nilai koersivitas Nilai magnetisasi remanen mengalami peningkatan menjadi 0 249 T karena efek induksi anisotropi oleh medan magnet luar sebesar 5 mT tanpa penurunan nilai koersivitas Dalam bentuk nanokomposit B7S3T B7S3HF dengan komposisi 1 1 dalam fraksi massa diperoleh hasil 0 115 T untuk nilai remanen dan 282 14 kA m 1 untuk nilai koersivitas tanpa induksi anisotropi Nilai magnetisai remanen ini adalah 46 nilai remanen B7S3HF tanpa induksi anisotropi Nilai remanen sampel nanokomposit meningkat menjadi 0 148 T tanpa perubahan nilai koersivitas setelah induksi anisotropi Maka dapat disimpulkan bahwa ada peningkatan sebesar 0 010 T atau 8 berasal dari efek kopling antara kristalit B7S3HF dan B7S3T merupakan salah satu sifat magnetoelektric Hasil inspeksi nilai remanen terhadap material B7S3HF baik dalam jaringan komposit B7S3T B7S3HF memperlihatkan bahwa efek induksi anisotropi telah meningkat nilai magnetisasi remanen serta memperlihatkan munculnya sifat magnetoelektrik dalam sistem komposit;

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ABSTRACT
In this Dissertation research synthesize of magnetoelectric nanocomposite which is multifunctional materials was carried out by combining ferromagnetic and ferroelectric components Nanocomposites were made of barium strontium hexaferrite Ba0 7Sr0 3O 6 Fe2O3 B7S3HF as ferromagnetic and barium strontium titanate dan Ba0 7Sr0 3TiO3 B7S3T as ferroelectric components Materials preparation was carried out trough mechanical alloying route which followed by mechanical refinement and high power ultrasonic destruction to obtain particle sizes in the nanometer scales Nanocomposite materials were prepared in pellet form In this case components of composite which are B7S3T and B7S3HF made of nanoparticles Phase identification by X Ray Diffraction XRD method showed that all samples B7S3T and B7S3HF are respectively single phase materials As to the characterization it was found that partial substitution of Ba ions by Sr ions in BT and BHF has increased the volume of their respective unit cell The magnetic properties of magnetic materials which evaluated by a Permagraph have derived values for remanent magnetization of B7S3HF and BHF were respectively 0 18 T and 0 16 T with their corresponding coercivity 275 54 kA m 1 and 322 14 kA m 1 respectively These values are almost similar to the values published elsewhere for BHF and BT which then confirmed once again that the synthesized BHF and BT based materials material are single phase Similarly results of material characterization for B7S3T with an electrometer has derived total polarization values obtained for BaTiO3 and B7S3T were 42 8 C cm 2 and 40 7 C cm 2 respectively Test results using Particle Size Analyzer PSA of the material components for the composites showed that the mean particle size of Ba0 7Sr0 3TiO3 or B7S3T is 78 nm and that of Ba0 7Sr0 3O 6 Fe2O3 or B7S3HF is 44 nm which were obtained after further refining under mechanical milling followed by high power ultrasonic destruction for 12 hours Whereas the remanent magnetization of B7S3HF is 0 180 T and 275 54 kA m 1 for the coercivity The remanent magnetization value increased to 0 249 T with no changing in the coercivity value after anisotropy induced by an external magnetic field of 5 mT In addition the isotropic B7S3T B7S3HF nanocomposite with a composition 1 1 mass fraction has a remanent magnetization value of 0 115 T with a corresponding coercivity of 282 14 kA m 1 The remanence value of 0 115 T is about 46 of that of an isotropic B7S3HF However the remanent magnetization value for nanocomposite samples increased to 0 148 T with no change in coercivity after induced anisotropy It then can be concluded that there was an increase of 0 010 T or 8 in a remanent value which rose from coupling effects between crystallites of B7S3HF and B7S3T Results of inspection in remanent values for a ferromagnetic B7S3HF material present alone as well as in B7S3T B7S3HF composites showed that the all samples have shown an increased in remanent magnetization values which rose from magneto electric properties , In this Dissertation research synthesize of magnetoelectric nanocomposite which is multifunctional materials was carried out by combining ferromagnetic and ferroelectric components Nanocomposites were made of barium strontium hexaferrite