The lead free double perovskite Cs2AgBiBr6 is an upcoming alternative to lead based perovskites as absorber material in perovskite solar cells. So far, the majority of investigations on this interesting material have focused on polycrystalline powders and single crystals. We present vapor and solution based approaches for the preparation of Cs2AgBiBr6 thin films. Sequential vapor deposition processes starting from different precursors are shown and their weaknesses are discussed. Single source evaporation of Cs2AgBiBr6 and sequential deposition of Cs3Bi2Br9 and AgBr result in the formation of the double perovskite phase. Additionally, we show the possibility of the preparation of planar Cs2AgBiBr6 thin films by spin coating.

In this experiment, a new bimetal low–cost Cu–Sn alloy was synthesized and it was tested as catalyst for oxygen reduction reaction (ORR) in MFC and the results were compared with the commercially available Pt-C catalyst. Cyclic voltammetry for evaluating ORR of the test cathode containing Cu-Sn catalysts under oxygen saturated environment displayed large ORR current peak, showing less overpotential demand for ORR. Maximum power density of 457 mW/m2 obtained from MFC using Cu–Sn catalyst, was found to be slightly higher than the power density of 446 mW/m2 demonstrated by MFC using Pt based cathode. Biochemical conversion of organic matter to direct electric current in Cu–Sn based MFC occurred at a coulombic efficiency of 55.8%, while demonstrating 92% of chemical oxygen demand removal. This study demonstrated application of low cost Cu–Sn bimetal alloy as excellent ORR catalyst in MFC and would be very helpful to commission larger MFCs for field applications to harvest energy in the form of direct electricity from wastewaters while offering wastewater treatment.

Chip-package interaction (CPI) and the related thermomechanical stress in microchips increase the risk of failure in on-chip interconnect stacks, caused by delamination along Cu/dielectrics interfaces (adhesive failure) and fracture in dielectrics (cohesive failure). High-resolution transmission X-ray microscopy (TXM) is a unique technique to image crack propagation in on-chip interconnect stacks. The visualization of crack evolution in Cu/low-k Backend-of-Line (BEoL) structures is demonstrated using an experimental setup which combines high-resolution X-ray imaging with mechanical loading. The application of an indenter manipulator at the TXM beamline of the synchrotron radiation source BESSY II provides an unprecedented level of details on the fracture behavior of microchips. This in-situ experiment allows to identify the weakest layers and interfaces and to evaluate the robustness of the BEoL stack against CPI.

The variation of the molecular architecture of multiblock copolymers has enabled the introduction of functional behaviour and the control of key mechanical properties. In the current study, we explore the synergistic relationship of two structural components in a shape-memory material formed of a multiblock copolymer with crystallizable poly(ε-caprolactone) and crystallizable poly[oligo(3S-iso-butylmorpholine-2,5-dione)] segments (PCL-PIBMD). The thermal and structural properties of PCL-PIBMD films were compared with PCL-PU and PIBMD-PU, investigated by means of DSC, SAXS and WAXS measurements. The shape-memory properties were quantified by cyclic, thermomechanical tensile tests, where deformation strains up to 900% were applied for programming PCL-PIBMD films at 50 °C. Toluene vapor treatment experiments demonstrated that the temporary shape was fixed mainly by glassy PIBMD domains at strains lower than 600%, with the PCL contribution to fixation increasing to 42±2% at programming strains of 900%. This study into the shape-memory mechanism of PCL-PIBMD provides insight into the structure-function relation in multiblock copolymers with both crystallizable and glassy switching segments.

Thermal evaporation is a simple method to fabricate a BaSi2 film, a new solar cell material consisting of earth-abundant elements. In this study, we optimized the evaporation process and suppressed near-interface oxidation in evaporated BaSi2 films on Si(100) substrates, which has been detected in previous studies. Composition depth profiles determined by Auger electron spectroscopy show the decrease of oxygen concentration near the interface to the background level by optimizing the source pre-melting condition. By reducing oxygen concentration, the BaSi2 film becomes more preferentially oriented toward [100] as long as the deposition rate is not changed, as evidenced by X-ray diffraction. It is also shown that the rectification behavior of n-BaSi2/p+-Si diodes improves by suppressing the near-interface oxidation.

