Owing to energy conservation of waste heat, Lead telluride, PbTe, based materials have promising good thermoelectric properties around a range of middle temperature (Fig. 1, from 300 to 600°C), due to their high melting point, fine chemical stability, and the high figure of merit Z. The general physical properties and factors affecting the figure of merit have been reviewed. This research is focused on the n-type of PbTe materials and collocated with analysis of densities, hardness, elastic modulus, and thermoelectric properties thermoelectric figure of merit ZT=GS2T/κ (where G is electrical conductivity, S is Seebeck coefficient , T is absolute temperature, and κ is thermal conductivity). Room temperature hardness and Young’s modulus are measured by nano-indentation. In this study, the hot-press compacts under the pressure of 4 ton/cm2 can reach the maximum density about 8.2 g/cm3, and hardness and elastic modulus are 0.6 GPa and 70 GPa, respectively. The figure of merit value (ZT) of PbTe in low temperature (around 340°C) was found about 1 with carrier concentration above 1019 cm−3. These results also indicate that the powder metallurgy parameters provide potentialities for further increase of the high efficiency of energy conversion in PbTe materials.

We will briefly review in situ synchrotron x-ray investigation of model thin film cathode systems for solid oxide fuel cells. The film cathodes examined in this study are (La,Sr)MnO3_δ (LSM), (La,Sr)CoO3_δ (LSC), and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) thin films epitaxially grown on YSZ single crystal substrates by the pulse laser deposition technique. We find in all cases that Sr is enriched or segregated to the surface of the film cathodes. We concluded that the Sr enrichments or segregations are mainly the results of annealing because they do not depend on whether the cathodes are electrochemically biased or not during annealing. However, at least in the case of LSCF, we find that B-site Co segregates rather uniformly to the surface and the segregation responds sensitively and reversibly to the electrochemical bias.

The transmission and reflection properties of a meta-stack composed of a periodic AB arrangement of an air(A)/metamaterial(B) bilayer is presented, with the multi layered system embedded between two semi-infinite layers of the A material. For oblique incidence, a finite projection along the growth direction of the electric or magnetic field of the incident wave associated with the TM or TE modes, respectively, leads to a coupling of the photon modes with the bulk electric or magnetic metamaterial plasmons, in each layer of the meta-stack. This field-matter coupling gives rise to plasmon-polariton modes and signatures of electric or magnetic longitudinal bulk-plasmon polariton modes in the transmission, as well as in the reflection properties of the meta-stack, by means of a plasmon-polariton gap. Such features survive even in the case of a single bilayer and experimental observation should be, therefore, easily achieved.

In this study, A H2-plasma is studied as a dry method to etch thin layers of amorphous silicon aSi:H(i) deposited on a crystalline wafer. It is found that H2-plasma etches aSi:H(i) selectively toward silicon nitrides hard masks with an etch rate below 3nm/min. Depending on power density and temperature of the substrate during the H2-plasma, the energy bandgap, the hydrides distribution and the void concentration of the aSi:H(i) layers are modified and the amorphous-to-crystalline transition is approached. At high temperature (>250C) and low plasma power (<20mW/cm2), the dihydride (SiH2) content increases and the bandgap widens. The etch rates stays below 0.5 nm/min. At low temperature (<150°C) and high power (>70mW/cm2), the void concentration increases significantly and etch rates up to 3nm/min are recorded.

These findings are supported by a theoretical model that indicates formation of Si-H-Si precursors in the layer during exposure to H2-plasma. According to the experimental conditions, these precursors either diffuses and forms Si-Si strong bonds or are removed from the film, causing layer etching.

Novel solutions and applications in the biomedical field could come from exploiting the electroactive properties of conducting polymers towards the development of responsive smart biointerfaces and of flexible, conformable, biocompatible systems. In this sense it is mandatory to control material’s conductivity in situ and this requires the development of suitable patterning processes and the fabrication of individually addressable microelectrodes. Based on the recent introduction by our group of free-standing nanofilms of conductive polymers, the aim of this work was to describe a method for the fabrication of patterned ultra-thin free-standing PEDOT:PSS/Poly (lactic acid) (PLA) bilayer nanosheets. The proposed method involves an ink-jet patterning technique, based on localized overoxidation of PEDOT:PSS by means of a sodium hypochlorite solution. Here we described the fabrication method and characterized the realized nanosheets in terms of their thickness, contact angle, conductivity. The overall process permitted to realize patterned free-standing nanosheets that, despite their low thickness, are very robust and conformable on tissues or on soft and rigid substrates, while allowing for an electrical control of their surface properties. Possible applications are foreseen in the field of conformable electronics, e.g. as electrodes on the brain or smart conductive substrates for cell culturing and stimulation.

