Low Atomic Weight Research Articles

Elemental changes in heart and coronaries after breast cancer radiotherapy assessed by synchrotron radiation soft X-ray spectromicroscopy

Radiotherapy (RT) plays a pivotal role in the treatment of breast cancer (BC) and various thoracic malignancies. Radiation induced heart disease (RIHD) is one such long term toxicity which can offset the improvement in cancer specific mortality. Long term normal tissue toxicity is becoming a bigger concern, as early diagnosis and the improvement in the treatment of these cancers has led to patients surviving longer. Our research group on Physics applied to biomedical sciences has been investigating the side effects of BC treatment (RT and chemotherapy) for more than ten years. The cardiac regeneration has been studied to better understand the damage that occurs following radiation procedures in the heart tissue after many thoracic cancer treatments. One possible complication is coronary artery disease induced by irradiation after radiotherapy in thoracic area. Studies on the structures of cardiac tissue and the distribution of low atomic weight element can help to understand mechanisms associated with damage to healthy tissue, as these are of fundamental importance to metabolism in biological systems. The present study aimed to elucidate how radiotherapy in the thoracic area causes damage in the coronary artery, and to verify the potential use of losartan in reducing, or even preventing, the side effects of irradiation in this artery. To assess elemental and morphological differences in aortic and coronary samples, the Low Energy X-Ray Fluorescence (LEXRF) technique using Synchrotron Radiation was employed. SR- LEXRF and scanning transmission X-ray microscopy measurements were carried out at the beamline TwinMic at Elettra Sincrotrone Triste, Italy.

Deciphering perovskite decomposition in a humid atmosphere with TOF-GISANS

Doping or alloying of the cations on the A-site and halides on the X site of ABX3 perovskites has been demonstrated as a successful technique for improving moisture stability of perovskite films for optoelectronic applications. Despite structural and electrical stability improvements, these films still undergo moisture induced degradation to Lead Iodide and other photo-inactive phases, reducing device lifetime and performance. Understanding of their moisture induced degradation has been limited by the contrast mechanisms and sensitivity of optical and x-ray scattering techniques. Time-of-Flight Grazing Incidence Small Angle Neutron Scattering (TOF-GISANS) presents itself as a powerful alternative capable of identifying low atomic weight phases and offering depth resolution. Herein we use TOF-GISANS to begin to uncover moisture induced degradation pathways in various mixed perovskite systems fabricated under ambient conditions and exposed to 90% rH in the dark for up to 12 h, showing poor stoichiometric homogeneity through the bulk of the film and facile formation of deuterated by-products at ambient temperatures. We find evidence indicative of formation of PbI2, and PbBr2 from peaks apparent in scattering from the surface of MAPbI3, FA0.83MA0.17Pb(I0.83Br0.17)3, and FA0.83Cs0.17Pb(I0.83Br0.17)3 thin films, with degradation less pronounced in the latter films containing Cs. Deuterated by-products form readily, resulting in decreasing average particle size as perovskite crystals swell and fragment from the grain periphery inwards. Cs0.05(FA0.83MA0.17)0.95Pb(I0.84Br0.16)3 shows impressive phase resilience compared to the other mixtures, with minimal segregation to other phases observed in vertical cuts through the 2D scattering image, though still exhibits deleterious morphological degradation. TOF-GISANS is demonstrated as a powerful tool for characterisation of these materials, with significant potential for future investigations into phase changes in thin films.

Hazardous elements present in coal nanoparticles in a Caribbean port region in Colombia

Scientific works examining coal-derived nanoparticles (NPs) containing potentially toxic elements (PTEs) confined in marine suspended sediments (MSSs) in port regions worldwide is an understudied topic, despite the fact that coal NPs have tremendous negative impacts on marine estuaries. The general objective of this study is to analyze the NP levels of coal, including PTEs, contained within MSSs in the general vicinity of the largest Caribbean port in Colombia. The morphology, size, chemical composition, and agglomeration states of NPs within MSSs of the sampled beaches were calculated through modern electron microscopy. The methodology used to detect chemical elements, unfortunately with EDS, it is not possible to precisely specify the chemical elements of low atomic weight (e.g. H, O, F, etc.) Therefore, with the EDS available today, it is only possible to have an idea of the chemical composition of each detected particle. Thus, it was possible to obtain the average frequency of the chemical elements identified in the 23 analyzed sampling points. Through the results, more than one thousand particles were detected in the most abundant phases, thus, the most frequent particles in the results of this manuscript were described. Sample point 8, located closest to the coal export port, had a higher concentration of nano-toxic elements (Al, Fe, Si, K, Mg, K) most concerning for human health in addition to being harmful to marine life. This study suggests that public policies dealing with MSS pollution need to be discussed by public managers to avoid further and sustained environmental degradation. The need to create projects will subsidize legacy liabilities generated by coal in seaports in other regions of the world.

