Properties Of Solid Phases Research Articles

Effect of Porosity Parameters on the Strength of Gas Turbine Compressor Blades Made of Titanium Alloys

A study on the effect of pore space parameters of sintered titanium alloys on the strength margin of gas turbine compressor blades has been carried out. It is shown that the endurance of parts made of sintered titanium alloys synthesized from powder mixtures based on PT5 titanium powder obtained by the mechanical milling of a titanium sponge must be evaluated taking into account the peculiarities of the morphology of the pore space. An approach to taking into account the effect of the peculiarities of the morphology of the pore space on the endurance limit of gas turbine compressor blades has been proposed and experimentally evaluated using an analysis of the fractal dimension of pore boundaries. The results of experimental studies of the endurance limit of specimens of VT1-0, VT6, and VT8 titanium alloys, which have a different porosity, mean pore size and fractal dimension, are presented. A modeling of the stress-strain state of an airfoil of full-scale low-pressure compressor blades of a shaft gas turbine engine has been performed. The results of fatigue tests of full-scale compressor blades are presented. Based on fracture mechanics approaches, an improved model for the estimation of the endurance limit of specimens of sintered titanium alloys taking into account solid phase properties, pore size and morphology, and total porosity is proposed. A relationship relating the strength margin of full-scale compressor blades to the endurance limit of laboratory specimens, their porosity parameters and the loads acting during the operation of gas turbine engines is proposed. A calculation of the strength margin and the probability of non-failure of gas turbine compressor blades made of a sintered titanium alloy with different pore size and shape, and porosity has been made. Their maximum permissible values have been determined, at which the strength margin and the probability of non-failure of blades are provided, which meet the requirements of normative documents. It is shown that to provide the required value of the strength margin and probability of non-failure of blades, the process to manufacture them must include operations aimed at avoiding pores in the surface layer.

Pairing Asymmetric Gas Diffusion Media for High-Power Fuel Cell Operation

Proton exchange membrane fuel cell (PEMFC) power production is highly influenced by the properties of the gas diffusion media (GDM). The GDM typically comprise a mesoporous carbon layer (MPL) on top of a porous carbon-fiber gas diffusion layer (GDL) which are both wetted with polytetrafluoroethylene (PTFE) to modify their water retention. In a PEMFC, the GDM are compressed to either side of the catalyst coated membrane. The GDM are active in the fuel cell transport processes including electron and heat conduction, water removal, and distributing reactant gases to the catalyst layers, which affects the electrochemistry in the catalyst layers. These transport phenomena rely on both the properties of the GDM solid phase and its voids, making optimization of GDM material properties challenging. The majority of reports in the PEMFC literature addressing GDM focus solely on the cathode, since water is produced at this electrode and its ineffective removal can block active sites and occlude O2 diffusion. Most research reports use symmetrical anode and cathode GDM. To date, there has been less discussion on the role of the anode GDM or how anode and cathode GDM properties can be selected in concert to increase fuel cell power output, despite that a significant amount of water in a fuel cell is rejected to the anode.We consider that anode and cathode GDM properties, such as air permeability, must be chosen in unison to improve cell water management. In our previous work, we used X-ray computed tomography to observe that dry-laid, non-woven, Freudenberg GDM maintain large void volume while permitting high compressive stress, ultimately resulting in lower contact and ohmic resistances and better mass transport compared to another distinct class of GDM (wet-laid, SGL).1 In this work, we make a range of PEMFCs using a suite of Freudenberg GDM to study the influence of anode and cathode GDM air permeability and how these properties may be paired to improve cell hydration and increase fuel cell power production in a broad range of operating conditions. Fuel cells are characterized with cyclic voltammetry, electrochemical impedance spectroscopy (EIS), gravimetric analysis, and limiting current measurements to quantify the sources of mass transport resistance. Gradients of GDM material properties from anode to cathode improve cell hydration and facilitate water removal to reduce mass transport resistances and enable higher power operation. 1. “The Role of Compressive Stress on Gas Diffusion Media Morphology and Fuel Cell Performance,” R. W. Atkinson III, Y. Garsany, B. D. Gould, K. E. Swider-Lyons, I. V Zenyuk, ACS Applied Energy Materials, 2017, 1 (1), 191–201.

