Search results for "Pore size"
showing 10 items of 45 documents
Preparation of Poly(l-lactic acid) Scaffolds by Thermally Induced Phase Separation: Role of Thermal History
2018
Abstract Poly-L-Lactic Acid (PLLA) scaffolds for tissue engineering were prepared via thermally induced phase separation of a ternary system PLLA/dioxane/tetrahydrofurane. An extension to solution of a previously developed method for solidification from the melt was adopted, the technique being based on a Continuous Cooling Transformation (CCT) approach, consisting in recording the thermal history of rapidly cooled samples and analysing the resulting morphology. Different foams were produced by changing the thermal history, the dioxane to THF ratio (50/50, 70/30, 90/10 v/v) and the polymer concentration (2, 2.5, 4 ° wt) in the starting ternary solution. Pore size, porosity, melting and crys…
Laboratory tests addressed to realize customized restoration procedures of underwater archaeological ceramic finds
2013
The present contribution is part of a biennial research project funded by the Italian Ministry of Education, Universities and Research (MIUR). This study, currently in progress, deals with innovative experimental approaches applied to the chemical, mineralogical and physical transformations occurring during the prolonged permanence of archaeological ceramic finds in seawater environments as well as to restoration and conservation issues of the same underwater artifacts. The experimental approach used in this research consisted in the manufacture of ceramic test-pieces (briquettes) and their successive placing in underwater environment. This work aims at assessing how textural and compositio…
Gelchromatographie. 7. Mitt.: Die auflösung bei der trennung von oligomeren
1969
Die optimalen Bedingungen und die Anwendungsgrenzen der Gelchromatographie zur Trennung von Gemischen in Einzelkomponenten werden diskutiert. Die Wahl eines Gels mit geeigneter Porengrosenverteilung hat einen entscheidenden Einflus auf die erzielbare Trennung. Niedermolekulare Polystyrole, Polybutylmethacrylate, Polyathylenoxide, Polyexpoxide und verschiedene Tenside werden getrennt. Eine polymerhomologe Reihe last sich etwa bis zum Polymerisationsgrad 15 in einzelne Glieder trennen; bis zum Polymerisationsgrad 30 sind in den Schreiberkurven nicht vollstandig aufgeloste Peaks zu erkennen. Optimal conditions and limits of application for gelchromatographic separation of mixtures into signle …
Chapter 8 Native and Bonded Silicas in Aqueous Sec
1988
Publisher Summary This chapter deals with the properties of packings and columns in correlation to chromatographic separations in size exclusion chromatography (SEC) and provides guidelines for optimum support design. The chapter provides a survey of the current state-of-the-art with respect to the surface modification of silica for SEC packings in aqueous eluents. The properties of commercial packings and columns are listed and compared. An advice is also discussed on the operation and maintenance of columns with a view to achieving high resolution and long life-time. In SEC, solute elution is based on equilibrium, entropy-controlled size exclusion process. According to their size, the so…
Evidence of Mechanisms Occurring in Thermally Induced Phase Separation of Polymeric Systems
2014
Thermally induced phase separation is a fabrication technique for porous polymeric structures. By means of easy-to-tune processing parameters, such as system composition and demixing temperature, a vast latitude of average pore dimensions, pore size distributions, and morphologies can be obtained. The relation between demixing temperature and morphology was demonstrated via cloud point curve measurement and foams fabrication with controlled thermal protocols, for the model system poly-l-lactide–dioxane–water. The morphologies obtained at a temperature lower than cloud point showed a closed-pore architecture, suggesting a “nucleation-and-growth” separation mechanism, which produced larger po…
Formation of hierarchically ordered silicas prepared by spray drying of nanosized spheres
2002
We report on our strategy to synthesise defined arrangements of macro- and mesopores in one single material with spherical morphology using the spray drying technique. As starting materials, nano-sized silica spheres and colloidal suspensions were chosen. The intra-particle as well as inter-particle pore size was independently controlled which allowed to obtain materials with varied bimodal pore networks. The spherical agglomerates were characterised regarding their pore structural parameters and are potential adsorbents in liquid chromatographic separations.
Impact of secondary succession in abandoned fields on some properties of acidic sandy soils
2020
Abstract Abandonment of agricultural lands in recent decades is occurring mainly in Europe, North America and Oceania, and changing the fate of landscapes as the ecosystem recovers during fallow stage. The objective of this study was to find the impact of secondary succession in abandoned fields on some parameters of acidic sandy soils in the Borská nížina lowland (southwestern Slovakia). We investigated soil chemical (pH and soil organic carbon content), hydrophysical (water sorptivity, and hydraulic conductivity), and water repellency (water drop penetration time, water repellency cessation time, repellency index, and modified repellency index) parameters, as well as the ethanol sorptivit…
A simple approach towards one-dimensional mesoporous carbon with superior electrochemical capacitive activity.
2009
One-dimensional (1D) mesoporous carbons with highly ordered 3D interconnected pore structure and large-diameter pore size (10–20 nm) have been synthesized by a simple precursor-controlled thermolysis approach; such unique carbonaceous frameworks show superior capacitive behavior in electrochemical double-layer capacitors.
New force field for GCMC simulations of D 2 /H 2 quantum sieving in pure silica zeolites
2020
International audience; We report a study on adsorption and coadsorption of H2 and D2 in FAU, MFI and CHA pure silica zeolites having different pore sizes and shapes. Adsorption capacities, selectivities, enthalpies and entropies are determined by combining experiments and GCMC simulations. We show that the force fields available in the literature cannot predict the adsorption equilibria below 77 K with sufficient accuracy. Here we propose a new force field adjusted by using our experimental data obtained for the pure silica MFI zeolite at 65 K and 77 K. With this new force field, it is possible to predict the adsorption and coadsorption equilibria on the three zeolite structures in a tempe…
Silica-based macrocellular foam monoliths with hierarchical trimodal pore systems
2005
Abstract Silica-based large monoliths exhibiting a trimodal hierarchical pore system have been successfully prepared through a nanotectonic approach starting from sub-micro/nanometric mesoporous particles (as building blocks), and using a polyurethane foam as macrotemplate. Large trimodal pieces with macrocellular like interconnected macropores in the micrometer range are a mineralized replica of the polyurethane foam. Textural large-mesopores/macropores (in the 20–70 nm range) have their origin in the inter-particle voids. The small intra-particle mesopore system (with pore diameters around 2–3 nm) is due to the supramolecular templating effect of the surfactant.