Carboxylated carbon nanotubes (C or cCNTs) were incorporated in polyethersulfone hollow fiber membranes (P HFMs) to improve the gas separation performance, i.e., pure gas permeability and ideal gas selectivity. The developed CP HFMs showed the remarkable improvement in thermal stability and mechanical strength as compared to that of the pristine P HFMs. The pure gas permeability of CO2, CH4, O2, and N2 gases for the HFMs were measured at 3 bar feed pressure and room temperature. It was observed that the presence of cCNTs in HFMs significantly improved the CO2 and O2 permeability for CP HFMs by 10.8-and 11.7- fold, respectively, as compared to that measured for P HFMs. Furthermore, the ideal gas selectivity for CO2/CH4, O2/N2, and CO2/N2 gas pairs for CP HFMs was also remarkably enhanced by almost 8.6-, 10.7-and 9.9-times, respectively, as compared to that measured for P HFMs. CP HFMs exhibited gas separation performance better than or comparable to that of the literature-reported CNTs-based membranes. Remarkably, the gas separation performance of CP HFMs crossed Robeson’s 2008 upper bound curve for O2/N2 gas-pair and was almost closer to the upper bound curves drawn by Robeson in 2008 for CO2/CH4 and CO2/N2 gas pairs. The improved separation performance can be attributed to the presence of cCNTs in HFMs. Thus, the results obtained in this study clearly showed that the CP HFMs can potentially be used as a membrane material for the industrially relevant gas separations.

Ceramic Matrix Composite (CMC) materials are of interest for use in next-generation turbine engine components, offering a number of significant advantages, including reduced weight and high operating temperatures. However, in the hot environment in which such components operate, the presence of water vapor can lead to corrosion and recession, limiting the useful life of the components. Such degradation can be reduced through the use of Environmental Barrier Coatings (EBCs) that limit the amount of oxygen and water vapor reaching the component. Candidate EBC materials include Yttrium and Ytterbium silicates. In this work we present results of kinetic Monte Carlo (kMC) simulations of oxygen diffusion, via the vacancy mechanism, in Yttrium and Ytterbium disilicates, along with a brief discussion of interstitial diffusion.

An EBC system typically includes a bond coat located between the EBC and the component surface. Bond coat materials are generally chosen for properties other than low oxygen diffusivity, but low oxygen diffusivity is nevertheless a desirable characteristic, as the bond coat could provide some additional component protection, particularly in the case where cracks in the coating system provide a direct path from the environment to the bond coat interface. We have therefore performed similar kMC simulations of oxygen diffusion in this material.

Copper Zinc Tin Sulphide (Cu2ZnSnS4) materials are of interest for Photovoltaic applications. In this work, i.e., the first phase of Cu2ZnSnS4 synthesis, Cu-Zn-Sn film precursors were synthesised using electron beam deposition. The crystal structure of the synthesised film precursors were characterised by X-ray Diffraction (XRD) and elemental composition identification performed using Rutherford Backscattering Spectrometry (RBS). The synthesis results obtained are in agreement with those presented in the literature indicating that the metallic CZT film precursors were successfully synthesised.

The reprocessing of tailings or gold mine waste dumps to extract gold has become an attractive proposition for mining houses worldwide because of the availability of gold which was not easily recovered using old technologies. This study seeks to exploit the novel properties of nanostructured materials in enhancing gold extraction from gold mine tailings. The beneficiation of slimes or tailings involved taking samples for mineralogical studies, synthesis of a novel adsorbent medium (nano C-MgO) prepared by using both chemical and mechano-synthesis methods, oxidative pre-treatment of flotation concentrates, cyanidation and final recovery of the precious metal from solution in a Carbon in Column (CIC) system. The nanocomposite adsorbent was studied by powder X-ray Diffraction (XRD) for structural analysis, Field Emission Scanning Electronic Microscopy (FESEM) for surface morphology, Energy-dispersive X-ray spectroscopy (EDX) for elemental analysis and Fourier Transform Infrared (FTIR) spectroscopy for chemical structure analysis. The Brunauer-Emmett-Teller (BET) Surface Area Analysis procedure was employed to determine the total specific surface area of the nano-adsorbent. Representative tailings samples of 100-500 g were obtained for different analytical investigations using a riffle splitter. The tailings grade was analysed using the Atomic Absorption Spectroscopy (AAS) technique and was found to be an average of 0.5 g/tonne. A comparative Pseudo-Equilibrium test showed that the novel C-MgO nano adsorbent had an average of 84% recovery against 70 % for convectional activated carbon. The average crystalline size of 4.5 -11nm for the majority of MgO nanoparticles was obtained using Debye-Scherrer formula. FESEM confirmed that nano MgO was porous in nature and highly agglomerated whilst EDX exhibited the successful synthesis of the nano-composite product. This work also shows that the nano-adsorbent presents a huge potential for application in the conventional processes for gold adsorption.

