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La spectroscopie de fluorescence induite par laser et par rayonnement synchrotron a été utilisée pour analyser l'intense émission de l'ion Eu3+ dans les fluorures K2YF5 et K2GdF5. L'utilisation conjuguée de la spectroscopie résolue dans le temps, de la variation de la concentration en ions Eu3+ a permis d'identifier les niveaux électroniques de l'ion Eu3+ après excitation dans les niveaux 5D2, 5D1 et 5D0. Les répartitions spectrales de la fluorescence se corrèlent parfaitement avec un ion Eu3+ inséré dans un site de symétrie C1 . A basse température, en dessous de 100 K, des structures satellites apparaissent de part et d'autre des raies principales d'excitation 7F0 -> 5D0-2. L'analyse des évolutions spectrales et temporelles des fluorescences à partir du niveau 5D0 sous excitation sélective dans les raies principales d'excitation et dans les raies satellites en fonction de la température et de la concentration en ion EU3+ a permis d'attribuer les structures supplémentaires à des signatures de paires Eu3+-Eu3+ dont l'existence est favorisée par le caractère unidimensionnel de la structure cristallographique, y compris le composé K2EuF5. Des mécanismes de cascades et de divisions de photons impliquant les ions Gd3+ et Eu3+ ont été identifiés dans K2GdF5 sous excitation VUV. Finalement le caractère unidimensionnel de la structure s'avère être un handicap pour réaliser des luminophores à rendement quantique supérieur à l'unité.

As of 21st September 2017, industrial use of hexavalent chromium (Cr(VI)) will, due to its environmental toxicity and carcinogenicity, be restricted by REACH regulations. Saab Aeronautics is therefore shifting anticorrosion surface treatment of aluminum alloys from hexavalent chromium conversion to trivalent chromium (Cr(III)) passivation. The purpose of this thesis is to investigate the characteristics of conversion coatings formed with the passivation chemical SurTec 650V, in order to facilitate transfer to the more environmental friendly alternative. Process parameters, such as pH and immersion time in SurTec 650V passivation baths, have been investigated for passivation of three different aluminum alloys; 2024, 6061 and 7075. The characteristics of the Cr(III) conversion coatings achieved at laboratory scale in the thesis work have been compared with SurTec 650V process in production scale and with Cr(VI) containing Alodine 1200 and Alodine 1500 processes. The impact of varying process parameters have been investigated with goniometry, x-ray photoelectron spectroscopy (XPS), auger electron spectroscopy (AES), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to analyse characteristics of the conversion coatings. Differences in chemical composition on the surface and in depth profile was detected with XPS and AES, respectively and topology of coatings was found to differ for different aluminium alloys and parameter combinations. With TEM, the thickness of the conversion coating was found to be approximately 30-50 nm, which is thinner than the coatings formed with Cr(VI) passivation. Characteristics of coatings formed with Cr(III) passivation is concluded to be very dependent on parameter variation, especially for alloy 2024. Differences also occur between passivation at laboratory and production scale. Further evaluation of the production scale SurTec 650V process and corrosion testing should be performed, and an elaboration of a process control is required before the shift to an environmental friendly passivation process can be completely successful at Saab.

Knot theory is not generally considered an algebraic subject, due to the fact that knots don’t have much algebraic structure: there are a few operations defined on them (such as connected sum and cabling), but these don’t nearly make the space of knots finitely generated. In this thesis, following an idea of Dror Bar-Natan’s, we develop an algebraic setting for knot theory by considering the larger, richer space of knotted trivalent graphs (KTGs), which includes knots and links. KTGs along with standard operations defined on them form a finitely generated algebraic structure, in which many topological knot properties are definable using simple formulas. Thus, a homomorphic invariant of KTGs provides an algebraic way to study knots. We present a construction for such an invariant. The starting point is extending the Kontsevich integral of knots to KTGs. This was first done in a series of papers by Le, Murakami, Murakami and Ohtsuki in the late 90’s using the theory of associators. We present an elementary construction building on Kontsevich’s original definition, and discuss the homomorphicity properties of the resulting invariant, which turns out to be homomorphic with respect to almost all of the KTG operations except for one, called “edge unzip”. Unfortunately, edge unzip is crucial for finite generation, and we prove that in fact no universal finite type invariant of KTGs can intertwine all the standard operations at once. To fix this, we present an alternative construction of the space of KTGs on which a homomorphic universal finite type invariant exists. This space retains ii all the good properties of the original KTGs: it is finitely generated, includes knots, and is closely related to Drinfel’d associators. The thesis is based on two articles, one published [Da] and one preprint [BD1], the second one joint with Dror Bar-Natan.

