Pore Size Ratio Research Articles

Estimation of effective thermal conductivity in open-cell foam with hierarchical pore structure using lattice Boltzmann method

• Hierarchical pore structure is built in open-cell foam by an artificial algorithm. • Effective thermal conductivity (ETC) was calculated by lattice Boltzmann method. • Effects of hierarchical pore structure on ETC were investigated. • ETC correlation for open-cell foam with hierarchical pore structure is derived. Effective thermal conductivity in open-cell foam with hierarchical pore structure was estimated using lattice Boltzmann method. A new structure algorithm was proposed to reconstruct hierarchical pore structure in open-cell foam. In order to elucidate the heat transfer characteristics in hierarchical pore structure, the effect of structure parameters, namely the hierarchical pore size ratio ( d 2 / d 1 ), the hierarchical pore volume ratio ( V 2 / V 1 ), and temperature on the effective thermal conductivity was investigated. These results indicated that hierarchical pore structure is unfavorable to the effective thermal conductivity in open-cell foam for the heat conduction process. At high temperatures ( T ave =450-1650 K ), however, the effective thermal conductivity in hierarchical pore structure is higher than that in uniform pore structure considering heat radiation. Furthermore, for the heat conduction process, a correlation of the effective thermal conductivity related to open-cell foam with hierarchical pore structure was proposed and validated by available experimental data.

Lattice Boltzmann study on the effect of hierarchical pore structure on fluid flow and coke formation characteristics in open-cell foam for dry reforming of methane

Dry reforming of methane (DRM) is one of the feasible strategies for carbon capture and utilization. However, the DRM process has a high tendency toward carbon deposition, which is restricted to industrial applications. In order to further improve coke formation resistance, open-cell foam with hierarchical pore structure was investigated. An artificial algorithm was adopted to construct a hierarchical pore structure in open-cell foam. Based on a 3-D lattice Boltzmann model, this work explored the effect of two hierarchical pore structure parameters on the fluid flow and coke formation characteristics in open-cell foam, which are hierarchical pore volume ratio (V2/V1) and hierarchical pore size ratio (d2/d1). The results indicated that increasing V2/V1 and d2/d1 can significantly promote permeability. Under the restriction ofV2/V1 = 4, from d2/d1 = 1 to 4, the coke formation rate decreases by approximately 57.49 %. These findings provide a theoretical basis and technical guidance for designing and developing open-cell foam reactors.

Evaluation of Soil-Water Characteristic Curve and Pore-Size Distribution of Fine-Grained Soils

A soil’s physical properties, mineral types, and pore structure significantly influence the shape and properties of the soil-water characteristic curve (SWCC). This study investigated the effects of the soil’s physical properties and mineral types on the SWCC and pore-size distribution (PSD). Eight different soils from an alluvial deposit in Istanbul and Adapazarı/Türkiye were used in the study. The test samples were prepared by compaction at optimum water content (OWC) and wet side of optimum water content (wet of OWC). The samples were prepared by consolidation from the slurry. The PSDs of the samples were calculated using the SWCCs and evaluated with scanning electron microscope (SEM) analysis. In addition, the mineral types of all soils were determined by X-ray diffraction analysis. The soil which contains illite-type minerals has higher matric suction than containing kaolin-type. The effect of the clay percentage is more pronounced in silty soils than in plasticity and activity. Soil suction increased with decreasing compaction water content in clayey soils. The air entry water contents rose as the void ratio, liquid limit, clay content, and plasticity increased. The compaction conditions affected the macropore structure more than the micropore structure. In addition, the ratio of macro-micro pore sizes increased with the rise of the compaction water content.

High frequency response of adenine-derived carbon in aqueous electrochemical capacitor

Electrochemical capacitors are attractive power sources, especially when they are able to operate at high frequency (high current regime). In order to meet this requirement their constituents should be made of high conductivity materials with a suitable porosity. In this study, enhanced power and simultaneously high capacitance (120 F g−1 at 1 Hz or 10 A g−1) electrode material obtained from carbonized adenine precursor is presented. A micro/mesoporous character of the carbon with optimal pore size ratio and high surface area was proven by the physicochemical characterization. The beneficial pore structure and morphology resembling highly conductive carbon black, together with a significant nitrogen content (5.5%) allow for high frequency response of aqueous capacitor to be obtained. The carbon/carbon symmetric capacitor (in 1 mol L−1 Li2SO4) has been tested to the voltage of 1.5 V. The cyclic voltammetry indicates a good electrochemical response even at high scan rate (50 mV s−1). The cyclability of the capacitor is comparable to the one operating with commercial carbon (YP50F). The adenine-based capacitor is especially favourable for stationary applications requiring high power.

