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"Nanopartikel oksida seng (ZnO) yang diberi dopan kromium (Cr) dan penambahan 10 % montmorillonite (MMT) disintesis dengan metode kopresipitasi untuk empat variasi persen atom Cr. Nanopartikel dikarakterisasi menggunakan X-Ray Diffraction (XRD), Energy Dispersive X-Ray (EDX), Fourier Transform Infrared (FTIR), UV-Visible Diffuse Reflectance (UV-Vis) dan Electronic Spin Resonance (ESR). Pengujian aktivitas fotokatalitik dilakukan menggunakan model polutan methylene blue dengan paparan sinar UV. Penambahan montmorillonite dan dopan Cr pada ZnO dapat meningkatkan degradasi methylene blue dengan Cr doped ZnO/MMT 10 at.% menunjukkan degradasi maksimum dengan kondisi optimum dosis fotokatalis 0.7 g/L dan konsenstrasi larutan 20 mg/L. Spesies dominan pada aktivitas fotokatalitik adalah hole dan OH● berturut-turut.

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Chromium (Cr) doped zinc oxide (ZnO) nanoparticles with 10% montmorillonite (MMT) addition were synthesized by co-precipitation method for four chrome atomic percentage variations. Samples were characterized by X-Ray Diffraction (XRD), Energy Dispersive X-Ray (EDX), Fourier Transform Infrared (FTIR), UV-Visible Diffuse Reflectance (UV-Vis) and Electronic Spin Resonance (ESR). Photocatalytic were evaluated using methylene blue under UV light irradiation. MMT addition and Cr dopant to ZnO nanoparticles enhance methylene blue degradation with the optimum conditions are 0.7 g/L of nanoparticle and 20 mg/L of methylene blue initial concentration. Hole and OH● were identified as dominant species of photocatalytic activity."

"Nanokomposit TiO2/CuO dengan variasi rasio Cu/Ti disusun menggunakan metode sol-gel. Sampel komposit dikarakterisasi dengan X-Ray Diffraction, Energy Dispersive X-Ray Spectroscopy, Field Emission Scaning, Brunauer-Emmett-Teller, UV-Visible Diffuse Reflectance Spectroscopy dan Electronic Spin Resonance Spectroscopy. Methylene blue digunakan sebagai model pewarna tekstil untuk mengevaluasi fotokatalitik, sonokatalitik dan fotosonokatalitik. Difraksi sinar-X dan dispersif energi analisis X-ray menegaskan bahwa hanya struktur monoklinik CuO dan struktur anatase TiO2 yang muncul di nanokomposit TiO2/CuO. Degradasi methylene blue menunjukkan bahwa penggabungan CuO di nanokomposit TiO2/CuO menunjukkan aktivitas fotokatalitik yang cukup tinggi, dan energi cahaya yang dapat dimanfaatkan lebih banyak dibandingkan TiO2 murni. Selain itu, degradasi methylene blue juga diselidiki menggunakan sistem sonokatalisis dan sistem fotosonokatalisis. Hasil penelitian menunjukkan bahwa semua data eksperimen mengikuti model pseudo-first order tapi laju konstanta fotosonokatalisis lebih tinggi dari proses fotokatalisis dan sonokatalisis individu masing-masing. Selain itu, kegiatan fotokatalitik, sonokatalitik dan fotosonokatalitik akan berkaitan dengan sifat struktural dan optik sampel. Mekanisme kegiatan katalitik akan dibahas.

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TiO2/CuO nanocomposite with different Cu/Ti ratios were prepared using sol-gel method. The obtained composite samples were characterized with X-Ray Diffraction, Energy Dispersive X-Ray Spectroscopy, Field Emission Scaning, Brunauer-Emmett-Teller, UV-Visible Diffuse Reflectance Spectroscopy and Electronic Spin Resonance Spectroscopy. Methylene blue was used as a model of textile dye to evaluate their photocatalytic, sonocatalytic and photosonocatalytic activities. X-ray diffraction and energy dispersive X-ray analysis confirmed that only monoclinic CuO and anatase TiO2 structures are present in TiO2/CuO nanocomposites. The degradation of methylene blue indicated that the incorporation of CuO in TiO2/CuO nanocomposite exhibited an appreciable higher photocatalytic activity, and more light energy could be utilized than pure TiO2. In addition, the degradation of methylene blue was also investigated using sonocatalysis and photosonocatalysis systems.

