Quaternary cubic (TixCr1 − xAl~ 0.60)1 N1 coatings with 0 &lt; x &lt; 0.33 have been grown using reactive cathodic arc evaporation. When adding Ti the hardness was retained after annealing up to 1100 °C which is a dramatic improvement compared to CrAlN coatings. The coatings showed an age hardening process caused by spinodal decomposition into coherent TiCr- and Al-rich cubic TiCrAlN domains and the formation of hexagonal AlN precipitates and cubic TiCrN domains in the vicinity of the grain boundaries. The improved hardness was attributed to the stabilization of the cubic structure suppressing the formation and growth of hexagonal AlN. Furthermore, the presence of Ti atoms generated incoherent nanometer-sized crystallites within the hexagonal AlN precipitates disrupting the hexagonal lattice during the coarsening process. The addition of Ti promoted the formation of a TiO2 layer over Al2O3 resulting in a lower oxidation resistance. However, by tuning the composition it is possible to design coatings to have both good oxidation resistance and good high temperature mechanical stability. / <p>Funding Agencies|SSF project Designed multicomponent coatings, MultiFilms||</p>

In an age in which the microchip is ubiquitous, the rewards for novel methods of microfabrification are great, and the vast possibilities of nanotechnology lie just a little ahead. Various methods of microlithography offer differing benefits, and even as older techniques such as optical lithography are being refined beyond what were once considered their upper limits of resolution, new techniques show great promise for going even further once they reach their technological maturity. Recent developments in optical lithography may allow it to break the 100-nm limit even without resorting to x-rays.

In this work, we investigate the relation between the diffusion behavior of Ti1-xAlxN at elevated temperatures and the microstructure. Thinfilm samples are synthesized by reactive co-sputtering with two cathodes. One cathode equipped with Ti target is connected to a highpower impulse magnetron sputtering (HiPIMS) power supply, and the other cathode equipped with Al target is operated with a directcurrent power source. The spinodal decomposition of cubic metastable Ti1-xAlxN controlled by thermally activated diffusion is observe fordiffusion behavior. Various HiPIMS pulsing frequencies are used to achieve different microstructure, while altered power applied to Altarget is used to change the Al content in films. In the phase composition analysis achieved by GI-XRD, the right-shift of (111) film peakalong with increasing Al-power is observed. A saturation of the right-shift and h-AlN peaks are also observed at certain Al-power. Thechemical composition determined by ERDA shows trends of reducing Al solubility limit in metastable phase and O contamination upondecreasing the pulsing frequency. More N deficiency is found in samples deposited with higher frequency. In the 500 Hz and 250 Hzsamples deposited into similar composition and thickness, no apparent difference of the microstructure is observed from the SEM crosssectionalimages. From HT-XRD, we observe higher intensity of TiO2 and h-AlN peaks in 500 Hz sample at elevated temperature ascompared with 250 Hz one. From the reduction of O contamination, denser Ti1-xAlxN films are able to be deposited with lower HiPIMSpulsing frequency. In addition, the higher intensity observed in HT-XRD patterns indicates that the 500 Hz sample is more open todiffusion and therefore allows the new formed phases to grow in larger grains.

The quantal Boltzmann&ndash / Langevin equation is used to obtain a dispersion relation for the growth rates of instabilities in infinite nuclear matter. The dispersion relation is solved numerically for three different potentials. The quantal results are compared with the semi-classical solutions. It is seen that with the inclusion of the quantal effects the growth rates of the fastest growing modes in the system are reduced and these modes have the tendency to occur at longer wavelengths for all the potentials considered. Furthermore, the boundaries of the spinodal region is determined by the phase diagrams using the same three potentials and it is observed that the expanding nuclear matter undergoes liquid-gas phase transition at reduced temperatures when the quantum effects are included.