In-situ analysis of the lithium occurrence in the No.11 coal from the Antaibao mining district, Ningwu Coalfield, northern China

The occurrence of lithium (Li) in coal serves as the foundation for understanding the mechanism of its enrichment in coal and migration during combustion. However, owing to its low atomic weight, Li cannot be detected using conventional microbeam analyses, severely limiting its use. The high-Li Antaibao No.11 coal seam with a concentration of 99.1 μg/g Li was studied to determine the mode of occurrence and enrichment of Li. When compared to Chinese coal, the Antaibao No.11 coal is richer in SiO2, Al2O3, and TiO2. The carrier of Li was preliminarily determined using statistical correlation. In addition, two high-Li coal benches were subjected to in-situ analysis using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The TOF-SIMS data show three types of Li occurrences in the first high-Li coal sample with a content of 179 μg/g. The main carriers of Li in this sample are illite, montmorillonite, chlorite, and tourmaline, according to the chemical maps for Li, Si, Al, Na, K, Ca, Mg, and Fe. This high-Li sample was formed by the interaction of two seawater-influenced coal seams. The interaction of fresh and saline waters makes the Li occurrence more variable. However, with a Li concentration of 260 μg/g in the second Li-enriched coal sample, Li only matches with Si and Al, indicating that Li is primarily found in kaolinite. This sample is formed between the parting and the seam with the greatest transgression. Boehmite is found in this sample in relation to the bauxite-bearing weathering crust. Locally, boehmite acts as a barrier to the infiltration and interaction of Li and other alkali and alkaline elements. As a result, Li is only associated with Si and Al. The terrigenous materials deposited within the original peat are responsible for the enrichment of Li in this sample.

FeBO3 as a low cost and high-performance anode material for sodium-ion batteries

The research of borate materials as sodium-ion batteries (SIBs) anode is still in the early stages, but the boron polyoxoanions are attracting intense interest due to their low atomic weight and high electronegative features. In this work, FeBO3 was prepared with low-cost raw materials and evaluated as SIBs anode. The FeBO3 shows a high reversible capacity of 328 mAh/g at the current density of 0.4 A/g. In addition, the electrochemical performance of FeBO3 can be improved by carbon coating. The prepared carbon-coated FeBO3 composite has a reversible capacity of 426 mAh/g (at 0.4 A/g) and an outstanding rate capability of 272 mAh/g (at 1.6 A/g). Furthermore, the sodium storage mechanism of FeBO3 was studied by in-situ XRD and ex-situ XPS.

Laser-Induced Breakdown Spectroscopy-Based Coal-Rock Recognition: An in Situ Sampling and Recognition Method

Coal and rock recognition (CRR) has important theoretical and practical significance in unmanned coal mining. Laser-induced breakdown spectroscopy (LIBS) is considered a cutting-edge technology in the field of material analysis due to its real-time analysis capability, minimal to no sample preparation scheme, high sensitivity to low atomic weight elements, and ability to perform nearby and distant detection. In this research, a new fast and accurate coal-rock recognition method for unmanned coal mining based on LIBS is presented. The LIBS in situ sampling method of the coal mining face and the LIBS-based CRR method are discussed. Partial least squares discriminant analysis (PLS-DA) is used to analyze the LIBS spectrum and to construct a simplified spectral model (SSM). Finally, SSM and neural network classifiers are used to recognize coal and rock, and the results are presented and discussed. These results show that the CRR method proposed in this research has a high recognition accuracy rate.

