Solute Concentration In Liquid Research Articles

Linear Fiber Laser Configurations for Optical Concentration Sensing in Liquid Solutions

In this study, different configurations based on linear fiber lasers were proposed and experimentally demonstrated to measure the concentration of liquid solutions. Samples of paracetamol liquid solutions with different concentrations, in the range from 52.61 to 201.33 g/kg, were used as a case-study. The optical gain was provided by a commercial bidirectional Erbium-Doped Fiber Amplifier (EDFA) and the linear cavity was obtained using two commercial Fiber Bragg Gratings (FBGs). The main difference of each configuration was the coupling ratio of the optical coupler used to extract the system signal. The sensing head corresponded to a Single-Mode Fiber (SMF) tip that worked as an intensity sensor. The results reveal that, despite the optical coupler used (50:50, 60:40, 70:30 or 80:20), all the configurations reached the laser condition, however, the concentration sensing was only possible using a laser drive current near to the threshold value. The configurations using a 70:30 and an 80:20 optical coupler allowed paracetamol concentration measurements with a higher sensitivity of (−3.00 ± 0.24) pW/(g/kg) to be performed. In terms of resolution, the highest value obtained was 1.75 g/kg, when it was extracted at 20% of the output power to the linear cavity fiber laser configuration.

Modeling Segregation of Fe–C Alloy in Solidification by Phase-Field Method Coupled with Thermodynamics

The primary carbide in high carbon chromium bearing steels, which arises from solute segregation during non-equilibrium solidification, is one of the key factors affecting the mechanical properties and performance of the related components. In this work, the effects of carbide forming element diffusion, primary austenite grain size, and the cooling rate on solute segregation and carbide precipitation during the solidification of an Fe–C binary alloy were studied by the phase-field method coupled with a thermodynamic database. It was clarified that increasing the ratio of solute diffusivity in solid and liquid, refining the grain size of primary austenite to lower than a critical value, and increasing the cooling rate can reduce the solute segregation and precipitation of primary carbide at late solidification. Two characteristic parameters were introduced to quantitatively evaluate the solute segregation during solidification including the phase fraction threshold of primary austenite when the solute concentration in liquid reaches the eutectic composition, and the maximum segregation ratio. Both parameters can be well-correlated to the ratio of solute diffusivity in solid and liquid, the grain size of primary austenite, and the cooling rate, which provides potential ways to control the solute segregation and precipitation of primary carbide in bearing steels.

Multi-scale simulation of columnar-to-equiaxed transition during laser selective melting of rare earth magnesium alloy

• A model for studying the columnar-to-equiaxed transition during selective laser melting of rare earth magnesium alloy is developed. • The liquid undercooled layer under the combined action of forced cooling, the temperature gradient and the liquid solute concentration gradient leads to columnar-to-equiaxed transition. • The effects of Zr solubility in magnesium matrix and preheating temperature on columnar-to-equiaxed transition are obtained. A model of coupling macro finite volume method (FVM) and cellular automata (CA) is proposed in this paper to explore the columnar-to-equiaxed transition (CET) during selective laser melting (SLM) of rare earth magnesium alloy. Taking into account the impact of recoil pressure and Marangoni convection on the molten pool temperature field, the grain structure is simulated. As suggested by the simulation results, with the undissolved Zr serving as heterogeneous nucleation sites, the liquid undercooled layer under the combined action of forced cooling, the temperature gradient and the liquid solute concentration gradient leads to CET. While considering the dissolution of Zr in magnesium matrix, the results demonstrate that the dissolution of element Zr is effective in significantly inhibiting the growth of columnar crystals and ensuring the sufficient constitutional supercooling (CS) required for nucleation. In addition, to raise the preheating temperature contributes to enhancing the outcome of nucleation and incresing the grain size. Invoking the interdependence model (IM), with the cooling rate gradually increasing in the SLM process of magnesium alloy, the nucleation-free zone (NFZ) reduces by decreasing the solute diffusion layer in the front of the solid/liquid (SL) interface and the temperature gradient. The reduction in temperature gradient can promote undercooling for nucleation and facilitate the development of equiaxed crystals. The simulation results are qualitatively verified as highly consistent through experimentation.

