Search results for "huokoisuus"

Selective gas adsorption by calixarene-based porous octahedral M32 coordination cages

2022

Giant octahedral M32 coordination cages were prepared via self-assembly of sulfonylcalix[4]arene-supported tetranuclear M(II) clusters (M = Co, Ni) with hybrid linker based on tris(dipyrrinato)cobalt(III) complexes appended with peripherical carboxylic groups. Due to intrinsic and extrinsic porosity, the obtained solid-state supramolecular architectures demonstrated good performance as adsorbents for the separation of industrially important gases mixtures. peerReviewed

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…

Activated carbon from hydrolysis lignin: Effect of activation method on carbon properties

2022

This study presents the effects of different activation methods to produce activated carbon from the hydrolysis lignin. Pretreatment of the feedstock with common mineral acids (HCL, HNO3, and H3PO4), different steam rates for physical activation, and different chemical activating agents (ZnCl2, Na2CO3, and KOH) for chemical activation were investigated. The pretreated biomass was carbonized and activated in one-stage process and the surface characteristics, such as total pore volume, pore size distribution and specific surface area, were investigated. The results showed that the activated carbon surface properties were not greatly affected by acid pretreatment. Brunauer-Emmett-Teller (BET) …

Analysis of fluid flow through porous media based on x-ray micro-tomographic reconstructions

2010

This thesis deals with creeping fluid flow through fibrous porous materials. Permeability through a porous medium is a measure of the ability of the material to transmit fluids. For testing and demonstration purposes the permeability values of a few fibrous heterogeneous materials, namely synthetic non-woven felt, wet pressing felt, cardboard, newsprint and hardwood paper, were measured experimentally. Reconstructions of the same materials under similar compression states were captured by x-ray micro-tomography. The actual microscopic pore structure thus obtained was utilised in the numerical lattice-Boltzmann analysis for solving the fluid flow permeability of the materials. Agreement betw…

The effect of steric hindrance on the packing of elongated objects

2016

Fibres of various materials can be deposited to form planar mats of fibres. These kinds of structures have gained substantial attention owing to their direct relation to both large industrial fields, such as paper and nonwovens, and biological structures, such as natural networks of fibrin, actin and collagen. In addition, similar structures are important in new emerging fields such as flexible electronics and tissue engineering. The physical properties of these structures are directly related to the connectivity of the network, thus a thorough understanding of the contact formation of the system is of great importance from both a scientific viewpoint as well as for its application in the e…

The microstructure of bentonite clay

2018

Bentonite is a common clay having many applications. One of them will be in the spent nuclear fuel repository, as a buffer material between host rock and the canisters containing the radioactive waste. This application has high requirements for the material used, ranging from, among others, appropriate mechanical properties, chemical stability, fine porous structure to sufficient hydraulic conductivity. The material should maintain its properties over time as the life span of the repository is hundreds of thousands years. The aim of this thesis was to investigate the structure of bentonite clay in a condition similar to expected in the repository. The research focused mainly on the pore str…

Morphological analysis of human cortical bone using high-resolution X-ray microtomography

2012

Structural and elastic properties of bone are related to microstructural parameters such as porosity and anisotropy. Microtomography (μCT) enables assessment of bone microstructural geometry, typically down to a voxel size of 5 microns. The purpose of this thesis was to evaluate whether using a higher (sub-micrometer) voxel resolution in X-ray μCT enables detection of new, finer, details in human cortical bone. The second objective was to measure several morphological parameters that determine the microstructure, and to compare two different microtomographs. To this end, twenty four human cadaveric femur samples were imaged by Xradia XCT-400 at a voxel size of 0.56 - 0.59 μm and spatial res…

Tracer migration in crystalline rock : application to geological barriers of nuclear waste storage

2016

This work deals with transport of radionuclides in the geosphere. The subject is investigated through characterisation of water conducting fractures, determining of rock transport properties and development of new methods for characterising geological samples. Here, as is often the case, radionuclide transport is investigated indirectly by characterising the structures, where the transport takes place, and directly by measuring transport properties in the gas phase. First water conducting fractures of three different types and the rock matrix surrounding them were analysed through rock samples from Olkiluoto. The analysis was done using X-ray tomography, the 14C-PMMA autoradiography techniq…