A facile electrochemical synthesis of crystalline (100) oriented Zinc oxide (ZnO) nanowires on indium tin oxide films is presented. The effect of copper doping in modifying the morphology, structure, photoluminescence and band-gap of ZnO nanorods has also been investigated. Remarkably during the process of Cu doping, although the nanorods retain their crystalline orientation, a lattice expansion, defect generation as well as morphological modifications are observed using X-ray diffraction, Raman spectroscopy and Scanning electron microscopy. Results also confirm a band-gap tuning of the as-synthesized nanorods as well as after Cu doping. A red shift in the band-gap from 3.23, for pristine ZnO nanorods, to 2.37 eV after 10% Cu incorporation is noticed. Significantly, PL results indicate that although the pristine ZnO nanorods are in photoluminescence ON state with highest PL intensity, a PL OFF state (with 98% visible PL quenched) is present after 1% Cu incorporation.

The unique physical and chemical properties of platinum group elements are making them indispensable in many modern industrial applications. Platinum-group minerals are usually beneficiated by flotation or gravity separation followed by flotation. Due to poor liberation characteristics and interstitial attachment of these minerals with base metal sulfides, chromites, and silicates, fine grinding is necessitated. Significant variability of platinum group element deposit types and their mineralogical characteristics create a challenge to choose a proper reagent suite. The present article critically discusses all the factors that affect the flotation of platinum group element bearing minerals, flotation routes, essential gaps, the problems associated with their processing, and suitable reagent suites used in different ore deposits and plant practices.

Comprehensive characterization studies are carried out to develop a suitable beneficiation process for treating low-grade platinum group elements (PGEs) ore from Mesoarchean Boula-Nuasahi Igneous Complex in southern part of Singhbhum Craton, eastern India. The PGE mineralization is magmatic and hydrothermal in origin and found in association with NNW–SSE-trending mafic–ultramafic igneous rocks in the tectonic brecciated zone toward the eastern part of the complex. The PGE-bearing minerals are very fine grained (< 1–50 µ) and exhibit heterogeneous distribution, with a total grade of 2.094 g/t. Chalcopyrite, pyrrhotite, pentlandite, pyrite, etc. are found as discriminate grains while the altered silicates (tremolite, riebeckite, enstatite, etc.) are the main gangue minerals present in this ore. The common PGE minerals, such as sperrylite, sudburyite, braggite, laurite, and testibiopalladite, are identified, and individual elemental distribution is analyzed by electron probe micro-analyzer mapping. Based on the studies, different flow schemes are proposed and discussed.

The present study explores the role of Ti ion implantation in structural phase transition in TiO2 thin films. Raman and TEM results reveal that after implantation Rutile phase in films increases at the expense of Anatase nanostructures. Though the as-deposited films display the presence of bigger anatase nanoparticles, after implantation, predominantly phonon confined smaller (similar to 8 nm in size) anatase nanostructures are observed. GIXRD and Raman results further reflect presence of a critical fluence, 1 x 10(13) ions/cm(2), where the initial transformation from anatase to Rutile phase is observed. The role of Oxygen vacancies, in this transformation, has been explored here by XPS. Modifications in UV-Vis and Bandgap results show rich behavior which also reflects phase transformation at the critical fluence. Results further indicate that the phase transition gets first initiated deeper in the film and later on the surface. Interestingly, aggregation of larger Anatase nano-particles appears to be responsible for the structural transformation as observed here.

