Effect of Ball-milling Time on Particle Size of Ca3Co4O9+d

Abstract

Spiral waves are ubiquitously observed in a variety of physical and biological systems, including superconductors, superfluids, CO-oxidation on platinum surfaces, cell aggregation of slime mold and arrhythmia in cardiac tissues. Such spiral waves are uniquely explained by a reaction-diffusion mechanism. Due to easy preparation and convenient detection, the excitable chemical Belousov-Zhabotinsky (BZ) reaction is employed to study spiral waves in experiments. We studied the influence of initial concentration of H 2 SO 4 ([H 2 SO 4 ]) on the dynamics of spiral waves in a thin layer of the BZ reaction with pyrogallol. This reaction has an advantage over the classical BZ reaction with malonic acid, as it is bubble-free. We found that the spiral tip, i.e., the organizing center, moved along so-called meandering trajectories with three or four outward petals. In addition, the area occupied by the spiral tip decreased when [H 2 SO 4 ] was increased. We further investigated the dynamics far from the organizing center by measuring properties of propagating fronts. An increase of [H 2 SO 4 ] resulted in a simultaneous decrease of the wavelength and wave period. In contrast, the wave speed grew with [H 2 SO 4 ]. Since disturbances by the byproduct CO 2 bubbles are avoided and the wave velocity is sufficiently low, the results present a suitable guideline for further investigations on propagating excitation waves in two-and three-dimensional excitable media, especially observations of wave instabilities in three-dimensional systems using optical tomography.

PENINGKATAN FASA Ca3Co4O9 MELALUI PROSES PENGGERUSAN MEKANIK

“…Nilai ukuran kristalit yang dihasilkan lebih besar dibandingkan dengan pekerjaan sebelumnya [15]. Ukuran kristalit yang besar ini disebabkan karena durasi milling yang lebih pendek dibandingkan dengan penelitian sebelumnya [16].…”

Enhanced dimensionless figure-of-merit of Ca3Co4O9 by nano-sized precursor

“…18) Figure1(d)shows the phase-composition analysis of the calcined samples showed a strong influence of the particle size of the CaCO 3 and the Co 2 O 3 in the starting-powder mixtures on the formation of the Ca 3 Co 4 O 9 phase. The calcined powder showed a major crystal phase of the Ca 3 Co 4 O 9 matched with the ICDD No.…”