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 vivo research following ingesting of commercially available Lactobacillus tablets, which contain about 2X10⁶ cfu/tablet of Lactobacillus acidophilus and Lactobacillus bulgaricus cells in a dose of four tablets daily, showed serum lipoprotein concentrations did not change significantly. In order to increase the number of viable Lactobacillus bacteria after challenging in low pH solution (gastric fluid), enteric coating polymer was applied over dried calcium alginate beads containing Lactobacillus. Survival of Lactobacillus bacteria was generally higher from freeze dried calcium alginate beads compared to vacuum dried products. However, after pretreatment with simulated gastric fluid (pH = 1.5) for 2 hours, only the coated products from vacuum drying showed promising results. Lactobacillus bacteria were fully protected against gastric pH after formulating the bacteria inside mini-tablets which were coated with Eudragit L30D, an enteric coating polymer. Alginic acids are naturally occurring substances found only in the brown seaweeds. Alginic acid salts formed with most di-, and polyvalent metals are insoluble in water. The most common application of alginate precipitation in drug product formulation is based on insolubilization of alginate by addition of calcium salt. By altering the composition of calcium alginate, drug loading, enteric coating thickness, and sustained release coating thickness, the lag time for drug dissolution can be controlled. This formulation research provides oral dosage form design for targeted delivery of drug to any desired site in the gastrointestinal tract. Examples of site specific targeted delivery are given for Lactobacillus bacteria, ibuprofen, sulfasalazine, and 5-aminosalicylic acid. / Graduation date: 1991

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.

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references.

Thesis (doctoral)--Helsinki University of Technology, 2001. / Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.) in Chemical Engineering--University of Maine, 2002. / Includes vita. Bibliography: leaves 65-68.

Thesis (M.S.) in Chemical Engineering--University of Maine, 2002. / Includes vita. Bibliography: leaves 182-193.

Thesis (Ph. D.) in Chemical Engineering--University of Maine, 2001. / Includes vita. Includes bibliographical references (leaves 141-149).

published_or_final_version / Physics / Master / Master of Philosophy

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