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In this article, the magnetocaloric effect on thermally reduced CoFe 2 O 4 /CoFe 2 composite was reported. Co-precipitated CoFe 2 O 4 nanoparticles were thermally reduced at 500 and 800 °C for 2 h under H 2 atmosphere. The reduction process resulted in different fractions of soft and hard (CoFe 2 O 4 /CoFe 2 ) magnetic composites and the products were characterized through various procedures. The structure of CoFe 2 O 4 /CoFe 2 composites was found to be cubic with an average crystallite size of 31 and 30 nm for the samples reduced at 500 and 800 °C, respectively. The stoichiometry of the composites confirmed that the percentage of soft CoFe 2 magnetic phase was increased to 87% with temperature up to 800 °C for 2 h, besides showed accumulation of nanoparticles. The room temperature saturation magnetization of the CoFe 2 O 4 /CoFe 2 composites increases from 184 to 190 emu/g as a consequence of high concentration of CoFe 2 phase. Conversely, the sample reduced at 800 °C attained the maximum magnetization of 200 and 221 emu/g at 300 and 5 K, respectively. Field cooled (FC) and zero field cooled magnetization (ZFC) and the isothermal magnetic entropy change ( Δ S m ) on the CoFe 2 O 4 /CoFe 2 composite (with 87% of soft CoFe 2 magnetic phase) were estimated. The composite showed the interesting positive and negative magnetic entropy change ( Δ S m ) of 0.923 and −0.923 J/kg.K −1 near room temperature at around 310 and 290 K, respectively. [ABSTRACT FROM AUTHOR]

Nano cobalt ferrites (CoFe 2 O 4 ) were co-precipitated at various reaction temperatures (60, 70 and 80 °C) for 1 h. The reaction temperature greatly influenced the crystallite size and the magnetic behaviours of the nano CoFe 2 O 4 . The mean crystallite size ranged from 9 to 15 nm with the increase in the reaction temperature and the intensity of metal oxide vibrations at 568–550 cm −1 were also inclined. The synthesized samples were in the stoichiometric ratio of 1:2 (Co:Fe) with roughly spherical morphology. The synthesized cobalt nanoferrites exhibited ferromagnetism at room temperature and 5 K, and the saturation magnetization increased from 6.4 to 20 emu/g with the crystallite size. [ABSTRACT FROM AUTHOR]

Highly crystalline cobalt nano ferrites have been synthesized by the combustion route using d l -alanine, a racemic mixture of right handed ( d ) and left handed ( l ) chemical forms of alpha-alanine, as fuel. The synthesized samples were annealed at two different temperatures, viz. 500 °C and 800 °C, for 2 h to investigate the temperature effect on crystallite size, phase purity, thermal stability, Curie temperature, and magnetic properties. Formation of single-phase spinel nanoparticles in both the as-prepared and annealed conditions has been observed. High saturation magnetization (71.1 emu/g) for as-prepared sample and a high coercive field (1400 Oe) for the sample annealed at 500 °C/2 h were obtained. [ABSTRACT FROM AUTHOR]

Abstract: Nickel ferrite nanoparticles have been synthesized by sol–gel auto combustion route. The significant role played by nitric acid added to the precursor solution in controlling the reaction rate phase purity, crystallinity, crystallite size, thermal and magnetic properties of nanoparticles was explored and reported. Also, the influence of annealing on the properties were studied. Samples of average crystallite size ranging from 10nm to 40nm have been obtained by controlling the HNO3 concentration and by increasing the annealing temperature. The size-dependent structural, thermal and magnetic properties were investigated and reported. The Hopkinson peak was observed for all the crystalline samples near the Curie temperature. The highest value 47.3emu/g of saturation magnetization was obtained for the sample prepared with higher concentration (6mol/L) of HNO3. [Copyright &y& Elsevier]

Abstract: The fabrication of flexible Poly (vinylidine Fluoride)/Fe3O4 magnetoelectric nanocomposite films with different weight fractions of Fe3O4 nanoparticles is explained in this paper. The effects of nano Fe3O4 content on the structural, chemical, thermal, and magnetoelectric properties of PVDF matrix are discussed. XRD and FTIR results reveal the interaction between the filler and the matrix and also they suggest that the β phase contribution can be significantly controlled by the inclusion of nano Fe3O4. Thermal stability and melting point behavior of the composite films are investigated through TG/DTA. The existence of ferrimagnetism and ferroelectric properties in the films are proved through the magnetization and polarization studies. The hysteresis loops show the largest polarization and magnetization values at 0.14 wt% of Fe3O4. Also, the dependence of ferroelectric polarization on temperature is investigated and reported. [Copyright &y& Elsevier]

Abstract: A combustion route of synthesizing highly crystalline single phase nickel ferrite (NiFe2O4) spinel nanoparticles using various amounts of dl-alanine as fuel has been reported in this paper. The role of the amount of fuel is found to be significant in the size control and phase purity of nano crystalline samples. The structural, thermal, morphological and magnetic studies have been carried out. XRD patterns reveal the formation of highly crystalline nano NiFe2O4 with high degree of phase purity when fuel concentration is maintained at 1M and 2M. FTIR spectra also prove the formation of pure nano NiFe2O4. The temperature and fuel effects are found to have strong influence on size, structural, and magnetic properties of materials. The magnetic measurements show that the nano NiFe2O4 samples exhibit soft ferromagnetism with the highest saturation magnetization Ms at room temperature as 42.53emu/g. [Copyright &y& Elsevier]

