By tailoring the coordination sphere of vanadium to accommodate a 7-coordinate geometry, a highly soluble (>1.3 M) and reducing (−1.2 V vs Ag/AgCl) flow battery electrolyte is generated from ...V(DTPA)2–/3– (DTPA = diethylenetriaminepentaacetate). Bulk spectroelectrochemistry is performed in situ to assess material properties in both oxidized and reduced states. Flow batteries are assembled in near neutral pH conditions and operated with discharge energy densities of 12.5 Wh L–1 and high efficiency. Further, the first chelated flow battery using the same aminopolycarboxylate ligand for both electrolytes is generated. The presented batteries demonstrate comparable performance to the iron–vanadium and all-vanadium flow batteries while doubling the effective discharge energy of vanadium (Wh per mol V) and minimizing safety and operating risks, offering grid-scale energy storage alternatives.
Titanium is essentially absent from biological systems yet reliably integrates into bone. To achieve osseointegration, titanium must activate biological processes without entering cells, defining it ...as a bio-activating material. Nanostructuring bulk titanium reduces grain size, increases strength, and improves other quantifiable physical properties, including cytocompatibility. The biological processes activated by increasing grain boundary availability were detected with total RNA-sequencing in mouse pre-osteoblasts grown for 72 hours on nanometrically smooth substrates of either coarse grain or nanostructured ultrafine grain titanium. The average grain boundary length under cells on the conventional coarse grain substrates is 273.0 μm, compared to 70,881.5 μm for cells adhered to the nanostructured ultrafine grain substrates; a 260-fold difference. Cells on both substrates exhibit similar expression profiles for genes whose products are critical for mechanosensation and transduction of cues that trigger osteoconduction. Biological process Gene Ontology term enrichment analysis of differentially expressed genes reveals that cell cycle, chromatin modification, telomere maintenance, and RNA metabolism processes are upregulated on ultrafine grain titanium. Processes related to immune response, including apoptosis, are downregulated. Tumor-suppressor genes are upregulated while tumor-promoting genes are downregulated. Upregulation of genes involved in chromatin remodeling and downregulation of genes under the control of the peripheral circadian clock implicate both processes in the transduction of mechanosensory information. Non-coding RNAs may also play a role in the response. Merging transcriptomics with well-established mechanobiology principles generates a unified model to explain the bio-activating properties of titanium. The modulation of processes is accomplished through chromatin remodeling in which the nucleus responds like a rheostat to grain boundary concentration. This convergence of biological and materials science reveals a pathway toward understanding the biotic-abiotic interface and will inform the development of effective bio-activating and bio-inactivating materials.
Synthesis of an Al/Al2O3 composite by severe plastic deformation Kunčická, Lenka; Lowe, Terry C.; Davis, Casey F. ...
Materials science & engineering. A, Structural materials : properties, microstructure and processing,
10/2015, Letnik:
646
Journal Article
Recenzirano
The influence of severe plastic deformation on fabrication of an aluminum/alumina composite made from pre-sintered Al powders was evaluated. Spherical powder particles with diameters up to 45μm were ...pre-compacted using cold isostatic pressing (CIP), subsequently vacuum sintered for 60min at 500°C, and subjected to processing using either 4 passes of swaging or 1 or 10 revolutions of high pressure torsion (HPT). For all the samples we calculated average strain and measured microhardness. Results showed an increase in microhardness with an increase of the imposed strain. However, the microhardness values and uniformity were also influenced by possible residual porosity. The smallest and most uniform grain size was achieved for the samples processed by HPT, especially after 10 revolutions (average diameter of 0.22μm). Residual porosity was completely eliminated only after 10 HPT revolutions. Texture evaluations showed 〈111〉 fiber texture development after swaging, while grain orientations after HPT were more random.
Deformation behaviors during swaging of an Al/Cu/Al layered clad composite were investigated experimentally and by finite element (FE) analysis. Measured and predicted deformation responses were ...compared and found to be in generally good agreement. These comparisons also validated the design and operation of a custom device that measures the total force required for swaging. An average effective strain of 0.5 was predicted for the first swaging pass, but the strain distribution was significantly inhomogeneous. Predicted strain gradients and stresses were consistent with experimentally observed gradients in grain size and subgrain size. The highest flow stresses were predicted in the Cu layer, where the measured subgrain size was correspondingly small. The predicted gradients in temperature and strain also correlated well with the observation of recrystallization in the outer Al layer.
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•Verification of our newly designed swaging force measuring device was performed.•Strain distribution in the layers within the composite during a pass was predicted.•Plastic flow of individual layers was predicted and differences were explained.•Microhardness increased after swaging and corresponded to the predicted strain.•Microstructure analyses showed significant grain refinement and subgrains formation.
Magnesium (Mg) alloys are promising candidate materials for use in absorbable implants. For this purpose, they must possess a combination of properties needed for specific medical applications such ...as coronary stents or trauma fixation screws. The typically low strength, low ductility, and rapid biodegradation of many Mg alloys limit their suitability for medical use. However, these problems can be addressed by creating ultrafine-grain (UFG) variants of Mg alloys. For this purpose, an economical continuous equal channel angular pressing (ECAP-C) method was applied to produce UFG AZ31 Mg. An ultimate tensile strength of 333.5 MPa with an elongation of 28% was achieved, and continuous coil-to-coil ECAP-C processing was demonstrated.
