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Behavior of BaCe0.9ax Zr x Y0.1O3aI' in water and ethanol suspensions
The stability of perovskite proton conductors BaCe0.2Zr0.7Y0.1O2.95 and BaCe0.5Zr0.4Y0.1O2.95 (referred to as BCZY) has been tested by exposure of powders to water and ethanol at room temperature. The liquid phase was monitored as a function of time with inductively coupled plasma-optical emission spectrometry. With water, leaching of barium continued for over 200 days, the duration of the test. There was no systematic difference in leaching with solutions of native pH or alkalified with NH4OH. The powders, before and after treatment, were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM confirmed the degradation of the perovskite phase and revealed barium carbonate nanobranches and nanoparticles from the agglomeration of the fragmented perovskite. The effect of ethanol was much less severe; leaching of elements after immersion was negligible for up to 17 days, and XRD patterns before and after treatment did not show any structural degradation. It is concluded that ethanol is an appropriate choice as a processing solvent for tapecasting BCZY powders.
Journal Article
Mercury, Mining, and Empire
On the basis of an examination of the colonial mercury and
silver production processes and related labor systems, Mercury,
Mining, and Empire explores the effects of mercury pollution in
colonial Huancavelica, Peru, and Potosí, in present-day Bolivia.
The book presents a multifaceted and interwoven tale of what
colonial exploitation of indigenous peoples and resources left in
its wake. It is a socio-ecological history that explores the toxic
interrelationships between mercury and silver production, urban
environments, and the people who lived and worked in them. Nicholas
A. Robins tells the story of how native peoples in the region were
conscripted into the noxious ranks of foot soldiers of
proto-globalism, and how their fate, and that of their communities,
was-and still is-chained to it.
eBook
Polyurethane Recycling and Disposal: Methods and Prospects
Growing water and land pollution, the possibility of exhaustion of raw materials and resistance of plastics to physical and chemical factors results in increasing importance of synthetic polymers waste recycling, recovery and environmentally friendly ways of disposal. Polyurethanes (PU) are a family of versatile synthetic polymers with highly diverse applications. They are class of polymers derived from the condensation of polyisocyanates and polyalcohols. This paper reports the latest developments in the field of polyurethane disposal, recycling and recovery. Various methods tested and applied in recent years have proven that the processing of PU waste can be economically and ecologically beneficial. At the moment mechanical recycling and glycolysis are the most important ones. Polyurethanes’ biological degradation is highly promising for both post-consumer and postproduction waste. It can also be applied in bioremediation of water and soil contaminated with polyurethanes. Another possibility for biological methods is the synthesis of PU materials sensitive to biological degradation. In conclusion, a high diversity of polyurethane waste types and derivation results in demand for a wide range of methods of processing. Furthermore, already existing ones appear to be enough to state that the elimination of not reprocessed polyurethane waste in the future is possible.
Journal Article
Kinetic model study of moisture sorptionadesorptionaresorption in triangular-shaped vinyl ester filler/epoxy composites
A phenomenological diffusion model was used to study and describe moisture sorptionadesorptionaresorption kinetics in triangular-shaped vinyl ester filler/epoxy composites at 80 degree C. The model was derived to predict the experimental anomalous weight gain behaviors of epoxy composites during moisture sorption and resorption, and estimate the degree of material degradation and loss observed as negative weight change during desorption. To verify the applicability of the model, acid anhydrideacured epoxy composites were prepared at varied alignment (parallel or staggered), spacing (1 or 5 mm), and orientation (pointed or flat) of triangular-shaped vinyl ester fillers. Moisture sorptionadesorptionaresorption experiment was performed by immersion of specimens in deionized water for 1200 h, followed by vacuum drying for 300 h, and water reimmersion for 300 h. The parameters of the model were calculated from nonlinear regression of percent weight change versus time experimental data. The model was found to be in good agreement with the weight change kinetic curves of all specimens. Results of three-way analysis of variance of model parameters showed the degree of material degradation and moisture diffusion coefficients during sorption, desorption, and resorption to be significantly affected by triangular-shaped filler alignment, spacing, and orientation. Using staggered over parallel alignment and 5-mm over 1-mm spacing decreased material degradation and moisture transport rate during desorption in composites. Increasing the spacing from 1 to 5 mm decreased moisture diffusion during sorption. Orienting the fillers from pointed to flat decreased moisture diffusion during resorption. Effect of interaction of filler spacing and orientation was also found to be statistically significant on the diffusion rate during sorption.
Journal Article
Molecular Pathways for Polymer Degradation during Conventional Processing, Additive Manufacturing, and Mechanical Recycling
The assessment of the extent of degradation of polymer molecules during processing via conventional (e.g., extrusion and injection molding) and emerging (e.g., additive manufacturing; AM) techniques is important for both the final polymer material performance with respect to technical specifications and the material circularity. In this contribution, the most relevant (thermal, thermo-mechanical, thermal-oxidative, hydrolysis) degradation mechanisms of polymer materials during processing are discussed, addressing conventional extrusion-based manufacturing, including mechanical recycling, and AM. An overview is given of the most important experimental characterization techniques, and it is explained how these can be connected with modeling tools. Case studies are incorporated, dealing with polyesters, styrene-based materials, and polyolefins, as well as the typical AM polymers. Guidelines are formulated in view of a better molecular scale driven degradation control.
Journal Article