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Liquid fueled molten salt reactors (MSRs) have seen renewed interest because of their inherent safety features, higher thermal efficiency and potential for efficient thorium utilisation for power generation. Thorium fluoride is one of the salts used in liquid fueled MSRs employing Th–U cycle. In the present study, ThF4 was prepared by hydro-fluorination of ThO2 using anhydrous HF gas. Process parameters viz. bed depth, hydrofluorination time and hydrofluorination temperature, were optimized for the preparation of ThF4 in a static bed reactor setup. The products were characterized with X-Ray diffraction and experimental conditions for complete conversion to ThF4 were established which also corroborated with the yield values. Hydrofluorination of ThO2 at 450 °C for half an hour at a bed depth of 6 mm gave the best result, with a yield of about 99.36% ThF4. No unconverted oxide or any other impurity was observed. Rietveld refinement was performed on the XRD data of this ThF4, and Chi2 value of 3.54 indicated good agreement between observed and calculated profiles.

The present work reports the results of structural investigations on strontium titanate (STO), synthesized by two different methods, by time-differential perturbed angular correlation (TDPAC) technique and X-ray diffraction (XRD) technique. STO was synthesized by two different methods: gel-combustion and in-gelation (also known as internal gelation) method and the samples were doped with 181Hf as TDPAC probe to study local structure at cationic sites of Titanium. The XRD analysis of sample synthesized by gel-combustion method (hereafter referred to as STO-GC) was found to be pure STO phase whereas that synthesized by in-gelation method (hereafter referred to as STO-IG) was found to have titania (19.9% w/w) as impurity phase. TDPAC spectroscopy was found to be very sensitive method for revealing the presence of miniscule amount of rutile phase of TiO2 in STO-GC, which was difficult to detect by conventional XRD. TDPAC study on STO-IG showed the presence of only rutile TiO2 phase, which indicated preferential doping of TDPAC probe (181Hf) at Ti-site of rutile TiO2 than Ti-site of STO. Probable route of formation of rutile phase in STO obtained from in-gelation method has been discussed.

While destruction associated with floods during the monsoon season and cyclones receives wide attention, the extreme weather in the form of hail, lightning and high winds have also caused widespread devastation over India on a small spatial scale in recent years, especially during the period of March to June. India Meteorological Department (IMD) organized a special forecast improvement campaign during the period March to June of 2017–2019 when the weather forecasts at all offices of IMD were targeted towards an accurate forecast of the extreme form of thunderstorms and their associated impact in short range to nowcasting timescale and their dissemination. The purpose of this study is to quantify the improvement in operational thunderstorm forecast accuracy, in short range (24 h Severe Weather Guidance at subdivisional level) and nowcast scale (nowcasts for individual stations valid for 3 h and issued every three hours) during March to June of 2017 to 2019 and compare the same with the accuracy of previous years. As a result of these efforts, there has been a significant jump in forecast accuracy in the 24-h thunderstorm forecast as well as 3-h nowcast guidance for thunderstorms across the country. Probability of Detection (POD) scores for India as a whole for the 24-h thunderstorm forecast has doubled, while the false alarms (FAR) have remained at the same level as before the start of the forecast campaign. The results indicate that since a thunderstorm is a disastrous weather event, the forecasters generally tend towards spatial over-forecasting. However, this is not uniform across the months. There is systematic lower accuracy in the season transition months of March (winter to summer) and June (dry summer to wet summer). While POD decreases in both March and June, FAR decrease throughout the season. The significant evolution of atmospheric parameters (moisture in particular) as the season changes, favours the maturation of thunderstorms to cumulonimbus stage as the season progresses, and the problem of over forecasting in March becomes a problem of under forecasting of thunderstorms in June. Another reason for false alarms is the unconscious linkage of the thunderstorm with the pattern of rainfall occurrence. However, since all rain-giving clouds over India do not necessarily mature to the cumulonimbus stage, and vice versa, the two are not always related. This is particularly true for the more arid regions of the country, especially in March, where false alarms are higher. The poor density of reporting observatories compared to the mesoscale nature of the events may also increase false alarms, especially over the small maritime islands and the arid regions of the mainland. The accuracy of the All India 3 hourly station level nowcast also improved systematically since 2017. Despite these constraints, the improvements at all scales were possible due to (a) augmentation of observation network by the rapid expansion of Doppler radars network throughout the Indian mainland as well as the installation of a ground-based lightning detection network, (b) numerical modeling products introduced in 2019 to provide short-range forecasts for all aspects of convection; both of which are incorporated into the forecast framework through Standard Operating Procedures (SOP) to standardize the forecast procedure throughout the Indian region. A more objective forecast strategy, using data generated from a denser network of DWRs and crowdsourcing methods as well as more accurate mesoscale models will go a long way to further improve the thunderstorm forecasts.

Background: Synthesis of nano composite materials is very important topic in recent times for its wide application as a catalyst in various chemical processes. Among various nano composite platinum-mutliwall Carbone Nano Tubes is of particular interest in recent past due to its unique application in methanol fuel cell as a catalyst. Now the challenge is to make a chemical process for definite size and shape selective platinum-mutliwall Carbone Nano Tubes catalyst/composite with well distribution and easy scale up. Methods: The aim of the present work is to develop a chemical process for synthesis of platinum- Mutliwall Carbone Nano Tubes nano catalyst/composite with very low size (1-3nm) using reduction of Pt4+ and subsequently deposition to the Mutliwall Carbone Nano Tubes surface using ultrasound technique. Results: The platinum nano materials synthesized in trioctylmethyl ammonium hydrogen phthalate is characterized using TEM technique. The results show that the particle size of platinum nano are in the range of 1-3 nm. The platinum-mutliwall Carbone Nano Tubes catalyst/composite prepared using ultrasound technique does not change the particle size of the platinum nano particles. The distribution of platinum nano on Functionalized Mutliwall Carbone Nano Tubes surface is uniform compared to Non-functionalized Mutliwall Carbone Nano Tubes. Conclusion: The preparation of platinum-mutliwall Carbone Nano Tubes nano composite with very low size of platinum (1-3nm) is achieved in trioctylmethyl ammonium hydrogen phthalate as functionalized ionic liquid in presence of ultrasound.

