The effects of metastable tetragonal zirconia on the properties of Ordinary Portland
Cement were observed during which the effect of crystallite size pH on the preparation
solution, precursor salt, and the presence of co-precipitates, Fe(OH)3, SnO2 and SiO2 on
the crystallization temperature, enthalpy and crystal structure, immediately following the
crystallization exothermic burst phenomenon in ZrO2 were measured. Thermal analysis
and x-ray methods were used to determine crystallite sizes and structures immediately
following the exothermic burst. Comparisons were made for zirconias prepared from
oxychloride, chloride and nitrate solutions. The existence of tetrameric hydroxidecontaining
ions in oxychloride precursor is used to rationalise low values of
crystallization enthalpy.
The position of the crystallization temperature, Tmax was not dependent on crystallite size
alone but also on the pH at which the gel was made, the surface pH after washing, and the
presence of diluent oxides. Enthalpy v r1/2 and Tmax v (diluent vol)1/3 relationships
indicate that surface coverage effects dominate a surface nucleated phenomenon. The
data established for ZrO2 systems was used to develop tetragonal-ZrO2-SnO2 powders
capable of improving the mechanical properties of Ordinary Portland Cement discs.
The ZrO2-OPC discs were prepared by powder mixing, water hydration and uniaxial
pressing. Vicat needle tests showed that tetragonal-ZrO2 increases the initial setting rate.
Microscopy indicated that porosity distribution changes near to ZrO2 particles. Zirconia
has also been introduced into OPC discs by vacuum infiltration methods developed for
solutions and colloidal suspensions. Comparisons between OPC discs and the OPCtetragonal
ZrO2 composites have been made on the basis of diametral compression strength, Young’s modulus, hardness and toughness (K1c), as estimated by the cracked
indentation method. Bell-shaped curves are found for the way the mechanical properties
are changed as a function of Zirconia content.
| Identifer | oai:union.ndltd.org:BRADFORD/oai:bradscholars.brad.ac.uk:10454/7315 |
| Date | January 2012 |
| Creators | Almadi, Alaa |
| Contributors | McColm, Ian, Tait, Simon J. |
| Publisher | University of Bradford, School of Engineering, Design and Technology |
| Source Sets | Bradford Scholars |
| Language | English |
| Detected Language | English |
| Type | Thesis, doctoral, PhD |
| Rights | <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-nc-nd/3.0/88x31.png" /></a><br />The University of Bradford theses are licenced under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative Commons Licence</a>. |
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