Multiple Phase Behavior Research Articles

New insights on the thermal analysis of low moisture composite foods

Low moisture baked products were investigated with a view to characterising the effect of both formulation and humidity on their physical stability. At the end of the baking process, the samples were in the amorphous state as a result of starch gelatinization and sugar melting. Their thermal properties were analyzed with differential scanning calorimetry and their glass transitions were studied. The DSC thermograms were thoroughly studied through a Gaussian deconvolution of the first derivative of their heat flow. This approach evidenced a multiple phase behavior with different glass transitions in composite systems. They were associated with either a polymer-rich phase and/or a plasticizer (sugar)-rich phase whose behavior depended on the sample water content.This novel approach of thermal properties suggested new insights: considering the phase behavior of complex systems and thus the properties of their individual phases could contribute to a better understanding of the physical stability of the products.

In-situ high-energy synchrotron X-ray diffraction study of micromechanical behavior of multiple phases in Ni47Ti44Nb9 shape memory alloy

High-energy synchrotron X-ray diffraction technique was used to in-situ characterize microstructure, lattice strain, and phase transition behavior of a Ni47Ti44Nb9 shape memory alloy. Phase transformation kinetics and deformation mechanisms were studied under a uniaxial tension at three testing temperatures, i.e., −70°C, 25°C, and 150°C. At a testing temperature of −70°C, a complicated phase transformation with four stages of micromechanical deformation was identified which is associated with changes of martensite substructures. At room temperature of 25°C, there was no stress-induced selection process of variants of B19′ phases observed. Whereas at a testing temperature of 150°C, there was no any phase transformation observed. It is verified that β-Nb phase, an effective stabilizer for the austenite, delays the process of martensitic transformation and relaxes the strain energy without strengthening the matrix. This new finding is important to understand the relationship between the micromechanical deformation behavior and phase transformations in the Ni47Ti44Nb9 SMA.

Polymer electrolytes based on a ternary miscible blend of poly(ethylene oxide), poly(bisphenol A-co-epichlorohydrin) and poly(vinyl ethyl ether)

Ternary blends of poly(ethylene oxide) (PEO), poly(bisphenol A-co-epichlorohydrin) (PBE) and poly(vinyl ethyl ether) (PVEE) were obtained as films and characterized by differential scanning calorimetry (DSC) and vibrational spectroscopy (FTIR). From the DSC results, phase diagrams for the ternary blends were determined, where the variation of the viscoelastic phase extent as a function of the polymers composition was determined. The DSC results also indicated miscibility of the system, exhibiting only one glass transition temperature (Tg) and decrease in the crystallinity of the system, as well as decrease in the crystallinity of PEO present in the blends. Vibrational spectroscopy (FTIR) provided information on the intermolecular interactions between the pairs PBE/PEO and PBE/PVEE, via hydrogen bond interaction. From the FTIR analyses, molecular model systems of equilibrium among the interacting structures were proposed as a molecular basis for the miscibility of the system.Polymer electrolytes based on the ternary blend containing 60/25/15 (PEO/PBE/PVEE) mass percent and lithium perchlorate (LiClO4) were obtained and characterized by DSC, FTIR, optical microscopy and electrochemical impedance spectroscopy (EIS). Solid electrolytes containing up to 10 wt% LiClO4 exhibited a single-phase behavior, evidenced by the DSC results. For these electrolytes, FTIR spectra indicated the formation of polymer–ion complexes, in which the cation (Li+) acts favoring the polymer–polymer miscibility. Electrolytes containing LiClO4 higher than 10 wt% exhibit a multiple phase behavior, in which a PEO-rich, salt-containing phase is present in equilibrium with PBE or PVEE-rich phases. Maximum ionic conductivity at room temperature, for the electrolyte containing 20 wt% LiClO4, reached 4.23 × 10−3 Ω−1 cm−1, while all samples exhibited conductivity of approximately 10−1 Ω−1 cm−1 at 80 °C.

