Calculation of the P-T phase diagram and tendency toward decomposition in equiatomic TiZr alloy

Electronic, structural and thermodynamic properties of the equiatomic alloy TiZr are calculated within the electron density functional theory and the Debye-Gruneisen model. The calculated values of the lattice parameters a and c/a agree well with the experimental data for the alpha, omega and beta phases. The omega phase is shown to be stable at atmospheric pressure and low temperatures; it remains energetically preferable up to T=600K. The alpha phase of the TiZr alloy becomes stable in the range 600K<T<900K, and the beta phase at temperatures above 900K. The constructed phase diagram qualitatively agrees with the experimental data available. The tendency toward decomposition in the equiatomic alloy omega-TiZr is studied. It is shown that in the ground state the omega phase of the ordered equiatomic alloy TiZr has a tendency toward ordering, rather than decomposition.Comment: 6 pages, 8 figure

Strain-induced phase transformations under compression, unloading, and reloading in a diamond anvil cell

Strain-induced phase transformations (PTs) in a sample under compression, unloading, and reloading in a diamond anvil cell are investigated in detail, by applying finite element method. In contrast to previous studies, the kinetic equation includes the pressure range in which both direct and reverse PTs occur simultaneously. Results are compared to the case when “no transformation” region in the pressure range exists instead, for various values of the kinetic parameters and ratios of the yield strengths of low and high pressure phases. Under unloading (which has never been studied before), surprising plastic flow and reverse PT are found, which were neglected in experiments and change interpretation of experimental results. They are caused both by heterogeneous stress redistribution and transformation-induced plasticity. After reloading, the reverse PT continues followed by intense direct PT. However, PT is less pronounced than after initial compression and geometry of transformed zone changes. In particular, a localized transformed band of a weaker high pressure phase does not reappear in comparison with the initial compression. A number of experimental phenomena are reproduced and interpreted

Application of Thin Piezoelectric Films in Diamond-Based Acoustoelectronic Devices

The theory of external loading influence on acoustic parameters of piezoelectric five-layered structure as “Al/(001) AlN/Mo/(001) diamond/Me” has been developed. Oscillations in diamond-based high-overtone bulk acoustic resonators (HBARs) have been investigated in terms of 3D FEM simulation. Peculiarities of technology of aluminum-scandium nitride (ASN) films have been discussed. Composition Al0.8Sc0.2N was obtained to create the diamond-based HBAR and SAW resonator. Application of ASN films has resulted in a drastic increasing an electromechanical coupling up to 2.5 times in comparison with aluminum nitride. Development of ASN technology in a way of producing a number of compositions with the better piezoelectric properties has a clear prospective. SAW resonator based on “Al IDT/(001) AlN/(001) diamond” structure has been investigated in the band 400–1500 MHz. The highest-quality factor Q ≈ 1050 was observed for the Sezawa mode at 1412 MHz. Method of measuring HBAR’s parameters within 4–400 K at 0.5–5 GHz has been developed. Results on temperature dependence of diamond’s Q-factor at relatively low frequencies were quite different in comparison with the ones at the frequencies up to 5 GHz. Difference could be explained in terms of changing mechanism of acoustic attenuation from Akhiezer’s type to the Landau-Rumer’s one at higher frequencies in diamond

Surface tension of copper-nickel alloy, silicon and graphite at normal and high pressure

Translated from Russian (Fiz. Khim. Obrab. Mater. 1997 (3) p. 105-108)SIGLEAvailable from British Library Document Supply Centre-DSC:9023.190(9586)T / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Electrical conductivity of nanostructured and C-60-modified aluminum

In this paper, we study the electrical conductivity of nanostructured C-60-modified aluminum, and the possibility of optimizing its electrical and mechanical properties. The model proposed allows estimating the electrical conductivity of the material at low surface filling factor. A number of samples with different C-60 mass fractions and aluminum crystallites sizes have been obtained and investigated; a mean crystalline size, conductivity, and hardness of these samples have been determined. A theoretical model has been compared to the experimental data. The model is in qualitative agreement with the experiment. The X-ray photoelectron spectroscopy and Raman spectroscopy studies of the material structure indicate the presence of covalent bonds between the aluminum in the clusters and the C-60 molecules, and they are consistent with the proposed shell model

Electrical conductivity of nanostructured and C60-modified aluminum

In this paper, we study the electrical conductivity of nanostructured C60-modified aluminum, and the possibility of optimizing its electrical and mechanical properties. The model proposed allows estimating the electrical conductivity of the material at low surface filling factor. A number of samples with different C60 mass fractions and aluminum crystallites sizes have been obtained and investigated; a mean crystalline size, conductivity, and hardness of these samples have been determined. A theoretical model has been compared to the experimental data. The model is in qualitative agreement with the experiment. The X-ray photoelectron spectroscopy and Raman spectroscopy studies of the material structure indicate the presence of covalent bonds between the aluminum in the clusters and the C60 molecules, and they are consistent with the proposed shell model