Bimodal Pore Size Research Articles

Fabrication of porous high-entropy Mn-Fe-Co-Ni-Cu-Zn alloys by vapor phase dealloying

Porous multicomponent 3d transition-metal (TM) alloys were fabricated by eliminating Zn from rapidly quenched ribbons with distinct compositions, TM7Zn93 and TM4Zn96 (TM – a mixture of Mn, Fe, Co, Ni, and Cu) using vapor phase dealloying (VPD). Phase composition and microstructure of the ribbons in an as-quenched state and resulting porous materials were investigated in detail by S/TEM-EDS, XRD, SEM, and EDXRF methods. In the as-quenched state, the majority of the alloy is composed of the CoZn13 type structure (C2/m space group). Atomically resolved EDS mapping clarified the chemical site occupancy of the TM elements in the structure. The resulting fabricated porous high-entropy alloys (HEA) have a spongy microstructure with a bimodal pore size and their surface area was estimated at 2–4 m2/g. Analysis of pore size distribution revealed their macro-mesoporous structure. The formation of the solid solution with the FCC (Fm3̅m space group) crystal structure during VPD was confirmed by XRD data. STEM-EDS analysis revealed the existence of several FCC solid solution phases within the porous HEA. A nanoscale elemental/phase separation into Co- and Cu-rich FCC solid solution regions with coherent interfaces across the individual crystalline grains has been found. A general route to prepare porous HEA using rapid solidification and vapor phase dealloying has been discussed.

Preparation of homogeneous super-circular alumina microspheres in microchannels by controlling extraction and motion processes

The sol–gel technique combined with microfluidics is an effective approach for the preparation of microspheres. The formation and solidification of the sol can be influenced by the motion and extraction processes. The effects of extraction and motion were investigated using a real-time moisture content test, in situ observations, and CFD simulations. The microspheres retained their homogeneous internal structure with a narrow pore distribution when the extraction rate was less than 1 × 10−4 ml/min·mm2, whereas extraction rates greater than 2 × 10−4 ml/min·mm2 resulted in clear hollows and stacking. A continuous phase devoid of extraction capability results in an internal hierarchy and bimodal pore size. Higher surface tension (greater than 4 mN/m) and lower fluid shear forces promoted high sphericity. These novel methods offer a promising approach for the preparation of alumina microspheres with a high spherical degree of 0.987 by matching the motion and extraction curing techniques.

One-Pot Synthesis of Aminated Bimodal Mesoporous Silica Nanoparticles as Silver-Embedded Antibacterial Nanocarriers and CO2 Capture Sorbents.

Mesoporous silica nanoparticles have highly versatile structural properties that are suitable for a plethora of applications including catalysis, separation, and nanotherapeutics. We report a one-pot synthesis strategy that generates bimodal mesoporous silica nanoparticles via coassembly of a structure-directing Gemini surfactant (C16-3-16) with a tetraethoxysilane/(3-aminopropyl)triethoxysilane-derived sol additive. Synthesis temperature enables control of the nanoparticle shape, structure, and mesopore architecture. Variations of the aminosilane/alkylsilane molar ratio further enable programmable adjustments of hollow to core-shell and dense nanoparticle morphologies, bimodal pore sizes, and surface chemistries. The resulting Gemini-directed aminated mesoporous silica nanoparticles have excellent carbon dioxide adsorption capacities and antimicrobial properties against Escherichia coli. Our results provide an enhanced understanding of the structure formation of multiscale mesoporous inorganic materials that are desirable for numerous applications such as carbon sequestration, water remediation, and biomedical-related applications.

Pore size distribution and reservoir characterization: evaluation for the Eocene beach-bar sequence, Dongying Depression, China

Pore size distribution and associated heterogeneities of thinly bedded beach-bar sandstone reservoir from upper fourth member of Eocene Shahejie Formation (Es4s) are characterized with the help of mercury injection capillary pressure (MICP) and nuclear magnetic resonance (NMR) transversal relaxation time (T2) data. Permeability and porosity are two represented important characteristics of rocks that control the movement and storage of fluids. The aim of this paper is to establish relationships between pore throat sizes and reservoir quality. The results derived from thin-section petrography, scanning electron microscopy (SEM), MICP, NMR T2 relaxation time, and 3D micro-CT (μ-CT) are compared to characterize pore space dimensions and types comprehensively. Average pore throat size from MICP ranges between 0.47 μm and 2.83 μm while maximum pore throat size ranges between 2.48 μm and 7.36 μm. The combination of pore size distribution obtained from MICP and NMR seems appropriate to cover the range of pore size from beach-bar sand and overcome the individual method limits. Afterwards, digital 3D μ-CT tomographic images are used to characterize and visualize pore space and pore network model to compare with the experimental data. MICP and NMR experiment showed generally bimodal (meso and micro) pore size distribution. Usually mesopore corresponding to intergranular pores is dominant, while heavily cemented sandstones show large amounts of intercrystalline micropores. Complex and heterogeneous beach-bar sandstone reservoir requires comprehensive study program to evaluate the reservoir.

