Uniform Microporous Structure Research Articles

A microfluid-on-microfluid phase separation strategy fabricates high-throughout porous polyimide separator for lithium-ion batteries

The microstructures and thermal stability of separators are critical for the safety and performance of lithium-ion batteries; however, it is still challenging to fabricate advanced separators simultaneously achieving uniform and high-throughput interconnected microporous structures with high thermal stability. Here, based on a soluble polyimide (PI) with high thermal stability, we report a microfluid-on-microfluid phase separation strategy (MF2-PS) to address the above challenge. Compared to the traditional non-solvent induced phase separation by immersion, the MF2-PS strategy can achieve more controlled porous structures with sponge-like open channels at submicron scale. The high surface polarity of the PI-separator also exhibited good wettability with liquid electrolytes, and a high electrolyte uptake (182 wt%) for achieving a high ion-conductivity. It also showed much superior thermal stability as compared to PP separator. Finally, due to the unique porous structures, the PI-separator by MF2-PS strategy successfully delivered a discharge capacity of 161.9 mA h g−1 for LiFePO4 electrode, and very stable cycling performance. All these results indicates that the PI-separator by MF2-PS may find significant applications in safe and high-performance batteries.

Zeolite Imidazolate Frameworks-8@SiO2-ZrO2 Crystal-Amorphous Hybrid Core-Shell Structure as a Building Block for Water Purification Membranes.

Metal-organic frameworks (MOFs) are emerging as promising materials for water purification membranes, owing to their uniform microporous structures and chemical functionalities. Here, we report a simple procedure for depositing MOF-based nanofiltration membranes on commercial TiO2 ceramic tubular supports, completely avoiding the use of dispersants or binders. Zeolite imidazolate frameworks-8 (ZIF-8) nanocrystals were synthesized in methanol at room temperature and subsequently coated with an amorphous SiO2-ZrO2 gel to generate a dispersion of ZIF-8@SiO2-ZrO2 core-shell nanoparticles. The amorphous SiO2-ZrO2 gel served as a binding agent for the ZIF-8 nanocrystals, thus forming a defect-free continuous membrane layer. After repeating the coating twice, the active layer had a thickness of 0.96 μm, presenting a rejection rate >90% for the total organic carbon in an aquaculture effluent and in a wastewater treatment plant, while reducing the concentration of trimethoprim, here used as a target pollutant. Moreover, the oxide gel provided the MOF-based active layer with good adhesion to the support and enhanced its hydrophilicity, resulting in a membrane with excellent mechanical stability and resistance to fouling during the crossflow filtration of the real wastewater samples. These results implied the high potential of the MOF-based nanocomposite membrane for effective treatment of actual wastewater streams.

Exceptional cyclability of thermally stable PVdF-co-HFP/SiO2 nanocomposite polymer electrolytes for sodium ion batteries

Thermally stable composite polymer electrolyte (CPE) devising PVdF–co–HFP polymer with in–situ generated silica (SiO2) as filler is synthesised via non–solvent– induced phase inversion technique. The filler loading of in–situ synthesised silica in PVdF–co–HFP is varied from 0 to 9 wt% and its morphological, thermal and electrochemical characterization is carried out. Among the different composite electrolytes, the PVdF–co–HFP containing 6 wt% SiO2 shows the uniform microporous structure with a highest porosity (84 %), surface area (784.14 m2 g−1), electrolyte uptake (262 %) and electrolyte retention value (0.48). The incorporation of in–situ SiO2 on CPE shows not only the enhancement in thermal stability but also reduced thermal shrinkage with an increase in the filler content. The electrochemical studies of PVdF–co–HFP containing 6 wt% SiO2 shows a higher ionic conductivity (0.71 mS cm−1) and potential stability >4.5 V verses Na/Na+. The Na–ion half–cells assembled with PVdF–co–HFP/SiO2 composite electrolyte show a specific capacity of ∼120 mAh g−1 at 0.3C rate in room temperature and a stable cycle performance with a Coulombic efficiency of around 100 % for 200 cycles.

