In this study, three types of WC based coating were characterised in terms of both microstructure and performance in abrasive wear, corrosion and a combination of both. The coating types were high velocity oxy-fuel (HVOF) sprayed WC-Co and WC-CoCr and a tungsten carbide-nickel alloy weld-overlay plasma transferred arc welded (PTAW) coating . For the PTAW deposit, the nominal carbide content was varied. All coatings were characterised using x-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) analysis. The abrasive wear behaviour of the coatings was examined using micro-scale abrasion and dry sand rubber wheel (DSRW) abrasive testing. Corrosion behaviour of the coatings in sulphuric acid and alkaline drilling fluid were assessed through potentiodynamic testing. In addition, the combined effect of abrasion and corrosion was assessed through the use of micro-scale abrasion. Both HVOF coatings contained angular carbides with size of N 0.5 to 5 ~lm. The main carbide is WC in both HVOF sprayed coatings. In contrast, the carbides in the PTAW coating are a combination of WC and W2C, are spherical in shape and are much larger than those in the HVOF-sprayed coatings, being N 40 to 150 f.lm in diameter. Due to variation of carbide distribution through the coating resulting from carbide sinking during solidification in PTAW coatings, the local carbide content is considered when discussing the coating behaviour. It has been shown that the wear behaviour is strongly dependent on the relative size of the carbide and the abrasive employed in the test. The wear rate was shown to decrease with increasing local carbide content in the PTAW coatings. The precipitates in the matrix phase of the PTAW coating actively contribute to increasing the wear resistance of these materials. Both HVOF coatings have similar wear resistances to each other when abraded with either alumina or silica abrasive in both the micro-scale abrasion and DSRW test. In micro-scale abrasion, the wear rate of PTAW with the largest fraction of carbides (65 wt%) was approximately 1.5 times that of the HVOF-sprayed coatings when abraded with alumina, but was more than ten times that of the HVOF-sprayed coatings when abraded with silica. In contrast, in DSRW abrasion, the wear rate of PTAW with the largest fraction of carbides (65 wt%) was approximately twice that of the HVOF-sprayed coatings when abraded with alumina, but was only around half of that of the HVOFsprayed coatings when abraded with silica.

Daylight simulators are widely used in industries for visual assessments and internal light sources of colour measuring instruments. As the CIE defined its standard daylight illuminants based on a combination of various measurement results, the precise realisation of CIE daylight illuminants is virtually impossible. Daylight simulators have therefore been developed to simulate the CIE daylight illuminants only approximately. The variety of daylight simulators used in practice caused a big concern on the quality of daylight simulators for industrial colour quality control. This study aims to investigate the variations of practical daylight simulators and the performances of standard methods including the BS950 band value method, CIE metamerism index method and CIE colour rendering index method for evaluating daylight simulators. The study also aims to reveal the discrepancies between various standards for specifying daylight simulators and to highlight the influence of these discrepancies on industrial colour quality control. An industrial survey on viewing cabinets was first carried out. The variations of D65 and D50 simulators accumulated were analysed in terms of colorimetric and spectral results. The results show that the D65 simulators generally performed better than the D50 simulators with higher CIE metamerism index and colour rendering ratings. The filtered tungsten lamps exhibit the best quality while the three-band fluorescent lamps show the worst quality. It was also found that both the CIE and ISO might not give appropriate specifications for the chromaticities of daylight simulators, i. e. too lenient for the former and too strict for the latter. A psychophysical experiment using real metameric pairs was conducted for evaluating the quality of six D65 daylight simulators. It was found that in general, all the simulators studied agreed well with each other in terms of the visual results, except for the three-band fluorescent lamp. The results show that BS 950 band value method and CIE metamerism index method are equally reliable for evaluating the quality of daylight simulators. It was also revealed that a simulator having band-value deviations well below the BS 950 tolerance corresponds to a high CIE metamerism index rating and therefore is judged as good qualitySeven metamer sets were generated based on different principles. These metamer sets were used to compare various metamerism indices for quantifying metamerism as well as to evaluate two methods, goodness-of-fit of SPD and CIE metamerism index for assessing daylight simulators. The results show that the measure of goodness-of-fit of SPD does not agree well with the CIE metamerism index method. It was proved that the CIE metamers are representatives of real metamers, however, the CIE metamer set gives smaller colour differences for the test simulators because it exhibits lower metamerism degree comparing to the generated metamer sets. It was also found that a limited number of metamers could be selected from a range of real metamers to perform as effective as the CIE set for evaluating daylight simulators. The CIE colour rendering index method for evaluating daylight simulators was investigated using the CIE test colours and new sets of test colours. It was found that the CIE test colour sets agreed better with the paint sample sets than with the textile or thread sample sets. The four colour difference formulae, CIELAB, CMC, CIE94 and CIEDE2000, exhibit a similar performance for 'calculating CIE colour rendering index, and they all outperform CIEU*V*W*. No significant difference was found for the performance between two chromatic adaptation transforms, von Kries and CMCCAT2000. The results also show that it might be more appropriate to adopt the total CIE test colours instead of the first eight colours for calculating CIE colour rendering index. A new set of test colours, selected from the CIE'and other test colours for showing medium to large colour inconstancy as well as covering a large colour gamut, was proved to have a better performance than the CIE test colours. " `" Finally, a method was developed for optimisingthe spectral power distributions of daylight sithulators. Significant improvements' inquality were' achieved for the test lamps after the optimisation. A guideline for viewing cabinet design was also proposed based on the relevant standards and information accumulated from the industrial survey on viewing cabinets

