Different Types Of Ions Research Articles

Modelling contaminant transport in fly ash\u2013bentonite composite landfill liner: mechanism of different types of ions

Generated hazardous or toxic waste posses a serious threat if dumped into ponds or low lying areas which leads to contamination, this necessitates the effective landfill liner system. Mainly compacted clayey soils are used as an engineered barrier. Recently, composite materials have gained popularity as landfill liner materials, including the use of waste materials amended with low permeable soils. Though, studies on the composite optimum mix and its corresponding thickness are very scarce. Here, we evaluated the unconfined compressive strength and hydraulic conductivity of fly ash–bentonite composites. Efforts were also made to determine the thickness of landfill liner composite using a finite difference method (i.e. MATLAB). The results reveal that composite consists of 30% bentonite and 70% fly ash is suitable for landfill liner, which meets strength and permeability criteria. Numerical simulation for five major contaminants shows that the composite plays a crucial role in reducing the leaching of heavy metals and suggests an optimum thickness in the range of 126–154 cm. Overall, the findings of the study indicate that fly ash–bentonite composite can be used to solve real-life challenges in a sustainable way.

Integrated proposal for management of root rot caused by Phytophthora cinnamomi in avocado cv. Hass crops

Phytophthora cinnamomi is the most important pathogen in avocado crops that causes the disease named avocado root rot (PRR). This disease affects the root system and induces multiple symptoms that end with plant death and causes large economic losses. PRR management is based almost exclusively on the use of fungicides (metalaxyl and phosphites). This situation led to inefficient management practices with apparently satisfactory results only in short periods. The objective of this work was to evaluate different PRR management practices under in vitro, net house and field conditions. The initial part of the study was carried out under in vitro and net house conditions evaluating different types of ions (boron, zinc and manganese chelate), the auxin α naphthaleneacetic, fungicides (potassium phosphite, fosetyl aluminium and metalaxyl) and microorganisms associated with biological control of diseases. For field conditions, the most promising strategies were selected, which included fungicide use (rotation of metalaxyl and phosphites), organic matter in the form of residues of vegetables and mushrooms, use of foliar (manganese) and soil (calcium, magnesium, phosphorus, and silicon) ions, additions of bovine manure, beneficial microorganisms (Rizoglomus fasciculatum, Trichoderma sp., and Bacillus sp.), edaphic application of auxin and an energy source (sucrose). Results indicated that individual control methods of PRR are not sustainable over time. However, the implementation of a disease integrated management program including several strategies of control proved to be effective for PRR. At the same time that PRR was satisfactorily managed, the economic sustainability was achieved and it was possible to reduce the reliance on phosphonate applications.

Effect of Solvent of Ionomer Dispersion on Porous Electrodes with Three Phase Boundary

Electrichemically driven energy conversion devices requires anodic and cathodic reactions to complete their electrochemical cells. Recent energy conversion devices such as water electrolyzers or fuel cells is comprised of anodic and cathodic reactions in which gases, ions and electrons participate. In particular, the movement of proton or hydroxyl ions generated and consumed at two electrodes, i.e., anode and cathode, are essential to determine the reaction rates due to low mobility compared to electrons. Ions moved through ion conducting membranes should be transported inside electrodes to participate in anodic or cathodic reactions. Ion pathway is normally in liquid electrolyte. Regardless, the introduction of any aqueous phase in energy conversion devices causes many problems during fabrication, operation, maintenance, and so on. In addition, if gas penetration or gas evolution is one of phenomena taking place at electrodes, the electrodes should be porous. Thus, much efforts have been devoted to develop quasi-solid electrolytes such as gel polymer, ion conducting polymers, impregnation of ions in porous matrix and so on. Among the candidates, ion conducting polymers are quite often chosen as ion conducting media for energy conversion devices. The technique to introduce ion conducting polymers within electrodes for oxidation and reduction reactions is to solidify catalyst inks consisting of electrocatalyst, dispersion of ion exchangeable polymers, controlling solvents and additives by evaporation of all solvents in catalyst inks. Ion conducting polymers could be dispersed in various solvents. It causes different shapes of ion conducting polymers in solvents, for instance, cylindrical rods, a less-defined large particles, coils and so on. Such different types of ion conducting polymers form distinguished structure catalyst layers. In this study, the effect of solvents dispersing ion conducting polymers on the performance and durability of catalyst layers was investigated. Electrochemical characterization such as I-V polarization, cyclic voltammetry, impedance and so on and microscopic characterization such as SEM and TEM were carried out to evaluate the performance and durability of catalyst layers.AcknowledgmentsThis research was supported by the Hydrogen Energy Innovation Technology Development Program of the National Research Foundation (NRF) funded by the Ministry of Science, ICT, & Future Planning(NRF-2019M3E6A1063677).

