While research on alternatives to growth at the level of the economy as a whole is accumulating, few studies have related the criticism of growth to the business level. This paper starts to address this gap by investigating mechanisms of growth for small and medium sized enterprises (SMEs), presenting a case study that applies Q methodology and interviews with owner-managers of both growing and non-growing SMEs in Austria. Some mechanisms stimulating growth are identified across SMEs including contributing to innovativeness and motivation of employees. Others are only of relevance for some SMEs: competition, financial stability and a desire for market power. The owner-managers of non-growing SMEs hold values and pursue goals that free them from mechanisms of growth or prevent them from being triggered. Moreover, they exhibit a strong identification with their SME, operate in niche markets and strive for financial independence. This illustrates that a growth imperative is neither inevitable nor are growth mechanisms always operative, but depend upon structures and institutions. / Series: SRE - Discussion Papers

Ce travail de thèse consiste en une étude des mécanismes de croissance des nanotubes de carbone monofeuillets par spectroscopie Raman in situ. La première partie de ce travail est consacrée à la mise en évidence des limites en température et en pression partielle de précurseur carboné du domaine de croissance des nanotubes de carbone monofeuillets. L’atout principal de la spectroscopie Raman in situ étant de pouvoir corréler informations structurales et cinétiques, cette approche a aussi permis d'étudier l'influence des principaux paramètres de synthèse (T, P, nature du précurseur carboné et du catalyseur) sur les cinétiques de croissance et de désactivation, ainsi que sur la nature et la quantité des espèces carbonées désordonnées produites. Enfin, l’influence de la température et de la pression partielle de précurseur sur le diamètre des nanotubes formés a également été étudiée. Ce travail a finalement conduit à la mise en évidence de plusieurs processus élémentaires impliqués dans : l’activation, la croissance, la désactivation, la qualité structurale, la pureté et la sélectivité en diamètre des nanotubes. / This work presents a study of the Single-Walled Carbon Nanotubes growth mechanisms by in situ Raman measurements. The first part of the manuscript is devoted to the determination of the temperature and precursor partial pressure limits of the Single-Walled Carbon Nanotubes growth domain. Furthermore, in situ Raman spectroscopy allows to correlate structural information and kinetics: this approach permits to study the influence of the main synthesis parameters (T, P, nature of the carbon precursor and of the catalyst) on the growth and deactivation kinetics, and on the nature and the quantity of disordered carbon species synthesized. Lastly, a study on the temperature and precursor partial pressure effects on the nanotubes diameters is reported. All the data collected have finally led to a discussion about the elementary processes involved in: activation, growth, deactivation, structural quality, purity and diameter selectivity of Single-Walled Carbon Nanotubes.

<div>Understanding grain growth in dielectric ceramics is essential to controlling the electrical and mechanical properties necessary to produce ceramic capacitors and sensors. The effect of alloying barium titanate with strontium titanate on the equilibrium crystal shape was investigated in order to determine possible impacts on grain growth. The equilibrium crystal shape was studied through three experimental methods to identify possible changes in grain boundary energy or anisotropy with changing composition.</div><div>The first method was by imaging intergranular pores to observe faceting behavior and relative interfacial energies. Intergranular pores were reconstructed to determine the relative surface energies of the identified facets. The second method was to perform atomic force microscopy on surface facets to collect topography data. The topography data was combined with orientation data obtained by EBSD analysis from the same region, and used to calculate the normal vector of the surface facets. These datasets were plotted in a stereographic projection to study the faceting anisotropy. The third method involved collecting EBSD orientation data and images of surface faceting behavior. The surface faceting behavior of each grain was categorized by type of facet and plotted on a stereographic projection at the corresponding orientation. This allowed for the analysis of faceting transitions and the differentiation of faceted and continuous regions of the equilibrium crystal shape. The analysis of faceting behavior across compositions has implications on grain growth of the barium titanate/strontium titanate system.</div>

