Pore Diameter Distribution Research Articles

Effect of twin-screw extrusion pretreatment on starch structure, rheological properties and 3D printing accuracy of whole potato flour and its application in dysphagia diets

Twin-screw extrusion pretreatment has great potential for the development of three-dimensional (3D) printed food as dysphagia diets. This study aimed to investigate the effect of twin-screw extrusion pretreatment on starch structure, rheological properties and 3D printing accuracy of whole potato flour and its application in dysphagia diets. The results indicated that twin-screw extrusion pretreatment was found to change chain length distributions, short-range ordered structure and relative crystallinity of whole potato flour (WPF), thereby improving its 3D printing performance. With the increasing proportion of long linear chains (DP > 12), the intensity of hydrogen bonds, linear viscoelastic region, storage modulus (G′), loss modulus (G″), viscosity and n of whole potato flour paste were increased, enhancing high printing accuracy and shape retention of 3D printed samples with a denser microstructure and smaller pore diameter distribution. The whole potato flour paste extruded with a peristaltic pump speed at 5.25 mL/min (WPF-4) displayed the highest printing accuracy with excellent rheological properties, good water distribution state and dense network structure, which classified as class 5 level dysphagia diets. This research provides an effective guidance for the modification of whole potato flour using twin-screw extrusion pretreatment as 3D printed food inks for dysphagia patients.

Highly Graphitized Coal Tar Pitch-Derived Porous Carbon as High-Performance Lithium Storage Materials.

Because of its high specific capacity and superior rate performance, porous carbon is regarded as a potential anode material for lithium-ion batteries (LIBs). However, porous carbon materials with wide pore diameter distributions suffer from low structural stability and low electrical conductivity during the application process. During this study, the calcium carbonate nanoparticle template method is used to prepare coal tar pitch-derived porous carbon (CTP-X). The coal tar pitch-derived porous carbon has a well-developed macroporous-mesoporous-microporous hierarchical porous network structure, which provides abundant active sites for Li+ storage, significantly reduces polarization and charge transfer resistance, shortens the diffusion path and promotes the rapid transport of Li+. More specifically, the CTP-2 anode shows high charge capacity (496.9 mAh g-1 at 50 mA g-1), excellent rate performance (413.6 mAh g-1 even at 500 mA g-1), and high cycling stability (capacity retention rate of about 100 % after 1,000 cycles at 2 A g-1). The clean and eco-friendly large-scale utilization of coal tar pitch will facilitate the development of high-performance anodes in the field of LIBs.

Applicability of a Fractal Model for Sandstone Pore-Fracture Structure Heterogeneity by Using High-Pressure Mercury Intrusion Tests

Pore structure heterogeneity affects the porosity and permeability variation of tight sandstone, thereby restricting sandstone gas production. In total, 11 sandstone samples were taken as a target in the northwest margin of the Junggar Basin. Then, scanning electron microscope and high-pressure mercury injection tests are used to study the distribution of a pore and fracture system in the target sandstone. On this basis, single and multifractal models are used to quantitatively characterize the heterogeneity of pore structure, and the applicability of the classification model in characterizing the heterogeneity of the pore-fracture structure is explored. The results are as follows. (1) The target samples are divided into two types, with the mercury removal efficiency of type A samples ranging from 44.6 to 51.8%, pore size mainly distributed between 100 and 1000 nm, and pore volume percentage ranging from 43 to 69%. The mercury removal efficiency of type B samples ranges from 14 to 28%, and pore diameter distribution is relatively uniform. (2) Different fractal models represent different physical meanings. The calculation results of sponge and thermodynamic fractal models indicate that the heterogeneity of pore structure distribution in the type B sample is significantly stronger than that in type A, which is inconsistent with the conclusions of the Sierpinski model. This is because the aforementioned two models characterize the complexity of pore surface area, while the Sierpinski model characterizes the roughness of pore volume. The comparison shows that there is a significant correlation between the thermal dimensionality value DT and the volume percentage of macropores and mesopores. Therefore, the thermodynamic model can better quantitatively characterize the heterogeneity of macropore and mesoporous pore distribution. (3) The results indicate that higher pore volume range is mainly influenced by mesopores and macropores. From the relationship curve between mercury removal efficiency and single fractal dimension, it can be seen that mercury removal efficiency is greatly affected by distribution heterogeneity of the lower value area of pore volume, and it has no obvious relationship with distribution heterogeneity in the lower value area of the pore volume.

