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Variable energy positron beam with Doppler broadening spectroscopy (DBS) was used to investigate the depth-resolved defects formed by two fluencies of 130 keV N+ implanted in Semi Insulating (SI) 6H-SiC. The implanted ions induced damages near the surface and to a depth of 300 nm as simulated by SRIM analysis. Defects recovery, accumulation, and its behavior with two annealing temperatures were also considered. Defect types and its effect on annealing were analyzed from the changes in electron momentum and modeled as layers using variable energy positron fitting (VEPFIT) methods. Inclusion of electric field strength in the fitting procedure supported layer characteristics and the state of charge carriers. Di-vacancies, vacancy complexes observed in the damaged layers were agglomerated at the surface and tend to cure on annealing.

Corrosion fatigue crack initiation (CFCI) life of AISI Type 316 N weldment in as-welded (AW) and heat treated (Solution annealed (SA), 550 °C/4h and 750 °C/1h) conditions was studied in high cycle fatigue regime (above 104 cycles) with a frequency (η) of 0.1 Hz and and R-ratio (σmin/σmaxwhere σmin and σmax signify minimum and maximum tensile stress in MPa, respectively) of 0.5 for different stress amplitude (σa) values in boiling acidified 5 M NaCl + 0.15 M Na2SO4 + 2.5 ml/l HCl solution under axial loading in load controlled mode. In-situ electrochemical measurements were employed during corrosion fatigue tests to study the passive film characteristics. SA weldment showed better corrosion fatigue (CF) resistance as compared to AW and heat treated conditions. Homogenization of microstructural and microchemical heterogeneities facilitates highest resistance to CF cracking process for SA weldment condition. Number of cycles to failure (Nf) increased with decrease in stress amplitude for all material conditions. CFCI mechanism was identified based on variation in the strain rate (e°) due to combined effect of both emergence of persistant slip bands (PSBs) casued by rupture of passive film and initiation of microcrack caused by dissolution around depassivation site. The failure of weld metal occurred by a combination of transgranular (TG) and stress-assisted dissolution (SAD) of delta-ferrite. Crack growth zone was minimum for AW and heat treated (550 °C/4h and 750 °C/1h) conditions as compared to SA weldment.

The effect of Mo concentration on pit initiation rate and pit growth in austenitic stainless steels (SS) were investigated by electrochemical noise (EN) and confocal laser scanning microscopy (CLSM) techniques for the first time. We used 304LN, 316LN and 317LN containing different concentrations of Mo (0.02, 2.53 and 3.58 wt.%) for our studies. Using EN technique, initiation of pits and growth of pits were analyzed using Weibull and Gumbel distribution function, respectively. Pit depth was obtained using CLSM and the correlation between pit aspect ratio and Mo concentration were studied. Weibull probability plots showed that the Mo present in the alloy reduces the pit generation rates and improves the passivity. The plot for the pit size distribution using Gumbel distribution function showed the lowest metastable pit in 317LN and the highest in 304LN, suggesting the improvement in the pitting corrosion resistance due to Mo addition. The CLSM imaging showed maximum pit depth for specimen 304LN and minimum for specimen 317LN SS. Specimen 316LN SS showed intermediate pit depth. The depth of the pits observed in 304LN, 316LN and 317LN ranged from 80-100 µm, 30-40 µm and 20-30 µm, respectively. Alloy 317LN containing highest Mo concentration (3.58 wt.%) showed the lowest pit aspect ratio values followed by alloy 316LN with 2.53 wt.% Mo. These results indicate that Mo present in the stainless steel helps in arresting the pit growth and improve the resistance to pitting corrosion.

The origin of magnetism in RF magnetron sputtered deposited carbon thin films is reported. Three different carbon thin films were deposited using RF magnetron sputtering of carbon target by Ar ions at RF power of 50 W, 100 W and 150 W, respectively. Microstructural characterization of films using Raman spectroscopy confirms the presence of graphitic crystallites in all three films and the crystallite edges are terminated with the sp3 bonding. However, increasing RF power results in an increase in graphitic crystallite size as well as the sp2/sp3 hybridization ratio, while the average density of the films decreases. The observed magnetization (measured using SQUID-VSM) in all the three-carbon films has a contribution from both superparamagnetic (SPM) particles (due to the interaction between unpaired spins) and the paramagnetic term due to isolated unpaired spins distributed throughout the film. The origin of experimentally observed magnetization in the carbon thin films and their correlation with the change in density and sp2/sp3 hybridization ratio due to variation in RF power is discussed.