In the continuous dyeing of polyester/cellulose blends, the trend over the last 20 years, towards shorter production runs and greater numbers of fashion shades, has led to the development of more productive processes, in particular, the use of a onepass Pad-Dry-Thermofix-Wash-off process for the application of disperse and reactive dyes. However, there are limitations to such a one-pass process, of which the most important is the colour depth that can be achieved on polyester/unmercerisedc otton blends, economically. The current study, which has focused on the performance of the dyes (disperse/reactive) used in DyStar's one-pass (TTN) continuous dyeing process, showed that it was the reactive dyes, which were responsible for the difficulty in achieving heavy shades, economically. It also suggested that the level of reactivity of the medium - low reactive dyes, most commonly recommended for use in this process, was not the prime reason for the poor performance in the one-pass process. The constituents of the pad liquor were varied to determine if the visual colour yield of selected reactive dye could be improved. In so doing, it was possible to speculate whether the low colour yield from some of the reactive dyes used in the one-pass process was due to inefficient `delivery' of the dye to the reactive sites on the cotton. It was also observed that, in a modification of the one-pass (TTN) continuous dyeing process, fixation efficiency of the reactive dyes but not the visual colour yield can be improved up to the level of that on mercerised cotton, if humidity (approx 25%) is injected during the drying stage @ 110°C. Furthermore, in the case of the yellow reactive dyes currently recommended for use in the process, the level of hydrophilicity (number and distribution of sulphonate groups) was a more important factor than the level of reactivity, in improving the fixation efficiency of these dyes on unmercerised cotton.

No description available.

The principal aims of this project are to develop an understanding of colour and constitution relationships and the factors which influence the fluorescence properties in benzoxazinone-based fluorescent dyes, aza analogues of coumarin dyes, to explore the synthesis of a range of these benzoxazinone-based fluorescent dyes and to investigate their UV/visible and fluorescent spectral properties. A particular focus of this investigation was optimized of the synthesis of the dyes and the effect of solvents and other environmental influences on the electronic absorption and emission spectra of the dyes which might be usefully explored to give biological probe molecules. Molecular modeling studies using the CAChe system (AMI, MM2 PM3, ZINDO calculations) and PPP-MO calculations were used to investigate relationships between the chemical structure, spectral properties and technical performance. Reasonable spectral correlations were found using PPP-MO calculations to predict the colour of the benzoxazinone dyes. Weak solid-state fluorescence was observed under UV-light for the benzoxazinone dyes. This interesting feature was investigated in two cases by x-ray crystallography to explore the reasons for this observation. A test for cytotoxicity was carried out on benzoxazinone and coumarin dyes by the ISO 10993-5 method, which showed slight toxicity for the dyes. On the basis of the results of the investigation it was concluded that the benzoxazinone dyes have potential as probe molecules for biological application. Textile dyeing procedures using the dyes as disperse dyes for polyester were optimized. Colour measurement and assessment of fastness properties were carried out on the dyed fabrics.

