Το πρόγραμμα συντήρησης του μοναστηριακού συγκροτήματος του Αγίου Λωτ περιελάμβανε in situ επεμβάσεις συντήρησης, σωστική αποκόλληση και επανατοποθέτηση ενός από τα έξι ψηφιδωτά δάπεδα που βρίσκονταν στην Βασιλική και την ανασκαφή ενός ψηφιδωτού που είχε καταρρεύσει και κατακερματιστεί σε εκατοντάδες θραύσματα στην κλιτύ του λόφου, όπου βρίσκεται η Μονή. Η αποκόλληση του πρώτου ψηφιδωτού δαπέδου και η επακόλουθη ανακάλυψη ενός πρωιμότερου ψηφιδωτού δαπέδου κάτω από αυτό, καθώς και η εύρεση ενός ακόμα σε θραύσματα μας έδωσε την ευκαιρία να παρατηρήσουμε και να καταγράψουμε επιμελώς τις τεχνικές που χρησιμοποιήθηκαν στην κατασκευή των ψηφιδωτών. Ο χαρακτηρισμός επιλεγμένων δειγμάτων κονιαμάτων μας επέτρεψε να προσδιορίσουμε τη σύστασή τους και να ταυτοποιήσουμε το είδος των αδρανών και των προσμίξεων που εμπεριέχει. Οι τεχνικές που χρησιμοποιήθηκαν για την ανάλυση των κονιαμάτων είναι οι: η Περιθλασιμετρία κόνεως ακτίνων-Χ (XRD), η Ηλεκτρονική Μικροσκοπία Σάρωσης (SEM- EDS), η Φασματοσκοπία Απορρόφησης Υπερύθρου (FTIR) και η Οπτική Μικροσκοπία (ΟΜ). Επιπλέον, η πετρογραφική ανάλυση των ψηφίδων, που έγιναν από συνεργάτες του έργου, μας έδωσαν πληροφορίες σχετικά με την προέλευση των πρώτων υλών που χρησιμοποιήθηκαν. Μετά από αναλύσεις και λεπτομερή παρατήρηση, λάβαμε πληροφορίες σχετικά με τις πρώτες ύλες, την προετοιμασία των κονιαμάτων, την στρωματογραφία του ψηφιδωτού δαπέδου, την μέθοδο εκτέλεσης των εργασιών κατασκευής, αλλά και τον τρόπο επεξεργασίας της επιφάνειας. Οι διαφορές που παρατηρούνται στην στρωματογραφία και τη σύσταση των κονιαμάτων, όπως και στις ψηφίδες σε ψηφιδωτά που δημιουργήθηκαν σε διαφορετική χρονική περίοδο συμβάλλουν στην αρχαιολογική μελέτη και κυρίως στην κατανόηση της αρχιτεκτονικής ενότητας και μετατροπών που υπέστη κατά την διάρκεια της χρήσης του χώρου. / The conservation project at the monastic complex of Saint Lot involved the rescue lifting of one of the six mosaics which paved the basilica as well as the excavation of a second one that was found in hundreds of fragments fallen on the slope. The lifting of the first mosaic and the consequent discovery of fragments of an earlier mosaic floor underneath it, as well as the fragmentary state of the second mosaic gave us the opportunity to observe and record thoroughly the techniques employed in the construction of these mosaics. Characterization of selected mortar samples allowed the determination of their composition, identification of the aggregate and its additives. X-Ray Diffraction, Fourier transform infrared spectroscopy, Optical Microscopy and Scanning Electron Microscopy with EDS were the main techniques employed. Mineralogical analyses of tesserae samples, that was employed from other partners of the project, provided information about the provenance of the raw materials that were used. Through detailed observation and analysis, significant information on the raw material selection, preparation of mortars, bedding stratigraphy, method of execution, as well as aspects of tesserae cutting and surface finishing techniques were documented. The variation in the bedding stratigraphy, the composition of the mortars as well as the petrography of the tesserae between mosaics that were executed in different periods contribute in the study of the archaeological context and especially in understanding the succession of the renovation and modification phases of the building.

