Effects of annealing at high pressure on structure and mechanical properties of Al87Ni7Gd6 metallic glass

The effects of annealing and annealing with a superimposed pressure of 940 MPa on the primary crystallization behaviour of α-Al and the resulting micro-hardness have been studied for as-quenched Al₈₇Ni₇Gd₆ metallic glass. Isothermal annealing experiments were conducted for 30 min at 188 °C, 191 °C, and 205 °C in silicone oil maintained either at atmospheric pressure (i.e. 0.1 MPa) or at 940 MPa. XRD analyses detected the evolution of structure with annealing at 0.1 MPa, while specimens annealed with 940 MPa pressure exhibited sharper diffraction peaks than those annealed at 0.1 MPa. DSC measurements were conducted on the as-received amorphous ribbons as well as ribbons annealed at different temperatures at either 0.1. MPa or with 940 MPa superimposed pressure. Specimens annealed with 940 MPa pressure exhibited higher onset temperatures (i.e. T_x1) and temperatures for the first exothermic peak (i.e. T_p1) for primary crystallization. TEM measurements revealed an increase in the volume fraction of α-Al with increases in annealing temperature, while micro-hardness measurements revealed an increase in hardness with increasing amounts of α-Al. Specimens annealed with 940 MPa pressure exhibited further increases in both the volume fraction of α-Al and resulting micro-hardness.     

EPR studies on NO interaction with MoOx/t-ZrO2 catalysts obtained by slurry deposition

Variable temperature adsorption of nitric oxide on MoO₃ supported on tetragonal zirconia (MoO_x/t-ZrO₂), obtained by slurry deposition, was investigated by EPR spectroscopy. The influence of molybdenum loading and co-adsorbed oxygen on the adsorption process of NO was elucidated. Particular attention was devoted to redox character of NO activation. Another important aspect concerned is the nature of surface nitrosyl complexes of molybdenum and their thermal stability. The role of oxygen in NO transformation over catalyst surface was also discussed.     

Polylactide‐pine wood flour composites

Biobased and biodegradable polylactide (PLA)‐pine wood flour (PWF) composites were investigated as a means to reduce the overall material cost and tailor the material properties. The composites were prepared using a kinetic‐mixer and an injection molding machine. The tensile modulus of the PLA‐PWF composites increased with the PWF content whereas the toughness and strain‐at‐break decreased. The tensile strength remained the same irrespective of the PWF content (up to 40%). The storage modulus also increased with the PWF content. Additionally, composites containing PWF treated with silane showed higher storage modulus than those without the silane treatment. The area integration underneath the tan δ peaks decreased with increasing PWF, indicating that the PLA‐PWF composites exhibited more elastic behavior with increasing PWF. The degree of crystallinity of the PLA‐PWF composites increased significantly with the PWF content. Furthermore, the treatment of PWF with silane had a positive effect on its nucleating ability, as treated PLA‐PWF composites showed higher crystallinity compared with their untreated counterparts. The morphology of the fracture surfaces were studied using a scanning electron microscope. Finally, a Halpin‐Tsai analytical model to predict Young's modulus of PLA‐PWF composites was presented to compare the theoretical results with that of experimental results. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Prediction of Oxygen and Ozone Solubility in Liquids with the Peng-Robinson Equation of State

The results of predictions of ozone solubility in the inert organic solvents based on the Peng-Robinson EOS have been reported. A hypothesis that there is a possible similarity of the values of the binary coefficients, k₁₂, between oxygen and ozone has been tested. Some attempts to estimate ozone solubility in perfluorocarbons have been discussed.     

Research of the physical-chemical properties of adhesive radiation-modified thermosetting materials based on polyolefins and their composites

The present paper surveys the investigation results of the adhesive behavior with steel of different polyethylenes (LDPE, HDPE) irradiated with γ-radiation in vacuum, oxygen, and air, using rheological, optical, thermomechanical and other methods. To study the adhesive contact, the technological parameters applicable to thermosetting polymer material were taken into consideration. The results show the suitable methods in order to obtain thermosetting polymer materials with improved adhesive and thermomechanical properties.     

Tribological Properties of the Oxide Coatings Produced onto 6061-T6 Aluminum Alloy in the Hard Anodizing Process

The aim of this work was to establish the influence of the thickness of the anodic coatings on their mechanical properties and to understand the relation between their hardness and the abrasion resistance. The coatings were produced in the hard anodizing process onto the 6061-T6 aluminum alloy. Their thickness was in the range between 19 and 43 µm. The abrasion resistance was determined by using Taber abrasion test. The weight losses of the coatings obtained were in the range between 15 and 11 mg and decreased with their increasing thickness. It has been shown that the hardness measured on the cross sections of the coatings did not correspond to their abrasion resistance. Thus, the new approach has been proposed. The hardness of the coatings was estimated on the basis of the results of the scratch test performed at the constant load. The results obtained correspond to the abrasion resistance of the coatings.     

Testing of thin-walled steel joints fabricated by spot welding and plug welding

Selected methods of joining which can be used for manufacturing and repairing of car bodies by means of welding are presented in this article. Three kinds of 1 mm-thick steel sheets were used in the tests: deep drawing steel (DC04) and two-phase steels of increased high strength (DP600 and DP800). The comparative connections were carried out by means of resistance spot welding and with plug joints made by means of the MAG method and through braze welding. Comparative assessment of the strength and geometrical parameters of the test joints was then conducted.