Uniform Pore Distribution Research Articles

FORMATION OF ANODIC POROUS ALUMINA IN OXALIC ACID AND ELECTRODEPOSITION OF NI.

Nanoporous anodic aluminum oxide (AAO) tubular membranes were fabricated from aluminum alloy tubes in sulfuric and oxalic acid electrolytes using a two-step anodization process. The membranes were investigated for characteristics such as pore size, interpore distance and thickness by varying applied voltage and electrolyte concentration. Morphology of the membranes was examined using light optical and scanning electron microscopy and characterized using Image software. Results showed that membranes having narrow pore size and uniform pore distribution with parallel channel arrays were obtained. The pore sizes were ranging from 10 to 100 nm and the wall thicknesses 60 μm. The catalysts are obtained by impregnation of 3d metals into nanosized pores of aluminum oxide. The obtained catalysts based on nickel and porous Al2O3 are studied by scanning microscopy (SEM-EDX). The results of SEM-EDX analysis shows that a spongy structure with filament sizes of 100 nanometers containing particles of 3d metals formed on the surface of the aluminum oxide matrix.

Influence of Powder Particle Morphology on the Static and Fatigue Properties of Laser Powder Bed-Fused Ti-6Al-4V Components

In this work, two Ti-6Al-4V powder lots were produced using two different techniques: plasma atomization and gas atomization, with the first producing more spherical particles than the second. Testing specimens were then manufactured with these powder lots using an identical set of printing parameters and the same laser powder bed fusion system. Next, the porosity levels and distributions as well as the static and fatigue properties of the specimens from both powder lots were compared. Regarding the static mechanical properties, a noticeable difference was observed between the plasma-atomized powder specimens and their gas-atomized equivalents (7% greater ultimate and 4% greater yield strengths, but 3% lower elongation to failure, respectively). However, with regard to the fatigue resistance, the advantages of the plasma-atomized powder specimens in terms of their mechanical resistance were somewhat counterbalanced by the presence of pores aligned in the direction perpendicular to that of applied load. Conversely, specimens printed with the gas-atomized powder manifested a similar level of porosity, but a uniform pore distribution, which reduced the impact of the processing-induced porosity on fatigue cracks initiation and propagation.

Accurate and uniform fabrication of Li2TiO3 pebbles with high properties based on Stereolithography technology

Li2TiO3 is a vital candidate breeder to solve tritium self-consistency of fusion reaction. In this study, Digital Light Processing (DLP) based on Stereolithography technology was used to fabricate Li2TiO3 pebbles for the first time. Ceramic suspensions with different solid loadings were prepared by mixing modified Li2TiO3 powder with UV-curable premixture. The size error of Li2TiO3 green pebbles was corrected by adjusting the deformation factor of equatorial radius, and the Li2TiO3 green pebbles were successfully fabricated with an accurate size. After sintering processing, the Li2TiO3 pebbles with a uniform diameter of 1.5 mm and better sphericity of 1.01 were yielded. The sintering behavior of Li2TiO3 pebbles were investigated. Results showed that the Li2TiO3 pebbles formed with 35 vol% solid loading, and sintered at 1050 ℃ had a uniform pore distribution, and also had optimal properties, such as high relative density of 93.6 %TD, and prominent crush load of 92.3 N.

Copper (I)–Organic Frameworks for Catalysis: Networking Metal Clusters with Dynamic Covalent Chemistry

Metal clusters exhibit diverse structures, emerging functions, and applications; thus, incorporating clusters into metal–organic frameworks (MOFs) brings tremendous merits. Although the constructio...

Preparation of Porous Titanium Dental Implant by 3D Printing/Composite Coating and Its Biomechanical Properties and Flexural Strength