Analytical expression for isolated pore shape in solid

Algebraic expressions for the pore shape after a bubble completely entrapped in solid are provided in this study. Properties of functional materials in micro-or nano-technologies strongly depend on pore shapes in solid. The model is based on a previous work by accounting for transient gas pressure in the pore affected by solute transfer for different cases, and balance of gas, capillary and hydrostatic pressures, and physico-chemical equilibrium at the bubble cap. The results find that algebraic prediction of the pore shapes with exact expressions of the maximum pore radii in different cases can be accomplished by dividing the pore length into three segments with inclination angles greater than initial contact angle, between initial contact angle and 90 degrees, and less than 90 degrees. The shape of an isolated pore is thus delineated by the bottom spherical cap, radius and length at the initial contact angle and maximum pore radius and length at inclination angle of 90 degrees, and top spherical cap. Dimensionless independent parameters controlling the pore length include initial contact angle, mass transfer coefficient, supersaturation ratio, product of Bond number with initial solute concentration in liquid, Henry's law constant (in Cases 1-3), and partition coefficient (in Cases 3 and 4). The predicted lengths in three segments and shapes of the isolated pore agree with numerical computations confirmed by experimental data.

A Noncontact Microwave Sensor Based on Cylindrical Resonator for Detecting Concentration of Liquid Solutions

This article presents a microwave sensor composed of a cylindrical cavity resonator and thin plastic liquid container for noncontactual detection of the liquid solution concentration. The resonant frequency is tuned to around 11 GHz, resulting in miniaturized dimensions and easy integration with a wireless sensor system. The sensor is with a small volume of 21 cm3 and sensitivity of 0.4 kHz/(mg/L). Simulated results show a good linear relationship between the concentration of the sample solution and resonant frequency shift with the high sensitivity, which is consistent with the experimental result. Compared with other designs, the sensor also has a simple structure, low cost and easy implementation to in-situ and in-vitro detection scenarios.

Supercritical antisolvent precipitation of calcium acetate from eggshells

The search for sustainable resources remains a matter of global interest. The presence of calcium in food waste may be a material to be valued. In this paper we show a new way of precipitating calcium acetate, produced from eggshells, using the supercritical antisolvent technique (SAS). It also presents the study of the precipitation efficiency as a function of the experimental conditions that affect the SAS results - temperature, pressure, liquid solution concentration and injection flow. It was possible to obtain good results under almost all experimental conditions, highlighting a higher yield for 200 bar pressures and lower solution injection flows. The obtained particles have a rod-like appearance having different sizes depending on the operating conditions.

D-optimal experimental designs for precise parameter estimation of adsorption equilibrium models

D-optimal experimental designs were obtained for Langmuir, Freundlich, Jovanovich, Sips, Redlich-Peterson and BET isotherms using two different approaches. In the first one, it is assumed that liquid solution equilibrium concentration is the independent system variable and solid equilibrium concentration is the dependent variable, which is the usual procedure for parameter estimation of adsorption isotherm models. In the second approach, initial liquid solution concentration, liquid solution volume and adsorbent mass are the independent variables and liquid solution equilibrium concentration is the dependent variable, which is closer to what actually occurs in adsorption experiments. In both cases, one of the designed conditions is an experiment using the maximum concentration value in the experimental range, while other conditions are functions of one or more isotherm parameter. When using equilibrium concentration as the independent variable, the linear parameter of the equilibrium model did not affect the experimental design. In this case, analytical solutions for 2-parameter equilibrium isotherm were obtained, while only numerical solutions were obtained for 3-parameter equilibrium models. When considering the initial concentration as the independent variable, with a constant liquid solution volume to adsorbent mass ratio, it was possible to observe that the experimental conditions of the optimum design depend on all model parameters, for all isotherms evaluated. Additionally, as liquid solution volume to adsorbent mass ratio increases, the experimental design obtained using the initial concentration as the independent variable approaches the one obtained when equilibrium concentration is assumed to be independent variable; therefore, this approach is just a particular case of the first one.

Effect of Ca addition on solidification microstructure of hypoeutectic Al-Si casting alloys

The effect of Ca addition on the solidification microstructure of hypoeutectic Al-Si casting alloys was investigated using scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) methods with particular attention focused on the change of morphologies of primary α-Al and eutectic silicon. Meanwhile, solute distribution in solid-liquid was simulated according to Scheil-Gulliver law. Results showed that primary α-Al and eutectic silicon were refned as Ca content increased because of the variation of the solute concentration in liquid. The addition of Ca increased the nucleation sites like Al3Ti or Al2Cu to promote the nucleation of primary α-Al. Affected by modifcation effect of Ca, the shape of eutectic silicon changed from fake to fbrous structure. In addition, coarse plate Ca-rich phases could be found along the grain boundary with high Ca content.