A novel 2SSS (2 Step Solid Selenization) CIGS (Cu, In, Ga, Se) thin film solar cell recipe was developed which can be a replacement to the conventional co-deposition process usually employed for large-scale manufacturing. The co-deposition procedure is faced with multiple problems such as selenium incorporation, effective gallium incorporation in the absorber. It is a 2-step proprietary procedure with better control over growth mechanisms and material utilization for the absorber layer for the CIGS thin film solar cells. It makes use of solid selenium source as preferred by manufacturers. Each step of the 2-step procedure was dealt with separately for stoichiometric analysis and interesting trade-offs between materials such as gallium, indium and selenium was found. Solar cells with this proprietary absorber were fabricated on soda lime glass substrates. Results of the solar cells made with the 2SSS process matched with that of the co-deposition process with the quantum efficiencies near 80% of the co-deposition cells. These experiments are going to serve as the test bed for the pilot line that is intended to be installed at USF's research campus soon. The finished solar cells were characterized. The scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were some of the important tools during the analysis of stoichiometry and structural properties. The device performances were measured with the help of current-voltage (I-V) testing and quantum efficiency (QE) measurements.

Junctions are the key component for 3D carbon nanotube (CNT)-graphene seamless hybrid nanostructures. Growth mechanism of junctions of vertical CNTs growing from graphene in the presence of iron catalysts was simulated via quantum mechanical molecular dynamics (QM/MD) methods. CNTs growth from graphene with iron catalysts is based on a ‘‘base-growth’’ mechanism, and the junctions were the mixture of C-C and Fe-C covalent bonds. Pure C-C bonded junctions could be obtained by moving the catalyst during CNT growth or etching and annealing after growth. The growth process of 3D CNT-graphene junctions on copper templates with nanoholes was simulated with molecular dynamic (MD) simulation. There are two mechanisms of junction formation: (i) CNT growth over the holes that are smaller than 3 nm, and (ii) CNT growth inside the holes that are larger than 3 nm. The growth process of multi-layer filleted CNT-graphene junctions on the Al2O3 template was also simulated with MD simulation. A simple analytical model is developed to explain that the fillet takes the particular angle (135°). MD calculations show that 135° filleted junction has the largest fracture strength and thermal conductivity at room temperature compared to junctions with 90°,120°, 150°, and 180° fillets. The tensile strengths of the as-grown C–C junctions, as well as the junctions embedded with metal nanoparticles (catalysts), were determined by a QM/MD method. Metal catalysts remaining in the junctions significantly reduce the fracture strength and fracture energy. Moreover, the thermal conductivities of the junctions were also calculated by MD method. Metal catalysts remaining in the junctions considerably lower the thermal conductivity of the 3D junctions.

Cette étude est dédiée à la compréhension du processus de granulation humide en mélangeurs à haut taux de cisaillement. Une étude systémique et méthodologique a été menée permettant l'investigation de l'influence des paramètres opératoires, de la technologie employée et des propriétés physico-chimiques des matières premières. Cette investigation est réalisé a travers des techniques de caractérisation morphologiques, rhéologiques et mécaniques. En reliant les courbes de couple enregistrés lors de la granulation humide à la cinétique de croissance des granules, aux caractérisations microscopiques et aux propriétés mécaniques des granules la prédiction du comportement lors de la granulation devient possible. La caractérisation des propriétés mécaniques des granules a été étudié à deux échelles: à l'échelle du milieu humide la consistance a été caractérisé par un rheometre à torque et à l'échelle de l'agglomérat sec la résistance mécanique a été caractérisé par des mesures de compression directe des grains individuelles. Cette approche permet d'avoir des informations complémentaires permettant de mieux décrire l'évolution des courbes de couple dépendantes de propriétés de la masse humide et la compétition entre les forces interfaciales et visqueuses conditionnant la qualité des grains secs résultés. Les paramètres investigués par cette approche sont l'effet du taux de remplissage du réacteur, l'effet de la vitesse d'agitation, de la présence et de la conception de l'émotteur, de la conception du réacteur employé, des propriétés physico-chimiques de la solution liante et des propriétés des mélanges binaires des poudres hydro-solubles / hydro-insolubles. / This study is dedicated to the understanding of the wet granulation process in high shear mixers. A systematic study has been carried out that allows the investigation of the influence of operating conditions, technology and physico-chemical properties of the starting materials. This investigation is achieved by morphological, rheological and mechanical characterization methods. By linking recorded torque curves during the granulation process to granule growth kinetics, microscope characterizations and to the end-granule properties granulation outcome prediction becomes possible. The characterization of the mechanical properties has been done at two scales: at the granule bed scale the bulk wet mass consistency has been determined on a mixer torque rheometer, at the granule scale single dry granule direct compression tests were carried out. This approach gives complementary information allowing better description of the torque curves directly related to the wet mass properties and the competition between static and viscous forces conditioning the dry end granule quality. The factors investigated in this study are: the effect of fill ratio, impeller speed, chopper presence and design, mixer design, binder physico-chemical properties and formulation properties for binary water-soluble / water insoluble powder mixtures.

