Highly porous α-Al2O3 ceramics obtained by sintering atomic layer deposited inverse opals

Furlan, Kaline P.; Pasquarelli, Robert M.; Krekeler, Tobias; Ritter, Martin; Zierold, Robert; Nielsch, Kornelius; Schneider, Gerold A.; Janßen, Rolf

doi:10.1016/j.ceramint.2017.05.176

Cited by 28 publications

(26 citation statements)

References 30 publications

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“…A detailed analysis of the sintering evolution of noncoated alumina inverse opals can be found elsewhere. [47] After heat treatment at 1400 °C for 4 h (Figure 8c,d), the alumina noncoated opal presented a flattening of the shell-like structure and widening of the lines, strongly supporting the cracks hypothesis, on the one hand. In such case, the opal body shall crack to release the stress imposed by the substrate constraint.…”

Section: Photonic Crystal Stabilitymentioning

confidence: 56%

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: Photonic Crystal Stabilitymentioning

confidence: 56%

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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“…Particular emphasis was placed on exploring the experiment condition for attaining the ceramic particles self-assemble by theoretical calculation and comparing the micro structure characteristics (e.g., pore morphology, pore volume, pore size distribution, retention rate of porosity, specific surface area) between the assembled and un-assembled samples based on the experimental results. The incorporated fabrication means proposed in this paper could be identified as an eco-friendly, convenient and cost-effective method to prepare high-performance porous materials from the point of mutual interactions of the ceramic particles, and the resulting hierarchical networked structure is deemed to be a promising candidate for employment in the areas of filtration or catalysis [20]. In general, our work may provide a new and facile method for the preparation of porous ceramics with high porosity, and the prepared ceramics show excellent stability at high temperature.…”

Section: Introductionmentioning

confidence: 99%

Porous Alumina Ceramics Obtained by Particles Self-Assembly Combing Freeze Drying Method

Feng

Tang

et al. 2019

Materials

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An innovative approach for fabricating porous alumina ceramics is demonstrated in this paper. The distinguished feature is that the construction of the porous structure stems from the interaction between ceramic particles, which is a poorly explored area. By tailoring the Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy to the second minimum, the dilute ceramic slurry would be gelled by the weakly assembled particle network, and the assembled structure is conserved via a freeze drying strategy. The DLVO theoretical analyses revealed that the second minimum of interaction energy could be obtained when the counter-ion concentration in colloidal suspension is 1.5 × 10−2 mol/L. The properties of the as-assembled samples were compared with one produced by the conventional freeze drying method. Results showed that the self-assembly of alumina particles has a positive influence on micro structures. Unlike the laminar pores generated by the traditional freeze drying procedure, the assembled samples show homogeneously interconnected and hierarchical open pores which were stable even after a 24 h dwell time at 950 °C (open porosity is 79.19% for the slurry of vol 20% solid loading). Particularly, after sintering at 1550 °C for 2 h, open porosity (67.01%) of the assembled samples was significantly greater than that of their un-assembled counterparts (39.97%). Besides, the assembled sample shows a narrower pore size distribution and a relatively higher cumulative pore volume.

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“…Moreover, it has to be noted that neither the low nor the high‐alumina mullite composition resulted in structures, which exhibited a photonic bandgap after either burnout or annealing at moderate or high temperatures . We attribute this to two effects acting simultaneously: (a) a low shell thickness and thereby less effective thickness of the structures synthesized here; (b) a slight distortion of the short range ordering during infiltration by spin coating.…”

Section: Resultsmentioning

confidence: 78%

High‐temperature stable inverse opal photonic crystals via mullite‐sol‐gel infiltration of direct photonic crystals

et al. 2018

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Three-dimensionally ordered macroporous materials for photonic or refractory applications have been developed by an innovative approach based on mullite sol-gel infiltration of direct photonic crystals followed by burn-out and calcination. Direct photonic crystals were obtained using polystyrene spheres templates either by vertical convective self-assembly or by drop casting. The samples were then infiltrated by spin coating with mullite sol-gels prepared with two different compositions (74 wt.% Al 2 O 3 , 26 wt.% SiO 2 and 80 wt.% Al 2 O 3 , 20 wt.% SiO 2 ). The inverse opal photonic crystals prepared with both sol-gels presented a highly ordered porosity and the high-alumina composition showed stability up to 1500°C. After inversion of the structure (polymeric template burn-out), the high-alumina composition showed roundness of the PS templated pores closer to an ideal sphere (Ø = 0.967) when compared to the low-alumina composition (Ø = 0.954). Although the inverse opal photonic crystals did not present a photonic bandgap, they showed structural stability at high temperatures, which enable their application as refractory materials.

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Highly porous α-Al2O3 ceramics obtained by sintering atomic layer deposited inverse opals

Cited by 28 publications

References 30 publications

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

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

Porous Alumina Ceramics Obtained by Particles Self-Assembly Combing Freeze Drying Method

High‐temperature stable inverse opal photonic crystals via mullite‐sol‐gel infiltration of direct photonic crystals

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