High Gas Permeability Research Articles

Metal-organic framework/ 2D boron nitride nanosheets composite fillers in mixed matrix membranes for H2 /CO2 separation

Nanometer-thick two-dimensional (2D) materials are becoming ideal fillers for designing mixed matrix membranes (MMMs) with high gas permeability and selectivity due to their unique structures. ZIF-67@BNNS composite fillers were prepared by combining boron nitride nanosheets (BNNS), a thermally stable and chemically inert two-dimensional material, with the metal-organic framework ZIF-67. By incorporating these materials into polyetherimide (PEI), MMMs with efficient hydrogen (H2) separation performance have been developed. The -NH2 groups on the BNNS surface provide a growth site for cobalt (Co) ions, facilitating the construction of a two-dimensional continuous channel by growing a ZIF-67 layer in situ on the BNNS surface. The inherent micropores of ZIF-67 create internal channels for gas transport within the composite packing, increasing gas permeability. The interlaced BNNS layer provides an external channel for gas transport, increasing resistance and contributing to improved gas selectivity. At a low loading of 1 wt%, the PEI/ZIF-67@BNNS-0.2 MMMs exhibited a 199 % increase in H2 permeability and 87 % improvement in H2/CO2 selectivity compared to pure PEI membranes. In addition, these MMMs exhibit strong thermal stability and mechanical properties, making them promising for H2 separation applications.

Orderly Coating of Bilayer Polymer to Tailor Microenvironment for Efficient C−N Coupling Toward Highly Selective Urea Electrosynthesis

AbstractElectrosynthesis of urea from co‐reduction of carbon dioxide and nitrate is a promising alternative to the industrial process. However, the overwhelming existence of proton and nitrate as well as the insufficient supply of CO2 at the reaction interface usually result in complex product distributions from individual nitrate reduction or hydrogen evolution, instead of C−N coupling. In this work, we systematically optimize this microenvironment through orderly coating of bilayer polymer to specifically tackle the above challenges. Polymer of intrinsic microporosity is chosen as the upper polymer to achieve physical sieving, realizing low water diffusivity for suppressing hydrogen evolution and high gas permeability for smooth mass transfer of CO2 at the same time. Polyaniline with abundant basic amino groups is capable of triggering chemical interaction with acidic CO2 molecules, so that is used as the underlying polymer to serve as CO2 concentrator and facilitate the carbon source supply for C−N coupling. Within this tailored microenvironment, a maximum urea generation yield rate of 1671.6 μg h−1 mg−1 and a high Faradaic efficiency of 75.3 % are delivered once coupled with efficient electrocatalyst with neighboring active sites, which is among the most efficient system of urea electrosynthesis.

A Janus-gas diffusion electrode with suitable hydrophilicity and aerophilicity for highly efficient H2O2 electrosynthesis

Low solubility and slow oxygen transport in the electrolyte lead to poor hydrogen peroxide (H2O2) generation performance through oxygen reduction reactions (ORR) at traditional submerged cathodes. Herein, we fabricated a Janus-gas diffusion electrode with asymmetric wettability, high gas permeability, and abundant catalytic active sites using HNO3-modified graphite felt as the substrate, polytetrafluoroethylene (PTFE) as a hydrophobic gas diffusion layer (GDL), and polyvinylidene fluoride (PVDF)/acetylene black(AB) composite as a hydrophilic and aerophilic catalyst layer (CL). Using air as an oxygen supply and a working current density of 10.0mA∙cm-2, the constructed Janus-gas diffusion electrode achieves an H2O2 yield of 39.0mg∙L-1∙cm-2, a current efficiency of 97.8%, and an oxygen utilization ratio of 3.5% at 60min, indicating excellent two-electron ORR performance. The enhanced performance is attributed to the superaerophilicity of the PTFE-based hydrophobic GDL, which provides sufficient oxygen mass transfer and supply. The hydrophilic PVDF-based CL remains good aerophilicity and contains abundant active functional groups due to the AB and graphite felt modified with nitric acid. AB increases the electrode’s specific surface area and gas permeability, allowing for more effective oxygen collection and transport. The electrode is stable for continuous use and indicates a promising application in in-situ H2O2 production.