Continuous-feed carbonation of waste incinerator bottom ash in a rotating drum reactor

Carbonation is a key process in the aging of waste incinerator bottom ash (BA). The reaction with CO2 decreases the BA alkalinity and lowers the leachability of amphoteric trace metals. Passive ageing over several months is usually performed in intermittently mixed BA heaps. Here we aimed at accelerating the process in a rotating drum reactor continuously fed with the BA and the reactant gas (10 vol-% CO2, volumetric flow rate 60 L/min). In one test, the gas was heated and humidified. Since carbonation depends on the specific CO2-supply, experiments were conducted at varied BA residence time (60, 80, and 100 min). Residence time was calculated by mass balancing and confirmed by the breakthrough time of two tracers. Leachates and solid phase properties of the treated BA served to evaluate the carbonation performance. The residence time of BA could be adequately controlled by the reactor loading and feed rate. A residence time of 80 min was sufficient to reduce the BA leachability such as to comply with the German regulatory standards for non-hazardous waste, whereas the untreated BA was hazardous waste. Decreased alkalinity was indicated by lower leachate pH and Ca(OH)2 contents of the BA as compared to the input. Leachate concentrations of amphoteric trace metals (Pb, Zn, Cu) decreased by at least one order of magnitude while oxyanions became slightly more mobile upon carbonation. In view of relatively short residence times and stable process performance, the rotating drum reactor seems promising for a full-scale implementation of BA carbonation.

Modified MFIX code to simulate hydrodynamics of gas-solids bubbling fluidized beds: A model of coupled kinetic theory of granular flow and discrete element method

The coefficient of restitution (CoR) of monodisperse particles used in the kinetic theory of granular flow (KTGF) is predicted using a coupled Euler solid phase-Euler gas phase-Lagrangian discrete particles (CEEL) approach in a bubbling fluidized bed (BFB). In the CEEL model, the CoR is obtained from dynamic information of Lagrangian discrete particles by means of discrete element method (DEM), and used to predict Euler solid phase properties in KTGF. The flow behavior of Euler solid phase, Euler gas phase and Lagrangian discrete particles is predicted in a gas and monodisperse particles BFB. The distributions of velocities and volume fractions using CEEL model are compared to numerical simulations using Euler-Euler two-fluid model (TFM) and Euler gas phase-Lagrangian discrete element method (CFD-DEM) in a BFB. The predicted distributions of granular temperature of Euler solid phase using KTGF are compared to Lagrangian discrete particles granular temperatures by means of DEM. The predicted distributions of velocities of Euler solid phase and volume fractions of Euler gas phase using CEEL model agree with experimental results.

Changes of ultimate analysis and properties of solid and gas phases at the heating wood in an inert medium. A new view

A new approach to the study and description of the process of thermal destruction of wood when heated in an inert environment (torrefication and pyrolysis) is presented. Dependencies for determining the sequence of changes in the ultimate analysis of wood at the destruction process are proposed. Dependencies for determining the calorific value and volatile matter for the solid phase as a function of the ultimate analysis, as well as for determining the ultimate analysis and calorific value of volatile matter are proposed. A possibility of extending the method to other fuels of plant origin (straw, peat, coal) is shown. It has been suggested that standard methods do not accurately determine the moisture content of wood.

The potential of mechanical alloying to improve the strength and ductility of Mo–9Si–8B–1Zr alloys – experiments and simulation

Multi-phase Mo–Si–B alloys were intensively researched during the last decade as they are promising candidates for high temperature applications beyond the capabilities of single-crystalline Ni-based superalloys. Small additions of Zr improve the mechanical properties of the Mo solid solution phase (Moss), especially it lowers the brittle-to-ductile transition temperature and improves the fracture toughness. This work shows how mechanical alloying (MA) as the crucial step of powder metallurgical (PM) production will significantly influence the materials mechanical properties of Mo–9Si–8B–1Zr alloys in a wide temperature range from room temperature up to 1400 °C. The formation, continuity and length scale of the individual phases during PM processing is evaluated in detail using experimental methods and numerical studies. Furthermore, the mechanisms of deformation and fracture of the bulk materials are discussed with respect to the microstructural features. For comparison of the mechanical properties achieved by PM processing we produced the similar alloy composition by a conventional solidification process and characterized it by the same evaluation methods.

