Silicon nanoparticles are useful materials for optoelectronic devices, solar cells and biological markers. The synthesis of air-stable nanoparticles with tunable optoelectronic properties is highly desirable. The mechanochemical synthesis of silicon nanoparticles via high-energy ball milling produces a variety of covalently bonded surfaces depending on the nature of the organic liquid used in the milling process. The use of the C₈ reactants including octanoic acid, 1-octanol, 1-octaldehyde and 1-octene results in passivated surfaces characterized by strong SiC bonds or strong SiO bonds. The surfaces of the nanoparticles were characterized by infrared spectroscopy and nuclear magnetic resonance spectroscopy. The nanoparticles were soluble in common organic solvents and remarkably stable against agglomeration and air oxidation. The luminescence and optical properties of the nanoparticles were very sensitive to the nature of their passivating surface. Copyright © 2009 John Wiley & Sons, Ltd.

A solid state method of Nafion®/ceramic nanocomposite membrane preparation is described. A nanocomposite powder from Nafion pellets and a zirconium phosphate ceramic is formed by mechanical milling. The nanoparticles are then consolidated into membrane form by mechanical pressing. Cross-sectional analysis by scanning electron microscopy indicates that the ceramic particles exist in agglomerates that are evenly dispersed across the membrane. Dynamic mechanical analysis and tensile testing found the membranes to be mechanically equivalent, and in some cases superior, to a commercial extruded membrane. Increasing ceramic content is accompanied by an increase in modulus and shift in the alpha peak to higher temperature. Maximum water uptake of the membranes, as measured by thermal gravimetric analysis, is double that of values reported for the commercial membrane, and complete dehydration is postponed to higher temperature. The proton conductivity of fully hydrated membranes, measured by the 4-probe method at 60°C in water, is comparable with that of the extruded membrane. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

A solid-state method of Nafion/ceramic nanocomposite membrane preparation was used. Nanocomposite powders from Nafion pellets and a zirconium phosphate ceramic were formed by mechanical attrition. The powders were consolidated into membrane form by mechanical pressing. A decrease in the particle size and improved dispersion of the ceramic within the polymer phase were confirmed with scanning electron microscopy. An evaluation of membrane hydration by thermogravimetric analysis indicated that the prepared membranes had increased water uptake in comparison with a commercially available membrane. However, as the distribution of the ceramic was improved, the hydration of the sample was reduced. Low-temperature differential scanning calorimetry indicated that the additional water contributed to an increase in the contents of both freezing and nonfreezing water in the membranes. Proton conductivity testing at various relative humidities and temperatures revealed that the prepared membranes had conductivities comparable to but somewhat lower than those of the commercial membranes. An increase in conductivity was seen with decreased particle size and improved dispersion of the ceramic. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Polystyrene (PS) and poly(ethylene terephthalate) (PET) were blended together in the solid state via cryogenic mechanical attrition (CMA) and in the melt through conventional twin-screw extrusion. Consecutive modulated differential scanning calorimetry (MDSC) and thermogravitometric analysis (TGA) investigations allowed for the quantitative estimation of the extent of blend compatibility through the accurate determination of sample composition. The extent of blend compatibility, i.e., the amount of PET calculated to have been removed from the bulk and into interphase entanglements with PS, was found to be higher for milled blends than for extruded blends. This compatibility enhancement was the most pronounced for PET-rich blends. The other benefits of CMA are more precise compositional homogeneity through intimate mixing and the ability for more amorphous PET chains to be entangled with the amorphous PS phase at the interphase. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

Polystyrene (PS) and poly(ethylene terephthalate) (PET) were blended together in the solid state via cryogenic mechanical attrition (CMA) and in the melt through conventional twin-screw extrusion. CMA PS/PET blend morphologies were characterized both qualitatively and quantitatively through microscopy and thermal analysis. Specifically, CMA reduced the dispersed-phase domain size and its distribution relative to simple melt extrusion, although not to the extent attained with added chemical compatibilizers. CMA also amorphized the PET phase and depressed the PET cold crystallization rate, which was measured by post-CMA nonisothermal MDSC analysis. The PET amorphization efficiency and crystallizability for CMA PS/PET blends were the highest and lowest, respectively, at the PS/PET phase inversion. These concomitant phenomena are known to be caused by CMA-induced PET crystal defect formation and subsequent entropic stabilization. Such behaviors are linked to the enhanced presence of an uncrystallizable rigid amorphous PET phase, and the weight fraction of this rigid amorphous fraction (RAF PET) was quantified and also maximized near the PS/PET phase inversion. Moreover, the increased compatibilization and amorphization efficiencies and reduced PET crystallizability were determined to be interdependent. These studies have verified that CMA of PET with PS is more efficient than extrusion due to the formation of nonequilibrium, metastable morphologies that can be more precisely controlled and better stabilized with an interesting, composition-dependent interplay between PET crystallizability and the extent of PS/PET compatibilization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1348–1359, 2008