Th. doct.-ing.--Méc.--Toulouse--I.N.P., 1981 : 181.

Th. doct.-ing.--Besançon, 1977. N°: 77.

In this thesis we investigate various aspects of SAW devices and strain sensitive spin species in ZnO and LiNbO₃ for coupling surface acoustic waves to spin ensembles. Firstly, we performed a series of ESR experiments exploring the potential of Fe³⁺ impurities in ZnO for spin-lattice coupling. This spin system has already been identified as a high potential quantum technology component due to its long coherence time. We show that the system also has good properties for spin-lattice coupling experiments, with a strain-coupling parameter G₃₃ = 280 ± 5GHz/strain, which is about 16 times larger than the largest reported for NV centres in diamond. We found that the LEFE effect as well as the spin Hamiltonian parameter D have a linear temperature dependence. As the relative change in each coincide, this strongly supports the notion that the modification of D by an electric field is a multiplicative effect rather than an additive one, D = D₀(1 + κΕ). The LEFE coefficient we measured is several times larger for Fe³⁺:ZnO than for Mn²⁺:ZnO. Secondly, we have fabricated and characterised SAW devices on bulk ZnO crystals and Fe doped lithium niobate. We found that the nominally pure ZnO was conductive at room temperature due to n-type intrinsic doping, and electrical losses inhibited any transmission through a SAW delay line above T = 200K. The one-port resonator measured down to milli-Kelvin temperatures showed excellent quality factors of up to Q ≃ 1.5 x 10⁵ in its superconducting state. Finally, we performed a surface acoustic wave spin resonance (SAWSR) experiment using a one-port SAW resonator fabricated on Fe²⁺:LN. We observed a clear signal at T ≃ 25 K, at a field near the expected one for a Δm_s = 2 transition between the |−1⟩ and |+1⟩ states. We concluded it to be a transition induced by acoustic coupling since the signal intensity did not tend to zero when the magnetic field was parallel to the crystal anisotropy axis. Furthermore, this tells us that the coupling is due to a modulation of the E zero-field splitting parameter rather than D. We investigated the dependence on microwave power and found the saturation limit. We performed a measurement of Fe³⁺:LN as well to reassure ourselves that the resonance is not magnetically excited by the field around the IDT.

Ce travail de thèse, porte sur le développement d’une technique originale de traitement de surface par jet d’azote cryogénique. Ce procédé a été initialement développé pour le décapage et le nettoyage des surfaces. Il est ici utilisé pour obtenir un durcissement superficiel sans altération ou endommagement de la surface du matériau traité. Sous certaines conditions, dans un premier temps, nous avons appliqué la technique jet d’azote en conditions statiques de traitement afin de cartographier les domaines d’utilisation du jet en fonction des paramètres de procédé (distance de tir et temps d’exposition). On montre, un durcissement superficiel sans endommagement de la surface du matériau cible (acier austénitique AISI 316L). L’influence de la distance à laquelle la surface est traitée (distance de tir) et le temps d’exposition du jet sur l’évolution de la microstructure, le durcissement et l’endommagement en surface de l’acier AISI 316L a été étudiée. Des analyses par microscopie électronique à balayage, des analyses d’images ainsi que des mesures de microdureté ont été effectuées sur les microstructures des surfaces traitées pour quantifier les effets de traitement par jet d’azote. Le durcissement en surface, du essentiellement à la transformation martensitique, est ainsi quantifié selon les conditions d’essai. Dans un second temps, un traitement en conditions cinématiques a été réalisé en vue d’obtenir un durcissement superficiel sans endommagement de matière. Les essais de traitement en conditions cinématiques ont été essentiellement réalisés sur les surfaces d’aciers austénitiques instables, l’AISI 316L et l’AISI 304L et, ponctuellement sur l’acier stable, l’AISI 310s. L’influence de la vitesse d’avance du jet et la pression de consigne sur l’évolution de la microstructure, les fractions de martensites formées et le niveau de durcissement en surface d’aciers AISI 316L et AISI 304L ont été étudiées. Les analyses EBSD, MEB ainsi que les mesures de microdureté réalisées sur les surfaces traitées ont permis de mettre en évidence le lien entre le niveau de durcissement et la quantité de martensite induite. Le durcissement de la surface de l’acier AISI 310s, qui reste très faible comparé à celui d’aciers instables, est le résultat de l’écrouissage de sa phase austénitique. Il a été également montré qu’un traitement avec un double passage du jet conduit à l’amélioration de la microdureté en surface des trois aciers traités / This work focuses on the study of an original surface treatment technique that uses supercritical cryogenic nitrogen jet. This process was initially designed for environmentally friendly surface cleaning, where indeed such gas recycles in the air after operation. In the present work, this technique is implemented for surface hardening use without damage of the surface to be treated. Two types of operation cases are studied: static jet tool impingement, cinematic using jet tool scanning on the top surface. In fact, these two static and cinematic treatment cases can be used in industrial operations. In the first stage, the treatment was performed under static conditions in order to map the domains of use of the process. Variation of the experimental parameters (standoff distance and dwell time - treatment time-) made possible to define several uses of the nitrogen jet. In particular the hardening without any damage of the surface of the material to be treated such as AISI 316L stainless steel. Thus, the influence of the standoff distance and the dwell time on the evolution of surface microstructure and damage and hardening was studied. To quantify the effects of nitrogen jet on the microstructure, SEM (Scaning Electrons Microscope) observations and micro hardness measurements were carried out on the treated surfaces. As a result, for different conditions of treatment, the relationship between hardness and martensite rate during surface transformation process, is shown and plotted. Secondly, we focus on hardening without surface damage. The treatments were essentially carried out on both AISI 316L and AISI 304L metastable stainless steels. The influence of both torch velocity and jet static pressure on the variation of microstructure, martensite fractions and hardening level, was also studied and discussed. Thanks to both SEM/EBSD analysis and micro hardness measurements, the relationship between martensite rate and increase of hardness, is highlighted. It is also established that the treatment using several passes allows to increase the surface micro hardness without damage. Finally, it is found that, for some particular working parameters, the nitrogen jet process can also be used for surface hardening without martensitic transformation

