Porous Solids Research Articles

Hydro-mechanical coupled B-spline material point method for large deformation simulation of saturated soils

Numerical simulation for large deformation problems of saturated soil poses an ongoing challenge since it requires the capabilities of modeling large deformations, interactions between solid skeleton and pore water, as well as fluidization behaviors. A hydro-mechanical coupled B-spline material point method is developed to simulate large deformations of saturated soils. Based on Biot's mixture theory, a single set of material particles is adopted to represent saturated soils where Darcy's law is employed to govern the motion of pore water and the momentum conservation of the mixture is used to govern the motion of solid skeleton. The convergence and effectiveness of the proposed method are examined by one-dimensional consolidation tests and quasi-static footing penetration into two-dimensional elastic saturated soils. The capability of simulating practical engineering for the proposed method is demonstrated by reproducing the dynamic process of three-dimensional saturated soil slopes with a strain-softening Drucker-Prager constitutive model. Results show that the coupled BSMPM well reveals the overall dynamic process of saturated soil slope involving evolution of shear bands, formation of graben and horst, and fluidization of progressive failures with improved computational accuracy and enhanced convergence, which demonstrates the proposed method is a promising approach for large deformation problems of saturated soils.

Theoretical insights into CO2/N2 selectivity of the porous ionic liquids constructed by ion-dipole interactions

Porous liquids, a new class of materials, containing solid pores and liquid properties, have greatly aroused attention. In terms of gas absorption, porous liquids exhibit excellent advantages. Nevertheless, a variety of reports still lack the understanding of its absorption mechanism at the molecular level. Herein, we have figured out the factors contributing to the formation of porous liquids made of porous organic cages that can be dissolved in the crown ether, and the absorption mechanism of carbon dioxide, as well as CO2/N2 selectivity. Through charge and Wiberg index analysis, the results show that crown ethers can interact with alkali metals to form alkali metal complexes by ion–dipole interactions, the dominant driving force of which is electrostatic interaction rather than coordination effect. Besides, the metal complexes should be regarded as a whole entity, which increases the steric hindrance of the cations and greatly reduces the probability of the crown ether blocking the cavity. The porous organic cage does provide unoccupied pores for gas storage. Furthermore, compared with N2, cages prefer to absorb CO2 mainly through hydrogen bonding. It is hoped that this work can facilitate the design and synthesis of porous liquids for gas absorption and selectivity.

Modular Type III Porous Liquids Based on Porous Organic Cage Microparticles

AbstractThe dispersion of particulate porous solids in size‐excluded liquids has emerged as a method to create Type III porous liquids, mostly using insoluble microporous materials such as metal–organic frameworks and zeolites. Here, the first examples of Type III porous liquids based on porous organic cages (POCs) are presented. By exploiting the solution processability of the POCs, racemic and quasiracemic cage microparticles are formed by chiral recognition. Dispersion of these porous microparticles in a range of size‐excluded liquids, including oils and ionic liquids, forms stable POC‐based Type III porous liquids. The flexible pairing between the solid POC particles and a carrier liquid allows the formation of a range of compositions, pore sizes, and other physicochemical properties to suit different applications and operating conditions. For example, it is shown that porous liquids with relatively low viscosities or high thermal stability can be produced. A 12.5 wt% Type III porous liquid comprising racemic POC microparticles and an ionic liquid, [BPy][NTf2], shows a CO2 working capacity (104.30 µmol gL−1) that is significantly higher than the neat ionic liquid (37.27 µmol gL−1) between 25 and 100 °C. This liquid is colloidally stable and can be recycled at least ten times without loss of CO2 capacity.

