Molecular simulation of water and chloride ion diffusion in nanopores of alkali-activated aluminosilicate structures

In this paper, a molecular model is proposed to investigate sorption of water molecules and chloride ions in nanopores of alkali-activated binders (geopolymer) gels. The structure of water molecule and geopolymer matrix was optimised by molecular dynamics simulation, and sorption of water molecules and chloride ions was performed by Monte Carlo approach. Totally, four systems containing nanoscale geopolymer structure, 50 molecules of water and 0, 2, 5 or 7 chloride ions were investigated. The results showed that water molecules can be absorbed by nanopores and remain in the system where this absorption releases heat. Thermodynamic analysis showed that the water absorption is temperature-independent. Absorption of chloride ions was suggested to depend on chloride ion concentration. As concentration of chloride ions raises, more absorption occurs and as a result, heat release of absorption and possible degradation of geopolymer structure increases. The thermodynamic analysis showed that higher concentration of chloride ions may decrease Gibbs free energy and raise configurational entropy of the systems. It is proposed that by increasing the temperature, absorption of chloride ion by the geopolymer gel nanopores diminishes and more corrosion may occur in other parts/structures of the matrix.     

An XPS study of argon ion beam and oxygen RIE modified BPDA-PDA polyimide as related to adhesion

Modification of polymer surfaces by changing the chemical structure, surface energy, and bonding characteristics has considerable technological importance in the area of adhesion. Reactive ion etching (RIE) and ion beam (IB) bombardment were employed to modify the surfaces of fully imidized 3,3',4,4'-biphenyl tetracarboxylic acid dianhydride-p-diaminophenyl (BPDA-PDA)-based polyimide (PI) films. These modification techniques affect only a shallow surface region, approximately 10-20 nm, and the bulk properties of the polymer are unaffected. The angle-resolved X-ray photoelectron spectroscopy (XPS) technique was used to characterize the PI surfaces modified by argon IB bombardment or oxygen RIE treatment. On the argon ion-bombarded surfaces, the XPS spectra indicate that the carbonyl and imide groups are decreased. Oxygen RIE treatment resulted in an increase in the atomic concentration of oxygen. To understand the surface aging effect, the freshly modified PI surfaces were exposed to laboratory air for 1 and 2 days. The changes in composition as a function of the depth of the modified surface region right after treatment and after aging were determined by the angle-resolved XPS technique (ARXPS). Contact angle measurements were used to determine the polar and dispersion components, the sum of which is the surface free energy. The polar component of the surface free energy shows the greatest change, with an increase of 8.0-9.4 times for both the oxygen RIE and ion beam treatments as compared with the as-cured PI surface. Aging of these modified surfaces resulted in a decrease of surface free energy as compared with the just-modified surfaces. In the case of oxygen RIE treatment, the dispersion component of the surface free energy showed little or no change from the as-cured sample. Adhesion of chromium/copper/chromium (Cr/Cu/Cr) films on PI was determined by peel strength measurements. Significant increases in peel strength, by a factor of 10-80, were shown for the modified surfaces. A good correlation between the peel strength and the experimentally determined polar component of surface energy was shown.     

Effects of the aluminum filler content on moisture diffusion into epoxy adhesives in distilled water and sea water

Epoxies are the most common of high‐performance structural adhesives, especially in automotive and aircraft manufacturing. In a variety of industrial applications, epoxy adhesives are required to have enhanced thermal conductivity. The normal method of changing this property is to add to the epoxy a filler of higher conductivity than the continuous phase. Although the improvement in the thermal properties of adhesives by the addition of metal fillers is obvious, their influence on water sorption characteristics of adhesives is not clear. It was the objective of this study to shed light on these aspects, which are lacking in the literature. The emphasis was placed on determining the moisture sorption behavior of aluminum‐powder‐filled epoxy adhesives under complete immersion in distilled water and sea water. Moisture diffusion tests show that the addition of aluminum filler into epoxy decreases the total amount of water intake at saturation in both fluids. However, there appears to be no significant effect of the aluminum filler content on the moisture diffusivity in epoxy adhesive specimens in either distilled water or seawater. It has also been determined that the adhesives adsorb a larger amount of water upon exposure to distilled water than when exposed to seawater, whereas the moisture diffusion rate in the adhesive immersed in seawater is higher than that in distilled water. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1165–1171, 2005     

Processing of biodegradable and multifunctional protein-based polymer materials for the potential controlled release of zinc and water in horticulture

