X-ray diffraction study of the structure of Al-Ni melts

The structures of Al-Ni melts with 0, 10, 18, 25, 28, 32, 40, 75, 90, and 100 at % Ni are studied by X-ray diffraction. The structural models of the melts, which were analyzed by the Voronoi-Delaunay transformation method, are reconstructed by a procedure that is inverse to the Monte Carlo method using experimental structure-factor curves. The parameters characterizing atomic ordering at short and longer distances are determined to change nonmonotonically in the range 10–40 at % Ni with an extreme in the vicinity of the melt containing 28 at % Ni. In this concentration range, nickel atoms are predominantly located in the pentagonal rings of polytetrahedral clusters of the icosahedral type; these atoms are ～4.1 Å from each other. Such clusters generate a prepeak in the structure-factor curves of the melts in the range 10–40 at % Ni.     

Enhancement of Upconverted Fluorescence by Interference Layers

Upconverting nanoparticles show potential applications in the field of photovoltaics and array‐based detection devices. While fluorescence enhancement using interference of incident radiation is well known in Stokes‐shift type systems such as fluorescent dyes; the effect of such interference geometry in nonlinear Anti‐Stokes type emission, such as in upconversion rare earth photophysics is demonstrated for the first time. This work describes in detail the influence of the interference modulation on both the excitation (interion energy transfer) and radiative decay with nonradiative decay processes active between emissive levels. These effects are illustrated in the thickness dependence of the decay rate and rise time. Single particle upconverted spectra and time‐resolved measurements show concurrent optimization of the infrared absorption and emission at 540 and 650 nm, with an average enhanced emission of 20 times at λ = 540 and 45 times at λ = 650 nm, dependent on the interference layer thickness and on the excitation intensity. The experimental results are correlated with finite element modeling. Both experiments and calculations show emission enhancement at an interference layer thickness of about 740 ± 20 nm, where such tolerance and the planar design, leads to ease in implementation in applications.     

Recent progress in continuous and semi-continuous processing of solid oral dosage forms: a review

Context: Continuous processing is an innovative production concept well known and successfully used in other industries for many years. The modern pharmaceutical industry is facing the challenge of transition from a traditional manufacturing approach based on batch-wise production to a continuous manufacturing model.

Objective: The aim of this article is to present technological progress in manufacturing based on continuous and semi-continuous processing of the solid oral dosage forms.

Methods: Single unit processes possessing an alternative processing pathway to batch-wise technology or, with some modification, an altered approach that may run continuously, and are thus able to seamlessly switch to continuous manufacturing are briefly presented. Furthermore, the concept of semi-continuous processing is discussed. Subsequently, more sophisticated production systems created by coupling single unit processes and comprising all the steps of production, from powder to final dosage form, were reviewed. Finally, attempts of end-to-end production approach, meaning the linking of continuous synthesis of API from intermediates with the production of final dosage form, are described.

Results: There are a growing number of scientific articles showing an increasing interest in changing the approach to the production of pharmaceuticals in recent years. Numerous scientific publications are a source of information on the progress of knowledge and achievements of continuous processing. These works often deal with issues of how to modify or replace the unit processes in order to enable seamlessly switching them into continuous processing. A growing number of research papers concentrate on integrated continuous manufacturing lines in which the production concept of “from powder to tablet” is realized. Four main domains are under investigation: influence of process parameters on intermediates or final dosage forms properties, implementation of process analytical tools, control-managing system responsible for keeping continuous materials flow through the whole manufacturing process and the development of new computational methods to assess or simulate these new manufacturing techniques. The attempt to connect the primary and secondary production steps proves that development of continuously operating lines is possible.

Conclusion: A mind-set change is needed to be able to face, and fully assess, the advantages and disadvantages of switching from batch to continuous mode production.     

The Functional Properties Acquired by Antifriction Composites Produced from Silumin Grinding Waste

Powder Metallurgy and Metal Ceramics - The paper analyzes how the antifriction composites produced from AK12MMgN silumin grinding waste with MoS2 solid lubricant additions acquire their structure...     

