Degradation of Al2O3-�SiC-Al composites prepared by the oxidative growth of Al-alloys into SiC particulate

Composites of Al2O3-SiC-Al have been prepared by the oxidative infiltration of Si-free aluminium alloys into SiC particulate that were coated with spray-pyrolysed alumina. Moisture degradation studies were carried out to evaluate the extent of formation of aluminium carbide, the formation of which was also inferred by the determination of the residual silicon content in the composite. The efficiency of the coating technique in protecting the SiC from attack by the melt was evaluated at 1000 and 1200 degrees C

Structural aspects and porosity features of nano-size high surface area alumina-silica mixed oxide catalyst generated through hybrid sol-gel route

Alumina-silica mixed oxide nano-catalyst materials with compositions 83.6wt.% Al2O3-16.4wt.% SiO2 (3Al(2)O(3)center dot lSiO(2)), 71.82wt.% Al2O3-28.18wt.% SiO2 (3Al(2)O(2)center dot 2SiO(2)), 62.84wt.% Al2O3-37.16wt.% SiO2 (3Al(2)O(3)center dot 3SiO(2)) and 56.03wt.% AI,O-3-43.97wt.% SiO2 (3Al(2)O(3)center dot 4SiO(2)) have been prepared by a hybrid sol-gel technique using boehmite as the precursor for alumina and tetraethoxysilane as that for silica. The bonding characteristics and coordination features around Al and Si in the mixed oxide catalysts have been studied using FTIR and Al-27 MAS NMR after calcination at 400 degrees C which is the temperature region where cross-condensation is seen to take place. A high BET specific surface area of 287 m(2)g(-1) is obtained for 3Al(2)O(3)center dot lSiO(2) mixed oxide composition. The porosity features are further established by BET adsorption isotherms and pore size distribution analysis. The temperature-programmed desorption studies showed more surface active sites for the silica-rich composition, suggesting enhanced catalytic potential. The TEM features of the mixed oxides showed a homogeneous distribution of alumina and silica phases with particle sizes in the nano-range. The low silica-containing mixed oxide showed a needle-like morphology with a high aspect ratio of 1:50 and similar to 10nm particle size while the silica-rich composition had particle size in a wide range (similar to 20-75 nm

A decade of advances in transposon-insertion sequencing.

It has been 10 years since the introduction of modern transposon-insertion sequencing (TIS) methods, which combine genome-wide transposon mutagenesis with high-throughput sequencing to estimate the fitness contribution or essentiality of each genetic component in a bacterial genome. Four TIS variations were published in 2009: transposon sequencing (Tn-Seq), transposon-directed insertion site sequencing (TraDIS), insertion sequencing (INSeq) and high-throughput insertion tracking by deep sequencing (HITS). TIS has since become an important tool for molecular microbiologists, being one of the few genome-wide techniques that directly links phenotype to genotype and ultimately can assign gene function. In this Review, we discuss the recent applications of TIS to answer overarching biological questions. We explore emerging and multidisciplinary methods that build on TIS, with an eye towards future applications