Graphene oxide/waterborne polyurethane nanocoatings: effects of graphene oxide content on performance properties.

Graphene oxide (GO) is a good nanofiller candidate for waterborne coatings because of its outstanding physical and mechanical properties, good dispersibility in water, and low cost relative to graphene. Here, we report on the performance of a one-part, waterborne polyurethane (WPU) nanocoating formulated with four different GO loadings ([0.4% to 2.0%] by mass). The degree of GO dispersion/adhesion was evaluated using scanning electron microscopy, laser scanning confocal microscopy, and Raman microscopy. Nanocoating performance was evaluated using a dynamic mechanical thermal analyzer for mechanical properties, a customized coulometric permeation apparatus for oxygen barrier properties, a combustion microcalorimeter for flammability, a hot disk analyzer for thermal conductivity, thermogravimetric analysis for thermal stability, and a moisture sorption analyzer for water uptake. The results show that GO sheets were well dispersed in, and have good adhesion to, WPU. At the higher mass loadings ([1.2% or 2%] by mass), GO increased the modulus and yield strength of WPU by 300% and 200%, respectively, increased the thermal conductivity by 38%, reduced the burning heat release rate (flammability) by 43%, and reduced the oxygen permeability by up to sevenfold. The presence of GO, however, increased water vapor uptake at high humidity; the moisture content of 2% mass loading GO/WPU nanocoatings at 90% RH was almost twice that of the moisture content for unfilled WPU. Overall, with the exception of water uptake at very high humidity (> 70% RH), the observed improvements in physical and mechanical properties combined with the ease of processing suggest that GO is a viable nanofiller for WPU coatings.

Boundary layer profiles in plasma chemical vapor deposition.

A nonlinear optical spectroscopy based on degenerate four-wave mixing has made possible direct measurements of species temperature and concentration profiles through the boundary layer of a reactive plasma at atmospheric pressure. Spectra were obtained for CH and C(2) radicals over a range of conditions including those for the plasma chemical vapor deposition of diamond films. Numerical simulations based on a one-dimensional stagnation-point flow model are in good agreement with the measurements. The CH mole fraction is shown to rise and fall as a function of distance from the substrate, which is compelling experimental evidence for the complex chemistry that is occurring in the plasma boundary layer.

Species-specific auditory discrimination in bobtail quail neonates.

Incubator-hatched bobwhite quail neonates were tested individually in a variety of single call and simultaneous auditory choice tests involving 6 adult quail vocalizations and a chicken exodus call. The quail showed a high degree of responsiveness (100%) to 3 adult quail vocalizations and significantly less responsiveness (40-50%) to 3 other quail calls and to the chicken exodus call in single call tests. In simultaneous choice tests, the quail were selectively responsive to a call of their own species over the chicken call, and they also showed certain intraspecific preferences. Because of their high degree of responsiveness, coupled with selectivity of their approach responses, bobwhite quail neonates are ideal for the laboratory investigation of the development of auditory perception.