Variable Porosity Research Articles

Impacts of Stress‐dependent Hydraulic Properties on Hillslope‐Scale Groundwater Flow

AbstractGroundwater flow at the hillslope scale is controlled by hydraulic properties and topography. Geological media are inherently heterogeneous, with properties depending on both lithology and external factors such as weathering, erosion, and tectonic activity. The effects of stress‐dependent variations in porosity and hydraulic conductivity on groundwater flow and residence times remain unexplored. Using process‐based hillslope models, we demonstrate how external lateral stresses cause significant variations in stress and strain, particularly on slopes steeper than 30%. These stresses reorganize porosity and hydraulic conductivity, with compressive regimes reducing these properties at valley bottoms and tensional regimes elevating values at crests. This redistribution of porosity and hydraulic conductivity leads to a channeling of groundwater flow near the surface. Channeling increases discharge rates in the upper seepage zone and the proportion of rapid flows. Our results highlight geomechanical‐hydraulic property relationships as critical controls on critical zone processes in mountain settings.

Influence of temperature and layer height on the structural and mechanical properties of continuous biocomposites by in–nozzle impregnation additive manufacturing

Purpose This study aims to assess the relationships between limit parametric settings of in-nozzle impregnation additive manufacturing, namely, nozzle temperature and layer height, on the micromorphology and induced mechanical properties of continuous flax yarns-reinforced biocomposites. Design/methodology/approach The additively manufactured biocomposites with different printing parameters were characterized by X-ray microcomputed tomography and tensile testing to link the process–structure–properties relationships regarding the internal morphologies of yarns, matrix and porosities and tensile properties. Findings Several types of morphology were defined regarding fiber, void, raster and interfaces. The results showed a competition between porosity development, coating effect and variation in fiber volume fraction on the biocomposite quality and mechanical performance when simultaneously varying the layer height and the temperature due to rheology-related phenomena and process-induced defects. Originality/value To the best of the authors’ knowledge, no previous study has been carried out on the relation between the internal micromorphologies in three directions of continuous biocomposites manufactured by in-nozzle impregnation additive manufacturing and the limit printing parameters. The findings are thought to help manufacturers master this technology for high-end applications.

Effect of Lithiation-Dependent Porosity Variation on the Mechanical Integrity of Silicon Composite Electrode

Effect of Lithiation-Dependent Porosity Variation on the Mechanical Integrity of Silicon Composite Electrode

Non-linear thermoelastic analysis of circular sandwich porous plates reinforced with functionally graded graphene platelets

The investigation of graphene-reinforced porous composites has garnered significant interest due to their exceptional mechanical, thermal, and electrical properties, positioning them as promising materials for advanced structural applications. To fully harness the potential of these materials, numerical modeling becomes essential for understanding their behavior and optimizing their performance for specific engineering applications. In the present study, the non-linear bending response of functionally graded (FG) circular sandwich porous plates reinforced with graphene platelets is systematically analyzed under varying boundary conditions. The plates are subjected to a uniform transverse load and a thermal gradient, with distributions of graphene platelets and porosity graded along the thickness. The effective material properties, including Poisson’s ratio, are computed using the Gaussian random field scheme in conjunction with the Halpin-Tsai micromechanical model. The governing equations of motion are derived from Von Kármán’s non-linear relations, utilizing both first-order shear deformation theory (FSDT) and modified higher-order shear deformation theory (MHSDT). These equations are subsequently solved using dynamic relaxation (DR) coupled with finite difference methods. To validate the results, comparisons with existing literature and finite element method (FEM) are conducted, ensuring the accuracy and reliability of the obtained solutions. A comprehensive parametric study is performed to investigate the influence of various factors, including boundary conditions, graphene distribution patterns, porosity variations, and the thickness-to-radius ratio, on the non-linear bending behavior of the composite plates.

Influence of Process Parameter and Build Rate Variations on Defect Formation in Laser Powder Bed Fusion SS316L.

