Changes in structure and electrical conductivity of rare-earth titanate pyrochlores under highly reducing atmosphere

Cioateră, Nicoleta; Voinea, Elena-Adriana; Panaintescu, E.; Rolle, Aurélie; Şomăcescu, Simona; Spinu, C.I.; Vannier, R-N.

doi:10.1016/j.ceramint.2015.09.095

Cited by 31 publications

(5 citation statements)

References 27 publications

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“…show the change in weight and heat flow vs. temperature, along with the CO2 emitted as a function of temperature for the LSZ and LSZN6 respectively. The profiles observed for the weight loss and heat flow are consistent with other materials produced by this method[113]. It can be seen for both materials there are several steps that occur during the calcination.…”

supporting

confidence: 83%

“…The other probable factor contributing to the lower values in the lattice parameters is cooling effects. Decreasing temperature is known to cause a shrinkage in the lattice parameter of the pyrochlore through a decrease in thermal expansion [113]. In addition, there could also be the potential shrinkage as the material is cooled due to the segregation of additional Ni cations which can have a misfit in the pyrochlore lattice in the surface and grain boundary regions [120].…”

Section: In-situ Xrdmentioning

confidence: 99%

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Steam Reforming of CH4 Using Ni- Substituted Pyrochlore Catalysts

Haynes¹

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The steam reforming of methane (SMR) continues to remain an important industrial reaction for large-scale production of H2 as well as synthesis gas mixtures which can be used for the production of useful chemicals (e.g. methanol). Although SMR is a rather mature technology, traditional nickel based catalysts used industrially are subjected to severe temperatures and reaction conditions, which lead to irreversible activity loss through sintering, support collapse, and carbon formation. Pyrochlore-based mixed oxide have been identified as refractory materials that can be modified through the substitution of catalytic metals and other promoting species into the structure to mitigate these issues causing deactivation. For this study, a lanthanum zirconate pyrochlore catalyst was substituted with Ni to determine whether the oxide structure could effectively stabilize the activity of the catalytic metal during the SMR. The effect of different variables including calcination temperature, a comparison of a substituted versus supported Ni pyrochlore catalyst, Ni weight loading, and Sr promotion have been evaluated to determine the location of the Ni in the structure, and their effect on catalytic behavior.

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supporting

confidence: 83%

Section: In-situ Xrdmentioning

confidence: 99%

Steam Reforming of CH4 Using Ni- Substituted Pyrochlore Catalysts

Haynes¹

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“…It is known that at elevated temperatures in a reducing atmosphere (such as 98% Ar + 2% H 2 ), some species can decompose into rare earth oxide and titanium dioxide as follows: RE 2 Ti 2 O 7−δ → RE 2 O 3 + TiO 2−δ (RE = Y, Gd, Sm). [29] In addition, Seki and Yamaura [30] proposed a method for the formation of TiN from titanium oxides using nitridation. On this basis, the Y 2 Ti 2 O 7 -TiN composite can be obtained by heating titanate in a nitrogen (N 2 ) atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Titanium Nitride and Yttrium Titanate Nanocomposites, Endowed with Renewable Self‐Healing Ability