Dental implants have been widely used in clinical practice. The 3D modeling software was used to design threedimensional (3D) models (in the shapes of long strips, discs, and screws), i.e., the Ti2.6Al1.2 V0.42 specimens. Meanwhile, the implant material was electrochemically precipitated, and a layer of chitosan nano-coating was added to the surface. To test the bone-binding ability and planting success rate of the material, the mechanical properties of the specimens with different porosity (0%∼70%) were firstly analyzed by the three-point bending method. Then, the screw-shaped titanium alloy specimens were divided into the solid group, the solid coating group, the solid 30% group, the coating 30% group, the solid 50% group, and the coating 50% group. The MC3T3-E1 cells were cultured, and the in vitro biological properties of the specimens were tested from different angles. The biomechanical properties and flexural strength of screw-shaped titanium alloy specimens in different groups were tested by using a universal testing machine. In the experiment, the prepared dental implants had the complete surface, uniform pore distribution, dense coating distribution, and less overall cracks. The elastic gradient of porous titanium specimens would decrease due to the increase of porosity. The cell activity of the test specimen was higher, and the percentage of viable cells exceeded 80%. The MTT test confirmed that the pores of the test specimen could promote the increase of MTT value (P < 0.05), and the test specimen/composite coating had higher ALP levels compared with the test pieces with no surface treatments (P < 0.05). In biomechanical properties and flexural strength tests, the increase of pores increased the biomechanical properties (P < 0.05) and decreased the flexural resistance (P < 0.05), while the increase of coating decreased the biomechanical properties and increased the flexural resistance (P < 0.05). The porous titanium alloy specimens were successfully prepared, and the chitosan-based composite coating was applied. The material was non-toxic, which was beneficial to cell proliferation and had good mechanical properties, thereby contributing to the growth of new bone.

Self-assembled reduced graphene oxide films with different thicknesses as high performance supercapacitor electrodes

Graphene-based materials have attracted considerable attention as the electrochemical energy storage and conversion material due to their high electronic conductivity and large ion-accessible surface area. Herein, a series of self-assembled reduced graphene oxide (rGO) films are facilely prepared via a scalable vacuum filtration method, whose thickness is regulated by changing the concentration of the filtering rGO solution. The effect of the mass loading (thickness) of rGO film electrodes on its electrochemical performance is investigated. These rGO film electrodes with mass loading of 6.7 mg cm−2 exhibit a high specific capacitance of 173.4 F g − 1 (1.16 F cm−2) at 1 A g − 1 and show high utilization of the active material due to their large specific surface area and uniform pore distribution. Moreover, a quasi-solid supercapacitor fabricated with the as-prepared rGO film electrode shows a high area capacitance of 1.03 F cm−2 and large specific energy of 0.073 mWh cm−2 at the specific power of 3.3 mW cm−2, as well as excellent cycling stability of 85.6% retention after 10,000 cycles. Such remarkable performance suggests that this rGO film is promising electrode material for supercapacitor application.

Advanced Filter Membrane Separator for Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries with low cost and inherent safety are considered to be the next-generation energy storage device. However, they suffer from poor cycling stability and low coulombic efficiency caused by the serious zinc dendrites during the cycling. In this work, a porous water-based filter membrane is first proposed as separator due to its good toughness and uniform pore distribution. The results demonstrate that the symmetrical cell using a filter membrane can cycle over 2600 h with a low voltage hysteresis of 47 mV. Moreover, an aqueous Zn//NaV3 O8 ·1.5H2 O cell based on the filter membrane is constructed, which demonstrates a high capacity retention of 83.8% after 5000 cycles at 5 A g-1 . The mechanism research results reveal that the excellent dendrites inhibiting the ability of the filter membrane should be attributed to its uniform pore distribution rather than its composition. This work proposes a filter membrane separator and reveals the great influence of separator on the zinc stripping/plating process, which will shed light on the development of high-performance aqueous zinc-ion batteries.

The Fabrication of Geopolymer Foam Composites Incorporating Coke Dust Waste

This paper reports the results of an experimental investigation on the mechanical properties of geopolymer foams incorporating filler from the coke dust waste (CDW). In this work, CDW was used to replace a part of geopolymer paste at 5%, 10%, 20%, and 30% by geopolymer binder mass. The physico-mechanical properties and thermal resistance against high temperatures of CDW/geopolymer foams are presented. The primary results obtained show that the use of CDW in the production of geopolymer foam composites made it possible for them to achieve relatively good mechanical properties. However, the incorporation of the CDW into the geopolymer had a slightly negative effect on thermal conductivity, but significantly improved the mechanical strength of the final product. Moreover, this waste also helped the composite foam to achieve a structure with more uniform open pores distribution, compared to the pure foam. After exposure to elevated temperatures, the residual strength of the composite foams maintained well compared to the pure foams.

