In the present work, a new class of high entropy materials for energy storage applications is introduced. Multi-anionic and -cationic compounds are prepared by facile mechanochemistry using a ...recently designed multi-cationic transition-metal-based high entropy oxide as the precursor and LiF or NaCl as the reactant, leading to formation of lithiated or sodiated materials. Notably, the Li-containing entropy-stabilized oxyfluoride described herein (Li
x
(Co
0.2
Cu
0.2
Mg
0.2
Ni
0.2
Zn
0.2
)OF
x
) exhibits a working potential of 3.4 V
vs.
Li
+
/Li, enabling its use as a cathode active material. Unlike conventional (non-entropy-stabilized) oxyfluorides, this new material shows enhanced Li storage properties due to entropy stabilization, which, in general, facilitates tailoring the cycling performance by varying the constituent elements in yet unprecedented ways. In addition, we demonstrate that the concept of entropy stabilization is also applicable to Na-containing oxychlorides with a rock-salt structure, thus paving the way toward development of (next-generation) post-Li battery technologies.
For the first time, a multi-anionic and multi-cationic high entropy oxyhalide is presented as high capacity cathode for Li-ion batteries.
Surface coating is a viable strategy for improving the cyclability of Li1+x (Ni1–y–z Co y Mn z )1–x O2 (NCM) cathode active materials for lithium-ion battery cells. However, both gaining synthetic ...control over thickness and accurate characterization of the surface shell, which is typically only a few nm thick, are considerably challenging. Here, we report on a new molecular surface modification route for NCM622 (60% Ni) using organophosphates, specifically tris(4-nitrophenyl) phosphate (TNPP) and tris(trimethylsilyl) phosphate. The functionalized NCM622 was thoroughly characterized by state-of-the-art surface and bulk techniques, such as attenuated total reflection infrared spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry (ToF-SIMS), to name a few. The comprehensive ToF-SIMS-based study comprised surface imaging, depth profiling, and three-dimensional visualization. In particular, tomography is a powerful tool to analyze the nature and morphology of thin coatings and is applied, to our knowledge, for the first time, to a practical cathode active material. It provides valuable information about relatively large areas (over several secondary particles) at high lateral and mass resolution. The electrochemical performance of the different NCM622 materials was evaluated in long-term cycling experiments of full-cells with a graphite anode. The effect of surface modification on the transition-metal leaching was studied ex situ via inductively coupled plasma optical emission spectroscopy. TNPP@NCM622 showed reduced transition-metal dissolution and much improved cycling performance. Taken together, with this study, we contribute to optimization of an industrially relevant cathode active material for application in high-energy-density lithium-ion batteries.
Layered Delafossite-type Li
(M
M
M
M
M
…M
)O
materials, a new class of high-entropy oxides, were synthesized by nebulized spray pyrolysis and subsequent high-temperature annealing. Various metal ...species (M = Ni, Co, Mn, Al, Fe, Zn, Cr, Ti, Zr, Cu) could be incorporated into this structure type, and in most cases, single-phase oxides were obtained. Delafossite structures are well known and the related materials are used in different fields of application, especially in electrochemical energy storage (e.g., LiNi
Co
Mn
O
NCM). The transfer of the high-entropy concept to this type of materials and the successful structural replication enabled the preparation of novel compounds with unprecedented properties. Here, we report on the characterization of a series of Delafossite-type high-entropy oxides by means of TEM, SEM, XPS, ICP-OES, Mössbauer spectroscopy, XRD including Rietveld refinement analysis, SAED and STEM mapping and discuss about the role of entropy stabilization. Our experimental data indicate the formation of uniform solid-solution structures with some Li/M mixing.
