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76 p. Los capítulos 5,6,7 y 8 están sujetos a confidencialidad por la autora, Esta tesis doctoral propone un proceso integrado para la valorización de residuos de la producción secundaria de aluminio (Paval de escoria salina) a través de la reducción de su contenido en flúor y minimizando la consecuente reducción de aluminio, mediante un proceso hidrometalúrgico que reduce su contenido en flúor y minimiza la pérdida de alúmina, así como del tratamiento del efluente producido para su reciclado, lo que conlleva una reducción en la producción de residuos. Se estudió el efecto de los principales parámetros de operación (agentes lixiviantes ácidos y básicos, temperatura, pH, tiempo de reacción y ratio S/L) en la lixiviación selectiva de flúor y aluminio, utilizando muestras de Paval industriales mediante el método Taguchi de diseño de experimentos y análisis de varianzas (ANOVA). El proceso hidrometalúrgico resultante de este estudio produce un efluente alto en sulfatos cuya purificación y recirculación al proceso se estudió con el objetivo de minimizar la generación de residuos. Para ello se adaptaron y optimizaron distintos tratamientos de eliminación de sulfatos.

In this paper we report characteristics and electrochemical properties of silicon fibers used as lithium-ion battery anode. All samples were synthesized by potentiostatic electrodeposition from molten KCl K2SiF6. From molten KCl CsCl K2SiF6 deposition was carried out in galvanostatic mode. Despite the synthesis in inert atmosphere and absence of oxygen containing compounds in the melt resulting silicon after washing contains at least 15 at% oxygen. Silicon fibers synthesized at ?250 mV (vs Si) were the thinnest with diameter as small as 100 nm; average fiber length increased with increasing overvoltage. Addition of CsCl to the melt results in decrease of the average fibers diameter. Silicon fibers synthesized at ?250 mV (vs Si) in KCl K2SiF6 melt showed the best cycling performance with capacity of 1030 mAh g?1 at 0.2 A g?1 discharge current and capacity of 715 mAh g?1 after 10 cycles. Lithium diffusion coefficients calculated from galvanostatic intermittent titration technique (GITT) are common for silicon-based anode. The highest initial diffusion coefficient value of 6.68 10?11 cm2 s?1 was achieved for silicon synthesized from melt with addition of CsCl. Low capacity and rapid capacity fading for all samples can be caused by high silicon dioxide content, further treatment of synthesized silicon is necessary to achieve higher performance. © 2022 The Author(s).

Fluoride as a geogenic contaminant is commonly encountered in groundwater-based drinking water sources. In the present study Watermelon Rind (Citrullus lanatus) Biochar (WMRBC) was investigated for its defluoridation potential. The factors affecting the removal of fluoride, including pH, adsorbent dosage, initial concentration, and contact time were investigated. The experimental data were fitted well by Freundlich isotherm and pseudo-second-order model, the maximum fluoride adsorption capacity being 9.5 mg/g. Thermodynamic parameters indicated that the fluoride adsorption process was a spontaneous exothermic process. The presence of other anions like HCO3–, CO32–, Cl−, SO42−, and NO3– (100 mg/L) had little effect on the adsorption of fluoride at 50 mg/L. Characterization studies of WMRBC before and after fluoride adsorption by SEM, ATR, EDX and XRD techniques, indicated that the adsorption of fluoride may be by electrostatic attraction through protonated basic functionalities present in WMRBC and by precipitation at the mineral sites. WMRBC could be a viable adsorbent for effective removal of fluoride from drinking water and industrial wastewater., QC 20220428

76 p. Los capítulos 5,6,7 y 8 están sujetos a confidencialidad por la autora, Esta tesis doctoral propone un proceso integrado para la valorización de residuos de la producción secundaria de aluminio (Paval de escoria salina) a través de la reducción de su contenido en flúor y minimizando la consecuente reducción de aluminio, mediante un proceso hidrometalúrgico que reduce su contenido en flúor y minimiza la pérdida de alúmina, así como del tratamiento del efluente producido para su reciclado, lo que conlleva una reducción en la producción de residuos. Se estudió el efecto de los principales parámetros de operación (agentes lixiviantes ácidos y básicos, temperatura, pH, tiempo de reacción y ratio S/L) en la lixiviación selectiva de flúor y aluminio, utilizando muestras de Paval industriales mediante el método Taguchi de diseño de experimentos y análisis de varianzas (ANOVA). El proceso hidrometalúrgico resultante de este estudio produce un efluente alto en sulfatos cuya purificación y recirculación al proceso se estudió con el objetivo de minimizar la generación de residuos. Para ello se adaptaron y optimizaron distintos tratamientos de eliminación de sulfatos.

On the basis of the first-principles evolutionary crystal structure prediction of stable compounds in the Cu-F system, we predict two experimentally unknown stable phases - Cu2F5and CuF3. Cu2F5comprises two interacting magnetic subsystems with Cu atoms in the oxidation states +2 and +3. CuF3contains magnetic Cu3+ions forming a lattice by antiferromagnetic coupling. We showed that some or all of Cu3+ions can be reduced to Cu2+by electron doping, as in the well-known KCuF3. Significant similarities between the electronic structures calculated in the framework of DFT+Usuggest that doped CuF3and Cu2F5may exhibit high-Tcsuperconductivity with the same mechanism as in cuprates. © the Owner Societies 2021.

