Tooth cleaning and household cleaning are common tasks people undertake on a daily basis and they share significant analogies. Both rely on the combined action of a detergent - usually a fluid which may contain abrasive particles - and an applicator on a cleaning surface. While scientific information covers some of the aspects related to abrasive tooth cleaning, such as the main tooth wear mechanisms and the influence of dental care products on tooth cleaning and wear, household cleaning has not been covered in such detail. The aim of this work was to investigate abrasive tooth cleaning and abrasive household cleaning from a tribological perspective in terms of the interactions between human/applicator, applicator/abrasive particles and abrasive particles/substrate, in order to expand the knowledge on both subjects and gather information useful to improve the design of current cleaning products. A study has been carried out by means of a hand operated friction rig to measure the loads applied by human subjects while performing simulated abrasive cleaning operations in order to better understand the interaction between human test subject and applicator. The analysis investigated the loads applied during tooth cleaning processes and household cleaning processes, and the results (from 180g to 4230g for tooth cleaning tests and from 290g to 4.3Skg for household cleaning tests) helped Unilever in developing their friction analysis techniques. Particle entrainment into the contact area between the applicator and the surface has been analysed using two types of test rig- one with a unidirectional motion and the other a reciprocating motion - and an optical apparatus featuring a microscope and a camera for image and video capturing. The scratches produced by abrasive particles were studied with an optical microscope and a Scanning Electron Microscope in order to understand how they scratch the surface during abrasive cleaning processes. The investigation helped to gather information on how abrasive particles were trapped at the tip of the toothbrush filaments and between the cloth fibres and the observation of the scratched surfaces led to identify grooving abrasion as the main wear mechanism taking place in both abrasive tooth cleaning and household cleaning. A friction analysis of both tooth cleaning and household cleaning processes was carried out using the hand operated rig and a friction rig on which the applicators were mounted, to study the connection between the friction coefficient )l and the ability of the particles to remove material from the test surface. It was found that under the adopted experimental conditions, the lubricating action exerted by the carrying fluids in both tooth cleaning and household cleaning is mainly based on boundary lubrication. The values of the friction coefficient determined from the experiments ranged from around 0.20 (in wet condition, without abrasive particles) to 0.37 (in dry condition, without abrasive particles) for brushing tests, and from around 0.20 (in lubricated condition, with 5 urn Calcium Carbonate particles) to 0.66 (in dry condition, without abrasive particles) for cloth tests. The influence of the applied load, the particle size and concentration on friction coefficient was also investigated. Finally, a semi-empirical model was developed to estimate the rate of material removal during a simulated household cleaning process, in order to gather information useful to improve the ability of cleaning fluids to remove stain while reducing the damage to the cleaning surfaces. Results from the modelling were compared with data from reciprocating cleaning tests. Although the model often overestimated the amount of material removed from the test surface due to the assumptions made in order to simplify its implementation, it produced results of the same magnitude order of those obtained from material removal experiments within the ranges of applied loads, particle sizes and concentrations. lJ

Ultrasonics, that is mechanical waves with a frequency greater that 18 kHz. are employed in a number of diverse and distinctive industries. One important niche occupied by ultrasound, and the focus of this thesis, is its application in ultrasonic cleaning systems whereby the rapid pulsing of mechanical waves at ultrasonic frequencies forms thousands of microscopic voids (or cavities) in the liquid. It is the implosions of these voids during the positive pressure phase of the wave that assists th removal of contaminants from the surface of an immersed load and is known as cavitation. A thorough literature review conducted as the foundation of this work uncovered a significant deficit in knowledge regarding the positions of cavitating fields within ultrasonic vessels. Further to this, the effects on the cavitating field of a number of industrially relevant parameters, such as transducer placement. the introduction of baskets and cleaning loads to the liquid and variations in the level of the cavitating medium, were found to be deficient within both academic and industrial knowledge base. The outcomes of the literature review clearly indicated that it was evident that the development of a "toolset" capable of modelling the bulk cavitating fields within ultrasonic vessels would not only sustain the strong industrial relevance of the programme of work, but would also add significantly to extant knowledge concerning the design and production of commercial ultrasonic vessels. This work describes the development of such a toolset, detailing the mathematical modelling behind the simulation system and the logical progression of the work, from basic 2D models used for rapid prototyping to full 3D models used to simulate a wide variety of complex systems with parameters hitherto un-described within the literature. A variety of methods of quantifying the simulation outputs are reviewed and discussed during the thesis, leading to the logical selection of one qualitative and one quantitative indicator of cavitating fields. A comparison of the simulation outputs to the respective empirical data showed an excellent degree of con-elation, leading to a high level of confidence in the simulation toolset. Use of the verified model together with the developed design methodology was used to address the industrially relevant issues detailed in the literature review and this further promoted the contribution to knowledge presented in this work. As in any industrial design. pragmatic approximations were used in the production environment and this occasionally appeared to show discrepancies between the simulation outputs and the practical data obtained. Specific causes behind these differences are critically analysed. and along with further questions arising from such analysis. The outcomes formed the backbone of a future work proposal presented along with a comprehensive review and summary of the results and improved synthesis techniques.