Laser powder bed fusion (LPBF) is an additive manufacturing process that has gained interest for its material fabrication due to multiple advantages, such as the ability to print parts with small feature sizes, good mechanical properties, reduced material waste, etc. However, variations in the key process parameters in LPBF may result in the instantiation of porosity defects and variation in build rate. Particularly, volumetric energy density (VED) is a variable that encapsulates a number of those parameters and represents the amount of energy input from the laser source to the feedstock. VED has been traditionally used to inform the quality of the printed part but different values of VED are presented as optimal values for certain material systems. An optimal VED value can be maintained by changing the key process parameters so that various combinations yield a constant value. In this study, an optimal constant VED value is maintained while printing SS316L with variable key processing parameters. Porosity analysis is performed using optical microscopy, as well as X-ray computed tomography, to reveal the volume density and distribution of those pores. Two primary defect categories are identified, namely lack of fusion and porosity induced by balling defects. The findings indicate that, even at optimal VED, variations in process parameters can significantly influence defect type, underscoring the sensitivity of defect formation to the variation of these parameters. Furthermore, a minor change in the build rate, driven by adjustments in process parameters, was found to influence defect categories. These findings emphasize that fine tuning the process parameters and build rate is essential to minimize defects. Finally, fiducial marks have been identified as a source of unintentional porosity defects. These results enable the refinement of process parameters, ultimately optimizing LPBF to achieve enhanced material density and expedite the printing.

Evaluation of wave-induced flow through marine porous media accounting for transition of seepage properties across multiple flow regimes

Wave-induced flow through marine porous media has been attracting coastal engineers and researchers because of their strong correlation with scouring, internal erosion, piping and other destructions of marine porous structures. Previous studies chose Darcy-Forchheimer equation for wave-induced seepage behavior analyses because of its simplicity and perceptiveness. However, numerous experiment observations suggested that significant flow regime transition occurred in porous media with high variations in porosity and particle size, while Darcy-Forchheimer equation is only applicable to flow within Forchheimer regime. In this paper, a mathematical model linking the resistance of porous medium to its porosity and particle size is proposed to characterize the seepage properties across Darcy and Forchheimer regime under wave loadings. The proposed seepage model is then incorporated into volume-averaged Reynolds-averaged Navier-Stokes equations, and thus enabling evaluating fluid motions in waves and marine porous media via a unified framework. Through validation against experimental observations, analytical solutions and well accepted computed results in the literature, the proposed model is shown to replicate the characteristics of resistance of porous media with different porosities and particle sizes under different flow regimes. Numerical analyses are conducted to elucidate that seepage velocities of wave-induced flow in marine porous materials can be over- or under-estimated if not considering transitional seepage properties across multiple flow regimes. Such discrepancies can become significant when strong variations occur in porous media with respect to particle size and/or porosity.

The Small-Strain Stiffness Properties of Clay-Gravel Mixture Subjected to Freeze-Thaw Cycles

Abstract In this paper, the resonant column tests were utilized to examine the small-strain stiffness and attenuation of clay-gravel mixture (CGM) under various effective consolidation pressures and freeze-thaw cycles, on the basis of investigating the electrical resistivity variation trend of CGM samples undergoing various freeze-thaw cycles. It is shown that the resistivity of CGM tends to stabilize when the freeze-thaw cycles (N) reach 9, and, thus, the samples after 0, 3, 6, 9, and 12 cycles were selected for resonance column testing. The results show that, once N > 9, the decay in dynamic shear modulus demonstrates a weakened association with N and the stiffness degradation effect of freezing-thawing would be weakened and inhibited by high effective consolidation stress. Additionally, a mathematical model was constructed to predict the maximum dynamic shear modulus (Gmax) in the basis of freeze-thaw cycles and effective consolidation stress. Microscopic analysis results suggest that the freeze-thaw effect on CGM lies in the development of soil aggregates and porosity variation within the fine-grained soil. Compared to gravel soils and frozen soil, the cementation of matrix soil and the effect of blocky structure are considered as fundamental reasons for the improved small-strain stiffness and reduced vulnerability to freeze-thaw cycles of CGM.

