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Synthese und Untersuchungen zur Reaktivität NHC-stabilisierter Kobaltverbindungen / Synthesis and reactivity of NHC-stabilized cobalt complexesLubitz, Katharina January 2020 (has links) (PDF)
Die vorliegende Arbeit befasst sich mit der Synthese und den Eigenschaften verschiedener NHC-stabilisierter Kobaltkomplexe. Der Fokus liegt dabei einerseits auf der Entwicklung geeigneter Organokobaltverbindungen, welche sich in CVD bzw. ALD-Prozessen zur Abscheidung von elementarem Kobalt eignen. Hierfür wurden verschiedene NHC-stabilisierte sowie gemischt substituierte Kobalt(carbonyl)(nitrosyl)komplexe dargestellt und die thermischen Eigenschaften dieser Verbindungen untersucht. Andererseits wurden Studien zur Synthese und Reaktivität NHC-stabilisierter Halbsandwichverbindungen des Kobalts durchgeführt. Dabei wurde unter anderem überprüft, inwiefern sich der sterische Einfluss des NHC-Liganden auf die Fähigkeiten auswirkt, Element-Element-Bindungen in Silanen und Diboranen zu aktivieren. Ferner wurden weitere Untersuchungen zur Reaktivität derartiger Komplexe, insbesondere gegenüber Alkinen, vorgenommen. Ein weiterer Teil dieser Arbeit beschäftigt sich mit der Darstellung und Reaktivität NHC-Phosphiniden-stabilisierter Kobaltverbindungen. / The present work concerns the synthesis and reactivity of various NHC-stabilized cobalt complexes. The first part focuses on the development of cobalt compounds suitable for depositing elemental cobalt in chemical vapor deposition processes (CVD and ALD). Therefore, a variety of NHC-stabilized cobalt carbonyl nitrosyl complexes, as well as asymmetrically substituted cobalt complexes, were synthesized and the thermal properties were investigated. Secondly, the thesis addresses the synthesis and reactivity of NHC-stabilized cobalt half sandwich complexes with a focus on the investigation of the influence of sterically demanding carbene ligands in the stoichiometric activation of element-element bonds, as well as further reactivity studies of this class of compounds. Furthermore, studies have been performed on the synthesis and reactivity of NHC-phosphinidene substituted cobalt complexes.
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Příprava nové metodiky pro screening chelatorů kobaltu / Preparation of a novel method for screeing of cobalt chelatorsMoravcová, Monika January 2020 (has links)
Charles University Faculty of Pharmacy in Hradec Králové Department of Pharmacology & Toxicology Student: Monika Moravcová Supervisor: Assoc. Prof. Přemysl Mladěnka, Pharm.D., Ph.D. Title of thesis: Preparation of a Novel Method for Screening of Cobalt Chelators Cobalt as a structural part of the vitamin B12 is an essential microelement for living organisms including humans. However, its excess is associated with pathological conditions. Cobalt poisoning can be caused for example by exposure to cobalt metal dust during the production of hard metals or follow the corrosion of metal hip prosthesis. Patients intoxicated by cobalt can develop different manifestations including neurological impairment, hypothyroidism or cardiomyopathy. The aim of this work is to prepare a standardized, rapid, cheap but precise method for the screening of cobalt chelators. For this purpose, spectrophotometric detection using 1-nitroso-2-nafphhol-3,6-disulfonic acid disodium salt as the indicator was used. Firstly, it was found that the addition of cobalt ions led to a clear bathochromic shift of the maximum absorbance of the indicator. The relationship between the absorbance and cobalt concentration was highly linear from 470 to 560 nm at all 4 tested pH conditions (4.5, 5.5, 6.8 and 7.5). The sensitivity of the method...
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Laser treatment of alloys: processing, microstructure and structural propertiesOliveira, Uazir Orion Bezerra de. January 2007 (has links)
Proefschrift Rijksuniversiteit Groningen. / Met lit.opg.
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Tvorba magnetických nanostruktur pomocí EBID a optimalizace jejich chemického složení a morfologie / Deposition of magnetic nanostructures using EBID and optimalization of their chemical composition and morphologyVyroubal, Ondřej January 2016 (has links)
This master's thesis deals with deposition of cobalt nanostructures using Electron Beam Induced Depositon (EBID). The thesis firstly describes theoretical background regarding EBID. In the following experimental part, the deposition process is optimized via analysis of exposition parameters and their influence on the final shape of nanostructures. These are analyzed via Atomic Force Microscopy (AFM). Optimized exposure parameters are then applied to the deposition of functional 3-dimensional nanostrucutres. In particular, the deposition of cobalt spheres. The elemental composition is analyzed by the means of element composition using Energy-dispersive X-ray Spectroscopy (EDX) and the nanostructures of desired morphologies are studied with Magnetic Force Microscopy (MFM) and Magneto-Optical Kerr Microscope).