Developing sustainable and recyclable high-efficiency electromagnetic interference shielding nanocomposite foams from the upcycling of recycled poly(ethylene terephthalate)

The demand for high-performance electromagnetic interference (EMI) shielding composite foams with satisfactory environmental friendliness and high sustainability has increased considerably. However, considerable obstacles are frequently encountered in the practical development of incorporating upcycling of plastic wastes and environmentally friendly foaming technologies into the manufacture of such EMI shielding systems. In this research, we developed a lightweight sustainable nanocomposite foam system with outstanding EMI shielding performance from the integration of chemical upcycling of recycled poly(ethylene terephthalate) (PET) and supercritical carbon dioxide (sc-CO2) microcellular foaming. First, a green thermoplastic polyamide elastomer (TPAE) system was synthesized using a renewable bis(6-aminohexyl)terephthalamide (BAHT) monomer derived through the aminolysis of recycled PET, followed by adding single-walled carbon nanotubes (SWCNTs) into the TPAE system for the manufacture of TPAE/SWCNT nanocomposites. The π–π stacking of BAHT efficiently enhanced the melt strength of the material system, which was conducive for microcellular foaming process. After sc-CO2 foaming, a series of highly expanded nanocomposite foams with uniform microporous structure that could enable multiple reflections of electromagnetic waves were fabricated. Upon adding only 2 wt% SWCNTs, the foam system achieved a favorable conductivity of 0.15 S/cm and an extremely high specific shielding effectiveness (SSE) of 213.26 (dB cm3/g). Furthermore, the green nanocomposite foam possessed excellent durability. After being bent or twisted 1000 times, the foam maintained EMI shielding effectiveness of > 90% of the original value. Moreover, the foam could be easily recycled, reprocessed, and refoamed. For developing sustainable EMI shielding products, we believe that this study provides a promising direction with benefits of alleviating waste accumulation and reducing the use of virgin plastics in manufacture of foams, showing potential for advanced sustainable electronic applications.

Quest for high-performance gel polymer electrolyte by enhancing the miscibility of the bi-polymer blend for lithium-ion batteries: performance evaluation in extreme temperatures

A novel approach to enhance the miscibility of polyvinylidene difluoride (PVdF)/polymethyl methacrylate (PMMA) blend polymer electrolyte is introduced by in-situ polymerization of methyl methacrylate monomers in PVdF matrix. The phase inversion membrane of PVdF/PMMA blend exhibits uniform microporous structure with high porosity, better electrolyte uptake (413%), retention, and lower contact angle. The structural characterization of the membranes is analyzed with Fourier transform infrared spectroscopy. The thermal stability is examined by thermogravimetric analysis and differential scanning calorimetry. The miscibility of the blend is confirmed from examining the blend solution for 100 days. The optimized blend electrolyte system with 50 wt% of the PMMA (gel polymer electrolyte [GPE-50]) reveals better ionic conductivity of 5.2 mS/cm at room temperature. The GPE is capable to establish high anodic stability up to 4.8 V vs. Li/Li+ and a better electrode compatibility. The initial discharge capacity observed for the Li/LiFePO4 cell with GPE-50 is about 162 mAh/g at 0.1C at 25 °C with 95% of cathode utilization of the material. The device-level evaluation ensures that the GPE with good charge–discharge performance and stable cycling can be used for future lithium-ion batteries.

Regulating Li-ion flux via engineering oxidized ZIF-8/polyacrylonitrile fiber interlayer for Li metal batteries with high performance

A novel oxidized ZIF-8/polyacrylonitrile fiber interlayer with excellent lithophilicity and uniform microporous structure could regulate Li-ion flux to obtain high performance of Li metal batteries.

MOF-derived 3D porous carbon aerogels as an efficient adsorbent for toluene in humid air

Due to the ecological and health hazards of volatile organic compounds (VOCs), the removal of industrial VOCs has become an important issue of increasing concern. In this work, we synthesized easy-processing ZIF-8/agarose composite porous carbon aerogels and investigated their toluene adsorption performance. Results indicated that carbon aerogels had large specific surface area, uniform microporous structure and high nitrogen content. The toluene adsorption capacity of carbon aerogel was 511.2 mg/g under RH50%, which was higher than that of commercial adsorbents and other MOFs with the same specific surface area. The adsorption mechanism of carbon aerogels was further studied via DFT method and was determined as pore-filling effect, π-π interaction and electron donor/acceptor interaction. In addition, carbon aerogels also showed high efficiency and recyclability which kept 70% adsorption capacity at ambient humidity and successfully regenerated after three cycles without obvious loss of adsorption capacity. Therefore, the high adsorption capacity and recyclability facilitate the synthesized aerogels become a promising adsorbent in VOCs adsorption field.