Nous avons étudié la croissance, sur des tissus en polyester, de nano-colonnes de ZnO par méthode hydrothermale. Un prétraitement par plasma a permis de générer des groupements polaires à la surface des fibres. Ces groupements permettent d’accrocher des nano-germes de ZnO à partir desquels d’effectue la croissance des cristaux de ZnO. La nature de la composition chimique de surface à chaque étape du traitement a été suivie par XPS. La morphologie et la structure des cristaux formés a été caractérisée par MEB, XRD et MET. La quantité totale de ZnO déposée sur le tissu a été déterminée par spectroscopie d’absorption atomique. La croissance de ces nano-colonnes de ZnO sur les microfibres de PET génère une structure rugueuse hiérarchique. Les tissus obtenus sont superhydrophiles : le mouillage et la capillarité de l’eau deviennent très importants et augmentent avec la concentration en germes. Après hydrophobisation avec l’ octadecyltrimethoxysilane (ODS), le tissu fonctionnalisé présente un effet lotus autonettoyant avec des angles de contact et de glissement de l’eau caractéristiques. L’effet chimique autonettoyant a été aussi mis en évidence avec la décoloration de solutions et de taches sous rayonnement UV. La cinétique de ces 2 effets photocalytiques a été étudiée avec différents colorants. Ce tissu présente un caractére antibactérien, il est donc aussi autonettoyant vis-à-vis des espèces biologiques Escherichia coli, Pseudomonas aeruginosa et Staphyloccocus aureus. Cette étude met en évidence les relations entre les procédés de nanostructuration de la surface des fibres dans les tissus et leurs propriétés autonettoyantes selon les 3 mécanismes proposés. / ZnO nanorods were grown on polyester fabric by hydrothermal method. The plasma treatment was carried out to generate the polar groups. These groups attached the ZnO seeds which provided the site for the growth of nanorods. XPS analysis was carried out to study the chemical composition of surface at each stage of growth. The morphology and crystal structure was characterized by SEM, XRD and TEM. The atomic absorption spectroscopy was carried out to determine the amount of Zn present on fabric in the form of nanorods. The growth of nanorods on microfibers of PET generated hierarchical roughness structure. The functionalized fabric showed superhydrophilicity: very high wettability and capillarity which increased with the increase in seed concentration. On modification with hydrophobic chemical (octadecyltrimethoxysilane ODS), the functionalized fabric showed physical self-cleaning (lotus effect) which was characterized by measuring water contact angle and water roll off angle. The chemical self-cleaning was studied by solution discoloration and stain degradation under the effect of UV light. It was found that solution discoloration followed first order kinetics whereas; stains were degraded by second order kinetics. The biological self-cleaning (antibacterial activity) was also observed on Escherichia coli, Pseudomonas aeruginosa and Staphyloccocus aureus. This study highlights the relationship between nanostructuring process of the fibers and self-cleaning properties according to the three proposed mechanisms.