A room temperature, templated synthesis of lanthanide trifluoride nanoparticles and their unusual self-assembly

A new methodology has been developed for synthesizing lanthanide trifluoride (LnF(3)) nanoparticles using a simple diffusion technique. The approach uses a lanthanide based hydrogel matrix to control the kinetics of the reaction, which also acts as a stabilizing platform, thus enabling the room temperature, in situ synthesis of finely sized (3-5 nm), monodisperse nanoparticles that were found to form in an ordered pattern on the gel fibers.

Dynamic compression behavior of reactive spark plasma sintered ultrafine grained (Hf, Zr)B-2-SiC composites

This paper reports the dynamic compression behavior of ultrafine grained (Hf, Zr)B-2-SiC composites, sintered using reactive spark plasma sintering at 1600 degrees C for 10 min. Dynamic strength of similar to 2.3 GPa has been measured using Split Hopkinson Pressure Bar (SHPB) tests in a reproducible manner at strain rates of 800-1300 s(-1). A comparison with competing boride based armor ceramics, in reference to the spectrum of properties evaluated, establishes the potential of (Hf, Zr)B-2-SiC composites for armor applications. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Integrating AlGaN/GaN high electron mobility transistor with Si: A comparative study of integration schemes

AlGaN/GaN high electron mobility transistor stacks deposited on a single growth platform are used to compare the most common transition, AlN to GaN, schemes used for integrating GaN with Si. The efficiency of these transitions based on linearly graded, step graded, interlayer, and superlattice schemes on dislocation density reduction, stress management, surface roughness, and eventually mobility of the 2D-gas are evaluated. In a 500 nm GaN probe layer deposited, all of these transitions result in total transmission electron microscopy measured dislocations densities of 1 to 3 x 10(9)/cm(2) and <1 nm surface roughness. The 2-D electron gas channels formed at an AlGaN-1 nm AlN/GaN interface deposited on this GaN probe layer all have mobilities of 1600-1900 cm(2)/V s at a carrier concentration of 0.7-0.9 x 10(13)/cm(2). Compressive stress and changes in composition in GaN rich regions of the AlN-GaN transition are the most effective at reducing dislocation density. Amongst all the transitions studied the step graded transition is the one that helps to implement this feature of GaN integration in the simplest and most consistent manner. (C) 2015 AIP Publishing LLC.

High temperature deformation behavior of Nb-1 wt.%Zr alloy

The hot deformation behavior of Nb-1 wt.%Zr alloy was studied using uniaxial compression tests carried out in vacuum to a true strain of 0.6 in the temperature range of 900 to 1700 degrees C and the strain rate range of 3 x 10(-3) to 10 s(-1). The optimum regime of hot workability of Nb-1Zr alloy was determined from the strain rate sensitivity (m) contour plots. A high m of about 02 was obtained in the temperature and strain rate range of 1200-1500 degrees C and 10(-3) to 10(-1) s(-1) and 1600-1700 degrees C and 10(-1) to 1 s(-1). Microstructure of the deformed samples showed features of dynamic recrystallization within the high strain rate sensitivity domain. Compared to the study on Nb-1Zr-0.1C alloy, Nb-1Zr showed a lower flow stress and an optimum hot working domain at lower temperatures. In the 1500 to 1700 degrees C range the apparent activation energy of deformation for Nb-1Zr was 259 kJ mol(-1), the stress exponent 5, and the activation volume about 200 to 700 b(3). (C) 2015 Elsevier Ltd. All rights reserved.