ABSTRACT
The paper represents the "state of the art" on sustainability in construction materials. In Part 1 of the paper, issues related to production, microstructures, chemical nature, engineering properties, and durability of mixtures based on binders alternative to Portland cement were presented. This second part of the paper concerns the use of traditional and innovative Portland-free lime-based mortars in the conservation of cultural heritage, and the recycling and management of wastes to reduce consumption of natural resources in the production of construction materials. The latter is one of the main concerns in terms of sustainability since nowadays more than 75% of wastes are disposed of in landfills.
Subject(s)
Construction Materials , Waste Management/methods , Calcium Compounds/chemistry , Clay/chemistry , Green Chemistry Technology/methods , Oxides/chemistry , Recycling , Rubber/chemistry , Silicon Dioxide/chemistryABSTRACT
BACKGROUND: Titanium has outstanding corrosion resistance due to the thin protective oxide layer that is formed on its surface. Nevertheless, in harsh and severe environments, pure titanium may suffer localized corrosion. In those conditions, costly titanium alloys containing palladium, nickel and molybdenum are used. This purpose investigated how it is possible to control corrosion, at lower cost, by electrochemical surface treatment on pure titanium, increasing the thickness of the natural oxide layer. METHODS: Anodic oxidation was performed on titanium by immersion in H2SO4 solution and applying voltages ranging from 10 to 80 V. Different anodic current densities were considered. Potentiodynamic tests in chloride- and fluoride-containing solutions were carried out on anodized titanium to determine the pitting potential. RESULTS: All tested anodizing treatments increased corrosion resistance of pure titanium, but never reached the performance of titanium alloys. The best corrosion behavior was obtained on titanium anodized at voltages lower than 40 V at 20 mA/cm2. CONCLUSIONS: Titanium samples anodized at low cell voltage were seen to give high corrosion resistance in chloride- and fluoride-containing solutions. Electrolyte bath and anodic current density have little effect on the corrosion behavior.
Subject(s)
Electrochemical Techniques , Sulfuric Acids/chemistry , Titanium/chemistry , CorrosionABSTRACT
PURPOSE: The aim of this study was to evaluate whether an Anodic Spark Deposition treatment, which assures increased resistance of titanium alloys to fretting corrosion, improves the structural reliability of Ti6Al4V modular hip prostheses, thus preventing the recently noticed in vivo mechanical failures of these components due to fatigue events. METHODS: Three commercial treatments were tested in this work. Microhardness, roughness and fatigue resistance measurements were carried out to investigate the treatment performances. RESULTS: The experimental tests showed that the implant responded differently based on the treatment. The treatment that assured the best performances induced an increase in fatigue resistance with respect to the initial properties of the non-treated Ti6Al4V alloy. CONCLUSIONS: Since in previous research the same surface treatment was shown to prevent fretting corrosion phenomena, the study tests confirmed that the Anodic Spark Deposition treatment can significantly increase the structural reliability of Ti6Al4V multi-component prostheses.
