Ultraviolet-induced fluorescence and photo-degradation in zinc oxide watercolour paints

Paper conservators tasked with the care and treatment of collections containing watercolours often encounter paper which has undergone severe discolouration and deterioration around Chinese white pigments, an effect caused by the photocatalytic reaction between surface electrons on the pigment particles and atmospheric moisture, leading to peroxide formation and oxidation of surrounding paper. This discolouration is difficult to treat and best avoided if possible. While conservators use ultraviolet-induced fluorescence to identify zinc oxide pigments by their intense visible fluorescence, they cannot presently relate zinc oxide’s variety of fluorescent colours and intensities to its rate of photocatalysis. This thesis aims to link types of ultraviolet-induced fluorescence with zinc oxide’s photocatalytic behaviour by examining the physical, chemical and optical properties of mock-up zinc oxide pigments in gum medium and historic watercolour painting case studies and determine whether this fluorescence could be quantified using commercially available DSLR cameras for predicting and diagnosing degradation in watercolours. The investigation first collected and summarising art manuals and literature detailing zinc oxide’s history and use as a watercolour pigment. This uncovered a near-consensus in the nineteenth century about the inert nature of zinc oxide, along with evidence that Winsor and Newton, the only supplier for nearly a century, annealed their pigments to improve their working properties and reduce their photoconductivity. No other suppliers could produce a good pigment and there were lone voices warning that zinc oxide may be damaging to surrounding materials. Physical properties of pigments produced by the direct and indirect method as well as commercial and historic case study pigments were examined via x-ray diffraction (XRD), x-ray fluorescence (XRF), energy-dispersive x-ray spectroscopy (EDX) and digital image analysis of micrographs and scanning electron microscopy (SEM) images. XRD and EDX verified the purity of all samples, while XRF revealed a much higher impurity content among direct method pigments than all others. Particle and crystallite sizes and morphologies derived from image analysis of micrographs and SEM images found that commercial and case study pigments were produced by the indirect method, that these had much smaller and shorter crystallites than direct method pigments and that these crystallites were more likely to be photoactive than the long crystallites of the direct method pigments. The photocatalytic properties of mock-ups were studied via light exposure for 50 hours and subsequent measurements of peroxide formation via Russell-grams which imaged peroxides on indirect and commercial pigments. Colour changes were measured via a colorimeter and indicated that bleaching was the dominant effect, with most pigments causing browning on Whatman filter paper. Analysis of absorption spectra indicated that band gaps were narrowest for direct method pigments and wider for all others, a quality which lengthens the time that excited electrons are available for reactions. Visible deterioration was localised to materials in direct contact with pigments, evidenced by the embrittlement of binding media when paint sat on highly-sized paper and the browning of paper fibres when size was not present and paint was more embedded in the paper substrate. Fluorescent characteristics were studied with fluorimetry and digital image processing with the goal of determining what qualities relate to photocatalysis. Indirect method pigments including commercial and case study pigments had a strong blue contribution, quantified via a green/blue ratio derived from the fluorescent peak areas and sRGB colour channel intensity values. This ratio was consistently low for photocatalytic pigments as evidenced by peroxide formation and visual deterioration. Historic case studies which were photographed using different cameras and lighting scenarios still were grouped according to this ratio, which was low if visible deterioration was present. Green/blue sRGB colour channel ratios increased after 50 hours of light exposure, indicating that the surface defects responsible for green fluorescence increased over time. These defects are also responsible for reducing photoactivity; however, given the age of case studies and the similarity in fluorescence between historic pigments and modern photoactive pigments, an endpoint for reactions could not be determined and may not exist. The green/blue ratio appears to be a reliable indicator of photoactivity even after periods of a century or more. More work is needed to standardise image processing procedures to make the method more quantitative, though comparisons within data sets in this study are a reliable indicator of peroxide formation on pigment particle surfaces. Given the difficulty in treating watercolours damaged by zinc oxide and the evidence presented here of its lengthy photoactivity, paper conservators should avoid using the pigment for retouching and focus on stabilisation and prevention. Localised reduction of staining using alkalis below pH8 may be carried out with caution as strong alkalis dissolve zinc oxide pigments. Consolidation of cracked paint, when carried out after the removal of sulphate salts in a wash, both reintroduces the binder and provides a temporary barrier between surface electrons on pigment particles and surrounding paper, slowing the oxidation of paper cellulose by peroxides

Microcharacterisation of Halogenated Copper Phthalocyanines Using Transmission Electron Microscopy

