Production Of Nbc from Nb2O5 in a rotating cylinder reactor: Kinetic study of reduction/carburization reactions

Fontes, Francisco de Assis Oliveira; Sousa, João Fernandes de; Souza, Carlson Pereira de; Bezerra, M. B. D.; Benachour, Mohand

doi:10.1016/j.cej.2011.09.105

Cited by 11 publications

(4 citation statements)

References 4 publications

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“…There are two possible explanations for this. Native oxides are expected on surface of powders such as NbC and ZrC, and Figure shows N1 powder contained ~1.1wt% oxygen. The SPS/PECS process is expected to remove surface oxides, but the absence of niobium compounds in the collected exhaust suggests oxides of niobium were not removed.…”

Section: Discussionmentioning

confidence: 99%

“…It has been attributed to the pentagonal bipyramidal coordination structures in Nb and Ta, thus, Group (V) carbides forced into fcc‐configuration result in stable long‐range ordered vacancies . Other differences of the Group (V) to (IV) include a more stable formula of M 2 O 5 compared with MO 2 ; NbO 2 is actually a metastable, intermediate structure during carbothermal reduction and oxidation between Nb 2 O 5 and NbC 1‐x . These indicate the relative stability of the carbon sublattice.…”

Section: Discussionmentioning

confidence: 99%

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Niobium carbide as a technology demonstrator of ultra‐high temperature ceramics for fully ceramic microencapsulated fuels

Ang

Snead

Benensky

2019

Int J Ceramic Engine & Sci

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The consolidation of Fully Ceramic Microencapsulated (FCM) fuels has been extended from matrices based on SiC to ultra-high temperature ceramics (UHTCs). Specifically, sintering conditions of NbC 1-x were compatible with hosting of microencapsulated fuel. NbC powder in as-received, chemically treated, and composite forms was consolidated. Elemental analysis, shrinkage of powder compacts, contents of ejected vapor, density, microstructure, and NbC lattice constants were analyzed. As-received NbC showed more shrinkage due to the presence of a liquid phase compared with the chemically treated powder. Removal of impurity metals was observed from chemical treatment and during sintering of as-received powders. An increase in true density during sintering was attributed to removal of compounds with lower density than NbC.Chemically treated powder showed reduced densification rate and absence of a liquid phase after sintering. Smaller grain sizes were observed in the NbC composite. The implications for NbC and other binary carbides as matrices for FCM fuels are discussed. K E Y W O R D Scarbides, niobium/niobium compounds, nuclear thermal propulsion, sinter/sintering, spark plasma sintering

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Niobium carbide as a technology demonstrator of ultra‐high temperature ceramics for fully ceramic microencapsulated fuels

Ang

Snead

Benensky

2019

Int J Ceramic Engine & Sci

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“…Ideally, nanostructured materials are required. Traditionally synthesis uses a temperature-programmed carburization of transition metal oxide precursors using a gas mixture such as 20 (v/v) % CH 4 /H 2 . , Niobium carbide cannot be produced below 950 °C by this approach, , and these conditions result in samples that possess low specific areas . A different method for the synthesis of niobium carbonitride was reported by Chagas et al, who used lower temperatures and a helium environment .…”

Section: Introductionmentioning

confidence: 99%

Nanostructured Niobium and Titanium Carbonitrides as Electrocatalyst Supports

McLeod,

Spikes,

Zalitis

et al. 2024

ACS Appl. Nano Mater.

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Nanostructured niobium−titanium carbonitrides, (Nb,Ti)C 1−x N x , with the cubic-rock salt structure are prepared without the use of reactive gases via thermal treatment (700−1200 °C) under nitrogen of mixtures of guanidine carbonate and ammonium niobate (V) oxalate hydrate, with addition of ammonium titanyl oxalate monohydrate as a titanium source. The bulk structure and chemical composition of the materials are characterized using powder X-ray diffraction (XRD) and powder neutron diffraction, elemental homogeneity is studied using energy dispersive spectroscopy (EDS) mapping using transmission electron microscopy (TEM), and surface chemical analysis is examined using X-ray photoelectron spectroscopy (XPS). Nanoscale crystallites of between 10 and 50 nm are observed by TEM, where EDS reveals the homogeneity of metal distribution for the mixed-metal materials. Titanium carbonitrides are found to be air sensitive, reacting with air under ambient conditions, while titanium−niobium carbonitrides are found to degrade in aqueous sulfuric acid. The niobium carbonitrides, however, show some stability toward acidic solutions. Materials are produced with composition NbC 1−x N x with x between 0.35 and 0.45, and more carbon-rich materials (x ≈ 0.35) are found as the synthesis temperature is increased, as proven by Rietveld refinement of crystal structure against powder neutron diffraction data. Despite phase purity seen by diffraction and negligible bulk carbon content, XPS shows a complex surface chemistry for the NbC 1−x N x materials, with evidence for Nb 2 O 5like oxide species in a carbon-rich environment. The NbC 1−x N x prepared at 900 °C has a surface area around 50 m 2 g −1 , making it suitable as a catalyst support. Loading with iridium provides a material active for the oxygen evolution reaction in 0.1 M sulfuric acid, with minimal leaching of either Nb or Ir after 1000 cycles.

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“…Several variables may affect the reaction rate, thus it is necessary to consider the nature of the reaction, the number of phases involved, as well as the presence of catalysts. Kinetic studies for carbide synthesis investigate, for instance, the production of TiC via calciothermic reduction in an argon atmosphere [13] NbC from Nb 2O5 from two methodologies, namely rotary cylinder, and a fixed bed reactor [14,15], and the non-isothermal synthesis of WC from metallic W and methane using the Joule effect [16]. Concerning the WC synthesis, [17] attained pure WC after 60min of reaction at 850 °C using a heterogeneous gas-solid reaction, with CH4 and H 2 gas mixture in a fixed bed reactor.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Kinetic Data of the WC’s Synthesis Via Gas-Solid Reaction

Araújo¹

2022

J Miner Sci Materials

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Tungsten carbide (WC) stands out in the mechanical industry, chemical and aerospace by presenting a unique combination of properties, such as high hardness, high melting point, high wear resistance, great chemical, and thermal stability. Refractory carbides’ synthesis via gas-solid reaction is an interesting processing route as it can produce those materials in nanoscale and thus, enhance several of its properties. In this paper, the WC production process was studied upon the evaluation of kinetic data available in the literature. The synthesis data were obtained through the “Digitize” tool of the Origin® software and two kinetic models were evaluated regarding its agreement with those data: 1st order powerlaw and Avrami model. Kinetic constants using a 1st order reaction were estimated and a k=0.00181min-1 with R² =0.9646 for the reaction at 850 ° C and 120min of soaking time.

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Production Of Nbc from Nb2O5 in a rotating cylinder reactor: Kinetic study of reduction/carburization reactions

Cited by 11 publications

References 4 publications

Niobium carbide as a technology demonstrator of ultra‐high temperature ceramics for fully ceramic microencapsulated fuels

Niobium carbide as a technology demonstrator of ultra‐high temperature ceramics for fully ceramic microencapsulated fuels

Nanostructured Niobium and Titanium Carbonitrides as Electrocatalyst Supports

Evaluation of Kinetic Data of the WC’s Synthesis Via Gas-Solid Reaction

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