Barium titanate (BTO) nanoparticles show great potential for use in electrostatic capacitors with high energy density. This includes both polymer composite and sintered capacitors. However, questions about the nanoparticles' size distribution, amount of agglomeration, and surface ligand effect on performance properties remain. Reducing particle agglomeration is a crucial step to understanding the properties of nanoscale particles, as agglomeration has significant effects on the composite dielectric constant. BTO surface functionalization using phosphonic acids is known reduce BTO nanoparticle agglomeration. We explore solution synthesized 10 nm BTO particles with tert-butylphosphonic acid ligands. Recent methods to quantifying agglomeration using an epoxy matrix before imaging shows that tert-butylphosphonic acid ligands reduce BTO agglomeration by 33%. Thermometric, spectroscopic, and computational methods provide confirmation of ligand binding and provide evidence of multiple ligand binding modes on the BTO particle surface.
Novel multilayered FeSiCrB-Fe x N (x = 2-4) metallic glass composites were fabricated using spark plasma sintering of FeSiCrB amorphous ribbons (Metglas 2605SA3 alloy) and Fe x N (x = 2-4) powder. Crystalline Fe x N can serve as a high magnetic moment, high electrical resistance binder, and lamination material in the consolidation of amorphous and nanocrystalline ribbons, mitigating eddy currents while boosting magnetic performance and stacking factor in both wound and stacked soft magnetic cores. Stacking factors of nearly 100% can be achieved in an amorphous ribbon/iron nitride composite. FeSiCrB-Fe x N multilayered metallic glass composites prepared by spark plasma sintering have the potential to serve as a next-generation soft magnetic material in power electronics and electrical machines.
Van Ginhoven, Renee M.; Monson, Todd M.; Stevens, Tyler E.; Vargas, David A.; Beck, Marisol B.; Kaufman, Jonas K.; Martos-Repath, Isabel M.; Orellana, Cesar O.; Zhao, Carmel Z.; Haskell, Richard C.; Dato, Albert D.
The photosensitization of photorefractive polymeric composites for operation at 633 nm is accomplished through the inclusion of narrow band gap semiconductor nanocrystals composed of PbS. Unlike previous studies involving photosensitization of photorefractive polymer composites with inorganic nanocrystals, we employ an off-resonance approach where the first excitonic transition associated with the PbS nanocrystals lies at ∼1220 nm and not the wavelength of operation. Using this methodology, internal diffraction efficiencies exceeding 82%, two-beam-coupling gain coefficients of 211 cm-1, and response times of 34 ms have been observed, representing some of the best figures of merit reported for this class of materials. These data demonstrate the ability of semiconductor nanocrystals to compete effectively with traditional organic photosensitizers. In addition to superior performance, this approach also offers an inexpensive and easy means by which to photosensitize composite materials. The photoconductive characteristics of the composites used for this study will also be considered.
Devices with nano-crystalline microstructures have been shown to possess improved electrical properties. Further advantages include lower processing temperatures; however, device fabrication from nano-particles poses several challenges. This presentation describes a novel aqueous synthesis technique to produce large batch sizes with minimal waste. The precipitate is readily converted at less than 550 C to a phase pure, nano-crystalline Pb{sub 0.88} La{sub 0.12}(Zr{sub 0.70} Ti{sub 0.30}){sub 0.97} O{sub 3} powder. Complications and solutions to sample fabrication from nano-powders are discussed, including the use of glass sintering aids to improve density and further lower sintering temperatures. Finally, electrical properties are presented to demonstrate the potential benefits of nano-crystalline capacitors.