Solute convection effects on a bubble entrapped as a pore during unidirectional upward solidification

A transport model is proposed to predict entrapment of a bubble during unidirectional upward solidification. Pore formation and its shape in solid influence not only microstructure of materials, but also contemporary issues of various sciences of biology, engineering, foods, geophysics and climate change, etc. In this study, COMSOL computer code is used to solve conservation equations of mass, momentum, energy and solute concentration in liquid, gas and solid phases satisfied by their interfacial conditions. It shows that strong convection deflects the pore growth toward the downstream direction. Time for bubble entrapment, however, depends on the ratio between square of concentration boundary layer thickness and solute diffusivity. Concentration boundary layer thickness is proportional to solute diffusivity divided by difference in bubble growth rate and vertical component of fluid velocity at the bubble cap. The latter is almost independent of incoming horizontal flow. Solute diffusion is therefore the mechanism responsible for bubble entrapment, where the bubble growth rate and vertical velocity component of fluid at the bubble cap are of the same order of magnitude. A triangle region with local high concentration is also found to occur in solid region near the triple-phase line. Predicted contact angle agrees with that obtained from the Abel’s equation of the first kind during solidification. This work provides a general model for a fundamental and systematical understanding of mechanisms of a bubble entrapped as a pore in solid.

Effects of initial contact angle on pore shape in solid

The pore shape affected by initial contact angle of a bubble entrapped by a solidification front is predicted. Initial contact angle affects bubble nucleation, surface area and solute transport across the bubble cap, solid gas pressure in the pore and shape of pores in solid. Porosity influences microstructure and functional properties of materials, etc. This work accounts for solute transport across the coupled shape of cap in balance of pressures and physico-chemical equilibrium. Similar to previous work, it shows that pore shape depends on directions and magnitudes of solute across the cap. In contrast to Case 2, solute transport in Case 1 is from the pore into surrounding liquid in the early stage. The results find that a decrease in initial contact angle expedites bubble entrapment in Case 1. Solute gas pressure in the pore further exhibits three stages for initial contact angle greater than 90°. Significant drops occur in the early and late stages. In the middle stage, where contact angle is near 90°, solute concentration at the cap is about initial solute concentration in liquid, and responsible for length of the pore. Except for initial contact angle less than 90°, an isolated pore cannot be formed in Case 2. The predicted pore shape agrees with experimental data.

Effects of physico-chemical interfacial equilibrium on pore shape in solid

The shape of a pore, resulting from a bubble entrapped by a solidification front, for different Henry’s law constants at the cap is predicted in this work. Henry’s law, indicating an interfacial physico-chemical equilibrium, is essentially required to relate solute concentration in liquid at the cap by solute gas pressure in the pore. Pore formation and its shape in solid influence contemporary issues of biology, engineering, foods, geophysics and climate change, etc. This work applies a previous model accounting for mass and momentum transport of solute across a self-consistently determined shape of the bubble cap subject to different cases characterized by different directions and magnitude of solute transport across the cap. Case 1 is referred to solute transport from the pore across cap to surrounding liquid in the early stage. Cases 2a and 2b, corresponding to low and high Henry’s law constants, respectively, indicate opposite directions of species transport across the cap. An increase in Henry’s law constant decreases pore radius and time for entrapment in Case 1. The pore cannot be entrapped asa pore in solid in Cases 2. The predicted pore shape in solid agrees with experimental data. Understanding, prediction and control of the growth of the pore shape have therefore been obtained.

ThermoCalc Application for the Assessment of Binary Alloys Non-Equilibrium Solidification

Abstract The paper presents the possibility of application of the developed computer script which allows the assessment of non-equilibrium solidification of binary alloys in the ThermoCalc program. The script makes use of databases and calculation procedures of the POLY-3 module. A solidification model including diffusion in the solid state, developed by Wołczyński, is used to describe the non-equilibrium solidification. The model takes into account the influence of the degree of solute segregation on the solidification process by applying the so-called back-diffusion parameter. The core of the script is the iteration procedure with implemented model equation. The possibility of application of the presented calculation method is illustrated on the example of the Cr-30% Ni alloy. Computer simulations carried out with use of the developed script allow to determine the influence of the back-diffusion parameter on the course of solidification curves, solidus temperature, phase composition of the alloy and the fraction of each phase after the solidification completion, the profile of solute concentration in liquid during solidification process, the average solute concentration in solid phase at the eutectic temperature and many other quantities which are usually calculated in the ThermoCalc program.