Fabrication of Zn-MOF derived graphitic carbon materials with mesoporous structure for adsorptive removal of ceftazidime from aqueous solutions

Antibiotic-resistant genes (ARGs) and antibiotics were detected in various environmental media. Metal-organic framework materials (MOFs) have great advantages in removing many pollutants in water. However, their microporous structure and poor hydrothermally stability make them difficult to realize efficient adsorption performance of macromolecular pollutants. Therefore, this study is devoted to preparing MOF-derived mesoporous carbon materials with excellent pore structure and stability so as to improve the adsorption performance of macromolecular antibiotics in water. In this study, the surface morphological structure of the MOF material was regulated from the preparation process. Firstly, the template agent formed micelles in the MOF framework, so that self-assembly and crystal growth were carried out under the guidance of cooperative templates. Secondly, the morphological structure of the material surface was modified by high-temperature calcination and surface etching. A series of graphitic carbon material MC-X with tunable mesoporous structure were prepared using Zn-MOF materials as precursors and N-Cetyldimethylamine as template. The pore size and mesoporous ratio of the MC-0.3 material had undergone large changes, the pore size varied from 1.73 nm to 3.94 nm, and the mesoporous ratio transformed from 12.6% to 97.71%. Unexpectedly, the material converted from hydrophilic to hydrophobic, and possessed an ultra-high ceftazidime (CAZ) adsorption capacity of 371.18 mg·g−1. The adsorption mechanisms of CAZ on MC-0.3 were mainly molecular size matching selection, hydrophobic effect and hydrogen bonding. After 5 adsorption-desorption cycles, MC-0.3 could maintain about 90% of the initial adsorption capacity.

FRACTAL-BASED MODEL FOR EVALUATING THE FILTRATION EFFICIENCY OF THE NON-WOVEN FIBROUS COMPOSITES

The classic single-fiber efficiency model based on ordered packing of fiber composites has been widely used to predict filtration efficiency of fibrous filters for 40 years. However, the simplified single-fiber model often overestimates the filtration efficiency as most fibrous composite filters are composed of randomly distributed fibers. The numerical methods have been successfully employed to re-construct the realistic fiber composites, but simulation of the multi-mechanism filtration process in the complex fibrous architecture is computationally expensive and case-based and derivation of a compact versatile model for broad applications remain challenging. In this work, a fractal-based homogenization model is developed to predict the filtration efficiency of the fibrous composites, by considering the spatially randomly distributed fibers and the quasi-random distribution of pore size. A comparison with available experimental results collected from references shows that the proposed model is of high accuracy in predicting the filtration of submicron aerosol particles. The calculated results show that the Kuwabara hydrodynamic factor is sensitive to the pore fractal dimension. The filtration efficiency for different particle diameters can be divided into three stages, which increase as the proportion of fibers warped by the fluid decreases. In addition, the total efficiency decreases with the increasing pore fractal dimension in a nonlinear trend. For the given fractal dimension, the filtration efficiency increases with the increase of pore size ratio, indicating that the more uniform the pore size distribution, the higher the efficiency.