The limited ionic conductivity of polymer electrolytes is a major issue for their industrial application. Enhancement of ionic conductivity in the poly(ethylene oxide), PEO, based electrolyte has been achieved by loading passive nanofillers such as SiO2 nanoparticles (NPs). To investigate the role of modifications in free volume characteristics and the polymer chain dynamics induced by the loading of passive fillers on the ionic conductivity of the PEO based ternary electrolyte, a systematic investigation has been carried out using positron annihilation and broadband dielectric spectroscopy. As a result of interfacial interactions, the loading of SiO2 NPs alters the semi-crystalline morphology of PEO resulting in a higher crystallinity at lower loadings due to the surface confinement of PEO chains, and the formation of smaller PEO crystallites at higher loadings due to interparticle nanoconfinement. These modifications are accompanied by a decrease in free volume fraction at the lowest loading (0.5 wt%) followed by an increase at higher loadings (≥2.0 wt%). The Almond–West formalism considering two different universalities in different temperature and frequency ranges has been used to explain the ion-conduction process at different NP loadings. The Li ion conductivity is observed to be maximum for a 5.0 wt% loading of SiO2 NPs. The enhancement in ionic conductivity is observed to be directly correlated with the free volume characteristics and segmental dynamics of the PEO matrix, confirming their role in ion transport in polymer electrolytes.

The glass–ceramic form of phosphor materials can overcome the many serious issues of phosphor/silicone composite in commercial phosphor-converted LEDs and are considered as new-generation color converters. In this report, we have shown a novel approach of developing inorganic red phosphor [Eu3+:La2(MoO4)3] in the glass–ceramic form based on lanthanum molybdate system. The ceramic form of the compound was found to have a glass transition temperature of 1002 °C, as confirmed by TGA and DSC studies. Further, XRD, FTIR and Raman studies also confirmed that the compounds prepared at 1050 °C are in glass–ceramic form, while those prepared at 750 °C are in ceramic form. Photoluminescence studies showed that both the ceramic and glass–ceramic forms of the phosphor are red color-emitting materials. However, the glass–ceramic forms have better color purity and more radiation transition probabilities. Further, the decay kinetics of both ceramic and glass–ceramic forms confirmed that only those Eu3+ ions which exist in the grain boundaries of the ceramics go inside the glass network structure upon heating the compound at or above the glass transition temperature. On the other hand, Eu3+ ions which exist at the La-site in the bulk of the particles are retained in the ceramic form in the glass–ceramic mixture.

Pr6UO12(s) and Er6UO12(s) were synthesized by the citrate nitrate gel combustion method. The synthesis conditions were optimized by characterising the precursors of these uranates heated in the temperature range from 973 to 1473 K using X-ray diffraction analysis and thermo-gravimetric techniques. The solid-state oxide ion conducting galvanic cells were constructed to determine the standard molar Gibbs energy of formation of Pr6UO12(s) and Er6UO12(s) from the measured e.m.f.s in the temperature range of 904–1237 K. The standard molar enthalpy of formation and standard entropies at 298.15 K for RE6UO12(s) (RE = Pr and Er) were derived from the measured Gibbs energy and required data from the literature, using second and third law analysis. The calculated ΔfHom(Pr6UO12,s,298.15 K) and ΔfHom(Er6UO12,s,298.15 K) were −6669 and −6951 kJ mol−1, respectively. The standard entropy values of Pr6UO12(s) and Er6UO12(s) were calculated as 561 and 563 J mol−1 K−1, respectively. A similar trend was observed in ΔfHom(RE6UO12,s,T) and Som(RE6UO12,s,298.15 K) to that of RE2O3 along the rare earth series. The oxygen potential and ternary phase diagrams of the Pr–U–O and Er–U–O systems were calculated using the Gibbs energy data measured in this study.

A study on the crystal structure of monoclinic HfO2 has been performed using synchrotron X-ray and neutron diffraction data separately, as well as a combination of both. The precision of the structural parameters increases significantly due to application of the neutron diffraction technique. The experimental oxygen positions in HfO2, derived precisely, are visualized only by semi-local density functional calculations in terms of the calculated electronic band gap, but are not captured as accurately by using hybrid functionals.

In this paper, recovery of uranium from carbonate ore leach solution has been reported using a novel precipitation method. The method is based on the precipitation of uranium as yellow color magnesium diuranate (MDU) using MgO/NaOH mixture. The process has been finalized by optimizing various process parameters such as concentration of CO32-, HCO3-, HCl, NaOH, MgO and reaction temperature. The overall recovery of uranium was 97%. The chemical composition of the yellow precipitate (MDU) was evaluated employing XRD technique. A process flow-sheet has been developed for recovery of U(VI) from low concentration carbonate ore leach solution.

The RE 6 UO 12 (s) (RE= La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, Lu) compounds were synthesized by citrate nitrate combustion method and characterized by X-Ray Diffraction (XRD) technique. Standard molar Gibbs energy of formation of RE 6 UO 12 (s) (RE= La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, Lu) was determined from the equilibrium electromotive force (e.m.f) data obtained from solid-state Galvanic cell with oxide ion conducting yttria-stabilized-zirconia (YSZ) electrolyte. The cells were operated under high pure argon atmosphere. E.m.f. measurements were carried out in the temperature range of 850-1150 K. Phase transition in Sm 6 UO 12 (s) and Yb 6 UO 12 (s) were detected at 1125 K and 1065 K, respectively. The transition temperatures were confirmed from high temperature XRD technique. The standard enthalpy of formation and entropy at temperature of 298.15 K for RE 6 UO 12 (s) was calculated from the Gibbs energy data using second and third law analysis and the data were compared with the corresponding data reported for RE 2 O 3 (s). Similar trend in enthalpy as well as entropy was observed for RE 6 UO 12 (s) and RE 2 O 3 (s) along the series of 4f elements.