Implementation of a state of the art data acquisition and analysis program for variable low energy positron beam using LabVIEW based automation software is described. The program does the following functions: (a) controlling the remote programmable high voltage–power supply to bias the sample negatively (i.e., to vary the positron beam energy), (b) control of Windows based PCI MCA card, (c) calculating the S, W, R and ortho-positronium self-annihilation fraction (fPs) parameters, errors, and other relevant parameters, (d) saving the raw spectra, results and log data file and (e) dynamic display of raw spectrum and S, W, fPs versus energy for easy visualization of progress of the experiment. The USB based interfacing standard of this design provides easy connectivity to the personal computers.

The study is intended to investigate the low energy nitrogen ion implantation induced behavior and re-crystallization in semi-insulating 6H-SiC from surface to 5 µm, by Raman spectroscopy. The nature of defects accumulation related to the SiC bond breakages and re-crystallization on vacuum annealing were analyzed from the A1(LO) phonon mode and probed at successive depth from the surface. Variations on the asymmetrical A1(LO) peaks of as-implanted samples were made to order upon annealing, and the mode regained. The peak intensity variation of A1(LO) mode indicated the disorder accumulation. The identified damage depth was in good agreement with Stopping and Ranges of Ions in Matter (SRIM). The changes in Si-Si, deformed-Si-C, C-C vibrations and crystalline-SiC were used to explain the defect role in the implanted and annealed samples.

Positron beam measurements carried out on high temperature Ni+ implanted FeCrCoNi show no void formation but only presence of monovacancies. With thermal treatment, evidence for the formation of nano sized σ-CoCr are obtained from positron based ratio curve analysis in the temperature range 973–1123 K. Corroborative evidence for the presence of these precipitates are obtained from EBSD and GIXRD measurements. Further annealing beyond 1150 K leads to coarsening of these precipitates and they no longer trap the positrons.

Corrosion fatigue behavior of type 316N stainless steel (SS) weldments on the damage characteristics is studied. The S–N curve of the fatigue life versus stress amplitude showed a specific two slope Basquin relationship. At low stress amplitude, the deformation microstructure consists mainly of planar slip dislocation structure and at high-stress amplitudes, planar multiple slip dislocations govern the cyclic behavior. A correlation between microstructural changes and the corresponding susceptibility of 316N SS weldment in as-welded condition towards environmental cracking in boiling acidified aqueous solution has been presented. The objective of the present study is to investigate the environmental effects on the corrosion fatigue crack initiation of type 316N weldmetal under the influence of cyclic stress amplitude. The difference in deformation micro mechanisms with stress amplitude in a corrosive environment is believed to be the major reason for the occurrence of a specific bilinear Basquin relationship in the S–N curve. A schematic of corrosion fatigue crack initiation involving the emergence of a slip step and dissolution of the step on the surface: (a): before cyclic loading (b): fatigue crack initiation and (stage I and II) crack propagation during cyclic loading.

During welding of 316L stainless steel (SS), heat-affected zone (HAZ) is susceptible to sensitisation and fusion zone is susceptible to pitting corrosion in stainless steel welds. High-nitrogen electrodes with 0.045–0.055 wt% C and with different Cr contents were used for welding of prototype fast breeder reactor components. As-welded and thermally aged (823 K for 2 h) weldments of type 316LN SS with different N contents made by arc welding were studied for localised corrosion. ASTM A262 Practice A and E tests and double-loop electrochemical potentiokinetic reactivation studies on as-welded and thermally aged specimens revealed the absence of sensitisation in the HAZ and in fusion zone. However, pitting potential of the weldments was found to vary with the concentration of N + Cr + Mo in fusion zone and found to be lower in the thermally aged samples. The correlation between weld microstructure, alloying elements and pitting corrosion behaviour has been discussed.

Thin films of MoS2 were deposited on glass substrates by electron beam evaporation. The films were characterized by Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-ray Spectroscopy (EDS), Raman, optical spectroscopy and X-ray Photoelectron Spectroscopy (XPS). FESEM and EDS showed the formation of MoS2 nano-particles of sizes around ~10 nm. Raman spectra showed the formation of 2-H MoS2 with trace amounts of Mo-oxides. Optical band-gap was calculated to be ~2.13 eV. XPS studies were performed to evaluate the different oxidation states of Mo and S present in the films. Surface oxidation and elemental composition as a function of depth was studied using Angle-Resolved X-ray Photoelectron Spectroscopy.

