Formation Of Microporous Structure Research Articles

Thermonanomechanics of graphene oxide-M13 bacteriophage nanocomposites -towards graphene-based nanodevices

The self-assembly of graphene oxide (GO) and M13 bacteriophage results in the formation of micro-porous structures, known as GraPhage13 aerogels (GPA). Given the limited applications of aerogels in industry due to their nanomechanical properties, along with the previously observed temperature-dependent characteristics in graphene-based nanocomposites, a thorough exploration of the thermosensitive nanomechanical properties of GPA is essential. Herein, a comprehensive characterisation of the morphology, composition, and spectroscopic analysis of the GPA for a range of temperatures has been conducted and correlated with its nanomechanical properties. Elevated temperatures have been found to lead to gradual removal of oxygen-containing functional groups (OCFGs) from GPA, resulting in increased structural defects and reduced stiffness. Notably, unique nanomechanical behaviours of GPA have been further identified, where the thermal expansion of sp3 bonds exceeds that of a crystalline sp3 structure, while the thermal contraction of sp2 bonds in GPA is found to be between graphite and GO. This underscores the impact of GO functionalisation on the thermal expansion behaviour of GPA. The obtained insights enhance the overall comprehension of the temperature annealing impact on GPA and highlight the tunability of its nanomechanical properties, showcasing a broad potential of this novel nanocomposite across a diverse range of applications.

Facile synthesis of regenerable NaY zeolite adsorbent relying on alcohol-terminated compounds for efficient trace sulfur dioxide capture

The selective removal of sulfur dioxide (SO2) is of importance for the desulfurization and purification of exhaust gases, but it is still challenging to design adsorbents with high capture capacities (particularly at low partial pressures) and great cyclic stability. Herein, a facile strategy is proposed to optimize the adsorption performance of NaY zeolites, where various alcohol-terminated compounds (n-pentanol, ethylene glycol, polyethylene glycol) with different molecular structures are introduced as auxiliaries to facilitate the zeolite nucleation process and the formation of microporous structures. These alcohols promote the crystallization of NaY, increase the specific surface area and expand the microporosity due to the formation of micelles during synthesis. Coupled with the rise of surface basic sites, the chemisorption and physisorption of SO2 on designed zeolites is considerably improved. The PEG-Y sample derived from polyethylene glycol gives the highest dynamic adsorption of SO2 (315 mg/g), high-level SO2 equilibrium adsorption (2.18 mmol/g) under exceptionally low pressure (0.002 bar), preferred separation performance of SO2 from SO2/N2, robust stability and great regenerability. This technique can be further employed to fabricate analogous adsorbents for other gas adsorption and separation processes.

Preparation of modified CO2‐based polyurethane for wet‐type artificial leather with excellent alkali resistance

AbstractPoly (propylene carbonate) diol (PPCD) is one of the most attractive CO2 copolymers. PPCD‐based polyurethane has excellent mechanical properties and hydrophilicity, and is widely used in various fields. However, poor alkali resistance limits the application of PPCD‐based polyurethane in wet‐type artificial leather (WPL). In order to solve this problem, polyurethane solution (PUS) for wet‐type artificial leather was prepared by using PPCD and polytetramethylene ether glycol (PTMG) as soft segments. The chemical structure, viscosity, molecular weight and distribution, physical and mechanical properties, thermal properties and dynamic mechanical thermal properties of PUS were characterized. The changes of the physical and mechanical properties of PUS films and surface morphology of WPLs after soaking in 10 wt% NaOH solution at room temperature for 24 h were studied, so as to evaluate the alkali resistance of polyurethane. The retention of tensile strength and tearing strength of PUS films modified by PTMG increased from 80% to 96% and from 89% to 100%, respectively. The scanning electron microscopy results showed that appropriate PTMG was beneficial to the formation of microporous structure for CO2‐based polyurethane leather. The leather without PTMG showed agglomeration phenomenon, the micropores were not obvious, and the changes were obvious after soaking in alkali solution. After being modified by PTMG, the morphology of leather after soaking in alkali solution was basically unchanged. Polyurethane leather prepared with PTMG and PPCD as soft segments has excellent alkali resistance. These results suggest that PPCD could be a potential artificial leather material.

Microporous Structure Formation of Poly(methyl methacrylate) via Polymerization-Induced Phase Separation in the Presence of Poly(ethylene glycol).

