The electrical and electromechanical properties of lithium niobate single crystals are investigated at high-temperatures. The total electrical conductivity is determined as a function of temperature by impedance spectroscopy for Z-cut crystals with different lithium content. For stoichiometric lithium niobate (sLN) the activation energy is found to be (1.49 ± 0.03) eV in the temperature range from 500 to 900 °C.

Further, the piezoelectric properties (resonance frequency, Q-factor) of X-cut lithium niobate crystals are determined at high temperatures for samples with compositions ranging from congruent to stoichiometric and, subsequently, compared to the conductivity data in order to identify loss contributions.

In this context, the high-temperature stability is examined for X- and Z-cut samples with compositions ranging from congruent to stoichiometric. Series of samples with and without additional alumina protection layers are annealed in air at 900 °C for approximately 50 h. Subsequently, depth profiles are measured by SNMS. In all cases, no lithium loss is observed and, therefore, a high-temperature stability of sLN for at least 50 h at 900 °C can be assumed in ambient air.

Further, the influence of protective layers with different thicknesses and compositions is investigated for X- and Z-cut samples. A lithium loss in the first 300 nm is observed for the Z-cut samples, while the X-cut samples show a behavior dependent on the type of protecting layer.

Ti-Ni-Sn type half-Heusler alloys which have the versatility to be either p- or n-type depending on the type of substitution, have been synthesized and investigated in the present work. The added advantage of doping them with multiple elements is that they will be amenable to bulk amorphous phase formation. The hole doped alloys were predominantly single phase with a cubic structure, while the electron doped alloys were found to have minor additional phases. All the alloys exhibit extremely weak metallic-like or degenerate semiconductor transport behaviour in the temperature range 20 K to 1000 K. The resistivity of p-type alloys exhibits semi-metallic-to-semiconducting transition at ∼ 500 K while the n-type alloys exhibit a weak metallic-like behaviour in the complete temperature range. The Seebeck coefficient has strong temperature dependence with a maximum of 45 μV K−1 in the temperature range 600-700 K in the p-type alloys. The n-type alloys however exhibit a linear variation of the Seebeck coefficient with temperature. The total thermal conductivity of the alloys increases with increasing temperature without any peak at low temperatures indicating significant disorder induced scattering. The p-type alloys have the lowest thermal conductivity compared to the n-type alloys. These alloys become amorphous after pulsed laser deposition except one alloy which exhibits compensated transport behaviour.

A fundamental challenge in solar-thermal-electrical energy conversion is the thermal stability of materials and devices at high operational temperatures. This study focuses on the thermal stability of selective emitters for solar thermophotovoltaic (STPV) systems to enhance the conversion efficiency. 2-D photonic crystals are periodic micro/nano-scale structures that are designed to affect the motion of photons at certain wavelengths. The structured patterns, however, lose their structural integrity at high temperature, which disrupts the tight tolerances required for spectral control of the thermal emitters. Through analytical studies and experimental observations, the four major mechanisms of thermal degradation of 2-D photonic crystal are identified: oxidation, grain growth and re-crystallization, surface diffusion, and evaporation and re-condensation. In this work, the design of a flat surface photonic crystal (FSPC) is proposed and experimental validations are performed.

In this study, slurry formulations in the presence of self-assembled surfactant structures were investigated for Ge/SiO2 CMP applications in the absence and presence of oxidizers. Both anionic (sodium dodecyl sulfate-SDS) and cationic (cetyl trimethyl ammonium bromide-C12TAB) micelles were used in the slurry formulations as a function of pH and oxidizer concentration. CMP performances of Ge and SiO2 wafers were evaluated in terms of material removal rates, selectivity and surface quality. The material removal rate responses were also assessed through AFM wear rate tests to obtain a faster response for preliminary analyses. The surfactant adsorption characteristics were studied through surface wettability responses of the Ge and SiO2 wafers through contact angle measurements. It was observed that the self-assembled surfactant structures can help obtain selectivity on the silica/germanium system at low concentrations of the oxidizer in the slurry.

