Suchergebnisse

[EN] The improvement of high temperature materials with lower heat transfer coefficients lead to the development of thermal barrier coatings (TBCs). One of the most widely used materials for thermal barrier coatings is Y2O3 stabilized ZrO2 (Y-TZP) because of its excellent shock resistance, low thermal conductivity, and relatively high coefficient of thermal expansion. The aim of this work is to study the TBCs mechanical behavior with the addition of SiC into the suspension of Y-TZP/Al2O3 by acoustic emission (AE). Additionally, a microstructural analysis and a finite elements model were carried out in order to compare results. The coatings were made by suspension plasma spray (SPS) on metal plates of 70 x 12 x 2 mm(3). An intermetallic was deposited as a bond coating, followed by a coating of Y-TZP/Al2O3 with and without 15 wt.% SiC, with thicknesses between 87 and 161 mu m. The AE becomes a fundamental tool in the study of the mechanical behavior of thermal barriers. The use of wavelet transforms streamlines the study and analysis of recorded sound spectra. The crack generation arises at very low stress levels. ; The authors wish to thank the financial contribution of the Ministry of Economy, Industry, and Competitiveness of the Government of Spain, (MINECO), and to the RTI 2018-099033-B-C32-RETOS. A. Borrel acknowledges her contract (RyC-2016-20915). ; Busquets Mataix, DJ.; Bloem, C.; Borrell Tomás, MA.; Salvador Moya, MD. (2021). Influence of SiC addition on mechanical behavior of thermal barriers with the aid of acoustic emission. Journal of Composites Science. 5(1):1-19. https://doi.org/10.3390/jcs5010016 ; S ; 1 ; 19 ; 5 ; 1

[EN] We propose a model for the consistent interpretation of the transport behavior of manganese perovskites in both the metallic and insulating regimes. The concept of polarons as charge carriers in the metallic ferromagnetic phase of manganites also solves the conflict between transport models, which usually neglects polaron effects in the metallic phase, and, on the other hand, optical conductivity, angle-resolved spectroscopy, and neutron scattering measurements, which identify polarons in the metallic phase of manganites down to 6 K. Transport characterizations of epitaxial La0.7Sr0.3MnO3 thin films in the thickness range of 5-40 nm and temperature interval of 25-410 K have been accurately collected. We show that taking into account polaron effects allows us to achieve an excellent fit of the transport curves in the whole temperature range. The current carriers density collapse picture accurately accounts for the properties variation across the metal-insulator transitions. The electron-phonon coupling parameter gamma estimations are in a good agreement with theoretical predictions. The results promote a clear and straightforward quantitative description of the manganite films involved in charge transport device applications and promises to describe other oxide systems involving a metal-insulator transition. ; The authors P.G., A.G., M.P., A.R., and I.B. thank F. Bona for technical help and A. Dediu and V. Kabanov for fruitful discussions. Financial support from the FP7 Projects No. NMP3-LA-2010-246102 (Interfacing oxides, IFOX), No. NMP-2010-SMALL-4-263104 (Next generation hybrid interfaces for spintronic applications, HINTS), No. NMP3-SL-2010-246073 (Graphene for nanoscaled applications, GRENADA), and the Italian government FIRB (Molecular nanomagnets on metallic and magnetic surfaces for applications in molecular spintronics) Project No. RBAP117RWN is acknowledged. ; Graziosi, P.; Gambardella, A.; Prezioso, M.; Riminucci, A.; Bergenti, I.; Homonnay, N.; Schmidt, G. (2014). Polaron framework to account for ...

[EN] The present work reports on the fabrication of hollow ZnO nanocolumns by a sequential combination of electrochemical deposition, chemical attack and regeneration. Initially, ZnO nanocolumns were deposited in two different substrates, namely Fluor Tin Oxide and Indium Tin Oxide. In a further step, a statistical analysis on the most influencing control parameters in the dissolution stage to produce the hollow ZnO nanowires on the FTO substrates was carried out. The control variables considered were electrolyte concentration, dissolution time and temperature, whereas the output variable was the percentage of the hollow nanocolumns obtained. The statistical analysis consisted of a two-level factorial design of experiments on three variables, therefore involving a series of 8 experiments. An analysis of variance (ANOVA) on the results was also carried out. The results showed that all the control variables were significant, the most important being the dissolution time. ; This work was supported by the Spanish Government through MCINN Grant MAT2009-14625-C03-03, Generalitat Valenciana programme PROMETEO/2009/063 and European Commission through NanoCIS project FP7-PEOPLE-2010-IRSES (ref. 269279). Technical support given to the authors by the Servei de Microscopia at the Universitat Politecnica de Valencia (Spain) is greatly acknowledged. ; Cembrero Cil, J.; Busquets Mataix, DJ.; Rayón Encinas, E.; Pascual Guillamón, M.; Pérez Puig, MA.; Marí Soucase, B. (2013). Control parameters on the fabrication of ZnO hollow nanocolumns. Materials Science in Semiconductor Processing. 16:211-216. https://doi.org/10.1016/j.mssp.2012.04.014 ; S ; 211 ; 216 ; 16