A study of the influence of TiO2 addition in Al2O3 coatings sprayed by suspension plasma spray

In this work, five different concentrations of a mixture of TiO2/Al2O3 nanopowders in an alcoholic suspension at 10wt.% solid content were sprayed by Suspension Plasma Spraying on steel discs. The influence of the presence of TiO2 at 0, 13, 40 and 75wt.% in Al2O3 was analysed by studying the properties of the sprayed coatings. Microscopy analysis of the projected coatings revealed a homogeneously distributed microstructure, where the densification of the coating increases with TiO2 content, while the original nanostructure is maintained. A nanoindentation study revealed an increment of nanohardness and elastic modulus due to the densifying effect of TiO2. The addition of significant amounts of TiO2 has been revealed as necessary in order to favour the fusion of Al2O3 in the SPS process

Molten salt attack on multilayer and funcionally-graded YSZ coating

[EN] Thermal barrier coatings have been extensively studied in the last years in order to increase the operational temperature of the current gas turbines as well as to improve the coating lifetime. Many coating characteristics must be met to achieve these requirements (low thermal conductivity, high thermal fatigue resistance...); therefore, complex systems have been engineered for these purposes. One of the possibilities to optimise the different properties deals with the design of multilayer or functionally-graded coatings where various types of microstructures with different characteristics are combined. One of the most important cause of gas turbines degradation relates to the attack of different type of particles which are suspended in the atmosphere (sand, fly ash...). These solid particles are molten at the operational temperatures and then, the molten salts chemically react with the coating. For this reason, the present research was focused on this type of attack. In the present work, the molten salt attack of various YSZ coatings with multilayer and functionally-graded design was addressed. Two different type of microstructures were specifically combined for this design: the APS coating microstructure obtained from conventional (microstructured) powder and a bimodal structure with nanozones obtained from nanostructured feedstock. Besides, different salts were used to simulate different attack environments (desert sand and volcanic fly ash). Findings show that nanozones act as barrier against the penetration of molten salts toward deeper layer. However, a layer formed by nanozones can detach when the salt attack is too aggressive. Hence, functionally-graded coatings, where two types of microstructures are combined through the whole coating, become ideal to diminish the molten salt attack.This work has been supported by the Spanish Ministry of Economy and Competitiveness (project MAT2015-67586-C3-R) as well as A. Borrell and L. Navarro thanks for their post-doc (RyC-2016-20915) and pre-doc (BES-2016-077792) contracts respectively. P. Carpio acknowledges the Valencia Government for his post-doc contract (APOSTD/2016/040).Carpio-Cobo, P.; Salvador Moya, MD.; Borrell Tomás, MA.; Navarro-López, L.; Sánchez, E. (2018). Molten salt attack on multilayer and funcionally-graded YSZ coating. Ceramics International. 44(11):12634-12641. https://doi.org/10.1016/j.ceramint.2018.04.062S1263412641441

Structure Features and Properties of Graphene/Al2O3 Composite

[EN] Since its discovery, graphene has attracted worldwide attention in the scientific community owing to its unique combination of properties. Thus, graphene is an ideal second phase to improve the structure and properties of metal, ceramic and polymer composite materials. This work presents a comparative study of two types of alumina-graphene composites fabricated with two sizes of delta-Al2O3 powders, nanometer and submicrometer, reinforced by graphene nanoplatelets (GNPs) and consolidated with the spark plasma sintering technique. The microstructure, mechanical and tribological properties of Al2O3-GNPs composites are influenced by the grain size of the ceramic matrix. Hardness values improve notably. The maximum value reached was 27.4 GPa for a composite fabricated with nanometric alumina powders, which is about 27 % higher than that of the Al2O3 monolithic material. Also, the methodology of powder mixing has a fundamental importance in obtaining materials with high-level properties.This work has been supported by the Competitiveness Program National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Russian Ministry of Education and Science No. 02. A 03.21.0005; the Russian Science Foundation No16 - 19 - 10213; the Spanish Ministry of Economy and Competitiveness project MAT2015 - 67586-C3-R. E. Klyatskina acknowledges the Valencian Government for her Post-Doc. Contract APOSTD/2014/046 and A. Borrell acknowledges the Spanish Ministry of Economy and Competitiveness for her contract RYC2016 - 20915.Klyatskina, E.; Borrell Tomás, MA.; Grigoriev, E.; Zholnin, A.; Salvador Moya, MD.; Stolyarov, V. (2018). Structure Features and Properties of Graphene/Al2O3 Composite. Journal of Ceramic Science and Technology. 9(3):215-223. https://doi.org/10.4416/JCST2018-00006S2152239

