Thin Dense Layer Research Articles

Double layer silica antireflective films with high strength and rub resistance prepared by sol gel method

The single-layer silica antireflective film with base catalysis prepared by sol gel method is an important part of the high-power laser facility for inertial confinement fusion, while the weak adhesion between the single-layer silica film and the substrate during the preparation process makes it susceptible to be contacted erasure and unable to be used. Double-layer silica antireflective (DLAR) films of different thicknesses were obtained using the base catalysis sol–gel method, in which the upper layer was coated with a relatively dense thin layer, and the performances of the films were characterized. The results showed that the transmittances of the DLAR films with different thicknesses were ˃99.0%, and in which one of the maximum transmittance peaks reached to 99.83% @ 1000 nm. The surface roughness of the DLAR films was < 2.0 nm, and the surfaces of the films were flat. The contact angles between DLAR films and water reached 118° and maintained stable in high humidity environment. The laser induced damage thresholds for different thickness DLAR films (peak transmittances @ 400, 600, 800, 1000 nm) were comparable to device requirements by 1-on-1 testing method, and the DLAR films exhibited high strength and good friction resistance.Graphical abstract

Pervaporation Membranes Based on Polyelectrolyte Complex of Sodium Alginate/Polyethyleneimine Modified with Graphene Oxide for Ethanol Dehydration.

Pervaporation is considered the most promising technology for dehydration of bioalcohols, attracting increasing attention as a renewable energy source. In this regard, the development of stable and effective membranes is required. In this study, highly efficient membranes for the enhanced pervaporation dehydration of ethanol were developed by modification of sodium alginate (SA) with a polyethylenimine (PEI) forming polyelectrolyte complex (PEC) and graphene oxide (GO). The effect of modifications with GO or/and PEI on the structure, physicochemical, and transport characteristics of dense membranes was studied. The formation of a PEC by ionic cross-linking and its interaction with GO led to changes in membrane structure, confirmed by spectroscopic and microscopic methods. The physicochemical properties of membranes were investigated by a thermogravimetric analysis, a differential scanning calorimetry, and measurements of contact angles. The theoretical consideration using computational methods showed favorable hydrogen bonding interactions between GO, PEI, and water, which caused improved membrane performance. To increase permeability, supported membranes without treatment and cross-linked were developed by the deposition of a thin dense layer from the optimal PEC/GO (2.5%) composite onto a developed porous substrate from polyacrylonitrile. The cross-linked supported membrane demonstrated more than two times increased permeation flux, higher selectivity (above 99.7 wt.% water in the permeate) and stability for separating diluted mixtures compared to the dense pristine SA membrane.

Efficient pure oxygen separation with the unique graded porous supported symmetric flat mixed conductor ceramic membrane

A graded porous supported symmetric (GPSS) flat ceramic membrane made of a K2NiF4+δ type oxide (Pr0.9La0.1)2(Ni0.74Cu0.21Ga0.05)O4+δ (PLNCG) is fabricated by aqueous tape casting. This membrane design stands out for its unique structure, consisting of a thin dense layer at its core and two graded porous substrates that adhere symmetrically to this middle layer. In comparison to previously reported PLNCG hollow fiber membranes, the GPSS membrane offers superior oxygen permeation flux, exceeding that of the hollow fiber membrane by more than four times. When using air as the feed gas and even when introducing CO2 into the feed gas or sweep gas, the membrane maintains a consistent oxygen permeation flux of 4.41 mL min−1 cm−2 (STP). This work demonstrates that by paying close attention to membrane structure, the oxygen permeation flux of flat membranes can surpass that of hollow fiber membranes. Given its exceptional oxygen separation performance, the PLNCG-GPSS membrane holds great potential for practical applications such as high-purity oxygen production, pure hydrogen production, oxygen-involved catalytical reactions, and CO2 capture and storage.

