Publications

Abstract not provided.

The impact of humidity and temperature on a zinc oxide based transparent conducting oxide (TCO) was assessed under accelerated aging conditions. An in situ electroanalytical method was used to monitor the electrical properties for a conducting zinc oxide under controlled atmospheric (humidity, temperature and irradiation) conditions. A review of thin film photovoltaic (PV) literature has shown one major failure mode of cells/modules is associated with the ingress of water into modules in the field. Water contamination has been shown to degrade the performance of the TCO in addition to corroding interconnects and other conductive metals/materials associated with the module. Water ingress is particularly problematic in flexible thin film PV modules since traditional encapsulates such as poly(ethyl vinyl acetate) (EVA) have high water vapor transmission rates. The accelerated aging studies of the zinc oxide based TCOs will allow acceleration factors and kinetic parameters to be determined for reliability purposes.

The purpose of this project is to develop multi-layered co-extrusion (MLCE) capabilities at Sandia National Laboratories to produce multifunctional polymeric structures. Multi-layered structures containing layers of alternating electrical, mechanical, optical, or structural properties can be applied to a variety of potential applications including energy storage, optics, sensors, mechanical, and barrier applications relevant to the internal and external community. To obtain the desired properties, fillers must be added to the polymer materials that are much smaller than the end layer thickness. We developed two filled polymer systems, one for conductive layers and one for dielectric layers and demonstrated the potential for using MLCE to manufacture capacitors. We also developed numerical models to help determine the material and processing parameters that impact processing and layer stability.

Abstract not provided.

Microencapsulation is the process of placing a shell composed of a synthetic or biological polymer completely around another chemical for the purpose of delaying or slowing its release. We report that Sandia National Laboratories was interested in microencapsulating concentrated sulfuric for a specific application. Historically, acids have been encapsulated many times using various techniques. However, the encapsulation of mineral acids has proven difficult due to the lack of a shell material robust enough to prevent premature leakage of the capsule. Using the Polymer-Polymer Incompatibility (PPI) technique, we screened a variety of shell materials and found our best results were with Derakane® 411-350, an epoxy vinyl ester resin (EVER) polymer.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Silsesquioxanes are a family of siloxane network polymers that have become important as vehicles for introducing organic functionalities into sol-gel materials. However, there has not been a systematic study of the capacity of organotrialkoxysilanes to form gels through the sol-gel process. In this study, we examined the sol-gel chemistry of organotrialkoxysilanes (RSi(OR′)3) with different organic groups (R = H, Me, Et, Pr, i-Pr, n-Bu, i-Bu, t-Bu, hexyl, octyl, decyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, vinyl, phenyl, benzyl, phenethyl, chloromethyl, chloromethylphenyl, and tridecafluoro-1,1,2,2-tetrahydrooctyl) with methoxide or ethoxide substituents on silicon, at varying monomer concentrations, and under acidic, neutral, and basic conditions. Gels were obtained from the sol-gel polymerization of the monomers with R′ = Me and R = H, Me, vinyl, chloromethyl, chloromethylphenyl, hexadecyl, and octadecyl and R′ = Et and R = H, Me, Et, chloromethyl, vinyl, dodecyl, hexadecyl, and octadecyl. Formation of gels, even with these monomers, was often circumvented by phase separation phenomena, giving rise to crystalline oligomers, resinous materials, and precipitates. Gels obtained from these polymerizations were processed as xerogels and characterized by solid-state NMR, microscopy, and nitrogen sorption porosimetry.

Polysilsesquioxane xerogels were prepared by the sol-gel polymerization of organotrialkoxysilanes, RSi(OR′)3, with R′ = Me: R = H, Me, vinyl, chloromethyl, chloromethylphenyl, hexadecyl, and octadecyl and R′ = Et: R = H, Me, Et, cyanoethyl, chloromethyl, vinyl, dodecyl, and hexadecyl. The majority of the gels were opaque and colloidal in appearance. The porosity of the xerogels was characterized by nitrogen porosimetry and scanning electron microscopy. Many of the remaining organotrialkoxysilanes formed porous polymeric gels, but the surface areas were lower and the mean pore sizes larger. Some of the xerogels, especially those prepared under acidic conditions were non-porous.