M. R. Pai

Bhabha Atomic Research Centre | BARC · Chemistry Division

In this work we have developed a Total reflection X-Ray Fluorescence (TXRF) based methodology for the determination of uranium in natural water samples at ultra-trace concentration level. The methodology involves functionalization of quartz sample supports used for TXRF measurements with (3-Amidoxy) triethoxysilane, which has very high uranium upta...

Ce based Metal Organic Framework (MOF) (UiO-66 (Ce)) and a MOF-composite (CeO2@UiO-66 (Ce)) were prepared by conventional heating and hydrothermal method respectively. Both the MOFs were characterized using X-ray Diffraction (XRD) technique, Fourier Transform Infra Red (FT-IR) spectroscopy, Field Emission-Secondary Electron Microscopy (FE–SEM), Sma...

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...

Fe2O3 nanoparticles immobilized on SiO2 xerogel beads were prepared using a sol–gel-based method. Two different acid catalysts, namely citric acid and acetic acid, were used to modify the preparative conditions and materials with desirable surface characteristics and pore structure. Three sets of samples with 1, 5, and 10 wt% Fe2O3 dispersed on sil...

Recently, we reported detailed investigations on a hydrolysis step of Cu–Cl thermochemical cycle (Singh et al. in Int J Energy Res 44:2845–2863, 2020) where we demonstrated CuCl2 hydrolysis using a fixed-bed reactor under optimized conditions. Thermolysis of CuCl2 and oxide formation are associated hindrances in achieving 100% phase-pure hydrolysis...

Considering the low temperature demand (~550°C maximum) and high efficiency (~43%), Cu–Cl thermochemical water splitting cycle has immense potential as a futuristic scalable hydrogen generation process. CuCl/HCl electrolysis is the crucial hydrogen generation step in the Cu–Cl thermochemical cycle. The efficiency of this electrolysis process is hig...

NiFe based layered hydroxides (LDH) is an efficient oxygen evolution catalysts used in energy conversion and storage devices. Herein, we used in-situ electrochemical impedance spectroscopy (EIS) to study the role of Fe in improving the oxygen evolution reaction (OER) of NiFe-LDH, as an alternative to expensive techniques. Optimized Ni0·46Fe0.54-LDH...

To address the issues of catalytic activity and stability of the promising Fe2O3/SiO2 catalyst for sulfuric acid decomposition, Fe2O3 was immobilized on SiO2 support by polyol, solvothermal and wet-impregnation methods and examined. The different methods yielded catalysts with varying crystal structure, porosity, morphology and redox properties whi...

Recent research suggests that molybdenum carbide (β-Mo2C) has the potential to be a cheap and active substitute for Pt-based electrocatalyst for hydrogen evolution reaction. In this article molybdenum carbide (Mo2C) electrocatalysts immobilized on carbon support were synthesized and evaluated for hydrogen evolution reaction (HER). The quantity of M...

Visible light driven photocatalysis by Cu and Ag incorporated mesoporous titania nanocuboids is monitored in this work. The mesoprous titania is obtained by using non-ionic triblock copolymer P123 as the structure-directing agent, which yields self-organized meso structured titania nanocuboids. The catalysts are well characterized using XRD, SEM, T...

Detailed investigations of CuCl2 hydrolysis step of Cu–Cl thermochemical cycle were carried out on various aspects: (a) characterization and thermal properties of reactants/products using X‐ray diffraction (XRD), thermogravimetry–mass spectrometry (TG‐MS), scanning electron microscopy (SEM), temperature‐programmed desorption (TPD), and extended X‐r...

Zn1−xFexOy nanocomposites have been investigated for bi-functional performance towards photoelectrochemical (PEC) and photocatalytic (PC) splitting of water to produce hydrogen. Prepared at varying Zn/Fe atomic ratio via co-precipitation through controlled addition of NH4OH to the aqueous solution of iron (III) nitrate nonahydrate [Fe(NO3)3·9H2O] a...