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Dermal and respiratory exposure to cobalt salts in a packaging area of a base metal refinery / Lelani van der WesthuizenVan der Westhuizen, Lélani January 2010 (has links)
Cobalt is a commonly known sensitiser in industrial settings and has been classified
by the IARC as a possible group (2B) human carcinogen. Workers at a South African
base metal refinery are potentially exposed to cobalt in the cobalt packaging area.
The respiratory and dermal exposure to cobalt is a possible health risk. Quantifying
the exposures levels assists in determining the degree of the risk as well as the
management thereof. The objectives of this study were to assess dermal and
respiratory exposure of workers at a cobalt packaging area and to assess their skin
condition by measuring transepidermal water loss (TEWL) and skin hydration indices.
The skin hydration index was measured on the back of the hand, forehead, wrist and
palm at the start, during and end of the shift. The TEWL index was measured at the
start and end of the shift on the same areas as the hydration index. Ghostwipes
was chosen as preferred wipe sampling media to collect dermal and surface
samples. Wipe samples were also taken on suspected contaminated workplace
surfaces. Respiratory samples were taken by using the Institute of Occupational
Medicine (IOM) inhalable aerosol sampler at a flow rate of 2 l/min. Wipes and
respiratory samples were analysed for cobalt according to NIOSH method 9102
using inductively coupled plasma–atomic emission spectrometry (ICP–AES). The
hydration indices indicated that worker’s skin are slightly dry to normal at the
beginning of the shift. Hydration on the wrist increased significantly during the shift.
TEWL indices increased significantly on the back of the hand, wrist and forehead
during the shift. TEWL indices of the palm showed a low barrier function before the
shift and deteriorated further to a very low barrier function at the end of the shift.
Significant dermal cobalt loading occurred on the back of the hand, forehead, wrist
and palm during the shift. The palm was the most exposed and the forehead least.
The barrier function of the skin is most likely to be affected by exposure to cobalt.
The skin condition of workers put them at greater risk to develop adverse health
effects of cobalt. Workplace surfaces were contaminated with cobalt. Airborne
cobalt was visible at different working stations. Cobalt exposure is due to numerous
sources in the packaging area, thus contributing to the dermal exposure. Respiratory
exposure exceeded the 8 hour occupational exposure limit for most of the workers.
The guidance limit for short term exposure was exceeded by half of the workers. It is
important to minimise the exposure to cobalt in packaging area. Manifestation of the
adverse health effects are usually not visible in the short term, the necessary
precautions have to be taken to protect the workers. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2011.
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Dermal and respiratory exposure to cobalt salts in a packaging area of a base metal refinery / Lelani van der WesthuizenVan der Westhuizen, Lélani January 2010 (has links)
Cobalt is a commonly known sensitiser in industrial settings and has been classified
by the IARC as a possible group (2B) human carcinogen. Workers at a South African
base metal refinery are potentially exposed to cobalt in the cobalt packaging area.
The respiratory and dermal exposure to cobalt is a possible health risk. Quantifying
the exposures levels assists in determining the degree of the risk as well as the
management thereof. The objectives of this study were to assess dermal and
respiratory exposure of workers at a cobalt packaging area and to assess their skin
condition by measuring transepidermal water loss (TEWL) and skin hydration indices.
The skin hydration index was measured on the back of the hand, forehead, wrist and
palm at the start, during and end of the shift. The TEWL index was measured at the
start and end of the shift on the same areas as the hydration index. Ghostwipes
was chosen as preferred wipe sampling media to collect dermal and surface
samples. Wipe samples were also taken on suspected contaminated workplace
surfaces. Respiratory samples were taken by using the Institute of Occupational
Medicine (IOM) inhalable aerosol sampler at a flow rate of 2 l/min. Wipes and
respiratory samples were analysed for cobalt according to NIOSH method 9102
using inductively coupled plasma–atomic emission spectrometry (ICP–AES). The
hydration indices indicated that worker’s skin are slightly dry to normal at the
beginning of the shift. Hydration on the wrist increased significantly during the shift.
