Ni–YSZ(111) solid–solid interfacial energy

Solid-state dewetting of continuous Ni films deposited on the (111) surface of yttrium stabilized zirconia (YSZ) was used to produce equilibrated Ni particles, and the solid–solid interface energy was determined using Winterbottom analysis. The ~150 nm thick Ni films were dewetted (annealed) at 1350 °C in Ar + H₂ (99.9999 %) at an oxygen partial pressure of 10^?20 atm for 6 h. Transmission electron microscopy of equilibrated particles was conducted, and two low-energy low-index orientation relationships were found: $ {\text{Ni[1}}\overline{ 1} 0 ] ( 1 1 1 )\left\| {{\text{YSZ[1}}\overline{ 1} 0 ]} \right. ( 1 1 1 ) $ and $ {\text{Ni[}}\overline{ 1} 1 0 ] ( 1 1 1 )\left\| {{\text{YSZ[1}}\overline{ 1} 0 ]} \right. ( 1 1 1 ) $ , and the interface energies were measured to be 1.8 ± 0.1 and 2.1 ± 0.1 J/m², respectively. A model including grain growth concurrent with dewetting is used to explain the formation of the higher energy orientation relationship.     

Application of dilatometric analysis to the study of solid–solid phase transformations in steels

This article outlines the use of dilatometry in solid–solid phase transformation research in steel. It describes how dilatometric data are interpreted, with an emphasis on continuous heating and cooling transformation diagrams. These diagrams show the microstructural constituents that result from given heating and cooling conditions, and are an invaluable tool for the metallurgist in characterizing steels with respect to their response to heat treatments. Several practical examples and applications of dilatometry in steel research are briefly described in this work.     

How does solid helium rotate?

It is shown that solid helium near the solidification curve at temperature T 1.3 K has the properties of a jelly-like substance with viscosity 10²–10⁴ P. In the same conditions the surface of rotating solid helium (at a rate of linear crystal growth u < 10^–3 cm/sec) acquires a concave shape.     

Y xBayCuzO7− δ solid solutions

Y_xBa_yCu_zO_7– ceramics forming at isobaric conditions were studied by x-ray diffraction analysis, dynamic magnetic measurements and potentiometric titration. It was established that compositions: 0.8 x 1.2 y=2, z=3; x-1, 1.8 y 2.2, z=3; x=1, y=2, 2.7 z 3.4: are in the homogeneity range of 123. It was found that compositions with nonstoichiometric cations rations have minimum T_c.     

Zirconia-toughened sodium beta″-alumina solid electrolyte

The effect of a 15 vol% zirconia dispersion on the critical current density for failure initiation of beta-alumina solid electrolyte was examined. Single phase and composite electrolytes were tested in standard sodium-sodium test cells and subjected to increasing ionic currents. Onset of degradation in the electrolyte was detected by monitoring acoustic emissions from the cell. Preliminary examination of the electrolyte material showed that the problem of producing a uniform dispersion of zirconia in pure beta-alumina had not been solved. However, the electrolytes were of sufficient quality to draw important conclusions about the potential of transformation toughening for improving electrolyte performance.     

CFD simulation of solid–liquid stirred tanks

Solid liquid stirred tanks are commonly used in the minerals industry for operations like concentration, leaching, adsorption, effluent treatment, etc. Computational Fluid Dynamics (CFD) is increasingly being used to predict the hydrodynamics and performance of these systems. Accounting for the solid–liquid interaction is critical for accurate predictions of these systems. Therefore, a careful selection of models for turbulence and drag is required. In this study, the effect of drag model was studied. The Eulerian–Eulerian multiphase model is used to simulate the solid suspension in stirred tanks. Multiple reference frame (MRF) approach is used to simulate the impeller rotation in a fully baffled tank. Simulations are conducted using commercial CFD solver ANSYS Fluent 12.1. The CFD simulations are conducted for concentration 1% and 7% v/v and the impeller speeds above the “just suspension speed”. It is observed that high turbulence can increase the drag coefficient as high as forty times when compared with a still fluid. The drag force was modified to account for the increase in drag at high turbulent intensities. The modified drag is a function of particle diameter to Kolmogorov length scale ratio, which, on a volume averaged basis, was found to be around 13 in the cases simulated. The modified drag law was found to be useful to simulate the low solids holdup in stirred tanks. The predictions in terms of velocity profiles and the solids distribution are found to be in reasonable agreement with the literature experimental data. Turbulent kinetic energy, homogeneity and cloud height in the stirred tanks are studied and discussed in the paper. The presence of solids resulted in dampening of turbulence and the maximum deviation was observed in the impeller plane. The cloud height and homogeneity were found to increase with an increase in impeller speed. The work provides an insight into the solid liquid flow in stirred tanks.     

