Microwave assisted low temperature synthesis of MnZn ferrite nanoparticles

MnZnFe2O4ferrite nanoparticles were prepared by co-precipitation method using a microwave heating system at temperature of 100 °C. X-ray diffraction reveals the samples as prepared are pure ferrite nanocrystalline phase, transmission electron microscopy image analysis shows particles are in agglomeration state with an average size of about 10 nm, furthermore, crystal size of samples are increased with longer microwave heating

Hierarchically Porous Gd3+-Doped CeO2 Nanostructures for the Remarkable Enhancement of Optical and Magnetic Properties

Rare earth ion-doped CeO2 has attracted more and more attention because of its special electrical, optical, magnetic, or catalytic properties. In this paper, a facile electrochemical deposition route was reported for the direct growth of the porous Gd-doped CeO2. The formation process of Gd-doped CeO2 composites was investigated. The obtained deposits were characterized by SEM, EDS, XRD, and XPS. The porous Gd3+- doped CeO2 (10 at% Gd) displays a typical type I adsorption isotherm and yields a large specific surface area of 135 m2/g. As Gd3+ ions were doped into CeO2 lattice, the absorption spectrum of Gd3+-doped CeO2 nanocrystals exhibited a red shift compared with porous CeO2 nanocrystals and bulk CeO2, and the luminescence of Gd3+-doped CeO2 deposits was remarkably enhanced due to the presence of more oxygen vacancies. In addition, the strong magnetic properties of Gd-doped CeO2 (10 at% Gd) were observed, which may be caused by Gd3+ ions or more oxygen defects in deposits. In addition, the catalytic activity of porous Gd-doped CeO2 toward CO oxidation was studied

Magnetism, FeS colloids, and Origins of Life

A number of features of living systems: reversible interactions and weak bonds underlying motor-dynamics; gel-sol transitions; cellular connected fractal organization; asymmetry in interactions and organization; quantum coherent phenomena; to name some, can have a natural accounting via $physical$ interactions, which we therefore seek to incorporate by expanding the horizons of `chemistry-only' approaches to the origins of life. It is suggested that the magnetic 'face' of the minerals from the inorganic world, recognized to have played a pivotal role in initiating Life, may throw light on some of these issues. A magnetic environment in the form of rocks in the Hadean Ocean could have enabled the accretion and therefore an ordered confinement of super-paramagnetic colloids within a structured phase. A moderate H-field can help magnetic nano-particles to not only overcome thermal fluctuations but also harness them. Such controlled dynamics brings in the possibility of accessing quantum effects, which together with frustrations in magnetic ordering and hysteresis (a natural mechanism for a primitive memory) could throw light on the birth of biological information which, as Abel argues, requires a combination of order and complexity. This scenario gains strength from observations of scale-free framboidal forms of the greigite mineral, with a magnetic basis of assembly. And greigite's metabolic potential plays a key role in the mound scenario of Russell and coworkers-an expansion of which is suggested for including magnetism.Comment: 42 pages, 5 figures, to be published in A.R. Memorial volume, Ed Krishnaswami Alladi, Springer 201

LiNi0.5Mn1.5O4cathode materials for high-voltage, next-generation automotive Li-ion cells

The insufficient autonomy of Electric Vehicles (EVs), which is mainly due to the limited energy density of automotive batteries, can be addressed by increasing the specific energy and/or the average operating voltage of the active cell materials. LiMn1.5Ni0.5O4 (LNMO) is a top candidate active cathode material due to its access to a rare two-electron transition from Ni2+ to Ni4+ at two voltage plateaus near 4.7 V vs. Li+/Li, a theoretical capacity of 147 mAhg-1 and fast three-dimensional Li-ion diffusion paths within the cubic lattice. Furthermore, LNMO is a relatively low-cost material with fairly good charging rate capability, suitable for EV requirements. However, the employment of LNMO in next-generation Li-ion batteries is prohibited by phenomena related to structural stability due to manganese dissolution and electrolyte compatibility. Structural modification via the inclusion of suitable dopants and proper surface treatment constitute promising solutions to these problems. Materials development for more efficient automotive batteries is an urgent task. In this work, four research organizations have joined efforts to realize LNMO cathodes appropriate for EVs. Three partners in this team worked on the materials development, and the fourth partner worked on the benchmarking of the materials. We have exploited nine different synthesis technologies for the pristine LNMO. From the evaluated technologies, three have been identified as most promising and were optimized for the specific application: the co-precipitation, the sol-gel and the aerosol spray pyrolysis methods. Several calcination profile conditions of the produced powder were studied obtaining two LNMO spinel phases: the ordered (P4332) and the disordered (Fd-3m) with the latter identified as the most electrochemically active. Five dopants have been introduced into the most promising LNMO lattices with Fe and Al proven to be the best-performing ones. Twelve materials have been considered for the LNMO particle surface treatment, and the Al2O3 was evaluated as the one showing satisfactory cyclic stability. We have used Scanning and Transition Electron Microscopy (SEM/TEM), micro-Raman spectroscopy, X-Ray Powder Diffraction (XRD) and Particle Size Analysis (PSD) for the structural characterization of the products. The most promising compositions have been scaled up to quantities sufficient for the manufacture of battery cells used in the automotive sector. In this work, we will present the most significant results from the above developments including results from electrochemical performance tests of electrodes in half and full coin cells (HCC/FCC). At HCC and C/5 we managed to obtain a specific capacity of more than 130 mAh/g with about 10% irreversible capacity loss. In FCC (vs. graphite) and C/20 we have obtained materials with 118 mAh/g specific capacity and about 20 % irreversible loss. During cycling of FCCs at 1C, with the best performing material, we have attained about 80 % of the initial capacity after 100 charging/discharging cycles. Future developments should focus on increasing the cycling ability of the full-cell by optimising the active materials (both cathode and anode), the electrolyte as well as the electrode structure