Computational micromechanics of porous brittle solids

Porous brittle solids evidence complex mechanical behavior, where localized failure patterns originate from mechanical processes on the microstructural level. In order to investigate the failure mechanics of porous brittle solids, we outline a general stochastic and numerical microstructure-based approach. To this end, we generate random porous microstructures by level-cutting Gaussian random fields, and conduct numerical simulations using the material point method. This allows investigating both small and large deformation characteristics of irregular porous media where a segmentation into grains and bonds is ambiguous. We demonstrate the versatility of our approach by examining elasticity and failure as a function of a wide range of porosities, from 20% to 80%. Observing that onset of failure can be well described through the second order work, we show that the stress at failure follows a power law similar to that of the elastic modulus. Moreover, we propose that the failure envelope can be approximated by a simple quadratic fitting curve, and that plastic deformation appears to be governed by an associative plastic flow rule. Finally, large deformation simulations reveal a transition in the mode of localization of the deformation, from compaction bands for highly porous samples to shear bands for denser ones.

Technological Advances of 3D Scaffold-Based Stem Cell/Exosome Therapy in Tissues and Organs.

Recently, biomaterial scaffolds have been widely applied in the field of tissue engineering and regenerative medicine. Due to different production methods, unique types of three-dimensional (3D) scaffolds can be fabricated to meet the structural characteristics of tissues and organs, and provide suitable 3D microenvironments. The therapeutic effects of stem cell (SC) therapy in tissues and organs are considerable and have attracted the attention of academic researchers worldwide. However, due to the limitations and challenges of SC therapy, exosome therapy can be used for basic research and clinical translation. The review briefly introduces the materials (nature or polymer), shapes (hydrogels, particles and porous solids) and fabrication methods (crosslinking or bioprinting) of 3D scaffolds, and describes the recent progress in SC/exosome therapy with 3D scaffolds over the past 5 years (2016–2020). Normal SC/exosome therapy can improve the structure and function of diseased and damaged tissues and organs. In addition, 3D scaffold-based SC/exosome therapy can significantly improve the structure and function cardiac and neural tissues for the treatment of various refractory diseases. Besides, exosome therapy has the same therapeutic effects as SC therapy but without the disadvantages. Hence, 3D scaffold therapy provides an alternative strategy for treatment of refractory and incurable diseases and has entered a transformation period from basic research into clinical translation as a viable therapeutic option in the future.

Challenges and Opportunities for the Encapsulation of Enzymes over Porous Solids for Biodiesel Production and Cellulose Valorization into Glucose

AbstractDifferent porous supports of enzyme catalysts are reviewed here for the valorization of biomass and production of biodiesel, given the high yields and mild reaction conditions in the presence of the biocatalysts. Two main types of enzymes have been widely employed for such endeavors, i. e. lipase and cellulase, which are able to produce fatty acid alkyl esters and glucose from fats and cellulose, respectively. Robust and versatile porous silica, carbon, polymers and metal‐organic frameworks are among the most employed supports of the enzymes, via simple adsorption or covalent grafting. Herein, we provide a comprehensive review by comparing the catalytic performance of the enzymes supported over porous solids with respect to the bulk/free enzymes in terms of yields, stability and recycling, highlighting the benefits of the porous support for an optimal biocatalytic performance in the biodiesel production and cellulose valorization into glucose. The final section provides our views for further developments in this field.

Point-cloud deep learning of porous media for permeability prediction

We propose a novel deep learning framework for predicting the permeability of porous media from their digital images. Unlike convolutional neural networks, instead of feeding the whole image volume as inputs to the network, we model the boundary between solid matrix and pore spaces as point clouds and feed them as inputs to a neural network based on the PointNet architecture. This approach overcomes the challenge of memory restriction of graphics processing units and its consequences on the choice of batch size and convergence. Compared to convolutional neural networks, the proposed deep learning methodology provides freedom to select larger batch sizes due to reducing significantly the size of network inputs. Specifically, we use the classification branch of PointNet and adjust it for a regression task. As a test case, two and three dimensional synthetic digital rock images are considered. We investigate the effect of different components of our neural network on its performance. We compare our deep learning strategy with a convolutional neural network from various perspectives, specifically for maximum possible batch size. We inspect the generalizability of our network by predicting the permeability of real-world rock samples as well as synthetic digital rocks that are statistically different from the samples used during training. The network predicts the permeability of digital rocks a few thousand times faster than a lattice Boltzmann solver with a high level of prediction accuracy.

