Effects of pretreatment on the structure and properties of electroless nickel coatings
The pretreatment process can significantly affect the corrosion resistance of electroless nickel (EN) coatings. One of the most important reasons is that different pretreatment processes can give different surface morphologies of the substrate. The scanning electron microscope (SEM) and the scanning tunneling microscope (STM) have been used to investigate the structure and properties of EN coatings in the as-plated condition for various deposition times, in relation to different mechanical/chemical pretreatment processes. The morphology of the substrate surface is found to be a key factor in control of the porosity of EN coatings. It can significantly affect the formation of EN deposits, not only in the early stage but also in the morphology/ structure during the continued growth of the deposit
Formation, Microstructure, Surface Roughness, and Porosity of Electroless Nickel Coatings
AbstractThe structure and properties of electroless nickel coatings containing 11% phosphorus have been studied in the as plated condition for various deposition times and after heat treatment. In addition to a general covering, in the early stages of deposition nodules of nickel form associated with the lay of the polished substrate, and as the thickness of the coating increases so do the surface roughness and the uniformity of the coating thickness. Porosity is associated with the surfaces of the vestigial nickel nodules. Porosity measured using the ferricyanide test is observed to decrease monotonically with the as plated thickness, and is a maximum after heat treatment at 400°C. Large non-metallic inclusions do not affect the porosity or coating uniformity. Information on the microhardness, crystal structures, and microstructure of the coatings is also presented.
Researches on Structural Factor Involvement in Oral Tribology
This study is focused on two ceramic materials, D.SING (Ivoclar) and VM13 (emphasis the VITA TN), frequently used in restorative dentistry practice and it comes to complete a full set of results obtained by the authors over several years of research on oral tribology with main influence on oral health. In this way there are involved more specific structural aspects of dental restorative ceramic materials quality as is shown in [1].