Fraction Of Pores Research Articles

Study on the use of CO2 to strengthen recycled aggregates and pervious concrete

Recycled aggregates (RA) are crushed materials derived from waste concrete or construction debris that play a crucial role in the recycling of construction waste resources. However, RA's irregular particle shape and surface cement paste adhesions limit its potential in pervious concrete applications. To overcome this limitation, the use of carbonation treatment methods to process RA and produce recycled aggregate pervious concrete (RAPC) was investigated. RA was subjected to a pre-carbonation treatment, followed by the production of RAPC mixtures using three slurry-to-aggregate ratios, carbonation curing, and two-step carbonation strengthening, which enhanced the physical and mechanical properties of the specimens. Then, the measurements including permeability coefficient, connected pore fraction, splitting tensile strength, and CT microstructure analysis were performed. A carbon footprint accounting system from "cradle to gate" was conducted to assess the specimens. Our results highlight that an increase in the slurry-to-aggregate ratio in RAPC mixtures results in enhanced mechanical properties but negatively affects permeability performance. By pre-carbonating RA, we significantly increase the pervious concrete's splitting tensile strength, up to 100%, and maintain the compactability while ensuring permeability performance (maximum 3.91% reduction for specimens with slurry-to-aggregate ratio of 0.3). The carbonation treatment method used in our study has ideal environmental effects, as it theoretically sequesters up to 58.12% of the total carbon emissions produced during the production process.

Coupling radiative properties with detailed char conversion kinetics

In pulverized solid fuel combustion, radiation is the primary heat transfer mechanism. Especially in the near-burner region with high particle loadings, particle radiation dominates gas radiation. Thus, adequate modeling of particle-radiation interactions in full-scale simulations of combustion chambers may primarily affect the overall accuracy. The radiation behavior depends strongly on the particles? optical properties, characterized by the complex index of refraction (IOR). The IOR depends on particle morphology and material composition which change during pyrolysis and char conversion. For char conversion, the focus of the present paper, the change depends on how the structural transformations take place inside the particle, characterizes by the reaction regimes, boundary layer diffusion limited, pore diffusion limited or kinetically controlled. The formation of an outer ash film layer with progressing burnout can complicate the situation even more.To quantify the effects of the structural changes during the char conversion process on the radiative properties, the output data of the char conversion kinetics (CCK) model (particle size, ash/carbon content, pore fraction) are used to build artificial particles at different conversion degrees and for the different regimes. Finally, the radiation interaction is calculated by applying an extension of the Mie theory for coated particles, and these results are compared to simplified approaches.Simplified approaches were tested to derive the IOR by applying mixing rules based on the available char and ash content with progressing char conversion. The results indicate that only a non-linear mixing rule for the IORs of ash and char lead to appropriate approximations of the radiation behavior of the particle. Furthermore, it is not necessary to model the spatial arrangement of carbon core and ash film for the radiative properties. Modeling a sphere and calculating an effective IOR depending on the carbon, ash, and pore volume fraction results in an average deviation of less than 3% to the exact solution.

Computation of the effective permeability of 2D doubly porous materials with elliptical shaped pores by using boundary element method

In recent years, the prediction of the effective transport properties have received a great number of investigations. The present work is dedicated to determining the effective permeability of two-dimensional (2D) doubly porous materials made of an isotropic permeable solid matrix in which elliptical shaped pores of any size are embedded. At the interface between the fluid and the solid, the Beaver–Joseph–Saffman conditions are applied. To achieve this objective, the Boundary Element Method (BEM) is first elaborated in the simulation of velocity and pressure solution fields of two coupled Stokes and Darcy problems. Afterwards, with the help of this solution results, the effective permeablity of the doubly porous material under investigation can be determined. For the purpose of assessing the accuracy and convergence of the BEM solution, the results obtained for the velocity and pressure fields are compared with the ones provided by the finite element method (FEM). Finally, several numerical examples are carried out to analyze the fluid/solid interface influence, the effect of area fraction and geometrical properties of pores, such as the size and distribution of the pores within the matrix phase.

