Mercury Porosimetry Measurements Research Articles

Preparation of high performance MgO ceramic filter and its interaction with molten steel: Effect of porous MgO powder

In this study, two kinds of MgO ceramic filters were prepared by using porous magnesia powder and fused magnesia powder as raw material, respectively. The microstructures, mechanical properties and purification efficiency on the molten steel of two MgO ceramic filters were investigated by mercury porosimetry measurement, SEM, EDS and immersion test with molten steel, etc. The results demonstrate that compared with the filter FM prepared from the fused magnesia powder, the rheological property of the slurry of the filter PM was improved via the finer and uniformly distributed nano-sized Mg(OH)2 particles generated by the hydration of the porous magnesia powder, which not only optimized the macropore structure but also promoted the growth of the sintering neck between the microparticles of the skeleton. Therefore, the MgO filter skeleton with a microporous structure was obtained, which elevated the strength and thermal shock resistance of the filter PM. According to the immersion tests with the molten steel, both filters significantly reduced the number of inclusions with size < 5 µm2 in the molten steel as well as their total oxygen contents, and the filter PM had better purification efficiency than the filter FM. The reason for the better purification efficiency of the filter PM was related to its smaller micro-sized pores, larger surface roughness, and certain high-temperature liquid phase in their skeletons. In general, the porous magnesia powder resulted in higher compressive strength, better thermal shock resistance and superior purification efficiency on the molten steel of the filter compared with the fused magnesia powder.

Effect of sintering atmosphere on microstructures and properties of synthesized microporous MgO refractory raw material

AbstractEffects of sintering atmosphere on the microstructure and strength of magnesite were investigated using magnesite powder as raw material through X‐ray diffraction, scanning electron microscopy, mercury porosimetry measurement, and so on. The results showed that the sintering atmosphere strongly affected the sintering behavior of magnesite. The specimens sintered in the reducing atmosphere had more and finer micro‐sized pores inside the MgO particles compared with that in the oxidizing atmosphere at the same sintering temperature. Besides, MgO refractory raw material containing porous MgO microparticles with core–shell structure was obtained through the carbothermal reduction of MgO microparticles and subsequent oxidation of Mg vapor at the surface of MgO particles at 1500°C in the reducing atmosphere. At the reducing atmosphere and 1500°C, the microporous MgO refractory raw material with the core–shell structure of external dense and internal porous had an apparent porosity of 22.1% and a compressive strength of 51.6 MPa.

Multiscale Fracturing in Medium- to Low-Rank Coals and Its Implications on Coalbed Methane Production in the Baode Area, Eastern Ordos Basin, China

Coal fractures are crucial in affecting the production of methane from coal. Multiscale fracturing and its implications on coalbed methane production have still not been fully understood. Herein, we present a case study, combining underground coal mine surveying and specimen, thin section, and scanning electron microscope observations for illustrating the ~m-, ~cm-, ~mm-, and ~μm-scale fractures present in the Baode area, eastern Ordos Basin, China. Then, the fracture connectivity is evaluated by helium permeability and mercury porosimetry measurement. The coals are mainly of semibright, semidull, and dull macrolithotypes. And main maceral composition is vitrinite, accounting for 73%~95%, with around 26% inertinite. The coals are ultralow-ash and low-ash content, belonging to high-volatile bituminous coal. The ~m scale fractures can penetrate the whole coal seams, dominant by S-N and following E-W direction, which were generated during the Yanshanian and Himalayan movements. The ~cm fractures are generally parallel to the lamina, influenced by the bright and dull coal band extension caused by the depositional differences. The ~mm fractures are mainly shown as endogenous fractures perpendicular to the lamina restricted within bright macrolithotypes. There are also ~mm fractures that are perpendicular to the lamina while penetrating dull components and fractures parallel to the lamina. The ~μm fractures are widely distributed and connect each other. Some of the fractures are filled with carbonate and clay minerals and are beneficial for methane migration, caused by hydraulic fracturing. The average mercury withdrawal efficiency of the coals was 75%. The helium permeability of the coals was between 10 × 10 − 3 and 50 × 10 − 3 μm2, indicating good fracture connectivity. The study findings, which indicated the presence of fractures of different scales in the coals studied, can be used for fully understanding the coalbed methane performance of medium- and low-rank coals.