Efficient hydrogen generation via photocatalytic splitting of water, using methanol as hole-scavenger, has been recorded using CuO core/Ag–TiO 2 shell nano-hetero-structures. Ag incorporation in TiO 2 ranged 1, 3, 5 and 7% at. XRD, SEM and TEM analyses of samples confirmed the dominant evolution of tenorite CuO and anatase TiO 2 . Average crystalli...

Supported iron oxides have been established as an important class of catalyst for high temperature sulfuric acid decomposition. With an objective to elucidate the role of support in modifying the overall catalytic properties of dispersed iron oxide catalysts, a series of supported iron oxide based catalysts, Fe2O3 (15 wt%)/MO2 (M = Zr, Ce, Ti and S...

We have demonstrated earlier that maximum H2 generated @ 1.167 l/h/m² over Cu0.02Ti0.98O2-δ photocatalyst with apparent quantum efficiency, AQE of 7.5% and solar fuel efficiency, SFE of 3.9% under sunlight. With an aim to scale-up the solar photocatalytic hydrogen process to pilot plant, optimization studies at lab scale as well as in upscaled phot...

To accentuate the role of pn heterojunctions in composites, the photocatalytic properties of two composites NTC11 (NiO and TiO2 in 1:1 molar ratio) and NTC36 (0.35:0.65) were investigated in detail for H2 evolution reaction and compared with the component pure oxides, NiO, TiO2 and NiTiO3 prepared by sol-gel route. Among all samples, NTC11 was dist...

Through our previous studies it was established that non-precious Fe2O3 based catalyst has the potential to replace Pt based catalyst for high temperature sulfuric acid decomposition, the energy conversion step in iodine-sulfur or hybrid-sulfur thermochemical cycles for water splitting (Banerjee et al. [11] and [25]). However, issues like agglomera...

Thorium uranium oxide powder with uranium concentrations 10, 20, 30, 40, 50 and 70 mole% was prepared by gel combustion method. The sintering behaviour of the powders studied by dilatometry indicated that samples containing uranium up to 30 mole % had similar shrinkage behaviour with single step sintering. However, samples containing 40, 50 and 70%...

A series of Cu doped titania, CuxTi1−xO2−δ (x=0.0, 0.02, 0.06) and copper oxide-titanium oxide nanocomposites, xCuO-yTiO2 (x:y=1:9, 2:8, 5:5) were synthesized by sol-gel method and characterized by relevant techniques. The role of Cu ions in enhancement of photocatalytic evolution of H2 from H2O-methanol/glycerol mixtures in both sunlight and UV–vi...

(Th0.7-xU0.3Gdx)O2+y microspheres where x = 0, 0.05, 0.10 and 0.15 were prepared by internal gelation method. Good quality translucent microspheres of size ∼1.70 to 2.0 mm were obtained when low metal ([M]) and high [hexamethylenetetramine + urea]/[M] (R) concentration was used. The solid solutions prepared from these microspheres were subjected to...

UO2 microspheres prepared by internal gelation technique were coated with pyrolytic carbon and silicon carbide using CVD technique. The particles which were not meeting the specifications were rejected. The rejected/failed UO2 based coated particles prepared by CVD technique was used for oxidation and recovery and recycling. The oxidation behaviour...

Background: Since last two decades, there has been rigorous efforts are going on to develop a hydrogen storage system for large-scale application in fuel cells, mobiles and for automotive uses. The early experimental data on hydrogen storage using CNTs contradicted theoretical calculations, and there has been a large variation􀀁in the CNT hydrogen s...

Nominal compositions of In2Ti1−x Tm x O5−δ, (0.0 ≤ x ≤ 0.2 and Tm = Fe3+ and Cr3+) were synthesized by ceramic route and characterized by relevant techniques. In2Ti1−x Fe x O5−δ samples were single phased isomorphic with In2TiO5 phase while Cr substitution has resulted in mixed phased compositions. Dynamic light scattering experiments showed the in...