The Impact of NaOH on the Micro-Mechanical Properties of the Interface Transition Zone in Low-Carbon Concrete.

To tackle carbon emissions from cement production and address the decline in concrete's mechanical properties due to the substitution of cement with solid waste (glass powder) and natural mineral admixture (zeolite powder) materials, we employed glass powder and zeolite powder to create composite cementitious materials. These materials underwent alkali activation treatment with a 4% NaOH dosage, replacing 50% of cement to produce low-carbon concrete. Nanoindentation tests and mercury intrusion porosimetry (MIP) were employed to uncover the micro-mechanical properties and influencing mechanisms of alkali-activated low-carbon concrete. The results indicate a notable enhancement in the indentation modulus (19.9%) and hardness (25.9%) of alkali-activated low-carbon concrete compared to non-activated concrete. Simultaneously, the interfacial transition zone thickness decreased by 10 µm. The addition of NaOH led to a reduced volume fraction of pores (diameter >100 nm) and an increased fraction of pores (diameter < 100 nm), thereby reducing porosity by 2.6%, optimizing the pore structure of low-carbon concrete. The indentation modulus, hardness and volume fraction of the hydrated phase derived from Gaussian fitting analysis of the nanoindentation statistics showed that NaOH significantly improved the modulus and hardness of the hydration products of low-carbon concrete. This activation resulted in decreased LDC-S-H gel (low-density hydrated calcium silicate Ca5Si6O16(OH)·4H2O) and pore content, while the HD C-S-H gel (high-density hydrated calcium silicate Ca5Si6O16(OH)·4H2O) and CH (calcium hydroxide crystals Ca(OH)2) content increased by 13.91% and 23.46%, respectively. Consequently, NaOH influenced the micro-mechanical properties of low-carbon concrete by generating more high-density hydration products, reducing pore content, enhancing the pore indentation modulus and hardness, and shortening the interfacial transition zone. This study offers novel insights into reducing carbon emissions and promoting the use of solid waste (glass powder) and natural mineral admixture (zeolite powder) materials in concrete, contributing to the advancement of sustainable construction practices.

Cubic elasticity of porous materials produced by additive manufacturing: experimental analyses, numerical and mean-field modelling

Although the elastic properties of porous materials depend mainly on the volume fraction of pores, the details of pore distribution within the material representative volume are also important and may be the subject of optimisation. To study their effect, experimental analyses were performed on samples made of a polymer material with a predefined distribution of spherical voids, but with various porosities due to different pore sizes. Three types of pore distribution with cubic symmetry were considered and the results of experimental analyses were confronted with mean-field estimates and numerical calculations. The mean-field ‘cluster’ model is used in which the mutual interactions between each of the two pores in the predefined volume are considered. As a result, the geometry of pore distribution is reflected in the anisotropic effective properties. The samples were produced using a 3D printing technique and tested in the regime of small strain to assess the elastic stiffness. The digital image correlation method was used to measure material response under compression. As a reference, the solid samples were also 3D printed and tested to evaluate the polymer matrix stiffness. The anisotropy of the elastic response of porous samples related to the arrangement of voids was assessed. Young’s moduli measured for the additively manufactured samples complied satisfactorily with modelling predictions for low and moderate pore sizes, while only qualitatively for larger porosities. Thus, the low-cost additive manufacturing techniques may be considered rather as preliminary tools to prototype porous materials and test mean-field approaches, while for the quantitative and detailed model validation, more accurate additive printing techniques should be considered. Research paves the way for using these computationally efficient models in optimising the microstructure of heterogeneous materials and composites.

