High yield nanomanufacturing is important to turning nanotechnology advances into industrial products. Electrospinning is a nanomanufacturing process that has been used to process advanced ceramic nanofibers suitable for functional applications in sensing and catalysis, yet it has been limited in its scalability thus far. In this study a novel design of the electrospinning process and related equipment that could produce large qualities of ceramic nanofibers is described. This scaled-up approach to traditional needle electrospinning allows the formation of 24 jets operating under the same conditions as those set in the single jet lab-based process. Due to a thin metallic disc design, with tiny (0.5mm) holes drilled at the bottom corner of the disc, all jets experience a uniform impact of the electrostatic field. Continuous replenishment of the source disk at higher flow rates allows for high yields of nanofibers.

We consider finite size effects on energy transfer between nanoparticles mediated by quantum systems. The nanoparticles are considered as heat reservoirs with a finite number of modes. An expression for the quasi-static energy transport between the heat reservoirs having a finite mode frequency spacing Δ is derived. The resulting equations describing long-term (t ≥1/Δ) relaxation for the mode temperatures and the average temperatures of the nanoparticles are solved. The solutions depend on small number of measurable parameters and show unusual peculiarities in their temporal variations. As is shown, Fourier’s law in a chain of identical subsystems (nanoparticles) can be validated only on a short time scale. For a larger times, when t ∼ 1/Δ, the temperatures of different modes deviate from each other, thus preventing thermal equilibrium in each subsystem, and the validity of Fourier’s law cannot be established.

This study reports a novel class of biodegradable polyurethane biomaterials and three-dimensional scaffolds for tissue engineering. Solvent casted polyurethane films were studied for biocompatibility by seeding with human bone marrow derived stromal cells. In order to develop a three-dimensional and porous structure, a dynamic solvent sintering method was applied to the polyurethanes for the first time. Microstructural studies on the sintered scaffolds reveal porous structure formation with bonding between the adjacent microspheres. In conclusion, this study establishes new polyurethane biomaterials that are fully absorbable for tissue engineering applications.

The p-type conducting Copper-oxide compound semiconductors (Cu2O, CuO) provide a unique possibility to tune the band gap energies from 2.1 eV to the infrared at 1.40 eV into the middle of the efficiency maximum for solar cell applications. By a pronounced non-stoichiometry the electronic properties may vary from insulating to metallic conduction. They appear to be an attractive alternative absorber material in terms of abundance, sustainability, non-toxicity of the elements, and numerous methods for thin film deposition that facilitate low cost production. The synthesis and characterization of Cu2O thin films used as p-type absorbers in heterojunction solar cells will be reported. We discuss properties of the undoped non-stoichiometric Cu2O, controlled p-type doping by nitrogen, analysis of band offsets by X-ray photoelectron spectroscopy (XPS). In addition we show proof of concept for an increase in photovoltaic conversion efficiency in AlGaN/Cu2O heterostructures due to a more favorable band alignment.

Recently, a team of archaeologists discovered the existence of the oldest burial in a pyramid known to date in Mesoamerica. The tomb, referred to as Tomb 1, was discovered in Chiapa de Corzo, Chiapas, Mexico. In here, two skeletons were excavated along with a rich offering of green stone pieces, indicating their elite origin. The burial dresses consist of various necklaces, bracelets, belts, and anklets from which some beads were carved in the shape of gourds, monkeys, and alligators. Here we present a full, integrated methodology based on a variety of non-invasive and non-destructive analytical techniques, such as X-ray fluorescence (XRF), Raman, and Fourier Transform infrared (FT-IR) spectroscopy. These techniques are used to characterize and identify the minerals which were found in these burials. This information contributes not only to conservation and restoration purposes, but also gives more insights on the green stone (jadeite and other minerals) trading networks between different cultures in south Mesoamerica in the Pre-Classic period (c.a. 750 – 700 B. C.).