Deformation behavior of fluid-filled porous elastomers: Analytical estimates and validation

Fluid-filled elastomers are used in soft body wearable electronics devices, optics, soft pressure transducers, vibration damping and impact protection. Deformation behavior of these materials is complex and would depend on elastomer properties, fluid properties, loading rate, porosity, pore size, pore shape, and pore end conditions. In this work, closed form analytical estimates are derived for effective behavior of a special class of fluid-filled elastomers composed of incompressible, hyperelastic matrix with mono-disperse circular pores, distributed in a square grid, filled with an incompressible, Newtonian fluid. The analytical estimates are validated using three dimensional numerical simulations modeled in COMSOL multiphysics software. The analytical estimates for pressure and velocity fields in the fluid, deformation of the matrix, viscous dissipation in fluid, and stored energy in the solid are seen to match well with that from numerical simulations. For small deformations and small porosities, while storage modulus is seen to be linearly proportional to shear modulus of elastomer and inversely proportional to the porosity, the loss modulus is seen to be linearly proportional to the product of loading frequency and fluid viscosity and inversely proportional to the product of porosity and square of ratio of pore radius to pore length. The analytical estimates presented here can be used to design fluid-filled elastomers with desired stiffness and damping by selecting appropriate elastomer stiffness, fluid viscosity, porosity, pore size and pore aspect ratio.

Effect of Dope Flow Rate and Post-Treatment on the Morphology, Permeation and Metal Ion Rejection from PES/LiBr-Based UF Hollow Fiber Membranes.

This study investigated the influence of dope extrusion rate (DER) and post-treatment effect on the morphology, permeation, and metal ion rejection by polyethersulfone/lithium bromide (PES/LiBr)-based hollow fiber (HF) membranes. HF fibers were spun with 2.25, 2.5, and 3.1 ratios of DER to bore fluid rate (BFR), wherein DER varied from 11.35, 12.5, to 15.6 mL/min with a fixed BFR (5 mL/min). Molecular weight cutoff (MWCO), pore size, water flux, and flux recovery ratio were determined, whereas lake water was used to observe the rejection rate of dissolved metallic ions. Results showed that with the increase of the DER wall thickness (WT), HFs increased from 401.5 to 419.5 um, and furthermore by the post-treatments up to 548.2 um, as confirmed by field emission scanning electron microscope (FESEM) analysis. Moreover, MWCO, pore size, and the pure water permeation (PWP) of the HF membranes decreased, while the separation performance for polyethylene glycol (PEG) solute increased with increasing DER. Post-treated HFs from 11.35 mL/min of DER showed 93.8% of MWCO value with up to 90% and 70% rejection of the arsenic and chromium metallic ions, respectively, in comparison with all other formulated HFs.

Enhanced wickability of single-columnar, non-uniform pore-size wick using Lattice Boltzmann Method

Optimal wick designs are essential to develop high heat flux two-phase thermal management systems in various applications including miniaturized power electronics, energy, high power battery, and spacecraft systems, as they require both large permeability and improved capillary pressure, i.e., enhanced wickability. The enhanced wickability is examined using non-uniform pore size wicks, while the larger pores increase the permeability and the smaller pores improve the capillary pressure. A two-phase single component free-energy-based Lattice Boltzmann Method (LBM) is employed to study the enhanced wickability, i.e., pore-scale rate-of-rise through wicks. The rate-of-rise is predicted for uniform and non-uniform pore size wicks having a single-column-particle between the two parallel plates for given porosities (ε = 0.67 and 0.8) and pore size ratios (lr = 1.3 and 2.6). The study shows that the non-uniform pore size wicks enhance the rate-of-rise and capillary pressure up to 298 and 157%, respectively, compared to those of the uniform pore size wicks, by improving the permeability through larger pores and increased capillary pumping capability through smaller pores. Also, the wickability enhances as the pore size ratios increase at given porosity or the porosity decreases at given pore size ratio. The cumulative enhancements of the maximum/minimum dimensionless liquid heights and the liquid saturation of non-uniform pore size wick are found to be up to 90, 114, and 112%, respectively, at ε = 0.67 and lr = 2.6. The capillary pressure enhancement of non-uniform particle size wicks results from the presence of the small pores. Also, the vertically graded wicks increase the capillary pressure due to the smaller pores at the top of the wicks, while they marginally decrease the rate-of-rise compared to the non-uniform pore size wicks at given porosity and pore size ratio. The simulation results provide insights into the optimal thin wick structures for high heat flux two-phase thermal management system by enhancing the wickability through the non-uniform pore sizes.