Ba0 7Sr0 3O 6 Fe2O3 B7S3HF as ferromagnetic and barium strontium titanate dan Ba0 7Sr0 3TiO3 B7S3T as ferroelectric components Materials preparation was carried out trough mechanical alloying route which followed by mechanical refinement and high power ultrasonic destruction to obtain particle sizes in the nanometer scales Nanocomposite materials were prepared in pellet form In this case components of composite which are B7S3T and B7S3HF made of nanoparticles Phase identification by X Ray Diffraction XRD method showed that all samples B7S3T and B7S3HF are respectively single phase materials As to the characterization it was found that partial substitution of Ba ions by Sr ions in BT and BHF has increased the volume of their respective unit cell The magnetic properties of magnetic materials which evaluated by a Permagraph have derived values for remanent magnetization of B7S3HF and BHF were respectively 0 18 T and 0 16 T with their corresponding coercivity 275 54 kA m 1 and 322 14 kA m 1 respectively These values are almost similar to the values published elsewhere for BHF and BT which then confirmed once again that the synthesized BHF and BT based materials material are single phase Similarly results of material characterization for B7S3T with an electrometer has derived total polarization values obtained for BaTiO3 and B7S3T were 42 8 C cm 2 and 40 7 C cm 2 respectively Test results using Particle Size Analyzer PSA of the material components for the composites showed that the mean particle size of Ba0 7Sr0 3TiO3 or B7S3T is 78 nm and that of Ba0 7Sr0 3O 6 Fe2O3 or B7S3HF is 44 nm which were obtained after further refining under mechanical milling followed by high power ultrasonic destruction for 12 hours Whereas the remanent magnetization of B7S3HF is 0 180 T and 275 54 kA m 1 for the coercivity The remanent magnetization value increased to 0 249 T with no changing in the coercivity value after anisotropy induced by an external magnetic field of 5 mT In addition the isotropic B7S3T B7S3HF nanocomposite with a composition 1 1 mass fraction has a remanent magnetization value of 0 115 T with a corresponding coercivity of 282 14 kA m 1 The remanence value of 0 115 T is about 46 of that of an isotropic B7S3HF However the remanent magnetization value for nanocomposite samples increased to 0 148 T with no change in coercivity after induced anisotropy It then can be concluded that there was an increase of 0 010 T or 8 in a remanent value which rose from coupling effects between crystallites of B7S3HF and B7S3T Results of inspection in remanent values for a ferromagnetic B7S3HF material present alone as well as in B7S3T B7S3HF composites showed that the all samples have shown an increased in remanent magnetization values which rose from magneto electric properties ]

Abstrak :
[ABSTRAK
Telah dilakukan penelitian pembuatan beton ringan atau lightweight concrete (LWC) menggunakan batu apug (BA) dan abu sekam padi (ASP). Sampel beton ringan yang dibuat mengandung BA dengan fraksi berbeda, adapun material semen, pasir, dan abu sekam padi volumenya dijaga tetap. Terdapat dua parameter utama yang menentukan sifat mekanik sampel LWC masing-masing adalah densitas sampel dan rasio air/semen (w/c). Sifat mekanik yang paling utama dari LWC adalah kekuatan tekan. Pada campuran dengan fraksi volume batu apung terbesar (100%) menghasilkan densitas dan kekuatan tekan paling rendah masing-masing sebesar (1389,6 kg/m3 dan 11,1 MPa). Diketahui bahwa makin rendah fraksi batu apung dalam sampel beton makin tinggi nilai densitas dan kekuatan tekannya, disebabkan oleh tingginya nilai fraksi pori baik pori terbuka maupun pori tertutup dalam sampel beton. Observasi terhadap fotomikro SEM batu apung menunjukkan bahwa terdapat sejumlah besar pori dengan bentuk memanjang ke bagian dalam dari permukaan sampel beton. Pori hadir dengan kerapatan jumlah pori relatif besar serta dengan ukuran yang bervariasi. Fakta ini menjelaskan mengapa batu apung besifat ringan karena memiliki densitas massa yang rendah. Pola difraksi sinar X sampel beton ringan memperlihatkan dominasi fasa kristalin diidentifikasi sebagai fasa quartz (SiO2). Namun dapat dipastikan sampel beton ringan terdiri dari fasa campuran antara fasa kristalin dan dengan sedikit fasa amorph. Fotomikro SEM beton ringan menunjukkan bahwa senyawa Kalsium