The results showed that all experimental data followed the pseudo-first order model but the rate constant of the sonophotocatalysis is higher than the respective individual photocatalysis and sonocatalysis process. Furthermore, the photocatalytic, sonocatalytic and photosonocatalytic activities will be related to their structural and optical properties. The mechanism of catalytic activities will be discussed."

"Salah satu kajian penelitian penting dalam ranah penelitian plasmonik adalah penelitian tentang bahan yang dapat digunakan sebagai saklar pada perangkat plasmonik yang dapat dikontrol melalui mekanisme optik. Sejauh ini, beberapa penelitian telah dilakukan pada material isotropik dan disimpulkan bahwa material tersebut sebenarnya membutuhkan kerapatan daya switching yang sangat tinggi dan kemampuan switching optiknya yang sangat rendah. Baru-baru ini, studi eksperimental telah dilakukan pada bahan anisotropik SrNbO3:4 menggunakan mikroskop pump-probe dengan kerapatan daya yang sangat rendah dan ditemukan bahwa bahan ini menunjukkan penurunan reflektansi jika polarisasi medan listrik untuk mekanisme pompa berada di arah sumbu b kristal sementara Polarisasi medan listrik probe searah sumbu kristal. Menariknya lagi, kontras switching yang dihasilkan oleh material ini mencapai sekitar 90% yang dapat menjadi tanda bahwa material ini dapat digunakan sebagai plasmonic switch masa depan. Namun, penjelasan teoritis mengapa bahan ini memiliki kemampuan untuk mengubah kontras yang sangat baik belum tersedia. Dalam tesis ini, kami mencoba menjawab pertanyaan tersebut dengan menggunakan model sederhana untuk menjelaskan pengaruh bahan pada mikroskop probe pompa dan dengan menghitung prinsip utama kami menghitung nilai reflektansi sebagai fungsi waktu. Dengan memvariasikan interaksi yang diperhitungkan dalam perhitungan ini, kami menemukan bahwa ada peran penting interaksi lubang elektron dalam fenomena ini

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One of the important research studies in the realm of plasmonic research is research on material that can be used as a switch in a plasmonic device that can controlled via an optical mechanism. So far, several studies have been conducted on isotropic material and it is concluded that the material actually requires very high switching power density and its optical switching capability so low. Recently, experimental studies have been carried out on anisotropic materials SrNbO3:4 uses a pump-probe microscope with a very low power density and it was found that this material showed a decrease in reflectance if the polarization the electric field for the pump mechanism is in the direction of the b axis of the temporary crystal The polarization of the electric field of the probe is in the direction of the a-axis of the crystal. Interestingly again, The switching contrast produced by this material reaches around 90% which can be a sign that this material can be used as a future plasmonic switch. However, the theoretical explanation of why this material has the ability to switch contrast very good ones are not yet available. In this thesis, we try to answer the question using a simple model to explain the effect of material in pump-probe microscopy and by calculating our main principles calculate the reflectance value as a function of time. By varying the interaction taken into account in this calculation, we find that there is an important role of electron-hole interactions in this phenomenon."

"Nanokomposit Perak, Titanium dioksida, dan Mangan (II,III) oksida (Ag/TiO2/Mn3O4) dengan berbagai rasio molar telah disintesis menggunakan metode hidrotermal. Pengukuran difraksi sinar-X (XRD) mengkonfirmasi struktur nanokomposit Ag/TiO2/Mn3O4 yang terdiri dari struktur kubik Ag, TiO2 anatase, dan Mn3O4 tetragonal. Rasio komposisi unsur nanokomposit Ag/TiO2/Mn3O4 diselidiki dengan fluoresensi sinar-X (XRF). Efek sinergis Ag, TiO2 dan Mn3O4 dapat meningkatkan efisiensi nanokomposit sebagai fotokatalis. Peningkatan efisiensi ditunjukkan dengan melebarnya rentang absorbansi pada hasil pengukuran UV-Vis Diffuse Reflectance. Pengukuran adsorpsi-desorpsi nitrogen menunjukkan bahwa penambahan geraham TiO2 mengakibatkan penurunan luas permukaan spesifik nanokomposit Ag/TiO2/Mn3O4, sedangkan hasil sebaliknya diberikan dengan penambahan geraham Mn3O4. Pada uji fotokatalitik, hasil terbaik ditunjukkan oleh nanokomposit Ag/TiO2/Mn3O4 dengan dominasi Mn3O4 untuk radiasi UV dan cahaya tampak. Pada kondisi optimum, nanokomposit Ag/TiO2/Mn3O4 mampu mendegradasi metilen biru hingga 91% dengan penyinaran selama 2 jam. Uji scavenger mengidentifikasi lubang sebagai spesies yang berkontribusi paling besar pada proses fotokatalitik ini. Uji reusabilitas dan stabilitas pada nanokomposit Ag/TiO2/Mn3O4 menunjukkan hasil positif.

