The vibrational properties of kesterite Cu2ZnSnS4 (CZTS) single crystals were studied by polarization-dependent Raman scattering measurements. The CZTS crystals grown by chemical vapor transport technique using iodine trichloride as a transport agent consist of several mirror-like planes. The detailed analysis of the experimental spectra obtained from different planes allows determining the symmetry assignment of the observed Raman-active modes. The wavenumber values of Raman-active modes are compared with the results of recent theoretical calculations. The presented data are useful for examination of CZTS absorber films applied for solar cells to clarify the existence of structural or phase inhomogeneities.

In this work is discussed the synthesis of a novel antishrinking agent (SOC DA) and the evaluation of its performance in an acrylic dental resin. SOC DA was photopolymerized in conjunction with the components of a conventional acrylic resin, which includes a mixture of diacrylate monomers [glycerolate bisphenol A dimethacrylate (BIS-GMA) / Urethane dimethacrylate (UDMA) / triethyleneglycol dimethacrylate (TEGDMA)] in 50/30/20 molar ratio). SOC DA was added in a range between 5.0-20.0 mol % with respect to the total amount of moles of the acrylic monomers. It was found that increasing concentrations of SOC DA, promoted higher conversions of the dimethacrylate monomers without decreasing the photopolymerization rate of the acrylate monomers. The study of the effect of SOC DA on the mechanical properties of the dental composite filled with 70 % of silicon dioxide, revealed that the presence of the antishrinking agent improved both the compressive and the flexural strength of the dental materials. Besides, it was found that by using the SOC DA at 20%, the shrinkage was reduced 52%, compared with the same formulation without SOC DA.

Developments of composites materials had begun in the 1970's. They aimed in improving mechanical properties due to the presence of reinforcement particles. The addition of particles in a matrix led to different modifications: considering the nature of the phases and the microstructure, we can mention interface reactivity between matrix and particles, changes in the chemical composition of the matrix and modified kinetics of microstructure evolution in the matrix (as compared to the matrix without particles); considering the mechanical aspects, thermal stresses may be generated due to the differences in expansion coefficients between the particles and the matrix, or any changes in the matrix leading to a phase transformation. In the present work, we studied the evolution of the phases and the behavior of a steel based MMC during thermal treatments, for which a phase transformation occurred on cooling. Experiments and numerical simulation are considered.

Ionic liquid (IL) is used as the working electrolyte in ionic polymer metal composite (IPMC) electromechanical bending actuators because of its high stability and conductivity, which are crucial for the consistency and speed of the actuation. Because the bending actuation is caused by the migration and accumulation of the cations and anions of the IL, it is clear that both the overall number of ions and the effectiveness of ion transport and accumulation play important roles in the actuation behavior. In this paper, the effect of enhancing the ion accumulation by the self-assembled conductive network composite (CNC) layers is investigated by comparing the bending behavior of actuators with and without CNC layers. In addition, IPMC actuators with various IL uptakes are also tested in order to study the dependence of the bending performance on the amount of the ions available. It is found that, with the CNC layers, the maximum bending curvature of the actuator increases with increased IL, which shows the crucial role played by the IL. However, under the same conditions, the performance improvement of actuators without CNC layers saturates when the IL uptake reaches around 10% wt. This demonstrates the role of the CNC layers to provide a porous electrode with increased capacitance that thus accommodates accumulation of more ions near the electrodes, which in turn boosts the overall bending curvature of the actuator.

Magnesium doped ZnO films were electrochemically grown on the NESA conductive glass substrate from the magnesium nitrate aqueous solution with zinc sulfate, kept at 323K and the cathodic potential of -0.9V vs. Ag/AgCl. The Mg/(Mg+Zn) atomic ratio of Zn1-xMgxO films increased with the decrease in the zinc sulfate concentration. The optical band gap energy of these Zn1-xMgxO films decreased with increasing content of zinc sulfate. Thus, the optical band gap energy and Mg/(Mg+Zn) atomic ratio of Zn1-xMgxO films would depend on the zinc sulfate concentration.

Much attention has been given to bulk metallic glasses (BMG) in recent years, particularly those based on binary alloys due to the simplicity of their atomic composition. Although efforts to understand the atomistic features that give rise to their exceptional properties have been made, the electronic and vibrational properties have been disregarded. We undertook the task of simulating the Cu64Zr36 glassy metal using a supercell with 108 atoms and a different simulational approach: the undermelt-quench approach [1]. The structure was characterized by means of the radial (pair) distribution function and the bond-angle distribution and the electronic density of states was calculated. We find that our results agree well with experimental data.