This study reports on the fabrication of nanofluids/microfluids (NFs/MFs) with experimental and theoretical investigation of thermal conductivity (TC) and viscosity of diethylene glycol (DEG) base NFs/MFs containing copper nanoparticles (Cu NPs) and copper microparticles (Cu MPs). For this purpose, Cu NPs (20-40 nm) and Cu MPs (0.5-1.5 μm) were dispersed in DEG with particle loading between 1 wt% and 3 wt%. Ultrasonic agitation was used for dispersion and preparation of stable NFs/MFs, and thus the use of surfactants was avoided. The objectives were investigation of impact of size of Cu particle and concentration on TC and viscosity of NFs/MFs on DEG as the model base liquid. The physicochemical properties of all particles and fluids were characterized by using various techniques including Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Dynamic Light Scattering (DLS) techniques. Fourier Transform Infrared Spectroscopy (FTIR) analysis was performed to study particles’ surfaces. NFs and MFs exhibited a higher TC than the base liquid, while NFs outperformed MFs showing a potential for their use in heat exchange applications. The TC and viscosity of NFs and MFs were presented, along with a comparison with values from predictive models. While Maxwell model was good at predicting the TC of MFs, it underestimated the TC of NFs, revealing that the model is not directly applicable to the NF systems.

Deposition of semiconductor films is a key process for production of thin-film solar cells, such as CdTe or CIGS cells. In order to optimize photovoltaic properties of the film a comprehensive model of the deposition process should be build, which can relate deposition conditions and film properties. We have developed a multiscale model of deposition of CdTe film in close space sublimation (CSS) process. The model is based on kinetic Monte Carlo method on the rigid lattice, in which each site can be occupied by either Cd or Te atom. The model tabulates the energy of the site as a function of its local environment. These energies were obtained from first-principles calculates and then approximated with analytical formulas. Based on determined energies of each site we performed exchange (diffusion) processes using Metropolis algorithm. In addition the model included adsorption and desorption processes of Cd and Te2 species. The results of the model show that a steady-state structure of the surface layer is formed during film growth. The model can reproduce transition from film deposition to film etching depending on external conditions. Moreover, the model can predict deposition rates for non-stoichiometric gas compositions.

The photothermal photodeflection technique is shown to provide information on the homogeneity of fuel pellets, pore distribution, clustering detection of pure urania and gadolinea and to provide a two-dimensional mapping of the thermal diffusivity correlated to the composition of the interdiffused Gadolinium and Uranium oxide. Histograms of the thermal diffusivity distribution become a reliable quantitative way of quantifying the degree of homogeneity and the width of the histogram can be used as a direct measure of the homogeneity. These quantitative measures of the homogeneity of the samples at microscopic levels provides a protocol that can be used as a reliable specification and quality control method for nuclear fuels, substituting with a single test a battery of expensive, time consuming and operator dependent techniques.

A major challenge in utilizing living botanical materials, such as cellular leaf structures, as templates is that they are filled with water and conventional dehydration strategies often collapse or degrade the intricate botanical structure. This restricts the ability to introduce water reactive precursors into such structures. We have developed a room-temperature chemical method using acidified 2,2-dimethoxypropane to dehydrate water-rich botanical materials (e.g., fern leaves and water-rich jade succulents). This mild dehydration process leaves much of the porous cellular leaf structure intact even with ∼90% mass loss. These chemically dehydrated templates have been utilized in the growth of porous and ordered leaf replicate structures consisting of TiO2 and SiO2 via sol-gel precursor impregnation methods. These white metal oxide products exhibit external and internal structures that look very similar to their original templates, but are shrunken intact versions of the original. This paper details the chemical procedures that enable one to effectively use sensitive botanical templates in metal oxide growth. The physical and structural properties of several dried porous templates and macroporous anatase TiO2 and amorphous or crystoballite SiO2 products will be described. Recent efforts to use these botanical templates to produce other porous metal oxides (e.g., Co3O4, NiO, and CuO) using both halide and acetate precursor impregnation strategies are noted. Porous metal oxides with interconnected pore walls may have use in electrochemical energy storage systems, including in photocatalytic, photovoltaic or battery systems.