Recent high levels of horticulture production cause an impoverishment of soil nutrients that may seriously impair crop yields. This forces farmers to rely on the use of fertilizers. However, it also involves an increase in the contamination risks associated with their supply. A possible alternative to supply these fertilizers could be the use of biodegradable protein-based matrices, which can contain the essential elements required by the soil. Therefore, the main objective of this work is the evaluation of different alternative methods for the incorporation of a selected micronutrient (MN) zinc (Zn) to soy protein-based matrices. As a result, it has been possible to incorporate high levels of Zn into the matrices. However, depending on the method used for MN incorporation, there are variations in the microstructure, MN distribution, and mechanical properties. This work brings forward an innovative application of these matrices as a source of controlled release of MN for horticulture applications.     

A nanoparticulate raloxifene delivery system based on biodegradable carboxylated polyurethane: Design,optimization, characterization,and in vitro evaluation

Biodegradable carboxylated polyurethanes with three molecular weights were synthesized to prepare a nanoparticulate sustained delivery system of raloxifene hydrochloride, the drug with poor bioavailability. The nanoparticles were prepared by coprecipitation method. Optimal conditions for the preparation of nanoparticles were obtained using Box–Behnken design. Independent factors were ratio of polymer to drug, M_w of polymer and speed of magnetic stirrer. Dependent variables include zeta potential, polydispersity index (PdI), particle size, and loading efficacy (LE). Results of the fractional factorial design based on an analysis of variance demonstrated that the model for particle size, zeta potential, PdI and loading efficacy was statistically significant. The size of nanoparticles in design experiments were 46–96 nm in diameter and had entrapment efficiency of 84–92%. The nanoparticles were evaluated for in vitro release and showed a sustained release profile (24.19% ± 4.35% after 4 weeks), following the Fickian diffusion‐based release mechanism. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39668.     

Pore-network analysis of two-phase water transport in gas diffusion layers of polymer electrolyte membrane fuel cells

A pore-network model was developed to study the water transport in hydrophobic gas diffusion layers (GDLs) of polymer electrolyte membrane fuel cells (PEMFCs). The pore structure of GDL materials was modeled as a regular cubic network of pores connected by throats. The governing equations for the two-phase flow in the pore-network were obtained by considering the capillary pressure in the pores, and the entry pressure and viscous pressure drop through the throats. Numerical results showed that the saturation distribution in GDLs maintained a concave shape, indicating the water transport in GDLs was strongly influenced by capillary processes. Parametric studies were also conducted to examine the effects of several geometrical and capillary properties of GDLs on the water transport behavior and the saturation distribution. The proper inlet boundary condition for the liquid water entering GDLs was discussed along with its effects on the saturation distribution.     

Determination of water uptake and diffusion of Cl ion in epoxy primer on aluminum alloys in NaCl solution by electrochemical impedance spectroscopy

The electrochemical impedance spectroscopy (EIS) of epoxy-coated aluminum alloy LY12 has been investigated during exposure to 3.5% NaCl solution. Using the continuous simulation of EIS by expanded general electrical model, the time-dependent impedance model of the alloy/coating/solution system was deduced. The results shown that the composite electrode displayed a barrier behavior before water and oxygen penetrated to alloy base. After water and oxygen reached the base, the impedance associated with corrosion of alloy base changed with the immersion time as following: (i) active corrosion period at the beginning (double-layer capacitance, C_dl, in parallel to the charge transfer resistance of electrochemical corrosion R_ct), (ii) impeding of the diffusion of corrosion production at the intermediate period as a result of the presence of coated film (a constant phase element Z_diff was additionally in series with R_ct), and (iii) appearance of the characteristic impedance related to Cl⁻ ion-participating reaction with alloy base at the later stage. From the linear part of ln C_c–t^0.5 curve in the early immersion stage, the apparent diffusion coefficient of water was obtained. The diffusion coefficient of water and Cl⁻ ion through the coating was also calculated by the required time for diffusion of permeation species through the coating to the metal interface obtained from the simulation of EIS data by which the occurrence of characteristic impedance element(s) corresponding to special species arrival can be determined.     