Suppression of AC conductivity by crystalline transformation in poly(vinylidene fluoride)/carbon nanofiber composites

Poly(vinylidene fluoride) (PVDF) is an important ferroelectric semi-crystalline polymer with multiple-phase behavior. In this study, remarkable effects of the various crystalline structures of PVDF nanocomposites on alternating current (AC) conductivity were discovered using carbon nanofibers (CNF). It was found that the transformation from α-phase to β-phase in PVDF, induced by the addition of CNFs, had a surprisingly suppressive effect on the AC conductivity of the nanocomposites. These unexpected results indicate that the decline in conductivity occurs after re-crystallization treatment (annealing) of the nanocomposites, and the reduction levels increase with increasing amounts of CNFs. Interestingly, the AC conductivity of annealed 5 wt% CNF/PVDF composites becomes even lower than that of re-crystallized nanocomposites with 3 wt% CNFs. These findings are believed to be very significant for fabrication and long-term service of PVDF composites in industry, which often involves exposure to repeated thermal cycling.

Modeling of Blast Furnace with Layered Cohesive Zone

An ironmaking blast furnace (BF) is a moving bed reactor involving counter-, co-, and cross-current flows of gas, powder, liquids, and solids, coupled with heat exchange and chemical reactions. The behavior of multiple phases directly affects the stability and productivity of the furnace. In the present study, a mathematical model is proposed to describe the behavior of fluid flow, heat and mass transfer, as well as chemical reactions in a BF, in which gas, solid, and liquid phases affect each other through interaction forces, and their flows are competing for the space available. Process variables that characterize the internal furnace state, such as reduction degree, reducing gas and burden concentrations, as well as gas and condensed phase temperatures, have been described quantitatively. In particular, different treatments of the cohesive zone (CZ), i.e., layered, isotropic, and anisotropic nonlayered, are discussed, and their influence on simulation results is compared. The results show that predicted fluid flow and thermochemical phenomena within and around the CZ and in the lower part of the BF are different for different treatments. The layered CZ treatment corresponds to the layered charging of burden and naturally can predict the CZ as a gas distributor and liquid generator.

An in situ high-energy X-ray diffraction study of micromechanical behavior of multiple phases in advanced high-strength steels

The micromechanical behavior of high-strength steels with multiple phases was characterized using the in situ high-energy X-ray diffraction technique. For the materials investigated, the {2 0 0} lattice strains of the constituent phases (ferrite, bainite and martensite) with similar crystal structures were determined by separating their overlapped diffraction peaks and then examining the respective changes in peak positions during deformation. Based on those experimental data, the anisotropic elastic and plastic properties of the steels were simulated using a self-consistent model for predicting the grain-to-grain and phase-to-phase interactions. The constitutive laws for describing the elastic and plastic behavior of each constituent phase were directly obtained by comparing the predicted lattice strain distributions with the measured ones. The transmission electron microscopy observations of the microstructure development verified the partitioning of plastic strains among different phases. The present investigations provide a fundamental understanding of the stress partitioning of soft and hard phases, and the different work-hardening rates of the multiphase steels.

High pressure phase equilibria of supercritical alcohols with triglycerides, fatty esters and cosolvents

The transesterification of vegetable oils, esterification of fatty acids and glycerolisis reactions, with supercritical alcohols, are of interest in the production of fine chemicals and biodiesel. The partial miscibility between the reactants and products of these processes have raised interest in the multiple phase behavior under reaction and separation conditions of mixtures of triglycerides and derivatives, fatty esters, alcohols and glycerin. In the present work, recent experimental studies under separation and reaction conditions are compared with modeling predictions using a group contribution with association equation of state.

Mesophase structure-mechanical and ionic transport correlations in extended amphiphilic dendrons.