This paper investigates the underlying physics governing the explosion driven expansion and fragmentation of spherical beds packed of partially saturated sand with varying mass fractions of interstitial oil. The breakup onset of the sand shells is characterized by the formation of fragments/agglomerates consisting of a large number of constituent grains, which in later time present themselves as prolific and regular jetting streams. Test data show a postponed jetting formation when sand shells are subject to the explosion with a higher detonation velocity, meanwhile a reduced jet mass scale is observed. A kinetic energy driven breakup model is proposed based on the instability criterion involving the opposing forces of stabilizing inertial pressures and destabilizing viscous resistance. This analytical model is capable of predicting the onset of granular material fragmentation as well as the characteristic fragment size, which is consistent with the experimental results.

Cd0.9Zn0.1Te (CZT) single crystal has been grown using a tellurium solvent method. Two CZT crystals have been chosen from two different locations of the grown ingot. The two crystals were characterized using infrared transmission (IR) imaging and radiation detectors in planar geometry were fabricated on them. Current-voltage characteristics (I-V) revealed a resistivity of ∼8.6×1010 Ω−cm for detector A (6.9×6.9×4.8 mm3) and 6.7×1010 Ω−cm for detector B (11.5×11.7×2.6 mm3). IR imaging showed a lesser concentration of Te inclusions/precipitates in detector A. The transport properties viz., electron drift-mobility and electron mobility-lifetime product were measured using alpha spectroscopy in these detectors in a planar configuration. Detector A showed better charge transport properties compared to detector B. The superior transport properties of crystal A were reflected in the spectroscopic properties of the detectors. Gamma pulse height measurements using a 241Am isotope revealed an energy resolution of ∼5 % for detector A and ∼7 % for detector B. A digital spectrometer and a biparametric correction scheme was incorporated to recover the pulse height spectrum of high energy gamma rays (137Cs source) from the effect of poor hole movement.

Density functional theory (DFT) based on the spin-polarized relativistic Korringa-Kohn-Rostoker (SPR-KKR) method is used to investigate the magnetic properties of nonstoichiometric Fe2+xMn1-xAl Heusler alloys, where 0 ≤ x ≤ 0.9. The composition dependences of the magnetic exchange couplings and the Curie temperature for the cubic L21 phase are obtained. Our simulations have shown that the Fe-Fe nearest neighbors present a strong ferromagnetic coupling. Moreover, these exchange interactions are larger than other interactions. The substitution of Mn by Fe in Fe2+xMn1-xAl (0 ≤ x ≤ 0.9) leads to an increase in the Curie temperature. This tendency and the values of Curie temperatures are in agreement with the experimental results for Fe2+xMn1-xAl (x = 0, and 0.1). The highest Curie temperature was observed for the Fe-richer alloy.

Thermoelectric power generation has been attracting attention as a technology for waste heat utilization in which thermal energy is directly converted into electric energy. It is well known that layered cobalt oxide compounds such as NaCo2O4 and Ca3Co4O9 have high thermoelectric properties in p-type oxide semiconductors. However, in most cases, the thermoelectric properties in n-type oxide materials are not as high. Therefore, n-type magnesium silicide (Mg2Si) has been studied as an alternative due to its non-toxicity, environmental friendliness, lightweight property, and comparative abundance compared with other TE systems. In this study, we fabricated π-structure thermoelectric power generation devices using p-type NaCo2O4 elements and n-type Mg2Si elements. The p- and n-type sintering bodies were fabricated by spark plasma sintering (SPS). To reduce the resistance at the interface between elements and electrodes, we processed the surface of the elements before fabricating the devices. The end face of a Mg2Si element was covered with Ni by SPS and that of a NaCo2O4 element was coated with Ag by silver paste and soldering.