A Metalgel with Liquid Metal Continuum Immobilized in Polymer Network.

Gels are formed by fluids that expand throughout the whole volume of 3D polymer networks. To unlock unprecedented properties, exploring new fluids immobilized in polymer networks is crucial. Here, a new liquid metal-polymer gel material termed "metalgel" is introduced via fluid replacement strategy, featuring 92.40%vol liquid metal fluid as a continuum immobilized by interconnected nanoscale polymer network. The unique structure endows metalgel with high electrical conductivity (up to 3.18×106 S·m‒1), tissue-like softness (Young's modulus as low as 70kPa), and low gas permeability (4.50×10‒22m2·s‒1·Pa‒1). Besides, metalgel demonstrates electrical stability under extreme deformations, such as being run over by a 4.5-metric-tonne truck, and maintains its integrity in various environments for up to 180 days. The immobilization of high-volume-fraction liquid metal fluid is realized by electrostatic interactions is further revealed. Potential applications for metalgel are diverse and include soft electromagnetic shielding, hermetic sealing, and stimulating/sensing electrodes in implantable bioelectronics, underscoring its broad applicability.

Innovative thermal crosslinked polyimide gas separation membrane with highly selective and resistance to physical aging base on phenyl ethynyl

In this study, a high performance phenyl ethynyl thermal crosslinked 6FDA-based polyimide (CR-4ETA-x) was developed, which has high gas permeability and selectivity, resistance to physical aging. By introducing 4,4′-(Acetylene-1,2-diyl) diphthalic anhydride (4ETA) monomer into the polyimide structure, the thermal crosslinking precursor membrane was formed. The precursor membrane was heat treated at 440℃ to obtain CR-4ETA-x. After heat treatment, we detected the olefin radical in the crosslinked membrane by electron paramagnetic resonance, which proved that the polyimide network was formed. This allows the crosslinked membrane to have greater d-spacing, higher rigidity, and BET surface area. The CO2 permeability of CR-4ETA-5% is 4114 barrer and the CO2/CH4 selectivity is 19.22. Compared to 6FDA-DAM, the CO2 permeability increased by 477% while the selectivity decreased by only 17%. CR-4ETA-20% shows the CO2 permeability of 3560 Barrer and CO2/CH4 selectivity of 21.1 in CO2/CH4 mixed-gas. After 60 days of aging the permeability maintenance of CR-4ETA-20% were 88%, 84%, 83% and 91% for O2, N2, CO2 and CH4. In addition, in the long-term stability test of more than 100 h, the separation performance of CR-4ETA-20% did not decrease significantly. However, CR-4ETA-x also has limitations, such as poor stability in alkaline environments and lower gas permeability than some advanced carbon molecular sieve membranes. In general, the method of phenyl ethynyl thermal crosslinking provides an effective way for the development of CO2 separation membranes with possible applications.

A liquid static culture using a gas-permeable film bag contributes to microbiology

We propose a simple tool for liquid static culture using a copolymer film with high gas permeability. The film bags were successfully used to culture microorganisms Escherichia coli, Komagataella phaffii (methylotrophic) and Bacillus sp. (biofilm-forming), with cells cultured under physical stress-free conditions with sufficient oxygen supply. Similar growth curves and plasmid productivity were observed for liquid shake and film bag E. coli cultures. The early growth response of the film bag culture following colony inoculation of liquid media differed from conventional shake cultures. Our results indicate that a gas-permeable film bag is a promising liquid culture tool and provides novel microbiology materials.