We have studied the self-assembly of amphiphilic dendrons extended with linear polyethylene oxide (PEO) chains and their ion complexes. Keeping the dendron core and linear PEO chain compatible allows for the combination of dendritic core-shell and conventional blockcopolymer characteristics for complex mesophase behavior. An unexpected sequence of crystalline lamellar, cubic micellar (Pm3n), hexagonal columnar, continuous cubic (Ia3d), and lamellar mesophases is observed. Multiple phase behavior within single compounds allows for the study of charge transport and mechanical property correlations as a function of structure. The results suggest an advanced molecular design concept for the next generation of nanostructured materials in applications involving charge transport.

Multiple-phase behavior and memory effect of polymer gel

A poly(4-acrylamidosalicylic acid) gel (PASA gel) exhibits multiple phases as characterized by distinct degrees of swelling; the gel can take one of four different swelling values, but none of the intermediate values. The gel has remarkable memory: the phase behavior of the gel depends on whether the gel has experienced the most swollen phase or the most collapsed phase in the immediate past. The information is stored and reversibly erased in the form of a macroscopic phase transition behavior. The structure factors corresponding to these four phases were obtained by SANS, which indicated the presence of characteristic structures depending on pH and temperature, particularly in the shrunken state.

Fluorescence study on multiple phase behavior of dimethylacrylamide–methacrylic acid copolymer gel

Multiple phase behavior was found in copolymer gels consisting of dimethylacrylamide and methacrylic acid. They are characterized by distinct degrees of swelling; the gel can take one of a set of swelling values, but none of the intermediate values. Three different phases, denoted as phase051 (as-prepared), phase376 (swollen at high pH), phase440 (swollen after treatment by pH 12) were clearly resolved, where the three digits denote their linear swelling ratios in percentage with respect to the size at preparation. Each phase was stable and did not change its swelling ratio with pH or temperature as long as the values of pH or temperature were within limited ranges. Transitions among different phases were discrete with hysteresis loops. The microenvironment of these three phases was observed by steady-state and transient fluorescence spectroscopy, which indicated the multiple phase behavior appeared as the result of the coexistence of hydrophilic and less-hydrophilic (hydrophobic) domains in the gel and their fraction varied depending on pH.

Multiple-phase behavior and its microscopic implication for 4-acrylamidosalicylic acid gel

Poly(4-acrylamidosalicylic acid) gels exhibited multiple-phase behavior depending on their histories in the parameter space of pH and temperature. Four different phases, denoted as phase091 (as-prepared), phase244 (swollen at high pH), phase064 (heat-treated), and phase233 (swollen at high pH after heat treatment) were clearly resolved, where the three digits denote their linear swelling ratios in percentage with respect to their sizes at preparation. Each phase was stable and did not change its swelling ratio with pH or temperature as long as the values of pH or temperature were within limited ranges. Transitions among different phases were discrete with hysteresis loops. The structure factors corresponding to these four phases were obtained by small-angle neutron scattering, which indicated the presence of characteristic structures depending on pH and temperature, particularly in the shrunken state (i.e., phase064).

The gel that memorizes phases

A poly(4-acrylamidosalicylic acid) gel exhibits multiple phases as characterized by distinct degrees of swelling; the gel can take one of four different swelling values, but none of the intermediate values. The multiple phase behavior appears as a result of the combination of hydrogen bonding and hydrophobic interaction between polymer segments. The gel has remarkable memory: The phase behavior of the gel depends on whether the gel has experienced the most swollen phase or the most collapsed phase in the immediate past. The information is stored and reversibly erased in the form of a macroscopic phase transition behavior. These phenomena are explained by a mean field theory where the number of hydrogen bonds is added to the equation of the state of a gel.

