Trapped-energy flexural mode filter

An electromechanical filter using trapped-energy flexural modes in a rectangular plate is proposed. The filter is amenable to fabrication by planar techniques and it can operate in the l.f. range, including the voice band. Bandwidth is easily controllable. A considerable gain in size can be obtained with respect to flexural bar filters.     

Control of birefringence in Ti:LiNbO3optical waveguides by proton exchange of lithium ions

The control of birefringence in Ti: LiNbO3optical waveguides by proton exchange is investigated in detail. It is shown that annealing of deep proton exchanged waveguides (7-8 mum) in an oxygen atmosphere allows precise control of the birefringence over a broad range of values. Even optically isotropic guides can be fabricated.     

Mixing strategies for zinc oxide nanoparticle synthesis via a polyol process

We report on the effect of mixing on the morphology of ultrafine zinc oxide nanoparticles synthesized via a polyol process using zinc acetate and water in a diethylene glycol medium. Three mixing strategies were considered: stirred batch, T‐mixer, and impinging free jets. The particle granulometry was accessed using the transmission electron microscopy and x‐ray diffraction methods. The nanoparticle size and polydispersity decreased with an increase in the local dissipated energy. In particular, the polyol process conducted in the same chemical environment at 353 K did not lead to the observation of nanoparticles in the stirred batch reactor but resulted in unconventionally small 6‐nm particles in the T‐mixer and impinging jet configurations. This result is apparently related to the micromixing eddy geometry described by the Kolmogorov length. The hydrodynamic flow patterns and energy dissipation were obtained from computational ?uid dynamics simulations, which are essential in the design, optimization, and scale‐up of the polyol process. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1708–1721, 2015     

Magnetic nanowire synthesis: A chemical engineering approach

Bimetallic one‐dimensional cobalt–nickel magnetic nanowires capped on both sides with conical heads were synthesized using the polyol process. Then, the process was scaled up to produce magnetic nanowires in sample aliquots of approximately 20 g. The scale‐up strategy involved improving the mixing reagents using either axial or radial mixing configurations and was experimentally validated by comparing the structural and magnetic properties of the resulting nanowires. The results indicated a connection between the flow patterns and the size and shape of the nanowires. When a Rushton turbine was used, shorter nanowires with unconventional small heads were obtained. Because the demagnetizing field is strongly localized near or inside these heads, the coercive field was enhanced nearly twofold. These results were confirmed by micromagnetic simulations using isolated nanowires. In addition, the development of flow patterns at the small and pilot scales was predicted and compared using three‐dimensional turbulent computational fluid dynamics simulations. © 2014 American Institute of Chemical Engineers AIChE J, 61: 304–316, 2015     

Influence of Mg on the superconductivity and phase composition of samples from the Bi-Pb(Sb)-Mg-Sr-Ca-Cu-O system

Superconducting oxide materials, containing Bi, Mg, Pb(Sb), Sr, Ca and Cu in various nominal stoichiometric proportions, are synthesized. The critical temperature of the samples is in the range of 90 to 96 K. The chemical and phase composition of the materials is investigated by emission spectral analysis and X-ray diffraction measurements, and the microstructure by scanning electron microscopy. It is established that the addition of magnesium results in the formation of a 15 K phase Bi₂Sr₂Cu₁O₆₊. Superconductivity is also observed at around 95 K in the Bi-Sb-Mg-Sr-Ca-Cu-O system.     

Orbital reflectometry of oxide heterostructures

The occupation of d orbitals controls the magnitude and anisotropy of the inter-atomic electron transfer in transition-metal oxides and hence exerts a key influence on their chemical bonding and physical properties. Atomic-scale modulations of the orbital occupation at surfaces and interfaces are believed to be responsible for massive variations of the magnetic and transport properties, but could not thus far be probed in a quantitative manner. Here we show that it is possible to derive quantitative, spatially resolved orbital polarization profiles from soft-X-ray reflectivity data, without resorting to model calculations. We demonstrate that the method is sensitive enough to resolve differences of ~3% in the occupation of Ni e(g) orbitals in adjacent atomic layers of a LaNiO(3)-LaAlO(3) superlattice, in good agreement with ab initio electronic-structure calculations. The possibility to quantitatively correlate theory and experiment on the atomic scale opens up many new perspectives for orbital physics in transition-metal oxides.