Sulfonated Polystyrene/Polybenzimidazole Bilayer Membranes for Vanadium Redox Flow Batteries

AbstractPolybenzimidazole has been widely examined as a separator for vanadium redox flow batteries (VRFBs) due to its low vanadium permeability. Its low conductivity can be tackled by combining 1–4 µm thin dense PBI layers with highly conductive mechanically supporting layers, either by lamination or loose stacking. While gel‐PBI is very soft and conductive, the shadow effect of the non‐conductive pore walls of porous supports adds resistance. In this work, these issues are addressed by coating a 25 µm thick highly conductive sulfonated polystyrene layer (S) with a 1 µm thin selective PBI layer (P) to block vanadium crossover. To reduce the number of potential defects, two bilayer membranes can be stacked. A 52 µm thick stack of two membranes (PS–SP, PBI faces the electrodes) shows an area‐specific resistance of 144.8 mΩ cm2 in VO2+‐containing electrolyte and a permeability of 6.85 × 10−14 m2 s−1, both lower than the values for Nafion 212. A VRFB cell test over 3500 charging cycles (1660 h) with an energy efficiency of up to 88.5% at 100 mA cm−2 is shown. Performance losses are reversed by electrolyte rebalancing. With material costs of 1.84 USD m−2, the PSSP(1‐25‐25‐1) membrane promises high performance at low costs.

Investigation of Medium-Term Performance of Porous Asphalt and Its Impacts on Tire/Pavement Noise

To assess the medium-term performance of porous asphalt pavement during service and its influence on tire/pavement noise level, a seven-year continuous observation and data analysis study was conducted. Key performance indicators were measured and calculated by using automated pavement technology testing equipment. The noise levels were tested by using the on-board sound intensity (OBSI) method on three types of porous asphalt pavements (PUC-10, PAC-13, and PUC-10 + PAC-13) and one dense thin layer course (DTC) for comparison. The findings indicated that the Damage Rate (DR) and Surface Friction Coefficient (SFC) of porous asphalt pavements diminished greatly over time, while the International Roughness Index (IRI) and Rut Depth (RD) remained relatively stable. The two-layer porous asphalt pavement showed the largest noise reduction over the medium-term. Compared to DTC, the OBSI noise levels of these structures were lower by 2.09 dB, 1.53 dB, and 2.88 dB, respectively. The OBSI was found to be closely correlated with the SFC, IRI, test speed, lane, and pavement type. The RD had a notable effect on the OBSI in PUC-10 pavements. In PUC-10 + PAC-13 pavements, a significant linear relationship was observed between the OBSI and SFC. This is mainly because of the polishing of the coarse aggregates, which leads to micro-texture reduction, high frequency noise increase, and SFC decrease. This study makes a valuable contribution to understanding the laws of porous asphalt pavement performance changes and the relationship between tire/pavement noise and pavement characteristics.

Evaluation of PTFPMS membrane towards application in artificial oxygenation

The tradeoff between efficient gas exchange and blood leakage as well as thrombosis caused by contact between blood and membrane are existing challenges in extracorporeal membrane oxygenation (ECMO). Herein, poly (3,3,3-trifluoropropyl) methylsiloxane/polyetherimide (PTFPMS/PEI) composite membranes, with a thin PTFPMS dense layer for functional CO2 and O2 exchange coated on microporous PEI substrate membrane for mechanical support, were synthesized, characterized and evaluated for potential application as oxygenation membrane. Characterization data from scanning electron microscopy with energy dispersive spectroscopy, thermogravimetric analysis, contact angle and zeta potential measurements confirmed that PTFPMS/PEI composite membrane with different coating concentrations were successfully prepared, and the composite membranes obtained exhibited thermal stability, surface hydrophobicity as well as surface electronegativity. Analysis on gas permeance and hemocompatibility performance demonstrated that the composite membranes displayed effective gas transfer and good blood compatibility in terms of hemolysis rate, protein adsorption, platelet adhesion as well as plasma recalcification time. More notably, the membrane also displayed excellent long term anti-fouling performance. In summary, the PTFPMS/PEI composite membrane showed impressive application potential for use as oxygenation membrane in ECMO.