Silikat Hidrat (CSH) mulai tumbuh pada waktu awal proses hidrasi dan terus berkembang sampai umur beton mencapai umur hidrasi 28 hari yang ditandai dengan sifat fisik yang padat dan peningkatan kekuatan beton. Dapat dipastikan bahwa senyawa CSH ini memiliki peranan penting terhadap pengaturan sifat mekanik seperti kekuatan tekan. Penelitian ini menyimpulkan bahwa batu apung dan abu sekam padi adalah material berbasis silika amorph yang memiliki densitas lebih rendah terutama dibandingkan dengan material pembentuk beton lainnya. Baik densitas dan kekuatan tekan sampel beton ringan ditentukan oleh rasio antara batu apung dan abu sekam padi. Ditemukan rasio terkecil BA/ASP yaitu 8 menghasilkan nilai densitas dan kekuatan tekan optimal, masing-masing pada usia beton 28 hari sebesar 1891 kg/m3 dan 23 MPa. Komposisi beton ringan yang terbaik diperoleh dari hasil penelitian ini adalah komposisi campuran PCC (1,00) : Pasir (1,00) : ASP (0,05) : BA (0,50) dengan nilai Slump 8 cm ditandai oleh nilai rasio antara kuat tekan dan densitas tertinggi adalah 1285.;

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ABSTRACT
Research studies on the manufacture of lightweight concrete (LWC) using pumice and rice husk ash (RHA) materials have been done. LWC samples were made of pumice materials with a different mass fraction, while the cement, sand, and rice husk ash materials were keep fixed. It was found that there are two main parameters that determine the mechanical properties of LWC which are density and the water and cement ratio (w/c ratio). The main mechanical properties of LWC sample is the power press. Samples with the largest volume fraction of pumice (100%) resulted in lightest density (1389.6 kg/m3) and the smallest strength of LWC (11.1 MPa). It was found that, the lower the mass fraction of pumice in LWC samples, the higher the density values and compressive strength were obtained. This was caused by the high mas fraction value of pores, which were both open and closed pores. Scanning electron micorscopy (SEM) images for the pumice showed that the there are a large number of regular and structured pores extending deep inside the surface of the sample. It was observed that pores present with pore size does not vary significantly but with the density of the relatively large number of pores, indicating pumice has a low mass density. The XRD pattern of the lightweight concrete samples indicated that the samples were dominated by crystalline phases in which the quartz (SiO2) is the main phase and a small fraction of amorphous phase was also obtained. SEM images of lightweight concrete samples showed that the structure of Calcium Silicate Hydrates (CSH) started growing at the beginning of hydration time and continue to evolve into a more solid structure until the age of 28 days, where the compound has an important role to the mechanical properties such as compressive strength. The study concluded that the pumice and rice husk ash is are amorphous silica-based material which has a lower density compared to other concrete forming material such as cement and sands. Both density and light weight concrete compressive strength are determined by the ratio between pumice and rice husk ash, in which the smallest ratio 8 resulted in the largest density and compressive strength, which are 1890.5 kg/m3 and 23.2 MPa respectively at the age of 28 days. The study concluded that the best composition for lightweight concrete samples was the following: PCC (1,00): Sand (1,00): ASP (0,05): BA (0,50) with a slump value of 8 cm resulted in the largest value of a ratio between compressive strength and density of 1285.;Research studies on the manufacture of lightweight concrete (LWC) using pumice and rice husk ash (RHA) materials have been done. LWC samples were made of pumice materials with a different mass fraction, while the cement, sand, and rice husk ash materials were keep fixed. It was found that there are two main parameters that determine the mechanical properties of LWC which are density and the water and cement ratio (w/c ratio). The main mechanical properties of LWC sample is the power press. Samples with the largest volume fraction of pumice (100%) resulted in lightest density (1389.6 kg/m3) and the smallest strength of LWC (11.1 MPa). It was found that, the lower the mass fraction of pumice in