Microstructure and Residual Stress Effect on the Flexural Strength of Porcelain Tiles Formulated from Locally Available Materials in Uganda

Quartz is an inexpensive raw material used in the production of porcelain tiles. The presence of quartz prevents pyroplastic deformation during sintering. However, the use of quartz particle size exceeding 32 µm has a deleterious effect on the flexural strength of porcelain tiles. Therefore, the aim of this study was to investigate the effect of microstructure and residual stress on the flexural strength of porcelain tiles formulated with different quartz particle sizes, within the range of 45 to 200 µm. The samples made of kaolin, feldspar and quartz were mixed in the ratio of 5:3:2 respectively, and die pressed at 40 MPa. Afterwards, the green body was sintered at 1300 0C for 2 hours at a rate of 60 0C/min. The microstructure of the sintered body was characterized by using a scanning electron microscope (SEM) to examine the nature and size of the pores. In addition, the residual stress was evaluated based on X-ray diffraction (XRD) method and corroborated with SEM. The flexural strength was determined using three points loading method. The samples formulated with quartz particle size of 45 µm exhibited smooth granules, and isolated pores within the range of 3-8 µm. But, those with 200 µm particles size exhibited rough granules, and interconnected pores between 10-34 µm. Initially, there was an increase in the residual stress, but above 90 µm particle size, it decreased due to evolution of cracks. Also, an increase in quartz particle size resulted in a decline in flexural strength from to MPa. These results show that increasing quartz particle size affected the pore morphology and the residual stresses. Therefore, fine quartz particle milling should be taken into account for further improvement of flexural strength.

SHS of Oxide Systems Based on the “Mechano-Chemical” Quartz Modified by Organometallic Compounds

<p>The differences of the effects of mechanical substance pre-activation in the mills with divers force effect schemes on the self-propagating high temperature synthesis (SHS) of the SiO₂ + 37.5 % Al system are shown. The power saturation of activated material is determined by particle defect intensity and effects on the thermal and physical characteristics of the material. The variations of activated material state are estimated referring on the variations of dilatometry curve paths. The effects of activation time on the temperature of sample self-ignition in the furnace, combustion temperature and completeness of the quartz reaction with aluminum are determined. The enhancing effects of organic modificators of quartz particle surfaces on the further SH synthesis development are shown.</p>

Quartz Particles Electron-Microscopic Investigations Modified by Mechanochemical Processing

There were taken and analyzed electron-microscopic images of quartz particles after mechanochemical processing in mill-activator with different organic modifiers. It was stated that quartz surface suffers serious changes the peculiarities of which are defined by used modifiers. Quartz particle has a complex flaky morphology.<br />Friable surface layers represent as carbonic element-organic formations with ferrous additives. The change of particle's surface layers are responsible to modified quartz physicochemical properties transfer.