Interparticle Porosity Research Articles

Zeolite membrane separators for fire-safe Li-ion batteries – Effects of crystal shape and membrane pore structure

The state-of-the-art lithium-ion batteries (LIB) use carbonate-based liquid electrolytes and polymeric separators which pose safety issues including fire-hazard. The use of fire-retarding salt-concentrated electrolytes can address the safety issues of LIBs, but these electrolytes have high viscosity and low wettability with polymeric separators making it difficult to fabricate high performance LIBs with the electrolytes. Here we report development of zeolite membrane separators with tailored pore structure and surface chemistry for preparation of fire-safe LIBs using salt-concentrated electrolytes. The zeolite membrane separators are made of zeolite particles with a specific zeolite structure, Si/Al ratio, and different particle shapes, coated on cathode by a scalable blade coating method. Intermediate pore, pure silica MFI-type zeolite (silicalite) was selected as the fire-proof material for membrane separators which also offer high wettability for the fire-retarding salt-concentrated electrolyte of lithium bis(fluorosulfonyl)imide (LiFSI) in tri-methyl phosphate solvent (TMP) solvent. Two silicalite membrane separators of similar pore size but different porosity and tortuosity were coated on cathode (LiNi0.5Mn0.3Co0.2O2 or NMC) using plate-shaped silicalite particles of low aspect ratio (LAR) and high aspect ratio (HAR). Both zeolite separators show significantly better wettability for the LiFSI/TMP electrolyte than the commercial polypropylene (PP) separator allowing fabrication of high-performance NMC/LiFSI-TMP/graphite cells with the non-combustible silicalite separator. The new fire-safe zeolite-membrane-based LIBs with the fire-retarding electrolyte exhibit excellent charge and discharge characteristics and cycle performance (similar to the state-of-the-art, but fire-unsafe LIBs with LiPF6-carbonate electrolyte and polymer separator). The membrane separators made of HAR plate-shaped zeolite showing low interparticle porosity and high tortuosity perform better than the membrane made of LAR zeolite particles, due to a more uniform lithium-ion flux from both interparticle pores and intraparticle zeolitic pores at the separator/anode interface.

Diagenesis and sequence stratigraphy of Miocene, Nyalau Formation, Sarawak, Malaysia: A case study for clastic reservoirs

The link between sequence stratigraphy and diagenetic alterations is quite familiar for the last two decades in different types of reservoir rocks. Understanding the lithologic characteristics and diagenetic alterations is key to deciphering the various complex controls on porosity and permeability. Although, the sandstone heterogeneity is a product of a complex history of depositional and diagenetic modifications. However, much deeper augmentation is required to achieve the desired resolution and precision to fill this research deficit. This case study focuses on the diagenesis and reservoir potential of the early Miocene, Nyalau Formation. This study is based on conventional sedimentological and sequence stratigraphical measurements, petrographic observations, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) images and Energy dispersive X-ray spectroscopy (EDS) analysis. The main diagenetic processes are compaction, dissolution and cementation. The Transgressive System Tract (TST) is dominated by iron oxide, calcite cementation, and mechanical compaction in eodiagenesis. In HST (Highstand System Tract), the principal diagenetic signatures are iron oxide cements and/or grain dissolution. In sandstones primary porosity is controlled by deposition and is in the form of interparticle pores. Later, secondary pores become more significant with help of grain dissolution. Diagenetic alterations, e.g. cementation, compaction, dissolution are discussed in the sandstone reservoir within an outcrop sequence stratigraphic framework. Our conceptual model shows that the porosity is controlled by deposition and is preserved in the form of interparticle porosity and later enhanced by secondary grain dissolution. Diagenetic alterations presented here in sandstone reservoir in a sequence stratigraphic framework can help in other similar tectono-sedimentary basins, globally.

