Water Adsorption and Desorption Kinetics on Silica Insulation

Feng, A.; McCoy, Benjamin J.; Munir, Zuhair A.; Cagliostro, D. E.

doi:10.1006/jcis.1996.0300

Cited by 48 publications

(51 citation statements)

References 3 publications

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“…Feng and co-workers [34] studied the rate of adsorption and desorption of water on silica surface by gravimetric, FTIR and X-ray photoelectron spectroscopy. They heated silica powder in vacuum from 200-1000 o C and analyzed IR spectra of silica and found that the silica surface becomes hydrophobic on thermal treatment but then becomes hydrophilic immediately on contact with water at low temperature.…”

Section: Methodsmentioning

confidence: 99%

Influence of relative humidity on the wettability of silicon wafer surfaces

Hołysz¹,

Mirosław²,

Terpiłowski³

et al. 2008

Annales UMCS, Chemistry

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Investigation of wetting properties of the original silicon wafers and modified by oxidation was carried out by contact angles measurements of water at varying relative humidity (RH) of the atmosphere present in the measuring chamber. At three selected humidities (10, 30 and 50%) contact angles of diiodomethane and formamide were also determined for the original silicon wafer only. The topography of the tested surfaces was determined with the help of atomic force microscopy (AFM). Using the measured contact angles the total apparent surface free energy and its components of studied silicon wafers were determined using two models: the contact angle hysteresis (CAH) and Lifshitz-van der Waals acid-base (LWAB) approaches. In the former approach the advancing and receding contact angles are employed, and in the latter only the advancing angles. It was found that in the case of original silicon wafer the contact angels and surface free energy depend on the humidity only in the RH range from 10 to 40% with a minimum at 30% RH, and then they fluctuate around a mean value. For the oxidized silicon wafer the changes in the contact angles and the surface free energy depend on the relative humidity and change periodically with increasing RH. These changes can result from water adsorption on the hydrophilic silicon surface.

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Section: Methodsmentioning

confidence: 99%

Influence of relative humidity on the wettability of silicon wafer surfaces

Hołysz¹,

Mirosław²,

Terpiłowski³

et al. 2008

Annales UMCS, Chemistry

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“…The number of surface silanol sites (SiOH) on porous silica increases on water adsorption. 19,20 We found that, in the region of multilayer adsorption (º < 0.3), more water is adsorbed in the second than in the first measurement, but the rate constant is the same in both measurements. This suggests that an increase in the number of silanol sites does not significantly affect the rate constant for water adsorption.…”

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confidence: 76%

Kinetic Analysis of the Adsorption of Polar and Nonpolar Molecules onto Ordered Mesoporous Silica Using the Pressure-feedback Method

et al. 2015

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The rate constants for the adsorption of water and nitrogen onto ordered mesoporous silica SBA-15 were determined at 298 and 77 K, respectively, using the novel pressure-feedback method (PFM) that measures the rate of adsorption directly. The rate constant for the adsorption of water is smaller than that of nitrogen, even though the adsorption of water was measured at a higher temperature (298 K) than that of nitrogen (77 K).Gas-adsorption phenomena involving porous materials have various applications, such as gas storage, gas separation, removal of toxic substances, and heat transfer.1 These applications have mainly been investigated using equilibrium-state data, such as adsorption isotherms and heats of adsorption. However, knowledge about adsorption kinetics is important for the application of adsorption technologies. For gas-storage applications, it is important that not only large amounts of gases can be stored, but quick and low-energy adsorption/desorption switching is also desirable. Mesoporous silica attracts attention in the areas of catalysis, 24 photosensitive materials, 37 and other new functionalized mesoporous materials, 8,9 and understanding of adsorption kinetics is of great importance to such applications. Furthermore, knowledge about the rate of adsorption of water is important because the adsorption of the target gas is frequently obstructed by the adsorption of water. 10Recently, the discovery of new porous materials, such as metalorganic frameworks (MOFs), porous coordination polymers (PCPs), and periodic mesoporous organosilicates (PMOs), 11 has enabled the design of pore structure and pore functionality. Most of the investigations on these materials have been focused on the equilibrium state of the adsorption process; the kinetics have not yet been investigated enough because they are difficult to measure. Therefore, the relationship between macroscopic kinetic data (such as adsorption rate constants) and microscopic structures of porous materials remains unclear. A systematic investigation of adsorption kinetics is needed to improve the functions of porous materials. Furthermore, to understand the kinetic behavior on a microscopic level, the microscopic and macroscopic information must be measured simultaneously. However, performing such in situ measurements with a conventional microbalance is quite difficult. Therefore, we have recently developed a new kinetic measurement method that does not require a microbalance: the pressure-feedback method (PFM). 12Using this method and a metal sample cell, we were successful in directly measuring adsorption rates as a function of time and assessing the adsorption rate constants with high accuracy.In this paper, we report the kinetics of the adsorption of polar (water) and nonpolar (nitrogen) molecules onto mesoporous silica SBA-15, which we recorded with our apparatus. The adsorption isotherms of water and nitrogen are of IUPAC types V and IV, respectively. This suggests that both water and nitrogen, when adsorbed onto mesopore surfaces, first for...

