The utilization of Electroless Nickel-Phosphorus (EN) coatings has witnessed a staggering increase during the last two decades. Many outstanding characteristics of the EN coating method have generated a lot of interest in various industries including oil and gas, electronic, chemical, automotive, aerospace, and mining. Some of the highlighted characteristics of EN coatings are superior corrosion and wear resistance especially in environments containing H2S and CO2, superior mechanical properties, uniform coating thickness, excellent surface finish properties, superb adhesion characteristics, and wide range of thickness. The EN coating process is based on a redox reaction in which a reducing agent is oxidized and Ni+2 ions are reduced on the surface of the substrate materials. Once the first layer of Ni is deposited, it acts as a catalyst for the process. Consequently, a linear relationship between coating thickness and time usually occurs. If the reducing agent is sodium hypophosphite, the deposit obtained will be a nickel-phosphorus alloy. The objective of this research was to evaluate various properties of three types of EN coatings, namely, low, medium, and high phosphorus. In the first phase of this work an automated prototype EN bath was designed and engineered. As a result, three types of EN coatings were deposited on various substrates. In the second phase of this research, various qualitative and quantitive methods were implemented to evaluate various properties of EN coatings. Also, the effects of various coating parameters including coating thickness and phosphorus content on properties of EN coatings were comprehensively investigated. Furthermore, the effect of post heat treatment on various properties of EN coatings was studied. Heat treatment on EN deposits in the range of 300-400 °C for one hour caused the hardness to increase due to the formation of various types of nickel phosphide (NixPy). The results of this study showed that various properties of EN coatings are directly related to the phosphorus content of the coatings. EN coatings with lower phosphorus content are crystalline, hard and brittle. As a result, they have superior wear resistance. On the other hand, EN coatings with higher phosphorus content are amorphous with superior corrosion resistance. iii EN coatings in general have excellent adhesion properties. However, the degree of adhesion is affected by several parameters including coating thickness, phosphorus content, post heat treatment, and ductility of the substrate. Moreover, it was shown that due their brittle nature EN coatings in general and heat-treated low phosphorus EN coating in particular have a detrimental effect on fatigue properties of their substrates. It was also shown that EN coatings in general, improve the kinetic coefficient of friction. In other words, EN coatings exhibit a self-lubricating behavior. Also, it was shown that EN coatings completely follow the surface profile of their substrate unlike conventional electroplating. Corrosion and wear studies on EN coatings revealed that EN coatings are excellent candidates for materials subjected to excessive corrosion and wear in a potash brine environment. Finally, the microstructure study of EN coatings using TEM and STEM electron microscopy revealed valuable information regarding the phase transformation during the heat treatment. It was shown that heat treatment at 400°C for one hour caused the precipitation of various nickel phosphide particles. As a result, significant changes in various properties of EN coatings occurred.

In the past, hardness measurements on nanocrystalline metals were limited to Vickers micro-hardness and nano-indentation tests, mainly due to sample size/thickness limitations. On the other hand, most industries require hardness values on the Rockwell scale and make extensive use of hardness conversion relationships for various hardness scales. However, hardness conversions currently do not exist for nanocrystalline metals. With recent advances in electrodeposition technology, thicker specimens with a wide range of grain sizes can now be produced. In this study, the relationships between Vickers and Rockwell hardness scales have been developed for such materials. In addition, hardness indentations were used to gain further insight into the work hardening of nanocrystalline and polycrystalline nickel. Vickers microhardness and nano-indentation profiles below large Rockwell indentations showed that polycrystalline nickel exhibited considerable strain hardening, as expected. On the other hand, for nanocrystalline nickel the micro-Vickers and nano-indentations hardness profile showed low strain hardening capacity.

In the past, hardness measurements on nanocrystalline metals were limited to Vickers micro-hardness and nano-indentation tests, mainly due to sample size/thickness limitations. On the other hand, most industries require hardness values on the Rockwell scale and make extensive use of hardness conversion relationships for various hardness scales. However, hardness conversions currently do not exist for nanocrystalline metals. With recent advances in electrodeposition technology, thicker specimens with a wide range of grain sizes can now be produced. In this study, the relationships between Vickers and Rockwell hardness scales have been developed for such materials. In addition, hardness indentations were used to gain further insight into the work hardening of nanocrystalline and polycrystalline nickel. Vickers microhardness and nano-indentation profiles below large Rockwell indentations showed that polycrystalline nickel exhibited considerable strain hardening, as expected. On the other hand, for nanocrystalline nickel the micro-Vickers and nano-indentations hardness profile showed low strain hardening capacity.