Comparative Evaluation of LMR-NCM and NCA Cathode Active Materials in Multilayer Lithium-Ion Pouch Cells: Part I. Production, Electrode Characterization, and Formation

A lithium- and manganese-rich layered transition metal oxide (LMR-NCM) cathode active material (CAM) is processed on a pilot production line and assembled with graphite anodes to ≈7 Ah multilayer pouch cells. Each production step is outlined in detail and compared to NCA/graphite reference cells. Using laboratory coin cell data for different CAM loadings and cathode porosities, a simple calculation tool to extrapolate and optimize the energy density of multilayer pouch cells is presented and validated. Scanning electron microscopy and mercury porosimetry measurements of the cathodes elucidate the effect of the CAM morphology on the calendering process and explain the difficulty of achieving commonly used cathode porosities with LMR-NCM cathodes. Since LMR-NCMs exhibit strong gassing during the first cycles, a modified formation procedure based on on-line electrochemical mass spectroscopy is developed that allows stable cycling of LMR-NCM in multilayer pouch cells. After formation and degassing, LMR-NCM/graphite pouch cells have a 30% higher CAM-specific capacity and a ≈5%–10% higher cell-level energy density at a rate of C/10 compared to NCA/graphite cells. Rate capability, long-term cycling, and thermal behavior of the pouch cells in comparison with laboratory coin cells are investigated in Part II of this work.

Porous PTFE reinforced SPEEK proton exchange membranes for enhanced mechanical, dimensional, and electrochemical stability

The pores of polytetrafluoroethylene (PTFE) film were filled with the sulfonated poly (ether ketone) (SPEEK) electrolyte molecules to prepare the proton exchange membrane with the enhanced mechanical, dimensional and electrochemical stability for fuel cell application. Catechol/polyethyleneimine was co-deposited on the PTFE pore surface as an adhesive mediator for the feasible impregnation of SPEEK. The chemical composition, morphology, and wettability of the porous PTFE film were investigated by electron spectroscopy for chemical analysis, scanning electron microscope, mercury porosimetry, and water contact angle measurements. After pore filling with SPEEK electrolytes, several essential properties of membranes (e.g. water uptake, proton conductivity, mechanical property) and wet/dry cyclic cell performance were examined. The prepared pore-filled electrolyte membranes showed the superior mechanical and dimensional stability at the reduced water uptake to the pristine SPEEK membrane. Those excellent properties of the electrolyte membranes are reflected in the stable electrochemical cell performance over the repeated wet/dry cycles with suppression of crack/void formation and edge breakdown.

Wet chemical porosification with phosphate buffer solutions for permittivity reduction of LTCC substrates

The wireless high-frequency technology requires a robust, cost-effective, and highly integrated substrate technology offering the capability for areas of tailored permittivity. The wet-chemical porosification of low temperature co-fired ceramics (LTCC) substrates offers such an approach by locally embedding air. Porosification of LTCC in both extremely acidic and alkaline media has been investigated in previous works. However, for improving the available knowledge on the porosification of LTCC with H3PO4 as a standard and a widely used etching solution, the impact of solution concentration was systematically investigated and a substantial improvement in the etching performance was achieved. Moreover, in the present study, for the first time, the intermediate pH values, and the impact of pH as a key parameter on the etching process have been investigated. For this purpose, the applicability of phosphate buffer solution (PBS) as a prospective novel etchant mixture for the porosification of a commercially available LTCC tape (Ceramtape GC) was explored. Valuable information about surface morphology, crystalline composition, and the pore structure of the etched LTCCs was gathered employing scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and mercury porosimetry measurements. Based on these findings, the performance of PBS-based etchant systems towards the generation of porous LTCCs combining high depths of porosification with acceptable surface characteristics for subsequent metallization is demonstrated. Based on the obtained results, by application of a 0.2 mol L−1 solution of PBS, the effective relative permittivity of test samples with a thickness of approximately 600 µm and a porosification depth of 186 µm from each side, could be reduced up to 10% of its initial “as fired” value. Also, based on the measurement results and by measuring the depth of porosification, the permittivity of the etched layer was estimated to show a reduction of up to 22% compared to the initial “as fired” value.