Preparation of Centella asiatica loaded gelatin/chitosan/nonwoven fabric composite hydrogel wound dressing with antibacterial property

Antibiotics abuse and the emergence of massive drug-resistant bacteria have become the major obstacles in the medical system. Thus, designing an antibiotic-free wound dressing with antibacterial activity and decent biocompatibility is urgently desired. Herein, the sandwich-like composite hydrogel wound dressings were developed by intercalating nonwoven fabrics (NF) as the middle layer, gelatin and chitosan (Gel-CS) hydrogel loaded with Centella asiatica (CA) as the base materials. In addition, soaking strategy was employed to improve the mechanical properties of hydrogels. The hydrogels exhibited uniform microporous structure, stable mechanical property, high water absorbency, as well as water vapor transmission rate. After loading with CA, the composite wound dressing showed the sustained drug release properties in vitro and excellent antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The cytotoxicity results demonstrated that the composite hydrogels had good biocompatibility. This work indicates that the nonwoven composite hydrogels have broad application prospects in the field of medical care in the future.

Microreactor facilitated preparation and Ni-doping of MnO2 nanoparticles for supercapacitors

Clustered countercurrent-flow micro-channel reactors (C-CFMCR) with varying magnification times were applied for the preparation of Ni-doped manganese dioxide (Ni-MnO2) via co-precipitation processes. Effects of the feeding flow rate of reactants and the concentration of the doping agent on the doping processes were investigated. The C-CFMCR, which is of intensified micromixing efficiency as compared with conventional stirred reactors (STR), played a crucial role in facilitating the uniform nucleation and growth of MnO2 crystals and then the doping of Ni. As a result, the prepared Ni-MnO2 had a decreased particle size and a more uniform microporous structure. EDS analysis showed an even distribution of Ni2+ within the nanocomposites and thus enhanced electrochemical performance of the MnO2 composite materials as supercapacitor electrodes was achieved. The 1.0 at% Ni-MnO2 nanocomposites prepared under optimal conditions exhibited the highest specific capacitance of ~ 389.6 F g−1 at a current density of 1 A g−1 and showed excellent cycling stability with 79.3% retention of the initial capacitance after 5000 charge/discharge cycles in 2 M KOH aqueous solution. The as-assembled Ni-MnO2//activated carbon (AC) asymmetric supercapacitor displayed a wide operating voltage (0–1.6 V), high energy and power densities (13.3 W h kg−1 and 187.52 W kg−1 at 0.25 A g−1, respectively), and a stable cycling behavior (83.8% capacitance retention after 1000 cycles at 1 A g−1). In addition, only a weak scaling-up effect of C-CFMCR on the co-precipitation process was observed, suggesting that C-CFMCR is a prospective technique for the continuous and large-scale production of nanoparticles.

A Facile and In-situ Methanol-mediated Fabrication of Low Pd Loading, High-efficiency and Size-selectivity Pd@ZIF-8 Hydrogenation Catalyst.

In-situ encapsulation of tiny and well-dispersed Pd nanoparticles (Pd NPs) in zeolitic imidazolate frameworks (ZIFs) was firstly achieved using a one-pot and facile methanol-mediated growth approach, in which methanol served as both solvent and a mild reductant. The microstructure, morphology, crystallinity, porosity as well as evolution process of the catalysts were determined by TEM, XRD, N2 adsorption and UV-vis spectra. Due to the complete encapsulation of such Pd NPs combined with ultrahigh surface area and uniform microporous structure of ZIF-8, the resulting Pd@ZIF-8-60 min nanocomposite exhibited more superior catalytic activity for olefins hydrogenation with TOF of 7436 h-1 and excellent size selectivity than previously reported catalysts. Furthermore, the catalyst displays excellent recyclability for 1-octene hydrogenation and without any loss of the Pd active species.