CdSe quantum dots produced by organometallic synthesis are useful as tunable emitters for photonic devices and as multi-colored protein markers for biomedical imaging, applications requiring bright and narrow emission. A diffusion-limited model helped monitor growth rates via photoluminescence and absorbance spectroscopy, in order to characterize synthesis kinetics in stearic acid, dodecylamine, and in trioctylphosphine oxide. The nucleation rate increased with Se concentration, while the growth rate followed the Cd concentration. Emission peak widths, emission redshift rates, nanocrystal growth rates, and reactant concentrations all decreased to a minimum when emission reached the critical wavelength, at a reaction completion time, tc. The temperature dependence of 1/tc and of redshift rates followed Arrhenius behavior governed by activation energies, which were tailored by the choice of solvent. Synthesis in solvents, such as stearic acid, with lower activation energies produced faster initial nanocrystal growth and longer critical wavelengths. The highest photoluminescence quantum yield was generally at wavelengths shorter than the critical wavelength, when moderate growth rates enabled surface reconstruction while precursors were still available. / Ph. D.

Les films de ZrO2 pur sont déposés par MOCVD (Metal-Organic Chemical Vapor Deposition) en variant de nombreux paramètres du processus. L’influence des conditions de dépôt sur l’évolution de la microstructure (morphologies, structure cristalline/phase, texture et contrainte résiduelle) a été étudiée et clarifiée. Par des analyses approfondies des résultats expérimentaux, trois mécanismes typiques de croissance de dépôt de ZrO2 ont été proposées. Les contraintes de croissance de compression sont en relation directe avec la diffusion atomique et la quantité d’espèces piégées dans les films. La formation de la texture cristallographique est complexe et deux types de textures ont été analysées dans la phase tétragonale : la texture de fibre {1 1 0}t est contribuée par l’effet superplastique des nano-cristallites de ZrO2 et par la contrainte de croissance de compression ; tandis que la morphologie en facette est due à la croissance concurrentielle de différents plans cristallographiques. La stabilisation de la phase tétragonale de ZrO2 a été analysée et discutée. En plus de la taille critique des cristallites, la stabilisation de la phase tétragonale est favorisée par deux autres mécanismes : la grande quantité des défauts cristallins et la morphologie des cristallites. / Pure ZrO2 films were deposited by MOCVD (Metal-Organic Chemical Vapor Deposition) by varying the deposition parameters over large range. The influence of deposition conditions on the evolution of the microstructure (morphology, crystal structure / phase, texture and residual stress) was studied and clarified. Through careful study and analysis of experimental results, three typical mechanisms of deposition of ZrO2 have been proposed. The compressive growth stresses are directly related to atomic diffusion and the trapped-in effects during deposition. The formation of crystallographic texture is complex and two types of textures were analyzed in the tetragonal phase: the fiber texture {1 1 0}t is supposed to be the result of the effect of superplastic of ZrO2 nano-crystallites and the compressive growth stress, while the facet morphology (the {0 1 1}t fiber) is due to the competitive growth of different crystallographic planes. The stabilization of the tetragonal phase of ZrO2 was analyzed and discussed. In addition to the critical size of crystallites, the stabilization of the tetragonal phase can be favored by two mechanisms: the large amount of crystal defects and morphology of crystallites.

