High-pressure Mercury Porosimetry Research Articles

Structure and properties of ZrO2-Al2O3-MgO porous ceramic for biomedical applications

Starch consolidation casting (SCC), which involves pouring starch-containing slurries into an impermeable mould, is a flexible, easy, not harmful, not expensive, and firmly established method for manufacturing ceramic green structures. The procedure depends on the fact that the starch granules, when heated to about 80 °C, start to swell and absorb the water from the ceramic slurries. Following sintering, the starch granules have been completely destroyed by burning, resulting in the formation of porous-structured ceramics. In the current study, porous zirconia-alumina–magnesia (77.5 wt% ZrO2, 2.5 wt% MgO, and 20 wt% Al2O3) ceramic composites have been produced using starch consolidation casting method at different suspension concentration (60, 65, and 70 wt%). Potato or tapioca starches with varying quantities (10, 20, and 30 wt% related to the solid ceramics) were used as a pore and body forming agents. The sintered microstructures were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Furthermore, the research activity investigates how the apparent density and apparent porosity of the porous ceramic structure that has been produced are affected by the addition of different proportions of starches in different suspension concentrations. The XRD result after sintering reveals monoclinic zirconia, indicating that the tetragonal phase of zirconia is not stabilized by MgO and returns to monoclinic upon cooling. Magnesia does not act as a stabilizer for zirconia, but it is combined with alumina to produce a spinel structure. Maximum apparent porosity value of around 73% were demonstrated for porous-structured ceramics made with (30 wt%) potato starch and (60 wt%) suspension concentration. The SEM analysis of porous-structured ceramics revealed the presence of pore fills in the shape of miniature sintered ceramic shells within the pores. These shells form throughout the drying and burn-out processes, when the starch granules undergo a process that causes them to shrink. For nominal starch quantities of approximately 10 wt%, starch swelling is noticeable, and the pores left behind by sintering are bigger than the starch granules. Swelling is limited for greater amounts of starch by the amount of available space and/or water, and the matrix shrinkage that occurs during sintering more than compensates for the swelling impact, resulting in ceramic pores much smaller than the initial starch granule size. SEM and high-pressure mercury porosimetry results indicated that the prepared porous-structured ceramics have a bimodal pore structure. The maximum compressive strength at around 15.87 MPa for a sample containing 10 wt% tapioca starch and 70 wt% suspension concentration. Compressive strength drastically reduced when starch content increased from 10 to 30 wt% and suspension concentration reduced from 70 to 60 wt%.

Experimental study on the feasibility of microwave heating fracturing for enhanced shale gas recovery

Microwave heating fracturing is potentially a green stimulation technology for gas shale recovery. However, the mechanism together with permeability evolution of microwave irradiated reservoir remain unclear. To fill this knowledge gap, the responses of Longmaxi shale from the Sichuan Basin, southwest China, to both continuous and intermittent microwave stimulation along variable microwave heating paths were explored. A complex thermally-induced fracture network can be formed gradually without sudden collapse under intermittent microwave irradiation. Changes in the petrophysical parameters of the shale including wave velocity, weight and volume at different intermittent microwave irradiation steps were measured together with temperature variation. The evolution of permeabilities for the two shale samples with alternately parallel and vertical beddings at different effective stresses was analyzed both before and after microwave irradiation. After the last step of intermittent microwave irradiation in this study, the shale permeability increased by two to four orders of magnitude for the shale sample with flow parallel to bedding and one to two orders of magnitude with flow perpendicular to bedding. Microwave treatment accentuates the anisotropy between bedding-parallel and bedding-normal permeabilities. Evolving pore size was measured by high-pressure mercury porosimetry and thermal-induced fracture characteristics and the changes of mineral composition were characterized by SEM combined with Energy Dispersive Spectroscopy (EDS). Thermally- and chemically-induced swelling stresses are mainly responsible for the development of fractures and micro-porosity in the shale. A permeability model with variable compressibility coefficient was adopted to fit the experimental data for shale permeability across a wide range of effective stresses from 2.5 MPa to 59.5 MPa. Shale fracture compressibility decreases in the later stage of microwave irradiation, suggesting the hardening of thermal-induced fractures.

Silicon bioceramic loaded with vancomycin stimulates bone tissue regeneration.