Carbon molecular sieve gas separation membranes derived from in-situ crosslinked polyimide containing bromine groups

The network polyimide (PI) precursor is a promising candidate to fabricate the advanced carbon molecular sieve (CMS) membrane since its robust crosslinked structure could prevent pore structure collapse during CMS formation. Exploring the relationship between network PI precursor structure and CMS membrane is highly significant. Herein, a novel brominated network PI precursor was fabricated via in-situ cross-linking technique firstly, and then the thermally induced bromination/debromination process was applied to tune the microporosity and gas transport properties of network PI precursor and its derived CMS membranes. After the bromination/debromination and carbonization at 550 °C, the resultant CMS membrane exhibited both high gas permeability and gas selectivities compared to its un-brominated network PI precursor derived CMS membrane. This is due to the bromination/debromination and carbonization enable the CMS membrane possesses large d-spacing values (11.06 Å), high BET surface areas (538.57 m2/g), and high percentage (∼71 %) of ultra-micropores. For instance, 6F-TA/TA-Br-550/30 membrane exhibits great CO2/CH4 separation ability, with a CO2 permeability of 6300 Barrer and a CO2/CH4 selectivity of 46.11, which is suppressed the latest 2019 trade-off curves. We anticipate that the present bromination/debromination and carbonization could provide a fresh perspective on the rational design of network PI precursor and its derived CMS membrane with excellent gas separation performance.

Wearable Inorganic Oxide Chemiresistor Based on Flexible Al2O3-Stabilized ZrO2 Ceramic Sponge Substrate for NO2 Sensing.

Wearable gas sensors, possessing the advantages of high sensitivity, excellent flexibility, high permeability, low weight, and workability at ambient conditions, hold great promise for real-time health monitoring and early warnings of poisonous gases. However, obtaining high-performance wearable gas sensors utilizing the current well-developed inorganic semiconductor oxide sensing materials is still very limited due to their fragile and rigid nature. Herein, a newly designed wearable gas sensor based on an all-inorganic ASZ (Al2O3-stabilized ZrO2)/ZnO/SnO2 nanofibers is introduced for the first time. The flexible ASZ ceramic sponge substrate (with a Young's modulus of 4.15 MPa) and ultrathin ZnO/SnO2 sensing layer endow the wearable gas sensor with promising properties such as super flexibility (with a bending radius of 5 mm), high gas permeability, and low weight. Furthermore, driven by UV light irradiation, this all-inorganic wearable sensor also demonstrates a stable NO2 sensing response under different bending states at room temperature, which enables the gas sensor to be more compatible with wearable sensing applications. This work offers a general method to achieve a high-performance wearable gas sensor based on inorganic materials and provides new insights into their potential in wearable gas-sensing applications.

Enhanced CO₂ Detection Using Potentiometric Sensors Based on PIM‐1/DBU Imidazolate Membranes

AbstractA novel potentiometric sensor for carbon dioxide (CO2) detection utilizing a composite membrane of Polymer of Intrinsic Microporosity (PIM‐1) and 18‐diazabicyclo[5.4.0]undec‐7‐ene imidazolate (DBU‐imidazolate) is presented. The high surface area and gas permeability of PIM‐1, combined with the chemical affinity and ion‐exchange properties of DBU‐imidazolate, contribute to enhanced CO2 sensitivity and selectivity. The research objectives included the synthesis of PIM‐1 and DBU‐imidazolate, the preparation of composite membranes, and the evaluation of their performance as CO2 sensors. Solvent casting and impregnation methods are employed to prepare the membranes, which are characterized using Thermal Gravimetric Analysis (TGA), and Field Emission Scanning Electron Microscopy (FESEM). CO₂ absorption tests and Electrochemical Impedance Spectroscopy (EIS) are conducted to assess the sensors' performance. The PIM‐1/DBU‐imidazolate membrane exhibited high efficiency in CO₂ capture and release. Open circuit voltage (OCV) measurements are performed under varying concentrations of CO2 exposure and cycles of adsorption/desorption. Results show that the membrane achieves steady state faster at higher CO2 concentrations, with a logarithmic relationship between CO2 concentration and voltage variation, indicating potential for CO2 detection in human environments. These results confirm the sensor's ability to detect varying CO2 concentrations, highlighting its potential for reliable and efficient CO2 monitoring in environmental and industrial applications.