Development of a High Energy Density, Long Cycle Life and Safety Enhanced Li-S Battery

Rechargeable lithium-sulfur (Li-S) batteries are widely considered the most promising “Beyond Li-ion” candidates, notably for their high theoretical energy density. The low and moderate atomic weight of Li and S, respectively, translates to a battery chemistry pairing that is lightweight. Since each S atom can ultimately host two lithium ions (Li+), compared with 0.5–0.7 Li+ per host atom in Li-ion batteries [1], the Li-S battery chemistry offers a much higher Li storage capacity potential. Assuming a complete redox couple reaction, S8 + 16Li+ + 16e- ↔ 8Li2S, the S cathode can have a high theoretical specific capacity of 1672 mAh/g with an average discharge voltage of ~2.1V (vs. Li/Li+), which leads to a theoretical specific energy of ~2500 Wh/kg based on the active material weight of a Li-S cell [2]. Other compelling attributes of Li-S batteries include high S natural abundance, low cost of S materials and safety characteristics owing to an intrinsic tolerance to overcharge [3]. In addition, the primary constituents of Li-S batteries are non-toxic and environmentally friendly [4].However, currently no commercial Li-S battery exists due to some significant technical challenges that have thus far prevented the realization of the tremendous energy density and performance potentials of Li-S batteries. These technical challenges include: low practical specific energy or energy density yield, significant capacity loss with cycling, high self-discharge rates, low Coulombic efficiency and safety concerns due to the use of Li metal anode [5].We will present our efforts in the development of a high energy density, long cycle life, safe and economically scalable Li-S battery technology via a holistic approach to nanoengineer/functionalize cell components including active components (i.e., S cathode, Li metal anode) and inactive components (e.g., separator, electrolyte), to address the Li-S battery cycle life degradation challenges and safety concerns. We will show that our comprehensive approaches afforded high discharge specific capacity, Coulombic efficiency (CE) and stable cycle life of the resultant Li-S cells (Figure 1).Our study demonstrates that the holistic approach of nanoengineering/functionalizing the active and inactive cell components represent a very promising strategy to develop a high energy density, long cycle life and safety enhanced Li-S battery technology. References Bullis, “Revisiting Lithium-Sulfur Batteries” MIT Review, May 22, 2009.Arumugam Manthiram, Yongzhu Fu, and Yu-Sheng Su, Acc. Chem. Res., 46 (5), pp 1125–1134 (2013)James R. Akridge, “Lithium Sulfur Rechargeable Battery Safety”, Battery Power Products & Technology, October 2001.Yongguang Zhang, Yan Zhao, Kyung Eun Sun and P. Chen, The Open Materials Science Journal, 5, 215-221 (2011).Monica Marinescu, Laura O’Neill, Teng Zhang, Sylwia Walus, Timothy E. Wilson, and Gregory J. Offer, J. Electrochem. Soc, 165 (1) A6107-A6118 (2018). Acknowledgement This material is based upon work supported by the C5ISR Center, Power and Integration Directorate (CP & I) under Contract No. W56KGU-18-C-0009. Figure 1

Changes in Halogen (F, Cl, Br, and I) and S Ratios in Rock-Forming Minerals as Monitors for Magmatic Differentiation, Volatile-Loss, and Hydrothermal Overprint: The Case for Peralkaline Systems

We determined the halogen (F, Cl, Br, and I) and sulfur (S) concentrations in Cl-rich rock-forming minerals from five peralkaline complexes. We investigated sodalite (N = 42), eudialyte-group minerals (N = 84), and tugtupite (N = 8) from representative rock samples derived from Ilímaussaq (South Greenland), Norra Kärr (Sweden), Tamazeght (Morocco), Lovozero, and Khibina (Russian Federation). Taken together, sodalite and eudialyte-group minerals dominate the Cl and Br budget of the investigated rocks. For F, however, several other phases (e.g., amphibole, fluorite, villiaumite, and minerals of the rinkite group and the apatite supergroup) are additional sinks, and parts of the S may be scavenged in generally rare sulfides. The investigated minerals contain Cl at the wt.% level, F and S concentrations are in the hundreds to thousands of µg/g-range, Br is less common (0.2–200 µg/g) and I is rare (mostly well below 1 µg/g). Normalized to Cl, sodalite prefers Br relative to eudialyte-group minerals, while F is always enriched in the latter. Our data show that both F and S may represent important components in eudialyte-group minerals, sometimes at similar levels as Cl, which normally dominates. Sulfur reveals redox-dependent behavior: Under reduced crystallization conditions, S is more compatible in eudialyte-group minerals (EGM) than in sodalite, which flips to the opposite under water-rich and presumably more oxidized conditions. We investigate the applicability of F/Cl, Br/Cl, and S/Cl ratios in these minerals in peralkaline systems to better understand the interplay of magmatic differentiation, fluid loss and hydrothermal overprint. Similar to apatite in metaluminous systems, fractionation of sodalite, and eudialyte-group minerals in peralkaline magmas leads to decreasing Br/Cl ratios. The data presented in this study bear implications for the mineral chemistry and compositional variation of sodalite and especially EGM in general. Volatile components in EGM that are not normally considered, such as F and S, can reach concentrations of thousands of µg/g. Especially in the case of F, with its low atomic weight, the results obtained in this study indicate that it is very significant for formulae calculations, neutral charge-balance, and similar aspects at such concentration levels. This study demonstrates that halogen contents and ratios are sensitive monitors for a variety of processes in magmatic-hydrothermal systems, including magmatic fractionation, volatile loss, and fluid–rock interaction.