An environmentally benign and facile bilayer coating comprised of graphene oxide (GO) and acrylic polymer is fabricated over cupronickel sample using electrophoretic deposition followed by dip coating. The infrared, Raman, and field emission scanning electron microscopy (FESEM) studies of the bilayer coating confirm the noncovalent functionalization of GO through H-bonding with acrylic polymer, reduction in local defects in GO structure, and distorted spherical void peripheries of polymer coating, respectively. The FESEM cross-sectional analysis showed that the coating thickness is 5–6 µm. The bilayer-coated sample showed a three- to fourfold increase in the corrosion resistance, as compared to GO-alone-coated sample in 3.5% (w/v) NaCl electrolyte, which is attributed to the reduction in the local defects in GO coating and the galvanic coupling between the GO and sample surface. The GO sheets make the diffusion pathway of corrosive media more tortuous for corrosive ions to reach the metal surface. The lower anodic current density observed with the new bilayer coating after 30 days of exposure confirms the active corrosion protection. The coating was intact and stable after 30 days of exposure in chloride medium with a water uptake of about 32.7%.

A dual ion beam radiation facility which provides co-implantation of heavy ion beams from a 1.7 MV accelerator and gaseous ions from an indigenously built 400 kV accelerator has been developed. Various aspects of the dual beam irradiation facility such as the beam optics design, electronics and instrumentation comprising of a distributed control system and details of the experimental end station have been discussed. Experiments to determine essential parameters for the conduct of dual irradiation such as the beam energy spread, the spatial and the depth overlap of both beams have been carried out. For a dpa rate of 1 × 10−3 dpa sec−1 the maximum He:dpa rate achieved using this system is 50 appm dpa−1. This facility enables us to study the effect of a combination of large levels of transmutant helium and displacement damage (dpa) on the dimensional stability and mechanical properties of structural materials, He/dpa ratios on swelling in advanced alloys and co-operative effects of nuclear and electronic energy losses in nuclear structural materials.

The formation of hydrogen and helium associated defect complexes and their influence on the nucleation and growth of helium bubbles in Indian Reduced Activation Ferritic/Martensitic steel have been investigated using positron annihilation spectroscopy. Isochronal annealing study has been performed on the samples individually irradiated with H and He ions, and sequentially irradiated with both H and He ions. All the as-irradiated samples show higher S-parameter as compared to the unirradiated sample due to the presence of irradiation-induced vacancy-type defects. Among the single ion irradiated samples, hydrogen irradiated sample shows the presence of H-vacancy complexes having high hydrogen content in the as-irradiated state, an increase in S-parameter due to the release of hydrogen from these complexes at 373 K, and complete defect recovery after annealing at 673 K. The helium irradiated sample shows three distinct stages of annealing; a defect annealing stage with decrease in S-parameter from as-irradiated to 573 K, bubble nucleation stage with a stable S-parameter from 573 to 673 K and the bubble growth region characterized by an increase in S-parameter is observed from 673 to 973 K. Among the sequential irradiated samples, the sample irradiated with helium first and then with hydrogen shows a reduced S-parameter which is due to the saturation of helium-induced vacancies by hydrogen or the formation of H-He-vacancy complexes. Both the sequential irradiated samples show a reduced S-parameter from 573 to 673 K due to the formation of H-He-vacancy complexes under post-irradiation annealing. The nucleation and growth stage of helium bubbles observed under isochronal annealing is independent of the sequence of irradiation. Both the sequential irradiated samples show the bubble nucleation and growth stage similar to helium irradiated sample and further, the presence of hydrogen has no noticeable role in this stage.

In this work, spinel-metal oxide (NiCo2O4–NiO) nanorods based electrode was fabricated and tested for their efficacy as supercapacitors. The NiCo2O4–NiO was synthesized by hydrothermal method and characterized using thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and transmission electron microscope (TEM) respectively. The TEM images reveal the morphology of the synthesized metal oxides in the form of nanorods with length of several micrometers and diameter in the range of 60–70 nm. The XRD pattern confirmed the formation of cubic spinel structure. A three electrode cell set up was employed to estimate the electrochemical performance of the material. It is observed that the NiCo2O4–NiO showed specific capacitance of 490 F/g at 0.5 A/g as compared to pure NiCo2O4 which is around 216 F/g at 0.5 A/g. The enhanced capacitance mainly arises from the incorporation of NiO secondary phases within the spinels which increases the number of redox active sites. The present work proves to be a promising strategy to improve the performance of the electrode material for supercapacitors.

