Search results for "Composite material"

2018

CrN thin films with an N/Cr ratio of 95% were deposited by reactive magnetron sputtering onto (0 0 0 1) sapphire substrates. X-ray diffraction and pole figure texture analysis show CrN (1 1 1) epitaxial growth in a twin domain fashion. By changing the nitrogen versus argon gas flow mixture and the deposition temperature, thin films with different surface morphologies ranging from grainy rough textures to flat and smooth films were prepared. These parameters can also affect the CrN x system, with the film compound changing between semiconducting CrN and metallic Cr2N through the regulation of the nitrogen content of the gas flow and the deposition temperature at a constant deposition pressur…

MOCVD growth of CdO very thin films: Problems and ways of solution

2016

Abstract In this paper the growth of CdO by the MOCVD technique at atmospheric pressure has been studied in order to achieve very thin films of this material on r-sapphire substrates. The growth evolution of these films was discussed and the existence of a threshold thickness, below which island-shaped structures appear, was demonstrated. Some alternatives to reduce this threshold thickness have been proposed in the frame of the analysis of the crystal growth process. The morphology and structural properties of the films were analyzed by means of SEM and HRXRD. High-quality flat CdO samples were achieved with thicknesses up to 20 nm, which is five times thinner than the values previously re…

Analysis of nonlinear time-dependent properties of carbon fiber reinforced plastic under off-axis loading

2021

Abstract Polymeric composites are rheonomic materials and their deformation can be described using the hereditary elasticity relations which allow for describing the mechanical behavior under time-variable loading with consideration of the influence of temperature and other operational factors. A system of hereditary-type constitutive relations is proposed for off-axis specimens of a unidirectional carbon fiber-reinforced plastic subjected to loading at different strain rates. Using the algebra of resolvent operators and inverted transformation, the constitutive equations allowing of description of anisotropy of rheological properties and, in particular, sensitivity to strain rates are deri…

The effects of the additive of Eu ions on elastic and electric properties of BaTiO3ceramics

2016

ABSTRACTThe BaTiO3 and BaTiO3+X%wt.Eu2O3 (X = 1, 2, 3) ceramics were prepared by a solid phase reaction. The structural and morphology studies were carried out by means of an X-ray diffraction technique and scanning electron microscopy, respectively. Elastic moduli were determined with the use of an ultrasonic method. The dielectric permittivity (ϵ′) and tanδ as a function of composition and temperature were investigated. The increasing concentration of Eu ions leads to a slight shift of the Curie temperature and changes the characteristics of ϵ′ and tanδ. The structural, mechanical and dielectric properties of the BTEX ceramics were discussed in terms of microstructure and dopants contents.

SrTiO3-doping effect on dielectric and ferroelectric behavior of Na0.5Bi0.5 TiO3 ceramics

2018

Lead-free (Na0.5Bi0.5)1-xSrxTiO3 ceramics (x = 0–0.04) were synthesized by a conventional mixed-oxide technique. The microstructure study showed a dense structure, in good agreement with that of ab...

OPTIMIZATION OF A NOVEL MAGNETO-RHEOLOGICAL DEVICE WITH PERMANENT MAGNETS

2017

In this paper a novel evolutionary algorithm is used for the optimization of the performance of a magnetorheological (MR) device, capable to transmit torque between two shafts and powered by a system of Permanent Magnets (PMs). The stochastic, evolutionary, global optimization algorithm is based on a modified version of the self-organizing map. It uses a dedicated simplified analytical model of the device, developed in order to obtain a fast and accurate evaluation of the torque. Then, by means this model, the cost function to find the optimal parameters of the device is defined. Once the optimal parameters are identified, the performance of the proposed device is simulated by means of a FE…

EBSD, XRD and SRS characterization of a casting Al-7wt%Si alloy processed by equal channel angular extrusion: Dislocation density evaluation

2019

Abstract Aluminum‑silicon (Al Si) alloys of high silicon contents are composite materials; they are used whenever high casting properties are required. They are slightly ductile below 8wt%Si. An increase in ductility can be obtained by refining Si-crystals in elaboration or by a further hot working. In the present work, an Al-7wt%Si alloy was processed by Equal Channel Angular Extrusion (ECAE) at temperatures 20 °C and 160 °C up to three passes. The die was formed by two cylindrical channels with characteristic angles Φ = 110° and Ψ = 0. EBSD, X ray diffraction (XRD) and Strain Rate Sensitivity (SRS) were used to characterize the microstructure and the mechanical properties. High levels of …

Influence of spray trajectories on characteristics of cold-sprayed copper deposits

2021

Abstract Industrial robots are widely used in cold spray (CS) as well as thermal spray to produce various coatings by precisely controlling kinematic parameters during the process. However, the robot trajectory and its effect on the characteristics of CS deposits are important, but not fully studied. This article introduces four typical spray trajectories, including zigzag path, cross path, parallel path, and spiral path, to elaborate thick CS Cu deposits, and characterizes the corresponding Cu deposits, respectively. The experimental results revealed that the spray trajectories have a major influence on the associated thermal history and the residual stress distribution. However, no signif…

Comparative Study on Micromechanical Properties of ZnO:Ga and ZnO:In Luminiscent Ceramics

2021

The research has been supported by the Project ERANET RUS_ST#2017-051(Latvia) and #18-52-76002 (Russia). The Institute of Solid State Physics, University of Latvia as the Centre of Excellence has received funding from the European Union’s Horizon 2020 Framework, Program H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2.

Mechanical properties of macroscopic magnetocrystals

2019

Abstract We studied experimentally and by numerical simulations the mechanical response of arrays of macroscopic magnetic spheres when an external stress is applied. First, the tensile strength of single chains and ribbons was analyzed. Then, simple cubic (cP), hexagonal (Hx) and hybrid (cP-Hx) structures, called here magnetocrystals , were assembled and subjected to tensile stress, bending stress and torsion until failure was reached. Atomistic crystalline structures are isotropic, but in the case of magnetocrystals, even when geometric isotropy is obeyed, dipolar magnetic interactions introduce a physical anisotropy which modifies, in a non-usual manner, the structures response to the kin…