Physics Commons^™

Electrical And Mechanical Properties Of Polymer Nanocomposites, Nuwansiri N.K. Getangama

Electronic Thesis and Dissertation Repository

This thesis consists of three projects concerning the electrical and mechanical properties of polymer nanocomposites. We study the effect of nanoscale filler particles on the polymer dynamics at different length and time scales. In the first study, poly(ethylene oxide) (PEO)-multiwalled carbon nanotubes (MWCNT) nanocomposites with a MWCNT concentration ranging from 0 to 5 wt\% were prepared by both melt-mixing and twin-screw extrusion. Their electrical properties were studied over a wide range of frequency and temperature using a dielectric spectrometer. A percolation transition is observed at which the electrical conductivity of the nanocomposites increases by several orders of magnitude. The percolation …

Confinement Effects And Magnetic Interactions In Magnetic Nanostructures, Kristen Lee Stojak Repa

USF Tampa Graduate Theses and Dissertations

Multifunctional nanocomposites are promising for a variety of applications ranging from microwave devices to biomedicine. High demand exists for magnetically tunable nanocomposite materials. My thesis focuses on synthesis and characterization of novel nanomaterials such as polymer nanocomposites (PNCs) and multi-walled carbon nanotubes (MWCNTs) with magnetic nanoparticle (NP) fillers.

Magnetite (Fe₃O₄) and cobalt ferrite (CoFe2O4) NPs with controlled shape, size, and crystallinity were successfully synthesized and used as PNC fillers in a commercial polymer provided by the Rogers Corporation and poly(vinylidene fluoride). Magnetic and microwave experiments were conducted under frequencies of 1-6 GHz in the presence of …

Dielectric Spectroscopy Of Polyvinyl Alcohol Hydrogels And Nanocomposites, Nuwansiri N.K. Getangama

Electronic Thesis and Dissertation Repository

Gels based on polyvinyl alcohol (PVA) can be formed by repeated freezing and thawing of a solution of the polymer. PVA cryogels have applications as biomaterials, including artificial tissue and drug delivery systems. The mechanical and electrical properties of polymeric materials can be changed significantly by adding a small amount of nanometer-sized particles. In this work, the dielectric properties of PVA solutions and gels were studied in the frequency range from 10 micro Hz to 1 MHz as a function of temperature, using a dielectric spectrometer. Comparison of the dielectric constant of a PVA solution to that of water indicates …

Synthesis, Integration, And Physical Characterization Of Graphene And Carbon Nanotubes, David P. Hunley

Theses and Dissertations--Physics and Astronomy

Graphene and carbon nanotubes are among the hottest topics in physics today. Both materials exhibit numerous remarkable mechanical, electrical, optical, and thermal properties that make them promising materials for use in a large number of diverse applications, especially in the field of nanotechnology. One of the ultimate goals driving the fields of nanoscience and nanotechnology has been the attainment of atomically precise construction of intricate integrated systems consisting of materials with diverse behavior. Specifically, it is desirable to have high performance conductors, semiconductors, and insulators integrated into complex atomically precise arrangements. This dissertation represents the culmination of work that has …

Synthesis And Electron Emission Properties Of Aligned Carbon Nanotube Arrays, Suman Neupane

FIU Electronic Theses and Dissertations

Carbon nanotubes (CNTs) have become one of the most interesting allotropes of carbon due to their intriguing mechanical, electrical, thermal and optical properties. The synthesis and electron emission properties of CNT arrays have been investigated in this work. Vertically aligned CNTs of different densities were synthesized on copper substrate with catalyst dots patterned by nanosphere lithography. The CNTs synthesized with catalyst dots patterned by spheres of 500 nm diameter exhibited the best electron emission properties with the lowest turn-on/threshold electric fields and the highest field enhancement factor. Furthermore, CNTs were treated with NH₃ plasma for various durations and the …

Rheology Of Solutions Of Polyisophrene And Polyisoprene-Carbon Nanotube Composites, Ruiping Ge

Electronic Thesis and Dissertation Repository

The addition of a small amount of carbon nanotubes to a polymer matrix can result in large changes in its mechanical properties. In this work, we study the rheological behavior of solutions of polyisoprene (PI) in chloroform and suspensions of multi-walled carbon nanotubes (MWCNT) and single-walled carbon nanotubes (SWCNT) in these PI solutions using shear rheometry.

We perform rheological measurements to study the viscoelastic properties of solutions of trans-PI in chloroform for polymer concentrations ranging from 1.0 wt% to 10.0 wt%. Oscillatory strain sweep tests show a concentration-and-frequency independent critical strain of that defines the limit of the linear viscoelastic …