Ordered, mesoporous cobalt oxide was synthesized via a nanocasting pathway from organically modified large-pore Ia3d silica. A replica structure could be obtained, which shows weak magnetic ordering ...at low temperatures due to the small size of the individual Co3O4 domains forming the mesostructure.
A comparative study of the behavior of various Ni-doped and undoped Mg-MgH sub 2 materials to be utilized for reversible (thermochemical) high temperature heat or hydrogen storage has for the first ...time been conducted over a broad range of hydrogenation /dehydrogenation (cycling) conditions. The storage capacity losses observed in the course of cyclic tests are found to be sensitively dependent to all the details of the applied cycling conditions and can be of temporary (reversible) or persistent (irreversible) nature. Based upon investigations via optical microscopy, the reversible capacity losses appear to be associated with an excessively high formation rate of MgH sub 2 -nucleation sites on the surface of Ni-doped Mg particles under intensified cycling conditions; irreversible capacity losses, especially pronounced in the case of Ni-doped materials, are the result of sintering of the material panicles in the dehydrogenated (metallic) form upon prolonged cycling at higher temperatures. Ni-doped Mg-MgH sub 2 materials have excellent cyclic stability and high hydrogenation rates even under very mild pressure/temperature cycling conditions (so-called standard cycling conditions or below them B. Bogdanovic, Th. Hartwig, B. Spliethoff, Int. J. Hydrogen Energy 18 (1993) 575; Final Report of Project No. 0328939 C, Federal Ministry for Research and Technology of the F.R.G., Bonn (1992)) suitable for applications such as solar generation of heat and cold, heat pumps, hydrogen storage, and the like. On the other hand, based on their cyclic stability and sufficient reaction rates under severe reaction conditions, neat Mg powders produced by brushing can be used as cheap materials for the purpose of reversible thermochemical high temperature heat storage in the temperature range of 450-500 deg C with heat storage capacities amounting to 0.6-0.7 kWh/kg Mg, applicable for solar power generation via Stirling engines or storage of industrial heat in the above temperature ranges.
Iron was incorporated into HAl-MFI by synthesis. The state of iron was characterized by e.s.r. and Mössbauer spectroscopies. Because of the location of iron species inside the channel system this ...zeolite showed a higher activity in the aromatization of ethane at 823 K than an iron-impregnated HAl-MFI.
Urban gardens provide affordable fresh produce to communities with limited access to healthy food but may also increase exposure to lead (Pb) and other soil contaminants. Metals analysis of 564 soil ...samples from 54 New York City (NYC) community gardens found at least one sample exceeding health-based guidance values in 70% of gardens. However, most samples (78%) did not exceed guidance values, and medians were generally below those reported in NYC soil and other urban gardening studies. Barium (Ba) and Pb most frequently exceeded guidance values and along with cadmium (Cd) were strongly correlated with zinc (Zn), a commonly measured nutrient. Principal component analysis suggested that contaminants varied independently from organic matter and geogenic metals. Contaminants were associated with visible debris and a lack of raised beds; management practices (e.g., importing uncontaminated soil) have likely reduced metals concentrations. Continued exposure reduction efforts would benefit communities already burdened by environmental exposures.
•We measured metals concentrations in soil from 54 New York City community gardens.•Pb and Ba exceeded health-based guidance values in 9%–12% of garden beds.•Pb concentrations were similar to those in other studies of urban garden soils.•Pb and Ba were associated with Zn, with visible debris, and with non-raised beds.•Observable details can help gardeners focus testing and exposure reduction efforts.
Pb and Ba, which exceeded health-based guidance values in 10–14% of NYC community garden soil samples, are associated with non-raised beds, visible debris, higher pH and Zn.
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