Atomic scale characterization of the La2Ni7 hydrides by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) revealed that not only the anisotropic expansion of the La2Ni4 unit layer previously reported but also the shearing on the basal plane of the La2Ni4 unit layers occur during one-cycle of hydrogen absorption/desorption process. Two different types of orthorhombic La2Ni7 hydrides with the same atomic arrangement of La and different atomic arrangement of Ni were observed depending on the maximum hydrogen concentration achieved during one hydrogen absorption/desorption cycle.

Ba0.8Sr0.2TiO3/ZrO2 heterostructured thin films are deposited on Pt/Ti/SiO2/Si substrates by a sol-gel process. The current versus voltage (I-V) measurements of metal-insulator-metal (MIM) devices using the above multilayered thin film as the dielectric have been taken in the temperature range of 310 to 410K. The electrical conduction mechanisms contributing to the leakage current at different field regions have been studied in this work. Various models are used to know the different leakage mechanisms contributing to the conduction current in these devices. It is observed that Poole-Frenkel mechanism is the dominant conduction process in the high field region with a deep trap level energy (φ t ) of 1.31 eV whereas space charge limited current (SCLC) mechanism and Ohmic conduction process are contributing to the leakage current in the medium and low field regions respectively. The estimated shallow trap level (E t ) for SCLC mechanism is 0.26 eV whereas the activation energy (E a ) for the electrons in the Ohmic conduction process is about 0.07 eV. An energy band diagram is given to explain the various leakage mechanisms in different field regions for these heterostructured thin films.

Polyaniline nanofibers (PANI-NFs)/graphite oxide (GO) nanocomposites with excellent interfacial interaction and elongated fiber structures were synthesized via a facile interfacial polymerization method. This method efficiently exfoliated the expanded layer structure of GO into individual sheet and thus significantly enhanced the specific surface area. The reduced diameter of PANI-NFs in PANI-NF/GO than that of pure PANI-NFs could shorten the diffusion distance and enhance the electro-active sites. The PANI-NFs/GO hybrid materials showed orders of magnitude enhancement in capacitance and better cycling stability than that of individual GO and PANI-NF components.

There is an extended concern related to renewable energies in South America. Particularly the Uruguayan government is encouraging initiatives in solar, biofuels and eolic wind energy issues. On the other hand, and in a similar manner than in other countries, Uruguay celebrates the “Science and Technology Week”, an activity annually organized, focused on sharing knowledge between scientists and technologists and society. In 2012, this week was devoted to energy and sustainability. In this framework we carried out an interactive activity in five primary school classes with the aim of bringing materials science and solar energy to children between 10 and 12 years old. In the beginning of the activity we asked students to complete a brief survey containing a few questions about materials and energy. This survey allowed us to further the children’s knowledge about these topics. Then, we introduced materials science history relating it with mankind development. From the active participation of children in the activity, we derived to materials applied in solar cells, performing demonstrations with real solar cells and showing their importance for improving our country energetic efficiency while preserving the environment. At the end of each activity students showed great enthusiasm about including alternative energies in their daily life. Furthermore, they realized the importance of materials science, and were capable of understanding the relation between materials and the development of solar cells. We consider the spread of this activity as an excellent way of creating consciousness from an early age, which will help in the achievement of a more sustainable country.

Different materials, such as triturated waste tire (WT) particles, have been proposed as aggregate to improve mortar properties and reduce its cost in recent years. Using WT as aggregate implies material recycling, providing an environmental benefit. Previous studies show controversy on the chloride ion diffusion coefficient in mortar test specimens as a function of the WT content. The objective of this investigation is to evaluate the corrosion rate of steel reinforcement embedded in mortar specimens using WT as aggregate when exposed to chlorides. Electrochemical techniques, mercury intrusion porosimetry and scanning electron microscope were used to measure corrosion rate, porosity and microstructure of mortar matrix, respectively. Corrosion rate and porosimetry results were found to directly correlate for test pieces with 7.5% of WT compared with control samples and test pieces containing 5%, 10% of WT; such results are supported by visual inspection of steel reinforcements. Our results show that substituting 7.5% of sand with WT when preparing mortar provides the optimum protection.