Membrane distillation (MD) is a rapidly developing field of research and finds applications in desalination of water, purification from nonvolatile substances, and concentration of various solutions. This review presents data from recent studies on the MD process, MD configuration, the type of membranes and membrane hydrophobization. Particular importance has been placed on the methods of hydrophobization and the use of track-etched membranes (TeMs) in the MD process. Hydrophobic TeMs based on poly(ethylene terephthalate) (PET), poly(vinylidene fluoride) (PVDF) and polycarbonate (PC) have been applied in the purification of water from salts and pesticides, as well as in the concentration of low-level liquid radioactive waste (LLLRW). Such membranes are characterized by a narrow pore size distribution, precise values of the number of pores per unit area and narrow thickness. These properties of membranes allow them to be used for more accurate water purification and as model membranes used to test theoretical models (for instance LEP prediction). © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Arsenic (As) and Fluoride (F) are two commonly occurring geogenic contaminants in groundwater environment, causing a range of carcinogenic and non-carcinogenic adverse health effects worldwide. Several studies have been conducted in past and many are ongoing to address As and F contamination issue of natural water. This special issue is conferring in recent times one of the emerging fields of science regarding co-occurrences of multi-contaminants within a given system and associated health risks. This special issue is divided into three sections. Section I deals with the occurrence and co-existence of As, F, and trace elements (TE) in the environment. As and F occurrence [including trace elements (TEs)] in groundwater at a global scale (example: India, Sri Lanka, Bangladesh, Ghana, and Iran, etc.) has been highlighted (Section I). The geological, and anthropogenic factors affecting As and F contamination have been observed. The state-of-art, removal techniques for As and F have been discussed. Section II and Section III incorporate all the advanced removal methods for As and F, respectively. Arsenic and F removal comprises assessing natural remediation potential (phytoremediation) including different advanced absorbents. The new findings published here, bring together a wide range of new insights on As and F behavior in the groundwater environment., QC 20210409

The expected widespread use of wearable and other low-power healthcare devices has triggered great interest in piezoelectric materials as a promising energy harvester. However, traditional piezoelectric materials suffer from poor interfacial energy transfer when used in self-charging power cells. Herein, piezoelectric supercapacitors (PSCs) are engineered using MXene-incorporated polymeric piezo separator and MXene (Ti3C2Tx) multilayered sheets as electrodes. The MXene-blended polymer film showed considerable improvement with maximum output voltage of 28 V and current of 1.71 µA. The electromechanical properties studied by piezoelectric force microscopy suggest that the integration of MXene in polyvinylidene fluoride (PVDF) matrix induces the degree of dipole moment alignment, thereby improving the piezoelectric properties of PVDF. At the device level, the PSC featured the capacitance of 61 mF cm–2, the energy density of 24.9 mJ cm−2, the maximum power density of 1.3 mW cm−3, and the excellent long-term cycling stability. A way is paved toward green, integrated energy harvesting and storing technology for next-generation self-powered implantable and wearable electronics. © 2021 Wiley-VCH GmbH

Transparent ytterbium doped yttria ceramics, 2 at.% Yb:Y2O3, were fabricated by hot uniaxial pressing in vacuum at 1550 degrees C/50 MPa followed by a two stage Hot Isostatic Pressing (HIPing) at 1200 1400 degrees C/100 MPa, using nanopowders obtained by self-propagating high-temperature synthesis (with lithium fluoride serving as a sintering aid). The addition of LiF during the powder synthesis markedly changed the morphology of powders, and at the stage of hot pressing, drastically reduced the carbon contamination of ceramics, as well as stimulated sintering without formation of the liquid phase. The spectroscopic properties of ceramics were studied. The stimulated-emission cross-section for Yb3+ ions is 0.90 x 10(-20) cm(2) at 1030.4 nm and the luminescence lifetime is 797 mu s. A continuous wave 2 at.% Yb:Y2O3 ceramic laser generated an output power of 735 mW at 1027 1034 nm with a slope efficiency of 64.5% and a laser threshold of 0.28 W.

We report on a comparative study of a transparent Fe:MgAl2O4 (spinel) ceramics and a transparent nanophase Fe: MgAl2O4-based glass-ceramics. The 0.1 mol% Fe:MgAl2O4 ceramics was synthesized by hot pressing (at 1500 degrees C/50 MPa) of powders obtained by the sol-gel method using LiF as a sintering aid. The Fe:MgAl2O4 ceramic is a single-phase material (cubic structure, sp. gr. Fd3(-) m, a = 8.083 angstrom) with a mean grain size of similar to 50 mu m. The ceramic exhibits a broadband transparency of 0.2-6.0 mu m and a high in-line transmission at similar to 1 mu m of 74.4%. The iron ions are presented in the ceramics in the single state of Fe2+ species in tetrahedral (T-d) sites. A broad absorption band spanning from similar to 1.2 to 3.7 mu m assigned to the E-5 -> T-5(2) (D-5) transition of Fe2+ ions in T-d sites is observed, corresponding to a ground-state absorption cross section of 0.28 x 10(-18) cm(2) at 1.90 mu m. The glass-ceramics were prepared by secondary two-stage heat-treatments of the magnesium aluminosilicate glass nucleated by titanium oxide and doped with 0.1 mol% FeO. Transparent Fe:MgAl2O4-based glass-ceramics obtained at the temperature of the second stage of 800-1000 degrees C were multi-phase materials containing two crystalline nanophases, i.e., spinel (mean size: 3.7-7.4 nm) and magnesium aluminotitanate solid solution (mean size: 6.4-20.6 nm), as well as residual silica-rich glass. Glass-ceramics obtained at the temperature of the second stage of 1050 degrees C were transparent and based on Fe-doped sapphirine. For glass-ceramics, absorption has a much more complex character as it is caused by interplay of iron and titanium ions in different valence states, coordination sites and locations. The iron ions enter the spinel nanocrystals but unlike

76 p. Los capítulos 5,6,7 y 8 están sujetos a confidencialidad por la autora, Esta tesis doctoral propone un proceso integrado para la valorización de residuos de la producción secundaria de aluminio (Paval de escoria salina) a través de la reducción de su contenido en flúor y minimizando la consecuente reducción de aluminio, mediante un proceso hidrometalúrgico que reduce su contenido en flúor y minimiza la pérdida de alúmina, así como del tratamiento del efluente producido para su reciclado, lo que conlleva una reducción en la producción de residuos. Se estudió el efecto de los principales parámetros de operación (agentes lixiviantes ácidos y básicos, temperatura, pH, tiempo de reacción y ratio S/L) en la lixiviación selectiva de flúor y aluminio, utilizando muestras de Paval industriales mediante el método Taguchi de diseño de experimentos y análisis de varianzas (ANOVA). El proceso hidrometalúrgico resultante de este estudio produce un efluente alto en sulfatos cuya purificación y recirculación al proceso se estudió con el objetivo de minimizar la generación de residuos. Para ello se adaptaron y optimizaron distintos tratamientos de eliminación de sulfatos.

