Patent Application
20250224324
The disclosure relates to an apparatus for determining an information indicative of a porosity of a sample. Further, the disclosure relates to a method of determining the information, e.g. using the apparatus. Furthermore, the disclosure relates to a use of gallium or a gallium alloy as an intruding agent in a porosity measurement.
Thus, the disclosure may relate to the technical field of measurement technology, in particular porosity measurements.
A plurality of materials comprises pores and, accordingly, a measurable porosity. The porosity is a measure of the void (empty) spaces in a material, and can be expressed for example as the volume fraction of voids over the total volume of the material, e.g. in percent. The porosity of a material can be an important or even crucial information in many technical fields, for example pharmaceutics, ceramics, metallurgy, material science, mechanical engineering, geology, hydrology, etc.
Several measurement techniques have been developed to measure the porosity of a sample, for example optical measurement (e.g. using a microscope), tomography measurement (e.g. CT scanning), water evaporation measurement, gas expansion measurement, and mercury intrusion measurement.
Mercury intrusion may be seen as the most common and economically most important porosity measurement. The technique involves the intrusion of a non-wetting liquid (i.e. mercury) at high pressure into a material within a porosimeter. The pore size can be determined based on the external pressure applied to force the mercury into the pores against the opposing force of the liquid's surface tension. In particular, the pore size determination is done using the Washburn equation. Further, mercury intrusion (and extrusion) measurements can also determine further pore-related properties such as pore diameter, total pore volume, and surface areas.
The primary measured quantities are the volume of intruded mercury volume and the corresponding applied pressure. In addition, when the pressure is reversed, especially in high-pressure mercury porosimetry, the extruded mercury volume can be measured.
However, the application of mercury has several drawbacks. Mercury is toxic and environmentally harmful, so that a costly recycling process for the used mercury is mandatory. Further, the used mercury may not be suitable for recycling within a porosity measurement apparatus, due to the toxicity of mercury vapors.
There may be a need to perform a porosity measurement in a cost-efficient and environmental/health-friendly manner.
An apparatus, a method, and a use are provided.
According to a first aspect of the disclosure, there is described an apparatus (in particular a liquid (intrusion) porosimeter) for determining an information indicative of a porosity of a sample, the apparatus comprising:
The intruding agent (is gallium-based, i.e. it) comprises or consists of gallium or a gallium alloy. The apparatus is configured to provide reducing conditions (e.g. using a reducing agent such as an acid) and/or inert conditions (e.g. store/transport in an inert gas) with respect to the intruding agent.
According to a second aspect of the disclosure, there is described a method of determining an information indicative of a porosity of a sample, the method comprising:
The method further comprises:
According to a third aspect of the disclosure, there is described a use (method of using) gallium or a gallium alloy as an intruding agent in a porosimeter, wherein oxidation of the intruding agent (in particular to gallium oxide) is prevented by providing reducing conditions and/or inert conditions.
In the context of the present document, the term “reducing conditions” may in particular refer to conditions in a specific region that favor a chemical reduction reaction (in contrast to an oxidation reaction). A reduction reaction may be a type of chemical reaction in which the oxidation states of atoms are changed. In particular, redox reactions may be characterized by the actual or formal transfer of electrons between chemical species, most often with one species (the reducing agent) undergoing oxidation (losing electrons) while another species (the oxidizing agent) undergoes reduction (gains electrons). An example for reducing conditions in the present document may be the provision of a reducing agent at the surface of the intruding agent (e.g. in the intruding agent reservoir or in the measurement chamber). For example, the reducing agent may be configured as an acid such as hydrochloric acid that prevents the formation of gallium oxide and/or chemically reacts with gallium oxide (Ga2O3) to the corresponding soluble gallium salt (e.g. gallium chloride (GaCl3) for HCl). In this manner, the reducing conditions may prevent the formation and/or the existence of gallium oxide.
In the context of the present document, the term “inert conditions” may in particular refer to conditions in a specific region that prevent a chemical reaction, in particular an oxidation reaction. Inert substances (in particular fluids) may not undergo chemical reactions under a set of given conditions. In an example, a noble gas such as argon is provided as an inert fluid to protect the intruding agent (e.g. in the intruding agent reservoir and/or in the measurement chamber) from oxidation. The inert fluid may be a cleaning gas and/or a working fluid, so that it may be used for both, providing inert conditions for the intruding agent, and fulfilling a specific task for the porosity measurement.