L'étude des nanobulles de vapeur générées autour de nanoparticules métalliques chauffées par un laser dans de l'eau a connu un intérêt croissant au cours de la dernière décennie, motivé notamment par leur utilisation potentielle pour des applications biomédicales. Ces travaux sont majoritairement expérimentaux et il n'existe pas de description complète des phénomènes physiques régissant la génération et la dynamique des nanobulles. L'objet de cette thèse est de répondre à ces questions fondamentales par la résolution numérique d'un modèle fondé sur les équations de conservation locales dans le fluide (masse, quantité de mouvement et énergie) et prenant en compte la thermodynamique du fluide, les effets capillaires et la résistance thermique à l'interface or-fluide. Par la résolution de ce modèle, nous avons accès à la thermodynamique du fluide avant sa vaporisation et pendant la durée de l'existence des nanobulles, ce qui permet la description de leur dynamique. Dans un second temps, nous définissons le critère de vaporisation dans le fluide par le franchissement de la température spinodale du fluide. Enfin, nous effectuons le bilan énergétique de la production et de la croissance des nanobulles, pour optimiser le transfert énergétique entre le laser et la nanobulle. Nous nous intéressons enfin à la conductance thermique d'interface due au couplage électron-phonon entre un métal et un diélectrique. Après avoir souligné l'influence de ce type de couplage sur le transfert énergétique interfacial, nous présentons des résultats préliminaires concernant le chauffage d'un fluide par des nanoparticules de type cœur-coquille or-silicium / Nanobubbles produced around metal nanoparticles heated by a laser pulse have received an increasing interest over the last decade. This interest is motivated by the possible use of those nanobubbles as an agent for cancer therapy. Existing studies are mainly experimental and a complete description of the mechanisms controlling the nanobubbles generation and evolution is still lacking. The aim of this thesis is to answer those fundamental issues by numerically solving a model based on the conservation equations inside the fluid (mass, momentum and energy). This model accounts for the thermodynamics of the fluid, capillary effects and a thermal interface resistance across the particle-fluid interface. Solving this model gives information about the thermodynamics of the fluid before and after its vaporization, which allows for the description of the bubbles dynamics. Then, we can define a criterion for bubbles generation, which corresponds to the crossing of the spinodal temperature of the fluid. Finally, we investigate the role played by the interface thermal resistance arising from electron-phonon couplings between a metal and a dielectric. We present some preliminary results concerning the heating of a fluid with core-shell nanoparticles

Les aciers martensitique inoxydables à durcissement structural sont un des matériaux constitutifs des mats réacteurs d'avion. Cette pièce est soumise aussi bien à des contraintes mécaniques qu'à des contraintes thermiques. Cette dernière engendre le vieillissement de ces aciers, du fait de la présence d'une lacune de miscibilité dans le diagramme Fe-Cr. Deux mécanismes sont possibles dans cette lacune de miscibilité, la précipitation d'une phase riche en chrome α' ou une démixtion suivant un mécanisme de décomposition spinodale. Cette thématique est l'objet du projet PREVISIA financé par l'ANR, dont cette thèse fait partie. Des vieillissements ont été effectués sur l'acier 15 5 PH jusqu'à 15 000 h afin d'étudier la cinétique de vieillissement par décomposition spinodale et son effet sur les propriétés mécaniques de l'alliage en traction, résilience et ténacité. Le vieillissement de l'acier engendre ainsi un durcissement et une fragilisation de l'alliage. De plus, des analyses microstructurales ont permis de mettre en lumière les différents stades de vieillissement, qui correspondent aussi bien à la décomposition spinodale qu'à un complément de phase durcissante. La dureté permet aussi bien de suivre le niveau de vieillissement de l'acier que de déterminer les différentes phases de durcissement. L'effet d'une contrainte appliquée tout au long du vieillissement sur la cinétique de vieillissement a été étudié. Une contrainte de type traction semble ainsi augmenter pour des contraintes élevées le durcissement induit par le complément de précipitation de la phase durcissante, mais aussi accélérer le vieillissement sur les temps de vieillissement plus longs. Une analyse multi échelle est ainsi proposée afin d'expliquer ces différents résultats. / Precipitation hardened martensitic stainless steels are constitutive of aircraft pylons. During there lifetime , these parts are subjected to mechanical loading and work in temperature. This last induces embrittlement of the steels, because of the miscibility gap in the Fe-Cr phase diagram. Two mechanisms are possible to lead to the demixing of the matrix, either precipitation of α', a chromium rich phase, or spinodal decomposition mechanism. This phenomena is the topic of the project PREVISIA, funded by the ANR, this work is part of. Long term agings have been performed on 15 5 PH stainless steel up to 15 000 hours in order to study the aging kinetic and its effect on the mechanical properties in tensile, resilience and toughness. An embrittlement of the alloy is observed. Furthermore, microstructural analyses have been conducted and lead to the definition of different stages of long term aging corresponding to spinodal decomposition and complementary precipitation of hardening phase. Hardness tests is a usefull tool in order to follow the aging and to detect the different stages of aging. The effect of a stress applied during the long term aging has been studied. A tensile stress seems to have an influence on the complementary precipitation of the hardening phase and to increase the rate of hardening. A multi-scale analysise is proposed in order to explain all these results.

A hetero-bimetallic alkoxide CrAl3(OiPr)12 was synthesised through metathesis of achromium(III)chloride THF complex (CrCl3 . 3 THF) and 3 KAl(OiPr)4.It was used as a single sourceprecursor to make oxide powders and films with 1:3 chromium/aluminium compositionthrough sol-gel synthesis. The final materials obtained and heat-treated samples of these wasstudied with thermogravimetric analysis (TG), X-ray diffraction (XRD) and IR spectroscopy. Itwas found that the as synthesised material was amorphous and elementally homogeneousand could be described as hydrated (oxo)-hydroxide with some loosely bonded carbonate,but no organics remaining. Above 600 oC crystallisation starts and eventually splits into twocorundum structured phases starting around 800 oC. At 1400  oC, the phases had joined backtogether in accordance with the Cr-Al-O phase diagram. Scanning Transmission ElectronMicroscopy with Electron Dispersive X-ray (STEM-EDX) tomography showed that the powderswere homogenous up to 800 oC, while after heating to 1000 oC showed chromiumenrichment in some crystals. Gracing Incidence X-ray diffraction (GI-XRD) on spin-coated filmsshowed that epitaxial growth might be achieved based on -Al2O3 (0001) substrate. The results show that the synthesis of the precursor and subsequent oxides was successful andyielded highly homogeneous gels that could be converted into oxide at ca. 600 oC andsubsequently be phase separated through spinodal decomposition at 1000 oC. The next stepwould be to try the precursor in the industrially used chemical vapour deposition (CVD)method.