High-performance nickel coating on SLM 316L stainless steel processed by jet electrochemical machining and jet electrodeposition

Selective laser melting (SLM) is an important method in additive manufacturing. SLM has obvious advantages for the fabrication of metal parts with complex structure that cannot be processed directly and are manufactured in relatively low amounts. However, the surfaces of the SLM-formed parts contain more adhesive particles and pores than those manufactured by traditional methods, leading to the poor corrosion resistance of the parts and preventing the widespread use of SLM. To solve these problems, jet electrochemical machining and jet electrodeposition combined processing techniques were investigated for the treatment of the substrate surface in this work. Jet electrochemical machining was used to remove the surface defects of the SLM-formed parts, and the results were compared with the traditional sandblasting and sandpaper grinding surface treatment methods. Then, the nickel coating was deposited on the surface of the SLM-formed parts using jet electrodeposition to protect the surface and extend the service life of the parts. The mechanisms of the different processing techniques were analyzed, and properties such as the substrate morphology, coating morphology, corrosion resistance of the coating, and adhesion of the coating were compared. The results show that holes, adhesive particles and other defects are still present on the substrate surface after sandpaper grinding and sandblasting and affect the quality of the nickel coating. After electrochemical machining, the SLM surface defects were almost completely removed, forming a uniform microporous structure that interlocked with the nickel coating. The coating was smooth and dense and showed the best corrosion resistance and binding force. In 3.5 wt% NaCl solution, the corrosion potential reached −0.196 V, and the maximum binding force reached 35 N.

A Robust Surface-Modified Separator Fabricated with Roll-to-Roll Atomic Layer Deposition and Electrohydrodynamic Deposition Techniques for High Temperature Lithium Ion Batteries

A multilayer separator is developed by the deposition of ultrathin polyvinylidene fluoride (PVDF) and aluminum oxide (Al2O3) layers on polyolefin separator using in-house designed novel roll-to-roll atmospheric atomic layer deposition (R2R-AALD) and electrohydrodynamic atomization (EHDA) methods. The conformal coatings of ultrathin PVDF (∼5 um) and Al2O3 (∼10 nm) layers form a highly uniform interconnect microporous structure, which enhances thermal stability and mechanical strength. The deposition of PVDF and Al2O3 layers also improves electrolyte wettability and electrolyte uptake (256%), which gives rise to ionic conductivity. The Al2O3/PVDF/Celgard separator shows excellent thermal stability with minimal shrinkage up to 180 °C and robust mechanical strength. The lithium cobalt oxide/graphite (LCO/graphite) cells based on as-developed multilayer separator deliver excellent discharge capacity of 130.9 mAh g−1 at 0.5 C after 150 cycles and capability of 99.6 mAh g−1 at 5 C after 100 cycles at room temperature. Moreover, the LCO/graphite cells with Al2O3/PVDF/Celgard separator also show remarkable cyclic performances at elevated temperatures. The as-developed separator proves to be a better candidate for high capacity lithium ion batteries, especially for high temperature conditions.

Modulating hierarchically microporous biochar via molten alkali treatment for efficient adsorption removal of perfluorinated carboxylic acids from wastewater

This work presented a three-dimensional (3D) hierarchically microporous biochar (HMB) via molten alkali treatment that achieved efficient adsorption of perfluorinated carboxylic acids (PFCAs), which was a significant environment concern due to the global distribution and potential health risks. The systematic optimization of fabrication process rendered the HMB large surface area and uniform microporous structure, leading to a high adsorption capacity and adsorption rate of 1269 mg/g and 197 mg/(g·min), respectively, when perfluorooctanoic acid (PFOA) was as a representative. The adsorption mechanisms were explored via controlling the interaction between PFCAs and the HMB900-2.4. Specifically, hydrophobic effect was verified by the enhanced adsorption performance with the increase of the PFCAs homologues hydrophobicity. The observed highly pH-dependent adsorption capacity additionally suggested the dominant contribution of electrostatic interaction. For long-chain PFCAs (CnF2n+1COOH, n > 5), the HMB900-2.4 presented a high removal efficiency (> 90%) within 30 min. Even for short-chain PFCAs (CnF2n+1COOH, n = 4–5), the removal efficiency reached to over 60%. The synthesized HMB900-2.4 exhibited high stability during recycling experiments and superior performance over commercial adsorbents, suggested a promise of utilizing it to remove PFCAs from wastewater.

