Carbon nanotubes by electrospinning with a polyelectrolyte and vapor deposition polymerization

Electrospinning of a polyelectrolyte and vapor deposition polymerization were combined to fabricate nanotubes of oxidatively stabilized poly(acrylonitrile) (PANDelta) with an outer diameter of 100 nm, a wall thickness of 14 nm, and centimeter-scale length. Poly(styrene sulfonate) sodium (PSSNa) nanofibers serves as sacrificial cores while vapor deposition polymerization was used to form smooth PAN sheaths of even thickness. After the PAN sheaths had been oxidatively stabilized, the PSSNa cores were etched away with water to form nanotubes of PANDelta. High-temperature carbonization of these nanotubes at 900 degrees C under Ar flow yielded carbon nanotubes with an outer diameter of 80 nm and wall thickness of 10 nm. Raman spectroscopy confirms that the carbon nanotubes were composed of highly disordered graphene sheets, consistent with the carbonization of PAN under similar conditions. These carbon nanotubes have many promising applications as catalyst supports, gas absorbents, and as encapsulants for controlled release of active compounds.     

Novel, nanoporous silica and titania layers fabricated by magnetron sputtering

Composite asymmetric membranes are fabricated through the deposition of submicrometer thick (100 nm) silica (SiO(2)) and titania (TiO(2)) films onto flat nanoporous silica and zirconia substrates by magnetron sputtering. The deposition conditions for both coating types were systematically altered to determine their influence on the deposited coating morphology and thickness. Ideal He/N(2) gas selectivity was measured for all of the membranes. The TiO(2) coatings, when deposited onto a ZrO(2) support layer with a pore size of 3 nm, formed a long columnar grain structure with average column diameter of 38 nm. A similar columnar structure was observed for TiO(2) coatings deposited onto a SiO(2) support layer with a pore size of 1 nm. Under the same conditions, SiO(2) coatings, deposited onto the same SiO(2) supports, formed a closely packed spherical grain structure whereas, when deposited onto ZrO(2) supports, the SiO(2) coatings formed an open grain structure. The average SiO(2) grain diameter was 36 nm in both cases. This preliminary investigation was aimed at studying the effect of sputtering parameters on the density and morphology of the deposited coatings. For the depositions carried out, the coating material was found to be very dense. However, the presence of grain boundaries resulted in poor ideal He/N(2) separation efficiencies.     

Microstructure, rheology and storage stability of low-fat yoghurt structured by carrot cell wall particles

Plant cell wall particles derived from fruits and vegetables are natural fibre materials with a low calorie content that can be used as a healthy alternative to gum stabilisers and starches for structuring low-fat yoghurt. In this study we investigated the effect of cell wall particle (CWP) addition on the gelation kinetics, viscoelastic properties, microstructure, texture and whey loss of the set yoghurt gels as a function of CWP concentration, particle size and storage time. Three particle sizes of dried carrot CWP (d_0.5 = 34, 71 and 80 ??m) were produced from an industrial carrot pomace. Rehydrated CWP was added to skim milk prior to acidification. The results showed that the addition of carrot CWP accelerated the rate of pH reduction and induced earlier gelation. The gel viscoelastic properties were enhanced with increased CWP concentration. This was accompanied with progressive reduction in the whey loss. The smallest cell wall particles (d_0.5 = 34 ??m) gave better gel strength and lower whey loss compared to the larger CWP particles, possibly due to higher contact between the CWP and casein particles thus contributing to the stronger gel network. The CLSM images of yoghurt gels containing CWP showed that carrot CWP occupied the void space within casein particle network. The enhanced gel strength and reduced whey loss achieved by the addition of CWP were maintained throughout the 28 day storage period. The reduction of fermentation processing by almost 1 h, yet still achieving good gel properties for the yoghurt type product could be a significant benefit from a manufacturing point of review.