Ab initio calculations of the atomic, electronic and vibrational structure of a pure and Co+2 doped MgF2 crystals were performed and discussed. We demonstrate that Co+2 (3d7) ions substituting for Mg is in the high spin state. In particular, the role of exact non-local exchange is emphasized for a proper reproduction of not only the band gap but also other MgF2 bulk properties. It allows us for reliable estimate of the dopant energy levels position in the band gap, and its comparison with the experimental data. Thus, the present ab initio calculations and experiment data demonstrate that the Co+2 ground state level lies at ≈2 eV above the valence band top. © 2020 Elsevier B.V.

The preparation of multicomponent coatings based on silicon and yttrium on the niobium substrate was investigated. Y-Si/NbSi2 coatings on the Nb substrate by currentless deposition in molten salts were produced. The preparation of NbSi2 layers is carried out in NaF-NaCl-Na2SiF6 melts with the addition of Si powder. The preparation of Y-Si layers is carried out in NaCl-KCl-YF3 melts containing Y powder. Coating samples are studied using SEM. It is established that sequentially synthesized coatings are characterized by a two-layer structure. Using the EDS method, the chemical composition of the obtained layers is established: Y - 26.68; Nb - 62.55; Si - 10.76 wt. %. The oxidation test of the obtained coatings Y-Si/NbSi2 on Nb samples is performed. It is found that testing at 1200 oC for 2 hours leads to a mass loss of 62 mg/cm2•h. © Published under licence by IOP Publishing Ltd.

Triboelectric nanogenerators (TENGs) are promising electric energy harvesting devices as they can produce renewable clean energy using mechanical excitations from the environment. Several designs of triboelectric energy harvesters relying on biocompatible and eco-friendly natural materials have been introduced in recent years. Their ability to provide customizable self-powering for a wide range of applications, including biomedical devices, pressure and chemical sensors, and battery charging appliances, has been demonstrated. This review summarizes major advances already achieved in the field of triboelectric energy harvesting using biocompatible and eco-friendly natural materials. A rigorous, comparative, and critical analysis of preparation and testing methods is also presented. Electric power up to 14 mW was already achieved for the dry leaf/polyvinylidene fluoride-based TENG devices. These findings highlight the potential of eco-friendly self-powering systems and demonstrate the unique properties of the plants to generate electric energy for multiple applications.[Figure not available: see fulltext.]. © 2020, © 2020, The Author(s).

In LiNiO2, the Ni3+ ion has a d7 configuration in a cubic crystal field with one electron on doubly degenerate eg orbitals, and such an ion is considered to be Jahn-Teller (JT) active. However, despite the fact that this compound is an insulator, and hence d-electrons are localized, a cooperative JT lattice distortion was not observed. This problem was usually supposed to be resolved by the presence of local JT distortions that do not order in a cooperative JT distorted crystal structure. In the present work, the DFT+DMFT approach, combining density functional theory with dynamical mean-field theory, was applied to study the electronic and magnetic properties of LiNiO2. In the result, an insulating solution with a small energy gap value was obtained in agreement with experimental data. However, in contrast to previous calculations by other methods, the symmetry was not broken and the calculated ground state is a thermodynamical mixture of αd7+βd8L (α≈60%,β≈40%) ionic states. The d8L state is JT inactive, and we have found that for the nickel d7 state two configurations with an electron on the Ni dx2-y2 or d3z2-r2 orbital have equal statistical weights. So the orbital degeneracy of the Ni3+ ion is not lifted, and that explains the absence of the cooperative JT lattice distortion in this compound. Also, the temperature dependence of inverse magnetic susceptibility of LiNiO2 has been calculated, and a good agreement with experimental data was obtained. © 2019 American Physical Society.

We introduce a protecting-group-free concept for the powerful para-fluoro-thiol reaction (PFTR) employing a source of fluoride ions as base. The reaction is shown to be self-propagating, with under-stoichiometric amounts of base, thus effectively foregoing the need for high base concentrations. Careful tuning of the solvent–thiol combination allows for quantitative conversion, in some cases within a short timeframe, when only minimal amounts of base are used, allowing the PFTR reaction to essentially proceed base-free.

In situ high temperature NMR spectroscopy was used to characterize the NaF-ScF3 melt over a wide range of compositions. 19F, 23Na, and 45Sc NMR spectra were acquired in NaF-ScF3 melts of up to 70 mol% of ScF3. The interpretation of all experimental results obtained in situ in the melt is significantly enhanced by the contribution of Molecular Dynamics (MD) calculations. A new interatomic potential for the molten NaF-ScF3 system was developed by using a Polarizable Ion Model (PIM). The potential parameters were obtained by force-fitting to density functional theory (DFT) reference data. MD simulations were combined with further DFT calculations to determine NMR chemical shifts for 19F, 23Na, and 45Sc. The agreement between the experimental NMR data and the corresponding calculated data from our applied computational protocol indicated the polymerization and network formation in the melt. Additionally, the density and the electrical conductivity in the molten state were calculated from the statistical analysis of ionic trajectories obtained through MD simulations. © 2019 Elsevier B.V.

Mesoporous CaF2 nanopowders with specific surface area up to 91.5 m2/g have been obtained through evaporation by electron beam in vacuum. The effect of relativistic e-beam irradiation in air on magnetic and texture properties of CaF2 nanoparticles has been studied. The influence of annealing and irradiation on the specific surface area and magnetization of CaF2 nanopowder has been discovered for the first time. © Published under licence by IOP Publishing Ltd.

