Phase Transformation of ZrO2 in MnZn-Ferrite under Magnetic Field

This letter reports the effect of an applied magnetic field on the phase transformation of ZrO2 particles in MnZn-Ferrite. Of the 10 wt% ZrO₂ in the as-sintered composite, 64% is retained as tetragonal ( t -) particles with a critical size of about 2.5 μ. The t -ZrO₂ particles with size between 1.5 and 2.5 μ are induced to transform to m -ZrO₂ under a critical magnetic field (between 40 and 60 kOe), due to the stress induced by the magnetostriction of the ferrite matrix.     

Formation of (H+, Al+, Al2+) co-doped bayerite and gamma-Al2O3 plates from spinel-type related nanocondensates in water

The Al2O3 nanocondensates of spinel-type related structures, i.e., gamma- and theta-type with a significant internal compressive stress via pulsed laser ablation in water were subjected to prolonged dwelling in water to form columnar bayerite plates for further transformation as platy gamma-Al2O3. Transmission electron microscopic observations indicated the gamma-Al2O3 follows the crystallographic relationship (100)b//(011)gamma; [001]b//[111]gamma with relic bayerite (denoted as b). The gamma-Al2O3 also shows {111} twin/faults and rock salt-type domains due to dehydroxylation of bayerite which involves {1111} shuffling and disordering of the Al ions in the octahedral and tetrahedral sites. The combined evidences of X-ray photoelectron spectroscopy, vibrational spectroscopy and UV-visible absorbance indicated that the H+, Al+ and Al2+ co-doped bayerite and gamma-Al2O3 composite plates have a minimum band gap as low as approximately 5 eV for potential catalytic and electro-optical applications in water environment.     

Spherulitic Growth from a Phase-Separated Vitreous Matrix in a Cordierite–Y-Stabilized Zirconia Glass-Ceramic

Crystallization behavior, especially spherulitic growth of a cordierite–3 mol% Y₂O₃–ZrO₂ glass composition annealed at 950° to 1370°C was studied by optical and electron microscopy. Microstructural analysis revealed that glass-inglass phase separation occurred prior to the crystallization of β-quartz solid solution ( ss ). ZrO₂ was involved in promoting the nucleation of β-quartz ss ; the crystallization evolved from a cellular to a spherulitic morphology, and β-quartz transformed to α-cordierite as the temperature was raised. ZrO₂ was eventually expelled intergranularly and intragranularly to form slightly misoriented domains upon annealing, and the dendritic or clustered tetragonal t -ZrO₂ crystals transformed to monoclinic ( m ) in symmetry. A possible dragging force exerted between α-cordierite and a glassy droplet phase is proposed to explain the corrugated cordierite/glass interface.     

Water quality impact assessment of large-scale biofuel crops expansion in agricultural regions of Michigan

The challenges we face in transitioning to a global production of biomass as renewable feedstock sources in a way that is both economical feasible environmentally sustainable are ubiquitous. In this study, the Soil and Water Assessment Tool (SWAT) was used to predict the possible long-term environmental implications, specifically water quality, due to large-scale bioenergy cropping system expansion based on four landuse scenarios and 15 bioenergy crop rotations for four watersheds, totaling 244 model simulations. The study area consists of four watersheds totaling 53,358 km² located in Michigan. The results suggest that perennial grass species are the most suitable for large-scale implementation, whereas traditional intensive row crops should be implemented with caution on such a broad scale. Row crops also had the highest increases of high priority areas for sediment, nitrogen, and phosphorus. Based on the data from this study, it is not recommended that marginal land be converted to any bioenergy rotation in areas with preexisting high nitrogen levels. Statistical analyses demonstrate that perennial grass species significantly reduce sediment on all lands except marginal lands. With the exception of row crops cultivated on marginal lands and all agricultural land, the majority of bioenergy crops significantly reduce total phosphorus loads.     

Quasi-static analysis of asymmetric cylindrical coplanar waveguides with finite-extent ground

Quasi-static characteristics of asymmetric cylindrical coplanar waveguides (CCPWs) with finite-extent ground are analysed using the conformal mapping technique. Closed-form expressions for the effective permittivity and characteristic impedance of inside and outside asymmetric CCPWs with finite ground are derived. Using these expressions, the effect of various parameters on the characteristics of CCPWs is studied.     

Effects on aquatic and human health due to large scale bioenergy crop expansion

In this study, the environmental impacts of large scale bioenergy crops were evaluated using the Soil and Water Assessment Tool (SWAT). Daily pesticide concentration data for a study area consisting of four large watersheds located in Michigan (totaling 53,358 km²) was estimated over a six year period (2000-2005). Model outputs for atrazine, bromoxynil, glyphosate, metolachlor, pendimethalin, sethoxydim, triflualin, and 2,4-D model output were used to predict the possible long-term implications that large-scale bioenergy crop expansion may have on the bluegill (Lepomis macrochirus) and humans. Threshold toxicity levels were obtained for the bluegill and for human consumption for all pesticides being evaluated through an extensive literature review. Model output was compared to each toxicity level for the suggested exposure time (96-hour for bluegill and 24-hour for humans). The results suggest that traditional intensive row crops such as canola, corn and sorghum may negatively impact aquatic life, and in most cases affect the safe drinking water availability. The continuous corn rotation, the most representative rotation for current agricultural practices for a starch-based ethanol economy, delivers the highest concentrations of glyphosate to the stream. In addition, continuous canola contributed to a concentration of 1.11 ppm of trifluralin, a highly toxic herbicide, which is 8.7 times the 96-hour ecotoxicity of bluegills and 21 times the safe drinking water level. Also during the period of study, continuous corn resulted in the impairment of 541,152 km of stream. However, there is promise with second-generation lignocellulosic bioenergy crops such as switchgrass, which resulted in a 171,667 km reduction in total stream length that exceeds the human threshold criteria, as compared to the base scenario. Results of this study may be useful in determining the suitability of bioenergy crop rotations and aid in decision making regarding the adaption of large-scale bioenergy cropping systems.     

Effects of CaO/P2O5 ratio on the structure and elastic properties of SiO2–CaO–Na2O–P2O5 bioglasses

The evolution of elastic properties and structure upon the change of CaO/P₂O₅ ratio in SiO₂–CaO–Na₂O–P₂O₅ glasses (45S5-derived and 55S4-derived) at ambient conditions has been studied by using both Brillouin and Raman spectroscopy coupled with X-ray diffraction. Under the same SiO₂/Na₂O ratio, it is found that a decrease in CaO/P₂O₅ molar ratio has caused a more-polymerized silicate network via a net consumption of Q⁰, Q¹, and Q² species yet enriching in Q³ and Q⁴ species. Brillouin experiments revealed that all the bulk, shear and Young’s moduli of the glasses studied increases with the increase of CaO/P₂O₅ molar ratio. The unexpected variation trend in shear modulus can be correlated to the contribution from cohesion, the less-polymerized phosphate Q species, and density. Compared to the 45S5-derived, the more-polymerized 55S4-deived glass has a lower bulk but slightly higher shear modulus at the given CaO/P₂O₅ ratio.