Halogenated copper phthalocyanines are widely used in the pigmentary form to colour paints, plastics, dyes and printing inks. Their colouring properties are strongly dependent on the size, shape and chemical composition of the individual pigment particles which have dimensions of typically 50nm. Batches of pigments, produced using nominally the same industrial process, can exhibit differences in their colouring properties. Electron microscopy can provide the high spatial resolution required to analyse both the physical and chemical properties of the pigment particles and thus help to determine the reasons for their differing colouring properties. Various techniques, available in electron microscopy, were used in an attempt to characterise as fully as possible samples of highly chlorinated CPC's. Low magnification images revealed differences in the particle size, shape and particle size distribution, between pigment samples, which would explain differences in their performance. These images also showed that the pigments consisted mainly of small aggregates with dimensions of the order of several pigment particles. Diffraction studies of these aggregates suggested that most of them were pieces of pigmentary material which had not been broken down by the pigmentation process. Further diffraction studies also suggested that the particles were faceted and that these facets coincided with preferred crystallographic planes. Lattice images showed that many particles deviated considerably from perfect crystallinity. The modified differential phase contrast imaging technique allowed simultaneous topographic and lattice images to be recorded from the same area, distinguishing aggregates which had not been broken down by the pigmentation process. The chemical composition of highly chlorinated CPC material was obtained using electron energy loss spectroscopy. An accuracy of +/-0.7Cl atoms per molecule could be obtained from a diameter of ~35nm on epitaxially grown thin films. However, the actual value obtained had a small dependence on thickness. With individual pigment particles, other effects were apparent, preventing a precise determination of the composition. The technique showed that with further refinements, it might be possible to analyse accurately single pigment particles

Microstructure and crystallographic texture evolution in TIMETAL® 6-2-4-6 billet.

The effects of thermomechanical processing via open die forging on the microstructure and crystallographic texture of three different diameter billets of the α+β titanium TIMETAL® 6AI-2Sn-4Zr-6Mo were analysed. This work included a quantitative study of primary alpha (αp) within the microstructure of the three billets with an objective of determining if any variation within the cross-section of the billet could be related back to the macroscopic deformation history during breakdown from the Vacuum Arc Remelting (VAR) ingot. The metallographic observation within two of the α+β TIMETAL® 6AI-2Sn4Zr-6Mo billets (313 mm and 213 mm diameter), that were manufactured using standard forging routes, revealed a bimodal microstructure consisting of relatively equiaxed αp within an acicular transformed β matrix throughout the whole cross-section. The results showed, with the exception of the extreme edge to a depth of 10 mm, that the microstructure, at least at the scale at which it was quantified, is homogeneous regardless of its location with respect to the deformation axes. However, despite the microstructure being homogeneous radially, analysis of the microstructure at the centre of the larger billet revealed continuous ex grains in addition to a slight increase in the total percentage of αp volume. Another difference between these two billets was variation in the percentage of αp volume. Although the total percentage of αp volume in the larger billet was generally uniform, there was a higher percentage of αp volume in the smaller sized billet when compared to the larger billet. A third alternatively forged billet was also analysed. This billet underwent a major difference in its forging route when compared to the standard route in that it was α+β forged following the ingot breakdown above β transus temperature therefore resulting in termination of the prestrain and β recrystallisation stages of the standard route. Results showed a significant difference in the αp size distribution meaning a higher percentage of αp having a smaller grain size. In fact, the actual scale of the alternatively forged billet microstructure was smaller; however, there were some larger grains demonstrating an inhomogeneous microstructure. In addition, the grains were longer and thinner in shape. This analysis was then further extended so as to determine whether the same could be said for crystallographic texture using the Electron Back Scatter Diffraction (EBSD) technique. It was shown that the textures of both large and small diameter billets were strongly dependent on the strain imposed by the deformation process. Macrozones (regions of closely aligned grains) were also observed throughout all three billets stretching along each billet's longitudinal axis. At the edge of the larger billet, however, the widths of the macrozones were wider in comparison to those of the smaller billet. In general, the billets' textures were quite weak, however, there were some noticeable differences in the textures from the edge towards the centre of each billet. At the edge of the billet the crystallographic texture was aligned with the compression direction and, unlike the centre of the billet, had a strong influence of the variant selection mechanism was observed. Deformation symmetry was also particularly noticeable at the centre of the billets. Within the alternatively forged billet, however, it was observed that the strong texture seen at the centre of both previous billets had been replaced by a less intense fibre like texture along the longitudinal direction. In order to analyse the global texture of the billet using EBSD, it was necessary to examine a number of samples from a variety of locations within the billet. There were, however, disadvantages to this procedure as there was a size limitation per sample and, although many samples were analysed, the results were not complete. For these reasons, heat tinting was used as an alternative method. During this research, results obtained from the heat tinting experiments were subject to adjustment in Corel PHOTOPAINT and then compared directly to the actual texture measurements obtained by EBSD. The obvious disadvantage of heat tinting in comparison to EBSD was that it could not identify texture at a very specific location or give a very detailed analysis. However, when comparing heat tinting and EBSD images, it was determined that the colours generated by heat tinting gave some degree of texture information as the basal (0001) and pyramidal {10-11} planes could be detected based on the colour of their oxide. Additional advantages of heat tinting were that there was no size limit to the sample (providing that it was possible to grind and polish the sample and a laboratory furnace was available) and the procedure was less time consuming. Heat tinting was also used to confirm the presence of two separate deformation regimes located at the centre and edge of the billets