Variations in the Plasma Parameters of the Earth’s Magnetotail during Substorm Initiation

A chain of events accompanying the occurrence of a substorm in the Earth’s ionosphere and magnetosphere is considered. Features of geomagnetic pulsations and mechanisms of their generation are indicated. Measurements of magnetic field fluctuations from fluxgate magnetometers, as well as the data on temperature, velocity, and concentration of electrons, and different types of ions from the PEACE and CIS-CODIF experiments of the Cluster-2 space mission, have been analyzed. It was found that a significant increase in temperature, velocity fluctuations, and concentration is observed during the initiation of a substorm that was accompanied by dipolarization (sharp change in the magnetic field configuration from the elongated tail-like force lines to a more dipole structure). A time delay in the heating of protons and oxygen ions, as well as in the concentration variations, was detected. The comparison of wave characteristics for different pressures was carried out using wavelet analysis. The magnetic field pressure, as well as dynamic and thermal pressure for different types of particles, was considered. Pc5 and strong Pc4 pulsations, as well as direct and inverse cascades, were observed in the fluctuations of the magnetic field pressure and thermal pressure of electrons and protons. The results point to a significant role of kinetic effects in the complex chain of processes in the Earth’s magnetosphere during the explosive phase of a substorm.

In Situ Study of Layer-by-Layer Polyelectrolyte Deposition in Nanopores of Anodic Aluminum Oxide by Reflectometric Interference Spectroscopy

The modification of cylindrical anodic aluminum oxide (AAO) nanopores by alternating layer-by-layer (LBL) deposition of poly(sodium-4-styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) was studied in situ by reflectometric interference spectroscopy (RIfS). In particular, the kinetics of polyelectrolyte deposition inside the pores with a diameter of 37 ± 3 nm and a length of 3.7 ± 0.3 μm were unraveled, and potential differences in the LBL multilayer growth compared to flat silicon substrates as well as the effect of different ionic strengths and different types of ions were investigated. RIfS measures the effective optical thicknesses, which is-for a constant pore length-proportional to the effective refractive index of the AAO sample, from which, in turn, the deposited mass of the polymer or the corresponding layer thickness can be estimated. Compared to the multilayer growth by the LBL deposition on the flat aminosilane-primed silicon wafers, which was assessed by spectroscopic ellipsometry, the thickness increment per deposited bilayer, as well as the dependence of this increment on the ionic strength (0.01-0.15) and the counterion type (Na+ vs Ca2+) inside the aminosilane-primed nanopores, was for the first bilayers to within the experimental error identical. For thicker multilayers, the pore diameter became smaller, which led to reduced thickness increments and eventually virtually completely filled the pores. The observed kinetics is consistent with the mass-transport-limited adsorption of the polyelectrolyte to the charged surface according to a Langmuir isotherm with a negligible desorption rate. In addition to fundamental insights into the buildup of polyelectrolyte multilayers inside the AAO nanopores, our results highlight the sensitivity of RIfS and its use as an analytical tool for probing processes inside the nanopores and for the development of biosensors.

Optical sensor film for metribuzin pesticide detection.