Porous ceramics doped with silicon and pure β-TCP were analyzed in terms of internal microstructure, cell behavior, and the percentage of newly formed bone. Additionally the materials were tested to determine which of the two had better properties to load and release vancomycin hydrochloride. Internal pore distribution and porosity were determined through high pressure mercury porosimetry and the specific surface area was measured by the Brunauer Emmet-Teller method. The proliferation and viability of the human osteoblast-like cell line MG-63 was studied to validate both materials. The materials were tested on eight New Zealand rabbits which created defects, 10 mm in diameter, in the calvaria bone. After 8 and 12 weeks a histological and histomorphometric analysis was performed. Si-β-TCP showed a higher porosity and specific surface area. The cytocompatibility test revealed acceptable results in terms of proliferation and viability whereas the percentage of new bone was higher in Si-β-TCP with a two-time study being statistically significant with 12 weeks of healing (p < 0.05).The vancomycin loaded within the ceramic scaffolds were burst released and the material had the ability to inhibit bacterial growth. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2307-2315, 2018.

Water absorption and P-wave velocity changes during freeze–thaw weathering process of crosscut travertine rocks

The Turkish travertine is widely used in the domestic and foreign construction industry as slabs and tiles. In this study, the travertine samples were obtained from four different quarries located in the part of southwestern Turkey. Mineralogical and petrographic properties of the travertine rocks were studied using a polarizing optical microscope and SEM. The laboratory tests (mechanical and physical properties, capillary water absorption, freeze–thaw (F–T) process, P-wave velocity) were performed according to Technical Specification European Standard (TS EN) standards. The pore size distribution was determined by means of high-pressure mercury porosimetry (MIP). The most of the pores (>80%) of tested travertine have a pore access diameter of <0.1 μm. Some engineering properties of the rock are severely affected by F–T cycles such as ultrasonic P-wave velocities, water absorption weight and strength. The porosity of the travertine presents significantly higher values after the cycles of freeze–thaw, which also leads to the increase in the absorption by immersion. The water absorption method showed that water absorption weight of the specimens varied from 0.32 to 0.88%, after the 25. period. The freeze and thaw effects of the samples which were tested after exposing to water were measured at a certain time. The obtained dry, saturated and frozen P-wave velocities were examined by the changes of four travertine samples. P-wave velocity increase is in the range of 4.99–5.97% for tested travertine rocks. These studies explain that the P-wave velocity changes in freezing travertine exclusively due to changing velocities of pore infill, i.e., water, air and ice.

An improvement of the fractal theory and its application in pore structure evaluation and permeability estimation

AbstractWe present an improved fractal model for pore structure evaluation and permeability estimation based on the high pressure mercury porosimetry data. An accumulative fractal equation is introduced to characterize the piecewise nature of the capillary pressure and the mercury saturation. The iterative truncated singular value decomposition algorithm is developed to solve the accumulative fractal equation and obtain the fractal dimension distributions. Furthermore, the fractal dimension distributions and relevant parameters are used to characterize the pore structure and permeability. The results demonstrate that the proposed model provides better characterization of the mercury injection capillary pressure than conventional monofractal theory. In addition, there is a direct relationship between the pore structure types and the fractal dimension spectrums. What is more, the permeability is strongly correlated with the geometric and the arithmetic mean values of fractal dimensions, and the permeability estimated using these new fractal dimension parameters achieve excellent result. The improved model and solution give a fresh perspective of the conventional monofractal theory, which may be applied in many geological and geophysical fields.

The investigation of static and dynamic capillary by water absorption in porous building stones under normal and salty water conditions

The presence of water in building stones is one of the main factors in deterioration. Capillary rise is the most usual mechanism of water penetration into building materials. In this study, the kinetics of the capillary rise phenomenon was studied for three porous building stones: two tuff stones and andesite. For each of the examined natural stones the capillary water absorption, pore size distribution, mineralogical–petrographic (optical microscope, XRD, SEM), chemical (XRF) and mechanical–physical properties were determined. The mechanism of capillary water absorption depends mainly on the pore size and the shape of the pore system. The pore size distribution was determined by means of high pressure mercury porosimetry. Iscehisar andesite, Ayazini tuffs and Seydiler tuffs have pore sizes ranging from about 0.01 to 10, 0.01 to 20 and 0.01 to 4 µm, respectively. The capillary water absorption of the building stones was determined on the basis of TS EN 1925. The effects were analyzed with a static and dynamic capillary by water absorption under normal and salty water conditions of porous building stones. Water content was determined by weighing after 1, 3, 5, 10, 15, 30, 60, 480, 1440 min until the free saturation was reached and the liquid uptake stopped. The results indicated considerable differences in the water absorption shown as a function of elapsed time. NaCl crystals are observed under SEM in pores and surface of the tested stones. According to the results, capillary absorption of salty water value is bigger than pure water in all stones at the end of test. It could be shown that primarily moisture properties, i.e., capillary and sorptive water uptake and salt crystallisation can be addressed to the deterioration processes.

