Search

To improve the electrochemical properties of Li(Ni 1/3 Mn 1/3 Co 1/3 )O 2 (NMC) like Lithium-diffusion rate or rate capability one way is to increase the surface between the cathode and electrolyte. By sputter etching of stainless steel substrates the surface topography is varied. Lithium-rich Li-Ni-Mn-Co-O thin film cathodes are deposited onto these modified stainless steel substrates by non-reactive r.f. magnetron sputtering from a ceramic Li 1.14 (Ni 0.37 Mn 0.18 Co 0.32 )O 1.19 target. Microstructure and electrical properties were characterized by X-ray diffraction (GIXRD), Raman spectroscopy, Atomic-force microscopy (AFM) and impedance spectroscopy (IS). The substrate roughness was increased from R a = 4 nm to R a = 63 nm after 180 min of sputter etching. The crystal orientation wasn’t influenced significant by the pre deposition surface topography modification. The results show that the activation energy E A of the conductivity mechanism is 0.23 eV, independent of the pre-deposition sputter etching treatment. Also the pre-deposition sputter etching increases the conductivity from 1.49·10 −11 Scm −1 to 1.75·10 −10 Scm −1 at 20 °C. Correlations between process parameters, microstructure and electrical behaviour are discussed in detail. [ABSTRACT FROM AUTHOR]

Be–30.8 wt.%Ti powder mixture was extruded in copper and steel containers at 700 and 900 °C, respectively. In both cases, achieved extrusion ratio was 7:1. Investigations of microstructure of manufactured Be–Ti rods revealed that processing temperature has a great influence on the metal flow during the extrusion as well as formation of beryllide phases. The results obtained by X-ray diffraction (XRD) analysis proved that brittle intermetallic phases were formed by processing at 900 °C; while no evidence of reaction between beryllium and titanium was detected after extrusion at 700 °C. Additionally, high-temperature annealing tests of produced Be–Ti samples were performed in order to study the evolution of the phase composition after the heat treatment. The effects of different mechanical properties of core materials (beryllium and titanium) and containers on uniform deformation are discussed in this work. [ABSTRACT FROM AUTHOR]

Abstract: Antiferromagnetic/ferromagnetic (AF/F) NiMn/Fe37Co48Hf15 films were investigated with respect to their exchange bias, in-plane unidirectional anisotropy, polarisation and high frequency behaviour. After deposition, carried out by r.f. magnetron sputtering, the films were post-annealed for 4h at 300°C in a static magnetic field, in order to induce exchange-bias, which results in a unidirectional anisotropy. Dependent on the presence of a bi-layer or multi-layer sandwich structure the films show a different exchange-bias field–ferromagnetic inter-layer thickness behaviour with exchange-bias fields μ 0⁎H eb between 2 and 10mT. The in-plane uniaxial (single film) or unidirectional anisotropy fields μ 0*H UF were between 4 and 18mT. This results in a significant increase of the cut-off frequency in the GHz range in comparison to a single Fe37Co48Hf15 film, which is shown by frequency-dependent permeability plots. High damping in the imaginary part of the permeability, i.e., high resonance line broadening could be observed for films with high coercivity μ 0*H c of around 7mT in the easy axis of magnetisation. [Copyright &y& Elsevier]

Abstract: Ferromagnetic nanocomposite (Fe44Co56)77Hf12N11 films were deposited to investigate their intrinsic damping mechanisms due to scattering of itinerant electrons, which carry the magnetic moment of the ferromagnetic transition elements. The films were produced by reactive r.f. magnetron sputtering using a 6in. Fe37Co46Hf17 target. They were annealed at 400°C in a static magnetic field, in order to induce in-plane uniaxial anisotropy. Subsequently, the films can be considered as uniformly magnetised. A ferromagnetic resonance frequency (FMR) of around 2.3GHz could be attained, which was determined by measuring the real and imaginary parts of the frequency dependent permeability up to 5GHz. The imaginary part, which represents a typical resonance curve, was utilised to obtain its full-width at half-maximum Δf eff (FWHM) for the total damping behaviour characterisation. Thereby, it is possible to extract the intrinsic Gilbert damping parameter α int, which in turn can be decomposed into two additional damping terms α sf and α os allocated to “spin-flip” and “ordinary scattering”, respectively. This result is correlated and discussed in terms of a verified theoretic model, to identify whether damping due to spin-flip scattering and/or ordinary scattering is dominant. [Copyright &y& Elsevier]