The purpose of this study is to understand mineral diagenesis authigenic mineral and the effect of climate on mineral of Pleistocene-Holocene sediment deposits in the Southern Kenya Rift. Lake Magadi unique geologic settings are characterized by extreme alkalinity and high silica activities. The mineralogical analysis was achieved by X-Ray diffraction (XRD) and Scanning Electron Microscopy (SEM) applications. The bulk mineralogy (quartz, halite, calcite) is the same on all localities due to similar volcaniclastics compositions throughout the Kenya Rift Valley. The clay mineralogy significantly differ among the groups of sample localities. The differences reflect different tectonic settings and ambient climate regime. In humid climate at higher elevation detrital clay minerals are abundant (feldspars, phillipsite). At lower elevation like Lake Magadi, the clay fractions dominated by authigenic minerals (zeolites and silicate minerals found with zeolites). These results show the potential of clay minerals as terrestrial climate proxies.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The 2:1 expandable clay minerals have high importance when present in soil, even in small amount, as in the case of soil with a high degree of secondary alteration. The study of these minerals is essential to understanding the physical and chemical behavior of soils, however, the techniques have not always permitted their suitable concentration, in order to facilitate their study. Therefore, this study aimed to analyze the concentration of phyllosilicates clay minerals with 2:1 structure through the technique of selective dissolution of oxides and kaolinite, aiming their study by X-ray diffraction and thermal analysis. The samples were collected in Rio Grande do Sul, in different weather conditions in profiles of Regosols (RRd and RRe), Ferralsol (LVd) and Vertisol (VEo). The clay fraction of A and B horizons of soil were separated and subjected to treatment with dithionite-citrate-bicarbonate and then with warm NaOH in 10 different concentrations, from 0.5 to 5 mol L-1. For mineralogical characterization we used the techniques of X-ray diffraction (XRD), thermogravimetry (TG) and differential thermal analysis (DTA). The results obtained by the analysis of X-ray diffraction showed that for most weathered soils as the Ferrasol, the NaOH solution does not contribute to the concentration of the 2:1 mineral. However, to the Vertisol the solution of NaOH 4.0 mol L-1 was more efficient in the concentration of minerals. To the Regossol RRd no concentration of NaOH solution was effective and to the RRe the concentration of 2.5 mol L-1 solution of NaOH was most suitable for concentrating the 2:1 clay. The extraction of kaolinite and gibbsite by NaOH solution was only partial for kaolinite. The thermal analysis showed predominance of kaolinite and gibbsite in relation to the 2:1 minerals in the samples free of oxides. The most effective treatment for the thermal analysis for 2:1 mineral concentration was NaOH 4 mol L-1 for samples LVd B, RRh A, RRe A and Veo A. The NaOH 3 mol L-1 treatment was more efficient for samples LVd A and VEo B. The relative concentration of 2:1 was higher in samples with dystrophic character. / Os argilominerais 2:1 expansíveis apresentam elevada importância quando presentes nos solos, mesmo em quantidade pequena, como no caso de solos com elevado grau de alteração secundária. O estudo destes minerais é fundamental para o entendimento do comportamento físico-químico dos solos, no entanto, as técnicas utilizadas nem sempre tem permitido a sua concentração adequada, de forma a facilitar o seu estudo. Por isso, este trabalho teve como objetivo analisar a concentração de argilominerais filossilicatos com estrutura 2:1 através da técnica de dissolução seletiva de óxidos e caulinita, visando o seu estudo por difratometria de raios-X e por análise térmica. As amostras analisadas foram coletadas no Rio Grande do Sul, em diferentes condições climáticas, em perfis de Neossolos (RRd e RRe), Latossolo (LVd) e Vertissolo (VEo). A fração argila dos horizontes A e B destes solos foram separadas e submetidas ao tratamento com ditionito-citrato-bicarbonato de sódio e posteriormente com NaOH a quente em 10 concentrações diferentes, a partir de 0,5 até 5 mol L-1. Para a caracterização mineralógica utilizou-se as técnicas de difração de raios-X (DRX), termogravimetria (TG) e análise térmica diferencial (ATD). Os resultados obtidos pelas análises de