X-ray characterization and phase transformation kinetics of ball-mill prepared nanocrystalline Mg–Zn-ferrite at elevated temperatures

Nanocrystalline Mg–Zn-ferrite is prepared by ball milling the stoichiometric powder mixture of MgO, ZnO and α-Fe₂O₃. A non-stoichiometric ferrite phase is noticed to form after 3 h of milling when particles of starting materials became nano-sized. After 25 h of milling, stoichiometric ferrite phase is formed with 9 nm particle size. Post annealing study of ball-milled sample reveals that the nanocrystalline ferrite phase is stable up to 873 K and then starts to decompose into individual starting phases. However, heat treatment of unmilled stoichiometric powder mixture even at 1473 K for 1 h duration does not result in formation of stoichiometric Mg–Zn-ferrite phase.     

Nanohybridization of Low-Dimensional Nanomaterials: Synthesis,Classification, and Application

Nanomaterials have attracted much attention from academic to industrial research. General methodologies are needed to impose architectural order in low-dimensional nanomaterials composed of nanoobjects of various shapes and sizes, such as spherical particles, rods, wires, combs, horns, and other non specified geometrical architectures. These nanomaterials are the building blocks for nanohybrid materials, whose applications have improved and will continuously enhance the quality of the daily life of mankind. In this article, we present a comprehensive review on the synthesis, dimension, properties, and present and potential future applications of nanomaterials and nanohybrids. Due to the large number of review articles on specific dimension, morphology, or application of nanomaterials, we will focus on different forms of nanomaterials, such as, linear, particulate, and miscellaneous forms. We believe that almost all the nanomaterials and nanohybrids will come under these three categories. Every form or dimension or morphology has its own significant properties and advantages. These low-dimensional nanomaterials can be integrated to create novel nano-composite material applications for next-generation devices needed to address the current energy crisis, environmental sustainability, and better performance requirements. We discuss the synthesis, properties, and morphology of different forms of nanomaterials (building blocks). Moreover, we elaborate on the synthesis, modification, and application of nanohybrids. The applications of these nanomaterials and nanohybrids in sensors, solar cells, lithium batteries, electronic, catalysis, photocatalysis, electrocatalysis, and bio-based applications will be detailed. The time is now ripe to explore new nanohybrids that use individual nanomaterial components as basic building blocks, potentially affording additionally novel behavior and leading to new, useful applications. In this regard, the combination or integration of linear nanorods/nanowires and spherical nanoparticles to produce mixed-dimensionality, higher-level nanocomposites of greater complexity is an interesting theme, which we explore in this review article.     

A modified method for the determination of uranium in Nb/Ta minerals by LED fluorimetry

A modified LED fluorimetry determination of uranium in Nb/Ta minerals has been developed. The mineral is brought into solution by fusion with mixed phosphate flux (NaH₂PO₄, H₂O and Na₂HPO₄). Iron quenches uranium fluorescence when it is present above the ratio of (iron to uranium) 100. Uranium is separated in ethyl acetate by solvent extraction and then stripped back into pyrophosphate buffer (pH ~ 7) prior to its LED fluorimetry determination. This modified method has been applied for the determination of uranium in synthetic mixtures and Nb/Ta minerals including Certified Reference Materials (X1807) with high degree of accuracy and precision.

     

Thermally exfoliated graphene oxide reinforced stress responsive conductive nanocomposite hydrogel

Lightweight and flexible biosensors that can sustain mechanical deformation and can be adhered to human skin is an interesting field of study. In the current article, a systematic study on development of thermally exfoliated graphene oxide (TEGO)–reinforced poly(vinyl alcohol) (PVA)–based conductive hydrogel nanocomposites has been reported. The free‐standing hydrogels were synthesized using controlled and repetitive freeze‐thaw cycles. The samples were then studied for their mechanical as well as electrical properties. The hydrogels were characterized for their microstructural, chemical, and rheological properties to understand the observed macroscopic properties. Additionally, a study on the behavior of hydrogels immersed in phosphate‐buffered saline (PBS) was carried out to investigate their hydrolytic stability within simulated biological environment. Overall, the nanocomposite hydrogels demonstrated excellent static and dynamic mechanical performance, stability in PBS, considerable electrical conductivity, and significant electrical response to applied external stress, establishing their potential for use as flexible biosensors.     