Effect of interstitial carbides on tribological properties of Co21Cr21Fe21Ni21V14.5C1.5 high entropy alloy at elevated temperature

High-entropy alloys (HEAs) with high wear resistance at elevated temperatures are desired for applications like turbine engine blades and internal combustion engines. By reducing the proportion of transition metal elements, the interstitial carbide in the form of doped non-metallic element C can reduce the preparation cost of HEA and improve its mechanical properties. The effect of 1.5 at% carbon doping at different sintering temperatures on microstructure, mechanical properties, and high-temperature tribological behavior was systematically investigated. The compressive strength and strain rate of C-doped HEAs sintered at 1200 °C were 969 ± 21 MPa, 8.43 ± 0.36%, which was improved by solution strengthening and carbide pegging dislocations. The wear mechanisms of C0 alloy at high-temperature are mainly oxidation wear, adhesion wear and delamination wear, while the wear mechanism of C10 alloy is mainly abrasive wear, adhesion wear, fatigue wear and oxidation wear. The combined effect of VC, M23C6 and M7C3 carbides and σ phase plays the role of anti-wear lubrication at RT∼800 °C, and the tribo-chemical reaction generates Cr2O3, NiCr2O4, NiO, and other compounds with high-temperature stability and oxidation resistance to form a thin dense oxide glaze layer, resulting in better anti-wear and friction reduction performance of C-doped alloy than undoped alloy.

Uniform Lithium Plating for Dendrite-Free Lithium Metal Batteries: Role of Dipolar Channels in Poly(vinylidene fluoride) and PbZrxTi1-xO3 Interface.

Conventional polymer/ceramic composite solid-state electrolytes (CPEs) have limitations in inhibiting lithium dendrite growth and fail to meet the contradictory requirements of anodes and cathodes. Herein, an asymmetrical poly(vinylidene fluoride) (PVDF)-PbZrxTi1-xO3 (PZT) CPE was prepared. The CPE incorporates high dielectric PZT nanoparticles, which enrich a dense thin layer on the anode side, making their dipole ends strongly electronegative. This attracts lithium ions (Li+) at the PVDF-PZT interface to transport through dipolar channels and promotes the dissociation of lithium salts into free Li+. Consequently, the CPE enables homogeneous lithium plating and suppresses dendrite growth. Meanwhile, the PVDF-enriched region at the cathode side ensures intermediate contact with positive active materials. Therefore, Li/PVDF-PZT CPE/Li symmetrical cells exhibit a stable cycling performance exceeding 1900 h at 0.1 mA cm-2 at 25 °C, outperforming Li/PVDF solid-state electrolyte/Li cells that fail after 120 h. The LiNi0.8Co0.1Mo0.1O2/PVDF-PZT CPE/Li cells show low interfacial impedances and maintain stable cycling performance for 500 cycles with a capacity retention of 86.2% at 0.5 C and 25 °C. This study introduces a strategy utilizing dielectric ceramics to construct dipolar channels, providing a uniform Li+ transport mechanism and inhibiting dendrite growth.

Enhanced strength of AlCoCrCu0.5FeNi high entropy alloy thin films reinforced by multi-phase hardening and nanotwins

High entropy alloy (HEA) thin films have become increasingly popular because they exhibit favorable properties but with lower material consumption. Here, this research demonstrates that annealing of AlCoCrCu0.5FeNi thin films results in multiphase hardening and the formation of nanotwins. HEA thin films were atmospherically annealed at different temperatures (300 – 700 °C) for 5 h. A thin dense oxide layer consisting of Al2O3 and Cr2O3 appeared at the top surface of the 700 °C annealed film. This oxide layer endows the HEA thin film with excellent antioxidant properties. As such, vacuum and inert gas might not be required for HEAs annealing process at up to 700 °C. A phase transformation was observed in the film annealed at 700 °C for 5 h from X-ray diffraction patterns. Results from transmission Kikuchi diffraction and energy dispersive X-ray spectroscopy mapping indicated the formation of three new phases, including the FeCo phase, Cr-rich phase and Cu nano-clusters. Variations also happened in HEA FCC matrix where two types of texture existed in the HEA FCC grains i.e., {012} <110> and {112} <110>. Of particular interest was that high-resolution transmission electron microscopy revealed a high density of annealing nanotwins among the HEA FCC grains, including lamellar and co-axial twins. The influence of these structural phenomena on mechanical properties was evaluated. The results showed that the hardness and modulus of 700 °C annealed HEA thin film increased by 25% and 24% to 8.4 ± 0.2 GPa and 149.4 ± 6.1 GPa when compared to the properties of as-deposited films.

