Neutron scattering study of adsorption in porous MCM-41 silicaSpecial issue on Neutron Scattering in Canada.

Abstract

Adsorption of n-pentane on MCM-41 silica has been studied by neutron scattering on both the adsorption and desorption isotherms. Adsorption takes place without hysteresis in either the isotherm or the neutron scattering profile. Adsorption of contrast-matched pentane in porous MCM-41 silica at first increases the intensity of the (10) Bragg peak but reduces the (11) and (20) peaks, and as the pores are filled the intensities of all Bragg peaks are reduced to zero. The SANS background has a 1/Q dependence, typical of a material prepared with templates of one-dimensional character (cylinders). The initial increase of (10) intensity allows estimation of the cylindrical pore diameter to be 37 Å based on the variation of form factor as a function of the cylinder radius. Résumé : Nous avons étudié l'adsorption du n-pentane sur de la silice MCM-41 par diffusion de neutrons sur les deux isothermes d'adsorption et de désorption. L'adsorption se produit sans hystérèse soit dans l'isotherme ou le profil de diffusion de neutrons. Au début, l'adsorption en appariement de contraste du n-pentane dans la silice MCM-41 augmente l'intensité du pic (10) de Bragg, mais réduit celle des pics (11) et (20). À mesure que les pores se remplissent, l'intensité de tous les pics de Bragg diminue à zéro. Le bruit de fond de la diffusion de neutrons à petits angles (SANS) a une dépendance en 1/ Q typique d'un matériau préparé avec des gabarits de type unidimensionnels (cylindres). L'augmentation initiale de l'intensité du pic (10) permet d'estimer que le diamètre des pores cylindriques est 37 Å en se basant sur la variation du facteur de forme en fonction du rayon du cylindre.[Traduit par la Rédaction]

Neutron and X-Ray Porosimetry

“…Adsorption of n-pentane on MCM-41 silica was studied using SANS in [19]. The synthesized sample of MCM-41 had spacing between the pore centers of 44.2 Å estimated using X-ray and neutron diffraction.…”

“…8.5). The inset shows the in-vacuo profile plotted on a log-log scale along with an underlying straight line, whose slope is À1 [19]. 2008 Canadian Science Publishing or its licensors.…”

Cavitation on Deterministically Nanostructured Surfaces in Contact with an Aqueous Phase: A Small-Angle Neutron Scattering Study

“…While there is a general agreement that the key processes governing gas phase nucleation occur on nano- and mesoscopic scales, the majority of experimental studies have been limited to mesoscopic and macroscopic observations , due to numerous challenges associated with direct experimental probing of the initial stages of gas nucleation at the nanoscale . Small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) techniques are widely used to characterize vapor adsorption and capillary condensation in nanoporous and mesoporous solids. − Synchrotron SAXS has also been recently applied to investigate nanowetting of superhydrophobic surfaces as well as the morphology of air bubbles trapped inside nanometer-scale hydrophobic cavities. − …”

A More Informative Approach for Characterization of Polymer Monolithic Phases: Small Angle Neutron Scattering/Ultrasmall Angle Neutron Scattering

“…pores. 21 The length scale probed (10À10 000 Å) using a combination of SANS and USANS is ideal for the characterization of pore dimensions for monoliths. In addition, it is possible to match the scattering density of the monolith with a mixture of the deuterated and nondeuterated forms of a mobile phase (contrast matching) and to make it "disappear" anywhere the solvent penetrates.…”

“…Porosity of monolithic media (as for other porous media) is generally carried out using either nitrogen or mercury porosimetry. , The utilization of small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and ultrasmall-angle neutron scattering (USANS) techniques for characterization of porosity has not been widespread for organic polymeric materials , However, these techniques have found use for materials such as porous glasses, − aerogels, polysiloxanes, molecular sieves, silica microparticles, geological specimens, ,− metallurgical samples, , graphite, activated carbon, and zeolites (Table ).…”