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Low‐temperature sintering of magnesium aluminate spinel doped with manganese: Thermodynamic and kinetic aspects
Author(s) -
Nakajima Kimiko,
Li Hui,
Shlesinger Noah,
Rodrigues Neto João B.,
Castro Ricardo H. R.
Publication year - 2020
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.17162
Subject(s) - sintering , materials science , spinel , coprecipitation , differential scanning calorimetry , grain boundary diffusion coefficient , grain boundary , grain growth , chemical engineering , doping , metallurgy , mineralogy , activation energy , aluminate , analytical chemistry (journal) , microstructure , thermodynamics , chemistry , physics , optoelectronics , chromatography , engineering , cement
This work describes the role of manganese (Mn) as a sintering aid for magnesium aluminate (MgAl 2 O 4 ) nanoparticles. Mn‐doped MgAl 2 O 4 nanoparticles, synthesized by coprecipitation method, showed increased surface area when contrasted to undoped MgAl 2 O 4 . Fast firing of compacted‐doped nanoparticles achieved high degree of densification at temperatures as low as 1100°C with very moderate grain growth, resulting in average sizes at the nanoscale (~60 nm). Differential scanning calorimetry was used to quantify the exothermic heat effects of sintering, which combined with quantitative microstructural evolution analysis enabled calculation of both surface and grain boundary energies. The results revealed that Mn effectively reduces the surface and grain boundary energies which led to dihedral angle broadening and consequently increased sintering stress. Experimental data also revealed a concomitant decrease in the activation energy of sintering with Mn doping which dropped from 644 kJ/mol for undoped MgAl 2 O 4 to 285 kJ/mol, informing Mn acts as a sintering aid in a thermokinetic manner.