We present photoabsorption (PA) response and resistive switching (RS) behavior of ZnO thin films that were ion implanted, at many fluences, with 50 keV Ti ions. Photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), UV-Visible spectroscopy and conductive- Atomic Force Microscopy (c-AFM) have been utilized to study the role of oxygen vacancies (O-v) in the evolution of the PA and RS properties. Grazing incidence X-ray diffraction (GIXRD) and Raman Scattering results suggest an improvement in the crystallinity of the films with ion fluence. Enhancement in oxygen vacancy, with fluence, appears to be responsible for higher photo response in the UV-Vis range. Additionally, engineering of bandgap, exhibiting systematic reduction in bandgap- energy with fluence, introduces enhanced absorption in visible regime. For the films implanted at the highest fluence, an asymmetric RS behavior is observed. A Switching behavior, from a high resistance state to a low resistance state, is demonstrated under positive bias conditions. However, for negative bias conditions a rectifying nature is seen. Oxygen vacancies play a crucial role in the modulation of PA response as well as in RS mechanism. Migration of these oxygen vacancies contribute to the formation of conducting filament which may be crucial for the observation of RS phenomenon at the highest fluence.

Aligned ZnO nanorods (NRs) were synthesized by a simple and inexpensive hydrothermal method. Morphological, structural, photoabsorbance and photoluminescence studies have been carried out using field emission scanning electron microscopy (FE-SEM), grazing incidence X-ray diffraction (GIXRD), Raman, UV–visible and Photoluminescence spectroscopy. Results show that crystallinity and alignment of ZnO NRs lead to good photocatalytic activity in the presence of visible light. The Photoluminescence spectra revealed a decrease in the UV emission, suggesting a reduced recombination of the photo generated carriers. The visible region emission is due to the surface oxygen vacancies. Increase of charge separation rate observed from emission spectra and the vacancy related sub-bands in the absorbance spectra are together responsible for the enhanced visible light photocatalytic activity of ZnO NRs. Vertically aligned 1-D morphology of ZnO NRs and the presence of oxygen vacancy states assist in the visible light photocatalytic degradation of Methylene Blue dye.

We investigate here the structural phase transformation and electrical resistive switching properties of TiO2 thin films (80 nm) after their self-ion implantation with 50 keV Ti+ ions at several fluences. UV-Raman, grazing incidence x-ray diffraction (GIXRD), transmission electron microscopy, x-ray photoelectron spectroscopy, and atomic force microscopy techniques have been utilized to investigate the modifications in thin films. Both, the as-grown and ion implanted, films display mixed phases of rutile (R) and anatase (A). Surprisingly, however, a phase transition from A to R is observed at a critical fluence, where some anatase content transforms into rutile. This A to R transformation increases with additional fluence. The critical fluence found by GIXRD is slightly smaller (1×1013 ions/cm2) than from UV-Raman (1×1014 ions/cm2), indicating the first initiation of phase transformation probably in bulk. All the films contain anatase in nanocrystalline form also and the phase transformation seems to take place via aggregation of anatase nanoparticles. Thin films also show the presence of oxygen vacancies (OV) Ti3+, whose number grows with fluence. These OV as well as thermal spikes created during Ti+ ion implantation are also crucial for the A-R transition. After implantation at the highest fluence, TiO2 thin films show bipolar resistive switching behavior. The development of conducting filaments, formed by the migration of many oxygen vacancies generated during ion implantation, can be responsible for this behavior.

Nanocrystalli ne tin dioxide (SnO2) has been synthesized by simple chemical route i.e., pyrophoric technique. The samples were annealed at various temperatures starting from 650 degrees C to 950 degrees C with a step scan of 100 degrees C using conventional high temperature furnace. The annealed samples were employed with X-ray diffractometer for structural analysis. The X-ray scanning manifests that annealed SnO2 samples have pure tetragonal rutile phase. The crystallite sizes and lattice strain on the peak augmentation of SnO2 nanoparticles are evaluated using Williamson Hall (W-H) plot and size-strain plot. The crystallite size and strain for all the samples were calculated using uniform deformation model (UDM), uniform stress deformation model (USDM), uniform deformation energy density model (UDEDM) and by the size -strain plot technique. The optical band gap (E9) for 650 degrees C annealed SnO2 sample is estimated to be 3.59 eV and there is not much variation in the optical band gap with the increase in annealed temperature of SnO2.