This work reports on the synthesis and the main physical and chemical properties of ZnO nanoparticles synthesized by an entirely green Bio-physical-chemical process using natural dye extract from Adansonia digitata leaves as an efficient reduction/oxidizing agent. Their structural and surfaces properties by electron microscopy, X-rays diffraction, Raman and TGA, as well as gas adsorption analysis are reported.

Rapid or explosive heating of electrically conductive films has several applications, and the use of reactive laminates to increase output energy is an intriguing concept. Past studies have shown electrically heated aluminum/nickel (Al/Ni) nano-laminate films to augment this energy by an amount approximately equivalent to the expected heat of mixing between the two elements, which for most intermetallics is a significant fraction of the total heat of reaction (86% for Al/Ni). In this study, we investigate the use of sputtered aluminum/boron (Al/B) laminates to determine whether a similar increase, as measured by the velocity of an ejected flyer layer, occurs. However, observed velocities in any samples containing boron were 38% to 45% lower than samples without boron, despite much higher heats of reaction reported in the literature for Al/B. We attributed this reduction to the vaporization temperature of boron being much higher than that of Al, and because Al electrical resistivity at elevated temperatures was still much lower than boron, boron heating was less efficient as vaporized Al expanded and drove the ejected flyer. These results and analysis give insight into other reactive material combinations in which one of the constituents is an electrical insulator.

We present some recently acquired results corresponding to the nature of the electron transport that occurs within bulk alloys of zinc-magnesium-oxide. These results are obtained using three-valley ensemble semi-classical Monte Carlo electron transport simulations. The impact that the magnesium content plays in shaping the form of the electron transport related characteristics associated with this alloy system is explored. Both steady-state and transient electron transport results are examined. The device implications of these results are then commented upon.

Vanadium dioxide thin films are considered as smart functional coatings for thermal shielding, and are attractive as a passive thermal shield for spacecrafts. In space they would, however, be subjected to bombardment by interstellar dust particles and electromagnetic radiation. Materials subjected to irradiation will suffer damages induced by the displacement cascades initiated by nuclear reaction. Such cosmic radiation can severely impact the structure and function of materials. To study this effect in the laboratory, we have deposited VO2 films on silicon wafers and exposed them to γ-radiation of doses up to 100 kGy by using a 60Co nuklid source with 1.17 and 1.33 MeV photon energy. We anticipate that the γ-radiation causes local structural perturbations which can amount to defects with a corresponding change in electronic structure and thermal shielding property. We report on the photo emission spectroscopy of gamma irradiated VO2 thin films.

Specific demand of lightweight and high efficient flexible energy unit is increased day by day for its integration into bendable electronics devices. Super-capacitor is one of the promising power unit to meet the current requirement. Flexible metal oxide and polypyrrole based flexible electrode materials are prepared using electrodeposition. The calculated specific capacitances of the devices shows 0.5 mill farad per gram. The super-capacitor is ultra-flexible, stable with operational voltage window expands from 0.8 to 2.5 V which can help to reduce the number of super-capacitor in series connection to obtain the same output. In this study, a conductive polymer can be coupled with MnO2 to improve capacitance and conductivity of a hybrid structure based on MnO2.

In this study, the synthesis of a clay-polymer composite was carried out by the in-situ polymerization method of two biopolymers, Alginate-Chitosan (Alg-Chit), with the intercalation of an organo-modified clay, for the removal of bromophenol blue dye (BP-Dye). For this purpose, a natural Montmorillonite clay from Mexico was modified with a cationic surfactant, in order to exchange the cations of the clay galleries with those of the surfactant, and to change its nature from hydrophilic to hydrophobic. Moreover, the synthesis of the copolymer was carried out using different ratios between both biopolymers. Once the copolymer was obtained, it was characterized through FTIR technique. On the other hand, the modified clay was used to obtain the polymer-clay composites using a ratio of 2%-wt of the homopolymer, and the obtained material was characterized with the same technique. Finally, a contact test was carried out by preparing a solution of BP-Dye at a concentration of 5 mg/L, with and without initial pH adjustment, for 1 h, in a bath at controlled room temperature and constant stirring (100 rpm). After this time, phases were separated, and the quantification of the dye was carried out by UV-Vis spectroscopy.