Performance of TiO2 nanoparticles synthesized by microwave and solvothermal methods as photoanode in dye-sensitized solar cells (DSSC)

In this work, a direct comparison of the properties of the TiO2 nanoparticles prepared by microwave and solvothermal methods were carried out and its performance as photoanode in dye-sensitized solar cells (DSSC) was analyzed. Though previously some works exist on the preparation of TiO2 nanoparticles by solvothermal or microwave methods, they could not be compared directly as the experiment conditions such as choice of solvent, precursors and reaction temperatures were not virtually same. Herein, TiO2 nanoparticles were synthesized by microwave and solvothermal methods using the same initial precursors and properties of the prepared nanoparticles were compared. From the X-ray diffraction pattern and Raman analysis, the prepared nanoparticles in both the cases were found to be of anatase phase. Optical properties and its carrier lifetime were studied using UV–Vis absorption, photoluminescence (PL) analysis and PL lifetime studies, respectively. Further, its morphology analyzed using scanning electron microscope (SEM) and transmission electron microscope (TEM) images, and SAED (selected area electron diffraction) patterns reveals the polycrystalline nature of the prepared nanoparticles. The surface area and the pore size distribution were studied using BET (Brunauer–Emmett–Teller) and BJH (Barrett–Joyner–Halenda) analysis, which revealed its mesoporous nature and uniform pore distribution. The chemical states of the prepared nanoparticles were further characterized using X-ray photoelectron spectroscopy. The DSSC was fabricated using the prepared TiO2 nanoparticles as photoanodes. Further, the power conversion efficiency and the electron transport properties were analyzed.

Superhydrophobic (polyvinylidene fluoride-co-hexafluoropropylene)/ (polystyrene) composite membrane via a novel hybrid electrospin-electrospray process

A novel hybrid electrospin-electrospray process was introduced to manipulate the membrane hierarchical structure towards enhanced surface superhydrophobicity and structural integrity. In this study, the two-nozzle mode was used to simultaneously electrospin PH (polyvinylidene fluoride-co-hexafluoropropylene) fibers and electrospray PS (polystyrene) beads to prepare a PH-PS composite membrane, during which fibers and beads alternatingly deposited and entangled together on the collector. Upon using the optimized PS solvent and PS content, the optimal PH-PS membrane exhibited superhydrophobicity (water contact angle of 157.6°) and good structural integrity, benefiting from the combination of the tough PH network and the interspersed porous irregular PS beads, as well as their homogeneous blending and good adhesion during this advantageous hybrid electrospin-electrospray process. In addition to superhydrophobicity, the PH-PS composite membrane was also endowed with a uniform pore distribution and high porosity, leading to a greatly enhanced liquid entry pressure of water (LEPw). Once applied in the direct contact membrane distillation (DCMD) process, it showed high desalination robustness and excellent anti-wetting performance with stable flux and high salt rejection under harsh feed conditions, providing great potential in practical desalination applications.

Synthesis and characterization of β-cyclodextrin centered polysiloxane star polymers

In this study, a macroinitiator of β-CD-ONa was prepared by a substitution reaction of β-cyclodextrin (β-CD) with sodium (Na). The macroinitiator was then used in the ring-opening polymerization of octamethylcyclotetrasiloxane (D4) to obtain a star polymer, in which β-CD is the core and polysiloxane is the arm. FTIR, NMR, TGA, CA, etc., were used to characterize the structure and properties of star polymers. The results indicated that there were four polysiloxane arms attached to each β-CD core, and the star polymer had good thermal stability. With the increase in D4 monomer dosage, the hydrophobicity of the star polymer slightly improved, but the reaction time had no significant effect on hydrophobicity. When the star polymer was coated onto polyethylene terephthalate membrane, the transmittance increased from 87.6% to 92.8%, and the haze did not change significantly. Furthermore, the surface of star polymer porous membranes was prepared by the static breath-figure method using n-hexane as solvent at 30 °C. The results showed uniform pore distribution and increased hydrophobicity.

In Situ Pyrolysis Tracking and Real‐Time Phase Evolution: From a Binary Zinc Cluster to Supercapacitive Porous Carbon

The in situ tracking of the pyrolysis of a binary molecular cluster [Zn7 (μ3 -CH3 O)6 (L)6 ][ZnLCl2 ]2 is presented with one brucite disk and two mononuclear fragments (L=mmimp: 2-methoxy-6-((methylimino)-methyl)phenolate) to porous carbon using TG-MS from 30 to 900 °C. Following up the spilled gas product during the decomposed reaction of zinc cluster along the temperature rising, and in conjunction with XRD, SEM, BET and other materials characterization, where three key steps were observed: 1) cleavage of the bulky external ligand; 2) reduction of ZnO and 3) volatilization of Zn. The real-time-dependent phase-sequential evolution of the remaining products and the processing of pore forming template transformation are proposed simultaneously. The porous carbon structure featuring a uniform nano-sized pore distribution synthesized at 900 °C with the highest surface area of 1644 m2 g-1 and pore volume of 0.926 cm3 g-1 exhibits the best known capacitance of 662 F g-1 at 0.5 A g-1 .

