Pore-Size Distribution by a Rapid, Continous Flow Method.

Abstract--Stable organomineral derivatives are formed by reaction of organochlorosilanes with certain phyllosilicates. Organosiloxyl functions are grafted on silanol groups present at external mineral surfaces.Water molecules adsorbed on external mineral surfaces may cause hydrolysis of the reactant organosilicon products, with liberation of HC1. This, in turn, may react with the silicate: octahedral cations are extracted from the lattice and fresh Si-OH groups, capable of further grafting, are formed on the mineral surface.On the other hand, when difunctional reagents such as methylvinyldichlorosilane are used and if the ratio of adsorbed water to added reactive is adequate, then polymeric species with polysiloxane chains are grafted on the mineral.Because of its high content of silanol groups, sepiolite forms organomineral compounds having a relatively high organic matter content. With chrysotile, the amount of organic matter grafted to the silicate, is considerably smaller, but it increases appreciably if water is added to the reacting products. This is attributed to hydrolysis of the organic reactant and subsequent destruction of external "brucitic" layers by acid attack.

“…Specific surface measurements (B.E.T., N2) were carried out in the apparatus described by Cahen et al (1965); the samples were previously degassed for 24 hours (10 .3 Torr at 100~…”

Section: Chemical Titrations and Physical Determinationsmentioning

confidence: 99%

Organomineral Derivatives Obtained by Reacting Organochlorosilanes with the Surface of Silicates in Organic Solvents

Ruiz‐Hitzky

1976

“…B.E.T. surface area measurements were performed by a dynamic flow method (Cahen et al, 1965) with N2 gas as the adsorbate.…”

Section: Instrumentationmentioning

confidence: 99%

Electrochemical Modifications in Kaolinite-Glass Bead Plugs

Sethi¹

1973

-Electrochemical treatment of kaolinite-glass bead plugs in the presence of water and CaCI~ solutions produces dissolution of the glass beads, corrosion of the anodes, and transport of the released elements toward the cathodic zone. In this area, new mineral phases (both amorphous and crystalline) are synthesized. Most of these new phases, and especially the calcium silicate hydrate (CSH-1), are well known to exhibit important cementing properties. The nature and the extent of the modifications brought about by the treatment are dependent on the nature of the electrodes, the pH and the ionic strength of the circulating electrolyte, and the duration of the treatment.

“…In order to obtain a statistically significant number of experimental data, a rapid and continuous flow method was set up for determining nitrogen desorption isotherms (Cahen et al, 1965). This technique involves passing a mixture of 15-20% nitrogen in helium through the sample cooled in liquid nitrogen at a total pressure of 4000 to 5000 mm of Hg, causing the Nu partial pressure to approach its liquefaction pressure and nitrogen to be adsorbed.…”

Section: Pore-size Distribution Curvesmentioning

confidence: 99%

“…Recent development of a rapid continuous flow method (Cahen et al, 1965) for measuring pore-size distributions has made this work possible. Moreover, the results obtained with N2 have been compared with those obtained with H~O.…”

Section: Introductionmentioning

confidence: 99%

Surface Properties and Texture of Chrysotiles

Fripiat

1967

Self Cite

I~ITROGEI~ surface areas and pore-size distribution curves of various chrysotiles have been measured using a continuous flow method. A model founded on a hexagonal close packing of fibers has been adjusted to fit the frequency distribution curve of the fiber outside diameters obtained from electron micrographs. From this model, theoretical distribution functions of the surface area versus the pore diameter were computed and compared to the experimental data. For one fiber only (i.e. Coalinga chrysotfle), the good agreement between the computed and experimental data allows one to conclude that the external pores (between the fibers) and the internal pores (within the fibers) are free from any amorphous material. For the other studied chrysotiles, the degree of filling of the pore system by amorphous materials was always higher than 50~o. Under these conditions, hydration water cannot be removed unless the samples are pretreated in the 300~176 temperature range. On the contrary, water is driven off from the "clean" Coalinga fibers at temperatures lower than 100~ Surface area measurements derived from water-adsorption isotherms correspond to those obtained with nitrogen after the hydration water has been removed.