Mercury porosimetry contact angle

Salmas C. and G. Androutsopoulos (2001). Mercury porosimetry Contact angle hysteresis of materials with controlled pore structure . Journal of Colloid and Interface Science 239 178-189. 

The wetting ability of the anode electrode was evaluated as the contact angle measured by the capillary rise method. The value of fractal dimension of anode electrode of MCFC was calculated by use of the nitrogen adsorption (fractal FHH equation) and the mercury porosimetry. 

Anode electrode Sintering temp. ("C) Initial porosity (%) FHH equation (Nitrogen adsorption) Mercury porosimetry Average Ds- Contact Angle with electrolyte 0C)... 

The experimental method of mercury porosimetry for the determination of the porous properties of solids is dependent on several variables. One of these is the wetting or contact angle between mercury and the surface of the solid. 

Using low-pressure porosimetry, Winslow measured contact angles by determining the breakthrough pressure required to force mercury into numerous holes drilled into the surface of solid discs. 

Pore size distributions are often determined by the technique of mercury intrusion porosimetry. The volume of mercury (contact angle c. 140° with most solids) which can be forced into the pores of the solid is measured as a function of pressure. The pore size distribution is calculated in accordance with the equation for the pressure difference across a curved liquid interface,... 

The poly-[HIPE] sample intrusion mercury porosimetry study reported in Figure 4.67 was carried out in a Micromeritics, Atlanta, GA, USA, AutoPore IV-9500 automatic mercury porosimeter.1 The sample holder chamber was evacuated up to 5 x 10-5 Torr the contact angle and surface tension of mercury applied by the AutoPore software in the Washburn equation to obtain the pore size distribution was 130° and 485mN/m, respectively. Besides, the equilibration time was 10 s, and the mercury intrusion pressure range was from 0.0037 to 414 MPa, that is, the pores size range was from 335.7 to 0.003 pm. The poly-(HIPE) sample was prepared by polymerizing styrene (90%) and divinylbenzene (10%) [157],... 

The applied pressure is related to the desired pore size via the Washburn Equation [1] which implies a cylindrical pore shape assumption. Mercury porosimetry is widely applied for catalyst characterization in both QC and research applications for several reasons including rapid reproducible analysis, a wide pore size range ( 2 nm to >100 / m, depending on the pressure range of the instrument), and the ability to obtain specific surface area and pore size distribution information from the same measurement. Accuracy of the method suffers from several factors including contact angle and surface tension uncertainty, pore shape effects, and sample compression. However, the largest discrepancy between a mercury porosimetry-derived pore size distribution (PSD) and the actual PSD usually... 

Incorporation of appropriate contact angles in textural characterization by mercury porosimetry... 

Incorporation of the measured contact angle in mercury intrusion porosimetry data is essential for an accurate determination of the pore size distribution. Both the advancing and static angle methods are suitable to carry out this measurement, leading to very similar results. For most oxidic materials and supported oxides, the contact angle is 140° and incorporation of the actual contact angle is less critical in the pore size determination. However, important deviations are observed in carbon and cement-like materials, with contact angles of > 150° and < 130°, respectively. This has been shown by comparison of the pore size distribution obtained from mercury porosimetry and N2 adsorption measurements. 

Nitrogen sorption measurements were performed by use of a Sorptomatic 1900 Turbo apparatus by Carlo Erba Instruments. All samples were degassed at 393 K before measurement for at least 24 hours at 10 mbar. The mercury porosimetry measurements were carried out on a Porosimeter 2000 apparatus by Carlo Erba Instruments. A contact angle of 141.3° for Hg was used. The samples were degassed at 393 K before measurement for 24 h. SEM of the porous glass membranes was carried out on a Phillips ESEM XL 30 PEG microscope. 

The mercury porosimetry experiments were carried out using an Autopore 9220 apparatus (Micromeritics). Around 4 g of sample were placed into the penetrometer. The initial results were obtained on a low pressure port between 0.004 and 0.1 MPa. The high pressure curve was obtained up to 400 MPa before extrusion and reintrusion. A contact angle of 130° was used to interpret the results using the Washburn equation. 

In this study mercury intrusion porosimetry (MIP) analyses were employed to determine the pore size distribution and pore volume over the range of approximately 100 pm down to 7.5 nm diameter, utilising CE Instruments Pascal 140/240 apparatus, on samples previously dried overnight at 150°C. The pressure/volume data were analysed by use of the Washburn Equation [14] assuming a cylindrical nonintersecting pore model and taking the mercury contact angle as 141° and surface tension as 484 mN m [10]. For the monolith... 

Mercury porosimetry is performed nearly exclusively on automatic commercial instruments that differ mainly in the highest operative pressure, which determines the size of smallest attainable pores. The highest pressure is limited by the uncertainty about the validity of the Washburn equation, which forms the basis of data evaluation. In pores with sizes similar to the mercury atom the assumption that physical properties of liquid mercury (surface tension, contact angle) are equal to bulk properties is, probably, not fully substantiated. For this reason the up-to-date instruments work with pressures up to 2000 - 4000 atm, only. 

Below 45 MPa, the high dispersive precipitated silica sample with or without membrane collapses without mercury intrusion. The buckling mechanism of pores edges can be assumed as in the case of low density xerogels. Consequently, equation (2) can be used to interpret the mercury porosimetry curve in this low pressure domain. The constant A, to be used in equation (2) can be calculated from the P, value using equation (4). With a mercury surface tension 0.485 N/m, a contact angle 0= 130° and P, = 45 MPa, one obtains K = 86.3 nm MPa" . 

Another technique for measurement of pore-size distributions is mercury poro-simetry [9]. Because mercury does not wet the surface of oxides (the contact angle varies from 135 to 143 °), pressure is required to force mercury into the pores. The pressure at which mercury is taken up indicates the diameter of the pores, and the volume of mercury intruding gives the volume of the pores. Modem equipment enables the use of very high pressures, and thus measurement of pore diameters of ca 4 nm. It can therefore be concluded that mercury porosimetry and nitrogen adsorption can both be used to measure pores down to a diameter of about 4 nm mercury porosimetry can, however, be used to determine pore of diameters as large as 200 pm. Modern equipment employs computer programs that enable ready calculation of the pore-size distribution from experimental data. 

Porosimeter An instrument for the determination of pore size distribution by measuring the pressure needed to force liquid into a porous medium and applying the Young-Laplace equation. If the surface tension and contact angle appropriate to the injected liquid are known, pore dimensions can be calculated. A common liquid for this purpose is mercury hence, the term mercury porosimetry. 

The textural characterization of the supports and catalysts pore size distribution, pore volume, and surface areas were determined by use of mercury intrusion porosimetry using a Micromeritics Poresizer 9320 and nitrogen gas adsorption/desorption isotherms carried out on a Micromeretics ASAP 2000 respectively. For the porosimetiy analysis a contact angle of 140° and surface tension of480mNm for mercury were assumed. 

The main uncertainties in mercury porosimetry are related to the selection of values for 7 and 0. A surface tension of 480 mJ m is usually assumed, but mercury is easily contaminated with impurities that significantly modify its surface tension. Likewise, a contact angle of 140° is typically assumed but it can significantly change from solid to solid, and can vary depending on the physical and chemical state of the solid surface under concern. Lowell and Shields, in their well-known monograph [60], have described in detail the fundamentals, practical aspects and interpretation of mercury porosimetry results. 

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