The pore morphology of fluoride catalyzed xerogels

Chan, Jar-Bee; Hua, Duen-Wu; Winter, Roland; Jonáš, J.

doi:10.1557/jmr.1989.0693

Cited by 10 publications

(4 citation statements)

References 22 publications

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“…The pore volume calculated by the envelope and skeleton density (Table 2) is close to the total pore volume determined by the nitrogen sorption analysis. These results are in agreement with the observations from Fidalgo et al [8] and Chan et al [31]. An increase in the concentration of ammonia respectively NaF during gelation leads to an increase in average pore size and a higher total pore volume.…”

Section: Surface Propertiessupporting

confidence: 93%

“…An increase in the ammonia concentration during gelation leads to a decrease in envelope density and an increase in porosity. Chan et al [31] found that the pore volume is increasing when the gel is synthesized with a higher concentration of NaF which is in agreement with our observed data.…”

Section: Density and Porositysupporting

confidence: 93%

“…A Physi ViewCalc tool from Micromeritics was used to calculate the micropore volume (V Micro ) with the t-plot method [30]. The total pore volume (V total ) was calculated from the volume of nitrogen adsorbed (V ads ) converted to liquid V liq at a pressure close to P/P 0 = 1 [31]. The mesopore volume (V Meso ) was calculated by subtracting the value of V Micro from V total [32].…”

Section: Characterizationmentioning

confidence: 99%

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The influence of the ammonia concentration and the water content on the water sorption behavior of ambient pressure dried silica xerogels

Huber

Comesaña

Koebel

2020

J Sol-Gel Sci Technol

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Porous silica xerogels were synthesized within 10 h by a two-step sol–gel process under atmospheric conditions. In the first step, tetraethylorthosiloxane (TEOS) was hydrolyzed with water using sulfuric acid as a catalyst. In the second step, water and ammonia were added to the prehydrolyzed silica sol prior to the drying of the samples at 150 °C. The influence of the ammonia concentration and the water content on the physicochemical properties and the water sorption behavior of silica xerogels produced in the aforementioned way was investigated. The resulting silica xerogels were characterized by helium pycnometry, scanning electron microscopy, fourier-transform infrared spectroscopy, nitrogen sorption, and water sorption. It was shown that a higher ammonia concentration leads to an increased pore size of the silica xerogel which starts to adsorb water at a higher relative pressure. With an increased water content during gelation, the silica xerogel has a higher specific surface area and a higher water sorption capacity. Furthermore, silica xerogels can be tailored by a controlled addition of ammonia and water to have a higher water sorption capacity than the reference silica gel over the whole range of relative pressure.

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Section: Surface Propertiessupporting

confidence: 93%

Section: Density and Porositysupporting

confidence: 93%

Section: Characterizationmentioning

confidence: 99%

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The influence of the ammonia concentration and the water content on the water sorption behavior of ambient pressure dried silica xerogels

Huber

Comesaña

Koebel

2020

J Sol-Gel Sci Technol

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“…A variety of salts have been shown to have good catalytic activity (249), with F-, fluoride ions, being particularly notable for their effectiveness (94,(253)(254)(255)(256)(257).…”

Section: Saltsmentioning

confidence: 99%

Ceramic‐reinforced polymers and polymer‐modified ceramics

Mark

1996

Polymer Engineering & Sci

327

174

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The composites discussed in this review are prepared using techniques similar to those used in the new sol‐gel approach to ceramics. Organometallis such as silicates, titanates, and aluminates are hydrolyzed in the presence of polymer chains (for example polysiloxanes and polyimides) that typically contain hydroxyl or amino groups. The functional groups are used to bond the polymer chains onto the silica, titania, or alumina being formed in the hydrolysis, thus forming organic‐inorganic composites. When the polymer chains are present in excess, they constitute the continuous phase, with the ceramic‐type material appearing as reinforcing particles. When present in smaller amounts, the polymer is dispersed in the continuous ceramic phase, to give a polymer‐modified ceramic. Under some conditions, bicontinuous systems are obtained. The composites thus prepared are characterized by electron microscopy, X ray, and neutron scattering intensities, density determinations, and stress‐strain and impact‐strength measurements.

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