Abstract
Glass composition of fixed values of the structural factor R(CdO/B2O3) = 0.5 and K(SiO2\B2O3) = 0.5 in borosilicate glass modified by CdO has been studied by different techniques. The amorphous structure of as prepared glass was confirmed by both XRD and EDP spectroscopy. The amorphous samples were treated thermally to be transformed to suitable type of crystalline glass ceramic. Based on SEM and TEM data, the bulk crystallized network was developed by treating the glasses at high treatment route (950°C - 1100°C) for a specific time (8 hours). Crystalline Al4B2O9 and Al18B4O33 whisker phases are simply detected by X-ray diffraction spectroscopy. The scanning and transmission electron microscopes (SEM and TEM) have confirmed that aluminum borate crystalline phases in the form of whiskers (rods) species are the main formed type. Both size and concentration of the whisker species were increased with increasing temperature of thermal heat treatment. Formation of this type of crystals (whiskers) leads to interlocking microstructure and as a direct result, an increase in hardness number, glass transition temperature is simply evidenced. Glass-ceramics synthesized in this study can be applied as high temperature resistant materials because their microstructures can resist micro-cracking upon indentation. The crack length due to indentation process is reduced by increasing concentration of crystalline road or whisker like structure.
Highlights
IntroductionSpecial attention has been paid toward glass ceramics containing some specific types of crystals
Glass-ceramics synthesized in this study can be applied as high temperature resistant materials because their microstructures can resist micro-cracking upon indentation
The amorphous nature of as prepared sample is further confirmed by electron diffraction patterns (EDP), Figure 4(c), since there is no any diffraction due to crystalline species could be observed
Summary
Special attention has been paid toward glass ceramics containing some specific types of crystals. In this regard whiskers type is useful substance applied to resist deformation and crack propagation in materials [2] [3] [4] [5]. The direct growth of dispersed whiskers in a glass matrix to form a glass-ceramic leads to improvements of material properties especially mechanical properties. This includes increased fracture toughness, hardness and improved thermal shock resistance [2] [4] [5]. Aluminum borate whiskers are considered to have great potentials for fabricating hard and tough topographical microstructures stable for applications
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