Impact of Polymer Binders on the Structure of Highly Filled Zirconia Feedstocks.

The impact of polypropylene and high-density polyethylene backbone binders on the structure of organic matrix, feedstock, and ceramic parts is investigated in terms of morphology in this paper. The miscibility of wax with polyethylene and polypropylene is investigated in the molten state via a rheological study, revealing wax full miscibility with high-density polyethylene and restricted miscibility with polypropylene. Mercury porosimetry measurements realized after wax extraction allow the characterization of wax dispersion in both neat organic blends and zirconia filled feedstocks. Miscibility differences in the molten state highly impact wax dispersion in backbone polymers after cooling: wax is preferentially located in polyethylene phase, while it is easily segregated from polypropylene phase, leading to the creation of large cracks during solvent debinding. The use of a polyethylene/polypropylene ratio higher than 70/30 hinders wax segregation and favors its homogeneous dispersion in organic binder. As zirconia is added to organic blends containing polyethylene, polypropylene, and wax, the pore size distribution created by wax extraction is shifted towards smaller pores. Above zirconia percolation at 40 vol%, the pore size distribution becomes sharp attesting of wax homogeneous dispersion. As the PP content in the organic binder decreases from 100% to 0%, the pore size distribution is reduced of 30%, leading to higher densification ability. In order to ensure a maximal densification of the final ceramic, polyethylene/polypropylene ratios with a minimum content of 70% of high-density polyethylene should be employed.

Influence of chemical composition, porosity and fractal dimension on the electrical conductivity of carbon blacks

Carbonaceous materials analyzed in this investigation were six nanometric particle size carbon blacks. Carbons were texturally characterized by gas adsorption (N2, 77 K), helium and mercury density and mercury porosimetry measurements. Electrical conductivity was determinated by impedance spectroscopy, at room temperature. Several works related to the electrical conductivity and to textural parameters of carbon blacks, such as: porosity, specific surface area, etc., have been carried out. However, there are a type of parameters, such as the fractal dimension, the percentage of macropores, the particle size, or the packing density, that are also related to the electrical conductivity, but they have not been previously investigated. In this work, it has been researched how the increase in interparticle/intraparticle porosity decreases the electrical conductivity of the samples studied. Therefore, it is possible to conclude that in this study a complete research work on electrical conductivity has been carried out.

Macroporous monoliths based оn natural mineral sources, clay аnd diatomite

Macroporous silica ceramic was obtained using clay and diatomite. Boric acid as a low-cost additive in the amount of 1 wt% was used. These porous materials were obtained at low forming pressure (40-80 MPa) and lower sintering temperature (850-1300 ?C) for 4h in air. The influence of boric acid, forming pressure, and sintering temperature on the microstructure, porosity parameters, and mechanical properties of obtained porous monoliths were investigated. As-received and the modified samples were characterized by X-ray diffraction, FTIR, SEM, and mercury porosimetry measurements. As for modified clay and diatomite, they were pressed at 60 MPa and then sintered at 1150 ?C, obtaining porosities of about 10 % and 60 %, respectively. Both of the analyzed samples had the pore diameter in the range of macroporous materials. The pore diameters of clay samples are ranging from 0.1-10 ?m, whereas the pore diameter of diatomite samples was slightly lower with values ranging from 0.05-5 ?m. Modified diatomite samples have a lower Young modulus in comparison to modified clay samples.

