Solid–liquid–liquid phase envelopes from temperature-scanned refractive index data

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Alcides J. Sitoe ◽  
Franco Pretorius ◽  
Walter W. Focke ◽  
René Androsch ◽  
Elizabeth L. du Toit
Keyword(s):  
Refractive Index ◽  
Liquid Phase ◽  
Volume Fraction ◽  
Solution Temperature ◽  
Linear Behavior ◽  
Upper Critical Solution Temperature ◽  
Novel Method ◽  
Using Data ◽  
Solid Liquid ◽  
Liquid Liquid Phase Separation

Abstract A novel method for estimating the upper critical solution temperature (UCST) of N,N-diethyl-m-toluamide (DEET)-polyethylene systems was developed. It was validated using data for the dimethylacetamide (DMA)-alkane systems which showed that refractive index mixing rules, linear in volume fraction, can accurately predict mixture composition for amide-alkane systems. Furthermore, rescaling the composition descriptor with a single adjustable parameter proved adequate to address any asymmetry when modeling the DMA-alkane phase envelopes. This allowed the translation of measured refractive index cooling trajectories of DEET-alkane systems into phase diagrams and facilitated the estimation of the UCST values by fitting the data with an adjusted composition descriptor model. For both the DEET- and DMA-alkane systems, linear behavior of UCST values in either the Flory–Huggins critical interaction parameter, or the alkane critical temperature, with increasing alkane molar mass is evident. The UCST values for polymer diluent systems were estimated by extrapolation using these two complimentary approaches. For the DEET-polyethylene system, values of 183.4 and 180.1 °C respectively were obtained. Both estimates are significantly higher than the melting temperature range of polyethylene. Initial liquid–liquid phase separation is therefore likely to be responsible for the previously reported microporous microstructure of materials formed from this binary system.

scholarly journals Aqueous Liquid-Liquid Phase Separation of Natural and Synthetic Polyguanidiniums

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 649 ◽  
Author(s):  
Prather ◽  
Weerasekare ◽  
Sima ◽  
Quinn ◽  
Stewart
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Liquid Phase Separation ◽  
Solution Temperature ◽  
Titration Calorimetry ◽  
Polymer Backbone ◽  
Critical Solution Temperature ◽  
Upper Critical Solution Temperature ◽  
Positively Charged ◽  
Liquid Liquid Phase Separation

Protamines are natural polyguanidiniums, arginine(R)-rich proteins involved in the compaction of chromatin during vertebrate spermatogenesis. Salmine, a protamine isolated from salmon sperm, contains 65 mol% R residues, with positively charged guanidino (Gdm+) sidechains, and no other amino acids with ionizable or aromatic sidechains. Salmine sulfate solutions undergo liquid-liquid phase separation (LLPS) with a concentration-dependent upper critical solution temperature (UCST). The condensed liquid phase comprises 50 wt % water and >600 mg·ml−1 salmine with a constant 1:2 ratio of sulfate (SO42−) to Gdm+. Isothermal titration calorimetry, titrating Na2SO4 into salmine chloride above and below the UCST, allowed isolation of exothermic sulfate binding to salmine chloride from subsequent endothermic condensation and exothermic phase separation events. Synthetic random polyacrylate analogs of salmine, with 3-guanidinopropyl sidechains, displayed similar counterion dependent phase behavior, demonstrating that the LLPS of polyguanidiniums does not depend upon subunit sequence or polymer backbone chirality, and was due entirely to Gdm+ sidechain interactions. The results provide experimental evidence for like-charge pairing of Gdm+ sidechains, and an experimental approach for further characterizing these interactions.

scholarly journals Upper Critical Solution Temperature (UCST) Behavior of Coacervate of Cationic Protamine and Multivalent Anions

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 691 ◽  
Author(s):  
Hyungbin Kim ◽  
Byoung-jin Jeon ◽  
Sangsik Kim ◽  
YongSeok Jho ◽  
Dong Soo Hwang
Keyword(s):  
Electrostatic Interactions ◽  
Solution Temperature ◽  
Complex Coacervation ◽  
Critical Factors ◽  
Critical Solution Temperature ◽  
Temperature Changes ◽  
Upper Critical Solution Temperature ◽  
Large Asymmetry ◽  
Positively Charged ◽  
Liquid Liquid Phase Separation

Complex coacervation is an emerging liquid/liquid phase separation (LLPS) phenomenon that behaves as a membrane-less organelle in living cells. Yet while one of the critical factors for complex coacervation is temperature, little analysis and research has been devoted to the temperature effect on complex coacervation. Here, we performed a complex coacervation of cationic protamine and multivalent anions (citrate and tripolyphosphate (TPP)). Both mixtures (i.e., protamine/citrate and protamine/TPP) underwent coacervation in an aqueous solution, while a mixture of protamine and sodium chloride did not. Interestingly, the complex coacervation of protamine and multivalent anions showed upper critical solution temperature (UCST) behavior, and the coacervation of protamine and multivalent anions was reversible with solution temperature changes. The large asymmetry in molecular weight between positively charged protamine (~4 kDa) and the multivalent anions (<0.4 kDa) and strong electrostatic interactions between positively charged guanidine residues in protamine and multivalent anions were likely to contribute to UCST behavior in this coacervation system.

