Sintering of sol-gel films

Scherer, George W.

doi:10.1007/bf02436865

Cited by 96 publications

(82 citation statements)

References 57 publications

(73 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It is also noteworthy that increasing the RTP temperature from 400 to 630 º C consistently reduced the surface area of the xerogels for the pH 1, 4 and 6. This suggest that the densification of the gels is enhanced by thermal effect which causes an increase in the volumetric strain of the network as a result of further evaporation of the remaining solvent from the ES40 gels [44]. The lack of porosity in the RTP pH 2 samples is interesting, though it is consistent with the CTP pH 2 samples.…”

Section: Chapter 5 82supporting

confidence: 57%

High performance ES40-derived silica membranes for desalination

Wang¹

View full text Add to dashboard Cite

Access to potable water has become one of the top 10 global problems facing our contemporary society. Desalination of vast amounts of seawater is a promising measure to ameliorate this stress.Numerous thermal and membrane processes have been employed to desalt seawater, of which reverse osmosis (RO) using polymeric membranes is the most mature technology and has been regarded as the benchmark in current desalination technologies. However, due to the high pressure requirement for RO operation, other membrane processes, such as membrane distillation and pervaporation have been developed as the alternatives to further reduce the energy cost.Furthermore, due to the lack of chemical/thermal stability and high tendency to scaling and fouling of polymeric membranes, novel inorganic membranes, in particular silica derived membranes, are emerging as potential candidates for desalination. The majority of published works on silica membranes utilizes tetraethyl orthosilicate (TEOS) as the silica precursor and interlayers are generally required to reduce the roughness of the porous substrates, followed by 4 to 6 thin-film coatings and calcinations with heating rates of 1-2 º C min -1 to form defect free silica membranes, which consume 10-14 days with extra cost. Therefore, the major target of this research is to produce interlayer-free silica membranes fabricated by rapid thermal processing (RTP) for desalination application.Ethyl silicate 40 (ES40) is used as precursor to prepare silica membranes in this work owing to their superior thermal stability as compared to the TEOS analogous product. Firstly, the sol-gel processing of ES40 was investigated in this thesis. At different temperatures and H 2 O/Si ratios, ES40 underwent various degrees of phase separation behaviour and sol-gel reactions. It was found that the hydrolysis and condensation reactions decreased with decreasing reaction temperature.Dense silica structures were obtained using low H 2 O/Si ratios, whereas higher porosity was produced from a phase-separated sol-gel system with high H 2 O/Si ratios. This tailoring process facilitated further condensation reactions and crosslinking of silica chains, leading to stronger silica matrices which were more resistant to densification.The second part of this work is focused on improvement of the hydrostability of ES40-derived silica membrane materials by adjusting the reactant ratios of sol-gel synthesis process, as the low resistance of silica membranes to water vapor attack, which induce enlargement of the pore size followed by failure in salt rejection, can be detrimental to desalination performance. Investigations were carried out on the effects of reactant ratios on the microstructure of the silica matrices and their hydrothermal stability under harsh conditions (550 °C, 75 mol% vapour). The most hydrothermally stable matrix was obtained by decreasing the ethanol ratio whilst increasing water II and acid ratios. The improved hydrothermal stability was attributed to the further transition of silanol to siloxa...

show abstract

Section: Chapter 5 82supporting

confidence: 57%

High performance ES40-derived silica membranes for desalination

Wang¹

View full text Add to dashboard Cite

show abstract

“…During the solution process used for metal-oxide thin films, metal hydroxides underwent a gradual conversion to metal oxides through either a thermally driven condensation reaction or direct oxidation upon thermal annealing. 23,24 The conversion of the IC to IO is clearly demonstrated in Figure 2c. At the early stage of annealing, thermally driven hydrolysis occurs.…”

