X-rays Diffraction Study On The Iron Nano Particles Prepared By Two Steps Milling Method

X-RAYS DIFFRACTION STUDY ON THE IRON NANO PARTICLES PREPARED BY TWO STEPS MILLING METHOD. X-rays diffraction study on the iron nanoparticles prepared by two-step milling method has been carried out. First, the raw material of micro-sized Fe was crushed by High Energy Milling (HEM) in the presence of isopropyl alcohol, here in after referred to as FI precursor. FI precursor then was crushed again with planetary balls mill in Cetyl-Trimethyl- Ammonium Bromide (CTAB)media, here in after referred to as FC sample. The phases analysis in the two samples were carried out by X-rays diffraction technique using the Rietveld method. Crystallites size were calculated with the Debye-Scherrer formula and the size of particles were measured by means of Particles Size Analyzer (PSA). The magnetic properties of the two samples were characterized with Vibration Sample Magnetometer (VSM). The analysis result showed that each of FI and FC samples consist of Fe, γ-Fe2O3 and Fe3O4 phases in the formof the nano-sized powder ranging fromaround 7 to 10 nm. PSA data indicate that the particle size of FI and FC are the same, i.e., 7.5 nm with narrow size distribution. The VSM data revealed that both FI and FC samples display super paramagnetic behavior at room temperature. The magnetization value in FC sample has been reduced due to more of the mass fraction of Fe transforms into iron oxide phases. The particle size is generally not the same as the size of the crystallites and in particular for the nano-sized particles, the size of crystallites could be equal to or greater than the particle size due to the presence of polycrystalline aggregates

Crystal Structure Analysis of Lamno3 with X-ray Diffraction Technique Using the Rietveld Method

Crystal structure analysis of LaMnO3 using the Rietveld metohod has been carried out. The LaMnO3 sample was synthesized with high energy mechanical milling from the raw materials of La2O3 and MnO2 with the appropriate mol ratio. Milling were performed for 10 hours, peletisized and hereinafter sintered at 1350 °C for 6 hours. The sample characterizations covered the crystal structure and electric-magnetic properties of the materials by X-ray diffraction technique using the Rietveld method and the four point probe, respectively. The Rietveld refinement results based on the X-rays diffraction data indicate that the sample of LaMnO3 is single phase with the crystal system: orthorhombic, the space group: Pnma No. 62 and the lattice parameters: a = 55.4405(9) Å; b = 7.717(1) Å dan c = 5.537(1) Å. The material owns Magnetic Resonance (MR) respond of 7%, the mean value of crystallite size, D = 17 nm and lattice strain, e = - 0.5%. So, the material go through a compressive strain, and according to the Nanda's strain model, it becomes a type G antiferromagnetic insulator. Because the insulator properties of the material does not change although being hit by the external magnetic field, hence the MR respon is only caused by the order of electron spin. Therefore at room temperature, LaMnO3.0 just exhibits a small MR respon

Structure and Magnetic Properties of Magnetic Nanoparticles (Fe-r) (R = Fe, Tb, Dy, Co) From High Energy Milling Process

One of the simple and effective preparation routes of nanosized magnetic particles is high-energymilling (HEM) process. In this method, the final properties of the particles obtained can be controlled by varying precursor composition, milling time and environment. This paper presentes the results of HEM process on microsize Fe powder of at least 95% weight fraction mixed with each microsize Co, Tb4O7 and Dy2O3 powders. The milling process was carried out in ethanol/water media for 40 hours. The phase analysis on the X-ray diffraction pattern using Rietveld analysis method showed the formation of mixture phase of Fe, Fe3O4/γFe2O3 with crystalline size of ~ 10 nm. This crystalline size of nanoparticles was confirmed by Transmission Electron Microscope (TEM) observation ensuring the formation of a single domain particle as a result of this milling process. Co atoms tend to partially replace Fe atoms on one of the Fe-site in the phase unit cell, while Tb and Dy atoms will just interstitially deform amorphous Fe oxide. These two mechanisms homogeneously occur within the samples and give no significant change to the structure of the initial phase. These two changes just impact on the formation of nanoparticles magnetic properties with the lowest magnetisation value reaching ~ 105 emu/g on powders with Co addition

Pengaruh Penambahan Ag2o terhadap Peningkatan Rapat Arus Kritis Superkonduktor Yba2cu3o7-x Hasil Proses Pelelehan

