Optimization of hydrogen generation process from the hydrolysis of activated Al–NaCl–SiC composites using Taguchi method

Abstract

Novel Al–NaCl–SiC composites for hydrogen generation were prepared by mechanical ball milling. NaCl is a well-known salt for the activation of Al. SiC, which is much harder and more rigid than NaCl, was added as a milling aid. In this optimization study Taguchi method was used for design of experiments. In the experimental design using the L16 (4 ˆ 3) orthogonal array, 4-levels of NaCl and SiC ratios and mechanical milling times were used. Confirmation tests were carried out for the optimum levels determined by Taguchi method. An analysis of variance was performed to determine the relative importance of the control factors and their contribution to the performance characteristic. It was found that NaCl has the greatest effect on hydrogen generation performance, followed by mechanical milling time and SiC ratio. The highest values of these parameters were determined as optimum levels for maximum hydrogen generation. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) analyzes were performed to investigate the relation between hydrogen generation performance and morphology of milled powders. The grain (crystal) dimensions of some milled powders were calculated from the XRD data using the Scherrer equation. Grain refinement, reduction in grain size during mechanical milling was used as a measure of the severity of plastic deformation. It was observed that the grain sizes were reduced to a few tens of nanometers with the ball milling process.