The nanoparticulate inorganic photosensitizer β-SnWO4 is suggested for photodynamic therapy (PDT) of near-surface tumors via reiterated 5 min blue-light LED illumination. β-SnWO4 nanoparticles are ...obtained via water-based synthesis and comprise excellent colloidal stability under physiological conditions and high biocompatibility at low material complexity. Antitumor and antimetastatic effects were investigated with a spontaneously metastasizing (4T1 cells) orthotopic breast cancer BALB/c mouse model. Besides protamine-functionalized β-SnWO4 (23 mg/kg of body weight, in PBS buffer), chemotherapeutic doxorubicin was used as positive control (2.5 mg/kg of body weight, in PBS buffer) and physiological saline (DPBS) as a negative control. After 21 days, treatment with β-SnWO4 resulted in a clearly inhibited growth of the primary tumor (all tumor volumes below 3 cm3) as compared to the doxorubicin and DPBS control groups (volumes up to 6 cm3). Histological evaluations of lymph nodes and lungs as well as the volume of ipsilateral lymph nodes show a remarkable antimetastatic effect being similar to chemotherapeutic doxorubicin butaccording to blood countsat significantly reduced side effects. On the basis of low material complexity, high cytotoxicity under blue-light LED illumination at low dark and long-term toxicity, β-SnWO4 can be an interesting addition to PDT and the treatment of near-surface tumors, including skin cancer, esophageal/gastric/colon tumors as well as certain types of breast cancer.
The cycling performance and in operando gas analysis of LiNi0.5Mn1.5O4 (LNMO)/graphite cells with reasonably high loading, containing a “standard” carbonate-based electrolyte is reported. The gas ...evolution over the first couple of cycles was thoroughly investigated via differential electrochemical mass spectrometry (DEMS), neutron imaging and pressure measurements. The main oxidation and reduction products were identified as CO2, H2 and C2H4. In different sets of experiments graphite was substituted with delithiated LiFePO4 (LFP) and LNMO with LFP to distinguish between processes occurring at either anode or cathode and gain mechanistic insights. Both C2H4 and H2 were found to be mainly formed at the anode side, while CO2 is generated at the cathode. The results from DEMS analysis further suggest that the Ni redox couples play a profound role in the evolution of CO2 at the LNMO/electrolyte interface. Lastly, it is shown that the cycling stability and capacity retention of LNMO/graphite cells can be considerably improved by a simple cell formation procedure.
Nebulized spray pyrolysis followed by consolidation and sintering was used for the first time to prepare Al-doped garnet-based Li7−3xLa3Zr2AlxO12 (x=0–0.25) (LLZO) ultra-fine grained ceramics. The ...structural changes from the tetragonal (x=0), via a mixture of the cubic and the tetragonal (x=0.07, 0.10) to the cubic modification (x=0.15–0.25) were observed. 27Al NMR study showed that aluminum occupy the tetrahedral 24d lithium sites. Despite their low relative density (47–56%), preliminary ionic conductivities of the LLZO ceramics, were found to be 1.2·10−6Scm−1 and 4.4·10−6Scm−1 for tetragonal and cubic LLZO at room temperature, with activation energies of 0.55eV and 0.49eV, respectively.
•New synthesis method for solid electrolyte preparation is reported.•Nanocrystalline powders free of organics are synthesized.•Ultra-fine grained ceramics is prepared.•Crystal structure and microstructure is studied.•Room temperature lithium-ion conduction is measured.
Using a simple bifunctional bridging linker, nanosized gold and titanium dioxide composites are prepared containing different Au loadings. Linker is synthesized to contain both catechol and thiol ...moieties to enable binding to the TiO2 and Au surface respectively. Au/TiO2 nanocomposites are prepared using simple synthetic route that allows the control over the amount of Au nanoparticles, a property which plays a significant role in the catalytic activity of hybrid materials. Photocatalytic activity of materials prepared using different TiO2 precursors is investigated using reactive oxygen species sensitive assay based on activation of horseradish peroxidase (HRP) enzyme. Significant increase in catalytic activity is observed for all Au/TiO2 nanocomposites with Au/TiO2 prepared by use of the bridging linker being up to 5.5 times more active than bare commercial TiO2 nanoparticles. In addition to 365 nm light excitation, less energetic 470 nm light, which is more suitable for the use with biological systems, is used to induce photocatalytic activity. Finally, prepared photocatalytic materials are successfully used to exert temporal control over enzymatic activity, a feature which is important for the study of both enzymatic activity and design of novel bio‐sensing platforms.