Shape memory conductive electrospun PVA/MWCNT nanocomposite aerogels

Shape memory polymers have promising applications in different fields. In this work, polyvinyl alcohol/multiwall carbon nanotube nanocomposite aerogels were fabricated through supercritical CO2 drying of electrospun hydrogel counterparts. Mercury porosimetry measurements and scanning electron microscopy results indicated that the nanofibrous aerogel had a high porosity (more than 80%), low density (0.025–0.036 g cm−3), high surface area (more than 1700 m2 g−1) and a pore size less than 100 nm. By incorporating multiwall carbon nanotubes, the density and Young’s modulus of the polyvinyl alcohol/multiwall carbon nanotube nanocomposite aerogel were increased up to 0.03 g cm−3 and 38 MPa, respectively. A percolation threshold of 1.5 wt% of the multiwall carbon nanotube was achieved for the conductive polyvinyl alcohol/multiwall carbon nanotube nanocomposite aerogel. The nanofibrous aerogel showed a perfect shape memory effect under thermal stimulus, and the corresponding results revealed that the shape recovery ratio and recovery speed of the nanocomposite aerogel were significantly higher than pure polyvinyl alcohol aerogel owing to the stabilizing of the crystalline domains and improvements in mechanical properties due to the presence of the multiwall carbon nanotubes. PVA/MWCNT nanocomposite aerogels were fabricated via the ScCO2 drying method. The aerogels were fully characterized, and their shape memory behaviors were examined. As the MWCNT content was increased, the electrical conductivity increased abruptly by up to 4 orders of magnitude, implying that an electrical percolation network had formed in the nanocomposite aerogels. The shape memory results illustrated the shape recovery ratio, and the recovery speed of the nanocomposite aerogels increased, due to the addition of the MWCNTs.

Electrochemical performances of supercapacitors from carbon-ZrO2 composites

Carbon xerogel-ZrO2 composites (CZrX) were successfully synthesized through a one-pot sol-gel synthesis. The XRD results confirm the presence of well dispersed (<4.5 nm) cubic ZrO2 on the carbon support, homogeneously distributed on the carbon surface. Gas adsorption and mercury porosimetry measurement pointed out that the increase of ZrO2 in the carbon matrix produces an increase in the mesopore volume as well as a widening of the microporosity at the expense of the narrow micropores (W0 (CO2)) that decreases causing simultaneously the progressive surface area decrease. The obtained composite materials possess specific surface areas ranging from 423 to 539 m2 g−1 and a very well-developed micro and mesoporosity with a total pore volume ranging from 0.361 to 0.480 cm3 g−1.A two-electrode symmetric supercapacitor based on the carbon xerogel-ZrO2 composites exhibits a high electrochemical performance better than other similar materials from the literature with high capacitances (up to 180 F g−1 at 0.125 A g−1 for 30% ZrO2 composite), a high retention capacitance and high energy density, 27.1 Wh kg−1, at a power density of 140 W kg−1 in the voltage range of 0 V–1.2 V. The presence of zirconium oxide in the carbon matrix improves in all case the capacitive behavior of samples in spite of the decrease of the surface area and micropore volume of the samples. That has been explained on the base of different textural properties and/or chemical characteristic of the material.

Research on a Nonwoven Fabric Made from Multi-Block Biodegradable Copolymer Based on l-Lactide, Glycolide, and Trimethylene Carbonate with Shape Memory.

The presented paper concerns scientific research on processing a poly(lactide-co-glycolide-co-trimethylene carbonate) copolymer (PLLAGLTMC) with thermally induced shape memory and a transition temperature around human body temperature. The material in the literature called terpolymer was used to produce smart, nonwoven fabric with the melt blowing technique. Bioresorbable and biocompatible terpolymers with shape memory have been investigated for its medical applications, such as cardiovascular stents. There are several research studies on shape memory in polymers, but this phenomenon has not been widely studied in textile products made from shape memory polymers (SMPs). The current research aims to explore the characteristics of the PLLAGLTMC nonwoven fabric in detail and the mechanism of its shape memory behavior. In this study, the nonwoven fabric was subjected to thermo-mechanical, morphological, and shape memory analysis. The thermo-mechanical and structural properties were investigated by means of differential scanning calorimetry, dynamic mechanical analysis, scanning electron microscopic examination, and mercury porosimetry measurements. Eventually, the gathered results confirmed that the nonwoven fabric possessed characteristics that classified it as a smart material with potential applications in medicine.

High strength and catalytic activity of polyacrylamide/graphene oxide porous metal alginates aerogels for phenol hydroxylation with H2O2

A series of polyacrylamide/graphene oxide metal cross-linked strengthened alginate porous aerogels were prepared by the freeze-drying method. These aerogels exhibit exceptional mechanical properties and have been assessed as catalysts for the liquid phase hydroxylation of phenol with H2O2 reaction. The aerogel catalysts were characterized by FT-IR, ICP-AES and SEM techniques, mercury porosimetry measurements and particle strength testing. The results showed that polyacrylamide and graphene oxide could improve effectively the mechanical property of aerogels. Additionally, graphene oxide could decompose H2O2 and shows significant catalytic activity with Cu ions present in the prepared solids. The highest conversion of phenol catalyzed by 4Cu-4PAAm-3GO-ALG was 78.5%, with selectivities to catechol (CAT) and hydroquinone (HQ) being 59.4% and 37.8%, respectively.

