Thermoelectric energy recovery is an important technology for recovering waste thermal energy in high-temperature industrial, transportation and military energy systems. Thermoelectric (TE) power systems in these applications require high performance hot-side and cold-side heat exchangers to provide the critical temperature differential and transfer the required thermal energy to create the power output. Hot-side and cold-side heat exchanger performance is typically characterized by hot-side and cold-side thermal resistances, Rh,th and Rc,th, respectively. Heat exchanger performance determines the hot-side temperature, Th, and cold-side temperature, Tc, conditions when operating in energy recovery environments with available temperature differentials characterized by exhaust temperatures, Texh, and ambient temperature, Tamb. This work analytically defined a crucially important design relationship between (P/Pmax) and (Rh,th / Rc,th) in TE power generation systems to determine the optimum ratio of (Rh,th / Rc,th) maximizing TE system power. A sophisticated integrated TE device / heat exchanger analysis was used, which simultaneously integrates hot- and cold-side heat exchanger models with TE device optimization models incorporating temperature-dependent TE material properties for p-type and n-type materials, thermal and electrical contact resistances, and hot side and cold side heat loss factors. This work examined the (P/Pmax) - (Rh,th / Rc,th) relationship for system designs employing single-material and segmented-material TE couple legs with various TE material combinations, including bismuth telluride alloys, skutterudite compounds, and skutterudite / bismuth telluride segmented combinations. This work defined the non-dimensional functional relationships and found the optimum thermal resistance condition: (Rh,th / Rc,th)opt > 10 to 30 created the maximum power output in TE optimized designs for various TE material combinations investigated. The non-dimensional relationships were investigated for various electrical contact resistances, differing thermal loss factors, and at various hot-side/cold-side temperature conditions. This work showed that the non-dimensional functional relationships were invariant under these differing conditions. It was determined that a condition of (Rh,th / Rc,th) = 1 creates power output far below maximum power conditions. The (P/Pmax) - (Rh,th / Rc,th) relationship also dictated certain temperature profile conditions, defined by the parameter, (Th – Tc) / (Texh – Tamb), which were directly associated with design points in this relationship including maximum power points. The value of (Th – Tc) / (Texh – Tamb) was generally less than 0.5 at maximum power conditions in TE energy recovery designs using TE materials investigated here. The wide-ranging ramifications on TE energy recovery systems and their design optimization for industrial and transportation-related applications are discussed.

A novel atom probe tomography (APT) method has been developed that enables a full description of the orientation relationship between individual grains to be determined together with estimates of the extents of solute segregation for all elements over the surface of the grain boundary with 1 nm by 1 nm spatial resolution. This approach also enables variations in the solute excess for the elements with the habit plane and curvature of the grain boundary to be evaluated. The method has been applied to a mechanically-alloyed nanostructured ferritic alloy (NFA) after high dose heavy ion irradiation. The innovative high-resolution two-dimensional mapping of the solute segregation across the surface of grain boundaries in the NFA clearly demonstrates that the distributions of chromium and tungsten are not uniform across the grain boundaries, and the distributions correlate with changes in its local curvature and the position of the grain boundary precipitates. These features pin the grain boundary against grain growth and provide the stability for excellent creep properties.

In this paper we show that a wide variety of composite structures can be obtained from structuring with multiaxial fields. The properties of these composites are highly responsive to field structuring and so significant increases in a variety of properties can be obtained. These composites have application as high-strain actuators, strain and temperature sensors, chemical sensors, and as thermal interface materials. We discuss these issues and provide a general summary of the research we have done in this area.

The present work focuses on the fabrication of environmental friendly ZnO nanocrystals and chitosan/cellulose films hosting ZnO nanoparticles (NPs) as an attempt to produce nanocomposites with enhanced bactericidal capacity. The solution casting method was used to fabricate the chitosan/cellulose blend films. Highly monodisperse ZnO nanoparticles were synthesized using Zinc acetate and Triethylene glycol (TEG) via a modified Polyol route. ZnO crystal size was controlled by the heterogeneous nucleation approach. Optical properties of ZnO nanoparticles were studied by UV–vis spectroscopy and Photoluminescence Spectroscopy (PL) techniques. The nanoparticles’ size and morphology were determined by Transmission Electron Microscopy (TEM) and X-ray diffraction (XRD), respectively. Obtained results confirmed the effectiveness of the size-controlled synthesis employed. The chitosan/cellulose/ZnO nanocomposites were characterized by Fourier Transform – Infrared spectroscopy (FTIR) and X-ray diffraction (XRD) methods. The mechanical properties of produced bare and ZnO-bearing composites were determined from stress-strain tests. The Standard Plate Count and the Halo Zone methods were used to evaluate the bactericidal properties of the ZnO nanoparticles, chitosan/cellulose blend films and chitosan/cellulose/ZnO nanocomposites against Escherichia coli (ATCC 35218).

