(391a) Preparation of Nano-Gypsum from Anhydrite Nanoparticles: Strongly Increased Vickers Hardness and Formation of Calcium Sulfate Nano-Needles
AIChE Annual Meeting
2006
2006 Annual Meeting
Particle Technology Forum
Functional Nanoparticles and Nanocoatings on Particles II
Wednesday, November 15, 2006 - 12:30pm to 12:51pm
Gypsum as one of the oldest known construction materials today accounts for a worldwide production of an estimated 100 million metric tons of calcium sulphate for renders, plasters, indoor finishings, retardants for cement, ceramics and medical supplements or implants. We show the production of nanosized gypsum allowing significant improvement of the mechanical properties of this construction material. Since possible applications of nano-anhydrite as a source for nano-gypsum are expected to rapidly require large volume production, we have investigated a suitable modification of the existing aerosol process currently applied for the manufacturing of silica, titania and soot (10 mio tons/year) to access nano-anhydrite or gypsum: more specifically, the preparation of nano-anhydrite by flame synthesis[1] resulted in the continuous production of anhydrite nanoparticles of 20-50 nm size. After compaction and hardening by the addition of water, the anhydrite nanoparticles reacted to nano-gypsum which was confirmed by X-ray diffraction, diffuse reflectance IR spectroscopy and thermal analysis. Mechanical properties were investigated in terms of Vickers hardness and revealed an up to three times higher hardness of nano-gypsum if compared to conventional micron-sized construction material[2]. The improved mechanical properties of nano-gypsum could in part be due to the presence of calcium sulphate nano-needles in the nano-gypsum as showed by electron microscopy.
References:
[1] Huber M, Stark W J, Loher S, Maciejewski M, Krumeich F, Baiker A 2006 , Chem. Commun. (2005) 648-650.
[2] Osterwalder N, Loher S, Grass R N, Brunner T J, Limbach L K, Halim S, Stark W J 2006 , submitted to Nanotechnology (2006).
Figure 1: Scanning electron micrograph of nano-gypsum after setting; insert: pressed nano-gypsum pill. The hardening of nano-anhydrite results in the formation of calcium sulphate nano-needles.