Chemometric comparison of almond oxidation rates using kinetic parameters obtained by infrared spectroscopy

BACKGROUND: The study of almond fat stability is essential from a quality control perspective meanly because, in most of the cases, almonds are sold skinned and thermally treated. In this work an alternative method to Rancimat test based on attenuated total reflectance‐Fourier‐transform infrared (ATR‐FTIR) spectrometry was adapted for checking the induced degradation at 75 °C of seven almond oil cultivars, three of the top Californian producing varieties, and, four traditional cultivars harvested in Spain. RESULTS: The thermal oil degradation evolution was followed by measuring the changes in the absorbance of the selected FTIR spectra bands (3470, 3006, 1730, 1630, 988 and 970 cm−1). A first‐order kinetic behaviour was observed, after an induction time in all bands. CONCLUSIONS: Kinetic coefficients and induction times were easily obtained as the absorbance values (from difference spectra) fitted to pseudo‐first‐order kinetics after the induction time. Principal component analysis was applied to the kinetic parameters to visualize which variables could be useful to classify the almond cultivars based on their resistance to thermal oxidation processes. It was found that selecting only the induction times corresponding to the bands 3470, 3006, 1630 and 970 cm−1 a separate classification of the Californian cultivars from the Spanish ones was possible. Finally, a linear discriminant analysis was assayed using only the four induction times previously selected. Validated classification and correct in 100% of the cases was obtained for all the samples based on their Spanish or Californian origin

Effect of TiO2 addition on the microstructure and nanomechanical properties of Al2O3 Suspension Plasma Sprayed coatings

Alumina–titania coatings are widely used in industry for wear, abrasion or corrosion protection components. Such layers are commonly deposited by atmospheric plasma spraying (APS) using powder as feedstock. In this study, both Al2O3 and Al2O3–13 wt% TiO2 coatings were deposited on austenitic stainless steel coupons by suspension plasma spraying (SPS). Two commercial suspensions of nanosized Al2O3 and TiO2 particles were used as starting materials. The coatings microstructure and phase composition were fully characterised using FEG-SEM and XRD techniques. Nanoindentation technique was used to determine the coatings hardness and elastic modulus properties. Results have shown that the addition of titania to alumina SPS coatings causes different crystalline phases and a higher powder melting rate is reached. The higher melted material achieved, when titania is added leads to higher hardness and elastic modulus when the same spraying parameters are use

Anatomía foliar y caulinar de Chascolytrum subaristatum (Poaceae, Pooideae, Poeae)

El objetivo del presente estudio fue describir la anatomía foliar y caulinar de Chascolytrum subaristatum (Poaceae) presente en áreas naturales de la provincia de Entre Ríos. Se realizaron transcortes y preparados epidérmicos de la parte media de hojas de innovaciones estériles y transcortes de tallo de innovaciones reproductivas. Las observaciones realizadas a nivel epidérmico manifestaron que Chascolytrum subaristatum es de tipo festucoide presentando cuerpos silícicos costales redondeados o alargados con paredes levemente onduladas, células epidérmicas más largas que anchas, con paredes anticlinales sinuosas y rectas, estomas de forma ovoide, células subsidiarias oblongas, tricomas tipo gancho. En transcorte la estructura anatómica foliar presenta un patrón anatómico de gramíneas C 3 , sin embargo, Chascolytrum presenta células de parénquima incoloro en el mesofilo, no descriptas para el tipo festucoideo.Las paredes periclinales externas de las células epidérmicas de las cara adaxial y abaxial se encuentran impregnadas de lignina. Los tallos presentaron sección circular. Se observó una epidermis uniestratificada, sin pelos y con cutícula gruesa y un anillo esclerenquimático subepidérmico. Los haces vasculares colaterales cerrados se disponen en 3-4 anillos concéntricos, con médula parenquimática o médula hueca

Long-Term Changes, Inter-Annual, and Monthly Variability of Sea Level at the Coasts of the Spanish Mediterranean and the Gulf of Cádiz

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Solvent Effects on the Structure−Property Relationship of Redox-Active Self-Assembled Nanoparticle−Polyelectrolyte−Surfactant Composite Thin Films: Implications for the Generation of Bioelectrocatalytic Signals in Enzyme-Containing Assemblies