Environmental evaluation of a clear coating for wood: toxicological testing and life cycle assessment

WoodLife is an on-going project under the EU Seventh Framework Programme aimed at developing a water-based clear coating for exterior wood products. Adding nanoparticles to a conventional coating could improve its UV-protecting properties, thus decreasing the need for maintenance of coated wood products. Wood products could thereby replace non-wood alternatives, which could result in lower environmental impacts.This paper describes an environmental evaluation carried out within the WoodLife project, in which we test whether the nanoparticles are toxic for the bacteria Vibrio fischeri, and use Life Cycle Assessment (LCA) to map the environmental consequences of applying the coating on a wood product. This goes beyond the scope of most environmental evaluations of nanotechnologies, which tend to include either an assessment of the possible toxicity of the nanomaterial or an LCA.The toxicological testing indicates low ecotoxicity of the nanoparticles, but further development of suitable testing methods is warranted to enable a full ecotoxicological evaluation. The LCA shows that a wooden window frame with the new coating can be environmentally superior to plastic and aluminium window frames. However, the potential in part depends on variables such as recycling rates and disposal practices, which are highly uncertain for future products with long service lives

Surfactant-Free Stabilization of Aqueous Graphene Dispersions Using Starch as a Dispersing Agent

Attention to graphene dispersions in water with the aid of natural polymers is increasing with improved awareness of sustainability. However, the function of biopolymers that can act as dispersing agents in graphene dispersions is not well understood. In particular, the use of starch to disperse pristine graphene materials deserves further investigation. Here, we report the processing conditions of aqueous graphene dispersions using unmodified starch. We have found that the graphene content of the starch–graphene dispersion is dependent on the starch fraction. The starch–graphene sheets are few-layer graphene with a lateral size of 3.2 μm. Furthermore, topographical images of these starch–graphene sheets confirm the adsorption of starch nanoparticles with a height around 5 nm on the graphene surface. The adsorbed starch nanoparticles are ascribed to extend the storage time of the starch–graphene dispersion up to 1 month compared to spontaneous aggregation in a nonstabilized graphene dispersion without starch. Moreover, the ability to retain water by starch is reduced in the presence of graphene, likely due to environmental changes in the hydroxyl groups responsible for starch–water interactions. These findings demonstrate that starch can disperse graphene with a low oxygen content in water. The aqueous starch–graphene dispersion provides tremendous opportunities for environmental-friendly packaging applications

Environmental evaluation of a clear coating for wood: toxicological testing and life cycle assessment

WoodLife is an on-going project under the EU Seventh Framework Programme aimed at developing a water-based clear coating for exterior wood products. Adding nanoparticles to a conventional coating could improve its UV-protecting properties, thus decreasing the need for maintenance of coated wood products. Wood products could thereby replace non-wood alternatives, which could result in lower environmental impacts.This paper describes an environmental evaluation carried out within the WoodLife project, in which we test whether the nanoparticles are toxic for the bacteria Vibrio fischeri, and use Life Cycle Assessment (LCA) to map the environmental consequences of applying the coating on a wood product. This goes beyond the scope of most environmental evaluations of nanotechnologies, which tend to include either an assessment of the possible toxicity of the nanomaterial or an LCA.The toxicological testing indicates low ecotoxicity of the nanoparticles, but further development of suitable testing methods is warranted to enable a full ecotoxicological evaluation. The LCA shows that a wooden window frame with the new coating can be environmentally superior to plastic and aluminium window frames. However, the potential in part depends on variables such as recycling rates and disposal practices, which are highly uncertain for future products with long service lives