Mesoporous CaF2 nanopowders with the specific surface area up to 88.7 m2/g have been produced by the evaporation by a pulsed electron beam in vacuum. The influence of thermal annealing in air on the size and morphology of CaF2 nanoparticles and their magnetic, luminescence, and texture characteristics has been studied. Ferromagnetism of CaF2 nanopowders was discovered for the first time. The influence of radiation defects (CaF2 dye centers) on magnetic properties of CaF2 nanoparticles has been examined. © Published under licence by IOP Publishing Ltd.

Dielectric properties of polyvinylidene fluoride based thin films and electrospun mats have been studied. Frequency dependences of samples capacity and tangent of dielectric losses have been obtained. The influence of trifluoroethylene presence in copolymer on dielectric properties has been investigated. Efficiency of using deposited contacts instead of pressed contacts was considered. © Published under licence by IOP Publishing Ltd.

In the present work, a new class of high entropy materials for energy storage applications is introduced. Multi-anionic and -cationic compounds are prepared by facile mechanochemistry using a recently designed multi-cationic transition-metal-based high entropy oxide as the precursor and LiF or NaCl as the reactant, leading to formation of lithiated or sodiated materials. Notably, the Li-containing entropy-stabilized oxyfluoride described herein (Lix(Co0.2Cu0.2Mg0.2Ni0.2Zn0.2)OFx) exhibits a working potential of 3.4 V vs. Li+/Li, enabling its use as a cathode active material. Unlike conventional (non-entropy-stabilized) oxyfluorides, this new material shows enhanced Li storage properties due to entropy stabilization, which, in general, facilitates tailoring the cycling performance by varying the constituent elements in yet unprecedented ways. In addition, we demonstrate that the concept of entropy stabilization is also applicable to Na-containing oxychlorides with a rock-salt structure, thus paving the way toward development of (next-generation) post-Li battery technologies.

The formation of oriented enamel-like fluoride doped hydroxyapatite (HA) nanorods on amorphous calcium phosphate (ACP) substrates in their bare form and containing citrate is compared. It is found that the presence of citrate delays the conversion into un-oriented HA that in turn affects the overgrowth of nanorods as well as their shape and surface features. With citrate being an important component of bones and teeth, this study is highly relevant to attain new insights into the biomineralization processes and to widen the range of strategies for the design of advanced biomaterials.

In the present work, a new class of high entropy materials for energy storage applications is introduced. Multi-anionic and -cationic compounds are prepared by facile mechanochemistry using a recently designed multi-cationic transition-metal-based high entropy oxide as the precursor and LiF or NaCl as the reactant, leading to formation of lithiated or sodiated materials. Notably, the Li-containing entropy-stabilized oxyfluoride described herein (Lix(Co0.2Cu0.2Mg0.2Ni0.2Zn0.2)OFx) exhibits a working potential of 3.4 V vs. Li+/Li, enabling its use as a cathode active material. Unlike conventional (non-entropy-stabilized) oxyfluorides, this new material shows enhanced Li storage properties due to entropy stabilization, which, in general, facilitates tailoring the cycling performance by varying the constituent elements in yet unprecedented ways. In addition, we demonstrate that the concept of entropy stabilization is also applicable to Na-containing oxychlorides with a rock-salt structure, thus paving the way toward development of (next-generation) post-Li battery technologies.

Low-parasitic-capacitance 4H-SiC nMOSFETs using a novel self-aligned process were suggested and demonstrated. In these nMOSFETs, device characteristics including parasitic capacitances (gate-source, gate-drain, drain-source capacitance) were investigated and low parasitic capacitance was achieved by the self-aligned structure, QC 20181025

Electrical impedance tomography (EIT) is a technique of image reconstruction of the electrical conductivity distribution in a tissue or region under observation. An electrical system for EIT comprises complex hardware and software modules, which are designed for a specific application which requires that the system to be able to detect conductivity variations within the study object. The Front-End for body composition measurement, AFE4300 from Texas Instruments allows a minimal implementation of an electrical impedance tomography system. It is the main device in the development of the EIT system presented in this paper, this device injects the current signal and measures the tensions generated on the study region boundary by 8 electrodes, the image reconstruction software was developed on the National Instruments platform Labview. The system includes a microcontroller PIC16F886 to configure the 8 channels for the definition of the patterns of injection and measurement of signals, also defines the current signal frequency and the bluetooth communication with the computer for the image reconstruction. The developed system was validated by a planar resistive phantom (CardiffEIT phantom), obtaining a stable voltage measurement every 50 ms per pair of electrodes, and a signal to noise ratio (SNR) maximum of 71.8 dB, for a current signal of 50 kHz. Additionally, tests were carried out in a saline tank with a concentration of 4 g/L, the developed system can simultaneously estimate the presence of conductive and non-conductive disturbances into the tank. Copyright, Peer Reviewed, Postprint (published version)

The mesoporous nanocrystal powders BaF 2 and CaF 2 with a specific surface up to 34.8 and 88.7 sq.m/g, respectively, are produced by the pulsed electron beam evaporation method in vacuum. The influence of thermal annealing of nanoparticles on air in the range of temperature from 200 to 900°C on the size, morphology of particles and change of their magnetic and luminescent properties investigated have been investigared. The essential stoichiometric impurity (overage of metals) and significant growth in a specific surface of nanopowders (NP) BaF 2 and CaF 2 after annealing at the temperature of 200°C have been detected. It is established that the synthesized NP BaF 2 is a paramagnetic while initial material in the bulk state is diamagnetic. After annealing at 900°C appears the small ferromagnetic contribution at NP BaF 2 . Produced NP CaF 2 showed ferromagnetic behavior. In literature there is no information about the ferromagnetism of CaF 2 . Appearance of the ferromagnetic response can be explained with formation of structural and radiation defects (F-centers, etc.). The analysis of PCL and magnetization curves of samples BaF 2 and CaF 2 allows drawing conclusions about their connection. © Published under licence by IOP Publishing Ltd.