Fabrication and optical hydrogen gas sensing property of hierarchical WO3 Porous/Nanowires film

The porous WO3 films and hierarchical WO3 porous/nanowires films were fabricated by the colloidal template method and solvothermal method, and Pt catalyst was loaded on films by sputtering. The porous WO3 films exhibited uniform and ordered porous structure with pore diameter of ∼1020, ∼810 and ∼360 nm. Morphology of hierarchical WO3 films showed that many nanowires with diameter of 20 ∼ 30 nm grew on the pore wall. The hierarchical Pt/WO3 films exhibited shorter response time to 4% H2 gas (24.8 s) at room temperature, about a third of that of porous Pt/WO3 films. And T% of hierarchical films can decrease by 65.1% at 1500 nm wavelength, twice higher than porous films (28.6%). This hierarchical structure combines the adjustable pore size and high aspect ratio nanowires, which provides a new reference for the structure design of WO3 based sensors.

Effect of Reservoir Structural Rhythm on Carbon Capture and Sequestration (CCS) Performance

In addition to the evolution of green and nano energy, sequestration of CO2 is also an evolving method to control the global CO2 footprint and greenhouse effect. Carbon Capture and Sequestration (CCS) is an established technique to capture carbon from anthropogenic sources, such as power and chemical plants, and then inject the same in subsurface rock micropores, to permanently store the CO2. Besides its environmental credentials, CCS also offers economic opportunities in Gas Enhanced Oil Recovery and Methane displacement in coalbed reservoirs. CCS process incorporates various geological, geometrical and engineering understandings of porous media and fluid dynamics. Previous investigators have identified low permeability rock as a better site for CCS. However, little is known of the propagation and effectiveness of CCS in reservoirs that have multiple layers of sedimentation, vis-à-vis well topology and density, flow direction, storage site, and power optimisation. In reality, these layers altogether form a structural rhythm and gradient. In this study, we investigated the structural rhythms and gradients that optimise CCS by using two objective functions (Darcy and interstitial flowrates) and 15 structural criteria (such as pore size, porosity, tortuosity, and aspect ratio). An experimental method has been applied. Five analogous reservoir porous core samples with varying structural parameters have been tested. The results indicate that CCS optimisation is responsive to structural parameters. The rhythm analysis from this study suggests that the CCS gas flow requires a compound rhythm that has a positive porosity and negative pore gradients. That is, the CCS injection wells should be placed in the reservoir area with relatively low porosity (3%) and large pore size (6000nm), while the storage site should be at a relatively high porosity (20%) and smaller pore size (200nm). This study can be directly applied to CCS practice, such that, given a layered reservoir, engineers can predict the well placement or topology that would optimize some of the essential performance objectives of CCS.

Giant Functional Properties in Porous Electroceramics through Additive Manufacturing of Capillary Suspensions

Dedicated hierarchical structuring of functional ceramics can be used to shift the limits of functionality. This work presents the manufacturing of highly open porous, hierarchically structured barium titanate ceramics with 3-3 connectivity via direct ink writing of capillary suspension-type inks. The pore size of the printed struts (∼1 μm) is combined with a printed mesostructure (∼100 μm). The self-organized particle network, driven by strong capillary forces in the ternary solid/fluid/fluid ink, results in a high strut porosity, and the distinct flow properties of the ink allow for printing high strut size to pore size ratios, resulting in total porosities >60%. These unique and highly porous additive manufactured log-pile structures with closed bottom and top layers enable tailored dielectric and electromechanical coupling, resulting in an energy harvesting figure of merit FOM33 more than four times higher than any documented data for barium titanate. This clearly demonstrates that combining additive manufacturing of capillary suspensions in combination with appropriate sintering allows for creation of complex architected 3D structures with unprecedented properties. This opens up opportunities in a broad variety of applications, including electromechanical energy harvesting, electrode materials for batteries or fuel cells, thermoelectrics, or bone tissue engineering with piezoelectrically stimulated cell growth.