difratometria de raios-X mostraram que para solos mais intemperizados como o Latossolo a solução de NaOH não contribui para a concentrar os minerais 2:1. No entanto, para o Vertissolo a solução de NaOH 4,0 mol L-1 foi mais eficiente na concentração desses minerais. Os Neossolos apresentaram comportamento distinto, sendo que para o RRd nenhuma concentração da solução de NaOH foi eficiente e para o RRe a concentração de 2,5 mol L-1 da solução de NaOH foi a mais adequada para a concentração dos argilominerais 2:1. A extração da caulinita e gibbsita através da solução de NaOH foi apenas parcial para a caulinita, observou-se a permanência deste mineral em boa parte das concentrações. As análises térmicas mostraram predominância de caulinita em relação à gibbsita e minerais 2:1 nas amostras desferrificadas. O tratamento mais eficiente, pela análise térmica, para concentração de minerais 2:1 foi o NaOH 4 mol L-1 para as amostras LVd B, RRh A, RRe A e VEo A e o tratamento NaOH 3 mol L-1 para as amostras LVd A e VEo B. A concentração relativa de 2:1 foi maior nas amostras com caráter distrófico.

The aim of this research project was to synthesise both the normal and inverse cobalt aluminate spinels by various methods and characterise them mainly by Raman spectroscopy with the support of X-ray powder diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR), energy disperse spectroscopy (EDS), and scanning electron microscopy (SEM). Four different synthesis methods (glycine-gel, citrate-gel, polyol and solid-state) were used to synthesise the cobalt aluminate powders with the general formula CoIICoIIIxAl2-xO4 (where x = 0-2). The gel or powder precursors were annealed at various temperatures ranging from 350ºC - 1000ºC. The properties of the intermediate and final products, influenced by the synthesis method, processing temperature, processing time and particle size, were compared. Raman spectra and XRD patterns indicating the presence of both normal and inverse cobalt aluminate spinel were observed. The inverse spinel was identified both as a transitional phase as well as a final phase, depending on the synthesis method and annealing temperature used. The various synthesis methods were also used to gain further insight into the crystal chemistry of cobalt aluminate. The solid-state method is the more traditional synthesis method. Solution techniques (glycine-gel, citrate-gel and polyol) were used in an attempt to synthesise blue cobalt aluminate at relatively low temperatures and processing times in order to obtain homogeneous, nanosized crystals with broad applicability. The polyol method was found to be most favourable for the synthesis of blue cobalt aluminate with regard to processing temperature and processing time. The various characterisation methods used, show that the intensity of the colour of the powders produced are strongly related to the degree of material crystallinity as well as Al/Co ratio. Inverse (Co2AlO4) and Co3O4 spinels are formed at lower temperatures or when the Co/Al ratio is greater than 0.5. The normal spinel (CoAl2O4) is produced at higher temperatures or when the Co/Al ratio is 0.5. The XRD patterns of CoAl2O4, Co2AlO4 and Co3O4, are very similar because they share the same spinel cubic structure (space group Fd3m) differing only slightly in the lattice size. It has been demonstrated that Raman and XRD can be used to distinguish between inverse and normal spinels while FT-IR and EDS are useful for assessing the purity of the powders produced. As predicted by group theory, five Raman and four IR active vibrations were evident in the results. / Dissertation (MSc)--University of Pretoria, 2009. / Chemistry / unrestricted

L’objectif de cette étude est d'évaluer la qualité de l'eau dans le basin inférieur du Litani (sud Liban) et d’évaluer son potentiel d'utilisation polyvalente comme une des solutions aux problèmes aggravés d’eau au Liban. Pour identifier les sources possibles de métaux et ensuite caractériser le comportement chimique de ces métaux dans l'eau et dans les sédiments, des échantillons d’eau et des sédiments ont été prélevés de six sites représentatifs. Ils ont été analysés durant les trois saisons de l'année 2011-2012 (c'est-à-dire pluvieuse, mi- pluvieuse et sèche). L’ACP (l'analyse en composante principale), a ensuite été utilisé pour interpréter les concentrations dans l'eau fluviale. Les résultats montrent que parmi les 18 variables, qui ont été évaluées pour Caractériser les propriétés