This work reports a novel high performance green concrete fabricated by incorporating fly ash, nanoparticles and corrosion inhibiting admixture into conventional M45 grade concrete. The optimal composition of the new mix was found to be 40 wt% fly ash, 2 wt% nano-TiO2 and nano-CaCO3 in 1:1 ratio, 2 wt% sodium nitrite based corrosion inhibitor and 56% Ordinary Portland Cement, referred hereafter as CFNI. The properties of CFNI were compared with that of conventional concrete to assess the synergistic role of various additives. Field Emission Scanning Electron Microscope images of CFNI showed a homogeneous distribution of hydration products over the surface. The Confocal Laser Scanning Microscopy images of concrete surfaces and pore size estimation from Mercury Ion Porosimetry confirmed that only gel pores at the nanoscale are present in the CFNI specimens. The compressive strength, flexural strength and split tensile strength of CFNI, measured as per ASTM/Indian standards, showed noticeable enhancement. The chloride ion penetration resistance, carbonation, water permeability and water sorptivity of CFNI was found to be superior as compared to conventional concrete. This study establishes that synergistic action of fly ash, nanoparticles and inhibitor facilitated the improvement in strength and durability of the new green concrete CFNI, which is very promising not only for cost reduction and improved properties of concrete structures, but also reduces energy consumption and green house gas emissions.

Bismuth and iron oxides subjected to ball milling followed by controlled annealing treatments showed the formation of core–shell nanostructures with Bi2Fe4O9 as the core and a shell of BiFeO3 and Bi25FeO40 phases as deduced based on the analysis of transmission electron microscopy results. The mechanism of formation of such bismuth iron oxide based core–shell structures with Bi richer phases distributed radially outwards has been elucidated based on a model proposed in this study. Hyperfine components at Fe sites have been studied using Mossbauer spectroscopy to understand the local structure and magnetic properties and defect associated components of each of the phases. The system of such core–shell particles surrounded and separated by haematite particles is observed to be ferroelectric and exhibit a giant dielectric response. Bulk magnetization studies indicate weak ferromagnetic ordering of the resultant phases. Both the giant dielectric and weak ferromagnetic properties are understood to be caused mainly by oxygen vacancies associated with nanoshells of bismuth ferrite of the core–shell structures.

Nitrogen is one of the most important alloying elements in alloy steels and even in small amounts can improve their properties. Because of its favorable properties, high performance nitrogen containing austenitic stainless steels are currently being developed for an advanced application that requires high strength along with better corrosion and wear resistance. The present study investigate the effects of cold work (CW) on the microstructure and corrosion fatigue (CF) resistance of AISI Type 316 LN stainless steel containing 0.11 wt. % nitrogen using microscopic, electrochemical and surface analytical methods. Potentiodynamic anodic polarization experiments were carried out in two chloride concentrations (1 M NaCl) and (5 M NaCl + 0.15 M Na2SO4) indicated that pitting potential (Epit) and passivity range drastically decreased with increase in chloride concentration and increased deformation from 0 to 20% CW. In 5 M NaCl + 0.15 M Na2SO4, corrosion resistance (Rp) decreases with an increase in cold work due to increased susceptibility of the passive film towards dissolution due to increase in dislocation density. CF behaviour of AISI Type 316LN SS with 0.11 wt.% nitrogen was studied in acidified 5 M NaCl + 0.15M Na2SO4 solution at a stress ratio (R) of 0.5 and a frequency (η) of 0.1 Hz with varying mean stress (σmean) and open circuit potential was monitored throughout till the failure of the specimen occur. Based on in-situ electrochemical measurements during corrosion fatigue tests, the shift in potential indicates the crack initiation process. The S-N curve of fatigue life (Nf) vs. stress amplitude was also generated. This study showed that the CF resistance increases with an increase in cold work and the number of cycles to failure and critical cracking potential decreases with increasing mean stress. The crack initiation and propagation show a transgranular mode in all the tested conditions.