Improved water purification by PVDF ultrafiltration membrane modified with GO-PVA-NaAlg hydrogel

This work presents a modified polyvinylidene fluoride (PVDF) ultrafiltration membrane blended with graphene oxide-polyvinyl alcohol-sodium alginate (GO-PVA-NaAlg) hydrogel (HG) and polyvinylpyrrolidone (PVP) prepared by the immersion precipitation induced phase inversion approach. Characteristics of the membranes with different HG and PVP concentrations were analyzed by field emission scanning electron microscopy (FESEM), Atomic force microscopy (AFM), contact angle measurement (CA), and Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The FESEM images showed an asymmetric structure of the fabricated membranes, and possessing a thin dense layer over the top and a layer finger-like. With increasing HG content, membrane surface roughness increases so that highest surface roughness for the membrane containing 1wt% HG is with a Ra value of 281.4 nm. Also, the contact angle of the membrane reaches from 82.5° in bare PVDF membrane to 65.1° in the membrane containing 1wt% HG. The influences of adding HG and PVP to the casting solution on pure water flux (PWF), hydrophilicity, anti-fouling ability, and dye rejection efficiency were evaluated. The highest water flux reached 103.2 L/m2 h at 3 bar for the modified PVDF membranes containing 0.3 wt% HG and 1.0wt% PVP. This membrane exhibited a rejection efficiency of higher than 92%, 95%, and 98% for Methyl Orange (MO), Conge Red (CR), and Bovine Serum Albumin (BSA), respectively. All nanocomposite membranes possessed a flux recovery ratio (FRR) higher than bare PVDF membranes, and the best anti-fouling performance of 90.1% was relevant to the membrane containing 0.3 wt% HG. The improved filtration performance of the HG-modified membranes was due to the enhanced hydrophilicity, porosity, mean pore size, and surface roughness after introducing HG.

Responsive polymer thin films

Responsive polymer thin films

Symmetric structured porous supported mixed conductor ceramic membrane boosting oxygen permeation flux

An effective symmetric structured dual phase mixed conducting oxygen separation membrane made of 60 wt% Ce0.9Gd0.1O2-δ − 40 wt% Ba0.5Sr0.5Co0.8Fe0.2O3-δ (60CGO-40BSCF) were prepared by the aqueous tape casting. The symmetric ceramic membranes consisted of a dense thin layer with a thickness of around 50 µm in the middle, and two porous substrates (around 290 µm thick) located on the two sides of the middle thin dense layer. In this case, both the bulk diffusion of oxygen ion and surface gas exchange are simultaneously optimized to enlarge the oxygen permeation flux. In addition, a symmetric structure favors to stabilize the ceramic membrane. Compared with monotonous dense membrane, the porous supported symmetric membrane delivered higher permeation fluxes, e.g., 3.78 ml cm−2 min−1 at 975 °C under an air/He gradient, while an oxygen permeation flux of 1.42 ml cm−2 min−1 was obtained for the monotonous dense membrane. As increasing the O2 partial pressure in the feed side to 0.8 atm, an oxygen permeation flux of 8.67 ml cm−2 min−1 was obtained. The current study implies that the porous supported symmetric membrane structure is an efficient strategy to enhance the oxygen permeation flux.

Nanofiltration Mixed Matrix Membranes from Cellulose Modified with Zn-Based Metal–Organic Frameworks for the Enhanced Water Treatment from Heavy Metal Ions

