Mercury intrusion porosimetry method

The mercury intrusion porosimetry method (Fig. 8.4) is a well-known technique that has been widely used to measure pore structure. Mercury is not wetted by nonwovens because the mercury—nonwoven interfacial free energy is greater than the gas—nonwoven interface. Mercury does not enter the pores spontaneously but can be forced into pores. Pressure required to intrude mercury into a pore is determined by the diameter of the pore. The measure of intrusion pressure and the intrusion volume yields the diameter and volume of passed and blinded pores. 

Although a number of methods are available to characterize the interstitial voids of a solid, the most useful of these is mercury intrusion porosimetry [52], This method is widely used to determine the pore-size distribution of a porous material, and the void size of tablets and compacts. The method is based on the capillary rise phenomenon, in which excess pressure is required to force a nonwetting liquid into a narrow volume. 

Measurements of particle porosity are a valuable supplement to studies of specific surface area, and such data are particularly useful in the evaluation of materials used in direct compression processes. For example, both micromeritic properties were measured for several different types of cellulosic-type excipients [53]. Surface areas by the B.E.T. method were used to evaluate all types of pore structures, while the method of mercury intrusion porosimetry used could not detect pores smaller than 10 nm. The data permitted a ready differentiation between the intraparticle pore structure of microcrystalline and agglomerated cellulose powders. 

One of the most popular methods to measure the pore size distribution in diffusion layers is mercury intrusion porosimetry (MIP) this technique is... 

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. 

In addition to surface fractal dimension ( Mercury Intrusion Porosimetry, under Boundary and Surface Fractal Dimensions ), this method can also be employed to determine mass fractal dimension of porous particles. Once the relative density of the particle at different pore volume, p, is obtained, then Dm can be deduced according to Eq. (20) ... 

A comparison of true particle density, apparent particle density, and bulk density can provide information on total porosity, interparticle porosity, and intraparticle porosity. Methods include true particle density measurements via helium pycnometry, mercury intrusion porosimetry, and poured and tapped bulk density. 

Three different sieved size fractions (20-45, 74-105 and 105-450 pm) of a SDDP batch have been characterized for their in vitro dissolution profiles and the textural properties of the three fractions and the original unsieved batch have been investigated by gas adsorption (B.E.T. method). Mercury Intrusion Porosimetry (MIP), light scattering and microscopy (optical and electron) techniques. 

Drug Substance (DS) Specific Surface Area (SSA) has been estimated by permeabilimetry, gas adsorption, laser light scattering and Mercury Intrusion Porosimetry (MIP). Because of the simplifying and different assumptions made, none of these experimental methods can provide the absolute SSA value and a perfect agreement between the values obtained by each technique is not found However, differences in theoretical assumptions made for each technique and observed results have been useful for understanding and interpreting the texture of the powder studied. 

As new membranes are developed, methods for characterization of these new materials are needed. Sarada et al. (34) describe techniques for measuring the thickness of and characterizing the structure of thin microporous polypropylene films commonly used as liquid membrane supports. Methods for measuring pore size distribution, porosity, and pore shape were reviewed. The authors employed transmission and scanning electron microscopy to map the three-dimensional pore structure of polypropylene films produced by stretching extended polypropylene. Although Sarada et al. discuss only the application of these characterization techniques to polypropylene membranes, the methods could be extended to other microporous polymer films. Chaiko and Osseo-Asare (25) describe the measurement of pore size distributions for microporous polypropylene liquid membrane supports using mercury intrusion porosimetry. 

In Table 1 the results obtained from the textural characterization of the supports and catalysts by nitrogen adsorption and mercury intrusion porosimetry are presented. In the table the values of surface area obtained from the gas adsorption results, using the BET method for which the linear portion was usually located in the relative pressure range of 0.05 to 0.3 Sbet [9], and those from the intrusion curve of the porosimetry analysis, using a nonintersecting cylindrical pore model Sng [10], are shown. The pore volume Vp is that recorded at the liighest intrusion pressure reached during the porosimetry analysis, and as such represents the pore volume of pores between ca. SOpm to 3mn pore radius. The pore radii were taken from the maxima of the curves of pore size distribution. 

