scholarly journals Short-range Li diffusion vs. long-range ionic conduction in nanocrystalline lithium peroxide Li2O2—the discharge product in lithium-air batteries

2014 ◽  
Vol 7 (8) ◽  
pp. 2739-2752 ◽  
Author(s):  
A. Dunst ◽  
V. Epp ◽  
I. Hanzu ◽  
S. A. Freunberger ◽  
M. Wilkening
Keyword(s):  
Short Range ◽  
Ionic Conduction ◽  
High Energy ◽  
Ion Dynamics ◽  
Nmr Relaxometry ◽  
Lithium Peroxide ◽  
Discharge Product ◽  
Energy Ball ◽  
Spin Locking ◽  
Lithium Air Batteries

Conductivity spectroscopy and 7Li spin-locking NMR relaxometry reveal enhanced ion dynamics in nanocrystalline Li2O2 prepared by high-energy ball milling.

Diffusion and Ionic Conduction in Nanocrystalline Ceramics

2001 ◽  
Vol 676 ◽  
Author(s):  
Paul Heitjans ◽  
Sylvio Indris
Keyword(s):  
Impedance Spectroscopy ◽  
Ball Milling ◽  
Ionic Conduction ◽  
Nmr Relaxation ◽  
High Energy ◽  
High Energy Ball Milling ◽  
Nanocrystalline Ceramics ◽  
Energy Ball ◽  
Li Ion ◽  
Mobile Ions

ABSTRACTDiffusion and ionic conduction in nanocrystalline ceramics, both monophase and composite, was studied by NMR relaxation and NMR lineshape as well as impedance spectroscopy. Measurements were mainly done on Li ion conductors prepared by high-energy ball milling. It was possible to discriminate between mobile ions in the interfacial regions and immobile ions in the grains. In general the diffusivity and conductivity are enhanced in the nanocrystalline monophase system as compared to the microcrystalline one, e. g. by about four orders of magnitude in the case of CaF2. An exception is, e. g., Li2O where the nano- and microcrystalline forms have similar conductivities. However, when the nanocrystalline insulator B2O3 is added to nanocrystalline Li2O the conductivity of the composite increases whereas it decreases in the corresponding microcrystalline system.

scholarly journals Structure and ion dynamics of mechanosynthesized oxides and fluorides

2017 ◽  
Vol 232 (1-3) ◽  
Author(s):  
Martin Wilkening ◽  
Andre Düvel ◽  
Florian Preishuber-Pflügl ◽  
Klebson da Silva ◽  
Stefan Breuer ◽  
...  
Keyword(s):  
Ion Transport ◽  
Short Review ◽  
High Energy ◽  
Ion Dynamics ◽  
Ball Mills ◽  
Local Structures ◽  
Equilibrium Structures ◽  
Energy Ball ◽  
Metastable Compounds ◽  
Preparation Techniques

AbstractIn many cases, limitations in conventional synthesis routes hamper the accessibility to materials with properties that have been predicted by theory. For instance, metastable compounds with local non-equilibrium structures can hardly be accessed by solid-state preparation techniques often requiring high synthesis temperatures. Also other ways of preparation lead to the thermodynamically stable rather than metastable products. Fortunately, such hurdles can be overcome by mechanochemical synthesis. Mechanical treatment of two or three starting materials in high-energy ball mills enables the synthesis of not only new, metastable compounds but also of nanocrystalline materials with unusual or enhanced properties such as ion transport. In this short review we report about local structures and ion transport of oxides and fluorides mechanochemically prepared by high-energy ball-milling.

Diffusion in Nanocrystalline Ion Conductors Studied by Solid State NMR and Impedance Spectroscopy

2009 ◽  
Vol 283-286 ◽  
pp. 705-715 ◽  
Author(s):  
Paul Heitjans ◽  
Martin Wilkening
Keyword(s):  
Dynamic Properties ◽  
Average Particle Size ◽  
High Energy ◽  
Average Particle ◽  
Ion Dynamics ◽  
Ionic Conductors ◽  
Present Contribution ◽  
Energy Ball ◽  
Phase Systems ◽  
Ion Conductors

Materials with an average particle size of less than about 50 nm often show new or at least enhanced physical properties. In many cases nanocrystalline ionic conductors exhibit a high increase of cation, e. g. Li+, or anion, e. g. F−, diffusivity. In the present contribution we review recent studies on ion dynamics in nanocrystalline ion conductors, both single-phase systems and composites, being prepared by high-energy ball milling. These include, e.g., LiTaO3, Li2O:Al2O3, LiF:Al2O3, BaF2, CaF2, BaF2:CaF2 and (BaF2:CaF2):Al2O3. Dynamic properties were probed by 7Li and/or 19F NMR line shape and relaxation as well as ion conductivity measurements.

scholarly journals Correlated fluorine diffusion and ionic conduction in the nanocrystalline F− solid electrolyte Ba0.6La0.4F2.4—19F T1(ρ) NMR relaxation vs. conductivity measurements

2014 ◽  
Vol 16 (20) ◽  
pp. 9580-9590 ◽  
Author(s):  
F. Preishuber-Pflügl ◽  
P. Bottke ◽  
V. Pregartner ◽  
B. Bitschnau ◽  
M. Wilkening
Keyword(s):  
Solid Electrolyte ◽  
Long Range ◽  
Short Range ◽  
Ionic Conduction ◽  
Nmr Relaxation ◽  
Conductivity Measurements ◽  
Nmr Relaxometry ◽  
Migration Pathways