It has been demonstrated that nano- or micro-structured polymeric materials have huge potential as advanced materials. However, most of the current fabricating methods have limitations either in cost or in size. Here, we investigate the bulk polymerization of methyl methacrylate in the presence of poly(ethylene glycol) (PEG). We found that phase separation occurs during bulk polymerization. After removal of PEG via sonication, microscopic structures of poly(methyl methacrylate), including porous structures, co-continuous monolith structures, or particle aggregation structures, are formed. These structures can be controlled by the amount of PEG added and the reaction temperature. The results are summarized in phase diagrams. The addition of PEG significantly affects the reaction kinetics. Phase separation is coupled with the reaction acceleration known as the Trommsdorff effect. As a result, the reaction completes in a shorter time when the PEG amount is higher. We demonstrate surface coating to fabricate an amphiphobic surface, repelling both water and oil. The methods presented here have the potential to fabricate microscopic structures in large areas cost-effectively.

Catalytic Performance and Sulfur Dioxide Resistance of One-Pot Synthesized Fe-MCM-22 in Selective Catalytic Reduction of Nitrogen Oxides with Ammonia (NH3-SCR)-The Effect of Iron Content.

The catalytic performance of Fe-catalysts in selective catalytic reduction of nitrogen oxides with ammonia (NH3-SCR) strongly depends on the nature of iron sites. Therefore, we aimed to prepare and investigate the catalytic potential of Fe-MCM-22 with various Si/Fe molar ratios in NH3-SCR. The samples were prepared by the one-pot synthesis method to provide high dispersion of iron and reduce the number of synthesis steps. We have found that the sample with the lowest concentration of Fe exhibited the highest catalytic activity of ca. 100% at 175 °C, due to the abundance of well-dispersed isolated iron species. The decrease of Si/Fe limited the formation of microporous structure and resulted in partial amorphization, formation of iron oxide clusters, and emission of N2O during the catalytic reaction. However, an optimal concentration of FexOy oligomers contributed to the decomposition of nitrous oxide within 250–400 °C. Moreover, the acidic character of the catalysts was not a key factor determining the high conversion of NO. Additionally, we conducted NH3-SCR catalytic tests over the samples after poisoning with sulfur dioxide (SO2). We observed that SO2 affected the catalytic performance mainly in the low-temperature region, due to the deposition of thermally unstable ammonium sulfates.

Supercapacitor based on polymeric binary composite of polythiophene and single-walled carbon nanotubes

The aim of this work is to fabricate supercapacitor electrode based on poly (3-hexyl-thiophene-2, 5-diyl) (P3HT) and single-walled carbon nanotubes (SWCNTs) nanocomposites with different ratios onto a graphite sheet as a substrate with a wide voltage window in nonaqueous electrolyte. Structural, morphological and electrochemical properties of the prepared nanocomposites of P3HT/SWCNTs were studied and discussed. The electrochemical properties included cyclic voltammetry (CV), galvanostatic charging-discharging (GCD), and electrochemical impedance spectroscopy (EIS) were investigated. The obtained results indicated that P3HT/SWCNTs nanocomposite possesses higher specific capacitance than that present in its individual component. The high electrochemical performance of the nanocomposite was due to formation of microporous structure which facilitates ions diffusion and electrolyte penetration in these pores. The morphological micrographs of the purified SWCNTs had buckypaper structure while the photomicrographs of P3HT/SWCNTs showed that SWCNTs appear behind and front of the P3HT nanospheres. The specific capacitance of 50% SWCNTs at 0.5 Ag−1 was found to be 245.8 Fg−1 compared with that of pure P3HT of 160.5 Fg−1.

The fabrication of porous hollow polysulfone microspheres with PEG as a porogen for methylene blue adsorption

A porous hollow polysulfone (donated as PHPSF) microspheres were prepared by non-solvent-induced phase separation using PEG as a porogen. The influence of the molecular weights (Mw) of PEG on the morphology and porous structure of the microspheres were investigated. As the Mw of PEG increasing from 600 to 10,000 g·mol–1, the viscosity of the system increases, leading to the increase of the viscosity difference between the dispersed phase and the continuous phase, and a delay in phase separation. Hence, the diameter and shell thickness of the obtained microspheres increase with the porosity reducing. Moreover, when the Mw of PEG is below 4000, the low |Δδ| between PEG and solvent is conducive to the formation of microporous structure with narrow pore distribution. The as-prepared PHPSF microspheres exhibit a separation efficiency of 6 times for MB than that of the original PSF microspheres. In addition, a reusability of 5 times of PHPSF is achieved even in the harsh acid or alkali condition. These results clarify the relationship between the different Mw of PEGs and microspheres morphology. Therefore, this kind of PHPSF microspheres holds a promising for the water organic pollution treatment.