We present a new ratiometric and colorimetric optical sensor film for detection one of the most prevalent pesticide metribuzin. The detection proceeds within the low concentration range between 0 and 1.5 μM. The optical film is based on (a) near infrared (NIR) dye 2-[2-[2-Chloro-3-[2-[1,3-dihydro-3,3-dimethyl-1-(4-sulfobutyl)-2H-indol-2-ylidene]-ethylidene]-1-cyclopen-ten-1-yl]-eth-enyl]-3,3-di-methyl-1-(4-sulfobutyl)-3H-indolium hydroxide and (b) upconverting nanoparticles UCNPs of the NaYF4:Yb,Er type (diameter ~40-100 nm) that can be emitted a dual (green and red) emission under 980 nm laser diode excitation. Commercially available polyvinyl chloride (PVC) was utilized as a homogeneous matrix for immobilizing NIR dye and UCNPs. The color of the NIR dye in the PVC matrix is based on the concentration of the metribuzin. When the sensor film is exposed to metribuzin the color changes from green to blue with a significant blue shift in the absorption peak (656 nm) of the NIR dye. Furthermore, the quenching of the red emission (659 nm) of the UCNPs is proceeded due to an inner filter effect. Thus, increasing the metribuzin concentration causes the red emission of UCNPs to be reduced. Conversely, the green emission (545 nm) of the UCNPs persists uninfluenced by metribuzin and can act as a reference signal. This optical sensor film provides great sensitivity based on their unique luminescence properties of UCNPs and recognition abilities within a very low detection limit for the metribuzin LOD 6.8 × 10-8 M with a linear range of 0.23 to 1.5 μM and a relative standard deviation RSDr (1%, n = 3). The novel optical sensor was applied to the detection of metribuzin in real water samples (surface and ground waters). The sensor film exhibits great selectivity in presence of different types of ions and pesticide molecules. But, atrazine pesticide interferes the analytical signal of the sensor film due to the presence of reactive amino groups in its structure. Memorably, we report the first optical chemical sensor film based on polymer film for metribuzin detection.

Terrestrial ion escape and relevant circulation in space

Abstract. Observations of the terrestrial ion escape to space and the transport of escaping ions in the magnetosphere are reviewed, with the main stress on subjects that were not covered in reviews over past 2 decades, during which Cluster has significantly improved our knowledge of them. Here, outflowing ions from the ionosphere are classified in terms of energy rather than location: (1) as cold ions refilling the plasmasphere faster than Jeans escape, (2) as cold supersonic ions such as the polar wind, and (3) as suprathermal ions energized by wave–particle interaction or parallel potential acceleration, mainly starting from cold supersonic ions. The majority of the suprathermal ions above the ionosphere become “hot” at high altitudes, with much higher velocity than the escape velocity even for heavy ions. This makes heavy hot ions more abundant in the magnetosphere than heavy ions transported by cold refilling ions or cold supersonic flow. The immediate destination of these terrestrial ions varies from the plasmasphere, the inner magnetosphere including those entering the ionosphere in the other hemisphere and the tailward outer boundaries, the magnetotail, and the solar wind (magnetosheath, cusp, and plasma mantle). Due to time-variable return from the magnetotail, ions with different routes and energy meet in the inner magnetosphere, making it a zoo of different types of ions in both energy and energy distribution. While the mass-independent drift theory has successfully disentangled this zoo of ions, there are many poorly understood phenomena, e.g., mass-dependent energization. Half of the heavy ions in this zoo also finally escape to space, mainly due to magnetopause shadowing (overshooting of ion drift beyond the magnetopause) and charge exchange near the mirror altitude where the exospheric neutral density is at its highest. The amount of heavy ions mixing directly with the solar wind is already the same as or larger than that entering into the magnetotail and is large enough to extract the solar wind kinetic energy in the cusp–plasma mantle through the mass-loading effect and drive the current system near the cusp independently of the global current system. Considering the past solar and solar wind conditions, ion escape might even have influenced the evolution of the terrestrial biosphere.

Nanoionic Resistive‐Switching Devices

AbstractAdvances in the understanding of nanoscale ionic processes in solid‐state thin films have led to the rapid development of devices based on coupled ionic–electronic effects. For example, ion‐driven resistive‐switching (RS) devices have been extensively studied for future memory applications due to their excellent performance in terms of switching speed, endurance, retention, and scalability. Recent studies further suggest that RS devices are more than just resistors with tunable resistance; instead, they exhibit rich and complex internal ionic dynamics that equip them with native information‐processing capabilities, particularly in the temporal domain. RS effects induced by the migration of different types of ions, often driven by an electric field, are discussed. It is shown that, by taking advantage of the different state variables controlled by the ionic processes, important synaptic functions can be faithfully implemented in solid‐state devices and networks. Recent efforts on improving the controllability of ionic processes to optimize device performance are also discussed, along with new opportunities for material design and engineering enabled by the ability to control ionic processes at the atomic scale.

