Stress Evolution and Cracking in Sol–Gel-Derived Thin Films

Kozuka, Hiromiutsu

doi:10.1007/978-3-319-19454-7_12-1

Cited by 4 publications

(6 citation statements)

References 64 publications

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“…However, when preparing dense or mesoporous films above 1 μm in thickness by a single coating step, using nanoparticle dispersions or sol−gel precursor solutions, the films are prone to crack during the firing step. 34 The cracking originates most prominently from the in-plane tensile stress development during the annealing, referred to as the intrinsic in-plane stress, which includes solvent evaporation and densification processes shrinking the films to 70% of their initial thickness. 35 During the cooling procedure to room temperature, the difference in the thermal expansion coefficients between the substrate and the film either raises or lowers the in-plane stress observed at room temperature labeled as the residual in-plane stress.…”

Section: ■ Introductionmentioning

confidence: 99%

“…35 During the cooling procedure to room temperature, the difference in the thermal expansion coefficients between the substrate and the film either raises or lowers the in-plane stress observed at room temperature labeled as the residual in-plane stress. 34 For the successful preparation of thicker films without repetitive deposition, the in-plane stress must be kept low, which can be obtained by introducing additives, for example, polymers or chelating agents to the precursor solutions. 36 In a previous study, we were able to demonstrate the inplane stress development of sol−gel-derived mesoporous titania and ceria-zirconia thin films revealing the impact of the used structure-directing agent and different sol−gel precursors such as metal alkoxides and chlorides on the inplane stress during the heat treatment until 500 °C.…”

Section: ■ Introductionmentioning

confidence: 99%

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Comparison of In-Plane Stress Development in Sol–Gel- and Nanoparticle-Derived Mesoporous Metal Oxide Thin Films

et al. 2019

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By using an evaporation-induced self-assembly (EISA) process, mesoporous metal oxide thin films are prepared via molecular precursors undergoing a sol–gel transition or by using nanoparticle dispersions as the starting materials. Both methods are employed together with PIB50-b-PEO45 as the structure-directing agent to produce porous TiO2 and ZrO2 thin films with spherical mesopores of around 14 nm in diameter. These nanoparticle- and sol–gel-derived films were investigated in terms of the intrinsic in-plane stress development during the heat treatment up to 500 °C to evaluate the impact of solvent evaporation, template decomposition and crystallization on the mechanical state of the film. The investigation revealed the lowest intrinsic stress for the nanoparticle-derived mesoporous film, which is assigned to the combination of the relaxing effects of the utilized diblock copolymer and the interparticular gaps between the precrystalline nanoparticles. Furthermore, the residual in-plane stress was studied after annealing steps ranging from 300 to 1000 °C and cooling down to room temperature. Here, TiO2 nanoparticle-derived mesoporous films possess a lower residual stress than the sol–gel-derived mesoporous films, while in the case of ZrO2 films, sol–gel-derived coatings reveal the smallest residual stress. The latter is based on the lower thermal expansion coefficient of the dominant monoclinic crystal phase compared to that of the silicon substrate. Hence, the present crystal structure has a strong influence on the mechanical state. The observation in this study helps to further understand the stress-related mechanical properties and the formation of mesoporous metal oxides.

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Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Comparison of In-Plane Stress Development in Sol–Gel- and Nanoparticle-Derived Mesoporous Metal Oxide Thin Films

et al. 2019

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“…The residual strain in sol-gel films depends on the processing parameters, and in general, as shown in Fig. 6.6, the uniaxial shrinkage in the direction perpendicular to the substrate produces tensile stress in the film and compressive stress in the substrate [8,9]. The presence of the organic template does not reduce the stresses generated during the shrinkage of supported films, and the formation of linear dislocations is favoured because it helps to release the induced strain.…”

Section: Dislocationsmentioning

confidence: 99%

“…The growth of twin mesophases is favoured when self-assembly occurs in a film which has a limited A, B, and C) on the left side denote the packing sequence of the {111} planes. Reproduced with permission from [9] thickness and restricts the growth along the vertical direction to the substrate. Preferentially the domains grow parallel to the surface and when they meet they create an interface because the energy at the interface is minimized by the formation of a twin because a twin boundary is a low energy interface.…”

Section: Planar Defects "Polycrystalline-monocrystalline" Mesostructuresmentioning

confidence: 99%

From Defects to Controlled Alignments

Innocenzi

2021

Advances in Sol-Gel Derived Materials and Technologies

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One of the most important challenges to be faced in the self-assembly of mesoporous films is the control of the organization on a dimensional scale that extends beyond the micron. Furthermore, defects of different types can form during the self-assembly process, similarly to what is observed in crystalline structures. Defect control is critical because many of the material's functional properties are directly dependent on them. Point or linear defects are observed both in atomic and liquid crystal structures and similarly in mesoporous materials. The other challenge to be faced is reducing the number of so-called punctual defects and obtaining an organization of the porosity on a macroscopic scale. Precisely as in the case of atomic crystals in which polycrystalline structures with domains oriented within every single crystallite, different organized structures are observed in mesoporous films, as discussed in previous chapters. Typically the order is confined to within a few microns.

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“…Although MTMS and DMDMS have been reported to eliminate cracking in the polymers, cracking was observed in some of the OSX polymers prepared. It is thought that the stress put upon the polymer as it equilibrates from the high reaction temperature to room temperature may account for the cracks [ 32 ]. To reduce the possibility of cracks forming in the polymers, the temperature was decreased to 25 °C (room temperature).…”

Section: 1 Preparation Of Organosiloxane (Osx) Polymersmentioning

confidence: 99%

Pathogen-Imprinted Organosiloxane Polymers as Selective Biosensors for the Detection of Targeted E. coli

Dulay¹,

Zaman²,

Jaramillo³

et al. 2018

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Early detection of pathogens requires methods that are fast, selective, sensitive and affordable. We report the development of a biosensor with high sensitivity and selectivity based on the low-cost preparation of organosiloxane (OSX) polymers imprinted with E. coli-GFP (green fluorescent protein). OSX polymers with high optical transparency, no cracking, and no shrinkage were prepared by varying several parameters of the sol-gel reaction. The unique shape and chemical fingerprint of the targeted inactivated E. coli-GFP were imprinted into bulk polymers by replication imprinting where the polymer solution was dropcast onto a bacteria template that produced a replica of the bacterial shape and chemistry on the polymer surface upon removal of the template. Capture performances were studied under non-laminar flow conditions with samples containing inactivated E. coli-GFP and compared to inactivated S. typhimurium-GFP. Capture selectivity ratios are dependent on the type of alkoxysilanes used, the H 2 O:silane molar ratio, and the polymerization temperature. The bacteria concentration in suspension ranged from~6 × 10 5 to 1.6 × 10 9 cells/mL. E. coli-imprinted OSX polymers with polyethylene glycol (PEG) differentiated between the targeted bacterium E. coli, and non-targeted bacteria S. typhimurium and native E. coli-GFP, achieving selectivity ratios up to 4.5 times higher than polydimethylsiloxane (PDMS) and OSX polymers without PEG.

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Stress Evolution and Cracking in Sol–Gel-Derived Thin Films

Cited by 4 publications

References 64 publications

Comparison of In-Plane Stress Development in Sol–Gel- and Nanoparticle-Derived Mesoporous Metal Oxide Thin Films

Comparison of In-Plane Stress Development in Sol–Gel- and Nanoparticle-Derived Mesoporous Metal Oxide Thin Films

From Defects to Controlled Alignments

Pathogen-Imprinted Organosiloxane Polymers as Selective Biosensors for the Detection of Targeted E. coli

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