Search

H1 NMR relaxometry is a method that is extremely sensitive to the presence of magnetic nanoparticles, which significantly affect the transverse relaxation time of the water proton. Accordingly, the use of magnetic nanoparticles as labels allows detection of even extremely small amounts of the test substance. This paper analyzes the prospects for applying the method of solid-phase NMR-relaxometric determination of biologically active molecules. The nitrocellulose membranes are chosen as a solid phase and nanoparticles based on iron core with a carbon shell are used as magnetic labels. The possibility of detecting small concentrations of magnetic particles in porous medium is demonstrated. Finally, the ability to detect extremely low concentrations of an analyte, in this case, streptavidin protein (0.5 ng/ml to 100 ng/ml), which is actively used in various fields of biology and medicine, is demonstrated. © Published under licence by IOP Publishing Ltd. Russian Science Foundation, RSF: 17-15-01116 The work was carried out within the Russian Science Foundation project 17-15-01116. equipment of the Ural Center for Shared Use Modern nanotechnology UrFU was used.

Theoretical and experimental study of the paper drying process are presented. A mathematical model developed for combined heat ad mass transfer analysis of paper drying is given for both impinging air jets and through air drying methods. In this model, it is simply assumed that during the drying period of the paper has porous media and on the drying surface the vapour pressure of the evaporating liquid remains at a quasi-saturated value corresponding to the temperature of the liquid. The calculated transient paper temperatures in both methods agree well with the experimental results.

Agradecimentos: We acknowledge financial support from the Brazilian agencies FAPESP (Grant Numbers: 2017/10522-5, 2018/16250-0, 2018/08782-1, 2009/054066-7, and 2007/54829-5), CAPES (Grant Number 3359/2014 Pró-Forenses Edital 25/2014), CNPq (grant numbers: 444498/2014-1, 438828/2018- 6, 306690/2015-2, and 305605/2017-8) and INCTBio (573672/2008-3). Additionally, the authors are grateful to Professor Dr. Susana Torresi and A. C. Silva for contact angle measurements. We thank Central Analítica e Central Multiusuário at IQ-USP and IQ-UNICAMP for providing the infrastructure Abstract: This study fabricated a portable, high-performance, and reagentless electrochemical devices using CO2 laser-scribing process, which allowed localized carbonization of a non-conductive and low-cost polymer platform, i.e., phenolic-paper. The carbonized material was extensively characterized by Raman spectroscopy, XPS, XRD, SEM, and electrochemical impedance spectroscopy. The carbon-based electrodes were obtained from the photothermal process induced by CO2 laser radiation and subsequently subjected to electrochemical treatment to fabricate a functional material with excellent conductivity and low charge-transfer resistance. Additionally, the laser-scribed electrodes presented a porous structure with graphene-like domains, thus indicating both potential for on-site electroanalytical applications and better performance than conventional carbon electrodes FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Fechado

Pyrazine‐linked hybrid ultramicroporous (pore size 99.95 % for SIFSIX‐17‐Ni) from a ternary equimolar mixture of ethylene, acetylene and CO2 thanks to coadsorption of the latter two gases. We attribute this performance to the very different binding sites in MFSIX‐17‐Ni versus SIFSIX‐3‐Zn., Hybrid ultramicroporous materials in which aminopyrazine ligands substitute pyrazine ligands are the first physisorbents that enable polymer‐grade (>99.95 %) ethylene production from ternary C2‐CO2 gas mixtures under ambient conditions thanks to coadsorption of both C2H2 and CO2.

Angewandte Chemie / International edition 60(32), 17455 - 17463 (2021). doi:10.1002/anie.202102982, Modular frameworks featuring well-defined pore structures in microscale domains establish tailor-made porous materials. For open molecular solids however, maintaining long-range order after desolvation is inherently challenging, since packing is usually governed by only a few supramolecular interactions. Here we report on two series of nanocubes obtained by co-condensation of two different hexahydroxy tribenzotriquinacenes (TBTQs) and benzene-1,4-diboronic acids (BDBAs) with varying linear alkyl chains in 2,5-position. n-Butyl groups at the apical position of the TBTQ vertices yielded soluble model compounds, which were analyzed by mass spectrometry and NMR spectroscopy. In contrast, methyl-substituted cages spontaneously crystallized as isostructural and highly porous solids with BET surface areas and pore volumes of up to 3426 m$^{2}$ g$^{−1}$ and 1.84 cm$^{3}$ g$^{−1}$. Single crystal X-ray diffraction and sorption measurements revealed an intricate cubic arrangement of alternating micro- and mesopores in the range of 0.97–2.2 nm that are fine-tuned by the alkyl substituents at the BDBA linker., Published by Wiley-VCH, Weinheim

International audience; The widespread use of facemasks throughout the population is recommended by the WHO to reduce transmission of the SARS-CoV-2 virus. As some regions of the world are facing mask shortages, reuse may be necessary. However, used masks are considered as a potential hazard that may spread and transmit disease if they are not decontaminated correctly and systematically before reuse. As a result, the inappropriate decontamination practices that are commonly witnessed in the general public are challenging management of the epidemic at a large scale. To achieve public acceptance and implementation, decontamination procedures need to be low-cost and simple. We propose the use of hot hygroscopic materials to decontaminate non-medical facemasks in household settings. We report on the inactivation of a viral load on a facial mask exposed to hot hygroscopic materials for 15 minutes. As opposed to recent academic studies whereby decontamination is achieved by maintaining heat and humidity above a given value, a more flexible procedure is proposed here using a slow decaying pattern, which is both effective and easier to implement, suggesting straightforward public deployment and hence reliable implementation by the population.