Using a 72-atom supercell we report ab initio calculations of the electronic and vibrational densities of states for the bismuth (111) bilayers (bismuthene) with periodic boundary conditions and a vacuum of 5 Å, 10 Å and 20 Å. We find that the electronic density of states shows a metallic character at the Fermi level and that the vibrational density of states manifests the expected gap due to the layers. Our results indicate that a vacuum down to 5 Å does not affect the electronic and vibrational structures noticeably. A comparison of present results with those obtained for the Wyckoff structure is displayed. Assuming that the Cooper pairing potential is similar for all phases and structures of bismuth, an estimate of the superconducting transition temperature gives 2.61 K for the bismuth bilayers.

The material and absorptive properties of a commercial selective solar absorber were studied after being exposed to temperatures that could be expected during its lifespan in a solar collecting device. The samples were tested as both flat sheets, and after being rolled into the shape of a tube. Moreover, the morphological analysis of the annealed samples at 100, 200, 300, 400 and 500 °C revealed an increase in the crystallite size of the thin films with increasing annealing temperature, and larger agglomerates where observed for samples annealed at temperatures above 200 °C . The total diffuse reflectance of the annealed samples was performed and the obtained data was used to calculate their solar absorption at wavelengths ranging from 200 to 2600 nm. Interestingly, optical performance degradation was observed above 200 °C indicating that the structural changes of the thin films at higher temperature induced a reduction in the efficiency of the selective absorber coating. Additionally, no significant difference in the physical properties and rate of efficiency decline between the flat and the rolled sheets of the solar absorber coating was observed indicating its potential use as a cylindrical shaped absorber for concentrating solar power application.

An investigation of the effect of experimental parameters on the temperature and uniformity of material deposition by atmospheric pressure dielectric barrier discharge (DBD) planar plasma reactors was conducted. The apparatus consisted of a pulsed AC high voltage power source with various electrode materials (aluminum, copper wire mesh, and aluminum/copper wire mesh) operating under a range of load resistances. Possible effects of non-ideal interfacial conditions for the contact surface between the electrode and the substrate were also studied with various modified surface thermal conditions. It was found that a hybrid electrode design with a fine copper (Cu) wire mesh attached to an aluminum plate of approximately 3 mm thickness produced the most visually uniform deposit, presumably as a result of both the superior conductivity provided by the Al metal plate and the stable plasma resulting from the relatively low breakdown voltage by using helium (He) as the dilution gas. Although the experimental conditions of plasma-enhanced chemical vapor deposition (PECVD) are often specific to particular systems and applications, this work provides insights on technical details which can be applied to various plasma DBD reactors.

Upgraded metallurgical-grade silicon (UMG Si) solar cells with different ranges of efficiencies were characterized through electroluminescence imaging (ELi) and light-beam induced current (LBIC) measurements. The results showed a good correlation between the EL intensity and the efficiency of the solar cells. ELi images gave a bright contrast at the defects, grain boundaries and intragrain defects, and dark contrast inside the grain bodies. Metallic impurities are much more present in some cells due to the directional solidification of the Si ingot. Local short-circuit current mapping with LBIC measurements revealed a bright zone in the neighborhoods of the defects due to the depletion of impurities. Internal quantum efficiencies (IQE) and effective diffusion lengths (Leff) were calculated using different excitation wavelengths. High resolution LBIC measurements revealed micrometric clusters of impurities around intragrain defects.

In this work we report the study of the effect of the deposition parameters on the photoluminescence (PL) intensity of hydrogenated amorphous silicon-carbide (a-SiC:H) films deposited at very low temperature (150 °C) by Plasma Enhanced Chemical Vapor Deposition (PECVD). We have observed that the main deposition parameter that influences the wavelength emission peak is the methane/silane (CH4/SiH4) ratio used for the films deposition, due to a change on the film carbon content. On the other hand the deposition RF power affects the PL intensity, without a change in the PL emission peak. Also we have studied the effect of the film thickness on the PL intensity and we have observed an optimal film thickness.