The utilization of Electroless Nickel-Phosphorus (EN) coatings has witnessed a staggering increase during the last two decades. Many outstanding characteristics of the EN coating method have generated a lot of interest in various industries including oil and gas, electronic, chemical, automotive, aerospace, and mining. Some of the highlighted characteristics of EN coatings are superior corrosion and wear resistance especially in environments containing H2S and CO2, superior mechanical properties, uniform coating thickness, excellent surface finish properties, superb adhesion characteristics, and wide range of thickness. The EN coating process is based on a redox reaction in which a reducing agent is oxidized and Ni+2 ions are reduced on the surface of the substrate materials. Once the first layer of Ni is deposited, it acts as a catalyst for the process. Consequently, a linear relationship between coating thickness and time usually occurs. If the reducing agent is sodium hypophosphite, the deposit obtained will be a nickel-phosphorus alloy. The objective of this research was to evaluate various properties of three types of EN coatings, namely, low, medium, and high phosphorus. In the first phase of this work an automated prototype EN bath was designed and engineered. As a result, three types of EN coatings were deposited on various substrates. In the second phase of this research, various qualitative and quantitive methods were implemented to evaluate various properties of EN coatings. Also, the effects of various coating parameters including coating thickness and phosphorus content on properties of EN coatings were comprehensively investigated. Furthermore, the effect of post heat treatment on various properties of EN coatings was studied. Heat treatment on EN deposits in the range of 300-400 °C for one hour caused the hardness to increase due to the formation of various types of nickel phosphide (NixPy). The results of this study showed that various properties of EN coatings are directly related to the phosphorus content of the coatings. EN coatings with lower phosphorus content are crystalline, hard and brittle. As a result, they have superior wear resistance. On the other hand, EN coatings with higher phosphorus content are amorphous with superior corrosion resistance. iii EN coatings in general have excellent adhesion properties. However, the degree of adhesion is affected by several parameters including coating thickness, phosphorus content, post heat treatment, and ductility of the substrate. Moreover, it was shown that due their brittle nature EN coatings in general and heat-treated low phosphorus EN coating in particular have a detrimental effect on fatigue properties of their substrates. It was also shown that EN coatings in general, improve the kinetic coefficient of friction. In other words, EN coatings exhibit a self-lubricating behavior. Also, it was shown that EN coatings completely follow the surface profile of their substrate unlike conventional electroplating. Corrosion and wear studies on EN coatings revealed that EN coatings are excellent candidates for materials subjected to excessive corrosion and wear in a potash brine environment. Finally, the microstructure study of EN coatings using TEM and STEM electron microscopy revealed valuable information regarding the phase transformation during the heat treatment. It was shown that heat treatment at 400°C for one hour caused the precipitation of various nickel phosphide particles. As a result, significant changes in various properties of EN coatings occurred.

A review of metal-mediated epoxidation is given. Jacobsen's catalyst and the Sharpless asymmetric epoxidation catalyst are discussed. The origins of enantioselectivity are explained using stereochemical models. Several new salen-type ligands were synthesized based on biphenol and binaphthol. The synthesis of these ligands and their subsequent coordination to transition metals were described. The transition metal complexes were structurally characterized by X-ray diffraction of single crystals. The manganese (III) complexes were evaluated for catalytic activity in epoxidation reactions. Despite the fact that these many of these complexes were optically active, little asymmetric induction was observed in any of the epoxidation reactions. The investigation of a soluble nickel salen complex for the epoxidation of olefins led to the discovery of a new heterogeneous catalyst for the epoxidation of α,β- unsaturated carboxylic acids. Nickel salen complexes, upon reaction with commercial bleach, yield a fine black powder, which we identified as nickel oxide hydroxide-a known but poorly characterized nickel peroxide containing species. The reaction of an aqueous nickel (II) source with commercial bleach also yields nickel oxide hydroxide. This material was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Extremely broad peaks in the X-ray diffraction pattern suggested that this material consisted of particles with a very small diameter and this was confirmed by TEM. This insoluble material was found to function as a heterogeneous catalyst for the epoxidation of α,β-unsaturated carboxylic acids in the presence of sodium hypochlorite. The high activity of this catalyst in the epoxidation of certain olefins is due in part to its small particle size, which increases the overall surface area of this heterogeneous catalyst. Large particles of nickel oxide hydroxide were prepared and the catalytic activity was comparatively less. The oxidation of several other organic substrates was also explored using this catalyst. Both primary and secondary alcohols can be oxidized with our nickel-based system. Primary alcohols go through an aldehyde intermediate which is then in turn oxidized to the carboxylic acid.

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Reproduction de : Thèse de doctorat : Chimie organique, minérale et industrielle : Poitiers : 2008. / Titre provenant de l'écran-titre. Bibliogr. [173] réf.

Thesis (Ph. D.)--University of Oregon, 2003. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 153-163). Also available for download via the World Wide Web; free to University of Oregon users.

Inaug.-Diss.--Basel. / Vita.

Thesis (Ph. D.)--University of Michigan. / Cover title. "Reprinted from the Physical review, vol. XXX, no. 4, April, 1910."