L’Oxydation par Plasma Electrolytique (PEO) est un procédé de traitement de surface des alliages métalliques légers (Al, Mg, Ti) qui permet de faire croître des couches protectrices d’oxydes épaisses et dures sur ces matériaux. Pour dépasser les limites de l’anodisation, le procédé PEO repose sur la génération de micro-Décharges anodiques résultant du claquage de la couche diélectrique dans un électrolytique aqueux sous l’effet d’une densité de courant ou d’une différence de potentiel élevées (typ. 20 A/dm2 ; 700 V). Les objectifs de ce travail sont d’une part d’étudier les caractéristiques des micro-Décharges (composition chimique, densité et température électronique) et leur comportement macroscopique (conditions d’amorçage, densité surfacique, taille, durée de vie), et d’autre part de corréler ces études aux mécanismes de croissance des couches d’oxydes dans différentes conditions électriques (forme du courant bipolaire pulsé) et de composition d’électrolytes alcalins. Ces études couplées ont permis notamment de mettre en évidence que le passage en régime d’autorégulation (précédemment identifié) s’accompagne de la croissance d’une couche spongieuse, vraisemblablement amorphe, autour et dans les fissures de structures composées d’alumine cristallisée et résultant des claquages diélectriques. De même, la caractérisation de couches traitées PVD + PEO a conduit à améliorer la compréhension de certains mécanismes de claquage intervenant dans le procédé PEO, et en particulier les processus à l’interface couche d’oxydes - substrat. Enfin, une étude spécifique des micro-Décharges cathodiques (inhabituellement observées en PEO) a conduit à proposer des mécanismes de claquage de la couche diélectrique durant cette demi-Période cathodique du courant. Il a en outre été montré que, bien que l’alternance négative du courant soit nécessaire pour améliorer la croissance des couches d’oxydes, les micro-Décharges cathodiques ont un effet néfaste sur celle-Ci. Il est ainsi nécessaire de contrôler la forme d’onde du courant appliqué afin d’éviter la génération de telles décharges / Plasma Electrolytic Oxidation (PEO) is a surface treatment of light metallic alloys (e.g Al, Mg, Ti) that makes possible to grow thick and hard oxide protective coating on those materials. To overcome the limitations of anodizing the PEO process takes benefit of anodic micro-Discharges resulting from the dielectric breakdown in an aqueous electrolyte under a high applied current density or voltage (typ. 20 A/dm2; 700 V). Therefore this work aims first at studying both the macroscopic parameters (breakdown conditions, surface density, lifetime, size) of such micro-Discharges and their behavior, and second to correlate these studies to the growth mechanisms of the oxide coatings within various electrical (applied current waveform) conditions and alkaline electrolyte composition. These coupled studies allowed us to evidence that the transition from arc regime to soft regime (previously determined) corresponds to the growth of a loose spongy silicon-Rich phase which is likely amorphous, inside and around cracks of the pancake structures issued from the dielectric breakdown and composed of crystalline alumina. Meanwhile, analyses of combined PVD + PEO coatings lead us to improve our understanding of some breakdown mechanisms occurring during the PEO process, with a particular attention to the phenomena at the coating-Substrate interface. Finally, a particular study of cathodic micro-Discharges (unusually observed in PEO) allowed us to propose breakdown mechanisms of the dielectric layer during that negative half-Period of the current. Besides it has been shown that those cathodic micro-Discharges are detrimental to the layer growth though the cathodic half-Period of the current is mandatory to improve the coating growth. It is therefore necessary to manage the current waveform to avoid creating such detrimental discharges

Due to the increasing use of cyclically loaded cast aluminum components in automotive and aerospace applications, fatigue and fatigue crack growth characteristics of aluminum castings are of great interest. Despite the extensive research efforts dedicated to this topic, a fundamental, mechanistic understanding of these alloys' behavior when subjected to dynamic loading is still lacking. This fundamental research investigated the mechanisms active at the microstructure level during dynamic loading and failure of conventionally cast and SSM Al-Si-Mg alloys. Five model alloys were cast to isolate the individual contribution of constituent phases on fatigue resistance. The major constituent phases, alpha-Al dendrites, Al/Si eutectic phase, and Mg-Si strengthening precipitates were mechanistically investigated to relate microstructure to near-threshold crack growth (Delta Kth) and crack propagation regimes (Regions II and III) for alloys of different Si composition/morphology, grain size, secondary dendrite arm spacing, heat treatment. A procedure to evaluate the actual fracture toughness from fatigue crack growth data was successfully developed based on a complex Elastic-Plastic-Fracture-Mechanics (EPFM/J-integral) approach. Residual stress-microstructure interactions, commonly overlooked by researches in the field, were also comprehensively defined and accounted for both experimentally and mathematically, and future revisions of ASTM E647 are expected.