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Register a new userReview of Best Practice Methods for Determining an Electrode Materials Performance for Ultracapacitors
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Ultracapacitors are rapidly being adopted for use for a wide range of electrical energy storage applications. While ultracapacitors are able to deliver high rates of charge and discharge, they are limited in the amount of energy stored. The capacity of ultracapacitors is largely determined by the electrode material and as a result, research to improve the performance of electrode materials has dramatically increased. While test methods for packaged ultracapacitors are well developed, it is often not feasible for the materials scientist to assemble full sized, packaged cells to test electrode materials. Methodology to reliably measure a materials performance for ultracapacitor electrode use is not well standardized with the different techniques currently being used yielding widely varying results. In this manuscript, we review the best practice test methods that accurately predict a materials performance, yet are flexible and quick enough to accommodate a wide range of material sample types and amounts.
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In this article we wish to provide a common set of best practice approaches that should be considered for all effective research grant proposal reviews. The federal government performs a critical role in American competitiveness and security by supporting basic research funded with taxpayer dollars. Effectively managing their allocation to scientists and researchers is a noble and crucial mission for advancing fundamental knowledge and deserves a heightened attention. Ensuring that proposals submitted are treated fairly and transparently is essential to both the health of any research program and also a duty to the public who ultimately funds the research. The paper describes the general requirements of a review process and at each step underlines the issues and suggests potential improvements and some fundamental requirements that should be included in any scientific review. We also included a series of tips geared to the scientific community. Our goals in this paper are 1) to demystify the process for everyone including policy makers who are sometimes flummoxed by the results of some scientific reviews, 2) to trigger some discussions about reviews and review process in the scientific community, 3) to inform scientists whose careers are directly impacted by review results about their own role in this process and 4) to suggest a road to more efficient, fairer and overall more transparent process. For experts in proposal reviews or for busy or impatient readers, the entire list of our recommendations is presented at the beginning. We describe in each section the context and rational of each recommendation.
Taking into account the phase fraction during transition for the first-order magnetocaloric materials, an improved isothermal entropy change determination has been put forward based on the Clausius-Clapeyron (CC) equation. It was found that the isothermal entropy change value evaluated by our method is in excellent agreement with those determined from the Maxwell-relation (MR) for Ni-Mn-Sn Heusler alloys, which usually presents a weak field-induced phase transforming behavior. In comparison with MR, this method could give rise to a favorable result derived from few thermomagnetic measurements. More importantly, we can eliminate the isothermal entropy change overestimation derived from MR, which always exists in the cases of Ni-Co-Mn-In and MnAs systems with a prominent field-induced transition. These results confirmed that such a CC-equation-based method is quite practical and superior to the MR-based ones in eliminating the spurious spike and reducing measuring cost.
Computational screening methods have been accelerating discovery of new materials and deployment of technologies based on them in many areas from batteries and alloys to photovoltaics and separation processes. In this review, we focus on post-combustion carbon capture using adsorption in porous materials. Prompted by unprecedented developments in material science, researchers in material engineering, molecular simulations, and process modelling have been interested in finding the best materials for carbon capture using energy efficient pressure-swing adsorption processes. Recent efforts have been directed towards development of new multiscale and performance-based screening workflows where we are able to go from the atomistic structure of an adsorbent to its equilibrium and transport properties for gas adsorption, and eventually to its separation performance in the actual process. The objective of this article is to review the current status of these emerging approaches, explain their significance for materials screening, while at the same time highlighting the existing pitfalls and challenges that limit their application in practice and industry. It is also the intention of this review to encourage cross-disciplinary collaborations for the development of more advanced screening methodologies. For this specific reason, we undertake an additional task of compiling and introducing all the elements that are needed for the development and operation of the performance-based screening workflows, including information about available materials databases, state-of-the-art molecular simulation and process modelling tools and methods, and the full list of data and parameters required for each stage.
We extend the nested sampling algorithm to simulate materials under periodic boundary and constant pressure conditions, and show how it can be used to determine the complete equilibrium phase diagram, for a given potential energy function, efficiently and in a highly automated fashion. The only inputs required are the composition and the desired pressure and temperature ranges, in particular, solid-solid phase transitions are recovered without any a priori knowledge about the structure of solid phases. We benchmark and showcase the algorithm on the periodic Lennard-Jones system, aluminium and NiTi.
We report on graphene-passivated ferromagnetic electrodes (GPFE) for spin devices. GPFE are shown to act as spin-polarized oxidation-resistant electrodes. The direct coating of nickel with few layer graphene through a readily scalable chemical vapour deposition (CVD) process allows the preservation of an unoxidized nickel surface upon air exposure. Fabrication and measurement of complete reference tunneling spin valve structures demonstrates that the GPFE is maintained as a spin polarizer and also that the presence of the graphene coating leads to a specific sign reversal of the magneto-resistance. Hence, this work highlights a novel oxidation-resistant spin source which further unlocks low cost wet chemistry processes for spintronics devices.
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