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Luận văn Thạc sĩ - Chưa phân loại | Hanoi University of Science, VNU tài liệu, giáo án, bài giảng , luận văn, luận án, đ...
INFORMATION ON MASTER’THESIS Full name: Hoang Thanh Cao Sex: Male Date of birth: 12/04/1981 Place of birth: Ha Noi Admission decision number: 3568/QĐ-CTSV Dated: 31/12/2009 Changes in academic process: No Official thesis title: “fabrication of amorphous Fe2O3 nanoparticles and the properties” Major: Solid State Physics Code: 604407 10 Supervisors: Associate Professor Dr Nguyen Hoang Hai– College of Science, VNU 11 Summary of the finding of the thesis: - Amorphous Fe2O3 and Fe2-xCrxO3 nanoparticles have been successfully prepared by sonochemical method Figure 1: XRD patterns of the iron oxide samples prepared at 70, 80 and 90oC before (as-prepared) and after heating to 600oC All the as-prepared materials presented very similar results with the absence of diffraction peaks This shows the amorphous structure of the as-prepared iron oxide particles After annealing the metastable amorphous state of the as-prepared sample has been transformed to crystalline states through solid state reaction occurring in the samples - The morphology of the as-prepared and the annealed particles of all samples are similar Particle size increased from nm for the as-prepared sample to 22 nm for the sample annealed at 600oC for 15 min, which is due to the particle growth and agglomeration process Figure 2: DSC data of the iron oxide sample prepared at Te = 80oC with the heating rate of 10 - 30oC/min - There are three obvious exothermic peaks located at around Tp1 = 215, Tp2 = 265 and Tp3 = 505oC corresponding to the heating rate β = 10oC/min All peaks have a tendency of shifting to higher temperature as increasing the heating rate The activation energy of 105, 130 and 186 kJ/mol for the solid state reactions corresponding to the three exothermic peaks Tp1, Tp2 and Tp3 were respectively deduced by fitting to the experimental DSC data - Chromium ions have been used to replace iron ions in its oxide compounds due to the ionic radius of same order We study effect of the presence of Cr on the crystallization process of materials We study effect of the pressence of Cr on the crystallization process of materials The initial concentration of Cr3+ in Fe2-xCrxO3 was adjusted to have x = 0.05, 0.10, 0.15, 0.20 compared with the concentration of Cr in the as-prepared samples determined from EDS data - All peaks have been shifted to higher temperatures compared to those of the iron oxide sample The activation energies relatively corresponding to T p1, Tp2 and Tp3 are 140, 156, 170 kJ/mol Comparing to the amorphous iron oxide samples, the activation energies were enhanced significantly for Tp1 and Tp2 whereas Tp3 reduced For practical application, the enhancement of Tp1 is important which leads to the fact that the amorphous state of the materials can last longer, stabilize at room temperatures - Using the Kissinger equation to calculate the reaction time for the sample Fe1.9Cr0.1O3, the reaction time can be up to 15 years 12 Practical applicability - Iron oxide nanoparticles have an important role in the arsenic filter Thus, research to slow the ageing process of the material is essential - The presence of Cr in the amorphous materials slow down the ageing effect by a factor of 15 times This is a good way for using the amorphous iron-chromium oxide materials in practice 13 Further research directions: - To study the effect of chromium on the practical applicability of amorphous iron oxide nanoparticles - Finding the best rate of chromium is to be able to slow the aging process of the nanoparticles of amorphous iron oxide 14 Thesis-related publications: Nguyen Dang Phu, Trinh Xuan Sy, Hoang Thanh Cao, Nguyen Ngoc Dinh, Le Van Thien, Nguyen Minh Hieu, Nguyen Hoang Nam, Nguyen Hoang Hai (2012), “Amorphous iron-chromium oxide nanoparticles prepared by sonochemistry”, J Non-Cryst Solids, 358, 537-543 Date:5/3/2012 Signature: Hoang Thanh Cao ... applicability of amorphous iron oxide nanoparticles - Finding the best rate of chromium is to be able to slow the aging process of the nanoparticles of amorphous iron oxide 14 Thesis-related publications:... data - Chromium ions have been used to replace iron ions in its oxide compounds due to the ionic radius of same order We study effect of the presence of Cr on the crystallization process of materials... crystallization process of materials We study effect of the pressence of Cr on the crystallization process of materials The initial concentration of Cr3+ in Fe2-xCrxO3 was adjusted to have x = 0.05, 0.10,