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Silver, Titanium dioxide, and Manganese (II,III) oxide (Ag/TiO2/Mn3O4) nanocomposites with various molar ratios have been synthesized using the hydrothermal method. X-ray diffraction (XRD) measurements confirmed the structure of the Ag/TiO2/Mn3O4 nanocomposite consisting of a cubic structure of Ag, TiO2 anatase, and tetragonal Mn3O4. The elemental composition ratio of Ag/TiO2/Mn3O4 nanocomposite was investigated by X-ray fluorescence (XRF). The synergistic effect of Ag, TiO2 and Mn3O4 can increase the efficiency of nanocomposites as photocatalysts. The increase in efficiency is indicated by the widening of the absorbance range on the measurement results of UV-Vis Diffuse Reflectance. The nitrogen adsorption-desorption measurements showed that the addition of TiO2 molars resulted in a decrease in the specific surface area of ​​the Ag/TiO2/Mn3O4 nanocomposite, while the opposite result was given by the addition of Mn3O4 molars. In the photocatalytic test, the best results were shown by the Ag/TiO2/Mn3O4 nanocomposite with the dominance of Mn3O4 for UV radiation and visible light. Under optimum conditions, Ag/TiO2/Mn3O4 nanocomposite was able to degrade methylene blue up to 91% with irradiation for 2 hours. The scavenger test identified pits as the species that contributed most to this photocatalytic process. Reusability and stability tests on Ag/TiO2/Mn3O4 nanocomposites showed positive results."

"Metode hidrotermal telah diterapkan dalam pembuatan katalis nanokomposit Ag/CeO2 dengan tiga variasi rasio molar katalis nanopartikel CeO2 dan penambahan graphene pada nanokomposit dengan variasi tiga persen berat (wt.%). Kotoran dan fase lain dalam sampel tidak ditemukan dalam pengukuran Difraksi sinar-X (XRD) dan fluoresensi sinar-X (XRF). Keberadaan graphene dikonfirmasi oleh pengukuran Thermal Gravimetric Analysis (TGA) dan Raman Spectroscopy. Luas permukaan spesifik nanokomposit terbesar diperoleh untuk rasio molar CeO2 1:2 dan peningkatan 10wt.% pada graphene berdasarkan hasil pengukuran BET. Tiga jenis proses katalitik yang digunakan untuk mendegradasi Methylene Blue (MB), yaitu sonocatalytic (paparan gelombang ultrasonik), fotokatalitik (paparan sinar tampak dan ultraviolet), dan kombinasi keduanya (sonophotocatalytic). Degradasi maksimum MB diperoleh untuk variasi rasio molar 1:2 dengan 5 wt.% graphene untuk dosis 0,5 g/L dengan konsentrasi MB 20 mg/L pada pH larutan 13 untuk ketiganya. jenis proses katalitik. Mekanisme degradasi maksimum MB dalam proses sonofotokatalitik untuk katalis nanokomposit graphene Ag/CeO2/5 wt.% adalah kontribusi kekosongan oksigen, luas permukaan spesifik, adanya resonansi plasmon permukaan (SPR) dan situs aktif. Spesies aktif lubang yang berperan dalam proses katalitik yang melibatkan cahaya yaitu proses fotokatalitik dan sonofotokatalitik, sedangkan radikal hidroksil merupakan spesies yang berperan aktif dalam proses sonokatalitik.The hydrothermal method has been applied in the manufacture of Ag/CeO2 nanocomposite catalysts with three variations of the molar ratio of the CeO2 nanoparticle catalyst and the addition of graphene to the nanocomposite with a variation of three percent by weight (wt.%). Impurities and other phases in the sample were not found in X-ray diffraction (XRD) and X-ray fluorescence (XRF) measurements. The existence of graphene was confirmed by Thermal Gravimetric Analysis (TGA) and Raman Spectroscopy measurements. The largest specific surface area of ​​nanocomposite was obtained for CeO2 1:2 molar ratio and 10wt.% increase in graphene based on BET measurement results. Three types of catalytic processes are used to degrade Methylene Blue (MB), namely sonocatalytic (exposure to ultrasonic waves), photocatalytic (exposure to visible and ultraviolet light), and a combination of both (sonophotocatalytic). The maximum degradation of MB was obtained for a variation of the molar ratio of 1:2 with 5 wt.% graphene for a dose of 0.5 g/L with a concentration of MB 20 mg/L at a solution pH of 13 for all three. type of catalytic process. The maximum degradation mechanism of MB in the sonophotocatalytic process for Ag/CeO2/5 wt.% graphene nanocomposite catalyst is the contribution of oxygen vacancies, specific surface area, presence of surface plasmon resonance (SPR) and active sites. Active species of holes that play a role in catalytic processes involving light are photocatalytic and sonophotocatalytic processes, while hydroxyl radicals are species that play an active role in sonocatalytic processes."