We report here the role of Ni substitution in modifying the crystal structure, optical absorption properties and electronic properties of indium titanate, In2(1-x)Ni2xTiO5-δ (0.0 ≤ 2x ≤ 0.4) and its consequent effect on the photocatalytic properties for H2 generation. Rietveld refinement of observed XRD patterns of the titanates revealed that Ni2+...

In continuation with our last communication on granular Fe2O3 catalysts (Banerjee et al., Applied Catalysis B: Environmental 127 (2012) 36–46), we report here a thorough investigations on Pt/Al2O3 catalyst in granular form of 4–6 mm diameter for sulfuric acid decomposition reaction in absence of any carrier or diluents gas in a dual tube quartz cat...

Varying amounts of Na and K doped lanthanum–titanium oxides were synthesized by gel entrapment technique. These ceramics were characterized by X-ray diffraction. Microstructural investigations revealed grain growth in the doped material compared to undoped sample. Dielectric relaxations of these compounds were investigated in the temperature range...

A Total Reflection X-Ray Fluorescence (TXRF) methodology, employing burn-leach test, was developed to assess the quality of SiC layer in tristructural isotropic (TRISO) coated UO2 particles prepared in BARC. The coated particles were heated at 1,123 K for about 96 h to constant weight. The calcined particles, thus obtained, were then heated in supr...

Fe3O4–TiO2 nanocomposites have been synthesized by hydrothermal method using sonochemically activated precursors. X-ray diffraction analysis of the samples reveals the formation of pure phase composites. The optical properties of the composites are superior to TiO2 as noted from the red shift in the diffused reflectance spectra of the composites. T...

Fuel fabrication technology, particularly once through utilization of uranium, has been mastered over the years. However, with the increasing demand of electricity at an affordable cost and depleting resources of uranium, introduction of thorium in the fuel cycle has become essential. The large-scale utilization of thorium requires adoption of clos...

We report here two different simple, one-pot, and low cost chemical synthetic routes for the preparation of Cu2O nanocrystals: (a) thermal decomposition of copper–organic precursors copper(II) acetate or copper(II) acetylacetonate in long chain organic solvents oleyl alcohol and trioctylamine, respectively, at 170 °C and (b) a surfactant-free solvo...

Nd doped TiO2 nanoparticles were synthesized by sol–gel method exhibiting photocatalytic activity in solar light together with UV light irradiation. Photoactivities of the catalysts were investigated in terms of degradation of Methyl Orange dye. 1.0% Nd doping appears to be optimum, yielding highest degree of degradation. Ag coating on 1.0% Nd dope...

A sol–gel based hybrid process was developed by manipulating different techniques in sol–gel process to synthesize γ-alumina and (CuO, CuO + ZnO) doped γ-alumina spherical particles. Catalysts having spherical geometry have an important advantage over powders or pellets which are impervious to fluids, when packed in a reactor. Boehmite sol was used...

It is proposed to irradiate experimental fuel pins containing 750 μm (U0.47,Pu0.53)O2 microspheres (coarse fraction) and 110 μm UO2 microspheres (fine fraction) in the Fast Breeder Test Reactor at Kalpakkam, with a view to develop sphere-pac fuel for Fast Breeder Reactors in India. This communication describes optimization of the internal gelation...

The overall water splitting reaction on a semiconductor photocatalyst occurs in three steps, which are as follows: the photocatalyst absorbs photon energy greater than the band-gap of the semiconductor material and generates photo-excited electron-hole pairs in the bulk; the photo-excited electrons and holes separate and migrate to the surface with...

In our earlier work (Banerjee et al. [29]) we have reported the catalytic properties of powders of Fe2(1−x)Cr2xO3 (x = 0.0, 0.1, 0.2) for sulfuric acid decomposition in a flow through quartz catalytic reactor with 2 g catalyst in presence of nitrogen as a carrier gas. With a practical application approach, in this work the two screened oxides, iron...