In this paper, studies of the luminescence properties of nanocrystalline BaF 2 samples synthesized by laser ablation and pulse electron beam evaporation method are presented. The measurements of X-ray excited luminescence (XEL) showed the dependence between luminescence intensity and the shape of the spectrum on the morphology and particle size. Also, studies of X-ray excited luminescence, decay curves and optical transmittance for nanocomposite materials containing BaF 2 nanopowder are presented. Barium fluoride nanopowder, obtained by pulsed electron beam evaporation method is characterized by a lower intensity than the initial microcrystalline powder, but at the same time, XEL spectrum of the nanocomposite material with this nanocrystalline filler is more intense, then that for nanocomposite material with initial powder. © Published under licence by IOP Publishing Ltd.

Groundwater pollution is a serious health concern in north-western India. In this study, we have reported very high concentration of fluoride i.e. 18.5 and 16.6 mg/l from Sainiwas locality in Siwani block of Bhiwani district, Haryana, India. The values are much higher than the permissible limit set by WHO and BIS. The evapotranspiration in the area leads to Ca2+ precipitation, which allows an increase in F- content in the groundwater. In addition, the replacement of hydroxyl of secondary clay mineral under alkaline condition is responsible for release of F-. In absence of alternative source, the fluoride polluted groundwater in some of these localities is also used for drinking. Further, the suitability of groundwater for irrigation is also evaluated by various parameters such as Sodium Adsorption Ratio (SAR), Sodium Percentage (Na%), Kelly's Ratio (KR), Magnesium Hazard (MH) and Residual Sodium Carbonate (RSC). It emerges out that in a few localities, groundwater is not suitable for irrigation and with respect to Magnesium Hazard (MH) almost all samples are unsuitable for irrigation. This article highlights groundwater quality of Siwani block in Haryana and proposes for immediate remedial measures., QC 20220620

We report on CPA-free multipass amplification of ps-pulses in Holmium-doped yttrium lithium fluoride (Ho:YLF) crystals up to µJ pulse-energy-covering repetition rates from 10 kHz up to 500 kHz. The seed pulses at a wavelength of 2.05 µm are provided by a Ho-based all-fiber system consisting of a soliton oscillator and a subsequent pre-amplifier followed by a free-space AOM as pulse-picker. Considering the achieved pulse peak power at MW-level, this system is a powerful tool for e cient pumping of parametric conversion stages addressing the highly demanded mid-IR spectral region.

In this work we investigate the strain, temperature and humidity sensitivity of a Fiber Bragg Grating (FBG) inscribed in a near infrared low-loss multimode perfluorinated polymer optical fiber based on cyclic transparent optical polymer (CYTOP). For this purpose, FBGs were inscribed into the multimode CYTOP fiber with a core diameter of 50 µm by using a krypton fluoride (KrF) excimer laser and the phase mask method. The evolution of the reflection spectrum of the FBG detected with a multimode interrogation technique revealed a single reflection peak with a full width at half maximum (FHWM) bandwidth of about 9 nm. Furthermore, the spectral envelope of the single FBG reflection peak can be optimized depending on the KrF excimer laser irradiation time. A linear shift of the Bragg wavelength due to applied strain, temperature and humidity was measured. Furthermore, depending on irradiation time of the KrF excimer laser, both the failure strain and strain sensitivity of the multimode fiber with FBG can be controlled. The inherent low light attenuation in the near infrared wavelength range (telecommunication window) of the multimode CYTOP fiber and the single FBG reflection peak when applying the multimode interrogation set-up will allow for new applications in the area of telecommunication and optical sensing.

Long-period fiber gratings (LPGs) are well known for their sensitivity to external influences, which make them interesting for a large number of sensing applications. For these applications, fibers with a high numerical aperture (i.e., fibers with highly germanium (Ge)-doped fused silica fiber cores) are more attractive since they are intrinsically photosensitive, as well as less sensitive to bend- and microbend-induced light attenuations. In this work, we introduce a novel method to inscribe LPGs into highly Ge-doped, single-mode fibers. By tapering the optical fiber, and thus, tailoring the effective indices of the core and cladding modes, for the first time, an LPG was inscribed into such fibers using the amplitude mask technique and a KrF excimer laser. Based on this novel method, sensitive LPG-based fiber optic sensors only a few millimeters in length can be incorporated in bend-insensitive fibers for use in various monitoring applications. Moreover, by applying the described inscription method, the LPG spectrum can be influenced and tailored according to the specific demands of a particular application. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.

Electrical impedance tomography (EIT) is a technique of image reconstruction of the electrical conductivity distribution in a tissue or region under observation. An electrical system for EIT comprises complex hardware and software modules, which are designed for a specific application which requires that the system to be able to detect conductivity variations within the study object. The Front-End for body composition measurement, AFE4300 from Texas Instruments allows a minimal implementation of an electrical impedance tomography system. It is the main device in the development of the EIT system presented in this paper, this device injects the current signal and measures the tensions generated on the study region boundary by 8 electrodes, the image reconstruction software was developed on the National Instruments platform Labview. The system includes a microcontroller PIC16F886 to configure the 8 channels for the definition of the patterns of injection and measurement of signals, also defines the current signal frequency and the bluetooth communication with the computer for the image reconstruction. The developed system was validated by a planar resistive phantom (CardiffEIT phantom), obtaining a stable voltage measurement every 50 ms per pair of electrodes, and a signal to noise ratio (SNR) maximum of 71.8 dB, for a current signal of 50 kHz. Additionally, tests were carried out in a saline tank with a concentration of 4 g/L, the developed system can simultaneously estimate the presence of conductive and non-conductive disturbances into the tank. Copyright, Peer Reviewed, Postprint (published version)