Modeling comparison and theoretical study of mass transfer characteristics for desiccant coated air channel under isothermal dehumidification

Coupled heat and mass transfer phenomena are encountered in desiccant coated dehumidifier, and their numerical modeling is becoming indispensable. In this study, three conjugate heat and mass transfer models were compared to clarify the effects of interparticle mass transfer and local kinetic non-equilibrium on modeling accuracy, and the models were validated by experiment results of silica gel and FAM Z01 coated dehumidifiers with single one air channel. Furthermore, a parametric study on the separate mass transfer characteristics of the dehumidifier under isothermal dehumidification was conducted based on one of the improved models. Results demonstrated that the effect of interparticle mass transfer should be involved, while the local kinetic non-equilibrium tends to be considered for desiccants with steep isotherm shape. Parametric study revealed that as air velocity increases, both air- and solid-side mass transfer change significantly, while desiccant layer thickness, interparticle porosity and isotherm shape mainly affect solid-side mass transfer. The average mass transfer Biot numbers Bim of desiccant layer with relative low thickness of 0.1 mm under various parameters are in the same order of magnitude as 1, indicating that the mass transfer resistance on solid side cannot be ignored generally.

Machine learning accelerated approach to infer nuclear magnetic resonance porosity for a middle eastern carbonate reservoir

Carbonate rocks present a complicated pore system owing to the existence of intra-particle and interparticle porosities. Therefore, characterization of carbonate rocks using petrophysical data is a challenging task. Conventional neutron, sonic, and neutron-density porosities are proven to be less accurate as compared to the NMR porosity. This study aims to predict the NMR porosity by implementing three different machine learning (ML) algorithms using conventional well logs including neutron-porosity, sonic, resistivity, gamma ray, and photoelectric factor. Data, comprising 3500 data points, was acquired from a vast carbonate petroleum reservoir in the Middle East. The input parameters were selected based on their relative importance with respect to output parameter. Three ML techniques such as adaptive neuro-fuzzy inference system (ANFIS), artificial neural network (ANN), and functional network (FN) were implemented for the development of prediction models. The model’s accuracy was evaluated by correlation coefficient (R), root mean square error (RMSE), and average absolute percentage error (AAPE). The results demonstrated that all three prediction models are reliable and consistent exhibiting low errors and high ‘R’ values for both training and testing prediction when related to actual dataset. However, the performance of ANN model was better as compared to other two studied ML techniques based on minimum AAPE and RMSE errors (5.12 and 0.39) and highest R (0.95) for testing and validation outcome. The AAPE and RMSE for the testing and validation results were found to be 5.38 and 0.41 for ANFIS and 6.06 and 0.48 for FN model, respectively. The ANFIS and FN models exhibited ‘R’ 0.937 and 0.942, for testing and validation dataset, respectively. Based on testing and validation results, ANFIS and FN models have been ranked second and third after ANN. Further, optimized ANN and FN models were used to extract explicit correlations to compute the NMR porosity. Hence, this study reveals the successful applications of ML techniques for the accurate prediction of NMR porosity.

Thermal transport-porosity-microstructural characteristics: unpicking the relationship in ultra-porous α-Al2O3 powder

This study deals with the effective thermal conductivity of porous and ultra-porous unconnected solid phase media composed of α-alumina in air at low temperature (<500K), and at ambient pressure. A multi-scale model is developed, starting from the quantum scale, to describe the conductivity of the single crystal, passing through a microscopic scale to describe the particles (grain size), a mesoscopic scale to take into account the intraparticle porosity and a macroscopic scale with the interparticle porosity. The model is based on percolation theory to describe the strong decrease in conductivity with porosity in this type of medium. This translates into the breaking of contacts between particles past a certain porosity, the critical porosity pc. This original approach makes it possible to consider this microstructural factor, which accounts for the thermal contacts between particles. These parameters are theoretically deduced or measured for certain samples using an X-ray micro-tomograph (µCT). Combining all these parameters, our model is able to predict 99.7% of the thermal conductivity decay from the pure crystal to the particle bed. Our model proves to be more consistent than current existing models on the same subject. Its validation range extends over the entire porosity range from 0 to 1.