Microstructure characterization of cement paste from micro-CT and correlations with mechanical properties evaluated from virtual and real experiments

As micro-CT devices have become widely available, the detailed 3D microstructures of cementitious materials can be more conveniently investigated. However, owing to the resolution required to appropriately represent the cement-paste microstructures, the domain size of the micro-CT sample is limited. By synergistically combining the virtual and real experiments, correlations between the microstructural characteristics and properties of cement paste with various w/c ratios (0.3, 0.4, 0.5, and 0.6) are investigated at different length scales. The porosity from the micro-CT images are correlated with the macro-scale properties obtained from real experiments. At the micro-scale, the homogenized solid phase properties are characterized from the linear attenuation coefficient (LAC) value distribution characteristic of the micro-CT images and are correlated with the modeling parameters of the phase field fracture. According to the results of virtual experiments conducted using the phase field fracture model and the characterization methods, the mechanical properties (stiffness/strength) at the micro- and macro-scale exhibited apparent relationships.

Forest monitoring: Substantiating cause-effect relationships

Monitoring of forest condition and tree performance is a long-term activity to provide data, substantiated cause-effects relationships and conclusions for environmental policies and forest management. Within this context the concept of tree and forest health, selection of response and predictor variables and challenges during statistical analyses are addressed.The terms tree and forest health are often used to characterise the performance of trees or the condition of forest ecosystems, however, the actual meanings may differ considerably. For the sake of a more coherent perception of the term health in scientific contexts and taking into account the meaning of disease(s) a more adjusted use of ‘health’ is recommended.Apart from the role of a working hypothesis, the selection process of meaningful response and predicting parameters is treated. On the response site the focus is on tree-related parameters like radial stem increment, crown condition, and foliar element concentrations. Each parameter reveals problems with specific implications for statistical model building. As drivers chemical properties of deposition, soil solution and soil solid phase, further foliar element concentrations, meteorological and air quality parameters are adduced. Additionally modelled plot-related values derived from external networks can be considered.Multiple regression as one of the core methods calls for unstructured residuals. To find optimal solutions especially in more intensive monitoring programmes with limited numbers of plots and many parameters is a challenge. Longitudinal and time series analyses may offer alternatives and widen the scope. While classical geostatistics may help to control spatial autocorrelation, possibilities to enlarge ecological and climatic gradients due to the inclusion of plots from similar programmes in suitable regions have to be considered as well.

Thermodynamic assessment of the Ni\u2013Te system

A thermodynamic assessment of the Ni–Te system has been performed using the Calphad method, based on experimental data available in the literature. The proposed description has been developed for use in the modeling of fission-product-induced internal corrosion of stainless steel cladding in Generation IV nuclear reactors. DFT calculations were performed to obtain 0 K properties of solid phases to assist the thermodynamic optimization. The ionic liquid two-sublattice model was used, and most solution phases were modeled using interstitial metal sub-lattices. With a strict number of parameters, the resulting description satisfactorily reproduces all thermodynamic properties and high-temperature phase transitions. The metastable miscibility gap in the Ni-rich liquid that is experimentally suggested is not present in the final description. The delta phase exhibits a metastable order-disorder transition between the CdI_{2} and NiAs types of interstitial nickel distribution. The CdI_{2} prototype is the stable space group at room temperature. Low-temperature ordering phase transitions have been disregarded in this description, since they are not of interest to the application of corrosion in nuclear reactors.

Ab-initio and molecular dynamics supported thermodynamic modeling of binary Cu – Ta system

The Cu–Ta system is a simple binary system with interesting properties, such as the formation of amorphous alloys and high-energy mechanical alloying capacity. Due to a high melting temperature of tantalum, experimental information about phase diagram is limited to one liquidus point. The ab initio and molecular dynamics approaches were used in this work for determination of thermodynamic properties of solid and liquid phases of Cu – Ta system. After that, the phase diagram was modeled with the aid of the Calphad method. As a consequence of these steps, a new thermodynamic description of the Cu – Ta system is proposed in this paper.

Numerical study on solid suspension characteristics of a coaxial mixer in viscous systems

Abstract A coaxial mixer consisting of an anchor and a Rushton turbine was selected as the research object, whose solid suspension characteristics were studied with the help of Computational Fluid Dynamics (CFD) method. Based on the Eulerian–Eulerian method and modified Brucato drag model, the just-suspension speed of impeller was predicted, and the simulation results were in good agreement with the experimental data. The quality of solid suspension under different rotation modes was also compared, and the results showed the coaxial mixer operating under co-rotation mode could get the best performance, and a larger anchor speed was beneficial to solid suspension by enhancing the turbulent intensity at the bottom. Compared with the anchor, the inner Rushton turbine played a dominant role in solid suspension due to its high rotational speed, whereas an extremely high inner impeller speed would make the uniformity of solid distributions become worse. Additionally, the effects of solid phase properties were also investigated, the results revealed that the higher the overall solid volume fraction and the smaller the Shields number, the worse the performance of solid suspension, meanwhile the solid suspension was more susceptible to solid density compared with particle diameter within the same Shields number gradient.