Computer Analysis of the Effects of Time and Gas Atmosphere of the Chemical Activation on the Development of the Porous Structure of Activated Carbons Derived from Oil Palm Shell

The results of the advanced computer analysis of the influence of time and gas atmosphere of the chemical activation process on the microporous structure formation of activated carbons prepared from oil palm shell via microwave irradiation and activation, using potassium hydroxide as an activation agent, are presented in this paper. The quenched solid density functional theory (QSDFT) and the new numerical clustering-based adsorption analysis (LBET) methods were used especially in the analysis of the microporous structure of the activated carbons, taking into account the surface heterogeneity, and the results obtained were confronted with the simple results achieved earlier using Brunauer–Emmett–Teller (BET) and T-plot methods. On the basis of the computer analysis carried out and taking into account the results obtained, it has been shown that the material with the best adsorption properties and suitable for practical industrial applications is activated carbon obtained in a gaseous nitrogen atmosphere at an activation time of 30 min. Moreover, the value of the heterogeneity parameter indicates that the surface area of this activated carbon is homogeneous, which is of particular importance in the practical application. The paper emphasizes that an erroneous approach to the interpretation of analytical results based on gas adsorption isotherms, which consists in basing conclusions only on the values of a single parameter such as specific surface area or micropore volume, should be avoided. Therefore, it is recommended to use in the analysis of measurement data, several methods of porous structure analysis, including methods considering the heterogeneity of the surface, and when interpreting the results one should also take into account the adsorption process for which the analyzed materials are dedicated.

Comparative Braking Performance Evaluation of a Commercial and Non-asbestos, Cu-free, Carbonized Friction Composites

Carbonization treatment contributes to improvement of tribological properties of friction composites. Pure Non-asbestos organic (NAO) friction raw materials were selected, friction composite specimens had been made using a new mixing process and carbonization treatment. Two types of specimens had been prepared to evaluate their performance, one was carbonized a pure non-asbestos organic friction composite specimen and the other was an original brake metal linings of a certain brand of vehicles. Two friction composites were evaluated by brake inertia dynamometer. Their performances were assessed according to the procedure in a European Union Automobile Standards (AK Master). Microscopic photographs of worn surfaces were obtained by scanning electron microscopy to characterize their tribological behavior and wear mechanism. The results showed that pure NAO friction composites had more suitable frictional properties, fade and recovery behavior than the copper-containing metal brake pad, but wear resistance was slightly lower. Carbonation promoted the formation of microporous structure in friction composites, which was helpful to reduce noise and vibration during work.

Nitrogen-Doped Microporous Carbon Prepared by One-Step Carbonization: Rational Design of a Polymer Precursor for Efficient CO2 Capture

Nitrogen-doped microporous carbon using carboxylic acid-functionalized imidazole-type polymers (PDVA) as a carbon precursor was fabricated by a one-step carbonization method without an additional activator. The introduction of acrylic acid was beneficial to promote the formation of microporous structures during the pyrolysis process. By changing the carbonization temperature, the textural properties and surface nitrogen content of the carbon materials were tuned. The synergistic effect of the microporous structure and basic nitrogen sites was conducive to enhancing the CO₂ adsorption performance of porous carbon materials. The CO₂ adsorption quantity of PDVA-C-800 obtained without an additional activator reached 3.18 mmol·g–¹ under 1 bar at 25 °C, which was comparable to that of the reported carbon materials. Besides, PDVA-C-800 possessed excellent cycle stability and recyclability. The fabrication of microporous nitrogen-doped carbon derived from carboxylic acid-functionalized imidazole-type polymers provided an original idea for CO₂ uptake.

The Characterization of Banana Blossom Peel and Floret as an Adsorbent for the Removal of Manganese in Groundwater

Manganese (Mn) is one of the most serious pollutants that have negative effects on the ecosystem and water supply. The water industry faces major challenges in its treatment for contaminant and in developing an alternative product with low cost. Among various adsorbents, agriculture waste is preferred due to its biodegradability and availability. The removal of manganese (Mn) from groundwater was investigated using two different adsorbents which are banana blossom peel and floret. SEM analysis shows the formation of microporous structure for both banana blossom peels and floret while FTIR analysis confirms the functional group of strong hydroxyl group that responsible for the adsorption process. The water quality index for the groundwater sample was classified into class III which required extensive treatment. Batch adsorption experiments revealed that both adsorbents had maximum removal efficiency using 0.5 g adsorbent dosage. The banana blossom peel reduces Mn to 0.10 mg/L with 81.1% removal, while the banana blossom floret reduces Mn concentration to 0.12 mg/L with 77.7% removal.