Reaction conditions 20% w/v TRIM based on volume of H2O, 2,2"-azobisisobutyronitrile (AIBN, 2% w/v), 0.5% w/v poly(vinyl alcohol) (88% hydrolyzed, 88,000 g/mol), 60 C, 6h. Mean diameter calculated fiom >100 particles. Measured by mercury intrusion porosimetry over the pore size range 7 nm-20 pm. Measured by N2 adsorption desorption using the Brunauer-Emmett-Teller method. 

Pore size and pore size distribution. Particularly two methods have been used to determine the pore size in adsorbing materials of both organic and inorganic nature, namely, the gas adsorption technique and the mercury intrusion porosimetry. On the basis of information provided by these methods, a number of serious conclusions have been drawn on the porous structure of macroporous styrene-DVB copolymers. This necessitates a more critical analysis of the possible errors in the interpretation of the results of measuring adsorption isotherms and mercury intrusion. 

Individual primary particles could be dense, while agglomerates are most likely porous. Therefore, it is desirable to quantitatively characterize the porosity and pore size and distribution of the agglomerates. For accessible pores, i.e., those that are not completely isolated from the external surface, they can be characterized by using two methods (i) gas adsorption, also known as capillary condensation and (ii) mercury intrusion porosimetry, also called mercury porosimetry for simplicity. The pore size can be diameter, radius, or width. Three types of pores have been classified according to their sizes micropores (<2 nm), mesopores (2-50 nm), and macropores (>50 nm). Generally, gas condensation is applicable to the measurement in mesopores, whereas mercury porosimetry is more suitable to macropores. 

The determination of the buckling constant h by calibration from mercury intrusion porosimetry, or from nitrogen adsorption-desorption, can lead in some cases to different results. It is likely that, beyond the imprecision due to the method, the differences in pore sizes observed arise from a fundamental difference in the pore size concept. lUPAC proposed to define pore size as the distance between two opposite pore walls (Rouquerol, 1994). In the case of materials from the sol-gel process, this definition is not applicable, because pores are not included between walls, but are only delimited by interconnected filaments. In practice, it is considered that the sizes obtained from analysis methods of the texture of porous materials are characteristic pore sizes. Because the different analysis methods are based on different physical phenomena, it is not astonishing that they lead to slightly different characteristic pore sizes. Discrepancies resulting from using different characterization methods appear in several publications, often when the same material is analyzed by nitrogen adsorption-desorption and mercmy intrusion porosimetry (Smith, 1990, Brown, 1974, Milburn, 1988, Minihan, 1994). Me Enaney et al. noted that the distribution profiles obtained by different characterization techniques are often similar, but that differences, sometimes important, between the absolute values of characteristic pore sizes are almost unavoidable (Me Enaney et al., 1995). 

For the detailed information, pore structure porosimetry techniques are used. These methods enable measurement of pore diameter, pore shape, pore volume, and pore distribution in the electrode catalyst and gas diffusion layers. However, for PEMFC, these layers have hydrophobic and hydrophilic pores and there is no suitable technique available for characterization of such complex pore structures. Combination of multiple porosimetry techniques are employed to characterize layers with both hydrophobic and hydrophilic pores. The pore structure characterization techniques include capillary flow porosimetry, water intrusion porosimetry, and mercury intrusion porosimetry (Jena and Gupta, 2002). In water... 

ASTM D4284-12. Standard test method for determining pore volume distribution of catalysts and catalyst carriers by mercury intrusion porosimetry... 

The technique of water (intrusion) porosimetry can be effectively used to characterize the number of hydrophobic pores however, it must be used in conjunction with mercury porosimetry to separate the hydrophobic pore volume from the total pore volume to quantify the hydrophilic pore volume. This dual-intrusion porosimetry method as applied to PEFC GDLs has been described previously (Gupta and Jena 2003). 

The test methods able to determine the complete geotextile PSD are mercury intrusion porosimetry (ASTM D4404), capillary flow (ASTM D6767), image analysis, and probabihstic approach (AydUek et al., 2005). 

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