Insights into role of microstructure in TNT adsorption performances onto zeolite, diatomite and kaolinite particles

Adsorption performances of one pollutant on different adsorbents likely depend on the adsorbent microstructures heavily. Hereon, zeolite, diatomite and kaolinite particles were selected as inexpensive adsorbents in this study with 2,4,6-trinitrotoluene (TNT) as an organic pollutant for the batch test to verify the effect of adsorbent microstructure on TNT adsorption performance. The results of kinetic, adsorption isothermic, and thermodynamic analyses indicated that the adsorption process of TNT on three particles is controlled by chemisorption, and that both are non-spontaneous entropic endothermic reactions, although they have their own specific adsorption capacities, equilibration times, and kinetic rates. Comprehensively analyzing the characterization data and adsorption performances of the particles shows that, the pore physical properties including the pore diameter distribution and volume obviously control the adsorption capacities, and well the pore surface chemical properties such as the functional groups affect the adsorption kinetics; the microstructure affects the performances through the synergistic effect of physical and chemical pathways and results in the special performances. Briefly, a particle has its special microstructure and then determinedly unique performance. The finding provides insights into the role of the microstructure of the particles in their performances, and significances for selecting and utilizing the adsorbents in water treatment.

Micro gas chromatography column using ionic liquid modified metal-organic framework as stationary phase for rapid breath analysis of gastric cancer

The micro gas chromatography columns (μGCs) were prepared for rapid breath analysis of gastric cancer. The synergistic effect of the specific surface area and the action of pore diameter on the separation capacity was investigated. The μGC-IL/UIO-66 was prepared using [P66614][Cl]/UIO-66 as the stationary phase. For comparison, the μGC-IL and the μGC-UIO-66 were prepared using [P66614][Cl] and UIO-66 as stationary phase, respectively. [P66614][Cl]/UIO-66 had a high specific surface area with a pore diameter distribution of 0.49 nm. The high specific surface area of [P66614][Cl]/UIO-66 improved the efficiency of adsorption and desorption, while the porous structure with an appropriate pore diameter acted as an efficient molecular sieve, synergistically enhancing separation efficiency. So compared to the μGC-IL and the μGC-UIO-66, the HETP of μGC-IL/UIO-66 was reduced by 68.2% and 22.6%, respectively. In the analysis of volatile biomarkers (acetone, benzene, n-hexane and toluene) for gastric cancer, the resolutions between adjacent peaks were 1.96, 2.13 and 3.67, which met the requirements for quantitative analysis (R > 1.5). The retention times of acetone, benzene, n-hexane and toluene were 0.72 min, 0.96 min, 1.33 min and 1.67 min, which enables rapid analysis. All may suggest that the μGC-IL/UIO-66 has a promising application in rapid breath analysis of gastric cancer.

Characterization of İscehisar Andesite (Afyonkarahisar-Turkey), Used as a Building Stone Source of Historical Heritages from Ancient Times to the Present

