Porous Granular Materials Research Articles

An acoustic evaluation of light weight granular porous materials for urban air mobility applications

Soon Urban Air Mobility (UAM) vehicles will become a reality. The UAM vehicles need to be safe, environmentally clean, quieter and affordable. Air vehicle noise and reduction of it is a major challenge in urban areas, where these vehicles are needed the most. This paper attempts to develop a lightweight noise absorbing material system using porous particles constructed such that one can have varying pore size, its distribution, surface roughness, tortuosity, and layering. Analytical modeling is used to develop material model consisted of special hollow microbubbles, aerogel granules and other lighter weight materials. These partials are bonded by coating with a very thin layer of binder and processed to produce different structural constructions. The target is to achieve at least 50% sound absorption and 15 dB transmission loss. Several designed material systems will be validated by impedance tube testing. Details of modeling, development of materials, test and test results will be discussed in the full paper and in the presentation.

Permeability Measurement of Granular Porous Materials by a Modified Falling-Head Method

AbstractLiquid flows through granular material are common phenomena in different engineering fields. Under certain conditions, this type of flow can be described by Darcy’s law, which involves the ...

Pressure-dependent bulk compressibility of a porous granular material modeled by improved contact mechanics and micromechanical approaches: Effects of surface roughness of grains

The change of the mechanical properties of granular materials with pressure is an important topic associated with many industrial applications. In this paper we investigate the influence of hydrostatic pressure (Pe) on the effective bulk compressibility (Ceff) of a granular material by applying two modified theoretical approaches that are based on contact mechanics and micromechanics, respectively. For a granular material composed of rough grains, an extended contact model is developed to elucidate the effect of roughness of grain surfaces on bulk compressibility. At relatively low pressures, the model predicts that the decrease of bulk compressibility with pressure may be described by a power law with an exponent of -1/2 (i.e., Ceff ∝Pe−1/2), but deviates at intermediate pressures. At elevated pressures beyond full contact, bulk compressibility remains almost unchanged, which may be roughly evaluated by continuum contact mechanics. As an alternative explanation of pressure-dependent bulk compressibility, we suggest a micromechanical model that accounts for effects of different types of pore space present in granular materials. Narrow and compliant inter-granular cracks are approximated by three-dimensional oblate spheroidal cracks with rough surfaces, whereas the equant and stiff pores surrounded by three and four neighboring grains are modeled as tubular pores with cross sections of three and four cusp-like corners, respectively. In this model, bulk compressibility is strongly reduced with increasing pressure by progressive closure of rough-walled cracks. At pressures exceeding crack closure pressure, deformation of the remaining equant pores is largely insensitive to pressure, with almost no further change in bulk compressibility. To validate these models, we performed hydrostatic compression tests on Bentheim sandstone (a granular rock consisting of quartz with high porosity) under a wide range of pressure. The relation between observed microstructures and measured pressure-dependent bulk compressibility is well explained by both suggested models.

Resiliency Evaluation of Contraction Universal Gripper based on Porous Granular Material

Resiliency Evaluation of Contraction Universal Gripper based on Porous Granular Material

Numerical derivation of a normal contact law for compressible plastic particles

A new contact law is proposed to describe the behaviour of plastically compressible particles. The law was derived from contact simulations in which a general continuum constitutive model, the von Mises Double Cap (VMDC) model, was introduced to represent the particle material behaviour, allowing distinct dilatory, shearing and densification plastic flow regimes. Elastic and plastic properties were prescribed as functions of density. Parametric studies were conducted covering the parameter space of published experimental data for a range of pharmaceutical powders and granules.The analysis showed plastic zones corresponding to the three flow regimes developing within the particle, with size, shape, location and onset conditions being dependent on the strength ratios of the constitutive model. The contact law established combines an initial quasi-linear region followed by an exponential hardening region, arising from the initiation, growth and hardening of plastic zones, and the development of dense and stable load-bearing structures within the particle.The outcome of these studies is a new contact law, relationships for predicting contact law parameters from material parameters for both loading and unloading, and guidelines for the analytical treatment of plastic compressibility in particle contact. The contact law can be employed in discrete element and homogenisation models to predict macroscopic properties of porous granular materials, while the analytical framework and qualitative findings can be used in the design of granules.