Ab initio molecular dynamics simulations using VASP was employed to calculate threshold displacement energies and defect formation energies of Y4Zr3O12 {\delta}-phase, which is the most commonly found phase in newly developed Zr and Al-containing ODS steels. The Threshold displacement energy (Ed) values are determined to be 28 eV for Zr3a primary knock-on atom along [111] direction, 40 eV for Zr18f atoms along [111] direction and 50 eV for Y recoils along [110] direction. Minimum Ed values for O and O' atoms are 13 eV and 16 eV respectively. The displacement energies of anions are much smaller compared to cations, thus suggesting that anion disorder is more probable than cation disorder. All directions except the direction in which inherent structural vacancies are aligned, cations tend to occupy another cation site. The threshold displacement energies are larger than that of Y2Ti2O7, the conventional precipitates in Ti containing ODS steels. Due to the partial occupancy of Y and Zr in the 18f position, the antisite formation energy is negligibly small, and it may help the structure to withstand more disorder upon irradiation. These results convey that Zr/Al ODS alloys, which have better corrosion resistance properties compared to the conventional Ti-ODS alloys, may also possess superior radiation resistance.

Conventional Oxide dispersion strengthened steels are characterized by thermally stable, high density of Y-Ti-O nanoclusters, which are responsible for their high creep strength. Ti plays a major role in obtaining a high density of ultrafine particles of optimum size range of 2-10 nm. In Al-containing ODS steels developed for corrosion resistance, Y-Al-O clusters formed are of size range 20 -100 nm, and Ti fails in making dispersions finer in the presence of Al. Usage of similar alloying elements like Zr in place of Ti is widely considered. In this study, binding energies of different stages of Y-Zr-O-Vacancy and Y-Al-O-Vacancy complexes in the bcc Iron matrix are studied by first-principle calculations. It is shown that in all the stages of formation, Y-Zr-O-Vacancy clusters have higher binding energy than Y-Al-O-Vacancy clusters and hence in ferritic steel containing both Zr and Al, Y-Zr-O-Vacancy clusters are more stable and more favored to nucleate than Y-Al-O-Vacancy clusters. The bonding nature in each stage is analyzed using charge density difference plots for the plausible reason for higher stability of Y-Zr-O-Vacancy clusters.

Anisotropic behaviour of the A1g vibrational mode of MoS2 at the edges has been reported. Polarized Raman spectroscopy is used to identify edges, and decipher angles between them have been discussed. The aberrant appearance of the A1g mode at the edges has been attributed to breaking of back-scattering geometry. The direction-dependent intensity of the A1g mode is used to characterize the angle between edges, thus finding the chirality of the edges.

Role of quenching induced defects in modifying local structural and magnetic properties at Fe sites in Co2FeAl has been studied in a detailed manner using 57Fe Mossbauer spectroscopy. Results of this study show that the effective hyperfine fields at Fe sites in as quenched sample is observed to be higher than that of the as melted sample, which is understood to be due to an enhanced antisite defect fraction formed in the sample. Annealing behaviour of quenching induced defects in Co2FeAl has also been elucidated in this study.

Indian reduced activation ferritic-martensitic steel was irradiated with 1.1 MeV Fe ions to various doses from 1 to100 dpa at room temperature. The depth profiling of irradiation-induced vacancy-ty...

Fly ash is used in concrete industry to reduce the amount of cement and to enhance the durability of concrete. Nuclear industry recently adopted fly ash concrete as a government initiative to reduce carbon footprint and also to provide an impermeable skin for the several structures in the cooling water system exposed to marine environment for enhanced durability. Earlier detailed studies on fly ash concrete has shown that despite its superiority over conventional concrete with respect to strength and durability, some concerns such as delayed setting and hydration, low early-age strength, and higher carbonation may pose a problem for its wider application. The present work is an attempt to overcome these deficiencies by nanophase modification of concrete with the incorporation of nano-titania and nano-calcium carbonate at 2% by weight of cement. Four different types of concrete mix were arrived and specimens of different sizes were cast in order to explore the various properties of concrete. After 28 days of curing in potable water, the samples were exposed to seawater at Nuclear Desalination Demonstration Plant (NDDP) sump at Kalpakkam and were withdrawn for testing at different ages like 56, 90, 180 and 365 days. Nanophase modification increased the pozzolanic activity resulting in faster hydration, early-age strength and long-term compressive and split tensile strength, permissible electrical resistivity for corrosion, lower chloride ion penetration, carbonation depth biofilm formation and higher internal pH. Among the different mixes, the synergy of 1% NC and 1% NT emerged superior with excellent concrete properties related to mechanical properties, pore structure, durability and optimum antibacterial activity.

