The troubadour Marcabru and his public

Vanadium(V)-containing oxides show superior intercalation properties for alkaline ions, although the performance of the material strongly depends on its surface morphology. In this work, intercalation activity of LiV$_{3}$O$_{8}$, prepared by a conventional solid state synthesis, is demonstrated for the first time in non-aqueous Li,Na-ion hybrid batteries with Na as negative electrode, and different Na/Li ratios in the electrolyte. In the pure Na-ion cell, one Na per formula unit of LiV$_{3}$O$_{8}$ can be reversibly inserted at room temperature via a two-step process, while further intercalation leads to gradual amorphisation of the material, with a specific capacity of 190 mAhg$^{−1}$ after 10 cycles in the potential window of 0.8–3.4 V. Hybrid Li,Na-ion batteries feature simultaneous intercalation of Li$^+$ and Na$^+$ cations into LiV$_{3}$O$_{8}$, resulting in the formation of a second phase. Depending on the electrolyte composition, this second phase bears structural similarities either to Li$_{0.7}$Na$_{0.7}$V$_{3}$O$_{8}$ in Na-rich electrolytes, or to LiV$_{3}$O$_{8}$ in Li-rich electrolytes. The chemical diffusion coefficients of Na+ and Li+ in crystalline LiV$_{3}$O$_{8}$ are very close, hence explaining the co-intercalation of these cations. As DFT calculations show, once formed, the Li$_{0.7}$Na$_{0.7}$V$_{3}$O$_{8}$-type structure favors intercalation of Na$^+$, whereas the LiV$_{3}$O$_{8}$-type prefers to accommodate Li$^+$ cations

In situ Raman spectroscopy on silicon nanowire anodes integrated in lithium ion batteries

Rapid decay of silicon anodes during lithiation poses a significant challenge in application of silicon as an anode material in lithium ion batteries. In situ Raman spectroscopy is a powerful method to study the relationship between structural and electrochemical data during electrode cycling and to allow the observation of amorphous as well as liquid and transient species in a battery cell. Herein, we present in situ Raman spectroscopy on high capacity electrode using uncoated and carbon-coated silicon nanowires during first lithiation and delithiation cycle in an optimized lithium ion battery setup and complement the results with operando X-ray reflection diffraction measurements. During lithiation, we were able to detect a new Raman signal at 1859 cm−1 especially on uncoated silicon nanowires. The detailed in situ Raman measurement of the first lithiation/delithiation cycle allowed to differentiate between morphology changes of the electrode as well as interphase formation from electrolyte components

An efficient two-polymer binder for high-performance silicon nanoparticle-based lithium-ion batteries: A systematic case study with commercial polyacrylic acid and polyvinyl butyral polymers

Silicon is one of the most promising anode materials for high energy density lithium ion batteries (LIBs) due to its high theoretical capacity and natural abundance. Unfortunately, significant challenges arise due to the large volume change of silicon upon lithiation/delithiation which inhibit its broad commercialization. An advanced binder can, in principle, reversibly buffer the volume change, and maintain strong adhesion toward various components as well as the current collector. In this work, we present the first report on the applicability of polyvinyl butyral (PVB) polymer as a binder component for silicon nanoparticles-based LIBs. Characteristic binder properties of commercial PVB and polyacrylic acid (PAA) polymers are compared. The work focuses on polymer mixtures of PVB polymers with PAA, for an improved binder composition which incorporates their individual advantages. Different ratios of polymers are systematically studied to understand the effect of particular polymer chains, functional groups and mass fractions, on the electrochemical performance. We demonstrate a high-performance polymer mixture which exhibits good binder-particle interaction and strong adhesion to Cu-foil. PAA/PVB-based electrode with a Si loading of ∼1 mg/cm2 tested between 0.01 and 1.2 V vs. Li/Li+ demonstrate specific capacities as high as 2170 mAh/g after the first hundred cycles. © The Author(s) 2019

Fully sp²‐carbon‐linked crystalline two‐dimensional conjugated polymers: insight into 2D poly(phenylenecyanovinylene) formation and their optoelectronic properties