The search for strategies to improve the performance of bioelectrochemical platforms based on supramolecular materials has received increasing attention within the materials science community, where the main objective is to develop low-cost and flexible routes using self-assembly as a key enabling process. Important contributions to the performance of such bioelectrochemical devices have been made based on the integration and supramolecular organization of redox-active polyelectrolyte−surfactant complexes on electrode supports. Here, we examine the influence of the processing solvent on the interplay between the supramolecular mesoorganization and the bioelectrochemical properties of redox-active self-assembled nanoparticle−polyelectrolyte−surfactant nanocomposite thin films. Our studies reveal that the solvent used in processing the supramolecular films and the presence of metal nanoparticles not only have a substantial influence in determining the mesoscale organization and morphological characteristics of the film but also have a strong influence on the efficiency and performance of the bioelectrochemical system. In particular, a higher bioelectrochemical response is observed when nanocomposite supramolecular films were cast from aqueous solutions. These observations seem to be associated with the fact that the use of aqueous solvents increases the hydrophilicity of the film, thus favoring the access of glucose, particularly at low concentrations. We believe that these results improve our current understanding of supramolecular nanocomposite materials generated via polyelectrolyte−surfactant complexes, in order to use the processing conditions as a variable to improve the performance of bioelectrochemical devices.Facultad de Ciencias ExactasInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Optimization and validation of a simplified methodology for simultaneous extraction of fatty acids and tocopherol homologues in peanuts

A new sample treatment methodology was developed for the simultaneous determination of oleic, linoleic, palmitic and stearic fatty acids (FA), and α-, β-, γ- and δ-tocopherol homologues in peanut samples. Usually, the determination of these compounds is carried out after oil extraction with an organic solvent at boiling temperatures of the solvent. The innovative analytical methodology developed in this work was performed in a 20 mL vial in which the FA and tocopherols were simultaneously extracted, and the derivatization of the FA was, afterwards, conducted. The reduction in analysis time from 1 h 30 min (reference methodology) to 20 min (new methodology) increased the sample throughput. Furthermore, the amount of organic solvent used decreased from 40 mL to 6 mL The new methodology was validated based on the analysis of a certified reference peanut butter sample and the results were compared to those obtained by using the reference methodology and a suitable agreement with the certified values was found. Finally, the new sample treatment approach was used to analyse toasted and fried (with and without tegument) peanuts.The authors would like to acknowledge the Packaging, Transport and Logistics Research Center (ITENE) and the Generalitat Valenciana (FEDEGENT/2018/021) for their financial support and DAMEL group© for providing some of the peanut samples

Impact of Feedstock Nature on Thermal Conductivity of YSZ Thermal Barrier Coatings Obtained by Plasma Spraying

[EN] Yttria-stabilized zirconia (YSZ) coatings with low thermal conductivity were obtained using three different particle size distributions as starting powder: nano-, submicron- and bimodal submicron/nano-sized particles. On the one hand, these particles were reconstituted into micrometric, spray-dry agglomerates, which were subsequently deposited by means of conventional atmospheric plasma spraying (APS). On the other hand, the starting particles were dispersed in water and the resultant suspensions were deposited by means of suspension plasma spraying (SPS). The coatings were thermally treated to assess their sintering resistance. As-sprayed and thermally treated coatings were then characterized in terms of microstructure (FEG-SEM) and thermal diffusivity (laser flash equipment). The results showed that SPS coatings exhibited extremely low thermal conductivity at low temperature which drastically augmented with increasing temperature. On the other hand, APS coatings also exhibited low thermal conductivities but their values were higher than those of the SPS coatings at the lowest temperature tested while the conductivities hardly varied with temperature.This work has been supported by the Spanish Ministry of Economy and Competitiveness (project MAT2015-67586-C3-R) and Research Promotion Plan of the Universitat Jaume I, action 2.1 (ref. E-2011 - 05) and action 3.1 (ref. PREDOC/2009/10). A. Borrell acknowledges the Spanish Ministry of Economy and Competitiveness for her Juan de la Cierva-Incorporacion contract (IJCI-2014-19839). M. Miranda would like to thank the European Commission (FP7-Marie Curie Intra-European Fellowship, BIOHYMAT).Carpio-Cobo, P.; Salvador Moya, MD.; Benavente Martínez, R.; Miranda, M.; Borrell Tomás, MA.; Sánchez, E. (2016). Impact of Feedstock Nature on Thermal Conductivity of YSZ Thermal Barrier Coatings Obtained by Plasma Spraying. Journal of Ceramic Science and Technology. 7(3):307-312. https://doi.org/10.4416/JCST2016-00022S3073127