Reduction−Diffusion (R-D) process has been attempted to synthesize U-Mo alloy powder for the first time, and the mechanism of alloy formation has been investigated. Calciothermic reduction of uranium dioxide in the presence of the alloying element Mo, followed by high temperature soaking; subsequent leaching to remove the calcia slag yields U-Mo alloy in powder form. Experiments were carried out to synthesize U-10 wt%Mo alloy powder. The alloy powder products were characterized by Scanning Electron Microscopy and X-ray Diffraction. Complete stabilization of the metastable isotropic gamma phase has been achieved in U-10 wt%Mo powder synthesized by R-D process, where the final soaking was carried out at 1300 °C and 4 h. Attempts were made to understand the mechanism of formation of U-Mo alloy by R-D process on two fronts, i.e. alloying within a single particle, and particle-to-particle homogenization. The intended application of the alloy powders is in high uranium density dispersion fuels for high flux nuclear research and test reactors.

The public acceptance of clean energy production from nuclear reactors demands the development of innovative methods to minimize and recycle the actinide waste with little or no impact to the environment. Nuclear fuel before it could be qualified has to undergo stringent quality control (QC) measures at various stages of fabrication. Analysis of carbon content in nuclear fuel is one such QC checks which produces refractory alumina crucibles containing plutonium embedded in molten solidified Cu. Development of a method for recovery of plutonium (Pu) from these refractory materials, accumulated over the years, is crucial prior to their disposal. The conventional process of acid leaching, using HF + HNO3 mixture, is time consuming and generates large volume of radioactive acid waste. To eliminate these drawbacks, a simple pre-treatment method of fusion with NaOH was adopted prior to acid leaching for recovery of Pu from these alumina crucibles. A number of small scale experiments were conducted by varying process parameters and fusion temperature of 600 °C and 16 M HNO3 as leachant were found to be optimum for maximum recovery of Pu. The final recovery of 96.5% was arrived by biamperometric analysis of Pu in acid leachate. The efficiency of recovery of Pu was reconfirmed by its gamma spectrometric assay in the residual precipitate. Experiments were also carried out by treating alumina crucible with NaOH in a single step and heating uninterruptedly to check the feasibility of scaling-up the process. The fused product and precipitates obtained during leaching were characterised using X-ray diffraction analysis (XRD).

The glass-ceramic form of phosphor materials can overcome the many serious issues of phosphor/silicone composite in commercial phosphor-converted LEDs and are considered as new-generation color converters. In this report, we have shown a novel approach of developing inorganic red phosphor [Eu

A study on the crystal structure of monoclinic HfO

Refractory plutonium oxide embedded inside molten solidified Cu in an alumina crucible was dissolved in dilute HNO3, after the pre-treatment solid state fusion reaction with (NH4)2SO4. The product obtained in various stages of reaction were characterised by X-ray diffraction analysis. The reaction between PuO2 and (NH4)2SO4 lead to formation of (NH4)2Pu(SO4)3 in the temperature range 350–440 °C. The reaction parameters such as amount of reactants, reaction temperature and isothermal heating time at different steps were optimised to maximise the recovery of plutonium. The efficiency of plutonium dissolution was found to be 98% by modified Drammond and Grant method.

An effort was taken to carry our speciation study of uranium ion in technologically important cerate host Sr2CeO4 using time resolved photoluminescence spectroscopy. Such studies are not relevant only to nuclear industry but can give rich insight into fundamentals of 5f electron chemistry in solid state systems. In this work both undoped and varied amount of uranium doped Sr2CeO4 compound is synthesized using complex polymerization method and is characterized systematically using X-ray diffraction (XRD), Raman spectroscopy, impedance spectroscopy and scanning electron microscopy (SEM). Both XRD and Raman spectroscopy confirmed the formation of pure Sr2CeO4 which has tendency to decompose peritectically to SrCeO3 and SrO at higher temperature. Uranium doping is confirmed by XRD. Uranium exhibits a rich chemistry owing to its variable oxidation state from +3 to +6. Each of them exhibits distinct luminescence properties either due to f-f transitions or ligand to metal charge transfer (LMCT). We have taken Sr2CeO4 as a model host lattice to understand the photophysical characteristics of uranium ion in it. Emission spectroscopy revealed the stabilization of uranium as U (VI) in the form of UO66- (octahedral uranate) in Sr2CeO4. Emission kinetics study reflects that uranate ions are not homogeneously distributed in Sr2CeO4 and it has two different environments due to its stabilization at both Sr2+ as well as Ce4+ site. The lifetime population analysis interestingly pinpointed that majority of uranate ion resided at Ce4+ site. The critical energy-transfer distance between the uranate ion was determined based on which the concentration quenching mechanism was attributed to electric multipolar interaction. These studies are very important in designing Sr2CeO4 based optoelectronic material as well exploring it for actinides studies.

In the present work, the influence of sonication on the reactive precipitation of ammonium uranyl carbonate (AUC) was investigated. Experiments were performed between uranyl nitrate pure solution (UNPS) and ammonium carbonate solution in a stirred vessel with ultrasound horn of 35 KHz. The prepared AUC powder was characterised by laser diffraction particle size analysis, surface area analysis, XRD, SEM, FTIR and Raman Spectroscopy. It was found that ultrasonic irradiation increases the precipitation kinetics and modifies the morphology of the crystals produced. The mean particle size was decreased with the increase in ultrasonic power and powders with more surface area are obtained at higher intensity ultrasound power. SEM study reveals more uniform and regular prismatic crystals of AUC during sonication compared to silent conditions. XRD results also indicate more crystalline powder of AUC in sonochemical mode compared to that prepared by conventional precipitation methods. Thus, the sonochemical technique suggested an improved quality of the precipitate of AUC in terms of physical morphology, surface area, crystallinity and homogeneity amenable for downstream process steps for the fuel preparation methods.