LWC samples, the higher the density values and compressive strength were obtained. This was caused by the high mas fraction value of pores, which were both open and closed pores. Scanning electron micorscopy (SEM) images for the pumice showed that the there are a large number of regular and structured pores extending deep inside the surface of the sample. It was observed that pores present with pore size does not vary significantly but with the density of the relatively large number of pores, indicating pumice has a low mass density. The XRD pattern of the lightweight concrete samples indicated that the samples were dominated by crystalline phases in which the quartz (SiO2) is the main phase and a small fraction of amorphous phase was also obtained. SEM images of lightweight concrete samples showed that the structure of Calcium Silicate Hydrates (CSH) started growing at the beginning of hydration time and continue to evolve into a more solid structure until the age of 28 days, where the compound has an important role to the mechanical properties such as compressive strength. The study concluded that the pumice and rice husk ash is are amorphous silica-based material which has a lower density compared to other concrete forming material such as cement and sands. Both density and light weight concrete compressive strength are determined by the ratio between pumice and rice husk ash, in which the smallest ratio 8 resulted in the largest density and compressive strength, which are 1890.5 kg/m3 and 23.2 MPa respectively at the age of 28 days. The study concluded that the best composition for lightweight concrete samples was the following: PCC (1,00): Sand (1,00): ASP (0,05): BA (0,50) with a slump value of 8 cm resulted in the largest value of a ratio between compressive strength and density of 1285., Research studies on the manufacture of lightweight concrete (LWC) using pumice and rice husk ash (RHA) materials have been done. LWC samples were made of pumice materials with a different mass fraction, while the cement, sand, and rice husk ash materials were keep fixed. It was found that there are two main parameters that determine the mechanical properties of LWC which are density and the water and cement ratio (w/c ratio). The main mechanical properties of LWC sample is the power press. Samples with the largest volume fraction of pumice (100%) resulted in lightest density (1389.6 kg/m3) and the smallest strength of LWC (11.1 MPa). It was found that, the lower the mass fraction of pumice in LWC samples, the higher the density values and compressive strength were obtained. This was caused by the high mas fraction value of pores, which were both open and closed pores. Scanning electron micorscopy (SEM) images for the pumice showed that the there are a large number of regular and structured pores extending deep inside the surface of the sample. It was observed that pores present with pore size does not vary significantly but with the density of the relatively large number of pores, indicating pumice has a low mass density. The XRD pattern of the lightweight concrete samples indicated that the samples were dominated by crystalline phases in which the quartz (SiO2) is the main phase and a small fraction of amorphous phase was also obtained. SEM images of lightweight concrete samples showed that the structure of Calcium Silicate Hydrates (CSH) started growing at the beginning of hydration time and continue to evolve into a more solid structure until the age of 28 days, where the compound has an important role to the mechanical properties such as compressive strength. The study concluded that the pumice and rice husk ash is are amorphous silica-based material which has a lower density compared to other concrete forming material such as cement and sands. Both density and light weight concrete compressive strength are determined by the ratio between pumice and rice husk ash, in which the smallest ratio 8 resulted in the largest density and compressive strength, which are 1890.5 kg/m3 and 23.2 MPa respectively at the age of 28 days. The study concluded that the best composition for lightweight concrete samples was the following: PCC (1,00): Sand (1,00): ASP (0,05): BA (0,50) with a slump value of 8 cm resulted in the largest value of a ratio between compressive strength and density of 1285.]