Revolutionizing High-Pressure Well Cementing: Enhancing Geopolymer Cement with Laponite for Sustainable and Sedimentation-Free Applications

Summary Sustainable geopolymer cement emerges as a prospective substitute to traditional Portland cement systems in the petroleum industry. Geopolymers offer different advantages over Portland cement, including reduced carbon emissions due to lower energy requirements during production, improved durability and chemical resistance, and the ability to use industrial byproducts as raw materials. This technology promotes sustainable waste management practices while maintaining high performance in various applications. This research aims to explore and maximize the geopolymer technology potential by addressing the issue of sedimentation in high-pressure well cementing applications. By incorporating Laponite particles into hematite-based Class F fly ash (FFA) geopolymer cement formulations, a solution is presented to mitigate sedimentation problems and ensure homogeneity and density uniformity along cement columns. Through the application of American Petroleum Institute (API) and non-API techniques, this study uncovers the remarkable benefits of Laponite in mitigating sedimentation problems and enhancing key characteristics such as strength and rheological properties. The findings reveal that Laponite-based geopolymer systems exhibit improved yield point (YP) and gel strength (GS), as well as reduced porosity and density variation. Adding 3% by weight of FFA of Laponite to the cement formulation reduced the density difference between cement sections from 39.38% when no Laponite was present in the system to only 0.58%. Additionally, the measured elastic properties indicate enhanced flexibility compared with Portland cement systems. By determining the optimal Laponite concentration, this study achieves a step forward in promoting sedimentation-free and environmentally friendly non-Portland cementing methods in the petroleum industry.

A holistic exploration of porous asphalt mixtures: From durability and permeability to low-temperature and functional properties.

This article provides a comprehensive review of the research progress on porous asphalt mixtures, focusing on their durability, permeability, low-temperature performance, and functionality. The study examines factors influencing the anti-raveling performance of porous asphalt, including modified asphalt binders, fibers, aggregates, traffic loads, and environmental conditions. It also discusses the impact of porosity, pore structure, and temperature variations on the low-temperature cracking resistance of porous asphalt. Furthermore, the article explores the permeability of porous asphalt mixtures, emphasizing the influence of pore characteristics, water flow directions, clogging processes, and pavement designs. The sound absorption and skid resistance properties of porous asphalt are also analyzed, highlighting the importance of porosity, texture depth, material properties, and water film thickness. The study concludes by proposing improvement measures and optimization suggestions for porous asphalt mixtures, providing valuable references for future research and applications. Finally, several future research topics for porous asphalt mixture are proposed. Further studies on porous asphalt pavement involves seeking performance balance, ensuring improvement without detriment. Researching factor interactions, building a model, exploring industrial waste use to cut costs, reduce pollution and promote its environmental application for diverse traffic and environment needs.

STUDY OF GRAIN FLOW IN A CYLINDRICAL VIBRATING SIEVE

The paper proposes a modified hydrodynamic model of steady grain flow of a heterogeneous mixture on the surface of a vertical cylindrical vibrating sieve. The main hypothesis of the model is the dependence of the mixture's porosity in the moving annular layer on the particle velocity. A linear dependence is assumed, where an increase in velocity leads to an increase in the mixture's porosity. To determine the grain flow velocity, the problem is reduced to solving a non-homogeneous Bessel-type differential equation. To simplify the solution, the "freezing" method of the variable coefficient is applied, which is permissible due to the relatively small thickness of the moving grain mixture layer compared to the sieve radius. As a result of this approximation, the velocity dependence on the radial coordinate is expressed using elementary functions. A compact formula for calculating the maximum grain flow velocity and the average velocity is derived by integrating the respective expression in elementary functions. Additionally, an approximate formula for calculating the sieve's throughput based on the mass of the overflow fraction is proposed. Simpson's integration method is used to avoid complex calculations of special functions for large arguments via asymptotic formulas. The study shows that the sieve's throughput is significantly affected by the porosity of the grain mixture. To assess the accuracy of the approximate formulas, numerical integration of the original Bessel-type differential equation was performed on a computer. Comparative analysis of the results confirmed that the proposed simplifications introduce minimal errors and ensure the adequacy of the theoretical results. Thus, by transitioning to the simplified differential equation, approximate formulas for calculating the key characteristics of grain flow in a vertical cylindrical vibrating sieve were developed and tested, taking into account the porosity variation of the mixture depending on the particle velocity. The generalization of theoretical results obtained using hydrodynamic models of grain mixture flow in a pseudo-fluidized state under vibrations only slightly complicated the model but resulted in compact and practically convenient formulas for use.

