Ti-catalyzed HfSiO4 formation in HfTiO4 films on SiO2 studied by Z-contrast scanning electron microscopy

Hoppe, E. E.; Cisneros-Morales, Massiel Cristina; Aita, C. R.

doi:10.1063/1.4818171

Cited by 2 publications

(4 citation statements)

References 25 publications

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“…The HfTi_PMS_Pr(/Bu) samples show a brighter appearance in contrast to that of the single Hf modified ones, suggesting the formation of a significant amount of hafnon. Previous work on nanolaminated TiO 2 /HfO 2 /HfTiO 4 films (~0.3 μm) on SiO 2 substrate validated that the formation of HfSiO 4 is accelerated in air by the presence of TiO 2 . Moreover it is reported that TiO 2 is formed at 1200°C and at 1500°C for Ti‐alkoxide modified siloxane derived ceramics.…”

Section: Resultsmentioning

confidence: 88%

“…However, no peaks assigned to residual carbon are visible in the HfTi_PMS_Pr(/Bu) cases, which manifests that no free carbon is present in the SiOC matrix after oxidation. In addition, Raman bands assigned to hafnium silicate, namely hafnon (HfSiO 4 ), are clearly detected in the two Ti‐containing SiOC/HfO 2 nanocomposites after high temperature oxidation. These findings show that the presence of Ti also influences the oxidation process of the SiOC/HfO 2 ceramic nanocomposites.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, we consider that in our work, TiO 2 crystallites are generated during oxidation of amorphous SiTiOC following the reaction Equations () and (). The formed TiO 2 enhances the reaction between the separated hafnia and silica fractions of the SiOC matrix to yield HfSiO 4 according to Equations () and ()

2 SiTiOC + {normalO}_{2} \to {SiO}_{2} + 2 TiC

TiC + 1.5 {normalO}_{2} \to {TiO}_{2} + CO false(normalg false)

{TiO}_{2} + {SiO}_{2} \to {TiSiO}_{4}

{HfO}_{2} + {TiSiO}_{4} \to {HfSiO}_{4} + {TiO}_{2}

…”

Section: Resultsmentioning

confidence: 99%

“…The formed TiO 2 enhances the reaction between the separated hafnia and silica fractions of the SiOC matrix to yield HfSiO 4 according to Equations (3) and (4). 33 ( In summary, based on the above analysis, the phase evolution of single-source precursor derived SiMOC ceramics and nanocomposites after pyrolysis, annealing, and oxidation can be outlined in brief as shown schematically in Figure 12. After annealing, t-HfO 2 is separated from the SiOC matrix in samples with and without Ti modification.…”

Section: Phase Evolution and Reactions Of Ceramic Nanocomposites Oxmentioning

confidence: 99%

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Phase evolution of SiOC‐based ceramic nanocomposites derived from a polymethylsiloxane modified by Hf‐ and Ti‐alkoxides

Sun

Wen

et al. 2019

J Am Ceram Soc

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SiOC/HfO2‐based ceramic nanocomposites with in situ formed HfO2 nanoparticles were prepared via a single‐source precursor (SSP) approach starting from a polymethylsilsesquioxane (PMS) modified by Hf‐ and Ti‐alkoxides. By varying the alkyl‐group of the employed Hf‐alkoxides, SiOC/HfO2‐based ceramic nanocomposites with different HfO2 polymorphs formed via thermal decomposition of the SSP under the same heat‐treatment conditions. Using PMS chemically modified by Hf(OnBu)4, tetragonal HfO2 phase was formed after the synthesis at 1100°C in Ar, whereas both, tetragonal and monoclinic HfO2 nanocrystals, were analyzed when replacing Hf(OnBu)4 by Hf(OiPr)4. After oxidation of the synthesized nanocomposites in air at 1500°C, a facile formation of oxidation‐resistant HfSiO4 (hafnon) phase occurred by the reaction of HfO2 nanocrystals with silica present in the SiOC nanocomposite matrix derived from Hf(OiPr)4‐modified SSPs. Moreover the amount of hafnon is dramatically increased by the additional modification of the polysiloxane with Ti‐alkoxides. In contrast, ceramic nanocomposites derived from Hf(OnBu)4‐modified SSPs, almost no HfSiO4 is detected after oxidation at 1500°C even though in the case of Ti‐alkoxide‐modified single‐source precursor.

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Section: Resultsmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 99%

2 SiTiOC + {normalO}_{2} \to {SiO}_{2} + 2 TiC

TiC + 1.5 {normalO}_{2} \to {TiO}_{2} + CO false(normalg false)

{TiO}_{2} + {SiO}_{2} \to {TiSiO}_{4}

{HfO}_{2} + {TiSiO}_{4} \to {HfSiO}_{4} + {TiO}_{2}

…”

Section: Resultsmentioning

confidence: 99%

Section: Phase Evolution and Reactions Of Ceramic Nanocomposites Oxmentioning

confidence: 99%

See 2 more Smart Citations

Phase evolution of SiOC‐based ceramic nanocomposites derived from a polymethylsiloxane modified by Hf‐ and Ti‐alkoxides

Sun

Wen

et al. 2019

J Am Ceram Soc

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Solid‐Solution Effects on the High‐Temperature Oxidation Behavior of Polymer‐Derived (Hf,Ta)C/SiC and (Hf,Ti)C/SiC Ceramic Nanocomposites

2018

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In the present study, two concepts to improve the oxidation resistance at high‐temperatures of ceramic nanocomposites consisting of 85–90 vol% SiC, 5–8 vol% group IV metal carbides (i.e., HfC, TaC), and 5–7 vol% carbon are introduced and discussed. First improvement concept relates to the passivation of the samples upon short‐term oxidation at 1400 °C (30 min). This is a critical step, especially with respect to silica formation, which is relatively sluggish at temperatures lower than 1000–1200 °C. Moreover, solid‐solution metal carbides (Hf,Ta)C and (Hf,Ti)C are shown to be clearly more oxidation resistant than the binary HfC and TaC phases. Whereas, the solid‐solution effect contributes to a significant improvement of the short‐term oxidation resistance of the studied nanocomposites, the passivation of the materials prior exposure of high‐temperature oxidation conditions provides a remarkably improved long‐term behavior thereof. Possible mechanisms involved in the oxidation processes of (Hf,Ta)C/SiC and (Hf,Ti)/SiC ceramic nanocomposites are highlighted and critically assessed.

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Ti-catalyzed HfSiO4 formation in HfTiO4 films on SiO2 studied by Z-contrast scanning electron microscopy

Cited by 2 publications

References 25 publications

Phase evolution of SiOC‐based ceramic nanocomposites derived from a polymethylsiloxane modified by Hf‐ and Ti‐alkoxides

Phase evolution of SiOC‐based ceramic nanocomposites derived from a polymethylsiloxane modified by Hf‐ and Ti‐alkoxides

Solid‐Solution Effects on the High‐Temperature Oxidation Behavior of Polymer‐Derived (Hf,Ta)C/SiC and (Hf,Ti)C/SiC Ceramic Nanocomposites

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