Effects of the Concentration of Inorganic Binders and Optical Absorbers on the Phase Formation and Microstructure of Flash‐Lamp‐Annealed Chemically Bonded Phosphate Ceramic Composites

• Published in: International journal of ceramic engineering & science Vol. 7; no. 4
• Main Authors: Ozmen, Eren, Losego, Mark D.
• Format: Journal Article
• Language: English
• Published: Westerville John Wiley & Sons, Inc 01.07.2025; Wiley
• Subjects: Absorbance; Absorbers; Alumina; Aluminum; Aluminum oxide; Aluminum phosphate; Annealing; Broadband; Ceramic bonding; Ceramic coatings; Ceramics; Chemical bonds; Composite materials; Curing; Flash lamps; Iron oxides; Laser sintering; layered ceramics; manufacturing; Metal oxides; Photonics; Ratios; Temperature; Thermal energy; Thermal stability; ultra–high temperature ceramics; Xenon lamps
• ISSN: 2578-3270; 2578-3270
• DOI: 10.1002/ces2.70019

ABSTRACT A chemically bonded ceramic composite is synthesized using nanosized alumina powder and aluminum dihydrogen phosphate (Al(H2PO4)3, ADP) as a binder with varying solid volumetric ratios from 50% to 75%. Photonic curing of such composites by flash lamp annealing (FLA) is of interest as a new route to additive manufacturing of ceramics or rapidly producing ceramic coatings. ADP undergoes a condensation reaction with Al2O3 around 300°C–350°C and forms an AlPO4 compound that is thermally stable up to 1500°C due to strong P─O─Al bonds. Herein, an FLA system that can deliver tens of kilowatts per square centimeter of radiant energy is used to rapidly transform this ADP/Al2O3 mixture into this AlPO4 ceramic phase. An ADP fraction of about 55 vol% results in the lowest porosity layers having the best layer cohesion. Absorbance of the photonic energy emitted by the FLA's broadband xenon lamp (400–800 nm) is also critical to rapidly transforming these layers because optical absorbance is needed to convert the photonic energy to thermal energy. Three different optical absorbers—graphite, black iron oxide, and liquid black organic ink—are investigated as optical absorbers. Adding these absorbers is found to lower the required photonic input for ADP‐to‐AlPO4 conversion from ∼350 to ∼220 J/cm2, making the process even more energy efficient. This study expands upon recent work investigating a novel energy delivery method for forming chemically bonded phosphate ceramic (CBPC) composites: flash lamp annealing (FLA). It involves the use of CBPC precursors, including the inorganic binder aluminum dihydrogen phosphate (ADP or Al(H2PO4)3), which can be photonically “cured” via reaction with metal oxides (e.g., Al2O3) to form high‐temperature‐stable aluminum phosphate (AlPO4) ceramic phases.