[en] A very simple atomistic model for predicting the heats of formation of alloys involving transition elements is presented. Because of the paucity of experimental thermodynamic data, the sign of the heat of formation was determined from the known behaviour of the binary phase diagrams. By assigning only two co-ordinates to each transition element, it was found that all those binary alloys with positive heats of formation could be separated from those with negative values. By fixing the magnitude of the heat of formation to known experimental values, it was possible to predict values for all those binary systems which had not yet been measured. This work is invaluable because it not only tabulates the predicted heats of formation of binary compounds involving transition elements, but it also updates Hultgren's 1973 compilation of the experimental thermodynamic data. Moreover, the collation of all binary T-X phase diagrams containing a given transition element T with respect to X's period and group will be very useful for providing a global view of trends across the periodic table. refs.; figs.; tabs

[en] The anomalous contraction that cerium undergoes when it is the A component in AB₂ Laves phase compounds is used to estimate its metallic radius when it is joined to a given B component. In each case, isostructural compounds of trivalent (rare earths) and tetravalent (zizconium, hafnium and thorium) A elements with the same B element are taken as the reference system. The trivalent metallic radius (r₃ = 1.846 A) of cerium proposed by Gschneidner and Smoluchowski was confirmed, but a tetravalent metallic radius (r₄ = 1.688 A) of cerium which exceeds their value by 1% was obtained. The presence of A-B contacts is related to the intermediate valency behaviour, and the valency calculated for each compound is compared with other physical properties. A distinction between localized conduction band hybridization and interconfigurational fluctuation is proposed. (Auth.)

[en] Structural materials used as cans and matrices of dispersion fuel elements are under consideration. Technological, mechanical, nuclear and corrosion properties of aluminium, tantalum, molybdenum, tungsten and alloys on the base of these metals are described in detail. Data on the behaviour of these materials under neutron irradiation are presented. A possibility of utilization of different grade graphite and glass carbon as fuel element structural materials is discussed

[en] Highlights: • A new family of metallic hydrogen permeation membranes was developed. • A new compositional window for hydrogen permeable Nb-ZrCo alloys is established. • DS Nb₂₅Zr₃₅Co₄₀ exhibits a substantial enhancement of hydrogen permeability. • Nb₂₅Zr₃₅Co₄₀ is promising to make high-performance membranes for H₂ separation.

[en] The study of complex materials (nonhomogeneous matrices containing medium and/or heavy atoms as major elements) by PIXE requires the tailoring of the experimental set up to take into account the high X-ray intensity produced by these main elements present at the surface, as well as the expected low intensity from other elements 'buried' in the substrate. The determination of traces is therefore limited and the minimum detection limit is generally lower by at least two orders of magnitude in comparison with those achievable for low Z matrices (Z≤20). Additionally, those high Z matrices having a high absorption capability, are not always homogeneous. The nonhomogeneity may be, on the one hand, a layered structure (which is uneasy to profile by RBS if the material contains elements of neighbouring masses or if the layered structure extends on several microns) or, on the other hand, inclusions which are to be localized. PIXE measurements at various incident energies (and with various projectiles (p, d, He³, He⁴)) are then an alternative method to overcome those difficulties. The use of special filters to selectively decrease the intensity of the most intense X-ray lines, the accurate calculation of the characteristic X-ray intensity ratios (Kα/Kβ, Lα/Lβ) of individual elements, the computation of the secondary X-ray fluorescence induced in thick targets are amongst the most important parameters to be investigated in order to solve these difficult analytical problems. Examples of Cr, Fe, Ni, Cu, Ag and Au based alloys with various coatings as encountered in industrial and archaeological metallurgy are discussed. RBS, PIGE and NRA are sometimes simultaneously necessary as complementary (or basic) approaches to identify corroded surface layers

[en] High-temperature shape memory effect (HTSME) takes place in different alloys and compounds, such as: TiNi with Pt, Pd, Zr and Hf additions, Zr-based quasibinary intermetallics, NiAl-based, Cu-Al-Mn, Cu-Al-Zn and Fe-Ni-Co-Ti. It can be presumably adopted that all materials exhibit SME higher than 200 C should be considered as high-temperature SMA. The origin of the HTSME can be associated with: reverse martensitic transformation; precipitation-dissolution processes during dynamic aging. (orig.)

[en] The crystal structure of Pr₈Ga₃Co compounds is studied by the method of monocrystal (autodiffractometer, MoKsub(α)): space group P6₃mc, a=10.489, c=6.910 A, Z=2. Coordination numbers of atoms are 11-14 for Pr, 11 for Ga, 7 for Co. The shortest interatomic distances are 3.365 for Pr-Pr, 3.047 for Pr-Ga, 2.75 A for Pr-Co. Pr₃Ga₃Co structure is akin to structures of R₂In compounds (Ni₂In type) and R₂Ga (Cl₂Pb type). Isostructural compounds form in systems of other rare earth metals with gallium and cobalt

[en] Major views and theories are briefly listed of the mechanism of adhesive wear, including the recrystallization theory and the theory of protective oxide layer formation. The results are reported of seizure resistance tests at a temperature of 20 and 350 degC, respectively, at different specific pressures (14.7, 24.5, 40 and 54.5 MPa). Samples were tested of a different hardness. The analysis of the test results showed that for alloys of the 1Cr18Ni8Si5Mo5Mn5Nb type used primarily for valves employed in nuclear power plants, the hardness alone of the alloy significantly increased the resistance to seizure. (Z.S.). 2 tabs., 21 refs

[en] Potentiodynamic polarization studies were carried out on virgin specimens of Zr-based amorphous alloys Zr₆₅Cu_17.5Ni₁₀Al_7.5 (Inoue alloy), Zr_46.75 Ti_8.25Cu_7.5 Ni₁₀Be_27.5 (Vitreloy-4 or V4) and Zr₆₅Ni₃₅ in 0.5 M H₂SO₄, 0.5 M HNO₃ and 0.5 M NaOH at room temperature. The corrosion rates of Zr₆₅Ni₃₅ were found to be the lowest, while the alloy V4 had the maximum corrosion rates in all the three media indicating that V4 is more prone to corrosion in these aqueous media. The observed differences in corrosion behaviour are attributed to different alloy constituents and compositions of the alloys investigated. (author)

[en] The La_0.7-xPr_xMg_0.3Al_0.3Mn-_0.4Co_0.5Ni_3.8 (x= 0 a 0.7) as-cast alloys to apply in negative electrodes for nickel-metal hydride batteries (Ni-MH). The characterizations of the alloys were realized by: scanning electron microscope (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction techniques. A study of hydrogen absorption capacity of the alloys realized. The hydrogenation of the material was performed in two processes: the low pressure (0.2 MPa of hydrogen and temperature of the 773 K) and high pressure (1 MPa of hydrogen and temperature of the 298 K). It was observed that with increasing Pr content occurred a decrease the hydrogen absorption capacity. The capacity of discharge of the batteries was determined utilizing an analyzer digital computerized composed of four channels. It was observed decreases of the discharge capacity of the batteries when increase praseodymium content in La_0.7-xPr_xMg_0.3Al_0.3Mn_0.4Co_0.5Ni-3_.8 (x= 0 a 0.3) alloys. The highest discharge capacity (386 mAhg^-1) and stability cyclic were obtained to La_0.2Pr_0.5Mg_0.3Al_0.3Mn_0.4Co_0.5Ni_3.8 alloy. This capacity can be related to the higher proportion of phase LaMg₂Ni₉ in the alloy with the addition of 0.5 at.% Pr. (author)