Synthesis and Ionic Conductivity of Nanophase Ca1-xLaxF2+x

1992 ◽  
Vol 286 ◽  
Author(s):  
Xijun Wu ◽  
Fang Su ◽  
Xiaoying Qin ◽  
Bin Xie ◽  
Xiaoli Ji
Keyword(s):  
Ionic Conductivity ◽  
Volume Fraction ◽  
Complex Impedance ◽  
Ionic Conductors ◽  
Gas Condensation ◽  
Large Volume Fraction ◽  
Average Grain Size ◽  
Order Of Magnitude ◽  
Compacting Pressure

ABSTRACTThe nanophase ionic conductors Ca1-xLaxF2+x with x=0 and 0.25 were synthesized by an inert gas condensation and in situ compacting technique. The samples with average grain size of 16 na for nanophase CaF2 and 11 nm for nanophase Ca0.75 La0.25F2.25 were prepared under the compacting pressure of 0.5 GPa. The alternating ionic conductivity was deduced from the temperature dependence of the complex impedance.The results indicated that the logarithm of ionic conductivity obeys Arrhenius relation in the temperature range from 300 °C to 530 °C both for nanophase CaF2 and for nanophase Ca0.75La0.25F2.25. Their activation energies are 1.14 eV and 1.00 eV, respectively. The ionic conductivity of nanophase CaF2 is about one and two orders of magnitude higher than that of polycrystalline and single crystal CaF2, respectively. While the ionic conductivity of nanophase Ca0.75La0.25F2.25 is about one order of magnitude higher than that of nanophase CaF2. Further analysis indicated that the enhanced ionic conductivity of nanophase Ca1-xLaxF2+x is related to the large volume fraction of interfaces.

Thermal Properties of Nanocrystalline Silver

1992 ◽  
Vol 286 ◽  
Author(s):  
Xijun Wu ◽  
Hongfei Zhang ◽  
Xiaoying Qin ◽  
Lifang Chen ◽  
Guanzhong Wang ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Grain Growth ◽  
Room Temperature ◽  
Nanocrystalline State ◽  
Gas Condensation ◽  
Average Grain Size ◽  
Endothermal Peak ◽  
Dsc Curves ◽  
Compacting Pressure

ABSTRACTThe thermal properties of the nanocrystalline metal Ag (n-Ag), with the average grain size of 10 run, synthesized by an inert gas condensation and in situ compacting technique under different pressures of 0.2 to 1.5 GPa were studied. The thermal stable temperature for asprepared state is 373K, above which the grain growth appears at different rates. An exothermal peak and an endothermal peak occur on the DSC curves of the n-Ag. The enthalpy of both peaks are dependent upon the compacting pressure. Tht enhancement of the specific heat in going from the polycrystalline to the nanocrystalline state varies between 5.4% and 3.6% in the temperature range of 380K to 540K. The thermal diffusivity at room temperature increases with grain growth, and approaches to the corresponding value of the polycrystalline Ag.

scholarly journals In-Situ Helium Implantation and TEM Investigation of Radiation Tolerance to Helium Bubble Damage in Equiaxed Nanocrystalline Tungsten and Ultrafine Tungsten-TiC Alloy

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 794 ◽  
Author(s):  
Osman El Atwani ◽  
Kaan Unal ◽  
William Streit Cunningham ◽  
Saryu Fensin ◽  
Jonathan Hinks ◽  
...  
Keyword(s):  
Damage Evolution ◽  
Bubble Formation ◽  
Coarse Grained ◽  
Irradiation Damage ◽  
Radiation Tolerance ◽  
Helium Bubble ◽  
Average Grain Size ◽  
Order Of Magnitude ◽  
Helium Implantation