Analysis of Contact Reaction Phenomenon between Aluminum–Silver and p+ Diffused Layer for n-Type c-Si Solar Cell Applications

In this study, the contact mechanism between Ag–Al and Si and the change in contact resistance (Rc) were analyzed by varying the firing profile. The front electrode of an n-type c-Si solar cell was formed through a screen-printing process using Ag–Al paste. Rc was measured by varying the belt speed and peak temperature of the fast-firing furnace. Rc value of 6.98 mΩ-cm−2 was obtained for an optimal fast-firing profile with 865 °C peak temperature and 110 inches per min belt speed. The contact phenomenon and the influence of impurities between the front-electrode–Si interface and firing conditions were analyzed through scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The EDS analysis revealed that the peak firing temperature at 865 °C exhibited a low atomic weight percentage of Al (0.72 and 0.36%) because Al was involved in the formation of alloy of Si with the front electrode. Based on the optimal results, a solar cell with a conversion efficiency of 19.46% was obtained.

Health care for deep space explorers.

There is a growing desire amongst space-faring nations to venture beyond the Van Allen radiation belts to a variety of intriguing locations in our inner solar system. Mars is the ultimate destinati...

Development of a High Energy Density, Long Cycle Life and Safety Enhanced Li-S Battery

Rechargeable lithium-sulfur (Li-S) batteries are widely considered the most promising “Beyond Li-ion” candidates, notably for their high theoretical energy density. The low and moderate atomic weight of Li and S, respectively, translates to a battery chemistry pairing that is lightweight. Since each S atom can ultimately host two lithium ions (Li+), compared with 0.5–0.7 Li+ per host atom in Li-ion batteries [1], the Li-S battery chemistry offers a much higher Li storage capacity potential. Assuming a complete redox couple reaction, S8 + 16Li+ + 16e- ↔ 8Li2S, the S cathode can have a high theoretical specific capacity of 1672 mAh/g with an average discharge voltage of ~2.1V (vs. Li/Li+), which leads to a theoretical specific energy of ~2500 Wh/kg based on the active material weight of a Li-S cell [2]. Other compelling attributes of Li-S batteries include high S natural abundance, low cost of S materials and safety characteristics owing to an intrinsic tolerance to overcharge [3]. In addition, the primary constituents of Li-S batteries are non-toxic and environmentally friendly [4].However, currently no commercial Li-S battery exists due to some significant technical challenges that have thus far prevented the realization of the tremendous energy density and performance potentials of Li-S batteries. These technical challenges include: low practical specific energy or energy density yield, significant capacity loss with cycling, high self-discharge rates, low Coulombic efficiency and safety concerns due to the use of Li metal anode [5].We will present our efforts in the development of a high energy density, long cycle life, safe and economically scalable Li-S battery technology via a holistic approach to nanoengineer/functionalize cell components including active components (i.e., S cathode, Li metal anode) and inactive components (e.g., separator, electrolyte), to address the Li-S battery cycle life degradation challenges and safety concerns. We will show that our comprehensive approaches afforded high discharge specific capacity, Coulombic efficiency (CE) and stable cycle life of the resultant Li-S cells (Figure 1).Our study demonstrates that the holistic approach of nanoengineering/functionalizing the active and inactive cell components represent a very promising strategy to develop a high energy density, long cycle life and safety enhanced Li-S battery technology.