The structure of shock and interphase layers for a heat conducting Maxwellian rate-type approach to solid–solid phase transitions

One continues the qualitative analysis started in Part I (F?ciu and Molinari in Acta Mech) concerning the thermomechanical characteristics of a steady, structured moving phase boundary in a shape memory alloy (SMA) by a quantitative investigation. The internal structure of these interphase layers is governed by a Maxwellian rate-type constitutive equation coupled or not with the Fourier heat conduction law. We consider as equilibrium stress–strain–temperature response function for the Maxwellian model an explicit piecewise linear thermoelastic relation for an SMA bar which can exist in the austenite phase A and in two variants of martensite M ^±. Its thermal properties are built in agreement with experimental results on NiTi. This equilibrium relation has the atypical property that not only the derivative of the stress response function with respect to the strain changes its sign, but also the derivative with respect to the temperature. Considerable temperature variation is generated by impact-induced phase transformations due to the large amount of latent heat released (absorbed) inside the transition layer. One gets strong heating (cooling) across a compressive A→ M ^? (expansive M ^? → A) propagating interphase layer. A significant lower (larger) temperature than that at the front and Hugoniot back state is obtained inside an impact-induced M ⁺→ M ^? (M ^?→ M ⁺) interphase layer. The experimental finding of this phenomenon of temperature undershoot (overshoot) could be a valuable indication for the existence of an interphase layer.     

Interdiffusion inα solid solutions of the Cu-Zn-Sn system

The interdiffusion coefficients in the f c c phase of Cu-Zn-Sn alloys, , have been determined at 1073 K. The concentration profiles indicate that the diffusion rate of tin is greater than that of zinc in the Cu-Zn-Sn alloy. The diffusion paths show the typical S-shaped curves. All of the four interdiffusion coefficients are positive and they are very sensitive to the solute concentration. The atomic mobilities of the three diffusing elements in Kirkendall planes increase in the order of Cu, Zn, Sn. The interaction energy of the Cu-Sn bond is much larger than that of the Zn-Sn bond. From the results of the present work it seems that the Onsager reciprocal relation holds in the a phase of the Cu-Zn-Sn system.     

Superionic solid: composite electrolyte phase – an overview

A general overview on the field of solid state ionics, including materials and transport property, is presented. Superionic systems in the composite electrolyte phase are discussed in great detail. Possible theoretical models suggested to understand the ion-transport mechanism in these systems are reviewed extensively.     

δ-FeO(OH) and its solid solutions

A transmission electron microscope imaging investigation was performed on small -FeO(OH) crystallites less than 50 Å thick and several hundred angstroms across. We have observed faceting, and a hexagonal plate-like morphology with topological features near atomic step heights. Because of the mutual magnetic attraction on these particles, they tend to align with their thin direction (c-axis) either parallel or perpendicular to the support film surface. It is therefore possible to view dislocations or buckling of lattice planes of these plates either edge-on or perpendicular to this direction by direct lattice imaging in both the bright-field and dark-field modes. A highly distorted lattice is apparent when viewing the particles edge-on, and it is possible to show lattice projections to a resolution of 2.1 Å.     

Impuriton vacancy “molecules” in solid 4He

The effects of thermally activated vacancies on ³He spin diffusion in solid ⁴He crystals are analyzed in a way analogous to the impuriton gas model of Richards, Pope, and Widom. It is found that the model is inconsistent with experimental diffusion results unless vacancies and ³He impuritons form highly mobile molecules. The theory with molecules is found to be in agreement with the diffusion data.     

δ-FeO(OH) and its solid solutions

-FeO(OH)-type solid solutions have been synthesized with compositions Fe_1–x M _x O_1–x (OH)_1+x ranging up tox=0.10 for M=Ca,x=0.35 for M=Mg or Cd andx=0.40 for M=Zn. The phases are characterized by X-ray diffraction and transmission electron microscope studies. A structural model giving satisfactory intensity agreement is postulated for Fe_1–x Zn _x O_1–x (OH)_1+x . In this model, Zn²⁺ ions are situated in the 0 0 0 octahedral sites of space group D _3d ³ -P¯3ml while the Fe³⁺ ions are almost equally distributed among both octahedral sites (0 0 0 and 0 0 1/2).     

