Praveen Bhimaraj

Bio: Praveen Bhimaraj is an academic researcher from Rensselaer Polytechnic Institute. The author has contributed to research in topics: Crystallinity & Nucleation. The author has an hindex of 5, co-authored 5 publications receiving 739 citations.

Crystal nucleation and growth in poly(ethylene terephthalate)/alumina‐nanoparticle composites

Abstract: The effect of nanoparticles on nonisothermal polymer crystallization was investigated using poly(ethylene terephthalate) (PET) nanocomposites with alumina (Al2O3) nanoparticles of average size 38 nm. The filler content in the nanocomposites was varied from 0 to 10 wt %. The interparticle spacing was observed to decrease (as expected) with an increase in loading of the nanoparticles. Contrary to previous reports in the literature on semicrystalline polymer-based composites with micron-size and macroscale particles, our differential scanning calorimetry, transmission electron microscopy, and X-ray studies showed that the addition of the nanoparticles did not cause heterogeneous nucleation of PET crystals in nanocomposites containing up to 3 wt % Al2O3. This is attributed to the nanoparticle curvature being comparable to the radius of gyration of the polymer. The addition of the nanoparticles was found to disrupt the spherulitic morphology of the PET because of their physical presence and their proximity to one another. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Crystal growth in alumina/poly(ethylene terephthalate) nanocomposite films

Abstract: The crystal growth and morphology in 150-nm-thick PET nanocomposite thin films with alumina (Al{sub 2}O{sub 3}) nanoparticle fillers (38 nm size) were investigated for nanoparticle loadings from 0 to 5 wt%. Transmission electron microscopy of the films showed that at 1 wt% Al{sub 2}O{sub 3}, the nanoparticles were well dispersed in the film and the average size was close to the reported 38 nm. Above 2 wt% Al{sub 2}O{sub 3}, the nanoparticles started to agglomerate. The crystal growth and morphological evolution in the PET nanocomposite films kept at an isothermal temperature of 217 C were monitored as a function of the holding time using in situ atomic force microscopy. It was found that the crystal nucleation and growth of PET was strongly dependent on the dispersed particles in the films. At 1 wt% Al{sub 2}O{sub 3}, the overall crystal growth rate of PET lamellae was slower than that of the PET homopolymer films. Above 2 wt% Al{sub 2}O{sub 3}, the crystal growth rate increased with nanoparticle loading because of heterogeneous nucleation. In addition, in these PET nanocomposite thin films, the Al{sub 2}O{sub 3} nanoparticles induced preferentially oriented edge-on lamellae with respect to the surface, which was not the case inmore » unfilled PET as determined by grazing-incidence X-ray diffraction.« less

Solution Combustion Synthesis of Nanoscale Materials

Abstract: Solution combustion is an exciting phenomenon, which involves propagation of self-sustained exothermic reactions along an aqueous or sol–gel media. This process allows for the synthesis of a variety of nanoscale materials, including oxides, metals, alloys, and sulfides. This Review focuses on the analysis of new approaches and results in the field of solution combustion synthesis (SCS) obtained during recent years. Thermodynamics and kinetics of reactive solutions used in different chemical routes are considered, and the role of process parameters is discussed, emphasizing the chemical mechanisms that are responsible for rapid self-sustained combustion reactions. The basic principles for controlling the composition, structure, and nanostructure of SCS products, and routes to regulate the size and morphology of the nanoscale materials are also reviewed. Recently developed systems that lead to the formation of novel materials and unique structures (e.g., thin films and two-dimensional crystals) with unusual...

Polymer-Nanoparticle Composites: From Synthesis to Modern Applications

Abstract: The addition of inorganic spherical nanoparticles to polymers allows the modification of the polymers physical properties as well as the implementation of new features in the polymer matrix. This review article covers considerations on special features of inorganic nanoparticles, the most important synthesis methods for ceramic nanoparticles and nanocomposites, nanoparticle surface modification, and composite formation, including drawbacks. Classical nanocomposite properties, as thermomechanical, dielectric, conductive, magnetic, as well as optical properties, will be summarized. Finally, typical existing and potential applications will be shown with the focus on new and innovative applications, like in energy storage systems.