Insights on influence of polymer molecular weight on gas sorption, transport and plasticization in glassy 6FDA-DAM polyimide membranes

It is well-known that spinning of defect-free asymmetric polyimide hollow fibers is promoted by using high polymer molecular weight. On the other hand, effects of polymer molecular weight on microstructure and separation performance of dense film 6FDA-based polyimide membranes relevant to sheath layers of composite membranes are less well-explored. In this work, gas sorption, diffusion and permeation of CO2, N2 and CH4 for 6FDA-DAM dense films are considered for 45 kDa and 176 kDa weight average molecular weights. Such molecular weights are relevant for practical hollow fiber spinning of membranes. Earlier results for polystyrene samples show similar trends in dual mode sorption model results like those noted here for the 6FDA-DAM polyimide case; however, effects on permeation like those considered here were not addressed for the polystyrene case. Here we also address actual pure and mixed gas CO2 and CH4 permeation and show higher free volumes, higher gas permeability but lower 50:50 CO2/CH4 selectivity associated with the higher molecular weight sample. Analysis using the self-consistent dual-mode sorption and transport models help understand the observed trends. Our results suggest denser packing of polymer segments exists in the Henry's law environment of the low molecular weight sample. Moreover, the higher polymer segmental packing in the Henry's law environment suppresses CO2 plasticization with a dual-mode microstructure controlling separation performance and plasticization behavior for this important member of the 6FDA polyimide family. We show evidence of effects of charge transfer complexes as possible main features in these trends. These dense film results help guide future work on dense sheath layers on composite hollow fiber membranes.

Slot-structured catalytic membrane for sustained oily particulate matter removal with a low pressure drop

Oily particulate matter (PM) filtration faces the problems of high pressure drop and difficult regeneration. Herein, vertical arrays of MnO2 nanosheets was assembled on Zr doped TiO2 (Zr-TiO2) nanofibers to construct a core–shell structure MnO2@Zr-TiO2 (CSMT-x) catalytic membranes for highly efficient oily PM filtration and decomposition. The confining effect of the ultrathin MnO2 nanosheets enhances PM capture efficiency, and the increase of effective contact area between MnO2 and oily PM accelerate the decomposition of oily PM. The optimized CSMT-3 catalytic membrane exhibited high gas permeability and redox capacity, outperforming the Zr-TiO2 (Bare T) membrane with over 99.97 % PM filtration efficiency and a low pressure drop at the temperatures of 25–425 °C. The catalytic decomposition of PM prevented the accumulation of particles on the membrane surface, which inhibited the formation of cake layer. Therefore, the CSMT-3 membrane exhibited a slight increase in pressure drop (less than 120 Pa) even after 120 h long-term filtration. This work may contribute to the development of advanced multifunctional membranes for purification of oily PM.

Investigation on the synthesis conditions of poly(4-methyl-1-pentene) hollow fiber membrane with high gas permeability and strong tensile strength

Investigation on the synthesis conditions of poly(4-methyl-1-pentene) hollow fiber membrane with high gas permeability and strong tensile strength

Poly(4-methyl-1-pentene)/ polypropylene alloy hollow fiber membrane with high rigidity for blood oxygenation