MOF-derived carbon/ZnS nanoparticle composite interwoven with structural and conductive CNT scaffolds for ultradurable K-ion storage

This study reports MOF-derived carbon/ZnS nanoparticle composite interwoven with CNT scaffolds for ultradurable K-ion storage. Metal–organic framework (MOF)-derived carbons possess in situ generated metal particles, which are subsequently utilized to prepare metal compounds. In MOF derivatives, the original morphology of MOF is rarely maintained due to the collapse of the framework and pyrolysis of organic ligands at high temperature. Accordingly, metal nodes aggregate, resulting in coarsening and non-uniform distribution of metal particles, which degrades their electrochemical properties. Moreover, the collapse dwindles micropore volume, decreases interparticle porosity and hinders diffusion of ions. Despite the importance in energy storage materials, however, these issues have been largely overlooked in MOF-assisted nanoparticle synthesis. We report a novel strategy for synthesizing robust MOF grown in situ on and interwoven with structural and conductive scaffolds of carbon nanotube networks (MOF-5@ACNT), which effectively stabilize the structure and morphology of the MOFs by preventing them from collapsing, thereby suppressing the aggregation and coarsening of metal particles during carbonization. To synthesize ZnS nanoparticles embedded in MOF-derived carbon (ZnS/C@CNT), MOF-5@ACNT and sulfur are mixed and heat-treated to prepare ZnS/C@CNT, wherein the initial cubic morphology of MOF-5 is retained and ∼15 nm ZnS nanoparticles are uniformly distributed without aggregation. ZnS/C@CNT exhibits a highly reversible conversion–alloying reaction with a high specific capacity (410 mA h g−1) and excellent cycling performance (87 % retention after 1000 cycles). The intimate contact between the ZnS nanoparticles and carbon through chemical interactions and structural and morphological stability make ZnS/C@CNT a promising anode material for KIBs.

Electrode-level strategies enabling kinetics-controlled metallic Li confinement by the heterogeneity of interfacial activity and porosity

Three-dimensional (3D) host architectures have emerged as promising strategies for resolving the critical issues of Li metal anodes, namely, severe volume changes and growth of Li dendrites during battery cycling. However, preferential Li plating on top of the host architecture often causes early cell failure. Herein, we demonstrate that the controlled heterogeneity of interfacial activity and the porous structure at the electrode level enables confined Li metal storage in host architectures consisting of metal-organic framework (MOF)-derived carbon. 3D electrochemical simulations show that carbon activity (lithiophilicity) and interparticle porosity play critical roles in controlling the competing kinetics of charge transfer and Li+ transport, thereby regulating the Li-plating behavior. The enhanced lithiophilicity at the electrode bottom, combined with the increased interparticle porosity at the top, is predicted to promote the preferential nucleation of Li and subsequent upward growth from the bottom. Based on the proposed design principles, high-capacity and long-cycling host architectures based on MOF-derived carbon are constructed via two-step electrophoretic deposition (EPD): densely populated Ag-incorporated carbon at the bottom in combination with sparsely populated Ag-free carbon at the top. The heterogeneous host architecture fabricated by EPD spatially confines a large amount of Li metal (6 mAh cm–2) without significant volume changes and exhibits a long cycle lifetime of over 900 cycles. This study provides an effective strategy for designing advanced Li metal anodes by controlling the competing reaction kinetics in 3D host architectures.

Towards realistic characterisation of chemical reactors: An in-depth analysis of catalytic particle beds produced by sieving

Optimization of large-scale fixed particle bed catalytic reactors requires extensive insight into the multi-scale bed structure, even down to the micrometre scale. Theoretical studies of chemical reactors provide a time- and cost-effective means to supporting the optimisation process. However, they rely on simplified assumptions for the particles, e.g. homogeneous perfect spheres. In practise, the preparation of catalytic particles cannot attain this level of uniformity. Typical preparation techniques, such as sieving, are conducted with the aim of obtaining particle size distributions within a pre-defined range, governed by the sizes of the sieves. However, such methods offer limited control in the actual particle sizes and shapes. This paper evaluates the impact of sieving on the resulting particles and overall structural morphology of catalytic beds. The bed structure is quantified using micro-focus computed tomography (µ-CT), enabling the non-destructive examination and analysis of over 150 thousand particles, in terms of particle size, shape, uniformity, and interparticle porosity. Furthermore, the chemical performance of the resulting beds is compared. The detailed characterisation achieved paves the way for the evolution of more rigorous computational models coupling intricate, localised hydrodynamics with realistic chemical processes. Validation of such models at the lab-scale will accelerate the development of more accurate large-scale models.