Modifications induced by 79MeV Br ions in rutile titanium dioxide thin films, synthesized by dc magnetron sputtering are presented. Irradiations did not induce any new XRD peak corresponding to any other phase. The area and the width of the XRD peaks were considerably affected by irradiation, and peaks shifted to lower angles. But the samples retained their crystallinity at the highest fluence (1×1013ionscm−2) of irradiation even though the electronic energy loss of 79MeV Br ions far exceeds the reported threshold value for amorphization of rutile TiO2. Fitting of the fluence dependence of the XRD peak area to Poisson equation yielded the radius of ion tracks as 2.4nm. Ion track radius obtained from the simulation based on the thermal spike model matches closely with that obtained from the fluence dependence of the area under XRD peaks. Williamson–Hall analysis of the XRD spectra indicated broadening and shifting of the peaks are a consequence of irradiation induced defect accumulation leading to microstrains, as was also indicated by Raman and UV–Visible absorption study.

Nanostructures (NS) have been fabricated on rutile TiO2(110) single crystal surfaces using Ar ion beam sputtering technique. Pronounced quantum confinement effects in TiO2 nanodots lead to reduction in optical reflectance and bandgap widening. Moreover, a direct correlation between the size of NS and magnetic behavior is observed. This suggests that the size of NS plays crucial role in the evolution of magnetic nature. Though the smallest (∼5nm) NS display superparamagnetic (SPM) behavior, ferromagnetism is observed for larger nanostructures. Single domain nature of TiO2 quantum dots is responsible for the observed SPM behavior.

Two sets of gold thin films of thickness of about 20 and 50 nm, grown by thermal evaporation method on (100) silicon wafers were irradiated by 197 MeV Au ions. Grazing incidence X-Ray diffraction (GIXRD) study has been revealed lattice expansion on decreasing the film thickness. 197 MeV Au ion irradiation was not affect either the cubic crystal structure of gold or its lattice parameter. Atomic force microscopy (AFM) study indicated that the evolution of the surface morphology with ion fluence crucially depended on the film thickness, the thinner film being more sensitive than the thicker one. Irradiation led to nanoparticles formation on the surface of the films. This observation is in contrast to the generally perceived damaging role of swift heavy ion (SHI) irradiation. Power spectral density analysis of the roughness along both the lateral and vertical directions demonstrated dominance of surface diffusion over volume diffusion induced by SHI irradiation. A comparison of the sputtering yield obtained from Rutherford back scattering (RBS) spectra of the irradiated films and transmission electron microscopy (TEM) of the particles sputtered from the films and collected by a catcher grid during irradiation indicated that more than the surface and volume diffusion processes, it is the irradiation induced sputtering that controls the overall surface morphology of the films. The surface roughness increase with ion fluence and the irradiation induced sputtering yield was found to be larger in thinner films. Film thickness dependence of the evolution of surface morphology and sputtering yield with 197 MeV Au ion irradiation clearly indicates the dominance of the electronic energy loss over the nuclear energy loss of the projectiles ions in the target medium and opens up the ways for examining the applicability of different models of ion-matter interaction in systems with reduced dimensions.

Gold thin films of varying thickness (10–100nm) grown on silica substrates by e-beam evaporation method were irradiated by 120MeV Au ions at 3×1012 and 1×1013ionscm−2 fluences. Irradiation induced modifications of these films were probed by glancing angle X-ray diffraction (GAXRD), atomic force microscopy (AFM), Rutherford backscattering spectrometry (RBS) and surface enhanced Raman scattering (SERS). Irradiation didn’t affect the structure, the lattice parameter or the crystallite size, but modified the texturing of grains from [111] to [220]. RBS indicated thickness dependent sputtering on irradiation. The sputtering yield was found to decrease with increasing thickness. AFM indicated increase of roughness with increasing irradiation fluence for films of all thickness. In agreement with the AFM observation, the gold nanostructures on the surface of 20nm thick film were found to increase the SERS signal of acridine orange dye attached to these structures. The SERS peaks were amplified by many fold with increasing ion fluence. The effect of 120MeV Au ion irradiation on the grain texture, surface morphology and SERS activity in addition to the thickness dependent sputtering in gold thin films are explained by the thermal spike model of ion-matter interaction.

