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Electrolysis of seawater gets an attention to produce hydrogen for renewable energy technology. It significantly reduces the use of fresh water instead of seawater. Development of low temperature fabrication of electrocatalyst can explore seawater splitting by avoiding chloride reduction during the hydrogen production. In the present work, we fabricated low temperature hydrothermal growth of Cu2S electrocatalyst on Ni foam at constant temperature of 80 °C at different growth times of 1–3 h. The prepared Cu2S electrocatalyst grown for 1 h exhibited low overpotentials of 76 and 118 mV at 10 mA/cm2 (289 and 358 mV overpotentials at 100 mA/cm2) in 1 M KOH deionized water and seawater, respectively for hydrogen evolution reaction (HER). The Tafel plot of Cu2S catalyst grown for 1 h showed lesser Tafel slope value of 128 mVdec−1 than that of other growth times 2 h (136 mVdec−1) and 3 h (142 mV dec−1) indicating elevated electrocatalytic behaviour of Cu2S grown for 1 h. Electrochemical impedance spectroscopy (EIS) showed charge transfer resistance of 12.8Ω, 19.6 Ω and 25.7Ω, for Cu2S grown for 1, 2 and 3 h, respectively, this lower charge transfer resistance indicated higher charge transfer properties. The Cu2S electrocatalyst grown for 1 h sustained retention of 80% after 12 h continuous stability test. Therefore, the cost-effective and low temperature fabrication of Cu2S electrocatalyst proceeds for development of largescale seawater splitting for hydrogen production.

Sesquioxides (Al2O3, Y2O3, Sb2O3) doped Oxy fluoro Cobalt borate novel luminescent series of glasses are prepared by melt quenching method. The structural characteristics of these glasses were studied by XRD, SEM and EDS techniques. The change in physical parameters such as density of all the series of glasses prepared gives a pathway for cobalt/Alumina/Antimony/Yttrium ions to enter in to borate glass network with the enhancement in the concentration of corresponding dopants. The depolymerization of the borate glass network is evident by the decline in various elastic parameters with B-O-Co/Y/Sb/Al bonds and by the modifier role of CoO/Y2O3/Sb2O3/Al2O3 transforming a fraction of tetrahedral BO3 units into BO4 units. Both FTIR and IR spectra indicate an increase in octahedral occupancy of cations Co2+, Y3+, Sb3+and Al3+ ions in the glass network with the increase of their concentration. The conversion rate of tetrahedral BO3 units to octahedral BO4 units leading to the formation of NBOs is more in Al3+ and least in Y3+ with the increase of concentration of sesquioxides at 0.05 mol% concentration of CoO. The optical absorption spectra of all series of glasses prepared reveal that octahedral occupancy of cobalt ions is dominant due to the ligand fields created by different sesquioxide ions in the glass network produce NBOs and number of electrons trapped at the donor centers. The PL spectra of all the series of these glasses reveal the octahedral occupancy of Co2+ ions, which is evident from the two emission transitions 2T1g(H) →4T1g(F) (531–556 nm) and 2Eg→5T2g (699–718 nm).The prepared series of glasses show efficient luminescence of Cobalt ions, and Al2O3 series of glasses are better candidates for luminescence as their emission Cross-sections are highest when compared with the remaining series of glasses.

Content-Based Image Retrieval (CBIR) is another yet broadly recognized method for distinguishing images from monstrous and unannotated image databases. With the improvement of network and mixed media headways ending up being increasingly famous, customers are not content with the regular information retrieval progresses. So nowadays, Content-Based Image Retrieval (CBIR) is the perfect and fast recovery source. Lately, various strategies have been created to improve CBIR execution. Data clustering is an overlooked method of hiding formatting extraction from large data blocks. With large data sets, there is a possibility of high dimensionality Models are a challenging domain with both massive numerical accuracy and efficiency for multidimensional data sets. The calibration and rich information dataset contain the problem of recovery and handling of medical images. Every day, more medical images were converted to digital format. Therefore, this work has applied these data to manage and file a novel approach, the “Clustering (MHC) Approach Using Content-Based Medical Image Retrieval Hybrid.” This work is implemented as four levels. With each level, the effectiveness of job retention is improved. Compared to some of the existing works that are being done in the analysis of this work’s literature, the results of this work are compared. The classification and learning features are used to retrieve medical images in a database. The proposed recovery system performs better than the traditional approach; with precision, recall, F-measure, and accuracy of proposed method are 97.29%, 95.023%, 4.36%, and 98.55% respectively. The recommended approach is most appropriate for recuperating clinical images for various parts of the body.