Preparation and characterization of microporous magnesia‐based refractory

AbstractIn recent years, there was a huge demand for basic lightweight insulation materials in the metallurgical industry, especially magnesia‐based refractories with low thermal conductivity. Therefore, the preparation of microporous magnesia‐based refractory products through the synthesis of lightweight aggregate and the different grain compositions to meet the supply of light basic refractories is discussed in this paper. The microstructure, pore size distribution, phase composition, coefficient of thermal expansion, thermal conductivity and sintering properties of the microporous magnesia‐based refractory products sintered at 1600°C were characterized. The results indicated that the original salt pseudomorph produced by the thermal decomposition of magnesite fine powder (porogenic agent) provides a uniform microporous structure for the synthesis of lightweight aggregates. The microporous morphology of the periclase phase was controlled by adjusting the content of the porogenic agent. The average pore size of microporous magnesia‐based refractory ranged from 1.5 to 4.2 μm, and the apparent porosity increased from 29.88% to 32.46%. In the same time, the thermal conductivity increased from 0.037 to 0.217 W/(m K), indicating that the introduction of homologous porogenic agents could produce lightweight alkaline refractories with high porosity and low thermal conductivity.

Highly Sensitive Strain Sensor Based on a Stretchable and Conductive Poly(vinyl alcohol)/Phytic Acid/NH2-POSS Hydrogel with a 3D Microporous Structure

Conductive hydrogel-based wearable strain sensors with tough, stretchable, self-recoverable, and highly sensitive properties are highly demanded for applications in electronic skin and human-machine interface. However, currently, hydrogel-based strain sensors put forward higher requirements on their biocompatibility, mechanical strength, and sensitivity. Herein, we report a poly(vinyl alcohol)/phytic acid/amino-polyhedral oligomeric silsesquioxane (PVA/PA/NH2-POSS) conductive composite hydrogel prepared via a facile freeze-thaw cycle method. Within this hydrogel, PA acts as a cross-linking agent and ionizes hydrogen ions to endow the material with ionic conductivity, while NH2-POSS acts as a second cross-linking agent by increasing the cross-linking density of the three-dimensional network structure. The effect of the content of NH2-POSS is investigated, and the composite hydrogel with 2 wt % NH2-POSS displays a uniform and dense three-dimensional (3D) network microporous structure, high conductivity of 2.41 S/m, and tensile strength and elongation at break of 361 kPa and 363%, respectively. This hydrogel is biocompatible and has demonstrated the application as a strain sensor monitoring different human movements. The assembled sensor is stretchable, self-recoverable, and highly sensitive with fast response time (220 ms) and excellent sensitivity (GF = 3.44).

Zeolite-Enhanced Sustainable Pd-Catalyzed C-C Cross-Coupling Reaction: Controlled Release and Capture of Palladium.

Supported palladium catalysts have attracted significant attention for use in cross-coupling reactions due to their recyclability. However, the inevitable progressive loss of Pd that occurs in the catalytic process deactivates the catalysts, which hinders their sustainable application. Herein, we report a zeolite-enhanced sustainable Pd catalyst for C-C cross-coupling reactions. Zeolite does a good job of acting as a sink for Pd2+ ions. This catalyst exhibits an excellent homogeneous catalytic performance by releasing Pd species from zeolite. In addition, the Pd2+ ions were successfully recaptured in a controlled catalytic system by combining the uniform microporous structure and good adsorption features of zeolite. The release/capture mechanism of the Pd species guaranteed the high loading and high dispersion of Pd on the recycled catalyst. The 0.84%Pd@USY catalysts were reused at least 10 times in water without an appreciable reduction in activity. This study presents a new perspective toward the design of a highly efficient and sustainable supported metal catalyst.

