Distribution Of Ions Research Articles

Effect of hydrophobic materials on alkali-silica reaction-induced deterioration of mortar: A comparative study

The deterioration of mortar or concrete caused by the alkali-silica reaction (ASR) significantly depends on its susceptibility to moisture imbibition and exposure. This study investigated how applying hydrophobic materials in cement mortar prevents ASR-induced deterioration. Three hydrophobic materials were used, including a hexamethyldisilazane (HMDS) treated fumed-silica, a silane-based emulsion, and a silane-based cream. These hydrophobic materials were applied by directly coating the aggregates before mortar preparation or added directly to the mixture as admixtures. The effect of the applied hydrophobic materials on mortar properties was evaluated based on compressive strength, dynamic modulus, water absorption, and linear expansion. Furthermore, the microstructure and ionic distribution of alkalis from the aggregates interface were appraised using scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) tests. The results were compared to a mortar with no admixtures and a mortar with 20% cement replaced by fly ash (a traditional method of ASR mitigation). Coating aggregates with hydrophobic fumed silica were more effective at reducing ASR-induced expansion than directly integrating the hydrophobic materials, although at a lower degree than fly ash.

Numerical simulations on loss of ICRF-heated NBI ions in EAST

The loss of ion cyclotron resonance frequencies (ICRF)-heated neutral beam injection ions in experimental advanced superconducting tokamak was numerically investigated by ORBIT code simulations. The effects of collisions and ripples on particle losses were taken into account, and the distributions of fast ions generated by different beams in combination with ICRF heating were calculated using the TRANSP code. Results showed that ICRF waves altered the orbital distributions of beam ions, causing an increase in trapped ions and fast ion losses. Additionally, for co-current injected beams, perpendicular injection resulted in higher fast ion losses in synergistic heating than tangential injection. The study also found that the synergistic effect of collisions and ripples enhanced fast ion losses, which were highly localized and generated a maximum heat load of 0.165 MW m−2 on the first wall. However, conducting synergy heating experiments at high plasma currents and low effective ion charge numbers can significantly reduce the loss of fast ions.

Investigating ion irradiation effects for modifying optical properties of CA/PANI films

In this study, flexible CA/PANI films, consisting of polyaniline (PANI) and cellulose acetate (CA), were created via a solution cast production process. Then, these films were irradiated using of handmade cold cathode ion device with argon fluence of 2x1017, 4x1017, and 6x1017 ions/cm2. The SRIM program was used to investigate the ion penetration depth, ion distribution in the composite and the energy stopping loss. Moreover, the FTIR technique was used to identify the changes of the treated CA/PANI. The UV-Vis technique was used to show the impact of argon beam on the optical characteristics of CA/PANI composite film. The oscillation energy (E0) dropped from 8.88 for CA/PANI to 7.83, 6.42, and 5.19 eV after exposed to 2x1017, 4x1017, and 6x1017 ions/cm2. The results showed that the ion altered the optical characteristics of the CA/PANI samples, which allow for applied these irradiated CA/PANI films in optoelectronic devices.

Enhancement of mineral density and mechanical properties in root caries treated with silver diammine fluoride and glass ionomer cement, with emphasis on silver ion distribution

