Cation grain‐boundary diffusivity in SiO₂‐ and MgO‐doped Al₂O₃

Abstract

Cation grain‐boundary diffusion in undoped and aliovalent‐doped Al2O3 is characterized using Cr2O3 as a chemical tracer. The compositional depth profiles measured by secondary ion mass spectrometry are fitted to the Whipple‐LeClaire model. The results indicate that cation grain‐boundary diffusivity is insensitive to MgO and SiO2 dopants between 1100°C and 1300°C.

Integrated Regeneration Method for Used Mineral Motor Oils

“…Lithium aluminosilicates have a low value of TCLE (0.5-2.0)•10 -6 K -1 , but the most acceptable crystalline phase in the composition of such coatings is magnesium aluminosilicate -cordierite. From the practice and theoretical studies of coatings for high-temperature protection it is known [7][8][9][10][11][12][13][14][15] that the maximum protective effect and minimum energy consumption can be achieved by forming the required phase component in the coating 1 Lviv Polytechnic National University, 12, Bandera St., 79013 Lviv, Ukraine * orest.m.vakhula@lpnu.ua ã Vakhula O., Pona M., Solokha I., Koziy O., Petruk M., 2021 layer during coatings pre-burning or operation. Therefore, the main attention in the studies was paid to the synthesis of cordierite α-phase directly in the coating.…”

Linking grain boundary structure and composition to microstructure in commercial‐grade‐doped specialty Aluminas

“…Interestingly, ultrafast grain boundaries can be controlled to facilitate solid‐state single crystal conversion 25 . Therefore, grain boundary segregation of impurity species has a direct role in influencing grain growth behavior and hence properties 26–32 . A secondary phenomenon related to high impurity concentrations is the increased likelihood of abnormal grain growth.…”

“…25 Therefore, grain boundary segregation of impurity species has a direct role in influencing grain growth behavior and hence properties. [26][27][28][29][30][31][32] A secondary phenomenon related to high impurity concentrations is the increased likelihood of abnormal grain growth. While there are many theories that mechanistically describe differences in grain growth behavior and abnormal grain growth within a single material system, 33,34 one widely believed mechanism is that a subset of grain boundaries have faster mobility than other grains boundaries, and if sufficient high-mobility grains are connected, certain grains will grow into elongated morphologies or abnormally large.…”

“…Studies on polycarbosilanederived SiC ceramic 25 and SiC/SiC composite 26,27 have shown that porosity decreases and mechanical properties improve with the increasing number of PIP cycles. Zhu et al 28 show that increasing pyrolysis temperature and the concentration of SiC fillers in polycarbosilane polymer result in improved mechanical properties in two-dimensional Carbon/ SiC (C/SiC) composites fabricated using the PIP process.…”