Study of the Effect of Selective Laser Melting Parameters on the Structure and Physico-Mechanical Properties of a Blank Made of Stainless Chromium-Nickel Steel

Currently, there are a number of additive technologies that are used in various industries (laser fusion of powder materials, electron beam melting, etc.). The formation of metal structures and products by methods of additive technologies occurs by adding a new layer of material and its further melting (sintering), ensuring the adhesion of each subsequent layer with the previous one in accordance with digital model data. The advantages of using and developing additive technologies include the possibility of using a wide range of materials, obtaining finished products with complex geometries, restoring and repairing damaged structures, as well as the possibility of applying protective and anticorrosive coatings. Metal powder materials with specified physical and mechanical properties are of crucial importance in additive manufacturing. The main requirements for such powders include requirements for their shape and size. The preferred particle shape is spherical, as it provides a more compact installation in a given volume and the necessary fluidity of the material, which is due to the low resistance in the supply systems of powder materials in 3D printers. The aim of the work is to study the influence of the parameters of the SLM printing process on the structure and mechanical properties of products made of 12Cr18Ni10Ti alloy. Samples obtained by selective laser melting were subjected to pycnometric and metallographic analysis. Based on the obtained microstructure images, a digital porosity analysis of the work piece under study was performed in the Thixomet Pro software package. The microhardness and acoustic characteristics were also measured over the entire section of the work piece under study. It was revealed that with an increase in the distance from the substrate (0...112 mm) in the transverse and longitudinal sections, the tendency remains to decrease the density values and increase the volume fraction of pores. It is shown that the acoustic parameter Dc can be used to control changes in the physical and mechanical properties of stainless chromium-nickel steel blanks obtained by selective laser melting.

A novel lattice model to predict chloride diffusion coefficient of unsaturated cementitious materials based on multi-typed pore structure characteristics

This paper develops a novel lattice diffusive model to quantitatively study the chloride diffusion coefficient in unsaturated cementitious materials, in which the pore voxels are redistributed to make a better representation of a real microstructure of hardened cement paste. Considering the hierarchical microstructure and different drying-wetting cycles, water distributions in multiscale pore structures are modelled and the structure characteristics of water-filled pores, including water connectivity, water tortuosity and effective porosity, are computationally extracted based on that. A lattice diffusion network is established to predict relative chloride diffusion coefficient by combining the effect of both water saturation degree and pore structure characteristics. The predicted results are validated against experimental data, and a concise analytical equation is proposed to predict the relative chloride diffusion coefficient. The equation indicated that the relative chloride diffusion coefficient is proportional to water connectivity but inversely proportional to the square of water tortuosity. Besides, the lattice model's quantitative results reveal that the water connectivity and water tortuosity are highly related to pre-water loading processes, and influenced by the gel pore fraction, which in turn will affect the relative chloride diffusion coefficient. Compared with existing equations and non-redistributed models, the present model could improve the prediction accuracy significantly.

Chloride accessible porosity fractions across the Jurassic sedimentary rocks of northern Switzerland

The Jurassic clay-rich sedimentary sequence in northern Switzerland was investigated in the context of nuclear waste disposal. Tracer profiles across this sequence play an important role when assessing transport processes and long-term evolution of the environment. Negatively charged clay-mineral surfaces cause a depletion of anions in the porewater close to the surfaces compared to free porewater further away. The chloride accessible porosity fraction (fCl) is an important parameter to scale Cl bulk porewater concentrations from aqueous extraction to free porewater concentrations, which are required to establish anion profiles used for transport modelling of anionic tracers. A vast set of fCl data from advective displacement (AD), squeezing (SQ) and through-diffusion (DI) experiments allowed for method comparison and yielded insight into controlling factors of fCl across the sedimentary sequence. Two observations were made: (1) fCl varies strongly depending on lithology and partly on ionic strength; (2) at high ionic strength, the three methods yield consistent results, but at low ionic strength, fCl from DI are lower than those from AD and SQ. The observations are discussed in terms of influencing factors, including structural charge, ionic strength, rock texture, pore sizes and the fact that the different methods sample different parts of the pore space. The stronger variation of fCl from DI experiments with the ionic strength of the experimental porewater is in agreement with theoretical concepts. The volume fraction of small pores (r < 2 nm) inversely correlates with fCl; it accounts for ∼50% of the anion depleted pore volume. Two empirical approaches were tested to derive functions for fCl valid for the lithologically diverse sequence: the clay-content model uses a constant fCl at a clay-mineral content >30% and extrapolates to a fCl of 1 at zero clay content. The formation model applies formation- or member-specific average values of experimental fCl for each unit. Both approaches work reasonably well, with the formation model producing less apparent outliers of free porewater concentrations than the clay-content model. Still some scatter remains, particularly in heterogeneous and low-porosity formations. This work results in a comprehensive and coherent fCl dataset for all studied Jurassic formations and serves as a basis to interpret the profiles of anions with regard to transport across the entire low-permeability sequence.