Structural and Mineralogical Characterization of the Clayey Deposits of Gb&amp;#233;dji-Kotovi in Lama Depression, B&amp;#233;nin

The objective of the study was to characterize the clays of the Lama depression in Benin. Macroscopic examination of hand soundings, dynamic penetration test and stratigraphic correlation of water borehole logs, as well as scanning electron microscopy (SEM) combined with energy-dispersive X-ray microanalysis (EDX) method were made on compact or stratified clays. The large grains are embedded in a sintered matrix. The texture is heterogeneous and open, including quartz, carbonates and organic matter. The fine fraction is dominated by mineral paragenesis characterizing Kaolinite-Quartz-Calcite-Gypsum dioctahedral smectites composed of: Oxygen, Silica, Carbon, Aluminum, Iron, Zinc, Titanium and Magnesium. This smectic and regular structure includes coarse grains of the order of 800 μm. The pore diameters vary from 130 μm to 1.14 μm. The inter-particle porosity is poorly developed unlike the inter-aggregate pores larger than 0.05 μm. The texture is laminar and shows elongated turbo static particles with more or less rounded edges and honeycomb particles. Quartz and carbonates induce an increase in heterogeneities which develop mechanical sensitivity and hydraulic conductivity. High contents of silica, iron or aluminum and low contents of calcium and magnesium, as well as the presence of other trace elements suggest an alumino-ferriferous clay resulting from the hydrothermal alteration of the acid granite massif. These heterogeneities promote less tortuous pores or paths, making these clays more permeable. Finally, other stabilization studies and improvements to hydraulic products and binders should favor the use of the studied clay as improved backfill or drilling muds.

Porosity Evolution and Microfacies Analysis of the Khurmala Formation (Paleocene-Early Eocene) from Selected Sections in Kurdistan Region, Northern Iraq Revealed by Cathodoluminescence Spectroscopy

The microfacies analysis and porosity evolution of the Khurmala Formation (Paleocene-Early Eocene) were studied in the Gomaspan and Sheraswar sections in the High Folded Zone, northeastern Erbil City, Kurdistan Region (N-Iraq). Lithologically, the Khurmala Formation in the Gomaspan section is about 23.5 m comprised of thick to massive bedded brecciated grey dolomitic limestone in lower and middle parts and interbedding of medium to thick beds of grey dolomitic limestone and yellow calcareous shale in the upper part. The Sheraswar section comprises 18.5 m yellow marl, thick yellowish-grey dolomitic marly limestone in the lower part, and bedded grey limestone interbedded with thin blue marl, shale, and mudstone in the upper part. The petrographic and cathodoluminescence (CL) studies of 20 thin sections of the Khurmala carbonates show that most skeletal grains are shallow marine derivative faunas and non-skeletal grains represent intraclasts, peloids, ooids, and extraclasts (monocrystalline quartz). Five main microfacies were identified in the studied rocks, and they integrated into two facies associations relating to their environmental interpretation: back reef/lagoon and patch reef. A new eight pore types were distinguished in the carbonate rocks of Khurmala Formation: interparticle, intraparticle, growth framework, intercrystalline, moldic, vuggy, fracture, and stylolite porosities. Most of the primary porosity was reduced by compaction and cementation due to effect of intensive diagenesis. Secondary porosity is predominant in both studied sections, the most common being the moldic porosity associated with different microfacies fabrics. CL investigations revealed that dolomitized lime wackestone microfacies has two types of different cementations in the late stages of blocky calcite cement which are discontinuous light to dull orange luminescence without zoning, and pure calcite cement of coarse to very coarse blocky calcite cement with characteristic bright orange luminescence and tight zoning.

