Volume 11 (2011): Issue 3 (September 2011)

The Ca_0.95Mg_0.05ZrO₃ nanopowder was successfully synthesized by the citrate method. The XRD diffraction method evaluated that the orthorombic CaZrO₃ phase was detected in powders or sintered samples. The sintered sample at 1450°C for 2 hours exhibits about 98% of theoretical density. The electrical conductivity was measured by a.c impedance spectroscopy method in the temperature range of 200-800°C. The transference oxygen ion number of CaZrO₃ sample was estimated from electromotive force measurements (E_m) of galvanic cell in the temperature range of 550-1100°C. The Ca_0.95Mg_0.05ZrO₃ exhibits purely oxygen ion conductivity. It was successfully applied as a solid electrolyte in the electrochemical oxygen sensor operating at 660°C. The measured electromotive force of investigated cell was found to be linear with the logarithm of oxygen partial pressure in the range of 10^-6 atm 1 atm and in the temperature range of 660-1000°C.

Analytical calculations and experimental measurements of volume fraction of bainitic ferrite and volume of the untransformed austenite indicate that there is a necessity of carbides precipitation. A consequence of the precipitation of cementite during austempering is that the growth of bainitic ferrite can continue to larger extent and that the resulting microstructure is not an ausferrite but it is a mixture of bainitic ferrite, retained austenite and carbides.

The results of investigations of resistance to cold cracking of high strength steel welded joints have been presented. The steel used was P460NL1 which is designed to work under pressure. Welding was carried out with coated electrodes (MMA) and flux cored wire by FCAW method. Parameters changed in the implant test were diffusible hydrogen content and weld heat input. Partial resistance to cold cracking of joints for the studied ranges of welding parameters have been shown. Cold cracking resistance decreases with increasing diffusible hydrogen content in the joint and increasing the cooling rate in the HAZ metal measured by cooling time in the temperature range 800-500°C.

The plasma aided flame retardation of wood, wooden products and cellulosic fibrous materials has been conceived and developed as a result of a plasma aided process of capillary impregnation. The dielectric barrier discharge surface pre-treatment modifies the chemical and capillary activity and improves such characteristics of the impregnation process as the penetration depth, speed of solution spreading and adsorption, and capacity of adsorbed solution. X-ray photoelectron spectroscopy (XPS) was applied to study the changed surface composition after plasma pre-treatment. The surface compositions of solid wood products, paper and board are critical to their end use performance. XPS is a powerful non-destructive surface analytical technique which provides valuable data on chemical surface composition and surface reorganization after plasma-chemical pre-treatment. The binding energy as a main characteristic of the atoms was used for elemental identification. Thermal analysis (TGA, DTA and DSC) was used to characterize the impact of the plasma surface activation on flame retardancy of Douglas fir wood. This study was developed as a part of large investigation on chemically activated wood surface and flame retarded wood.

Intergranular corrosion sensitivity is studied for the friction stir weld nugget of aluminum alloy 2050-T8. The weld nugget consists of fine equiaxed grains having average sizes from 4 to 20 μm, the grain size increases with decreasing of the distance from the weld surface. The weld nugget contains a particular microstructure called "onion rings" due to crystallographic orientations. The effect of the "onion rings" on stress corrosion cracks initiation is studied for stress corrosion cracking tests at a strain rate of 2.10^-6 s^-1. EBSD cartographies allow showing that the initiation site of the biggest cracks is located at boundaries between the texture bands. Corrosion and stress corrosion tests in 1.0 M NaCl are performed in order to show stress effect on intergranular corrosion. Pitting corrosion is observed during corrosion tests, whereas intergranular cracks appear during stress corrosion tests. The medium crack length is 20 μm and 168 cracks per mm² can be located. In these severe laboratory conditions, the order of magnitude of long crack growth rate is 5.10^-8 m.s^-1.

The intention of this paper is the discussion of different possibilities for the numerical modeling of elastomeric bearings. It is focused on issues of the complex material behavior and the specific mechanical conditions of the bearings. The relevant considerations are based on the experiences from extensive material tests on elastomer and reinforcement as well as from loading and deformation tests on full scale bearings. It shows the possibilities and the limitations of the numerical bearing models as a tool for research and bearing design.