Harnessing total chemical-free paper and packaging materials barrier properties by mechanical modification of cellulosic fibers for food security and environmental sustainability

Surging interest in finding sustainable alternatives for single-use plastics has galvanized research into cellulosic fiber-based paper and packaging materials. This investigation examines mechanical (refining & calendering) approaches to enhance paper's barrier properties comprising Southern bleached hardwood kraft (SBHK) and Southern bleached softwood kraft (SBSK) fibers. With increased refining intensity followed by calendering, paper thickness decreases while the apparent density increases. The refining process also generates more fibrils and fines, as reflected by reduced pulp freeness. Air resistance increases significantly due to denser fiber networks and reduced porosity. Refining also improves the water vapor transmission rate (WVTR) and oil & grease resistance (OGR). A 48 % reduction in WVTR and a Kit "9″ rating for OGR were observed in SBHK paper sheets refined at 16000 revolution. Notably, refining modifies cellulose fiber morphology, promoting 59 % and 94 % external fibrillation in SBSK and SBHK fibers, respectively. This change facilitates a more compact fiber arrangement, enhancing barrier properties. XRD patterns show an initial increase in cellulose crystallinity with refining, decreasing at a higher revolution of refining. SEM analysis reveals decreased surface roughness and pore fraction post-calendering, enhancing air and OGR. In a relative sense, hardwood fibers showed higher barrier performance than softwood fibers. Our work demonstrates mechanical modifications of fibers and paper web can effectively tune paper barrier performance such as WVTR, OGR, and air/oxygen resistance.

Effect of Zinc Content on Powder Characteristics, Porosity, Microstructure, and Corrosion Behavior of SLM-Printed Mg-xZn-0.2Mn Alloys for Biomedical Applications

This study investigated the effects of Zinc (Zn) content, specifically in the range of 1 wt.% to 7 wt.%, on the powder characteristics, porosity, microstructure, and corrosion behavior of Mg-xZn-0.2Mn alloys produced using selective laser melting (SLM). To evaluate the porosity of the printed parts and various powder attributes, such as size, circularity, void spaces between powders, and inherent imperfections, scanning electron microscopy (SEM) and optical microscopy (OM) were employed. The alloy microstructure, composition, and phase were examined using energy dispersive X-ray (SEM-EDX) and X-ray Diffraction (XRD). The corrosion resistance and degradation behavior were assessed through electrochemical corrosion tests and immersion tests in Hanks’ solution at 37.5 °C, respectively. Finally, OM and SEM-EDX were used to characterize the corrosion products. The findings of this study indicated that the powder size increased with Zn content, maintaining a 0.8 circularity. Powder defects were minimal, with occasional satellite particles. For the SLM-printed samples, it was evident that porosity characteristics could be influenced by Zn content. As Zn content increased, the pore fraction rose from 1.0% to 5.3%, and the pore size grew from 2.2 μm to 3.0 μm. All printed samples consisted of an α-Mg matrix. Additionally, a higher Zn content resulted in more distinct grain boundaries. Corrosion resistance decreased with Zn, leading to more pronounced localized corrosion after immersion in Hanks’ solution. Ca-P was found as white corrosion products on all samples.