Inverse effect of packing density on shear wave velocity of binary mixed soils with varying size ratios

This study evaluates the dependency of shear wave velocity (Vs) on packing density of binary mixed soils with varying size ratios of the small to large particles. 4 mixtures with different size ratios (sr = median grain size of small particles / median grain size of large particles) of 0.699, 0.282, 0.157, and 0.014 were prepared, bender element tests were then carried out to examine the variation of Vs according to the void ratio or relative density. The results demonstrate that when sr > 0.414 (the theoretical pore size ratio, which is the ratio between the diameter of interstitial sphere and the diameter of spherical particles, for simple cubic packing) and when sr < 0.155 (the theoretical pore size ratio for cubic tetrahedral packing), the measured Vs increases with increasing packing density due to the increase in interparticle coordination. However, when 0.155 < sr < 0.414 and the finer fraction < threshold finer fraction, the Vs of the tested mixture decreases with increasing packing density. This inverse impact of packing density on Vs may be attributed to the decrease in pore size between large particles in this situation and the consequent active disruption of direct contacts between large particles.

Leveling Transient and Spatial Gradients in Planar Solid Oxide Cells Using Spatially Varied Microstructures: A Numerical Study

Sharp spatial and transient gradients of overpotential, current density, gas species and temperature within planar solid oxide cells (SOCs) can lead to increased degradation rates, decreased active area utilization and high thermal stresses. Such issues will lead to decreased cell efficiency and functional lifetime while increasing the risk of sudden cell failure due to cracking or delamination. Spatial gradients occur in part due to the interconnect geometry. Commonly, the electrochemical reaction rate within SOC electrodes is disproportionately higher near the inlet regions of the fuel or steam channels and decreases towards the outlets as the concentrations of fuel or steam decreases for fuel cell and electrolysis modes, respectively. Transient gradients occur on short time scales due to rapid fluctuations in loading during ramp up or ramp down and for reversible operation when the current direction is reversed. It might be possible to greatly reduce both transient and spatial gradients by controlling the reaction rate distribution within SOC electrodes through the strategic manipulation of the electrode active layer microstructures. Advances in additive manufacturing techniques now facilitate the design of engineered electrodes with precisely controlled microstructure properties such as pore size, porosity and volume ratios of active layer materials (i.e. Ni or YSZ). The purpose of the present study is to explore the impact and possible benefits of applying functionally graded or regionally altered microstructural properties in the active layer of planar SOCs using a previously developed transient 3D multiphysics performance model of commercial sized planar SOCs. Percolation theory is used to estimate properties such as triple phase boundary (TPB) density and tortuosities from the applied variations of particle sizes, volume fractions and pore former properties as shown in Figure 1(a). It is shown that indeed both spatial and transient gradients can be significantly decreased by engineering gradients in composition and microstructure. For example, under the extreme conditions of ramping up from 0 to 0.75 A/cm2 current density and 75% H2 utilization in fuel cell mode, the multiphysics performance model predicts a nearly 300K temperature increase in approximately 100s for the baseline case as shown in Figure 1(d). Applying linear gradients of porosity and Ni/YSZ ratios such that TPB density increases from the fuel inlet to outlet significantly decreases this temperature gradient by 25-100K. However, there may be a tradeoff in terms of overall performance with decreasing steady state cell voltage corresponding with decreased temperature gradients. This is partly associated with the decreased temperature itself as the reaction kinetics are assumed to increase with increasing temperature resulting in decreased overpotential at the TPBs. Additional impacts of these and other functionally graded microstructures include decreased current density gradients and more uniform oxygen reduction in the oxygen electrode compared to the baseline case. Results indicate that functionally graded electrode microstructures could be designed based on the desired operating conditions to reduce degradation and thermal stresses within cell and stack assemblies. Such electrode designs have the potential to significantly reduce cell failure rate and increase cell lifetime particularly in transient loading and/or high current density applications. Figure 1

Analytical fractal models for permeability and conductivity of open-cell metallic foams

It is demonstrated that analytical models of permeability and effective thermal conductivity for open-cell metallic foams can be developed using fractal theory, for the theory lends itself better to the problem at hand where the pore morphology of the foam is typically random. Upon determining the average tortuosity based on selected representative flow streamlines in a representative structure (RS) of the foam, the permeability as a function of porosity, average tortuosity and pore size ratio is analytically obtained, with no empirical or fitting parameter needed. Similarly, the analytical fractal model of effective thermal conductivity does not include any empirical or fitting parameter. Good agreement with experimental data verifies both models, squarely justifying the applicability of using fractal theory to characterize open-cell metallic foams. It is also demonstrated that the present fractal models can better characterize the randomness of pore distributions than previous permeability and conductivity models built upon simplified geometries including periodically distributed unit cells.