Most historical structures that have survived to the present day are constructed from natural stones. One such natural stone is andesite. This study conducted a series of characterization studies on andesites used as building stones in Afyonkarahisar (Turkey). The building stones in question were determined by the petrographic-mineralogical (polarizing microscope, XRD, SEM), chemical, pore diameter distribution, and physico-mechanical properties. Although the İscehisar andesite is not as well-known as the İscehisar marble, it is a volcanic rock widely used in cultural heritage sites such as mosques, fountains, and bridges that have survived from the Seljuk and Ottoman periods to the present day in Afyonkarahisar. Despite the presence of pink, brown, and gray-black colors in the İscehisar andesite, it is evident that the preference in historical buildings is mainly for gray-black variants. Andesite, marble, and limestone, such as İscehisar Bridge from the Hellenistic period, Kırkgöz Bridge from the Byzantine era, Altıgöz Bridge from the Seljuk period, and Kanlı Göl Bridge from the Ottoman period, were used together in various combinations. Mosques are another group of structures in which andesite and other volcanic rocks are heavily used, such as bridges. While tuff is commonly used in examples of Seljuk and Ottoman architecture that have survived to the present day, andesite and other volcanic rocks along with bricks have also been used to construct dozens of mosques. Andesites found in the İscehisar region continue to be widely extracted, cut, and shaped using different surface processing techniques and are used today.

Eco-Friendly Superhydrophobic Modification of Low-Cost Multi-Layer Composite Mullite Base Tubular Ceramic Membrane for Water Desalination

This study aimed to investigate and develop a cost-effective and superhydrophobic ceramic membrane for direct contact membrane distillation (DCMD) applications. Two types of mullite-based composite membranes were prepared via extrusion and sintering techniques. To create a small and narrow pore diameter distribution on the membrane surface, the dip-coating technique with 1 µm alumina was employed. The hexadecyltrimethoxysilane eco-friendly grafting agent was adopted to modify low-cost multilayer mullite-based composite membranes, transforming them from hydrophilic to superhydrophobic. The prepared membranes were characterized via field emission scanning electron microscopy (FESEM), energy-dispersive spectrometry (EDS), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), liquid entire pressure (LEP), contact angle, atomic force microscopy (AFM), porosity, and membrane permeability. The results of the prepared membranes validate the appropriateness of the material for membrane distillation applications. The optimized membrane, with a contact angle of 160° and LEP = 1.5 bar, was tested under DCMD using a 3.5 wt.% sodium chloride (NaCl) synthetic solution and Persian Gulf seawater as a feed. Based on the acquired results, an average permeate flux of 3.15 kg/(m2·h) and salt rejection (R%) of 99.62% were found for the 3.5 wt.% NaCl solution. Moreover, seawater desalination showed an average permeate flux of 2.37 kg/(m2·h) and salt rejection of 99.81% for a 20-h test without any pore wetting. Membrane distillation with a hydrophobic membrane decreased the turbidity of seawater by 93.13%.

Best practices in the characterization of bulk catalyst properties

Bulk characterization of a solid provides us with a spatially-averaged description of its physical and chemical properties. These properties are not site-specific, but they are critical for categorizing materials and understanding their catalytic performance. Important bulk chemical properties include elemental composition, crystal structure, atomic coordination environment, and the oxidation states of elements comprising the catalyst. Significant physical properties include accessible surface area, pore volume, pore diameter, and particle size distributions that exist at the various length scales of catalysis. Each physicochemical property is sensitive to the conditions employed for catalyst synthesis, storage, pre-treatment, activation, and characterization. Thus, it is imperative that authors fully describe materials and methods in publications as this metadata provides context for observed phenomena and allows others to recreate the exact conditions that are essential for reproducibility. Such protocols are necessary for a meaningful interpretation of differences in catalyst performance observed across laboratories. This perspective article defines bulk characterization, provides guidance on bulk characterization methods, and emphasizes important considerations and best practices. Our aim is to build a more nuanced understanding of catalyst characterization. We hope that awareness and application of the principles outlined herein will improve rigor and reproducibility in catalysis science.