Abstrak :
Abu terbang hasil dari pembakaran batubara dapat digunakan sebagai prekursor geopolimer. Pengisi berupa serbuk alumina, serat asikular wolastonit, serat karbon dan serat kaca ditambahkan untuk menghasilkan komposit matrik geopolimer. Campuran prekursor dan aktivator dikarakterisasi dengan mesin uji viskositas dinamik Brookfield dan peralatan Vicat Needle. Sintesa geopolimersasi diamati dengan menggunakan XRD, FTIR dan pengamatan SEM, sedangkan pengujian mekanis menggunakan mesin uji tarik universal. Temperatur awal pembekuan dari campuran memberikan pengaruh besar terhadap kekuatan mekanis dari resin yang dihasilkan. Penambahan pengisi serat asikular wolastonit sebanyak 2,50 persen berat mampu meningkatkan kekuatan fleksural sebesar 13,52 persen dan penambahan pengisi alumina sebesar 7,50 persen mampu meningkatkan kekuatan tekan sebesar 26,62 persen. Setelah ekspos panas, komposit berpengisi serat kaca mampu menghasilkan kekuatan mekanis terbaik. ......Fly ash from coal combustion can be used as a geopolymer precursor. Fillers such as alumina powder, acicullar wolastonit, carbon fibers and glass fibers are added to produce geopolymer matrix composites. The mixture of precursors and activators characterized by Brookfield dynamic viscosity tester and Vicat Needle apparatus. Geopolymerisation syntesa observed using XRD, FTIR and SEM, while the mechanical testing using a universal tensile testing machine. The initial temperature of the mixture gives a major influence on the mechanical strength of the resin produced. The addition of acicullar wollastonite fillers as much as 2.50 percent by weight can improve the flexural strength of 13.52 percent and the addition of 7.50 percent alumina can improve the compressive strength of 26.62 percent. Upon heat exposure, composite using glass fiber as filler able to produce the best mechanical strength.

Abstrak :
Proses anodisasi pada aluminium menghasilkan struktur fenomenal berupa oksida logam yang terkenal dengan istilah Anodic Aluminum Oxide (AAO). AAO sangat diperlukan untuk meningkatkan daya adhesi pada proses pelapisan selanjutnya baik pada aluminium dan paduannya maupun komposit aluminium. Hal tersebut terjadi akibat adanya ikatan saling kunci antara lapisan oksida hasil anodisasi (AAO) dengan pelapis berikutnya. Morfologi pori pada AAO dapat dengan mudah dimodifikasi melalui perubahan parameter anodisasi. Namun, sayangnya penelitian-penelitian sebelumnya belum menyediakan informasi apapun mengenai pengontrolan diameter pori. Sedangkan seperti yang kita ketahui bahwa perbedaan aplikasi yang diinginkan membutuhkan diameter pori yang berbeda pula. Oleh karena itu guna mendapatkan diameter pori dengan ukuran tertentu maka pemilihan parameter proses anodisasi yang tepat sangatlah penting. Untuk memenuhi kebutuhan tersebut, dalam penelitian ini akan dihasilkan persamaan empiris yang dapat memprediksi ukuran diameter dan densitas pori AAO yang terbentuk hasil anodisasi dengan berbagai parameter tertentu agar dapat digunakan dalam aplikasi yang sesuai. Tujuan utama penelitian ini adalah pengembangan persamaan empiris yang menggambarkan hubungan konsentrasi oksalat, tegangan dan waktu anodisasi terhadap diameter pori. Namun penelitian ini juga menganalisis mekanisme pembentukan, karakteristik, dan ketahanan korosi lapisan terintegrasi pada Al7075/SiC. Serta menganalisis pengaruh konsentrasi, temperatur, dan resistivitas larutan elektrolit, dan tegangan anodisasi terhadap diameter dan densitas pori AAO pada aluminium foil. Proses anodisasi Al7075/SiC dilakukan dalam larutan asam sulfat 16% H2SO4 dengan rapat arus 15, 20, 25 mA/cm2 pada 25, 0, -25oC selama 30 menit. Selanjutnya dilakukan proses sealing dalam larutan CeCl3.6H2O + H2O2 pada temperatur ruang dengan pH 9 selama 30 menit. Proses anodisasi pada aluminium foil dilakukan dalam larutan 3 M H2SO4 + 0,5 M; 0,7 M; dan 0,9 M H2C2O4, dan 0,3; 0,5; 0,7 M H2C2O4 selama 40-60 menit. Proses anodisasi dilakukan pada tegangan konstan 35, 40, dan 45 V untuk larutan asam oksalat dan 15 V untuk larutan campuran. Pengamatan dan evaluasi morfologi lapisan pori hasil anodisasi dilakukan menggunakan alat FE-SEM (Field