Nowadays, nanofiltration is actively used for water softening and disinfection, pre-treatment, nitrate, and color removal, in particular, for heavy metal ions removal from wastewater. In this regard, new, effective materials are required. In the present work, novel sustainable porous membranes from cellulose acetate (CA) and supported membranes consisting of CA porous substrate with a thin dense selective layer from carboxymethyl cellulose (CMC) modified with first-time synthesized Zn-based metal-organic frameworks (Zn(SEB), Zn(BDC)Si, Zn(BIM)) were developed to increase the efficiency of nanofiltration for the removal of heavy metal ions. Zn-based MOFs were characterized by sorption measurements, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The obtained membranes were studied by the spectroscopic (FTIR), standard porosimetry and microscopic (SEM and AFM) methods, and contact angle measurement. The CA porous support was compared with other, prepared in the present work, porous substrates from poly(m-phenylene isophthalamide) and polyacrylonitrile. Membrane performance was tested in the nanofiltration of the model and real mixtures containing heavy metal ions. The improvement of the transport properties of the developed membranes was achieved through Zn-based MOF modification due to their porous structure, hydrophilic properties, and different particle shapes.

Red phosphorus infiltrated into porous C/SiOx derived from rice husks to improve its initial Coulomb efficiency in lithium-ion batteries

To overcome the poor initial Coulombic efficiency (ICE) of C/SiOx anode materials of lithium-ion batteries (LIBs) and promote its industrial application, porous C/SiOx materials have been fabricated by carbonization and activation of rice husks with H3PO4 as an activator. Then, red phosphorus (RP) is infiltrated on the surface and pore inner wall of porous C/SiOx to synthesize RP@C/SiOx using the evaporation-condensation method. In the RP@C/SiOx composite, SiP2 and SiP2O7 generated by the reaction between RP and SiOx particles successfully decrease the formation of inert Li2O and Li4SiO4 during the first Li+ intercalation process. Meanwhile, RP connects with C skeleton to form P-O and P-C bonds during the preparation process, which are conducive to the production of a thin dense solid electrolyte interphase layer. All of these are beneficial to enhance the ICE of C/SiOx. After infiltration of RP, the reversible capacity of porous C/SiOx increased from 435.2 mAh/g to 1147.4 mAh/g at 0.1 A/g, with an ameliorative ICE of 73.6% (51.02% for porous C/SiOx). Even at a higher current density of 2.0 A/g, the considerable specific capacity of 630.0 mAh/g can be obtained after 738.0 cycles.

Synthesis of hierarchical LTA zeolite membranes by vapor phase transformation

Weakening the mass transfer resistance inside the selective layer of membrane can effectively increase the membrane separation performance. In this study, we introduce macropores into the conventional LTA zeolite membrane layer, resulting in an unprecedented hierarchical membrane structure. Specifically, the hierarchical LTA zeolite membranes composed of a macroporous zeolite layer and a thin dense top layer (600 nm), are fabricated on rough α-Al2O3 tubular supports by vapor phase transformation method using mesoporous silica spheres (MSPs) as the porogen in the precursor layer. The H2 (N2) permeance of the hierarchical LTA zeolite membrane is near 10 times that of the conventional LTA zeolite membrane, indicating that the hierarchical pore structure can effectively weaken the mass transfer resistance inside the selective layer of membrane. And it has good pervaporation performance for 90 wt% ethanol aqueous solution at 348 K, i.e., the flux can reach 4.54 kg m−2 h−1 with a separation factor of >10,000, which is much higher than that of the conventional LTA zeolite membrane. The preparation of LTA zeolite membranes with hierarchical pore structure using MSPs as a porogen is expected to open up a new way for the construction of zeolite membranes.

Back Cover: Multilayered Ceramic Membrane with Ion Conducting Thin Layer Induced by Interface Reaction for Stable Hydrogen Production (Angew. Chem. Int. Ed. 6/2023)

Multilayered ceramic membranes with ion-conducting dense thin layers are essential platforms for solid-state electrochemical devices, gas separation membranes, and sensors. In their Research Article (e202210485), Heqing Jiang et al. develop a new interface-reaction-induced reassembly approach for the direct fabrication of zirconia- or ceria-based dense thin layers rooted in multilayered ceramic membranes that show robust and practical performance for upgrading fossil-fuel-derived hydrogen.