Active sound control (ASC) based on surface potentials is one of two methods of noise control using potential-based method. The method does not require detailed knowledge of the noise source parameters, boundary conditions, characteristics of the acoustic medium or the transmission path. It allows significant volumetric noise cancellation inside the shielded region using only the knowledge of the total acoustic field which includes the wanted sound at the boundary of the shielded region(s) to obtain additional secondary sound sources known as controls which are distributed at the boundary of the shielded region. It allows the presence of a wanted sound inside the shielded region, which it preserves while canceling the noise. In contrast, other methods require various detailed knowledge. In many cases, they do not allow the wanted sound to be generated inside the protected region. The aim of this thesis is to implement numerically the ASC method in 3D bounded regions and confirm its theoretical predictions. The theoretical framework for the method has already been established in previous related literature. Experimental work in this area is mostly limited to laboratory experiments in one dimensional settings. The algorithm was tested in 3D numerical test cases in the frequency domain involving single and composite regions. The Helmholtz equation was used to model the wave propagation. In both single and composite regions, volumetric noise cancellation of over 20 dB was achieved at most areas of the shielded regions. Outside the shielded region, the field remained practically unchanged during noise cancellation. On the other hand, in test cases involving wanted sound, the noise inside the shielded region was canceled while the wanted sound was preserved. However, outside the shielded region, the field was amplified. Moreover in composite regions, the selective cancellation/propagation of the wanted sound was demonstrated successfully in regions having two and three sub-regions by allowing the wanted sound to propagate to one region but not to the other. To enforce selective propagation of the wanted sound, additional steps are required to obtain the separate field of the wanted sound in addition to the total field. A study on the effect of the number of controls on noise cancellation showed that in both single and composite regions, as the number of controls fell there was a corresponding decrease in the level of noise cancellation. A doubling of the number of controls yields about ~3 dB of noise cancellation, and vice versa. The independence of the operation of the algorithm on characteristics or number of noise sources, shape, size or position of shielded region is also demonstrated via further test cases. In all test cases considered, the results confirmed the theoretical predictions. However, at resonance modes the method did not provide noise cancellation, though at near-resonance modes a lower level of noise cancellation was obtained. Although this work considered only monochromatic waves, the method is applicable to broadband noise. In real-time application of the method, the assumption in the thesis that only the field of the noise source(s) is known does not hold and therefore its implementation is more complicated.

No description available.