Surfactant Dissolution and Water Solubilization in Chlorine-Free Liquified Gas Propellants

The initial water content of a group of 15 pharmaceutically and toxicologically acceptable surfactants showed a tendency to increase with the surfactant hydrophilic-lipophilic balance (HLB) value. Surfactant solubility was determined in chlorine-free “alternative propellants” (n-butane, propane, dimethyl ether [DME], 1,1,1,2-tetrafluoroethane (HFA-134a), and 1,1,1,2,3,3,3-heptafluoropropane [HFA-227ea], and trichloromonofluoromethane [CFC-11] in the absence of cosolvents such as ethanol. Water-soluble surfactants such as Carbowax®, Sentry®, PEG 300, Tween® 20, and BrijSrG 30, with high HLB values showed appreciable solubility in HFA-134a and HFA-227ea. In systems containing ≥ 80% propellant by weight, each single-phase propellant-surfactant blend was screened for its ability to solubilize iodine and dissolve or solubilize water with increasing surfactant concentration. This screening was performed to investigate the possibility of formulating highvolatility, single-phase systems with increased polarity and solvency from these conventional excipients and vehicles. Ternary-phase diagrams show the regions of apparent single and multiple phase behavior in each system. Despite the increased polarity of the hydrofluoroalkanes (HFAs), appreciable water solubility was seen only with these surfactants in DME and in the hydrocarbons (HCs) n-butane and propane.

Multiple phase coexistence in finite systems.

Dynamic coexistence of several phaselike forms, a solid, microcrystalline phase, a homogeneously melted phase, and phases exhibiting a solid core and a melted surface, is found in isothermal molecular-dynamics simulations of magic-number rare-gas clusters. We present a theoretical model for the equilibrium and dynamics of phases of small systems that incorporates homogeneous and heterogeneous phases and gives necessary conditions for the material parameters if a cluster is to exhibit the observed multiple-phase behavior.

On the retrograde condensation of one or two liquids

This contribution discusses the phenomena of retrograde condensation of one or two liquids. It w1 be shown that both phenomena can be well understood. Also the relation of retrograde condensation of one liquid phase with the condensation behavior of natural gas will be discussed. Similarly that of two liquid phases with multiple phase behavior occurring in low temperature reservoir fluids will be pointed out.

Miscible ternary blends containing polycarbonate, SAN, and aliphatic polyesters

AbstractTernary blends comprising polycarbonate, (PC), poly(styrene‐co‐acrylonitrile) (SAN), and a polyester, either poly(1,4‐butylene adipate) (PBA), poly(1,4‐cyclohexanedimethylene succinate) (PCDS), or poly(ε‐caprolactone) (PCL), were found to be miscible based on the presence of a single glass transition temperature at many compositions. For all systems, the addition of just 1% by weight polyester resulted in a miscible blend for SAN/PC ratios of 1/1 and 3/1, and a region of immiscibility was generally observed for PC‐rich compositions with low polyester content. The melting point depression of PCL in the ternary and in binary mixtures was studied to obtain interaction parameters for the PCL/PC, PCL/SAN, and SAN/PC binaries. These parameters were used to calculate the locus of compositions which mark the boundary between single‐ and multiple‐phase behavior. Agreement between the calculated and experimental boundary was only fair. PCDS was found to be the most efficient of the three polyesters studied for solubilizing PC and SAN. SAN copolymer containing 25% acrylonitrile (AN), was found to be more easily solubilized in PC by PCDS than SAN containing 13% AN.

A generalized description of multiple phase behavior inisothermal, isobaric systems

Exact graphical descriptions of isothermal, isobaric multiple phase volumetric behavior are presented. Solutions for the distribution of n phases are given for n and n-1 component systems, where n = 2, 3, or 4. These graphical representations are derived from the combination of volumetric, mass and component material balances, which yields linear expressions for phase volumes as a function of the apparent density of the mixture. Experimental results for the 3-phase and 4-phase volumetric behavior of the CO 2/C 14H 30 and CO 2/C 14H 30/H 2O systems, respectively, demonstrate the capabilities of these simple graphs to serve not only as a predictive tool for multiple phase behavior, but also as a thermodynamic consistency test for experimental data.

Sphingomyelin multiple phase behavior as revealed by multinuclear magnetic resonance spectroscopy.