Poly (3-hexylthiophene) (P3HT) thin films were deposited using emulsion-based, resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) from emulsions containing different solvents and different alcohols, to investigate the impact of emulsion on film morphology. The atomic force microscopy (AFM) and grazing-incidence, wide angle x-ray scattering (GIWAXS) results show that surface morphology of RIR-MAPLE as-deposited films can be varied from rough to smooth and the microcrystalline domain orientations with respect to the substrate can be tuned from randomly oriented to preferentially oriented in the vertical direction. The demonstrated ability to tune the structural characteristics of polymer thin films by controlling the target emulsion is important for the application of organic optoelectronic devices deposited by RIR-MAPLE.

The effect of the heat input on the mechanical and metallurgical properties of the welds has been investigated in the heat affected zone (HAZ) of welds joined with gas metal arc welding (GMAW), using normal production welding parameters. The thermal effect in the HAZ of the welds is important for the optimization of the welding parameters used when weld transformed induced plasticity (TRIP) steels, because this will have a great influence in the mechanical and metallurgical properties of the weld. In this work 3 samples was welded a high, average and low heat input, with the variation of welding parameters to obtain different thermal affectation to investigate the variations in different parts of weld joint: weld, HAZ and base metal, due the heat applied for the welding process used. Mechanical properties were evaluated by tension test, microhardness and fatigue testing and metallurgical evaluation with optical metallograpy, scanning electron microscopy (SEM), fractograpy and X-Ray diffraction (XRD).The results obtained shows that the mechanical properties of the tension test decrease when the heat input increase and the microhardness exhibit a softening zone in the HAZ with lower hardness and the fatigue life were similar for all heat inputs for the high stress levels, but only in low stress there is a difference. For metallurgical properties the metallographic evaluation shows ferrite, bainite - martensite and retained austenite, and the fractography analysis exhibit a ductile fracture in all cases and the content in volume fraction of retained austenite increases in the HAZ of welds when increasing heat input in to the base metal due the thermal effect.

Bismuth vanadate (BiVO4) is a photoelectrode for the oxidation of water. It is of fundamental importance to understand the electrical and photoelectrochemical properties of this material. In metal oxides, the electronic transport is described by the small polaron model, first described by Mott. In this model, the resistivity varies with temperature as $\rho \,\left( T \right)\, \propto \,Te^{({{E_a } \mathord{\left/ {\vphantom {{E_a } {(k_B T))}}} \right. \kern-\nulldelimiterspace} {(k_B T))}}} $ , where E a is the hopping activation energy, k B is the Boltzmann constant and T is the absolute temperature. Resistivity measurements confirm that small polaron hopping dominates in temperature ranges from 250 K to 300 K. In addition measurements from 175K to 250K show the variable range hopping dominates the transport. To this end, the electronic transport properties of BiVO4 single crystal were characterized using resistivity measurements and Hall effect measurements over temperatures ranging from 175 K to 300 K.

We review the present state of the understanding and application of high temperature superconductor materials ranging from attempts to clarify pairing mechanisms on the energy scale of a few milli-electron-volts to their use to embody terra-kwh continental wide deployment within the electricity enterprise. Examples include the use of density functional theory to study the relative roles of spin-fluctuation and/or lattice vibration induced Cooper pairing to modelling the incorporation of long distance HTSC transmission cables within the same natural gas pipeline rights-of-way infrastructure now emerging worldwide.