Polycrystalline AgInSe2 thin films were prepared by DC magnetron sputtering on glass substrate. The selenization process was adopted for the preparation of the film from Ag/ln/Ag/In multilayer stack. The multilayer films were selenized and annealed at various temperatures. Evolution of the composition and structure of the films with selenization temperature and then on annealing each selenized films at different temperatures was studied by X-ray diffraction. The study revealed that the prepared films have polycrystalline structure with AgInSe2 as the major phase. The other phase is Ag2Se, whose volume fraction depended on the selenization and annealing temperatures. A systematic search by comparing the phase composition and structure of different films revealed that the film selenized at 350 degrees C and annealed at 500 degrees C is the optimum condition for preparing AgInSe2 with lattice parameter c/a ratio close to that of ideal chalcopyrite structure. The results obtained thus lead to a better understanding of the growth processes of Chalcopyrite AgInSe2 thin films.

Formation of preferentially (101) oriented rutile phase directly, without the conventionally observed intermediate anatase phase of TiO2 is reported in thin films prepared by direct current (dc) magnetron sputtering of titanium metal target. The films were annealed at different temperatures between 400 and 1000 degrees C in air for 1 hour. The structural and micro structural properties of TiO2 thin film, investigated by glancing angle X-ray diffraction and atomic force microscopy (AFM) indicated that the rutile grains are single crystalline and these grow preferentially along (111) plane with increasing annealing temperature. The as-deposited titanium thin film was amorphous, whereas the titanium thin film annealed in the range of 400-1000 degrees C showed phase pure rutile structure. The root mean square roughness estimated from AFM study is found to increase with annealing temperature and rate of increase was identical to that of the grain size. The present study thus addresses the question of the phase transformation mechanism in TiO2 on annealing at high temperatures leading to the formation of preferentially oriented rutile phase without the formation of the intermediate anatase phase.

BiFeO3 thin films deposited by sol-gel spin coating method were irradiated by 200 MeV Ag ions. Irradiation induced modification of the microstructure of the films was studied by X-ray diffraction (XRD), micro Raman, UV-Visible spectroscopy, atomic force microscopy and current-voltage (I-V) measurements. XRD analysis revealed that the pristine films are crystalline BiFeO3 phase. Ion irradiation led to fragmentation of the crystallites in the films up to the fluence of 3 x 10(12) ions cm(-2) and amorphization beyond this fluence. The crystallite size showed a monotonic decrease with increasing ion fluence. XRD peaks shifted to lower angles with increasing ion fluence, thus indicating irradiation induced increase of lattice parameter. Irradiation induced lattice expansion is understood on the basic of reduction of crystallite size. In agreement with this observation, the optical band gap showed blue shift with increasing ion fluence. I-V measurement showed a three orders of magnitude decrease of the leakage current density with increasing ion fluence up to 3 x 1012 ions cm(-2). This dramatic decrease of leakage current density is explained on the basis of widening of the band gap, which is a direct consequence of SHI induced crystallite size reduction.

Two dimensional nanostructures have been created on the rutile TiO2 (110) surfaces via ion irradiation technique. Enhanced anomalous photo- absorption response is displayed, where nanostructures of 15 nm diameter with 0.5 nm height, and not the smaller nanostructures with larger surface area, delineate highest absorbance. Comprehensive investigations of oxygen vacancy states, on ion- irradiated surfaces, display a remarkable result that the number of vacancies saturates for higher fluences. A competition between the number of vacancy sites on the nanostructure in conjunction with its size is responsible for the observed anomalous photo-absorption.