Structure characterisation of catalysts using x-ray micro-computed tomography

Knowledge of internal porous structure is essential in improving the development of a catalytic system and consequently leading to an optimized performance. XRCT has been used to show differences in density and pore distribution and that differences can be related to the process route by which the specimen was prepared. Alumina samples with defects prepared using different conditions have been investigated in order to acquire information on the introduction and development of cracks. Results indicated that cracks became larger when the water content, the ram speed of the extruder and the drying temperature were higher. The calcination process increased the number and the 3-D size of the cracks.Both concentration of the bulk solution and impregnation time appeared to have a significant impact on the metal distribution profile during the impregnation process. Drying had a strong impact on the metal profile, as a redistribution of copper was noticed. The redistribution was observed exclusively in the case of weak adsorption of copper with alumina support.Experiments on the newly established I13 beamline synchrotron in Diamond was carried out in order to gain an understanding of the cracks induction/propagation and of the diffusion of metallic solution inside the catalyst support

Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018

Innovation, Internationalization and Entrepreneurship

Over the past years, businesses have had to tackle the issues caused by numerous forces from political, technological and societal environment. The changes in the global market and increasing uncertainty require us to focus on disruptive innovations and to investigate this phenomenon from different perspectives. The benefits of innovations are related to lower costs, improved efficiency, reduced risk, and better response to the customers’ needs due to new products, services or processes. On the other hand, new business models expose various risks, such as cyber risks, operational risks, regulatory risks, and others. Therefore, we believe that the entrepreneurial behavior and global mindset of decision-makers significantly contribute to the development of innovations, which benefit by closing the prevailing gap between developed and developing countries. Thus, this Special Issue contributes to closing the research gap in the literature by providing a platform for a scientific debate on innovation, internationalization and entrepreneurship, which would facilitate improving the resilience of businesses to future disruptions

An in-silico study: Investigating small molecule modulators of bio-molecular interactions

Small molecule inhibitors are commonly used to target protein targets that assist in the spread of diseases such as AIDS, cancer and deadly forms of influenza. Despite drug companies spending millions on R&D, the number of drugs that pass clinical trials is limited due to difficulties in engineering optimal non-covalent interactions. As many protein targets have the ability to rapidly evolve resistance, there is an urgent need for methods that rapidly identify effective new compounds. The thermodynamic driving force behind most biochemical reactions is known as the Gibbs free energy and it contains opposing dynamic and structural components that are known as the entropy (ΔS°) and enthalpy (ΔH°) respectively. ΔG° = ΔH° - TΔS°. Traditionally, drug design focussed on complementing the shape of an inhibitor to the binding cavity to optimise ΔG° favourability. However, this approach neglects the entropic contribution and phenomena such as Entropy-Enthalpy Compensation (EEC) often result in favourable bonding interactions not improving ΔG°, due to entropic unfavorability. Similarly, attempts to optimise inhibitor entropy can also have unpredictable results. Experimental methods such as ITC report on global thermodynamics, but have difficulties identifying the underlying molecular rationale for measured values. However, computational techniques do not suffer from the same limitations. MUP-I can promiscuously bind panels of hydrophobic ligands that possess incremental structural differences. Thus, small perturbations to the system can be studied through various in silico approaches. This work analyses the trends exhibited across these panels by examining the dynamic component via the calculation of per-unit entropies of protein, ligand and solvent. Two new methods were developed to assess the translational and rotational contributions to TΔS°, and a protocol created to study ligand internalisation. Synthesising this information with structural data obtained from spatial data on the binding cavity, intermolecular contacts and H-bond analysis allowed detailed molecular rationale for the global thermodynamic signatures to be derived

Intelligent Systems

This book is dedicated to intelligent systems of broad-spectrum application, such as personal and social biosafety or use of intelligent sensory micro-nanosystems such as "e-nose", "e-tongue" and "e-eye". In addition to that, effective acquiring information, knowledge management and improved knowledge transfer in any media, as well as modeling its information content using meta-and hyper heuristics and semantic reasoning all benefit from the systems covered in this book. Intelligent systems can also be applied in education and generating the intelligent distributed eLearning architecture, as well as in a large number of technical fields, such as industrial design, manufacturing and utilization, e.g., in precision agriculture, cartography, electric power distribution systems, intelligent building management systems, drilling operations etc. Furthermore, decision making using fuzzy logic models, computational recognition of comprehension uncertainty and the joint synthesis of goals and means of intelligent behavior biosystems, as well as diagnostic and human support in the healthcare environment have also been made easier