Low-cost anion exchange membrane fuel cells have been investigated as a promising alternative to proton exchange membrane fuel cells for the last decade. The major barriers to the viability of anion ...exchange membrane fuel cells are their unsatisfactory key components-anion exchange ionomers and membranes. Here, we present a series of durable poly(fluorenyl aryl piperidinium) ionomers and membranes where the membranes possess high OH
conductivity of 208 mS cm
at 80 °C, low H
permeability, excellent mechanical properties (84.5 MPa TS), and 2000 h ex-situ durability in 1 M NaOH at 80 °C, while the ionomers have high water vapor permeability and low phenyl adsorption. Based on our rational design of poly(fluorenyl aryl piperidinium) membranes and ionomers, we demonstrate alkaline fuel cell performances of 2.34 W cm
in H
-O
and 1.25 W cm
in H
-air (CO
-free) at 80 °C. The present cells can be operated stably under a 0.2 A cm
current density for ~200 h.
A grand challenge in material science is to understand the correlation between intrinsic properties and defect dynamics. Radiation tolerant materials are in great demand for safe operation and ...advancement of nuclear and aerospace systems. Unlike traditional approaches that rely on microstructural and nanoscale features to mitigate radiation damage, this study demonstrates enhancement of radiation tolerance with the suppression of void formation by two orders magnitude at elevated temperatures in equiatomic single-phase concentrated solid solution alloys, and more importantly, reveals its controlling mechanism through a detailed analysis of the depth distribution of defect clusters and an atomistic computer simulation. The enhanced swelling resistance is attributed to the tailored interstitial defect cluster motion in the alloys from a long-range one-dimensional mode to a short-range three-dimensional mode, which leads to enhanced point defect recombination. The results suggest design criteria for next generation radiation tolerant structural alloys.
Anion exchange membrane fuel cells (AEMFCs) have attracted great interest as a low-cost fuel cell technology for clean energy conversion and utilization for the future. AEMFCs have been considered ...the most promising succedaneum to proton exchange membrane fuel cells (PEMFCs) for addressing the cost issues associated with PEMFCs due to utilizing non-platinum group metals as electrocatalysts under alkaline conditions (such as Ag, Ni, and Co). Herein, we focus on a critical topic of AEMFCs—-anion-exchange polyelectrolytes (AEPs)—which are essential materials for low-cost AEMFCs. Specifically, AEPs have been used as anion-exchange membranes (AEMs) and binders (or ionomers) in AEMFCs. Years of study have allowed AEMFCs to recently achieve unprecedented progress, specifically in terms of power density and durability. These properties are comparable to or higher thanPEMFCs due to the recent development of high performance AEPs. Currently, most AEPs focused on the application of AEMs, and the importance of ionomer research has not been widely recognized. Moreover, a comprehensive review involving a systematic performance comparison of the state-of-the-art AEMs and ionomers is still lacking, making future research on AEMFCs unclear. This review systematically and comprehensively summarizes the development of AEPs and highlights the importance of cationic species and polymer backbone structures on durability with an emphasis on the importance of ionomer research. We further describe the differences between AEMs and ionomers by comparing the advantages and disadvantages of the state-of-the-art AEMs and ionomers to accurately guide future research on AEMFCs. We cover synthetic methods, degradation mechanisms, strategies to enhance performance, water transport behaviors, structure design criteria, and new challenges for AEMs and ionomers. This review is expected to expand further understanding of AEMs and ionomers and provide a future direction for designing AEMs and ionomers for future AEMFCs.
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We have employed large-scale molecular dynamics simulations to study defect production, clustering, and its evolution in GaN for energies of a primary knock-on atom ranging from 500 eV to 40 keV. In ...the presence of proton radiation, a large number of atoms will be displaced during the collisional phase with a compacted cascade volume, but a great number of displaced atoms recombine significantly with vacancies at the same time, i.e., a pseudometallic behavior (PMB). This leads to the result that the majority of surviving defects are just single interstitials or vacancies for all recoil energies considered with only a small number of defects forming clusters. The total number of defects simulated in GaN can be very well predicted by the simplified Norgett, Robison, and Torrens (NRT) formula due to the PMB, in contrast to GaAs where the defect number becomes much larger than the NRT value. Moreover, the damage density within a cascade core is evaluated and applied to construct a model to calculate an energy-partition function for studying the nonionizing energy loss (NIEL) in GaN. The calculated NIEL in GaN is often found to be smaller than that predicted by a model based on the simple Kinchin-Pease formula. The comparisons of defect creation, density, and effective NIEL in GaN to those of GaAs suggest that GaN may be much more resistant to displacement damage than GaAs at low temperatures.