Dependence of carbon dioxide sorption on the petrographic composition of bituminous coals from the Czech part of the Upper Silesian Basin, Czech Republic

The effect of the rank and of the maceral composition of bituminous coal on carbon dioxide sorption capacity was studied on the basis of samples from two coal mines (Darkov, ČSM) from the Czech part of the Upper Silesian Basin. The samples from the two mines cover a small but very significant section of coalification within the transition zone between high-volatile bituminous A coal and medium-volatile bituminous coal, where porosity and sorption properties pass through their minima. The coal porous system was characterized by the micropore volume evaluated using the sorption isotherm of carbon dioxide and the volumes of meso-, macro- and coarse pores were determined by high-pressure mercury porosimetry. The micropore fraction in the coal porous system ranged between 53% and 75%. It was particularly high in coals with high vitrinite content, namely collotelinite, and also in coals with high inertinite content. The carbon dioxide sorption capacity was determined from the carbon dioxide sorption isotherms measured using a gravimetric sorption analyzer at 298 K until a relative pressure of 0.015 p/ p s, and was interpreted by characteristic parameters of the Dubinin and Langmuir equations. It was found that the adsorbed amount of CO 2 in the ČSM coal increases with the content of vitrinite and collotelinite, whereas no increase or only a slight increase was observed for the Darkov coal. The tendency of adsorption capacity to depend on maceral composition, and also to some extent on coalification, observed for the ČSM coal, may be related to higher microporosity due to the coalification process or oxidative processes leading to the formation of pseudovitrinite.

Dry pressed ceramic tiles based on fly ash–clay body: Influence of fly ash granulometry and pentasodium triphosphate addition

Fly ash from brown coal (70 wt.%) and stoneware clay (30 wt.%) were used for the dry pressed ceramic tiles (according to EN 14411) raw materials mixture. The effects of fly ash milling and pentasodium triphosphate addition as a deflocculant and fluxing agent on the properties of green body (flexural strength, bulk density) and fired body (EN ISO 10545—water absorption, bulk density, true density, apparent porosity, flexural strength, frost resistance) were studied and explained as a function of the firing temperature (1000–1150 °C). Fly ash milling (corresponding to 5 wt.% residue of fly ash grains on 0.063 mm sieve) increased the sintering abilities of the fly ash–clay body. A similar effect was achieved by 1.3 wt.% pentasodium triphosphate (PST) addition with an increase in green body flexural strength and a decrease in water content of the granulate. Fly ash–clay bodies can be frost resistant with water absorption above 10% due to positive pore size distribution, which were examined using the high-pressure mercury porosimetry method.

A methodology for blank and conformance corrections for high pressure mercury porosimetry

High pressure mercury porosimetry measurements suffer from two well-known systematic errors—blank errors and conformance errors. Blank errors result in an apparent mercury intrusion due to differential compaction of the mercury, sample and measurement apparatus. Conformance errors result from the mercury not completely filling the measurement container at the start of the measurement. A methodology for blank corrections that uses two calibration tables, one built from the experimentally determined apparent intrusion when a measurement is made with no sample present and one built from the apparent intrusion for a single non-porous sample, has been developed. These tables allow the blank effect to be calculated for a non-porous sample of the same material of any size. In principle, the blank material can be numerically constructed to match the mineralogy of the sample. The methodology is illustrated by using quartz blanks to correct measurement curves of two small low permeability samples. The conformance correction problem does not seem to be amenable to a generally applicable objective methodology. If the sample volume is accurately known, it can be used to perform a correction.

Removal of ammonia from waste air streams with clinoptilolite tuff in its natural and treated forms

Natural and impregnated clinoptilolite tuffs were studied to assess their potential to remove ammonia from air and, in a subsequent application, to use the spent adsorbent as a fertilizer. H2SO4, H3PO4 and HNO3, as agents containing important plant nutrients compatible with soil, were selected for impregnation to enhance sorption capacity of the natural clinoptilolite tuffs for ammonia removal. Sorbents were characterized using N2 adsorption isotherms at 77 K, X-ray analysis and high pressure mercury porosimetry. Ammonia breakthrough curves on fixed beds of sorbent were determined using appropriate NH3 and H2O input concentrations, flow rates and temperatures similar to the conditions in animal breeding farms. Impregnated clinoptilolite tuffs showed adsorption capacities comparable to SSP-4, an activated carbon that is commercially used for NH3 removal. Impregnations with H2SO4 and HNO3 are particularly important, since such modified adsorbents exhibit relatively high breakthrough capacities, thus rendering them potentially useful for practical applications in controlling ammonia emissions. The main contribution to the sorption capacity enhancement on impregnated clinoptilolite tuff samples seems to be due to the chemical reaction of ammonia with acids remaining in the macro- and mesopores.

