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Synthesis and Microwave Absorption Properties of Nano-Fe3O4/CNTs Composite Powder

Author: WeiYuan
Tutor: SunKangNing
School: Shandong University
Course: Materials Science
Keywords: Carbon nanotubes Composite absorber Tumor hyperthermia Hydrothermal treatment Absorbing properties
CLC: TB383.1
Type: Master's thesis
Year: 2008
Downloads: 406
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Abstract


Tumor hyperthermia most urgent problem to be solved is how uniform heating of the tissue to be heated to the treatment temperature (42 ℃), but without causing permanent damage nearby normal tissue. Develop a absorbing performance, the high rate of heat production, the good biocompatibility new tumor thermal seed material, microwave targeting positioning hyperthermia, opened up an efficient new way for the healing of the tumor, has a very important scientific significance and practical value. In this paper, ferrite and carbon nanotubes respective absorbing characteristics composite complementary methods of chemical synthesis - hydrothermal treatment successfully prepared Fe 3 O 4 / CNTs nano-absorbing biological materials. System Some Factors Affecting the preparation process, to optimize the process route. Testing, characterization and analysis of the microstructure of the composite powder absorbing properties and dielectric constant. The specific contents are as follows: chemical precipitation combined with hydrothermal method was successfully prepared Fe 3 O 4 / CNTs nano-absorbing biological materials. Sample preparation by means of XRD, TEM and VSM analysis: the composite in Fe 3 O 4 nano small particles uniformly coated the surface of CNTs achieve Fe < sub> 3 O 4 surface modification of CNTs universal; coated CNTs Fe 3 O 4 after having pure iron oxide ferrimagnetic composite system can be realized in a magnetic field orientation. Successfully obtained composite powder based on the optimized process route, trying to find the right process parameters. Mainly discussed the preparation process Fe 3 / the of Fe 2 ratio of R, the temperature and time of the hydrothermal process, the pretreatment method of carbon nanotubes, carbon nanotube content, and other factors composite. By means of XRD and TEM analysis show that: (1) Preparation of reaction in Fe 3 and Fe 2 best ratio of R = 1.75, the composite material in ferrite component is a single-phase Fe 3 O 4 . (2) After the process is preferably hydrothermal temperature of 160 ℃, prepared under the conditions of the holding time 6h composite powder grain size is more in line with the requirements. (3) carbon nanotubes after acidification oxidation treatment, and should not exceed 5% of the mass fraction of carbon nanotubes, the surface thereof coated Fe of 3 O 4 particles more evenly, rendered fully coated state, the results obtained is more satisfactory. Fe 3 O 4 / CNTs composites and sliced ??paraffin was prepared Fe 3 O 4 / CNTs / paraffin composite materials, carbon nanotube composites microwave electromagnetic parameters using a vector network analyzer test, the measured data of the electromagnetic parameters calculated reflectivity R (dB)-f (GHz) curve, and discuss the carbon nanotube pre- processing method, carbon nanotubes content of microwave absorbing properties of composite materials. The results showed that: the the Fe 3 O 4 carbon nanotubes coated played a role of adjusting the electromagnetic parameters of carbon nanotubes, increase in the the original dielectric loss while another four Fe3O4 hysteresis loss and resonance absorption loss mechanism. The fe 3 O 4 / CNTs composite has good absorbing performance in the range of 0.5-3GHz After acidification oxidation of carbon nanotubes and carbon nanotubes The mass fraction of 4%, the absorption peak of the composite material in the 2.2 GHz near the reflection rate of-20dB, the bandwidth is about 1G able to meet the requirements of microwave hyperthermia with hot seed material for absorbing properties. Through the composite heat up in the microwave field experiments, to characterize the thermal effect of the material, the experimental results show that: Fe 3 O 4 / CNTs composites in the microwave apparatus treatments probe irradiation, the effect of thermal effects; temperature of the composite system can be increased to 42 ℃. Impedance matching and loss mechanism of Fe 3 O 4 / CNTs composite absorbing mechanism. Studies have shown that, Fe 3 O 4 / CNTs nanopowder various loss mechanisms due to surface and interface effects, especially the microscopic structure, composite cladding effect effectively to meet the needs of broadband, the strong absorption of the composite material. Can be achieved through the preparation process, to adjust the complex permittivity and permeability of the composite system, impedance matching, and the better the absorption performance of the material in the medical microwave frequency.

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