Search results for "porosimetry"
showing 10 items of 38 documents
Alkali activated materials using pumice from the Aeolian Islands (Sicily, Italy) and their potentiality for cultural heritage applications: Prelimina…
2020
Abstract In this paper, the potentialities of pumice-based geopolymers have been explored with the aim to evaluate their use as restoration materials. In particular, the behaviour of Aeolian pumice during alkali activation process, either alone or in binary mixtures with metakaolin, has been assessed using sodium hydroxide and sodium silicate activators. Hardened products were characterized by: X-ray diffraction; infrared spectroscopy; thermo gravimetry and electron microscopy. Furthermore, Hg-intrusion porosimetry, water absorption, compressive strength and colorimetric measurements were carried out in order to define the technical features of the produced geopolymers. The results reveal t…
Hysteresis in nitrogen sorption and mercury porosimetry on mesoporous model adsorbents made of aggregated monodisperse silica spheres
1989
Abstract An elucidation of the hysteresis phenomena in nitrogen sorption (NS) and mercury porosimetry (MP) on porous aggregates of non-porous silica spheres of particle diameter 90–1000 nm is presented. First, it is demonstrated that highly ordered and dense aggregates of a porosity of 26–30% are formed by gravity settling and centrifugation. A hexagonal and cubic close-packed structure within the layers and a vertical stacking between the layers were observed. Minor deteriorations were seen between the ordered domains. Second, the pore size distribution (PSD) curves calculated from the adsorption branch of the nitrogen isotherms by means of the Cohan equation and from the desorption branch…
Influence of Temperature on Calcium Hydroxyapatite Nanopowders
2012
The aim of this work is to investigate the effects of thermal treatment, in the range of temperature between 80°C - 900°C, on crystallinity, morphology and particles size of calcium hydroxylapatite nanopowders (HAp). A complete study was carried out applying 31P Magic Angle Spinning NMR, X-ray diffraction, nitrogen porosimetry and Transmis- sion Electron Microscopy techniques. HAp specimens were prepared by chemical precipitation in an aqueous solution of calcium nitrate and ammonium hydrogen phosphate. The thermal treatment performed, showed the formation of crystals whose appearance has three main morphologies and different particles size. HAp treated up to 500°C showed a set of needle-li…
Studies and Researches on the Obtaining of Sintered Gradual Porous Structures by Irregular Nickel Powders Sedimentation
2012
The aim of this work is to obtain sintered porous membranes with graded structure for microfiltration by sedimentation and sintering of metallic powders. Our previous studies have demonstrated the possibility of obtaining sintered porous materials with graded structure by sedimentation. In this paper, irregular nickel particles were used having a grain size in the 2-90 µm range evaluated using scanning electron microscopy and laser scattering particle size analyzer. The powders were sedimented into a sintering die in a sedimentation medium consisting of water and dispersant agent. After drying, the samples were sintered at 1000°C for 10 minutes in vacuum (~1•10-3 Pa). The structures obtaine…
Spherical silica agglomerates possessing hierarchical porosity prepared by spray drying of MCM-41 and MCM-48 nanospheres
2003
Hierarchically ordered porous materials possessing both meso- and macropores can be obtained by agglomeration of spherical primary particles of mesoporous MCM-41 and MCM-48 materials using the spray drying technique. A highly interconnected bimodal pore network is obtained due to the intra- and inter-particle pore systems within the micron-sized spherical agglomerates. Further packing of the agglomerates will result in a three-modal hierarchical pore system, where the first level of porosity originates from the ordered mesopores inside the primary particles, the second level is a result of the particle internal porosity, and the third level is due to the voids between the agglomerates. The …
Pore shape affects the determination of the pore size of ordered mesoporous silicas by mercury intrusion.
2008
MCM-41 and SBA-15 micelle-templated silicas are ideal reference materials to study the effect of surface roughness on pore size measurement by mercury intrusion, as the inner surface of the mesoporous channels is much rougher in the case of SBA-15 than MCM-41. In the case of MCM-41, the pressure of mercury intrusion is related to the pore size by the classical Washburn−Laplace law, while in the case of SBA-15, the pressure of intrusion is much higher than expected and classical models underevaluate the size of the channels. Defects on the pore surface of SBA-15 affect the mercury intrusion in a similar way as the deviation from cylindrical geometry does for the pores of spongelike silica gl…
Flow-through pore characteristics of monolithic silicas and their impact on column performance in high-performance liquid chromatography
2008
Abstract In order to elucidate the role of the flow-through characteristics with regard to the column performance in high-performance liquid chromatography (HPLC) native and n -octadecyl bonded monolithic silica rods and columns, respectively of 100 mm length and 4.6 mm ID with mesopores in the range between 10 and 25 nm and macropores in the range between 0.7 and 6.0 μm were examined by mercury intrusion/extrusion, scanning electron microscopy, image analysis and permeability. The obtained data of the flow-through pore sizes and porosity values as well as surface-to-volume ratio of the stationary phase skeleton enabled to predict their influence to the chromatographic separation efficiency…
Comprehensive pore structure characterization of silica monoliths with controlled mesopore size and macropore size by nitrogen sorption, mercury poro…
2005
The porosity of monolithic silica columns is measured by using different analytical methods. Two sets of monoliths were prepared with a given mesopore diameter of 10 and 25 nm, respectively and with gradated macropore diameters between 1.8 and 7.5 microm. After preparing the two sets of monolithic silica columns with different macro- and mesopores the internal, external and total porosity of these columns are determined by inverse size-exclusion chromatography (ISEC) using polystyrene samples of narrow molecular size distribution and known average molecular weight. The ISEC data from the 4.6 mm analytical monolithic silica columns are used to determine the structural properties of monolithi…
Textural characterization of native and n-alky-bonded silica monoliths by mercury intrusion/extrusion, inverse size exclusion chromatography and nitr…
2008
Native and n-alkyl-bonded (n-octadecyl) monolithic silica rods with mesopores in the range between 10 and 25 nm and macropores in the range between 1.8 and 6.0 microm were examined by mercury intrusion/extrusion, inverse size exclusion chromatography (ISEC) and nitrogen sorption. Our results reveal very good agreement for the mesopore size distribution obtained from nitrogen adsorption (in combination with an advanced NLDFT analysis) and ISEC. Our studies highlight the importance of mercury porosimetry for the assessment of the macropore size distribution and show that mercury porosimetry is the only method which allows obtaining a combined and comprehensive structural characterization of m…
Hydric, thermal and mechanical properties of self-compacting concrete containing different fillers
2008
Abstract Water vapor diffusion coefficient, water absorption coefficient, water permeability, thermal conductivity, compressive strength and freeze resistance properties of two self-compacting concretes (SCC) containing limestone filler and fly ash are determined in the paper. The results indicate that strength development is faster in the material containing limestone filler but after 90 days the strength values in both materials are almost the same. Liquid water transport and heat transport are faster in SCC with limestone filler while the water vapor transport is faster in the material containing fly ash. This corresponds well with the much better freeze resistance of the material with f…