Synthesis and characterization of cubic cobalt oxide nanocomposite fluids

Narrow size distribution cubic Co₃O₄ nanoparticles were synthesized and rheological properties of suspensions of the cubes in oligomeric polyethylene glycol (PEG) were explored over a range of particle volume fractions and rotational shear flow conditions. At low and high particle volume fractions, the relative viscosity of the suspensions is described by a Krieger–Dougherty formula with an intrinsic viscosity consistent with expectations for suspensions of ideal cuboids. At intermediate to high particle loadings, the suspensions manifest complex rheological behavior, including shear thinning and shear-thickening features. These observations are discussed in terms of the charge carried by the cubes and the shear rate/volume fraction dependency of the transition from shear thinning to shear thickening.     

Stop flow lithography synthesis of non-spherical metal oxide particles

Non-spherical micron and nano-sized particles and their composites have become essential in select application areas of optics,wear resistance,personnel protection,chemical mechanical polishing,and biomedicine.In this paper,the synthesis of composite and ceramic non-spherical particles using stop flow lithography is reported.Precursor suspensions of poly(ethylene glycol) diacrylate,2-hydroxy-2-methylpropiophenone and SiO_2 or Al_2O_3 are prepared.The precursor suspension flows through a microfluidic device mounted on an upright microscope and is polymerized in an automated process.A photomask patterned with transparent geometric features,which define the cross-sectional shapes of the particles,masks the UV light to synthesize micron sized particles.Particles with axial dimensions ranging from 35 to 167 μm were synthesized.Control of device channel depth and objective lens magnification enables the manipulation of the particle size.Composite particles in triangular,square,pentagonal,hexagonal,and circular cross sections were synthesized.Subsequently,the transformation of the composite particles into the corresponding metal oxide particles was achieved through polymer burn-off and sintering.     

Electron spin density distribution in the polymer phase of CsC60: assignment of the NMR spectrum

We present high resolution 133Cs-13C double resonance NMR data and 13C-13C NMR correlation spectra of 13C enriched samples of the polymeric phase of CsC60. These data lead to a partial assignment of the lines in the 13C NMR spectrum of CsC60 to the carbon positions on the C60 molecule. A plausible completion of the assignment can be made on the basis of an ab initio calculation. The data support the view that the conduction electron density is concentrated at the C60 "equator," away from the interfullerene bonds.     

Compressed-air flow control system

We present the construction and operation of a compressed-air driven flow system that can be used for a variety of microfluidic applications that require rapid dynamic response and precise control of multiple inlet streams. With the use of inexpensive and readily available parts, we describe how to assemble this versatile control system and further explore its utility in continuous- and pulsed-flow microfluidic procedures for the synthesis and analysis of microparticles.