The effect of temperature on strength – porosity relationship for concrete

In this paper, the unsealed concrete samples are tested to determine the compressive strengths and porosities while hot at various temperatures ranging from 25 to 280 °C. All measurements have been carried out after cooling the of the material. Porosity of the same concrete was measured using high-pressure mercury porosimetry, performed on a set of small-drilled fragments (of the average volume 0.5 cm 3) of hardened cement paste. While the concrete at the age of 90 days exhibits expected dependency between compressive strength S and porosity P (i.e., S to be a decreasing function of P), specimens at the age of 28 days behave exactly conversely in this sense. Consequently, it seems to be that for the latter case the porosity does not influence dominantly the strength of concrete.

Mercury Porosimetry of Mannitol Tablets: Effect of Scanning Speed and Moisture

Purpose of the work was to study the effect of the scanning speed of mercury porosimetry and moisture content of the sample on the mercury porosimetry result for mannitol tablets. Tablets were compressed at three different compression pressures from nonhygroscopic mannitol powder and granules. Pore structure of tablets was determined with three different scanning speeds of a high-pressure mercury porosimeter after storage in three different moisture conditions. With low scanning speed, smallest pores of tablets were determined more accurately. Small amounts of moisture, even as low as 1%, before evacuation in nonhygroscopic mannitol tablets decrease the porosity. Decrease in porosity was observed at a pore diameter range of 50–1000 nm, not at the smallest determined pores. Thus, the role of water in pharmaceutical samples appears to be complicated. Reasonably slow scanning is recommended in high-pressure mercury porosimetry. If total pore volume is the only parameter of interest, fast scanning can be used. Pretreatment of the samples by proper drying before mercury porosimetry is important.

The effect of pore structure and gas pressure upon the transport properties of coal: a laboratory and modeling study. 1. Isotherms and pore volume distributions

The effect of coal composition upon pore structure and adsorption characteristics of four bituminous coals of the Cretaceous Gates Formation coal is investigated. All the coals have multi-modal pore volume distributions as determined from low-pressure (<127 kPa) nitrogen adsorption at 77 K, carbon dioxide adsorption at 273 K, and high-pressure (up to 200 MPa) mercury porosimetry. The individual lithotypes, however, differ in their pore volume distributions and adsorption characteristics. The dull coals (high inertinite, high ash content) have a greater percentage of mesoporosity and less microporosity than bright or banded bright coals (high vitrinite, low ash content) of the same rank. In addition, one banded bright coal has a greater amount of macroporosity than the other coals. High-pressure (up to ∼8 MPa) methane isotherms determined on dried and moisture-equilibrated coals, and carbon dioxide isotherms (up to ∼ 5 MPa) determined on dried coal at 303 K, show that bright coals tend to adsorb more gas than dull coals. The Dubinin–Astakhov equation provides a better fit to coal gas isotherm data, particularly for carbon dioxide, than the conventionally used Langmuir equation. There is a linear correlation between high-pressure methane and carbon dioxide Langmuir volumes and Dubinin–Radushkevich micropore volumes, indicating that micropore volume is a primary control upon high-pressure gas adsorption for the Gates coals.

Dependence between dissolution rate and porosity of compressed erythromycin acistrate tablets

The correlation between dissolution rate and porosity of compressed erythromycin acistrate tablets was studied. The total porosity of the tablets, the pore size distribution and the specific surface area of the pores were determined using high-pressure mercury porosimetry. The particle size and specific surface area of the raw material and of the dry granulated mass of the tablets were also determined. The results show that the pore size distribution, showing the differences in pore structure, is more informative than total intruded volume of mercury. However, it is very difficult to explain the dissolution behaviour of erythromycin acistrate tablets only by porosity results of the tablets, and more work is still needed in this field.

Porosity parameters of lactose, glucose and mannitol tablets obtained by mercury porosimetry

The effect of compression force, compression speed and the amount of granulation liquid on the porosity parameters determined from lactose, glucose and mannitol tablets by high-pressure mercury porosimetry was investigated. Compression force affected all parameters measured, except the total pore surface area of lactose tablets. The changes in tablet microstructure with increasing compression force were particularly well detected from the pore volume size distributions of tablets. Compression speed affected the total pore volume of lactose tablets, both mean and median pore diameters of lactose tablets and mannitol tablets compressed from granules produced with a low amount of liquid, and the median pore diameter of glucose tablets. The compression speed dependence of these parameters was a sign of the time-dependent deformation of materials during compression. The amount of granulation liquid affected the total pore surface area of lactose and mannitol tablets. With a high amount of liquid, the surface area of pores was greater. The mean pore size of all tablets and the median pore diameter of mannitol tablets were smaller when a high amount of granulation liquid was used. Even when compressed with a high force, the pore volume size distributions of mannitol tablets with a low amount of granulation liquid were broader and the maxima were at larger pore diameters. It was concluded that each porosity parameter measured characterised the pore structure of compressed tablets from a different aspect. Thus, the use of all porosity parameters proved to be useful.