Micro-Mechanical Properties of Expanded Clay Particles

The aim of this paper is to study the micro-mechanical behavior of an industrial crushable and highly porous granular material. Lightweight Expanded Clay Aggregates (LECA) was selected in this research for testing thanks to its brittle nature and highly porous character which makes it easier to study the crushable behavior of this material. LECA’s micro-mechanical properties were identified to understand the parameters that affect particle’s crushing. Uniaxial compression tests, consisting on compressing the particles between two rigid platens, were made on a set of single LECA’s particles to investigate the force displacement response and the Hertzian behavior was identified as the contact law. The particles’ strengths were determined for tested granules using the crushing force and grains’ Young moduli were calculated using the suggested contact law. Due to their high variability, the particles’ crushing stress and their Young moduli were related to particle’s dimension using a suggested power law to predict these mico-mechanical properties. Results have shown a high dependency between the particle’s micro-mechanical properties and their dimensions.

A thermodynamic constitutive model with temperature effect based on particle rearrangement for geomaterials

A thermo-hydro-mechanical constitutive model is developed for geomaterials based on the tenet of particle rearrangement in porous granular materials undergoing thermodynamic processes. In this model, the concepts of particle entropy, particle temperature, migration coefficient and potential energy density function are introduced. The effects of temperature and saturation variation on energy dissipation and the soil–water characteristic curve of the geomaterials are also considered. This model can accurately describe the irreversible consolidation of normally consolidated saturated soils induced by thermal loading and the aging effect induced by cyclic thermal loading, which is attributed to the irreversible rearrangement of solid particles in the soils. However, as the overconsolidation ratio increases, volumetric expansion will likely become reversible. In this case, temperature-induced elastic deformation of the solid particles is more dominant than particle rearrangement. The constitutive model can accurately describe the effects of static stress, suction and temperature on the consolidation of unsaturated soils. An increase in temperature can cause thermal contraction at low suction but thermal expansion at high suction and the physical mechanism is the same as that of the thermal consolidation of saturated soils.

A novel multifunctional sandwiched activated carbon between manganese and tin oxides nanoparticles for removal of divalent metal ions

Combination of nano-metal oxides (NMOs) with other granular materials of porous characteristics offer excellent and promising hybrid nanosorbents with the advantages of high efficient surface and hydraulic characteristics to break out the technical barriers for application in scaled-up water decontamination. Therefore, the present study is aimed to take advantage of activated carbon (AC) as granular-porous material with reactive functional groups to encapsulate in a sandwich between manganese oxide nanoparticles (MnO2-NPs) and tin oxide nanoparticles (MnO2-NPs) to produce a novel nanosorbent (SnO2-NPs-AC-MnO2-NPs). The characterization of this nanosorbent was evaluated using FT-IR, XRD, TGA, SEM and HR-TEM. The removal performance of lead (ІІ), cadmium (ІІ) and copper (ІІ) ions on SnO2-NPs-AC-MnO2-NPs was investigated and optimized by the batch adsorption technique and applying a number of controlling parameters as pH of contact solution, shaking time, nanosorbent dosage, ionic metal concentration and interfering species. The maximum metal up-take capacities were 4100, 2600 and 2500 μ mol g−1 for copper (ІІ), lead (ІІ) and cadmium (ІІ), respectively by applying concentration of Cu(II), Cd(II) and Pb(II) (0.2 mol L−1), time of reaction (30 min), pH 7 of reaction solution and mass of SnO2-NPs-AC-MnO2-NPs (5.0 mg). Several oxygenated functional groups, especially O-H, C-O, Mn-O, and SnO are suggested to take part in the adsorption with excellent affinity and superiority in removal of the target metal ions from wastewater. This study is aimed to confirm the capability of implementation SnO2-NPs-AC-MnO2-NPs as an excellent nanosorbent for decontamination of heavy metals from different water samples with percentage range (91.2–97.6%) Cu(II), (92.4–95.5%) Pb(II) and (92.9–99.1%) Cd(II).