Ordered mesoporous CoO/CeO2 heterostructures with highly crystallized walls and enhanced peroxidase-like bioactivity

With increasing requirements of replacing the high-cost and unstable natural enzymes, the rational design of highly efficient inorganic mimetic enzymes (nanozymes), as one of the most important bioactive materials, has attracted more and more attention in recent years. In our work, using the solvent evaporation induced co-assembly strategy with high-molecular weight poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymer as the template and two metal salts as the co-precursors in one-pot system, we synthesized ordered mesoporous heteroatom-doped CeO2 with high surface area, bimodal pore sizes and highly crystallized walls. The composite materials were then constructed as the mimetic enzymes to investigate their peroxidase-like catalytic performance and detect H2O2 and glucose as bioactive materials in diverse systems including complex biological samples. It was demonstrated that mesoporous 5%CoO/CeO2 catalyst was the best peroxidase mimic, following the typical Michaelis–Menten kinetics and exhibiting the excellent peroxidase-like catalytic performance toward 3,3′,5,5′-tetramethylbenzidine (TMB) with comparable Km and Vm values to horseradish peroxidase (HRP) enzyme. A highly sensitive and selective colorimetric assay was developed to detect H2O2 and glucose with detection limits of 0.88 and 19.6μM, respectively. The promising catalytic behavior of mesoporous 5%CoO/CeO2 as the peroxidase-like bioactive catalyst could be ascribed to its interconnected large mesopores, rich exposed surface defects and oxygen vacancies introduced by the heterojunction interface of ultrasmall CeO2 and CoO nanocrystals within pore walls.

The influence of chemical polishing of titanium scaffolds on their mechanical strength and in-vitro cell response

Selective Laser Melting (SLM) is a powder-bed-based additive manufacturing method, using a laser beam, which can be used to produce metallic scaffolds for bone regeneration. However, this process also has a few disadvantages. One of its drawbacks is the necessity of post-processing in order to improve the surface finish. Another drawback lies in the removal of unmelted powder particles from the build. In this study, the influence of chemical polishing of SLM fabricated titanium scaffolds on their mechanical strength and in vitro cellular response was investigated. Scaffolds with bimodal pore size (200 μm core and 500 μm shell) were fabricated by SLM from commercially pure titanium powder and then chemically treated in HF/HNO3 solutions to remove unmelted powder particles. The cell viability and mechanical strength were compared between as-made and chemically-treated scaffolds. The chemical treatment was successful in the removal of unmelted powder particles from the titanium scaffold. The Young's modulus of the fabricated cellular structures was of 42.7 and 13.3 GPa for as-made and chemically-treated scaffolds respectively. These values are very similar to the Young's modulus of living human bone. Chemical treatment did not affect negatively cell proliferation and differentiation. Additionally, the chemically-treated scaffolds had a twofold increase in colonization of osteoblast cells migrating out of multicellular spheroids. Furthermore, X-ray computed microtomography confirmed that chemically-treated scaffolds met the dimensions originally set in the CAD models. Therefore, chemical-treatment can be used as a tool to cancel the discrepancies between the designed and fabricated objects, thus enabling fabrication of finer structures with regular struts and high resolution.

Siliceous mesocellular foams modified via a partitioned cooperative self-assembly process using hexane as pore swelling agent

Siliceous mesocellular foams (S-MCFs), a series of mesoporous silicas with large and 3D-interconnected mesopores, have drawn great attention as a versatile support for various applications. In this work, we for the first time demonstrated that hexane can be an ideal pore swelling agent for the preparation of modified S-MCFs (designated as MS-MCFs) via a previously reported partitioned cooperative self-assembly (PCSA) process based on cheap silica precursor, i.e., sodium silicate (SS). The MCF structures can actually be achieved by simply adjusting the addition order of the hexane with respect to the first addition of SS under certain partitioning conditions. As a result, conventional MCF structures can be modified by either disordered (PCSA-I route, hexane being added before the 1st addition of SS) or ordered SBA-15 (PCSA-II route, hexane being added some interval time after the 1st addition of SS) mesophases, forming two series of bimodal mesopore systems, without resorting to additives or complicated synthetic process. The specific surface areas up to 600m2g−1, pore volumes up to 0.84cm3g−1, and bimodal pore sizes (1st series measuring 8–12nm and the 2nd series of 12–24nm) can be obtained. The control over interval time, in particular in the PCSA-II route, during which the condensation of the silicate species was allowed to proceed was found to be crucial for the evolution of bimodal pore system other than the normal MCF structures, i.e., the formation of MS-MCFs. The silicate synthesis strategy thus reported opens new pathways to the preparation and tuning of MCF structured silicas and will further promote their applications.

