Showing papers by "Cabot Corporation published in 1971"

Theory of particle formation and growth in oxide synthesis flames

Abstract: This work discusses those factors which determine ultimate particle size in the synthesis of pyrogenic silica. Pyrogenic or fumed silicas are produced commercially through the combustion of a premixed stream of silicon tetrachloride, hydrogen and air. Because of their minute size, silica particles assume translational velocities and collision frequencies characteristic of large gas molecules. When chemical reaction and nucleation times are short relative to the total formation period; growth, theoretically, approaches a rate which is independent of the early history of the system and is determined solely by the frequency of Brownian collisions. Under these conditions, the logarithm of particle size is directly proportional to the logarithm of growth time. In commercial flames, secondary air is inducted into the flame jet, causing particles to cool below their fusion temperature. Under such circumstances, the growth time and thus the ultimate particle size is a strong function of initial flame tem...

Multiple scattering calculations for technology.

Abstract: A many-flux (discrete ordinate) radiative transfer calculation procedure is described with the goal of making the mathematics easy to learn and use. The major approximation is the neglect of polarization. Emission within the scattering medium is not included, and the formulas are restricted to a scattering medium bounded by parallel planes. The boundary conditions allow for a variety of kinds of illumination, and the surface reflection coefficients at the boundaries of the scattering medium are accurately determined. A comparison is made with the two-flux (Kubelka-Munk) and four-flux calculation methods, and this leads to empirical expressions for the scattering and absorption coefficients in these simple theories, which make them give nearly the same results as exact theories. These empirical expressions provide a very simple method for estimating the absolute reflectance and transmittance of turbid media and greatly increase the utility of the two-flux and four-flux calculation methods. The two-flux equations give excellent results provided the absorption is small compared to scattering and the optical thickness is greater than 5. A comparison with experimental data taken with collimated illumination shows that the four-flux equations give good results at any optical thickness even if the absorption is strong.

Surface Properties of Carbon

Abstract: Carbon surface chemistry is relatively new as an independent subject of inquiry, and, judging by the volume of publications, is receiving increasing attention throughout the world. Our conception of carbon black and its functional behavior has changed significantly since the pioneering publication by Studebaker in 1957. Within the last few years there have been a number of excellent reviews covering various aspects of carbon chemistry by authors who are presently active in this field. Donnet, Puri, and Boehm discuss reactions of carbon and the characterization of surface functional groups while van der Plas is particularly thorough on the subject of adsorption properties and porosity. Deviney explores the relationship between surface chemistry and carbon-elastomer interactions, as does Studebaker from the point of view of the practical application of carbon black in rubber. Current monographs containing useful background information are collected in “Les Carbones” and in Walker's continuing serie...

Carbon black pigments

Abstract: A NEW AND NOVEL CLASS OF CARBON BLACK PIGMENTS HAVING WELL-DEFINED PROPERTIES WHICH ARE SUITABLE FOR USE IN SPECIAL BLACK APPLICATIONS AND ARE PARTICULARLY USEFUL IN THE PREPARATION OF REINFORCED RUBBER SYSTEMS.

Plant growth media and methods

Abstract: Methods of germinating seeds and growing easily transplantable seedlings are disclosed based upon the use of loose pulverulent bed materials the basic ingredient of which consists of a relatively stable form of finely dispersed aqueous liquid the individual droplets of which are enveloped and held within a coating network of smaller, strongly hydrophobic colloidal oxide particles. Methods of producing the basic ingredient are also disclosed as well as preferred proportions of various components and optimized pulverulent bed mixtures.

Silica urea formaldehyde polymer combination flatting additive composition

Abstract: THIS DISCLOSURE RELATES TO THE USE OF A COMBINATION OF NON-POROUS MATERIALS COMPRISING A CERTAIN GROUP OF UREAFORMALDEHYDE POLYMERS AND A CERTAIN GROUP OF PYROGENICALLY PREPARED COLLOIDAL SILICAS AS FLATTING ADDITIVES IN THE PREPARATION OF FLATTED COMPOSITIONS SUCH AS PAINTS, LACQUERS, VARNISHES AND THE LIKE.

Dispersion hardened metals having improved oxidation characteristics at elevated temperature

Abstract: Dispersion hardened metals based on nickel and containing from 8-35 percent of chromium (refractory oxides, such as thoria, are pervasively dispersed in the metal to harden the same) are modified by the inclusion of from about 2.5 to about 5 percent of aluminum in order to provide improved oxidation resistance at elevated temperature while subjected to high velocity gases.

Ductile consolidated beryllium

Abstract: A mass of consolidated beryllium particles is described having a ductility characterized by a tensile elongation of at least about 2 1/2 percent in all three orthogonal directions.