Membrane filtration of dextran solutions with water and formamide as solvent

ABSTRACT In this study, we investigated and compared the performance (permeate flux, solute rejection and membrane fouling) of an ultrafiltration membrane and a nanofiltration membrane with water and formamide as solvent. The dextran solutions with water as solvent had lower electrical conductivity and usually greater surface charge compared to that in formamide, which facilitated the electrostatic interactions taken place. As a result, faster flux decline and greater fouling resistance were usually observed in water-based solutions in both UF and NF with the same dextran used as solute. In UF, the solute rejection usually increased as the solvent switched from formamide to water, since stronger electrostatic interactions tended to impede the transport of solute through membrane. Opposite trend was found with NF, that formamide usually led to higher solute rejection compared to water as solvent. Despite the differences of surface charge altered the membrane performance prominently, no quantitative correlation was found between permeate flux and zeta potential values. The analysis using a modified Hermia’s pore blocking model indicates that the fouling mechanisms could be altered as the change of solute to membrane pore size ratio, surface charge of membranes and solutes, as well as the solvent properties.

Fractal analysis of CT images of tight sandstone with anisotropy and permeability prediction

For developing unconventional oil and gas resources, it is necessary to quantify the heterogeneity embodied in both pore-size distribution (PSD) and pore spatial distribution, on the basis of which the relationship between the seepage characteristics and the microstructure of heterogeneous porous media could then be clarified. In this work, micro computed tomography (μCT) and image processing technology were applied to characterise matrix pore structure in tight sandstone. Fractal theory was used to investigate the image-based heterogeneity of tight porous media. On the basis of the verification that the PSD of the tight rock is statistically self-similar at a certain scale, we investigated the relationships between porosity and fractal dimension, and between 2D and 3D fractal dimensions, respectively. The results showed that the pore structure characteristic parameters with anisotropy, i.e., the ratio of the minimum pore size to the maximum pore size λ max /λ min and a proportionality constant C KT , could be obtained by liner fitting fractal dimension and porosity. Moreover, the 2D PSD characteristics of the ‘standard cross section’ were consistent with the 3D PSD characteristics of pore network. A fractal permeability model was established by treating the connected pores in the matrix as a bundle of conical micropipes. The permeability values predicted by the proposed model agreed well with those predicted by finite volume method simulation under the condition where irreducible pores were removed. A sensitivity analysis indicated that increasing the heterogeneity of the PSD and pore spatial distribution reduced the flow capacity of the matrix, particularly for low-porosity porous media. • A method to verify the fractal self-similarity of pore size distribution in CT images. • D f-2 vs D f-3 of microstructure in heterogeneous porous media was explored. • Fractal anisotropic model for permeability prediction in heterogeneous porous media.

Effect of VAE emulsion and inorganic fillers on the properties of styrene-acrylic emulsion based cement composite joint sealant

A VAE emulsion was used to replace part of styrene-acrylic emulsion, and different inorganic fillers were used alone or compounded to prepare styrene-acrylic emulsion based cement composite joint sealant (SCJS). Leveling test, pour consistency test, constant elongation test, tensile test and shear test were conducted for the SCJS. The effect of VAE emulsion dosage and different inorganic fillers on the properties of SCJS were studied through measuring the working capabilities (leveling property and pour consistency), cohesive properties (form at the fixed tensile displacement and elastic recovery rate), tensile properties (tensile strength property, tensile deformation property, tensile energy consumption performance, and tensile failure mode) and shear properties (shear strength property, shear deformation property, shear energy consumption performance, and shear failure mode) of the SCJS. The effect of VAE emulsion and inorganic fillers on SCJS pore structure was also analyzed by a MIP test. The results showed that VAE emulsion and inorganic fillers did not affect working capabilities of SCJS. With the content of VAE emulsion increased, both tensile strength and shear strength of SCJS decreased, while in general, the deformation and energy consumption indexes increased significantly, with good cohesive properties, and both tensile and shear failure modes were of cohesiveness failure. The pore volume, pore size and large pore ratio decreased significantly. When talcum powder and heavy calciumcarbonate were used alone or compounded in a 1:1 ratio as inorganic fillers, SCJS had good cohesive properties and deformation flexibility, the tensile and shear failure modes were of cohesive failure. When the talcum powder and heavy calcium carbonate were compounded as inorganic fillers, the pore volume, pore size and large pores of SCJS decreased significantly. The optimal VAE emulsion dosage ranged from 30% to 40%, and for the inorganic fillers of SCJS, 50% talcum powder + 50% heavy calciumcarbonate compound was appropriate.

