Porosity structure and

Odler, I., RoEler, M. (1985) Investigations on the relationship between porosity, structure and strength of hydrated Portland cement pastes. II. Effect of pore structure and of degree of hydration . Cement and Concrete Research, 15 401-10. 

Additionally, porosity structure and strength development were determined for two Roman cements. For porosity structure measurements, prismatic specimens of 20 by 2 by 2 cm were cast in steel molds. The samples were demolded immediately after setting and cured under 100 % RH until tested. After the predetermined curing period, specimens for porosity stmctuie measurements were taken and immediately soaked in acetone for 24 h to stop the hydration of the cementitious materials. They were placed in a rotary vacuum flask at 20 °C for 4 h to remove acetone and to be dried. The porosity structure of the paste samples was determined using a Poremaster mercury intrusion porosimeter from Quantachrome, allowing the study of pore sizes in the range 440-0.0035 p,m. The measurements of strength are described in Ref. [4]. 

Polymer-based, synthetic ion-exchangers known as resins are available commercially in gel type or truly porous forms. Gel-type resins are not porous in the usual sense of the word, since their structure depends upon swelhng in the solvent in which they are immersed. Removal of the solvent usually results in a collapse of the three-dimensional structure, and no significant surface area or pore diameter can be defined by the ordinaiy techniques available for truly porous materials. In their swollen state, gel-type resins approximate a true molecular-scale solution. Thus, we can identify an internal porosity p only in terms of the equilibrium uptake of water or other liquid. When crosslinked polymers are used as the support matrix, the internal porosity so defined varies in inverse proportion to the degree of crosslinkiug, with swelhng and therefore porosity typically being more... 

The family of agarose-based gels, Sepharose, Sepharose CL, and Sepharose Fast Flow, are bead-formed gels prepared from 2, 4, or 6% agarose solutions. The matrix porosity decreases and rigidity of the bead structure increases with increasing agarose concentrations. The open pore structure and broad... 

Superdex and prepacked Superdex columns are supplied in 20% ethanol. All Superdex may be autoclaved repeatedly at pH 7, 120°C without significant changes in porosity or rigidity. Freezing and thawing of Superdex-based gels may result in disruption of the bead structure and should be avoided. 

The porosity and permeability of CP are the most important factors determining their ability to sorb and immobilize BAS. For solving these problems, it was necessary to synthesize various types of porous and permeable CP differing in the mobility of elements of the crosslinked structure and in the rigidity of the polymer backbone. For biological problems related to the application of CP as biosorbents, it has been found necessary to use CP with a marked structural inhomogeneity. 

The thud step gives a polymer-rich phase forming the membrane, and a polymer-depleted phase forming the pores. The ultimate membrane structure results as a combination of phase separation and mass transfer, variation of the production conditions giving membranes with different separation characteristics. Most MF membranes have a systematic pore structure, and they can have porosity as high as 80%.11,12Figure 16.6 shows an atomic force microscope... 

Metal carbonate decompositions proceed to completion in one or more stages which are generally both endothermic and reversible. Kinetic behaviour is sensitive to the pressure and composition of the prevailing atmosphere and, in particular, to the availability and ease of removal of C02. The structure and porosity of the solid product and its relationship with the reactant phase controls the rate of escape of volatile product by inter-and/or intragranular diffusion, so that rapid and effectively complete withdrawal of C02 from the interface may be difficult to achieve experimentally. Similar features have been described for the removal of water from crystalline hydrates and attention has been drawn to comparable aspects of reactions of both types in Garner s review [ 64 ]. 

Other key features in the analysis of pore structure are the length scales associated with the various micro- (nano)-scale obstacles and pores, the possible larger-scale variations in structure, and the averaging domain over which information is needed [6,341,436], The hterature refers to analysis of homogeneous and heterogeneous porous media, where homogeneous refers to media with no variation in physical properties (e.g., porosity, diffu-... 

Sedimentary rocks from oil reservoirs exhibit significant porosity where crude oils and water often coexist to share the pore space. The characterization of the pore structure and the fluids in situ is essential in the development of oilfields and specifically in the design of the production strategy and the facility. NMR has become an increasingly important well-logging and laboratory technique to quantify rock and fluid properties. 2D NMR has recently been introduced to the petroleum industry as a commercial well-logging service [58]. We will first review a few examples of the 2D NMR experiments on the sedimentary rocks in laboratory and well-logging applications. 

Water stability is a major challenge that has to be overcome before metal organic framework can be used in removing carbon dioxide from flue gas. The core structure of MOF reacts with water vapor content in the flue gas leading to severe distortion of the structure and even failure. As a consequence, the physical structure of MOF is changed, e.g., reduction of porosity and surface area, etc. that decreases the capacity and selectivity for C02. Complete dehydration of flue gas increases the cost of separation. It is therefore essential for MOFs to exhibit stability in the presence of water up to certain extent [91]. 

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