physico-chimiques, il y en a 4) Fe, NO2, CaCO3, Cu) qui permettent de qualifier le type d'environnement étudié; trois groupes ont été identifiés et différenciés par ACP selon les saisons. Le premier groupe inclut toutes les spécificités du milieu en saison pluviale et montre des concentrations importantes en Fe et NO2 et faibles en NH4. Le deuxième groupe est formé par les échantillons prélevés lors de la saison sèche et montre des caractéristiques physicochimiques opposés à celles observées dans le premier groupe. Enfin, le troisième groupe regroupe les observations de la saison mi- pluvieuse caractérisée par des concentrations faible en K+, PO43-et le Cl-. Les résultats montrent que les concentrations de Pb, Fe sont élevées sur deux sites avec dans un cas des valeurs de Cr et Ni importantes, Les sédiments ont été caractérisés par différentes techniques comme la capacité d'échange de cations, la granulométrie, la diffraction des rayons X (XRD) et la spectroscopie infrarouge à transformée de Fourier (FTIR). L'analyse FTIIR montre que la quantité de la montmorillonite est plus faible que la kaolinite et beaucoup inférieure que le quartz et la calcite. La corrélation de Pearson a été également effectuée dans cette étude pour comparer et déterminer la relation entre les métaux lourds dans les sédiments. L’indice de Géo accumulation (Igeo) , le facteur de Contamination (Cf), et le degré de contamination (Cd) ont été également déterminés pour évaluer le niveau de contamination dans les sites. Les valeurs obtenus montrent que les concentrations de Pb et de Fe sont élevés dans les deux sites et la valeur de Cr, Ni, sont élevés dans un seul site. Ces résultats suggèrent qu'une attention particulière doit être accordée à la question remobilisation des éléments, car une grande partie des éléments dans les sédiments sont susceptibles de se libérer dans l'eau. Tous les sites sont caractérisés par modérées à très polluée microbienne, nous avons encore observé que le dégrée de contamination a augmenté durant la saison sèche. Cependant, aucune pollution critique n'a été rapportée dans cette partie de la rivière ; sauf la haute concentration de Fe et NO2-dans tous les sites examinés en raison des rejets d'eaux usées et l'activité touristique dans le LLRB, les Concentrations de sept métaux lourds (Cu, Fe, Cd, Mn, Cr, Zn, Ni et Pb) dans les sédiments ont été déterminés pour évaluer leurs niveaux et leurs distribution spatiale / The objective of this study was to evaluate water quality of the lower Litani River and assess its feasibility for multi-purpose usage as one of the solutions to the aggravated water problems in Lebanon, To identify possible sources of metals (i.e. geological and/or anthropogenic) and then to characterize the chemical behavior of these metals in water and bed sediments, water and bed load sediments were sampled at six representatives sites which are investigated over three seasons of the year 2011-2012 (i.e. rainy, mid-rainy and dry seasons), The PCA (principal component analysis) method was used to interpret the elemental concentrations in the river water. Results show that among 18 variables, which were evaluated to characterize their physic-chemistry and metals, there are only 4 (Fe, NO2-, CaCO3, Cu) that were determined the type of environmental studied; Three groups were identified and differentiated by PCA according to the seasons. The first group includes all statements made in the mid rainy season and has a dialogue rich in Fe and NO2, and low in NH4 and EC. The second group formed in dry season, and surveys show physicochemical characteristics opposite to those in the first group, the third group formed in mid rainy, and showed the low concentration of K+, PO43- and Cl-. Sediments were characterized by a set of cations exchange capacity, granulometric, diffraction (XRD) and Fourier transformed infrared spectroscopy (FTIR( The FTIR analysis shows that the amount of montomorillonite is less than kaolinite and very much less than quartz and calcite. Pearson’s correlation was also performed in this study to compare to and determine the correlation between heavy metals in the sediments. Geo-accumulation (Igeo) index, Contamination Factor (Cf), and contamination degree (Cd) were also applying to assess the level of contamination in the sites. The results shows that the concentration of Pb, Fe are high in the site S5, S6 and the value of Cr ,Ni, are high in the S6, this results suggest that special attention must be given to the