The protocols of the crystalline sponge method, particularly those in the soaking, data collection and refinement processes, are considerably improved to give reliable structural information., Crystalline sponges are porous metal complexes that can absorb and orient common organic molecules in their pores and make them observable by conventional X-ray structure analysis (crystalline sponge method). In this study, all of the steps in the crystalline sponge method, including sponge crystal preparation, pore–solvent exchange, guest soaking, data collection and crystallographic analysis, are carefully examined and thoroughly optimized to provide reliable and meaningful chemical information as chemical crystallography. Major improvements in the method have been made in the guest-soaking and data-collection steps. In the soaking step, obtaining a high site occupancy of the guest is particularly important, and dominant parameters for guest soaking (e.g. temperature, time, concentration, solvents) therefore have to be optimized for every sample compound. When standard conditions do not work, a high-throughput method is useful for efficiently optimizing the soaking conditions. The X-ray experiments are also carefully re-examined. Significant improvement of the guest data quality is achieved by complete data collection at high angle regions. The appropriate disorder treatment of the most flexible ZnI2 portions of the host framework and refinement of the solvents filling the remaining void are also particularly important for obtaining better data quality. A benchmark test for the crystalline sponge method toward an achiral molecule is proposed with a guaiazulene guest, in which the guest structure (with ∼ 100% site occupancy) is refined without applying any restraints or constraints. The obtained data quality with R int = 0.0279 and R 1 = 0.0379 is comparable with that of current conventional crystallographic analysis for small molecules. Another benchmark test for this method toward a chiral molecule is also proposed with a santonin guest. The crystallographic data obtained [R int = 0.0421, R 1 = 0.0312, Flack (Parsons) = −0.0071 (11)] represents the potential ability of this method for reliable absolute structure determination.

We performed a combined theoretical and experimental study of hydrogen adsorption in graphene systems with defect-induced additional porosity. It is demonstrated that perforation of graphene sheets results in increase of theoretically possible surface areas beyond the limits of ideal defect-free graphene (∼2700 m2/g) with the values approaching ∼5000 m2/g. This in turn implies promising hydrogen storage capacities up to 6.5 wt% at 77 K, estimated from classical Grand canonical Monte Carlo simulations. Hydrogen sorption was studied for the samples of defected graphene with surface area of ∼2900 m2/g prepared using exfoliation of graphite oxide followed by KOH activation. The BET surface area of studied samples thus exceeded the value of single-layered graphene. Hydrogen uptake measured at 77 K and 296 K amounts to 5.5 wt% (30 bar) and to 0.89 wt% (120 bar), respectively.

The objective of this study was to compare the morphological and chemical composition of bone graft (BG) and coral graft (CG) as well as their osteogenic differentiation potential using rabbit mesenchymal stem cells (rMSCs) in vitro. SEM analysis of BG and CG revealed that the pores in these grafts were interconnected, and their micro-CT confirmed pore sizes in the range of 107-315 µm and 103-514 µm with a total porosity of 92% and 94%, respectively. EDS analysis indicated that the level of calcium in CG was relatively higher than that in BG. FTIR of BG and CG confirmed the presence of functional groups corresponding to carbonyl, aromatic, alkyl, and alkane groups. XRD results revealed that the phase content of the inorganic layer comprised highly crystalline form of calcium carbonate and carbon. Atomic force microscopy analysis showed CG had better surface roughness compared to BG. In addition, significantly higher levels of osteogenic differentiation markers, namely, alkaline phosphatase (ALP), Osteocalcin (OC) levels, and Osteonectin and Runx2, Integrin gene expression were detected in the CG cultures, when compared with those in the BG cultures. In conclusion, our results demonstrate that the osteogenic differentiation of rMSCs is relatively superior in coral graft than in bone graft culture system.

[60]Fullerene hexakisadducts possessing 12 carboxylic acid side chains form crystalline hydrogen-bonding frameworks in the solid state. Depending on the length of the linker between the reactive sites and the malonate units, the distance of the [60]fullerene nodes and thereby the spacing of the frameworks can be controlled and for the most elongated derivative, continuous channels are obtained within the structure. Stability, structural integrity and porosity of the material were investigated by powder X-ray diffraction, thermogravimetry and sorption measurements.

Monolithic macroporous zirconia (ZrO2) derived from ionic precursors has been successfully fabricated via the epoxide-mediated sol-gel route accompanied by phase separation in the presence of propylene oxide (PO) and poly(ethylene oxide) (PEO). The addition of PO used as an acid scavenger mediates the gelation, whereas PEO enhances the polymerization-induced phase separation. The appropriate choice of the starting compositions allows the production of a macroporous zirconia monolith with a porosity of 52.9% and a Brunauer–Emmett–Teller (BET) surface area of 171.9 m2 · g−1. The resultant dried gel is amorphous, whereas tetragonal ZrO2 and monoclinic ZrO2 are precipitated at 400 and 600 °C, respectively, without spoiling the macroporous morphology. After solvothermal treatment with an ethanol solution of ammonia, tetragonal ZrO2 monoliths with smooth skeletons and well-defined mesopores can be obtained, and the BET surface area is enhanced to 583.8 m2 · g−1.

Nuclear magnetic resonance (NMR) relaxation times are shown to provide a unique probe of adsorbate–adsorbent interactions in liquid-saturated porous materials. A short theoretical analysis is presented, which shows that the ratio of the longitudinal to transverse relaxation times (T1/T2) is related to an adsorbate–adsorbent interaction energy, and we introduce a quantitative metric esurf (based on the relaxation time ratio) characterising the strength of this surface interaction. We then consider the interaction of water with a range of oxide surfaces (TiO2 anatase, TiO2 rutile, γ-Al2O3, SiO2, θ-Al2O3 and ZrO2) and show that esurf correlates with the strongest adsorption sites present, as determined by temperature programmed desorption (TPD). Thus we demonstrate that NMR relaxation measurements have a direct physical interpretation in terms of the characterisation of activation energy of desorption from the surface. Further, for a series of chemically similar solid materials, in this case a range of oxide materials, for which at least two calibration values are obtainable by TPD, the esurf parameter yields a direct estimate of the maximum activation energy of desorption from the surface. The results suggest that T1/T2 measurements may become a useful addition to the methods available to characterise liquid-phase adsorption in porous materials. The particular motivation for this work is to characterise adsorbate–surface interactions in liquid-phase catalysis.