Novel multistage solid–liquid circulating fluidized bed: liquid phase mixing characteristics

Liquid phase axial mixing studies have been carried out in the novel solid–liquid circulating fluidized bed (SLCFB). The SLCFB primarily consists of a single multistage column (having an inner diameter of 100 mm i.d. and length of 1.40 m) which is divided into two sections wherein both the steps of utilization, namely loading (e.g., adsorption and catalytic reaction) and regeneration of solid phase, can be carried out simultaneously in continuous mode. Weak base anion exchange resin was used as the solid phase, whereas water as the fluidizing medium. The effects of physical properties of solid phase, superficial liquid velocity, and solid circulation rate on liquid phase axial dispersion coefficient were investigated. The dispersion coefficient increases monotonically with an increase in the size of solid particle, superficial liquid velocity, and solid circulation rate. The axial dispersion model (ADM) was used to model experimental residence time distribution (RTD) data. A good agreement was found between ADM predictions and the experimental measurements. A unified correlation has also been proposed to determine dispersion coefficient as a function of physical properties of solid and liquid phases, superficial liquid velocity, and solid circulation rate based on all previous and present experimental data on multistage SLCFB.

Sodium–Tin System: Thermodynamic Properties of Alloys and Prospects for Using Tin and Its Alloys and Compounds in Sodium-Ion Batteries (Review)

Data on thermodynamic properties of liquid sodium–tin alloys are summarized, analyzed, and compared, and thermodynamic properties of solid phases are estimated. The possibilities of using tin and its alloys and compounds as anode materials for sodium-ion batteries are briefly considered.

Solid solution softening and enhanced ductility in concentrated FCC silver solid solution alloys

The major adoptions of silver-based bonding wires and silver-sintering methods in the electronic packaging industry have incited the fundamental material properties research on the silver-based alloys. Recently, an abnormal phenomenon, namely, solid solution softening, was observed in stress vs. strain characterization of Ag-In solid solution. In this paper, the mechanical properties of additional concentrated silver solid solution phases with other solute elements, Al, Ga and Sn, have been experimentally determined, with their work hardening behaviors and the corresponding fractography further analyzed. Particularly, the concentrated Ag-Ga solid solution has been discovered to possess the best combination of mechanical properties, namely, lowest yield strength, highest ductility and highest strength, among the concentrated solid solutions of the current study. Microscopically, a clear evidence of narrow twin lamella feature has been observed in the Ag-Ga solid solution, and further identified as the deformation twinning, using high resolution transmission electron microscopy (HRTEM). To explain solid solution softening mechanism in low Peierls potential FCC metals, the authors have proposed a self-contained theoretical interpretation associated with fractional kink-pairs formation, and originally introduced the concept of the short range order (SRO) induced localized homologous temperature (LHT). Furthermore, the mechanism of twinning-induced plasticity (TWIP) can be referred as the underlying reason of the enhanced ductility in the Ag-Ga solid solution alloy. With such excellent mechanical properties, the Ag-Ga solid solution alloy is expected to have a great potential in the development of advanced joining materials for the various applications in electronics industries.

Modeling of PCM melting: Analysis of discrepancy between numerical and experimental results and energy storage performance

In this work, a comprehensive analysis of constrained melting of phase change material (PCM) is performed to identify the reasons for the discrepancy of numerical predictions. To identify this, models are proposed by accounting various experimental geometrical details. The predictions are compared and validated with the available experimental results. The results indicated a substantial influence of accounting geometrical details for reducing the difference between the numerical predictions and the experimental data. Further, the global and the local thermal and flow behavior during PCM melting, and their influence on heat storage is described. It is observed that the thermally induced flow patterns followed by formation of stratified layers aid in achieving improved heat storage. Moreover, undulations in the melting front and temperature fluctuations are observed due to thermal plumes and multiple counter-rotating vortices in the capsule. For evaluating the thermal performance, the stratified and the total energy storage densities, along with the thermal energy storage (TES) effectiveness, are also analyzed. At the end, for accounting different solid and liquid phase properties, a new physically consistent mathematical formulation of the conservative form of the energy equation is proposed. Simulation using this advanced model has shown further improvement in the predictions.