Uranium and cerium doped yttrium titanate pyrochlores Y2-xAxTi2O7±δ (A = U or Ce) were synthesized by gel combustion method. The Rietveld analysis of these pyrochlores showed that due to the large charge heterogeneity, uranium cannot be incorporated to a large extent at the intended A site of the pyrochlore in air atmosphere causing separation into brannerite phase containing yttrium and yttria stabilized UO2+x. Studies also showed that more than 10 mole% U could be accommodated at A site when reducing conditions were used. Unlike uranium, 15 mole% of Ce could be doped at A site as a single phase in air atmosphere. The observations in the crystal chemistry of these pyrochlores were confirmed by XRD, SEM, Raman and XPS. The gamma irradiation of these pyrochlores showed good radiation stability which was confirmed by XRD and PALS. PALS also confirmed uranium doping is preferably taking place at B site in oxidizing conditions. The thermo-physical properties of these pyrochlores were evaluated by HT-XRD and DSC.

Two new deep eutectic solvents, different from hitherto known and based on common choline chloride, were prepared. 1-methyl-3-decylimidazolium bromide mixed with hydrogen bond donors, malonic acid and diglycolic acid to form DES. Dissolution of uranium oxides (UO3 and UO2) was explored in both of them and characterization of the resultant solutions was carried out by IR, TGA and UV–Vis spectroscopy. Redox speciation of dissolved uranium oxides was probed in these redox-active DES through cyclic voltammetry, differential pulse voltammetry and in situ spectroelectrochemical measurements. Interestingly, the formation of uranium oxo species was observed through the dissolution of UO3 in both the DES. The electrochemical characteristics viz. redox thermodynamics (peak potential and formal redox potential), transport property (diffusion coefficient D0), heterogeneous electron transfer kinetic parameters (αn and k0) and mechanistic electron transfer of the dissolved uranium species in two DES were investigated. The speciation of uranium was decoded through the electronic absorption spectra of uranium in its lower oxidation states [U(V) and U(IV)] acquired through in situ spectroelectrochemical electrolysis with varying cathodic potentials. Studies were also carried out using Molecular Dynamics (MD) and density functional theory (DFT) simulations to authenticate the electrochemical outcomes and to acquire the binding energy, optimized structure and molecular orbital diagram of dissolved uranium species. Further, the MD simulation sheds light on the probable equatorial coordinating atoms of dissolved uranium species. This is the first report, to the best of our knowledge, on imidazolium-based DES and actinide ions.

Nuclear energy owing its low cost and being environmentally benign is considered a potential alternative to resolve global issues related to energy requirements and it mostly requires uranium dioxide as fuel. With the ssimilarintention, firstly we synthesized uranium type (IV) deep eutectic solvent (UT4D) employing uranyl nitrate hexahydrate (UNH) and Urea via mechanochemical synthesis which is indeed the first report on actinide deep eutectic solvent (AnDES). The optimum mole fraction for formation of DES was found to be 0.2:0.8 for UNH: Urea respectively which was further confirmed using thermodynamic phase diagram. The formation of DES was confirmed using Fourier Transform Infrared (FTIR) spectroscopy. Various physical properties were also evaluated for UT4D such as melting point, moisture contents, viscosity, and density. Thermal studies suggested that UT4D is stable from −5.2 to 300 °C and there is a strong interaction parameter obtained in the present UT4D which was attributed to hydrogen bonding and the complexation of urea with UNH. Uranium ion was found to exist in U(VI) oxidation state in the form of oxo uranyl ion in UT4D. Electrochemical investigation suggested the stabilization of most unstable U(V) state by virtue of the formation of hydrogen bonded complex of uranium and urea in the DES. Further scanning the potential to more negative direction leads to reduction of U(V) ion to UO2. The optimized electrochemical parameters were further used for the electrosynthesis of UO2 nanoparticles (UDNPs) and thus offer a very green and cost-effective synthesis of UDNPs.

Plutonium recovery is inevitable from plutonium bearing alumina crucibles generated over the years as part of carbon analysis during chemical quality control of nuclear fuels. This is a challenging task owing to the complex nature of matrix. The first stage of methodology development of plutonium recovery involved usage of CeO2 bearing crucibles. Cerium distribution in alumina crucible was investigated by examination of surface morphology. Various aqueous recovery routes were tested initially with CeO2 bearing crucibles and 4 M HF–8 M HNO3–NH4NO3 was found to be most promising (60% recovery). The same route yielded 90% plutonium recovery from alumina crucibles.

Thorium uranium oxide powder with uranium concentrations 10, 20, 30, 40, 50 and 70 mol% was prepared by gel combustion method. The sintering behaviour of the powders studied by dilatometry indicated that samples containing uranium up to 30 mol% had similar shrinkage behaviour with single step sintering. However, samples containing 40, 50 and 70% uranium followed two step sintering process. Though the air calcined powder shows two phase system beyond 30% uranium containing samples, sintering results into single phase system for samples containing up to 50% of uranium. The temperature programmed reduction-oxidation experiments showed that compositions containing up to 50-mol% of uranium show single reducible species throughout the temperature range. X-ray photoelectron spectroscopic studies of these sintered pellets showed presence of uranium in 6 + and 4 + oxidation states in these oxides. The experimentally determined heat capacities of solid solutions were found to have higher values than that of computed using Neumann–Kopp’s molar additivity rule.