issue of element re-mobilization, because a large portion of elements in sediments are likely to release back into the water column. All the sites are characterized by moderate to highly microbial polluted range. The degree of contamination was increased in dry season. However, no critical physicochemical pollution has been reported in this part of the river; except the high concentration of Fe and NO2- in all investigated sites due to the reject of wastewater and to the distribution of touristic activities in the LLRB, the Concentrations of seven heavy metals is high(Cu, Fe, Cd , Mn , Cr, Zn, Ni and Pb) for sediment is higher according to Consensus-based sediment quality guidelines of Wisconsin (Wisconsin Department of Natural Resources, 2003) were applied to assess metal contamination in sediment

In the present research, a novel method, namely sol-gel/laser-induced technique (SGLIT), has been developed to generate nano-structured TiO2-based films. The TiO2 films based on unloaded (pure) TiO2, Ce-TiO2, W-TiO2 and Ag-TiO2, have been investigated in attempt to stabilise the formation of anatase and consequently of enhancing photo-catalytic and anti-bacterial activities. The TiO2 precursor loaded with Ce2+, W6+ and Ag2+ ions (Ce-TiO2, W-TiO2 and Ag-TiO2) were separately prepared by sol-gel method and spin-coated on microscopic glass slides. A pulsed KrF excimer laser with a wavelength of 248 nm and pulse width of 13-20 ns was employed to irradiate on the sol-gel prepared films at various operating parameters, in terms of laser fluence, number of laser pulses and repetition rate. The work has been focussed on microstructural characterisation of various films prepared by both SGLIT and furnace, in the consideration of crystallographic structure, phase transformation, crystallite sizes, surface morphology, film thickness and optical properties, by means of Raman spectroscopy, XRD, FEG-SEM/EDX, TEM/HR-TEM/EDX, AFM and UV-Vis spectroscopy etc. The results showed that nano-crystallisation of the films after laser irradiation has been achieved, with controllable amount of anatase formation. These coatings presented a unique feature of surface morphology with meso-porosity and much enlarged surface areas, compared with the films prepared by furnace sintering technique. The addition of Ce and Ag, stabilized the anatase structure during the laser irradiations, whereas the addition of W destabilized the anatase structure. The Ce-TiO2 films prepared by SGLIT exhibited anatase structure which was stable up to 500 laser pulses at 35 mJ cm-2 fluence. The anatase was formed after 10 laser pulses only at 65-75 mJ cm-2 fluence in the W-TiO2 films. When a higher number of laser pulses, fluence or higher W6+ loading were chosen, rutile structure started to form. On the other hand, the Ag-TiO2 nano-composite films prepared by SGLIT presented the anatase up to 200 laser pulses at 85 mJ cm-2 fluence. On average, anatase crystallite size of about 38 nm was achieved from both the W-TiO2 and Ag-TiO2 films prepared by SGLIT. In contrast, the furnace-sintered W-TiO2 and Ag-TiO2 films produced anatase crystallite size of 49.4 nm and 29.8 nm respectively. Another achievement of the present research is the development of a single-step laser irradiation technique to generate an Ag-TiO2 nano-composite film on the glass substrate. A pulsed laser beam produced hexagonal Ag nanoparticles along with the crystallization of anatase-based nano-structured TiO2 film which was accomplished in 1 µs only. The films prepared by SGLIT displayed a higher photo-absorption compared to their furnace-sintered counterparts due to the unique surface features with a higher surface roughness. Overall, an enhanced bactericidal activity against E. coli cells was demonstrated under UV light by each of the W-TiO2 films compared to furnace-sintered films except the 1W-TiO2. The E. coli cells did not survive on the W-TiO2 films prepared by SGLIT, after 80 minutes under UV (365 nm) light. In contrast, E. coli cells still survived on the surface of furnace-sintered W-TiO2 films under the same conditions. Ag-TiO2 nano-composite films prepared by SGLIT, demonstrated an enhanced anti-bacterial activity against E. coli compared to the conventionally- made Ag-TiO2 films. No bacteria survived on the Ag-TiO2 films prepared by 50 laser pulses at 85 mJ cm-2 fluence, whereas E. coli colonies always survived on the furnace-sintered Ag-TiO2 films under the UV, natural light and the dark room conditions.

