This thesis is concerned with the problem of colour shade grading for Industrial Inspection and attempts to find accurate and robust solutions to this problem. The application we are interested in, is the automation of the ceramic tiles manufacturing process so as to replace the human inspectors responsible for the quality control of the product. Therefore our aim is to perform the colour grading in a way which is consistent with what the human experts and subsequently the clients would perceive. First an overview of colour vision, colour measurement and colour constancy is given. Then a method that tackles the problem of colour grading of uniform and patterned surfaces is proposed. This method is the first step towards colour grading since it involves various corrections of the data, so as to provide the necessary precision for any further attempt. The problem of colour grading of random textures is then addressed. A method based on the comparison between colour histograms is proposed, and various statistical aspects involved in the comparison of distributions such as the colour histograms are discussed. Since the real-time implementation of any industrial inspection method should be taken into account, we use a space-effective method of storing colour histograms. Having solved the problem of colour grading for the majority of uniform and textured surfaces, we then try to optimise the performance of the proposed techniques, for cases where it fails. We attribute that to the fact that every electronic sensor captures colour and patterns in a way which only approximates what the human vision system would perceive. First we propose a method of perceptual colour grading of uniform surfaces, which transforms the camera data to data as they would have been recorded by the human eye. This method makes use of metameric data, to determine the relation between the human and the electronic sensors. We use various methods of generating metamers, and we show how the need of a spectrophotometer can be overcome. In a similar way, we propose a method of perceptual colour grading of random textures, which involves the restoration of the electronically acquired data and then their transformation to a colour space which expresses the way we perceive colour texture. We test both methods with real data, and we compare them with the non-perceptual ones. All the methods proposed in this thesis have been tested with real data, from the ceramic tiles manufacturing industry, previously colour graded by human inspectors. The consistency of the methods has been tested by using various sets of all sorts of tiles, and by repeating the acquisition and grading processes many times for every set of tiles. Further, these experiments have been carried out using different apparatuses, thus allowing us to draw conclusions about their quality and to make our methods as hardware independent as possible.

This research involves a study of sane of the methods available for covering material substrates with a metallic coating. The materials studied were metal and ceramic powders, and the research attempted to produce composite powders, which could be used in the powder metallurgy industries as cheaper replacements for existing expensive powders. For example, iron powder particles coated with copper/tin could replace expensive bronze powders in machine bearing production.

M.Tech. (Ceramics) / The research project attempts to fill a void by assembling data dealing with a comprehensive range of South African clay and glaze materials, suited to the needs of the studio potter, and recording test results. South African kaolins, ball clays, fireclays, miscellaneous clays, grogs, bentonites, felspathic materials, alkaline earths, silica, refractory materials (other than clays) and mineral pigments are dealt with. A limited selection of foreign materials, frequently referred to in studio-potter publications, was also used in comparative tests. The materials are recorded with reference to the ultimate analysis, seger formula, proximate analysis (where applicable), properties and results of trials using the materials in clay bodies and/or glazes. It was demonstrated that South African materials are largely of good quality e.g. kaolin, felspars and silica. Variability of clay supplies because of lack of stockpiling and blending practices, especially by small suppliers, is often a problem. When the composition of glaze materials and trials indicated that imported equivalents were superior because of variability of local supplies or poor grade material, then substitutes were tested using South African materials. Basic clay bodies and glazes covering a wide temperature range from Egyptian Paste, low-fired wares such as raku, terracotta-and-white-earthenwares, stoneware and soft-porcelain bodies and glazes are dealt with giving a brief outline of the requirements for each type. Suggestions of suitable South African materials for their composition are made. Trials and results are recorded. The knowledge gained of South African materials available and a study of the materials enables the studio potter to utilize local materials with awareness and confidence

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The aim of this research is to investigate the functions of ceramic vessels from two well-defined contexts at Tell Ahmar that have been dated to the Middle Bronze Age II (c. 1800-1600 BC). In addition, correlations between socioeconomic activities and ceramic production at a local and regional level are further investigated. Since there is no one-to-one relation between vessel type and vessel function, the research adopts a multi-dimensional approach formed by the following hierarchical investigations. Firstly, a ceramic typology for the Middle Bronze Age pottery from Tell Ahmar, the first to be undertaken, is constructed to provide a working platform for further analyses. Secondly, interpretations of vessel functions are made based on the techno-morphological implications of vessel use. Moreover, since the ceramic assemblage under investigation represents the systemic inventory of artefacts in use in the rooms at the time of the site abandonment, function of the rooms and relative associations with the composition of the ceramic room assemblage at Tell Ahmar are investigated. In addition, comparative analysis from Northern Mesopotamian and Syrian sites are used in conjunction to suggest functional activities for the defined vessel shapes at Tell Ahmar. Inferences of vessel function are finally supported by the results of ceramic residue analysis and by epigraphic and iconographic evidence of vessel use. Functional activities (i.e. transport, storage and processing) are further discussed in order to make socioeconomic inferences at both local and regional levels. This analysis indicated that one of the major activities at Tell Ahmar was associated with long-distance transport and storage, while for those shapes characterised by a perforated base, an association with beer production is suggested. At a regional level, a general similarity of vessel shapes is noted, this being stronger among the Euphrates River Valley sites than in Inner Syria or in the Khabur Valley. However, when these similarities are examined in detail, ceramic production indicates some local distinctions. These variations, which are not associated with any ancient political boundaries, may be explained in terms of local preferences and requirements that emerged within long-distance flourishing relationships established during this period.