Sedimentological and petrophysical heterogeneities controls on reservoir characterization of the Upper Triassic shallow marine carbonate Kurra Chine Formation, Northern Iraq: Integration of outcrop and subsurface data

The lack of knowledge about the relationship between carbonate sedimentary facies and pore system modifiers in northwestern and northern Iraq severely restricts carbonate oil exploration in these areas. This research aims to highlight the significance and influence of sedimentological and petrophysical heterogeneity and their impact on reservoir characterization of the Kurra Chine Formation, which have been studied in oil wells at Ain Zalah (AZ-29), Butmah (Bm-15), and Kand (K-1), in addition to the Sararu outcrop in northern Iraq. In this study, integrated methods that incorporate thin section petrography, well logs, statistical techniques and core analysis were used for the investigation. The study revealed that the Kurra Chine Formation in the studied sections mainly consists of limestone, dolomite, shale, and anhydrite, the last of which is absent in the Sararu outcrop. Its thickness in previous outcrop and wells was 848 m, 1136 m, 985 m, and 1149 m for Sararu, AZ-29, Bm-15, and K-1, respectively. Petrographically, five main microfacies types and nine submicrofacies were identified in the Kurra Chine carbonates of the studied sections. The percentages and distribution of these submicrofacies in the study area are diverse and show their heterogeneity. Diagenetic processes like micritization, dolomitization, cementation, neomorphism, compaction, stylolitization, solution, pyritization, and silicification resulted in increasing heterogeneity in the formation. They played a significant role in improving or reducing the reservoir characterizations of the formation. Dolomitization and dissolution processes enhance the petrophysical properties of the studied formation, especially the medium-to coarse-grained crystalline idiotopic dolomite. On the other hand, cementation, compaction, and neomorphism reduce the pore volume of the Kurra Chine Formation rocks. Qualitatively, porosity in the Kurra Chine Formation was divided into two main groups: interparticle (intergrain and intercrystal) and vuggy pores. The interparticle pore space is subdivided into three petrophysical classes: Class 1, Class 2, and Class 3. Class 2 represents the most common interparticle porosity type and is very important because it contains bituminous material. Moldic and intragrain pores are the most abundant separate vug pores within formation successions. The touching vug pores are represented by fractures, microfractures, and fenestrals. Quantitatively, three types of porosity have been calculated for the formation using conventional well logs: effective, interparticle, and separated vuggy porosity. The Butmah-15 well reservoir property outperformed the other two wells in terms of reservoir property indicators, particularly in the middle of the studied formation at depths ranging from 3089 to 3399 m. Porosity in this depth interval is interparticle, with values ranging between 0 and 0.35, while permeability values range from zero mD in beds cemented by anhydrite cement to 6196 mD within MF6 in limestone beds that are rich in interparticle and fracture porosity. The AZ-29 and K-1 wells have poor reservoir properties, especially effective porosity and permeability. This research provides a better understanding of the relationship between carbonate sedimentary facies and pore system modifiers of shallow marine environment carbonates, and it can aid in reservoir evaluation for better exploitation of these valuable resources in Iraq and elsewhere in carbonate sedimentary basins.

Mobility of Dissolved Gases in Smectites under Saturated Conditions: Effects of Pore Size, Gas Types, Temperature, and Surface Interaction

