Dissertation > Excellent graduate degree dissertation topics show

Preparation and Magnetism of the Frustration Magnet CoCr2O4Nanocrystallites

Author: ChenZuoZuo
Tutor: TianZhaoMing
School: Huazhong University of Science and Technology
Course: Materials Physics and Chemistry
Keywords: Hydrothermal method Size effect Ferromagnetic/antiferromagnetic Spinfrustrated ferromagnetic Ac susceptibility
CLC:
Type: Master's thesis
Year: 2012
Downloads: 13
Quote: 0
Read: Download Dissertation

Abstract


The spinel AB2O4because of its unique structural features has many excellentprospect in physical and chemical properties. With the advancement of nanotechnology,thespinel ferrites has been widely used in various fields of social production and life. Wehave made partial results in the synthesis of nanoscale spinel ferrite by hydrothermalmethod.But its application prospects have not yet achieved a breakthrough. The mainreason is that there are some gaps between the nanocrystals synthesized by hydrothermalmethod in particle size and morphology of the regulation and t he actualrequirements.Therefore,the depth study have been made in process parameters of thehydrothermal synthesis of ferrite.And it caused widespread concern of many researchersto prepare ferrite nanocrystals with a series of different particle size,morphology andcomposition.The research of article contents of magnetic frustration CoCr2O4nanocrystallitespreparation,microstructure analysis,UV-visible spectroscopy analysis and magneticanalysis,and three main points including:1.An brief introduction about the crystal structure of the spinel CoCr2O4。Then morefocuses has been paid to the concept and the basic theory and research developments ofmagnetic geometrical frustration and the size effect as well as the intrinsic magnetic andresearch progress of CoCr2O4bulk. Subsequently,the basis of the subject background andsignificance of the article is put forward.2.CoCr2O4nanocrystallites of different particle size were successfully prepared byhydrothermal method.crystal phase and structure and particle size of the CoCr2O4crystallites were analyzed by XRD.The morphology of the CoCr2O4crystallite wasobserved by TEM. The visible light absorption of the CoCr2O4crystallite was observed byUV-visible spectrometer.Magnetism and ac susceptibility of the crystallites was measured by PPMS. The XRD patterns of the samples show that CoCr2O4nanocrystallites preparedby hydrothermal method are indeed pure phase and cubic spinel structure.The initialdesign of the experimental requirements of different particle size were reached.It seemsfrom the UV-visible absorption spectrum.The overlap of Absorption bands in the visiblelight range made CoCr2O4nanocrystallites ultimately showing a blue-green.TheseAbsorption peeks sttributed to the spin allowed transportation of Co2+in tetrahedron andCr3+in octahedron.3. The magnetism of CoCr2O4nanocrystallites in different particle size have beenobserved and compered.All CoCr2O4nanocrystallites from ferromagnetic tosuper-paramagnetic transition were occurd with decreasing particle size.As the particlesize increases,the ferromagnetism have been increased and the antiferromagnetic havebeen enhancement.But the magnetic anisotropy,the saturation magnetization and thecoercive force have been increased.The measurements of the ac susceptibility of CoCr2O4nanocrystallite at5nm between5and40K in10Oe field shows that nanocrystallite exhibitmagnetic frustration behavior.

Related Dissertations

  1. Study of Tin Alloy Carbon Composite Used for Lithium Ion Battery,TM912.9
  2. Synthesis and Characterization of Carbonate Intercalated Layered Double Hydroxides and Their Structure Recovery Properties,TQ424.2
  3. Preparation of Tungsten Carbide Loaded on Carbon Composite and Its Electrochemistry Performance,O614.613
  4. Preparation and Characterization of Superhydrophobic Films on Steel,TB383.2
  5. Photovoltaic effect on the BaTiO 3 ferroelectric properties of thin films,O484.4
  6. Synthesis and Luminescence Properties of Gd, Eu Co-doped LaPO4,O614.331
  7. Hydrothermal Synthesis of LiNi0.9Co0.1O2 and LiNi1/3Co1/3Mn1/3O2 for Lithium Ion Batteries,TM912
  8. Synthesis of Novel Ferrite Pigments and Its Application on Magnetic Inks,TQ622.15
  9. Study on Size Effect, Bearing Capacity and Residual Pressures of Large Diameter Grouted Pile,TU473.1
  10. Preparation and Sensing Properties of γ-Fe2O3 /ZnO Nano Double Layer Gas Sensing Films,TB383.2
  11. Experiment and Finite Element Analysis on Micro Forward Extrusion Process with Amorphous Alloy,TG139.8
  12. Synthesis, Characterization and Catalytic Properties of Vanadium Oxide Nanomaterials,TB383.1
  13. The Research of the Dye-Sensitized Nanocrystalline TiO2 Solar Cells,TM914.4
  14. Research on Influence Factors on Metal Fatigue Strength,TG115.57
  15. Research about Synthesis and Application of Magnesium Borate and Aluminum Borate Nanowiskers,TB383.1
  16. Synthesis and Characterization of Platinum Group and Their Oxide Nanoparticles by Bydrothermal Method,TB383.1
  17. Synthesis and Properties of the Molydbate Nanocrystals,TB383.1
  18. Preparation of tungsten trioxide research and photocatalytic properties of hexagonal phase,O643.36
  19. Preparation and Photo Hydrogen Production Properties of Carbon Materials Modified Nanostructured TiO2 Photocatalysts,TN304
  20. Synthesis of ZnNb2O6 and ZnTa2O6 Ceramic Powders,TB383.3
  21. Hydrothermal/solvothermal Synthesis, Characterization and Performance Research of Transitional Metal-based Micro-/nano- Materials,TB383.1

CLC: >
© 2012 www.DissertationTopic.Net  Mobile