TEWL indices increased significantly on the back of the hand, wrist and forehead
during the shift. TEWL indices of the palm showed a low barrier function before the
shift and deteriorated further to a very low barrier function at the end of the shift.
Significant dermal cobalt loading occurred on the back of the hand, forehead, wrist
and palm during the shift. The palm was the most exposed and the forehead least.
The barrier function of the skin is most likely to be affected by exposure to cobalt.
The skin condition of workers put them at greater risk to develop adverse health
effects of cobalt. Workplace surfaces were contaminated with cobalt. Airborne
cobalt was visible at different working stations. Cobalt exposure is due to numerous
sources in the packaging area, thus contributing to the dermal exposure. Respiratory
exposure exceeded the 8 hour occupational exposure limit for most of the workers.
The guidance limit for short term exposure was exceeded by half of the workers. It is
important to minimise the exposure to cobalt in packaging area. Manifestation of the
adverse health effects are usually not visible in the short term, the necessary
precautions have to be taken to protect the workers. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2011.
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Hybrid organic spin valves interfaces and transport /Popinciuc, Mihăiţă, January 2007 (has links)
Proefschr. Rijksuniversiteit Groningen. / Met lit. opg.-Met bibl.-Met samenvatting in het Nederlands.
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Assessment of dermal exposure and skin condition of refinery workers exposed to selected metals / J.L. du PlessisDu Plessis, Johannes Lodewykus January 2010 (has links)
Aims and objectives: The research aims and objectives of this thesis were: (i) to review literature
pertaining to different dermal exposure assessment methods; (ii) to assess dermal exposure of refinery
workers to nickel and/or cobalt by making use of skin wipes as a removal method; (iii) to assess
concurrently the skin condition of the above mentioned workers by measuring skin hydration,
transepidermal water loss (TEWL) and skin surface pH, and (iv) to compare South African skin
notations and sensitisation notations with those of other developed countries.
Methods: Refinery workers from two base metal refineries participated in this study. Skin condition
and dermal exposure was measured on different anatomical areas before, during and at the end of a
work shift. Dermal exposure to nickel and/or cobalt was assessed with Ghostwipes
TM
as a removal
method. Wipe samples of potentially contaminated surfaces in the workplace were also collected.
Wipes were analysed for nickel and/or cobalt according to NIOSH method 9102, using Inductively
Coupled Plasma-Atomic Emission Spectrometry. The assignment and use of skin notations and
sensitisation notations in South African legislation and six other developed countries were compared.
Results: To date, occupational dermal exposure has been reported for numerous substances by
making use of surrogate skin methods (interception methods), removal methods and fluorescent tracer
methods (in situ detection methods). From published literature it is evident that skin (dermal) wipes,
as a removal method, are the most appropriate method to assess dermal exposure to metals. Varying
degrees of skin dryness (low hydration indices) and impaired barrier function (high TEWL indices)
are reported, with the hands being implicated the most. However, normal skin condition is also
reported for some anatomical areas. Skin surface pH for all anatomical areas sampled decreased
significantly during the shift, but remained in normal range. Dermal exposure to nickel occurred
during the shift at the electro-winning plant of one refinery, while dermal co-exposure to cobalt and
nickel occurred at the cobalt plant of the other refinery. At both of the refineries, cobalt and/or nickel
was collected from the workers’ skin even before the shift. Also, dermal exposure to these metals was
highly variable between individual workers. Skin notations in South African legislation had a mean
agreement of between 42.9% and 45.8% with other countries, while agreement for sensitisation
notations was only 3.6% between countries. / Thesis (Ph.D. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2011.
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Assessment of dermal exposure and skin condition of refinery workers exposed to selected metals / J.L. du PlessisDu Plessis, Johannes Lodewykus January 2010 (has links)
Aims and objectives: The research aims and objectives of this thesis were: (i) to review literature
pertaining to different dermal exposure assessment methods; (ii) to assess dermal exposure of refinery
workers to nickel and/or cobalt by making use of skin wipes as a removal method; (iii) to assess
concurrently the skin condition of the above mentioned workers by measuring skin hydration,
transepidermal water loss (TEWL) and skin surface pH, and (iv) to compare South African skin
notations and sensitisation notations with those of other developed countries.
Methods: Refinery workers from two base metal refineries participated in this study. Skin condition
and dermal exposure was measured on different anatomical areas before, during and at the end of a
work shift. Dermal exposure to nickel and/or cobalt was assessed with Ghostwipes
TM
as a removal
method. Wipe samples of potentially contaminated surfaces in the workplace were also collected.