In a nuclear waste repository, the corrosion of metals and the degradation of the organic material in the waste matrix can generate significant amounts of gases. These gases should be able to migrate through the multibarrier system to prevent a potential pressure build-up that could lead to a loss of barrier integrity. Smectite mineral particles form a tortuous pore network consisting of larger interparticle pores and narrow interlayer pores between the platelets of the smectite minerals. These pores are normally saturated with water, so one of the most important mechanisms for the transport of gases is diffusion. The diffusion of gases through the interparticle porosity depends on the distribution of gas molecules in the water-rich phase, their self-diffusion coefficients, and the tortuosity of the pore space. Classical molecular dynamics simulations were applied to study the mobility of gases (CO2, H2, CH4, He, and Ar) in Na-montmorillonite (Na-MMT) under saturated conditions. The simulations were used to estimate the gas diffusion coefficient (D) in saturated Na-MMT as a function of nanopore size and temperature. The temperature dependence of the diffusion coefficient was expressed by the Arrhenius equation for the activation energy (Ea). The predicted D values of gases were found to be sensitive to the pore size as the D values gradually increase with increasing pore size and asymptotically converge to the gas diffusion coefficient in bulk water. This behavior is also observed in the self-diffusion coefficients of water in Na-MMT. In general, H2 and He exhibit higher D values than Ar, CO2, and CH4. The predicted Ea values indicate that the confinement affects the activation energy. This effect is due to the structuring of the water molecules near the clay surface, which is more pronounced in the first two layers of water near the surface and decreases thereafter. Atomic density profiles and radial distribution functions obtained from the simulations show that the interaction of the gas with the liquid and the clay surface influences mobility. The obtained diffusion coefficient for different gases and slit pore size were parameterized with a single empirical relationship, which can be applied to macroscopic simulations of gas transport.

Porous polymer-in-silica hybrid electrolyte for all-solid-state Li-ion battery applications

Porous hybrid electrolytes based on Poly(Ethylene Glycol) (PEG) and mesoporous silica (SBA-15) were prepared by a post-synthetic modification of the silica matrix. The complex composed of the lithium salt (LiTFSI) and PEG is embedded in the silica pores, which offers mechanical properties for the hybrid electrolyte. The textural properties and composition of pure SBA-15 and the hybrid materials were characterized by several techniques. It was evidenced that the inner pores of the inorganic matrix (hexagonally packed cylindrical mesochannels) surface were uniformly coated with the complex PEG-LiTFSI and that the hybrid materials remained slightly mesoporous after the post-synthetic modification. To study the ionic conductivity, the hybrid powders were shaped as a pellet having both inter- and intraparticle porosity. The parameters whose influence were addressed are: the filling of the inter- and intraparticle porosity with PEG-LiTFSI complex, the lithium ion concentration and the PEG molecular weight. First, filling the interparticle porosity is necessary to the formation of continuous lithium conducting pathways while the intraparticle conductivity appeared to be mandatory to improve the overall conductivity. The hybrid of SBA-15 with PEG having a molecular weight of 600 gmol-1 gives the highest conductivity (1.6 x 10−6 S cm−1 at 30 °C) when used with the optimum molar ratio nEO/nLi of 10 found in this study. Preliminary analysis showed that the conductivity is governed by the segmental dynamics of the polymer chains (VTF model) in the whole temperature range. Finally, this material has an electrochemical window compatible with classical Li ion batteries cathode materials.

Study on mesoscopic numerical parameters in numerical tests of sand-pebble geology

To study the influence of the meso-mechanical parameters of sand-pebble on macro-mechanical properties, the numerical simulation method of discrete-element method and the sand-pebble numerical triaxial tests are used, a test method for elliptical particles is proposed and the sensitivity analysis of the meso-mechanical parameters of sand-pebble is carried out. The results show that the effective modulus of the particles has a significant effect on the macroscopic elastic modulus of the material, and the increase in the macroscopic elastic modulus of the material has an approximately linear relationship with the increase in the effective modulus. The effect of the particle stiffness ratio on the macro-mechanical properties of the material is insignificant. The increase in the friction coefficient is roughly linearly related to the increase in the peak stress. The increase in the interparticle porosity has a negative correlation with the decrease in the peak stress, and the particle diameter ratio affects both the number of particles produced and the peak stress. This paper provides a reference for the theoretical basis for subsequent research on the physical and mechanical characteristics of sand-pebble geology.

