Mercury, contact angle

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,... 

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... 

K - Mayer and Stowe proportionality constant (K is a complex function of the solid/mercury contact angle 0 and of the packing arrangement of the particles)... 

The pore size distribution is derived, assuming a cylindrical pore model, from the intrusion volume-pressure curve using the Washburn law dp = -Ay cos0) / P, where y is the surface tension of mercury (484 mN/m), 6 the solid/mercury contact angle (130°) and P the pressure exerted by the mercury. 

Stepwise Pressurisation. A Micromeritics Pore Sizer 9310 was used in conjunction with Micromeritics software and a PC XT computer over the pressure range 1.6 psia to circa 30,000 psia. The pressure values were defined from a selectable Pressure Table within the program. The default values for mercury contact angle and mercury surface tension were 130 and 485 mNm respectively. The stepwise pressurisation equilibrium times can be selected from zero to 30+ seconds, the default time being 10 seconds. 

Adolphs J., M. Setzer and P. Heine (2002). Changes in pore structure and mercury contact angle of hardened cement paste depending on relative humidity . 

Usually one varies the head of mercury or applied gas pressure so as to bring the meniscus to a fixed reference point [118], Grahame and co-workers [119], Hansen and co-workers [120] (see also Ref. 121), and Hills and Payne [122] have given more or less elaborate descriptions of the capillary electrometer apparatus. Nowadays, the capillary electrometer is customarily used in conjunction with capacitance measurements (see below). Vos and Vos [111] describe the use of sessile drop profiles (Section II-7B) for interfacial tension measurements, thus avoiding an assumption as to the solution-Hg-glass contact angle. 

A procedure that is more suitable for obtaining the actual distribution of pore sizes involves the use of a nonwetting liquid such as mercury—the contact angle on glass being about 140° (Table X-2) (but note Ref. 31). If all pores are equally accessible, only those will be filled for which... 

The contact angle of mercury, like that of other liquids, depends not only... 

Values of the contact angle B of mercury at room temperature on various solid surfaces... 

Effect of the value of the contact angle 6 of mercury on the calculated value of pore radius at different values of applied pressure P... 

One other cause of hysteresis remains to be mentioned. As was pointed out earlier (p. 177) the contact angle may be different as the mercury is advancing over or receding from a solid surface, and it depends also on the chemical and physical state of the surface the mercury may even react with the surface layer of the solid to form an amalgam. A change in 9 of only a few degrees has a significant effect on the calculated value of pore radius (cf. Table 3.15). 

Figure 3 is a sketch made at the start of an experiment4,14 with a fresh piece of carbon. Clearly, the fresh carbon piece is wet by the molten KF-2HF. Figure 4 is a sketch of the same system a few minutes after the carbon is made anodic by applying 5 V between the carbon block and a piece of nickel wire in the KF-2HF electrolyte. The CFX layer forms (see Fig. 2) and is not wet by the KF-2HF. In fact, the KF-2HF forms a ball and behaves like water on clean polytetrafluoroethylene or mercury on clean glass. (The contact angle has been estimated10 to be 140°.)... 

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)... 

Since mercury has a contact angle with most solids of about 140°, it follows that its cosine is negative (i.e., it takes applied pressure to introduce mercury into a pore). In a mercury porosimeter, a solids sample is evacuated in a cell, mercury is then intruded, and the volume, V, is noted (it actually reads out), and the pressure, P, is then increased stepwise. In this fashion it is possible to deduce the pore volume of a particular radius [corresponding to P by Eq. (21)]. A pore size distribution will give the total internal pore area as well, which can be of importance in dissolution. 

The hydrophobic gas layer of the air electrode [4] possesses high porosity (ca. 0,9 cm2/g), such that an effective oxygen supply through this layer is obtained. From the experimental porogrames measured by both mercury and 7 N KOH-porometiy the contact angle 0en of the hydrophobic material with water electrolytes is obtained (0eff =116° 118°). Because of... 

Figure 2.1 (a) A schematic representation of the apparatus employed in an electrocapillarity experiment, (b) A schematic representation of the mercury /electrolyte interface in an electro-capillarity experiment. The height of the mercury column, of mass m and density p. is h, the radius of the capillary is r, and the contact angle between the mercury and the capillary wall is 0. (c) A simplified schematic representation of the potential distribution across the metal/ electrolyte interface and across the platinum/electrolyte interface of an NHE reference electrode, (d) A plot of the surface tension of a mercury drop electrode in contact with I M HCI as a function of potential. The surface charge density, pM, on the mercury at any potential can be obtained as the slope of the curve at that potential. After Modern Electrochemistry, J O M. 

The measured contact angle of mercury on various samples can range from 112 to 170° [39], but for most applications the average value of 140° is used. It should be noted, however, that the accuracy of the pore radii measurement is limited by the accuracy of the contact-angle measurement [40]. Contact angles can readily be measured on flat surfaces or compacts of powders [6], and the measurement of contact angles with powder systems has also been reported [41]. 

For mercury, the surface tension is 480 dynes/cm and the contact angle is equation follows in the specified units. 

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