The use of ultrafine and nanocrystalline materials is a proposed pathway to mitigate irradiation damage in nuclear fusion components. Here, we examine the radiation tolerance of helium bubble formation in 85 nm (average grain size) nanocrystalline-equiaxed-grained tungsten and an ultrafine tungsten-TiC alloy under extreme low energy helium implantation at 1223 K via in-situ transmission electron microscope (TEM). Helium bubble damage evolution in terms of number density, size, and total volume contribution to grain matrices has been determined as a function of He+ implantation fluence. The outputs were compared to previously published results on severe plastically deformed (SPD) tungsten implanted under the same conditions. Large helium bubbles were formed on the grain boundaries and helium bubble damage evolution profiles are shown to differ among the different materials with less overall damage in the nanocrystalline tungsten. Compared to previous works, the results in this work indicate that the nanocrystalline tungsten should possess a fuzz formation threshold more than one order of magnitude higher than coarse-grained tungsten.

scholarly journals In Situ Development and High Temperature Features of CoCrFeNi-M6Cp High Entropy-Alloy Based Hardmetal

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 408
Author(s):  
Huizhong Li ◽  
He Lin ◽  
Xiaopeng Liang ◽  
Weiwei He ◽  
Bin Liu ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Yield Strength ◽  
Volume Fraction ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Average Grain Size ◽  
Carbide Particles

In this work, an in-situ CoCrFeNi-M6Cp high entropy-alloy (HEA) based hardmetal with a composition of Co25Cr21Fe18Ni23Mo7Nb3WC2 was fabricated by the powder metallurgy (PM) method. Microstructures and mechanical properties of this HEA were characterized and analyzed. The results exhibit that this HEA possesses a two-phase microstructure consisting of the face-centered cubic (FCC) matrix phase and the carbide M6C phase. This HEA has an average grain size of 2.2 μm, and the mean size and volume fraction of carbide particles are 1.2 μm and 20%. The tensile tests show that the alloy has a yield strength of 573 MPa, ultimate tensile strength of 895 MPa and elongation of 5.5% at room temperature. The contributions from different strengthening mechanisms in this HEA were calculated. The grain boundary strengthening is the dominant strengthening mechanism, and the carbide particles are significant for the further enhancement of yield strength by the dislocation strengthening and Orowan strengthening. In addition, with increasing temperatures from 600 °C to 900 °C, the HEA shows a reduced yield strength (YS) from 473 MPa to 142 MPa, a decreased ultimate tensile strength (UTS) from 741 MPa to 165 MPa and an enhanced elongation from 10.5% to 31%.

Sample preparation of sub-micron precipitates in rapidly solidified Mg-20Nd

1988 ◽  
Vol 46 ◽  
pp. 984-985
Author(s):  
Ralph E. Omlor ◽  
Lt Erica Robertson ◽  
Pamela F. Lloyd
Keyword(s):  
Melt Spinning ◽  
Volume Fraction ◽  
Carbon Film ◽  
Large Volume Fraction ◽  
The Matrix ◽  
Carbon Coated ◽  
Order Of Magnitude ◽  
Rapidly Solidified ◽  
Oxide Precipitate ◽  
A Current

The Mg-20Nd melt spun ribbonsare being examined in depth because of their potentiodynamic polarization response as compared to that of 7075-T73 aluminum. The Mg-20Nd ribbon exhibited pseudopassivation behavior at a current density approximately one order of magnitude less than the aluminum alloy. In previous work, this was found to be due to the presence of a tessellatal precipitated network which formed in the ribbons during melt spinning. EDS results on TEM foils gave similar compositional values on both matrix and precipitates. These results were not trusted due to the small size and large volume fraction of the precipitates.The Mg-20Nd ribbon was swabbed with a dilute solution of sulfuric acid to loosen the particles in the matrix. A heavy oxide film was also formed on the surface at this time. Plastic replication solution was then applied to this surface and stripped away when dry. The particle side of the plastic film was then carbon coated. This film was placed on 3mm grids and the plastic dissolved away leaving the carbon film and the oxide precipitate mixture.