Metrology of crystal defects through intensity variations in secondary electrons from the diffraction of primary electrons in a scanning electron microscope

Understanding defects and their roles in plastic deformation and device reliability is important for the development of a wide range of novel materials for the next generation of electronic and optoelectronic devices. We introduce the use of gaseous secondary electron detectors in a variable pressure scanning electron microscope for non-destructive imaging of extended defects using electron channelling contrast imaging. We demonstrate that all scattered electrons, including the secondary electrons, can provide diffraction contrast as long as the sample is positioned appropriately with respect to the incident electron beam. Extracting diffraction information through monitoring the modulation of the intensity of secondary electrons as a result of diffraction of the incident electron beam, opens up the possibility of performing low energy electron channelling contrast imaging to characterise low atomic weight and ultra-thin film materials. Our methodology can be adopted for large area, nanoscale structural characterisation of a wide range of crystalline materials including metals and semiconductors, and we illustrate this using the examples of aluminium nitride and gallium nitride. The capability of performing electron channelling contrast imaging, using the variable pressure mode, extends the application of this technique to insulators, which usually require conducting coatings on the sample surface for traditional scanning electron microscope based microstructural characterisation.

Fractionation of Rare Earth Elements in Surface Sediment of Peninsular Malaysia Coastal Waters

The environmental fate of rare earth elements (REEs) in the Malaysian environment is limitedly known; however, industrial emission is increasing. This study focused on the REE assessment of the surface sediments obtained from rocky shore ecosystems along the Peninsular Malaysia coastal waters, on deliberating interspatial variability, and on describing their partitioning. Samples were treated with the Teflon Bomb technique, and the concentration of 14 natural REEs was measured through inductively coupled plasma mass spectrometry (ICP-MS). Through quality control practices, the results were verified by employing a standard reference material BCR 667. The tendency of REE distribution was the most mutual property of particular places worldwide and in Malaysia. Among REEs present in sediment, strong correlations were observed, which indicated REEs they behave coherently to each other in different processes of geochemical fractionation. The contaminant metals, namely manganese, arsenic, cadmium and copper, were strongly correlated with REEs (p < 0.01 and p < 0.05); hence, these metals may be nonanthropogenic in origin because REEs are geogenic in origin. The enrichment factor (EF) values of the comparative results were divided by the region-specified deficiency to minimal enrichment in all the regions, except in the east coast region, which presented considerable enrichment, suggesting a probability of discharge of the anthropogenic effluent. The results of the analysis normalized to chondrite presented patterns of low atomic weight rare earth elements (LREEs) enrichment, gradual downward pattern and depletion through high atomic weight rare earth elements (HREEs) concentrations.

Experimental study on the electrokinetic migration process of Hangzhou sludge

The migration of cations, which leads to the transportation of water molecules, is the essential driving force of electrokinetic dewatering. Several bench-scale experiments on Hangzhou sludge were performed using ferrum, graphite, copper, and aluminum electrodes. The element contents of Na, K, Mg, Ca, Fe, Al, and Cu in the effluent water as well as in the treated soil were measured to investigate the migration process of the corresponding cations. The electrokinetic drainage was noted to have a higher total content of the considered elements compared to that in gravity drainage, which demonstrated that electrokinetic treatment is effective for bound water. In the electrokinetic drainage, the contents of Na and K were much higher than those of other elements. Furthermore, the steady contents of Na and K in the electrokinetic drainage demonstrated the consistent electrokinetic mobility of Na and K ions. Ca and Mg ions tended to precipitate in the cathodic area. Most of the Fe ions generated from the reaction at the anode remained in the anodic area. The extremely low Cu content in the drainage and soil meant that no variations could be observed. Different cations were noted to have different electrokinetic mobilities. Higher electrokinetic mobilities were observed for cations having lower valency or smaller atomic weights. The order of ion electrokinetic mobility was noted to be Na+ > K+ > Mg2+ > Ca2+ > Al3+ > Cu2+ > Fe2+/Fe3+. Therefore, electrokinetic dewatering depends primarily on the presence of cations having a low valency or small atomic weight such as Na, K, Ca, Mg, and Al ions. Fe and Cu ions have low electrokinetic mobility and do not contribute considerably to the transportation of water molecules. The study provided guidance in the application evaluation of the electrokinetic technique in drying various soils.