The concept of low carbon, energy saving and sustainable design has been widely accepted all over the world. As a matter of fact, large amount energy is consumed to control the indoor environment to maintain a comfortable ambience for living and working. To increase the energy utilization efficiency, phase change material (PCM), which can store and release heat through phase change, has been recognized as an excellent candidate for green building. Analytical model is of great importance to describe and predict heat transfer with phase change. The classic Stefan problem solution is quite suitable for crystalline materials, which requires the input of certain phase change temperature. However, many PCMs widely used, like paraffin, are semi-crystalline materials, which have a much larger phase changing temperature range compared with small molecule crystalline materials. It is important to appropriately model the phase change of semi-crystalline polymers for the application of PCM. Furthermore, in large spatial scale prediction, widely used semi-infinite plane model is usually quite suitable to explain initial heat transfer. Unfortunately, semi-infinite plane is not the same as real situation. In this paper, by using the temperature at the end of the phase change as the equivalent melting temperature, a heat transfer model for semi-crystalline organic PCM is constructed. Meanwhile, this model concerns the phase change in a limited region. This model can serve as a fast tool to predict the one-dimensional heat transfer with phase change in an explicit form. The model is validated by the results of simulations and experiments reported in the literature.

La3-xTe4 is a state-of-the-art high temperature n-type thermoelectric material with a previously reported maximum zT∼1.1 at 1273 K. Computational modeling suggests the La atoms play a crucial role in defining the density of states for La3-xTe4 in the conduction band. In addition to controlling charge carrier concentration, substitution with Ca2+ atoms on the La3+ site is explored as a potential means to tune the density of states and result in larger Seebeck coefficients. High purity, oxide-free samples are produced by ball milling of the elements and consolidated by spark plasma sintering. Powder XRD and electron microprobe analysis are used to characterize the material. High temperature thermoelectric properties are reported and compared with La3-xTe4 compositions. A maximum zT of 1.3 is reached at 1273 K for the composition La2.22Ca0.775Te4.

Single phase, a FeVO4 triclinic crystalline structure was successfully synthesized by annealing the mechanochemically milled xV2O5·(1-x)α-Fe2O3 composites (x = 0.5) at 550 °C for 1 h. X-ray powder diffraction (XRD) and Mössbauer spectroscopy were combined for a detailed study of the assisting role of the mechanochemical milling process. Mechanochemical milling homogeneously mixed the starting materials of α-Fe2O3 and V2O5 and substantially decreased their average grain sizes. The partially V5+-substituted α-Fe2O3 phase and Fe3+-substituted V2O5 could be the important intermediate phases in the production of FeVO4 single phase. In addition, xV2O3·(1-x)α-Fe2O3 (x = 0.1, 0.3, 0.5, and 0.7) solid solutions were successfully synthesized by mechanochemical activation of V2O3 and α-Fe2O3 mixtures. Complete solid solutions exist after 12 h ball-milling time for all studied x values. The synthesized xV2O3·(1-x)α-Fe2O3 solid solutions with x = 0.5 and 0.7 were mainly paramagnetic at room temperature. The study demonstrates that the transformation pathway is related to the valence state of the metallic specie of the oxide used in connection with hematite.

The aim of this study was to develop a thermo-responsive and bioactive polymer with suitable mechanical properties for musculoskeletal tissue engineering applications. A copolymer was synthesized that comprised of hydrophilic polyethylene glycol, thermo responsive N-isopropylacrylamide (NIPAAm), 2-hydroxyethyl methacrylate-poly(lactide) (HEMA-PLA) to enhance mechanical strength and an active N-acryloxysuccinimide (NAS) group for conjugation to proteins to enhance biological properties. A model protein such as elastin was used to assess the feasibility of conjugating this polymer to protein. The results of 1HNMR analyses confirmed that random polymerization was viable technique for synthesis of this copolymer. The co-polymers synthesized with PEG content of 3 mol% were water soluble. A hydrogel was created by dissolving the copolymer and elastin below room temperature in aqueous media, followed by rapid gelation at 37°C. The results of Fourier transform infrared analyses confirmed the conjugation of protein to copolymer due to significant reduction of ester group absorption (1735 cm−1). This data confirmed molecular interaction between protein and the temperature responsive co-polymer. Our preliminary results demonstrated that it is viable to tune different properties of this hydrogel by changing the composition of co-polymer.

Heterogeneities at the meso-scale strongly influence the shock compression response of composite materials. Laminated geometries with full density and intimate particle contacts provide a unique system to investigate the influence of microstructure on a propagating shock wave. Computational analysis is used to understand the effects of layer orientation and bilayer spacing on the shock compression response of cold-rolled Ni/ Al multilayers. Real, heterogeneous microstructures, obtained from optical micrographs, are incorporated into the Eulerian, finite volume code CTH. The results show a marked difference in the dissipation and dispersion of the shock wave as the underlying microstructure varies.