Nanosized (8-9nm) Nd doped and Ag coated TiO(2) nanoparticles have been synthesized by sol-gel method. The physicochemical properties of these particles were investigated by X-ray diffraction (XRD), diffuse reflectance UV-visible (DRUV) spectra and Brunauer-Emmett-Teller (BET) surface area analysis. The antibacterial activities of the samples were...

A particle induced gamma-ray emission method using proton beam in conjunction with in situ current normalization approach was standardized for non-destructive determination of low Z element lithium and was applied for quantification of Li in lithium doped neodymium dititanate (Nd2Ti2O7) ceramic sample. Thick pellets of heat treated samples, their p...

A low temperature surfactant-free solution-phase method has been successfully developed for the synthesis of ternary In2TiO5, nanoparticles using a solvothermal route. The mechanistic aspects of synthesis of In2TiO5 nanoparticles from precursors, In(acac)3 and Ti(IV) isopropoxide in benzyl alcohol at 220 °C under solvothermal conditions, were inves...

We report here the role of Nd3+ ions in modifying the band structure of indium titanate and enhancement of photocatalytic evolution of H2 from H2O–methanol mixtures in both sunlight and visible irradiation over Nd3+–In3+2Ti4+O5 oxides. A series of neodymium, isovalent to In3+ ion, were doped at the A-site in indium titanate (In2(1–x)Nd2xTiO5) sampl...

Mesoporous γ-Al2O3 materials with high surface area and a narrow pore size distribution were synthesized by facile sol–gel procedure with application of the polymer–colloid complex as a template. KeywordsSol–gel synthesis–Polymer–colloid complex–Mesoporous alumina–Self-assembly

Nd2-xLixTi2O7-δ (x = 0, 0.1 and 0.15) (NDT) was synthesised by Gel Entrapment Technique. These ceramics were structurally characterized by analysis of X-ray diffraction (XRD) patterns, indicates that NDT ceramics present a monoclinic structure. Proton Induced Gamma Emission (PIGE) technique was used to determine the Li content in the as synthesised...

The catalytic decomposition of sulfuric acid is the most endothermic step of the sulfur based water splitting thermochemical cycles, which are promising technologies for large scale hydrogen production in future. In the present study the catalytic activities of three ferrospinels AFe2O4 (A = Co, Ni, Cu) were evaluated for high temperature sulfuric...

The thermal behavior of mixed metal oxides with nominal compositions of In2(1−x)Ni2xTiO5−δ where 0.0 ≤ x ≤ 0.2, were investigated by recording their temperature programmed reduction (TPR). The samples were synthesized by ceramic route and analyzed for phase composition using powder X-ray diffraction. The TPR profile of pristine In2TiO5 indicated th...

Iron substituted lanthanum titanates with nominal composition La2Ti2(1-x)Fe2xO7-delta (0.0 <= x <= 1.0) samples, were synthesized by gel combustion and conventional solid state reaction. The samples have been characterized by XRD, N-2-BET, SEM, FTIR, Mossbauer spectroscopy and TPR. Catalytic activity of these samples was evaluated for a decompositi...

Mesoporous γ-alumina samples were prepared by the sol–gel process from the boehmite sol having different template solutions. Copper doped material was also prepared from sol containing template solution along with copper nitrate. Studies were performed to understand the influence of templates on the morphology of the synthesized samples particularl...

Rare earth doped lead zirconate titanate of composition (Pb1−xRxZr0.65Ti0.35)O3 where x=0, 0.10 and 0.15 and R=Ce, Pr and Nd was prepared by Gel Entrapment Technique (GET). The gel was suitably calcined at 1073K and the resultant product was characterized by XRD, SEM, BET surface area analysis and Dynamic Light Scattering. The dielectric constants...