The study of diffusion of media in the organic coating films by BAW admittance analysis

The permeation of water and corrosive species in coating films is very important for the corrosion protection by organic coatings. As a new method for the study of diffusion of media in coating films, bulk acoustic wave (BAW) admittance analysis has been proposed in this article. Real-time information on the change of the film mass, mechanic property of the layer, and the permeation process of the media can be provided simultaneously by the parameters of BAW admittance analysis, f_s (series resonant frequency), ΔL₁ (inductance variance), R₁ (resistance), Q (quality factor), and C_s (film capacitance). The diffusion behavior of media and the corresponding film stability can be described by the following parameters: D (diffusion coefficient), P (permeation coefficient), S (the solubility of media), and SC (the swelling coefficient of the coating layer). © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2283–2290, 1998     

Measurement and analysis of ion distribution in laminar flame using an electrostatic probe

An electrostatic probe is utilized to determine the ion distribution in a laminar flame. The probe is developed to be implemented in the ion measurement of combustion process contained in a solid container, and therefore the probe fabrication and the construction of a whole measurement system are explained in detail. Also, a numerical analysis is conducted to compare experimental measurement with the computed temperature and concentration. The ion distribution of four different flames of various fuel/air ratios is measured to analyze the distribution for understanding the combustion process. An explicit method is implemented to solve a set of partial differential equations of material and energy balances. Comparison between the measured distribution and the computed distribution of temperature indicates that the ion formation is closely related to the temperature distribution.     

Content and diffusion of water and gases in MgAl2O4 spinel crystals synthesized to produce ceramics

Content, evolution and diffusion characteristics of water and gases in fine-crystalline spinel MgAl₂O₄ were studied by kinetic thermodesoption mass spectrometry. Water is the main volatile component by quantity in the spinel structure. From the spinel crystals with an average size of 0.52 μm, water is released in vacuum in three temperature ranges: at 100–200 °C due to desorption from micropores, at 300–600 °C due to near-surface dehydroxylation and at 500–800 °C due to diffusion of water from the crystal bulk. The content of structural water, diffusively released from the crystals, is about 3000 ppm. The coefficients and activation energy of diffusion of water from spinel crystals in the range 500–700 °C were calculated. This allows us to estimate at any temperature the degassing time of the spinel with a certain degree of dispersion and ceramics made of it, and thereby promote the production of high-quality ceramics.     

Development and characterization of gelatin‐based hydrogels,emulsion hydrogels,and bigels: A comparative study

This study was designed to examine the physicochemical and electrical properties of gelatin‐based hydrogels, emulgels, and bigels. The chemical studies suggested an increase in hydrogen bonding in the emulgel and bigel when sesame oil (SO; representative vegetable oil) and SO organogel (OG; representative OG) were incorporated within the gelatin matrix. The emulgel and bigel showed better mechanical properties and higher electrical impedances compared to the hydrogel. The hydrogel showed similar swelling at pH 1.2 and 7.2. The swelling of the emulgel and bigel was higher at pH 7.2. The formulations were found to be highly hemocompatible; this indicated their biocompatible nature. Ciprofloxacin, a model antimicrobial drug, was incorporated within the formulations. The release of the drug was found to be diffusion‐mediated. The antimicrobial efficiency of all of the drug‐loaded formulations was found to be equivalent. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41502.     

Characterizing various types of defects in nuclear graphite using Raman scattering: Heat treatment,ion irradiation and polishing

Raman spectroscopy has proved to be an appropriate technique to probe defects in carbon-based materials owing to its high sensitivity, most often focused on the commonly used I_D/I_G parameter. However, this ratio may be activated by various types of defects and in a completely independent manner. Therefore, discriminating between defects is challenging. The central idea of the present work is to provide a better understanding of the Raman response to the various types of defects that may appear in nuclear graphite (carbon–carbon composite) during its manufacturing process, its operation in the nuclear reactor, or even during its preparation process such as polishing which is usually used prior to Raman characterization. This work also demonstrates the discrimination of the defect types using the combination of the I_D/I_G and FWHM(G), two structural disorder indicators evolving differently according to the type and the concentration of the introduced defects into the carbon network. The ion-beam irradiation was used here as an effective way for creating defects that could be similar to those created by neutrons in the nuclear reactor.     