The Pressure Dependence of the Phase Diagram t-Butanol/Water

1985 ◽  
Vol 40 (7) ◽  
pp. 693-698 ◽  
Author(s):  
M. Woznyj ◽  
H.-D. Lüdemann
Keyword(s):  
Phase Diagram ◽  
Phase Separation ◽  
Liquid Phase ◽  
Pressure Dependence ◽  
Liquid Phase Separation ◽  
Temperature Range ◽  
Solid Liquid ◽  
Rich Side ◽  
Liquid Liquid Phase Separation

The phase diagram t-butanol/water is studied in the temperature range between 200 and 450 K at pressures up to 200 MPa. No liquid/liquid phase separation is observed in this range. The solid/liquid phase diagram reveals the presence of a stable t-butanol/dihydrate at all pressures. At the t-butanol rich side of the diagram solid mixtures with compositions t-butanol/water ~ 5 :1 and ~ 6 : 1 are observed.

scholarly journals Integral Solution of Two-Region Solid–Liquid Phase Change in Annular Geometries and Application to Phase Change Materials–Air Heat Exchangers

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4474 ◽  
Author(s):  
Hamidreza Shabgard ◽  
Weiwei Zhu ◽  
Amir Faghri
Keyword(s):  
Liquid Phase ◽  
Boundary Conditions ◽  
Phase Change ◽  
Phase Change Materials ◽  
Volume Fraction ◽  
Control Volume ◽  
Solid Volume Fraction ◽  
Solidification Time ◽  
Design And Optimization ◽  
Solid Liquid

A mathematical model based on the integral method is developed to solve the problem of conduction-controlled solid–liquid phase change in annular geometries with temperature gradients in both phases. The inner and outer boundaries of the annulus were subject to convective, constant temperature or adiabatic boundary conditions. The developed model was validated by comparison with control volume-based computational results using the temperature-transforming phase change model, and an excellent agreement was achieved. The model was used to conduct parametric studies on the effect of annuli geometry, thermophysical properties of the phase change materials (PCM), and thermal boundary conditions on the dynamics of phase change. For an initially liquid PCM, it was found that increasing the radii ratio increased the total solidification time. Also, increasing the Biot number at the cooled (heated) boundary and Stefan number of the solid (liquid) PCM, decreased (increased) the solidification time and resulted in a greater (smaller) solid volume fraction at steady state. The application of the developed method was demonstrated by design and analysis of a PCM–air heat exchanger for HVAC systems. The model can also be easily employed for design and optimization of annular PCM systems for all associated applications in a fraction of time needed for computational simulations.

3D Phase-Field Simulation and Characterization of Microstructure Evolution during Liquid Phase Sintering

2014 ◽  
Vol 87 ◽  
pp. 132-138 ◽  
Author(s):  
Hamed Ravash ◽  
Eckard Specht ◽  
Jef Vleugels ◽  
Nele Moelans
Keyword(s):  
Liquid Phase ◽  
Grain Boundary ◽  
Coordination Number ◽  
Dihedral Angle ◽  
Phase Field ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Liquid Phase Sintering ◽  
Study Phase ◽  
Solid Liquid

Liquid phase sintering (LPS) is widely used as a materials processing technique for hightemperature applications. In LPS, particle-particle contact size and distribution, 3-D coordination number, connectivity, and contiguity are important microstructure parameters which, to a large extent, determine the mechanical properties of the sintered materials. These features all depend on the grain size, solid volume fraction and dihedral angle during sintering. The dihedral angle is an important parameter in LPS. It is the angle formed between the 2 solid-liquid interfaces at the intersection of a grain boundary with the liquid. A higher solid volume fraction, on the other hand, favors a larger 3-D coordination number, connectivity, and contiguity. In practice, studying the correlation between these parameters and direct measurement of them is not a trivial task. Among them, 3-D measurement of dihedral angle is believed to be the most challenging one. In the current study, phase-field modeling is employed to simulate LPS in two phase systems (solid and liquid). Simulations are performed for the different ratios of grain boundary to solid-liquid energies and the different solid volume fractions. To create initial structures with high solid volume fraction, an advanced particle packing algorithm is employed. An extended sparse bounding-box algorithm is used to speed-up the computations and makes it computationally efficient for 3-D simulations. Contiguity, connectivity, and three dimensional coordination number were measured in the self similar regime. The results were compared with empirical rules and experimental data and are used to estimate the mean 3-D dihedral angle.

Low-Temperature Thermal Energy Harvesting Using Solid/Liquid Phase Change Materials

2018 ◽  
Author(s):  
Guangyao Wang ◽  
Dong Sam Ha ◽  
Kevin G. Wang
Keyword(s):  
Liquid Phase ◽  
Low Temperature ◽  
Phase Change ◽  
Thermal Energy ◽  
Peak Pressure ◽  
Volume Fraction ◽  
Energy Output ◽  
Prototype System ◽  
Hydraulic Fluid ◽  
Solid Liquid

This paper presents the design, fabrication, and analysis of a prototype system that demonstrates the use of a solid/liquid phase change material (PCM), namely pentadecane (C15H32), to harvest thermal energy associated with relatively low temperature and small temperature variation (e.g., 1°C to 20°C). The fundamental idea is to utilize the volume expansion of the PCM in the melting process to pressurize a hydraulic fluid, which is then released to drive a direct current (DC) water turbine generator. The prototype features the use of a tube system to store degassed and encapsulated PCM packages, therefore can be easily scaled to meet different energy output requirements. The performance of the prototype is assessed through measurements of the peak pressure of the hydraulic fluid and the produced power profile. The dependence of the electrical energy output on external load resistance is investigated within the range of 25 Ohm to 250 Ohm. Further, a thermomechanical model is developed to characterize the energy conversion process. Specifically, the thermodynamic behavior of PCM and hydraulic fluid is modeled with the Tait equation of state. The structural mechanics is modeled using the linear elasticity theory. The peak pressure predicted by the model agrees reasonably well with the experimental measurement, with a discrepancy of 3.40%. Finally, a series of numerical parameter studies are conducted to investigate the effects of the structural stiffness and the volume fraction of the PCM, indicating possible methods to improve the thermal efficiency and the specific energy output of the prototype system.

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