Synthesis And Microwave Absorption Properties Of Nano-Fe₃O₄/CNTs Composite Powder

One of the major problems of tumor hyperthermia is how to heat up the tumor,and the temperature in tumor can be increased to 42℃and therefore kill the tumor cells,but do not damage normal tissue nearby.A novel thermo-seed material with high thermal efficiency and good biocompatibility can carry out tumor target therapy in microwave hyperthermia.It will be a new and highly effective way for the tumor hyperthermia.In this experiment,ferrite materials and carbon nanotubes were used to compound for their good wave absorption properties respectively.Fe₃O₄/CNTs nano wave-absorbing material was made by means of chemistry precipitation and hydrothermal treatment method.Some influencing factors were studied systematically, and the preparation process was optimized.The microstructure,wave absorption properties and dielectric constant of the composite material powder were tested, attributed and analyzed.It contains as follows.Fe₃O₄/CNTs nano wave-absorbing material was successfully prepared by a simple and effective chemistry precipitation and hydrothermal treatment method.By the testing methods of XRD and TEM,Fe₃O₄ nanoparticles were densely decorated on CNTs, which in the surface of carbon nanotubes is uniform and universal;the hysteresis loops of the decorated CNTs were measured by vibrating sample magnetometer(VSM),and the result showed that Fe₃O₄/CNTs composite can be easily magnetized in a magnetic field orientation.This material can be used as a new tumor targeting hyperthermia material.Base on the preparation of material powder,the process was optimized to search for the suitable parameters.These factors were mainly discussed:the ratio of Fe³⁺/Fe²⁺ when preparation;temperature and holding time of the hydrothermal treatment;the content and preprocessor of the CNTs;Those conclusions can be indicated by means of XRD and TEM:(1)When the ratio of Fe³⁺/Fe²⁺in the prepare reaction R equals to 1.75, the constituent of ferrite in the composite was pure phase of Fe₃O₄.(2)When prepared by the temperature at 160℃and holding time for 6 hours,the size of crystal of the powder was satisfied.(3)Those powder whose CNTs treated by acidification and oxidation,and the mass percentage of CNTs not exceeding 5%,the Fe₃O₄ particles covered on can be more homogeneous,exhibiting overall covertures.This result was satisfied. The complex permittivity and complex permeability and microwave absorption properties of Fe₃O₄/CNTs/paraffin wax composite were measured by the transmission/reflection coaxial line method.Base on the theoretical calculation of reflection loss,the microwave absorption propertie of carbon nanotube composite has been made in the frequency range from 0.5-3 GHz.The results showed that: Fe₃O₄/CNTs composite also has good absorbing properties in the 0.5-3 GHz range. When CNTs content is 4%,the reflection loss value of-20dB,the bandwidth of 1G has been obtained at 2.2GHz.The result indicates that this composite has significant potential for electromagnetic wave absorption application in tumor hyperthermia.The thermal effect of thermo-seed material was described by heating experiment in the microwave field.The temperature of the system increased over 42℃.The results showed that:The thermal effect of Fe₃O₄/CNTs composite was evident in the microwave field.The microwave absorption mechanisms of those composites were analyzed.The Fe₃O₄/CNTs powder has many good features,including the effect of surface and interface,special microstructure,etc.It combined much deterioration and formed a composite material with broad banding and high absorption.By adjusting the preparation process to impact the complex dielectric constant and complex permeability, the impedance matching can be realized.The material can have good performance in medical microwave frequency.