Emission Scanning Electron Microscope), ketahanan korosi material diinvestigasi menggunakan pengujian polarisasi dan EIS, sedangkan analisa kualitatif terhadap morfologi pori (diameter dan densitas) pada AAO menggunakan perangkat lunak ImagePro. Pengembangan persamaan empiris menggunakan metode derajat terkecil dan permukaan respon. Proses terintegrasi yang diaplikasikan pada komposit Al7075/SiC pada temperatur anodisasi 0 oC menghasilkan terbentuknya deposit bulat kaya cerium dengan diameter 64 nm ( 3 nm) yang menutupi seluruh permukaan lapisan oksida dan rongga secara efektif. Proteksi terintegrasi anodisasi dan pelapisan cerium meningkatkan ketahanan korosi hingga 4 order perbesaran dibandingkan tanpa perlindungan akibat terjadinya ikatan saling kunci antara kedua lapisan tersebut. Peningkatan konsentrasi larutan elektrolit asam oksalat, temperatur, tegangan dan waktu celup anodisasi dalam larutan 0,3; 0,5; dan 0,7 M mengakibatkan peningkatan diameter pori permukaan pada AAO. Sedangkan, penambahan asam sulfat dalam asam oksalat menghasilkan pori dengan morfologi diameter pori yang jauh lebih halus dan densitas pori yang jauh lebih besar. Secara umum, densitas pori hanya tergantung pada diameter pori hasil anodisasi, dimana peningkatan diameter pori menghasilkan densitas pori yang semakin menurun. Persamaan empiris hubungan antara tiga faktor anodisasi (konsentrasi asam oksalat, tegangan, dan waktu anodisasi) dengan diameter pori hasil dari penelitian ini adalah : Dp = 0,140625 MVt + 0,33125 MV ? 523542 Mt + 35,64583 M ? 0,04006 Vt + 0,685764 V +1,792431 t ? 42,5053 (derajat terkecil) dan Dp = 33,3 ? 236,3 M ? 1,453 V + 0,3942 t + 7,60 MV (metode derajat satu) ......Anodizing process in aluminum produces a phenomenal structure in form of metal oxide which is known as Anodic Aluminum Oxide (AAO). AAOis a very useful morfology to improve the adhesion properties for further coating in aluminum alloy and composite aluminum. This phenomenon is related to the presence of interlock bond between AAO and the next layer. The AAO morphology can be modified simply by varying anodizing parameters. Therefore, selecting appropriate parameters plays an important role in order to obtain the desired pore size. Unfortunately, the preliminary studies did not provide any information on controlling the pore size and density (through increasing/decreasing the concentration of sulfuric acids, voltage, and duration of anodizing to determine pore diameter and density). For that purpose, in this research some empirical models were built to predict the pore size produced by anodizing process in various parameters. The grand design if this research aims to develop empirical equations which predict the relationship between oxalic acid concentration, anodizing voltage and time to the pore diameter. However, this research also aims to analyze the formation mechanism and of the integrated layer on Al7075/SiC, as well as the enhancement of corrosion resistance resulted from the integrated layer. Moreover, the influence of various anodizing parameters, i.e. resistivity, concentration, temperature, and type of electrolyte on pore characteristics of AAOis also conducted in this study. Anodizing process of Al7075/SiC was conducted in 16% H2SO4 solution in current densities 15, 20, 25 mA/cm2 at25, 0, -25oC for 30 minutes. Subsequently, cerium sealing process was carried out in CeCl3.6H2O+H2O2 at room temperature and pH 9 for 30 minutes. Anodizing of aluminum foil were carried out in 0,3; 0,5; 0,7M H2C2O4 solution and a mixture solution of 0.5M, 0.7M, and 0.9M H2C2O4 and 3M H2SO4 for 40-60 minutes. Anodizing processes were performed under potentiostatic conditions with constant potentials of 35, 40, and 45V for oxalic solution and 15 V for a mixture solution. Morphology of AAO layer observations were performed using field emission scanning electron microscopy (FE-SEM) FEI Inspect F50, while the corrosion resistance of materials were investigated by means of polarization and EIS, and qualitative analysis of pore characteristics (pore diameters and densities) accomplised by ImagePro software. The development of empirical equations using