We present our preliminary results on a novel technique to electrophoretically sort singlewall carbon nanotubes into metallic and semiconducting tubes using a free-solution nonionic surfactant in a homemade electrophoretic vertical cell. The technique is used to sort purified commercial product SWCNTs, (Thomas Swan Elicarb) into metallic and semiconducting tubes. In contrast to onventional electrophoresis techniques, which takes more than 24 hours to obtain efficient separation, our approach takes ∼ 6 hours to achieve efficient separation, which reduces the separation time by four fold. Characterization of the sorted tubes with micro-Raman spectroscopy analysis shows very strong enrichment of both metallic and semiconducting tubes.

In this paper, we provide the investigation about the controlled surface functionalization of acrylic toner particles for electro photography (“laser printing”) with sodium hydroxide and the subsequent carbodiimide-mediated coupling of numerous functional amines onto the generated carboxylic group. Various chemically valuable functionalities, comprising of thiol, alkyne and azide, were bound onto the particles’ surface and allow for further versatile modifications via huisgen cycloaddition as well as thiol-ene reaction. The functionalization of the acrylic toner surface with alkyne, azide and carboxylic groups increased the cell viability up to 178 % ± 22 % and might offer an interesting path for new applications using common laser printing techniques.

Large electrocaloric (EC) effects in ferroelectric polymers and in ferroelectric ceramics have attracted great attention for new refrigeration development which is more environmental friendly and more efficient and thus could be an alternative to the existing vapor-compression refrigerators which consume large energy and release large amount of green house gas. However in the past, all EC effects investigations have been focused on solid state dielectrics. It is interesting to ask whether a large EC effect can also be realized in dielectric fluids. A dielectric fluid with large EC effect could lead to new design of cooling devices with simpler structures than these based on solid state EC materials, for example, they can be utilized as both the refrigerant and heat exchange fluid. Here we present that a large EC effect can be realized in the liquid crystal (LC) 5CB near it's nematic-isotropic (N-I) phase transition. The LC 5CB possesses a large dielectric anisotropy which can induce large polarization change from the isotropic phase to the nematic phase near the N-I transition. An isothermal entropy change of more than 23 Jkg-1K-1 was observed near 39 oC that is just above the N-I transition.

Diamond was investigated as one of the superior dielectric materials for advanced wakefield accelerators. Both planar and cylindrical wakefield accelerating structures were constructed. An AsTex microwave plasma-enhanced CVD system was modified for synthesis of cylindrical polycrystalline diamond tubes. Cylindrical diamond tubes were successfully synthesized from hydrogen and methane and are characterized with micro Raman, photoluminescence spectroscopy and optical tests. In addition, planar wakefield structures were constructed from commercially available diamond. Wakefield tests on a rectangular diamond structure confirm that diamond can sustain microwave electric field strengths of 0.3 GV/m at its surface without material breakdown.

The sulfur-iodine thermo-chemical cycle (S-I cycle) is one of the promising nuclear hydrogen production methods combined with a high temperature gas-cooled reactor. However, extremely corrosive environments limit the selection of structural materials. Therefore, in this study, corrosion behaviors of several metallic materials were investigated to screen the candidate metallic materials. Coupon type specimens were exposed for 100 h in simulated SO3 and HI decomposer conditions at 850 °C. After 100 h exposure, the surface treated Alloy 617 showed the superior weight change in both environments. However, scanning electron microscope observation showed oxide spallation for EB-treated and NiAl coated Alloy 617. On the other hand, the Ni3Al coated Alloy 617 showed better corrosion resistance in SO3 decomposer condition, such that only formed external Al-rich oxide layer. Especially, in a HI decomposer condition, the damage on the Ni3Al coated Alloy 617 was considerably less significant probably due to the protection by very thin aluminum-rich oxide on the surface.

As ohmic contacts decrease in size and approach nanoscale dimensions, accurate electrical characterization is essential, requiring the development of suitable test structures for this task. We present here a new test structure derived from the standard three-contact circular transmission line model (CTLM) [1], for determining the specific contact resistivity of ohmic contacts. This test structure minimizes sources of error which arise from the CTLM by – (i) reducing the number of contacts within one test pattern from three to two, (ii) ensuring the assumption of equipotential metal contacts used in modelling is more easily attained experimentally, and (iii) allowing the fabrication of reduced geometrical dimensions essential for determining low specific contact resistivity values. The analytical expressions are presented and experiment results are undertaken to demonstrate the accuracy of the technique. There are no error corrections required for determining contact parameters using the presented test structure.

A Ni3(Si,Ti) intermetalic alloy was synthesized by the powder metallurgy method using elemental powders. The raw powder mixtures with various compositions were sintered by a spark plasma sintering apparatus and then homogenized at high temperatures. Microstructure, hardness, tensile properties and density of the sintered alloys were investigated as functions of the chemical composition and sintering temperature. It was found that a highly-densified Ni3(Si,Ti) sintered alloy was obtained by choosing proper chemical composition and sintering temperature. Also, the Ni3(Si,Ti) sintered alloy with an L12 single-phase microstructure exhibited high hardness and tensile strength.

PECVD growth of the microcrystalline silicon junction on a highly textured amorphous top cell often leads to defective absorber layers and finally to low quality bottom cell. This paper reports on the current status of using an innovative smoothening/reflective layer (SRL) as alternative intermediate reflector between top and bottom cell of a Micromorph tandem device deposited on as-grown highly textured LPCVD ZnO layer. Manufacturing of the SRL layer is realized by “liquid phase” deposition technologies. Optical and electrical properties, smoothening effect and photoelectrical results of Micromorph tandem devices are discussed. The implementation of our novel SRL results in the growth of a crack-free bottom cell and to an efficient current transfer from the bottom to the top cell.

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.