Online Social media are a huge source of regular communication since most people in the world today use these services to stay communicating with each other in their modern lives. Today’s research has been implemented on emotion recognition by message. The majority of the research uses a method of machine learning. In order to extract information from the textual text written by human beings, natural language processing (NLP) techniques were used. The emotion of humans may be expressed when reading or writing a message. Human beings are willing, since human life is filled with a variety of emotions, to feel various emotions. This analysis helps us to realize the use of text processing and text mining methods by social media researchers in order to classify key data themes. Our experiments presented that the two main social networks in the world are conducting text-based mining on Facebook and Twitter. In this proposed study, we categorized the human feelings such as joy, fear, love, anger, surprise, sadness and thankfulness and compared our results using various methods of machine learning.

Wire arc additive manufacturing is a promising reliable free-form fabrication technique suitable for producing large-scale components that feature a very low buy-to-fly ratio. This research work is...

In this study, solvothermal method was used for the synthesis of MnFe₂O₄ nanoparticles at different processing period of 7, 14, and 21 h. X-ray diffraction (XRD) pattern study confirms that MnFe₂O₄ nanoparticles correspond to the face-centered cubic spinel structure and belong to the Fd3m [227] space group. From Raman spectra analysis, two major peaks were observed at 476 and 616 cm-1, which correspond to the vibration modes of MnFe₂O₄ nanoparticles; especially, the broad peak at 620 cm-1 (A1g) corresponds to the symmetric stretching vibration of oxygen atoms at tetrahedral site. Infrared spectra (FTIR) analysis at 490 and 572 cm-1 can be attributed to the stretching vibration of tetrahedral groups of FeO₄, and the vibration of octahedral groups of FeO6 belongs to the intrinsic vibrations of manganese ferrites. The uniformly distributed MnFe₂O₄ nanospheres (RT2) can be affirmed by field emission scanning electron microscopy images and confirmed by the high-resolution transmission electron microscopic studies. The electrochemical properties of synthesized MnFe₂O₄ nanoparticles investigated by cyclic voltammetry, impedance spectroscopy and galvanstatic charging and discharging (GCD) studies clearly predict the reversible faradaic reactions of MnFe₂O₄ nanospheres. Further, the MnFe₂O₄ nanospheres (RT2) exhibit high specific capacitance of 697 F g-1 at 0.5 A g-1 current density in galvanostatic charging and discharging profile and after 1000 cycles exhibits 79% retain ability of initial specific capacitance and hence can be considered as the efficient electrode for supercapacitor applications.

Synthesis of polyoxometalates (Cu3Mo2O9 nanopowders) was obtained by using solvothermal method and confirmed by X-ray diffraction pattern, with orthorhombic crystalline structure belonging to the space group Pna21(33). Further, the synthesized Cu3Mo2O9 nanopowders were analyzed by using Raman, infrared, and photoluminescence studies. X-ray photoelectron spectroscopy study explained the oxidation states of Mo-3d, Cu-2p, and O-1s in Cu3Mo2O9 nanopowders. Field emission scanning electron microscopy images clearly revealed the formation of nanostructure randomly oriented to form an interconnected rout, which emerged as a good candidate for storing more charges at the surface of Cu3Mo2O9 nanopowders. The electrochemical studies, such as cyclic voltammetry, electro impedance analysis, and galvanostatic charging–discharging studies, were used to analyze its electrochemical properties. To ensure the stability of Cu3Mo2O9 nanopowders, continuous charging and discharging studies were conducted for 1000 cycles at a current density of 5 A g−1 and it exhibited good stability over a large number of cyclic studies with capacity retention of 99.2% after the first 500 cycles.

