18 research outputs found
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Reading tea leaves worldwide: decoupled drivers of initial litter decomposition mass-loss rate and stabilisation
The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large-scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass-loss rates and stabilization factors of plant-derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy-to-degrade components accumulate during early-stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass-loss rates and stabilization, notably in colder locations. Using TBI improved mass-loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early-stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models
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Ceramic-ceramic seals by microwave heating
Several conclusions may be drawn from this work. First, less energy is required to form a glass-ceramic seal by microwave heating than by conventional heating. Second, less time is required to form the seal by microwave heating, and third, the seal composition is different, and the bonding is different. The micostructure of the seal formed by microwave heating reflects extensive diffusion of the glass constitients throughout the alumina substrate; and alumina throughout the seal glassy matrix. Fourth, higher heating rates are possible with microwave heating than with conventional heating. Last, the energy is coupled differently to the reactants using microwave heating, and thus the reaction kinetics may be different, as indicated by the vastly different microstructures obtained
The crystal chemistry and electrical properties of Fe doped Ca12Al14O33 (Mayenite)
X-ray and neutron powder diffraction have been used to study the crystal chemistry of Fe doped mayenite (Ca12Al14-xFexO33). Solid- state synthesis was used to prepare Ca12Al14-xFexO33 where x = 0, 0.1, 0.2, 0.5 and 0.6 and the citrate gel route was used to prepare Ca12Al14-xFexO33 where x = 0, 0.05, 0.1, 0.2, 0.3 and 0.4. X-ray powder diffraction data indicate that samples with the same composition but synthesized by the citrate gel route were more likely to be phase pure than samples obtained by traditional solid-state synthesis. The refined lattice parameters were observed to increase with increasing Fe concentration, irrespective of the synthesis method. Refined neutron powder data confirm that Fe is going into Al site rather than Ca site. A 2-point probe was used to measure the electrical properties of the Fe doped citrate gel synthesized samples and showed that the resistivity increases for the Fe doped samples compared to the undoped mayenite
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Electromagnetic energy applied to and gained from lunar materials
Electromagnetic energy may be useful in microwave frequencies for in-situ melting or sintering of lunar regolith. Simple configurations of magnetron or gyrotron tubes might be constructed for unique melting geometries. For energy production, lunar ilmenite has potential applications in photovoltaic devices. 11 refs., 11 figs
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Microwave processing of lunar materials: potential applications
The microwave processing of lunar materials holds promise for the production of either water, oxygen, primary metals, or ceramic materials. Extra high frequency microwave (EHF) at between 100 and 500 gigahertz have the potential for selective coupling to specific atomic species and a concomitant low energy requirement for the extraction of specific materials, such as oxygen, from lunar ores. The coupling of ultra high frequency (UHF) (e.g., 2.45 gigahertz) microwave frequencies to hydrogen-oxygen bonds might enable the preferential and low energy cost removal (as H/sub 2/O) of implanted protons from the sun or of adosrbed water which might be found in lunar dust in permanently shadowed polar areas. Microwave melting and selective phase melting of lunar materials could also be used either in the preparation of simplified ceramic geometries (e.g., bricks) with custom-tailored microstructures, or for the direct preparation of hermetic walls in underground structures. Speculatively, the preparation of photovoltaic devices based on lunar materials, especially ilmenite, may be a potential use of microwave processing on the moon. Preliminary experiments on UHF melting of terrestrial basalt, basalt/ilmenite and mixtures show that microwave processing is feasible