In the context of the present document, the term “pressure profile” may in particular refer to a pre-defined pressure change over time applied to the measurement chamber. The pressure may force the intruding agent (due to its surface tension not entering pores under normal conditions) into the pores. The necessary pressure may depend on the size of the pores. The pressure may be applied during the pressure profile in a continuous or step-wise pressure increase manner. In an example, the pressure profile is applied in two steps: a low-pressure measurement and a high-pressure measurement, in particular using different working fluids.
In the context of the present document, the term “intruding agent” may in particular refer to a substance (in particular a fluid) suitable to be introduced into the pores of a sample under an applied pressure. Such an intruding agent may be preferably a non-wetting fluid that is essentially liquid at measurement conditions. Further, the intruding agent should be non-reactive with the sample. The common example of an intruding agent in porosimetry may be mercury. Nevertheless, a gallium-based intruding agent may be a surprisingly efficient substitute.
According to an exemplary embodiment, the disclosure may be based on the idea that a porosity measurement can be performed in a cost-efficient and environmental/health-friendly manner, when mercury is replaced as an intruding agent by a gallium-based agent, and when said gallium-based intruding agent is protected against oxidation (within the measurement apparatus environment) by providing inert conditions and/or reducing conditions.
Gallium and gallium alloys comprise physical/chemical properties comparable to mercury and aluminum. Like mercury, gallium (alloys) can be liquid at measurement conditions and are thereby non-wetting liquids. In comparison to mercury, gallium or gallium alloys may have the advantage that they are neither toxic nor environmentally harmful. Recycling gallium (alloys) in the context of porosity measurements may be done more efficiently, so that on the one hand cost can be saved, while on the other hand no environment/health-disturbing wastes may be produced, which can be a large cost factor. In particular, because the current legislation requires to use specifically equipped hazard rooms to work with mercury.
Nevertheless, gallium (alloys) have a strong drawback in comparison to mercury, so that they have not been considered as a substitute so far: gallium may be easily oxidized to gallium oxide (in particular Ga2O3), the later not being a non-wetting liquid (specifically, it is a dispersion of solid gallium oxide at the surface that is making the liquid wettable, whereby this solid is then dissolved/reduced; it will remain on top for cohesion/density surface tension reasons), and thereby hampering or even impede porosity measurements (for example by adhering to the measurement chamber, in particular the penetrometer column).
It has now been surprisingly found by the inventors, that gallium (and gallium alloys) can nevertheless be applied in a highly efficient manner in intrusion porosity measurements, when specific means are implemented that prevent the oxidation of gallium in the measurement environment. Said specific means include in particular the provision of reducing or inert conditions. Specific implementations of these conditions are described for the following exemplary embodiments.
Gallium (alloys) may further comprise a larger contact angle in comparison to mercury, so that it may intrude larger pores at the same pressure in comparison to mercury. Further, gallium is less dense than mercury (half its density roughly), therefore, in addition to the contact angle, the hydrostatic pressure is substantially lower (and therefore the largest measurable pore is substantially larger). Thus, even more accurate measurements may be enabled using gallium (alloys).
Furthermore, the described approach may be directly implemented into existing porosity measurement systems, thereby enabling a straightforward application.
According to an embodiment, the gallium alloy comprises at least one metal of the group which consists of indium, tin, zinc, potassium, sodium, copper, silver, cesium, bismuth, antimony, lead, gold, thallium, palladium, platinum, selenium, lithium, cadmium. In particular, the gallium alloy comprises at least one of the group which consists of GaIn, GaInSn, GaZn, GaInZn. This may provide the advantage that an established and industry-relevant gallium alloy can be directly applied as the intruding agent. GaIn consists for example of Ga 75.5% and In 24.5% and is liquid at room temperature. GaInSn (brand name Galinstan®) is an eutectic alloy being liquid at room temperature. GaInSn comprises a low toxicity and low reactivity, so that it may be well suitable to replace mercury. In a very specific example, the gallium alloy may comprise KNa, rubidium, or francium.
In an example, every gallium alloy that is liquid at measurement conditions (in particular room temperature) may be suitable.
According to a further embodiment, the inert conditions comprise a protection of the intruding agent at least partially by an inert fluid (in particular an inert gas). An inert fluid may be applied to (e.g. located on top of) the intruding agent in the apparatus. For example, the intruding agent reservoir, wherein the intruding agent is stored, can be partially filled with the inert fluid. In a further example, the inert fluid can be streamed into the measurement chamber and protect the intruding agent therein against oxidation. Additionally, the intruding agent may be streamed through supply lines of the apparatus together with the inert fluid. In this manner, an efficient protection against oxidation may be provided.