Structure formation in binary Al-TM (TM = Mn,Co, Ni,Cu) melts

The structures of binary Al-TM (transition metal TM = Mn, Co, Ni, Cu) melts at near-liquidus temperatures are studied by X-ray diffraction and simulation using the reverse Monte Carlo method. The melts are found to have chemical local atomic ordering, and this ordering depends on the nature and content of TM. Chemical local atomic ordering leads to a medium-range order as a result of TM atom localization at distances of 0.4–0.5 nm in the composition of polytetrahedral clusters having icosahedral symmetry. A medium-range order in the melts is identified due to the presence of an additional maximum (prepeak) in the left slope of the first peak in experimental structure factor curves. The local atomic orders in the melts and the corresponding crystalline and quasicrystalline phases are found to correlate with each other.     

Local atomic order in the Al-Cu-Fe melts corresponding to crystalline and quasicrystalline phases

The local atomic order in the Al₇₀Cu₂₀Fe₁₀ and Al_61.9Cu_25.4Fe_12.7 melts that correspond to the tetragonal τ₂ and quasicrystalline phases was studied. The structures of these ternary melts were investigated by high-temperature X-ray diffraction and Reverse Monte Carlo simulation at various temperatures. The structural models of the melts are analyzed using the Voronoi polyhedra and the Delaunay simplexes. The specific features in the structure factor curves were comprehensively discussed: a shoulder in the second maximum and a prepeak on the left side of the principal maximum. The prepeak in the structure factor curves in the diffraction vector range 11–22 nm^?1 is shown to be caused by chemical local atomic ordering, and the shoulder on the right side of the second maximum is shown to result from the presence of icosahedral polytetrahedral clusters in the melts.     

Pattern of the atom ordering in a melt and surface properties of systems with intermetallic compounds

A local atomic structure of the Ni-Al, Ni-Ge, and Ni-Sn melts has been analyzed using the models reconstructed from experimental curves of the structure factor employing the reverse Monte Carlo and Voronoy-Delaunay methods. It has been found that a decisive effect on the formation of the short-range structure, type of the atomic interaction, and surface properties of melts of systems with intermetallic compounds is exerted by the retention of the component interaction intensity and the chemical bond type in melting intermetallic phases, which causes the correlation between the structures of the liquid and solid phases. A change in the pattern of the atom ordering in melts (an intensification of the interaction between like atoms, while the interaction between unlike atoms weakens in the Ni-Al → Ni-Ge → Ni-Sn order) results in the change of thermodynamic and surface properties of melts.     

Structural and electrical properties of grain boundaries in Ce0.85Gd0.15O1.925 solid electrolyte modified by addition of transition metal ions

In this work we present studies on applicability of transition metal additives as sintering and electrical conductivity aids for cerium gadolinium oxide electrolyte. The nanosized Ce_0.85Gd_0.15O_1.925 powder obtained by coprecipitation method was modified with Cr³⁺, Fe³⁺, Ni²⁺ or Cu²⁺ ions. Using high-intensity high-resolution X-ray powder diffraction data we have determined that Cr, Fe and Ni ions do not incorporate into the cerium gadolinium oxide surface or bulk when sintered at 1300 °C, but react with Gd ions to form Cr_0.9Gd_0.1O, GdFeO₃ and GdNiO₃ phases, while Cu incorporates in the material up to 0.7 mol% with a significant fraction of remaining material showing poorly crystalline CuO phase. The nanosized Ce_0.85Gd_0.15O_1.925 material shows already improved sintering properties than previous reports but full sintering is not achieved below 1300 °C, however Cr, Fe and mainly Cu impregnation allows full sintering at 1300 °C. 0.5 mol% Ni impregnated material sintered at 1500 °C shows enhanced grain boundary conductivity that probably indicates that Ni incorporates into Ce_0.84Gd_0.15O_1.925 above 1300 °C. The global results indicate, however, that optimization of ceria microstructure is at least of equal importance for sinterability and grain boundary conductivity than impregnation of the material with transition metal ions.     

Modeling of Nonlinear Surface Impedance of High-Tc Superconductors Using an Exponential Vortex Penetration Model

We have modeled surface impedance of YBa₂Cu₃O_7– thin films, using an exponential dependence on an applied rf magnetic field. For verification of the model we compared simulation results with experimental data of Nguyen et al. [2] and of Hein [14] at differing temperatures, frequencies and rf power levels. Obtained temperature dependence of the model fitting coefficients exhibited the same character in both cases.