Entropy generation is an important aspect of modern thermal polymer processing optimization. Many polymers exhibit strongly non-Newtonian effects and dissipation effects in thermal processing. Motivated by these aspects in this article a numerical analysis of the entropy generation with viscous dissipation effect in an unsteady flow of viscoelastic fluid from a vertical cylinder is presented. The Reiner-Rivlin physical model of grade two (second grade fluid) is employed which can envisage normal stress variations in polymeric flow-fields. Viscosity variation is included. The obtained governing equations are resolved using implicit finite difference method of Crank-Nicolson type with well imposed initial and boundary conditions. Key control parameters are the second-grade viscoelastic fluid parameter (β), viscosity variation parameter (γ) and viscous dissipation parameter (e). Also, group parameter (BrΩ-1), Grashof number (Gr) and Prandtl number (Pr) are examined. Numerical solutions are presented for steady-state flow variables, temperature, time histories of friction, wall heat transfer rate, entropy and Bejan curves for distinct values of control parameters. The results specify that entropy generation decreases with augmenting values of β, γ and Gr. The converse trend is noticed with increasing Pr and BrΩ-1. Furthermore, the computations reveal that entropy and Bejan lines only occur close to the hot cylinder wall.

The glasses of composition (35–x) Li 2 O–5ZrO 2 –10Y 2 O 3 –50SiO 2 : x NiO (0 2 O–ZrO 2 –Y 2 O 3 –SiO 2 : NiO glasses indicated gradual increase of octahedral occupancy of Ni 2+ ions in the glass network with the increase in the concentration of NiO in the glass network.

Zinc doped tin oxide nanoparticles were synthesized by employing sol–gel method assisted with different surfactants namely cetyl trimethyl ammonium bromide (CTAB), hexamine and polyethylene glycol 400 (PEG-400). The synthesis of uniform distribution of spherical Zn-SnO2 nanoparticles in presence of PEG-400 was optimized. The synthesized Zn-SnO2 nanoparticles were characterized by employing standard characterization techniques. X-ray diffraction results confirmed the product high-quality crystalline formation. The photoluminescence peaks appeared at 360 nm revealed the recombination of electron and hole from band to band emission of SnO2 optical properties. The vibrational properties of Zn-SnO2 nanoparticles were confirmed by both Raman and infra red spectra. The spherical morphology and nano sized product was evident in 200 nm scale SEM images. The cyclic voltammetry result of the product Zn-SnO2 assisted PEG-400 exhibited the specific capacitance value of 312.7 F/g at scan rate of 10 mV/s and revealed the superior electrochemical properties. Moreover, the EIS and GCD studies also revealed the good supercapacitor nature with specific capacitance of 132.1 F/g at current density of 1 A/g for the product Zn-SnO2 (PEG-400).

Size and shape controlled nickel oxide/nickel vanadate (NiO/Ni3V2O8) nanocomposites were achieved by solvothermal method. Ammonium metavanadate and nickel chloride precursor solution in appropriate proportion was dissolved in solvent with sodium hydroxide as reducing and stabilizing agent. Three different products were obtained by varying solvothermal processing time as 10 h, 14 h and 18 h at 160 °C. X-ray diffraction (XRD), Fourier-transform infrared (FTIR), Raman and photo luminescence (PL) studies substantiate NiO/Ni3V2O8 formation. Field emission scanning electron microscope (FESEM) studies provides detailed information about NiO/Ni3V2O8 nanorods configuration. Electrochemical studies were carried out to understand pseudocapacitive properties of obtained products. Estimated specific capacitance for product PVK1 has superior value as 653 Fg−1 at current density 1 Ag−1 due to nanorods regular arrangement with uniform size distribution.

The characteristics of the plasma jet emanating from a dc non-transferred plasma torch is affected by many factors including arc current, type of gas, gas flow rate, gas injection configuration and torch geometry. The present work focuses on experimental investigation of the influence of shroud gas injection configuration on the I–V characteristics and electro-thermal efficiency of a dc non-transferred plasma torch operated in nitrogen at atmospheric pressure. The plasma gas is injected into the torch axially and shroud gas is injected through three different nozzles such as normal, sheath and twisted nozzles. The effects of flow rates of plasma/axial gas and arc current on I–V characteristics and electro-thermal efficiency of the torch holding different nozzles are investigated. The I–V characteristics and electro-thermal efficiency of the torch are found to be strongly influenced by the shroud gas injection configuration. The effect of arc current on arc voltage decreases with increasing the axial gas flow rate. At higher axial gas flow rate (> 45 lpm), the I–V characteristics of the plasma torch are similar irrespective of the nozzle used. The variation of electro-thermal efficiency with arc current is almost similar to that of arc voltage with arc current. As expected, the electro-thermal efficiency is increased when the axial gas flow rate is increased and at higher axial gas flow rate, it is not influenced by the arc current and shroud gas configuration. The plasma torch with normal nozzle may be better in the range of operating conditions used in this study.