Acid-activated natural zeolite and montmorillonite as adsorbents decomposing metsulfuron-methyl herbicide

Modern technologies of intensive crop production demand a wide application of various types of pesticides. The adverse effect of cropping intensification is that toxic organic compounds, in particular herbicides of the sulfonylurea family, are accumulated in the soil. The herbicide metsulfuron-methyl is soluble in water and accumulates in soil moisture, causing a toxic effect on plant development. The work examines the issue of the chemical stability of metsulfuron-methyl in a model aqueous environment for the targeted selection of a mineral that adsorbs the herbicide and simultaneously catalyzes the process of herbicide hydrolysis. Degradation processes of sulfonylurea herbicide metsulfuron-methyl in aqueous media in the presence of natural zeolite, acid-activated natural zeolite, and montmorillonite К10 were investigated. Under conditions of static contact of the adsorbents with an herbicide aqueous solution, montmorillonite was more active in the sorption and degradation of metsulfuron-methyl. During the first 1–2 days the herbicide concentration decreased by a factor of 5. An almost complete degradation of metsulfuron-methyl in aqueous dispersions of the acid-activated zeolite and montmorillonite was attained within 20 days. Pore size distribution functions (Barrett-Joyner-Halenda and standard non-local density functional theory methods) were evaluated. The acid treatment of the natural zeolite changed its porous structure - its specific surface area grew by a factor of 5. Three fractions of mesopores 4–10, 10–20, 20–30 nm were revealed in the original zeolite, and one fraction of pores 2.0–3.5 nm was found in the acid-activated zeolite. In the montmorillonite, only one group of 3–15 nm pores was detected. Studies of structural changes in natural zeolite after acid modification were carried out using the methods of X-ray fluorescence and X-ray phase analysis, scanning electron microscopy and infrared spectroscopy. The acid-activated montmorillonite and natural zeolite show promise for land reclamation work on detoxification of soils contaminated by sulfonylurea herbicides.

Study on the microstructure of recycled aggregate concrete strengthened by the nano-SiO2 soaking method

Herein, the study investigates the microstructure of recycled aggregates concrete (RAC) prepared by nano-silica strengthened recycled aggregates (RAs). Five concentrations (0 %,1.0 %,1.5 %,2%, 2.5 %) of nano-silica solutions in two different conditions (normal pressure and vacuum pressuring of 1ba) are selected to soak RAs. After the soaking process, the chemical composition, the porosity and pore structure, and micrographs of nano-silica strengthened RAs and RA-based concrete are investigated. Results show that the 2 % concentration alone with the vacuum pressing is optimal. It reduces CH content by more than 40 %, decreases porosity, narrows the average pore size, and increases the volume fraction of pores that are less harmful (less than 50 nm). These results, verified by ESEM, are attributed to the conversion mechanism of secondary hydration and the filling effect of nanoparticles. The research at a microscopic level explains the strengthening effect of nano-silica upon recycled aggregate concrete and lays a theoretical foundation for upcycling construction and demolition wastes.

Pore structure characteristics and mechanical property of engineered cementitious composites (ECC) incorporating recycled sand

The mechanical properties of recycled sand (RS) modified ECC are intimately linked to its pore structure characteristics, but the internal pore size and distribution of RS modified ECC and its impact mechanism on the mechanical properties are still unclear. This study employed mercury intrusion porosimetry (MIP) and low field nuclear magnetic resonance (LF-NMR) techniques to analyze the pore structure of ECC incorporating RS. Furthermore, compression and tension mechanical experiments were conducted to investigate the correlation between the evolution of pore structure and mechanical properties of ECC incorporating RS. The findings demonstrate that the addition of RS increases the porosity of ECC. When replacement ratio of RS is 100 %, the volume fraction of pores decreases within the range of 10 nm to 100 nm, whereas it exhibits an increasing trend within a ranging from 100 nm to 1 μm. The incorporation of RS results in a decrease of the volume fraction of gel pores and the increase of capillary pores in ECC owing to its high-water absorption and porous, as well as the reduction of calcium-silicate-hydrate (C-S-H) due to the surface attached old mortar. Therefore, addition of RS lead to a reduction in both the compressive strength and tensile strength of ECC. However, as a result of the pore structural flaw inherent in the recycled fine aggregate, the occurrence of multi-crack cracking, induced by interfacial imperfections between the recycled fine aggregate and matrix, contributing to development of cracks in ECC and thus enhancing its tensile strain capacity.