Cyano‐substituted polyphenylene vinylenes (PPVs) have been in the focus of research for several decades due to their interesting optoelectronic properties and potential applications in organic electronics. With the advent of organic two‐dimensional (2D) crystals, the question arose how the chemical and optoelectronic advantages of PPVs evolve in 2D compared to their linear counterparts. In this work, we present the efficent synthesis of two novel 2D fully sp²‐carbon‐linked crystalline PPVs and investigate the essentiality of inorganic bases for their catalytic formation. Notably, among all bases screened, cesium carbonate (Cs₂CO₃) plays a crucial role and enables reversibility in the first step with subsequent structure locking by formation of a C=C double bond to maintain crystallinity, which is supported by density functional theory (DFT) calculation. We propose a quantifiable energy diagram of a “quasi‐reversible reaction” which allows to identify further suitable C‐C bond formation reactions for 2D polymerizations. Moreover, we delineate the narrowing of the HOMO‐LUMO gap by expanding conjugation into two dimensions. To enable environmentally benign processing, we further perform the post‐modification of 2D PPVs, which renders stable dispersions in the aqueous phase

Structural Aspects of P2-Type Na0.67Mn0.6Ni0.2Li0.2O2 (MNL) Stabilization by Lithium Defects as a Cathode Material for Sodium-Ion Batteries

A known strategy for improving the properties of layered oxide electrodes in sodium-ion batteries is the partial substitution of transition metals by Li. Herein, the role of Li as a defect and its impact on sodium storage in P2-Na0.67Mn0.6Ni0.2Li0.2O2 is discussed. In tandem with electrochemical studies, the electronic and atomic structure are studied using solid-state NMR, operando XRD, and density functional theory (DFT). For the as-synthesized material, Li is located in comparable amounts within the sodium and the transition metal oxide (TMO) layers. Desodiation leads to a redistribution of Li ions within the crystal lattice. During charging, Li ions from the Na layer first migrate to the TMO layer before reversing their course at low Na contents. There is little change in the lattice parameters during charging/discharging, indicating stabilization of the P2 structure. This leads to a solid-solution type storage mechanism (sloping voltage profile) and hence excellent cycle life with a capacity of 110 mAh g-1 after 100 cycles. In contrast, the Li-free compositions Na0.67Mn0.6Ni0.4O2 and Na0.67Mn0.8Ni0.2O2 show phase transitions and a stair-case voltage profile. The capacity is found to originate from mainly Ni3+/Ni4+ and O2-/O2-δ redox processes by DFT, although a small contribution from Mn4+/Mn5+ to the capacity cannot be excluded. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH Gmb

Standardized treatment planning methodology for passively scattered proton craniospinal irradiation

Background: As the number of proton therapy centers increases, so does the need for studies which compare proton treatments between institutions and with photon therapy. However, results of such studies are highly dependent on target volume definition and treatment planning techniques. Thus, standardized methods of treatment planning are needed, particularly for proton treatment planning, in which special consideration is paid to the depth and sharp distal fall-off of the proton distribution. This study presents and evaluates a standardized method of proton treatment planning for craniospinal irradiation (CSI).Methods: We applied our institution\u27s planning methodology for proton CSI, at the time of the study, to an anatomically diverse population of 18 pediatric patients. We evaluated our dosimetric results for the population as a whole and for the two subgroups having two different age-specific target volumes using the minimum, maximum, and mean dose values in 10 organs (i.e., the spinal cord, brain, eyes, lenses, esophagus, lungs, kidneys, thyroid, heart, and liver). We also report isodose distributions and dose-volume histograms (DVH) for 2 representative patients. Additionally we report population-averaged DVHs for various organs.Results: The planning methodology here describes various techniques used to achieve normal tissue sparing. In particular, we found pronounced dose reductions in three radiosensitive organs (i.e., eyes, esophagus, and thyroid) which were identified for optimization. Mean doses to the thyroid, eyes, and esophagus were 0.2%, 69% and 0.2%, respectively, of the prescribed dose. In four organs not specifically identified for optimization (i.e., lungs, liver, kidneys, and heart) we found that organs lateral to the treatment field (lungs and kidneys) received relatively low mean doses (less than 8% of the prescribed dose), whereas the heart and liver, organs distal to the treatment field, received less than 1% of the prescribed dose.Conclusions: This study described and evaluated a standardized method for proton treatment planning for CSI. Overall, the standardized planning methodology yielded consistently high quality treatment plans and perhaps most importantly, it did so for an anatomically diverse patient population. © 2013 Giebeler et al.; licensee BioMed Central Ltd