The oxygenator with hollow fiber membranes (HFMs) is the key component of the extracorporeal membrane oxygenation which allows the blood to be oxygenated and the carbon dioxide to be removed. The poly(4-methyl-1-pentene) (PMP) is recognized as the optimal oxygenated membrane material with high gas permeability coefficient, and the oxygenated membrane fabricated from it has an asymmetric structure that can resist plasma leakage for a long period of time. However, the relatively low rigidity of PMP oxygenated membrane makes it difficult to be processed in subsequent weaving and applications, during which deformation and fracture of HFMs often happen. In this work, the polymer alloy oxygenated membranes are fabricated by blending polypropylene (PP) as a high rigidity reinforcement agent with PMP via thermally induced phase separation (TIPS). Firstly, the effect of the PP content on phase separation structure and crystallization of alloy flat sheet membrane are investigated. When the PP content is 15 wt%, the rigidity of the alloy membrane reinforces dramatically. The elastic modulus and tensile strength of the PMP-PP-15 alloy membrane is 288.5 ± 12.4 MPa and 8.3 ± 0.4 MPa, respectively, which is 275.7 % and 96.7 % higher than that of the PMP membrane. Furthermore, PMP-PP-15 alloy HFM are fabricated under the optimum polymer composition. The elastic modulus of the PMP-PP-15 alloy HFM is 312.6 ± 16.0 MPa, which is 679.6 % higher than that of the PMP HFM and 40.1 % higher than that of the commercial PMP HFM. Meanwhile, the tensile strength and fracture stress are 15.4 ± 0.7 MPa and 186 ± 12.2 cN, respectively, which are both higher than those of the PMP and commercial PMP HFM. In addition, the PMP-PP-15 alloy HFM shows high gas permeability and oxygenation performance. This study might provide a convenient method to achieve rigidity reinforcement of PMP-based oxygenated membranes with great potential for application.

Patterned design of porous carbon materials as microporous layers to enhance fuel cell performance over a wide humidity range

Microporous layers play a crucial role as one of the main components of the membrane electrode assembly (MEA) in facilitating effective water management for proton exchange membrane fuel cells (PEMFCs), which is vital for maintaining optimal performance in a wide humidity range. Herein, Zn-based zeolitic imidazolate framework-8 (ZIF-8)-derived material (ZDM) as a porous carbon material is first developed to construct the microporous layer (MPL). With higher gas permeability, improved water management, and increased electrical conductivity, the MPL equipped with a ZDM layer, denoted as MPL-Z, exhibits superior performance, surpassing commercial MPLs throughout the range of 30–100% relative humidity (RH). The peak power density of an H2/air PEMFC at 70% RH utilizing a MPL-Z is 3.3 times that of commercial MPL. Furthermore, a unique patterned dual MPL is designed to boost the performance, ultimately achieving a peak power density of 1.50 W cm−2 (H2/air) with a low total Pt loading of 0.3 mgPt cm−2 at 100 % RH. Even at only 30% RH, the peak power density can reach 0.72 W cm−2 (H2/air). The results demonstrate that the material and structural design of the MPL allows for the efficient operation of low Pt loading PEMFCs over a wide humidity range.

Molecular Dynamics Simulations of Gas Transport Properties in Cross-Linked Polyamide Membranes: Tracing the Morphology and Addition of Silicate Nanotubes.

This study employs molecular dynamics (MD) simulations to fundamentally provide insight into the role of cross-link density in the CO2 separation properties of interfacially polymerized polyamide (PA) membranes. For this purpose, two atomistic models of pure polyamide membranes with different cross-link densities are constructed by MD simulations to conceptually determine how the fractional free volume of polyamide affects the gas separation performance of the membrane. The PA membrane with a lower cross-link density (LCPA) shows a higher gas diffusion coefficient, a lower gas solubility coefficient, and a higher gas permeability than the PA membrane with a higher cross-link density (HCPA). Moreover, the pristine and modified silicate nanotubes (SNTs) as the fast gas transport channels are incorporated into the polyamide membranes to assess the effect of the SNT/PA interface chemistry on the CO2 separation properties of the membranes. SNTs are systematically modified by three modifying agents with different CO2-philic groups and different interfacial interaction energies with the polyamide matrix. The results of MD simulations demonstrate that the incorporation of silicate nanotubes into the PA matrix increases the gas diffusivity and permeability and decreases the CO2/gas selectivity. Moreover, the membranes containing modified SNTs possessing high CO2-philicity and high SNTs/PA interfacial interactions show a high CO2 separation performance.

