Comparative study of zinc bis-quinolates and lithium mono-quinolates: Investigation of the effect of coordination geometry on electroluminescence performance

Metal (8-quinolinolato) (Mqn) chelates have proven to be viable for use in organic light-emitting devices (OLEDs), both as the active emitter layer and as the electron-transporting host in dye-doped OLEDs. Whether serving as the emitter layer or host material the energy level-alignment affecting charge injection efficiency and charge mobility properties are of equal importance. Substitution of the 8-quinolinolato ligand or substitution of different metal ions has been shown to shift absorption and emission energies, which can modify the relative energy level alignments of the HOMO and LUMO levels at charge injection interfaces in an OLED. Furthermore, substitution of metal ions of different oxidation states will result in differing coordination geometries of the resulting metal chelates. For Alq3, the electron transport properties and the good thermal stability of vapor-deposited films have been attributed to its octahedral geometry. In this work, we present a comparative study of the photophysical (absorption and emission) properties and thermal stability properties of methylated zinc bis-quinolates and lithium mono-quinolates. Results are related to aluminum tris-quinolates and implications on electroluminescence performance will be discussed

Preface: emergent coatings and thin films for high‑temperature energy applications

Increasing the temperature capability of mechanical devices and components is a major requirement of the energy sector. The development of new coating and thin film compositions is of strategic importance for a wide range of energy applications, which can directly influence the transport, aerospace, and manufacturing industries. This special issue covers the design and development of innovative materials related to high-temperature energy conversion, conservation, harvesting, and storage

The impact of coating architecture on the hardness, friction and wear resistance of hard and tribological nanocomposite coatings

Future generations of mechanical systems will place new demands on the tribological performance of interacting surfaces. Vapor-deposited surface coatings can provide extended lifetimes, increased efficiencies and energy savings for mechanical components and tools. These benefits can also be extended to space mechanisms and satellites with the use of vacuum solid lubricants. The material properties of surface coatings such as hardness, friction, and wear resistance in a particular environment are influenced by the characteristics of the coating microstructure which include density, grain size, grain boundary chemistry, porosity, and grain orientation. In this research effort bias sputter deposition, co-sputtering, and magnetron sputtering-pulsed laser deposition are used to deposit and control the formation of composite coating architectures. The developed microstructures were studied by x-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical and tribological tests included nanoindentation and pin-on-disk. Results were analyzed in relation to the coatings\u27 chemical composition and microstructure with the objective of establishing structure-property relations for these films. Hard coatings presented in this thesis include carbides that form a solid solution (Ti-Hf-C) as well as carbides that form composite microstructures (WC-SiC, HfC-SiC). Hardness measurements on these films indicated the potential of transition metal carbide-silicon carbide composites to be utilized as protective coatings. With the use of a substrate bias potential, a hardness of over 35 GPa was achieved for some HfC-SiC samples. By co-depositing from carbide and silver targets, composite tribological coatings (e.g. SiC-Ag, WC-Ag, TiC-Ag, HfC-Ag) were developed. These systems revealed how critical materials selection can be in the determination of a coating\u27s architecture, and how carbide-silver films can be used to provide low friction and high wear resistance in vacuum applications. For instance, a titanium carbide-silver film (15% Ag) obtained by the MS-PLD technique yielded a vacuum friction coefficient of 0.21. This is lower than the 0.25 friction coefficient observed for a pure silver coating, and with half the wear. These results demonstrate that multi-component films of transition metal carbides and silver can be co-deposited with the individual phases can be retained

Effect of silver on the phase transition and wettability of titanium oxide films

The effect of silver on the phase transition and microstructure of titanium oxide films grown by pulsed cathodic arc had been investigated by XRD, SEM and Raman spectroscopy. Following successive thermal annealing up to 1000 °C, microstructural analysis of annealed Ag-TiO2 films reveals that the incorporation of Ag nanoparticles strongly affects the transition temperature from the initial metastable amorphous phase to anatase and stable rutile phase. An increase of silver content into TiO2 matrix inhibits the amorphous to anatase phase transition, raising its temperature boundary and, simultaneously reduces the transition temperature to promote rutile structure at lower value of 600 °C. The results are interpreted in terms of the steric effects produced by agglomeration of Ag atoms into larger clusters following annealing which hinders diffusion of Ti and O ions for anatase formation and constrains the volume available for the anatase lattice, thus disrupting its structure to form rutile phase. The effect of silver on the optical and wetting properties of TiO2 was evaluated to demonstrate its improved photocatalytic performance

The confinement of phonon propagation in TiAlN/Ag multilayer coatings with anomalously low heat conductivity

TiAlN/Ag multilayer coatings with a different number of bilayers and thicknesses of individual layers were fabricated by DC magnetron co-sputtering. Thermal conductivity was measured in dependence of Ag layer thickness. It was found anomalous low thermal conductivity of silver comparing to TiAlN and Ag bulk standards and TiAlN/TiN multilayers. The physical nature of such thermal barrier properties of the multilayer coatings was explained on the basis of reflection electron energy loss spectroscopy. The analysis shows that nanostructuring of the coating decreases the density of states and velocity of acoustic phonons propagation. At the same time, multiphonon channels of heat propagation degenerate. These results demonstrate that metal-dielectric interfaces in TiAlN/Ag coatings are insurmountable obstacles for acoustic phonons propagation