Processing of mineral part of refined ferrochrome slags to obtain pelleted porous heat insulator

In the wastes of the joint stock Aktobe Ferro-alloy plant, there are over 12 mln ton of refined ferrochrome slags that contain significant amounts of the metal dorebead. Dust-like mineral part of the slagof refined ferrochrome mainly consists of di-calcium silicate contaminated with poisonous compounds of hexatomic chrome. The metal can be separated from the mineral part by air separation and screen sizing, while the mineral part of the slag can be very efficiently mixed with Kazakhstani ferri-ferrous diatomite(opoka) and fluid glass and thermally processed to obtainglass-like heat insulating material. Being heated up to t ≥ 1000оС Di-calcium silicate interacts with finely divided ferrumdioxyde and hydrated silica to formporous glass phase of ferro-silica-calcium compounds that strengthen the heat-processed pellets against any mechanical influence. It was found that the optimum conditions for pellet production are: the ratio of diatomite ore to the mineral part of the RFX slag 2: 1, because at other ratios, the formation of a rolling glass-phase pellet is observed, the processing temperature is 1050 ° C, because at lower temperatures there is practically no formation of a glass phase. The compounds of hexatomic chrome het destroyed at heating and dissolve in the glass mass where they become insoluble. It is shown that the mineral part of RFX slags due to the relatively high content of calcium and silicon oxides is a valuable raw material for the production of granular porous heat-insulating material. The proposed technology makes it possible to extract a high-value metal component of RFX slags in the form of an expensive metal concentrate of refined ferrochromium and to obtain porous pellet fillers for reinforced concrete products.

Manganese oxide nanoparticles impregnated graphene oxide aggregates for cadmium and copper remediation

Loading metal oxide nanoparticles (NPs) into porous granular materials with excellent hydraulic characteristics offers a promising option to break the technical barriers of direct application of NPs in scaled-up water decontamination. By taking advantage of graphene oxide (GO) mediating the formation of manganese oxide (MO) nanoparticles at the same time aggregating to form macroporous structure under highly alkaline conditions, we fabricated a novel GO-MO composite (D = ∼160 μm). The intraparticle diffusivity of Cd(II) and Cu(II) onto GO-MO was determined to be 3.17 × 10−9 and 4.67 × 10−9 cm2 s−1, respectively, similar to macroporous resin. The GO-MO showed synergistic sorption capacity for Cd(II) and Cu(II) compared to bulky MO and GO due to the high dispersion of MO NPs (<10 nm) in the aggregated GO matrix and Donnan membrane effect. The GO-MO also had strong sorption selectivity in the presence of Ca(II) and humic acid. HADDF-EDS characterization visually showed that Cu(II) and Cd(II) was selectively adsorbed to MO even in the presence of 50 times higher competing Ca(II) ions, which was quantified as ∼93% of the total adsorbed metal for both Cu(II) and Cd(II) by XPS analysis. Moreover, GO-MO was successfully employed in the column operation with effective treatment volume of ∼1650 and ∼1995 BV for simulated Cd(II)- and Cu(II)-contaminated wastewater, respectively. The exhausted GO-MO can be effectively regenerated using acid-salt binary solution with desorption rate >97%. The results from this study may offer insights to rationally design highly efficient engineered nanocomposites for water purification.

Breakage mechanisms of highly porous particles in 1D compression revealed by X-ray tomography

Grain breakage affects a number of geotechnical engineering problems. In this research study, the breakage of an artificial, porous granular material (light-expanded clay aggregate (LECA)) has been studied in one-dimensional compression with both standard laboratory techniques and in situ X-ray tomography during loading. X-ray tomography has revealed that there is a wide distribution of internal porosity among LECA particles, and particle tracking has been used, for the first time, to give an objective measurement of each particle's life expectancy. Links between micro- and macro-scale quantities are discussed.

Numerical modeling of onset and rate of sand production in perforated wells

Shear-type failure at a wellbore or perforation is typically characterized by damage to the formation rock. For example during drilling, wellbore failure may occur with rock fragments breaking off from the wellbore wall, and for producing wells, the applied drawdown pressure can result in sanding. Perforations are more susceptible to such failures because, in general, they become less stable as the reservoir depletes. In this paper, a damage model using the Mohr–Coulomb failure criterion is formulated to better describe the failure of porous granular material. The damage variable is assumed to be related to the increase in porosity resulting from the loss of mass from the formation rock matrix. The comparisons of numerical predictions and triaxial compression tests data show that the model can accurately reproduce the mechanical behavior of sand materials. Numerical simulation of a sand production test on a perforated cylindrical specimen is performed. The proposed model demonstrated its capability to predict the accumulated sand mass and rate produced throughout the entire experiment. A threshold of equivalent plastic shear strain has been quantified to determine the onset of sand production in perforated wells; this threshold can be used for field application of sand production analysis on similar sand material. An application on a vertical well with horizontal perforations has been simulated numerically. The key objectives are to examine the critical drawdown pressure for different reservoir depletions and produced sand volume for different drawdown pressures. The critical drawdown window plot was generated and can be used to estimate the allowable drawdown pressure for different reservoir depletions. In addition, it was shown that the produced sand volume and sand mass rate increase with increase of drawdown pressure.