Sorption and diffusion of water,salt water,and concrete pore solution in composite matrices

In recent years, the use of fiber‐reinforced polymer composites in civil infrastructure has been promoted as a solution to the deterioration of bridges, buildings, and other structures composed of traditional materials, such as steel, concrete, and wood. Any application of a polymer composite in an outdoor environment invariably involves exposure to moisture. There is also potential for exposure to saline conditions in waterfront or offshore structures, and alkaline environments, as would be encountered by a reinforcing bar in a cementitious material. This study characterizes the sorption and transport of distilled water, salt solution, and a simulated concrete pore solution in free films of vinyl ester, isophthalic polyester (isopolyester) and epoxy resins, all commercially important materials for use in structural composites. Diffusion of all three liquids in each of the three materials was observed to follow a Fickian process. Mass loss was observed for the isopolyester in salt water and concrete pore solution at 60°C, suggesting hydrolysis that was accelerated by the high temperature exposure. Both the rate of uptake, as well as the equilibrium uptake, were greater at 60°C, compared with ambient conditions. Diffusion coefficients calculated from the mass uptake data revealed that, although the epoxy resin had the highest equilibrium uptake, it had the lowest diffusion coefficient. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 483–492, 1999     

Macroporous open cell polyester amphigel using citric acid and PEO: Solvent absorption,thermal behavior,and slow release of pesticide

This article describes citric acid cross-linked amphiphilic poly(ethylene oxide) (PEO) macroporous open cell polyester amphigel, optimally synthesized using response surface methodology by applying central composite design to screen significant reaction parameters for maximizing percent water sorption. The chemical structure of the amphigel was confirmed by proton nuclear magnetic resonance (¹H NMR), FT-IR and the thermal behavior was studied using thermo-gravimetric and DSC. Due to amphiphilic nature, the amphigels also showed high chloroform (1151.33%–1193.33%) and water (755.33%–865%) absorption capacity. Thermal analysis revealed that amphigels are less thermal stability as compared to PEO, however, the degradation process was found to be multi step. The amphigel was effectively used as a carrier for easy loading of a hydrophobic pesticide and showed a slow release of the same.     

Sorption,diffusion and pervaporation of water/ethanol mixtures in polyetherimide membranes

Homogeneous and composite aromatic polyetherimide membranes were prepared by casting from N-methylpyrrolidinone (NMP) solutions and by electrodeposition of polymer at the cathode, respectively. The membranes were evaluated for their sorption, diffusion and pervaporation separation of water from ethanol with emphasis on the breaking of azeotropic composition. The membrane performance was shown to be dependent on the feed concentration, but still selective towards water over the whole composition range of the feed mixture. By looking at the surface energy parameters, the determination of degree of swelling and the calculation of deviation coefficients (ε), an interesting insight was gained into the coupling effect in this solvent/membrane system. From the sorption, diffusion and temperature-dependent permeation behaviour, it could be concluded that in this system the diffusivity of permeant plays a major role in determining the pervaporation performance, rather than the solubility. © 1999 Society of Chemical Industry     

Effects of orientation and substrate on ion transport in fluoride heterostructures grown by molecular beam epitaxy

Ion conductor heterostructures of BaF₂ and CaF₂ with various spacings have been prepared by molecular beam epitaxy (MBE) technique as reported previously by Sata et al. [Nature 408 (2000) 946]. In this paper, we are especially interested in the effects of orientation and substrate on the conductivity. Four kinds of substrates have been investigated (Al₂O₃(0 1 2), Al₂O₃(0 0 6), MgO(1 1 1), and MgO(1 1 0)), generating [1 1 1] and [1 0 0] oriented heterostructures with smooth surfaces. The samples have been investigated by ac impedance, dc polarization techniques, X-ray diffraction (XRD) and atomic force microscopy (AFM). The polarization measurements confirm that electronic effects are minor and the conductivity is ionic. The substrate itself causes a space charge effect which adds to the overall conductance as a constant contribution and is of the order of the effect of a single CaF₂/BaF₂ interface (or less), and hence totally negligible if the number of CaF₂/BaF₂ interfaces is high. Variation of the substrate’s surface chemistry leads to a conductivity variation that is exactly opposite to the case of cation adsorption, and thus suggests F⁻ adsorption as defect inducing mechanism at the Al₂O₃/BaF₂ interface. The dominating contribution of the CaF₂/BaF₂ interfaces is approximately independent of the orientation, hence, favoring a fluoride ion transfer from one to the other phase rather than a charge accumulation at the interfacial core, in full agreement with the conclusions of Sata et al. [Nature 408 (2000) 946].     