This paper is an overview on some recent results concerning the variational analysis of static fracture in the so-called high-contrast brittle composite materials. The paper is divided into two main parts. The first part is devoted to establish a compactness result for a general class of free-discontinuity functionals with degenerate (or high-contrast) integrands. The second part is focussed on some specific examples which show that the degeneracy of the integrands may lead to non-standard limit effects, which are specific to this high-contrast setting.

International audience; This paper provides a time domain model for the propagation of transient ultrasonic waves in a self-similar porous material having a rigid frame. This model is based on the formalism of Stillinger-Palmer-Stavrinou, which consists in modeling the fractal material as a porous medium with a non-integer dimensional space. This paper is devoted to the time-domain analytical calculus of the reection and transmission operators that are expressed in terms of Mittag-Leer functions. A sensitivity numerical study using ultrasonic reected and transmitted waves is performed, highlighting the eect of of the material's physical parameters (fractal dimension, tortuosity, viscous characteristic length and porosity) on the waveforms.

This paper studied the aerodynamic characteristics of cylinder and pantograph based on large eddy simulation and the acoustic boundary element method, compared sound pressure levels of different observation points and adopted measures to reduce radiation noises. Pressure distributions on the upper and lower surfaces of the cylinder were symmetrical, and radiation noises were basically the same too. Sound pressure level in the front of the cylinder was more than that on the upper and lower surfaces of the cylinder. Sound pressure level at the back of the cylinder was the maximum. With the increase of the computational time, shedding vortexes gradually developed backwards, and the influence area was bigger. The radius of radiation sound field of the cylinder was obviously reduced after applying porous materials. Additionally, contours for noise were highly symmetrical in the whole analyzed frequency band. At 2000 Hz, the cylinder presented the obvious characteristics of dipole noise source. The aerodynamic drag and lift of pantographs through numerical computation were similar to experimental results and increased with the increase of flow velocity, which showed that the computational model for the aerodynamic characteristics of pantographs in this paper was effective. Pressure was large in the area close to the pantograph head, in the connection position between upper and lower pull rods and near the base. Long dragged airflow was formed at the pantograph head, upper and lower pull rods and at the back of the base, which had a serious influence on the distribution of aerodynamic noises of pantographs. Obvious shedding vortexes were formed in the area far away from the pantograph rather than near the pantograph. The density and strength of shedding vortexes were not large. Sound pressure levels of observation points which had the same distance from the center of pantograph base were basically the same in change trend, value and peak frequency. However, the sound pressure level of observation points around the pantograph head was obviously greater than that of other observation points when the analyzed frequency was over 1000 Hz. Radiation noises in the connection position between upper and lower pull rods were greater than that of other observation points. With the increase of the analyzed frequency, the dispersive-ness of aerodynamic noises of pantographs was increasingly obvious. The radiation noise of pantographs was mainly spread along the inclined plane of 45°. When a layer of porous materials was covered on the surface of pantographs, the influence area of radiation noises was obviously reduced. In addition, the sound pressure level of radiation noises was improved.

The paper presents the results of research concerning three fiber materials&mdash, mineral wool, hemp fiber and wood wool&mdash, as loose-fill thermal insulation materials. The analysis used the material parameters determined in previous works conducted by the authors, such as thermal conductivity and air permeability in relation to bulk density. These materials exhibit open porosity, thus, convection is an essential phenomenon in the heat transfer process. The paper aimed at conducting thermal simulations of various frame wall variants which were filled with the above-mentioned insulation materials. The simulations were performed with the Control Volume Method using the Delphin 5.8 software. The studies accounted for the effect of wind pressure and the time of its influence on a wall insulated by means of fiber material with a thickness of 150 as well as 250 mm. The simulation enabled us to obtain such data as maximal R-value reduction and time to return to equilibrium after filtration for the analyzed materials. The study proved that heat transfer in these insulations strongly depends on the bulk density, thickness of the insulation and wind pressure. The decrease in R is reduced as the density increases. This results from the decreased air permeability characterizing the material. Wind washing causes lower R reduction than air filtration in all models. The greater the thickness, the longer it takes for the models to return to the equilibrium state following air filtration (and wind washing). This period is comparable for air filtration and wind washing. Hemp fibers were characterized with the strongest susceptibility to air filtration, in the case of wood wool, it was also high, but lower than for hemp fibers, while mineral wool was characterized with the lowest.

There is a considerable number of research publications on the characterization of porous media that is carried out in accordance with ISO 10534-2 (International Standards Organization, Geneva, Switzerland, 2001) and/or ISO 9053 (International Standards Organization, Geneva, Switzerland, 1991). According to the Web of Science(TM) (last accessed 22 September 2016) there were 339 publications in the Journal of the Acoustical Society of America alone which deal with the acoustics of porous media. However, the reproducibility of these characterization procedures is not well understood. This paper deals with the reproducibility of some standard characterization procedures for acoustic porous materials. The paper is an extension of the work published by Horoshenkov, Khan, Bécot, Jaouen, Sgard, Renault, Amirouche, Pompoli, Prodi, Bonfiglio, Pispola, Asdrubali, Hübelt, Atalla, Amédin, Lauriks, and Boeckx [J. Acoust. Soc. Am. 122(1), 345-353 (2007)]. In this paper, independent laboratory measurements were performed on the same material specimens so that the naturally occurring inhomogeneity in materials was controlled. It also presented the reproducibility data for the characteristic impedance, complex wavenumber, and for some related pore structure properties. This work can be helpful to better understand the tolerances of these material characterization procedures so improvements can be developed to reduce experimental errors and improve the reproducibility between laboratories.