A simple approach was adapted to synthesis nanoplatelet, nano urchin-flower and nanosphere NiMoO4 by employing cetyl trimethyl ammonium bromide (CTAB) as a capping agent. Product pseudocapacitive property was studied by measuring suitable parameters. SEM studies revealed diverse morphology of NiMoO4 nanoplatelet, nano urchin-flower and nanosphere within nanoscale region. Electrochemical studies explored the better electrode behavior of NiMoO4 nanoplatelet (RC1) with specific capacitance of 178 F/g at 10 mV/s scan rate and 110 F/g at 100 mV/s scan rate. A Nyquist spectrum of products (RC1, RC2 and RC3) also revealed the better pseudocapacitive performance of NiMoO4.

Metal ions (M) (M=Ag+, Cu2+, Sm3+ and Eu3+) doped KAl0.33W1.67O6 are obtained at room temperature by ion exchange method. These materials are characterized by powder X-Ray diffraction (XRD), and UV–visible DRS. All these materials are crystallized in a cubic lattice with F d 3 ¯ m space group. The dependence of photoluminescence properties of Sm3+ and Eu3+ in KAl0.33W1.67O6 lattice is examined with reference to rare earth ion concentration. The AC conductivity measurements of Ag+ and Cu2+ doped KAl0.33W1.67O6 are carried out in the temperature range 30–450 °C. The variation of conductivity with frequency and temperature is explained.

The role of return currents in the plasma dynamics of a dc non-transferred arc plasma torch has been investigated. The anode arc root connects the main plasma column and return current in the anode and its motion governs the return current formation in the anode. Thus by investigating the return currents, we can explore complex spatio-temporal evolution of the plasma in detail. In this work, we have used electrical and magnetic diagnostics. The electrical diagnostic comprises of a high voltage probe, and the magnetic diagnostic consists of a garland of several B-dot probes incorporated inside the anode water cooling channels. The magnetic (B-dot) probes are designed to pick up the dominant component of the time-varying magnetic fields. Results show that, beyond a threshold, volume return currents transform to constricted line currents in the anode return path. This is attributed to eddy currents arising due to space varying rather than time varying return current components in the anode. The probes capture fast rotation of the arc root that is not captured by fast imaging. Also, arc root shunting (restriking) phenomena and its location on the anode periphery are clearly captured by the garland of magnetic probes. A physical model explaining the processes is also presented.

Defect pyrochlores of composition KM 0.33 Te 1.67 O 6 (M = Al, Cr and Fe) were prepared by solid state method. Structural, morphological and optical properties of these materials were obtained by XRD, Raman, SEM, particle size analyser, and UV–Visible diffuse reflectance techniques. The lattice parameter “ a ” was deduced for all the materials from Rietveld refinement program, Fullprof.2k by refining d-lines. The photocatalytic activities of these materials were evaluated by photodegradation of methylene blue. The mechanistic degradation pathway of methylene blue (MB) was studied in the presence of KAl 0.33 Te 1.67 O 6 using terepthalic acid. The DC conductivity measurements of all compositions were carried out in the temperature range 373–673 K. The variation of conductivity with temperature is explained.

A tunnel structure compositions of Ag+- and Sn2+-substituted K3Nb3WO9(PO4)2 photocatalysts were synthesized by an ion exchange method and characterized by powder XRD, SEM–EDS, UV–Vis (DRS), BET and FT-IR. The ion-exchanged products are isomorphous with parent K3Nb3WO9(PO4)2. Absorption edges of Ag+- and Sn2+-doped K3Nb3WO9(PO4)2 samples were red shifted remarkably into the visible light region. Photocatalytic activity of these materials was evaluated by studying the degradation of methylene blue, methyl violet, methyl orange and rhodamine B dyes under visible light irradiation. The photocatalytic properties of these compounds were explained based on their band gap energies, photoluminescence spectra and the amounts of ·OH radicals generated during photocatalysis. The possible photocatalytic mechanistic pathway was discussed. The stability of all catalysts during photocatalytic experiment was also investigated.