Investigation on the influence of gradation design on the road performance of cold mixed epoxy asphalt mixture based on microstructure evaluation

Cold mixed epoxy asphalt mixture (CMEAM) has excellent anti-deformation and fatigue performance which shows remarkable superiority on bridge pavements. Previous studies have done comprehensive researches on its properties through macroscopic experiments. However, few studies revealed the impact of gradation design on the road property of CMEAM through microscopic method. Thus, in this paper, X-Ray computed tomography (X-ray CT), nanoindentation (NI), field emission scanning electron microscopy (FESEM) and mercury intrusion porosimetry (MIP) are introduced to investigate the coarse aggregates contact degree, the thickness and elastic modulus of interfacial transition zone (ITZ) and the pore diameter distribution of CMEAM. Results showed that the contact points of coarse aggregates in EA-05 mixture are around 40 while those in EA-10 mixture are around 20. (40°, 50°) is the key inclination angle interval for EA-10 mixture type while (70°, 80°) and (10°, 20°) are of significance for EA-05 mixture type. The contact points and inclination angles are positively and inversely proportional to Marshall stability, respectively. In addition, the ITZ thickness of EA-05 and EA-10 mixture is below 10 μm and above 40 μm, respectively. The ITZ elastic modulus of EA-10 mixture is approximately 1.5 times than that of EA-05. The thickness and elastic modulus of ITZ are inversely proportional to low-temperature indirect tensile strain (εT). Meanwhile, EA-05 mixture has higher proportion in gel micropores and middle capillary pores while EA-10 mixture has higher proportion in mesopores and large capillary pores. Mesopores has the highest correlation coefficients with tensile strength ratio (TSR), followed by large capillary pores. The suggested proportion for above two type pores is around 21.5% and 51.0%, respectively.

Microvascular disease not type 2 diabetes is associated with increased cortical porosity: A study of cortical bone microstructure and intracortical vessel characteristics

IntroductionFracture risk is elevated in type 2 diabetes (T2D) despite normal or even high bone mineral density (BMD). Microvascular disease (MVD) is a diabetic complication, but also associated with other diseases, for example chronic kidney disease. We hypothesize that increased fracture risk in T2D could be due to increased cortical porosity (Ct.Po) driven by expansion of the vascular network in MVD. The purpose of this study was to investigate associations of T2D and MVD with cortical microstructure and intracortical vessel parameters. MethodsThe study group consisted of 75 participants (38 with T2D and 37 without T2D). High-resolution peripheral quantitative CT (HR-pQCT) and dynamic contrast-enhanced MRI (DCE-MRI) of the ultra-distal tibia were performed to assess cortical bone and intracortical vessels (outcomes). MVD was defined as ≥1 manifestation including neuropathy, nephropathy, or retinopathy based on clinical exams in all participants. Adjusted means of outcomes were compared between groups with/without T2D or between participants with/without MVD in both groups using linear regression models adjusting for age, sex, BMI, and T2D as applicable. ResultsMVD was found in 21 (55 %) participants with T2D and in 9 (24 %) participants without T2D. In T2D, cortical pore diameter (Ct.Po.Dm) and diameter distribution (Ct.Po.Dm.SD) were significantly higher by 14.6 μm (3.6 %, 95 % confidence interval [CI]: 2.70, 26.5 μm, p = 0.017) and by 8.73 μm (4.8 %, CI: 0.79, 16.7 μm, p = 0.032), respectively. In MVD, but not in T2D, cortical porosity was significantly higher by 2.25 % (relative increase = 12.9 %, CI: 0.53, 3.97 %, p = 0.011) and cortical BMD (Ct.BMD) was significantly lower by −43.6 mg/cm3 (2.6 %, CI: −77.4, −9.81 mg/cm3, p = 0.012). In T2D, vessel volume and vessel diameter were significantly higher by 0.02 mm3 (13.3 %, CI: 0.004, 0.04 mm3, p = 0.017) and 15.4 μm (2.9 %, CI: 0.42, 30.4 μm, p = 0.044), respectively. In MVD, vessel density was significantly higher by 0.11 mm−3 (17.8 %, CI: 0.01, 0.21 mm−3, p = 0.033) and vessel volume and diameter were significantly lower by −0.02 mm3 (13.7 %, CI: −0.04, −0.004 mm3, p = 0.015) and − 14.6 μm (2.8 %, CI: −29.1, −0.11 μm, p = 0.048), respectively. ConclusionsThe presence of MVD, rather than T2D, was associated with increased cortical porosity. Increased porosity in MVD was coupled with a larger number of smaller vessels, which could indicate upregulation of neovascularization triggered by ischemia. It is unclear why higher variability and average diameters of pores in T2D were accompanied by larger vessels.