Abstract: Ferromagnetic Fe–Co–Hf–N nanocomposite films were investigated concerning their microstructure-dependent frequency behaviour. To modify the composition, the films were deposited by reactive RF magnetron sputtering by using three different 6in. targets with various Hf fractions. The films were post-annealed up to 600°C in a static magnetic field to induce an in-plane uniaxial anisotropy and to obtain different crystal sizes. Depending on the annealing temperature, high-frequency losses were investigated by considering the full-width at half-maximum (FWHM) Δf eff of the imaginary part of the frequency-dependent permeability which showed a resonance frequency f FMR of 2.3GHz for an in-plane uniaxial anisotropy field H u of 4mT. The FWHM in correlation with the damping parameter α eff is discussed, e.g., in terms of two-magnon scattering. Damping occurs due to film inhomogeneity in magnetisation and uniaxial anisotropy caused by a magnetocrystalline anisotropy H a and/or non-magnetic phases. This will result in homogenous or even inhomogeneous resonance line broadening if additional and resonance as well as precession frequencies of independent grains arise. [Copyright &y& Elsevier]

A specific gradient in the constitution and properties of the growing film can be used to improve the mechanical properties and performance of magnetron-sputtered carbon films up to a thickness of 10 μm. The films were deposited on polished WC hard metal inserts and on silicon substrates. Additional argon ion bombardment of the growing film, caused by the substrate bias voltage applied during deposition, could be applied to raise the film density and hardness. The metal additions to carbon films were achieved in a physical vapor deposition process by adding titanium carbide to graphite targets. In a series of basic experiments, the substrate bias voltage for the deposition of homogeneous pure carbon and titanium added films was varied between 0 and −800 V. Afterwards, both pure carbon films and carbon films with metal additions were deposited with a gradient based on the effect of increasing the substrate bias voltage. The resultant residual stress of these graded films grown at various substrate bias voltages could be reduced in comparison to conventionally sputtered films. The mechanical properties and performance, such as Vickers hardness, critical load of failure, friction coefficient and the residual stress of the pure carbon films and the films with added metal, deposited with and without this gradient, have been compared. [Copyright &y& Elsevier]

• The influence of the transition layer of nanoporous silicon on the epitaxial growth of GaN. • The transition por-Si layer was introduced in the template of 3C-SiC/por-Si/c-Si. • The abovementioned approach enabled a 90% reduction in the stress levels in the crystalline lattice. • The use of the 3C-SiC/por-Si/c-Si template resulted in the formation of more uniform GaN film. Using the complexes of structural and spectroscopic diagnostic techniques, we investigated the influence of the layer of nanoporous silicon on the practical implementation and certain features of the epitaxial growth of GaN layers with the use of MBE PA on the templates of SiC/por-Si/c-Si. For the first time, the layer of nanoporous silicon has been introduced in the template of SiC/por-Si/c-Si where the layer of 3C-SiC was obtained by the substitution of the atoms; this had a number of indisputable advantages as compared to conventional silicon substrates. In particular, the abovementioned approach enabled a 90% reduction in the stress levels in the crystalline lattice of GaN layer that was synthesised on the SiC surface of the SiC/por-Si/c-Si template; it also decreased some of the vertical dislocations within the GaN layer. We also found that the use of the SiC/por-Si/c-Si template resulted in the formation of a more uniform (by its quality) GaN layer without any visible extensive defects. As a result, this enabled us to attain unique optical and electro-physical characteristics for the hybrid heteroepitaxial GaN/SiC structures. The obtained data will be very important for understanding the basic physics of nanoheterostructures of GaN/SiC/por-Si, thus promoting their potential applications in optoelectronics. [ABSTRACT FROM AUTHOR]