Defect pyrochlore of composition KFe0.33W1.67O6 (KFeW) was synthesized by ethylene glycol assisted sol–gel method. The divalent tin doped KFeW (SnFeW) was prepared by ion exchange process using acidified SnCl2. Structural, morphological and optical properties of both materials were characterized by XRD, TGA, SEM-EDS, BET surface analyses and UV–visible diffuse reflectance techniques. The composition of tin-doped KFeW was obtained from EDS and TGA profiles. The cubic lattice parameter 'a' was obtained from Rietveld refinement program, Fullprof.2k, by refining the d- lines of the KFeW. The optical properties of Fe3+ were investigated. Substitution of K+ by Sn2+ led to an absorption shift onset to longer wavelengths. The photocatalytic activities of both samples were evaluated by photodegradation of methylene blue, photooxidation of cyclohexene and solar water-splitting reactions. The mechanistic degradation pathway of methylene blue (MB) was studied in the presence of both photocatalysts.

The investigation of photocatalysis by efficient visible-light-active photocatalysts has been of interest in both the science and the engineering fields. The nitrogen (N) doped KAl0.33W1.67O6 (KAW) and KCr0.33W1.67O6 (KCW) are prepared by the solid state method. Urea was used as a nitrogen source. These materials were characterised by thermo gravimetric analysis, powder X-ray diffraction, scanning electron microscopy, energy dispersive spectra, X-ray photoelectron spectroscopy (XPS) and UV–visible diffuse reflectance spectroscopy (UV–vis DRS). Both the N-doped materials crystallised in a cubic lattice with space group Fd3m. The XPS analysis of the N-doped KAW (N-doped KCW) show the characteristic peaks belonging to K 2p, Al 2p (Cr 2p), W 4f, O 1s and N 1s along with C 1s. The bandgap energy was deduced from their UV–vis DRS profiles. The photocatalytic degradation of the methylene blue solution was investigated in the presence of these oxides. Compared with their parent materials, nitrogen doped KAW and KCW samples exhibit ∼230 and ∼130% increase, respectively, in visible light-induced photodegradation of methylene blue.

The monodispersed CuFe2O4 nanoparticles were synthesized and optimized by employing solvothermal method and were studied by employing X-ray diffraction (XRD) method. The obtained products have tetragonal crystalline cubic-spinel type structure belonging to I 4 1 / a m d space group. The Raman and infrared studies analyzed the different vibration and starching modes of metal-oxide and the pure phase of the obtained CuFe2O4 nanoparticles. The morphology nature of monodispersive CuFe2O4 nanoparticles can be easily identified from field-emission scanning electron microscopy images, and the role of different molarities of KOH at 1, 5, and 10 M (BS1, BS2, BS3) can be clearly observed. The X-ray Photon spectroscopy (XPS) studies the oxidation states of the Cu-2p, Fe-2p and O-1s in CuFe2O4 nanoparticles, which validates the XRD data and supports the crystalline formation. The specific capacitance of BS1 is 189.2 F/g at current density 0.5 A/g. As the current density increases, the diffusing rate of electrolyte ions into the electrodes will reduce, which is reflected in the specific capacitance of CuFe2O4 nanoparticles. The cyclic stability of CuFe2O4 nanoparticles (BS1) exhibits 84% retention after 1000 cycles of galvanostatic charging and discharging studies and the pattern of curve remains the same, which indicates very good coulomb efficiency after long cycles.

The influence of Larmor radius effects on the propagation of whistler waves is investigated experimentally in laboratory plasma. The waves are excited using a loop antenna of diameter less than the electron skin depth, the natural scale length in this regime. In an earlier experiment [G. Joshi et al., Phys. Plasmas 24, 122110 (2017)], it was shown that such waves assume an elongated shape with perpendicular dimensions of the order of skin depth. In the present work, we show that wave propagation is significantly modified when the external guiding magnetic field is decreased. The wave spreads in the perpendicular direction in spite of starting of as an elongated whistler due to electron inertia effects. In the near region, the antenna field becomes dominant even forming null points, with the physical processes taking shape and wave still being guided by the net background magnetic field. However, the feeble external magnetic field in the region away from the antenna is unable to guide the wave any further and the wave spreads. In spite of a large current pulse, the wave remains linear (ΔB/B0 ≤ 1). The observed results are attributed to the interplay between electron inertia and finite Larmor radius effects and are explained in terms of a modified physical model.The influence of Larmor radius effects on the propagation of whistler waves is investigated experimentally in laboratory plasma. The waves are excited using a loop antenna of diameter less than the electron skin depth, the natural scale length in this regime. In an earlier experiment [G. Joshi et al., Phys. Plasmas 24, 122110 (2017)], it was shown that such waves assume an elongated shape with perpendicular dimensions of the order of skin depth. In the present work, we show that wave propagation is significantly modified when the external guiding magnetic field is decreased. The wave spreads in the perpendicular direction in spite of starting of as an elongated whistler due to electron inertia effects. In the near region, the antenna field becomes dominant even forming null points, with the physical processes taking shape and wave still being guided by the net background magnetic field. However, the feeble external magnetic field in the region away from the antenna is unable to guide the wave any further ...

