Determination of surface areas by thermoporometry

Quinson, J.F.; Astier, M.; Brun, M.

doi:10.1016/s0166-9834(00)81016-7

Cited by 36 publications

(17 citation statements)

References 18 publications

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“…The heat-flow accompanied with freezing of water or thawing of ice within the porous solid is recorded as a function of the temperature in a linear temperature program. Thermoporometry enables one to measure ice ~" 2 and the penetration of the ice-meniscus in the solid, c ~ 10 j ~ crystal radii, R,, between 1 and 150 nm (Quinson et aL, 1987). The minimum value of 1 nm of the radius, Rn, that can be measured is due to 1) the minimum temperature of 210 K that can be established within the DSC apparatus used in this work with gaseous nitrogen as a cooling agent and 2) the fact that water present in pores of radii, Rp, smaller than approximately 1 nm or interlayer distances smaller than 2 nm is strongly bonded to the surface of the pore and does not freeze (Ehrburger et al, 1985).…”

Section: Theoretical Backgroundmentioning

confidence: 99%

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Characterization of Tubular Chrysotile by Thermoporometry, Nitrogen Sorption, Drifts, and TEM

Titulaer

1993

Clays and clay miner.

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Abstract--The maximum crystal radius R. of ice in hollow wet chrysotile tubes is established by thermoporometry to be between 2.8 and 3.2 nm, and the internal pore volume Vn of the tubes to be between 0.008 and 0.02 ml/g. The hollow tubes of chrysotile and, for comparative reasons, small plates of talc, are hydrothermally synthesized at temperatures between 563 and 600 K and at pressures between 75 and 120 hPa. Size and shape of the pores can be varied by changing the Mg/Si molar ratios in steps of 3/1.5 and 3/2 for chrysotile and 3/3.6 and 3/4 for talc. The tubular morphology of the aggregates dried at 393 K is investigated by 1) transmission electron microscopy (TEM), 2) nitrogen adsorption and desorption at 77 K, and 3) diffuse reflectance infrared fourier transformed spectroscopy (DRIFTS). The radius within the hollow tubes, R~, is between 2.5 and 4.0 nm as measured by TEM, and between 2.8 and 3.2 nm as determined by nitrogen adsorption and desorption. The measured radii agree well with the value calculated from crystallographic data, which is smaller than 5.3 nm. Within the dried aggregates the tubes are clustered in regular patterns, in which each tube is surrounded by six other tubes. The external radius, Ro, between the clustered tubes is from 1.6 to 2.9 nm as observed by TEM, and from 1.8 to 2.3 nm by Nz adsorption and desorption. The external radius is not measured by thermoporometry. Where thermoporometry only measures the average pore size and pore volume within the tubes, TEM and N2 adsorption and desorption additionally provide the corresponding values between the tubes. A third pore radius, 5 to 20 nm between the clusters of chrysotile tubes, is established with N2 adsorption and desorption.

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Section: Theoretical Backgroundmentioning

confidence: 99%

“…(8). The theoretical value ofF varies between 1 and 2, with a spherical and a cylindrical pore shape, respectively (Quinson et al, 1987):…”

Section: Freezing and Thawing Hysteresis The Shape Factor Fmentioning

confidence: 99%

Characterization of Tubular Chrysotile by Thermoporometry, Nitrogen Sorption, Drifts, and TEM

Titulaer

1993

Clays and clay miner.

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“…Thermoporometry was developed based on the relationship established between the size of the pores in which solidification occurs and the temperature of the triple point of the divided liquid, and the relationship between the temperature and the apparent solidification energy (Brun et al, 1977;Quinson et al, 1987). The pore radius was found related to triple point temperature of water in a porous material as:…”

Section: Characterization Of Sol-gel In the Wet State-thermoporometrymentioning

confidence: 99%

Characterization of sol‐gel entrapped chlorophyllase

Kermasha

Neufeld

2006

Biotech & Bioengineering

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Immobilization of membrane proteins remains a challenge compared to soluble proteins. The membrane protein-chlorophyllase was successful entrapped in tetramethoxysilane (TMOS)-based sol-gel in the presence of lipid. Activity was examined against mixing rate, incubation temperature, time, substrate, acetone, and canola oil concentration. The external mass transfer of chlorophyll is not the rate-limiting step at higher mixing rates. Stability against temperature and acetone as denaturant was enhanced. In spite of the fact that an initial reaction lag phase was observed, 20% more chlorophyll was hydrolyzed, compared to reaction with free enzyme by the end of a 12 h assay. The initial lower activity demonstrated by entrapped chlorophyllase is likely due to the diffusion resistance of chlorophyll into and within the entrapment matrix. This hypothesis was substantiated by a low diffusion coefficient on the order of 10(-14) m(2)/s obtained for chlorophyll in nanoporous sol-gel particles. Pore size distribution of nanoporous wet TMOS-based sol-gel with or without protein was determined by thermoporometry. The change in pore morphology upon doping with chlorophyllase suggests that protein acts as a template during the sol-gel process.

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“…(1) it gives the actual size of the cavities instead of indicating the size of the (2) it can be performed on nonrigid materials, and (3) it can be used for the study of materials in the medium in which they are opening, applied.…”

Section: Introductionmentioning

confidence: 99%

“…The method is not sensitive to the micropores since their size is about the same as the thickness of the liquid-like layer (0.8 nm) [2]. The upper limit, or the largest pore size that can be determined successfully by thermoporometry, is set by the effect of the curvature on the freezing point depression of water.…”

Section: Introductionmentioning

confidence: 99%

Thermoporometry

Stcker¹

2002

Handbook of Porous Solids

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The texture of porous materials with pore diameters larger than about 2 nm can be characterized by a calorimetric investigation of the liquid-solid state transition of a capillary condensate saturating these materials. The method, called thermoporometry, is based on the thermodynamic conditions of the liquid-solid transformation of the capillary condensate inside the porous material [l, 21. Thermoporometry is mainly used for the determination of pore-size distribution. Upon solidification and melting of a condensate that totally saturates the porous material, the phase change takes place inside the pores and no material transport occurs. This is not the case in most adsorption experiments. The resulting freezing-point depression of the confined probe molecules and the thermal energy released or absorbed are measured as a hnction of the temperature [3]. The thermal analysis of these transformations for condensates such as water or benzene leads to the pore-size distribution through the "solidification curve". The pore shape is related to the hysteresis phenomenon observed between the solidification and melting curves, allowing a shape factor to be calculated. Thermoporometry has the following advantages:(1) it gives the actual size of the cavities instead of indicating the size of the (2) it can be performed on nonrigid materials, and (3) it can be used for the study of materials in the medium in which they are opening, applied.Thermoporometry can be used also for studying materials in which the pore diameters are in the range of approximately 2-30 nm (i.e., in the mesopore range).

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Determination of surface areas by thermoporometry

Cited by 36 publications

References 18 publications

Characterization of Tubular Chrysotile by Thermoporometry, Nitrogen Sorption, Drifts, and TEM

Characterization of Tubular Chrysotile by Thermoporometry, Nitrogen Sorption, Drifts, and TEM

Characterization of sol‐gel entrapped chlorophyllase

Thermoporometry

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