Conducting macroporous carbon foams derived from microwave-generated caramel/silica gel intermediates

The current work reports the preparation of macroporous carbon/silica foams using sucrose as precursor in the presence of silica gel and water. After a preliminary fast transformation of sucrose into caramel by MW irradiation, the carbon/silica materials are obtained by thermal treatment at 800 °C under nitrogen atmosphere. In contrast to carbon/clay materials prepared by the same synthetic route, the use of microporous silica gel as inorganic support for the chemical transformation of sucrose gives rise to foam-like materials without requiring the addition of blowing agents. The resulting materials are low-density monoliths (0.17 g cm−3) that show several populations of macropores centered at 150 and in the range of 30–5 µm, as well as mesopores around 5–6 nm. The porosity is close to 97%, as determined from helium pycnometry, which gave a skeletal density value of 6.08 g cm−3. The resulting foams show electrical conductivity values around 3 mS cm−1 due to the generated graphene-like materials, as corroborated by Raman spectroscopy. A preliminary evaluation of these macroporous materials as adsorbents of aromatic pollutants was carried out using methylene blue (MB) as a model dye. The regeneration of the MB-loaded foams to make possible their application in successive adsorption cycles was assessed by solid–liquid extraction and electrochemical regeneration. In both cases, the treatment produced an increase in the uptake capacity, which could be due to an increment in porosity and specific surface area, from 360 to 440 m2 g−1, as determined from mercury porosimetry and N2 adsorption measurements. In addition, the electrochemical method allowed a partial degradation of the pollutant, as determined by UV–Vis and HPLC–MS. Thus, the carbon/silica materials here developed are promising adsorbents for treatment of polluted effluents.

Structural Characterization of Calcium Sulfate Bone Graft Substitute Cements

The aim of this work was to study the structural characteristics of commercially available bone graft substitute (BGS) ceramic cements. In particular, the microstructure of two calcium sulfate cements was investigated. For this purpose, nitrogen and mercury porosimetry, x-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements have been carried out. Mercury intrusion porosimetry results revealed that the structural characteristics of the two samples varied significantly. These structural differences can be justified when compared with their compression and bending strength properties. As a result, a proper understanding of microstructure of BGS materials is crucial in the search of what is optimal for bone regeneration.

Enhanced Photocatalytic Activity of Sol-Gel Derived Coral-like TiO2 Nanostructured Thin Film

To enhance photocatalytic degradation of organic pollutants, coral-like TiO2 nanostructured thin films were chemically synthesized through the sol-gel method. The fabricated thin films were characterized by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), nitrogen sorption isotherms, mercury porosimetry measurements, and UV-Vis Diffuse Reflectance Spectrum (DRS). The coral-like TiO2 structures were assembled from cashew-like nanoparticles, which were composed of numerous highly crystallized in anatase phase. The assembled materials possess a high specific surface area of 167 m2/g and mean pore size diameter of 12.3 nm. The coral-like TiO2 nanostructured thin film shows a significantly higher photocatalytic activity than that of the commercial photocatalyst P25-TiO2 based film on the degradation of Methylene Blue (MB) and Methyl Orange (MO). The high photocatalytic activity of film was ascribed to the large light absorption caused by small particle size, micro/meso, and macropore structures, and pore scattering, reduced band gap energy, and reduced recombination of electron-hole pairs. These findings open up a new approach for promising environmental applications.