Nanocarbon Type Xerogel Materials Designed for Water Desalination.

The relative performance of different porous solids in different applications is highly dependent on the internal pore structure of each material. Highly porous carbon materials can be prepared by evaporative drying and the pyrolysis of resorcinol-formaldehyde gels. By determining the correct synthesis parameters, the pore system of such materials can be reshaped. Depending on some important processing factors such as the dilution ratio or the initial pH of the precursor solution, various porous or non-porous carbon materials can be synthesized. This paper addresses carbon xerogels (CX) designed as a material electrode in capacitive deionization (CDI) systems for water desalination. In this work CX materials were synthesized via poly-condensation reactions of resorcinol with formaldehyde (RF) on a carbon felt sheet followed by pyrolysis. The resulting sheets were used as electrodes to develop a CDI experimental multi-cell laboratory system. The initial pH of the RF solution and the dilution ratio effect on the resulting carbon surface area and structure were analyzed. Surface area measurements using the BET method and an electrochemical capacitance evaluation of the obtained xerogels through electrochemical impedance spectroscopy were also performed. Finally, using our experimental CDI multi-cell laboratory system based on the obtained CX, we discuss the experimental data for the desalination rate as a function of the voltage and salt concentration. As a result, the developed model’s efficiency is demonstrated. The main goal of this work was to develop an efficient electrode-based novel carbon that could be commercially competitive, as well as to create guidelines for future desalination research using CX electrode materials.

A strain gradient plasticity model of porous single crystal ductile fracture

A strain gradient void-driven ductile fracture model of single crystals is proposed and applied to simulate crack propagation in single and oligo-crystal specimens. The model is based on a thermodynamical framework for homogenized porous solids unifying and generalizing existing thermodynamical formulations. This porous single crystal ductile fracture model relies on a multi-surface representation of porous crystal plasticity in which the standard Schmid law is enhanced to account for porosity, including void growth and void coalescence mechanisms. A new criterion to detect the onset of void coalescence in porous single crystals is proposed and validated by comparison to porous single crystal unit-cell simulations. This criterion can either be used as an additional yield surface or it can be used to follow the well established Gurson–Tvergaard–Needleman approach based on an effective porosity to model void coalescence. The strain gradient formulation relies on a Lagrange multiplier based relaxation of strain gradient plasticity. Material points simulations are performed in order to depict the elementary features of the porous single crystal ductile fracture model without strain gradient effects. The model is then applied to the simulation of plane strain single crystal specimen loaded in tension up to failure. The regularization ability and convergence with mesh refinement are demonstrated. Finally two- and three-dimensional simulations of ductile fracture of single and oligo-crystal specimens are presented. The significant influence of plastic anisotropy on the crack path, ductility and fracture toughness is highlighted.

Strip load on transversely isotropic elastic double porosity media with strong permeability contrast

In double porosity media, fluid could flow through the distributed micro-fractures at a larger scale as well as through the nanopores of the organic matrix at a smaller scale, while fluid mass could be transferred between them. Besides, the solid deformation acts as an important coupling term and leads to the two-way coupled process. However, these processes are not well presented in previous studies. In this work, a new coupled modeling approach was proposed for saturated double porosity media with strong permeability con-trast. Specifically, the transversely isotropic equivalent fracture permeability is considered for the preferentially oriented micro-fractures at the micro-scale or meso-scale; while at the nano-scale, the non-Darcy flow and mass transfer equations are employed to consider the interaction between fluid particles and the solid pore wall. Finally, the stabilized finite element method is developed to investigate the settlement and pressure dissipation behaviors of the strip load problem. Cited as: Zhang, Q. Strip load on transversely isotropic elastic double porosity media with strong permeability contrast. Advances in Geo-Energy Research, 2021, 5(4): 353-364, doi: 10.46690/ager.2021.04.02

Accelerating computational discovery of porous solids through improved navigation of energy-structure-function maps.

