Alumina Thin film Coatings at Optimized Conditions using RF Magnetron Sputtering Process

This study deals with the extensive investigation of Alumina thin film coating deposited on glass, stainless steel, and polycarbonate substrates at 25oC. The transmittance, reflectance, and surface roughness were determined. Transmittance was observed from 88 to 91 % for alumina thin film coating on glass and polycarbonate substrates. The stiffness, hardness, and elastic modulus were 58, 52, and 47 μN/nm, 7.52, 7.14, 6.87, 103, 112, and 122 GPa thin-film coating on different substrates. An increase in surface roughness and transmittance was observed with sputtering power and the thickness of the coating

A VALIDATED NORMAL PHASE CHIRAL LC METHOD FOR THE ENANTIOMERIC SEPARATION OF SERTRALINE AND ITS Cis-(1R, 4R) ENANTIOMER ON AMYLOSE BASED STATIONARY PHASE

ABSTRACT A simple and rapid chiral liquid chromatographic method was developed for the enantiomeric separation of Sertraline hydrochloride (cis-(1S, 4S)-4-(3, 4-dichlorophenyl)-N-methyl-1,2,3,4-tetrahydronaphthalen-1-amine hydrochloride) and its undesired cis-enantiomer (cis-(1R, 4R)-4-(3, 4-dichlorophenyl)-N-methyl-1,2,3,4-tetrahydronaphthalen-1-amine hydrochloride). Superior resolution between Sertraline and its cis-(1R, 4R) enantiomer was achieved on amylase based Chiralpak AD-H (250 x 4.6 mm, 5 µm particle size) column using hexane, isopropyl alcohol, ethanol and diethyl amine (850:100:50:0.1 v/v/v/v) as mobile phase at 25 °C temperature. Flow rate was kept as 1.0 ml/min and elution was monitored at 215 nm. The sample concentration was 0.3 mg/ml. The effects of the mobile phase composition, the flow rate and the temperature on the chromatographic separation were investigated. Developed method is capable to detect (LOD) and quantitate (LOQ) cis-(1R, 4R) enantiomer to the levels of 30 and 120 ng/ml respectively, for 10 µl injection volume. The percentage RSD of the peak area of six replicate injections of cis-(1R, 4R) enantiomer at LOQ concentration was 4.9. The percentage recoveries of cis-(1R, 4R) enantiomer from Sertraline were ranged from 93.8 to 103.9. The test solution and mobile phase was observed to be stable up to 24 h after the preparation. The developed method was validated with respect to limit of detection (LOD), limit of quantitation (LOQ), precision, linearity, accuracy, robustness and ruggedness

Mechanical properties and microstructure of spark plasma sintered nanostructured p-type SiGe thermoelectric alloys

SiGe based thermoelectric (TE) materials have been employed for the past four decades for power generation in radio-isotope thermoelectric generators (RTG). Recently "nanostructuring" has resulted in significantly increasing the figure-of-merit (ZT) of both n and p-type of SiGe and thus nanostructured Si80Ge20 alloys are evolving as a potential replacement for their conventional bulk counterparts in designing efficient RTGs. However, apart from Zr, their mechanical properties are equally important for the long term reliability of their TE modules. Thus, we report the mechanical properties of p-type nanostructured Si80Ge20 alloys, which were synthesized employing spark plasma sintering of mechanically alloyed nanopowders of its constituent elements with 12% boron doping. Nanostructured p-type Si80Ge20 alloys exhibited a hardness of similar to 9 +/- 0.1 GPa, an elastic modulus of similar to 135 +/- 1.9 GPa, a compressive strength of 108 +/- 02 MPa, and fracture toughness of similar to 1.66 +/- 0.04 MPalm with a thermal shock resistance value of 391 +/- 21 Wm(-1). This combination of good mechanical properties coupled with higher reported Zr of nanostructured p-type Si80Ge20 alloys are rendered to be a potential material for power generation applications, compared to its bulk counterpart

Microstructure and mechanical properties of thermoelectric nanostructured n-type silicon-germanium alloys synthesized employing spark plasma sintering