Various Multicharged Anions of Ginsenosides in Negative Electrospray Ionization with QTOF High-Resolution Mass Spectrometry.

When characterizing components from ginseng, we found a vast number of multicharged anions presented in the liquid chromatography-mass spectrometry (LC-MS) chromatograms. The source of these anions is unclear yet, while ginsenosides, the major components of ginseng, are the main suspected type of molecules because of their sugar moiety. Our investigation using 14 pure ginsenosides affirmed that the multicharged anions were formed by ginsenosides rather than other types of ingredients in ginseng. Various anions could be observed for each ginsenoside. These anions contain ions ([M-2H]2-, [M+Adduct]2-), as well as those formed by polymerization of at least two ginsenosides, such as [nM-2H]2-, [nM-H+Adduct]2-, and [nM-3H]3-. The presence of so different types of ions from a ginsenoside explains the reason for the large number of anions in the LC-MS analysis of ginseng. We further found that formation of [nM-2H]2- ions was influenced by the number of sugar chains: ginsenosides containing two sugar chains produced all [nM-2H]2- ion types, whereas ginsenosides containing one sugar chain did not produce [2M-2H]2-. Thus, [2M-2H]2- and [3M-2H]2- can be utilized to rapidly identify monodesmosidic and/or bidesmosidic ginsenosides as joint diagnostic anions. The position of the glycosyl radical might be the key factor affecting the formation of multicharged multimer ions from monodesmosidic ginsenosides. Consequently, three groups of ginsenoside isomers were differentiated by characteristic [nM-2H]2- anions. Using concentration-dependent characteristics and collision-induced dissociation (CID), we confirmed that [nM-2H]2- ions are non-covalently bound multimers whose aggregation has marked distinction between monodesmosidic and bidesmosidic ginsenosides, accounting for the differentiated formation of [nM-2H]2- between them. Graphical Abstract.

Cation-Activated Avidity for Rapid Reconfiguration of DNA Nanodevices.

The ability to design and control DNA nanodevices with programmed conformational changes has established a foundation for molecular-scale robotics with applications in nanomanufacturing, drug delivery, and controlling enzymatic reactions. The most commonly used approach for actuating these devices, DNA binding and strand displacement, allows devices to respond to molecules in solution, but this approach is limited to response times of minutes or greater. Recent advances have enabled electrical and magnetic control of DNA structures with sub-second response times, but these methods utilize external components with additional fabrication requirements. Here, we present a simple and broadly applicable actuation method based on the avidity of many weak base-pairing interactions that respond to changes in local ionic conditions to drive large-scale conformational transitions in devices on sub-second time scales. To demonstrate such ion-mediated actuation, we modified a DNA origami hinge with short, weakly complementary single-stranded DNA overhangs, whose hybridization is sensitive to cation concentrations in solution. We triggered conformational changes with several different types of ions including mono-, di-, and trivalent ions and also illustrated the ability to engineer the actuation response with design parameters such as number and length of DNA overhangs and hinge torsional stiffness. We developed a statistical mechanical model that agrees with experimental data, enabling effective interpretation and future design of ion-induced actuation. Single-molecule Förster resonance energy-transfer measurements revealed that closing and opening transitions occur on the millisecond time scale, and these transitions can be repeated with time resolution on the scale of one second. Our results advance capabilities for rapid control of DNA nanodevices, expand the range of triggering mechanisms, and demonstrate DNA nanomachines with tunable analog responses to the local environment.