Controlled annealing induced evolution of local structure and magnetic properties on oleic acid coated and bare nanoparticles composed of iron oxy hydroxide and cubic iron oxides were studied using Mossbauer spectroscopy. Mutually opposite variation of quadrupole splitting and magnetic hyperfine field with respect to that of isomer shift has been observed in both the cases of bare and oleic acid coated nanoparticles subjected to annealing treatments. This manifests in an interesting linear correlation between quadrupole splitting and magnetic hyperfine field. Physics of the observed linear correlation between hyperfine parameters has been elucidated based on the direct proportionality of superexchange interaction on the hyperfine contact interaction and a strong dependence of the strength of superexchange interaction on the structural distortion and point defects mainly due to anionic vacancies. Thus the result of this study plausibly points to a strong coupling between local structure in terms of structural distortions and point defects with magnetic properties while the nanoparticles of iron oxides are subjected to coarsening and reduction.

Criticality alarm systems (CASs) are mandatory in nuclear plants for prompt alarm in the event of any criticality incident. False criticality alarms are not desirable as they create a panic environment for radiation workers. The present article describes the design enhancement of the CAS at each stage and provides maximum availability, preventing false criticality alarms. The failure mode and effect analysis are carried out on each element of a CAS. Based on the analysis, additional hardware circuits are developed for early fault detection. Two different methods are developed, one method for channel loop functionality test and another method for dose alarm test using electronic transient pulse. The design enhancement made for the external systems that are integrated with a CAS includes the power supply, criticality evacuation hooter circuit, radiation data acquisition system along with selection of different soft alarm set points, and centralized electronic test facility. The CAS incorporating all improvements are assembled, installed, tested, and validated along with rigorous surveillance procedures in a nuclear plant for a period of 18,000 h. Keywords: Alarm Announcement, Criticality Alarm System, Failure Mode and Effect Analysis, False Criticality Alarm, Ionization Chamber, Radiation Data Acquisition System

Herein we present a new approach to develop nanocomposites based on plasticized poly (vinyl chloride)/multi-walled carbon nanotubes. The free volume is found to increase with increase in MWCNT content up to 1% CNT, but exceptional decrease was observed at higher loading. The increase in free volume is as a result of intercalation of carbon nanotubes between polymer chains, there by introducing slight disorder to nanocomposites. The decrease in free volume is as a result of bridging of polymer chains by carbon nanotubes, resulting in the decrease in free volume at the vicinity of carbon nanotubes. Structural studies via Raman spectra and Doppler Broadening reveals disorder and interfacial interactions in nanocomposites. A frequency up shift of G band is due to π electron transfer from MWCNT to chlorine in PPVC. Using Tao-Eldrup model, radius of free volume (R) and volume of free volume (Vf) are calculated for nanocomposites. Morphological studies via FESEM and TEM reveal uniform dispersion of MWCNT throughout the polymer matrix. Hence, nanocomposite with maximum MWCNT loading showed electrical conductivity of 4.2E-10 S/cm. Thus this is a new composite material for antistatic application.

Electrochemical measurements combined with high resolution transmission electron microscopy studies have been used to follow the microstructure changes in nanoporous Au subjected to electro-oxidation and oxygen reduction reactions. The microscopy results reveal that different types of lattice defects such as stacking fault tetrahedra present in as-dealloyed and oxide formed nanoporous Au. It is shown that Au inter-planar spacing in the defect concentrated regions in as-dealloyed nanoporous Au has increased by 8%. This anomalous change may be attributed to the binding of oxygen containing ads-species in the electrolyte on Au atoms, albeit weakly, in the presence of defects.

Preferential site occupancy of lithium in the phosphate based mineral strontium chlorapatite has been studied using solid state NMR spectroscopy and first principles calculations. 31 P Magic Angle Spinning (MAS) NMR shows evidence for strontium being substituted by lithium. The results are discussed on the basis of incommensurate lattice and lattice distortion caused by Li substitution. Detailed analysis of the 7 Li MAS NMR spectra as well as ab-initio calculations show preferential occupation of lithium in eight coordinated cation site (M(II)) rather than the nine coordinated M(I) site and also distribution of the local environment around the cation ion site.

This work reports multiferroic behaviour of bulk Bi2Fe4O9 exhibiting both weak ferromagnetic and ferroelectric behaviour at room temperature. Importantly the ferroelectric parameters and dielectric constant are observed to be sensitively dependent upon the magnetic field indicating the occurrence of spin charge coupling. Based on the dielectric measurements under the application of magnetic field, the magneto dielectric coupling (MD %) is found to vary from 0% to about −20% with increasing magnetic field. The observed variation in MD% is attributed to the weak magnetoelectric coupling in such systems.