Owing to their high thermoelectric (TE) figure-of-merit, nanostructured Si80Ge20 alloys are evolving as a potential replacement for their bulk counterparts in designing efficient radio-isotope TE generators. However, as the mechanical properties of these alloys are equally important in order to avoid in-service catastrophic failure of their TE modules, we report the strength, hardness, fracture toughness, and thermal shock resistance of nanostructured n-type Si80Ge20 alloys synthesized employing spark plasma sintering of mechanically alloyed nanopowders of its constituent elements. These mechanical properties show a significant enhancement, which has been correlated with the microstructural features at nano-scale, delineated by transmission electron microscopy

Ultrafine grain structure features in spray-formed AZ31 magnesium alloy

The ultrafine grain structure was developed in spray-formed AZ31 magnesium alloy by optimizing delivery tube orifice diameter. A significant refinement of grain size similar to 1 mu m in ultrafine level was achieved by using 2.25 mm delivery tube orifice diameter. The tensile strength value was increased from 145 MPa of as-cast alloy to 250 MPa of spray-formed alloy, registering an enhancement of similar to 72%. On the other hand, elongation was increased from 6% to 13% using 2.25 mm orifice, registering more than onefold increase in elongation. Also, hardness enhancement of similar to 49% was observed in spray-formed AZ31 alloy compared to as-cast alloy. The fracture surface of spray-formed AZ31 Mg alloy evidences the mixed type of ductile and brittle fracture

Recent developments in acid and base-catalyzed etherification of glycerol to polyglycerols

International audienceCommercial relevance of glycerol as a biosourced safe organic building block for valuable commodity chemicals has increased considerably with the rapid development of oleochemistry. Among the various reaction pathways for catalytic conversion of glycerol, oligomerization to polyglycerols (PGs) is one of the viable and demanding processes due to the wide field of applications of PGs in cosmetics, polymers, food-additives, antifogging film industry, pharmaceuticals, biomedicals and drug delivery systems. This short review is dedicated to the selective synthesis of polyglycerols preferentially to low molecular-weight oligomers with emphasis on the pros/cons of reported homogeneous and heterogeneous acidic and basic catalytic processes. In addition, recent advances conducted in our laboratory will be given for a selective glycerol oligomerization in the presence of powdered and shaped alkaline earth-based mesoporous catalysts and of hydrothermally synthesized layered structured materials as newly developed basic catalysts. Some critical issues and challenges regarding the rational design of solid catalysts with emphasis on their stability in hot glycerol as well as alternative reaction engineering to overcome the drawbacks stemming from batch reactions will be addressed. Selectivity to the desired fraction of short-chain oligomers for food and cosmetic applications with respect to the European Union regulations will be also introduce

Enhancement in thermoelectric performance of SiGe nanoalloys dispersed with SiC nanoparticles

SiGe is one of the most widely used thermoelectric materials for radioisotope thermoelectric generator applications for harnessing waste-heat at high temperatures. In the present study, we report a simple experimental strategy for enhancing the thermoelectric and mechanical properties of n-type SiGe nanoalloys by dispersing SiC nanoparticles in a SiGe nanoalloy matrix. This strategy yielded a high value of figure-of-merit (ZT) of similar to 1.7 at 900 degrees C in the SiGe/SiC nanocomposite, which is nearly twice that reported for its pristine bulk counterpart and similar to 15% higher than that of pristine SiGe nanoalloys. This significant enhancement in the ZT primarily originates from a reduction in the lattice thermal conductivity, owing to a high density of nano-scale interfaces, lattice-scale modulations and mass fluctuations, which lead to extensive scattering of heat-carrying phonons. The dispersion of SiC nanoparticles also significantly enhances the mechanical properties of the resulting SiGe/SiC nanocomposite, including fracture toughness and hardness. The enhancement in the thermoelectric and mechanical properties of the SiGe/SiC nanocomposites has been correlated with their microstructural features, elucidated employing X-ray diffraction, and scanning and transmission electron microscopy