OPTIMIZING VOLUMETRIC SOLAR AIR RECEIVERS: NUMERICAL ANALYSIS OF POROSITY AND FLOW EFFECTS ON TEMPERATURE DISTRIBUTION

Ceramic foams are promising as absorber materials for volumetric solar receivers (VSR) in concentrated solar thermal power (CSP) systems. The temperature distribution of the VSR is very important to ensure that it operates efficiently and steadily. This study aims to simulate and analyze the temperature distribution within a VSR considering both the solid and fluid phases. The modelling of the open-cell volumetric receiver employs combined volume-averaged equations, assuming the ceramic foam to possess isotropic and homogeneous properties. To assess the pressure-drop in the VSR a non-Darcian model is adopted. A local thermal non-equilibrium (LTNE) model is implemented to describe the energy equations for both the solid and fluid phases. Additionally, the study considers the influence of solar radiation as a heat source on the solid phase. The heat transfer between the surfaces of the volumetric solar air receiver's struts is calculated using the P1 model. At the same time, a macroscopic approach is utilized to evaluate the thermal profile of the ceramic foam. This study also aims to assess the impact of the VSR's porosity and cell size variation on the outlet air temperature. Moreover, the flow scheme of the flowing air, concerning the incident of concentrated radiation, is considered.

Mechanical Behavior of Marine Soft Soil with Different Water Contents Under Cyclic Loading

This study integrates macroscopic dynamic triaxial tests with microscopic discrete element simulations to comprehensively examine the dynamic deformation characteristics of marine soft soils under cyclic loading. Unlike previous research that typically focuses solely on experimental or numerical methods, this approach combines both techniques to enable a holistic analysis of soil behavior. The dynamic triaxial tests assessed macroscopic responses, including strain evolution and energy dissipation, under varying dynamic stress ratios, confining pressures, and water contents. Concurrently, discrete element simulations uncovered the microscopic mechanisms driving these behaviors, such as particle rearrangement, porosity variations, and shear zone development. The results show that (1) The strain range of marine soft soils increases significantly with higher dynamic stress ratios, confining pressures, and water contents; (2) Cumulative dynamic strain and particle displacement intensify at water contents of 50% and 55%. However, at a water content of 60%, the samples exhibit significant damage characterized by the formation of shear bands throughout the entire specimen; (3) As water content increases, energy dissipation in marine soft soils accelerates under lower confining pressures but increases more gradually under higher confining pressures. This behavior is attributed to enhanced particle packing and reduced pore space at elevated confining pressures. This integrated methodology not only enhances analytical capabilities but also provides valuable engineering insights into the dynamic response of marine soft soils. The findings offer essential guidance for the design and stabilization of marine soft soil infrastructure in coastal urban areas.

Design and Evaluation of 3D-Printed Lattice Structures as High Flow Rate Aerosol Filters.