No description available.

Steepest-entropy-ascent quantum thermodynamics (SEAQT) is a mathematical and theoretical framework for intrinsic quantum thermodynamics (IQT), a unified theory of quantum mechanics and thermodynamics. In the theoretical framework, entropy is viewed as a measure of energy load sharing among available energy eigenlevels, and a unique relaxation path of a system from an initial non-equilibrium state to a stable equilibrium is determined from the greatest entropy generation viewpoint. The SEAQT modeling has seen a great development recently. However, the applications have mainly focused on gas phases, where a simple energy eigenstructure (a set of energy eigenlevels) can be constructed from appropriate quantum models by assuming that gas-particles behave independently. The focus of this research is to extend the applicability to solid phases, where interactions between constituent particles play a definitive role in their properties so that an energy eigenstructure becomes quite complicated and intractable from quantum models. To cope with the problem, a highly simplified energy eigenstructure (so-called ``pseudo-eigenstructure") of a condensed matter is constructed using a reduced-order method, where quantum models are replaced by typical solid-state models. The details of the approach are given and the method is applied to make kinetic predictions in various solid-state phenomena: the thermal expansion of silver, the magnetization of iron, and the continuous/discontinuous phase separation and ordering in binary alloys where a pseudo-eigenstructure is constructed using atomic/spin coupled oscillators or a mean-field approximation. In each application, the reliability of the approach is confirmed and the time-evolution processes are tracked from different initial states under varying conditions (including interactions with a heat reservoir and external magnetic field) using the SEAQT equation of motion derived for each specific application. Specifically, the SEAQT framework with a pseudo-eigenstructure successfully predicts: (i) lattice relaxations in any temperature range while accounting explicitly for anharmonic effects, (ii) low-temperature spin relaxations with fundamental descriptions of non-equilibrium temperature and magnetic field strength, and (iii) continuous and discontinuous mechanisms as well as concurrent ordering and phase separation mechanisms during the decomposition of solid-solutions. / Ph. D. / Many engineering materials have physical and chemical properties that change with time. The tendency of materials to change is quantified by the field of thermodynamics. The first and second laws of thermodynamics establish conditions under which a material has no tendency to change; these conditions are called equilibrium states. When a material is not in an equilibrium state, it is able to change spontaneously. Classical thermodynamics reliably identifies whether a material is susceptible to change, but it is incapable of predicting how change will take place or how fast it will occur. These are kinetic questions that fall outside the purview of thermodynamics. A relatively new theoretical treatment developed by Hatsopoulos, Gyftopoulos, Beretta and others over the past forty years extends classical thermodynamics into the kinetic realm. This framework, called steepest-entropy-ascent quantum thermodynamics (SEAQT), combines the tools of thermodynamics with quantum mechanics through a postulated equation of motion. Solving the equation of motion provides a kinetic description of the path a material will take as it changes from a non-equilibrium state to stable equilibrium. To date, the SEAQT framework has been applied primarily to systems of gases. In this dissertation, solid-state models are employed to extend the SEAQT approach to solid materials. The SEAQT framework is used to predict the thermal expansion of silver, the magnetization of iron, and the kinetics of atomic clustering and ordering in binary solid-solutions as a function of time or temperature. The model makes it possible to predict a unique kinetic path from any arbitrary, non-equilibrium, initial state to a stable equilibrium state. In each application, the approach is tested against experimental data. In addition to reproducing the qualitative kinetic trends in the cases considered, the SEAQT framework shows promise for modeling the behavior of materials far from equilibrium.

An optical fiber has been developed that can be used as a chemical gas sensor. Fabrication of the optical fiber produces a fiber that has a solid core with a porous cladding. The porous cladding region is made from a spinodally phase separable glass where the secondary phase is removed through dilute acid leaching. A non-phase separable glass composition is used for the core region. The properties of the phase separable glass are dependent on the processing conditions and the thermal history of the glass after the porosity has been achieved. Investigation of how processing conditions affected the pore structure was conducted to determine what pore characteristics are achievable for the glass composition used. Phase separation temperature, removal of silica gel deposited in the pores, and the post fabrication heat treating were used as experimental processing conditions. A maximum useable average pore size of approximately 29 nm was achieved. Maximum pore volume in the experimental groups was 0.4399 cc/g. Most heat treatments of the porous glass caused consolidation of the pore structure, with some conditions producing pore coarsening. / Master of Science