While energy-structure-function (ESF) maps are a powerful new tool for in silico materials design, the cost of acquiring an ESF map for many properties is too high for routine integration into high-throughput virtual screening workflows. Here, we propose the next evolution of the ESF map. This uses parallel Bayesian optimization to selectively acquire energy and property data, generating the same levels of insight at a fraction of the computational cost. We use this approach to obtain a two orders of magnitude speedup on an ESF study that focused on the discovery of molecular crystals for methane capture, saving more than 500,000 central processing unit hours from the original protocol. By accelerating the acquisition of insight from ESF maps, we pave the way for the use of these maps in automated ultrahigh-throughput screening pipelines by greatly reducing the opportunity risk associated with the choice of system to calculate.

Enhancement of singlet oxygen generation based on incorporation of oxoporphyrinogen (OxP) into microporous solids

Singlet oxygen, 1O2, generating compounds are highly useful for photodynamic therapy or organic oxidative transformations. In this work, the synthesis and photochemical performances for singlet oxygen generation of a range of oxoporphyrinogen-containing porous coordination polymers (OxP-PCPs) are reported. Oxoporphyrinogens, a previously unreported class of singlet oxygen generators derived from the oxidation of the antioxidant-substituted porphyrin tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin, were converted to molecular tectons by the introduction of oligophenylene-carboxylate linkers and incorporated into porous coordination polymers using well-known oxo-Zr(IV)6 cluster chemistry. Their structures and textural properties were analyzed revealing substantial surface areas up to 650 m2 g−1 for the optimum linker length (biphenylyl). The oxoporphyrinogen precursors exhibit good quantum yields of singlet oxygen generation (up to Φ = 0.37), and a high level of activity is maintained in the resulting coordination polymers, which appear to be superior for singlet oxygen generation to the precursors and to a reported reference material. These OxP-PCP materials were applied for the selective oxidation of sulfides to sulfoxides. This work demonstrates that the excellent singlet oxygen generator oxoporphyrinogens can be successfully incorporated as porous solids and conveniently applied in heterogeneous oxidative transformations.

Designer porous solids tackle separations of fluoroorganics

Porous metal-organic framework (MOF) materials can be synthesized with precise spatial control of coordinatively unsaturated Mg²⁺ sites within the pore interior. Zick and co-workers show how these Mg²⁺ sites can dictate selective interactions between the MOF-based absorbent and molecules containing C-F bonds.

Pengaruh Pemberian Charcoal Tulang Ikan Kambing-kambing (Abalistes stellaris) pada Pakan untuk Mereduksi Kadar Amonia pada Media Budidaya.

Water quality is one of the most important factors in fish cultivation. Water quality is influenced by both physical and chemical factors. These factors include temperature, DO, PH, ammonia, nitrate, and nitrite. Charcoal in particular is a solid material that has pores to absorb ammonia, nitrogen and also remove poison and grimes in cultivation media. Charcoal has solid pores which contain 85-95% carbon produced by substances that heated in a furnace for around 2 hours with 600ºC temperature. This research aims to determine the effect of bonefish charcoal distribution in reducing the ammonia level towards Nile Tilapia’s (Oreochromis niloticus) growth and life sustainability. This research used descriptive analysis. There were 4 treatments done in this study: treatment A (0%), treatment B (1%), treatment C (2%), and treatment D (3%). The result showed that adding bonefish charcoal to the fish feed proved to be effective in reducing the ammonia level in cultivation media. The best result was found in treatment D (3%) valued 0,15 mg/l, followed by treatment B (1%) with 0,24 mg/l, treatment A (control) 40 mg/l, and treatment C (2%) with 0,51 mg/l.