Ba 1−x Eu x MoO 4 phosphors were synthesized by complex polymerization method. The prepared phosphor material was extensively characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetry (TG) and differential thermal analysis (DTA). The introduction of europium upto 2 mol% doesn’t change the crystal structure. The influence of Eu concentration on the luminescent properties of phosphors was analyzed. It was seen that, under UV irradiation, the pure BaMoO 4 sample shows multicolor emission. The blue and green emission was attributed to 1 T 2 → 1 A 1 transition within MoO 4 2− moeity (shallow defects), whereas the red- orange emission to the defect MoO 3 group (deep defects). The intensity of magnetic dipole transition (MDT) was found to be lower than that of electric dipole transition (EDT) which indicates the low -⁠ symmetry acentric environment of Eu 3+ ions. Based on Stark splitting, the actual site symmetry of Eu 3+ in BaMoO 4 was clarified as C 6v ; reduced from actual S 4 for Ba 2+ ion in BaMoO 4 . The decay curve shows two different lifetime value 11.2 µs (τ 1 ) (host contribution) and 693 µs (τ 2 ) (europium sitting at Ba 2+ site) with magnitudes 14% and 86% respectively. The value of host dopant energy transfer efficiency calculated under forbidden f-f transition excitation was found to be lower at 12.6% as compared to 76% in case of excitation by allowed charge transfer band. To find out the concentration quenching mechanism, the critical energy-transfer distance for the Eu 3+ ions was evaluated to be 33.81 A, which was found to be greater than 10 A and signify electric multipolar interactions as the only mode of energy transfer The intensity of peaks corresponds to EDT was found to be high in comparison to the peak due to MDT in all the Eu- doped samples: indicating the asymmetric local site symmetry around Eu 3+ . This is also reflected in the JO (Judo Ofelt) parameter trend; at all concentrations, Ω 2 value is greater than Ω 4 indicating the high covalency of the Eu 3+ ligand bonding and asymmetric environment around europium ion in BaMoO 4 , which is highly probable because it occupies the asymmetric Ba 2+ position.

The variation in thermophysical properties along the lanthanide series for RE6UO12(s) was investigated. Structural characterization of Er6UO12(s) was carried out by Rietveld refinement method. The trend in heat capacity along the rare earth series for RE6UO12(s) and RE2O3(s) as function of ionic radius of RE3+ was found to be similar. Hence, the sole cause of excess heat capacity in rare earth uranates was concluded to be the rare earth ion. Linear relation was found between the thermal expansion coefficient of RE6UO12(s) (RE = La, Gd, Lu) and the ionic radii of rare earth ion.

The present paper reports the synthesis, characterization and thermoluminescence (TL) behaviour of Eu3+ doped Gd2O3 phosphor. The sample was prepared by the solid state reaction method, which is the most suitable for large-scale production. The prepared phosphor sample was characterized using powder X-ray diffraction (PXRD), field emission gun scanning electron microscopy (FEGSEM), transmission electron microscopy (TEM) and thermoluminescence (TL) techniques. The calculated average crystal sizes of Eu3+ doped Gd2O3 phosphors are around 66.49 nm and 75.48 nm for 1 mol% Eu3+ and 2.5 mol% Eu3+ concentrations respectively. Thermoluminescence study was carried out for the phosphor with 254 nm UV irradiation. The TL glow curve was found at 116 °C. Computerized glow curve deconvolution (CGCD) was applied on TL response and kinetic parameters were calculated. A general thermoluminescence model is discussed to explain concentration quenching in thermoluminescence behaviour.

The sub-nanoscopic free volume structure of poly vinyl alcohol (PVA) matrix in its composite with nanosized BaTiO 3 (BT loading 0.2, 0.6, 1.0 and 2.0 wt%) is investigated using positron annihilation lifetime spectroscopy (PALS). The lamellar structure of PVA matrix at nm scale is investigated using Small Angle X-ray Scattering (SAXS) technique. The results indicate that the free volume and lamellar structure of PVA matrix is significantly altered even at very low BT loading (0.2 wt%) due to attractive interfacial interaction. The variations observed in the free volume characteristics are consistent with the existing theory of polymer-nanocomposites i.e. at low filler loading, the polymer-nanocomposites’ dynamics is polymer like with increased friction and a constrained interphase is created around the filler particles. The SAXS results supplemented by differential scanning calorimetry measurements show that the crystallization in PVA is altered due to physical restriction imposed by BT particles on PVA chains. These results are supported by the crystallinity measurements using X-ray diffraction technique.

Molar heat capacities of two hydride ion conductors, namely, CaHCl and CaHBr, were measured by differential scanning calorimetry. The measured molar heat capacity data of these compounds as a function of temperature is given by the following expressions: From the above expressions, molar enthalpy increments, entropies and Gibbs energy functions of these compounds were derived and reported. SYNOPSIS CaHCl and CaHBr are hydride ion conducting solid electrolytes find application in electrochemical hydrogen meter to determine dissolved hydrogen concentration in liquid sodium. Heat capacity of CaHCl and CaHBr were measured using DSC and reported.

The present paper, for the first time, reports the application of Ba2TiSi2O8 (BTS) for management of trivalent actinides present in radioactive waste. BTS was synthesized and thoroughly characterized. Uptake of Cm(III) by BTS in pH range 2.5–8.0 has been studied by batch sorption experiments using 244Cm as a tracer. The distribution coefficient K d of Cm(III) by BTS increased with pH reaching saturation value to nearly 60,000 mL/g. The stability of BTS in aqueous solution was evaluated in terms of lattice and hydration energy. The studies suggest that BTS can serve as a potential sorbing media for radioactive waste management.

In order to mimic co-loading of Pu and Am in zirconia, Nd 0.20 [Zr 1−x Ce x ] 0.80 O 1.90 (0.0 ≤ x ≤ 1.0) system was synthesized and thoroughly characterized by X-ray diffraction (XRD) and Raman spectroscopy. The entire system was found to be single-phasic fluorite-type and most interesting result is stabilization of multi-phasic ceria-zirconia system in a single-phasic system by substituting Nd 3+ . Raman spectroscopy revealed entirely different nature of defects prevalent in the solid solutions possessing F-type structure across the composition range. The heat capacity of representative compositions was measured by heat flux-type differential scanning calorimeter. Specific heat capacity of the solid solutions was found to increase with decreasing CeO 2 content. Different thermodynamic functions such as enthalpy increment, entropy and Gibbs energy functions were determined using heat capacity values. The lattice thermal expansion (298–1273 K) behaviour of the few selected compositions revealed a gradual increase in thermal expansion coefficient with increasing CeO 2 content.