Knot theory is not generally considered an algebraic subject, due to the fact that knots don’t have much algebraic structure: there are a few operations defined on them (such as connected sum and cabling), but these don’t nearly make the space of knots finitely generated. In this thesis, following an idea of Dror Bar-Natan’s, we develop an algebraic setting for knot theory by considering the larger, richer space of knotted trivalent graphs (KTGs), which includes knots and links. KTGs along with standard operations defined on them form a finitely generated algebraic structure, in which many topological knot properties are definable using simple formulas. Thus, a homomorphic invariant of KTGs provides an algebraic way to study knots. We present a construction for such an invariant. The starting point is extending the Kontsevich integral of knots to KTGs. This was first done in a series of papers by Le, Murakami, Murakami and Ohtsuki in the late 90’s using the theory of associators. We present an elementary construction building on Kontsevich’s original definition, and discuss the homomorphicity properties of the resulting invariant, which turns out to be homomorphic with respect to almost all of the KTG operations except for one, called “edge unzip”. Unfortunately, edge unzip is crucial for finite generation, and we prove that in fact no universal finite type invariant of KTGs can intertwine all the standard operations at once. To fix this, we present an alternative construction of the space of KTGs on which a homomorphic universal finite type invariant exists. This space retains ii all the good properties of the original KTGs: it is finitely generated, includes knots, and is closely related to Drinfel’d associators. The thesis is based on two articles, one published [Da] and one preprint [BD1], the second one joint with Dror Bar-Natan.

In this thesis work, a high grade chromite concentrate obtained from PinarbaSi, Kayseri region of Turkey was reacted with sulfuric acid solution to determine the optimum conditions of leaching of chromite ores. Conventional methods for producing chromium are still valid in industry. The main process in production includes soda melting and taking it into solution in the form of chemical compounds such as sodium dichromate. Three and six valence states of chromium have importance in production. Trivalent chromium, chrome ore or chromite have no harmful effects. However, compounds of hexavalent chromium show toxic, irritating and corrosive action to people and environment. In the mentioned conventional method, main products consist of hexavalent chromium compounds. In this study, only trivalent chromium remained in the leach solution and did not change to hexavalent state. Obtained product after leaching was chromium(III) sulfate. The maximum extraction of chromium in the absence of perchloric acid was 94.1 % under the conditions of 175 &deg / C, 6 hours and 84.6 wt % sulfuric acid. The maximum extraction of chromium in the presence of perchloric acid was 98.7 % under the conditions of 175 &deg / C, 2 hours, 84.6 wt % sulfuric acid and &frac12 / perchloric acid / chromite ratio. The latter one was also the highest recovery value obtained during the experiments. Moreover, in none of the analyzed samples, appreciable amounts of hexavalent chromium was found during analyses.

Physical, chemical and corrosion properties of a hexavalent chromium conversion coating (CCC) and that of a commercial third generation trivalent chromium system; Tripass LT1500, on zinc electrodeposited steel has been studied. Moreover, the role of additives has been studied to elucidate film formation and corrosion resistance mechanisms. Micro-cracking and self-repair corrosion protection behaviour commonly associated with hexavalent CCCs has also been investigated. Scanning Electron Microscopy (SEM) studies showed that for both hexavalent and trivalent CCCs were in general, flat with a spherical-like structure and in the case of the former microcracked beyond 122 nm conversion coating thickness. In general, the micro-crack pattern observed e.g. a dense crack network, depended upon the underlying zinc substrate morphology. The study has also demonstrated the effect of SEM imaging and prior specimen preparation conditions on hexavalent CCC micro-cracking and blistering. X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES) and Infrared (IR) data has indicated that the hexavalent CCC film formation appears to be a electrochemical/sol-gel mechanism given the lack of zinc content at surface and subsurface regions within the conversion coating, presence of H2O and in particular the contribution of Cr(OH)3 as opposed to Cr2O3. An alternative film formation mechanism may exist for trivalent CCC given a higher proportion of zinc at surface and sub-surface regions, IR data analysis indicating that chromium is possibly deposited from a chromium (III) complex ion such as [CrC2O4(H2O)4] + , moreover as Cr(OH)3 and Cr2O3 compounds as indicated by XPS data analysis. The role of cobalt nitrate during film formation is unclear given that cobalt was not detected within the trivalent CCC from XPS and AES data. Electrochemical LPR measurements, polarisation curves and XPS data has shown in general, self-repair corrosion protection properties for hexavalent CCC to be lacking. Instead, it is proposed that the corrosion protection behaviour for hexavalent and trivalent CCC to be barrier. Polarisation curves and LPR data showed that the corrosion resistance performance for trivalent CCC was higher than hexavalent CCC, in general. LPR data showed that the omission of cobalt nitrate and increased addition of sodium molybdate content within the Tripass LT1500 treatment solution formulation was found to overall decrease corrosion resistance within the trivalent CCC. In addition, silica based topcoat and black trivalent CCCs was also investigated and characterised using AES, SEM and LPR. Zinc whiskers was also observed from zinc electrodeposits following exposure to thermal treatment (150°C for 1 h). Elemental analysis and grain pattern investigations failed to help determine the cause of zinc whisker initiation. Zinc whiskers was seen to protrude out of hexavalent and trivalent CCCs, with the latter requiring a longer thermal exposure time.

