CeraMat

The unreinforced 6061 alloy and a 6061/SiC composite, at the beginning in the T6 temper, were submitted to thermal cycling (up to 2000 cycles) in the temperature ranges 25-180°C and 25-220°C. The microstructure of these materials was studied by scanning electron microscopy and mercury intrusion porosimetry. Mechanical and thermomechanical properties were also investigated. Tensile strength, hardness, Charpy impact resistance, fracture toughness, density, specimen dimensions and thermal expansion were compared before and after thermal cycling.

In Part I the chemical and microstructural nature of Cusingle bondKsingle bondV catalysts for diesel soot combustion was assessed. In this second communication the reaction mechanism of these catalysts is studied by testing their activity through either differential scanning calorimetry (DSC) or temperature-programmed oxidation (TPO), performed on catalyst-carbon mixtures.

Several formulations of a Cusingle bondKsingle bondV catalyst supported on α-Al2O3 with different Cu:K:V atomic ratios and with different loadings of the active components on the support were prepared by impregnation with aqueous solutions of KCl, CuCl2 · 2H2O and NH4VO3, drying and calcination. The composition of these catalysts, suitable for greatly accelerating the combustion of carbonaceous materials, was investigated by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR) and scanning electron microscopy (SEM).

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.

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).

The effect of Al2O3 (Saffil) short fibers on the response of 2014-Al2O3(f) composite to thermal treatment was investigated. Composite samples were produced by squeeze casting starting from ceramic preforms of Saffil (13% vol. of fibers). Their behaviour was compared to that of 2014 unreinforced alloy fabricated by squeeze casting as well. The best process parameters suitable for solution of alloying elements were assessed by means of differential scanning calorimetry (DSC) and electron microprobe analysis (SEM-EDS).

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.

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.

The first stages of the development of a catalytic trap for diesel particulate removal from vehicle exhaust gases are addressed, ranging from catalytic trap preparation (a ceramic foam is deposited with catalysts, suitable for soot combustion, based on mixtures of KCl and different vanadates) to catalytic trap testing in a specific pilot plant (an acetylene burner is used to produce a soot laden flue gas which is then treated by the apparatus while the pressure drop buildup throughout the trap and the trap collection efficiency is measured).