The narrow gap Mott insulators AM4Q8 (A = Ga, Ge; M= V, Nb, Ta; Q = S, Se) exhibit very interesting electronic properties when pressurized or chemically doped. We have recently discovered that the application of short electrical pulses on these compounds induces a new phenomenon of volatile or nonvolatile resistive switching. The volatile transition appears above threshold electric fields of a few kV/cm, while for higher electric fields, the resistive switching becomes non-volatile. The application of successive very short electric pulses enables to go back and forth between the high and low resistance states. All our results indicate that the resistive switching discovered in the GaM4Q8 compounds does not match with any previously described mechanisms. Conversely, our recent work shows that the volatile resistive switching is related to a purely electronic mechanism which suggests that the AM4Q8 compounds belong to a new class of Mott-memories for which Joule heating, thermochemical or electrochemical effects are not involved. Finally, it is possible to deposit a thin layer of GaV4S8 and to retrieve the reversible resistive switching on a metal-insulator-metal (MIM) device which proves the potential of this new class of Mott-memories for applications.

In-situ transmission electron microscopy (TEM) method is powerful in a way that it can directly correlate the atomic-scale structure with physical and chemical properties. We will report on the construction and applications of the homemade in-situ TEM electrical and optical holders. Electrical transport of carbon nanotubes and photoconducting response on bending of individual ZnO nanowires have been studied inside TEM. Oxygen vacancy electromigration and its induced resistance switching effect have been probed in CeO2 films.

Aqueous solutions containing Cd2+ and S2- ions have been brought together in a T-mixer, and the formation of CdS nanoparticles has been monitored by ultrafast X-ray small angle scattering down to 0.2 ms. While no particle formation is observed for a laminar flow, their growth can be followed in-situ for conditions of turbulent flow.

Corundum structured α-(GaFe)2O3 alloy thin films were obtained on c-plane sapphire substrates by the mist chemical vapor deposition method. Wide range of X-ray diffraction 2θ/θ scanning measurements indicated that these crystals were epitaxially grown on c-plane sapphire substrates and these are no other crystal oriented phase. The cross-sectional and plane-view transmission electron microscope images showed the growth along the c-axis of α-(GaFe)2O3 thin films on sapphire substrates, forming joint of columnar structure. The non-doped α-(GaFe)2O3 thin films showed ferromagnetic properties at 300 K, though the origin of ferromagnetism still remained unresolved. In order to enhance the spin-carrier interaction, Sn doped α-(GaFe)2O3 alloy thin films were fabricated on c-plane sapphire substrates. X-ray diffraction 2θ/θ and ω scanning measurement results indicated that the highly-crystalline films were epitaxially grown on substrates in spite of the Sn-doping.

Piezoelectric Microelectromechanical Systems (MEMS) has been proven to be an attractive technology for harvesting small energy from the ambient vibration. Recent advancements in piezoelectric materials and harvester structural design, individually or in combination, have improved MEMS energy harvesters to achieve high enough power density, compactness and ultra wide bandwidth, bringing us closer towards battery-less autonomous sensors systems and networks in near future. Among the breakthroughs, non-linear resonating beam for wide bandwidth resonance is the key development to enable robust operation of MEMS energy harvesters over the unpredictable and uncontrollable frequency spectra of ambient vibration. We expect that a coin size harvester will be able to harvest about 100μW continuous power at below 100 Hz and less than 0.5 g input vibration and at reasonable cost.

We present an in-depth transmission electron microscopy (TEM) study about the character of the Gd atom distribution in epitaxial GaN:Gd thin films grown by molecular beam epitaxy. High-resolution TEM (HRTEM) imaging reveals local lattice distortions of dimensions of a few atom planes only. Geometric phase analysis of HRTEM lattice images quantifies the associated displacement field. The results are explained by means of thin coherently strained GdN clusters with platelet shape being located along the basal plane. This is consistent with the observations obtained from strain contrast dark-field TEM images. Theoretically derived structure models provided by calculations based on density functional theory are used to simulate the HRTEM contrast and to determine the corresponding displacement field for matching the experimental data. Best fit is achieved in case of a coherent GdN bi-layer cluster that conclusively reflects the energy favorable configuration. The formation of the platelet clusters is explainable in the framework of spinodal decomposition.

The fracture behaviour of individual grain boundaries has been studied in order to understand the mechanisms controlling stress corrosion cracking in nuclear reactors. In particular, the role of oxidation in facilitating crack initiation and propagation has been reviewed. Nickel alloys from pressurized water reactors (PWRs) have been tested in simulated primary water conditions to induce grain boundary oxidation. Microcantilevers containing an oxidized grain boundary plane have been prepared and tested for fracture. The brittle nature of the oxide was demonstrated and the required stress to fracture measured.