The complexation behavior of ligating groups bearing ethylene glycol methacrylate phosphate (EGMP) units spaced in the polymer chain was studied to understand the coordination ability of segregated EGMP toward UO22+ and Pu4+ ions. The EGMP units in the polymer chain were copolymerized with a varying mol proportion of spacer monomer N-isopropylacylamide (NIPA) and methyl methacrylate (MMA) along with a cross-linker. These copolymer gels were characterized by FTIR, SEM/EDS, and thermal analysis. It was observed that the copolymer gels had homogeneity and concentration of phosphate groups systematically decreased with an increase in mol proportion of spacer monomer units. The hydrophlicity of (EGMP-co-MMA) copolymer gels decreased with an increase in mol proportion of MMA units whereas hydrophilicty of EGMP-co-NIPA copolymer increased with an increase in mol proportion of NIPA units in the copolymer gels. It was observed that UO22+ ions sorption decreased with an increase in MMA units in the polymer chain at...

RE6UO12(s) (RE = La, Pr, Nd, Sm) was synthesized by citrate-nitrate combustion method. The synthesis condition for Pr6UO12(s) was optimized. Nonstoichiometry in these rare earth uranates in argon atmosphere was analysed using various techniques like thermogravimetry (TG), X-ray photo electron spectroscopy (XPS), chemical analysis and electrical conductivity measurements. Thermal expansions of RE6UO12(s) (RE = Pr and Sm) was studied in the temperature range 298–1273 K by high temperature X-ray powder diffractometry and compared with that of similar rare earth compounds reported in the literature. Heat capacity of RE6UO12(s) (RE = La, Pr, Nd, Sm) was measured by differential scanning calorimetry in the temperature range 300–870 K. Enthalpy, entropy and Gibbs energy functions of these compounds were computed from the measured heat capacity data.

The present paper reports the Photoluminescence (PL) spectra of Erbium and lithium doped Gd 2 O 3 phosphor. Gd 2 O 3 :Er 3+ /Li + Phosphor was synthesized by combustion synthesis method. The Phosphor was characterized by using X-ray diffractometer (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), and photoluminescence emission spectra. Sample was characterized by XRD analysis and particle size was calculated by Debye–Scherrer formula The XRD patterns reveal that prepared Gd 2 O 3 :Er 3+ /Li + phosphor have monoclinic crystal structure and particle size of 11 nm. The photoluminescence emission spectrum was monitored at 976 nm excitation and the corresponding emission peaks at blue, green and red emissions are reported. The emission spectra was monitored as a function of Li + ion concentration.

A monoclinic Gd2O3:Yb3+ phosphor was prepared using the combustion synthesis method. This study is mainly centered on the thermoluminescence behaviour of this monoclinic Gd2O3:Yb3+ phosphor. TL glow curves were recorded for two different irradiations, UV and gamma irradiation. The effect of annealing temperature, irradiation dose and Yb3+ concentration on thermoluminescence behaviour is studied. Computerized glow curve deconvolution (CGCD) was applied using the peak fit method on the TL glow curve for optimized conditions. Kinetic parameters were calculated for the optimized TL glow curve as well as for the deconvoluted glow curve. The activation energy calculated for the gamma irradiated samples is greater than the UV irradiated samples, which is due to the deeper traps formed by gamma irradiation.

Er3+ doped Gd2O3 phosphors were prepared via solution combustion synthesis method. Structural characterization and the luminescence behaviour of the prepared phosphors were determined and compared. The average crystal size for the phosphors yielded was in the nanometre range, which was calculated using XRD and confirmed by SEM and TEM techniques. Compositional analysis was carried out using FTIR. Qualitative and quantitative information regarding the powder sample were measured using EDX spectroscopy. The EDX and FT-IR spectra confirm the Er3+ element was present in the Gd2O3:Er3+ phosphors. For the photoluminescence studies the emission spectra were recorded under excitation at 275 nm. All the phosphors give emission peaks in the visible region. The effect of annealing and the Er3+ concentration on the emission spectra was studied for the prepared phosphors. The specific colours produced by the prepared phosphors were determined using the CIE chromaticity technique. The emitted coloured was tuned by determining the CIE coordinates for different concentrations of Er3+.

The free volume characteristics (free volume size, density and size distribution) of the interfacial layer (IL) in PMMA–alumina (0.3 wt%) nanocomposites were investigated using the well-established positron annihilation lifetime spectroscopy (PALS) technique. Differential scanning calorimetry (DSC) measurements were carried out to investigate the glass transition process of the PMMA matrix in these nanocomposites. PALS results show significant variations in the free volume structure of the nanocomposite, contrary to the assumptions made in earlier reports, i.e., free volume in PMMA remains unaffected on alumina loading. The study shows that as a result of strong interfacial interaction between PMMA and alumina, a denser region is created in the vicinity of alumina particles (interfacial layer), having smaller-sized nanoholes with narrower size distribution compared to bulk PMMA. This observation is consistent with the studies wherein an interfacial layer with constrained segmental motion was inferred from spectroscopic and thermal analysis techniques. The glass transition temperature, Tg, determined from DSC is observed to vary with alumina loading qualitatively similar to the variation in the fractional free volume of PMMA. The study indicates that the critical free volume for PMMA to undergo glass transition process depends on the interfacial layer fraction and hence varies as a function of alumina loading.