Dynamic two-point fluidization model for gas–solid fluidized beds

In real fluidized beds various fluidization regimes may occur simultaneously resulting in quite distinct hydrodynamic characteristics in various regions of the bed. Classical approaches, generally, use a step drag function with a single switching point to distinguish dense and dilute regimes. In the present study, a new integrated hydrodynamic model (drag and viscosity) is developed using a smooth logistic function with two switching points dividing a fluidized bed into three dense, dilute and mixed regimes which is more in accordance with reality. Gas volume fraction at minimum fluidization velocity and particle Geldart’s group are employed to decide switching between dense and dilute drag and viscosity models. A spatiotemporal dynamic algorithm is used to implement the integrated model into the open source CFD package OpenFOAM 2.1.1. Reasonable predictions of various hydrodynamic characteristics in three different experimental data sets demonstrate wide applicability of the new integrated hydrodynamic model to any fluidization regime.     

Nanocrystalline FeNi solid solutions prepared by mechanical alloying

Mechanical alloying of FeNi36 was performed by the ball milling process. XRD studies revealed that the alloy was crystallized in a stable FCC phase. Structural analysis of the samples pointed out a crystallite size to 10 nm. Thermogravimetric measurements allowed the detection of both CO and CO₂. During thermomagnetic analyses, we observed unusual response of our samples.     

Vapour–liquid–solid growth of TiB2 whiskers

Whiskers of TiB₂ have been synthesised via a carbothermal vapour–liquid–solid (VLS) growth mechanism. The whisker growth was investigated in the temperature region 1100–1800°C in argon. The best result was obtained with a starting mixture of TiO₂:B₂O₃:C:NaCl:Ni in the molar ratios 1:1:6:0.25:0.1 at 1500°C. Thermogravimetric analyses and mass-spectroscopy measurements were used in studying the whisker growth. The obtained TiB₂ whiskers are 0.5–2 m in diameter and 10–50 m in length. TEM studies of the whiskers showed that the dominating growth direction is temperature dependent.     

Nanocrystalline CuFe solid solutions prepared by mechanical alloying

Nanocrystalline Cu_xFe(100_−x) solid solutions have been prepared by mechanical alloying. The average grain size of the powders (10–20 nm) depends on the composition of the material. The detailed process of nanocrystal formation was characterized by high resolution electron microscopy and many fine structure changes were revealed. The enhancement of solid solubility is explained according to the structural features of nanocrystals.     

Synthesis and thermal properties of polystyrene-graft-PEG copolymers as new kinds of solid–solid phase change materials for thermal energy storage

A series of polystyrene-graft-PEG₆₀₀₀ copolymers were synthesized as new kinds of polymeric solid–solid phase change materials (SSPCMs). The synthesized SSPCMs storage latent heat as the soft segments PEG₆₀₀₀ of the copolymers transform from crystalline phase to amorphous phase and therefore they can keep its solid state during the phase transition processing. The graft copolymerization reaction between polystyrene and PEG was verified by Fourier transform infrared (FT-IR) and ¹H NMR spectroscopy techniques. The morphology of the synthesized SSPCMs was characterized by polarization optical microscopy (POM). Thermal energy storage properties, thermal reliability and thermal stability of the synthesized SSPCMs were investigated by differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis methods. The DSC results showed that the synthesized SSPCMs had typical solid–solid phase transition temperatures in the range of 55–58 °C and high latent heat enthalpy in the range of 116–174 J g⁻¹. The TG analysis findings showed that the synthesized SSPCMs had high thermal durability above their working temperatures. Also, thermal conductivity measurements indicated that the synthesized PCMs had higher thermal conductivity compared to that of polystyrene. The synthesized polystyrene-graft-PEG₆₀₀₀ copolymers as new kinds of SSPCMs could be used for thermal energy storage.     

AlPbOAg as a solid electrolyte cell

Thin film AlPbOAg sandwich solid electrolyte cells are obtained by vacuum evaporation on glass substrates; PbO is grown thermally by oxidizing vapour-deposited lead at 150 °C on the bottom aluminium electrode. A.c. and d.c. conductivity studies on symmetrical AlPbOAl sandwich cells indicate that PbO is an ionic conductor. The AlPbOAg sandwich cell is seen to generate a short-circuit current of few nanoampères and a dark voltage in the range 400–800 mV in air ambient, silver being the positive electrode. The discharge characteristics of the cells are studied and a cell reaction is proposed. The variation in cell voltage with temperature and white light illumination is also studied. The photovoltage of the cell is found to add to its dark voltage. The short-circuit current of the cell is also observed to increase with illumination.