19F NMR relaxometry and conductivity spectroscopy precisely track the defect-mediated short-range and long-range anion migration pathways in nanocrystalline Ba0.6La0.4F2.4.

scholarly journals Fluorine Translational Anion Dynamics in Nanocrystalline Ceramics: SrF2-YF3 Solid Solutions

2018 ◽  
Author(s):  
Stefan Breuer ◽  
Bernhard Stanje ◽  
Veronika Pregartner ◽  
Sarah Lunghammer ◽  
Ilie Hanzu ◽  
...  
Keyword(s):  
Practical Method ◽  
High Energy ◽  
Coarse Grained ◽  
Heterogeneous Structure ◽  
Charge Carrier Density ◽  
Ion Dynamics ◽  
Size Mismatch ◽  
Nanocrystalline Ceramics ◽  
Defect Sites ◽  
Energy Ball

Nanostructured materials have already become an integral part of our daily life. In many applications ion mobility decisively affects the performance of, e.g., batteries and sensors. Nanocrystalline ceramics often exhibit enhanced transport properties due to their heterogeneous structure showing crystalline (defect-rich) grains and disordered interfacial regions. In particular, anion conductivity in nonstructural binary fluorides easily exceeds that of their coarse-grained counterparts. To further increase ion dynamics aliovalent substitution is a practical method to influence the number of (i) defect sites and (ii) the charge carrier density. Here, we used high energy-ball milling to incorporate Y3+ ions into the cubic structure of SrF2. As compared to pure nanocrystalline SrF2 the ionic conductivity of Sr1-xYxF2+x with x = 0.3 increased by 4 orders of magnitude reaching 0.8 x 10 -5 S/cm-1 at 450 K. We discuss the effect of YF3 incorporation on conductivities isotherms determined by both activation energies and Arrhenius pre-factors. The enhancement seen is explained by size mismatch of the cations involved, which are forced to form a cubic crystal structure with extra F anions if x is kept smaller than 0.5

scholarly journals Effects of Recycled Fe2O3 Nanofiller on the Structural, Thermal, Mechanical, Dielectric, and Magnetic Properties of PTFE Matrix

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2332
Author(s):  
Ahmad Mamoun Khamis ◽  
Zulkifly Abbas ◽  
Raba’ah Syahidah Azis ◽  
Ebenezer Ekow Mensah ◽  
Ibrahim Abubakar Alhaji
Keyword(s):  
Electron Microscopy ◽  
High Energy ◽  
Filler Loading ◽  
Complex Permeability ◽  
X Ray Diffraction ◽  
Thermal Expansion Coefficients ◽  
Transmission Electron ◽  
Energy Ball ◽  
Hematite Fe2o3 ◽  
Ptfe Composites

The purpose of this study was to improve the dielectric, magnetic, and thermal properties of polytetrafluoroethylene (PTFE) composites using recycled Fe2O3 (rFe2O3) nanofiller. Hematite (Fe2O3) was recycled from mill scale waste and the particle size was reduced to 11.3 nm after 6 h of high-energy ball milling. Different compositions (5–25 wt %) of rFe2O3 nanoparticles were incorporated as a filler in the PTFE matrix through a hydraulic pressing and sintering method in order to fabricate rFe2O3–PTFE nanocomposites. The microstructure properties of rFe2O3 nanoparticles and the nanocomposites were characterized through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). The thermal expansion coefficients (CTEs) of the PTFE matrix and nanocomposites were determined using a dilatometer apparatus. The complex permittivity and permeability were measured using rectangular waveguide connected to vector network analyzer (VNA) in the frequency range 8.2–12.4 GHz. The CTE of PTFE matrix decreased from 65.28×10−6/°C to 39.84×10−6/°C when the filler loading increased to 25 wt %. The real (ε′) and imaginary (ε″) parts of permittivity increased with the rFe2O3 loading and reached maximum values of 3.1 and 0.23 at 8 GHz when the filler loading was increased from 5 to 25 wt %. A maximum complex permeability of 1.1−j0.07 was also achieved by 25 wt % nanocomposite at 10 GHz.

scholarly journals Defect-induced B4C electrodes for high energy density supercapacitor devices

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Özge Balcı ◽  
Merve Buldu ◽  
Ameen Uddin Ammar ◽  
Kamil Kiraz ◽  
Mehmet Somer ◽  
...  
Keyword(s):  
Active Carbon ◽  
High Performance ◽  
Carbon Sources ◽  
High Energy ◽  
High Energy Density ◽  
Synthesis Conditions ◽  
High Energy Ball Mill ◽  
Energy Ball ◽  
G Ratio ◽  
Energy And Power Density

AbstractBoron carbide powders were synthesized by mechanically activated annealing process using anhydrous boron oxide (B2O3) and varying carbon (C) sources such as graphite and activated carbon: The precursors were mechanically activated for different times in a high energy ball mill and reacted in an induction furnace. According to the Raman analyses of the carbon sources, the I(D)/I(G) ratio increased from ~ 0.25 to ~ 0.99, as the carbon material changed from graphite to active carbon, indicating the highly defected and disordered structure of active carbon. Complementary advanced EPR analysis of defect centers in B4C revealed that the intrinsic defects play a major role in the electrochemical performance of the supercapacitor device once they have an electrode component made of bare B4C. Depending on the starting material and synthesis conditions the conductivity, energy, and power density, as well as capacity, can be controlled hence high-performance supercapacitor devices can be produced.

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