"Nanokomposit Fe2O3/Mn2O3-Grafena dengan variasi persen berat grafena berhasil disintesis dengan metode hidrotermal. Hasil X-ray Diffraction (XRD) dapat menunjukkan bahwa sampel tidak memiliki pengotor. Kehadiran graphene dalam nanokomposit telah berhasil ditunjukkan dengan mengukur spektroskopi Raman dan spektroskopi sinar-X dispersif energi (EDX). Peningkatan spesifik dalam area sampel seiring bertambahnya graphene, dapat dikonfirmasi melalui isoterm adsorpsi-desorpsi N2. Vibrating Sample Magnetometer (VSM) menunjukkan bahwa magnetisme sampel menurun dengan meningkatnya graphene. Uji aktivitas foto-Fenton nanokomposit Fe2O3/Mn2O3 dengan adanya graphene digunakan untuk mengevaluasi degradasi metilen biru (MB) dan jingga metil (MO) di bawah paparan sinar UV. Hasil foto-Fenton optimum diperoleh pada nanokomposit Fe2O3/Mn2O3-7G 0,2 g/L dengan 2 mL H2O2 pada pH 4. Spesies aktif yang berperan dalam aktivitas foto-Fenton adalah OH● . Nanokomposit Fe2O3 /Mn2O3-7G juga menunjukkan sifat dapat digunakan kembali.

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Fe2O3/Mn2O3-Graphene nanocomposite with various weight percent graphene was successfully synthesized by hydrothermal method. The results of X-ray Diffraction (XRD) can show that the sample has no impurities. The presence of graphene in nanocomposites has been successfully demonstrated by measuring Raman spectroscopy and energy dispersive X-ray spectroscopy (EDX). The specific increase in sample area as graphene increases, can be confirmed through the N2 adsorption-desorption isotherm. The Vibrating Sample Magnetometer (VSM) shows that the magnetism of the sample decreases with increasing graphene. Photo-Fenton activity test of Fe2O3/Mn2O3 nanocomposite in the presence of graphene was used to evaluate the degradation of methylene blue (MB) and methyl orange (MO) under UV light exposure. Optimum photo-Fenton results were obtained on Fe2O3/Mn2O3-7G 0.2 g/L nanocomposite with 2 mL H2O2 at pH 4. The active species that played a role in photo-Fenton activity was OH●. Fe2O3/Mn2O3-7G nanocomposites also showed reusability."

"ABSTRAKKami mengkaji paduan Half-Heusler NiMnSb dalam struktur kristal C1b dari aspek teori kemagnetannya. Kami melakukan perhitungan numerik pada sistem ini dengan metode Hamiltonian suku kinetik pendekatan tight-binding dan interaksi berbasis mean-field theory. Dari hasil perhitungan, sistem paduan NiMnSb menunjukkan karakter metal pada saat U J < 2.5 eV dan karakter semi metal pada U J ge; 2.5 eV. Menariknya, pada U=2.5 eV dan J=0.9 eV diperoleh moment magnet asymp; yang mana ini sesuai dengan prediksi Slater-Pauling.Kata kunci : Paduan Half-Heusler, Moment Magnet, Tight-Binding

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ABSTRACTWe study a Half Heusler alloy of NiMnSb in C1b crystal structure for magnetic theoretical aspect. We have done numerical calculation of the NiMnSb compound system using the model Hamiltonian kinetic term within tight binding approximation and the interaction based on mean field theory. From computational output, the NiMnSb compound system exhibit metal phase by the time U J 2.5 eV and half metal phase in U J ge 2.5 eV. Interestingly, the moment magnet results of U 2.5 eV J 0.9 eV is asymp which is agree with Slater Pauling prediction.Key words Half Heusler Alloy, Magnetic Moment, Tight Binding"

"[ABSTRAKPenggunaan 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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ABSTRACTIn 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.]"