The control of the SiGe NW composition is fundamental for the fabrication of high quality heterostructures. Raman spectroscopy has been used to analyse the composition of SiGe alloys. We present a study of the Raman spectrum of SiGe nanowires and SiGe/Si heterostructures. The inhomogeneity of the Ge composition deduced from the Raman spectrum is explained by the existence of a Ge-rich outer shell and by the interaction of the NW with the electromagnetic field associated with the laser beam.

Emerging applications for hydrogels such as soft robotics and tissue engineering require hydrogels with enhanced mechanical performance. We report the mechanical characteristics of two types of hydrogels: i) ionic-covalent entanglement (ICE) network hydrogels based on calcium cross-linked gellan gum and genipin cross-linked gelatin and ii) ICE microsphere reinforced gelatin hydrogels. This investigation showed that ICE gels can recover up 80% of their mechanical behavior during 5 repeated compressions. In addition, the optimum mechanical performance of gelatin reinforced gels was achieved with inclusion of 40% of ICE microspheres.

Organic thin-film transistors (OTFTs) are the most promising candidates for flexible electronics owing to their flexible structures, the simplicity of processing large-area devices, and excellent compatibility with flexible substrates. To date, many studies have been reported that have aimed at developing a wide range of plastic electronics such as flexible displays, sensors. In this paper, we discuss our recent work, focusing on OTFT arrays and their application to flexible display. An active-matrix (AM) backplane using a low-temperature cross-linkable olefin-type polymer as the gatedielectric and an air-stable DNTT as the organic semiconductor (OSC) was successfully fabricated on a plastic substrate. The short-channel TFT array exhibited a high hole mobility of over 0.5 cm2/Vs, a low subthreshold slope of 0.31, and excellent environmental and operational stability. A 5-inch flexible OLED display exhibited a high luminescence of over 300 cd/m2 by driving of the DNTT-based OTFTs. Solution-processed OTFTs are also attracting considerable attention owing to both their simple manufacturing process and excellent transistor performance. We present a simple patterning process for a solution-processable OSC that can be used to develop a high-mobility short-channel TFT array. The OSC film was directly patterned on the confined active channel region by a simple lamination coating technique and the resulting TFTs showed a high mobility of up to 1.3 cm2/Vs. In the final section, we report on eco-friendly paper-based organic TFT array. A transparent cellulose nanofibers paper was firstly applied to a flexible substrate for the TFT backplane. A solution-processed TFT on the transparent paper exhibited a high mobility exceeding 1 cm2/Vs, good air stability, and excellent mechanical stability.

Recently, the detection of non-bulk superconductivity with unexpectedly high onset-Tcs up to 49 K in Pr-doped CaFe2As2 [(Ca,Pr)122] single crystals and the report of a Tc up to 65 K in one-unit-cell (1UC) FeSe epi-films, offer an unusual opportunity to seek an answer to the question posed in the title. Through systematic compositional, structural, resistive, and magnetic investigations on (Ca,Pr)122 single crystals, we have observed a doping-level-independent Tc, the simultaneous appearance of superparamagnetism and superconductivity, large magnetic anisotropy, and the existence of mesoscopic-2D structures in these crystals, thus providing clear evidence consistent with the proposed interface-enhanced Tc in these naturally occurring rareearth-doped Fe-based superconductors, (Ca,R)122. Similar resistive and magnetic measurements were also made on the 3–4UC FeSe ultrathin epi-films. We have detected weak links in the Meissner state below 20 K, weakly coupled small superconducting patches between 20–45 K, and collective excitations of spin and/or superconducting nature between 45–80 K. The unusual frequency dependences of the diamagnetic moment observed in the films in different temperature ranges will be presented and their implications discussed.

Low-cost La(FexSi1-x)13 alloys exhibiting the large magnetocaloric effect (MCE) are one of the most promising magnetic refrigerant candidates for room temperature magnetic refrigeration. The NaZn13-type phase (hereinafter 1:13 phase) is believed to play a key role in the MCE of these alloys. While the formation of the 1:13 phase directly from the melt upon cooling was challenging, in this paper we demonstrate that the 1:13 phase can be formed directly during solidification. We found that three kinds of solidification microstructure were formed because a competitive nucleation occurred between the 1:13 and α-(Fe,Si) phase during the solidification of LaFe11.5Si1.5 alloy. In case of a high cooling speed, a large amount of NaZn13–type phase with equiaxed grains and a small amount of α-(Fe,Si) phase were formed because of a dominant nucleation rate of 1:13 phase. When the cooling rate was small, a large number of α-(Fe,Si) phase with dendrites were formed because the nucleation rate of α-(Fe,Si) phase is larger than that of the 1:13 phase. These results revealed that nucleation rates of phases is very important to the composition formation and microstructure of LaFe11.5Si1.5 alloys.