Development of ultra-lightweight foamed concrete modified with silicon dioxide (SiO2) nanoparticles: Appraisal of transport, mechanical, thermal, and microstructural properties

Over the last few decades, researchers have devoted significant consideration to the use of nanoscale elements in concrete. Silicon dioxide nanoparticles (SDNs) have been a popular subject of study among the several types of nanoparticles. This article describes the findings of a laboratory investigation that examined the properties of ultra-lightweight foamed concrete (ULFC) including different proportions of SDNs. Wide range of the properties was evaluated specifically the slump flow, density, consistency, flexural strength, modulus of elasticity, compressive strength, split tensile strength, thermal properties, porosity, water absorption, sorptivity, intrinsic air permeability, and chloride diffusion. Additionally, the scanning electron microscopy (SEM) and pore distributions analyses of different mixes were done. Results confirmed a noticeable increase in the mechanical properties of ULFC, with respective improvements in the 28-day compressive, split tensile, and flexural strengths of up to 70.49%, 76.19%, and 51.51%, respectively, at 1.5% of the SDNs inclusion. However, further increases in the SDNs percentage did not result in remarkable enhancements. As the SDN percentage increased from 1.5% to 2.5%, the ULFC's sorptivity, porosity, water absorption, intrinsic air permeability, and chloride diffusion showed substantial improvements. When compared to the control sample, ULFC with SDNs demonstrated higher thermal conductivity values. The reason for this occurrence was determined to be the smaller pore size observed in the ULFC specimens containing SDNs. A great adjustment in the distribution of pore diameters was witnessed in the ULFC mixes when the percentages of SDNs were adjusted. The ULFC specimens, which included SDNs at the percentages of 0.5%, 1.0%, and 1.5%, indicated a reduction in the total number of large voids measuring 500 nm or more, compared to the control ULFC specimen. The findings of this study highlight the potential benefits of incorporating SDNs into ULFC, which may improve its overall properties.

Monodispersed, Micron-Sized Supermicroporous Silica Particles by Cetyltrimethylammonium Bromide-Mediated Preparation.

In this study, we present a novel modified Stöber method utilizing cetyltrimethylammonium bromide (CTAB) as a mediator for the preparation of monodispersed, micron-sized supermicroporous silica particles. Observed results show prepared silica particles ranging in size from 0.64 to 1.36 μm with an increase in CTAB concentration from 1.0 to 5.0 mM. The particles exhibited low polydispersity (<5%), a high Brunauer-Emmett-Teller surface area (570 to 1064 m2/g), and pore volumes ranging from 0.22 to 0.39 cm3/g. The pore size, determined using the Barrett-Joyner-Halenda method from the adsorption branches of the isotherms, was approximately 1.9 nm, specifically 1.83, 1.85, and 1.90 nm, as the CTAB concentration increased from 1.0 to 2.5 and 5.0 mM, respectively. The resulting particles displayed a narrow distribution of pore diameters. In addition, to obtain an in-depth understanding of the role of CTAB on the preparation of silica particles, a possible mechanism is also investigated using conductivity, dynamic light scattering (DLS), zeta potential, FT-IR spectra, and transmission electron microscopy. Our findings demonstrate that CTAB plays multiple roles in the hydrolysis/condensation of TEOS (tetraethyl orthosilicate) and subsequent nucleation and growth of silica particles. CTAB acts as a template for superporosity, a stabilizer for colloids, and an accelerator for nucleation and growth, leading to formation of monodispersed micrometer silica particles. Further characterization through FT-IR and 29Si solid NMR spectra revealed that the micron silica particles were obtained with inhomogeneity in the condensation degree, allowing for selective etching through hot incubation to form micron-sized hollow silica spheres.