ObjectivesThis study aimed to measure the distribution of silver ion (Ag+), mineral recovery, and nanohardness in carious lesions and comprehensively evaluate the degree of dentin restoration. MethodsSixty human teeth with root caries were randomly assigned to the control, silver diammine fluoride (SDF) [Safo], and SDF+Glass ionomer cement (GIC) treatment [Safo+Fuji] groups. Micro-computed tomography (micro-CT) was performed at five time points for each sample before/after treatment to evaluate mineral density within and around carious lesions. Three months following treatment, 12 samples were selected for synchrotron radiation X-ray fluorescence analysis to evaluate Ag+ distribution, while 15 samples were selected for nanoindentation. Data were analyzed using Dunnett's T3 test for micro-CT and Wilcoxon rank sum test with Bonferroni correction (p = 0.017) for nanoindentation. The correlation between hardness and mineral change was analyzed using the Spearman rank correlation coefficient. ResultsThe Safo and Safo+Fuji groups showed significantly higher mineral recovery rates than did the control group (p < 0.001). In the Safo group, Ag+ accumulated in the deeper layers rather than the superficial layer of caries. In the Safo+Fuji group, Ag+ was found evenly distributed throughout caries, with only a few Ag+ detected in the GIC layer. Hardness in the Safo+Fuji group was significantly higher compared with the Safo group at depths in the range of 10–50 µm. ConclusionIn the presence of GICs, SDF exhibited high remineralization capacity when diffusing throughout carious lesions over time. Combined treatment with SDF and GIC could strengthen root dentin even in the presence of caries. Clinical significanceWe found that combination treatment with SDF and GIC could increase mineral density in caries and improve the hardness of the tooth structure compared with fluoride-based agents alone. These findings might pave the way for future clinical trials to determine the therapeutic potential of nanotechnology-based restorative materials.

Does the ionic distribution in the electrical double layer modify second harmonic scattering?

Surface-specific nonlinear optical techniques are ideally suited to investigate the complex structure of aqueous interfaces. For colloidal particles dispersed in aqueous solutions, interfacial properties can be retrieved with angle-resolved second harmonic scattering (AR-SHS). The mathematical framework of AR-SHS does not require a priori knowledge on the electrostatic distribution in the first few nanometers close to the interface, therefore allowing us to formulate a molecular-level description of the electrical double layer (EDL) based on the experimental data. However, farther away from the interface, an analytical form of the electrostatic potential decay is necessary to account for the distance dependence of the surface electrostatic field propagating into the solution. This requirement is especially important at low ionic strengths, where the electrostatic field is not efficiently screened by counterions. Here, we examine to what extent the analytical form of the electrostatic potential decay impacts the AR-SHS data analysis. We analyze the effect of different functions on the scattering form factors, on the integrated AR-SHS signal intensity, and on the surface parameters extracted from fitting the AR-SHS data. We find that the trends of the surface parameters remain similar regardless of the chosen function, demonstrating the robustness of our approach to establish a molecular-level picture of the EDL. At ionic strengths <10-4M for 100-nm diameter particles, a functional form that physically represents counterions packed more densely in the vicinity of the surface than in the case of the Poisson-Boltzmann distribution has the largest impact, resulting in an overestimation of the obtained surface potential.

Gas-phase ion mobility of protonated aldehydes in helium measured using a selected ion flow-drift tube.

In soft chemical ionization mass spectrometry, analyte ions are produced via ion-molecule reactions in the reactor. When an electric field E is imposed, the ion drift velocity vd determines the reaction time and the effective ion temperature. Agreement between experimental ion mobilities and theoretical predictions confirms the accuracy of the ion residence time measurement procedure. A selected ion flow-drift tube (SIFDT), an instrument with a chemical ionization source, was used to produce protonated aldehydes and selectively inject them into the resistive glass drift tube filled with He. Arrival-time distributions of ions were obtained using the Hadamard modulation. Reduced ion mobilities were then obtained at a pressure of 2hPa in the E/N range of 5-15 Td. Theoretical ion mobility values were calculated using two methods: hard-sphere approximation and trajectory modelling. The measured mobilities of three saturated and three unsaturated protonated aldehydes do not show substantial variation across the studied E/N range. Effective temperatures calculated using the Wannier formula from measured gas temperatures ranged from 300 to 315 K. Experimentally obtained values of the near-zero- E/N-reduced ion mobilities agree with both methods of calculations typically within ±3% standard deviation (maximum ±5%). The experimental SIFDT values of reduced mobilities in He of protonated aldehyde molecules generated from a chemical ionization source are in close agreement with two different theoretical methods based on the density functional theory calculations of ion geometries and partial atomic charges. Besides its fundamental importance, the ion mobility results validate the correct operation of the drift tube reactor and the ion residence time measurement procedure. Diffusion losses can also be determined from these results.

