Preparation and Stability of Al2O3 Nano-Particle Suspension of Ammonia-water Solution

In order to apply nano-particles to the ammonia-water absorption refrigeration, 4 different types of mixtures of nano-particle and surfactant, by mixing α-Al2O3 with polyacrylic acid (PAA), α-Al2O3 with cetyl trimethyl ammonium bromide (CTAB), γ-Al2O3 with PAA and γ-Al2O3 with sodium dodecyl benzene sulfonate (SDBS) respectively, were added to the ammonia-water solution respectively to prepare 4 kinds of nanofluid. A series of experiments were performed to investigate the dispersing stability of the prepared nanofluids with different concentrations of surfactant (PAA, CTAB and SDBS), different durations of ultrasonic vibration and different concentrations of ammonia-water basefluid. The results showed that the dispersity of Al2O3 nanofluids firstly increased to a maximum and then decreased with the increase of surfactant concentration. The dispersion of Al2O3 nanofluids were improved with the increase of the concentration of ammonia-water basefluid. The dispersions of three kinds of nanofluid containing the mixture of α-Al2O3 and PAA, γ-Al2O3 and PAA as well as γ-Al2O3 and SDBS respectively were improved by propar ultrasonic vibration. However, the dispersion of the nanofluid containing α-Al2O3 and CTAB was deteriorated after the treatment of ultrasonic vibration. It was found that PAA was the optimal dispersant among the three kinds of surfactant used in the experiments. Both the nanofluid containing α-Al2O3 and the nanofluid containing γ-Al2O3 achieved the best dispersing performance when the mass concentration of PAA was 0.3% and the duration of ultrasonic vibration was 30 minutes.