Single source precursor, antimony potassium tartrate, was used for the preparation of Sb2O3, KSb3O5, K0.51Sb 0.67 III Sb 2 V O6.26, and KSbO3. Antimony trioxide (Sb2O3) was prepared by hydrothermal method, while potassium antimony oxides (KSbO3, K0.51Sb 0.67 III Sb 2 V O6.26, and KSbO3) were obtained from the thermal decomposition of antimony potassium tartrate. All the compounds were characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FT-IR), UV–Vis diffuse reflectance spectra, and scanning electron microscopy (SEM). The decomposition process of antimony potassium tartrate with temperature was given. The product formation at different temperatures of thermal decomposition was monitored by PXRD and FT-IR. The TG profile of antimony potassium tartrate shows mass loss at three regions. The infrared spectra of parent and decomposed products gave characteristic Sb-O bands. The band gap energy of decomposed products was obtained. The SEM diagrams of Sb2O3 show different morphologies. Direct solid state preparation of KSb3O5 and K0.51Sb 0.67 III Sb 2 V O6.26 under identical experimental conditions was unsuccessful.

Materials belonging to NASICON family of compositions NaHfM(PO4)3 and AgHfM(PO4)3 (M = Ti and Zr) are prepared by sol–gel and ion exchange methods, respectively. Ethylene glycol is used as a gelating agent. All the compositions are characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, 31P MAS NMR, UV–Vis DRS, XPS and energy dispersive spectral methods. All these phosphates are crystallized in rhombohedral lattice with space group $$R\overline{3} c$$ . These compounds exhibit characteristic PO4 vibrational modes in their FT-IR spectra. The 31P MAS NMR gave broad signals indicating distribution of chemical environments around P ion. The dc and ac conductivity of AgHfM(PO4)3 (M = Ti and Zr) are higher compared to their sodium containing compounds. The Cole–Cole plots of impedance show semicircles between 373 and 623 K. The variation of dc conductivity with temperature follows the Arrhenius equation. The photocatalytic activity of all the samples was studied against methylene blue decomposition using sun light. AgHfM(PO4)3 (M = Ti and Zr) have shown higher photoactivity than the sodium containing Nasicons.

This paper presents an experimental investigation on the role of return current in excitation of electronmagnetohydrodynamic (EMHD) structures. It is shown that only when return currents are excited parallel or anti-parallel to the background magnetic field the EMHD structures can be excited by a biased electrode in the plasma.

In the present work, a controlled growth of ZnO nanostructures by manipulating Zn metal ion concentration by the chelating action of ethylene diaminetetra acetic acid in hydrothermal method is studied. EDTA produces metal–chelate complex by the formation of bidentate ligand with Zn 2+ in the solution and diminishes the reactivity of Zn metal cations. Concentration of EDTA in the mother solution was varied in different ranges like 3, 5 and 10 mM while retaining the zinc metal salt and the NaOH concentration the same. Three different morphologies of wurtzite structured ZnO nanostructures such as nanorods-bunch, separate/discrete uniformly sized hexagonal nanorods and tapered flower petals like shapes are achieved by 3, 5 and 10 mM strengths of EDTA, respectively. The medium concentration 5 mM of EDTA is found to have moderate control over producing ZnO nanostructures of uniform diameter and a high aspect (length to diameter) ratio. An array of vertically aligned free standing ZnO nanorods with uniform spacing is successfully achieved by the addition of 5 mM of EDTA in the mother solution and the same is studied for its fluorescence property at an excitation of 325 nm and it has exhibited a characteristic UV emission of ZnO around 383 nm.