The availability of natural gas hydrates and the continuing increase in energy demand, motivated researchers to consider gas hydrates as a future source of energy. Fundamental understanding of hydrate dissociation kinetics is essential to improve techniques of gas production from natural hydrates reservoirs. During hydrate dissociation, bonds between water (host molecules) and gas (guest molecules) break and free gas is released. This paper investigates the evolution of hydrate surface area, pore habit, and tortuosity using in-situ imaging of Xenon (Xe) hydrate formation and dissociation in porous media with dynamic three-dimensional synchrotron microcomputed tomography (SMT). Xe hydrate was formed inside a high- pressure, low-temperature cell and then dissociated by thermal stimulation. During formation and dissociation, full 3D SMT scans were acquired continuously and reconstructed into 3D volume images. Each scan took only 45 seconds to complete, and a total of 60 scans were acquired. Hydrate volume and surface area evolution were directly measured from the SMT scans. At low hydrate saturation, the predominant pore habit was surface coating, while the predominant pore habit at high hydrate saturation was pore filling. A second-degree polynomial can be used to predict variation of tortuosity with hydrate saturation with an R2 value of 0.997. The Authors, published by EDP Sciences, 2020. This publication was made possible by partial funding from NPRP grant # NPRP8-594-2-244 from the Qatar national research fund (a member of Qatar Foundation) and the Institute for a Secure and Sustainable Environment (ISSE), University of Tennessee-Knoxville, USA. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of funding agencies. The authors would like to thank Mr. Wadi Imseeh for his help during scanning and Mr. Jamal Hannun for his help in interfacial area analysis. This paper used resources of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory (ANL) under Contract No. DE-AC02-06CH11357. The PSMT images presented in this paper were collected using the x-ray Operations and Research Beamline Station 13-BMD at Argonne Photon Source (APS), ANL. We thank Dr. Mark Rivers of APS for help in performing the PSMT scans. We also acknowledge the support of GeoSoilEnviroCARS (Sector 13), which is supported by the National Science Foundation, Earth Sciences (EAR-1128799), and the DOE, Geosciences (DEFG02-94ER14466). Scopus

The paper presents chemical and structural analysis of geopolymer materials which are obtained by alkali-activated calcined clay (metakaolin) originated from Serbia under strictly defined conditions. Characterization of the metakaolin and geopolymers molecular structure has been done using X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The paper presents the possibility of obtaining geopolymer structure and differences in chemical and structural characterization of these materials taking into account the concentration of NaOH as a variable parameter. The results of MALDI analysis of metakaolin and synthesized geopolymer structures using various matrix system: 2,4,6 trihydroxyacetophenone (THAP), alpha-cyano-4-hydroxycinnamic, 2,6 dihydroxyacetophenone and laser desorption/ionization, have shown that THAP matrix is the most appropriate for analysing these aluminosilicate materials.

Fully porous particles of narrow particle size distribution (nPSD) are now commercially available. In this paper, the kinetic performance of columns packed with these particles (1.9 μm, 80 A pore size) has been investigated under typical reversed phase conditions by using a mixture of benzene derivatives as probes. The columns exhibited remarkably high efficiency (in the order of 300,000 theoretical plates per meter) and the possibility to be used at relatively high flow rates without loss of performance. These results contrast with previous studies on the same columns. Indeed we have found column efficiency comparable to that reported in previous work but, on the other hand, we could not observe the same dramatic loss of performance when columns were operated at high flow rates. The results presented in this paper, based on a set of six columns with different geometries (2.1 and 3.0 internal diameter × 50, 75 and 100 mm length), are not consistent with the previously proposed hypothesis that the unusually low intraparticle diffusion, which would characterize these particles, is the origin of the high efficiency of the columns. In a companion paper [1] , a detailed investigation of the different terms leading to band broadening will be performed to point out the major contribution to plate height on nPSD columns.

Composite materials are widely used in industrial applications because of their excellent properties and behaviors. While a composite material is defined as a mixture of two or more different materials, many research works in the literature dealt with composites of only two constituents, which are matrix and one type of particles. On the other hand, the theoretical research works that dealt with more than two constituents are rare. Using some additives affects the sintering behavior, the tribological behavior and the fracture mechanics behavior of composites. For example, a suitable amount of additives as sintering aids, in the sintering process, could lower the sintering temperature, enhance phase wettability and bonding strength and improve the interlaminar fracture resistance of a composite. Therefore, it is worthwhile to develop the constitutive laws that describe the behavior of such composite materials. Accordingly, the aim of this paper is to modify the previous paper, Shabana (2003) [Shabana, Y.M., 2003. Incremental constitutive equation for discontinuously reinforced composites considering reinforcement damage and thermoelastoplasticity. Computational Materials Science 28, 31–40], in order to propose constitutive laws that predict the thermomechanical behavior of composites containing multi-type ellipsoidal reinforcements. This includes reinforcements with different materials and/or different shapes that are represented by aspect ratios. These constitutive laws not only predict the macroscopic and microscopic thermoelastoplastic behaviors of composites containing multi-type ellipsoidal reinforcements, but also characterize their different overall effective properties such as modulus of elasticity, Poison’s ratio and thermal expansion coefficient in different directions. Beside this, they are applicable for porous materials and composites with multiple reinforcements and porosities of different shapes and distributions. In the present numerical analyses, composites with two, three and four constituents considering different materials and aspect ratios as well as reinforcement damage are discussed.

The acoustic absorption of granular aerogel layers with a granule sizes in the range of 2 to 40 μm is dominated by narrow-banded, high absorption regions in the low-frequency range and by reduced absorption values at higher frequencies. In this paper, we investigate the possibility of developing new, low-frequency noise reduction materials by layering granular aerogels with traditional porous sound absorbing materials such as glass fibers. The acoustic behavior of the layered configurations is predicted using the arbitrary coefficient method, wherein the granular aerogel layers are modeled as an equivalent poro-elastic material while the fibrous media and membrane are modeled as limp media. The analytical predictions are verified using experimental measurements conducted using the normal incidence, two-microphone impedance tube method. Our results show that layered configurations including granular aerogels, fibrous materials, and limp membranes provide enhanced sound absorption properties that can be tuned for specific noise control applications over a broad frequency range.

The model equation method (MEM) is a new method to measure the porosity of porous materials. This paper demonstrates the application value of the MEM in the preparation of titanium foams from an experimental point of view. The results showed that the porosities calculated by the MEM were in the range of 0.533–0.701 with the spacer contents between 0.55 and -0.75. The measured values were highly consistent with those of the mass volume method, which indicates that the MEM was feasible to measure porosity. The correlation equation between porosity and spacer content has a very high prediction accuracy by a linear fitting. The elastic modulus and yield strength of titanium foams were 4.8–29 GPa and 10.2–101.1 MPa, respectively. The relative elastic modulus and relative yield strength were directly proportional to the n-th power of relative density through a nonlinear fitting. The mathematical correlations between relative mechanical properties and spacer content were established. This study not only proves that the new method of porosity measurement has an important application value, but also realizes the source control of mechanical properties of titanium foams.