The work presented in this thesis consists of two parts: development and application of a novel passive acoustical approach for field measurement of breaking surface waves, and interpretation of the resulting observations in terms of wave field information so as to improve the understanding of wave breaking. The development of the acoustical approach has been motivated by the difficulties inherent in measurement of breaking waves. This approach makes use of an array of four broadband hydrophones which is able to track individual breaking waves by passive detection of the naturally generated sound of wave breaking. The Generalized Cross Correlation method is used to determine time differences of acoustic signals from breaking waves arriving at the array, allowing the breaking waves to be located with the given array geometry. Observations of breaking waves were made by means of this technique during the Surface Wave Processes Program (SWAPP). The spatial and temporal statistics of breaking waves, including breaking wave density, travel velocity, lifetime of breaking and spacing, are obtained from the observations. Statistical models are developed to assess, and where appropriate, correct for any bias resulting from limitations of the measurement approach. The breaking wave statistics provide important information about the physical process of wave breaking and its distribution in different wave fields. It is found that wave breaking in the open ocean occurs at a scale substantially smaller than the scale associated with the dominant wind wave component in the wave spectrum. Numerical simulation of breaking wave statistics and comparison with the observations demonstrates that the scale of breaking can be predicted from the directional wave spectrum by a linear model with a single breaking threshold. These results will provide input to comprehensive models of wave dissipation. Acoustical radiation properties of individual breaking waves are a further aspect of wave breaking that has been observed with the aforementioned technique. Investigation of the sound radiated from breaking waves reveals information both on the nature of the sound generation mechanism by breaking and the dimension of breaking waves. Statistical analysis of the acoustic source intensity associated with wave breaking suggests that the source intensity can be related to the breaking scale and wave energy dissipation, thus implying that surface wave dissipation could be remotely measured by using ambient sound. / Graduate

The unlubricated sliding wear behaviour of gas nitrided, plasma nitrided, and ferritic nitrocarburized BS970,905M39 (EN41B) steels was investigated systematically from an engineering point of view. Commercial nitriding processes were employed, and the wear studies were carried out using a pin-on-disc machine over a wide range of sliding speeds and applied loads. The worn specimens and wear debris were examined by several techniques; including optical and electron microscopy and X-ray analysis. A sharp wear rate transition between mild and severe regimes was identified by varying the load for both untreated and gas nitrided steels. The wear rate was reduced by gas nitriding by up to two orders of magnitude, depending on the sliding condition. Moreover, gas nitriding expanded the mild wear region toward higher loads and sliding speeds. In the mild regime an oxidative wear mechanism operated, contrasting with the metallic wear in the severe regime. Wear maps for untreated and gas nitrided steels have been constructed, which show the dominant regimes of the wear mechanisms. A "wear-face-limited" gas nitrided pin test showed that the benefit of the treatment was lost once the effective surface layer was completely worn away. It is suggested that hardness has a crucial role in determining the wear rate through nitrided diffusion layers. A thick and porous compound layer produced by gas nitriding showed a poor wear behaviour owing to its brittleness, while a thin nitrocarburized E-Fe3N compound layer exhibited a low wear rate. There was no significant difference between the nitride steels in terms of transition load and wear rate. However, the wear lives of the nitrided layers were dependent on their case depth. Severe wear should be avoided in engineering component design, and operating conditions should ensure that only mild wear occurs. Both the hardness profiles and the cost performance of nitriding processes should be considered in the selection of nitriding treatments.

Three norbornane fused dihydro-tetrathiafulvalene derivatives which contained the thiol, disulfide and acetylthio functionalities were synthesised. Cyclic voltammetry was used to measure the redox properties of the compounds, which showed that the molecules were able to undergo two reversible, one electron oxidation processes. X-ray structures of all three functionalities were obtained. The three compounds were sublimed onto Au(111) surfaces, and characterised using a number of surface science techniques. Disordered structures are formed initially for all three compounds when adsorbed at room temperature. Following progressive annealing of the substrate, highly ordered adlayer structures are formed that are believed to be bound to the surface via a gold adatom. Van der Waals and hydrogen bonding interactions are shown to play an important role in the formation of these ordered structures. The adsorption of triphenylphosphine sulfide on Au(111) is also investigated, using a combination of RAIRS and STM experiments. Here an extremely ordered (2√3×2√3)R30º structure is formed immediately upon deposition at 298 K. From the experimental data and DFT calculations, the orientation of the molecule is deduced. The attempted synthesis of a thiol functionalised donor-acceptor compound is also described, with a few previously unknown intermediate compounds being synthesised. Finally, a series of four known aryl amidoximes were synthesised. These were subsequently deposited on a Cu(111) crystal and studied using a vibrational spectroscopy. Three of the compounds were found to decompose to varying degrees during the sublimation process. The possible conformations of the amidoxime group on the copper surface are discussed.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第16407号 / 工博第3488号 / 新制||工||1527(附属図書館) / 29038 / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 岩田 博夫, 教授 田畑 泰彦, 教授 秋吉 一成 / 学位規則第4条第1項該当