Investigation of β-carotene–gelatin composite particles with a multiwavelength UV/vis detector for the analytical ultracentrifuge

A multiwavelength UV/vis detector for the analytical ultracentrifuge (MWL-AUC) has been developed recently. In this work, β-carotene–gelatin composite particles are investigated with MWL-AUC. Band centrifugation with a Vinograd cell is used to ensure maximum sample separation. Spectral changes of the system are observed in dependence of the sedimentation coefficient and are attributed to a previously unknown inhomogeneity of the β-carotene chemical composition with both H- and J-aggregates coexisting in a mixture. In addition, our data suggest that pure H- and J-aggregates exist in a particle while their relative concentrations in a mixture determine the color characteristics of the sample. The unique abilities and properties of MWL-AUC include sedimentation coefficient distributions for all possible wavelengths, full UV/vis spectra of each different species in the mixture and 3D movies of the sedimentation process. These properties significantly extend the scope of the analytical ultracentrifuge technique and show that complex biopolymer multicomponent mixtures can be resolved into their individual species

The impact of surface morphology on the magnetovolume transition in magnetocaloric LaFe_11.8Si_1.2

First order magnetocaloric materials reach high entropy changes but at the same time exhibit hysteresis losses which depend on the sample’s microstructure. We use non-destructive 3D X-ray microtomography to understand the role of surface morphology for the magnetovolume transition of LaFe11.8Si1.2. The technique provides unique information on the spatial distribution of the volume change at the transition and its relationship with the surface morphology. Complementary Hall probe imaging confirms that on a morphologically complex surface minimization of strain energy dominates. Our findings sketch the way for a tailored surface morphology with low hysteresis without changing the underlying phase transition

Amphiphiles with polyethyleneoxide-polyethylenecarbonate chains for hydrophilic coating of iron oxide cores, loading by Gd(III) ions and tuning R2/R1 ratio

© 2015 Elsevier B.V. The present work is aimed at the synthesis of hydrophilic colloids with convenient transverse and longitudinal NMR-relaxation times. Core-shell morphology with iron oxide cores and hydrophilic shell enriched by Gd(III) ions is the basis for the colloids with dual-mode relaxivities. Polyethyleneoxide-polyethylenecarbonate derivatives of p-tert-butylphenols are introduced as amphiphiles for efficient hydrophilization of oleate-stabilized iron oxide nanoparticles. The obtained results reveal the easy variation of the synthetic conditions as the route to switch from the recoating to the dissolution of the oleate-stabilized iron-oxide nanoparticles. The length of ethylenecarbonate chains is highlighted as the factor affecting the transverse relaxivity (R2) and the colloid properties of the synthesized colloids, evaluated from DLS data. The complex ability of ethylenecarbonate chains is the reason for loading of the synthesized colloids by Gd(III) ions in aqueous dispersions at specific conditions. These conditions are introduced herein as a route of gaining in longitudinal relaxivity (R1) and tuning R2/R1 ratio

Performance of a fast fiber based UV/Vis multiwavelength detector for the analytical ultracentrifuge

The optical setup and the performance of a prototype UV/Vis multiwavelength analytical ultracentrifuge (MWL-AUC) is described and compared to the commercially available Optima XL-A from Beckman Coulter. Slight modifications have been made to the optical path of the MWL-AUC. With respect to wavelength accuracy and radial resolution, the new MWL-AUC is found to be comparable to the existing XL-A. Absorbance accuracy is dependent on the light intensity available at the detection wavelength as well as the intrinsic noise of the data. Measurements from single flashes of light are more noisy for the MWL-AUC, potentially due to the absence of flash-to-flash normalization in the current design. However, the possibility of both wavelength and scan averaging can compensate for this and still give much faster scan rates than the XL-A. Some further improvements of the existing design are suggested based on these findings