Metal-organic frameworks (MOFs) are the object of intense research targeting their deployment as adsorbents for a wide range of gas separations, such as CO2 capture, biogas upgrading, air separation and small hydrocarbons separation. The scope of this review is to provide chemists, material scientists and engineers with an overview of the state-of-the-art and of the main challenges in the field of adsorption-based gas separations using MOFs. To do so, we first discuss current gas separation challenges for which adsorption could play a role. The following three sections of the paper describe process-level considerations in the design, selection and deployment of MOFs as sorbents and subsequently focus on material-level considerations. Both the process and the material aspects cover experimental and computational work. Going from the process scale to the atomic scale, we aim to highlight the links and synergies between the two and identify the current barriers that hamper the development of adsorption-based gas separations using MOFs as sorbents. Throughout the article, we also provide fundamental and technical information related to MOFs design, synthesis, characterisation and sorption testing.

The authors aimed to impart hydroxyapatite formation ability to ultra-high molecular weight polyethylene (UHMWPE) by deposition of apatite nuclei (ApN) by the following two methods. The first method was electrophoretic deposition (EPD). A porous UHMWPE was placed between electrodes in the ApN-dispersed ethanol and constant voltage was applied. By this treatment, the ApN were migrated from anode-side surface to the cathode one through the pores by an electric field in the pores of the UHMWPE and deposited inside the pores. The second method was direct precipitation (DP) of the ApN. A porous UHMWPE was soaked in a simulated body fluid (1.0SBF) with higher pH than the physiological one and subsequently, its temperature was raised. By this treatment, the ApN were precipitated in the pores of the UHMWPE directly in the reaction solution. For both methods, the ApN-deposited UHMWPE showed HAp formation ability not only on the top surface but also inside the pores near the surface of the porous UHMWPE in 1.0SBF although the adhesion strength of thus-formed HAp layer was higher in the case of the EPD in comparison with the DP, oxygen plasma treatment before the DP enabled to achieve a similar level of the HAp layer adhesion to the EPD., Special Section: Selected Extended Papers from the International Conference of the 19th Asian BioCeramic Symposium

Restricted diffusion of fluids in porous materials can be studied by pulsed field gradient nuclear magnetic resonance (NMR) non-invasively and without tracers. If the experiment is repeated many times with varying diffusion delays, detailed information about pore sizes and tortuosity can be recorded. However, the measurements are very time-consuming because numerous repetitions are needed for gradient ramping and varying diffusion delays. In this paper, we demonstrate two different strategies for acceleration of the restricted diffusion NMR measurements: time-resolved diffusion NMR and ultrafast Laplace NMR. The former is based on time-resolved non-uniform sampling, while the latter relies on spatial encoding of two-dimensional data. Both techniques allow similar 1–2 order of magnitude acceleration of acquisition, but they have different strengths and weaknesses, which we discuss in detail. The feasibility of the methods was proven by investigating restricted diffusion of water inside tracheid cells of thermally modified pine wood.

Reactive transport (RT) couples bio-geo-chemical reactions and transport. RT is important to understand numerous scientific questions and solve some engineering problems. RT is highly multidisciplinary, which hinders the development of a body of knowledge shared by RT modelers and developers. The goal of this paper is to review the basic conceptual issues shared by all RT problems, so as to facilitate advance along the current frontier: Biochemical reactions. To this end, we review the basic equations to point that chemical systems are controlled by the set of equilibrium reactions, which are easy to model, but whose rate is controlled by mixing. Since mixing is not properly represented by the standard advection-dispersion equation (ADE), we conclude that this equation is poor for RT. This leads us to review alternative transport formulations, and the methods to solve RT problems using both the ADE and alternative equations. Since equilibrium is easy, difficulties arise for kinetic reactions, which is especially true for biochemistry, where numerous frontiers are open (how to represent microbial communities, impact of genomics, effect of biofilms on flow and transport, etc.). We conclude with the basic 10 issues that we consider fundamental for any conceptually sound RT effort., This work is part of grants MEDISTRAES III funded by MCIN/AEI/ PID2019-110212RB-C22 and MCIN/AEI/PID2019-110311RB-C21 and Water JPI project MARadentro (PCI2019-103603), and by the Catalan Water Agency through the project RESTORA (CA210/18/00040). IDAEA-CSIC is a Center of Excellence Severo Ochoa (Grant CEX2018-000794-S funded by MCIN/AEI/ 10.13039/501100011033).

So far shock and vibration are the inherent properties of all packing systems, and various mitigation measures have been considered using packing materials, which result in a large packing size. Now the thing changes, this paper gives an effective thermodynamic technology that can completely avoid shock and vibration. An aerial delivery system is used as an example to elucidate the novel packing system, which requires zero loading velocity when loaded. A thermodynamic model is established to reveal the main factors affecting the packing system.

This article is a continuation of a series of articles on the production of porous composite nanomaterials. This paper presents an overview of the properties of porous, heat-resistant inorganic composite materials. The physicochemical and mechanical characteristics of various porous refractory materials produced industrially are presented. A separate class of materials with a regular and quasi-regular porous structure is considered. Such materials include the so-called cellular or «lattice» materials, that are becoming widely applied in modern industry. An example of such materials is ceramic foam – a sintered ceramic material with a foamy cellular structure. A special group of materials with opal pore structure has been also focused. Synthetic opals have received intensive development in recent years because they are model objects for the development and research of new spatial-periodic structures with nonlinear optical properties. Such structures include composites based on classical and inverted opals, in which the pores are filled with various dielectric, semiconductor, or metallic substances. The optical properties of these systems are determined by the size of the close-packed particles, as well as the dielectric constant of the components.