Intergrainular structure and deformation mechanism in nanocrystalline materials

1995 ◽  
Vol 53 ◽  
pp. 192-193
Author(s):  
H.Q. Ye ◽  
P.H. Ping ◽  
D.X. Li ◽  
J.Y. Huang ◽  
Y.K. Wu
Keyword(s):  
Deformation Mechanism ◽  
Structural Modification ◽  
Boundary Structure ◽  
X Ray Diffraction ◽  
Gas Condensation ◽  
Average Grain Size ◽  
Relationship Of ◽  
Structure Properties

It is recognized that boundary structure (GB) characterization is essential in order to understand the structure-properties relationship of nanocrystalline (NC). In most cases, NC materials have to suffer deformation during compacting or ball milling techniques, a deep and systematic study on deformation mechanism is also necessary. In this paper, characterization of microstructure in NC materials synthesized by three methods has been presented.1. Ordered and Disordered Regions at GBs of NC Pd The NC Pd samples were synthesized by the inert gas condensation and in situ compacting technique. The results of X-ray diffraction and HREM observations showed that the average grain size of the NC Pd is about 10 nm. It can be seen that most of the GBs have ordered structure and no 'gas-like' feature has been observed. Some disordered GB regions, such as nanovoid formed during compacting process, are also detected as marked by "V" in Fig.l. The structural modification from the disordered state was found during in situ HREM investigation.

On the elastic moduli of nanocrystalline Fe, Cu, Ni, and Cu–Ni alloys prepared by mechanical milling/alloying

1995 ◽  
Vol 10 (11) ◽  
pp. 2892-2896 ◽  
Author(s):  
T.D. Shen ◽  
C.C. Koch ◽  
T.Y. Tsui ◽  
G.M. Pharr
Keyword(s):  
Grain Size ◽  
Mechanical Milling ◽  
Nanocrystalline Materials ◽  
Volume Fraction ◽  
Vacuum Consolidation ◽  
Shear Moduli ◽  
Gas Condensation ◽  
Large Volume Fraction ◽  
Ni Alloys ◽  
Young’S Moduli

Young's moduli of nanocrystalline Fe, Cu, Ni, and Cu-Ni alloys prepared by mechanical milling/alloying have been measured by the nanoindentation technique. The results indicate that Young's moduli of nanocrystalline Cu, Ni, and Cu–Ni alloys with a grain size ranging from 17 to 26 nm are similar to those of the corresponding polycrystals. The dependence of Young's modulus of nanocrystalline Fe on grain size corresponds well to a theoretical prediction, which suggests that the change in the Young and shear moduli of nanocrystalline materials, free of porosity, with a grain size larger than about 4 nm, should be very limited (<10%). It is likely that reported large decreases in the Young and shear moduli of nanocrystalline materials prepared by gas-condensation/vacuum consolidation result from a relatively large volume fraction of pores.

scholarly journals Nucleation and Growth of Crystalline Grains in RF-Sputtered TiO2Films

2009 ◽  
Vol 2009 ◽  
pp. 1-4 ◽  
Author(s):  
J. C. Johnson ◽  
S. P. Ahrenkiel ◽  
P. Dutta ◽  
V. R. Bommisetty
Keyword(s):  
Volume Fraction ◽  
Classical Model ◽  
Grain Morphology ◽  
Carbon Support ◽  
Number Density ◽  
Crystalline Volume Fraction ◽  
Grain Number ◽  
Transmission Electron ◽  
Average Grain Size

AmorphousTiO2thin films were radio frequency sputtered onto siliconmonoxide and carbon support films on molybdenum transmission electron microscope (TEM) grids and observed during in situ annealing in a TEM heating stage at250∘C. The evolution of crystallization is consistent with a classical model of homogeneous nucleation and isotropic grain growth. The two-dimensional grain morphology of the TEM foil allowed straightforward recognition of amorphous and crystallized regions of the films, for measurement of crystalline volume fraction and grain number density. By assuming that the kinetic parameters remain constant beyond the onset of crystallization, the final average grain size was computed, using an analytical extrapolation to the fully crystallized state. Electron diffraction reveals a predominance of the anatase crystallographic phase.