Cr2−xTixO3+δ, where x varies from 0.1, 0.2 and 0.3 has been prepared by glycerol route and characterized by powder X-ray diffraction, dynamic light scattering, BET surface area and scanning electron microscopy. The thermal expansion coefficient of the powder samples was studied using a high-temperature X-ray diffractometer. The bulk thermal expansi...

Hydrogen adsorption-desorption characteristics of MWCNT and Transition metal (Ni, Cu and Fe) attached MWCNT nanocomposites were investigated. Transition metal-MWCNT nanocomposites were prepared by wet chemical method. Synthesis of carbon nanotubes was carried out using catalytic chemical vapor deposition, CCVD method. For copper nanoparticle attach...

Some newer mechanistic aspects investigated by in situ Fourier transform infrared (FTIR) in conjunction with catalytic activity under similar conditions over crystalline lanthanum titanates as a function of Fe substitution at the B-site for the CO + N2O reaction are reported for the first time in the present communication. La2Ti2(1-x)Fe2xO7-delta (...

Effect of H2O2 on synthesis and powder properties such as surface area and agglomerate size of nanocrystalline Ce0.8M0.2O1.90 (M: Sm, Gd) was explored by treating cerium nitrate and rare-earth nitrate with NaOH in the presence/absence of H2O2. The resultant products were characterized by x-ray diffraction, Raman spectroscopy, thermo-gravimetry–diff...

The effects of Zr substitution for Ti on the hydrogen absorption–desorption characteristics of Ti1−xZrxCrV alloys (x=0, 0.05, 0.1 and 1.0) have been investigated. The crystal structure, maximum hydrogen absorption capacity, kinetics and hydrogen desorption properties have been studied in detail. While TiCrV crystallizes in body centered cubic (BCC)...

ThO2 microspheres were prepared by internal gelation process using a pre-boiled hexamethylenetetramine (HMTA), urea solution. The microspheres were characterized with respect to tap density, specific surface area and pore size distribution. An indigenously designed and fabricated apparatus was used for the impregnation of uranium in thoria microsph...

The compounds with compositions Cr2 − xTixO3 + δ (where x = 0 to 0.3 with an interval 0.05) were prepared by gel combustion method and characterized by XRD, DLS, SEM and thermal techniques. The electrical properties, such as dielectric constant and ionic conductivity of these compounds, were studied in the frequency range 10 MHz–1 Hz, in the temper...

The crystal structure of thorium metavanadate (Th(VO3)4) at ambient temperature is determined by Rietveld refinement of the powder X-ray diffraction data. This compound crystallizes in a tetragonal lattice, with the unit cell parameters: a=8.5771(4)Å and c=28.9739(4)Å, V=2131.51(4)Å3 and Z=8 (space group I41/a, no. 88). The detailed structural anal...

This report investigates the formation of microbubbles in water–methanol mixtures upon ultrasound irradiation and its correlation with the yield of H2 obtained as a result of sonochemical splitting of water. The yield of hydrogen produced by sonochemical reaction is monitored at different compositions of water–methanol mixtures. The evidence for th...

The present paper deals with the catalytic decomposition of sulfuric acid reaction which is common to several sulfur based thermochemical water splitting cycles including the sulfur–iodine thermochemical cycle. The activity and stability of Cr substituted Fe oxide catalysts were studied for the sulfuric acid decomposition reaction. The samples Fe2(...

Lanthanum doped lead zirconate titanate of composition (Pb0.95La0.05Zr0.65Ti0.35)O3 was prepared by gel entrapment technique (GET). The gel was suitably calcined and the resultant product was characterized by XRD, BET surface area analysis, dynamic light scattering and SEM. X-ray analysis of the powder calcined at 1023 K indicated formation of prod...

