Crack formation in TiO2 films prepared by sol–gel processing: Quantification and characterization

Bockmeyer, Matthias; Löbmann, Peer

doi:10.1016/j.tsf.2006.11.193

Cited by 60 publications

(40 citation statements)

References 19 publications

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“…It can account for a submicrometer critical cracking thickness as it is often observed in the case of granular films obtained through sol-gel processes (<0.1 m). [31][32][33] Experimentally, the critical cracking thicknesses of the studied films fit reasonably well with this analysis. They can be estimated to be of the order of 100 nm when TiO 2 is deposited on mica and >140 nm when deposited on alumina or silica (Table 3).…”

Section: Influence Of Layer Thickness On the Cracking Of Dried Tio 2 supporting

confidence: 61%

Cracking of titania nanocrystalline coatings

Mahé

Heintz

Rödel

et al. 2008

Journal of the European Ceramic Society

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Cracking of wet-chemically precipitated nanocrystalline TiO 2 films deposited on different platelet-like substrates is investigated. The thicknesses of the films are also in the nanometric range: 60, 140 or 300 nm. Scanning electron microscopy, X-ray diffraction and nitrogen adsorption are employed to determine layer thickness, grain size, and porosity. The synthesis of TiO 2 films through an aqueous route affords very good reproducibility of these properties (layer thickness ±5 nm). Mica, SiO 2 and Al 2 O 3 platelets are used as substrates, providing different properties with regard to surface charge, structure and roughness. The drying step is found to be responsible for the cracking of some of the TiO 2 layers and the evolution of the cracks during sintering is related to shrinkage of the substrate. Film thickness as well as the chemical nature of the substrate influences the cracking of nanocrystalline TiO 2 films during the drying step.

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Section: Influence Of Layer Thickness On the Cracking Of Dried Tio 2 supporting

confidence: 61%

Cracking of titania nanocrystalline coatings

Mahé

Heintz

Rödel

et al. 2008

Journal of the European Ceramic Society

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“…This is particularly common on films made by sol-gel processes as cracks are often thickness-dependent. [8] Here we demonstrate that the microcracks also occur during the drying of a monolithic sol-gel sample and such microcrack surfaces can be utilized as the template to form interconnected silver structures (Scheme 1a). We also show that the density of silver structure is related to the volume shrinkage rate in the drying process while the density is not related to the final annealing stage where the induced stress and reductive polymer environment facilitate the formation of interconnected silver network without causing the sample to disintegrate (Scheme 1b).…”

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confidence: 80%

Controlling Interconnected Silver Network Structure in Sol–Gel Nanocomposite Via Shrinkage‐Induced Stress

2012

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Materials synthesized via solution route sol-gel method are suitable for applications that rely on selectivity in diffusion, [1] size exclusion and filtration, [2] and encapsulation [3,4] because of their intrinsic nanoporous structures. These pore structures that occur spontaneously during the gelation reaction are highly interconnected. Many literatures have reported on how pore diameters, pore structures, and pore volumes can be controlled. [5,6] However, using these nanoscale pores as the template to produce secondary interconnected structures has been difficult due to that limited diffusion and the existing defects usually result in uneven distribution. We have reported that by incorporating low molecular weight polyethylene glycol (PEG), silver nanoparticles and silver chloride nanoparticles inside the pores of sol-gel materials remain mobile and they are able to transport to the surface when the sol-gel material is under shrinkage-induced stress. [7] It is known that silica materials synthesized by sol-gel method tend to shrink during drying. Solvent evaporation causes the pore structure of sol-gel materials to collapse and shrink, and such shrinkage often induce stress, resulting in cracks. This is particularly common on films made by sol-gel processes as cracks are often thickness-dependent. [8] Here we demonstrate that the microcracks also occur during the drying of a monolithic sol-gel sample and such microcrack surfaces can be utilized as the template to form interconnected silver structures (Scheme 1a). We also show that the density of silver structure is related to the volume shrinkage rate in the drying process while the density is not related to the final annealing stage where the induced stress and reductive polymer environment facilitate the formation of interconnected silver network without causing the sample to disintegrate (Scheme 1b).The general procedure for creating interconnected silver network in sol-gel nanocomposites includes preparation of wet gels, followed by aging and drying to form xerogels, and then annealing heat-treatment at 160 8C. The drying step was carried out by heat treatment at various temperatures (40-80 8C) to achieve various degrees of drying states prior to the final annealing step at 160 8C. During the annealing treatment, black samples became sliver reflective color, indicating metallic silver layers have been produced. We have previously reported that interconnected silver layers appear on both surface and internal space of sol-gel materials, and their interconnectivity is related to the amount of polymer in the samples. [7] Here, the sample dimension at each stage was shown in order to evaluate the degree of drying for the drying process (Figure 1). All aged gels retained 85% of the original size of wet gel volume and, respectively, shrank to 78, 72, and 61% of the wet gel size when drying for 4 h at 40, 60, and 80 8C. The final size after annealing is %55% of the wet gel and this value is independent of the drying process. Therefore COMMUNICATION [*] Dr.An inter...

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“…If thermal and intrinsic stress during film formation and cooling exceeds the stability (inner coherence) of the material, cracking is observed. 13 The magnification morphology of plane coatings is shown in Fig. 1b.…”

Section: Methodsmentioning

confidence: 99%

Characterization of wollastonite coatings prepared by sol–gel on Ti substrate

2010

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Wollastonite coatings were prepared by sol-gel on Ti substrate and their microstructures have been studied. The phase compositions and the surface morphologies of these coatings were examined by X-ray diffraction and scanning electron microscopy. Thermal behavior of dried gel was examined by differential scanning calorimetry (DSC) and thermogravimetry (TG). There are many cracks among coatings and particles with size about 200-300 nm distributing inside cracks. DSC and TG results show that the glass transformation temperature of dried gel is about 850°C. After calcined at temperature 900°C, the phase of coatings consists of wollastonite, SiO 2 , and CaSi 2 O 5 .

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Crack formation in TiO2 films prepared by sol–gel processing: Quantification and characterization

Cited by 60 publications

References 19 publications

Cracking of titania nanocrystalline coatings

Cracking of titania nanocrystalline coatings

Controlling Interconnected Silver Network Structure in Sol–Gel Nanocomposite Via Shrinkage‐Induced Stress

Characterization of wollastonite coatings prepared by sol–gel on Ti substrate

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