Nguyen

Okawa

Iwasawa

et al. 2021

Adv Materials Inter

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were the two important inventions that significantly improved the fuel efficiency in a gas turbine engine, as they allowed higher inlet temperatures, [1,2] however, to further improve the thrust-to-weight ratio of the engine, light weight and high-temperature capability of the turbine parts should be enhanced. A promising material for the next-generation aircraft engines is silicon carbide matrix reinforced with silicon carbide fiber (SiC f /SiC m ). [3] The lightweight, good hardness, and thermal stability at the target temperatures of SiC made it an ideal replacement for superalloy. [4,5] SiC-based ceramic-matrix composites have been researched for the components of gas turbine engine, from first-stage turbine vane to high-pressure turbine blade. [6][7][8] However, a critical disadvantage of SiC for turbine blades is the rapid destruction of this material in a steam environment. [9] An environmental barrier coating (EBC) has been investigated to replace TBC when protecting the SiC f /SiC m blade from water vapor. Like TBC, EBC is also a multilayer structure, but the top ceramic coating should have excellent resistance not only to heat but also to corrosion in water vapor. Rare earth (RE) silicates, RE 2 Si 2 O 7 or RESiO 5 (RE = Lu, Sc, Y, Yb, etc.), have been considered as possible topcoat materials due to their excellent resistance to water vapor. Among explored RE silicates, ytterbium disilicate (Yb 2 Si 2 O 7 ) and ytterbium monosilicate (Yb 2 SiO 5 ) are most widely studied for the topcoat layer because these silicates have low thermal conductivity, thermal expansion coefficient (TEC) similar to that of SiC substrate, and the highest water corrosion resistance. [9][10][11][12] However, the research costs for Yb-based materials are still too expensive to implement on real gas turbine blade systems. Therefore, yttrium(Y)-based EBC materials, such as Y 2 Si 2 O 7 [13] or Y 2 Ti 2 O 7 , [14] also having good corrosion resistance, but cheaper than Yb 2 Si 2 O 7 , are considered as alternative candidates.Yb 2 Si 2 O 7 and other ceramic topcoat candidates are brittle with low fracture toughness and strength, [15,16] making them easily crack due to foreign debris impact or residual stress from thermal cycling. Cracks can propagate to the lower layers of the EBC, which leads to degradation, delamination, and spalling of this structure. [17] Therefore, inspired by the phenomenon of bone healing in nature, [18,19] structural ceramics with selfhealing ability were studied to solve this problem. [8,[20][21][22][23] At highThe environmental barrier coating (EBC) has been studied to protect the silicon carbide blades of the next-generation gas turbine engine of aircraft from superheated water vapor. The upper ceramic layer of EBC is brittle, therefore, cracks can occur under the impact of foreign debris and spread toward the lower layers, which leads to the destruction of this structure. Therefore, self-healing structural ceramics is a promising solution to this problem, but they still have some critical drawbacks. First...

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“…К подобным материалам относят-ся и титанаты Sm 2 Ti 2 O 7 и Er 2 Ti 2 O 7 [1][2][3]. Для них имеются данные о получении нано- [6,7] и монокри-сталлов [9], структуре [1][2][3], магнитных [10] и элек-трофизических [11] свойствах. В то же время сведения о теплофизических свойствах практически отсутствуют.…”

Section: Introductionunclassified

Высокотемпературная Теплоемкость Титанатов Самария И Эрбия Со Структурой Пирохлора

Денисова¹,

Чумилина²,

Денисов³

et al. 2017

Физика Твердого Тела

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Методом твердофазного синтеза на воздухе из стехиометрических смесей Sm 2 O 3 (Er 2 O 3 )−TiO 2 последова-тельно при температурах 1673 и 1773 K получены титанаты Sm 2 Ti 2 O7 и Er 2 Ti 2 O7 со структурой пирохлора. Методом дифференциальной сканирующей калориметрии измерена высокотемпературная теплоемкость оксидных соединений. По экспериментальным зависимостям C p = f (T ) рассчитаны их термодинамические свойства.Работа выполнена при финансовой поддержке работ, выполняемых в рамках Государственного задания Министерства образования и науки Российской Федерации Сибирскому федеральному университету на 2017−2019 (проект 4.8083.2017/БЧ " Формирование банка данных термодинамических характеристик сложнооксидных полифункциональных материалов, содержащих редкие и рассеянные элементы").

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Changes in structure and electrical conductivity of rare-earth titanate pyrochlores under highly reducing atmosphere

Cited by 31 publications

References 27 publications

Steam Reforming of CH4 Using Ni- Substituted Pyrochlore Catalysts

Steam Reforming of CH4 Using Ni- Substituted Pyrochlore Catalysts

Titanium Nitride and Yttrium Titanate Nanocomposites, Endowed with Renewable Self‐Healing Ability

Высокотемпературная Теплоемкость Титанатов Самария И Эрбия Со Структурой Пирохлора

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