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Organic–inorganic nanocomposite self-standing films of Gd3Ga3Al2O12(GGAG) uniformly dispersed in poly(methyl methacrylate) (PMMA) and polystyrene polymer are prepared for radiography application.

AbstractThe use of accelerator-driven systems for incineration of nuclear waste and energy production requires monitoring of different parameters that govern reactor safety. One of the most important parameters is the multiplication factor keff. The present paper describes the results of experiments carried out on a subcritical system (BRAHMMA) using a pulsed neutron source. The value of the multiplication factor keffobtained from time responses of the core that were measured in situ using neutron detectors after insertion of a neutron pulse matches well with the calculated value.

Single crystals of Gd3Ga3Al2O12:Ce with B codopants were successfully grown using the Czochralski technique. The timing characteristics of the crystal was measured by coupling the crystal to photomultiplier tubes (PMT) or silicon photodiodes [Si(PIN)]. The two prompt γ‐rays emitted in a cascade from 60Co or 22Na source were detected in coincidence using Gd3Ga3Al2O12:Ce,B crystal detectors and a BaF2detector. The time resolution of these crystals are observed to be better than that measured for CsI:Tl crystal coupled to PMT or Si(PIN) in an identical measurement setup.

Glass having composition 40SrO-10ZnO-40SiO2-2B2O3-2Al2O3-2TiO2-2Cr2O3-2Y2O3(mol%) was prepared by melt-quench technique and converted into glass-ceramics by controlled crystallization. Formed crystalline phases in glass-ceramics were identified using powder XRD. MAS-NMR spectroscopy shows the presence of mainly Q1and Q2silicate structural units and BO3structural units of boron in the glass network. It is inferred from 29Si NMR and XRD that glass-ceramics have high crystallinity and during crystallization initially Sr2ZnSi2O7crystalline phase is formed and later SrSiO3crystalline phase is crystallized. 11B and 27Al MAS-NMR of glass-ceramics depict an increase in the BO4and AlO4structural units with the crystallization. In accordance with XRD, NMR results also suggest the formation of solid solution of Sr2ZnSi2O7phase with substitution of Zn/Si tetrahedral sites with B/Al.

The field-emission properties of SnO2:WO2.72hierarchical nanowire heterostructure have been investigated. Nanoheterostructure consisting of SnO2nanowires as stem and WO2.72nanothorns as branches are synthesized in two steps by physical vapor deposition technique. Their field emission properties were recorded. A low turn-on field of ∼0.82 V/μm (to draw an emission current density ∼10 μA/cm2) is achieved along with stable emission for 4 h duration. The emission characteristic shows the SnO2:WO2.72nanoheterostructures are extremely suitable for field-emission applications.

In this paper, we report on PbMoO4crystals grown from melts of controlled stoichiometric variations under different ambient conditions. It is observed that PbMoO4crystals of different shades not only differ in their impurity contents but their stoichiometries with regard to both cationic and anionic compositions could be different. Annealing studies in airoxygen as well as in vacuum were carried out on the crystals for a better understanding of the defect centers responsible for the coloration. The role of nonstoichiometric giving rise to coloration is also described.

Thin films of highTcoxide superconductor were deposited on sintered SrTiO3substrates by 50 Hz a.c. sputtering. The superconducting onset temperature occurred at 90 K and the offset temperature at 72 K. The deposition conditions were found to influence the ordering of the annealed films.

The results of our initial efforts to deposit thin films of YBa2Cu3O7−xsystem on sapphire substrate are described. The deposited films are shiny black in appearance and are of quite uniform chemical composition. The annealed films exhibit zero resistance superconducting transition temperatureTc(R=0) ranging between 23 K and 30 K.

The preparation of ceramic superconductors based on the Bi-Sr-Ca-Cu-O system in a reproducible manner with zero-resistance transition temperatures (Tc) tailored between 65 and 85 K is described. Partial melting of the sample pellet during preparation helps in raising itsTc. Thick crystallographically oriented films of the material withTc=77 K have been prepared on sintered SrTiO3 substrates.

Thick films of Bi2Sr2CaCu2Ox superconducting at 84 K have been prepared on polycrystalline MgO substrates. The effect of heat treatment on phases formed at various stages of the film preparation is studied. Investigations show that a thin layer at the top is highly oriented while the bulk of the 212 phase material beneath it consists of randomly oriented grains. This appears to be the main reason for the low critical current densities obtained in practice.

Fluorine-doped tin oxide (FTO) coated glass substrates are etched by a mixture of Zn and HCl for solar cells, flat panel displays, and related applications. However, this chemical etching method has its own limitations, and the most important limitation is no control on the etching process. Here, we report a controlled etching of FTO-coated glass substrate by a chronoamperometric method. In this method, optimized step potentials, −3 V for 10 s, −5 V for 80 s and −9 V for 10 s are applied between the FTO substrate to be etched and a counter electrode dipped in acidic 0.1 M FeCl3(aq) electrolyte. The etched FTO was characterized by the energy dispersive X-ray spectroscopy showing complete removal of conducting FTO layer that was further studied by current-voltage characteristics. The chemical reaction involved in this etching process was investigated by the X-ray photoelectron spectroscopy that reveals similar chemical reaction as reported for the chemical method.