Hybrid photo‐switch: Enhanced photocatalytic activity of TiO2/Au hybrid nanocomposite is observed, enabling photo‐switchable activation of peroxidase enzyme. A nanocomposite is prepared using bifunctional bridging linker containing both TiO2 and Au NP binding groups affording precise control over the size and shape of Au NPs and their ratio to TiO2.
Metal-assisted chemical etching (MACE) is done with different metal species. The resulting silicon nanostructures appear strongly dependent on the choice of metal, but a deeper understanding of the ...MACE process is still missing. We report here direct evidence that the etching solution composition plays a major role in the chemical stability of the metal catalyst used. We show from an elemental analysis of post-MACE etch baths that dissolved silver is found in the bath with concentrations up to 3 orders of magnitude larger than when gold is used. Furthermore, the dissolved silver content also correlates with the amount of H2O2, either in different initial conditions, or as would be expected from its decomposition over time. We also show that silver dissolution leads to unintended etching elsewhere on the substrate. This species-dependent behavior of the metal catalyst is responsible for the different kinds of control possible over the nanostructures produced with silver- and gold-based MACE.
The interest in ceramic dental implants made of yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) or alumina toughened zirconia (ATZ) has increased in recent years. However, in the light of ...aging, corrosion, and potential impurities of zirconia ceramics, the material composition of these implants and the associated term “metal-free” is persistently questioned. Thus, the present study aimed to conduct an elemental analysis of commercial zirconia dental implants to specify their elemental composition and to identify contaminants.
Nine commercial zirconia dental implant systems and corresponding material samples were analyzed using inductively coupled plasma-mass spectrometry (ICP-MS) and optical emission spectrometry (ICP-OES).
While the elemental composition was dominated by the main components Zr, Y and Al (in ATZ samples), all investigated samples contained impurities with Hf and contamination with alkali and alkali earth elements (Na, K, Mg, Ca), essential trace elements (e.g. Fe, Cu, Zn) but also potentially noxious metal elements (e.g. Ni, Cr). Furthermore, ultra-trace level contamination with the radionuclides U-238 and Th-232 was found in the majority of samples.
The results indicate that, although all the investigated Y-TZP and ATZ dental implants meet the currently relevant ISO standards and manufacturer's specifications, from an elemental point of view, they are not devoid of metals. Due to the lack of a universal definition and thresholds for the term “metal-free”, the question of whether the examined zirconia dental implants can be holistically classified as “metal-free” or not remains a controversial, philosophical one.
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•ICP-/OES-MS elemental analysis of commercial zirconia dental implants.•The investigated implants contained impurities with different heavy metal elements.•Ultra-trace level contamination with U-238 and Th-232 in the majority of samples.•From an elemental point of view, the investigated implants are not “metal-free”.
According to the recently proposed changes of the HCPB design concept of tritium breeding blanket for the DEMO fusion reactor, massive Be12Ti blocks are considered to be used for neutron ...multiplication. The paper compares two possible fabrication routes of solid beryllide blocks: combination of hot extrusion with arc melting or with hot isostatic pressing (HIP). Be–Ti composite rods produced by powder extrusion were chosen as a starting material. After arc melting, the ingot had cellular microstructure revealing mixture of Be12Ti and Be10Ti phases with considerable porosity. The powder metallurgy route, including extrusion and HIP, allows to achieve 98.6% of theoretical density and fine-grained Be12Ti microstructure with small amount of residual Be phase. EBSD analysis together with TEM showed that titanium beryllide has a grain size of 0.3–2.5 μm. It was observed that fine BeO particles are distributed along the grain boundaries and can pin them. Titanium beryllide after HIP has high microhardness of 1420 HV and fracture toughness of about 2.4 MPa m1/2 comparable with that of many ceramics. The advantages of Be12Ti blocks manufacturing using extrusion and HIP are discussed.
•Be12Ti was synthesized via melting or powder metallurgy route.•Even after processing at 1100 °C, the microstructure has fine grains of 0.3–2.5 μm.•BeO particles pin Be12Ti grain boundaries.•Microhardness of Be12Ti reaches 1420 HV.
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