Thermal behaviour of mixtures of 1-alkylpyridinium halides with and without a common ion

The thermal behaviour of mixtures of 1-alkylpyridinium halide salts, comprising either three or four different types of ions, was investigated in order to develop a better understanding of this class of multi-ion systems. A total of six systems was examined, derived from all possible binary combinations of the following four salts: 1-butylpyridinium bromide ([C4Py]Br), 1-butylpyridinium chloride ([C4Py]Cl), 1-ethylpyridinium bromide ([C2Py]Br), and 1-ethylpyridinium chloride ([C2Py]Cl). The systems constituted by two of these salts with a common anion and therefore differing only in the length of the alkyl substituent of the cation (namely [C2Py]Br + [C4Py]Br and [C2Py]Cl + [C4Py]Cl) displayed a eutectic behaviour, with the eutectic compositions qualifying as ionic liquids (melting temperature below 373 K). In contrast, the systems having in common the cation and differing in the halide anion (namely [C2Py]Br + [C2Py]Cl and [C4Py]Br + [C4Py]Cl) showed the formation of solid solutions. The two remaining combinations ([C2Py]Br + [C4Py]Cl and [C2Py]Cl + [C4Py]Br), involving four different types of ions, were also found to display a eutectic behaviour. The melting point depressions of the eutectic points with respect to the parent salts were of about 30–70 K. This was also the liquid range increase achieved with the eutectic compositions, since their thermal stability was nearly the same as the similar thermal stabilities of their parent salts. All six binary combinations of the four 1-alkylpyridinium halides were also interpreted as subsystems of the general 4-ion system [C2Py]x[C4Py]1-xClyBr1-y (where x is the cationic fraction of [C2Py]+ and y is the anionic fraction of Cl−), and an analysis of the melting temperature throughout the domain of this system was carried out.

Influence of Na+ and Mg2+ ions on RNA structures studied with molecular dynamics simulations.

The structure of ribonucleic acid (RNA) polymers is strongly dependent on the presence of, in particular Mg2+ cations to stabilize structural features. Only in high-resolution X-ray crystallography structures can ions be identified reliably. Here, we perform molecular dynamics simulations of 24 RNA structures with varying ion concentrations. Twelve of the structures were helical and the others complex folded. The aim of the study is to predict ion positions but also to evaluate the impact of different types of ions (Na+ or Mg2+) and the ionic strength on structural stability and variations of RNA. As a general conclusion Mg2+ is found to conserve the experimental structure better than Na+ and, where experimental ion positions are available, they can be reproduced with reasonable accuracy. If a large surplus of ions is present the added electrostatic screening makes prediction of binding-sites less reproducible. Distinct differences in ion-binding between helical and complex folded structures are found. The strength of binding (ΔG‡ for breaking RNA atom-ion interactions) is found to differ between roughly 10 and 26 kJ/mol for the different RNA atoms. Differences in stability between helical and complex folded structures and of the influence of metal ions on either are discussed.

Extracellular Total Electrolyte Concentration Imaging for Electrical Brain Stimulation (EBS)

Techniques for electrical brain stimulation (EBS), in which weak electrical stimulation is applied to the brain, have been extensively studied in various therapeutic brain functional applications. The extracellular fluid in the brain is a complex electrolyte that is composed of different types of ions, such as sodium (Na+), potassium (K+), and calcium (Ca+). Abnormal levels of electrolytes can cause a variety of pathological disorders. In this paper, we present a novel technique to visualize the total electrolyte concentration in the extracellular compartment of biological tissues. The electrical conductivity of biological tissues can be expressed as a product of the concentration and the mobility of the ions. Magnetic resonance electrical impedance tomography (MREIT) investigates the electrical properties in a region of interest (ROI) at low frequencies (below 1 kHz) by injecting currents into the brain region. Combining with diffusion tensor MRI (DT-MRI), we analyze the relation between the concentration of ions and the electrical properties extracted from the magnetic flux density measurements using the MREIT technique. By measuring the magnetic flux density induced by EBS, we propose a fast non-iterative technique to visualize the total extracellular electrolyte concentration (EEC), which is a fundamental component of the conductivity. The proposed technique directly recovers the total EEC distribution associated with the water transport mobility tensor.