How Certain Are the Reported Ionic Conductivities of Thiophosphate-Based Solid Electrolytes? an Interlaboratory Study

2020 ◽  
Author(s):  
Saneyuki Ohno ◽  
Tim Bernges ◽  
Johannes Buchheim ◽  
Marc Duchardt ◽  
Anna-Katharina Hatz ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Ionic Conductivity ◽  
Relative Standard Deviation ◽  
Solid Electrolytes ◽  
Ionic Conductivities ◽  
Ionic Conductors ◽  
Energy Storage Devices ◽  
Activation Barriers ◽  
Storage Devices ◽  
Relative Standard

<p>Owing to highly conductive solid ionic conductors, all-solid-state batteries attract significant attention as promising next-generation energy storage devices. A lot of research is invested in the search and optimization of solid electrolytes with higher ionic conductivity. However, a systematic study of an <i>interlaboratory reproducibility</i> of measured ionic conductivities and activation energies is missing, making the comparison of absolute values in literature challenging. In this study, we perform an uncertainty evaluation via a Round Robin approach using different Li-argyrodites exhibiting orders of magnitude different ionic conductivities as reference materials. Identical samples are distributed to different research laboratories and the conductivities and activation barriers are measured by impedance spectroscopy. The results show large ranges of up to 4.5 mScm<sup>-1</sup> in the measured total ionic conductivity (1.3 – 5.8 mScm<sup>-1</sup> for the highest conducting sample, relative standard deviation 35 – 50% across all samples) and up to 128 meV for the activation barriers (198 – 326 meV, relative standard deviation 5 – 15%, across all samples), presenting the necessity of a more rigorous methodology including further collaborations within the community and multiplicate measurements.</p>

Defect-Mediated Conductivity Enhancements in Na3-xPn1-xWxS4 (Pn = P, Sb) using Aliovalent Substitutions

2019 ◽  
Author(s):  
Till Fuchs ◽  
Sean Culver ◽  
Paul Till ◽  
Wolfgang Zeier
Keyword(s):  
Ionic Conductivity ◽  
Vacancy Concentration ◽  
Sodium Ion ◽  
High Ionic Conductivity ◽  
Ionic Conductors ◽  
X Ray Diffraction ◽  
X Ray ◽  
Solid State Batteries ◽  
Ion Conducting ◽  
Very High

<p>The sodium-ion conducting family of Na<sub>3</sub><i>Pn</i>S<sub>4</sub>, with <i>Pn</i> = P, Sb, have gained interest for the use in solid-state batteries due to their high ionic conductivity. However, significant improvements to the conductivity have been hampered by the lack of aliovalent dopants that can introduce vacancies into the structure. Inspired by the need for vacancy introduction into Na<sub>3</sub><i>Pn</i>S<sub>4</sub>, the solid solutions with WS<sub>4</sub><sup>2-</sup> introduction are explored. The influence of the substitution with WS<sub>4</sub><sup>2-</sup> for PS<sub>4</sub><sup>3-</sup> and SbS<sub>4</sub><sup>3-</sup>, respectively, is monitored using a combination of X-ray diffraction, Raman and impedance spectroscopy. With increasing vacancy concentration improvements resulting in a very high ionic conductivity of 13 ± 3 mS·cm<sup>-1</sup> for Na<sub>2.9</sub>P<sub>0.9</sub>W<sub>0.1</sub>S<sub>4</sub> and 41 ± 8 mS·cm<sup>-1</sup> for Na<sub>2.9</sub>Sb<sub>0.9</sub>W<sub>0.1</sub>S<sub>4</sub> can be observed. This work acts as a stepping-stone towards further engineering of ionic conductors using vacancy-injection via aliovalent substituents.</p>

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