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“…This assignment is in agreement with recently publications of TPD data of water desorption from silica surfaces. 6,7,9 In these publications, physisorbed water was reported to have activation energies in the range …”

Section: Resultsmentioning

confidence: 99%

“…These peaks are associated with physisorbed and chemisorbed water from silica surfaces. 6,7 Note that, except for an observed shift of the desorption peaks to higher temperatures, the general features of the TPD spectra do not change with increases in the ramp rate from 0.3 to 3.3 K/s. In agreement with many recent reports on water desorption from silica, we associate the lowest desorption peaks in each spectra to physisorbed water.…”

Section: A Comparison Among the Analysis Techniquesmentioning

confidence: 93%

“…In agreement with many recent reports on water desorption from silica, we associate the lowest desorption peaks in each spectra to physisorbed water. 6,7 As will be shown later, physisorbed water can be effectively pumped out in a vacuum environment at room temperature while chemisorbed water cannot. This explains why the ratios of the desorption-peaks at temperatures below 450 K to the desorption-peaks at higher temperatures vary from sample to sample depending on the pumping time prior to TPD experiment as seen in Fig Later on, we will deconvolve these broad and/or extended desorption peaks into distinct desorption curves using the technique of iterative regression analysis to obtain more detailed information on the kinetic parameters associated with these peaks.…”

Section: A Comparison Among the Analysis Techniquesmentioning

confidence: 98%

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Desorption Kinetics of H2O from Cab-O-Sil-M-7D and Hi-Sil-233 Silica Particles

Dinh¹,

Balooch²,

LeMay³

2000

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Temperature programmed desorption (TPD) was performed at temperatures up to 850K on Cab-O-Sil-M-7D and Hi-Sil-233 silica particles. Physisorbed water molecules on both types of silica had activation energies in the range of 9-14.5 kcal/mol. However, the activation energies of desorption for chemisorbed water varied from ~ 19 kcal/mol to > 59 kcal/mol for Cab-O-Sil-M-7D, and ~ 23-37 kcal/mol for Hi-Sil-233. Our results suggest that physisorbed water can be effectively pumped away at room temperature (or preferably at 320 K) in a matter of hours. Chemisorbed water with high activation energies of desorption (>30 kcal/mol) will not escape the silica surfaces in 100 years even at 320 K, while a significant amount of the chemisorbed water with medium activation energies (19-26 kcal/mol) will leave the silica surfaces in that time span. Most of the chemisorbed water with activation energies < 30 kcal/mol can be pumped away in a matter of days in a good vacuum environment at 500 K. We had previously measured about 0.1-0.4 wt. % of water in M9787 polysiloxane formulations containing ~ 21% Cab-O-Sil-M-7D and ~ 4% Hi-Sil-233. Comparing present results with these formulations, we conclude that absorbed H 2 O and Si-OH bonds on the silica surfaces are the major contributors to water outgassing from M97 series silicones.2

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Water Adsorption and Desorption Kinetics on Silica Insulation

Cited by 48 publications

References 3 publications

Influence of relative humidity on the wettability of silicon wafer surfaces

Influence of relative humidity on the wettability of silicon wafer surfaces

Kinetic Analysis of the Adsorption of Polar and Nonpolar Molecules onto Ordered Mesoporous Silica Using the Pressure-feedback Method

Desorption Kinetics of H2O from Cab-O-Sil-M-7D and Hi-Sil-233 Silica Particles

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