In the latest years, the addition of glass-ceramics systems to porcelain stoneware bodies has been experimented to assess their expected technological benefits and aesthetic advantages. The aim of this study is to investigate the influence of glass-ceramics on mechanical properties appraising the intimate changes occurring as a consequence of the addition and particularly on microstructural characteristics and technological features. For this purpose a very deep mechanical characterisation has been carried out on industrial and laboratory products obtained by mixing up to 20% glass-ceramic systems to current industrial bodies, in particular elastic constants, Vickers hardness, toughness and failure strength have been measured. The glass-ceramic systems taken into account were BaO-Al2O3-SiO2 (BAS), Na2O- Al2O3-SiO2 (NAS), K2O-CaO-MgO- Al2O3-SiO2 (KCMAS) and ZrO2-CaO-SiO2 (ZCS). Information about material quality have been got from fractographic analysis, such as the observation of fracture-generated surfaces in terms of nature, size, shape, orientation and place of fracture origin. Moreover, microstructure and texture of the products have been studied and density, open and close porosity and phase composition, have been determined for this purpose. Industrial bodies resulted characterised by very low water absorption (0.07-0.12%) and closed porosity (1.6-4.1%), their bulk density ranging from 2.33 to 2.43 g.cm-3, flexural strength 30-40 MPa, Young modulus 63-71 GPa, and Poisson coefficient 0.18. The addition of NAS and KCMAS glass-ceramics precursors led to 3.7-4.3% of residual porosity and to bulk density of about 2.43 g.cm-3, with flexural strength 39-43 MPa and Young modulus 69-73 GPa, equal or higher than the industrial product ones. The sintering in standard conditions of bodies containing BAS and ZCS glass-ceramics was not complete, leaving significant residual porosity (12-14%) and the resulting flexural strength and Young modulus were rather low (26-29 MPa and 51 GPa, respectively). However, an appropriate mixture of BAS and ZCS systems allowed to achieve excellent mechanical performances (flexural strength 40 MPa, Young modulus 74 GPa, Poisson coefficient 0.26) notwithstanding the remarkable residual porosity (7.3%).
Mechanical properties of porcelain stoneware tiles: the effect of glass-ceramic systems
Biasini V;Dondi M;Melandri C;Raimondo M;
2001
Abstract
In the latest years, the addition of glass-ceramics systems to porcelain stoneware bodies has been experimented to assess their expected technological benefits and aesthetic advantages. The aim of this study is to investigate the influence of glass-ceramics on mechanical properties appraising the intimate changes occurring as a consequence of the addition and particularly on microstructural characteristics and technological features. For this purpose a very deep mechanical characterisation has been carried out on industrial and laboratory products obtained by mixing up to 20% glass-ceramic systems to current industrial bodies, in particular elastic constants, Vickers hardness, toughness and failure strength have been measured. The glass-ceramic systems taken into account were BaO-Al2O3-SiO2 (BAS), Na2O- Al2O3-SiO2 (NAS), K2O-CaO-MgO- Al2O3-SiO2 (KCMAS) and ZrO2-CaO-SiO2 (ZCS). Information about material quality have been got from fractographic analysis, such as the observation of fracture-generated surfaces in terms of nature, size, shape, orientation and place of fracture origin. Moreover, microstructure and texture of the products have been studied and density, open and close porosity and phase composition, have been determined for this purpose. Industrial bodies resulted characterised by very low water absorption (0.07-0.12%) and closed porosity (1.6-4.1%), their bulk density ranging from 2.33 to 2.43 g.cm-3, flexural strength 30-40 MPa, Young modulus 63-71 GPa, and Poisson coefficient 0.18. The addition of NAS and KCMAS glass-ceramics precursors led to 3.7-4.3% of residual porosity and to bulk density of about 2.43 g.cm-3, with flexural strength 39-43 MPa and Young modulus 69-73 GPa, equal or higher than the industrial product ones. The sintering in standard conditions of bodies containing BAS and ZCS glass-ceramics was not complete, leaving significant residual porosity (12-14%) and the resulting flexural strength and Young modulus were rather low (26-29 MPa and 51 GPa, respectively). However, an appropriate mixture of BAS and ZCS systems allowed to achieve excellent mechanical performances (flexural strength 40 MPa, Young modulus 74 GPa, Poisson coefficient 0.26) notwithstanding the remarkable residual porosity (7.3%).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