Gravitational modulation of filler distribution in asymmetric mixed matrix membrane: Achieving high loading in skin layer

The fillers in asymmetric mixed matrix membranes (AMMMs) by phase inversion tend to distribute across the membrane, but less in the skin layer, resulting in limited enhancement of gas separation performance. In this work, an external gravity field is proposed to induce polystyrene-acrylate (PSA) modified hollow ZIF-8 nanospheres (PHZ) to settle and accumulate in the skin layer by the density difference between ZIF-8 and the polymer solution, then through phase inversion, the gravity induced AMMMs (GAMMMs) with improved ZIF-8 loading in skin layer is constructed. This is confirmed by the EDS analysis of the membrane cross-sections that more PHZ settle and accumulate in the skin layer, which enhances the filler loading by 330 % in comparison to the AMMMs without gravity sedimentation. Together with the hollow cavity of PHZ, the gas permeation can be improved greatly. Meanwhile, the PHZ can also guarantee the favorable interfacial compatibility by the hydrogen bonding interaction between the carboxyl groups in PSA with the PES polymer matrix, which is demonstrated by the slightly elevated Tg of GAMMMs over the ZIF-8/PES membrane. Consequently, the PHZ/PES GAMMMs can achieve high gas permeation while keeping sufficient selectivity at high filler loading in the skin layer. The PHZ-8d/PES GAMMM shows H2 permeance of 29.11 GPU and H2/CH4 of 83.04, which are 142.85 % and 5.99 % higher than those of ZIF-8/PES AMMM without gravity sedimentation, and exceeding the corresponding 2008 Robeson upper bound. This proposed GAMMM shows a great potential in the large-scale MMMs based gas separation.

Sodium content in fermented shrimp paste with varying packaging materials

Shrimp and fish paste are fermented products with high amounts of added salt. Sodium (Na+ ) ions in salt are growth factors for halophilic lactic acid bacteria (LAB), essential in shrimp paste. However, an overabundance of Na+ negatively affects the human body and may increase blood pressure and the risk of heart attacks, strokes, kidney damage, and other health issues. Commercial shrimp paste can be found in various packaging materials. The permeability of the packaging material affects air availability during fermentation, which affects LAB growth and sodium levels. This study aimed to determine the effect different packaging materials have on rebon (Acetes sp.) shrimp paste sodium levels, precisely that of teak leaf, paper, and plastic. A completely randomized design and an experimental laboratory were used for the experiments. The data were analyzed using ANOVA and Honest Significant Differences tests. The different packaging materials significantly affected (P < 5%) the acidity, sodium levels, and total plate count (TPC) of LAB but did not affect the water activity or salt content. Shrimp paste consisted of 1.32±0.12% sodium when packaged in teak leaves, 1.51±0.08% in paper packaging, and 1.69±0.07% in plastic packaging. Teak leaves packaging resulted in shrimp paste with the lowest sodium content because of its many pores and high gas permeability, thus supporting the growth of microbes that use Na+ .

Bioinspired Robust Gas-Permeable On-Skin Electronics: Armor-Designed Nanoporous Flash Graphene Assembly Enhancing Mechanical Resilience.

Soft on-skin electrodes play an important role in wearable technologies, requiring attributes such as wearing comfort, high conductivity, and gas permeability. However, conventional fabrication methods often compromise simplicity, cost-effectiveness, or mechanical resilience. In this study, a mechanically robust and gas-permeable on-skin electrode is presented that incorporates Flash Graphene (FG) integrated with a bioinspired armor design. FG, synthesized through Flash Joule Heating process, offers a small-sized and turbostratic arrangement that is ideal for the assembly of a conductive network with nanopore structures. Screen-printing is used to embed the FG assembly into the framework of polypropylene melt-blown nonwoven fabrics (PPMF), forming a soft on-skin electrode with low sheet resistance (125.2 ± 4.7 Ω/□) and high gas permeability (≈10.08mg cm⁻2 h⁻¹). The "armor" framework ensures enduring mechanical stability through adhesion, washability, and 10,000 cycles of mechanical contact friction tests. Demonstrating capabilities in electrocardiogram (ECG) and electromyogram (EMG) monitoring, along with serving as a self-powered triboelectric sensor, the FG/PPMF electrode holds promise for scalable, high-performance flexible sensing applications, thereby enriching the landscape of integrated wearable technologies.

