Jamal Talla

Electrical transport measurements of highly conductive carbon nanotube/poly(bisphenol A carbonate) composite

Acid-treated and pristine chemical vapor deposition grown multiwalled carbon nanotube (MWNT) and poly(bisphenol A carbonate) (PC) composites were prepared through a simple solution blending with varied nanotube weight fractions. The electrical conductivities of the composites can be described by the scaling law based on percolation theory with unprecedented high saturated ac conductivity of pristine nanotubes (σsat=1598.4 S cm−1, pc=0.19 wt %) and acid-treated nanotubes (σsat=435.4 S cm−1, pc=0.3 wt %), which correlates well with the dc behavior. We attribute the high saturated conductivities to managing the dispersions, rather than looking to have a well dispersed three-dimensional network thin film. The comparison was made between acid-treated nanotubes and pristine nanotube, both dispersed in PC at various loadings. It was found that the pristine nanotubes in PC possessed an even higher conductivity than the more evenly dispersed composites consisting of lightly acid-treated MWNT in PC.

Microconcentrator photovoltaic cell (the m-C cell): Modeling the optimum method of capturing light in an organic fiber based photovoltaic cell

We propose a new architecture as an alternative method when constructing organic photovoltaics (PVs) by addressing the best method to trap resonant light within the devices using fiber optics to concentrate light in the form of a microconcentrator cell (m-C cell). Our initial effort is to address how the m-C cells manage light absorption using a mathematical model that considers all the required parameters including the incident angle, meridional plane, cross sectional area, and path length. By knowing the materials,refractive index, we are able to calculate the optical angular input to achieve maximum absorption of resonant light. We also addressed the complexity of how changing refractive indices in a multilayer device can alter the angular dependence when considering the incident input light. The consequence is that we can ensure efficient absorption of resonant light in a thin film yet without issues of transmission losses which are evident in all other thin film organic PVs.

Formation of highly conductive composite coatings and their applications to broadband antennas and mechanical transducers

Tight networks of interwoven carbon nanotube bundles are formed in our highly conductive composite. The composite possesses propertiessuggesting a two-dimensional percolative network rather than other reported dispersions displaying three-dimensional networks. Binding nanotubes into large but tight bundles dramatically alters the morphology and electronic transport dynamics of the composite. This enables itto carry higher levels of charge in the macroscale leading to conductivities as high as 1600 S/cm. We now discuss in further detail, the electronic and physical properties of the nanotube composites through Raman spectroscopy and transmission electron microscopy analysis. When controlled and usedappropriately, the interesting properties of these composites reveal their potential for practical device applications. For instance, we used this composite to fabricate coatings, whic improve the properties of an electromagnetic antenna/amplifier transducer. The resulting transducer possesses a broadband range up to GHz frequencies. A strain gauge transducer was also fabricated using changes in conductivity to monitor structural deformations in the composite coatings.

Defect Analysis of Carbon Nanotubes

Raman spectroscopic analysis of plasma treated MWNTs was used characterize defects in MWNTs. Raman spectroscopy was also used to characterize defects induced via acid treatment. The Raman‐active disorder modes are used to fingerprint PSF attachment to MWNTs via defect states.