Breast cancer (BrCa) is the second commonest cause of cancer-related deaths in women. The metastatic breast cancer exhibits a high affinity to bone, leading to debilitating skeletal complications associated with significant morbidity and poor prognosis. Traditional in vitro and in vivo BrCa bone metastasis models contain many inherent limitations with regards to controllability, reproducibility, and flexibility of design. Thus, the objective of this research is to use a 3D bioprinting system and nanomaterials to recreate a biomimetic and tunable bone model suitable for the effective simulation and study of metastatic BrCa invading and colonizing a bone environment. For this purpose, we designed and 3D printed a series of scaffolds, comprised of a bone microstructure and nano hydroxyapatites (nHA, inorganic nano components in bone). The size and geometry of the bone microstructure was varied with 250 and 150 µm pores, in repeating square and hexagon patterns, for a total of four different pore geometries. 3D bioprinted scaffolds were subsequently conjugated with nHA, using an acetylation chemical functionalization process and then characterized by scanning electron microscope (SEM). SEM imaging showed that our designed microfeatures were printable with the predesigned resolutions described above. Imaging further confirmed that acetylation effectively attached nHA to the surface of scaffolds and induced a nanoroughness. Metastatic BrCa cell 4 h adhesion and 1, 3 and 5 day proliferation were investigated in the bone model in vitro. The cell adhesion and proliferation results showed that all scaffolds are cytocompatible for BrCa cell growth; in particular the nHA scaffolds with small hexagonal pores had the highest cell density. Given this data, it can be stipulated that our 3D printed nHA scaffolds may make effective biomimetic environments for studying BrCa bone metastasis.

Spherical submicrometer-sized silica particles were prepared by the sol-gel method and deposited as a monolayer onto silicon wafers, in order to use them as a mask to create regular arrays of nanoscale surface features. Thus, by e-gun evaporation of a 50 nm thick Ag film through the silica mask, Ag nanostructures were obtained after removal of the silica monolayer. In order to tailor the mask characteristics (size and interparticle spacing), the silica masks were irradiated at room temperature with 4 and 6 MeV Si ions at different fluences up to 5×1015 ion/cm2, perpendicularly to the sample surface. After the irradiation the silica particles turned into oblate particles, as a result of the increase of the particle dimension perpendicular to the ion beam and the decrease in the parallel direction. By this way, the mask openings of the silica particle monolayer were modified as a function of the irradiation parameters, and the subsequent Ag e-gun evaporation allowed the formation of ordered arrays of Ag features. The size, shape and interparticle spacing of both the silica particles and the Ag deposits were determined by scanning electron microscopy.

We describe appropriate wafer cleaning procedure and surface passivation characteristics of various passivants used for making measurement of minority carrier lifetime (τB ) of very high quality Si wafers. These passivants include: iodine ethanol (I-E), quinhydrone methanol (QH-M), SiO2, and Al2O3. The issues related to the passivation stability and the spatial uniformity for mapping τB are also discussed.

Orthorhombic titanium-based Ti2AlNb alloys cannot be used above a temperature limit of about 800°C due to accelerated oxidation and environmental embrittlement. This embrittlement is caused by the high oxygen solubility which deteriorates the mechanical properties. Even if these materials possess an Al content up to ca. 25at.% no protective alumina layer is formed. Instead a non-protective fast growing mixed scale is found. Several attempts have been made to increase their operation temperature e.g. by coatings but none has proven sufficiently protective so far. One new way presented in this paper is to enrich Al in a narrow surface zone by using a powder pack process (aluminization) followed by a fluorination step. Exposure tests at elevated temperature have shown that the aluminized specimens form an alumina layer during exposure in oxidizing environments. Due to the gradient in the Al-concentration interdiffusion with the substrate and the Al-rich diffusion zone occurs which lowers the Al concentration in the diffusion zone. If the Al content drops below a critical value, Ti oxides will also form, which deteriorates the protection provided by the alumina scale. The subsequent fluorination triggers the fluorine effect which stabilizes the protective alumina layer. Untreated specimens are covered with a thick non protective scale and exhibit oxygen ingress in the subsurface zone while treated specimens reveal a thin protective alumina layer and no inward diffusion of oxygen. In this paper results of exposure tests of untreated and treated orthorhombic Ti2AlNb alloys will be presented and compared with the Nb-free α2-phase Ti3Al and Nb-containing Ti3Al-based alloys.

We propose and study the feasibility of a THz GaN/AlGaN quantum cascade laser (QCL) consisting of only five periods with confinement provided by a spoof surface plasmon (SSP) waveguide for room temperature operation. The QCL design takes advantages of the large optical phonon energy and the ultrafast phonon scattering in GaN that allow for engineering favorable laser state lifetimes, and the SSP waveguide provides the optical confinement for the ultrathin QCL. Our analysis has shown that the waveguide loss is sufficiently low for the QCL to reach its threshold at the injection current density around 6 kA/cm2 at room temperature.