Thermally evaporated gold thin films of 10 to 50 nm thickness deposited on Si (100) substrate were annealed at 250 degrees C under vacuum for different period. The as-deposited and annealed films were characterized by glancing angle X-ray diffraction (GAXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Rutherford backscattering spectrometry (RBS) and d. c. resistivity. GAXRD indicated improvement of crystallite size up to 2 hours of annealing and degradation of the same thereafter. In agreement with XRD result, AFM and SEM indicated grain growth with annealing time up to 2 hours and stagnation or even decrease of grain size thereafter. The dependence of the grain size evolution with annealing time on the thickness of the film was seen from RBS, which corroborated the XRD, AFM and SEM results. The electrical resistivity of the films of different thickness also showed the same trend of evolution with annealing time, clearly indicating the importance of microstructure in controlling the electrical conduction in the films. Power spectral density (PSD) analysis of AFM images indicated that surface morphology evolution in gold thin films under annealing is dominated by surface diffusion mass transport. This unusual result of the suppression of crystallinity on annealing beyond a particular period is understood by two competing processes: grain growth due to accelerated particle diffusion across rough surfaces under annealing and smoothening of grain surface with formation of grooves at the boundary between adjacent grains inhibiting further grain growth.

BiFeO 3 (BFO) thin films of thickness about 800 nm deposited on Si (100) substrates by sol–gel spin coating method were irradiated by 200 MeV Ag ions. Modification of structure and surface morphology of the films under irradiation was studied using glancing incidence X-ray diffraction (GIXRD) and atomic force microscope (AFM). Fluence dependence of GIXRD peak intensity indicated formation of 10 nm diameter cylindrical amorphous columns in crystalline BFO due to 200 MeV Ag ion irradiation. AFM analysis indicated that the pristine film consists of agglomerated grains with diffuse grain boundary. Irradiation led to reduced agglomeration of the grains with the formation of sharper grain boundaries. The rms roughness ( σ rms ) estimated from AFM analysis increased from 6·2 in pristine film to 12·7 nm when the film irradiated at a fluence of 1 × 10 11 ions cm − 2 . Further irradiation led to decrease of σ rms which finally saturated at a value of 7–8 nm at high ion fluences. The power spectral density analysis indicated that the evolution of surface morphology of the pristine film is governed by the combined effect of evaporation condensation and volume diffusion processes. Swift heavy ion irradiation seems to increase the dominance of volume diffusion in controlling surface morphology of the film at high ion fluences.

Investigations were carried out on lime stone rejects (-1mm) generated at a lime stone washing plant in southern India. These rejects contain 12.09% CaO, 2.95% MgO, 10.73% Al2O3, 4.99% Fe2O3, 43.05% SiO2 and 24.92% LOI. Mineralogical studies including SEM-EDAX, XRD, FTIR and TGA were conducted to confirm relative distribution of minerals in the flotation feed and products. These studies revealed that feed sample consists of quartz and calcite as the major minerals with minor amounts of montmorillonite and dolomite whereas flotation concentrate dominantly consists of calcite, and tailings mostly of quartz and montmorillonite. A commercial grade sodium silicate, oleic acid and MIBC were used as depressant, collector and frother respectively in flotation studies. The effects of different operating parameters were evaluated for both conventional and column flotation. Two stage conventional cell flotation results indicate that a cleaner concentrate of 42.50% lime (CaO) content could be obtained at a yield of 15.65%. The lime (CaO) content of the concentrate was further enhanced up to 44.23% at 20.73% yield using single stage column flotation. The column flotation is more efficient in comparison to the conventional cell for treating this sample. A process flowsheet was developed to treat these rejects based on the studies carried out. This process can minimize the waste generation and the concentrate generated during this process can be directly utilized in the Indian cement industries.