Spin-polarized two-dimensional electron gas at oxide interfaces

The possibility of formation of a fully spin-polarized 2D electron gas at the SrMnO_3/(LaMnO_3)_1/SrMnO_3 heterostructure is predicted from density-functional calculations. The La(d) electrons become confined in the direction normal to the interface in the electrostatic potential well of the positively charged layer of La atoms, acting as electron donors. These electrons mediate a ferromagnetic alignment of the Mn t_2g spins near the interface via Zener double exchange and become, in turn, spin-polarized due to the internal magnetic fields of the Mn moments.     

Bianchi Type <Emphasis Type="Italic">VI</Emphasis><Subscript>0</Subscript> Magnetized Barotropic Bulk Viscous Fluid Massive String Universe in General Relativity

A model of a cloud formed by massive strings is studied in the context of the usual general relativity. This model is used as a source of Bianchi type VI ₀ massive with magnetic field and bulk viscosity. To get a determinate model, we assume that the expansion (θ) in the model is proportional to the shear (σ) and also the fluid obeys the barotropic equation of state. The behaviour of the models from physical and geometrical aspects in presence and absence of magnetic field and bulk viscosity is discussed.     

Synthesis and characterizations of water-based ferrofluids of substituted ferrites [Fe1−xBxFe2O4, B=Mn,Co (x=0–1)] for biomedical applications

Nanomagnetic particles have great potential in the biomedical applications like MRI contrast enhancement, magnetic separation, targeting delivery and hyperthermia. In this paper, we have explored the possibility of biomedical applications of [Fe_1−xB_xFe₂O₄, B=Mn, Co] ferrite. Superparamagnetic particles of substituted ferrites [Fe_1−xB_xFe₂O₄, B=Mn, Co (x=0–1)] and their fatty acid coated water base ferrofluids have been successfully prepared by co-precipitation technique using NH4OH/TMAH (Tetramethylammonium hydroxide) as base. In vitro cytocompatibility study of different magnetic fluids was done using HeLa (human cervical carcinoma) cell lines. Co²⁺-substituted ferrite systems (e.g. CoFe₂O₄) is more toxic than Mn²⁺-substituted ferrite systems (e.g. MnFe₂O₄, Fe_0.6Mn_0.4Fe₂O₄). The later is as cytocompatible as Fe₃O₄. Thus, Fe_1−xMn_xFe₂O₄ could be useful in biomedical applications like MRI contrast agent and hyperthermia treatment of cancer.     

Ultrafast sintering of La–Ca–Mn–O bulk ceramics by thermal plasma assisted heating

This paper reports a novel and low-cost thermal plasma assisted heating method for ultrafast sintering of rare-earth-based perovskite manganites. An indigenously designed DC thermal plasma reactor has been used to sinter La_0.67Ca_0.33MnO₃ (LCMO) colossal magnetoresistance (CMR) material. Highly dense (96% of theoretical density) crystalline bulk LCMO ceramics were prepared within 2.5 min of sintering time. Plasma-sintered LCMO bulk ceramics showed enhanced T_C (272 K), which is close to T_IM (275 K) as compared to the conventional sintered LCMO [J.M. De Teresa, M.R. Ibarra, J. Blasco, J. Garcia, C. Marquina, P.A. Algarabel, Z. Arnold, K. Kamenev, C. Ritter, R. von Helmolt, Phys. Rev. B 54 (1996) 1187] sample. We observe that the thermal plasma heating process offers a unique advantage for quick physical densification and hence sintering within a few minutes.     

Thermodynamic model for the size-dependent melting of prism-shaped nanoparticles

We report on the size-dependent melting of prism-shaped nanoparticles based on thermodynamic model and applied to understand the melting of prism-shaped indium nanoparticles. It is shown here that the bulk melting temperature cannot be extrapolated from the nanoscale and the extrapolated value will always be lower than the bulk melting temperature as has been observed experimentally.