Quantitative image analysis of influence of polysaccharides on protein network formation in GDL-acidified milk gels

Exopolysaccharides (EPS) are commonly used to improve the texture of yogurt. These polysaccharides interact with casein micelles, the major protein in milk, via electrostatic and depletion mechanisms during fermentation by lactic acid bacteria (LAB). However, the relationship between the physicochemical properties and monosaccharide composition of EPS and their impact on yogurt texture is not yet fully understood. To address this knowledge gap, we studied the effects of polysaccharides commonly used as food additives on acid-induced milk protein networks. Confocal laser scanning microscopy (CLSM) was used to image the network microstructures. Image analysis, including Fourier transform, autocorrelation, and binarization-based techniques, was applied to quantify key structural features of the mixed milk protein/polysaccharide gels. These parameters were then related to the macroscopic properties of the model food matrices, such as elastic and viscous moduli and yield point. We found that the addition of neutral polysaccharides resulted in a concentration-dependent increase in structure factor, protein domain size, and pore fraction. In contrast, the presence of charged polysaccharides led to an increase in protein domain size, a decrease in pore fraction, and a decrease in elastic and viscous moduli. These results demonstrate the use of a quantitative image analysis method for selecting LAB with favorable EPS properties to improve yogurt texture.

EOR Displacement Characteristics from Cluster Analysis and Fractional Pore Occupation

AbstractThe in situ saponification of crude oil lowers the interfacial tensions of oil–water systems in chemical-enhanced oil recovery (cEOR). When the interfacial tension is sufficiently low, emulsion phases occur, and the fluid phase distribution in the pore space changes, affecting oil displacement efficiency. This change in capillarity allows the injection water to penetrate different classes of pores, which must be reflected in the distribution of fluids in the pore space. This issue still needs to be adequately researched and is not reflected in the classic analyses of oil cluster size. We have performed μCT-based coreflood experiments to study the displacement efficiency of crude oil by alkaline solutions acting as cEOR agents for in situ saponification. The measured fluid distributions were analyzed using oil-cluster size statistics. In addition, the pore classes from which the oil was preferentially displaced and the degree of displacement as a function of alkali concentration were determined. Despite ultralow interfacial tension and emulsion formation, a clear separation of the oil and aqueous phases was observed over a wide range of alkali concentrations, allowing a two-phase analysis of the microscopic fluid distribution. It was found that (a) a Lorentz analysis of the cluster volume distribution is useful to characterize the cEOR displacement efficiency. It shows the tendency of oil clusters toward a more uniform size distribution toward optimal alkali concentration. (b) the additional oil recovery toward optimal displacement conditions comes from the fraction of smaller pores; at optimal conditions, all pore classes are flooded almost equally and to a high degree, equivalent to miscible displacement, i.e., extremely low interfacial tension.