Mixed metal oxide catalysts with nominal compositions of In2Ti1–xFexO5–δ, In2Ti1–xCrxO5–δ, where 0.0 ≤ x ≤ 0.2, have been synthesized by the ceramic route and characterized using the powder x-ray diffraction technique. The In2Ti1–xFexO5–δ samples were single-phase compositions, isomorphic with In2TiO5 phase. The particle size of the In2Ti1–xFexO5–δ...

Mixed uranium–plutonium oxide microspheres were prepared by internal gelation process using feed solution of optimized composition. In the feed, total metal concentration was maintained at 1.5 M and hexamethylenetetramine (HMTA)-urea to metal mole ratio (R) was kept at 1.0. The gel particles obtained from each batch were dried and heated at 250 °C...

The catalytic properties and reduction behavior of mixed metal oxides with nominal compositions of LaxTh1-x(VO3-delta)(4), where 0.0 <= x <= 1.0, have been investigated as a function of the value of x. These compositions were synthesized by ceramic route and characterized using powder X-ray diffraction, differential thermal analysis, and temperatur...

Nanosized crystallites of the mixed oxides LaMnO3+x (LM), La0.8Sr0.2MnO3-γ (LSM) and La 0.8Sr0.2Mn0.8Fe0.2O 3-δ (LSMF) were synthesized by alternative methods like nitrate route, drip pyrolysis and ceramic route followed by calcinations at different temperatures. The average crystallite size of LSMF was found to be 10, 25 and 90 nm respectively for...

The La0.8Sr0.2Mn1−xFexO3−δ (LSMF) samples of perovskite-type structure, with the value of x ranging from 0 to 1.0 were synthesized by using two different methods, viz. nitrate and solid-state routes, and by calcining at different temperatures. Efforts were directed to identify the microstructural and morphological properties responsible to the subs...

The substituted samples with nominal compositions of LaxTh1−xV2O7−δ (x = 0–0.5) were synthesized for the first time by ceramic route and the phase characterization was carried out by powder XRD technique. In addition to substitution at some of the thorium sites in ThV2O7, the substituted samples comprised of two new phases, viz., Th(VO3)4 and LaTh(...

A series of composite metal oxide catalysts of nominal composition LaxTh1−xV2O7−δ (x = 0.0–0.5) were synthesized by ceramic route and characterized using XRD, IR and temperature programmed reduction (TPR) measurements. The partial substitution at A-sites had profound effect on the catalytic behavior of thorium pyrovanadate for the dehydration of me...

Internal gelation process has been developed to prepare high density ThO2–3%UO2 pellets. The study indicated that by carefully controlling the feed composition and the heat treatment scheme, soft mixed oxide microspheres could be obtained which are amenable for pelletisation at relatively low compaction pressures (200–250 MPa). The green pellets co...

With an objective to elucidate the influence of structural changes on catalytic properties, the oxygen content, reducibility and chemical stability of substituted metavanadates of thorium, viz., Th(MnxV1-xO3-)4 with 0 × 1, were monitored using temperature programmed reduction / oxidation (TPR/TPO), powder XRD and FTIR techniques in conjunction with...

In a controlled trial of heat-treated factor VIII concentrate from Cutter Laboratories and from Connaught Laboratories Limited, 25 patients with hemophilia received Cutter factor VIII and 24 patients with hemophilia received Connaught factor VIII. The mean increase in factor VIII level was similar for the two products (1.88% and 1.98% per unit/kg o...

Acute mixed myeloid-lymphoid leukemia is uncommon. We report four cases in which myeloid and lymphoid cell markers were observed simultaneously or sequentially when 94 patients with acute leukemia were phenotyped according to the French-American-British (FAB) classification system, with cytochemical stains, and with immunologically defined differen...

Acute mixed myeloid-lymphoid leukemia is uncommon. We report four cases in which myeloid and lymphoid cell markers were observed simultaneously or sequentially when 94 patients with acute leukemia were phenotyped according to the French-American-British (FAB) classification system, with cytochemical stains, and with immunologically defined differen...