This paper is concerned with the linear theory of elastodynamics for homogeneous, isotropic, porous elastic materials with memory effects for the intrinsic equilibrated body forces. We are able to relax the conditions on constitutive coefficients and to determine the wider class of materials for which the internal energy is positive semi-definite, when boundary conditions are homogeneous. We found the class of semi-strongly elliptic porous elastic materials. For this class of materials, the above conditions may be relaxed without loss of some well-posedness properties of the solutions. In particular, we obtain uniqueness of the solutions and we study the spatial behavior problem.

Many engineering applications and geological processes involve embedded discontinuities in porous media across multiple length scales (e.g. rock joints, grain boundaries, deformation bands and faults). Understanding the multiscale path-dependent hydro-mechanical responses of these interfaces across length scales is of ultimate importance for applications such as CO2 sequestration, hydraulic fracture and earthquake rupture dynamics. While there exist mathematical frameworks such as extended finite element and assumed strain to replicate the kinematics of the interfaces, modeling the cyclic hydro-mechanical constitutive responses of the interfaces remains a difficult task. This paper presents a semi-data-driven multiscale approach that obtains both the traction-separation law and the aperture-porosity–permeability relation from micro-mechanical simulations performed on representative elementary volumes in the finite deformation range. To speed up multiscale simulations, the incremental constitutive updates of the mechanical responses are obtained from discrete element simulations at the representative elementary volume whereas the hydraulic responses are generated from a neural network trained with data from lattice Boltzmann simulations. These responses are then linked to a macroscopic dual-permeability model. This approach allows one to bypass the need of deriving multi-physical phenomenological laws for complex loading paths. More importantly, it enables the capturing of the evolving anisotropy of the permeabilities of the macro- and micro-pores. A set of numerical experiments are used to demonstrate the robustness of the proposed model.

International audience; In this paper, the influence of the transverse wave on sound propagation in a porous medium with a flexible structure is considered. The study is carried out in the time domain using the modified Biot theory obtained by the symmetry of the Lagrangian (invariance by translation and rotation). The viscous exchanges between the fluid and the structure are described by fractional calculus. When a sound pulse arrives at normal incidence on a porous material with a flexible structure, the transverse waves interfere with the longitudinal waves during propagation because of the viscous interactions that appear between the fluid and the structure. By performing a calculation in the Laplace domain, the reflection and transmission operators are derived. Their time domain expressions depend on the Green functions of the longitudinal and transverse waves. In order to study the effects of the transverse wave on the transmitted longitudinal waves, numerical simulations of the transmitted waves in the time domain by varying the characteristic parameters of the medium are realized whether the transverse wave is considered or not.

International audience; In ductile fracture, strain localization can often be a precursor to the failure of the material. The paper proposes to investigate this phenomenon in the case of random microstructures. Such microstructures are cubic cells made of an elastic-perfectly plastic matrix embedding distribution of identical spherical voids. They allow a better representation of the interaction between voids and greater diversity of failure modes than single-void (or unit) cells. The cells are simulated by finite element for proportional stress loading paths. Strain localization is detected with Rice's criterion computed at the level of the cell. This criterion is shown to accurately detect the onset of localization and the type of failure mode: in extension or in shear. Moreover, the influence of the loading orientation (that is, the orientation of the principal frame of the applied stress with respect to the microstructure) is systematically studied. A strong anisotropy of failure behavior is observed, which can be attributed to the intrinsic anisotropy of the simulation cells. Finally minimal failure strain values on all loading orientations are found. A zone of reduced ductility is observed in generalized shear.

The bonding of copper ions to lattice oxygens dictates the activity and selectivity of copper exchanged zeolites. By 17O isotopic labelling of the zeolite framework, in conjunction with advanced EPR methodologies and DFT modelling, we determine the local structure of single site CuII species, we quantify the covalency of the metal-framework bond and we assess how this scenario is modified by the presence of solvating H216O or H217O molecules. This enables to follow the migration of CuII species as a function of hydration conditions, providing evidence for a reversible transfer pathway within the zeolite cage as a function of the water pressure. The results presented in this paper establish 17O EPR as a versatile tool for characterizing metal-oxide interactions in open-shell systems., The identification of catalytically active sites with atomic-scale precision occupies a central place in the theory and practice of heterogeneous catalysis. Here the authors assess the nature of the copper-oxygen bond in a Cu-CHA zeolite and recover the microscopic structure of single-metal sites.

Since the outbreak of the COVID-19 pandemic, most countries have recommended their citizens to adopt social distance, hand hygiene, and face mask wearing. However, wearing face masks has not been well adopted by many citizens. While the reasons are complex, there is a general perception that the evidence to support face mask wearing is lacking, especially for the general public in a community setting. Face mask wearing can block or filter airborne virus-carrying particles through the working of colloid and interface science. This paper assesses current knowledge behind the design and functioning of face masks by reviewing the selection of materials, mask specifications, relevant laboratory tests, and respiratory virus transmission trials, with an overview of future development of reusable masks for the general public. This review highlights the effectiveness of face mask wearing in the prevention of COVID-19 infection., Graphical abstract Image 1

In this paper, novel micro-architectures with X-type lattice unit cell (namely, face-centered cubic (FCC), and X-type) are constructed and prepared by additive manufacturing technology. The compression behaviors of micro-architectures are explored in detail by experimental measurement and theoretical prediction. It is found that the strength of FCC micro-lattice structure is higher than that of the X-type micro-lattice structure with the same relative density. The X-type micro-lattice structure exhibits a zero Poisson’s ratio during compression deformation. In addition, the compressive strength and energy absorption efficiency of proposed micro-architectures shows a higher advantage over other previously cellular materials in a map for material selection.

The present paper investigates strain-induced sorption in mesoporous silicon. Contrarily to a previous report based on indirect evidence, we find that external mechanical strain or stress has no measurable impact on sorption isotherms, down to a relative accuracy of 10-3. This conclusion is in agreement with the analysis of the sorption-induced strain of porous silicon and holds for other stiff mesoporous materials such as porous silicas.