The synergetic interaction of chemical admixtures on the properties of eco-friendly lightweight concrete from industrial technogenic waste

It is important to know how different superplasticisers (SP) types affect the rheological properties of foamed cement pastes and influence the physical and mechanical properties of eco-friendly porous lightweight aggregate concretes based on industrial technogenic waste. Three tested superplasticisers—lignosulfonates SP(S), polycarboxylates SP(C), polyacrylates SP(A), air-entraining admixture (AEA) and their combinations—differently prolong the setting time of Portland cement (OPC) pastes. The results show that SP(A) retards the setting time of OPC paste to the minimum extent both in individual use or in combination with AEA. The dynamic viscosity of OPC pastes depends on the metakaolin additive (MA) to OPC ratio and AEA. In pastes with the highest MA to OPC ratio, the dynamic viscosity is 2.46 times higher than in a paste without MA. The effect of AEA in the pastes expresses itself in increased dynamic viscosity, up to 50.8% compared to the same samples without AEA. Increasing the MA to OPC ratio in pastes with AEA and SP(A) allows entraining a higher volume of air, which results in uniform pore distribution and increasing apparent porosity by 2.2 times. Increasing the MA to OPC ratio in a eco-friendly lightweight aggregate concrete (LAC) sample creates a highly porous macrostructure, resulting in decreased density, up to 40.1%, and thermal conductivity coefficient, up to 2.1 times (from 0.152 to 0.073 W/(m·K) and increased water absorption, up to 44.8% (from 5.73% to 8.3%). With an increased MA to OPC ratio in a LAC sample series, the compressive strength decreased up to 14 times after 7 days of hardening, however, after 56 days of hardening, the tendency of increase for compressive strength is observed.

Preparation of pore-controllable zirconium carbide ceramics with tunable mechanical strength, thermal conductivity and sound absorption coefficient

Porous ZrC ceramics with uniform pore distribution were successfully prepared using evaporating solvent and hot-pressing sintering. A sintering model of porous ZrC ceramics was established under applied sintering pressure to illustrate the formation mechanism of controllable pore. As the sintering pressure increases, the porosity of porous ZrC ceramics decreases from 73.5% to 55.4%, and the corresponding compressive strengths increase from 5.67 MPa to 31.25 MPa and the thermal conductivities decrease at different temperature. Sound absorption measurement shows that as the median pore sizes of porous ZrC ceramics decrease from 12.48 μm to 4.83 μm, their optimum sound absorption frequency shifts from 2.7 kHz to 4.5 kHz, which is attributed to the fact that porous ceramics with different pore sizes have different responses to specific frequency bands.

Hydroxyethyl Chitosan-Reinforced Polyvinyl Alcohol/Biphasic Calcium Phosphate Hydrogels for Bone Regeneration.

Fabrication of reinforced scaffolds for bone regeneration remains a significant challenge. The weak mechanical properties of the chitosan (CS)-based composite scaffold hindered its further application in clinic. Here, to obtain hydroxyethyl CS (HECS), some hydrogen bonds of CS were replaced by hydroxyethyl groups. Then, HECS-reinforced polyvinyl alcohol (PVA)/biphasic calcium phosphate (BCP) nanoparticle hydrogel was fabricated via cycled freeze-thawing followed by an in vitro biomineralization treatment using a cell culture medium. The synthesized hydrogel had an interconnected porous structure with a uniform pore distribution. Compared to the CS/PVA/BCP hydrogel, the HECS/PVA/BCP hydrogels showed a thicker pore wall and had a compressive strength of up to 5–7 MPa. The biomineralized hydrogel possessed a better compressive strength and cytocompatibility compared to the untreated hydrogel, confirmed by CCK-8 analysis and fluorescence images. The modification of CS with hydroxyethyl groups and in vitro biomineralization were sufficient to improve the mechanical properties of the scaffold, and the HECS-reinforced PVA/BCP hydrogel was promising for bone tissue engineering applications.

High thermal conductivity and low thermal expansion coefficient of isotropic graphite-reinforced aluminum matrix composites prepared by in situ curing of silicon aerogel

In this study, graphite with different weight fraction of copper plating was obtained through electroless coating, then a new way called in situ curing of silicon aerogel was introduced to fabricate the preform of graphite-reinforced metal matrix composites, which has the advantages of short production cycle, low energy consumption, high mechanical strength, uniform pore distribution, and near net size formation, followed by aluminum impregnation through vacuum gas pressure infiltration. The obtained results prove that the composites made of copper-coated graphite have isotropic high thermal conductivity and low coefficient of thermal efficiency, with machinability and low density determined by raw materials making them competitive in the related fields.

