142 research outputs found
Corrosion Behavior of Smy(FexNi1−x)4Sb12(0.40 ≤ x ≤ 0.80) in NaCl Solutions Studied by Electron Microscopy and ICP-AES
No full textFilled skutterudites are currently studied as thermoelectric materials to be used in the automotive and nautical field; the study of their resistance to a saline environment is therefore mandatory. To this purpose, the corrosion behavior of several compositions belonging to the Smy(FexNi1−x)4Sb12skutterudites system was investigated by immersing samples in differently concentrated (0.1 and 0.5 M) NaCl solutions. The effect of the treatment was analyzed both by SEM–EDS on the sample surface and at fixed times by ICP-AES on the solution. The formation of an oxide layer was observed on the surface of all the samples: the film results uniformly grown on specimens treated in NaCl at the lower concentration, while it is cracked and not spread over the whole surface in the other samples. Relying on the oxide layer thickness, the oxidation resistance results to increase with increasing the Fe content; correspondingly, the Sb concentration in the more diluted solution decreases at each time considered with increasing the Fe amount, pointing at a strict correlation between the cationic release and the oxide formation, and suggesting a possible mechanism for the growth of the protective film
Effect of the sintering pressure on structure and microstructure of the filled skutterudite Sm-y(FexNi1-x)(4)Sb-12 (x=0.50-0.80, y=0.17-0.55)
No full textA structural and microstructural study was performed on several compositions of the Sm-y(FexNi1-x)(4)Sb-12 system treated at three different pressures during the spark plasma sintering (SPS) process. Aim of the study is to recognize the effect of applied pressure at a fixed temperature on composition, microstrain and domains size, due to the relevance of these parameters in driving the thermoelectric properties of the material. Increasing pressure induces a change in the Sm amount, as well as an increase in microstrain and a decrease in the diffraction domains size. At the same time, enhancing pressure above a certain threshold promotes the formation of the extra phase (Sm,Fe,Ni)Sb-2, and hence a large power factor reduction. Relying on data collected in this work, applying a pressure close to 180 MPa during SPS results to be a good compromise between advantages in terms of microstructure and transport properties, and disadvantages in terms of phase purity
Low-temperature thermoelectric properties of p-type and n-type filled skutterudite compounds Sm y (Fe1−x Ni x )4Sb12 prepared under high pressure
No full textFilled skutterudite compounds Smy(Fe1−xNix)4Sb12 (nominal composition 0 ⩽ x ⩽ 0.56, 0.1 ⩽ y ⩽ 1.2) were synthesized under high pressure using a cubic anvil press. The samples were characterized by X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectrometry and electron probe microanalyzer. Thermoelectric properties of Smy(Fe1−xNix)4Sb12 were investigated in the temperature range of 2–300 K. The Seebeck coefficient of samples exhibits the feature of p-type and n-type conductors depending on Sm-filling ratio and Fe/Ni content. The highest dimensionless figure of merit ZT value of 0.167 is achieved for nominal composition Sm0.2(Fe0.6Ni0.4)4Sb12 at room temperatur
The doubly filled skutterudite (La,Sm) (Fe Ni1-)4Sb12 (y = 0.19–0.70, x = 0.52–0.85): Structural and thermoelectric features
No full textA comprehensive investigation of the double-filled skutterudite system (La,Sm)y(FexNi1-x)4Sb12 (y = 0.19–0.70, x = 0.52–0.85) has been carried out with the aim of exploring the influence of multi-filling with rare-earth elements on the structural and thermoelectric properties of the material. The introduction of La alongside Sm leads to a progressive increase in the filling degree as the Fe content increases, associated with structural modifications without evident slope changes in the cell parameter. The p/n crossover is identified at x ∼ 0.67 and y ∼ 0.45, and it is bound to changes in several physical parameters. Thermoelectric measurements reveal notably low thermal conductivity values in heavily filled compositions, attributed to enhanced phonon scattering due to the mass contrast and rattling effects of the two different fillers. As a result, the sample with x = 0.79 and y = 0.65 achieves a remarkable ZT value of approximately 1 at 650 K. These outcomes confirm that double-filling with La and Sm represents an effective strategy to reduce lattice thermal conductivity and improve the thermoelectric performance in Fe/Ni-based skutterudites
Enhancing the thermoelectric performance of Sb-based filled skutterudites through filler modifications
No full textLong noncoding RNA: A new player of heart failure?
No full textOne the most important discoveries of the post-genomic era is that a large fraction of the genome transcribes a heterogeneous population of noncoding RNAs (ncRNA). ncRNAs shorter than 200 nucleotides are usually identified as short/small ncRNAs - examples include PIWI-interacting RNAs, small interfering RNAs, and microRNAs (miRNAs) - whereas those longer than 200 nucleotides are classified as long ncRNAs (lncRNAs). These molecules are emerging as important regulators of cellular process, such as development, differentiation, and metabolism. Not surprisingly, ncRNAs are involved also in human diseases, such as cancer and metabolic and neuronal disorders. Although the role of miRNAs is being largely investigated in cardiovascular biology, little is known about other classes of ncRNA in this field. However, recent reports have started to reveal the importance of lncRNA in heart development and suggest also an involvement in heart failure. Here, we will discuss these reports and the therapeutic potential of lncRNA for heart failure. © 2013 The Author(s)
Epigenetics: A new mechanism of regulation of heart failure?
No full textHeart failure is a syndrome resulting from a complex genetic predisposition and multiple environmental factors, and is a leading cause of morbidity and mortality. It is frequently accompanied by changes in heart mass, size, and shape, a process known as pathological cardiac remodeling. At the molecular level, these changes are preceded and accompanied by a specific gene expression program characterized by expression of certain 'fetal' genes. This re-expression of fetal genes in the adult heart contributes to the development of the syndrome. Therefore, counteracting the gene expression changes occurring in heart failure could be a therapeutic approach for this pathology. One mechanism of gene expression regulation that has gained importance is epigenetics. This review gives an overview of the roles of some epigenetic mechanisms, such as DNA methylation, histone modifications, ATP-dependent chromatin remodeling, and microRNA-dependent mechanisms, in heart failure. © 2013 The Author(s)
Effect of the annealing treatment on structural and transport properties of thermoelectric Smy(FexNi1-x)4Sb12thin films
No full textThe crystallographic and transport properties of thin films fabricated by pulsed laser deposition and belonging to the Sm- y (Fe x Ni1-x )(4)Sb-12 filled skutterudite system were studied with the aim to unveil the effect exerted by temperature and duration of thermal treatments on structural and thermoelectric features. The importance of annealing treatments in Ar atmosphere up to 523 K was recognized, and the thermal treatment performed at 473 K for 3 h was selected as the most effective in improving the material properties. With respect to the corresponding bulk compositions, a significant enhancement in phase purity, as well as an increase in electrical conductivity and a drop in room temperature thermal conductivity, were observed in annealed films. The low thermal conductivity, in particular, can be deemed as deriving from the reduced dimensionality and the consequent substrate/film interfacial stress, coupled with the nanometric grain size
Tailoring thermoelectric properties in double-filled skutterudites (La,Sm)y(FexNi1-x)4Sb12: insights from bulk and thin-film studies
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