You are here


Surface engineering and chemical characterization in ion-nitrided titanium and titanium alloys

The chemical and physical characteristics of ion-nitrided surface layers, obtained on α-β titanium alloys, are examined and correlated both with the working conditions adopted in the ion-nitriding process and with the alloy chemical composition. Besides the influence of the working parameters on the morphology and on the microstructures of the ion-nitrided surface layers, mainly the alloy element distributions both in surface coatings and in the substrate are analysed for five α-β titanium alloys of industrial use, and for titanium c,p.

Interfacial reactions in a Ti-6Al-4V based composites: role of the TiB2 coating

The characterization of TiB2/C-coated SiC fibres and their interface region in a Ti-6Al-4V based composite has been performed by using scanning electron microscopy (SEM), energy-dispersion X-rays (EDX) and Auger electron spectroscopy (AES). The features of the as-received fibre and the reactivity between fibre and matrix occurring during preparation of the composite have been studied in this paper.

Suitability of some promising soot combustion catalysts for application in diesel exhaust treatment

In this work, the effect of thermal treatment at 380°C and 600°C, under gaseous atmospheres containing some typical components of diesel emissions (SO2 and water), was studied on some promising catalysts for diesel particulate combustion. In particular, the ageing behaviour of two novel catalysts (based on CsVO3+KCl and KVO3+KCl, respectively) and of a more widely studied Cu–K–V–Cl catalyst was investigated.

Combustion of carbon particulate catalysed by mixed potassium vanadates and KI

A K-V-I-containing catalyst for low-temperature combustion of carbonaceous materials was studied so as to check its potential in diesel particulate removal. X-ray diffraction (XRD) and scanning electron microscopy (SEM-EDS) showed that its main constituting compounds are KVO3, KI and K4O7. Differential scanning calorimetry (DSC) and temperature-programmed oxidation (TPO) tests enlightened that the catalyst is active well below 400°C (peak combustion temperature: Tp = 380°C).

Effect of chemical composition of isomorphous metavanadates on their catalytic activity towards carbon combustion

Metal vanadates of K, Rb, and Cs and their solid solutions were prepared by reaction between carbonates and vanadium(V) oxide, characterized by X-ray diffraction and tested as catalysts for carbon combustion. These vanadates are all orthorhombic but show different lattice parameters depending on the ionic radius of alkali metals. A complete solubility in the solid state was found to exist for the systems KVO3-RbVO3 and RbVO3-CsVO3, while only terminal solid solutions were found in the KVO3-CsVO3 system.

Development of catalysts based on pyrovanadates for diesel soot combustion

Pyrovanadates of potassium and cesium were prepared and tested as catalysts for low-temperature combustion of carbon. Their catalytic activity was investigated by both temperature-programmed oxidation and thermogravimetric analysis and compared with that displayed by the metavanadates of the same elements, previously proposed as promising catalysts for soot combustion in diesel emissions. Pyrovanadates show an intrinsic catalytic activity noticeably higher than that of the corresponding metavanadates.