<i>In situ</i> Brillouin study of sodium alumino silicate glasses under pressure

Sonneville, Camille; Ligny, Dominique de; Mermet, A.; Champagnon, B.; Martinet, C.; Henderson, G. H.; Deschamps, Thierry; Margueritat, Jérémie

doi:10.1063/1.4818335

Cited by 26 publications

(20 citation statements)

References 43 publications

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“…[8a, 19] Raman spectroscopy,w ith the wavelength range 0-1200 cm À1 ,w as appliedt os crutinize the presence of Magneli phases.A st he outer layer of the sample was treated by HMDS, SiO 2 shells were introduced and accompanied by the appearance of characteristics SiO 2 peaks at 422 cm À1 . [20] In general, the E g anatase mode has an average peak position of 145.5 cm À1 ,t he E g rutile mode has an average peak positiono f 440.4 cm À1 ,a nd the A 1g rutile mode has an average peak position of 611.8 cm À1 . [21] The characteristic peak at 140 cm À1 and humps in this wavelength range are the signature of Magneli Ti 4 O 7 .…”

Section: Resultsmentioning

confidence: 99%

In Situ Confined Synthesis of Ti₄O₇ Supported Platinum Electrocatalysts with Enhanced Activity and Stability for the Oxygen Reduction Reaction

Duma

et al. 2018

ChemCatChem

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Herein, an in situ confined synthesis of highly conductive titanium oxide supported Pt catalysts is successfully employed. The method involves crystallization and formation of TiO2 particles inside the inert silica shell introduced by using hexamethyldisilazane (HMDS). The conductivity of titania is found to be greatly enhanced by increased annealing temperature, whereas the inevitable decrease in the specific surface area was effectively inhibited by the confining silica shell derived from HMDS. The optimal catalyst (20Pt 850 FHST), exhibited better oxygen reduction reaction (ORR) activity with a maximum current density of 0.049 mA cm−2 at 0.9 V (vs. normal hydrogen electrode (NHE)) and an onset potential of 0.86 V (vs. NHE). The prolonged cycling test demonstrated superior stability compared with Pt/C (JM 20). Moreover, X‐ray absorption spectroscopy asserts that the increased electron population in the Pt 5d orbital, emanating from the strong metal–support interaction, improves the electrochemical performance in the ORR. The in situ HMDS‐assisted synthesis can also be extended to other oxide‐supported catalytic systems.

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Section: Resultsmentioning

confidence: 99%

In Situ Confined Synthesis of Ti₄O₇ Supported Platinum Electrocatalysts with Enhanced Activity and Stability for the Oxygen Reduction Reaction

Duma

et al. 2018

ChemCatChem

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“…Therefore, understanding the atomic structure (e.g., coordination numbers and degree of polymerization) of glasses upon compression is essential for understanding the pressure dependence of the macroscopic properties. The pressure-induced structural changes that occur include changes in the next-nearest neighbor (NNN) distributions and ring statistics (Lee, 2010;Sonneville et al, 2013), number of non-bridging oxygen (NBO) (Xue and Stebbins, 1993;George and Stebbins, 1996), atomic coordination number of network-former cations (Smedskjaer et al, 2014b), and network-former/modifier-oxygen bond distances (Xue and Stebbins, 1993;Sonneville et al, 2013).…”

Section: Pressure-induced Structural Changesmentioning

confidence: 99%

Pressure-Induced Densification of Oxide Glasses at the Glass Transition

2017

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Densification of oxide glasses at the glass transition offers a novel route to develop bulk glasses with tailored properties for emerging applications. Such densification can be achieved in the technologically relevant pressure regime of up to ~1 GPa. However, the present understanding of the composition-structure-property relationships governing these glasses is limited, with key questions, e.g., related to densification mechanism, remaining largely unanswered. Recent advances in structural characterization tools and high-pressure apparatuses have prompted new research efforts. Here, we review this recent progress and the insights gained in the understanding of the influence of isostatic compression at elevated temperature (so-called hot compression) on the compositionstructure-property relationships of oxide glasses. We focus on compression at temperatures at or around the glass transition temperature (Tg), with relevant comparisons made to glasses prepared by pressure quenching and cold compression. We show that permanent densification at 1 GPa sets in at temperatures above 0.7Tg and the degree of densification increases with increasing compression temperature and time, until attaining an approximately constant value for temperatures above Tg. For glasses compressed at the same temperature/pressure conditions, we demonstrate direct relations between the degree of volume densification and the pressure-induced change in micromechanical properties such as hardness, elastic moduli, and extent of the indentation size effect across a variety of glass families. Finally, we review the results on relaxation behavior of hot-compressed glasses. In summary, all the pressure-induced changes in the structure and properties exhibit strong composition dependence. The experimental results highlight new opportunities for future investigation and identify research challenges that need to be overcome to advance the field.

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“…10(a)], in a good agreement with experimental observation. 44 The above results clearly show that it is such local beta-to alpha-ring transitions giving rise to the elastic softening upon initial compression in silica glass. Therefore, by eliminating localized ring conformation changes, the mechanical anomaly in silica glass can be completely eradicated.…”

Section: Tuning Elastic Anomaly Via Microscopic Structurementioning

confidence: 66%

Tailoring structure and properties of silica glass aided by computer simulation

et al. 2016

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By using a combination of experiments and molecular dynamics simulations, our studies show that the elastic response of silica glass to initial compression gradually changes from abnormal to normal with increasing quench pressure, helium content or alkali modifier added in the glass matrix. We uncovered the structural origin of the elastic anomaly in silica glass as localized structural transitions between motifs of different stiffness that are similar to those found in its crystalline counterparts. Pressure-quenching, helium-stuffing, or alkali-modifying plays a different role in changing the structure of silica glass, but all of the resulting structures reduce the propensity for such local structural transitions to take place, thus the degree of elastic anomaly. Our studies demonstrate that by processing in ways that gradually eliminates the elastic anomaly, the degree of silica glass to undergo irreversible densification can be eventually eradicated. This provides a solid foundation for the bottom-up design of new glasses with tunable structure and properties.

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In situ Brillouin study of sodium alumino silicate glasses under pressure

Cited by 26 publications

References 43 publications

In Situ Confined Synthesis of Ti₄O₇ Supported Platinum Electrocatalysts with Enhanced Activity and Stability for the Oxygen Reduction Reaction

In Situ Confined Synthesis of Ti₄O₇ Supported Platinum Electrocatalysts with Enhanced Activity and Stability for the Oxygen Reduction Reaction

Pressure-Induced Densification of Oxide Glasses at the Glass Transition

Tailoring structure and properties of silica glass aided by computer simulation

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In situ Brillouin study of sodium alumino silicate glasses under pressure

Cited by 26 publications

References 43 publications

In Situ Confined Synthesis of Ti4O7 Supported Platinum Electrocatalysts with Enhanced Activity and Stability for the Oxygen Reduction Reaction

In Situ Confined Synthesis of Ti4O7 Supported Platinum Electrocatalysts with Enhanced Activity and Stability for the Oxygen Reduction Reaction

Pressure-Induced Densification of Oxide Glasses at the Glass Transition

Tailoring structure and properties of silica glass aided by computer simulation

Contact Info

Product

Resources

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In Situ Confined Synthesis of Ti₄O₇ Supported Platinum Electrocatalysts with Enhanced Activity and Stability for the Oxygen Reduction Reaction

In Situ Confined Synthesis of Ti₄O₇ Supported Platinum Electrocatalysts with Enhanced Activity and Stability for the Oxygen Reduction Reaction