Host-Guest Assembly of H-Bonding Networks in Covalent Organic Frameworks for Ultrafast and Anhydrous Proton Transfer.

An anhydrous proton conductor represents a key material for the manufacture of high-energy electrical devices. Incorporation of proton carriers into the vacancies of the porous solid provides an effective method for their preparation, but the weak or even no interactions between the ion carriers and the porous solids causing a serious leaking of ion carriers result in trade-off of long-term conductivity. In this term, we developed a host-guest supramolecular chemistry-induced strategy to assemble hydrogen bond networks along the 1D nanochannels of covalent organic frameworks (COFs) for ultrafast and anhydrous proton transfer (1.33 × 10-2 S cm-1 at 140 °C). Solid-state NMR was applied to explore guest interaction between protic ionic liquids (PILs) and the COFs to investigate the proton transport mechanism. This work presents an excellent example of accumulation of PILs into the nanochannels of COFs for anhydrous proton conduction at high temperature, demonstrating great advantages of COFs to serve as a supramolecular host for holding/transiting ions in the solid state.

Changes in rock matrix compressibility during deep CO2 storage

AbstractGeologic carbon storage projects aim to permanently trap large volumes of CO2 in reservoir rock sealed with low permeability layers. As high‐pressure supercritical or liquid CO2 is injected, hydromechanical and chemical processes caused by the reaction between the rock and acidic mixture of brine and CO2 are initiated. The compressibility of reservoir rock needs to be properly characterized in order to assess the deformation and stability of the host formations, and there are a number of factors to be considered, including the matrix structure, solid, pores, and fluid. This study triggers from a fundamental question whether CO2 treatment affects the compressibility of the rock matrix and its dominant composing solid minerals. Three different reservoir representatives are selected: Berea sandstone for silica‐rich rock, and Apulian limestone and Indiana limestone for calcite‐rich rock. Quartz and calcite are the main composing minerals of the reservoir rock, and their crystals are separately examined. Experimental methods are introduced for high‐pressure CO2 treatment of water‐saturated materials, and measurements of the unjacketed and solid compressibilities are conducted. No change in the solid compressibility of the sandstone and quartz after CO2 treatment is observed, whereas it increases by 18–21% for the limestones and by 15% for calcite. The latter observation is inconsistent with the ultrasonic wave velocities measurements and is believed to be due to the local dissolution of the calcite crystal surface. The results show that only the solid matrix of the limestones becomes more compressible after CO2 treatment. Consequent microimaging and mercury intrusion porosimetry analyses allowed observations of dissolution and precipitation of calcite, and creation of new connected and non‐connected pores. Finally, the changes in limestone solid compressibilities and pore structure could significantly affect the rock properties and behavior during and after CO2 injection and should be accounted for in the reservoir models. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.

Correlation Between Microstructure and Macroscopic Properties of Solid Oxide Fuel Cell Composite Anode: Mesoscale Modeling and Deep Learning with Convolutional Neural Network

In this paper, we propose a framework for studying the linkage between microstructure and performance of Ni-YSZ anode in solid oxide fuel cells (SOFCs) by using meso-scale modeling and deep learning. The discrete element method (DEM) and the mesoscale kinetic Monte Carlo (KMC) method were respectively used to model the particle packing and sintering of composite Ni-YSZ anodes. Anodes with various microstructures were numerically synthesized by varying volume fraction, sizes and size distributions of solid phases and pores. Then, representative volume elements (RVEs) of anode microstructures were meshed for finite element modeling of the effective elastic modulus and thermal coefficient of expansion of the anode based on the homogenization theory. The triple phase boundary length density ( L TPB), tortuosity factor for each phase were also calculated based on RVEs. Based on a large dataset which consists of various anode microstructures (represented as ternary image stacks) and corresponding macroscopic properties, a deep convolutional neural network (CNN) was trained to capture the nonlinear functional relationship between anode microstructures and macroscopic properties. The deep learning CNN model was finally well validated against extra new samples with excellent predictive performances. This indicates that the CNN model can be used as a surrogate model for rapid direct access to macroscopic properties of composite anodes, if the microstructure of the anode is known. The macroscopic properties can be further used for continuum modeling of SOFCs. This framework is highly extendable for other single-phase or composite electrodes of SOFCs. In addition, the proposed framework provides a new ideal for multiscale and multiphysics modeling of SOFCs.