Long-period fiber gratings (LPGs) are well known for their sensitivity to external influences, which make them interesting for a large number of sensing applications. For these applications, fibers with a high numerical aperture (i.e., fibers with highly germanium (Ge)-doped fused silica fiber cores) are more attractive since they are intrinsically photosensitive, as well as less sensitive to bend- and microbend-induced light attenuations. In this work, we introduce a novel method to inscribe LPGs into highly Ge-doped, single-mode fibers. By tapering the optical fiber, and thus, tailoring the effective indices of the core and cladding modes, for the first time, an LPG was inscribed into such fibers using the amplitude mask technique and a KrF excimer laser. Based on this novel method, sensitive LPG-based fiber optic sensors only a few millimeters in length can be incorporated in bend-insensitive fibers for use in various monitoring applications. Moreover, by applying the described inscription method, the LPG spectrum can be influenced and tailored according to the specific demands of a particular application. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.

In this work we investigate the strain, temperature and humidity sensitivity of a Fiber Bragg Grating (FBG) inscribed in a near infrared low-loss multimode perfluorinated polymer optical fiber based on cyclic transparent optical polymer (CYTOP). For this purpose, FBGs were inscribed into the multimode CYTOP fiber with a core diameter of 50 µm by using a krypton fluoride (KrF) excimer laser and the phase mask method. The evolution of the reflection spectrum of the FBG detected with a multimode interrogation technique revealed a single reflection peak with a full width at half maximum (FHWM) bandwidth of about 9 nm. Furthermore, the spectral envelope of the single FBG reflection peak can be optimized depending on the KrF excimer laser irradiation time. A linear shift of the Bragg wavelength due to applied strain, temperature and humidity was measured. Furthermore, depending on irradiation time of the KrF excimer laser, both the failure strain and strain sensitivity of the multimode fiber with FBG can be controlled. The inherent low light attenuation in the near infrared wavelength range (telecommunication window) of the multimode CYTOP fiber and the single FBG reflection peak when applying the multimode interrogation set-up will allow for new applications in the area of telecommunication and optical sensing.

Fluoride-Promoted Carbonylation (FPC) polymerization is herein presented as a novel catalytic polymerization methodology that complements ROP and unlocks a greater synthetic window to advanced polycarbonates. The overall two-step strategy is facile, robust and capitalizes on the synthesis and step-growth polymerization of bis-carbonylimidazolide and diol monomers of 1,3- or higher configurations. Cesium fluoride (CsF) is identified as an efficient catalyst and the bis-carbonylimidazolide monomers are synthesized as bench-stable white solids, easily obtained on 50-100 g scales from their parent diols using cheap commercial 1,1′-carbonyldiimidazole (CDI) as activating reagent. The FPC polymerization works well in both solution and bulk, does not require any stoichiometric additives or complex settings and produces only imidazole as a relatively low-toxicity by-product. As a proof-of-concept using only four diol building-blocks, FPC methodology enabled the synthesis of a unique library of polycarbonates covering (i) rigid, flexible and reactive PC backbones, (ii) molecular weights 5-20 kg mol-1, (iii) dispersities of 1.3-2.9 and (iv) a wide span of glass transition temperatures, from -45 up to 169 °C., QC 20171101

Paper reports the effect of a 10 keV, 110 keV and 10 MeV electron beam irradiation on optical and luminescence properties of LiBaAlF6 (LBAF) single crystals at 10, 90, and 293 K. Five absorption bands at 2.0, 3.2, 4.3, 4.9 and 5.5 eV were revealed in irradiated crystals in the energy range of 1.2–9.5 eV. Several PL emission bands (1.7–1.8, 2.2 and 2.5–3.5 eV) related to defects were found in the luminescence spectra at room temperature, while only one luminescence band at E = 2.2 eV appears at T = 90 K in LBAF crystals after a 10 MeV electron bombardment. The PL excitation spectra and time-response for these emission bands were studied at 10, 90, and 293 K. Thermoluminescence (TL) of irradiated crystals was studied in the temperature range of 90–740 K. New TL glow peaks at 166, 530 and 670 K were revealed and their parameters were determined. Temperature dependence of relative photoluminescence yield recorded monitoring emission at the 1.87 and 2.23 eV in the temperature range from 130 to 450 K, were fitted using five quenching processes related to TL glow peaks revealed in our research. Significant similarity in the manifestation of radiation-induced defects for LBAF and previously studied LiBaF3 single crystals is noted. The effect of an electron beam irradiation on optical and luminescence properties of LBAF single crystals and possible origin of the radiation defects were discussed. © 2017 Elsevier B.V.

Focuses on the application of membrane technologies in removing toxic metals\metalloids from water. Particular attention is devoted to the removal of arsenic, uranium, and fluoride. These compounds are all existing in the earth's crust at levels between two and five thousands micrograms per kg (parts per million) on average and these compounds can be considered highly toxic to humans, who are exposed to them primarily from air, food and water. In order to comply with the new maximum contaminant level, numerous studies have been undertaken to improve established treatments or to develop novel treatment technologies for removing toxic metals from contaminated surface and groundwater. Among the technologies available, applicable for water treatment, membrane technology has been identified as a promising technology to remove such toxic metals from water. The book describes both pressure driven (traditional processes, such as Nanofiltration, Reverse Osmosis, Ultrafiltration,etc) and more advanced membrane processes (such as forward osmosis, membrane distillation, and membrane bio-reactors) employed in the application of interest. Key aspect of this book is to provide information on both the basics of membrane technologies and on the results depending on the type of technology employed., QC 20211011

LaF3/SrF2 multilayer heterostructures with thicknesses of individual layers in the range 5-100 nm have been grown on MgO(100) substrates using molecular beam epitaxy. The longitudinal conductivity of the films has been measured using impedance spectroscopy in the frequency range 10-1-106 Hz and a temperature range 300-570 K. The ionic DC conductivities have been determined from Nyquist impedance diagrams and activation energies from the Arrhenius- Frenkel equation. An increase of the DC conductivity has been observed to accompany decreased layer thickness for various thicknesses as small as 25 nm. The greatest conductivity has been shown for a multilayer heterostructure having thicknesses of 25 nm per layer. The structure has a conductivity two orders of magnitude greater than pure LaF3 bulk material. The increasing conductivity can be understood as a redistribution of charge carriers through the interface due to differing chemical potentials of the materials, by strong lattice-constant mismatch, and/or by formation of a solid La1-xSrxF3-x solution at the interface during the growth process. © 2016 The Author(s).

