Sheet aluminium 2024-T3 alloy was treated in a range of acid solutions. These acid solutions included HNO 3 , H 2 SO 4 , and H 3 PO 4 alone, with HF, and with a combination of the oxidant sodium persulphate (Na 2 S 2 O 8 ) and HF. Changes in the surface chemistry and morphology of the matrix and intermetallics were characterised by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), Rutherford backscattering spectroscopy (RBS), and X-ray photoelectron spectroscopy (XPS). Etch rates for each acid solution were determined by weight loss after repeated immersion. In addition, the acid solutions were analysed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) to determine the amount of aluminium and alloy component dissolution.MST/4948

Using a finite difference formulation of the Navier-Stokes equation coupled with a mathematical description of electrical charge migration. The authors examined transient electrohydrodynamic (EHD) phenomena in an electrically stressed liquid duct. Perturbations resulting from electrode injection are studied as a function of time by examining the liquid vorticity vector and stream function. The response of local pressure to advancing charge fronts is evaluated. The theoretical simulation is supported by previous laboratory studies of EHD motion. Experimentally recorded flow patterns are compared with the predicted results.

A mathematical model for the transient electrohydrodynamic (EHD) motion in liquid dielectrics is used to examine the behaviour of dielectric fluids flowing at various velocities between high-voltage electrodes. The resulting flow patterns and space charge distribution profiles are correlated with observed variations in transformer-oil breakdown properties, and explanations for these variations are proposed.

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