The fabrication of strong photocatalysts applied to the degradation of organic pollutants is necessary in environmental applications. In a single-stage method, acetate precursor and poly vinyl pyrolydine are used to produce ZnO nanostructures with various morphologies in annealing temperatures ranging from 300 °C to 900 oC. The physical properties of the prepared nanostructures were characterized by SEM, XRD and PL spectroscopy. The SEM images exhibit a variety of the as-prepared hexagonal zinc oxides including wires, rods, particles and porous network of welded particles of ZnO nanoparticles. The results of the photocatalytic degradation of methylene blue as an organic dye in aqueous suspension showed that the morphology of ZnO nanostructures influences on the photocatalytic efficiency of ZnO nanostructures, greatly. For the best result, the highest MB degradation occurs by ZnO nanowires within 16 minutes and in others samples, degradation of higher than 95 percent occurs within 20 minutes. The XRD and PL spectroscopy revealed neither VZn nor Oi are in all of samples but only VO −, VO 2− and Zni exist in ZnO nanostructures.

In this work, spherical copper (core) - silver (shell) nanoparticles with diameter of 40-50 nm were synthesized through polyol successive reduction process in glycerol with addition of sodium hydroxide (NaOH). The process involves microwave-assisted reduction of copper nitrate by glycerol under atmospheric conditions and successive reduction of silver nitrate at the surface of copper nanoparticles synthesized. We investigated the influence of synthesis parameters including molar ratio of NaOH:Cu (0:1, 1:1, 3:1 and 5:1), the molar ratio of Ag:Cu (0.01:1, 0.05:1, 0.10:1, 0.15:1 and 0.20:1) on the size, structure and composition of the resulting particles. High-resolution transmission electron microscopy with energy dispersive X-ray spectroscopy (TEM/EDS), scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were used to characterize the particles obtained. The average size of the nanoparticles decreased with increasing of the ratio of sodium hydroxide. With the molar ratio of Ag:Cu greater than 0.05:1, the silver protective shell can prevent forming of copper oxide on the surface of nanoparticles.

Zirconolite (CaZrTi2O7) is one of the components of Synroc materials, which are regarded throughout the world nuclear as the second generation of high-level nuclear waste forms. The zirconolite phase was synthesized by a sol-gel method, with one variant of the method making use of ascorbic acid as a strong complexing agent. Into the structure of the zirconolite was incorporated 10 mol% Sr. Undoped and doped samples were examined by thermal analyses and X-ray diffraction. Addition of ascorbic acid to the sols lowered the firing temperature and promoted formation of the zirconolite phase.

The effect of interfacial phases on the electrical properties of Au/Ti/SiO2/InSb metal-insulator (oxide)-semiconductor (MIS or MOS) structures was investigated by capacitance-voltage (C-V) measurements. With increasing the deposition temperature of silicon oxide from 100 to 350°C using PECVD, the change in the interfacial phases between SiO2 and InSb were analyzed by resonant Raman spectroscopy to verify the relation between the breakdown of C-V characteristics and the change of interfacial phases. The shape of C-V characteristics was dramatically changed when the deposition temperature was above 300°C. The C-V measurements and Raman spectra represented that elemental Sb accumulation resulted from the chemical reaction of Sb oxide with InSb substrate was responsible for the failure in the C-V characteristics of MIS structure.

We have developed a low cost and convenient approach to fabricate ITO-comparable transparent electrodes by using solution process of silver nanowires mixed with poly peroxotitanic acid (PPT) gel. The PPT gel is applied to connect the dispersed silver nanowires to preserve its high conductivity while remaining transparency and reducing surface roughness of the transparent electrode. The silver nanowires were synthesized via a modified polyol method, and the PPT gels were prepared by sol-gel method in appropriate concentrations. After applying the PPT gels, the sheet resistance of the transparent electrodes was improved from 192 Ω/□ to 44.7 Ω/□ with a transmittance of 81 %. And the roughness (RMS) was decreased from 106.3 nm to 48.1 nm. The PPT gel also improved the reliability of the proposed electrodes, which the conductivity was remained after general atmospheric storage of 6 months. We also demonstrate an Alq3 based OLED with the proposed transparent electrodes.

An alternative approach for reduction of interface traps density at 4H-SiC/SiO2 interface is proposed. Silicon nitride / silicon oxide stack was deposited on p-type 4H-SiC (0001) epilayers and subsequently over-oxidized. The electrical characterization of the interface was done by employing metal-oxide semiconductor (MOS) devices, inversion-channel MOS devices and lateral MOS field effect transistors (MOSFETs).