Blend Cellulose Acetate Butyrate Membrane with Molecular Weight 12,000, 30,000 and 65,000 for CO2/N2 Separation

The demand for energy has been increasing gradually due to the rapid growth of the global economy. The emission of greenhouses gases (GHGs) especially, carbon dioxide (CO2), which is a major greenhouse gas, has contributed to the global warming issue. Therefore, to reduce emissions and eliminate the serious consequences, membrane separation technology was introduced as an alternative option that has high CO2 separation efficiency. It requires lower energy consumption, lower capital costs and it is commercial and environmentally friendly. Most importantly, it is easy to operate. In this study, the blend cellulose acetate butyrate (CAB) membrane was synthesised from the CAB polymers using the wet-phase inversion method with molecular weights of 12,000:30,000:65,000 in the ratio of 1:2:2, respectively. The blend CAB membrane casted at 250 μm (M2) was the best performing membrane among all the membranes due to its relatively high CO2 gas permeance and the highest CO2/N2 selectivity, which were 7,560.80 ± 20 GPU and 1.5319 ± 0.05, respectively. The fabricated CAB membrane was then characterised by using the Attenuated Total Reflectance Fourier-Transform Infrared Spectroscopy (ATR-FTIR) and surface contact angle. It showed strong stretching bands around 1,044.07 cm−1, 1,226.25 cm−1 and 1,744.04 cm−1, which indicated a single bond C-O and carboxyl group (C=O). The higher the hydrophobicity of the membrane, the stronger the affinity for CO2 molecules. In this case, the contact angle of the membrane casted at 150 μm (M1) was 120.460, which was the highest. This newly synthesised CAB membrane is expected to benefit major industries by its cost effective and high energy saving properties. Most importantly, the gas separation efficiencies are better than the current technologies.

Fabrication of high-permeance SiC filters reinforced with in situ-grown mullite whiskers for gas/solid filtration

The pursuit of cost-efficiency, superior strength, and excellent gas permeance has driven the development of silicon carbide (SiC) membranes or filters for gas/solid filtration. In this study, SiC filters with high gas permeance reinforced with in situ-grown mullite whiskers were successfully prepared through reaction bonding. Low-cost kaolin and bauxite were used as sintering aids and raw materials for mullite whisker formation, and MoO3 was used as an additive to promote mullite whisker growth. The effects of different sintering temperatures and the addition of kaolin, bauxite, and MoO3 on filter performance were systematically investigated. When the sintering aid and MoO3 content additions were 6 and 1.5 wt%, respectively, and the sintering temperature was 1450 °C, the resulting ceramic filter exhibited a porosity of 45.5 %, a bending strength of 17.9 MPa, and an average pore size of 47.7 µm. Moreover, the filter exhibited a high Darcy’s permeability coefficient of 2.42 × 10−11 m2, satisfactory chemical stability, and thermal shock resistance. The addition of MoO3 facilitated the consumption of the molten phases and increased the anisotropic growth rate of the mullite whiskers, which contributed to the fabrication of the high-permeance filters. Finally, the ceramic filters demonstrated good performance for the filtration of dusty gases loaded with fly ash particles with a mean size of 15.3 µm at room temperature and 300 °C, and the removal rate reached > 99.9 %. The pressure drop was a little lower than that of our commercially available SiC filters. The SiC filters showed good prospects in the field of gas/solid filtration.