LaF3/SrF2 multilayer heterostructures with thicknesses of individual layers in the range 5-100 nm have been grown on MgO(100) substrates using molecular beam epitaxy. The longitudinal conductivity of the films has been measured using impedance spectroscopy in the frequency range 10-1-106 Hz and a temperature range 300-570 K. The ionic DC conductivities have been determined from Nyquist impedance diagrams and activation energies from the Arrhenius- Frenkel equation. An increase of the DC conductivity has been observed to accompany decreased layer thickness for various thicknesses as small as 25 nm. The greatest conductivity has been shown for a multilayer heterostructure having thicknesses of 25 nm per layer. The structure has a conductivity two orders of magnitude greater than pure LaF3 bulk material. The increasing conductivity can be understood as a redistribution of charge carriers through the interface due to differing chemical potentials of the materials, by strong lattice-constant mismatch, and/or by formation of a solid La1-xSrxF3-x solution at the interface during the growth process. © 2016 The Author(s).

This dissertation discusses the nonlinear optical properties and influence of molecular environment on the optical properties of several novel organic compounds developed by collaborators in chemistry. When z-scan technique is adopted to determine the nonlinear absorptive and refractive coefficient, femtosecond pulses with a 1 kHz repetition rate are more suitable as the incident source than the 76 MHz ones, as the latter would introduce a significant thermal effect. Performing the open aperture z-scan under several irradiances and estimating the two-photon absorption (2PA) coefficients from fitting would help to avoid the exaggeration of 2PA cross-sections due to other nonlinear effects such as excited state absorption, resulting in 2PA cross-sections estimated consistent with and comparable to other literature. The organic fluorophores investigated for nonlinear optical properties all have donor-π-acceptor structure motifs, whose lowest-energy 2PA bands are identical to those in one-photon absorption. The molecular 2PA cross-sections of these fluorophores are 50-250GM, increasing with the addition of donor/acceptor moieties, and influenced by alternation of donor/acceptor groups. For these fluorophores studied, the molecular environment, such as whether the fluorophores are dispersed or aggregated, what solvent is used, and the formation of crystals, can all influence optical properties, in aspects like absorption and emission spectra, fluorescence quantum efficiencies and lifetimes, as well as nonlinear optical properties. The aggregation enhancement in two-photon excited fluorescence can reach around two-orders of magnitudes. The 2PA cross-sections studied can be enhanced by the formation of aggregations, slightly influenced by solvent polarity, and reduced by the formation of a twisted intramolecular charge-transfer state for dipolar molecules with large charge separation. The changes in molecular conformations and molecular stacking modes in crystal polymorphs

We theoretically demonstrate a novel approach for generating Mid-InfraRed SuperContinuum (MIR SC) by using concatenated fluoride and chalcogenide glass fibers pumped with a standard pulsed Thulium (Tm) laser (TFWHM=3.5ps, P0=20kW, νR=30MHz, and Pavg=2W). The fluoride fiber SC is generated in 10m of ZBLAN spanning the 0.9–4.1μm SC at the −30dB level. The ZBLAN fiber SC is then coupled into 10cm of As2Se3 chalcogenide Microstructured Optical Fiber (MOF) designed to have a zero-dispersion wavelength (λZDW) significantly below the 4.1μm InfraRed (IR) edge of the ZBLAN fiber SC, here 3.55μm. This allows the MIR solitons in the ZBLAN fiber SC to couple into anomalous dispersion in the chalcogenide fiber and further redshift out to the fiber loss edge at around 9μm. The final 0.9–9μm SC covers over 3 octaves in the MIR with around 15mW of power converted into the 6–9μm range.

Efficient light absorption, for which the absorbing substrate should be designed in such a way that it provides as large a specific surface area as possible and good light trapping effect, is a critical point for photovoltaic devices. 3D structures could greatly increase specific surface area and help light absorption. AAO is a low-cost and easily accessible template to build ordered 3D structures, which is undergoing fast development. Many 3D substrates, such as metal nanospike arrays and organic polymer 3D structures, have been fabricated by AAO template-assisted method in recent years for different kinds of applications. However, compared to mostly used commercial FTO planar substrates, those 3D-structured substrates are generally unstable in strong base, acid or high temperature environments. With the growing shortage of fossil fuels, batteries, fuel cells and many kinds of solar-energy conversion devices have emerged as a class of more and more important technologies that increasingly rely on electrodes derived from nanoparticles. Among them, PEC cells have been experiencing fast developments. PEC cells offer the ability to convert the energy from our largest renewable source, the Sun, to stored chemical energy through the splitting of water into molecular oxygen and hydrogen. Among many commonly used PEC active materials, hematite (α-Fe2O3) has emerged as a promising photo-electrode material due to its significant light absorption, chemical stability in aqueous environments, and earth abundance. However, up to now, most of the hematite photoanodes were constructed on plane FTO substrate, which provided limited specific surface area and light absorption. In this study, we have designed and fabricated 3D hexagonal ordered FTO nanocone array on glass substrate by using AAO template assisted method. Compared with planar FTO substrates, the 3D FTO substrate has greatly enlarged specific surface area and light trapping effect, which results in