Boron carbide (B₄C) is a non-oxide ceramic in the same class of nonmetallic hard materials as silicon carbide and diamond. The high hardness, high elastic modulus and low density of B₄C make it a nearly ideal material for personnel and vehicular armor. B₄C plates formed via hot-pressing are currently issued to U.S. soldiers and have exhibited excellent performance; however, hot-pressed articles contain inherent processing defects and are limited to simple geometries such as low-curvature plates. Recent advances in the pressureless sintering of B₄C have produced theoretically-dense and complex-shape articles that also exhibit superior ballistic performance. However, the cost of this material is currently high due to the powder shape, size, and size distribution that are required, which limits the economic feasibility of producing such a product. Additionally, the low fracture toughness of pure boron carbide may have resulted in historically lower transition velocities (the projectile velocity range at which armor begins to fail) than competing silicon carbide ceramics in high-velocity long-rod tungsten penetrator tests. Lower fracture toughness also limits multi-hit protection capability. Consequently, these requirements motivated research into methods for improving the densification and fracture toughness of inexpensive boron carbide composites that could result in the development of a superior armor material that would also be cost-competitive with other high-performance ceramics. The primary objective of this research was to study the effect of titanium and carbon additives on the sintering and mechanical properties of inexpensive B₄C powders. The boron carbide powder examined in this study was a submicron (0.6 μm median particle size) boron carbide powder produced by H.C. Starck GmbH via a jet milling process. A carbon source in the form ofphenolic resin, and titanium additives in the form of 32 nm and 0.9 μm TiO₂ powders were selected. Parametric studies of sintering behavior were performed via high-temperature dilatometry in order to measure the in-situ sample contraction and thereby measure the influence of the additives and their amounts on the overall densification rate. Additionally, broad composition and sintering/post-HIPing studies followed by characterization and mechanical testing elucidated the effects of these additives on sample densification, microstructure development, and mechanical properties such as Vickers hardness and microindentation fracture toughness. Based upon this research, a process has been developed for the sintering of boron carbide that yielded end products with high relative densities (i.e., 100%, or theoretical density), microstructures with a fine (∼2-3 μm) grain size, and high Vickers microindentation hardness values. In addition to possessing these improved physical properties, the costs of producing this material were substantially lower (by a factor of 5 or more) than recently patented work on the pressureless sintering and post-HIPing of phase-pure boron carbide powder. This recently patented work developed out of our laboratory utilized an optimized powder distribution and yielded samples with high relative densities and high hardness values. The current work employed the use of titanium and carbon additives in specific ratios to activate the sintering of boron carbide powder possessing an approximately mono-modal particle size distribution. Upon heating to high temperatures, these additives produced fine-scale TiO ₂ and graphite inclusions that served to hinder grain growth and substantially improve overall sintered and post-HIPed densities when added in sufficient concentrations. The fine boron carbide grain size manifested as a result of these second phase inclusions caused a substantial increase in hardness; the highest hardness specimen yielded a hardness value (2884.5 kg/mm²) approaching that of phase-pure and theoretically-dense boron carbide (2939 kg/mm²). Additionally, the same high-hardness composition exhibited a noticeably higher fracture toughness (3.04 MPa•m¹/²) compared to phase-pure boron carbide (2.42 MPa• m¹/²), representing a 25.6% improvement. A potential consequence of this study would be the development of a superior armor material that is sufficiently affordable, allowing it to be incorporated into the general soldier’s armor chassis.

Este trabalho apresenta uma revisão bibliográfica a respeito dos rejuntes para revestimento cerâmico. A nomenclatura internacional é explorada e os tipos de rejunte e seus empregos são enumerados. Para embasar o leitor sobre o reves-timento cerâmico, os principais conceitos a ele relacionados são exibidos de forma sucinta. Uma vez que o rejunte é um componente importante do revestimento ce-râmico, suas funções dentro desse subsistema são abordadas em detalhes. O as-pecto de alívio de tensões é amplamente comentado, uma vez que essa é uma função essencial do rejunte, particularmente no caso de fachadas. Ao final, são abordados os aspectos de preparo e aplicação dos rejuntes, particularmente os produtos cimentícios. O rejuntamento de locais específicos, como encontros com selantes e interfaces com aparelhos sanitários são detalha-dos com vistas à diminuição da ocorrência de manifestações patológicas futuras. No trabalho experimental, painéis em forma de laje revestidos com placas cerâmicas são submetidos à flexão até a ocorrência de desplacamento, objeti-vando detectar qual a influência da largura da junta e do tipo de argamassa ade-siva na ruptura do corpo-de-prova. Os resultados indicam que a largura das juntas de assentamento assumem importância apenas quando a argamassa adesiva apresenta alta resistência de aderência. / This study presents a bibliographical revision regarding the ceramic tile grouts. Here, the international nomenclature is explored and the types of grouts as well as its employments are enumerated. To base the reader on the ceramic tile cladding, its main concepts are shown succinctly. Being the grout an important component of the ceramic tile cladding, its functions in this subsystem are broached in details. The aspect of stress relief is widely mentioned, for this is an essential function of grout, particularly in the case of facades. In the end, the aspects of the preparation and the application of grouts are broached, particularly the cementitious products. The grouting of specific places such as meetings of sealants and interfaces with sanitary devices is detailed viewing the decrease of the occurrence of future problems. In the experimental study, panels in flagstone form tiled with ceramic plates are submitted to flexion until the occurrence of rupture of these panels, aiming to detect the influence of the joint thickness and of the type of the adhesive mortar in the rupture of the sample. The results indicate that the nesting joint thickness only assumes importance when the adhesive mortar presents high resistance of adherence.