The microbial free single crystals of α and γ glycine were grown from gel at room temperature in a new chemical route. These crystals showed a superior quality than the solution grown crystals. The metastable α-form and the stable γ-form of glycine were crystallized in silica gel by solubility reduction method. The form of crystallization is confirmed by single crystal and powder X-ray diffraction analyses. The crystals of α and γ glycine were found to crystallize in monoclinic and hexagonal crystal systems, respectively. For analyzing the functional group and thermal stability of α and γ glycine crystals, spectroscopic and thermal analyses have been carried out. The dielectric studies were performed to find the dielectric constant of the grown crystals and the results are discussed. Second harmonic generation efficiency of the crystal was measured by Kurtz’s powder method using Nd:YAG laser and it was found to be 2.68 times that of potassium dihydrogen phosphate crystals.

We have studied the effect of chemical pressure on the magnetic properties of a series of Pr 0.7 Ca 0.3− x Sr x MnO 3 ( x = 0.0–0.3) (PCSMO) compounds. The parent compound Pr 0.7 Ca 0.3 MnO 3 (PCMO) is a well known charge-ordered compound. The selective substitution of Sr for Ca in PCMO leads to increase in electron count as a 4s metal (Ca) is being replaced by a 5s (Sr) alkali metal, resulting in melting of CO-state (in PCSMO) and increase in magnetic transition temperature ( T o ) from 85 K (for x = 0.0) to 260 K (for x = 0.3). The lattice distortion factors, such as A -site variance ( σ 2 ) and tolerance factor ( T f ) vary linearly with T o . The magnetocaloric effect (MCE shown as, Δ S ) calculated from isothermal magnetization measurement exhibits maximum (at T = T o ) for x = 0.2 for a field change from 0 to 50 kOe. The variation of Δ S ( x ) mimic the variation of Δ S ( σ 2 ), indicating the strong influence of Mn–O–Mn bond angle on the MCE. We discuss these results in terms of modification of magnetic properties in PCSMO through chemical pressure.

Experimental observations of a new regime of whistler propagation in the laboratory are reported in this paper. The experiments are carried out in a large laboratory unbound uniform plasma with a density of ne ∼ 109–1011 cm−3 and a magnetic field of 1–20 G. Studies are performed in the electron magnetohydrodynamic regime, which is governed by electron dynamics with Le ≪ L ≪ Li and τci ≫ τ ≫ τce, where L and τ are the spatial and temporal scale lengths of the perturbations, Le and Li the electron and ion Larmor radii, respectively, and τci and τce the temporal scales corresponding to the ion gyrofrequency and electron gyrofrequency, respectively. The complete topology of the perturbed wave magnetic field is unravelled by mapping it on a two dimensional grid over repeated plasma shots. It is observed that the excited waves are elongated whistlers in the propagation direction. However, in the perpendicular direction, the extent is limited to scale lengths of the order of natural scale length of plasma, i.e...

Thermoelectric power studies of cobalt substituted calcium ferrites of various compositions were investigated from room temperature to well beyond the Curie temperature by the differential method. The Seebeck coefficient is negative for all the compositions showing that these ferrites behave as n-type semiconductors. Plots of the Seebeck coefficient versus temperature show a maximum at Curie temperature. On the basis of these results an explanation for the conduction mechanism in Ca–Co mixed ferrites is suggested.

Thermoelectric power studies of Ni–Cu ferrites were investigated from room temperature to well beyond the Curie temperature by the differential method. The Seebeck coefficient is negative for all the compositions showing that these ferrites behave as n-type semiconductors. A plot of the Seebeck coefficient ( S ) versus temperature ( T ) shows a maximum at the Curie temperature ( T c ). On the basis of these results, an explanation for the conduction mechanism in Ni–Cu mixed ferrites is suggested.

This paper reports experimental investigations of nonlinear electron magnetohydrodynamic (EMHD) structures of the size of skin depth. It is shown that the difficulty of exciting EMHD structures with k⊥de∼1 is not related to any specifics of antenna–plasma coupling mechanisms but to a general attenuation scaling with antenna size. Formation of null-point or mirror geometry with contribution from antenna current leads to nonlinear effects in case of EMHD structures with k⊥de≪1. However, there is weakening of nonlinearity in case of k⊥de∼1. Observations indicate that reconnection rates in EMHD may not be independent of the plasma skin depth, in contrast to theoretical predictions. It is pointed out that electron inertia takes the role of magnetic field in the region where adiabatic constants of motion do not remain constant.