Effects of Strain Rate and Temperature on the Mechanical Properties of Simulated Silica Ionogels.

Ionogels are hybrid materials formed by impregnating the pore space of a solid matrix with a conducting ionic liquid. By combining the properties of both component materials, ionogels can act as self-supporting electrolytes in Li batteries. In this study, molecular dynamics simulations are used to investigate the dependence of mechanical properties of silica ionogels on solid fraction, temperature, and pore width. Comparisons are made with corresponding aerogels. We find that the solid matrix fraction increases the moduli and strength of the ionogel. This varies nonlinearly with temperature and strain rate, according to the contribution of the viscous ionic liquid to resisting deformation. Owing to the temperature and strain sensitivity of the ionic liquid viscosity, the mechanical properties approach a linear mixing law at high temperature and low strain rates. The median pore width of the solid matrix plays a complex role, with its influence varying qualitatively with deformation mode. Narrower pores increase the relevant elastic modulus under shear and uniaxial compression but reduce the modulus obtained under uniaxial tension. Conversely, shear and tensile strength are increased by narrowing the pore width. All of these pore size effects become more pronounced as the silica fraction increases. Pore size effects, similar to the effects of temperature and strain rate, are linked to the ease of fluid redistribution within the pore space during deformation-induced changes in the geometry of the pores.

Flexible Zn-MOF with Rare Underlying scu Topology for Effective Separation of C6 Alkane Isomers.

Adsorptive separation by porous solids provides an energy-efficient alternative for the purification of important chemical species compared to energy-intensive distillations. Particularly, the separation of linear hexane isomers from its branched counterparts is crucial to produce premium grade gasoline with high research octane number (RON). Herein, we report the synthesis of a new, flexible zinc-based metal-organic framework, [Zn5(μ3-OH)2(adtb)2(H2O)5·5 DMA] (Zn-adtb), constructed from a butterfly shaped carboxylate linker with underlying (4,8)-connected scu topology capable of separating the C6 isomers nHEX, 3MP, and 23DMB. The sorbate-sorbent interactions and separation mechanisms were investigated and analyzed through in situ FTIR, solid state NMR measurements and computational modeling. These studies reveal that Zn-adtb discriminates the nHEX/3MP isomer pair through a kinetic separation mechanism and the nHEX/23DMB isomer pair through a molecular sieving mechanism. Column breakthrough measurements further demonstrate the efficient separation of linear nHEX from the mono- and dibranched isomers.

An implicit constitutive relation for describing the small strain response of porous elastic solids whose material moduli are dependent on the density

In this short note, we develop a constitutive relation that is linear in both the Cauchy stress and the linearized strain, by linearizing implicit constitutive relations between the stress and the deformation gradient that have been put into place to describe the response of elastic bodies (Rajagopal, KR. On implicit constitutive theories. Applications of Mathematics 2003; 28: 279–319), by assuming that the displacement gradient is small. These implicit equations include the classical linearized elastic constitutive approximation as well as some classes of constitutive relations that imply limiting strain in tension, as special subclasses. Moreover, the constitutive relations that are developed allow the material moduli to depend on the density; thus, they can be used to describe the response of porous materials, such as porous metals, bone, rocks, and concrete undergoing small deformations.