Microstructural Study of the Hot Corrosion of a Calcium Aluminosilicate Glass-Ceramic and a Si-C-O-Fiber-Reinforced Calcium Aluminosilicate Matrix Composite via Sodium Sulfate in Air and Argon at 900°C

The hot corrosion of a calcium aluminosilicate (CAS) glass-ceramic and a composite of CAS matrix that has been reinforced with Si-C-O (Nicalon) fiber has been investigated by X-ray diffractometry, scanning electron microscopy, and transmission electron microscopy. Samples of the monolithic CAS and the Si-C-O-CAS composite were subjected to corrosion using liquid sodium sulfate at 900°C for 50 h in air and argon environments. The monolithic and composite samples both were corroded by sodium sulfate, and corrosion damage in the composites was more severe than in the monolithic CAS, irrespective of the gaseous environment. The increased corrosion damage in the composites was due to the presence of Si-C-O fibers, which changes the mechanism of corrosion. The corrosion products in monolithic CAS were different from those in the composites; this disparity was also due to the presence of the fibers in the composite. The corrosion zones in all the samples were severely cracked, and the cracks extended into the unaffected regions of the samples. Mechanisms of hot corrosion have been proposed and discussed for both the monolithic and composite samples.     

Evaluation of hydroxyapatite and β-tri calcium phosphate microplasma spray coated pin intra-medullary for bone repair in a rabbit model

Here we report a comparative study of the healing kinetics of surgically created artificial defects in the tibia of New Zealand white rabbits. Comparison of the healing kinetics was made for uncoated conventional SS316L intramedullary pins, and the same pins with microplasma sprayed (MIPS) pure hydroxyapatite (HAp) and beta-tri calcium phosphate (β-TCP) coatings. After thorough material characterizations including XRD, FTIR, SEM, etc., MIPS coated pins were implanted to such animals. Serum biochemistry, radiology and fluorochrome labelling were used to evaluate the comparative healing kinetics of these implants in vivo. In comparison to those of the uncoated pins, the pins coated with both MIPS HAp and β-TCP showed significant increment of alkaline phosphatase up to 15th postoperative day, insignificant changes in serum phosphorus and calcium with uneventful healing of bone defect. There was development of Havarsian canals and well-defined peripherally placed osteoblasts along with evidence of angiogenesis and comparatively more new bone formation in the defect site. On a comparative scale, the performance of the β-TCP coated intramedullary pins was much better than that of the pure HAp coated pins than the uncoated intramedullary pins.     

Chiral resolution of differently substituted racemic acetyl‐1‐phenyl ethanol using lipase from Bacillus subtilis

In the present investigation a Lipase producing strain, Bacillus subtilis (MTCC‐121) was grown on various media containing different sources of carbon, nitrogen and other nutrients. The best media found for the production of lipase was M2 media containing 0.4% peptone, 0.2% beef extract and 1% NaCl. Lipase produced from this culture was used for the kinetic resolution of racemic acetyl‐1‐phenyl ethanol and its derivatives, which are important as chiral auxiliaries and intermediates in the synthesis of natural products, pharmaceuticals and agrochemicals. The lipase resolved these substrates after 48 h with enantiomeric excess of 90–98% and conversion 40–48%. Copyright © 2010 Society of Chemical Industry     

Physico-chemical properties of silica aerogels prepared from TMOS/MTMS mixtures

In the present work, results on the physico-chemical properties of the silica aerogels prepared by sol–gel process using mixtures of TMOS and MTMS as precursor are reported. The wide range of precursor mixture was studied with ratio of MTMS/TMOS in precursor mixtures as 0:100, 25:75, 50:50, 75:25, and 100:0 by volume. The gels with these precursor mixtures were successfully prepared using two step acid–base catalysis for gelation. Acetic acid (0.001 M) and NH₄OH (1.5 M) were used for catalysis and resulting alcogels were subsequently dried by supercritical solvent extraction method. FTIR spectroscopy revealed that the aerogels show more intense peak at 1,260 and 790 cm⁻¹ attributed to Si–CH₃ resulting in more hydrophobic nature and these results were concurrent with adsorbed water content measurements made using Karl Fischer’s titration technique. The resulted aerogels were characterized using differential thermal analysis, thermo gravimetric analysis and surface area measurements. The surface area measurements showed an interesting trend that the surface area increased from 395 to 1,037 m²/g with increase in MTMS content in the precursor mixture from 0 to 50% and then again decreased to 512 m²/g for further increase in MTMS content from 50 to 100% in the precursor mixture. It was observed from our studies that silica aerogels prepared using a starting mixture of 50% TMOS and 50% MTMS resulted in high moisture resistance (adsorbed water content of 0.721% w/w), low density of 90 kg/m³ and the highest surface area of 1,037 m²/g, which has great potential for catalysis support applications.     

SOLUBILITY AND TIE-LINE DATA FOR WATER + FORMIC ACID + METHYL ISOBUTYL KETONE TERNARY SYSTEM AT DIFFERENT TEMPERATURES

The solubility and tie-line data of the ternary system comprising water, formic acid, and methyl isobutyl ketone were experimentally determined at the temperatures 288.15, 298.15, and 308.15 K, and atmospheric pressure 101.3 kPa. The plait points were also determined using Treybal's method. The results indicate that formic acid distributes preferentially in MIBK compared to water. Experimental tie-line data were regressed with the NRTL model to obtain binary interaction parameters. It is found that the NRTL model correlates the present system satisfactorily with average root-mean-square deviation of 0.34%.     

An analytical index for evaluating manufacturing cost and performance of low-pressure hollow fibre membrane systems

Water and waste-water treatment through the use of the membrane filtration technology is one of the processes utilized currently to meet the growing demand for water. While new technologies can harness water from various non-traditional sources such as oceans, there remains the possibility of making drinking water more expensive through the use of costly water treatment equipment. To prevent this and ensuing catastrophes in the world, the water industry needs a strategy that keeps the price of water and price of products aiding the treatment of water controlled in to the future.     

Effect of depth on onset of engulfment in rectangular micro-channels

The mixing behavior at different Reynolds numbers is analyzed for different T-shaped micro-channels with a rectangular cross-section. The focus is on analyzing the effect of aspect ratio on the critical Reynolds number at which engulfment occurs. Soleymani et al. (2008) have recently proposed an empirical equation based on extensive numerical simulations to determine this critical Reynolds number. This is valid only when the depth of the channels (C) is lower than the widths of the mixing (A) and inlet (B) channels i.e. when A/C and B/C are both greater than unity. We find that when they are both less than unity there is a delay or even absence of engulfment even when Re is increased. The predictions of these simulations are validated experimentally for two geometries.     

Raman spectroscopy and microscopy based on mechanical force detection

The Raman effect is typically observed by irradiating a sample with an intense light source and detecting the minute amount of frequency shifted scattered light. We demonstrate that Raman molecular vibrational resonances can be detected directly through an entirely different mechanism-namely, a force measurement. We create a force interaction through optical parametric down conversion between stimulated, Raman excited, molecules on a surface and a cantilevered nanometer scale probe tip brought very close to it. Spectroscopy and microscopy on clusters of molecules have been performed. Single molecules within such clusters are clearly resolved in the Raman micrographs. The technique can be readily extended to perform pump probe experiments for measuring inter- and intramolecular couplings and conformational changes at the single molecule level.     

Analysis of Nanofluids as Cutting Fluid in Grinding EN-31 Steel

Nano-Micro Letters - Grinding requires high specific energy which develops high temperatures at wheel work piece interface. High temperatures impair work piece quality by inducing tensile residual...