Photochromic dyes are a very important and relatively novel class of dyes. The usual, though not exclusive, behaviour of these dyes is to show a reversible colour change from colourless to coloured when exposed to UV light. Among the photochromic dye classes, spirooxazines and naphthopyrans were selected for investigation. An attempt was made to construct molecules with a permanent chromophore (azo) in spirooxazines as well as naphthopyrans separately, with a view to providing a colour change from one colour to another. Three different isomers of dihydroxynaphthalene were used as one group of starting materials for the synthesis of spirooxazines with the introduction of the azo (hydrazone) chromophore by coupling. Other starting materials used were anthraquinones, naphthoquinones and pyrazolones. A range of molecular modelling techniques (molecular mechanics, MM2 and quantum mechanics, AM1) using the CAChe system, were applied to predict optimized geometrical conformations and energies of the ring-closed form and ringopened merocyanine forms of all the dyes. PPP-MO calculations were also carried out to predict the potential colour of the dyes. The dyes were characterized using DSC, FTIR, NMR, UV-Visible spectroscopy and elemental analysis. The photochromic properties of one of the azospirooxazines was subjected to a detailed study under different experimental conditions, and showed a unique slow colour change from orange to grey.

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No description available.

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The understanding of the dyeing of cellulosic fibres has been limited by the lack of fundamental knowledge about the structures and processes that occur on the molecular scale. The work reported in this dissertation has begun to address some of the areas where greater insight into these structures and processes is required. This information can then be used as input into existing empirical models of the dyeing process used in industry. The solid state structure of various cellulosic fibres were investigated using carbon-13 cross polarisation/magic angle spinning nuclear magnetic resonance (<SUP>13</SUP>C CP/MAS NMR) spectroscopy. The percentage crystallinities and the proportions of the different crystalline forms of cellulose, Iα, Iβ and II, in each sample were calculated from lineshape analyses of the spectra. The presence of cellulose II in mercerised cotton was confirmed and it is proposed that the degree of mercerisation is indicated by the percentage crystallinity and the proportion of cellulose II present in the sample. The pulsed-gradient spin-echo (PGSE) NMR technique has been used to characterise the self-diffusion of water within various cellulose samples. A new model, defined by a three-component diffusivity, has been proposed to describe this diffusion and it is consistent with the known structures of various cellulosic fibres, such as native cotton and Tencel. It is also proposed that some of the variations in dyeability of cellulose fibres might be partially explained by the observed differences in the self-diffusion of water within the samples. The characterisation of the self-diffusion and aggregation of acid dyes in aqueous solution has been investigated for the first time using the PGSE NMR method. The results found agree well with the literature, and the main trends, such as an increase in the average aggregation number caused by a corresponding increase in dye molecular weight, dye concentration or addition of NaCl, were observable by this method. Finally, the self-diffusion of dye molecules within cotton fibres was investigated using the PGSE NMR technique. Not all dyes could be studied using this method as it was found that an increase in the affinity of the dye for the cotton fibre surface caused the dye molecules to be associated with fast relaxation times and therefore become 'invisible' to the NMR experiment. Major variations were apparent when comparing the diffusion of dye within the unmercerised and mercerised cotton. It is proposed that this difference is found because of the increased affinity of dyes towards the surface of mercerised cotton.