Molecular dynamics (MD) simulations are used to reveal the mechanisms of defect substructure evolution and atomic mixing in nanocrystalline Cu/Ni composites under severe shear deformation and ...subsequent thermal annealing. A continuous shear scheme of MD simulation utilizing an on-the-fly periodic boundary adjustment approach enables it to reach any large shear strain. The comprehensive evaluation on the evolution of dislocation structures at various strain states indicates partial dislocation-mediated plastic deformation and triple junction slide via partial dislocation nucleation and emission from triple junctions and grain boundaries. The analysis of atomic structures in unique mixing regions suggests that triple junction sliding can result in a long-range region of atomic mixing facilitated by net dislocation flux, which is the key mechanism of atomic mixing in nanocrystalline Cu/Ni composite under severe shear, while dislocation emissions at interfaces result in short-range mixing. It is also found that thermal annealing causes the evolution of non-equilibrium defect substructures which assists atomic mixing.
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As one of the most versatile and universal second messengers, calcium plays an essential role in cell life. Here we briefly reviewed the research progress of how different calcium channels are ...located at the cell plasma membrane, including voltage-gated calcium channels (VGCCs), receptor-operated channels (ROC), and store-operated channels (ROC). These channels can regulate different cancer progression. Afterward, the patch clamp technique's development and operating principle, an important quantitative method used for ion channel investigation, are introduced in this paper.
In Liquid Phase Catalytic Exchange (LPCE), the strength and hydrophobicity of styrene-divinylbenzene copolymer (SDB) carrier are key limitation factors for practical applications. In this paper, a ...surface-modified nano-SiO
2
(KH570-SiO
2
) was used to improve the strength and hydrophobicity of SDB. Then, copolymerization of KH570SiO
2
with St, DVB to produce KH570-SiO
2
/SDB, Divinyl benzene (DVB), styrene (St) glycidyl methacrylate (GMA) to produce KH570-SiO
2
/GMA/SDB. The two kinds of new carriers were characterized by scanning electron microscope, static water contact angle, N
2
adsorption–desorption, transform infrared spectrometry and thermogravimetric analysis. Compared with SDB, both KH570-SiO
2
/SDB and KH570SiO
2
/GMA/SDB show better performances, such as a higher hydrophobicity(147° and 145°, respective), a higher strength(107.11 N and 115.37 N, respectively), a better thermal stability(373.8 and 435.67 ℃, respectively), and a larger specific surface area(487.253 and 463.673 m
2
/g, respective). The Nickel ion was uesd as the model ion of Platinum ion. And then the Ni
2+
adsorption performances of KH570-SiO
2
/SDB and KH570-SiO
2
/GMA/SDB were studied. Experiments show that KH570-SiO
2
/GMA/SDB has a much higher adsorption rate and a bigger adsorption amount. Refinement indicates that the adsorption behaviors of SDB, KH570-SiO
2
/SDB and KH570-SiO
2
/GMA/SDB with Ni
2+
are according to pseudo-first-order kinetic. The adsorption of SDB and KH570-SiO
2
/GMA/SDB obeyed Freundlich isotherm, while the adsorption of KH570-SiO
2
/SDB obeyed Langmuir isotherm.
We have systematically investigated the energetics and stability of Ag atom in 3C-SiC with various charge states using first-principles calculations within large supercells. Up to 18 Ag-defect ...configurations have been examined, including substitutionals, interstitials, and vacancy-based complexes. A general trend is that the formation energy of Ag-defect complexes is generally lower than interstitial typed defects. With the lowest formation energy, the configuration with Ag_TSi-VC3+ turns out to be the most stable one. It has also been found a neutral Ag is more likely to substitute a silicon lattice site with a nearest carbon vacancy, thus forming an AgSi-VC pair. All these data are important inputs in the next coarser-level modeling to understand the Ag migration in and release from 3C-SiC under both thermal and radiation conditions.
Tens-nanometer sized defect substructures such as dislocation network, nanotwin and new grain or phase may form during solid phase processing (SPP), which affect the energy landscape, hence, the ...stability and evolution of phase and structure. Developing non-equilibrium thermodynamic models needs the correlation among the energy, defect substructure and deformation. In the current work, we use molecular dynamics (MD) method to simulate defect substructure evolutions in polycrystalline Al under compress and shear stresses. The effect of local stresses on the formation and transformation of typical defect substructures were analyzed. It was found that transitions from FCC, nanotwin, HCP, BCC, HCP to FCC lead to the formation of subgrains facilitated with large grain rotation. Our results demonstrate that point defect concentrations (e.g., HCP, dislocation core atoms) can be used as internal variables to describe defect substructures, such as dislocations, nanotwins and sub-grain boundaries. An energy landscape of defect substructures in polycrystalline Al under compress and shear stresses was established which shows unstable and metastable defect substructures. Approaches to developing more accurate energy landscapes for understanding and predicting microstructure evolution under SPP was discussed.
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