Single step synthesis of GdAlO3 powder

A novel method for preparation of nano-crystalline gadolinium aluminate (GdAlO₃) powder, based on combustion synthesis, is reported. It was observed that aluminium nitrate and gadolinium nitrate exhibit different combustion characteristics with respect to urea, glycine and β-alanine. While urea was proven to be a suitable fuel for direct formation of crystalline α-Al₂O₃ from its nitrate, glycine and β-alanine are suitable fuels for gadolinium nitrate for preparation of its oxide after combustion reaction. Based on the observed chemical characteristics of gadolinium and aluminium nitrates with respect to above mentioned fuels for the combustion reaction, the fuel mixture composition could be predicted that could lead to phase pure perovskite GdAlO₃ directly after the combustion reaction without any subsequent calcination step. The use of single fuel, on the other hand, leads to formation of amorphous precursor powders that call for subsequent calcination for the formation of crystalline GdAlO₃. The powders produced directly after combustion reactions using fuel mixtures were found to be highly sinterable. The sintering of the powders at 1550 °C for 4 h resulted in GdAlO₃ with sintered density of more than 95%. T.D.     

Wear Performance of Laser Processed Tantalum Coatings

This first generation investigation evaluates the in vitro tribological performance of laser-processed Ta coatings on Ti for load-bearing implant applications. Linear reciprocating wear tests in simulated body fluid showed one order of magnitude less wear rate, of the order of 10(-4)mm(3)(N.m)(-1), for Ta coatings compared to Ti. Our results demonstrate that Ta coatings can potentially minimize the early-stage bone-implant interface micro-motion induced wear debris generation due to their excellent bioactivity comparable to that of hydroxyapatite (HA), high wear resistance and toughness compared to popular HA coatings.     

Controlling Plastic Flow across Grain Boundaries in a Continuum Model

A framework for modeling controlled plastic flow through grain boundaries using a continuum plasticity theory, phenomenological mesoscopic field dislocation mechanics (PMFDM), is presented in this article. The developed tool is used to analyze the effect of different classes of constraints to plastic flow through grain boundaries, as it relates to dislocation microstructure development and mechanical response of a bicrystal. It is found that in the case of low misorientation angle between adjacent grains, impenetrable grain boundaries cause significant work hardening as compared to penetrable grain boundaries due to the accumulation of excess dislocations along them. However, a penetrable grain boundary with a high misorientation angle effectively behaves as an impenetrable boundary, with respect to the stress-strain response.     

Extruded tellurite glass optical fiber preforms

The extrusion behavior of tellurite glass in the supercooled liquid region was investigated. Good extrusion formability was observed under low strain rates at various temperatures in the glass transformation region investigated. Tube and holey fiber (HF) preforms were fabricated from tellurite glass billets using a laboratory press. In particular, the results for three-spoke HF design and round tube preforms with composition 75TeO₂·20ZnO·5Na₂O (TZN) are presented. The extruded preforms with precise geometrical features, an excellent surface quality and no crystallization were achieved in the temperatures range from 344 to 360 °C and at ram speeds ranging from 0.002 to 0.01 mm/s. Discrete shear bands were observed in the preforms, increasing in number and/or becoming better defined with increasing load and ram speed. Fewer shear bands were present when increasing the extrusion temperature from 344 to 360 °C. Thus, subsequent extrudates were successfully fabricated free of shear bands, providing good optical homogeneity that yielded solid and holey fibers that could provide much improved optical performance.     

Relations between anxiety sensitivity, distress tolerance, and fear reactivity to bodily sensations to coping and conformity marijuana use motives among young adult marijuana users.

The present investigation examines anxiety sensitivity, distress tolerance, and fear reactivity to bodily sensations in relation to Coping and Conformity marijuana use motives among a sample of young adult marijuana users (n = 135; 46.7% women; Mage = 20.45, SD = 5.0). After controlling for current marijuana use frequency (past 30 days), daily cigarette smoking rate, average volume of alcohol used over the past year, negative affectivity, and other marijuana use motives, anxiety sensitivity was significantly and uniquely associated with Coping and Conformity motives for marijuana use. Distress tolerance evidenced significant and unique incremental relations to Coping motives, whereas fear reactivity to bodily sensations was unrelated to any marijuana use motive. These results provide novel information related to the role of emotional sensitivity and tolerance factors as they pertain to specific types of motives for marijuana use among young adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Processing and characterization of nanostructured Cu-carbon nanotube composites

Carbon nanotube (CNT) reinforced nanostructured Cu matrix composite with a grain size less than 25 nm has been successfully fabricated via a combination of ball milling and high-pressure torsion. CNTs were found to be homogeneously dispersed into the metal matrix, leading to grain refinement with a narrow grain size distribution and significant increase in hardness.     

Effect of Pre-heat and Inert Gas Species on Cryogenic Aerosol Cleaning Performance in Semiconductor Manufacturing

Cryogenic aerosol cleaning is a dry cleaning method used in the back end of line (BEOL) semiconductor manufacturing to remove defects from planar hydrophobic surfaces such as SiCOH and SiCxNyHz. Cryogenic aerosol cleaning is preferred over conventional wet cleaning methods as it is a non-contact cleaning method, which uses inert gases to generate sub-micrometer-sized solid aerosol particles that physically remove nanometer-sized contaminants on wafer surfaces. Particle removal mechanism involves detachment of the particles upon impact with aerosol, diffusion, and finally entrainment away from the wafer. In BEOL metal line patterning, particles on the dielectric isolation surfaces translate through the subsequent lithography and copper fill steps in to single or multiple metal line open defects that are yield killers. In this study, we show that the particle removal performance of the standard aerosol cleaning can be enhanced by pre-heating the wafer and use of a higher molecular weight inert gas, namely Ar, for aerosol generation. Both the addition of a Pre-heat step and the use of Ar as the aerosol source showed 47–52% reduction in single and multiple line opens detected through wafer electrical tests during high volume semiconductor manufacturing process.     

Experimental investigation on effects of dielectric mediums in near-dry electric discharge machining

Journal of Mechanical Science and Technology - A dielectric fluid plays a significant role on the machining efficiency of Electric discharge machining (EDM). Two phase (liquid-air) dielectric...     

Phase Transformations in Third Generation Gamma Titanium Aluminides: Ti-45Al-(5, 10) Nb-0.2B-0.2C

Third generation γ-titanium aluminides with nominal compositions Ti–45Al–5Nb–0.2B–0.2C and Ti–45Al–10Nb–0.2B–0.2C were investigated to identify the phase transformation and their morphological stability with temperature. Electron microscopy and differential scanning calorimetry were employed for the characterization of phases and for recording the corresponding transformations, respectively. It has been inferred that the order–disorder transformation temperatures α₂ → α increased with increasing Niobium (Nb), while the α-transus temperature decreases. The stability of the microstructure for both alloys with temperature were also investigated. Mass change measured for the heating rates 20 °C s⁻¹ and 30 °C s⁻¹ reveals that the alloy Ti–45Al–10Nb–0.2–0.2C shows stability up to 1100 °C, and the alloy Ti–45Al–5Nb–0.2B–0.2C is stable up to 900 °C. The orientation relationship between the phases indicates that with the change in shape of the α phase from lamellar to equiaxed, it deviates from the Blackburn orientation relationship.