Section: Resultsmentioning

confidence: 93%

An ‘aqueous route’ for the fabrication of low-temperature-processable oxide flexible transparent thin-film transistors on plastic substrates

et al. 2013

View full text Add to dashboard Cite

Metal-oxide semiconductors have attracted considerable attention as next-generation circuitry for displays and energy devices because of their unique transparency and high performance. We propose a simple, novel and inexpensive 'aqueous route' for the fabrication of oxide thin-film transistors (TFTs) at low annealing temperatures (that is, o200 1C). These results provide substantial progress toward solution-processed metal-oxide TFTs through naturally formed, unique indium complex and post annealing. The fabricated TFTs exhibited acceptable electrical performance with good large-area uniformity at low temperatures. Additional vacuum annealing facilitated the condensation reaction by effectively removing byproduct water molecules and resulted in the activation of the In 2 O 3 TFT at low annealing temperatures, even temperatures as low as 100 1C. In addition, we have demonstrated that the flexible and transparent oxide TFTs on plastic substrates exhibit good resistance to external gate bias stress. INTRODUCTIONMetal-oxide semiconductors (MOSs) are a unique class of materials that have both transparency and electronic conductivity. 1-3 Increasing demand for transparent semiconducting active materials has resulted in increased attention on the MOSs for next-generation electronics, including electronics for use in high-performance, flexible and transparent applications, because of their favorable field-effect mobility, high optical transparency and good environmental stability. 4,5 In the early studies, these materials were primarily prepared using a vacuum process. 6,7 Although the vacuum-based deposition method has advantages, the high fabrication cost and large-area device uniformity restrict its areas of application. We suggest a simple and novel 'aqueous route' for the fabrication of oxide thin-film transistors (TFTs) at low annealing temperatures (that is, o200 1C). These results provide substantial progress toward solutionprocessed metal-oxide TFTs via a unique indium complex (IC) and post annealing. In addition, we have demonstrated that the flexible and transparent oxide TFTs on plastic substrates exhibit good resistance to external gate bias stress.The solution-based synthesis approach is considered a promising solution to the issues of fabrication cost and device uniformity. This

show abstract

“…The energy gained by the decrease in surface area during densification is equal to the energy dissipated for viscous flow. Frenkel's model is valid within the first 10% of linear shrinkage in which there is considerable neck growth but insignificant densification [29,30]. Corrected neck growth between two spherical particles can be generalised to describe linear rate of shrinkage of an array of particles…”

Section: Resultsmentioning

confidence: 99%

“…where P is the number of pores per particle and it was estimated as 1 for uniform microstructure by assuming simple cubic packing [30]. Experimental values were fitted to the MS model by plotting reduced times derived from theoretical curve (Fig.…”

Section: Resultsmentioning

confidence: 99%

Preparation of monodisperse silica spheres and determination of their densification behaviour

Topuz¹,

Şimşek²,

Çiftçioğlu³

2015

Ceramics International

View full text Add to dashboard Cite

Monodisperse silica spheres in the 50-520 nm size range were prepared by using the Stober process. Diffusive growth has been determined from Nielsen chronomal analysis for the 520 and 310 nm monodisperse silica spheres. The densification behaviour and evolution of the microstructure of the sphere compacts indicated an inverse dependence of shrinkage rate on the sphere size due to viscous sintering. The increase in sphere size from 50 to 500 nm shifted the densification temperature from $ 1120 1C to 1240 1C. The amorphous nature of the spheres was conserved up to 1200 1C where cristobalite crystal nucleation started and complete transformation to cristobalite phase has been observed upon heat treatment at 1300 1C. The activation energies for viscous sintering according to the Frenkel and Mackenzie/Shuttleworth models were calculated as 125 and 335 kJ/mol, respectively. These substantially low activation energies can be attributed to the presence of a significant level of silanol groups.

show abstract

Sintering of sol-gel films

Cited by 96 publications

References 57 publications

High performance ES40-derived silica membranes for desalination

High performance ES40-derived silica membranes for desalination

An ‘aqueous route’ for the fabrication of low-temperature-processable oxide flexible transparent thin-film transistors on plastic substrates

Preparation of monodisperse silica spheres and determination of their densification behaviour

Contact Info

Product

Resources

About