M3D-K simulations of beam-driven instabilities in an energetic particle dominant KSTAR discharge

We perform a systematic simulation study of energetic passing particle-driven instabilities in KSTAR using the kinetic-MHD hybrid code M3D-K. Linear simulation results show that the observed n = 1 mode in the early phase of the discharge is the low-frequency fishbone driven by energetic passing beam ions. The mode frequency computed is in a good agreement with the experimental measurement. Nonlinear simulations show that the frequency of the n = 1 mode jumps up to a higher value corresponding to the β-induced Alfvén eigenmode (BAE). In the later phase of the discharge, the simulated n = 5 mode is identified as a BAE in its linear phase. In the nonlinear phase, the n = 5 mode exhibits a similar frequency jump to a higher value of an energetic particle (EP) mode after mode saturation. Analysis of perturbed beam ion distributions in phase space shows that these new modes in nonlinear stages are driven by new resonances due to nonlinearly evolved beam ion distributions. Further simulations of a beam beta scan for the n = 5 mode show that the frequency jump disappears for a sufficiently small beam beta or beam ion drive. This result may explain the non-existence of frequency jump in the experiment. Finally, the impact of toroidal rotation on mode characteristics is investigated, showing that it has a marginal influence on EP driven modes.

Ecophysiology and Seedlings Nutrient Contents of Forest Species &amp;lt;i&amp;gt;Ricinodendron heudelotii &amp;lt;/i&amp;gt;(Mull. Arg.) and &amp;lt;i&amp;gt;Cola acuminata &amp;lt;/i&amp;gt;(P. Beauv.) Influenced by Biofertilizer and Salinity

&amp;lt;i&amp;gt;Ricinodendron heudelotii&amp;lt;/i&amp;gt; and &amp;lt;i&amp;gt;Cola acuminata, &amp;lt;/i&amp;gt;are important plants species whose exploitation became abusive over the years due to the high utilization of their fruits as Non-Timber Forest Products (NTFP). They face to multiple challenges: a recalcitrance of seeds and salinity that limits regeneration. Therefore, regeneration seems an appropriate corridor for domestication with the optimization of plant mycorrhizal symbiosis otherwise called arbuscular mycorrhizal fungi (AMF). But alongside this domestication can be added constraints due to salinity of the soils in coastal region. This justify the aim of this work which was to study dynamics and evaluate the effect of salinity and mycorrhizal biofertilizers on the &amp;lt;i&amp;gt;Ricinodendron heudelotii&amp;lt;/i&amp;gt; and &amp;lt;i&amp;gt;Cola acuminata &amp;lt;/i&amp;gt;seedlings. To undergo this purpose, data were collected in two villages (Kendje and Njombeng) in Mungo division, and assay were conducted in greenhouse at the Faculty of Science, University of Douala-Cameroon. In the field, the identification of species was assessed over an area of 1600 m² as well as the circumference of the trees, the individual number of &amp;lt;i&amp;gt;Ricinodendron heudelotii&amp;lt;/i&amp;gt; and &amp;lt;i&amp;gt;Cola acuminata&amp;lt;/i&amp;gt; among other species in order to assess their maturity and rarity in the forest. The second part was carried out in the greenhouse for the purpose of germination, obtaining seedlings and evaluating the effects of arbuscular mycorrhizal fungi (&amp;lt;i&amp;gt;Gisgaspora margarita&amp;lt;/i&amp;gt;) as biofertilizers on the seedlings in saline conditions (0, 50, 100 and 200 mM of NaCl). Some parameters were determined on seedlings (plant growth, dry weight, distribution of ions in plant organs, chlorophyll and carotenoid content) over a period of twenty-six weeks. Globally &amp;lt;i&amp;gt;Cola acuminata &amp;lt;/i&amp;gt;is more present in the forest (5.88%) than &amp;lt;i&amp;gt;Ricinodendron heudelotii&amp;lt;/i&amp;gt; (1.47%) with average circumference of 105cm for both species. AMF-biofertilizer alleviates the deleterious effect of salt stress on plants growth parameters depending of concentration. Moreover, for those species, the distribution of Na&amp;lt;sup&amp;gt;+&amp;lt;/sup&amp;gt; is more accumulated in the root’s plants unlike K&amp;lt;sup&amp;gt;+&amp;lt;/sup&amp;gt; and P which are more concentrated in the leaves.