Aerosol contamination presents significant challenges across various industries, ranging from healthcare to manufacturing. Over the past few years, open foam filters have gained prominence for their ability to efficiently capture particles while allowing reasonable airflow. In this work, we present the use of 3D-printed idealized open foam-like lattice structures as aerosol filtration media, leveraging advances in additive manufacturing to generate these highly tunable and modular filters. Using parametric design approaches, we fabricated lattice filters with four different unit cell geometries (Cubic, Kelvin, Octahedron, and Weaire-Phelan) via Digital Light Synthesis 3D printing and characterized these structures with X-ray microcomputed tomography. We compared the aerosol filtration performance of the different lattice unit cell geometries using 1 μm polystyrene latex (PSL) aerosol particles, finding the filtration performance to be positively correlated with the single-unit-cell specific surface area. We then expanded our evaluation of deposition efficiency in Kelvin cell lattice structures of varied porosities, again finding a correlation between the specific surface area and deposition performance. Experimental analysis confirmed that deposition primarily occurs through impaction and electrostatic mechanisms within the parameter space. Overall, our findings demonstrate that unit-cell-based lattices can achieve a wide range of aerosol filtration efficiencies (∼10-100%) across various operating conditions (1-4 m/s superficial velocity), offering a highly tunable in-line filtration medium capable of maintaining high efficiency even at elevated airflow rates. This work not only provides essential guidelines for designing and manufacturing 3D-printed lattices as customizable aerosol filters but also highlights the current limitations and challenges in producing these structures.

Can a Light Detection and Ranging (LiDAR) and Multispectral Sensor Discriminate Canopy Structure Changes Due to Pruning in Olive Growing? A Field Experimentation.

The present research aimed to evaluate whether two sensors, optical and laser, could highlight the change in olive trees' canopy structure due to pruning. Therefore, two proximal sensors were mounted on a ground vehicle (Kubota B2420 tractor): a multispectral sensor (OptRx ACS 430 AgLeader) and a 2D LiDAR sensor (Sick TIM 561). The multispectral sensor was used to evaluate the potential effect of biomass variability before pruning on sensor response. The 2D LiDAR was used to assess its ability to discriminate volume before and after pruning. Data were collected in a traditional olive grove located in Tenute di Cesa Farm, in the east of Tuscany, Italy, characterized by a 4x6 m planting layout and by developed plants. LiDAR data were used to measure canopy volumes, height, and diameter, and the generated point cloud was studied to assess the difference in density between treatments. Ten plants were selected for the study. To validate the LiDAR results, manual measurements of the canopy height and diameter dimensions of the plants were taken. The pruning weights of the monitored plants were obtained to assess the correlation with the canopy characterization data. The results obtained showed that pruning did not affect the results of the multispectral sensor, and the potential variation in canopy density and porosity did not lead to different results with this instrument. Plant volumes, height, and diameters calculated with the LiDAR sensor correlated well with the values of manual measurements, while volume differences between before and after pruning obtained good correlations with pruning weights (Pearson correlation coefficient: 0.66-0.83). The study of point cloud density in canopy thickness and height showed different shapes before and after pruning, especially in the former case. Correlations between point cloud density obtained from LiDAR and multispectral sensor results were not statistically significant. Even if more studies are necessary, the results obtained can be of interest in pruning management.

Prediction of Reservoir Properties Using the RDQ Crossplot Workflow

We present the Rotated Distance and Quadrant (RDQ) Crossplot, an innovative alternative to the conventional amplitude versus offset (AVO) analysis using amplitude versus gradient (AB) crossplots. This new display is made possible through integration of the Distance and Quadrant (DQ) trace attribute, and offers significant advantages over traditional methods. The RDQ Crossplot reduces shale datapoint overprinting on wet and gas sand clusters, better separates lithology and pore fluid points, and analyzes all seismic trace samples. Unlike AB crossplots, which require specialized processing and conversion of seismic amplitudes, the RDQ workflow uses readily available near and far partial-stack seismic sections as input, expediting the AVO analysis. An AVO catalog of well log suites and their synthetic modeled seismic traces are used to develop and test new theories, revealing linear trends in RDQ Crossplot displays that correlate to variations in thickness, porosity, lithology, and pore fluid. A new seismic trace attribute, DQOpx, is derived from the RDQ Crossplot and used to better delineate fluid types and augment lithology predictions. We demonstrate a DQOpx seismic display for a dim spot, AVO Class 1 sand model, revealing a hydrocarbon fluid contact not visible on stack seismic sections. Additionally, a Signed Half Isochron preconditioning filter is introduced to distinguish between sand and shale lithologies. The RDQ workflow and Crossplot represent a significant advancement in seismic AVO interpretation and reservoir characterization, allowing for earlier integration of geology, petrophysics, and basin properties.