31P and 13C nuclear magnetic resonance (NMR) spectra are employed to study the phase behavior of bovine brain sphingomyelin as a function of temperature. The 31P NMR data suggest that, while at low temperatures sphingomyelin can form a lamellar phase, at physiological temperatures and higher the lamellar phase is unstable, and a new phase, best described as a hexagonal phase, is formed. Egg phosphatidylcholine is suggested to play an important role in stabilizing bilayers in natural membranes. Cholesterol also exhibits a sphingomyelin bilayer-stabilizing ability. The 13C NMR spectra suggest a gelling of the hydrocarbon chains of sphingomyelin at low temperature. Thus, bovine brain sphingomyelin undergoes both a gel to liquid-crystalline phase transition and a lamellar to nonlamellar transition.

Multiple Phase Behavior in Porous Media During CO2 or Rich-Gas Flooding

Mixing oil with high-ethane-content hydrocarbon gases or CO2 can produce multiple liquid phases and an asphaltic precipitate in low-temperature reservoirs. The residual saturation that occurs in a reservoir displacement is not significant from a recovery standpoint, but may produce three-phase relative permeability effects that reduce injectivity produce three-phase relative permeability effects that reduce injectivity and, thus, oil recovery rate during alternate gas-water injection. Introduction Multiple-contact miscible gas flooding has the potential for economically recovering a significant amount of incremental oil over that recoverable by conventional waterflooding. Under appropriate reservoir pressure and temperature conditions, rich gas or carbon dioxide will miscibly displace the oil it contacts. Water is injected alternately with the gas to decrease the mobility ratio and, thus, improve the sweep. One such project using rich gas in a West Texas reservoir has been described previously. However, unanticipated reduction in water injectivity occurred after injection of the first batch of rich gas, and indications were that the problem existed in depth within the reservoir and was not just a wellbore problem. Harvey et al. present the results of field studies that led to the work presented in this paper. Native-state reservoir core tests showed that the injectivity reduction could be caused by a residual oil saturation of a few percent of pore volume behind the rich-gas bank. A small amount of residual oil resulted in unusually high trapped gas saturation and a resulting decrease in water relative permeability. permeability. A small residual oil saturation and, hence, a lowered water injectivity, could arise in the field if oil was bypassed because of small-scale reservoir rock heterogeneities or if the rich gas did not completely displace all the oil contacted. Factors that produce incomplete displacement of contacted oil are presented. PVT cell data are presented that show the occurrence of PVT cell data are presented that show the occurrence of two liquid phases and an asphaltic precipitate when high-ethane-content rich gas and reservoir oil are mixed at reservoir conditions. Core tests are described showing that the formation of multiple phases results in a residual hydrocarbon saturation during displacement. Similar but less detailed studies of a CO2-oil system are also presented. Other authors, observed multiple liquid-phase presented. Other authors, observed multiple liquid-phase phenomena with some miscible gases and West Texas phenomena with some miscible gases and West Texas oils, but did not evaluate the effect on oil displacement. Windowed Cell Tests Procedure Procedure The general procedure used was to place the driving gas into a variable-volume windowed cells that was held at the reservoir temperature. The driving gases used were rich gas and CO2. A known amount of recombined reservoir oil was combined with the driving gas in the cell. A phase distribution test starting at a high pressure (usually 4,000 to 8,000 psi) was performed on this oil-driving gas mixture. This test consisted of a constant-composition expansion, during which the total volume of the cell and the distribution of the phases in the cell were measured at a known pressure. Upon completion of the phase distribution test, additional oil was introduced into the cell and another phase distribution test was performed. These tests, which were designed to simulate mixtures in the driving gas-rich region of all possible oil-driving gas mixtures, were terminated when sufficient oil had been added to dissolve all the driving gas in the cell. Any mixtures containing additional oil would have bubblepoint pressures that decrease regularly down to the saturation pressure of the recombined oil. JPT P. 1171