Domenick E. Cagliostro

Wettability of transition metal oxide surfaces

Abstract The wettability of transition metal oxide surfaces (TiO 2 , ZrO 2 and HfO 2 ) by water was investigated by measuring the contact angles using the sessile drop method. The oxide surfaces were prepared by thermal oxidation of polished metal foils of Ti, Zr and Hf, which had been polished to different levels of surface roughness. The surfaces were also characterized by optical microscopy, X-ray diffraction (XRD), atomic force microscopy (AFM) and Auger/XPS (AES/ESCA) methods. From the dependence of contact angles on surface roughness for the three investigated oxides, contact angles on flat surfaces were calculated as 70.7°, 59.9° and 74.0° for TiO 2 , ZrO 2 and HfO 2 , respectively. These results suggest that the three oxides do not provide acceptable waterproofing coatings on silica fibers used for space shuttle thermal insulation.

Chemical vapor infiltration: modelling solid matrix deposition in ceramic—ceramic composites

Abstract A model is developed to predict the effect of diffusion, the rate of deposition, and spatial distribution of a solid matrix in a woven fabric forming a ceramic—ceramic composite. To the knowledge of the authors there has been no prior treatment of chemical vapor infiltration in a system of plies consisting of an assembly of woven tows containing bundles of filaments. The model predicts the times to fill the gaps around the filaments of a tow, the space between plies, and the holes between the tows. It also predicts the porosity of the composite as a function of position and processing time. Predictions are made for an illustrative case of deposition of silicon carbide matrix within a woven carbon fabric.

Chemical vapor infiltration: modelling solid matrix deposition for ceramic composites reinforced with layered woven fabrics

Abstract A model is developed for chemical vapor infiltration in a sample of overlapping, woven plies. The holes through each ply, formed by the interweaving of filamentous tows, are considered to be staggered maximally for the overlapping plies. The results are compared with another bounding case, the aligned-hole model studied previously. The staggered-hole model predicts concentration profiles, deposition amounts, porosities, and changes of dimensions with time. The model also explains the effects of diffusion, rate of deposition, and spatial distribution of filaments in the woven fabric. Staggering the holes leads to somewhat less uniform deposition in the holes between tows and in the spaces between plies.

A kinetic model for the acid-catalyzed decomposition of Delrin

Abstract A kinetic model is derived for the acid-catalyzed decomposition of Delrin, an acetal-formaldehyde resin. The kinetic model proposed assumes the hydrolysis of Delrin to form polyformaldehyde and the subsequent decomposition of polyformaldehyde to formaldehyde.

Modeling the toxicity of burning polymethylmethacrylate

This paper reports the findings from a study of the candle-like burning of polymethylmethacrylate sheet.