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Pore Dimensions (pore + dimension)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Nanoporous Membranes of Hydrogen-bridged Smectic Networks with Nanometer Transverse Pore Dimensions,

ADVANCED MATERIALS, Issue 7 2008
Carmen Luengo Gonzalez
Nanoporous membranes are made based on photoreactive hydrogen-bridged smectic liquid crystal dimers. The self-assembled layered structure is locked by photopolymerization. The hydrogen bridges are reversibly opened by heating or by changing the pH. This forms periodic pores of which the integrity is conserved by a covalent crosslinker, setting the spacing at ca. 1 nm. The pores are covered with carboxylic anions that bind to cations or to amines. [source]

Synthesis of Highly Porous Yttria-Stabilized Zirconia by Tape-Casting Methods

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2003
Martha Boaro
Porous ceramics of Y2O3 -stabilized ZrO2 (YSZ) were prepared by tape-casting methods using both pyrolyzable pore formers and NiO followed by acid leaching. The porosity of YSZ wafers increased in a regular manner with the mass of graphite or polymethyl methacrylate (PMMA) to between 60% and 75% porosity. SEM indicated that the shape of the pores in the final ceramic was related to the shape of the pore formers, so that the pore size and microstructure of YSZ wafers could be controlled by the choice of pore former. Dilatometry measurements showed that measurable shrinkage started at 1300 K, and a total shrinkage of 26% was observed, independent of the amount or type of pore former used. Temperature-programmed oxidation (TPO) measurements on the green tapes demonstrated that the binders and dispersants were combusted between 550 and 750 K, that PMMA decomposed to methyl methacrylate between 500 and 700 K, and that graphite combusted above 900 K. The porosity of YSZ ceramics prepared by acid leaching of nickel from NiO,YSZ, with 50 wt% NiO, was studied as a function of NiO and YSZ particle size. Significant changes in pore dimension were found when NiO particle size was changed. [source]

The relation between stomatal aperture and gas exchange under consideration of pore geometry and diffusional resistance in the mesophyll

PLANT CELL & ENVIRONMENT, Issue 8 2009
HARTMUT KAISER
ABSTRACT The quantitative relation between stomatal aperture and gas exchange through the stomatal pore can be described by physical models derived from Fick's first law of diffusion. Such models, usually based on a simplified pore geometry, are used to calculate leaf conductance from stomatal pore dimensions or vice versa. In this study a combination of gas-exchange measurements and simultaneous microscopical observations of stomatal apertures was used to empirically determine this relationship. The results show a substantial deviation between measured stomatal conductance and that calculated from the simplified models. The main difference is a much steeper increase of conductance with aperture at small apertures. When the calculation was based on a realistic pore geometry derived from confocal laser scanning microscopy, a good fit to the experimentally found relationship could be obtained if additionally a significant contribution of a mesophyll diffusional resistance was taken into account. [source]

Can Metal,Organic Framework Materials Play a Useful Role in Large-Scale Carbon Dioxide Separations?

CHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 8 2010
Seda Keskin Dr.
Abstract Metal,organic frameworks (MOFs) are a fascinating class of crystalline nanoporous materials that can be synthesized with a diverse range of pore dimensions, topologies, and chemical functionality. As with other well-known nanoporous materials, such as activated carbon and zeolites, MOFs have potential uses in a range of chemical separation applications because of the possibility of selective adsorption and diffusion of molecules in their pores. We review the current state of knowledge surrounding the possibility of using MOFs in large-scale carbon dioxide separations. There are reasons to be optimistic that MOFs may make useful contributions to this important problem, but there are several critical issues for which only very limited information is available. By identifying these issues, we provide what we hope is a path forward to definitively answering the question posed in our title. [source]