Use of a bioactive matrix glove in the treatment of paediatric hand burns: a case series.

Burns to the hand are a common injury in paediatrics and can be traumatic to children, both physically and psychologically. Timely conservative or operative management is critical to maximise healing and minimise long-term complications in these young patients. Here, we present the cases of patients treated with a novel skin substitute formed into a prefabricated glove. The glove (PermeaDerm, Inc., US) is a bioactive matrix composed of a silicone composite membrane embedded with collagen and aloe extract with variable porosity that allows moisture to pass to a secondary dressing. To our knowledge, our group was the first to treat a small set of paediatric patients with hand burns with the glove. A chart review was conducted to analyse hospital course, treatment length, complications and outcomes for each patient. The age range of the five patients included in this case series was seven months to three years. All five patients had scald burns to the hand. Overall, healing with the glove was successful, with little scarring or altered skin pigmentation, and a full range of motion at the affected joints. Hand burns in paediatric patients are traumatic and cumbersome to the patient and their families. This bioactive matrix glove allows for a one-time application, decreases operating room time and need, and reduces the demand for multiple dressing changes. In our set of five patients, the glove showed promising results as a safe and effective noninvasive treatment option for hand burns in paediatric patients.

Validating ex210Pb sediment dating methods applied to a large anthropogenically-impacted river basin

Sediment dynamics in five sites within the Mobile River Basin, Alabama, impacted by (i) dam-and-lock use, (ii) urbanization, (iii) industrial/mining practices, (iv) flooding, and (v) storm surge events were evaluated to understand better anthropogenic impacts on regional sediment budgets. Three widely used sediment dating models based on excess 210Pb (ex210Pb) (i.e., Constant Rate of Supply, CRS, Constant Initial Concentration, CIC, and Advective Dispersion Equation, ADE) and two recently developed ones (i.e., Porosity Variation, PV and Porosity Variation Without Diffusion, PVWD) were tested to determine their applicability to these anthropogenically altered lacustrine and coastal areas. To verify results from ex210Pb models, we used conventional time markers, including regional hydrograph records and historical aerial images. We found that the traditional time-marker 137Cs is no longer helpful due to its current low inventories in the sediments. Drainage-to-lake area ratios were used to determine relative runoff and atmospheric radionuclide contributions. Statistical analysis of physical properties such as porosity, bulk and dry density, water content, and sediment geochemical compositions were utilized to support sediment transport and site development hypotheses. When constructing the sediment history at each site using these proxies, we found that the conventional CIC and ADE models produced unreliable ages because of violation of requirements for exponentially decreasing porosity and ex210Pb activity with depth. We found that two new models, PV and PVWD, that account for heterogeneous porosity, produced more reliable sediment ages. These two models produced ages with lower uncertainties than the CRS model, outperforming the other conventional models tested. We conclude that the PV and PVWD models are more appropriate for environments experiencing erosional and abrupt depositional events, which in our study resulted from dam construction and storm-surge events. Model sensitivity analysis showed that decreasing average particle density produces younger sediment ages by the PV and PVWD models. Higher ex210Pb activity analytical uncertainty resulted in lower sedimentation rates and higher estimated ages by all five models.

Promoting photoswitching in mismatching mixed-linker multivariate Zr6 MOFs.