The spatial and temporal distribution of dendrite fragmentation in solidifying Al-Cu alloys under different conditions

The directional columnar solidification of Al-Cu alloy dendrites was studied in-situ by synchrotron X-ray radiography to investigate the spatial and temporal distribution of dendrite fragmentation, without and with an applied pulsed electromagnetic field (PEMF) and in different solidification directions. The differing arrangements had a strong and reproducible influence on fragmentation behaviour that was rationalised using a model of solute-driven re-melting of dendrite arms in microstructural regions of high vulnerability. Although absolute rates of fragmentation varied, all the fragmentation distributions had a characteristic peak in fragmentation rate at a distance of 500–800 μm into the mushy zone. Consistent with the need for solute-rich liquid flow for dendrite root re-melting, this peak was explained to occur under conditions where there was both comparatively steep liquid solute concentration gradients, measured directly from the radiographs, and relatively high permeability of the dendrite network to liquid flow.

Effects of solute concentration in liquid on pore shape in solid

The effects of initial solute gas concentration in the liquid on the shape of a pore, resulting from a nucleated bubble entrapped by a solidification front, are predicted in this work. Solute concentration in liquid is responsible for solute transfer across the bubble cap, gas pressure in the pore, and shapes of the cap and pore in solid. Distributions and shapes of pores in solids influence not only microstructure of materials, but also contemporary issues of biology, engineering, foods, geophysics and climate change, etc. In this work, the relevant pore shape delineated by tracing contact angle of the cap to a first approximation is determined by accounting for mass and momentum transport across a self-consistent shape of the cap whose surface is satisfied by physico-chemical equilibrium, as proposed previously. This work finds that there exist three different mechanisms for pore formation, depending on directions and magnitude of solute transfer across the cap. Case 1 is subject to solute transport from the pore into surrounding liquid as a result of the cap emerged from a thin concentration boundary layer on the solidification front. An increase in initial solute concentration in liquid decreases pore radius and times for bubble entrapment. Opposite directions of solute transport across the cap submerged into a thick concentration boundary layer along the solidification front, however, cannot result in bubble entrapment, because solute concentration at the cap increases and decreases rapidly in late stage in Cases 2a and 2b, respectively. The predicted pore shape in solid agrees with experimental data. The pore shape therefore can be controlled by initial solute concentration to change directions and magnitudes of solute transport across the cap.

Spiral finned crystallizer for progressive freeze concentration process

Progressive freeze concentration (PFC) has emerged as a viable technology for concentration of liquid solution. In this study, a newly designed spiral finned crystallizer to improve productivity of PFC process was proposed. Performance of the crystallizer was analyzed through the system efficiency assessed in parallel with the effect of operating conditions. It was found that the efficiency of the system has significantly improved signalled by the lower effective partition constant and higher solute recovery. Effective partition constant of 0.35 and solute recovery of approximately 0.96g of glucose obtained per 1g of initial glucose were obtained. 1.71gm−2s−1 of maximal ice production was attained, reflecting good function of the spiral fin. A mass balance has successfully validated the obtained experimental results. Thus, the spiral finned crystallizer is highly potential to be integrated in a PFC system as an effective system to concentrate a solution and to produce pure ice crystal. This proposed system can also offer an attractive alternative for the food industry as it involves no heating and has high potential in producing highly concentrated solution.

Effect of Circulation Flowrate on the Performance of a Spiral Finned Freeze Concentrator

Progressive freeze concentration (PFC) has emerged as a viable technology for concentration of liquid solution. In this study, a newly designed spiral finned crystallizer to improve productivity of PFC process was proposed. The spiral fin is presented based on the advantage of additional surface area to the spiral finned crystallizer. The performance of spiral finned crystallizer was analysed by the system efficiency and the effect of circulation flowrate. It was found that the efficiency of the system has significantly improved in terms of a lower effective partition constant and a higher recovered solute. An effective partition constant of 0.35 and a recovered solute of approximately 0.96 g of glucose per 1 g of initial glucose were obtained. Thus, spiral finned crystallizer for PFC system is evidently an effective system to concentrate solution and to produce pure ice crystal.