Understanding the effect of chlorine-related defects on the CdTe electric properties is important both for obtaining high resistivity CdTe-based detectors and for high efficiency CdTe-based thin-film solar cells. The actual mechanism of the effect of Cl on electric properties of CdTe is not clear and different sometimes contradictory hypotheses appear. For example ClTeVCd shallow acceptor complex defect was proposed both as a reason of increased carrier concentration in CdTe thin film and also as a reason of high resistivity of CdTe:Cl thin films. In the present work we are trying to clarify the effect of Cl on CdTe electric properties and to find the reason of high resistivity of CdTe:Cl crystals using first principles calculations and defect chemistry modeling. For the first time we are trying to develop a model capable to describe experimental data on both high temperature and room temperature conductivity of CdTe:Cl.

The dependence of dark conductivity and room temperature Raman spectra on boron and hydrogen incorporation in thin films of hydrogenated amorphous silicon (a-Si:H) prepared by plasma enhanced chemical vapor deposition was investigated. It was found that the dominant conductivity is Mott variable range hopping conduction. However, at lower temperatures, Efros-Shklosvkii hopping conduction is observed and contributes to the total conductivity. For structural characterization, transverse optical (TO) and transverse acoustic (TA) modes of the Raman spectra were studied to relate changes in short- and mid-range order to the effects of boron and hydrogen incorporation. With an increase of hydrogen incorporation and/or substrate temperature, both short and mid-range order improve, whereas the addition of boron results in the degradation of the short range order. The line width and frequency of the Raman TO Raman peak correlate with electrical measurements and suggest that this technique can be used for non-destructive characterization of a-Si:H.

An Ultraviolet (UV) photodetector with high responsivity and relative fast response speed was fabricated from three dimensional WO3 nanowires/reduced graphene oxide (3D WO3 NWs/RGO) composite materials. The 3D WO3 NDs/GN composite was synthesized using a facile three-step synthesis. First, the Na2WO4/Graphene Oxide (GO) precursor was synthesized by homogeneous precipitation. Second, the Na2WO4/GO precursor was transformed into H2WO4/GO composites by acidification. Finally, the H2WO4/GO composites were reduced to 3D WO3 NWs/RGO via hydrothermal reduction process. A maximum photoresponsivity of 4.2 A/W at 374 nm was observed under 20 V bias. The UV photodetector showed relative fast transient response, which is at least 2 orders of magnitude faster than UV photodetectors fabricated from WO3 nanowires. The good photoresponsivity and fast transient response are attributed to improved carrier transport and collection efficiency through graphene.

Proton conductivity of the natural diatomite was studied by ac complex impedance technique. At room temperature, the highest proton conductivity was found to be 4.5 x 10-7 S·cm-1. By hydrating the diatomite, the proton conductivity was increased to two orders of magnitude higher. The room temperate proton conductivity of the hydrated diatomite (5.5 x 10-5 S·cm-1) was comparable to other hydrated solid proton conductors. The natural diatomite could be used as potential cost-effective proton conductor for electrochemical applications.

In this paper, we will describe the nature of defects and impurities in thick epitaxial-Si layers and their influence on the cell efficiency. These wafers have very low average dislocation density. Stacking faults (SFs) are the main defect in epi layers. They can occur in many configurations—be isolated, intersecting, and nested. When nested, they can be accompanied by formation of coherent twins resulting in dendritic growth, with pyramids protruding out of the wafer surface. Such pyramids create large local stresses and punch out dislocations. The main mechanism of dislocation formation is through pyramids. Stacking faults degrade solar cell performance. Analyses of the solar cells have revealed that the nested SFs have a controlling effect on the solar cell performance. A well-controlled growth can minimize defect generation and produce wafers that can yield cell efficiencies close to 20%.