Redox flow batteries (RFBs) have attracted significant attention as a promising electrochemical energy storage technology, offering various advantages such as grid-scale electricity production with ...variable intermittent electricity delivery, enhanced safety compared to metal-ion batteries, decoupled energy and power density, and simplified manufacturing processes. For this review, we exclusively focus on organic, non-aqueous redox flow batteries. Specifically, we address the most recent progress and the major challenges related to the design and synthesis of robust redox-active organic compounds. An extensive examination of the synthesis and characterization of a wide spectrum of redox-active molecules, focusing particularly on derivatives of posolytes such as quinone, nitroxyl radicals, dialkoxybenzenes, and phenothiazine and negolytes such as viologen and pyridiniums, is provided. We explore the incorporation of various functional groups as documented in the references, aiming to enhance the chemical and electrochemical stability, as well as the solubility, of both the neutral and radical states of redox-active molecules. Additionally, we offer a comprehensive assessment of the cell-cycling performance exhibited by these redox-active molecules.
Stepwise covariate modeling (SCM) is a widely used tool in pharmacometric analyses to identify covariates that explain between-subject variability (BSV) in exposure and exposure–response ...relationships. However, this approach has several potential weaknesses, including over-estimated covariate effect and incorrect selection of covariates due to collinearity. In this work, we investigated the operating characteristics (i.e., accuracy, precision, and power) of SCM in a controlled setting by simulating sixteen scenarios with up to four covariate relationships. The SCM analysis showed a decrease in the power to detect the true covariates as model complexity increased. Furthermore, false highly correlated covariates were frequently selected in place of or in addition to the true covariates. Relative root mean square errors (RMRSE) ranged from 1 to 51% for the fixed effects parameters, increased with the number of covariates included in the model, and were slightly higher than the RMRSE obtained with a simple re-estimation exercise with the true model (i.e., stochastic simulation and estimation). RMRSE for BSV increased with the number of covariates included in the model, with a covariance parameter RMRSE of almost 135% in the most complex scenario. Loose boundary conditions on the continuous covariate power relation appeared to have an impact on the covariate model selection in SCM. A stricter boundary condition helped achieve high power (> 90%), even in the most complex scenario. Finally, reducing the sample size in terms of number of subjects or number of samples proved to have an impact on the power to detect the correct model.
Electrolytes containing multiple redox couples are promising for improving the energy density of flow batteries. Here, two chelated chromium complexes that are structural isomers are characterized ...and combined to generate electrolytes containing up to 2 M of active species, corresponding to 53.6 Ah L−1. The mixed isomer approach enables a significantly higher active material content than the individual materials would allow, affording energy dense cells with Coulombic efficiencies of ≥99.6% at 100 mA cm−2 and an open circuit voltage of 1.65 V at 50% state-of-charge. This high concentration, however, comes with a caveat; at a given concentration, an equimolar mixed electrolyte leads to lower voltage efficiency compared to using the individual isomers, while Coulombic efficiency remains constant. Our work demonstrates that exploiting structural isomerism is an efficient approach to improve capacity, but active materials must be selected carefully in mixed systems as differences in operating potentials negatively affect energy efficiency.
In High Pressure Shearing (HPS) a flat sample is subjected to large shear strain by displacing one of its flat surfaces with respect to the other under high compressive force. The process is driven ...by non-sliding friction provided by the large compressive stress. The HPS process was first proposed by Fujioka and Horita Materials transactions, 50 (2009) 930–933, and was applied to aluminum strips; upscaling was also developed. In the present work we introduce a modified version of HPS where the compression strain is relevant, so the new process is called High Pressure Compressive Shearing (HPCS). In HPCS, the experiments are conducted similarly to HPS but with the addition of a confining-pressure and more compression strain to increase the shear strain. This paper presents the mechanical analysis of stress and strain states during HPCS and demonstrates in situ measurements of stress-strain relations in ARMCO® steel subject to HPCS at room temperature up to an equivalent strain of 33.3. The strain hardening characteristics, the texture and the microstructure were analyzed. It has been shown that compression during HPCS results in a non-hydrostatic stress state and that ultimate steady state of grain fragmentation can be readily reached by HPCS.
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•A new shear testing is presented, called High Pressure Compressive Shearing (HPCS).•A plasticity analysis is established for constructing strain hardening curve in HPCS testing.•Multi-pass HPCS testing were done on an ARMCO® Steel up to equivalent strain of 33.•A characteristic bcc simple shear texture was obtained via HPCS of ARMCO® steel.•The grain size was reduced by a factor of 170 reaching the steady state.
Polymer semiconductors are fascinating materials that could enable delivery of chemical fuels from water and sunlight, offering several potential advantages over their inorganic counterparts. These ...include extensive synthetic tunability of optoelectronic and redox properties and unique opportunities to tailor catalytic sites via chemical control over the nanoenvironment. Added to this is proven functionality of polymer semiconductors in solar cells, low-cost processability, and potential for large-area scalability. Herein we discuss recent progress on soft photoelectrochemical systems and define three critical knowledge gaps that must be closed for these materials to reach their full potential. We must (1) understand the influence of electrolyte penetration on photoinduced charge separation, transport, and recombination, (2) learn to exploit the swollen polymer/electrolyte interphase to drive selective fuel formation, and (3) establish co-design criteria for soft materials that sustain function in the face of harsh chemical challenges. Achieving these formidable goals would enable tailorable systems for driving photoelectrochemical fuel production at scale.
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