Rücktitelbild: Multilayered Ceramic Membrane with Ion Conducting Thin Layer Induced by Interface Reaction for Stable Hydrogen Production (Angew. Chem. 6/2023)

Multilayered ceramic membranes with ion-conducting dense thin layers are essential platforms for solid-state electrochemical devices, gas separation membranes, and sensors. In their Research Article (e202210485), Heqing Jiang et al. develop a new interface-reaction-induced reassembly approach for the direct fabrication of zirconia- or ceria-based dense thin layers rooted in multilayered ceramic membranes that show robust and practical performance for upgrading fossil-fuel-derived hydrogen.

Multilayered Ceramic Membrane with Ion Conducting Thin Layer Induced by Interface Reaction for Stable Hydrogen Production

AbstractConventional methods for fabricating multilayered ceramic membranes with ion conducting dense thin layers are often cumbersome, costly, and limited by poor adhesion between layers. Inspired by the architectural structure of the rooted grasses in soil, here, we report an interface‐reaction‐induced reassembly approach for the direct fabrication of Ce0.9Gd0.1O2−δ (CGO) thin layers rooted in the parent multilayered ceramic membranes by only one firing step. The CGO dense layers are very thin, and adhered strongly to the parent support layer, ensuring low ionic transport resistance and structural integrity of the multilayered membranes. When using as an oxygen permeable membrane for upgrading fossil‐fuel‐derived hydrogen, it shows very long durability in harsh conditions containing H2O, CH4, H2, CO2 and H2S. Furthermore, our approach is highly scalable and applicable to a wide variety of ion conducting thin layers, including Y0.08Zr0.92O2−δ, Ce0.9Sm0.1O2−δ and Ce0.9Pr0.1O2−δ.

Multilayered Ceramic Membrane with Ion Conducting Thin Layer Induced by Interface Reaction for Stable Hydrogen Production.

Conventional methods for fabricating multilayered ceramic membranes with ion conducting dense thin layers are often cumbersome, costly, and limited by poor adhesion between layers. Inspired by the architectural structure of the rooted grasses in soil, here, we report an interface-reaction-induced reassembly approach for the direct fabrication of Ce0.9 Gd0.1 O2-δ (CGO) thin layers rooted in the parent multilayered ceramic membranes by only one firing step. The CGO dense layers are very thin, and adhered strongly to the parent support layer, ensuring low ionic transport resistance and structural integrity of the multilayered membranes. When using as an oxygen permeable membrane for upgrading fossil-fuel-derived hydrogen, it shows very long durability in harsh conditions containing H2 O, CH4 , H2 , CO2 and H2 S. Furthermore, our approach is highly scalable and applicable to a wide variety of ion conducting thin layers, including Y0.08 Zr0.92 O2-δ , Ce0.9 Sm0.1 O2-δ and Ce0.9 Pr0.1 O2-δ .

Double stimuli‐responsive perforated lamellar structure formed by linear ABC triblock terpolymer monoliths

AbstractAmphiphilic block copolymer (BCP) thick films with stimuli‐responsive pores are promising candidates for the manufacturing of next‐generation ultrafiltration (UF) membranes since their smart nanochannels facilitates the removal of fouling which is considered as one of the biggest challenges in membrane technology. In this work, a well‐defined polystyrene‐block‐poly(2‐vinylpyridine)‐block‐poly(N‐isopropylacrylamide) (PS‐b‐P2VP‐b‐PNIPAM) terpolymer was prepared for the first time via reversible addition‐fragmentation chain transfer polymerization. The combination of the nonsolvent‐induced phase separation process with a solvent vapor annealing treatment was used to produce nanostructured pH‐ and thermo‐double sensitive ABC‐type BCP thick films. Here, the NIPS‐made PS‐b‐P2VP‐b‐PNIPAM thick film, comprising a microporous spinodal‐type network substructure, topped by a dense thin layer of poorly defined nanopores is transformed into a monolith entirely composed of a well‐ordered perforated lamellar (PL) phase upon exposure to a chloroform vapor during 6 h. Such kind of PL‐structured monoliths, showing a permeance value as high as 18 L h−1 m−2 bar−1 at 46°C and pH = 7 with an excellent temperature cyclability, are highly desired to manufacture smart separation‐based UF materials able to transit their pore state from hydrophilic to hydrophobic (and vice versa), thereby leading to much more efficient detachment of foulants during the cleaning process.