Non-destructive three-dimensional characterization of micronized pulse seeds using X-ray microcomputed tomography

Non-destructive quality evaluation techniques are vital in 3D visualization and quantification of microstructural changes in micronized pulse kernels. The effects of micronization (infrared heating) on pulse microstructure are highly dependent on its treatment efficiency. This study employed X-ray micro-computed tomography (micro-CT) to characterize, visualize, and quantify the microstructural changes non-destructively. Four major pulses, chickpeas, fava beans, lentils, and yellow peas, were subjected to micronization at 180 °C of surface temperature for four different infrared (IR) exposure times (60, 80, 100, and 120 s). All samples were pre-conditioned at 20 % moisture content before the micronization process. Morphometric parameters (pore size, diameter, and pore distribution) were qualitatively measured using the reconstructed 2D and 3D images acquired by the X-ray micro-CT. Physico-chemical parameters, including loss of moisture (%), total porosity (%), volumetric expansion/shrinkage (%), and density (%) were quantified using Micro-CTAn software. The results showed that the porosity is significantly increased (p < 0.05) in all pulse types ranging from 0.60 ± 0.42 % to 12.1 ± 2.68 %, at prolonged IR exposure time. Significant volume expansion ranging from 3.82 %–33.56 % was shown by chickpeas and yellow peas, while fava beans and lentils showed volume shrinkage ranging from 4.26 %–24.31 % after micronization. Furthermore, density was decreased ranging from 0.79 ± 0.25% to 33.49 ± 0.42 % with increased IR time for all pulses except fava beans. The authors found that the microstructural changes in all tested pulses were optimum at 100 s–120 s of exposure time. Results emphasize the higher potential in modifying the microstructure of pulses using micronization processing. Therefore, future studies are suggested on developing predictive models to explore the relationships between microstructural changes and techno-functional properties.

Improving the performance of porous volumetric solar reactor with biomimetic leaf vein structures and spectrally selective gradual porous parameters

The steam reforming of methane to hydrogen production in porous volumetric solar reactor is a promising way for solar energy utilization, which realize the conversion of solar energy to chemical energy. Due to the strong non-uniform volumetric inner heat source distribution in the porous catalyst and the varying concentration of methane, the porosity and pore diameter distribution of the porous catalyst should be carefully designed to improve the thermochemical performance. We firstly design a solar porous media volumetric reactor with a leaf vein bionic structure. Then, we numerically analyze the impact of leaf vein structure and pore size on the thermochemical performance of the reactor. The results show that the bionic leaf vein structure can regulate the distribution of methane and improve the chemical reaction rate. Compared with the traditional reactor, the reactor with non-parallel biomimetic leaf vein structure II can increase the methane conversion rate by 8.11 %. The pore size difference between the two regions is 0.5 mm that is limited within a small range, and the reactor has good performance. This paper can provide a guidance for porous volumetric solar reactor design to improve the thermochemical reactions performance.

Three-dimensional model of normal human dermal tissue using serial tissue sections.