The thermoelectric device consisted of 18 pairs of p-type and n-type legs connected with Ag electrodes. The cross-sectional and thickness dimensions of the p-type elements were 3.0 mm × 5.0 mm × 7.6 mm (t) and those of the n-type elements were 3.0 mm × 3.0 mm × 7.6 mm (t). The open circuit voltage was 1.9 V and the maximum output power was 1.4 W at a heat source temperature of 873 K and a cooling water temperature of 283 K in air.

The local strain field and the intermixing of a Ge nano-islands (NIs)/Si spacer stacked structure in a novel solar cell with a p-i-n type Si single crystal with two-dimensional photonic nanocrystals connecting to the vertically aligned NIs were analyzed using electron microscopy. High-angle annular dark field-scanning transmission electron microscope (HAADF-STEM) images show intermixing between Ge and Si clearly and reveal that the surface segregation of Ge becomes advanced. The average composition of the NIs is Ge0.42Si0.58, which is almost constant in a row of vertically aligned NIs. The local strain analysis results obtained from the high-resolution transmission electron microscope (HRTEM) images show that the strain state is partially relaxed after the elastic relaxation of NIs.

Molybdenum disulfide (MoS2) nanostructures with three different morphologies are synthesized and tested with respect to their applicability in lithium ion batteries. Thereby, electrolytes based on ionic liquids are used. The electrochemical performance of nanostructures and thin films is compared to evaluate the influence of the morphology. Characterization methods include X-Ray diffraction (XRD), cyclic voltammetry (CV), galvanostatic cycling and thin film calorimetry. The thin film and the nanostructured samples show a reversible capacity of 525 mAh/g and a maximum capacity 225 mAh/g, respectively.

Two dimensional (2D) carbon nanomaterials such as few graphite layers or graphene are extensively studied due to their unique properties suitable to be exploiting in a wide range of technological applications. Recently, the growth of high quality graphene monolayers using insects and waste as carbon precursors was reported in the literature. This methodology opened a new way to convert the waste carbon into a high-value-added product. In the present work coconut coir dust, an agroindustrial biomass, was used as biotemplate for preparing carbonaceous materials. Carbon structures were synthesized through pyrolysis under nitrogen atmosphere (100mL/min) at 500, 1000, and 1500°C during 2 hours. Starting materials were coconut coir dust in natura and coconut coir dust hydrothermally treated. The samples were characterized by X-ray diffraction, Raman Spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Raman spectra showed the D band for all samples, related to the presence of defects in sp2 carbon structure and G band, indicative of graphite crystallites. It was also observed that the sample carbonized at 1500°C from coconut coir dust treated by hydrothermal method showed G’ band at 2685cm-1 associated with the stacking order along the c-axis. X-ray diffraction analysis showed a broad peak around 2θ= 22° related to the presence of amorphous carbon. By increasing the pyrolysis temperature changes in XRD diffractograms were observed and the sample which was pyrolysed at 1500°C from coconut coir dust hydrothermally treated showed peaks at 2θ= 26.5°, 43° e 45° assigned to (002), (100) (101) graphite plans, respectively. Scanning electron microscopy images showed the presence of overlapping sheets and plates. Transmission Electron Microscopy (TEM) images of coconut coir dust in natura unveiled the formation of amorphous sheet. Coconut coir dust in natura and treated by the hydrothermal method pyrolysed at 1500°C, lead to the formation of some graphitic domains and few graphene layers.

