Combustion aided in situ consolidation of high strength porous ceramic structures with a minimum thermal budget

• Published in: Materials letters 2020-04, Vol.265, p.127410, Article 127410
• Main Authors: Pujar, Pavan, Pal, Abhishesh, Mandal, Saumen
• Format: Article
• Language: English
• Subjects: Ammonium nitrate; Ceramics; Combustion; Compressive strength; Consolidation; Exothermic reactions; Flammability; High temperature; Hydroxyapatite; Low temperature; Materials science; Porosity; Porous materials; Sintering; Sintering (powder metallurgy)
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2020.127410

•Low-temperature sintering of porous ceramics using combustible pore formers.•Exothermic reaction between urea and ammonium nitrate drives the consolidation.•Enthalpy of the reaction (=898 kJmol−1) boosted the externally supplied heat energy.•~82% achievement in strength of pellets sintered at 300 °C compared to 1100 °C. The exothermic reaction between a pair of combustible pore formers (urea-ammonium nitrate) is the driving force in realizing low-temperature consolidation of hydroxyapatite (HA) particles. The particles are allowed to sinter in the proximity to the combustible pore formers. The exothermic (ΔH°rea = -898 kJ/mol) redox reaction between combustible pore formers is successfully utilized in deriving high compressive strength (~24 MPa) of HA at 300 °C. The evolution of gaseous products of combustion results in an interconnected porous network of HA. The estimated compressive strength of sintered HA at 300 °C is comparable with high temperature (1100 °C) conventionally sintered HA, at a fixed open porosity (~40%); which depicts nearly ~82% achievement with a reduction of sintering temperature by ~72%. Also, the pellets sintered at 600 °C have shown ~90% achievement in compressive strength of sintered HA. Further, the saturated pore area of 15% requires a sintering time of 9.58 h at a sintering temperature of 600 °C. Thus, combustion-assisted sintering is an alternative technique proves its potentiality in achieving remarkable compressive strength and paves the way for low-cost porous ceramics.