Design and characterization of flat membrane supports elaborated from kaolin and aluminum powders

Porous flat ceramic-metal composite (Cermet) membrane supports were elaborated from kaolin and aluminum powder mixtures by the press drying–sintering process. The evolution of structure and surface properties was followed by water permeation, tensile strength, mercury porosimetry, surface charge and contact angle measurements. These characterizations have demonstrated that the addition of aluminum to the kaolin matrix has a beneficial effect on the membrane support properties. In particular, the water permeability and mechanical strength increased gradually in the presence of aluminum. In addition, the hydrophilicity of the cermet supports was found to increase gradually with the aluminum load. However, the surface charge was not affected by the aluminum introduced into the cermet composition. Filtration experiments were carried out with the support containing 4% wt of aluminum. The results have indicated that this support could be used to purify dye-containing water. Des supports membranaires plans poreux céramique–métal (cermets) ont été élaborés par pressage d’une poudre sèche à partir d’un mélange de kaolin et d’aluminium. L′évolution de la structure et des propriétés de surface a été suivie par des mesures de perméabilité à l'eau, de résistance à la traction, de porosimètrie au mercure, de charge de surface et d'angle de contact. Ces caractérisations ont démontré que l'addition d'aluminium dans la matrice kaolinitique a un effet bénéfique sur les propriétés des supports membranaires. En particulier, la perméabilité à l'eau et la résistance mécanique ont augmenté progressivement en présence d'aluminium. En outre, l’hydrophilicité des supports céramique–métal a augmenté progressivement avec la teneur en aluminium. Toutefois, la charge de surface n'a pas été affectée par la présence de l’aluminium dans la composition du cermet. Les expériences de filtration ont été réalisées avec le support contenant 4% en masse d'aluminium. Les résultats ont montré que ce support peut être utilisé pour purifier l'eau contenant un colorant.

Effect of boric acid on the porosity of clay and diatomite monoliths

Porous silica ceramics were obtained at low forming pressure (40–80MPa) and low sintering temperature (850–1300°C) for 4h in air. Boric acid was used as a low-cost additive, in the amount of 2wt%. Relatively high porosities of nearly 40% and 65% are obtained for the samples of clay and diatomite pressed at 40MPa, and sintered at 1000°C, respectively. The samples sintered at 1150°C and 1300°C have the average pore size diameters in the range of macroporous for clay 0.2–10μm and for diatomite 0.2–5μm. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and mercury porosimetry measurements were employed to characterize of the obtained samples. Measurements of densities and open porosities by immersion technique were used, according to the Archimedes principle. The relations between mechanical characteristics of the samples formed by using different pressures and sintered at different temperature, were discussed.

Effect of pore formers on properties of tape cast porous sheets for electrochemical flue gas purification

Ce0.9Gd0.1O1.95 (CGO) electrolytes for electrochemical flue gas purification multilayers were fabricated by tape casting and sintering using different types, shapes and sizes of pore formers. The resulting tapes (with thickness of about 400μm) were characterized by scanning electron microscopy, gas permeability measurements, mercury porosimetry and pore orientation measurements, to investigate the role of the different pore formers on the properties after sintering at a temperature of 1250°C. Those tapes prepared from different non-spherical pore formers with comparable porosity of about 43%, showed significant differences in gas permeability which could be correlated to an increase in mean pore size and pore connectivity. The degree of pore orientation in the tape casting direction was determined by best-fit ellipse method and a modified linear intercept method and the obtained data were correlated with the corresponding gas permeability.

Synthesis of mono- and bi-layer MFI zeolite films on macroporous alumina tubular supports: Application to nanofiltration

This work is dedicated to the development of MFI-type structure zeolite films (single-layer or bilayer) on the internal layer of a specific macroporous alumina tubular support for nanofiltration applications. The bottom MFI layer was obtained by direct hydrothermal synthesis while a secondary growth method was used for the top MFI layer. A complete characterization of the obtained MFI membranes (single-layer or bilayer) is proposed using various techniques, such as X-ray diffraction, scanning electron microscopy, mercury porosimetry and nitrogen sorption measurements. Dense and highly crystallized films of MFI-type structure zeolite were obtained for both single-layer and bilayer MFI films. The total film thickness were around 7.1±0.5μm and 14.5±1μm for single-layer and bilayer MFI films respectively. The Si/Al molar ratio of the MFI films varied between 185 and 305 for single-layer and bilayer MFI films respectively. The hydraulic permeability of the tubular MFI membrane was achieved by the filtration of pure water. The hydraulic permeability of the single-layer and bilayer MFI membranes decreased rapidly at the beginning of the conditioning process, and stabilized at 1.08×10–14m3m−2 and 1.02×10–15m3m−2 after 15h and the rejection rates of neutral solute (Vb 12) are 10% and 50% for the single-layer and bilayer MFI films respectively.