In an example, the inert fluid is chosen from one of the group, which consists of a noble gas (in particular argon), nitrogen, carbon monoxide (can also be a reducing agent). In an example, the inert fluid may be used as a cleaning fluid that cleans the intruding agent and/or the (parts of the) apparatus. In a further example, the inert fluid may be used as a working fluid.
According to a further embodiment, the reducing conditions comprise an application of a reducing agent (to the intruding agent). While the inert fluid (see above) provides inert conditions for the intruding agent, a reducing agent (or reducing fluid) can provide reducing conditions that prevent oxidation and/or reduce oxidized (intruding agent) substances such as gallium oxide. Additionally or alternatively to the inert fluid, the reducing fluid may be provided to the intruding agent in the apparatus, for example in the intruding agent reservoir, the measurement chamber, and/or the supply lines. In this manner, an efficient protection against oxidation may be provided.
According to a further embodiment, the reducing agent comprises a gallium oxide dissolving fluid. This may provide the advantage that oxidized gallium substances (in particular gallium oxide) are efficiently reduced (removed), thereby recycling the intruding agent. According to a further embodiment, the reducing agent is applied as a fluid to a surface and/or a phase border of the intruding agent. In this manner, the reducing conditions can be directly provided to the intruding agent, especially, during storage of the intruding agent (in the reservoir). Further, also in the measurement chamber, the reducing agent may cover the surface of the intruding agent. In a specific embodiment (see
According to a further embodiment, the reducing agent comprises a chemically active substance such as an acid or a base. In a specific example, at least one of hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, and nitric acid is used. In another example, a base such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) is applied.
According to a further embodiment, the intruding agent reservoir is configured to store the intruding agent and to provide the inert fluid and/or the reducing agent to the stored intruding agent. Thereby, inert/reducing conditions may be provided directly and efficiently to the stored intruding agent.
According to a further embodiment, the intruding agent reservoir is configured to cover the surface of the stored intruding agent, in particular so that the inert fluid and/or the reducing fluid floats on the intruding agent. In this manner, the surface of the intruding agent may be efficiently protected against oxygen and oxidizing substances.
According to a further embodiment, the determination device is further configured to determine the information indicative of the porosity of the sample using the Washburn equation. This may provide the advantage that an established evaluation scheme can be directly applied. While in other techniques, evaluation of the porosity may take place using image analysis or magnetic resonance, the described method may apply a pressure profile that is evaluated in context of measured pressure (and intruding agent volume) using the established Washburn equation.
According to a further embodiment, the apparatus is further configured to provide a cleaning fluid (for example the inert fluid) and/or the reducing agent to at least part of the apparatus and/or to the intruding agent before the measurement and/or after the measurement (for example within the intruding agent reservoir). While the cleaning fluid rather provides inert conditions, the reducing agent is configured to provide reducing conditions. The described apparatus may be designed to protect the intruding agent against oxidation at different locations and in different manners. Accordingly, a plurality of combinations is possible in an actual implementation. This in turn increases the design flexibility.
According to a further embodiment, the apparatus is configured to recover used intruding agent by the reducing agent. In particular, during the measurement, the intruding agent may become at least partially oxidized and may be recovered by the reducing agent.
According to a further embodiment, the measurement chamber is cleaned before the measurement. In an example, there can be applied: rinsing and brushing (with reducing fluid), rinsing with a cleaning solution (e.g. an alcohol such as isopropyl), drying with pressurized air. In particular example, it may be advantageous to remove all high-pressure working fluid (oil) after a high-pressure measurement form the measurement chamber.
According to a further embodiment, a cleaning step (e.g. with the cleaning fluid) may help to remove oxygen/oxidizing agents from the measurement chamber/apparatus, in particular by further using a vacuum pump.
According to a further embodiment, the (recovered) intruding agent and the recovery agent are separated from each other, for example using a filter.
According to a further embodiment, the porosity measurement is done in vacuum conditions (for example below 20 mBar, in particular below 10-2 mBar). In a preferred example, the oxygen concentration during measurement in the measurement chamber is below 100 ppm, in particular below 50 ppm, more in particular below 20 ppm, more in particular below 10 ppm.
According to a further embodiment, the apparatus is further configured to be operated in a low-pressure mode. In the low-pressure mode, a working fluid in form of a gas may be applied as a pressure-conveying medium to press the intruding agent into the pores of the sample. Pressures in the hundred bar range may be used, e.g. around 600 bar.
