Review of mullite synthesis routes by sol–gel method

Cividanes, Luciana De Simone; Campos, Tiago Moreira Bastos; Rodrigues, Liana Álvares; Brunelli, Deborah Dibbern; Thim, Gilmar Patrocínio

doi:10.1007/s10971-010-2222-9

Cited by 161 publications

(87 citation statements)

References 94 publications

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“…[26] Sintering of mullite powders usually requires high temperatures for densification because of the low bulk and grain-boundary diffusion coefficients and the processing of nanosized powders to full density is a remaining challenge. [27] Manufacturing mullite by sintering of silica and alumina powders usually requires temperatures of 1450 °C or even higher for phase conversion, [28] with undesired resulting glassy phase from silica sources.…”

Section: Introductionmentioning

confidence: 99%

Low‐Temperature Mullite Formation in Ternary Oxide Coatings Deposited by ALD for High‐Temperature Applications

Furlan

Krekeler

Ritter

et al. 2017

Adv Materials Inter

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coatings on geometrically complex substrates, [2][3][4] such as anodic aluminum oxide membranes, aerogels, photonic crystals, and nanorods, with a film thickness control on the Å-scale. Additionally, by combining two or more binary ALD processes in a super cycle ALD process, multicomponent materials can be achieved, such as nanolaminates, doped thin films, and ternary or quaternary oxides. [5] The ability of compositional control of thin films at an atomic level provides the possibility for development of tailor-made atomically mixed systems, pointing to novel materials functionalities.Direct and inverse opals are examples of photonic crystals, which can be manufactured by colloidal self-assembly [6,7] and ALD. [8,9] Its high ordered porosity of interconnects is attractive for a variety of technological applications, such as porous membranes, catalysts, solid oxide fuel cells, and photonics applications. [10][11][12] The 3D periodic arrangement of pores provides a photonic bandgap to these artificial materials, which prohibits the transmission and hence leads to a reflection of electromagnetic radiation in spectral range which is determined by the materials' properties. Specifically, the radiation wavelength, which will be reflected, is influenced by the material microstructure assemble, mono-or multistacked, and also the macropore size. [8,9,[13][14][15] This selective behavior in transmission and reflection might pave the way to effective solar thermo photovoltaic energy conversion devices [16,17] and also next-generation thermal barrier coatings.However, retention of the 3D structure for high-temperature applications remains a significant challenge. [10,18] As the length scales in these porous materials are decreased, as higher is the surface area and specific activity. When exposed to high temperatures, the material's structure may suffer from detrimental morphological changes, such as extensive grain growth, distortion, and eventually destruction of the total periodically organized structure. [9,10] Therefore, this material needs to not only interact with electromagnetic radiation but also have structural stability and keep its function up to high temperatures (usually higher than 1000 °C). The latter fact could be addressed by coating the substrate material with a ceramic oxide that is stable at high temperatures, either by chemical vapor deposition (CVD) [19] or ALD [20] processes.Herein, mullite has been chosen: A ceramic material, which is well known for its stability at high-temperature environments, Atomic layer deposition (ALD) process presents thickness control in an Ång-strom scale due to its inherent surface self-limited reactions. In this work, an ALD super cycle approach, where a superposition of nanolaminates of SiO 2 and Al 2 O 3 is generated by cycling the precursors APTES-H 2 O-O 3 and TMA-H 2 O, is used to deposit thin films with varying ratio of Al 2 O 3 :SiO 2 into silicon wafers and into inverse photonic crystals. The resulting ternary oxide films deposited at low temperature (150 °C) ar...

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Section: Introductionmentioning

confidence: 99%

Low‐Temperature Mullite Formation in Ternary Oxide Coatings Deposited by ALD for High‐Temperature Applications

Furlan

Krekeler

Ritter

et al. 2017

Adv Materials Inter

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“…3. FTIR band at 1,170 cm -1 is more intense than the band at 1,130 cm -1 for orthorhombic mullite, while the opposite indicates the domination by the tetragonal phase [23]. The absence of band in the 1,070-1,090 cm -1 range indicates that there is no amorphous silica phase in the oxide network [8].…”

Section: Membrane Characterizationmentioning

confidence: 88%

“…4. There is no indication for the formation of the spinel phase (sharp 2h peaks at 46 and 67°) indicating the formation of a very homogeneous structure because of a high degree of mixing [12,23]. A transient phase (spinel) formation is generally Fig.…”

Section: Membrane Characterizationmentioning

confidence: 99%

“…A transient phase (spinel) formation is generally Fig. 2 DLS particle size distributions of 2 months aged (processing step #3 sols) polymeric boehmite sol observed in the diphasic systems due to heterogeneities created by uncontrolled hydrolysis reactions before mullite crystallization [23].…”

Section: Membrane Characterizationmentioning

confidence: 99%

“…Kansal et al [12] used the splitting of the peak at 26.15°2h in tetragonal mullite (on heat treatment at temperatures above 1,000°C) as a means of estimating the extent of conversion of the tetragonal phase to the orthorhombic phase. Orthorhombic phase is a more stable structure compared to the metastable tetragonal phase which is characterized by the XRD peak at 26.15°(2h CuKa) [23]. The extended scale of 2h values in 25-27°range is shown in the insert in Fig.…”

Section: Membrane Characterizationmentioning

confidence: 99%

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Preparation and characterization of diphasic sol-gel derived unsupported mullite membranes

Topuz

Çiftçioğlu

2010

J Sol-Gel Sci Technol

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Diphasic gels prepared by mixing freshly prepared polymeric silica and polymeric boehmite sols through a modified Al-alkoxide route in mullite compositions led to the crystallization of mullite upon heat treatment at 775°C. Mullite formation was observed at a 100°C higher temperature when diphasic gels were formed by mixing aged polymeric sols containing about 2 nm in diameter boehmite species. These relatively low mullite formation temperatures were attributed to the nanoscale sizes of the polymeric species of the two amorphous phases present in the diphasic gels.

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