The 0.6(Bi0.85La0.15)FeO3-0.4PbTiO3 (BLF-PT) ceramics were prepared by tape casting method. Effects of binder (polyvinylbutyl dibutyl PVB), plasticizer (phthalate-polyethylene glycol DBP-PEG) and dispersant (triethylolamine, TEA) concentration on the rheological properties of BLF-PT slurry were investigated. The optimized component ratio for ceramics powders, binder, plasticizer, dispersant and solvent (ethanol, EtOH) in the slurry was 50 wt.%, 4 wt.%, 6 wt.%, 1 wt.% and 39 wt.%. The dielectric constant ε r , loss tanδ, and remnant polarization P r of BLF-PT ceramics laminated from the tapes were 525 (1 kHz), 1.7% (1 kHz) and 30 μC/cm2 (45 kV/cm), respectively, which were comparable to those of BLF-PT ceramics prepared by traditional solid state reaction method.

We examine the microwave reflection from the high mobility GaAs/AlGaAs two-dimensional electron system (2DES). Strong correlations have been observed between the microwave induced magnetoresistance oscillations and the microwave reflection oscillations in a concurrent measurement of the microwave illuminated magnetoresistance and the microwave reflection from the 2DES. The correlations were followed as a function of the microwave frequency and the microwave power dependent. Different existing theories are considered to explain the results.

Using first-principles calculations, we investigate lithium vacancy and interstitial defects in lithium phosphate (γ-Li3PO4) and in its interface with metallic Li. We find that γ-Li3PO4 is good electronic insulator with a wide band gap of 6 eV. The calculated formation energies of Li vacancies are higher than those of Li interstitials, which indicate that the ionic conductivity is determined by the migration of Li interstitial defects in bulk electrolyte. The Li vacancy-interstitial pair defect formation energy in the Li/γ-Li3PO4 interface is comparable to the sum of Li vacancy defect at the electrode and Li ion interstitial defect in the electrolyte. Our calculation indicates that the low ionic conductivity of Li/electrolyte interface is associated with the high Li ion defect formation energy. Our study provides some useful insights on Li defect formation and migration mechanisms at the electrode-electrolyte interface and, hence, a research direction for designing future Li-ion batteries.

Surface smoothing of a barium borosilicate glass substrate by irradiation of ionic liquid ion beams were investigated. 1-ethyl-3-methylimidaolium tetrafluoroborate (EMIM-BF4) and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6) were used for the source liquid. Surface roughness represented as the arithmetic mean value decreased from 0.17 nm to 0.13 nm by the BMIM-PF6 negative ion beam. Secondary electron microscope (SEM) observation for the glass surface irradiated with the BMIM-PF6 negative ion beam showed a clear image without an electrical charge-up, though the EMIM-BF4 negative ion beam irradiated glass yielded a charged up image. X-ray photoelectron spectroscopy (XPS) analysis implied that the surface layer including cation-anion pair of BMIM-PF6 was deposited by the BMIM-PF6 negative ion beam irradiation, while an insulated surface with barium fluoride was formed by the EMIM-BF4 negative ion beam irradiation.

Alloying ZnO with isovalent compounds allows tailoring the material’s optoelectronic properties. In this work, we theoretically analyze the ZnO-based alloys ZnO–X ≡ (ZnO)1−x (X)x where X = GaN and InN, employing a first-principles Green’s function method GW0 based on the density functional approach. Since the alloy compounds are isovalent to ZnO, we find relatively small distortion of the crystalline structure, however, nanocluster structures are expected to be present in the alloy. ZnO–X reveal intriguing optoelectronic properties. Incorporating GaN or InN in ZnO strongly narrows the energy gap. The band gap energy is reduced from E g = 3.34 eV in intrinsic ZnO to ∼2.17 and ∼1.89 eV in ZnO–X by alloying ZnO with 25% GaN and InN, respectively. Moreover, clustering enhances the impact on the electronic structure, and the gap energy in ZnO–InN is further reduced to 0.7–1.5 eV if the 25% compound contains nanoclusters. The dielectric function ε 2(ω) varies weakly in ZnO–GaN with respect to alloy composition, while it varies rather strongly in ZnO–InN. Hence, by properly growing and designing ZnO–X, the alloy can be optimized for a variety of novel integrated optoelectronic nano-systems.