Intercalation chemistry and thermal characteristics of layered double hydroxides possessing organic phosphonates and sulfonates

The distinct roles of organic sulfonates that enable delamination in water and formation of microporous structures via thermal activation are elucidated.

Understanding reactions and pore-forming mechanisms between waste cotton woven and FeCl3 during the synthesis of magnetic activated carbon.

FeCl3 is a valuable iron salt used in the synthesis of magnetic waste cotton woven-based activated carbon. Although it has received extensive research attention, more information is required regarding its interactions with the carbon matrix. This systematic study describes the potential reactions of FeCl3 and waste cotton woven. First, the textural properties of waste cotton woven-based activated carbon synthesized under various conditions were investigated via element analysis, N2 sorption/desorption isotherms, and scanning electron microscopy. Then, the possible reaction mechanisms were deduced through various characterization methods. The results demonstrate that FeCl3 can lower the initial decomposition temperature of WCW to 135 °C and catalyze decarboxylation and decarbonylation at 100-330 °C to elevate the formation of microporous structures. Moreover, FeCl3 can also form Lewis acid sites at 330-700 °C and promote the cross-linking reaction to develop intricate microporous structures and carbonaceous materials with the synergistic effect of Fe3+ and Cl-. FeCl3 could be used as a template-like agent to form mesoporous structures. Meanwhile, it can also act as a magnetizer that Fe3O4 derived from the decomposition of FeCl3 would insert into the carbon matrix and combine with C-Cl to tailor the magnetic controllable activated carbon. Finally, we confirmed that extending the activation time could convert the structure of waste cotton woven-based activated carbon and increase the number of active sites, thereby further improving the catalytic properties of FeCl3 in pore formation.

3D Plotting using Camphene as Pore-regulating Agent to Produce Hierarchical Macro/micro-porous Poly(ε-caprolactone)/calcium phosphate Composite Scaffolds.

This study demonstrates the utility of camphene as the pore-regulating agent for phase separation-based 3D plotting to produce hierarchical macro/micro-porous poly(ε-caprolactone) (PCL)–calcium phosphate (CaP) composite scaffolds, specifically featuring highly microporous surfaces. Unlike conventional particulate porogens, camphene is highly soluble in acetone, the solvent for PCL polymer, but insoluble in coagulation medium (water). In this study, this unique characteristic supported the creation of numerous micropores both within and at the surfaces of PCL and PCL–CaP composite filaments when using high camphene contents (40 and 50 wt%). In addition, the incorporation of the CaP particles into PCL solutions did not deteriorate the formation of microporous structures, and thus hierarchical macro/micro-porous PCL–CaP composite scaffolds could be successfully produced. As the CaP content increased, the in vitro biocompatibility, apatite-forming ability, and mechanical properties (tensile strength, tensile modulus, and compressive modulus) of the PCL–CaP composite scaffolds were substantially improved.

Recent progress in microfiltration polypropylene membrane fabrication by stretching method

Microfiltration polypropylene (MF-PP) membrane has been widely used in many industries due to their excellent combination of good separation performances and low production cost. In addition to membrane configuration, the structure of MF-PP membrane also plays an important role in separation performance. MF-PP membrane is commonly produced by thermal induced phase separation (TIPS) and stretching. TIPS is the simplest one where the polymer is dissolved in a solvent at a decent temperature and then cooled to induce phase separation which leads to the formation of microporous structure. However, this method is limited by the nature of PP that is difficult to dissolve in organic solvents and the solvent-contaminated effluent produced during the fabrication process. Therefore, the stretching method is more favorably used. The Stretching method involves four processing stages in sequence (i.e. melt-extrusion, annealing, stretching, and heat setting). Polymer composition, extrusion draw ratio, as well as stretching rate and temperature, are important parameters that significantly affect the pore structures evolved and thus the properties as well as the performances of MF-PP membrane. In this paper, the recent development of MF-PP fabrication by stretching methods as well as the parameters involved in each method will be reviewed and discussed comprehensively.

Highly Microporous Nitrogen-doped Carbon Synthesized from Azine-linked Covalent Organic Framework and its Supercapacitor Function.

Porous carbons with nitrogen-doped (N-doped) structures are promising materials for advanced energy conversion and storage applications, including supercapacitors and fuel cell catalysts. In this study, microporous N-doped carbon was successfully fabricated through carbonization of covalent organic frameworks (COFs) with an azine-linked two-dimensional molecular network (ACOF1). In the carbonized ACOF1, micropores with diameters smaller than 1 nm are selectively formed, and a high specific surface area (1596 cm2  g-1 ) is achieved. In addition, the highly porous structure with N-doped sites results in enhancement of the electrochemical capacitance. Detailed investigation for the micropore-forming process reveals that the formation of nitrogen gas during the thermal degradation of the azine bond contributes to the microporous structure formation. Therefore, the present direct carbonization approach using COFs allows the fabrication of microporous heteroatom-doped carbons, based on molecularly designed COFs, toward future electrochemical and energy applications.