Nanoengineered Separators for a High Energy Density, Long Cycle Life Li-S Battery

Rechargeable lithium-sulfur (Li-S) batteries are widely considered the most promising “Beyond Li-ion” candidates, notably for their high theoretical energy density. The low and moderate atomic weight of Li and S, respectively, translates to a battery chemistry pairing that is lightweight. Since each S atom can ultimately host two lithium ions (Li+), compared with 0.5–0.7 Li+ per host atom in Li-ion batteries [1], the Li-S battery chemistry offers a much higher Li storage capacity potential. Assuming a complete redox couple reaction, S8 + 16Li+ + 16e- ↔ 8Li2S, the S cathode can have a high theoretical specific capacity of 1672 mAh/g with an average discharge voltage of ~2.1V (vs. Li/Li+), which leads to a theoretical specific energy of ~2500 Wh/kg based on the active material weight of a Li-S cell [2]. Other compelling attributes of Li-S batteries include high S natural abundance, low cost of S materials and safety characteristics owing to an intrinsic tolerance to overcharge [3]. In addition, the primary constituents of Li-S batteries are non-toxic and environmentally friendly [4]. However, currently no commercial Li-S battery exists due to some significant technical challenges that have thus far prevented the realization of the tremendous energy density and performance potentials of Li-S batteries. These technical challenges include: low practical specific energy or energy density yield, significant capacity loss with cycling, high self-discharge rates, low Coulombic efficiency and safety concerns due to the use of Li metal anode [5]. We will present our efforts in the development of a high energy density and long cycle life Li-S battery technology via nanoengineered battery separators. We will show that our atomic and/or molecular level, functional material coated separators exhibit much improved physical properties including tensile strength, thermal shrinkage, and electrolyte wettability (Figure 1). When used in Li-S cells, the nanoengineered separators (coated) afforded a significant increase in specific capacity compared with the control (uncoated) separator, as illustrated in Figure 2. The enhanced Li-S cell performance suggests polysulfide blockage from the nanoscale functional material coated separators used in the resultant Li-S cells. Our study demonstrates that the nanoengineered separator approach represents a very promising strategy to develop a high energy density, long cycle life, safe and economically scalable Li-S battery technology. References Bullis, “Revisiting Lithium-Sulfur Batteries” MIT Review, May 22, 2009.Arumugam Manthiram, Yongzhu Fu, and Yu-Sheng Su, Acc. Chem. Res., 46 (5), pp 1125–1134 (2013)James R. Akridge, “Lithium Sulfur Rechargeable Battery Safety”, Battery Power Products & Technology, October 2001.Yongguang Zhang, Yan Zhao, Kyung Eun Sun and P. Chen, The Open Materials Science Journal, 5, 215-221 (2011).Monica Marinescu, Laura O’Neill, Teng Zhang, Sylwia Walus, Timothy E. Wilson, and Gregory J. Offer, J. Electrochem. Soc, 165 (1) A6107-A6118 (2018). Figure 1

Metallomimetic Chemistry of Boron.

The study of main-group molecules that behave and react similarly to transition-metal (TM) complexes has attracted significant interest in recent decades. Most notably, the attractive idea of replacing the all-too-often rare and costly metals from catalysis has motivated efforts to develop main-group-element-mediated reactions. Main-group elements, however, lack the electronic flexibility of TM complexes that arises from combinations of empty and filled d orbitals and that seem ideally suited to bind and activate many substrates. In this review, we look at boron, an element that despite its nonmetal nature, low atomic weight, and relative redox staticity has achieved great milestones in terms of TM-like reactivity. We show how in interelement cooperative systems, diboron molecules, and hypovalent complexes the fifth element can acquire a truly metallomimetic character. As we discuss, this character is powerfully demonstrated by the reactivity of boron-based molecules with H2, CO, alkynes, alkenes and even with N2.

Working toward fluoride batteries

Batteries Owing to the low atomic weight of fluorine, rechargeable fluoride-based batteries could offer very high energy density. However, current batteries need to operate at high temperatures that are required for the molten salt electrolytes. Davis et al. push toward batteries that can operate at room temperature, through two advances. One is the development of a room-temperature liquid electrolyte based on a stable tetraalkylammonium salt–fluorinated ether combination. The second is a copper–lanthanum trifluoride core-shell cathode material that demonstrates reversible partial fluorination and defluorination reactions. Science , this issue p. [1144][1] [1]: /lookup/doi/10.1126/science.aat7070

Room-temperature cycling of metal fluoride electrodes: Liquid electrolytes for high-energy fluoride ion cells

Fluoride ion batteries are potential "next-generation" electrochemical storage devices that offer high energy density. At present, such batteries are limited to operation at high temperatures because suitable fluoride ion-conducting electrolytes are known only in the solid state. We report a liquid fluoride ion-conducting electrolyte with high ionic conductivity, wide operating voltage, and robust chemical stability based on dry tetraalkylammonium fluoride salts in ether solvents. Pairing this liquid electrolyte with a copper-lanthanum trifluoride (Cu@LaF3) core-shell cathode, we demonstrate reversible fluorination and defluorination reactions in a fluoride ion electrochemical cell cycled at room temperature. Fluoride ion-mediated electrochemistry offers a pathway toward developing capacities beyond that of lithium ion technology.

