Mrinmoy Garai; Basudeb Karmakar
Abstract
This study exemplifies the effects of 5 wt.% Pb2+ addition replacing the same Zn2+ content on crystallization and microstructure of 10B2O3-16Al2O3-39SiO2-12MgO-12MgF2-4K2O-1Li2O-1AlPO4 (wt.%) glass-ceramic composite. Increase of linear thermal-expansion (6.93 to 7.18×10-6/K at 50-600°C) in ...
Read More
This study exemplifies the effects of 5 wt.% Pb2+ addition replacing the same Zn2+ content on crystallization and microstructure of 10B2O3-16Al2O3-39SiO2-12MgO-12MgF2-4K2O-1Li2O-1AlPO4 (wt.%) glass-ceramic composite. Increase of linear thermal-expansion (6.93 to 7.18×10-6/K at 50-600°C) in substituting Zn2+ by Pb2+ is attributed to the field-strength of cations. Opaque crystalline glass-ceramics are derived from the transparent glasses (synthesized by single-step melt-quenching at 1500OC) by controlled heat-treatment at 1050°C and the predominant crystalline-phase was identified as fluorophlogopite mica, KMg3AlSi3O10F2. FFESEM of the ZnO containing glass-ceramics revealed that 100-200 µm sized plate-like crystals are in ‘well-packed interlocked arrangement’; which changed to ‘nanocrystalline microstructure’ combined of ‘spherical droplet like’ nanocrystals (crystal size = 10-50 nm) in attendance of PbO. Decrease in linear thermal-expansion (11.03 to 7.93 × 10-6/K at 50-700°C) due to the substitution of ZnO is ascribed to the crystallization inhibiting tendency of PbO towards boroaluminosilicate system. Thermal-expansion of ZnO containing glass-ceramic is large (> 11 × 10-6/K at 50-700 and 50-800°C) which can exhibit their enough thermal shock resistivity to be suitable for high-temperature sealing application. Copyright © 2017 VBRI Press.
Madan Singh; Spirit Tlali; Krishna Chandra
Abstract
A simple theoretical model is developed to explore the size and shape dependence of thermal expansion and Debye temperature of nanomaterials. The model theory is based on cohesive energy and surface area change of the nanocrystals compared to the bulk crystals. It is found that the Debye temperature ...
Read More
A simple theoretical model is developed to explore the size and shape dependence of thermal expansion and Debye temperature of nanomaterials. The model theory is based on cohesive energy and surface area change of the nanocrystals compared to the bulk crystals. It is found that the Debye temperature decreases with the decrease in particle size whereas, the thermal expansion increases as the particle size decreases. The present modelling results and predictions are very consistent with the available experiment results, implying that the model could be expected to be a general approach to understand the thermodynamic properties of nanomaterials. Copyright © 2017 VBRI Press