Numerical Analysis of Coupled Heat and Mass Transfer Phenomena in Concrete at Elevated Temperatures

Based on well-established physical laws, a one-dimensional model that describes coupled heat and mass transfer phenomena in heated concrete has been developed. The mathematical model is based on the fully implicit finite difference scheme. The control volume approach was employed in the formulation of the finite difference equations. The primary variables considered in the analysis are temperature, vapor density, and pore pressure of the gaseous mixture. Several phenomena have been taken into account, such as evaporation, condensation, and dehydration processes. Temperature-, pressure-, and moisture content-dependent properties of both gaseous and solid phases were also considered. Numerical case studies that deal with extremely rapid heating of concrete are validated against experimental results with good agreement in spatial and temporal trends for temperature and pressure. Outputs from the numerical model demonstrated the influence of the coupling relationship between heat and mass transfer phenomena on temperature, vapor, and pressure distributions. Furthermore, it was noted that the temperature distribution trends are significantly affected by the vapor migration phenomenon; such an effect becomes more pronounced when moving deeper toward the concrete core.

The Influence of Monolayer Morphology and Dynamics on Lung Stability

For the past 100 years, surfactant monolayers have been studied on the planar interface of Langmuir trough, even though most physiological interfaces are curved at the micron to millimeter scale. Here we show that as a lung surfactant monolayer-covered bubble approaches a critical radius, the equilibrium morphology changes from dispersed circular solid domains in a continuous liquid to a continuous solid phase linear mesh separating discontinuous liquid phase domains. Monolayer dynamics and surfactant adsorption properties are also strongly influenced by the interfacial curvature. The phase morphology transition phenomena cannot be readily explained by current theories based on isotropic domains but rather on the anisotropic properties of the semi-crystalline solid phase. The changes in morphology and dynamics may have important physiological consequences for lung stability and function as the morphological transition occurs at alveolar dimensions. The anisotropy of the condensed-phase monolayers of the primary lipid component of lung surfactant, dipalmitoylphosphatidylcholine, DPPC is shown in its rheological properties that differ between monolayers sheared clockwise (C) or counter-clockwise (CC). The nonlinear elastic modulus and yield stress of R-DPPC monolayers are greater when sheared clockwise, i.e. against the natural CC winding of individual DPPC domains than when sheared counter-clockwise. These differences disappear for racemic mixtures. Direct visualization of the deforming domains shows a different evolution of defect structures for shear in the C or CC directions. We argue that the coupling between the tilt grain boundaries and applied shear can give rise to the chiral rheology we observed. The long-time, macroscopic consequences of the underlying molecular chirality are remarkable given the single-component, non-cross-linked nature of DPPC monolayers.

MISKONSEPSI MAHASISWA MENGENAI IKATAN ION DALAM SENYAWA NaCl

Research on new university student misconceptions about bond in NaCl compounds has been done to identify possible misconceptions. Student misconceptions are observed using a misconception analysis instrument consisting of statements accompanied by right and wrong choices and open reasons. Based on the analysis of the instrument that has been done found that the students experience the concept of ionic bonding in the compound NaCl. Students experience misconceptions why NaCl is an ionic compound. In addition, misconceptions are also found about the physical properties of the associated NaCl compounds, ie students believe that NaCl is a compound with a brittle bond and no breaking of bonds in NaCl solution and NaCl has electrolyte properties in solid phase.

Investigation of sand transport in an undulated pipe using computational fluid dynamics

A CFD model has been implemented to investigate the effects the pipe undulation on sand transport. Of particular interest of the present study is the sand deposition in small angled V-inclined bend relevant to oil and gas subsea flowlines where sand deposition could be a major problem. The model used is the two-fluid Eulerian-Eulerian model with the granular temperature to tackle the solid phase properties. A number of sub-models for tackling solid-fluid and fluid-fluid interaction has been incorporated in the modelling frame work to capture the transition of flow regimes. The simulation results show that the seemingly small angled V-inclined has significant impact on sand disposition compared to the horizontal section. Sand is deposited at the downstream section of the V-inclined pipe at much higher velocities compared to the minimum transport velocity of the horizontal pipe.

Thermodynamic Analysis of Alloys in Sodium–Tellurium System in Liquid and Solid States

The whole set of available data on the thermodynamic properties of liquid alloys and solid phases in the sodium–tellurium system is considered, beginning from the first study in 1970 and till the recent reports in 2015. The application of the sodium–tellurium system in chemical power cells is discussed.