This paper discusses a large area multifilamentary plasma source used in the large volume plasma device. This source, based on directly heated filaments, is simple in design and produces quiescent (δn/n≈1%) plasmas of high density (≤1018 m−3), low temperature (~1–2 eV), over a large area (≈1.1 m2) and a large volume (≈1.6 m3). With the investment of ≈40 kW (1350 A, 30 V) power, the filaments are heated to ≈2000 K to yield emission current density ~1 A cm−2 at the filament surface. Experiments demonstrate that this source is suitable for carrying out electromagnetic wave excitation studies in the electron magnetohydrodynamics regime. There are certain inherent difficulties associated with direct heating which sets a maximum limit to the filament length and with the requirement of field tailoring. As far as the present study is concerned, these difficulties are acceptable in comparison with the distinct advantages the source possesses, in terms of its low cost and technical features, making it user-friendly.

The dynamical behaviour of the plasma in a dc non-transferred plasma torch is the result of complex interactions between various forces acting on the plasma column. We have studied this behaviour in a novel experiment comprising a low power (∼25 kW) torch and fast imaging diagnostics. The nitrogen gas plasma torch was operated at atmospheric pressure for a wide range of gas flow rates (20–60 lpm) and currents (70–120 A). A strong axial external magnetic field (100–500 G) was introduced and end-on images of the plasma column were captured using a high speed camera of frame rate ∼117 000 fps. The studies have yielded dominant role of external magnetic on the arc root dynamics. The column is clearly distinguishable in three main parts: central plasma, cathode-anode junction, and radial component of column that attaches to the anode. The dynamics of the column, especially the angular rotational speed of the radial part of the column, is analyzed in detail in terms of the forces that act upon it. The nature of...

Two alternative techniques based on coating and chemical co-synthesis for making W/Cu powder composite with improved thermal properties were evaluated. The properties of W/Cu synthesised by these techniques were compared with mechanically blended powders. The distribution of copper in the consolidated samples was analysed using an optical microscope. The influence of copper distribution on the properties, such as thermal conductivity and coefficient of thermal expansion, was evaluated. The thermal conductivity of a coated sample was the highest (190 W m−1 K−1) when compared with that of co-synthesised (140 W m−1 K−1) and ball milled (165 W m−1 K−1) specimens. Although the co-synthesised sample has the better distribution of copper in the tungsten matrix, the poor densification was attributed to the lack of formation of continuity among copper phase. The coated sample has a lower thermal expansion coefficient (4·7 ppm/K) than that of co-synthesised sample (6·8 ppm/K).

Nanocrystalline transition alumina tape casts were used as interlayers to join conventional alumina ceramic pellets. The joining experiments were performed by hot pressing at 1200–1300 °C under uniaxial pressures of 55 and 80 MPa for 1- and 5-h durations, with and without a nanocrystalline interlayer. Successful joints were enabled only above 1250 °C in the presence of the interlayer. Generally, the joint 4-point bending strength increased with the increase in joining temperature, pressure, and duration. The average bending strength of the interface joined at 1250 °C was 245 ± 65 MPa compared to the pellet strength of 268 MPa. Postjoining heat treatments at 1400 °C for 3 h caused reduction in the joint strength. The interlayer at the joint exhibited homogeneous and crack-free microstructure. The changes in the joint strength were discussed with respect to the densification and grain growth behavior of the nanocrystalline interlayer.

Bulk GdBa2Cu3Oy superconductors with uniformly distributed inclusions of micron-sized Gd2BaCuO5 (211) have been prepared by the infiltration and texturing of pre-shaped porous 211 preforms with liquid phases, in a high purity Ar atmosphere. The microstructural features at various stages of processing with particular emphasis on the nature of the 211 inclusions are studied. The superconducting properties like the transition temperatures and critical current densities of the resulting composites are discussed.

The effect of quenching on the disorder of fluoride ions and the resultant ionic conductivity in CaF 2 single crystals has been studied by impedance measurements. It has been observed that the samples quenched at a higher temperature have a higher conductivity, σ=8×10 −6 S cm −1 and a lower activation energy, E a = 0.70 eV in the extrinsic region (260 to 460 °C). The effect of low concentration of europium (0.1 mol%) in the ionic conductivity of CaF 2 has also been studied.