This paper investigates the mechanisms by which flow-permeable materials provide noise reduction in an installed jet configuration. Numerical simulations are carried out with a flat plate placed in the near field of a single-stream subsonic jet ( M a = 0 . 3 and M a = 0 . 5 ). The trailing-edge region of the plate is replaced by three different permeable structures, with different properties: a metal foam, a perforated plate and a diamond-shaped structure. Due to its complex geometry, the metal foam is modeled with an equivalent region governed by Darcy’s law. The perforated plate has the highest resistivity among all investigated configurations, whereas the metal foam and diamond inserts have similar properties. Far-field spectra show significant noise reduction when the solid trailing edge is replaced with the permeable materials, with a maximum decrease of 12 dB at S t = 0 . 12 , for M a = 0 . 5 . Beamforming results show that the dominant acoustic source is located at the solid-permeable junction for the metal foam and diamond structures, whereas the perforated one has the source positioned near the trailing edge, similarly to the solid case. A breakdown of the far-field noise generated by the plate is also performed, where the contributions from the solid and permeable sections are computed separately. The former has distinct regions in the noise spectrum, which are dominated either by surface pressure fluctuations or trailing-edge scattering. However, for the permeable region, the results point to a significant mitigation of the noise due to scattering, which is no longer the dominant mechanism in any frequency range. This is confirmed by lower values of spanwise coherence, computed from the surface pressure, for the permeable trailing edge, compared to the solid case. Therefore, the clear dominant mechanism in the permeable region of the plate is the unsteady loading to pressure wave impingement. This is verified for all investigated configurations so that even with a low permeability structure, significant noise reduction can still be achieved.

This paper presents a novel approach of using in‐situ microbially induced Ca2+‐alginate polymeric sealant for seepage control in porous materials. This process comprises two steps: (i) generation of insoluble calcium carbonate inside the pores of porous materials (such as sand) through a microbially induced carbonate precipitation (MICP) process in‐situ and (ii) injection of sodium alginate for in‐situ gelation via reaction between alginate and Ca2+ ions. The experimental results showed that the hydraulic conductivity/permeability of sand decreased with the increase in alginate concentration. When 5% alginate was used with a CaCO3 concentration of 0.18 g g−1 sand, the permeability of the alginate‐treated sand reduced from 5.0 × 10−4 to 2.2 × 10−9 m s−1. The scanning electron microscopy images revealed that a film‐type coating was formed around sand particles with spherical round crystals embedded. Furthermore, the in‐situ formed Ca‐alginate polymeric sealant can also be used for the removal of Cu2+ ion and suspended particles from contaminated water by more than 90%. Built on the current research, the envisioned practical application of the proposed method may include clogging fractured rock, reducing seepage and prevent piping through dams, excavation dewatering, and forming barriers for remediating specific contaminants. MOE (Min. of Education, S’pore) Published version

The accurate determination of permeability is one of the parameters essential for the study of fluid flow and transport state. However, a large number of fractured coal bodies are faced during the production of coal mines. The study of permeability of these special media composed of grains of a certain size, whose structure is different from that of raw coal, has been in the exploratory stage. In this paper, inspired by the calculation method of median particle size and the calculation principle of KC’s equation, we calculate the permeability parameters of broken coal particles. It is considered that its permeability is closely related to the compaction and re-crushing process of skeletal grains. The lateral limit compression test of the crushed coal body was designed, and the pore-dominated permeability calculation method was given to reveal the mechanism of the action of the effective stress. The dependence relationship between the effective stress and the pore-correlation permeability is obtained by data analysis, and the force and deformation process of the crushed coal grain media is described. In contrast to the conventional Darcy series of permeability discussions, our approach excludes the influence of fluid factors on the permeability of porous media. The permeability of porous media is considered to be determined only by its own pore structure.

This paper presents the development of a microwave puffed wood (MPW) with novel and unique structural features in its internal structure that are based on natural wood (NW). The focus of the research was on the comprehensive visualization of the structural characteristics of MPW from the macroscopic to the microscopic scale followed by an exploration of its impregnation capabilities. The results showed that the volume of MPW increased by about 9% compared to NW due to the presence of a large number of cracked cavities. The CT images indicated that there was a significant difference between the macroscopic cracks produced by microwave processing and the natural cracks in the wood. The mercury intrusion test results showed that macro-pores increased while the micro-pores decreased in the MPW compared to in the NW. The MPW showed good fluid permeability and liquid absorption performance. The phenolic resin penetration rate of the MPW was about 20 times that of the NW, and the material absorption was more than 2 times that of the NW. The crack space enabled the MPW to serve as a fluid transportation and a storage warehouse. MPW is a super container based on natural materials. It has broad potential in more fields, such as in wood composite materials.

The strong impulse recently experienced by the manufacturing technologies as well as the development of innovative biocompatible materials has allowed the fabrication of high-performing scaffolds for bone tissue engineering. The design process of materials for bone tissue scaffolds represents, nowadays, an issue of crucial importance and the object of study of many researchers throughout the world. A number of studies have been conducted, aimed at identifying the optimal material, geometry, and surface that the scaffold must possess to stimulate the formation of the largest amounts of bone in the shortest time possible. This book presents a collection of 10 research articles and 2 review papers describing numerical and experimental design techniques definitively aimed at improving the scaffold performance, shortening the healing time, and increasing the success rate of the scaffold implantation process.

Having come of age, gas film bearings enable high-speed oil-free (micro) rotating machinery with gains in efficiency and reliability, longer maintenance intervals, and a reduction in contaminants released to the atmosphere. Among gas bearing types, porous surface gas bearings (PGBs) have proven successful for 50+ years and presently are off-the-shelf mechanical elements. This paper reviews the literature on PGBs since the 1970s and reproduces an exact solution for the performance of cylindrical PGBs. Both the analytical model and an accompanying finite-element (FE) model predict the performance for two PGBs, a commercially available 76 mm diameter bearing and a smaller 25 mm diameter laboratory unit whose experimental performance is available. As expected, the FE model results reproduce the analytical predictions obtained in a minuscule computing time. For a set external supply pressure, as the radial clearance increases, the flow rate through the bearing grows until reaching a peak magnitude. The PGB load capacity is a fraction of the product of the set pressure difference (pS − pa) and the bearing projected area with a significantly large centering static stiffness evolving over a narrow region of clearances. Operation with shaft speed enhances the bearing load capacity, however, at sufficiently high speeds, significant magnitude cross-coupled forces limit the stable operation of a PGB. At constant operating shaft speed, as the whirl frequency grows, the bearing effective stiffness (Keff) increases, while the effective damping (Ceff) becomes positive for whirl frequencies greater than 50% shaft speed. Similar to a plain hydrodynamic journal bearing, the PGB is prone to a half-frequency whirl, albeit the system natural frequency can be high, mainly depending on the external supply pressure. In essence, for the cases considered, PGBs are linear mechanical elements whose load capacity is proportional to the journal eccentricity.