Effects of Ca&lt;sup&gt;2+&lt;/sup&gt;/Mg&lt;sup&gt;2+&lt;/sup&gt; ions in recycled water on the reverse flotation properties of iron oxides

Water quality, particularly hardness, plays an important role in affecting the floatability of minerals as it interferes with the chemical/electro-chemical characteristics of mineral surfaces and their interactions with flotation reagents. It could become unpredictable when water sources characterized by different calcium or magnesium ion distributions were involved. This study aimed to identify the role of Ca&lt;sup&gt;2+&lt;/sup&gt;/Mg&lt;sup&gt;2+&lt;/sup&gt; ions in the recycled water on the cationic reverse flotation selectivity of iron oxides through a series of bench/micro flotation tests, zeta potential, powder contact angle, and Fourier Transform Infrared (FTIR), etc. The results pointed out that the use of recycled tailing water deteriorates the flotation selectivity and dilutes the concentrates. This can be largely attributed to the presence of Ca&lt;sup&gt;2+&lt;/sup&gt; ions at higher concentrations as they induce a drop in the Fe recovery and an increase in SiO2 content while an increase in the content of Mg&lt;sup&gt;2+&lt;/sup&gt; ions seems to have little effect on the quality of concentrate. As evidenced by the data from micro-flotation, powder contact angle, zeta potentials, and FTIR, a hydrophilic colloidal layer formed by Ca-based hydrolyzed compounds, such as Ca(OH)&lt;sup&gt;+&lt;/sup&gt; or, CaCO&lt;sub&gt;3(s)&lt;/sub&gt;, etc., on quartz could change its zeta potentials and disturb its interactions with a cationic collector. They also play a role in weakening the flocculation of starch on hematite probably by pre-locking the acidic groups on the starch remnants and contracting their configurations, thus preventing their adsorption on mineral surfaces. However, magnesium ions seem to be beneficial to in strengthening the flocculation of starch on hematite as magnesium-based species could act as adsorption bridges of between starch and mineral surfaces.

Multifunctional features of rare-earth based perovskite-like ferrocobaltite Eu(Fe0.5Co0.5)O3

Currently, the search for new materials that allow the electronic manipulation of spin for the transport of both electric charge and spin has intensified, since their applications in spintronic devices depend on this adjustment. The aim of this work is the analysis of the crystallographic properties and their correlation with the semiconducting ferromagnetic response of the compound Eu(Fe0.5Co0.5)O3 synthesised by solid reaction. It is observed that this material crystallizes forming an orthorhombic structure (Pnma space group) with disorder in the distribution of Fe and Co ions. Optical evaluation shows a bandgap of 1.15 eV, typical in semiconductors, which is corroborated by electrical transport measurements. Magnetic characterization reveals a predominantly antiferromagnetic behaviour in the low temperature regime, while at high temperatures a soft ferromagnetic response predominates as results of super-exchange interactions between magnetic moments. First-principles electronic structure calculations suggest the occurrence of direct semiconductor-type band gap but of different value for the two orientations spin up and spin down. This result allows inferring the technological applicability of the material in devices based on polarized spin currents.

Multi-Interface Electromagnetic Wave Absorbing Material Based on Liquid Marble Microstructures Anchored to SEBS.