Background: This study aims to construct a three-dimensional model of skin dermis utilizing continuous tissue sections, with the primary objective of obtaining anatomical structure data for normal human dermal tissues. Methods: Normal skin tissue specimens were acquired, paraffin-embedded, and subjected to HE staining. Panoramic images of skin sections were captured using a microscope. Tissue section images were aligned using the SIFT and StackReg image alignment methods, with analysis conducted using the OpenCV module. Mimics17 software facilitated the reconstruction of the skin dermal 3D model, enabling the calculation of dermal porosity and the void diameter. Results: Panoramic skin slices exhibited high-resolution differentiation of dermal fibers and cellular structures. Both SIFT and StackReg image alignment methods yielded similar results, although the SIFT method demonstrated greater robustness. Successful reconstruction of the three-dimensional dermal structure was achieved. Quantitative analysis revealed a dermal porosity of 18.96 ± 4.41% and an average pore diameter of 219.29 ± 34.27 μm. Interestingly, the porosity of the dermis exhibited a gradual increase from the papillary layer to the fourth layer, followed by a transient decrease and then a gradual increase. The distribution of the mean pore diameter mirrored the pattern observed in porosity distribution. Conclusion: Utilizing the continuous skin tissue slice reconstruction technique, this study successfully reconstructed a high-precision three-dimensional tissue structure of the skin. The quantitative analysis of dermal tissue porosity and average pore diameter provides a standardized dataset for the development of biomimetic tissue-engineered skin.

Synthesis of Cadmium Oxyorthosilicate by a Sol-Gel Method

Cadmium silicates are materials of interest due to their stability and possible application as phosphors. There are three stable forms: cadmium metasilicate, CdSiO3, cadmium orthosilicate, Cd2SiO4 and cadmium oxyorthosilicate, Cd3SiO5. Of these, oxyorthosilicate is particularly challenging to obtain, leading to fewer studies. We have successfully prepared Cd3SiO5 using a sol-gel approach, employing cadmium acetate and tetraethylorthosilicate as precursors in a stoichiometric proportion of 2:1. Additionally, cetyltrimethylammonium bromide served as a template for creating a mesoporous structure. Adjusting the pH to 3 and subjecting the material to calcination at 800 °C for 6 h, we achieved the formation of cadmium oxyorthosilicate compound, identified by X-ray diffraction. Electron diffractometry and energy dispersive X-ray spectrometry confirm the phase purity. Characterization via nitrogen adsorption analysis and transmission microscopy shows aggregates of nanoparticles with a surface area of 6 m2 g-1 and a narrow pore diameter distribution centered at 5 nm.

Balancing proton and mass transfers in cathode catalyst layer of high-temperature proton exchange membrane fuel cell via gradient porous structure design

The porous structure within the cathode catalyst layers (CLs) plays a crucial role in facilitating phosphoric acid (PA) invasion and oxygen diffusion, which was essential for establishing the triple-phase boundaries (TPBs) in high-temperature proton exchange membrane fuel cells (HT-PEMFCs).In this work, a gradient porous structure is deliberately constructed within the cathode CL by carefully controlling the microstructures of the double CLs. The effects of pore diameter distribution in the cathode CL and PA content in the membrane electrode assembly (MEA) on the single cell performance of HT-PEMFC are systematically investigated. By incorporating an appropriate amount of PA in the MEA, along with the optimized gradient porous structure, the inner pores effectively stored acid and prevented its outward diffusion. Simultaneously, the pores in the outer CL provided additional pathways for oxygen transfer. Consequently, the optimized gradient porous structure enhanced the peak power density of H2/Air fuel cells to 0.510 W cm−2 at a Pt loading of 0.5 mgPt cm−2, a notable improvement compared to 0.396 W cm−2 of the traditional single CL. The mechanism analysis further reveals that the cathode CL with gradient porous structure can successfully balance proton transfer and mass transfer, hence reducing the polarizations in fuel cell.