Control over Multi-Scale Self-Organization-Based Processes under the Extreme Tribological Conditions of Cutting through the Application of Complex Adaptive Surface-Engineered Systems

This paper features a comprehensive analysis of various multiscale selforganization processes that occur during cutting. A thorough study of entropy production during friction has uncovered several channels of its reduction that can be achieved by various selforganization processes. These processes are (1) self-organization during physical vapor deposition PVD coating deposition on the cutting tool substrates; (2) tribofilm formation caused by interactions with the environment during operation, which consist of the following compounds: thermal barriers; Magnéli phase tribo-oxides with metallic properties at elevated temperatures, tribo-oxides that transform into a liquid phase at operating temperatures, and mixed action tribo-oxides that serve as thermal barriers/lubricants, and (3) multiscale selforganization processes that occur on the surface of the tool during cutting, which include chip formation, the generation of adhesive layers, and the buildup edge formation. In-depth knowledge of these processes can be used to significantly increase the wear resistance of the coated cutting tools. This can be achieved by the application of the latest generation of complex adaptive surface-engineered systems represented by several state-of-the-art adaptive nano-multilayer PVD coatings, as well as high entropy alloy coatings (HEAC)

A Guiding Framework for Process Parameter Optimisation of Thermal Spraying

Currently, most thermal spray coating service providers expect original equipment manufacturers (OEMs) to suggest the coating recipe, comprising of the right coating equipment, starting process parameters, type of inert gases, and robot program. The microstructure and mechanical properties may not comply in the first few runs. Feedback from a competent material testing service provider forms the initial step to adjust the parameters in the development journey, toward identifying the processing parameters required to obtain an acceptable coating. With the surge of interest in sustainable manufacturing, the time spent on trials in the future will shrink, and a more rigorous process needs to be applied to achieve the “right-first-time manufacturing” approach in thermal spraying. However, a framework for the systematic development of thermal spray parameter optimisation is lacking. This article provides a framework, based on a logical acumen, in selecting the right process parameters, using available data and prior knowledge about the thermal spraying process. To that end, the article summarises the extant developmental journey of thermal spray process parameters, by covering the aspects of equipment choice, robot and spray parameters, and how to minimise iterations, using diagnostic tools to get to the end solution most efficiently. This article, in its current form, will serve as a good guide for early career engineers and scientists or workers, to minimise the time processing window, by avoiding endless iterations to deposit a certain type of coating using thermal spraying. Besides, this work is also aimed at transforming academic research innovations to a robust and repeatable industrial manufacturing process

Interface-Induced Plasmon Nonhomogeneity in Nanostructured Metal-Dielectric Planar Metamaterial

Transformations of the electronic structure in thin silver layers in metal-dielectric (TiAlN/Ag) multilayer nanocomposite were investigated by a set of electron spectroscopy techniques. Localization of the electronic states in the valence band and reduction of electron concentration in the conduction band was observed. This led to decreasing metallic properties of silver in the thin films. A critical layer thickness of 23.5 nm associated with the development of quantum effects was determined by X-ray photoelectron spectroscopy. Scanning Auger electron microscopy of characteristic energy losses provided images of plasmon localization in the Ag layers. The nonuniformity of plasmon intensities distribution near the metal-nitride interfaces was assessed experimentally

On the Use of the Theory of Critical Distances with Mesh Control for Fretting Fatigue Lifetime Assessment

This work analyses the viability of the theory of critical distances (TCD) using mesh control for fretting fatigue lifetime assessment. More than seven hundred sets of simulations were performed by taking seventy different experimental tests reported previously in the literature. The outcome of the present study suggests that the TCD mesh control method can be extended to fretting fatigue problems by the reasonable assumption of setting the right element size proportional to critical distance. In this study, a significant computational time reduction of up to 97% was obtained. Thus, this study provides a simple method to design complex 3D industrial components subjected to fretting fatigue phenomena using finite element analysis efficiently without requiring complex remeshing techniques

El dol: un procés emocional...

Màster en Educació Emocional i Benestar, Facultat de Pedagogia, Departament de Mètodes d’Investigació i Diagnòstic en Educació, Universitat de Barcelona, curs: 2012-2013, Tutor/Tutora: Maria José Tapiador CarreteroLa publicació centra el seu interès en l’aprenentatge d’eines i estratègies bàsiques d’enfrontament del dolor (regulació emocional), a fi i efecte de millorar el benestar tant dels professionals com dels usuaris implicats en aquest tipus de processos. A partir d’un marc teòric es planteja un taller sobre el procés de dol, ja que com a futurs professionals, s’enfrontaran a situacions molt doloroses i mobilitzadores emocional i relacionalment. El taller pretén tenir una funció preventiva i a l’hora oferir als alumnes unes eines bàsiques per a poder fer intervencions