Fe K edge X-ray absorption (XAS) and Fourier Transform Infra-Red (FT-IR) spectroscopies have been used to study potential structural modifications in sodium borosilicate glasses as a consequence of Kr+ irradiation. Glasses were doped with simulant waste elements and irradiated at room temperature with 450 keV Kr+ ions to a fluence of 2x1015 Kr+ ions cm-1. According to SRIM calculations, a damaged surface region approximately 400nm wide was produced. In order to probe only the damaged surface layer, XAS measurements were taken in total electron yield mode and FT-IR spectroscopy was conducted in reflectance off the glass surface. No change in Fe valence state was detected by XAS following irradiation. Reflectance FT-IR data revealed a shift to higher wavenumbers in the absorption bands located between 850 and 1100 cm-1 in the doped glasses, corresponding to bond stretching in the silicate network. Deconvolution of FT-IR spectra revealed the shift was due to polymerisation of the silicate network. Network connectivity was found to decrease in the un-doped glass, following irradiation. The results suggest an increase in silicate network connectivity by a cation mediated process, and demonstrates the successful application of surface sensitive XAS and FT-IR to the investigation of ion beam induced damage in amorphous materials.

Humanity currently extracts almost 70 billion tons of materials per year. During the last century global materials extraction and use have increased by one order of magnitude. Growth accelerated in the last decade, when materials extraction grew with the global economy at an annual rate of 3.6%. For sustainable development it is of key importance to understand the spatial and temporal dynamics of global material use and the underlying drivers. This paper explores changes in global material use during the last century from a systemic perspective based on the concept of socio-economic metabolism.

In recent years socio-economic (or, more narrowly termed industrial) metabolism became a prominent concept in sustainability science as many global sustainability problems are directly associated with humanities growing demand for raw materials and their transformation into wastes and emissions after processing and use. Material Flow Analysis (MFA) is one of the approaches available to study social metabolism. It provides data and headline indicators for resource use in national economies and is widely used in science and by policy makers.

This paper presents results from a global material flow analysis and explores long term the development of global material extraction and use. It shows that in particular the period after WWII was characterized by a rapid expansion of resource use, driven by both population and economic growth. Within this period a shift from the dominance of renewable biomass towards mineral and fossil materials, which now account for 70% of all used materials, was observed. Overall, material use increased at a slower pace than the global economy, but faster than world population. As a consequence, material intensity (i.e. the amount of materials required per unit of GDP) declined throughout the 20th century, while materials use per capita doubled. The use of materials is by no means equally distributed around the globe. Per capita material use varies by a factor of 20 across countries. At the turn of the millennium, 15% of the global population living in industrialized countries were using half of all mineral and fossil resources; in contrast, the least developed countries, inhabiting 11% of global population, appropriated only 1% of these strategically important materials. In recent years, however, the emerging economies gained significance as drivers for physical growth. So far there is no evidence that growth of global materials use is slowing down. The paper discusses the implications of the results from the material flow analysis for sustainable development.

Strategies are described for modeling the kinetics of non-equilibrium film growth during deposition of metals on quasicrystalline substrates. We review previous atomistic-level lattice-gas modeling and Kinetic Monte Carlo simulation for pseudomorphic (or commensurate) submonolayer growth based on a “disordered or irregular bond-network” (DBN) of neighboring adsorption sites. We describe extensions to treat strain effects and multilayer growth, and discuss a type of commensurate-incommensurate transition expected around 2-3 layers. We also describe a coarse-grained “step dynamics” modeling which tracks the dynamics of island edges in each layer rather than individual atoms. Step dynamics models can also include key aspects of the physics such as layer-dependent energetics, including quantum size effects, and strain effects.

In this paper we described using ruthenium (Ru) nanoparticles for surface modification on our hybrid PV/a-SiC photocathode for hydrogen production by water splitting under sunlight. Ru nanoparticles with size less than 5nm in diameter made the photocathode showed promising results: in an aqueous electrolyte an anodic shift of photocurrent onset potential around 450 mV and an increase in the photocurrent density up to 1.8mA/cm2 from a negligible value. Initial discussion the influence of Ru nanoparticles is presented.