5527
Dores Adel Ramzy Wissa
Study The Physical Properties Of Poly Methyl Methacrylate Doped With Magnetite Nanoparticles Treated By Laser
Magnetite Nanoparticles , Magnetite particles, casting method, polymethyl methacrylate, electrical properties and conductivity
High dielectric constant (high ε') materials are of extraordinary demand for the miniaturization of electronic devices. In particular (high ε') polymer/ inorganic composites can be tailored to the thermal and electrical applications. Magnetite nanoparticles (Fe3O4) ~ (100200 nm) was prepared by co-precipitation technique. Laser photo fragmentation technique has been utilized as a versatile method to decrease the particle size of the prepared magnetite nanoparticles (Fe3O4). Three different wavelengths namely; Nd-YAG laser first harmonic with wavelength 1064nm, second harmonic with wavelength 532nm and diode laser with wavelength 808 nm were used. However, the most effective one was diode laser beam as it reduces the average particle size of Fe3O4 from ~ 45 nm to ~ 11.8 nm. Different ratios of Fe3O4 before and after laser fragmentation up to 20wt% were successively mixed with Poly Methyl Methacrylate (PMMA) by using casting method. The structural and morphology properties of PMMA/Fe3O4 nanocomposites were inspected by X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. (XRD) data reveals an increase in the degree of crystallinity by increasing of laser fragmented Fe3O4 nanoparticles. Whereas, scanning electron microscopy (SEM) indicates fine and good dispersion of Fe3O4 inside PMMA matrix at low Fe3O4 content for laser fragmented samples. The magnetic properties of the Fe3O4 were evaluated using the VSM at room temperature before and after laser fragmentation. The magnetic results of the PMMA / Fe3O4 nanocomposites clearly show ferromagnetic behavior. Moreover, the microhardness of PMMA/Fe3O4 nanocomposites increases with the increase in the concentration of Fe3O4. In addition, the dielectric parameters (dielectric constant ' and dielectric loss ") were measured over a wide range of frequency (0.1 Hz - 1 MHz) and different temperatures (30-90 oC). Both ' and " were found to increase gradually by increasing Fe3O4 content up till 10% after which a dramatic increase was noticed. Also it is found that both parameters increased dramatically by increasing the temperature showing positive temperature coefficient. ' and " values were found to be higher after laser fragmentation when compared to those before fragmentation. This finding is logic due to the decrease in the particle size of Fe3O4 particles which led to an increase in the number of particles per unit volume and consequently an increase in both ' and " values. The electrical conductivity  was calculated for such composites at different temperature 30-90 oC before and after laser fragmentation. The electrical conductivity  at 30 oC before laser fragmentation was found to be in the order of 10-9 S cm-1 which recommends such composites to be used for antistatic applications as the range needed for such application is 10-9–10-14 S cm-1. On the other hand, after fragmentation  values were found to be in the order of 10-7 S cm-1 which recommends such composites to be used for electrostatic dissipation applications due to the fact that the range needed for such application was 10-5–10-9 S cm-1. On the other hand, the values of  at 90 oC were found to be in the order of 10-3 S cm-1 and 10-1 S cm-1 before and after laser fragmentation respectively which are assumed to act as semiconductor.
2018
M.Sc
Cairo
National Institute of Laser Enhanced Science