Chromium exists largely in two oxidation states, namely hexavalent chromium (Cr(VI)) which is carcinogenic, mutagenic to living organisms including humans and trivalent chromium (Cr(III)) which is known to be 1000 times less toxic than Cr(VI). It is therefore desirable in most cases to reduce Cr(VI) to Cr(III). Various studies have been conducted on the Cr(VI) reduction process either in situ or ex situ. However in situ bioremediation using permeable reactive barrier system appears as a potential and attractive technology compared to other in situ technologies. This study was conducted to evaluate the reduction of Cr(VI) to Cr(III) in the short term and regeneration of the biological reactive barrier to achieve continuous long term operation. It was observed from the study that the chromium hydroxide Cr(OH)3(s) precipitated and thus affected the porosity and hydraulic conductivity of the barrier system. It was therefore proposed to implement a regeneration process involving remobilization of precipitated Cr(OH)3 using a dilute acid (0.1% HCl) and recover Cr(III) by electrokinetics. Lowering the pH in the reactor introduced harsh conditions which necessitated the evaluation of a possible culture shift during the regeneration phase. Microbial culture composition during bioremediation and after soil washing was evaluated using a 16S rRNA finger printing method. The microbial barrier was initially inoculated with indigenous bacterial species from dried sludge. The results presented in the phylogenic tree diagrams confirm that, after microbial barrier system operation, the well-known Cr(VI) reducers Bacillus mycoides, Lysinibacillus fusiformis and Micrococcus lylae were the predominant species in the microbial community of the barrier. The microbial barrier system successfully achieved near complete removal of Cr(VI), whereby approximately 75% Cr(VI) removal was achieved within 63 days of operation. The formation of Cr(OH)3(s) was observed in the second week of operation. After 4 weeks of operating the mesocosm under soil washing with 0.1% HCl and electrokinetics remediation with a DC voltage of 50-150 V an increase in total chromium (73%) was observed suggesting that the trapped chromium species in the mesocosm was effectively remobilized with the assumption that Cr(III) had attached to the cathode forming a white-yellow precipitate layer around the cathode. Additionally more than 95% Cr(VI) was transformed to lower toxicity Cr(III) during electrokinetics and soil washing remediation. However, one of the limitations of electrokinetics is near anode focusing effect whereby a layer of precipitate is formed around the anode that lead to the reduction of efficiency of the technology. / Dissertation (MSc)--University of Pretoria, 2014. / lk2014 / Chemical Engineering / MSc / Unrestricted

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22068号 / 工博第4649号 / 新制||工||1725(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 邑瀬 邦明, 教授 宇田 哲也, 教授 杉村 博之 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Content: In this study, equipped charcoal of Ficus carica without impregnation, impregnated with potassium hydroxide (KOH), zinc chloride (ZnCl2) and phosphoric acid (H3PO4) was used for sorption comparison of trivalent chromium from tannery wastewater. The equipped charcoal is characterized before and after used by Fourier transforms infrared spectroscopy (FT-IR). The quantitative elemental analysis is performed of the charcoal using PGT Energy dispersive X-ray spectrometry (EDX). The trivalent chromium sorption efficacy of charcoal was examined investigating charcoal dose, contact time, and relative pH parameters. Batch sorption test revealed that Ficus carica charcoal without impregnation had the maximum sorption capacity of trivalent chromium as depicted Fig. 1a. At the same conditions, trivalent chromium sorption on the Ficus carica charcoal without impregnation, impregnated with potassium hydroxide, zinc chloride and phosphoric acid was 98.9%, 98.8%, 8.9 and 2.5%, respectively. It is noticeable that without impregnation charcoal has a higher sorption capacity. Conversely, impregnation with chemical required cost involvement, time-consuming, long process time, and safe. Fig.1b depicts a shift in the peak intensity which indicated the change of frequency in the functional groups of the charcoal due to chromium adsorption. It indicates various responsible functional groups for the removal of trivalent chromium through Ficus carica charcoal. The trivalent chromium removal efficiency with the Ficus carica charcoal without impregnation was achieved 98.9%. The study could be helpful to design the sorption of trivalent chromium from the tannery wastewater in-house prior to discharge. Take-Away: 1. Without impregnation, Ficus carica charcoal has a better trivalent chromium sorption capacity 2. Trivalent chromium sorption capacity was 98.9%