The direct application of liquid marbles in electromagnetic wave (EMW) absorption is challenging due to their poor stability, susceptibility to gravitational collapse, and shaping difficulties. To address this issue, a novel strategy is proposed to incorporate liquid marble microstructures (NaCl/nano-SiO2) encapsulated in organic phases (Octadecane) into the rubber-matrix (SEBS) using the ultrasound-assisted emulsion blending method. The resulting NaCl/SiO2/Octadecane microstructures anchored to SEBS offer a substantial solid-liquid interface consisting of NaCl solution and SiO2. When subjected to an alternating electromagnetic (EM) field, the water molecules and polysorbate within SiO2 exhibit heightened responsiveness to the EM field, and the movement of Na+ and Cl- within these microstructures leads to their accumulation at the solid-liquid interface, creating an asymmetric ion distribution. This phenomenon facilitates enhanced interfacial polarization, thereby contributing to the material's EMW absorption properties. Notably, the latex with 16wt% SEBS (E-3), exhibiting a surface morphology similar to human cell tissues, achieves complete absorption of X-band (fE=4.20GHz, RLmin=-33.87dB). Moreover, the latex demonstrates light density (0.78gcm-3) and environmental stability. This study not only highlights the predominant loss mechanism in rubber-based wave-absorbing materials but also provides valuable insights into the design of multifunctional wave-absorbing materials.

Axisymmetric hybrid Vlasov equilibria with applications to tokamak plasmas

We derive axisymmetric equilibrium equations in the context of the hybrid Vlasov model with kinetic ions and massless fluid electrons, assuming isothermal electrons and deformed Maxwellian distribution functions for the kinetic ions. The equilibrium system comprises a Grad–Shafranov partial differential equation and an integral equation. These equations can be utilized to calculate the equilibrium magnetic field and ion distribution function, respectively, for given particle density or given ion and electron toroidal current density profiles. The resulting solutions describe states characterized by toroidal plasma rotation and toroidal electric current density. Additionally, due to the presence of fluid electrons, these equilibria also exhibit a poloidal current density component. This is in contrast to the fully kinetic Vlasov model, where axisymmetric Jeans equilibria can only accommodate toroidal currents and flows, given the absence of a third integral of the microscopic motion.

EMIC Wave Energy Dissipation as a Source of O+ Conics and Warm Plasma Cloak in the Earth's Inner Magnetosphere

AbstractThis study focuses on a specific source of the O+ conics and warm plasma cloak in the Earth's inner magnetosphere due to electromagnetic ion cyclotron (EMIC) wave energy dissipation. We analyze the EMIC wave event observed by Van Allen Probe‐A in the early afternoon off equatorial magnetosphere on 18 November 2015, where the two dominant EMIC wave bands, He+‐band and H+‐band, were observed for ∼4 min. All the wave and plasma parameters, the DC magnetic field, and ion distributions needed for our analysis are taken from the Van Allen Probe‐A observations during the event. The major results of our analysis are as follows. (a) The H+ and He+ heating by EMIC waves is negligible. (b) A strong heating of O+ by the wave energy dissipation around the third, fifth, and sixth harmonics of the O+ gyrofrequency is revealed, where the majority of energy dissipated goes into heating of O+ with the energies ≲100 eV and pitch angles ∼20°–90°. The estimated energy deposition rate is ∼0.1–3.4 eV/s per O+, totaling to the deposition of ∼20–800 eV per O+ during the event. (c) EMIC waves substantially contribute to the formation of O+ conics and warm plasma cloak by heating the upgoing low‐energy ionospheric O+ because waves heat ions with the energies and pitch angles that are characteristic of conics and warm plasma cloak, and the energy deposition per O+ is comparable to those characteristic energies.

