Research project NM/A/04 (Research action NM)
CONTEXT
The aim of the project was:
- to develop porous reference materials for MIP (Mercury Intrusion Porometry) measurements;
- to develop a method to correct MIP measurements for their "bottle neck" behavior;
- to apply the method to practical problems.
In the first year, porous materials were produced in a broad pore size range with different manufacturing techniques and analysed with different techniques.
In the second year, the study was concentrated on materials with pore sizes between 5 and 100 µm. These materials were extensively characterized with MIP and IA (Image analysis) measurements. A method was worked out to correct MIP measurements with a model based on image analysis of SEM (Scanning Electron Microscopy) pictures of the microstructure. The obtained method could successfully be demonstrated on real brick materials.
THE PROJECT
Results of measurements of porosity, pore volume, pore size and pore size distribution, are always strongly dependent on the method and on the apparatus used to perform the measurements. Therefore, it is not only sensible to compare the measurements of different techniques on the same material, but to compare them also with measurements obtained on well-defined reference materials.
MIP is a fast, cheap and reproducible method to study porous materials. Moreover, MIP measurements cover a large pore size range from 5 nm to 0.3 mm. Originally, the objective of this OSTC project was to develop MIP reference materials for this whole range of pore sizes. In view of the work already done by the "Bundesanstalt fur Materialforschung und-prufung" (BAM), we have focused our efforts to pore sizes starting from 5 µm.
In a first part of the project, the MIP results on the obtained reference materials are compared with other pore size analysing techniques, and especially IA. Indeed, with the arrival of strong hardware and computer processing of images, IA becomes an important additional tool for the study of pores. It gives especially the possibility to quantify the morphological aspects of the pores. MIP does not consider these morphological aspects in a pore size measurement, because all the data are interpreted by a model based on cylindrical pores.
Therefore, it is the main objective of this project to be able to correct the pore size distribution obtained by MIP measurements for their known "bottle neck" behavior, by IA. In this way, better exploitable measurement data by MIP can be obtained.
This objective was extensively worked out in part two, especially for materials with maximum pore size of 5 µm and 50 µm, in view of the considerations of the users committee.
THE PARTNERS
The collaboration regrouped teams of two research institutes: Vito (coordinator, responsible Dr. ir. J. Luyten) and CSTC-WTCB (responsible Dr. J. Elsen, later on replaced by ir. F. de Barquin).
EXPECTED PRODUCTS AND RESULTS
1. Manufacturing routes for porous references for the whole range of pore sizes were worked out.
For the materials used in the pore size range of 3 to 15 nm, we produced flakes by a sol gel method. A Reaction Bonded Al2O3 manufacturing route could be used to produce strong materials with pore sizes between 0.15 and 10 µm.
The pore size range of 10 to 100 µm can be covered by a system where large agglomerates are mixed with 5 to 10 wt% of fine powder and synthesized by pressing and sintering. Finally, materials with pore sizes bigger than 100 µm can be produced by ceramic foam techniques.
MIP measurements can only be done for pore sizes between 6 nm and 0.3 mm. This was a first limitation. Sol gel and ceramic foam techniques are therefore excluded. After a year, we decided to concentrate on pore sizes between 5 and 100 µm, because there are no reference materials of BAM in that pore-size range.
2. The different materials originally produced were tested with different analytical techniques and compared to MIP measurements.
MIP measurements were performed with two apparatus to optimize the materials, their structure, their shape and volume and the way of measurement. Very reproducible materials could be produced.
3. The same materials were also extensively study by image analysis and a method was worked out to correct MIP measurements with a model based on image analysis measurements.
4. The obtained techniques and their interpretation were demonstrated on materials with pore sizes between 5 and 100 µm and on a few real brick materials with a well known pore structure.
5. An onset was made to study the water transport behavior in brick materials.
6. A paper, describing the first part of the project, was already published in Key Engineering Materials, vols. 206-213 (2002) p. 681, J. Luyten, A. Buekenhoudt, F. de Barquin and J. Elsen , "Reference Materials for adequate porosity measurements."
SCIENTIFIC COLLABORATION
Documentation and some samples, very helpful for the project, could be obtained from BAM.
USERS COMMITTEE
- J. M. Linster and N. Lens (Koramic Building Products, Central Lab)
- W. Coppens and L. Jacobs (N.V.Bekaert S.A.)
- K. Meyer (Bundesanstalt fur Materialforschung und-prufung)
- F. Devreese (Ankersmid)
PROMOTERS
Jan LUYTEN
Vlaamse Instelling voor Technologisch Onderzoek
Boeretang 200
B-2400 MOL
Tel: +32 14 33.56.67
Fax: +32 14 32.11.86
E-mail: jan.luyten@vito.be
Fabrice DE BARQUIN
Centre Scientifique et Technique de la Construction
Boulevard Poincaré 79
B-1060 BRUXELLES
Tel: +32 2 655.77.11
Fax: +32 2 653.07.29
E-mail: Fabrice.de.Barquin@bbri.be
Reference materials for adequate porosity measurements : final report
Brussels : Federal Science Policy, 2005 (SP1466)
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