Partial Miscibility of Metals as a Key for Improved Properties

Platinum and iridium are known to belong to a family of partly miscible metals. On the other hand, these metals are high demanded as active components of the catalysts for a variety of industrially important processes. In the present work, a series of bimetallic Pt-Ir catalysts supported on alumina were prepared using a “single source precursor” concept. The ratio of metals in the alloy was varied from 1:3 to 3:1. The thermal stability and catalytic activity in CO oxidation of the samples were studied in a prompt thermal aging regime. Monometallic Pt/γ-Al2O3 and Ir/γ-Al2O3 samples were used as references. All the studied catalysts were characterized by UV-vis spectroscopy in initial state and after the aging treatment. It was found that the bimetallic nanoparticles being subjected to the high temperature aging at 600 and 800 °C undergo redistribution with further stabilization in a noticeably more active state. The observed increase in the catalytic activity is explained by an enrichment of the particles’ surface with platinum.

Influence of heat treatment and stress state on the functional and mechanical properties of the [001]-oriented single crystals of fenicoalti alloy

The effect of the γ'- and β-phase particles on the thermoelastic γ-α' martensitic transformation (MT) during cooling/heating and under stress was studied under tension and compression on the [001]-oriented single crystals of Fe-28%Ni-17%Co-11.5%Al-2.5%Ti (at.%) alloy. The effect of the aging regime on the Ms temperature was shown. Maximum increase in the Ms temperature by 100 K was found with the simultaneous precipitation of the γ'- and β-phase particles after two-stage aging of 4+4h at 873 K, in comparison with single-stage aging for 8h. In crystals with γ' and γ'+β-phases particles the difference (asymmetry) of the stresses for the stress-induced γ-α' MT σcr and value α = d σcr/ dT under tension and compression were not observed. The absence of asymmetry of the σ cr and value α = d σcr/ dT are due to close values of the shape memory effect (SME) and superelasticity (SE) under tension and compression. The values of SME and SE were decreased when β-phase particles are precipitated.

New Trends in Automotive Exhaust Gas Purification Materials: Improvement of the Support against Stability of the Active Components

Lanthanum and zirconium oxides are well known to be applied as an additive to improve the properties of the commercial alumina. Such modified aluminas are widely used in different catalytic fields including three-way catalysis. In the present research we have paid attention to the possible effects of the doping on the catalytic performance and stability of bimetallic Pd-Rh catalysts. The samples were prepared via an incipient wetness impregnation of the commercial supports, tested in CO oxidation under prompt thermal aging regime and characterized by physicochemical methods.

Estimation of the lifetime of solar cells in real conditions using accelerated aging under the influence of neutron and gamma radiation

In the paper, in a long-term test procedure, monocrystalline silicon cells were subjected to examination. Cells were tested in well-controlled laboratory conditions and real conditions. In laboratory conditions, white light of the artificial sun and monochromatic brightness of yellow sodium lamps were used. The testing was aimed at achieving the same aging regime in the laboratory conditions as in real conditions. This would allow for the laboratory aging algorithm of solar cells as in real conditions, to be defined, hence their working life of commercial exploitation in urban areas to be determined. By complex mathematical methods, i. e. using the theory of time duration, it was found that laboratory exposing solar cells to thermal neutrons causes their aging with the same mechanism as in real conditions.