Latitudinal Profiles of Auroral Forms/Motions and Plasma Properties Based on Simultaneous Image‐Particle Measurements by Reimei in the Midnight Auroral Oval

AbstractWe present the simultaneous and conjugated auroral emission and particle data obtained by a low‐altitude polar‐orbiting micro‐satellite, Reimei, for elucidating their latitudinal distributions and variations in the nightside auroral oval. Here are reported a few notable examples of the Reimei observations with high time and spatial resolutions, namely ∼120 msec. and ∼1.2 km × 1.2 km for multispectral auroral images and 40 msec. for energy‐pitch angle distributions of electrons and ions with energies of 10 eV–12 keV, respectively. The auroral images show various fine‐scale auroral activities characterized by the following types of auroral forms and variations: faint bands, streaming multiple arcs, shearing arcs, and vortices/curls, which are typical of the latitudinal properties of auroras. The particle analyzer simultaneously observed various properties of electron energy‐pitch angle and latitudinal distributions, and their temporal variations, each of which corresponds to a type of the auroral activities. Their features are summarized below. Reimei repetitively observed inverted‐V signatures of low‐energy (&lt;1 keV) field‐aligned electrons in addition to the higher‐energy (several keV) diffuse electrons in low‐latitude auroral oval. In more active regions at higher latitudes, the dominant energy flux responsible for the multiple‐arc emissions was carried by the well‐known inverted‐V electron precipitation. The rapidly rotating vortices or so‐called curls of fine‐scale discrete auroras near the poleward boundary of the auroral oval were closely associated with the significant energy fluxes of spiky field‐aligned electron bursts with energy‐time dispersions produced by dispersive Alfvén waves.

Time-resolved laser-induced fluorescence spectroscopy using CW diode laser for diagnostics of argon-ion velocity distribution near AC-biased electrode.

Controlling the ion velocity in an ion sheath by applying an alternating current (AC) voltage to an electrode and/or a substrate is critical in plasma material processes. To externally control the velocity distribution of incident ions on a substrate, the application of tailored-waveform AC voltages instead of sinusoidal voltages has garnered interest in recent years. In this study, to investigate temporal changes in ion-velocity distributions, we developed a time-resolved laser-induced fluorescence spectroscopy (LIF) system using a continuous-wave diode laser as an excitation-laser source. A time-resolved LIF system entails the capture of temporally continuous and spectrally discrete LIF spectra during an AC voltage cycle. By measuring temporal changes in the LIF signal intensity at various excitation-laser wavelengths, the argon-ion velocity distribution near the electrode following the AC voltage can be characterized. The results of applying sinusoidal, triangular, and rectangular bias waveforms indicate that the LIF measurement scheme proposed herein can be used to investigate the dynamic behavior of ion-velocity distributions controlled by tailored-waveform AC voltages.

Generation of plasma from multiple targets by laser ion source for TIARA ion implanter

We investigated a laser ion source for use as an ion source for the ion implanter in Takasaki Ion Accelerators for Advanced Radiation Application to increase the number of ion species that can be produced and to enable rapid switching of ion species. Herein, we analyzed the charge state distribution of ions in a laser plasma generated through irradiation of graphite, titanium, copper, and tantalum targets with 30 mJ Nd:YAG laser to determine the particle number of low-charge ions per pulse at 1.1 m from the target. The particle number of singly charged ions could be increased by adjusting the laser power density. For carbon, titanium, and tantalum, the particle numbers were in the order of 1010 ions per pulse, whereas for copper, the particle numbers were in the order of 109, lower than for other target materials.

Magnetosheath Ion Field‐Aligned Asymmetry and Implications for Ion Leakage to the Foreshock

AbstractThe ion foreshock is highly dynamic, disturbing the bow shock and the magnetosphere‐ionosphere system. To forecast foreshock‐driven space weather effects, it is necessary to model foreshock ions as a function of upstream shock parameters. Case studies in the accompanying paper show that magnetosheath ions sometimes exhibit strong field‐aligned asymmetry toward the upstream direction, which may be responsible for enhancing magnetosheath leakage and therefore foreshock ion density. To understand the conditions leading to such asymmetry and the potential for enhanced leakage, we perform case studies and a statistical study of magnetosheath and foreshock region data surrounding ∼500 Time History of Events and Macroscale Interactions during Substorms mission bow shock crossings. We quantify the asymmetry using the heat flux along the field‐aligned direction. We show that the strong field‐aligned heat flux persists across the entire magnetosheath from the magnetopause to the bow shock. Ion distribution functions reveal that the strong heat flux is caused by a secondary thermal population. We find that stronger asymmetry events exhibit heat flux preferentially toward the upstream direction near the bow shock and occur under larger IMF strength and larger solar wind dynamic pressure and/or energy flux. Additionally, we show that near the bow shock, magnetosheath leakage is a significant contributor to foreshock ions, and through enhancing the leakage the magnetosheath ion asymmetry can modulate the foreshock ion velocity and density. Our results imply that likely due to field line draping and compression against the magnetopause that leads to a directional mirror force, modeling the foreshock ions necessitates a more global accounting of downstream conditions.