Effect of Chlorination and Acidification on Clogging and Biofilm Formation in Drip Emitters Applying Secondary Sewage Effluent

Abstract. The risk and inducing mechanism of emitter clogging vary with the types of ions in the irrigation water. The effectiveness of chlorination and acidification treatments in reducing emitter clogging has seldom been comparatively studied. The objective of this study was to quantify the influence of chlorination and acidification in reducing clogging in emitters applying secondary sewage effluent with different types of ions. Two types of emitters with plain channels and one type of emitter with a labyrinth structure were selected to investigate the clogging control strategy by measuring the dry weight of biofilm substance (DW) and the organic matter fraction in the biofilm and analyzing the mineral constituents of the clogging solids and the extracellular polymeric substance (EPS) of the attached biofilm. In general, chemical injection decreased the DW and EPS, resulting in less clogging than in emitters without chlorine and acid injection. For the emitter structures tested, chemical injection was more effective in controlling clogging in plain channel emitters than in labyrinth emitters. Different chemical injections produced similar mineral constituents of the clogging solids: quartz, calcium + magnesium carbonate, silicate, and iron oxide. Chlorine injection interval and targeted acidification pH are both important parameters in determining chemical injection schemes. Under the experimental conditions, weekly chlorination of sewage effluent acidified to pH 6.5 was more effective in reducing the growth and reproduction of microorganisms and the precipitation of solid particles in the drip emitters when applying sewage effluent containing high iron + calcium. However, when sewage effluent containing high calcium was used, acidification was more effective in removing the chemical precipitates. We conclude that the selection of chemical treatment strategies should consider the constituent ions in the sewage effluent. Keywords: Acid injection, Chlorine injection, Extracellular polymeric substance (EPS), Mineral constituents, Microirrigation.

An experimental study of the agglomeration of coal fines in suspensions: Inspiration for controlling fines in coal reservoirs

Coal fines are among the key issues that restrict the highly efficient production of coalbed methane (CBM) because they cause blockages in reservoirs and accidents in wellbores. Coal fines always agglomerate to migrate and plug flow paths in formation water. Therefore, an investigation of their agglomerate behaviour in deionized, standard saline and NaHCO3 suspensions was conducted on different rank coals (81.95 and 92.22% Cdaf) collected in the Ordos and Qinshui basins. The particle size distributions (PSD) of the suspended coal fines in suspensions over time were monitored to analyse the sizes and number of aggregations using a particle size analyser. The dispersive coal fines that were mostly less than 10μm in size aggregated into several ranges of aggregations larger than 10μm in a rapid process until reaching a stable period of sedimentation, inducing the average sizes of the suspended particles to increase rapidly and their quantities to suddenly decrease. As observed under a scanning electron microscope, the dispersive fine particles, which had quasi-ellipsoid, plate and flake shapes, clustered together. The average sizes of the suspended particles in the NaHCO3 suspensions were the greatest, and their quantities were the smallest after the rapid agglomeration, exhibiting a capacity for agglomeration somewhat better than that in the standard saline suspensions and much better than that in the deionized suspensions. The PSD differences of the suspended bituminous coals in the three suspensions were more remarkable than those for anthracites because the former, which had higher ζ potentials measured using a microscopic electrophoresis instrument, were more easily impacted by different types of ions. Bituminous coal has more oxygen-containing functional groups than anthracite, which forms thicker hydration layers that prevent coal fines from agglomerating. According to extended DLVO (Derjguin-Landau-Verwey-Overbeek) theory, cations (Na+ and H+), especially H+ ionized by HCO3−, can neutralize the charge of electrical double-layers and help coal fines to agglomerate. In addition, OH− hydrolysed by HCO3− can reduce the viscosity of suspensions. Therefore, in CBM reservoirs, NaHCO3 may fix some portions of coal fines at their sources by agglomeration and contribute to the other fine particles migration by reducing the viscosity. NaHCO3 may be a potential additive in fracturing fluid, which needs to be further researched.

Dissociative Recombination of Acetone Fragments, Adducts, and Dimer Ions.

The room temperature dissociative recombination of ions formed in an acetone/argon plasma has been studied using the flowing afterglow Langmuir probe-mass spectrometer method. By changing the concentration of acetone density, it is possible to have a plasma dominated by different types of ions (fragments, adducts, and dimer ions). The application of these measurements to astrophysical plasmas is discussed.

Biological imaging using light-addressable potentiometric sensors and scanning photo-induced impedance microscopy.