It is proposed to continue operating the graphite moderated Advanced Gas-cooled Reactor (AGR) fleet past its design life. Nuclear graphite's properties change in reactor and our limited mechanistic understanding of the relationship between graphite structure, across different lengthscales, and its properties limits our ability to predict its future behaviour. An improved understanding of the relationship between graphite's structural features, the relationship between features across different lengthscales and their effect on material properties would all contribute to a mechanistic understanding of graphite behaviour. Thermal expansion generates thermal strains and stresses in the graphite core during thermal transients, such as during reactor start-up and shut-down. Thermal expansion is a function of graphite crystal thermal expansion, crystallographic preferred orientation and microstructure, although the exact relationship between these is not understood. It is also altered by neutron irradiation. This thesis investigates graphite microstructure, virgin and irradiated, and its crystallographic preferred orientation, specifically as they pertain to thermal expansion. The microstructure of British nuclear graphites PGA and Gilsocarbon, used in the Magnox and AGR fleet respectively, have been investigated using scanning electron microscopy (SEM). Trepanned AGR graphite, that is, graphite drilled from the reactor brick during routine inspection is examined. These samples are from the 2012 Hinkley Point B inspection campaign and are taken from several points through the brick thickness. This provides a 'snap shot' of current AGR graphite condition. Deep trepan samples removed from further into the brick thickness are observed for the first time. Neutron damage was observed in Magnox graphite, irradiated in an inert environment in the material test reactor programme INEEL. The spatial variation in texture of PGA and Gilsocarbon, and the change in such texture after prestress was observed using synchrotron x-ray diffraction. Numerical models were used to identify the required texture change to produce changes in CTE, observed by other authors, during in-situ stress. PGA filler lamellae are arranged in parallel arrays and Gilsocarbon's smaller platelets are arranged in bunched clusters. Severe radiolytic oxidation is observed at all trepan locations, with oxidation decreasing away from the fuel. Radiolytic oxidation occurs at platelet edges. Texture measurements have indicated that PGA graphite exhibits significant spatial variation in texture. Gilsocarbon exhibits less variation but the variation observed is large enough to cause increased thermal stresses. Texture measurements of prestressed graphite have indicated that texture changes also vary spatially. Texture results and SEM observations indicate that spatial variation in texture is caused by spatial variation in microstructure. Changes to the filler particle during prestress may alter local texture. These results indicate there is a link between nuclear graphite's microstructure and its texture. The texture, a function of lamellae or platelet arrangement, determines its thermal expansion. Spatial variations in microstructure formed during manufacturing leads to spatial variations in CTE and possibly other texture sensitive properties, such as dimensional change. Deformation of the lamellae or platelets during stress; thermal creep or irradiation creep is expected to contribute to the observed change in properties associated with these stimuli.