Effects of selected cathode materials on a magnetically enhanced vacuum arc thruster

We discuss the effects of the ion distribution of a magnetically-enhanced Vacuum Arc Thruster using different cathode materials (Fe, Al, Cu) and magnetic field strengths. We develop a formalism, which is based on physical and geometric ideas, that describes the data for the inclusion of a magnetic field better than previous models (R2 > 0.89 for worst case). Our tests were performed on a Vacuum Arc Thruster with 270 A discharge current and an average pulse length of 3.5 ms. The magnetic field generator, driven by a separate capacitive discharge circuit, produced field strengths ranging from 0 to 250 mT along the thruster's centerline. We obtained the thrust correction factor and theoretical thrust from our measurements. It was found that application of magnetic fields increased ion density and axial momentum along the plasma plume's centerline. At higher magnetic field strengths (∼250 mT) the thrust factor decreased across all materials. For our electrodes, the inclusion of a protruding magnetic nozzle was seen to cancel the benefits arising from beam collimation due to the magnetic field. The iron electrode performed best, which may be due to its ferromagnetic nature.

Investigation of structural phase stability, modified magnetic spin order and low temperature spin glass-like phase transitions in Sc-doped M-type BaFe12O19 hexaferrite

This work used two approaches of mechanical alloying before high temperature solid state reaction to synthesize BaFe12-xScxO19 (x = 0.5 to 6.0) system. Rietveld refinement of X-ray diffraction patterns showed the formation of extra phases at higher Sc doping, along with the main magnetoplumbite structure. Raman spectroscopy suggested random distribution of Sc ions at the Fe-sites of hexaferrite structure. X-ray photoelectron spectroscopy (XPS) confirmed the +3 charge state at the Fe/Sc-sites. The Fe 3s band suggested dilution of ferromagnetic 3s-3d spin exchange interactions. The neutron diffraction study re-confirmed random occupancy of the non-magnetic Sc3+ ions at Fe3+ sites of the Sc doped Ba hexaferrite system. The transformation of magnetic spin order from collinear to non-collinear state has shown spin glass-like features at low temperature regime in the dc magnetization curves. This is an effect of dilution of Fe–O–Fe ferrimagnetic super exchange interactions and spin frustration in Sc-doped samples.

Study on the Ionic Transport Properties of 3D Printed Concrete

Three-dimensional printed concrete (3DPC) is an anisotropic heterogeneous material composed of a concrete matrix and the interfaces between layers and filaments that form during printing. The overall ion transport properties can be characterized by the equivalent diffusion coefficient. This paper first establishes a theoretical model to calculate the equivalent diffusion coefficient of 3DPC. Verification through numerical calculations shows that this theoretical model is highly precise. Based on this, the model was used to analyze the effects of dimensionless interface parameters on the equivalent diffusion coefficients in different directions of 3DPC. Finally, the dynamic ionic transport properties of 3DPC were investigated through finite element numerical simulation. The results of the dynamic study indicate that interfaces have a significant impact on the ion distribution and its evolution within 3DPC. The product of the interface diffusion coefficient and interface size can represent the ionic transport capacity of an interface. The stronger the ionic transport capacity of an interface, the higher the ion concentration at that interface. Due to the “drainage” effect of lateral interfaces, the ion concentration in the middle of 3DPC with a smaller equivalent diffusion coefficient is higher than that in 3DPC with a larger equivalent diffusion coefficient.