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The fumes evolved from hot rubber vulcanisates have concerned industrial hygienists for the last three decades. Analyses of such fumes reveal components as diverse in nature as the chemistry required to yield the finished article.

The present work forms part of a larger programme concerned with the interaction between the processing, structure and properties of rigid PVC compounds.

This thesis investigates the use of CO2 laser radiation to treat concrete surfaces. Specimens were treated with varying laser parameters, and the resultant surfaces were analysed mechanically and chemically. A glass was formed by laser interaction, with underlying decomposition of both the cement paste and aggregate. The application of a cement-based coating prior to processing protects the concrete from excessive temperature rises during treatment. Processing of the coated material resulted in a glazed surface with no decomposition of the concrete substrate. With low energy density, OPC concrete exhibits only surface dehydration. However, when the energy density is increased, a glassy layer, with surrounding and underlying dehydration, is formed. Increasing the spot size results in a change in behaviour when the material is laser treated: several mm of concrete are removed, leaving either rough, bare concrete or a glazed trench. The resulting surface condition is dependent on the laser power. Thermal analysis techniques were used to identify the degradation reactions and the temperatures at which they occur during laser treatment. These are dehydration of the ettringite and ferrite phases at 1149C, dehydration of Ca(OH)2 at 462C, decarbonation of CaCO3 and ejection of material from 8129C onwards and the formation of a fiised glass layer at 1283 `C. The strength of attachment of the glass to the concrete decreases with increasing power or decreasing traverse speed due to the dehydration of the underlying material. The strength also decreases with time after treatment, due to rehydration of CaO. Mechanical failure occurs several mm below the glassy area into the dehydrated substrate, where dehydration of Ca(OH)2 has caused disruption to the structure of the material. The temperature rise in the material was monitored using embedded thermocouples at various depths. A one dimensional theoretical model agrees well with the experimental results over only a limited range of depth and time. A three dimensional finite difference model shows close agreement with experimental results over a range of operating parameters equivalent to those determined experimentally. Operating maps were generated which predict the depths to which the identified reactions occur. II A combination of pozzolanic Portland cement, chamotte, sand and waterglass can be successfully applied to the concrete surface. It acts both as a thermal insulator and provides vitrifiable material for laser treatment. Low power levels drive water out of the coating resulting in dehydration and colour changes, whilst higher power levels result in the formation of a glass on the coating surface. The attachment of the glass shows an area of maximum strength when power levels are below 150 Watts and traverse speeds below 2mm/s. Beyond these parameters the attachment becomes progressively weaker. Thermal analysis of the coating material shows no evidence of Ca(OH)2 dehydration and no decarbonation, resulting in no ejection of material. The underlying concrete is unheated, and therefore undergoes no decomposition reactions. Mechanical failure occurs at the limit of the glassy region rather than several mm below it as with bare concrete. Thus, the weakest point is the interface of the glazed-unglazed regions now that no significant Ca(OH)2 dehydration occurs.

Dans le cadre d’une collaboration entre l’Institut des Matériaux Jean Rouxel (IMN) et STMicroelectronics Tours, cette étude vise à développer un simulateur de gravure du silicium par procédé Bosch. Actuellement utilisé dans le domaine de la microélectronique pour la gravure de vias, le procédé Bosch est un procédé pulsé de gravure par plasma. Un plasma de SF₆ permet la gravure du silicium par voie chimique, par adsorption de fluor atomique en surface du silicium pour créer des molécules volatiles. Un second plasma de C₄F₈ permet de protéger la surface exposée au plasma de gravure chimique, à l’aide d’un dépôt de polymère de fluorocarbonés. Ce polymère est supprimé dans la zone exposée au bombardement ionique. La répétition de pulses SF₆/C₄F₈ permet alors la création de motifs à fort facteur de forme (plus profonds quelarges).Afin de mieux connaître les mécanismes physico-chimiques qui régissent ce procédé, nous avons développé un simulateur de gravure basé sur une approche multi-échelle. Cet outil sert à reconstituer des profils de gravure en fonction des conditions opératoires renseignées (pression, puissance, débit, géométrie du réacteur). Le modèle cinétique calcule les densités et flux d’espèces neutres et ioniques crées dans le plasma. Le modèle de gaine détermine les fonctions de distributions énergétiques et angulaires des ions. Le modèle de surface détermine l’évolution spatio-temporelle des structures gravées par procédé Bosch. Pour calibrer le simulateur, des campagnes expérimentales ont été réalisées à l’IMN sur la phase plasma, ainsi que sur le site STMicroelectronics Tours, sur l’impact des conditions opératoires sur l’évolution des profils de gravure. / Due to a collaborationbetween IMN of Nantes and STMicroelectronics Tours, the aim of this study is the development of silicon etching simulator using Bosch process Nowadays used for microelectronics devices such as 3D capacitors or vias, Bosch process is a cyclic plasma etching process. Two plasmas are needed, a SF₆ plasma to etch silicon by chemical way, using mainly chemical processes. A C₄F₈ plasma which allows the deposition of fluorocarbon species into a “Teflon-Like” polymer, to passivate sidewalls of the trenches and protect them from chemical etching. This polymer is removed by ion bombardment. By the repetition of a large amount of SF₆/C₄F₈pulses, the process leads to the creation of features with a high aspect ratio (a high depth for a low aperture).To develop an intimate knowledge about physical and chemical interactions involved in Bosch process, we develop a simulation tool based on a multiscale approach. This software allows to track the etch profile evolution versus operating conditions (pressure, power, flow rate, reactor diameter and height). Kinetic model provides space-avergaed values of plasma paramters at steady state. Sheath model determines ion energy and angular distribution functions. Surface model manages these data to know temporal evolution of a representative feature into the substrate surface exposed to Bosch process. To validate the model, we carried out some experiments at IMN, dedicated to plasma phase measurements, and at STMicroelectronics Tours, dedicated to the study of the influence of theoperating conditions on the etch profile evolution.

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