Laboratory assessment on factors controlling the acoustic properties of carbonates: A case study from Bombay offshore

Carbonates are known to have a heterogeneous, complicated pore structure, characterized by textural variations. This complex nature of carbonates makes it challenging to establish correlations to interpret petrophysical properties from acoustic properties. The present study focuses on investigating various parameters that influence carbonates by integrating parameters estimated from laboratory based measurements along with digital image analysis (DIA) technique, to capture the heterogeneity in pore architecture. A generalized rock physics model for carbonates of Bombay offshore basin has been developed based on compressional wave velocity (Vp) measured at laboratory conditions using ultrasonic measurement techniques. Our study maximizes the use of information obtained from the laboratory analysis that is usually constrained by accurate geological details. For this purpose, we measured Vp of carbonate core plugs using transducers of 54 kHz frequency by utilizing the through transmission technique. The parameters investigated at the laboratory include bulk density, porosity, permeability, mineral content, pore size and pore aspect ratio. Statistical analysis was performed using single as well as multiple parameter function. Mineral content was correlated with Vp and porosity. Bulk Density and porosity showed greater correlation with Vp as single parameter function while pore size showed poor correlation. A combination of bulk density, porosity and mode pore size was able to explain more than 83% of the deviation of Vp. It was observed that the predictability of Vp increases when it is modeled as a multi-parameter function of bulk density, porosity and pore size. The effectiveness of the velocity model improved when Vp was modeled as a function of these investigated parameters collectively rather than in isolation. Thus, an integrated study such as multi-regression analysis would help to present a more realistic picture that affect the relations between petrophysical, mineralogical and acoustic properties. Furthermore, while considering different saturation conditions, our study suggest that porosity and mineral composition have an effect on Vp, while effect of porosity is more prominent. We observed approximate 50% decrease in Vp values when porosity varied from 2 to 40% for different saturation conditions. Hence, the results potentially allow the interpretation of different petrophysical properties from acoustic data and thereby help in connecting geology and seismology.

Multi-Scale Digital Image Correlation Analysis of In Situ Deformation of Open-Cell Porous Ultra-High Molecular Weight Polyethylene Foam.

Porous ultra-high molecular weight polyethylene (UHMWPE) is a high-performance bioinert polymer used in cranio-facial reconstructive surgery in procedures where relatively low mechanical stresses arise. As an alternative to much stiffer and more costly polyether-ether-ketone (PEEK) polymer, UHMWPE is finding further wide applications in hierarchically structured hybrids for advanced implants mimicking cartilage, cortical and trabecular bone tissues within a single component. The mechanical behaviour of open-cell UHMWPE sponges obtained through sacrificial desalination of hot compression-moulded UHMWPE-NaCl powder mixtures shows a complex dependence on the fabrication parameters and microstructural features. In particular, similarly to other porous media, it displays significant inhomogeneity of strain that readily localises within deformation bands that govern the overall response. In this article, we report advances in the development of accurate experimental techniques for operando studies of the structure–performance relationship applied to the porous UHMWPE medium with pore sizes of about 250 µm that are most well-suited for live cell proliferation and fast vascularization of implants. Samples of UHMWPE sponges were subjected to in situ compression using a micromechanical testing device within Scanning Electron Microscope (SEM) chamber, allowing the acquisition of high-resolution image sequences for Digital Image Correlation (DIC) analysis. Special masking and image processing algorithms were developed and applied to reveal the evolution of pore size and aspect ratio. Key structural evolution and deformation localisation phenomena were identified at both macro- and micro-structural levels in the elastic and plastic regimes. The motion of pore walls was quantitatively described, and the presence and influence of strain localisation zones were revealed and analysed using DIC technique.