Hexagonal boron nitride (h-BN), also known as white graphite, is the inorganic analogue of graphite. Single layers of both structures have been already experimentally realized.

In this work we have investigated, through fully atomistic reactive molecular dynamics simulations, the dynamics of hydrogenation of h-BN single-layers membranes.

Our results show that the rate of hydrogenation atoms bonded to the membrane is highly dependent on the temperature and that only at low temperatures there is a preferential bond to boron atoms. Unlike graphanes (hydrogenated graphene), hydrogenated h-BN membranes do not exhibit the formation of correlated domains. Also, the out-of-plane deformations are more pronounced in comparison with the graphene case. After a critical number of incorporated hydrogen atoms the membrane become increasingly defective, lost its two-dimensional character and collapses. The hydrogen radial pair distribution and second-nearest neighbor correlations were also analyzed.

Single-phase calcium chlorosilicate and sodalite, two potential ceramic waste-forms for the immobilisation of CaCl2-based pyroprocessing wastes, have been fabricated at temperatures below the volatilisation point of CaCl2. Solid solutions doped with Sm3+ as an inactive analogue for trivalent actinides have been fabricated and characterised. XRD analysis shows both phases will successfully accommodate Sm3+, with the sodalite in particular remaining single-phase. Fabrication of Sm-doped calcium chlorosilicate in air results in the formation of SmOCl and Ca(Si2O5) secondary phases, however, calcination in an inert atmosphere is shown to successfully retard the formation of SmOCl allowing for higher levels of doping.

A study on the individualization of commercially purchased SWCNT and MWCNT were made in an N-N dimethyl tetraformamide solvent by a combination of ultrasonication and centrifugation, and processing of these individualized CNTs are applied as a stacking layer in bulk-heterojunction (BHJ) solar cells. The wt% (mg) of pristine CNTs loading was optimized in respect to volume of solvent (ml). Then as prepared BHJ devices were modified by spin casting at 4000 rpm/30s of these pristine individualized CNTs by incorporating a stacking layer (∼30 nm) for efficiency evaluation. Comparisons of the devices made with known functionalized CNTs (acid treated) and found that stacking of pristine individualized CNTs between the PEDOT:PSS and active (P3HT:PCBM) layer demonstrate a significantly enhanced efficiency of 2.1% (JSC of 9 mA/cm2, VOC of 0.6, FF of 39) from the normal BHJ of 1.2% (JSC of 5.3 mA/cm2, VOC of 0.62, FF of 33). However, SWCNT with acid treated when applied in BHJ shows degrading efficiency (0.51%) which can be attributed to the degradation of corrugated tubular side walls leading to potential loss of opt-oelectric properties. The enhanced efficiency of devices with pristine individualize CNTs can be conjectured due to better opto-electrical properties and undamaged tubes. The microstructures of the heterojunction active layer were examined by using UV-Vis spectra, IV curve and EQE techniques.

Papers in the Appendix were published in electronic format as Volume 1534

The device performance of GaAs p-i-n solar cells containing stacked layers of self-assembled InAs quantum dots is investigated. The solar cells demonstrate enhanced external quantum efficiency below the GaAs band gap relative to a control device without quantum dots. This is attributed to the capture of sub-band gap photons by the quantum dots. Analysis of the current density versus voltage characteristic for the quantum dot solar cell reveals a decrease in the series resistance as the device area is reduce from 0.16 cm2 to 0.01 cm2. This is effect is not observed in control devices and is quantum dot related. Furthermore, low temperature measurements of the open circuit voltage for both quantum dot and control devices provide experimental verification of the conditions required to realise an intermediate band gap solar cell.

Dimethyl sulfoxide (DMSO) has been used for several decades as the most efficient cryoprotective agent (CPA) for many types of cells in spite of its cytotoxicity and its effect on differentiation. Recently we showed that carboxylated poly-L-lysine, which is classified as a polyampholyte, has a cryoprotective effect on cells in solution without any other cryoprotectant. Here we developed high molecular weight polyampholytes with an appropriate ratio of amino and carboxyl groups and evaluated their cryopreservation efficiency. A novel polyampholyte based on naturally available polymer dextran, in which we introduced both amino and carboxyl groups shows an excellent post thaw-survival efficiency of more than 90% of murine L929 cells. It can serve as the sole high molecular weight CPA for tissue engineering applications without animal derived materials.