22 research outputs found
Reactive Infiltration of Silicon Melt Through Microporous Amorphous Carbon Preforms
The kinetics of unidirectional capillary infiltration of silicon melt into microporous carbon preforms have been investigated as a function of the pore morphology and melt temperature. The infiltrated specimens showed alternating bands of dark and bright regions, which corresponded to the unreacted free carbon and free silicon regions, respectively. The decrease in the infiltration front velocity for increasing infiltration distances, is in qualitative agreement with the closed-form solution of capillarity driven fluid flow through constant cross section cylindrical pores. However, drastic changes in the thermal response and infiltration front morphologies were observed for minute differences in the preforms microstructure. This suggests the need for a dynamic percolation model that would account for the exothermic nature of the silicon-carbon chemical reaction and the associated pore closing phenomenon
Patterned Poly(acrylic acid) Brushes Containing Gold Nanoparticles for Peptide Detection by Surface-Assisted Laser Desorption/Ionization Mass Spectrometry
Patterned polyÂ(acrylic acid) (PAA)
brushes was successfully generated
via photolithography and surface-initiated reversible addition–fragmentation
chain transfer (RAFT) polymerization of acrylic acid as verified by
water contact angle measurements and FT-IR analysis. The carboxyl
groups of PAA brushes can act as reducing moieties for in situ synthesis
of gold nanoparticles (AuNPs), without the use of additional reducing
agent. The formation of AuNPs was confirmed by transmission electron
microscopy and X-ray photoelectron spectroscopy. The glass surface-modified
by PAA brushes and immobilized with AuNPs (AuNPs-PAA) can be used
as a substrate for SALDI-MS analysis, which is capable of detecting
both small peptides having <i>m</i>/<i>z</i> ≤
600 (glutathione) and large peptides having <i>m</i>/<i>z</i> ≥ 1000 (bradykinin, ICNKÂQDCPÂILE) without
the interference from matrix signal suggesting that AuNPs were stably
trapped within the PAA brushes and the carboxyl groups of PAA can
serve as internal proton source. By employing AuNPs as the capture
probe, the AuNPs-PAA substrate can selectively identify thiol-containing
peptides from the peptide mixtures with LOD as low as 0.1 and 0.05
nM for glutathione and ICNKÂQDCPÂILE, respectively. An ability
to selectively detect ICNKÂQDCPÂILE in a diluted human serum
is also demonstrated. The patterned format together with its high
sensitivity and selectivity render this newly developed substrate
a potential platform for high-throughput analysis of other biomarkers,
especially those with low molecular weight in complex biological samples
Effect of carboxymethyl cellulose concentration on physical properties of biodegradable cassava starch-based films
<p>Abstract</p> <p>Background</p> <p>Cassava starch, the economically important agricultural commodity in Thailand, can readily be cast into films. However, the cassava starch film is brittle and weak, leading to inadequate mechanical properties. The properties of starch film can be improved by adding plasticizers and blending with the other biopolymers.</p> <p>Results</p> <p>Cassava starch (5%w/v) based films plasticized with glycerol (30 g/100 g starch) were characterized with respect to the effect of carboxymethyl cellulose (CMC) concentrations (0, 10, 20, 30 and 40%w/w total solid) and relative humidity (34 and 54%RH) on the mechanical properties of the films. Additionally, intermolecular interactions were determined by Fourier transform infrared spectroscopy (FT-IR), melting temperature by differential scanning calorimetry (DSC), and morphology by scanning electron microscopy (SEM). Water solubility of the films was also determined. Increasing concentration of CMC increased tensile strength, reduced elongation at break, and decreased water solubility of the blended films. FT-IR spectra indicated intermolecular interactions between cassava starch and CMC in blended films by shifting of carboxyl (C = O) and OH groups. DSC thermograms and SEM micrographs confirmed homogeneity of cassava starch-CMC films.</p> <p>Conclusion</p> <p>The addition of CMC to the cassava starch films increased tensile strength and reduced elongation at break of the blended films. This was ascribed to the good interaction between cassava starch and CMC. Cassava starch-CMC composite films have the potential to replace conventional packaging, and the films developed in this work are suggested to be suitable for low moisture food and pharmaceutical products.</p