A Holistic Approach in the Development of a High Energy Density, Long Cycle Life and Safe Li-S Battery

Rechargeable lithium-sulfur (Li-S) batteries are widely considered the most promising “Beyond Li-ion” candidates, notably for their high theoretical energy density. The low and moderate atomic weight of Li and S, respectively, translates to a battery chemistry pairing that is lightweight. Since each S atom can ultimately host two lithium ions (Li+), compared with 0.5–0.7 Li+ per host atom in Li-ion batteries [1], the Li-S battery chemistry offers a much higher Li storage capacity potential. Assuming a complete redox couple reaction, S8 + 16Li+ + 16e- ↔ 8Li2S, the S cathode can have a high theoretical specific capacity of 1672 mAh/g with an average discharge voltage of ~2.1V (vs. Li/Li+), which leads to a theoretical specific energy of ~2500 Wh/kg based on the active material weight of a Li-S cell [2]. Other compelling attributes of Li-S batteries include high S natural abundance, low cost of S materials and safety characteristics owing to an intrinsic tolerance to overcharge [3]. In addition, the primary constituents of Li-S batteries are non-toxic and environmentally friendly [4]. However, currently no commercial Li-S battery exists due to some significant technical challenges that have thus far prevented the realization of the tremendous energy density and performance potentials of Li-S batteries. These technical challenges include: low practical specific energy or energy density yield, significant capacity loss with cycling, high self-discharge rates, low Coulombic efficiency and safety concerns due to the use of Li metal anode [5]. We will present our efforts in the development of a high energy density, long cycle life, safe and economically scalable Li-S battery technology via a holistic approach to nanoengineer/functionalize cell components including active components (i.e., S cathode, Li metal anode) and inactive components (e.g., separator, electrolyte), to address the Li-S battery cycle life degradation challenges and safety concerns. We will show that our comprehensive approaches render much improved discharge specific capacity/energy, Coulombic efficiency and cycle life of the resultant Li-S cells. Our experimental evidence suggests (i) much reduced polysulfide dissolution and (ii) much improved safety characteristics of the cycled Li-S cells constructed from the nanoengineered/functionalized cell components. Our study demonstrates that the holistic approach of nanoengineering/functionalizing the active and inactive cell components represent a very promising strategy to develop a high energy density, long cycle life, safe and economically scalable Li-S battery technology. References Bullis, “Revisiting Lithium-Sulfur Batteries” MIT Review, May 22, 2009.Arumugam Manthiram, Yongzhu Fu, and Yu-Sheng Su, Acc. Chem. Res., 46 (5), pp 1125–1134 (2013)James R. Akridge, “Lithium Sulfur Rechargeable Battery Safety”, Battery Power Products & Technology, October 2001.Yongguang Zhang, Yan Zhao, Kyung Eun Sun and P. Chen, The Open Materials Science Journal, 5, 215-221 (2011).Monica Marinescu, Laura O’Neill, Teng Zhang, Sylwia Walus, Timothy E. Wilson, and Gregory J. Offer, J. Electrochem. Soc, 165 (1) A6107-A6118 (2018).

Defects analysis on the strengthening of solid solution Nb additions in Mo3Si alloys

Molybdenum silicides alloys with different Nb additions were produced by the arc-melting technique ranging from 0 to 20 Nb at.%. Physical characterization has been performed for each one of the alloys. Experimental and calculated density shown a decreasing value when Nb additions increment up to 20 Nb at.%, showing the effect produced by the atoms additions with lower atomic weight. Vacancy concentration indicates that point defect do not strongly affect the alloy performance. Mechanical evaluation shown positive strengthening, which is attributed to the lattice distortion, increasing with Nb content. TEM analysis supports such assumption by the observation of dislocations network. Results in this work are interpreted in terms of substitutional process.