Fixation of borate-anions in lamellar AFm-phases in the system CaO-Al2O3-B2O3-H2O at 20 °C, 40 °C and 50 °C
Synthesis of boron containing lamellar calcium aluminum hydroxy salts were performed at different relative humidities and the behaviour and properties of the lamellar phases were investigated. The following AFm compound could be synthesized in pure form and their properties were determined:AFm-phase: 3CaOrad Al2O3rad CaHBO3.nH2O. With excess boron an Ettringite-compound AFt with the following composition is coexisting in the investigated system: Ettringite-phase: 3CaOrad Al2O3rad 2Ca[B(OH)4]2rad Ca(OH)2·30H2O. The incorporation of boron in the interlayer of LDH-phases under the influence of OH-ions at different temperatures were investigated. Carbonate was excluded by using a glove box to get definite lattice parameters. Different boron containing AFm-phases, using pure phase compositions in the system OH-lamellar AFm phase and the boron containing AFm phase, were synthesized. The solid solution between the so called compounds Monoborate and Monohydroxide at different temperatures and different relative humidities, with careful control of the different water contents of the lamellar phases, was investigated. Boron contents in solution and the uptake in the interlayer of the AFm-phases was studied . The uptake of boron from pure solutions and the newly formed relevant phases with AFm structure and at higher boron contents of the ettringite structure were determined.