Multivariate metal-organic frameworks (MTV MOFs) have emerged as promising materials due to their ability to combine properties that enhance features beyond those of their pristine counterparts. Despite the potential for tailoring electronic properties through structural distortions and defects introduced by linkers of variable lengths, examples remain scarce, and information on the electronic structure is limited. Here, we present the multivariate mismatching linker approach to generate photoswitching nanoparticulated MOFs with variable lattice parameters and porosity features controlled by mixed-linker composition. Structural defects, such as dangling linkers, are generated due to mismatching crystal lattices, tuning the electronic structure. Combining biphenyl and azobenzene ditopic linkers promotes cis-trans photoswitching of dangling azobenzene linkers, which is constrained in Zr6-azobenzene MOFs. Moreover, introducing low quantities of azobenzene drastically reduces the bandgap of the materials due to the contribution of the azo group, which is supported by first-principles calculations. This paves the way for new photo-responsive materials for photo-switching applications.

Estimating petrophysical properties using Geostatistical inversion and data-driven extreme gradient boosting: A case study of late Eocene McKee formation, Taranaki Basin, New Zealand

Estimation of petrophysical properties holds significant importance in evaluating the feasibility of hydrocarbon extraction and enhancing production efficiency. Therefore, theintegration of seismic data with well data for reservoir characterization has garnered significant attention in the oil and gas industry. This approach provides a comprehensive view of the lateral variations across the entire reservoir. In this study, our goal is to establish a relationship between seismic attributes and the petrophysical properties of the reservoir, enabling the prediction of property distribution across the entire reservoir. We employed geostatistical inversion to generate detailed P-impedance maps of the reservoir, capturing its spatial heterogeneity. A total of 100 realizations were produced and ranked into P10, P50, and P90 scenarios, representing different probabilistic outcomes. The P90 scenario, considered the most representative of the reservoir's average properties, was selected for interpretation, enabling a comprehensive analysis of reservoir heterogeneities and their distribution. Subsequently, we estimated porosity using various seismic attributes, employing a Data-driven Extreme Gradient Boosting (Xgboost) approach within the reservoir analysis. This method enabled us to estimate a high-resolution acoustic impedance and porosity with minimal root mean square error of 3.8 and r2score of 66 % across the spatial gap which ranges from 8468.84 to 9367.85(g/cc) *(m/s) and 10 to 45 % between wells, revealing the lateral variation of acoustic impedance and porosity within the reservoir interval of interest. The information provided was found to be of significant value in the identification of potential sweet spots and plays a pivotal role in the development of a reservoir management strategy for future hydrocarbon exploration.

Enabling in-Line Silicon Wafer Porosification: An Experimental and Simulation Study

Silicon is the dominant material of microelectronic and solar cell devices but also a very promising material for Li-ion battery anodes. For many of these applications thin silicon layers are needed for which a layer transfer is a very efficient way to produce them. In this paper, results of large-scale etched porous silicon wafers using an in-line pilot production tool will be presented. The tool uses a wet chemical front-side contact that periodically changes polarity and thus just needs one side of the wafer in contact to the electrolyte. However, the proportion of the wafer that is exposed to each polarity is a function of its current location, leading to large current density fluctuations. Therefore, multiple electrodes have been positioned within the half-cells of the setup. Voltage and current data were recorded as a function of time, and the respective position of wafer, for all electrodes. A finite element simulation using COMSOL allowed for a very good reproduction of these in-operando measured data. A clear correlation to lateral and vertical porosity variations within the porous layers has been found.All etching inhomogeneities in the porous layer can be clearly explained by changes in the series resistance and the corresponding voltage losses as the wafer is moving through the setup. These series resistance changes are almost exclusively related to the geometrical shape of the half cells and the positions of the counter electrodes. This means that the passive series resistance network is the reason for non-perfect etching of the porous layers rather than non-linear electrochemical processes. This network also includes the anode and the cathode that are used for contacting the electrochemical half cells. The smart contacting scheme of the in-line etching tool showed up to be fully reliable. The COMSOL studies displayed, that changes of the half-cell geometries can drastically decrease the current fluctuations. Adjustments have shown that a decrease from an initial 40% fluctuation to less than 6% fluctuation are achievable. This allows for the etching of laterally homogeneous porous layers suitable for a layer transfer.