least square and response surface methods Integrated protection by conducting anodization at 0oC prior to cerium sealing in Al7075/SiC leads tothe formation of cerium spherical deposit in the diameter of 64 nm ( 3nm) which effectively covered most of the surface of oxide film as well as cavity. Moreover, this integrated protection enhanced four orders magnification of corrosion resistance than that of bare composite due to interlock bonding between the layers. The increasing of electrolyte concentration and temperature, as well as voltage and duration of anodizing in 0.3; 0.5; dan 0.7 M oxalic acid leads to the increasing of pore diameter in AAO surface. While, the addition of sulfuric acid in oxalic acid provides much smaller pore diameters and higher pore densities at lower voltages than single electrolyte of oxalic acid. In general, pore density is only dependent on pore diameter, which decreases with the increases of pore diameter. The empirical equations built in this research are : Dp = 0,140625 MVt + 0,33125 MV ? 523542 Mt + 35,64583 M ? 0,04006 Vt + 0,685764 V +1,792431 t ? 42,5053 (least square) and Dp = 33,3 ? 236,3 M ? 1,453 V + 0,3942 t + 7,60 MV (first order model)

Abstrak :
Barium hexaferrite (BaFe12O19) dan strontium titanate (SrTiO3) telah luas dikenal masing masing sebagai material magnet permanen dan piezoelektrik. Kedua jenis material tersebut sangat potensial untuk diaplikasikan pada pembuatan komponen produk magnet dan elektronik. Sifat ekstrinsik kedua jenis material tergantung kepada mikrostrukturnya yang sangat ditentukan pula oleh metode sintesis material yang diterapkan. Kajian literatur menunjukkan bahwa telah banyak dikembangkan berbagai macam metode sintesis senyawa magnetik BaFe12O19 dan dielektrik SrTiO3 dalam bentuk partikel halus dengan ukuran berskala nanometer. Kegiatan penelitian ini lebih difokuskan kepada sintesis dan karakterisasi material sistem nanokomposit BaFe12O19/SrTiO3, dimana senyawa BaFe12O19 (kode BHF) memiliki fasa feromagnetik dan senyawa SrTiO3 (kode STO) memiliki fasa feroelektrik dipersiapkan melalui metode pemaduan mekanik (mechanical alloying). Sedangkan pembuatan nanopartikel kedua senyawa diperoleh melalui penghalusan mekanik dan destruksi ultrasonik daya tinggi. Material BHF dipersiapkan dari campuran prekursornya berupa serbuk BaCO3 dan Fe2O3. Sedangkan material STO menggunakan prekursor SrCO3 dan TiO2. Aparatus yang digunakan adalah planetary ball mill dengan perbandingan berat antara material dan ball mill adalah 1 : 10. Ukuran rata-rata partikel dievaluasi menggunakan particle-size analyzer (PSA) dan ukuran rata-rata kristalit dihitung menggunakan metode Williamson Hall Plot dengan software High Score Plus dari data pola difaksi x-ray masing-masing senyawa. Adapun sampel berupa material kristalin diperoleh setelah kompaksi serbuk hasil pemaduan mekanik dan pemanasan pada temperatur 1100°C selama 3 jam dimana kemudian sampel material kristalin tersebut dihaluskan kembali menggunakan ball mill selama 20 jam. Serbuk halus BHF dan STO tersebut masing-masing menjalani destruksi lanjut secara ultrasonik daya tinggi untuk menghasilkan nanopartikel. Hasil evaluasi dengan PSA dan Williamson Hall Plot data XRD terhadap material BHF memperlihatkan nanopartikel dicapai setelah destruksi ultrasonik selama 14 jam. Dalam hal ini hasil PSA menunjukkan ukuran partikel rata-rata BHF adalah 28 nm sedangkan hasil evaluasi ukuran rata-rata kristalit adalah 26 nm. Untuk STO diperoleh hasil evaluasi ukuran rata-rata partikel sebesar 144 nm dan ukuran rata-rata kristalit adalah 30 nm. Kedua jenis material dalam bentuk nanopartikel ini digunakan sebagai komponen nanokomposit sistem BHF-STO. Berdasarkan hasil karakterisasi material komposit baik melalui pengujian XRD maupun permagraph bahwa sampel komposit tersusun dari dua fasa yaitu BaO.6(Fe2O3) dan SrTiO3 yang dipastikan dari pola difraksi dan sifat kemagnetannya. Dari kajian efek destruksi ultrasonik terhadap partikel STO dapat disimpulkan bahwa ukuran partikel rata rata dapat direduksi 8 kalinya yaitu dari ukuran 797 nm menjadi 144 nm setelah durasi watuk destruksi 14 jam. Sedangkan untuk partikel BHF tereduksi 