Monoclinic and cubic Gd2O3 phosphors were prepared by using two different methods solution combustion synthesis and solid state reaction method. The present paper deals with comparison of specific color emitted by the pure Gd2O3 phosphors prepared by combustion synthesis and solid state reaction methods. The Commission International de I'Eclairage (CIE) coordinates for combustion synthesized Gd2O3 phosphor and for the solid state synthesized Gd2O3 phosphor X = 0.207 and Y = 0.206, and X = 0.29 and Y = 0.29 respectively.

Ba 1− x Sr x MoO 3 (s) ( x = 0, 0.2, 0.4, 0.5, 0.8, 1) solid-solutions were synthesized by reduction of corresponding Ba 1− x Sr x MoO 4 (s) and were characterized using X-ray diffraction (XRD). Thermal expansion behavior of Ba 1− x Sr x MoO 3 (s) ( x = 0, 0.4, 0.8 and 1) were investigated in the temperature range 298–873 K by high temperature X-ray diffraction (HTXRD). The average volume thermal expansion coefficient of Ba 1− x Sr x MoO 3 (s) ( x = 0, 0.4, 0.8 and 1) was found to be 2.83 × 10 −5 , 2.20 × 10 −5 , 2.02 × 10 −5 and 2.27 × 10 −5 K −1 , respectively. Heat capacity of Ba 1− x Sr x MoO 3 (s) ( x = 0, 0.4, 0.8, 1) was measured with a heat flux-type differential scanning calorimeter (DSC) in the temperature range 290–870 K. The specific heat of Ba 1− x Sr x MoO 3 (s) was found to increase with increase in concentration of strontium. The thermodynamic functions such as enthalpy increment, entropy and Gibbs energy functions of Ba 1− x Sr x MoO 3 (s) were also calculated.

Nanocrystalline BaMoO 4 samples doped with varying Dy 3+ content were prepared by acrylamide assisted sol–gel combustion process. The prepared samples were characterized by X-ray diffraction (XRD), Fourier transform Raman spectroscopy (FT-Raman), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and photoluminescence (PL) techniques. The crystalline phase and structure of all the Dy 3+ doped BaMoO 4 prepared samples were confirmed from the analysis of the obtained results of XRD, FT-Raman and FTIR. The average crystallite sizes of all the prepared samples, calculated using Scherrer׳s formula and XRD data, were found to be less than 100 nm. Microstructures of all the prepared Dy 3+ doped BaMoO 4 samples were analyzed from the obtained SEM micrographs. Excitation, emission and lifetime spectroscopic studies of undoped and Dy 3+ doped BaMoO 4 were carried out. Effect of concentration of Dy 3+ on the luminescence properties of the prepared phosphors viz. emission intensity and PL decay, was also investigated. Based on critical distance calculation, mechanism for concentration quenching was proposed. Undoped sample was found to give reddish blue emission, whereas doped samples showed yellowish white emission.

LaPO4 nanoparticles were synthesized using complex polymerization method and characterized systematically using X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. Varied concentration of europium ion is doped in the LaPO4 lattice and optical properties and Judd–Ofelt analysis were investigated. It is observed that LaPO4 nanoparticles give violet–blue emission when irradiated with UV light. On doping europium ion the band gap of LaPO4 decreases. Based on DFT calculations it is proposed that energy range over which d and f states of Eu are distributed is coincident with the valence band of LaPO4 so causing an efficient energy transfer from LaPO4 to europium ion. The actual site symmetry for europium ion in lanthanum orthophosphate was also evaluated as D2d based on the Stark splitting pattern although it is C1 for La3+ in LaPO4. The critical energy-transfer distance for the Eu3+ ions was evaluated, based on which the quenching mechanism was verified to be an electric multipolar interaction. It is also observed that the red emission intensity of LaPO4:Eu3+ (2.0 mol%) is almost 85% of a commercial red phosphor, which clearly demonstrates that the as-prepared samples are promising red phosphors under near-UV for use in white-light emitting diodes.

Undoped and europium doped CaMoO4 and SrMoO4 scheelites are synthesized using a complex polymerization method. The phase purity of the sample is confirmed using powder X-ray diffraction (PXRD). X-ray photoelectron spectroscopy (XPS) was carried out to confirm the oxidation states of various constituents and dopant elements and also the presence of oxygen vacancies. Interestingly both CaMoO4 and SrMoO4 on irradiation with UV light give blue and green emission respectively. On europium doping, it was found that molybdate to Eu(3+) ion energy transfer is more efficient in SrMoO4:Eu compared to CaMoO4:Eu. It is also justified using a luminescence lifetime study which shows biexponential decay in the case of CaMoO4:Eu corresponding to both the host and europium ion; whereas a single lifetime is observed in the case of SrMoO4:Eu. Anomalies in host-dopant energy transfer are suitably explained using density functional theory (DFT) calculations and XPS. The actual site symmetry for the europium ion in CaMoO4 and SrMoO4 was also evaluated based on a Stark splitting pattern which turns out to be D2 and C2v respectively although it is S4 for Ca/Ba(2+) in AMoO4. This is also reflected in higher Ω2 values for SrMoO4:Eu than CaMoO4:Eu.

Nanocrystalline Zn 2 P 2 O 7 :Sm 3+ was synthesized using citrate precursor route. Rietveld refined XRD shown the formation of pure phase at 900 °C. Based on scanning electron microscopy, size distribution of the pyrophosphate particle was found to be in the range of 50–100 nm. Upon near UV light excitation (403 nm), Zn 2 P 2 O 7 :Sm 3+ exhibits host emission at 450 nm along with characteristic emission lines of Sm 3+ . Based on PL decay measurement, it was inferred that two different types of Sm 3+ ions were present in the zinc pyrophosphate. The first type was a short lived species (∼ τ = 100 μs) present at less symmetric ‘5-coordinated Zn’ sites, while the second was a long lived species (∼ τ = 1.9 ms) present at symmetric ‘6-coordinated Zn’ sites. The color coordinates of the system were evaluated using CIE index diagram to be 0.36 and 0.37, which suggest that the prepared material is a potential near white light emitting phosphor.