Surface interactions between two like-charged polyelectrolyte gels

Due to the migration of mobile molecules and ions, a thin diffusive layer of distributed charge--the electric double layer--forms at the interface between a polyelectrolyte gel and a liquid ionic solution. When two polyelectrolyte gels are brought closely together, the electric double layers overlap and interact with each other, resulting in an effective repulsion. The multiphysics-coupling nature of soft gels makes their surface interactions significantly different from the interactions between rigid solids. Using the recently formulated nonlinear theory, this paper develops a continuum model to study the surface interactions between two like-charged polyelectrolyte gels, accounting for the coupled electric, concentration, and deformation fields in both the gels and the liquid. Numerical solutions of the surface interactions are obtained and compared to a qualitative scaling law derived via linearization. The results suggest that the structure of double layers, as well as their interactions, depends not only on the concentration of liquid solutions, but more on the bulk properties of the gels such as stiffness and fixed-charge density. This model also provides insights to the mechanism of the low-friction phenomena on the surface of a polyelectrolyte gel.

A review of modified surfaces for high speed inkjet coating

There are many interaction phenomena occurring between inks and the printed surface during the inkjet ink setting and drying process on coated papers. First, the ink wets the surface and then absorption into the capillary network occurs. After milliseconds, the colourant and solvent/diluent parts of the ink separate. Wetting of the coating surface, and the interior of the capillary network, depends on the relative surface energies of the components being brought into contact, and their interaction may include selective adsorption. Additionally, diffusion phenomena occur a few seconds after the ink arrives at the surface, which may be vapour dependent or liquid–liquid and liquid–solute concentration dependent. The final ink drying and polymerization can last for hours. The interactions have a direct connection to the final print quality. The most important properties of the coated surface are the porous structure parameters – pore size, amount and the network they form – and the chemical nature. In the beginning, at the first contact of the ink with the surface, the chemical properties of the coating layer and the ink dominate. As the mobile ink components penetrate deeper into the coating structure, the pore structure becomes more important. In some cases, depending on the nature of the binder (water soluble and/or emulsion polymer-based), the ink diluent or solvent may enter the intermolecular structure of the binder of the coating layer by diffusion, and the binder often swells as a result. A more hydrophilic binder in contact with water-based ink swells more than the one that is less hydrophilic. The most important control parameters in designing inkjet print surfaces, from the point of view of ink spreading and penetration, are the porosity, permeability, thickness/bulk, sizing (hydrophobizing), moisture content, temperature, and capillary structure of paper. Depending on whether an ink is dye-based or pigment-based, a main aspect that affects the print quality is the distribution and permanence of the colourant. The aim, in the inkjet ink setting process, apart from providing a dried ink surface, is to fix the colourant part of ink at or in the uppermost layer of the coating whilst allowing the diluent/solvent part of ink to penetrate deeper into the structure. Proper colourant fixation produces high optical print density, bright colour tones, high sharpness, low bleeding, low print-through, and high rub and wet resistance.

Fabrication and Microstructure Characteristic of YBCO Bulk by Directional Top-Seeded Power Melting Process

Abstract Top-seeded power melting process (TSPMP) is an effective melting processing technique for the preparation of high J c bulk YBCO. The directional solidification is also a quite common technique used to produce well-oriented cylinder grains. The two processes were combined (named Directional Top-Seeded Power melting Process, DTSPMP) to fabricate good YBCO bulk with well-oriented domains. The seed transferring effect and the change of the solute concentration in liquid were analyzed. The effects of temperature gradient (TG) on the orientation and continuous growth of large grains were also investigated. The microstructure dependence on pulling rate was analyzed through scanning electric microscopy(SEM), and it is found that the large domains can be obtained and the fine dispersive 211 particles are entrapped at a slower pulling rate.

Supercritical CO 2 antisolvent precipitation of polymer networks of l-PLA, PMMA and PMMA/PCL blends for biomedical applications

A supercritical carbon dioxide (SCCO 2) antisolvent technique was used for the precipitation of several biopolymers into fibers organized in a three-dimensional network. The work was first focused on separately processing either a biodegradable (polycaprolactone or polylactic acid) or a non-biodegradable (polymethylmetacrylate) homopolymer. Second, we established that the antisolvent supercritical technique can be also used to make fibrous networks of blends constitute by non-biodegradable and biodegradable polymers (polymethylmetacrylate/polycaprolactone). The influence of several operating variables (e.g., liquid solution concentration or flow rate and nozzle design) on the polymers morphology and properties was evaluated. For all studied systems, fibers with a rough textured surface and an extremely high surface area in the order of 100–400 m 2 g −1 were precipitated. Prepared materials have potential applications in tissue engineering, since they have intrinsic advantages from a biomimetic approach.