Foaming phenomena in sol-gel-derived glasses

Matsuyama, Iwao; Susa, K.; Satoh, Shin; Goo, Jaehark

doi:10.1016/0022-3093(92)90024-e

Cited by 8 publications

(8 citation statements)

References 4 publications

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“…Indeed, one can discuss the stability of the sol-gel-derived glass in comparison with the melt one. Matsuyama et al 5 have investigated this point and reported the study of the foaming of solgel materials during consolidation at 1000 °C and at higher temperatures around 2000 °C. A distinction was made between two types of foaming.…”

Section: Introductionmentioning

confidence: 99%

Microstructures and Structural Properties of Sol−Gel Silica Foams

et al. 2005

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Silica xerogels were synthesized and annealed at 1000 degrees C for different durations to yield stable silica materials. The samples were prepared through base-catalyzed hydrolysis and condensation of tetramethyl orthosilicate in methanol. After aging and drying steps, clear and solid xerogels exhibiting a narrow pore size distribution were achieved. The annealing treatment of these xerogels was performed at 1000 degrees C and proved in the present study to lead to a monolithic glass when a progressive heat-treatment procedure was employed to attain 1000 degrees C. In addition to the expected glass, silica foams and ordered phases were observed when the samples were instantaneously heat-treated at 1000 degrees C. Raman spectra of the foamed materials exhibit the classical features of amorphous silica, whereas transmission electronic microscopy pictures reveal the presence of crystallized domains within the vitreous matrix. These crystallites are prone to nucleation and growth processes, which jeopardize the believed stability of the silica foam. The assessment of the hydroxyl content by IR spectroscopy reveals the role played by the latter polycondensation of silanols. The occurrence of foaming process was thus found to result from two competitive phenomena occurring at 1000 degrees C: evacuation of water-related species and viscous sintering.

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Section: Introductionmentioning

confidence: 99%

Microstructures and Structural Properties of Sol−Gel Silica Foams

et al. 2005

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“…A decrease in the content of OH groups can be observed at the NIR range; after 800 °C, three absorption peaks are observed at the NIR range: 1364, 1890, and 2213 nm, which are attributed to hydroxyl groups of water and silanols. , During the densification of the obtained structures, a bloating phenomenon may occur because of the presence of OH groups and water within the structure . When the heating treatment is performed at above 900 °C, the viscosity of the structure decreases and the pressure of the water inside the structure increases, leading to bloating which causes deformation of the structure . Furthermore, at these temperatures, the amorphous silica can crystallize to cristabolite, causing light scattering and loss of transparency .…”

Section: Results and Discussionmentioning

confidence: 98%

“…48 When the heating treatment is performed at above 900 °C, the viscosity of the structure decreases and the pressure of the water inside the structure increases, leading to bloating which causes deformation of the structure. 50 Furthermore, at these temperatures, the amorphous silica can crystallize to cristabolite, causing light scattering and loss of transparency. 51 To avoid these phenomena, the objects were heated slowly under vacuum, to prevent uneven densification and to completely remove the free water and the water generated from merged hydroxyl groups.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Additive Manufacturing of Transparent Silica Glass from Solutions

Cooperstein

Shukrun

Press

et al. 2018

ACS Appl. Mater. Interfaces

121

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A sol, aqueous solution-based ink is presented for fabrication of 3D transparent silica glass objects with complex geometries, by a simple 3D printing process conducted at room temperature. The ink combines a hybrid ceramic precursor that can undergo both the photopolymerization reaction and a sol-gel process, both in the solution form, without any particles. The printing is conducted by localized photopolymerization with the use of a low-cost 3D printer. Following printing, upon aging and densifying, the resulting objects convert from a gel to a xerogel and then to a fused silica. The printed objects, which are composed of fused silica, are transparent and have tunable density and refractive indices.

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“…These can be sintered at lower temperatures than the gels with larger pores [13]. However, before the completion of the sintering, water molecules originating from the condensation of adjacent SiOH groups must be released to avoid explosion and bloating (forming) [14][15][16]. Slow drying is commonly used to suppress inhomogeneous shrinkage during drying and reduce the stress that leads to fracture.…”

Section: General Approachmentioning

confidence: 99%

“…Sol-gel method is a melt-free process and is advantageous for preparing glasses with high melting temperatures, high crystallization tendencies, and compositions within the stable or metastable liquid-liquid immiscibility region. Thus, it has been used to form various monolithic binary silicates containing B 2 O 3 [62][63][64], Al 2 O 3 [62,65], TiO 2 [66][67][68][69][70][71], ZrO 2 [72], GeO 2 [16,40,[73][74][75], Bi 2 O 3 [76], and alkali [77,78] and alkaline earth oxides [79,80]. Multicomponent glasses have also been fabricated [3,4,[81][82][83][84].…”

Section: Binary and Multicomponent Glassesmentioning

confidence: 99%

Recent advances in sol–gel synthesis of monolithic silica and silica-based glasses

Kajihara

2013

Journal of Asian Ceramic Societies

136

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Studies on sol-gel synthesis of monolithic silica and silicate glasses are summarized. Major research efforts have been devoted to avoid the fracture problems, associated with the extensive shrinkage of wet gels during drying. Supercritical drying, incorporation of silica fillers, and reduction of the surface tension of pore liquid have been used to form monolithic dried gels without fracture. More recent studies have shown that wet gels derived from alkoxides can be dried in a relatively short time without fracture at ambient pressure, by employing controlled drying accompanied by the cavitation of the pore liquid, macroscopic phase separation in parallel with gelation, and fluorine modification. By optimizing the synthesis procedure, it is also possible to reduce the use of reagents such as external alcohols, organic solvents, and other additives, which are removed during synthesis and are unnecessary in the final products. Another subject of considerable interest is the development of silica-based functional glasses that are difficult to form by conventional melt-quench and vapor-phase methods, by taking advantage of melt-free processes conducted at relatively low temperatures. Most of the recent studies on the functionalization of sol-gel-derived silica glasses are concerned with the doping of nanoparticles, rare earth ions, and/or fluorine.

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Foaming phenomena in sol-gel-derived glasses

Cited by 8 publications

References 4 publications

Microstructures and Structural Properties of Sol−Gel Silica Foams

Microstructures and Structural Properties of Sol−Gel Silica Foams

Additive Manufacturing of Transparent Silica Glass from Solutions

Recent advances in sol–gel synthesis of monolithic silica and silica-based glasses

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