Abstract In this work, we presented our effort to understand the effect of the operating parameters of the microwave oven (power and irradiation time) on the structural and morphological changes in ceria (CeO 2) nanostructures. A series of controlled experiments were carried out to understand the crucial factors determining the formation of ceria nanostructures with spheres and rods like morphology. By adjusting the experimental parameters different ceria nanostructures such as spheres, cubes and rods were obtained. The variation of the lattice parameter and morphology of the prepared samples was discussed by structural studies. The W H analysis was implemented to calculate the average crystallite size and microstrain. The influence of morphology and microstrain on the band gap energy, luminescence and photocatalytic activity of the synthesized samples was discussed. The observed variation in the band gap was explained based on the variation of the crystallite size. Also, the observed variation in the ratio of the intensity of band gap related emission (I Bg) and defects related emission (I def) was discussed. In addition, the enhanced photocatalytic performance of the prepared ceria nanostructures with different morphology was discussed. Graphical abstract Hierarchical ceria nanostructures are prepared using the commercial microwave oven. The selection of operating parameters of the microwave oven (output work power and different irradiation cycles) resulted in the ceria nanostructures such as spheres, cubes and rods. The as-prepared nanostructures possessed morphology dependent photocatalytic activity. Image 1 Highlights • The crystallization of ceria nanostructures is ultrafast (≤2 min). • Commercial Microwave oven (power and irradiation time) variation induced changes in morphology. • Crystallite size dependent bandgap of ceria nanostructures. • Luminescence in the visible range due to the various F -centers (oxygen vacancies). • Microstrain and morphology influence on photocatalytic properties. • Relaxation of microstrain favored the enhanced photocatalytic activity. [ABSTRACT FROM AUTHOR]

The ground and vertical profiles of particulate matter (PM) were mapped as part of a pilot study using a Tethered balloon within the lower troposphere (1000 m) during the foggy episodes in the winter season of 2015–16 in New Delhi, India. Measurements of black carbon (BC) aerosol and PM < 2.5 and 10 μm (PM 2.5 & PM 10 respectively) concentrations and their associated particulate optical properties along with meteorological parameters were made. The mean concentrations of PM 2.5 , PM 10 , BC 370 nm, and BC 880 nm were observed to be 146.8 ± 42.1, 245.4 ± 65.4, 30.3 ± 12.2, and 24.1 ± 10.3 μg m − 3 , respectively. The mean value of PM 2.5 was ~ 12 times higher than the annual US-EPA air quality standard. The fraction of BC in PM 2.5 that contributed to absorption in the shorter visible wavelengths (BC 370 nm ) was ~ 21%. Compared to clear days, the ground level mass concentrations of PM 2.5 and BC 370 nm particles were substantially increased (59% and 24%, respectively) during the foggy episode. The aerosol light extinction coefficient (σ ext ) value was much higher (mean: 610 Mm − 1 ) during the lower visibility (foggy) condition. Higher concentrations of PM 2.5 (89 μg m − 3 ) and longer visible wavelength absorbing BC 880 nm (25.7 μg m − 3 ) particles were observed up to 200 m. The BC 880 nm and PM 2.5 aerosol concentrations near boundary layer (1 km) were significantly higher (~ 1.9 and 12 μg m − 3 ), respectively. The BC (i.e BC tot ) aerosol direct radiative forcing (DRF) values were estimated at the top of the atmosphere (TOA), surface (SFC), and atmosphere (ATM) and its resultant forcing were - 75.5 Wm − 2 at SFC indicating the cooling effect at the surface. A positive value (20.9 Wm − 2 ) of BC aerosol DRF at TOA indicated the warming effect at the top of the atmosphere over the study region. The net DRF value due to BC aerosol was positive (96.4 Wm − 2 ) indicating a net warming effect in the atmosphere. The contribution of fossil and biomass fuels to the observed BC aerosol DRF values was ~ 78% and ~ 22%, respectively. The higher mean atmospheric heating rate (2.71 K day − 1 ) by BC aerosol in the winter season would probably strengthen the temperature inversion leading to poor dispersion and affecting the formation of clouds. Serious detrimental impacts on regional climate due to the high concentrations of BC and PM (especially PM 2.5 ) aerosol are likely based on this study and suggest the need for immediate, stringent measures to improve the regional air quality in the northern India. [ABSTRACT FROM AUTHOR]

The high-resolution (1 km) forecasts are evaluated during the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX). The rainfall observations from a network of rain gauge stations and at high spatial resolution are used for verification purposes. Observed variations in the daily rainfall were adequately reproduced by the model. Several verification indices are used to evaluate the skill of the model forecast. The high rainfall events are overestimated by the model during the first half of the monsoon season and vice versa for the second half. The validated model was used to develop cloud seeding scores for a decision support system during the experiment. The systematic comparison of the model-derived seed score and actual seeding locations from the experiment satisfying the seeding criteria are verified. It is demonstrated that the high-resolution model forecast (<1 km) could be very valuable in identifying possible target regions for cloud seeding. A few real time applications of seed score maps generated from these high resolution forecasts are illustrated in the study. • The high resolution (1 km) WRF forecasts are verified with CAIPEEX observations. • WRF model reasonably simulates variation of thermodynamic variables. • High rainfall events are overestimated, and low rainfall events underestimated. • High-resolution forecast is utilized to identify target regions for cloud seeding. [ABSTRACT FROM AUTHOR]