Characteristic Analysis of Contraction Universal Gripper with Porous Granular Material

Characteristic Analysis of Contraction Universal Gripper with Porous Granular Material

A Study on Microstructural Parameters for the Characterization of Granular Porous Ceramics Using a Combination of Stochastic and Mechanical Modeling

To correlate the mechanical properties of granular porous materials with their microstructure, typically porosity is being considered as the dominant parameter. In this work, we suggest the average coordination number, i.e., the average number of connections that each grain of the porous material has to its neighboring grains, as additional — and possibly even more fundamental — microstructural parameter. In this work, a combination of stochastic and mechanical modeling is applied to study microstructural influences on the elastic properties of porous ceramics. This is accomplished by generating quasi-two-dimensional (2D) and fully three-dimensional (3D) representative volume elements (RVEs) with tailored microstructural features by a parametric stochastic microstructure model. In the next step, the elastic properties of the RVEs are characterized by finite element analysis. The results reveal that the average coordination number exhibits a very strong correlation with the Young’s modulus of the material in both 2D and 3D RVEs. Moreover, it is seen that quasi-2D RVEs with the same average coordination number, but largely different porosities, only differ very slightly in their elastic properties such that the correlation is almost unique. This finding is substantiated and discussed in terms of the load distribution in microstructures with different porosities and average coordination numbers.

HEAT RESISTANT BUILDING ENVELOPES MADE OF LIGHTWEIGHT CONCRETE WITH THE USE OF POROUS GRANULAR WASTES

The paper focuses on building envelopes for industrial thermal generating units, their efficiency and its increase. Building envelopes made of lightweight heat-resistant concretes are considered most effective from the point of their building construction, maintenance, repair and cost-effectiveness. One of the unresolved problems here is that porous granular materials suitable for use as concrete fillers operating at temperatures over 1000 OC are not industrially manufactured at the moment The article also characterises commonly used heat resistant porous fillers. It indicates that the use of exhaust zeolites is potentially perspective General properties and characteristics of zeolites are also given. The paper demonstrates that it is quite possible to use exhaust zeolites in building envelopes of lightweight heat-resistant concretes. The work describes testing experiments of typical exhaust zeolites (petrochemical and oil refining industries wastes) in Samara region and the Republic of Tatarstan. Their stress-strain properties and chemical compositions as well as X-ray crystallographic analysis (including analysis under high temperature) are presented. They prove that zeolites are heat-resistant and fire-proof because of corundum formation. Phosphate binder was used for tesing in heat-resistant concretes. The composition of the concrete mixture is given in the paper. As a result, concrete with the following characteristics was obtained: 1550 kg/m3 density, with compressive strength of approximately 21 MPa, having high thermal resistance and maximum permissible application temperature of 1450° c.

Capillary pressure–saturation relationships for porous granular materials: Pore morphology method vs. pore unit assembly method

In studies of two-phase flow in complex porous media it is often desirable to have an estimation of the capillary pressure–saturation curve prior to measurements. Therefore, we compare in this research the capability of three pore-scale approaches in reproducing experimentally measured capillary pressure–saturation curves. To do so, we have generated 12 packings of spheres that are representative of four different glass-bead packings and eight different sand packings, for which we have found experimental data on the capillary pressure–saturation curve in the literature. In generating the packings, we matched the particle size distributions and porosity values of the granular materials. We have used three different pore-scale approaches for generating the capillary pressure–saturation curves of each packing: i) the Pore Unit Assembly (PUA) method in combination with the Mayer and Stowe–Princen (MS–P) approximation for estimating the entry pressures of pore throats, ii) the PUA method in combination with the hemisphere approximation, and iii) the Pore Morphology Method (PMM) in combination with the hemisphere approximation. The three approaches were also used to produce capillary pressure–saturation curves for the coating layer of paper, used in inkjet printing. Curves for such layers are extremely difficult to determine experimentally, due to their very small thickness and the presence of extremely small pores (less than one micrometer in size). Results indicate that the PMM and PUA-hemisphere method give similar capillary pressure–saturation curves, because both methods rely on a hemisphere to represent the air–water interface. The ability of the hemisphere approximation and the MS–P approximation to reproduce correct capillary pressure seems to depend on the type of particle size distribution, with the hemisphere approximation working well for narrowly distributed granular materials.