One-step combustion synthesis of undoped c-ZrO2 for Cr(VI) removal from aqueous solutions

The active practical application of materials based on cubic zirconium dioxide (c-ZrO2) for catalysis, luminescence, and sorption of heavy metals demands the development of methods for its preparation in a nanostructured form. In this work, nanoparticles of undoped cubic zirconia were obtained by solution combustion method, the features of their structure and morphology were investigated, and the efficiency of their use as a basis for sorbents for the removal of hexavalent chromium Cr(VI) from aqueous solutions was evaluated. Based on XPS, it was established that the stabilization of the high-temperature cubic phase of c-ZrO2 occurred due to oxygen vacancies which were formed during the synthesis by glycine-nitrate combustion. From the results of PXRD and Raman spectroscopy cubic structure of the obtained zirconium dioxide nanoparticles is concluded, the average crystallite size was approximately 2 nm. Adsorption structural analysis and SEM indicated aggregation of c-ZrO2 nanocrystals into primary (45–95 nm) and secondary (submicron) agglomerates. The specific surface of the nanopowder determined by the Brunauer–Emmet–Teller method was 25.4 m2 g−1, the pore volume was 0.1670 cm3 g−1, the major part of which is associated with interparticle porosity. Using kinetic pH-metry, it was found that on the surface of synthesized c-ZrO2, rapidly hydrated aprotic Lewis acid centers predominated, and the point of zero charge was 5.8. The results of the sorption of Cr(VI) from aqueous solutions with a concentration of 48–242 mg l−1 at 25 °C and pH = 5 are described by the Freundlich isotherm (R 2 = 0.971), which corresponds to multilayer adsorption. The maximum adsorption capacity according to Langmuir was 33 mg g−1 or 1.34 mg m−2 per unit area. These results allow us to consider the obtained undoped zirconium dioxide as a promising base for sorbents of heavy metals.

Spherical nanoparticles can be used as non-penetrating tracers to determine the extra-particle void volume in packed-bed chromatography columns

The optimization of downstream processing in silico can accelerate bioprocess development by limiting experiments to the most promising separation conditions that have been identified using chromatography models. Such models describe protein binding and mass transport in packed-bed columns and thus require precise knowledge about the columns and the resins they contain. One important set of properties is the resin porosities, often determined using combinations of penetrating and non-penetrating tracers. However, the former can be disproportionately small, providing data of limited practical relevance, and the latter can undergo unwanted interactions with the resin, interfering with porosity calculations. Here we characterize and minimize the interactions of three novel hard-sphere non-penetrating tracers with the model resin Q Sepharose HP under various conditions and determine the corresponding inter-particle porosities. We found that conductivities > 100 mS cm−1 were necessary to suppress tracer–resin interactions despite them sharing the same surface charge. We combined these data with those from proteins studied under non-binding conditions, which can be used as authentic penetrating tracers, to determine both the intra-particle and total porosities. Furthermore, we found that the inter-particle porosity was below the theoretical limit of dense sphere packing (25.95%) and provide experimental data showing that the discrepancy is caused by resin particle deformation during the packing of columns under pressure.

Estimation of the Size and Type of Porosity in an Albian Carbonate Reservoir of the Campos Basin, Southeastern Brazil

Abstract —The Albian carbonates of the Quissama Formation in the Campos Basin, southeastern Brazil, are important oil reservoirs. They make part of a carbonate platform that formed along the eastern coast of Brazil and the western coast of Africa during the Albian, which resulted in the opening of the South Atlantic Ocean. Subsequently, this reservoir was subjected to different postdepositional diagenetic processes. The present study utilized geophysical well logs to estimate the porosity of this reservoir, based on density, neutron porosity, and sonic logs. The estimates do not show good results when compared with the laboratory measurements. Then, exploring the fact that these logs are obtained with different physical principles, a multiple linear regression and an artificial neural network with Bayesian stochastic approach were applied, which resulted in a better porosity estimate. As porosity is a petrophysical parameter considered significant in the characterization of reservoirs, it was used, hereafter, to estimate permeability and water saturation of the reservoir, applying empirical equations. From there, it was not enough just to estimate the porosity, but was necessary to know what type it is. For this purpose, the concepts of the electrical formation factor, cementation coefficient, tortuosity, and anisotropy were used. With them, the zones with primary intergranular and interparticle porosity as well as secondary porosity, such as fractures, fissures, and vugs, were mapped. It was concluded that, with studies of this type, it is also possible to identify the connected and nonconnected porosities, which permits estimation of the effective porosity along the well.