Microstructure Control for Improving Swelling Behavior of Lithium Ion Batteries

With the growing demands for high energy density of lithium ion batteries (LIBs), the electrode is thicker and denser to maximize the proportion of the active materials compared to the electrochemically inactive components such as current collectors and a separator. Accordingly, the electrode could lose the interconnection between pores and have reduced pore volume in the electrode, resulting in poor electrochemical properties due to the degradation of electrolyte permeability. Furthermore, the inhomogeneous volume changes of active materials in the electrode could cause the severe swelling issues in the thick and dense electrode system. Here, we report the thick and dense graphite anodes with the controlled pore distribution in the electrode to improve the electrochemical properties and secure the stable electrode swelling behaviors by two-step roll pressing. The uniform pore distribution in the electrode is confirmed by 3D X-ray microscopy (3D XRM). The graphite anode with the uniform pore distribution exhibits improved cycling performance (retention 85.83% @200cycle), and presents stable swelling behavior (4.47% @25cycles). We demonstrate that the improved electrochemical properties and stable swelling behaviors are realized in the thick and dense graphite anodes by facile two-step roll pressing.

3D soil void space lacunarity as an index of degradation after land use change

In this work, lacunarity analysis is performed on soil pores segmented by the pure voxel extraction method from soil tomography images. The conversion of forest to sugarcane plantation was found to result in higher sugarcane soil pore lacunarity than that of native forest soil, while the porosity was found to be lower. More precisely, this study shows that native forest has more porous soil with a more uniform spatial distribution of pores, while sugarcane soil has lower porosity and a more heterogeneous pore distribution. Moreover, validation through multivariate statistics demonstrates that lacunarity can be considered a relevant index of clustering and can explain the variability among soils under different land use systems. While porosity by itself represents a fundamental concept for quantification of the impact of land use change, the current findings demonstrate that the spatial distribution of pores also plays an important role and that pore lacunarity can be adopted as a complementary tool in studies directed at quantifying the effect of human intervention on soils.

Self‐assembly Mesoporous FeP Film with High Porosity for Efficient Hydrogen Evolution Reaction

AbstractExploring efficient noble metal‐free electrocatalysts is of significance for water electrolysis. In this work, we fabricated a high‐efficiency self‐supporting electrode with mesoporous FeP film coated on carbon cloth (meso‐FeP film/CC) for the hydrogen evolution reaction (HER). Compared with nanoparticle‐stacked disordered porous structure, the ordered mesoporous iron phosphide film exhibits high porosity as high as 2.3×1017 site per mg, as well as small pore size and uniform pore distribution, which enables the exposure of abundant active sites. Moreover, the self‐supporting structure with enhanced conductivity further optimizes its electrocatalytic performance towards the HER. As a result, the meso‐FeP film/CC displays a low overpotential (65 mV at current density of 10 mA cm−2) and a small Tafel slope (44 mV dec−1) in acid condition, which is competitive among most of noble‐metal free electrocatalysts.

One-step fabrication of TiO2/graphene hybrid mesoporous film with enhanced photocatalytic activity and photovoltaic performance

We synthesized a mesoporous film based on TiO2–reduced graphene oxide (RGO) hybrids using a one-step vapor-thermal method without the need for an additional annealing process. The vapor-thermally prepared TiO2-graphene hybrid (VTH) features unique structures with an ultra-large specific surface area of ˜260 m2 g−1 and low aggregation, giving rise to enhanced light harvesting and increased charge generation and separation efficiency. It was observed that a mesoporous film with uniform pore distribution is simultaneously obtained during the VTH growth process. When a 5.0 wt% RGO VTH film was used as the active layer in photocatalysis, the highest photocatalytic activity for degradation of methyl orange was achieved. For another, when a 0.75 wt% RGO VTH film was used as the photoanode in a dye-sensitized solar cell, the power conversion efficiency reached 7.58%, which represents an increase of 73.1% compared to a solar cell using an a photoanode of pure TiO2 synthesized by a traditional solvothermal method. It is expected that this facile method for the synthesis of TiO2/graphene hybrid mesoporous films will be useful in practical applications for preparing other metal oxide/graphene hybrids with ultra-high photocatalytic activity and photovoltaic performance.