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The effect of nano and microstructured powders in cored wires on formation and properties of Fe-TiB2 composite coatings by high velocity arc spraying (HVAS) was investigated. Six cored wires filled with different average ceramic particle sizes (20-40 nm, 2 µm, and 420 µm) and fine powder contents (0, 8, 16, 20, 24, 32wt.%) were sprayed. The flattening behavior of sprayed particles was characterized and compared by using optical microscopy (OM) and 3D Surface Profiler. The microstructure of the coatings and phase compositions were characterized by means of Laser Confocal Scan Microscopy, SEM, EDAX and XRD. Hardness and wear properties were evaluated. The results showed that the splat shape of the cermets has a transitional tendency to change from a distorted heavy splash to a disk with little splash with (i) increasing the percentage of fine ceramic particles and (ii) decreasing coatings porosity. Fe –2 µm 32% TiB2 coatings reveals a dispersion of fine ceramic particles and less scattering of hardness, which improved the wear resistance and changed the abrasion mode.

Al-based coating was prepared with Al-based cored wire by arc spraying. The properties of high-temperature oxidation resistance and corrosion resistance of Al-based coating were compared with those of Fe-Al coating and 45CT coating. The property of H2S corrosion resistance of Al-based coating was compared with that of A304 stainless steel and Fe-Al coating. The results suggest that the Al-based coating has better properties of high-temperature oxidation resistance and corrosion resistance than Fe-Al coating and 45CT coating. Al-based coating has better property of H2S corrosion resistance than A304 stainless steel and Fe-Al coating.

The presence of tuning screws can shift spurious modes resonance of the dielectric resonators to frequency close to or even equal to resonant frequency of the principal mode, therefore interfering with the filter's performance. A simple mode suppressing scheme is presented to solve this potentially serious problem.

Scattering by small discontinuities in single- or multimode waveguides is expressed concisely by the ‘small-obstacle’ formula, which constitutes a lowest-order approximation, in which only dipole moments are considered and wall interactions are neglected. The present study deals with the general and systematic derivation of self-consistent corrections to this formula, which are then applied to the calculation of the scattering coefficients for a centred and noncentred perfectly conducting sphere in a rectangular waveguide. The noncentred case is analysed in the dipole approximation, whereas both dipole and quadrupole moments are included for the centred case. Results for dominant-mode (H10) operation are compared with measurements, and it is found that the discrepancy between experiment and uncorrected small-obstacle theory is reduced substantially, though not completely, by inclusion of corrections for larger sphere sizes.