The trigonal/bcc orientation relationships (ORs) and their likelihood of occurrence are extensively studied using dispersed Y4Zr3O12 ( δ ) nano-precipitates in bcc Fe ( α ) matrix by means of transmission electron microscopy, image simulations and a crystallographic model. Two orientation relationships related by a rotation: [ 1 2 0 ] δ | | [ 111 ] α with ( 21 2 ) δ | | ( 1 10 ) α and [ 1 2 0 ] δ | | [ 111 ] α with ( 00 3 ) δ | | ( 1 10 ) α , are established and periodic arrays of misfit dislocation doublets are identified at the strained interface in ( 110 ) α for both ORs. Further eighteen energetically feasible ORs in Y4Zr3O12/bcc system are deduced by combining stereographic projections, which include the two predominant ORs in this study and other ORs in literature. The orientation relationship which generates interface with a minimum number of dislocation doublets is the most frequent. The precipitate size dependence of ORs and the role of predominant OR in strengthening mechanism are discussed.

Continuous monitoring of the ambient air for the presence of radioactivity is a mandatory requirement in nuclear facilities to be able to initiate prompt actions for the protection of workers from internal exposures. The dual-phosphor scintillator-based continuous air monitor (DPCAM) is an instrument to measure airborne of alpha and beta radioactivities. The functionality of the detector, photomultiplier tube (PMT) along with electronics of DPCAM, is to be tested at periodic intervals to ensure reliability. This paper describes the development of a technique for remote online performance evaluation of PMT along with its electronics, using an LED light source activated from the central monitoring station. A detailed study was made on the response of DPCAM subjected to a pulsed light source of different wavelengths using LEDs. The most suitable LED was selected based on alpha–beta pulse discrimination with zero crosstalk and minimum relative intrinsic error for the full range. The selected LED was fixed on PMT. The DPCAM test circuit was designed and developed for the generation of test frequency to drive this LED. A dedicated radiation data acquisition system was configured using ZigBee wireless network. The remote online performance evaluation of the prototype DPCAM was carried out using loaded filter paper in the field and alpha–beta radioactive sources along with the pulsed light source. The real-time trend graphs generated during the evaluation provides five-point calibration, verification of relative intrinsic error, and verification of crosstalk between alpha–beta channels.

Nanocrystalline lithium magnesium borate (LiMgBO3) powders were synthesized by a Pechini process. Thermal behavior of the polymeric intermediate of LiMgBO3 sample was studied by TG-DTA. Structure and the local structural coordination of the as-prepared and calcined polymeric intermediate at 750 °C of LiMgBO3 sample were investigated by FT-IR and 7Li & 11B magic angle spinning - nuclear magnetic resonance (MAS-NMR) measurements respectively. XRD results confirm the formation of the pure nanocrystalline monoclinic phase of the LiMgBO3 sample prepared at 750 °C. The BET surface area of the calcined polymeric intermediate of LiMgBO3 sample is found to be 60.48 m2g-1. The observed SEM micrographs of the LiMgBO3 sample showed the formation of agglomerated sheet-like morphology particles and the existence of Mg and O elements in LiMgBO3 are confirmed from the SEM-EDX spectral result. The band gap energy of LiMgBO3 sample is evaluated and it was found to be 3.64 eV. From the analysis of the measured impedance data, at different frequencies and temperatures, the evaluated electrical conductivity of LiMgBO3 sample was found to be 9.706 × 10−5 S cm−1 at 200 °C. From the temperature dependence of conductivity (log σT vs. 1000/T) plot of the LiMgBO3 sample, the evaluated activation energy (Ea) for the migration of the charge carrier was found to be 0.62 eV. The measured impedance data and the LiMgBO3 sample pellet dimensions were used for calculating AC conductivity (σac), dielectric (e′, e″, tan δ), electric modulus (M′ and M″) data and were analyzed to find out the electrical and dielectric properties of the LiMgBO3 sample.