Textural and hydrogen sulphide adsorption behaviour of double metal–silica modified with potassium permanganate

A new MgCa-silica material with bimodal pore size is impregnated with KMnO4 for dynamic adsorption of H2S. The MgCa-silica was synthesized using sodium silicate and calcium and magnesium salts as p ...

Effect of Catalyst Diffusion Coefficient on Ethylbenzene Dehydrogenation

The effective diffusion coefficients for a single catalyst pellet were determined by numerical integration of the Johnson-Stewart equation for bimodal and unimodal pore size distributions assuming a transitional diffusion regime. The effectiveness factors of a spherical catalyst pellet were determined at various pore size distribution probability density functions. Using effectiveness factors the production rates were determined. The results showed that the effectiveness factor and production rate are sensitive to catalyst pore size distribution and diffusion coefficient.

Synthesis and characterization of bimodal rod-like mesoporous carbons from raffinose by SBA-15 templates

Mesoporous carbons with bimodal rod-like pore structures and tunable pore sizes from 3.66 to 5.42 nm were for the first time obtained by employing SBA-15 as templates and raffinose as carbon precursors. Small angle X-ray diffraction, transmission electron microscopy, scanning electron microscopy, N2 sorption analysis, and Raman spectroscopy were used to determine the textural properties of the resulting materials. Bimodal frameworks with mesopores (4–5 nm) as well as macropores (125–130 nm) were achieved. The mesoporous carbons lost its ordered structure from the templates due to mesostructural shrinkage and collapse of mesopores, which resulted in partial duplicate of the template and pore-widening effect (meso to macropores). With the increasing of carbonization temperature from 500, 700 to 900 °C, the textural parameters such as specific surface areas, pore volumes, and mean pore diameters all increased significantly. In the temperature range studied, higher carbonization temperature would generate much more abundant porosity. The ratio of I D to I G (I D/I G) indicated a rather low crystallinity with the varying of aging temperature and the carbonization temperatures. The advantage of the procedure was that no acid or other chemical catalysts were involved during the infiltration and carbon formation process.

Structure and properties of clinical coralline implants measured via 3D imaging and analysis

The development and design of advanced porous materials for biomedical applications requires a thorough understanding of how material structure impacts on mechanical and transport properties. This paper illustrates a 3D imaging and analysis study of two clinically proven coral bone graft samples ( Porites and Goniopora). Images are obtained from X-ray micro-computed tomography (micro-CT) at a resolution of 16.8 μm. A visual comparison of the two images shows very different structure; Porites has a homogeneous structure and consistent pore size while Goniopora has a bimodal pore size and a strongly disordered structure. A number of 3D structural characteristics are measured directly on the images including pore volume-to-surface-area, pore and solid size distributions, chord length measurements and tortuosity. Computational results made directly on the digitized tomographic images are presented for the permeability, diffusivity and elastic modulus of the coral samples. The results allow one to quantify differences between the two samples. 3D digital analysis can provide a more thorough assessment of biomaterial structure including the pore wall thickness, local flow, mechanical properties and diffusion pathways. We discuss the implications of these results to the development of optimal scaffold design for tissue ingrowth.

Porous apatite ceramics with bimodal pore size

Porous apatite ceramics with bimodal pore size

石炭液化油中鉱物質の水素化処理用触媒上での挙動

In order to make clear the behavior of coal mineral remaining in coal liquid on the hydrotreating catalyst, a Wandoan coal derived liquid containing high contents of liquefaction solid was hydroprocessed over the Ni-Mo-γ-Al2O3 catalyst having bimodal pore size distributions.In these liquefaction residues, kaolin and quartz were not chemically altered and magnetite was undergone chemical transformation to pyrrhotite during hydroprocessing. From the shell like deposits of these metals around the spent cata lysts, these matters might be finely dispersed particles that had equivalent spherical diameter larger than about 1-2μm, which corresponded to maximum size of macropore in used catalysts.Titanium and calcium metals, which were more concentrated in THF insoluble residue in feed coal liquid, were tend to accumulate in preasphaltene after hydro processing. Furthermore from the more penetrated depth profile of titanium and calcium metals, these metal containing matters might have equivalent spherical diam eter larger than about 0.6μm and 4.4nm micro-pore diameter were too small to be utilized against carbonaceous material deposits. Because active sites might be occupied with sodium metal, which interacted more strongly with those than titanium and calcium metals, titanium and calcium metals migrated more deeper on the catalyst pore walls by surface diffusions.As a result, silicon and iron metals were tend to plug the catalyst pore mouth and sodium, alkaline earth metals and titanium metals were tend to poison active sites and change micro-pore structure.