多孔質粉体の収縮を利用したJamming Gripperの提案

多孔質粉体の収縮を利用したJamming Gripperの提案

Technology of obtaining thermal insulation material on the basis of liquid glass by a method of low temperature processing

The paper deal with the development of energy saving technology for obtaining thermal insulation material on the basis of liquid glass. The aim of the research is to study processes of chemical and physical modification of soluble sodium silicate and change its rheology. The paper also considers development of technology for the production of thermal insulation material with porosity uniformly distributed throughout the volume and with the specified pores size. In this research the authors used both traditional methods (chemical analysis, physical-mechanical tests) and “thin” methods, i.e. differential thermal analysis, electron microscopy. For research in the field of rheology changes the authors developed a methodology for determination of viscoelastic properties of materials with variable rheology. For the development of resource-saving technologies the researchers used the method of laboratory simulation which is as close as possible to real production conditions. The research identifies regularities of processes of modification and swelling of liquid-glass compositions and suggests methods for increasing viscosity of liquid-glass compositions by introducing various modifying additives. It also introduces an energy-saving technology of porous granular material production, and proposes options for the production of effective thermal insulation material based on sodium silicate composition.

Water retention against drying with soft-particle suspensions in porous media.

Polymers suspended in granular packings have a significant impact on water retention, which is important for soil irrigation and the curing of building materials. Whereas the drying rate remains constant during a long period for pure water due to capillary flow providing liquid water to the evaporating surface, we show that it is not the case for a suspension made of soft polymeric particles called microgels: The drying rate decreases immediately and significantly. By measuring the spatial water saturation and concentration of suspended particles with magnetic resonance imaging, we can explain these original trends and model the process. In low-viscosity fluids, the accumulation of particles at the free surface induces a recession of the air-liquid interface. A simple model, assuming particle transport and accumulation below the sample free surface, is able to reproduce our observations without any fitting parameters. The high viscosity of the microgel suspension inhibits flow towards the free surface and a drying front appears. We show that water vapor diffusion over a defined and increasing length sets the drying rate. These results and model allow for better controlling the drying and water retention in granular porous materials.

Agricultural Drainage Filters. I. Filter Hydro-Physical Properties and Tracer Transport

Drainage filters using porous granular material constitute new innovative technologies for remediating phosphorus (P) from agricultural tile drainage water. In drainage filters where convective velocities are often high, we hypothesize that intragranular diffusion may affect solute transport depending on filter characteristics and flow rate. This was investigated for six drainage filter materials (Leca, Filtralite-P®, granulated limestone, crushed seashells, calcined diatomite earth (CDE), and a poorly ordered Fe oxide aggregate (CFH)) conducting a tritium (3H2O) tracer experiment at low (0.26 cm h−1), medium (23 cm h−1), and high (41 cm h−1) flux densities. The filter materials differed widely with respect to grain-size distribution (D 50 from 1.6 to 3.3 mm), uniformity coefficient (1.7 to 2.2), particle density (1.75 to 2.76 g cm−3), bulk density (0.34 to 1.46 g cm−3), and water-filled porosity (0.39 to 0.73 cm3 cm−3). Measurements of specific surface area (SSA) included both SSABET and SSAEGME to ensure inclusion of the intragranular microporosity, not accounted by N2-BET. SSA varied widely across methods and allowed the differentiation of filters according to the significance of the intragranular porosity. Tritium transport varied from approximately equilibrium transport at all flow rates in Leca, Filtralite-P®, and limestone, to progressive non-equilibrium transport as flow rate increased in Seashells, CDE, and CFH. In general, the filter materials were highly variable in hydro-physical properties. Filters with (approximately) equilibrium transport were, however, all characterized by low specific surface areas. The non-equilibrium transport was explained by an intragranular diffusion in filters with larger specific surface area (Seashells, CDE, and CFH).