PENGARUH PENAMBAHAN Ag2O TERHADAP PENINGKATAN RAPAT ARUS KRITIS SUPERKONDUKTOR YBa2Cu3O7-x HASIL PROSES PELELEHAN. Telah dilakukan pembuatan superkonduktor YBa2Cu3O7-x (YBCO) dan YBa2Cu3O7-x/Ag (YBCO/Ag) menggunakan metode Modified Melt Textured Growth (MMTG). Pembuatan prekursor menggunakan metode reaksi padatan dari bahan-bahan dasar Y2O3, BaCO3 dan CuO dengan kemurnian 99,99 persen. Pembuatan cuplikan YBCO/Ag dilakukan dengan cara menambahkan serbuk Ag2O untuk 10 dan 30 persen berat. Pengujian cuplikan dilakukan dengan efek Meissner, teknik difraksi sinar-x (XRD), Scanning Electron Microscope (SEM), mikroscop optik (MO), Electron Dispersion X-rays (EDX), dan metode probe empat titik. Hasil pengukuran menunjukkan bahwa cuplikan merupakan bahan superkonduktor YBCO yang memperlihatkan fenomena superkonduktivitas pada suhu nitrogen cair dan telah mengkristal dengan baik dengan dicirikan oleh puncak pola difraksi yang tajam. Cuplikan hasil sinter memiliki sedikit porous, berbutir halus dan strukturmikro yang terorientasi secara acak. Sebaliknya, cuplikan hasil proses pelelehan memperlihatkan strukturmikro yang rapat dan highly textured yang tersusun dari butiran berukuran panjang berbentuk pelat. Butiran bentuk pelat diidentifikasi sebagai fasa YBCO. Fasa lain yang diendapkan didalam dalam bulk YBCO diketahui sebagai fasa Y2BaCuO5 (211) dan fasa Ag. Suhu kritis, Tc ≈ 91 K dari semua cuplikan dan tidak memperlihatkan Perubahan yang signifikan. Dari kurva I-V diperoleh rapat arus kritis Jc = 3,98 A.cm-2; 135,35 A.cm-2; 143,32 A.cm-2 dan 282,644 A.cm-2, berturut turut untuk cuplikan CSIN, YM-Ag2O, YM-10Ag2O dan YM-30Ag2O. Dapat disimpulkan bahwa dengan substitusi Ag2O pada bulk YBCO dapat meningkatkan nilai Jc

Pengaruh Laju Pendinginan terhadap Strukturmikro dan Derajat Preferred Orientation pada Bulk Tekstur Yba2cu3o7-x

PENGARUH LAJU PENDINGINAN TERHADAP STRUKTURMIKRO DAN DERAJAT PREFERRED ORIENTATION PADA BULK TEKSTUR YBa2Cu3O7-x. Telah dilakukan sintesis superkonduktor YBa2Cu3O7-x dengan metode melt texture growth modifikasi. Selama proses pendinginan pada suhu di bawah suhu peritektik Tp (900 oC–1000 oC) YBCO fasa–211 bereaksi dengan cairan (3 BaCuO2+2CuO) membentuk YBCO fasa–123. Pada percobaan ini dilakukan lima variasi laju pendinginan, yaitu 5 oC/jam, 8 oC/jam, 10 oC/jam, 12 oC/jam dan 15 oC/jam. Data SEM menunjukkan telah terjadi keteraturan butir-butir kristal pada arah tertentu. Analisis data difraksi neutron menunjukkan bahwa semakin lambat laju pendinginan, intensitas puncak (00l) meningkat dan intensitas puncak (hk0) menurun. Perbandingan intensitas puncak (005) I005 dengan puncak (110) I110 yang dihubungkan dengan koefisien March G bersesuaian dengan fungsi preferred orientation dari March–Dollase dengan persamaan empiris: I005 / I110 = 0,3501 . G (-4,0914). Laju pendinginan 15 oC/jam, 12 oC/jam, 10 oC/jam, 8 oC/jam, dan 5 oC/jam berturut-turut memiliki koefisien March sebesar 0,88; 0,84; 0,81; 0,78; dan 0,75. Disimpulkan bahwa laju pedinginan sangat mempengaruhi derajat preferred orientation pada bulk tekstur YBa2Cu3O7-x. Semakin lambat laju pendinginan, derajat preferred orietation semakin kecil atau keteraturan butir-butir kristalnya semakin baik