Light-addressable potentiometric sensors (LAPS) and scanning photo-induced impedance microscopy (SPIM) use photocurrent measurements at electrolyte-insulator-semiconductor substrates for spatio-temporal imaging of electrical potentials and impedance. The techniques have been used for the interrogation of sensor arrays and the imaging of biological systems. Sensor applications range from the detection of different types of ions and the label-free detection of charged molecules such as DNA and proteins to enzyme-based biosensors. Imaging applications include the temporal imaging of extracellular potentials and dynamic concentration changes in microfluidic channels and the lateral imaging of cell surface charges and cell metabolism. This paper will investigate the current state of the art of the measurement technology with a focus on spatial and temporal resolution and review the biological applications, these techniques have been used for. An outlook on future developments in the field will be given.

Zeta potential in porous rocks in contact with monovalent and divalent electrolyte aqueous solutions

Electrokinetic phenomena are the result of a coupling between a fluid flow and an electric current flow in porous rocks. The zeta potential is an important parameter that influences the electrokinetic coupling. Most reservoir rocks are saturated or partially saturated by natural water containing various types of ions. Therefore, it is important to understand how the zeta potential and therefore the electric double layer (EDL) behave for different types of ions or electrolytes. Types of electrolytes influence the zeta potential most by affecting the surface charge — by changing the thickness of the EDL and the exact location of the shear plane. To study the dependence of the zeta potential on various electrolytes, we have carried out streaming potential measurements for consolidated rock samples saturated by monovalent and divalent electrolytes. From streaming potential coefficients, the zeta potential is obtained for different systems of electrolytes and rocks. The experimental results of silica-based rocks are then compared with theoretical models. For 1:1 or 1:2 electrolytes, a theoretical model for the zeta potential that has been available in literature is used. For 2:2 or 2:1 electrolytes, we have developed a new model to calculate the Stern potential and the zeta potential. The comparison found that the theoretical models can explain the main behavior of the zeta potential against types of electrolytes and types of silica-based rocks. The results show that the zeta potential for monovalent electrolytes is higher than that for divalent electrolytes. The zeta potential of the silica-based samples is higher than that of the nonsilica-based samples when they are saturated by the same types of electrolyte.

1H, 23Na and 35Cl Imaging in Cementitious Materials with NMR.

A set-up especially designed for semi-simultaneous measurements of 1H, 23Na and 35Cl in ordinary cementitious materials using nuclear magnetic resonance was built. This setup makes use of the main field of a whole body magnetic resonance imaging system (Philips Intera), which has allowed us to combine two measurement setups into one, i.e., a 23Na/35Cl and a 1H insert. This 1.5 T field was chosen as a compromise between the signal-to-noise ratio of the spin-echo signal, which increases at higher frequencies, and the line broadening due to the presence of magnetic impurities of these materials, which leads to a decrease of the resolution at higher magnetic fields. The preliminary experiments show that this setup can be used to the study the interaction of different types of ions with cementitious materials. One-dimensional profiles of the moisture and dissolved ions can be measured with a spatial resolution of about 2 mm for 1H, 6 mm for 23Na and 9 mm for 35Cl.

The roles of temperature and thickness of barrier layer in the electrodeposition efficiency of nickel inside anodic alumina templates

As a dielectric interface, the alumina barrier layer has so far been shown to influence the electrochemical deposition mechanism of different types of ions inside nanopores of anodic alumina templates. Here, the roles of temperature (Tb) and thickness of the barrier layer in the electrodeposition efficiency (EE) of nickel inside 45 nm pore diameter anodic alumina templates, made by the two step anodization process, are reported. By performing a pulsed electrodeposition method, the former role is investigated by increasing Tb from 10 to 50 °C, whereas the latter role is realized by decreasing the final anodization voltage (Vth) from 40 V to 12, 16 and 20 V. While using Tb ~ 20 °C and Vth = 16 V leads to a maximum EE of 65 % in the fabrication of 8.5 μm long nickel nanowires (NWs), the use of Tb ~ 50 °C is indicative of the growth of approximately 3 μm long NWs, resulted from an EE of 20 %. However, by increasing Vth up to 20 V, EE reaches a plateau with an average value of 45 % as a function of Tb. On the other hand, although the crystallinity of the resulting NWs increases by increasing Tb up to 30 °C, the magnetic properties are found to be almost independent of Vth and Tb.