Cabot Corporation

About: Cabot Corporation is a company organization based out in Boston, Massachusetts, United States. It is known for research contribution in the topics: Carbon black & Carbon. The organization has 1279 authors who have published 1399 publications receiving 36736 citations.

Processes. framed membranes and masks for forming catalyst coated membranes and membrane electrode assemblies

Abstract: A process for preparing catalyst coated membranes and membrane electrode assemblies for use in direct methanol fuel cells is provided. Cathode and anode layers are formed by spraying catalyst-containing inks onto a novel framed electrolytic membrane to form a catalyst coated membrane. The spraying process optionally employs one or more masks, which carefully control where the catalyst-containing ink is deposited. Following application of the cathode and anode layers, diffusion layers are prepared and inserted onto the catalyst coated membranes, and pressed to form membrane electrode assemblies.

Reduction of phosphate ore by carbon: Part II. Rate limiting steps

Abstract: Considerations of intraparticle mass transport processes are presented for the reduction of phosphate ore by carbon in the presence of silica. Under conditions of temperature and composition which produce reaction rates of commercial interest, the conversion is limited by product mass transport away from the reaction sites. This results in a pseudo-first order dependence of conversion on reaction time which is explained by our model. Thermochemical data derived from conversion is consistent with published data on heat of formation. At lower temperatures, where the reaction is limited by reactant diffusion in a silicate melt, contained within the overall matrix, diffusivities and activation energy were measured. Detailed diffusion studies were conducted in a graphite crucible where the interfacial reaction between the apatite-silica mixture and the graphite boundary could be detected. A mathematical model based on diffusion theory was developed, and it was found to be consistent with the diffusion data and the overall conversion at lower temperature.

High temperature rotating vacuum kiln and method for heat treating solid particulate material under a vacuum

Abstract: A rotating vacuum kiln (1) and method for heat treating solid particulate material under vacuum conditions uses a rotating refractory metal cylindrical vessel (2) with a cool inlet zone (3), hot intermediate zone (6), and cool exit zone (7), with a first series of inner radiation shields (25) provided at the hot intermediate zone adjacent the cool inlet zone (5) and a second series of inner radiation shields (29) provided at the hot intermediate zone (6) adjacent the cool exit zone (7) to protect those two zones from the high temperatures in the hot intermediate zone. Heat for the hot intermediate zone of the cylindrical vessel is provided indirectly by electrical resistance heaters (35) that surround the vessel and outer radiation shields (37, 38) are provided about the heaters to direct heat to the cylindrical vessel.

Surface-treatment chemistry in the manufacture of aerogels: computational modelling of cyclic and linear siloxanes

Abstract: An essential feature of some aerogel manufacturing processes is the `end-capping' of reactive silanol groups in the undried silica gel. Whilst the chemistry associated with the monofunctional trimethylsilanol-based processes is relatively straightforward, alternative chemistry involving multifunctional silylation reagents is not. An example of a multifunctional reagent is dimethyldichlorosilane, which rapidly hydrolyzes in aqueous environments, and in the hydrolyzed form, can condense with itself, yielding linear silanols. The resulting silanols may then further condense to form cyclic siloxanes. Such reactions will inevitably occur under typical end-capping conditions, so it is necessary to consider these when addressing the details of such treatments. We have used a variety of computational methods, including semi-empirical AM1 and PM3 as well as quantum mechanical HF/MP2 at the 6-31+G * and 6-311++G ** levels of theory, to investigate some of the siloxane species as isolated molecules. These calculations permit us to compare the enthalpies of formation of the various molecules. Furthermore, we are able to calculate various geometric attributes of the siloxanes. The calculations indicate that in the isolated state, the initial hydrolyses are nearly isoenthalpic, so other mechanisms are needed to explain the strong exothermicity observed in the laboratory. Chain extension of the linear diols is seen to be mildly exothermic with each step. Of the cyclic siloxanes, formation of the trimer, tetramer and pentamer are enthalpically most favored.