Surface structural changes of coal upon heat treatment at 200-900.degree.C

Surface properties of the chars obtained from two Australian coals at different temperature of 200-290 o C were characterized by means of high-pressure mercury porosimetry, adsorption of CO 2 (0 o C), CH 3 OH (25 o C), and H 2 O-immersional microcalorimetry at 25 o C. With increasing temperatures of char preparation, the volume of macropores in a diameter range of 50nm-10μm increased with a maximum at 600 o C, while the amounts of CO 2 , CH 3 OH, and H 2 O adsorbed, depending on the micro- and mesoporosity of char, changed with a minimum at a temperature (400-600 o C) dependent on the nature of coal. In contrast, surface hydrophilicity of char, estimated from the specific immersional heat of char into water, monotonously decreased with increasing temperatures of char preparation from 200 to 750 o C

Very high-pressure mercury porosimetry as a tool in reservoir characterization

Three methodological considerations critical to the use of mercury porosimetry for reservoir characterization are the analytical pressure ranges which should be covered, sampling density, and the effects of variation in sample weight. Of these, the analytical pressure range is most likely to be inappropriately scaled. Mercury porosimetry analyses should be carried out to very high pressures for two reasons: first, although mercury-air capillary pressure corresponding to subsurface conditions at a given depth varies greatly depending on fluid densities, viscosities, and interfacial tensions, and on rock wettability, hydrostatic gradients yield capillary pressures equivalent to 10,000 PSIA (Hg-air) at 4,600 feet (1.4 km) or less. To evaluate the range of conditions likely to be encountered at subsurface depths where hydrocarbon production is economically feasible, mercury porosimetry should attain pressures of at least 10,000 PSIA. Second, substantial amounts of mercury intrusion occur at capillary pressures greater than 10,000 PSIA (Hg-air): up to 41% in the studied samples.

Narrow pore distribution formed in steam and CO 2 gasified cokes of different origin

A new high resolution sorption (HRS) technique has been employed to characterize steam and/or CO 2 gasified petroleum cokes, coal chars, and carbons derived from peat and bone char. A lignite gasified by mild oxidation in steam was also studied. We have found that all of these coke samples show a very narrow pore feature centered at 3.9 nm diameter. High pressure mercury porosimetry of a petroleum coke gasified in a fluidized bed at temperatures >900°C confirm the HRS analysis of 3.9 nm pores formed on gasification. We propose that a primary structural unit, analogous to a micelle or a spherulitic polymer micro domain, forms during the coke-formation process, and this unit is 4 nm in diameter. We believe that gasification attacks these structural units generating a very narrow pore structure within the coke. In other work, gasification of carbon blacks by mild oxidation has been shown to attack the center of the particle and proceed to the exterior of the spherulitic structure. Such a process would account for the generation of narrow pores within a coke following gasification in steam and/or CO 2.

The General Equation of the High Pressure Mercury Porosimetry

On the basis of the Gibbs condition of the thermodynamic equilibrium of a heterogeneous system in the field of force, a general expression is derived for the dependence of the pressure p' of the intruded liquid mercury as a function of the equivalent pore radius r. For pore radii greater than 30 nm, this equation goes over into the well known Washburn equation. For pores with r smaller than 2.5 nm sizeable deviations from the Washburn relation occur. It is shown that supermicropores (r from 0.8 to 1.4 nm), communicating with the system of meso and macropores, are filled by mercury at the same pressures pl at which the filling of mesopores (r from 2 to 10 nm) takes place.

The complete pore structure analysis of fine porous solids

A new method is presented for the determination of the distribution of pore volume and surface in micropores. The analysis facilitates obtaining typical parameters of micropore structure from the adsorption isotherm. The calculated characteristic micropore radii and the micropore surface area for a model of cylindrical pores agree with the data from small-angle X-ray scattering. Micropore cumulative distribution curves for two typical active carbons were joined together with a high pressure mercury porosimetry data. The overall porosity cumulative distribution curve agrees with the Dubinin model of the porous structure of active carbons.