Mechanical properties and abrasion resistance of polyurethane mortar subjected to freeze–thaw cycles and sulfate attack

The objective of this paper is to investigate the properties of polyurethane mortar subjected to freeze–thaw cycles in sulfate environment. Na2SO4 solutions with 5% and 10% sulfate concentrations were prepared. The mass loss, compressive strength, flexural strength and abrasion resistance of the polyurethane mortar were investigated. The interface transition zone and pore structure were then analysed. Results revealed that the damage degree of the mass, compressive strength and flexural strength of polyurethane mortar subjected to freeze–thaw cycles in sulfate solution are greater than that in water, and the high concentrations of sulfate solution can cause severe damage. The polyurethane mortar subjected to freeze–thaw cycles and sulfate attack will appear to have more severe surface damage after abrasion. The abrasion resistance of polyurethane mortar decreases as the freeze–thaw cycles and abrasion time increase. The freeze–thaw cycles and sulfate attack can cause the crack width at the interface transition zone of polyurethane mortar to expand, and the abrasion action accelerates this evolution. With the increase in freeze–thaw cycles, the gel and transition pores are gradually transformed into capillary and large polyurethane mortar pores. The volume fraction of capillary and large pores gradually increases, and the fractal dimension tends to decrease. Furthermore, the fractal dimension of the pore structure is positively correlated with mechanical properties and abrasion resistance. The mechanism analysis shows that abrasion can cause the detachment of loose mortar matrix of polyurethane mortar surface and form a weak area.

In-situ X-ray computed tomography tensile tests and analysis of damage mechanism and mechanical properties in laser powder bed fused Invar 36 alloy

Laser powder bed fusion (LPBF) is a potential additive manufacturing process to manufacture Invar 36 alloy components with complicated geometry. Whereas it inevitably introduces specific microstructures and pore defects, which will further influence the mechanical properties. Hence, aiming at exploring the LPBF process-related microstructures and pore defects, and especially their influences on the damage mechanism and mechanical properties, Invar 36 alloy was manufactured by LPBF under designed different laser scanning speeds. The microstructure observations reveal that higher scanning speeds lead to equiaxed and short columnar grains with higher dislocation density, while lower scanning speeds result in elongated columnar grains with lower dislocation density. The pore defects analyzed by X-ray computed tomography (XCT) suggest that the high laser scanning speed gives rise to numerous lamellar and large lack-of-fusion (LOF) pores, and the excessively low laser scanning speed produces relatively small keyhole pores with high sphericity. Moreover, the in-situ XCT tensile tests were originally performed to evaluate the damage evolution and failure mechanism. Specifically, high laser scanning speed causes brittle fracture due to the rapid growth and coalescence of initial lamellar LOF pores along the scanning direction. Low laser scanning speed induces ductile fracture originating from unstable depressions in the surfaces, while metallurgical and keyhole pores have little impact on damage evolution. Eventually, the process-structure-property correlation is established. The presence of high volume fraction of lamellar LOF pores, resulting from high scanning speed, leads to inferior yield strength and ductility. Besides, specimens without LOF pores exhibit larger grain sizes and lower dislocation density at decreased scanning speeds, slightly reducing yield strength while slightly enhancing ductility. This understanding lays the foundation for widespread applications of LPBF-processed Invar 36 alloy.

The importance of pore-fracture connectivity in overmature marine shale for methane occurrence and transportation

Pore-fracture connectivity is a critical factor in gas occurrence and transportation in shale plays. To investigate the limiting factors of multiscale pore-fracture connectivity, which might control methane occurrence and transportation in shale reservoirs, small-angle neutron scattering (SANS) under vacuum and high-pressure conditions incorporated with repeated mercury intrusion capillary pressure (MICP), and field emission-scanning electron microscopy (FE-SEM) imaging after Wood's metal (WM) impregnation were performed on overmature marine shale samples of the Wufeng-Longmaxi and Niutitang Formations from south China. Based on the electron micrographs of the WM-injected samples, it was found that the sealing of the pore system by brittle minerals is the root cause for a reduction in overall pore connectivity within the shale matrix. Aside from being favorable to the preservation of organic and clay mineral pores, brittle minerals however, resulted in the closure of pore network, thus, forming an isolated pore system. The novel approach of integrating repeated MICP measurement and FE-SEM imaging after WM impregnation provides a new evaluation method for pore-fracture connectivity of shale. The minimum fraction of pores within the overmature shales accessible to methane was at 38% and 78% within 100 nm. Moreover, because of confinement effects, the density of methane in a pore space less than 20 nm under high pressure was greater than that of an ideal gas under the same pressure conditions which even increased with decreasing of pore size to several times of its inert state and formed nanoscale methane clusters. The combination of contrast-matching SANS (CM-SANS) and repeated MICP measurements can effectively reveal the connectivity of pores within the matrix and the connectivity between such pores and microfractures, which helps to evaluate the distribution of closed pores and dominant transport spaces of gas in shale reservoirs. Overall, the pore-fracture connectivity in overmature marine shale controls the amount of gas that is supplied from matrix pores into fracture systems and also affects the density of the gas in pore spaces within the matrix.