In this paper, an analytical solution for free vibration of rectangular porous-cellular plates enclosed by piezoelectric layers is presented by using third-order shear deformation plate theory. Using Hamilton’s principle and Maxwell equation, the governing equations of the system are obtained for both closed and open circuit conditions. Due to the coordinate dependency of mechanical properties of porous materials, the governing equations of motion are highly coupled. By using four auxiliary functions, these equations convert into two independent partial differential equations. The decoupled equations are solved analytically by employing Levy-type boundary conditions for the plate. Finally, after validation of the obtained results, the effects of various parameters such as porosity and geometrical dimensions on the natural frequencies of plate are investigated for different electrical and mechanical boundary conditions. It is found that the natural frequencies of the plate decrease as the coefficient of plate porosity increases. Also, the piezoelectric layers cause the natural frequency of the plate to increase in various vibrating modes.

This paper is concerned with the effect of deformation coupling between solid and fluid on the free vibration characteristics of isotropic rigid porous rectangular plates under undrained condition. Mindlin plate theory is employed to model the moderately thick porous plate. The problem addressed is formulated by using Hamilton's principle, which leads to a set of partial differential equations dealing with frequency response of the plate. The governing equations of motion are solved analytically for Levy-type porous plates by introducing some auxiliary functions. The fluid viscosity is assumed to be very low so that it cannot cause energy dissipation in system. Numerical results are obtained in non-dimensional form. The accuracy of the solution is confirmed by making some comparisons of the obtained frequencies with those available in literature. It is found that the effect of coupled solid-fluid deformation cannot be neglected when the Biot-Willis constants are considerable compared to mechanical properties of solid skeleton of the plate. It is also observed that the plate's effective stiffness increases as fluid is trapped in pore network of the porous medium.

The onset and propagation of the cracks and compaction bands, and the interactions between them in the host matrix, are important for numerous engineering applications, such as hydraulic fracture and CO2 storage. While crack may become flow conduit that leads to leakage, formation of compaction band often accompanies significant porosity reduction that prevents fluid to flow through. The objective of this paper is to present a new unified framework that predicts both the onset, propagation and interactions among cracks and compaction bands via an eigen-deformation approach. By extending the generalized Griffith’s theory, we formulate a unified nonlocal scheme that is capable to predict the fluid-driven fracture and compression-driven anti-crack growth while incorporating the cubic law to replicate the induced anisotropic permeability changes triggered by crack and anti-crack growth. A set of numerical experiments are used to demonstrate the robustness and efficiency of the proposed model.

In this paper we use an eXtended Finite Element Method based model for the simulation of shear fracture in fully saturated porous materials. The fracture is incorporated as a strong discontinuity in the displacement field by exploiting the partition of unity property of finite element shape functions. The pressure is assumed to be continuous across the fracture. However, the pressure gradient, i.e. the fluid flow, can be discontinuous. The failure process is described by the cohesive zone approach and a Tresca fracture condition without dilatancy. We investigate the propagation of a shear fracture under compression asking the question whether or not a Tresca criterion can result in stepwise propagation in a poroelastic medium. In order to evaluate possible numerical artefacts, we also look at the influence of the element size and the magnitude of a time increment. The performance of the X-FEM model and the influence of the pore pressure on the fracture propagation are addressed. Our simulations do not show evidence for step wise progression in mode II failure.

International audience; In this paper, we study the drying of water-saturated porous polydimethylsiloxane (PDMS) elastomers with closed porosity in which the evaporation of water is possible only via the diffusion across the PDMS. Starting from water/PDMS emulsions, we fabricate soft macroporous samples with different pore diameter distributions and average diameters ranging from 10 to 300 µm. In these materials, the drying may lead either to a collapsed state with low porosity or to the cavitation and reopening of a fraction of the pores. Using optical microscopy and porosity measurements, we showed the importance of the pore diameters and interactions on the result of drying. At pore diameters lower than 30 µm, the majority of pores remain collapsed. We attribute the permanence of the collapse of most small pores to a low probability of cavitation and to the adhesion of the pore walls. Pores with diameters larger than 100 µm tend to reopen after the water they contain cavitates. The behavior of pores with diameters ranging from 30 to 100 µm depends on the porosity and drying temperature. We also visualize collective cavitation upon drying of sponges initially saturated with a sodium chloride solution. In this case, the cavitation in the largest pores leads to reopening of small pores in a neighboring zone of the sample. To our knowledge, our results present the first experimental proof of the pore-size-dependent and cooperative nature of the response of soft sponges with closed porosity to drying.

This paper proposes an inverse estimation method for the extraction of the equivalent, static elastic, Hooke’s tensor. The inversion is based on a fitting of the displacements, obtained from a combination of static compression and shear traction loads, on the faces of a sample specimen. An equivalent, homogenised material model is found by varying the elastic moduli until a defined cost function, based on the error measured as the difference between the displacement fields, has reached a minimum, at which an anisotropic constitutive solid model has been identified. The method is built on a multi-level step-wise approach, both from a computational as well as an assumed constitutive model symmetry point of view. The principle of the method is validated for a target anisotropic solid material model. The proposed multi-level approach is developed and refined for a known open-cell structure based on the Kelvin cell geometry. The accuracy of the method is verified and various strategies for increasing the rate of convergence in the inversion are discussed.