硼酸、硼酸盐及其络合物在反渗透膜内扩散过程的分子模拟

利用分子模拟的方法建立了交联的反渗透膜模型,采用分子动力学模拟方法研究了水、氯化钠、硼酸、硼酸盐、山梨醇-硼酸盐络合物在反渗透膜和溶液中的扩散过程,以及其他几种硼酸盐与多羟基化合物（D-甘露醇、N-甲基D-葡糖胺和D-葡萄糖酸钠）的络合物在4种反渗透膜中的扩散过程。分析各粒子的均方位移曲线可得,各粒子在溶液中的扩散系数均大于在膜体系的扩散系数,水分子的扩散系数远大于各溶质分子和离子。与硼酸分子相比,硼酸盐离子与其体积相差不大,但受电荷效应的影响,其扩散系数小于硼酸分子一个数量级。与单络合物相比,双络合物由于分子体积增大,扩散系数更小。因此在反渗透络合强化脱硼过程中应保持过量的山梨醇添加量,以提高其双络合物浓度。在1,3,5-环己烷三甲酰氯/4-甲基间苯二胺（HT/MMPD）反渗透膜中,N-甲基D-葡糖胺-硼酸盐络合物的扩散系数是5种络合物中最低的,D-葡萄糖酸钠-硼酸盐络合物在含有间苯二胺（MPD）单体的膜类型中扩散系数较低,而D-甘露醇-硼酸盐络合物在含有MMPD单体的膜类型中扩散系数较低。由各粒子的轨迹图可知,各粒子在溶液中做较稀疏的无规则扩散运动,在膜内粒子由于受到聚酰胺膜结构的限制做较密集的扩散运动。     

Determination of the diffusion coefficients of organic solvents in polyepichlorohydrin: A comparative study of inverse gas chromatography and sorption methods

The diffusivity of organic solvents in polyepichlorohydrin was studied with two different experimental setups: inverse gas chromatography (IGC) with packed columns and sorption measurements in gravimetric experiments monitored in a Cahn electrobalance. The aim of this work was to test the possibility of solving an inherent problem in the data reduction of IGC measurements, that is, the necessity of characterizing the morphology of the polymer coated on the support (usually given in the so‐called geometric factor of the column). Temperatures between 35 and 65°C were used in the IGC experiments, whereas the sorption measurements were performed between 30 and 40°C. Glass beads were used as supports in IGC for obtaining data concerning the variation of the plate height with the average gas velocity, with which the use of the Van Deemter equation allowed the determination of the diffusion coefficient if the geometric factor was known. In the sorption experiments, the diffusion coefficients at different penetrant activities were directly measured. For their extrapolation within the same concentration range used for IGC (infinite dilution of the penetrant), the theoretical model of Vrentas and Duda was used. By a combination of sorption and IGC experiments, the geometric factor of an IGC column could be adjusted, and this allowed the determination of the diffusion parameters of any other solvent in the same column. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2216–2223, 2003     

A study of the axial and radial competition segregation in a rotating drum with internal diameter changing

A binary mixture is mixed in a rotating drum composed by 19 rings with different inner diameters. It is found that the larger particles are concentrated in the rings with smaller inner diameters. The collection of the larger particles in these rings is due to the particle dynamic angle of repose. The transition from the particle segregation core pattern at the end wall to the good radial mixing rings is through a transient turning comet segregation pattern. This transition is closely related to the distance from the ring with the smallest inner diameter to the ring with the largest inner diameter. Having a higher fraction of larger particles in a ring requires both the collection ring having a smaller inner diameter and a smoother inner diameter transition to the neighboring rings.     

Effect of water on extractive desulfurization of fuel oils using ionic liquids:A COSMO-RS and experimental study

When evaluating ionic liquids(ILs) for extractive desulfurization(EDS) of fuel oils, the inevitable presence of water in the system may have a significant and in many cases strongly negative effect. However, few studies have considered this particular issue and a promoted water effect on EDS is scarcely reported. In this work,COSMO-RS was firstly employed to calculate the capacity and selectivity for EDS of various IL/H_2 O mixtures,which cover different IL characters and a wide water concentration range. Experiments were then conducted with a representative IL [C_4MIM][H_2PO_4], whose stable and even promoted extraction performance with a small amount of water was suggested by COSMO-RS. Through analyses of the desulfurization ratio, the crosssolubility and the water content in the desulfurized fuel, the promoted effect of water within a certain range(b 10 wt%) was experimentally demonstrated. Moreover, such effect of water was explained combining the viscosity, the solvent–solute interactions and the COSMO-RS based analysis.