Lanetra M. Clayton

Effects of gamma radiation on poly(methyl methacrylate)/single-wall nanotube composites

Single-wall carbon nanotube (SWNT)/poly(methyl methacrylate) (PMMA) composites were fabricated and exposed to ionizing radiation for a total dose of 5.9 Mrads. Neat nanotube paper and pure PMMA were also exposed for comparison, and nonirradiated samples served as controls. A concentration of 0.26 wt% SWNT increased the glass transition temperature ( T g ), the Vickers hardness number, and modulus of the matrix. Irradiation of the composite did not significantly change the T g , the Vickers hardness number, or the modulus; however, the real and imaginary parts of the complex permittivity increased after irradiation. The dielectric properties were found to be more labile to radiation effects than mechanical properties.

Ionizing Radiation Effects on Interfaces in Carbon Nanotube-Polymer Composites

The purpose of this research was to probe nanotube-polymer composites for evidences of radiation induced chemistry at the interface of the host polymer and the nanotube structures. Single wall carbon nanotube (SWNT) / poly (methyl methacrylate) (PMMA) composites were fabricated and exposed to gamma radiation with a Co 60 source at a dose rate of 1.28 X 10 6 rad/hour in an air environment for a total dose of 5.9 Mrads. Neat nanotube paper and neat PMMA were also exposed. Spun coat films of SWNT/PMMA were exposed to gamma radiation with a Ce157at a dose rate of 4.46 x 10 3 rad/hr for a total dose of 3.86 Mrads. Both irradiated and non-irradiated samples were compared. Glass transition temperatures were characterized by differential scanning calorimetry. Dynamic mechanical analysis and dielectric analysis evidenced changes in relaxations induced by irradiation. Irradiated composites exhibited radiation induced chemistry distinct from degradation effects noted in the pure polymer. Scanning electron microscopy provided images of the SWNTs and SWNT/PMMA interface before and after irradiation. This investigation imparts insight into the nature of radiation induced events in nanotubes and nanocomposites.

Characterizations of Enriched Metallic Single-Walled Carbon Nanotubes in Polymer Composite

Using different processing conditions, we disperse the single-walled carbon nanotube (SWNT) into the polymethyl methacrylate (PMMA) to form composites. In the melt-blended sample, the SWNTs originally semiconducting - became predominantly metallic after dispersion into the melt-blended composite. The interaction of the PMMA and SWNT is investigated by the polarized Raman studies. The structure changes in the PMMA and SWNT shows that the anisotropic interactions are responsible for SWNT electronic density of states (DOS) changes. The increased metallic SWNT percentage is confirmed by the conductivity and dielectric constant measurements .

An Impact Study of the Implementation of a Materials Science and Engineering Module at the Fifth Grade Level

An impact study of the implementation of a newly developed Materials Science and Engineering Module was conducted as part of a National Science Foundation funded GK-12 project at the University of South Florida. The objective of GK-12 STARS ( Students, Teachers and Resources in the Sciences ) program is to foster systemic change in elementary by enriching math and science curricula and encouraging long-term professional development for teachers in the K-5 band. The program also aims to decrease the current educational gap in science and math curricula prevalent among certain schools within the same school district, which is reflected in the outcome of the Florida Comprehensive Assessment Test (FCAT). The module was developed for the purpose of enhancing existing textbook driven science instruction and creating a fundamentally sound scientific exposure in elementary school students. As part of this activity, students from three different schools (one private, one suburban, and one urban) were introduced to basic concepts in materials science and engineering through hands-on experiments, presentations, and field trips to the universitys material research related laboratories (i.e. polymer chemistry, microelectronics, nanotechnology, geotechnics, corrosion, etc.) The developed module offered information ranging from basic definitions to newly discovered cutting edge phenomenon in the field of nanotechnology. Subsequently, pre and post test instruments were administered to assess student performance. Results from the pretest showed that students from all participating schools performed within the standard deviation. The post assessment test showed that the experimental group had twice as many correct answers, as the control group from each school.