The oxygen tracer diffusion coefficient, Db∗, and the oxygen tracer surface exchange coefficient, k, were measured in Ba0.5Sr0.5Co0.8Fe0.2O3 - δ (BSCF5582) over the temperature range of 310-800 °C and the oxygen partial pressure range of 1.3 × 10- 3-0.21 bar. Several measurement techniques were used: isotope exchange followed by depth profiling (IEDP) within individual single grains or line scanning (IELS) along the sample cross-section and gas-phase analysis (GPA). Surface exchange kinetics was initially found to be slow and presumably inhibited by the formation of a passivating layer on the sample surface. High temperature pre-anneals (900-950 °C) changed the nature of this layer and enhanced surface exchange. Fast bulk oxygen diffusion and surface exchange kinetics were observed after high temperature pre-anneals within the temperature range studied. The activation energies for 18O tracer diffusion and surface exchange at 0.21 bar were 0.72 ± 0.05 and 1.10 ± 0.15 eV, respectively. The tracer diffusion coefficient showed weak dependence upon oxygen partial pressure, whereas the surface exchange coefficient exhibited strong oxygen partial pressure dependence. The microstructure of the samples (the porosity and grain size) had a profound effect on the measured tracer diffusion coefficient. © 2014 Elsevier B.V.

Owing to the intermittent output of renewable energies, better energy storage systems are in pressing need. Among various technologies, lithium-ion batteries outstand for their high energy density and long life. Nevertheless, their capacity is still limited for large-scale applications, and new materials with much improved performance are to be developed. Lithium iron fluorosulfate (LiFeSO4F) is a novel cathode material and also a strong contender for next generation lithium-ion batteries. However, the inconsistency in synthesizing high-performance LiFeSO4F hinders its fundamental research. In the present study, two experimental protocols concerning the ionothermal and solvothermal methods have been developed. Impacts of precursor morphology, reaction temperature, and reaction time on the phase purity and electrochemical performance of resultant LiFeSO4F have been assessed. In addition, an undesired spinodal decomposition of LiFeSO4F in high humidity has been addressed for the stability concern of the material. Detailed experiments revealed that precursor size played a determining role in synthesizing LiFeSO4F with good phase purity. Specifically, owing to the low solubility of LiF in organic solvents, submicron-sized LiF powders were prepared by a precipitation reaction. LiFeSO4F powders were successfully synthesized at 305˚C for 24 hours in ionic liquid, or at 230˚C for 60 hours in tetraethylene glycol. Succeeding characterizations confirmed the crystallinity and phase purity. The electrochemical performance was assessed in both coin cell and swagelok cell configurations. Using a current density of C/20, the best sample delivered a reversible discharge capacity of 100 mAh g-1 in coin cells, and 128 mAh g-1 in swagelok cells. The significant difference was attributed to the superior configuration of swagelok cells, where electronically insulating binder was not employed. Moreove

Owing to the intermittent output of renewable energies, better energy storage systems are in pressing need. Among various technologies, lithium-ion batteries outstand for their high energy density and long life. Nevertheless, their capacity is still limited for large-scale applications, and new materials with much improved performance are to be developed. Lithium iron fluorosulfate (LiFeSO4F) is a novel cathode material and also a strong contender for next generation lithium-ion batteries. However, the inconsistency in synthesizing high-performance LiFeSO4F hinders its fundamental research. In the present study, two experimental protocols concerning the ionothermal and solvothermal methods have been developed. Impacts of precursor morphology, reaction temperature, and reaction time on the phase purity and electrochemical performance of resultant LiFeSO4F have been assessed. In addition, an undesired spinodal decomposition of LiFeSO4F in high humidity has been addressed for the stability concern of the material. Detailed experiments revealed that precursor size played a determining role in synthesizing LiFeSO4F with good phase purity. Specifically, owing to the low solubility of LiF in organic solvents, submicron-sized LiF powders were prepared by a precipitation reaction. LiFeSO4F powders were successfully synthesized at 305˚C for 24 hours in ionic liquid, or at 230˚C for 60 hours in tetraethylene glycol. Succeeding characterizations confirmed the crystallinity and phase purity. The electrochemical performance was assessed in both coin cell and swagelok cell configurations. Using a current density of C/20, the best sample delivered a reversible discharge capacity of 100 mAh g-1 in coin cells, and 128 mAh g-1 in swagelok cells. The significant difference was attributed to the superior configuration of swagelok cells, where electronically insulating binder was not employed. Moreove

Owing to the intermittent output of renewable energies, better energy storage systems are in pressing need. Among various technologies, lithium-ion batteries outstand for their high energy density and long life. Nevertheless, their capacity is still limited for large-scale applications, and new materials with much improved performance are to be developed. Lithium iron fluorosulfate (LiFeSO4F) is a novel cathode material and also a strong contender for next generation lithium-ion batteries. However, the inconsistency in synthesizing high-performance LiFeSO4F hinders its fundamental research. In the present study, two experimental protocols concerning the ionothermal and solvothermal methods have been developed. Impacts of precursor morphology, reaction temperature, and reaction time on the phase purity and electrochemical performance of resultant LiFeSO4F have been assessed. In addition, an undesired spinodal decomposition of LiFeSO4F in high humidity has been addressed for the stability concern of the material. Detailed experiments revealed that precursor size played a determining role in synthesizing LiFeSO4F with good phase purity. Specifically, owing to the low solubility of LiF in organic solvents, submicron-sized LiF powders were prepared by a precipitation reaction. LiFeSO4F powders were successfully synthesized at 305˚C for 24 hours in ionic liquid, or at 230˚C for 60 hours in tetraethylene glycol. Succeeding characterizations confirmed the crystallinity and phase purity. The electrochemical performance was assessed in both coin cell and swagelok cell configurations. Using a current density of C/20, the best sample delivered a reversible discharge capacity of 100 mAh g-1 in coin cells, and 128 mAh g-1 in swagelok cells. The significant difference was attributed to the superior configuration of swagelok cells, where electronically insulating binder was not employed. Moreove