Search results for "POROSITY"

Porosity and dimension of sets and measures

2009

Imaging connected porosity of crystalline rock by contrast agent-aided X-ray microtomography and scanning electron microscopy

2018

We set out to study connected porosity of crystalline rock using X‐ray microtomography and scanning electron microscopy with energy dispersive X‐ray spectroscopy (SEM‐EDS) with caesium chloride as a contrast agent. Caesium is an important radionuclide regarding the final deposition of nuclear waste and also forms dense phases that can be readily distinguished by X‐ray microtomography and SEM‐EDS. Six samples from two sites, Olkiluoto (Finland) and Grimsel (Switzerland), where transport properties of crystalline rock are being studied in situ, were investigated using X‐ray microtomography and SEM‐EDS. The samples were imaged with X‐ray microtomography, immersed in a saturated caesium chlorid…

Catalytic effect of transition metals (copper, iron, and nickel) on the foaming and properties of sugar-based carbon foams

2019

Abstract Recently, bio-based carbon foams have gained much interest in many chemical industry fields because of their unique structure and properties. This study provides new information on the effects of catalytic metals (iron, nickel, and copper) on the foaming process. Specifically, the effects of these catalysts on the density, foam growth, and cell size and then further on the pore size distribution and specific surface areas after the physical activation are considered. Furthermore, some of the activated sugar foams were used in adsorption tests using methylene blue as adsorbent. Results showed that the highest effect on foam density was obtained using the iron catalyst in the foaming…

Graphitically encapsulated cobalt nanocrystal assemblies

2010

Graphitically encapsulated cobalt nanocrystal assemblies are chemically prepared by one-pot reaction at380 degrees C followed by a reversed etching process to produce porous graphitic structure for revealing their self-assembling nature.

Comparison of Structure and Properties of Differently Treated Illite Clay and Products

2014

The investigation is focused on modification of the structure 2:1 sheet silicates - illite clay by subjecting them to chemical and microbiological impact. It is shown that alkaline activation of illite clay by sodium hydroxide leads to the slight structural changes mainly characterized by water link changes. The effect of bacteria Ps. fluorescens AM PS11on structure changes of illite is small and is influenced on rheology of treated clay.It is shown that the influence of chemical treatment on porosity, bulk density and increase of compressive strength of sintered ceramic samples is notable.

Birefringent porous silicon membranes for optical sensing

2012

In this work anisotropic porous silicon is investigated as a material for optical sensing. Birefringence and sensitivity of the anisotropic porous silicon membranes are thoroughly studied in the framework of Bruggeman model which is extended to incorporate the influence of environment effects, such as silicon oxidation. The membranes were also characterized optically demonstrating sensitivity as high as 1245 nm/RIU at 1500 nm. This experimental value only agrees with the theory when it takes into consideration the effect of silicon oxidation. Furthermore we demonstrate that oxidized porous silicon membranes have optical parameters with long term stability. Finally, we developed a new model …

Eco-friendly cavity-containing iron oxides prepared by mild routes as very efficient catalysts for the total oxidation of VOCs

2018

Iron oxides (FeOx) are non-toxic, non-expensive and environmentally friendly compounds, which makes them good candidates for many industrial applications, among them catalysis. In the present article five catalysts based on FeOx were synthesized by mild routes: hydrothermal in subcritical and supercritical conditions (Fe-HT, Few200, Few450) and solvothermal (Fe-ST1 and Fe-ST2). The catalytic activity of these catalysts was studied for the total oxidation of toluene using very demanding conditions with high space velocities and including water and CO2 in the feed. The samples were characterized by X-ray diffraction (XRD), scanning and high-resolution transmission electron microscopy (SEM and…

Establishing material hygrothermal characteristics via long-term monitoring and best-fit numerical models

2020

Numerical models of heat and moisture transfer for performance forecast of lightweight insulating assemblies require many inputs. These include exterior climate data (i.e. temperature, relative humidity, solar radiation), interior climate data or standard models, transfer coefficients, correct initial conditions, etc. Most importantly, one needs reliable material models. A material model includes porosity, density, heat capacity, but also non-constant properties, such as thermal conductivity, vapor/liquid water diffusivity, sorption curves. These are, in general, difficult to determine, and material database entries often are incomplete, or simply non-existent. However, if one performs long…

The boson peak of deeply cooled confined water reveals the existence of a low-temperature liquid-liquid crossover.

2014

International audience; The Boson peak of deeply cooled water confined in the pores of a silica xerogel is studied by inelastic neutron scattering at different hydration levels to separate the contributions from matrix, water on the pore surfaces and "internal" water. Our results reveal that at high hydration level, where the contribution from internal water is dominant, the temperature dependence of the Boson peak intensity shows an inflection point at about 225 K. The complementary use of differential scanning calorimetry to describe the thermodynamics of the system allows identifying the inflection point as the signature of a water liquid-liquid crossover.

Using static and dynamic indicators to evaluate soil physical quality in a Sicilian area

2016

Both capacitive indicators derived from the water retention curve and dynamic measurements of the flow-weighted mean pore radius, R0, were used to assess the soil physical quality of two agricultural areas (cropland and olive orchard) and two natural areas (grassland and managed woodlot plantation) potentially subject to soil degradation. The overall idea of the study was to investigate whether a dynamic indicator quantitatively derived from hydraulic conductivity measurements could be used to supplement the traditionally applied capacitive indicators retrieved from water retention measurements. According to the available criteria, only the surface layer of the cropland site showed optimal …