PREDICTION OF FUNCTIONAL PARAMETERS FOR A NANOSTRUCTURED POLYMER-CERAMIC COATING ON THE BASIS OF ANODIC OXIDES OF METALS

Strength and strain sensitivity of a thin polymer-ceramic coating in the form of a nanoporous anodic aluminum oxide impregnated with a piezoelectric polymer are studied. The coating is considered as a unidirectionally reinforced composite containing cylindrical polymer fibers oriented perpendicular to the coating surface. A three-phase micromechanical model of the specified material is proposed and the stress-strain state of the coating under the influence of uniformly distributed pressure is analyzed. As a result of solving the related problem of electroelasticity, calculated estimates of the specific piezoelectric sensitivity of the coating used as a pressure sensor and the maximum allowable pressure were obtained according to the strength criteria of the ceramic matrix and the plastic flow of the polymer filler. The article shows dependences of the indicated parameters on the volumetric content of the polymer for the coating, adhesively bonded to a non-deformable foundation and freely (without friction) lying on the foundation. At low volume content of polymer, the strength loss of coating is caused by local failure of matrix. At high filler content the transition of polymer into plastic state precedes to the beginning of matrix failure. After increasing the filler content above 80 % the value of maximal pressure according to yield criteria for polymer filler scarcely changes.

FORMATION OF ANODIC POROUS ALUMINA IN OXALIC ACID AND ELECTRODEPOSITION OF NI.

Nanoporous anodic aluminum oxide (AAO) tubular membranes were fabricated from aluminum alloy tubes in sulfuric and oxalic acid electrolytes using a two-step anodization process. The membranes were investigated for characteristics such as pore size, interpore distance and thickness by varying applied voltage and electrolyte concentration. Morphology of the membranes was examined using light optical and scanning electron microscopy and characterized using Image software. Results showed that membranes having narrow pore size and uniform pore distribution with parallel channel arrays were obtained. The pore sizes were ranging from 10 to 100 nm and the wall thicknesses 60 μm. The catalysts are obtained by impregnation of 3d metals into nanosized pores of aluminum oxide. The obtained catalysts based on nickel and porous Al2O3 are studied by scanning microscopy (SEM-EDX). The results of SEM-EDX analysis shows that a spongy structure with filament sizes of 100 nanometers containing particles of 3d metals formed on the surface of the aluminum oxide matrix.

Power Generation from Concentration Gradient by Reverse Electrodialysis in Anisotropic Nanoporous Anodic Aluminum Oxide Membranes

In this study, reverse electrodialysis power generation using an anisotropic anodic aluminum oxide membrane with nanopores of two different pore diameters is proposed and experimentally investigated for the first time. A number of experiments were carried out for various combinations of concentrations to show that the anisotropic anodic aluminum oxide membrane is superior to the conventional isotropic membrane. As a result, the highest power density that was measured from the anisotropic membrane was 15.0 mW/m2, and it was 7.2 times higher than that from the isotropic membrane. The reasons why the anisotropic membrane is superior to the isotropic membrane are explained in detail. The experiments on the anisotropic membranes with various active layer lengths and pore diameters were also conducted for exploring the effects of these engineering parameters on the power generation performance. As a result, it was shown that the length of the active layer is a more important engineering parameter than the pore diameter of the active layer. Additionally, it was also shown that a low concentration solution should be brought into contact with the active layer side of the membrane whenever an anisotropic membrane is used for reverse electrodialysis.

Understanding the thermal conductivity variations in nanoporous anodic aluminum oxide

An important variation in the thermal conductivity of porous alumina membranes has been observed from RT up to 1300 °C. This is due to the water loss at low temperatures or phase transitions at higher temperatures.