Periodical surveillance, checking, testing, and calibration of the installed Area Gamma Radiation Monitors (AGRM) in the nuclear plants are mandatory. The functionality of AGRM counting electronics and Geiger-Muller (GM) tube is to be monitored periodically. The present paper describes the development of online electronic calibration and testing of the GM tube from the control room. Two electronic circuits were developed, one for AGRM electronic test and another for AGRM detector test. A dedicated radiation data acquisition system was developed using an open platform communication server and data acquisition software. The Modbus RTU protocol on ZigBee based wireless communication was used for online monitoring and testing. The AGRM electronic test helps to carry out the three-point electronic calibration and verification of accuracy. The AGRM detector test is used to verify the GM threshold voltage and the plateau slope of the GM tube in-situ. The real-time trend graphs generated during these tests clearly identified the state of health of AGRM electronics and GM tube on go/no-go basis. This method reduces the radiation exposures received by the maintenance crew and facilitates quick testing with minimum downtime of the instrument.

We report the detailed thermal, structural, microstructural and electrical transport studies on PbxGe42 − xSe58 with (0 ≤ x ≤ 20) glasses. The influence of Pb content on thermal and local atomic structure and its qualitative consequences on the electronic properties has been elucidated. The composition dependent variation of glass transition temperature (Tg), change in specific heat capacity at the glass transition (ΔCp) and non-reversing enthalpy change (ΔHNR) complement with each other for enabling the role of Pb content on structural relaxation behavior of these glasses. The Raman spectroscopic studies reveal the presence of different structural species and its variation with Pb content, i.e. pronounced decrease in the amount of ethane-like structural units with the incorporation of Pb content. The addition of Pb content into Ge42Se58 glass, the network connectivity becomes loosened due to the depolymerization. The observed Raman band position of ethane-like structural units show noticeable blue shift with an increase of Pb content, which dictates the development of stress in the network structure caused by the predominant ionic character. The microstructural studies by positron annihilation life-time spectroscopy reveal the nature of defect states and its variation with Pb content. The composition dependent dc conductivity and its activation energy shows marked change across the p-n transition threshold due to the change in the charged defect concentration. The influence of local atomic structure and nature of defect states responsible for the carrier type reversal (CTR) has been discussed.

In the present study, indium–tin-oxide (ITO) nanoparticles were synthesized using solid-state reaction and studied for their structural, vibrational and magnetic properties. The ITO nanoparticles were prepared under reduced pressure, which can increase the oxygen vacancies in the samples. The X-ray diffraction studies confirmed singe-phase cubic bixbyite structure of ITO with average crystallite size of 47 nm. The lattice vibrational studies (FT-IR and Raman spectroscopy) at room temperature indicated that Sn ions were occupied in In2O3 lattice and gives corresponding active vibrational modes in the respective spectra. The magnetic studies at room temperature reveal the ferromagnetic nature of ITO and the strength of magnetization is superior to those of In2O3 and SnO2. However, the magnetic studies at 100 K revealed reduced ferromagnetism, which could be attributed to reduced itinerary electrons at low temperature. Blue and blue–green emissions were found from the ITO nanoparticles, which could be due to vacancies or surface defects present in the system.

High-temperature irradiation damage studies of Indian Reduced Activation Ferritic/Martensitic (INRAFM) steel have been carried out at doses relevant to fusion reactor first-wall irradiation conditions. The samples were irradiated up to 70 dpa with 1.1 MeV Fe ions at various temperatures viz., room temperature (RT), 473 K, 673 K and 773 K, with and without pre-injected helium. Depth-wise distribution of irradiation-induced defects and their thermal stability has been studied using positron beam based Doppler broadening spectroscopy. Samples without pre-injected helium show an overall reduction in S-parameter with respect to the irradiation temperature and no growth of voids has occurred, and complete defect recovery is observed at 673 K. In samples that were pre-injected with helium, a decrease in S-parameter due to annealing of vacancies and the formation of HemVn clusters is observed from RT to 673 K, and an increase in S-parameter associated with the growth of helium bubbles is observed at 773 K. Thus, helium is found to be necessary and crucial in stabilization and growth of the bubble cavities.

Stability of superparamagnetic magnetite nanoparticles as formed in Zeolite has been addressed in a detailed manner based on isochronal annealing studies using Mossbauer spectroscopy. A strong binding of these nanoparticles in Zeolite has been deduced as the coarsening of the nanoparticles is observed following annealing treatments beyond 825 K. In addition, the magnetic interactions between these superparamagnetic magnetite nanoparticles in the as dispersed condition in Zeolite have been elucidated by means of low temperature Mossbauer studies. A strong dependence of the dipole–dipole interactions between superparamagnetic particles of cubic iron oxides is deduced based on this study.