According to a further embodiment, a low-pressure working fluid is applied as a pressure-conveying medium to the intruding agent.
According to a further embodiment, the low-pressure working fluid comprises an inert gas or a reducing gas. This may provide the advantage that, at the same time, inert/reducing conditions are provided to the intruding agent, and the function of a working fluid is fulfilled.
According to a further embodiment, the low-pressure working fluid comprises a gas with an oxygen concentration of less than 100 ppm, in particular less than 50 ppm, in particular less than 20 ppm, more in particular less than 10 ppm. The same oxygen conditions may also be applied to the whole measurement chamber. Thereby, oxidation of the intruding agent may be efficiently prevented.
According to a further embodiment, the intruding agent is recovered using the reducing agent after the low-pressure measurement.
According to a further embodiment, the apparatus is further configured to be operated in a high-pressure mode. In the high-pressure mode, a working fluid in form of a liquid may be applied as a pressure-conveying medium to press the intruding agent into the pores of the sample. Pressures in the thousand bar range may be used, e.g. around 6000 bar.
According to a further embodiment, a high-pressure working fluid is applied as a further pressure-conveying medium to the intruding agent.
According to a further embodiment, the high-pressure working fluid comprises an inert liquid or a reducing liquid. This may provide the advantage that, at the same time, inert/reducing conditions are provided to the intruding agent, and the function of a working fluid is fulfilled.
In an example, the high-pressure working fluid is a silicon oil or a mineral oil. Such an oil may be essentially inert. Nevertheless, the high-pressure working fluid may comprise oxygen that oxidizes the gallium (alloy)).
According to a further embodiment, the reducing agent comprises a low miscibility or no miscibility with respect to the pressure working fluid, in particular the high-pressure working fluid.
According to a further embodiment wherein the reducing agent is located, in particular in the measurement chamber, between the intruding agent and the pressure working fluid, in particular the low-pressure working fluid or the high-pressure working fluid (see
According to a further embodiment, at least one measurement chamber (inner) sidewall comprises a coating that is configured to prevent adhesion of gallium oxide. This may provide the advantage that sticking of gallium oxide to the sidewalls is prevented, thereby removing it more easily. In particular, the upper part of a penetrometer (stem) may be coated. In an example, this coating is especially applied in the context of high-pressure measurements. Hereby, the coating may substitute a reducing agent (measurement free of reducing agent) between the intruding agent and the high-pressure working fluid (as is e.g. shown in
According to a further embodiment, the reducing agent is of low miscibility or no miscibility with respect to the pressure working fluid (in particular the high-pressure working fluid), thereby serving as a protection from oxidation during low/high pressure measurement. In particular, aqueous acids/bases are applied as a reducing agent together with a lipophilic pressure medium (working fluid).
According to a further embodiment, the intruding agent is recovered using the reducing agent after the high-pressure measurement. Since the high-pressure working fluid (e.g. in case of oil) may form a film on the intruding agent, said film may be removed before the recovery with a film-removing agent, e.g. an alcohol such as isopropyl.
In a specific example, reducing agent/fluid (or inert fluid) is provided between the intruding agent and the (high-pressure) working fluid (see e.g.
According to a further embodiment, the reducing conditions comprise an application of an exchange process to remove oxidizing agents and/or oxidized intruding agent, in particular gallium oxide, and/or reducing agent and/or reduced gallium substances from the intruding agent. This may provide the advantage that undesired species may be efficiently removed. Under specific conditions, the reducing agent may not be suitable (e.g. due to corrosion) and should then be removed. Reduced gallium substances (e.g. gallium chloride) may be undesired and could then be removed.
According to a further embodiment, the exchange process comprises at least one of a membrane, an ion exchange, an osmosis, a density separation, a filter. Thereby, establishes means may be directly applied to enable an efficient separation.
According to a further embodiment, the apparatus further comprises an oxygen sensor, configured to monitor the oxygen concentration in at least part of the apparatus, in particular the inert fluid. Since oxygen provides oxidizing conditions, which may be a main issue in the use of gallium-based intruding agents, an oxygen sensor may be applied as a versatile and advantageous monitoring tool and/or as an alarm function to keep the oxygen content as low as possible.
According to a further embodiment, the apparatus is further configured to recycle the intruding agent after the measurement, and to apply the recycled intruding agent in a further measurement. This may provide the advantage that the (recovered) intruding agent can be applied several times, thereby saving (significant) costs for buying new intruding agent and for recycling used intruding agent. As described above, the used intruding agent may be treated with reducing agent to remove oxidized substances. Furthermore, separation techniques such as a filter may be applied to remove undesired substances and/or reaction products. The recycling may be directly implemented into the described apparatus. In another example, the recycling may be done in a separate device.