Pore structure of reactively synthesized nanolaminate Ti3SiC2 alloyed with Al

Ti3SiC2 has the unique properties integrating the advantages of metals and ceramics, and good open pore structure when alloyed with Al. In this work, porous Ti3SiC2 compounds with different Al/Si atom ratios were prepared through the reactive synthesis of elemental powders at 1300 °C. The results indicate that the phase compositions are determined by Al element mole number, and that the pore structure can be controlled through varying Ti particle size. The MAX phase transits from Ti3SiC2 with Al element mole number no more than 0.6 to Ti3AlC2 with Al element mole number in the range of 0.8–1.2. When Al element mole number is 0.6, the porous compound has a single MAX phase of Ti3SiC2 with uniform microporous structure and high bending strength. Porous Ti3SiC2 alloyed with 0.6Al has a slow linear increase rate of 0.0083%/μm in open porosity with increasing Ti particle size, and a strict linear relationship between the maximum aperture and Ti particle size with the increase rate of 0.0342 μm/μm. The pore structure formed by the phase transition mechanism for porous MAX phase has the smallest tortuosity factor compared with that formed by the clearance mechanism and the Kirkendall effect.

MOF-Confined Sub-2 nm Stable CsPbX3 Perovskite Quantum Dots.

The metal halide with a perovskite structure has attracted significant attention due to its defect-tolerant photophysics and optoelectronic features. In particular, the all-inorganic metal halide perovskite quantum dots have potential for development in future applications. Sub-2 nm CsPbX3 (X = Cl, Br, and I) perovskite quantum dots were successfully fabricated by a MOF-confined strategy with a facile and simple route. The highly uniform microporous structure of MOF effectively restricted the CsPbX3 quantum dots aggregation in a synthetic process and endowed the obtained sub-2 nm CsPbX3 quantum dots with well-dispersed and excellent stability in ambient air without a capping agent. The photoluminescence emission spectra and lifetimes were not decayed after 60 days. The CsPbX3 quantum dots maintained size distribution stability in the air without any treatment. Because of the quantum confinement effect of CsPbX3 quantum dots, the absorption and photoluminescence (PL) emission peak were blue shifted to shorter wavelengths compare with bulk materials. Furthermore, this synthetic strategy provides a novel method in fabricating ultra-small photoluminescence quantum dots.

Enhanced thermal and electrochemical properties of poly(vinylidene fluoride-co-hexafluoropropylene)-based composite polymer electrolytes doped with CaTiO3 dielectric ceramics

Poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP))-based composite polymer electrolytes (CPEs) doped with different amounts of CaTiO3 inorganic fillers are prepared by phase inversion. With adding the CaTiO3 fillers into the P(VDF-HFP) polymer matrix, the CPE membranes show more abundant and uniform micro-pore structure with lower crystallinity, better thermal stability and mechanical strength. The characterization results show that the ionic conductivity at room temperature and electrochemical working window of the CPE doped with 5 wt% CaTiO3 fillers (CPE-5) can be up to about 3.557 mS cm−1 and 5.1 V, respectively. The interfacial resistance of the Li/CPE-5/Li simulated cell can quickly stabilize at 750 Ω after 5 days storage, and the assembled LiCoO2/CPE-5/Li coin cell shows excellent rate and cycle performance. Moreover, the CPE-5 membrane can still well maintain the original micro-pore structure after 100 cycles at 1.0 C without visible cracks. Those results suggest that the as-fabricated CPE doped with 5 wt% CaTiO3 inorganic fillers may become a promising polymer electrolyte for the lithium ion battery

Complete encapsulation of zeolite supported Co based core with silicalite-1 shell to achieve high gasoline selectivity in Fischer-Tropsch synthesis

Zeolite-based capsule catalysts have exhibited significant results in terms of catalytic activity and product selectivity in Fisher-Tropsch synthesis. Herein, we synthesized a ZSM-5 supported Co based microcapsule catalyst encapsulated by microporous silicalite-1 shell via hydrothermal synthesis process. Synthesized microcapsule catalyst has a uniform microporous structure with an additional stay zone for both reactants as well as product inside its channels and showed significantly high CO conversion rate (68.9%) and gasoline range hydrocarbon selectivity (74.7%) with a low CO2 and CH4 selectivity (2.8% and 8.7%, respectively). This microcapsule catalyst may consider to be used on commercial scale because of its facile preparation method and promising performance.