This paper describes the organometallic synthesis of pure rhenium nanoparticles (Re NPs) and their characterization by a combination of state-of-the art techniques (TEM, HAADF-STEM, EDX, WAXS, EA, FT-IR). The Re NPs synthesis is achieved by reducing the [Re2(C3H5)4] complex in solution under a dihydrogen atmosphere and in the presence of hexadecylamine or polyvinylpyrrolidone as stabilizing agents. The so-obtained Re NPs are monodisperse with a mean size of 1.1 nm (0.3) nm and display a spherical shape with a disordered hcp structure.

We analyze and compare optoelectronic properties and hot carrier relaxation dynamics in different forms of TiO2 anatase materials: nanowires and thin films. The models are chosen in such way that the same crystallographic surfaces are exposed and any difference in properties is attributed to the change of the dimensionality of the nanostructure. Specifically, we give a brief review of the electronic properties and non-adiabatic excited state dynamics of <001> anatase TiO2 nanowire as well as (100) and (001) anatase TiO2 surfaces. The calculated band gap of nanowire is larger than the ones of surfaces. The hole relaxation rate is higher than the electron relaxation rate for both the surfaces and nanowire, and the electron and hole relaxation rates of surfaces are larger than the ones of nanowire.

The Next Generation Science Standards make scientific discourse a vital part of the classroom and arguing with evidence needs to become a common practice for students. Analysis and interpretation of data are an integral part as well. We present an approach using 21st-century technology combined with collection of laboratory data that is suitable for middle school through college. In an experiment using common nuts and bolts first semester chemistry students form six groups and determine a bolt mass indirectly. They collect mass data; then enter the data into an online form that compiles the data into a spreadsheet in Google Drive, a free cloud-based application. Once all the groups have submitted their data, they access the spreadsheet online and start an emulated online discussion in the laboratory as if the groups were globally dispersed using the chat feature available in Google Drive. Each group is identified by a group number having a unique group email address so there is a semi-anonymous sense among the members that allows for a fairly free discussion among students.

CTGS (Ca3TaGa3Si2O14) is a commercially available, Czochralski-grown piezoelectric material from the langasite family that has an ordered crystal structure. It can be excited piezoelectrically up to at least 1285 °C, which is very close to the melting temperature of 1350 °C. In order to determine the loss at elevated temperatures, two different resonance techniques are used. A contactless transduction method is employed up to about 600 °C, whereas transduction involving standard keyhole-shaped film electrodes is employed up to 1285 °C. Comparison of the temperature-dependent inverse Q factor shows that contactless measurements are best suited for the lower temperature range, where sample clamping and losses caused by the electrodes contribute significantly to the total loss. However, at higher temperatures, measurement of the electrical impedance of samples with film electrodes in the vicinity of the resonance frequency proves to be suitable. Even at 1100 °C, 5 MHz CTGS resonators are found to have a Q factor of about 1200, which is great enough to enable numerous bulk-acoustic-wave applications. Further, a nearly linear temperature dependence of the resonance frequency with a temperature coefficient of 210 Hz/K makes Y-cut CTGS well suited for temperature-sensing applications.

Black liquor is a by-product of the paper mill Kraft process that deserves more valorization than its present use as low-grade fuel. In this work, SiC/C composite foams were prepared for the first time from concentrated emulsions by carbothermal reduction of bio-sourced precursors combining sodium silicate by lignin at 1400°C. The composition of the materials was determined by XRD, FTIR and Raman analyses. Their porous structure was characterized by SEM, mercury intrusion porosimetry, and nitrogen sorption, while their thermal properties were measured by TGA and dynamic DSC. Concerning their heat transport properties, we found out that when the starting lignin content was increased, the final C/Si ratio, the specific surface area and the heat diffusivity increased as well. Its high values were attributed to a cooperative effect between radiative heat transfer and the presence of partially graphitized carbon.