Tuning the ultra-microporosity in hierarchical porous carbons derived from amorphous cellulose towards a sustainable solution for hydrogen storage

Activated carbons exhibit a high grade of porosity, which together with structural stability, regenerability and cyclability makes them capable of achieving excellent hydrogen adsorption capacity. A further advantage comes from the ease of production and the use of recyclable and biocompatible materials. A simple way to produce activated carbons from amorphous cellulose involves procedures in which a pyrolysis process is combined with physical activation in CO2.We used this approach by optimizing the production process tuning the activation times. The aim is to evaluate the influence of this process parameter on the formation of the specific surface area, the pore volume and fraction of micropores with a typical size <2 nm. The influence of these structural parameters on the hydrogen adsorption properties was then evaluated. The textural and adsorption characteristics were investigated using a commercial volumetric apparatus (ASAP 2460, Micromeritics) at −196 °C and pressures between 0 and 1 bar, while the morphological properties were investigated using scanning electron microscopy.The results show that the nanostructured samples are characterized by a very high degree of ultra-microporosity (<0.7 nm) with an average pore size between 0.5 and 0.6 nm and a high specific surface area, reaching maximum values around 1500 m2/g and micropore volume up to 0.58 cc/g. These morphological characteristics strongly influence the hydrogen adsorption properties, where the molecules adsorbed reach values very close to the coverage of ideal monolayer. The synthesized activated carbon samples show a higher hydrogen adsorption capacity than similar commercial materials tested under the same thermodynamic conditions.

Managing the pore system: Regenerating the functional pore spaces of natural soils by soil-health oriented farming systems

Transition towards soil-health sustaining crop production is at the core of climate change mitigation and adaptation efforts in agriculture. Improving soil conditions for resilience to variable and extreme weather conditions are among the main expectations of farmers implementing sustainable management practices. In this study, we evaluate whether the transition from conventional arable towards soil-health oriented farming systems restores soil pore characteristics towards non-arable natural soils and identify factors predominantly shaping different pore domains. Pore size distributions (PSD) at 20 sites with diverse soil types from adjacent fields of (1) standard arable, (2) soil health-oriented pioneer farming and (3) non-arable natural reference soils were measured. Based on parametric PSD descriptors, management-responsive functional pore classes and the role of textural, biochemical and structural drivers in different pore domains were analysed by a novel data-driven evaluation method. Parametric descriptors indicate an evolution from non-disturbed natural to intensively disturbed standard arable soils towards larger structural pores within a less heterogeneous structural domain. These shifts go along with less medium-sized storage pores, which overall was the most management sensitive pore fraction. Our novel data-driven approach confirmed a partial regeneration of natural pore characteristics with soil-health oriented practices. The most responsive pore domain was found in the range of ∼0.3–0.5 µm. The SOC-to-clay ratio was the predominant driver for structural porosity in both pioneer arable and natural reference soils. On the contrary, soil texture exerted the main control on the PSD pattern over the entire range of pore classes for standard farming systems. Overall, our study demonstrated that soil-health oriented pioneer farmers could effectively advance in managing functionally relevant pore domains for climate change resilience by promoting biological agents of structure formation.