Wipes were analysed for nickel and/or cobalt according to NIOSH method 9102, using Inductively
Coupled Plasma-Atomic Emission Spectrometry. The assignment and use of skin notations and
sensitisation notations in South African legislation and six other developed countries were compared.
Results: To date, occupational dermal exposure has been reported for numerous substances by
making use of surrogate skin methods (interception methods), removal methods and fluorescent tracer
methods (in situ detection methods). From published literature it is evident that skin (dermal) wipes,
as a removal method, are the most appropriate method to assess dermal exposure to metals. Varying
degrees of skin dryness (low hydration indices) and impaired barrier function (high TEWL indices)
are reported, with the hands being implicated the most. However, normal skin condition is also
reported for some anatomical areas. Skin surface pH for all anatomical areas sampled decreased
significantly during the shift, but remained in normal range. Dermal exposure to nickel occurred
during the shift at the electro-winning plant of one refinery, while dermal co-exposure to cobalt and
nickel occurred at the cobalt plant of the other refinery. At both of the refineries, cobalt and/or nickel
was collected from the workers’ skin even before the shift. Also, dermal exposure to these metals was
highly variable between individual workers. Skin notations in South African legislation had a mean
agreement of between 42.9% and 45.8% with other countries, while agreement for sensitisation
notations was only 3.6% between countries. / Thesis (Ph.D. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2011.
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Functionalization of particles and selective functionalization of surfaces for the electroless metal plating processMondin, Giovanni 04 December 2014 (has links) (PDF)
Electroless plating is a metal deposition technique widely used in the coating industry. It is the method of choice to plate substrates with complex geometries and nonconductive surfaces, such as polymers and ceramics, since it is based on a chemical reduction in solution rather than on an external electrical energy source like the electroplating method. Among others, examples of well-established applications are the electroless deposition of decorative metal coatings such as gold and silver, wear and corrosion resistant nickel coatings, particularly to coat drive shafts, rotors, and bathroom fixtures, as well as the electroless deposition of copper in electronic devices as diffusion barriers and conductive circuit elements.
In the academic research, electroless plating is extensively used thanks to its low cost, simple equipment and versatility that allow rapid prototyping. Two common applications are the coating of small particles and the selective plating of flat surfaces. Metal coated ceramic particles are of enormous interest in many scientific fields, e.g. fluorescent diagnostics in biochemistry, catalysis, and fabrication of photonic crystals. Metal coated ceramic nanoparticles and microparticles are also gaining attention as potential candidates in the fabrication of higher quality metal matrix Composites, which is one of the applications addressed by this work. Metal coated ceramic particles are easier to integrate in metal matrix composites, avoiding aggregation caused by the low wettability of the particles by the matrix metal, and are potentially shielded from oxidation and undesired chemical reactions that take place at the interface between the particles and the metal Matrix.
Electroless plating is an autocatalytic process, meaning that the deposited metal atoms catalyze the deposition of further metal. In order to achieve the first stable metal seeds on a surface, the latter has to be functionalized. Without this functionalization the metal ions in the electroless plating bath are not reduced or are simply reduced to metal nanoparticles in solution. The traditional activation step for nonconductive surfaces is performed by immersion of the substrate in palladium based solutions, which is very time-consuming and extremely expensive. In particular for nanoparticles, previous work showed that at least 1015 Pd atoms/cm2 are required for a uniform activation of a surface, meaning that in the case of nanoparticles with a surface area of about 100 m2/g are necessary 6.4 g of palladium for each gram of substrate. Assuming a price of about 150 €/g (laboratory scale) for palladium nanoparticles and palladium precursors used for surface activation, it results that the activation of 1 g of nanoparticles costs around 1000 €.
Such costs are suboptimal considering the typical production scale, and therefore alternative functionalization methods are desired. In this work, new organic-based functionalization methods based on (3-mercaptopropyl)triethoxysilane to functionalize oxide particles, 3-aminopropylphosphonic acid to activate carbide particles and a substrate-independent method based on the bioinspired polydopamine are developed and investigated in detail, together with the respective electroless plating baths, which often have to be specifically tailored regarding the different reactivity of the different molecules and substrates. Furthermore, in the fabrication of metallic patterns on substrates by electroless plating, new, simple, and cost-effective activation and metal deposition processes are desired. In this work, two new methods are presented, one based on the printing of (3-mercaptopropyl)triethoxysilane by microcontact printing, the other based on the capillary force lithography of polymethylmethacrylate.
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