Liquid-phase adsorption of nitrogen compounds from model diesel fuel on activated carbons

One of the great challenges in deep hydrodesulfurization (HDS) to produce ultra-low-sulfur diesel (ULSD) is the coexisting heterocyclic nitrogen-containing compounds in middle distillates, which significantly inhibit the HDS reactions. This study investigates various activated carbon (AC) samples for selectively removing nitrogen compounds from a model diesel fuel through adsorption. The physical and chemical properties of the AC samples were characterized using low-temperature N2 adsorption–desorption, SEM–EDS, and FT-IR to explore their impact on the adsorption performance. The results indicate that the adsorption performance is influenced not only by the surface area and by the number of oxygen-containing functional groups on the surface but also by the pore diameter distribution. Among all AC samples tested, AC-W exhibited the highest adsorption capacity, achieving a nitrogen removal rate of 97.8% with the addition of 10 wt.% of AC-W. The adsorption capacity was approximately 24.0 mg-N/g-A at a nitrogen equilibrium concentration of 200 ppmw. The adsorption isotherms for total nitrogen and individual nitrogen compounds in the fuel over AC can be described well by the Freundlich isotherm model. An approach for improving the ADN performance of AC is discussed based on the findings in this study.

Revealing the impact of isolated pores on the properties of foam cement using hollow microspheres

Since foam concrete inevitably leads to foam bursting and merging during the molding process, the relationship between specific pore connectivity and pore diameter distribution on foam concrete properties is still difficult to characterize exactly. This study intentionally introduced hollow microspheres of three sizes (40 µm, 60 µm, and 80 µm) into foam concrete to control the number and diameter of isolated pores. The influence of isolated porosity and pore diameter distribution on the properties of foam concrete were evaluated by dry density, mechanical property and thermal conductivity. Meanwhile, the SEM and X-CT technologies were employed to assess the pore structure of the sample, and the measured thermal conductivity was compared with the theoretical thermal conductivity calculated by the formula based on the isolated porosity. Finally, the correlation between isolated pores and heat transfer paths were analyzed by the calculated tortuosity. The results of the dry density and mechanical tests indicated that the dry density tended to be lower with the increase of isolated pores’ diameter, which 80 µm hollow microspheres resulted in a notable reduction in the dry density within the three size groups, whereas 28 days compressive strength trended oppositely. The 40 µm hollow microsphere specimen with a dry density of 400 kg/m3 exhibited the better mechanical property among three groups, which was 1.82 MPa, due to the uniform distribution within the matrix, preventing fusion between foams. Specifically, the trend of the theoretical value calculated by the formula was consistent with that of the measured value, proving that the decrease in thermal conductivity of sample can be attributed to the increase of isolated porosity. The lowest thermal conductivity and highest tortuosity were achieved by specimens mixed with 80 µm hollow microspheres at the dry density of 300 kg/m3, which were 0.07045 W/(m·K) and 2.015, respectively, demonstrating that specimens mixed with 80 µm hollow microspheres exhibited a more complex heat transfer path than the other two groups.

Pyrrolidinium-functionalized Cardo (TPM) poly(arylene ether sulfone)s membranes for acid recovery: The effects of Cardo (TPM) microstructures

To explore the intrinsic correlation between the rigidity and distortion degree of polymer backbones and the diffusion dialysis (DD) performance of anion exchange membranes (AEMs), pyrrolidinium-functionalized poly(arylene ether sulfone)s containing different Cardo (TPM) moieties were prepared. The structures, properties and DD performance of above AEMs were systematically evaluated. As the Cardo (TPM) group angle increased, the d-spacing, fractional free volume, and membrane area resistance increased, and the microphase separation structures, hydrophilicity, and acid flux decreased, mainly because larger Cardo (TPM) group angles are unfavourable for the close packing of polymer chains in space. Both the Cardo-type and TPM-type AEMs exhibited universal ultrahigh H+/Fe2+ selectivity (S > 3819), which was mainly attributed to the synergistic influence of their rigid narrow ion transport channels, small pore diameter (0.48–0.62 nm) and narrow pore size distribution (0.24–0.68 Å). Additionally, due to the high-density amide groups of TPM units, which decreased the hydrophobicity of the polymer skeleton and induced the formation of an additional transport pathway for Fe2+ through hydrogen bonding interactions, the TPM-type AEMs showed both lower acid flux and selectivity, suggesting that the structure of hydrophilic auxiliary groups should be carefully designed when improving the DD performance of AEMs.