Microstructure properties of lead silicate glasses

In the present work, lead silicate glasses have been prepared withdifferent amount of lead oxide content. Structure properties such asX-ray diffraction, AFM, and FTIR analyses have been done. Theexceeding of PbO content more than 25wt% revealed a decreasing indensity. The X- ray revealed that the strongest peak related toHexagonal silica dioxide and the other crystal phases formed wererelated to silica oxide (SiO2) and lead oxide (PbO). Growth anddecayed phases in X-ray have been observed with changing leadoxide content. Homogeneous surface was obtained using AFManalyzer with an average diameter around 100 nm. Infrared spectrumis characterized by the presence of large absorption band between1200 and 900cm-1 and have its maximum at 1080 cm-1 which istypical to stretching vibrations of Si–O–Si bonds, another bandsnoticed were attributed to Pb–O–Pb, Pb–O–Si, [AlO4]-tetrahedron,and to Si–O–Al bond.

Dissolution-Reorientation-Polycondensation Process of Metakaolin in Alkaline Solutions Related to Geopolymerization

Geopolymer is a novel type of inorganic cementitious materials, which has become a hot topic across the world. Geopolymerization process of metakaolin in alkaline solutions shows important effects on final properties of hardened geopolymer. In this paper all the possible reaction pathways involved in the dissolution-reorientation-polycondensation process of metakaolin in alkaline solution were studied according to thermodynamic theory. The corresponding reaction energy of every possible pathway was also calculated using computation chemistry methodsemi- empirical AM1 calculation. The optimum reaction pathway was analysized based on the energy-minimized principle. The calculation results showed that highly alkaline accelerated the dissolution of 6-membered tetrahedron rings of SiO4 or AlO4 tetrahedron representing the molecular structure of metakaolin during dissolution process. Si-Al hybrid reorientation should theoretically be primary reorientation pathway during reorientation process. Framework clusters should be primary polycondensation products during polycondensation process. The above studies enhanced our understanding of formation mechanisms of metakaolin in alkaline solutions related to geopolymerization.