According to a further embodiment, the apparatus is configured as an intrusion porosimeter. Thereby, the described approach may be directly implemented into existing (see e.g.
According to a further embodiment, the pressure device is coupled to a pressure cell, in particular around the measurement chamber. Again, the described approach may be directly implemented into existing (see e.g.
The aspects defined above and further aspects of the disclosure are apparent from the examples of embodiment to be described hereinafter and are explained with reference to these examples of embodiment.
The illustrations in the drawings are schematic. In different drawings, similar or identical elements are provided with the same reference signs.
The apparatus 100 further comprises an intruding agent reservoir 120 that stores the intruding agent 125, being gallium or a gallium alloy. In the case of gallium alone, a further heating step may be necessary (melting point 29.8° C.). The intruding agent reservoir 120 is connected to the measurement chamber 110 (in particular the column), so that the intruding agent 125 can be streamed directly from the reservoir 120 through a valve into the (column of the) measurement chamber 110. In the example shown, the intruding agent 125 already fills the measurement chamber 110 up to a meniscus 114 in the column. The intruding agent reservoir 120 is furthermore connected to a supply of intruding agent 125. The supply can be fresh intruding agent 125, recycled intruding agent 125 (from the same or a different measurement) or a mixture of both.
An inert fluid 126 (e.g. a cleaning and/or protection fluid) can be supplied to the intruding agent reservoir 120 in order to provide (chemically) inert conditions within the intruding agent reservoir 120. Specifically, the inert fluid 126 prevents that the intruding agent 120 becomes oxidized within the intruding agent reservoir 120.
Additionally or alternatively, a reducing fluid 180 can be supplied to the intruding agent reservoir 120 in order to provide (chemically) reducing conditions within the intruding agent reservoir 120. Specifically, the reducing fluid 180 prevents that the intruding agent 125 becomes oxidized within the intruding agent reservoir 120 and/or reacts with oxidized species.
The apparatus 100 further comprises a pressure device 130, configured to apply a pressure profile to the measurement chamber 110, so that the intruding agent 125 is pressed into at least part of the pores of the sample 111. In this example, the pressure device is configured as a piston connected to the pressure cell. A measurement device 140 of the apparatus 100 is coupled to the pressure device 130 and is configured to measure a pressure related to the provided pressure profile (with respect to a corresponding intruding agent volume). In this example, the measurement device 140 comprises a capacitance measurement 141 that is connected to the bottom of the measurement chamber. A drop in the intruding agent level in the capillary is recorded capacitively and thus also the exact amount of intruded gallium (alloy) volume with respect to the corresponding applied pressure.
Further, the apparatus 100 comprises a determination device 150, coupled to the measurement device 140, that configured to determine the information indicative of the porosity of the sample 111 based on the measured pressure using the Washburn equation.
Through a further supply line 129, an inert fluid 126, a reducing agent 180, a low pressure working fluid 127, and/or a high pressure working fluid 128 can be introduced into the measurement chamber 110. Each of these fluids can be configured to provide inert conditions or reducing conditions for the intruding agent 125 in the measurement chamber 110. Working fluid and cleaning fluid can be identical here, but both provide inert/reducing conditions.
The apparatus 100 is thus configured to provide reducing or inert conditions with respect to the intruding agent 125, as described above, by providing respective fluids 126, 127, 128, 180 in the measurement chamber 110 and/or in the intruding fluid reservoir 120.
Each of the intruding agent 125 and the reducing agent 180 comprises a separate inlet and outlet. In this manner, intruding agent 125 can be streamed from the cleaning portion to the intruding agent 125 compartment and then further out of the reservoir 120 to the measurement cell 110. The reducing agent 180 can be streamed into the reducing agent compartment and then further out of the reservoir 120. At the membrane, the reducing agent 180 provides reducing conditions, so that oxidation of the intruding agent 180 is prevented, in particular oxidized substances are reduced.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 116 546.9 | Jul 2022 | DE | national |
The present application is a U.S. National Phase Patent Application of International Patent Application Number PCT/EP2023/063461, filed on May 19, 2023, which claims priority to German Patent Application Number 10 2022 116 546.9, filed on Jul. 1, 2022, the entire content of each of the two applications is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2023/063461 | 5/19/2023 | WO |