Drying shrinkage characteristics and mechanism primary exploration of MgO-slag mortars

In this work, seven groups of MgO-slag mortars and pastes were prepared with different MgO types and MgO contents. The setting time, compressive strength and drying shrinkage were characterized. The mechanism of drying shrinkage was discussed by means of microscopic test XRD, FT-IR, MIP and SEM-EDS. The results show that the setting time decrease with the increase of MgO activities and contents. The high-activity MgO only shows a higher compressive strength advantage in the early stage, and the higher content of S-MgO, the higher the compressive strength advantage in the later stage. The 120d drying shrinkage first increases and then decreases with the increase of S-MgO contents, and the maximum drying shrinkage is obtained when the S-MgO content is 15%. The drying shrinkage of the mortar mixed with M-MgO is about half of the mortar mixed with S-MgO; the mortar mixed with R-MgO shows expansion change. Intraparticle porosity, interparticle porosity, and MgO particle size are important factors that affect the drying shrinkage of MgO-slag mortars. This study will provide the theoretical basis for the preparation of cementing materials with no length change by using a MgO activator.

Silica‐Coated Gold Nanorod Supraparticles: A Tunable Platform for Surface Enhanced Raman Spectroscopy

AbstractPlasmonic nanoparticle assemblies are promising functional materials for surface‐enhanced Raman spectroscopy (SERS). Gold nanorod (AuNR) assemblies are of particular interest due to the large, shape‐induced local field enhancement and the tunable surface plasmon resonance of the AuNRs. Designing the optimal assembly structure for SERS, however, is challenging and requires a delicate balance between the interparticle distance, porosity, and wetting of the assembly. Here, a new type of functional assemblies–called supraparticles–fabricated through the solvent‐evaporation driven assembly of silica‐coated gold nanorods into spherical ensembles, in which the plasmonic coupling and the mass transport is tuned through the thickness and porosity of the silica shells are introduced. Etching of the AuNRs allowed fine‐tuning of the plasmonic response to the laser excitation wavelength. Using a correlative SERS‐electron microscopy approach, it is shown that all supraparticles successfully amplified the Raman signal of the crystal violet probe molecules, and that the Raman signal strongly increased when decreasing the silica shell thickness from 35 to 3 nm, provided that the supraparticles have a sufficiently high porosity. The supraparticles introduced in this study present a novel class of materials for sensing, and open up a wide parameter space to optimize their performance.

Shrinkage and sorptivity of mortars with thermoactivated recycled cement

This study aims to characterise the shrinkage and sorptivity behaviour of mortars produced with thermally activated recycled cement (RC) sourced from reference waste cement paste (RCP) or from the cementitious fraction of old concrete (RCC), the latter following a new patented method. Ordinary Portland Cement (OPC) was replaced with 5–100% RC, in mortars of similar consistency or equal water/binder (w/b). The influence of RC particle size and source material composition were also assessed. Moreover, selected mortars were produced with partial incorporation of fly ash to explore the high alkalinity of RC. Compared to OPC mortars of equal w/b, the compressive strength was not significantly altered for up to 15% RCP and reduced less than 25% for up to 100% RCP. For similar flowability, the water absorption and shrinkage were higher in RC mortars, following the necessary increase of the w/b. However, for fixed w/b, RC mortars presented a more refined interparticle porosity, and the coefficient of absorption decreased with RC content. Shrinkage consistently increased with RC content due to the refined interparticle microstructure, higher water demand and lower particle hardness of RC. Nevertheless, the 90 days shrinkage increased less than 17% for up to 50% RCP. Overall, RC's high potential was shown as an active supplementary cementitious material, with a negligible influence on shrinkage for up to 50% replacement.