Investigation of Antibacterial and Fouling Resistance of Silver and Multi-Walled Carbon Nanotubes Doped Poly(Vinylidene Fluoride-co-Hexafluoropropylene) Composite Membrane.

Composite membranes were successfully prepared using a phase-inversion method. The X-ray powder diffraction (XRD) and energy dispersive X-ray (EDX) profiles has confirmed formation of 4.8 wt % Ag/poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP), 3 wt % Ag-MWCNTs/PVDF-HFP (EDX surface composition of Ag nanoparticles) and 1.5 wt % MWCNTs/PVDF-HFP composite membranes. The MWCNTs crystallites are mainly encapsulated by a layer of PVDF-HFP, as evidenced by disappearance of graphitic peak. The scanning electron microscopy (SEM) images have depicted the formation of microporous structure, with few MWCNTs on the surface and strongly interacting with PVDF-HFP as demonstrated by thermogravimetric analysis (TGA), XRD and Fourier transform infrared (FTIR) data. The data indicated an increase in porosity, swellability and water content of the PVDF-HFP membrane with the addition of MWCNTs and/or Ag nanoparticles, showing an improved hydrophilicity. The 1.5 wt % MWCNTs/PVDF-HFP composite membrane showed good desalination and fouling resistance rates, which correlates with a low water contact angle. The combined effects of Ag nanoparticles and MWCNTs do not promote fouling resistance of PVDF-HFP membranes, as shown during NaCl microfiltration (this is linked with high water contact angle as compared to that of MWCNTs/PVDF-HFP composite). Both 1.5 wt % MWCNTs/PVDF-HFP and 3 wt % Ag-MWCNTs/PVDF-HFP composite membranes prevented the bacteria passing through the membrane (100% bacterial load reduction). The surface of 3 wt % Ag-MWCNTs/PVDF-HFP showed good bactericidal and non-leaching properties of the dopant materials (MWCNTs and Ag), as evidenced by bacterial growth on the edges of the membranes.

Preparation and formation mechanism of porous carbon cryogel

A facile fabrication of a porous carbon cryogel from a blend (PAEO) of fluorinated poly(amic acid) and poly(ethylene oxide) (PEO) is demonstrated. The porous carbons are prepared by carbonizing the freeze-dried cyrogels of polymer blend with various contents. The original channel structures of the cryogels with PEO content below 5 wt% are perfectly maintained in the carbon cryogels. In particular, the carbon cyrogel derived from the blend (PEO content: 5 wt%) shows very high specific surface areas, 2646 m2/g. From investigation of the carbonization mechanism, it is found that the incorporation of PEO creates mesoporous structure without generating hydrophobic or ambiphilic components, while elimination of fluorine moiety affects the formation of microporous structure in resulting-carbon. In addition, the porous structure in carbon cryogels of high PEO loading is shrunk because PEO component reduces the rigidity of the structure. Lastly, the performance of the carbon cryogels as a capacitor is investigated.

Numerical analysis of the influence of the impregnation ratio on the microporous structure formation of activated carbons, prepared by chemical activation of waste biomass with phosphoric(V) acid

This paper presents the results of the application of new mathematical adsorption models with the unique numerical fast multivariate identification procedure as the tool for analysing the influence of the impregnation ratio i.e. activator to the raw material mass ratio on the microporous structure development of the activated carbons, obtained from sugarcane bagasse and rice husk by chemical activation with phosphoric(V) acid.

3D printed PEGDA microstructures for gelatin scaffold integration and neuron differentiation

Three dimensional (3D) printing techniques can be used for scaffold fabrication but the most of them are limited by resolution and material choice. To bypass these limitations, we developed an approach by combining conventional 3D printing and freeze-drying techniques to produce lattice-type backbone and embedding microporous structures. Polyethylene glycol diacrylate (PEGDA), a biocompatible and photosensitive pre-polymer, was chosen for 3D printing of the backbone, while gelatin was used for the formation of microporous structures. The fabricated PEGDA/gelatin scaffolds were used for culture and differentiation of neural progenitor cells (NPCs), showing infiltration of the cells and outgrowth of differentiated neurites. This strategy of combined use of 3D printing and freeze-drying techniques might be useful for scaffold fabrication in terms of easy design and easy material processing.