The compounds, Cr2TeO6 (s), Fe2TeO6 (s) and Ni3TeO6 (s) were synthesized by solid-state route and characterized using X-ray diffraction technique. Thermal expansion of Fe2TeO6 (s) and Ni3TeO6 (s) were studied by high temperature X-ray diffraction technique in the temperature range 298–973 K and 298–923 K, respectively. The average volume thermal expansion coefficient of Fe2TeO6 (s) and Ni3TeO6 (s) were determined to be 2.46 × 10−5 and 3.02 × 10−5 K−1, respectively. Heat capacity of Cr2TeO6 (s), Fe2TeO6 (s) and Ni3TeO6 (s) was measured, in the temperature range of 300–870 K, employing temperature modulated differential scanning calorimeter. The Gibbs energy of formation of Fe2TeO6 (s) and Ni3TeO6 (s) were measured using transpiration method. An empirical function was derived to compute enthalpy of formation of AnTeO6 (s) (where A = various elements of periodic table, n = 2, 3 or 6). Self consistent thermodynamic functions of Cr2TeO6 (s), Fe2TeO6 (s) and Ni3TeO6 (s) were calculated. The chemical potential diagrams of A–Te–O (A = Cr, Fe, Te) system were also constructed.

Zn2P2O7: Mn was synthesized by wet chemical route and characterized by X-ray diffraction (XRD), electron paramagnetic resonance (EPR) and photoluminescence (PL) techniques. EPR spectroscopic studies confirmed the presence of both Mn2+ and Mn4+ ions in zinc pyrophosphate. The presence of EPR signal at g = 2 is attributed to Mn2+ at Zn2+ site having octahedral coordination of oxygen whereas the presence of an EPR signal at g = 1.998 is attributed to Mn4+ at Zn2+ site having considerably lower symmetry due to the presence of extra interstitial oxygen ions required for charge compensation or due to the substitution of manganese at distorted 5-coordinated zinc site. Photoluminescence spectrum also shows two bands, one at 500 nm (green emission), which is attributed to the 4T1 (4G)–6A1 (6S) transition of Mn2+ and the other centered at 686 nm (red emission), which is attributed to the electronic transition between 2E and 4A2 of Mn4+.

In this paper a quaternary ammonium based room temperature ionic liquid (IL) trioctylmethylammonium hydrogen phthalate has been reported as promising extractant for separation of U(VI) from other metal ions from aqueous media. The IL was synthesized via metathesis route and characterized using various techniques such as hydrogen nuclear magnetic resonance, electron spray ionization mass spectrometry and infra red etc. The newly synthesized IL was evaluated for extraction of U(VI), Th(IV), La(III), Y(III), Nd(III) and Fe(III) from aqueous solutions and follow the order: U(VI) > Th(IV) > Fe(III) > Y(III) >> Nd(III) ~ La(III).

Ion conduction in poly (ethylene oxide), PEO, based electrolytes are explained considering the ion movement coupled with polymer segmental motions or free volume. Herein, we describe the application of positron annihilation spectroscopy to investigate the free volume structure of PEO-LiTFSI solid state electrolyte with varying electrolyte concentration. Addition of LiTFSI indicates plasticization effect through the increase in free volume size of polymer matrix. Depth dependent Doppler broadening measurements have shown a decrease in positron/positronium diffusion length and S-parameter value on addition of electrolyte. The observed decrease in S-parameter and positronium intensity could not be ascribed to positronium reaction (inhibition) with dissociated ions or salt aggregates as the variation does not follow the established inhibition expression. The S W correlation curves indicate that the chemical environment at positron/positronium annihilation sites in PEO-LiTFSI is similar to pristine PEO. It again confirms that reduction in positronium intensity and S-parameter cannot be attributed to positronium inhibition. The present study shows that resultant positron/positronium annihilation parameters can be directly attributed to the change in molecular packing or free volume structure of the solid state electrolytes.

Citrate–nitrate combustion method was adopted for the synthesis of RE6UO12 (RE = Dy and Tb). These compounds were characterized by X-ray diffraction. Thermal expansion coefficient of these compounds were measured in the temperature range of 298–1,273 K by high temperature X-ray powder diffractometry (HT-XRD) and compared with other rare earth compounds reported in the literature. There was no observed phase transition in Dy6UO12, but Tb6UO12 showed a second-order phase transition at 670 K which was confirmed using differential scanning calorimeter. The average volume thermal expansion coefficient of Dy6UO12 in the temperature range of 298–1,273 K is (29.82 ± 4.02) × 10−6 and that of Tb6UO12 in the temperature range of 298–673 K is (13.76 ± 2.64) × 10−6 K−1.

Ba1−xSrxMoO4 (x = 0, 0.18, 0.38, 0.60, 0.81, 1) solid-solutions were synthesized by complex polymerization method. The solid solutions were characterized using X-ray diffraction (XRD) and the Raman spectroscopy. Heat capacity measurements on Ba1−xSrxMoO4(s) were performed with heat flux-type differential scanning calorimeter in the temperature range of 140–870 K. The measured heat capacity values were used to calculate different thermodynamic functions such as enthalpy increment, entropy and Gibbs energy functions. Thermal expansion behavior of Ba1−xSrxMoO4(s) (x = 0, 0.6 and 1) were investigated in the temperature range 298–1273 K by high temperature X-ray diffraction (HTXRD). The specific heat and average volume thermal expansion coefficient of Ba1−xSrxMoO4(s) was found to increase with increase in concentration of strontium. The average volume thermal expansion coefficient of Ba1−xSrxMoO4(s) (x = 0, 0.6 and 1) was found to be 25.59 × 10−6, 33.86 × 10−6 and 34.37 × 10−6 K−1 respectively.