100 kalinya yaitu dari 2931 nm menjadi 26 nm pasca durasi waktu destruksi yang sama. Penelitian ini juga mempelajari perilaku kinetika pertumbuhan ukuran kristalit fasa-fasa material penyusun material komposit dalam sistem komposit yang mengikuti persamaan Avrami. Berdasarkan kajian kinetika dapat diketahui energi aktivasi pertumbuhan kristalit fasa material STO dan BHF masing masing adalah 16 kJ.mol-1 dan 4 kJ.mol-1. Dapat disimpulkan bahwa kombinasi antara teknik penghalusan mekanik dan destruksi sonikasi daya tinggi terhadap partikel kristalin BHF dan STO dapat dijadikan metode alternatif yang efektif untuk menghasilkan nanopartikel. ...... Barium hexaferrite (BaFe12O19) and strontium titanate (SrTiO3) are well established permanent magnet and piezoelectric materials which are technologically and scientifically attractive due to their potential for various applications in the field of magnetic electronics functional materials. The extrinsic properties of these materials depend largely on the microstructure, which in turn depends on the method of synthesis. Different methods have been developed for the preparation of ultrafine BaFe12O19 and SrTiO3 particles in nanometer scale. In this work, research activivities were focused on synthesis and characterization of BaFe12O19/SrTiO3 nanocomposites in which feromagnetic materials of BaFe12O19 phase (coded BHF) and a ferroelectric materials of SrTiO3 phase (coded STO) were prepared by a mechanical alloying technique. In addition, nanoparticles of BHF and STO were obtained by physical destruction through a combined method between mechanical milling and high power ultrasonication. BHF materials were made of their precursors which consisted of the mixture between BaCO3 and Fe2O3. Whereas for STO materials the precursors were SrCO3 and TiO2. The process of mixing and alloying was caried out under the used of a planetary ball mill apparatus with a weight ratio between mixture and ball mill was 1:10. The mean particle size of milled powders was further characterized by Particle Size Analyzer (PSA). Whereas the mean crystallite size was derived from Williamson Hall Plots using the High Score Plus software to evaluate data of x-ray diffraction patterns for each materials. The crystalline materials were obtained after sintering step at 1100°C for 3 hours to the green compact samples which further followed by remilling the sintered samples for 20 hours. Further refining the powders for BHF and STO was carried out under the use of a high power sonicator for 14 hours to produce nanoparticles. Results of evaluation indicated that the mean particle size of BHF and STO was respectively 28 nm and 144 nm which refer to results of particles characterization by PSA whereas for their mean crystallite size were respectively 26 nm and 30 nm. Those nanoparticles of BHF and STO were then used as component materials in BHF-STO nanocomposite system. According to results of characterization for composite materials by XRD and permagraph, it was found that the composites consisted of two phases which were identified as BaO.6(Fe2O3) and SrTiO3 based on their diffraction pattern and magnetic properties. Further to the characterization results, it was also found that the mean particle size of STO was reduced 8 times in which the mean size of 797 nm was brought down to 144 after ultrasonically destruction for 14 hours. However, much larger reduction in particle sizes were obtained in BHF in which the initial mean particle size of 2931 nm was reduced 100 times downed to 26 nm after the same duration periode of ultrasonic destruction. Crystallite growth kinetics behavior of BHF and STO phases in the composite system was also studied in which data of mean crystallite sizes at different sintering temperatures and time were fitted into the Avrami equation. It was found that the activation energy for crystallite growth kinetics of BHF and STO is 16 kJ.mol-1 and 4 kJ.mol-1 respectively. We conclude that mechanical alloying coupled with ultrasonication can be used as an effective alternative tools for the preparation of fine and homogeneous powder materials leading to nanoparticle-based materials.