High strength 7xxx aluminium alloys are used extensively in the aerospace industry because the alloys offer excellent mechanical properties. Unfortunately, the alloys can suffer localised corrosion due to the presence of large intermetallic particles at the alloy surface that are aligned in the rolling direction. Laser surface melting (LSM) techniques offer the potential to reduce and/or to eliminate the intermetallic phases from the surface of the alloy without affecting the alloy matrix.The present study concerns the application of LSM using an excimer laser to enhance the corrosion resistance of AA 7075-T6 aluminium alloy. The initial stage of the project was aimed at optimising the laser conditions for production of a uniform microstructure, with the increase in the corrosion resistance of the alloy being determined by potentiodynamic polarization measurements in sodium chloride solution. Low and high laser energy densities were used with a different number of pulses per unit area to treat the alloy surface, which were achieved by changing both the laser fluence and the pulse repetition frequency. A laser fluence of 3.3 J/cm2 with 80 pulses was subsequently selected as the optimum condition to treat the surface of the alloy. The composition and microstructure of the alloy before and after LSM treatment, and following corrosion tests, were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD).After the laser treatment, the surface and the cross-sections of the alloy showed a significant reduction in the number of large intermetallic particles and a relatively homogenous melted layer was generated that provided significant improvement in the resistance of the alloy against corrosion, as assessed by several corrosion test methods, including exfoliation corrosion (EXCO) tests. However, delamination of the melted layer was observed after extended testing in the EXCO solution which is possibly related to the formation of bands of fine magnesium and zinc-rich precipitates within the melted layer. Therefore, anodising in sulphuric acid was applied to the LSM alloy, in order to further increase the corrosion resistance and to protect the laser treated layer from delamination by generating a thin oxide film over the LSM layer. The results revealed that the anodic treatment increased the resistance of the alloy to exfoliation attack.

The semiconducting silicides offer significant potential for use in optoelectronic devices. Full implementation of the materials, however, requires the ability to tailor the energy gap and band structure to permit the synthesis of heterojunctions. One promising approach is to alloy the silicides with Ge. As part of an investigation into the synthesis of semiconducting silicide heterostructures, a series of β-Fe(Si1−xGex)2 epilayer samples, with nominal alloy content in the range 0 < x < 0.15, have been prepared by molecular beam epitaxy on Si(100). I present results of the epitaxial and crystalline quality of the films, as determined by reflection high-energy electron diffraction, Rutherford backscattering spectroscopy, and double crystal x-ray diffraction, and of the band gap dependence on the alloy composition, as determined by Fourier transform infrared spectroscopy. A reduction in band gap was observed with increasing Ge content, in agreement with previous theoretical predictions. However Ge segregation was also observed in β-Fe(Si1−xGex)2 epilayers when x > 0.04. Osmium silicide films have been grown by molecular beam epitaxy on Si(100). The silicides have been grown using e-beam evaporation sources for both Os and Si onto Si(100) substrates at varying growth rates and temperatures ranging from 600-700ºC. The resulting films have been analyzed using reflection high-energy electron diffraction, Raman spectroscopy, reflectivity measurements, in-plane and out of plane X-ray diffraction and temperature dependent magnetotransport. A change in crystalline quality is observed with an increase in Si overpressure. For a lower silicon to osmium flux ration (JSi/JOs=1.5) both OsSi2 and Os2Si3 occur, whereas with a much larger Si overpressure (JSi/JOs>4), crystalline quality is greatly increased and only a single phase, Os2Si3, is present. The out-of-plane X-ray diffraction data show that the film grows along its [4 0 2] direction, with a good crystal quality as evidenced by the small FWHM in the rocking curve. The in-plane X-ray diffraction data show growth twins with perpendicular orientation to each other.

Lead's uptake on magnetite has been quantitatively evaluated in the present study at a temperature of 200°C and pH of 8.5 with lead concentrations ranging from 5 ppm to175 ppm by equilibrium adsorption isotherms. The pH independent sorption behavior suggested lead sorption due to pH independent permanent charge through weak electrostatic, non-specific attraction where cations are sorbed on the cation exchange sites. The permanent negative charge could be a consequence of lead substitution which is supported by increase in the lattice parameter values from the X-ray diffraction (XRD) results. Differential scanning calorimetry (DSC/TGA) results showed an increase of exothermic (magnetite to maghemite transformation) peak indicating substitution of lead ions due to which there is retardation in the phase transformation. Presence of outer sphere complexes and physical sorption is further supported by Fourier transformed infrared spectroscopy (FTIR). None of the results suggested chemisorption of lead on magnetite.