Formation and stability of Al-Mn quasicrystalline thin films prepared by high temperature successive deposition

This article reviews the results on the formation of i-QC thin films prepared by high-temperature successive deposition in the Al-Mn system and the metastable quasicrystalline Al₄Mn and crystalline Al₆Mn phase transformation in detail. Experimental evidence is given for the location of the solid-phase reaction. New data concerning the effects of preparation parameters (temperature, Mn deposition rate, composition) on the formation processes are reported. The phase formation and transformation processes are described by the combination of thermodynamic and kinetic factors.     

Contact melting temperature of small-dimensional phases

Bulletin of the Russian Academy of Sciences: Physics - An attempt is made to derive the relation for the contact melting temperature of small-dimensional phases (nanoparticles, nanofilms) with...     

Freezing and melting of a colloidal adsorbate on a 1D quasicrystalline substrate

Using Monte Carlo simulations and an extended Landau-Alexander-McTague theory, we demonstrate that colloids in a one-dimensional quasicrystalline potential order in triangular and rhombic-alpha crystalline phases. Increasing the strength of the potential further, a new type of light-induced melting is discovered that has its origin in the nonperiodicity of the potential. In contrast to reentrant melting in periodic potentials, the quasicrystalline potential melts the crystalline phases even when they already exist at zero potential.     

Plasmon electron energy loss spectroscopy and electrical resistivity of AlMn and AlMnSi quasicrystalline phases

The electrical resistivity of the icosahedral and decagonal phases is investigated in AlMn and AlMnSi melt-spun ribbons by means of EELS in a dedicated STEM. The RT-resistivity of the i-phase is reported to be 66 μΩ cm and is controlled essentially by the solute content. The intrinsic effect due to the quasiperiodic distribution of the Mn scatterers is weak.     

Correlation between the size-dependent melting and crystallization temperatures of metal nanoparticles

The correlation between the melting and crystallization temperatures of metal nanoparticles is investigated by means of the thermodynamic approach. Size-dependent variations in the melting temperature of aluminum, tin, and copper nanoparticles are calculated with allowance for the corresponding size dependences of surface tensions in solid and liquid phases and interfacial tension. Size-dependent variations in crystallization temperature are determined under the assumption that a certain effective surface layer (skin-layer) arises before melting.     

Measurements of nitrogen-broadened line widths of acetylene at low temperatures

Spectral transmittance measurements have been performed on N₂-broadened lines of C₂H₂ in the 7.53 μm region at 153 and 200 K with a spectral resolution of 0.06 cm^-1. The line widths have been determined as functions of temperature and rotational quantum number using line-by-line comparison of theoretical and experimental values of spectral transmittance.     

Empirical correlation between melting temperature and cohesive energy of binary Laves phases

A list of 143 binary Laves phases with their melting temperature and melting type is collected, and used to study a correlation between melting temperature and cohesive energy. It is found that the melting temperature of Laves phases is roughly proportional to its cohesive energy calculated by Miedema's empirical model from their intrinsic atomic properties. The average predicted error of melting temperature of compounds is as low as 8.0%. This empirical rule is consistent with the result of the universal binding energy theory of solids.     

Measurements of the CO first overtone bandstrength at elevated temperatures

The spectrally resolved emission from the CO first overtone vibration-rotation band has been studied over the temperature range of 1100-2600 K in a shock-tube experiment. First overtone bandstrengths have been deduced from the data. These compare favorably with theoretical expectations.     

Thermodynamic approach to the size dependence of the melting temperatures of films

The size dependence of melting temperature T _m of metallic films (tin and copper) on different substrates, including amorphous carbon and another refractory metal (i.e., the dependence of T _m on film thickness h) is investigated. It is found that the effect of the interfacial boundary can result in the growth of T _m for thin metallic films on carbon substrates with a reduction in film thickness h. For a system with a metallic film on a metallic substrate, the size dependence of T _m is less pronounced and T _m falls with a reduction in h.     

Separation of phases at low temperatures in a one-dimensional continuous gas

We show the existence of a phase separation at low temperatures in a one-dimensional one-component classical gas in the canonical ensemble with interactionhard core –1/r , 1<2. This implies that for sufficiently low temperatures there are values of the chemical potential at which the pressure is not differentiable as a function of the chemical potential.Research supported by the Swedish research councils NFR and STUF     

Mössbauer study of the stability of quasicrystalline phases: Al78Fe22 and Al82Fe18

A quasicrystal of Al-Fe with a stoichiometric composition very close to a crystalline phase is shown to transform to the crystalline phase with simple thermal cycling from 300 K through 78 K and 300 K.     

Measurements of hydrogen-helium radiation at shock-layer temperatures appropriate for jupiter entry

Shock waves traveling at approximately 16 km/sec into a gas mixture of 7% H₂ and 93% He were used to simulate the shock-layer conditions for a representative shallow entry into the Jovian atmosphere. The absolute intensities of line and continuum radiation were measured and the radiative cooling of the shock-heated gas is shown.