Unsupported Membranes Research Articles

Effects of porous supports and binary gases on hydrogen permeation in Pd–Ag–Y alloy membrane

This study investigates the effects of various porous supports and the presence of additional gases in the feed on hydrogen permeation using an unsupported Pd82–Ag15–Y3 membrane. The pore sizes and thicknesses of metallic supports varied from 1 to 270 μm and 50–3000 μm, respectively. The membrane was unsupported, synthesized by cold-rolling, and characterized by a thickness of 38 μm. The tests were performed at 400 °C with pressures ranging from 1.4 to 3 bar. Results showed that the unsupported Pd82–Ag15–Y3 membrane reached 12 % and 267 % higher hydrogen permeation than the supported membrane by 1 μm pore size and 50 μm thick woven mesh, and 1 μm pore size and 3 mm thick of porous stainless steel (PSS), respectively. The unsupported Pd82–Ag15–Y3 membrane showed one of the highest hydrogen permeability in the literature (7.5 × 10−8 mol m−1 s−1.Pa−0.5 at 400 °C). However, the presence of porous supports used to enhance the mechanical stability of the membrane negatively affected the hydrogen permeation due to mass transfer limitation. In addition, the presence of supports induced an unreal ‘n’ value for the Pd-based membrane, where the ‘n’ value is the exponent of the driving force in the equation of hydrogen transport, varying between 0.5 and 1. In particular, for the unsupported membrane, the ‘n’ value was 0.6, but it increased to 0.7 and 0.8 when supports with 1 μm pore size and 50 μm thick and 5 μm and 80 μm thick were utilized. Binary hydrogen permeation tests were also performed in the presence of N2, CH4, CO2, and CO at 400 °C by using unsupported and supported membranes to investigate the reduction in hydrogen permeation flux due to the effect of the supports plus the effect of the presence of other gas. The results revealed that CO had the highest inhibition effect for all the unsupported and supported membranes tested due to competitive adsorption on the surface. No superficial adsorption on the membrane was observed for N2, CH4, and CO2 during permeation, and they inhibited hydrogen permeation mainly due to depletion, dilution, and concentration polarization. The PSS_1–3000 indicated the lowest hydrogen permeation between the gas mixture and the porous support, whereas the presence of 40 % of the binary gas mixture had lower hydrogen permeation than porous support except for the PSS.

Mechanics of biomimetic free-standing lipid membranes: insights into the elasticity of complex lipid compositions.

The creation of free-standing lipid membranes has been so far of remarkable interest to investigate processes occurring in the cell membrane since its unsupported part enables studies in which it is important to maintain cell-like physicochemical properties of the lipid bilayer, that nonetheless depend on its molecular composition. In this study, we prepare pore-spanning membranes that mimic the composition of plasma membranes and perform force spectroscopy indentation measurements to unravel mechanistic insights depending on lipid composition. We show that this approach is highly effective for studying the mechanical properties of such membranes. Furthermore, we identify a direct influence of cholesterol and sphingomyelin on the elasticity of the bilayer and adhesion between the two leaflets. Eventually, we explore the possibilities of imaging in the unsupported membrane regions. For this purpose, we investigate the adsorption and movement of a peripheral protein, the fibroblast growth factor 2, on the complex membrane.

Influence of CO and PES support modules on filtration performance of 3D printed chitosan/AgNP/GO composite membranes

The filtration performance of Chitosan/silver-nanoparticles/graphene oxide (CS/AgNP/GO) composite membranes modified with Dimethyl acetamide (DMAc) were investigated in relation to the impacts of cotton (CO) and polyester (PES) fabric support modules. The contact angle of the modified CS matrix decreased with proper blending of membrane composites, which improved fluid transport due to strongly bound water oxygen-containing functional groups present in the modified chitosan, according to the FTIR report. After the addition of DMAc to the CS matrix, the composite's thermal stability increased, and the water absorption of the CO fabric was 16.3 % higher than that of the polyester (PES), indicating enhanced wettability. The average permeation flux for the CO-supported CS/AgNP/GO membrane was 50.38 Lm−2h−1, while that of PES and unsupported membranes were 46.28 Lm−2h−1 and 38.8 Lm−2h−1 respectively. Additionally, all the membrane samples demonstrated acceptable tensile strength and antifouling characteristics against Bovine Serum Albumin (BSA), with the unsupported CS/AgNP/GO composite displaying the highest fouling inhibition of 97.3 %. Therefore, the 3D-printed modified CS membranes can effectively be used for inhibiting fouling in water treatment.

Effects of structure and chemistry on electrochemical transport properties of anion exchange membranes for separation of CO2

ABSTRACT The effects of structure, chemistry, and morphology of an anion exchange membrane (AEM) for separation of CO2 from a humidified gas mixture were characterized to determine the influence on the kinetics and transport properties of a membrane electrode assembly (MEA). Supported and unsupported membranes with thicknesses of 30 µm and 50 µm were used to determine through-plane resistance, ion transport capacity, and gas diffusion properties. The effects of membrane saturation on the membrane resistance was characterized by impedance measurements under conditions with varying relative humidity from 0% to 100%. Permeability measurements with varying CO2 concentration from 1% CO2 to 10% CO2 at temperatures of 25°C and 35°C determined changes in the membrane behavior, which could influence the performance of the CO2 separating MEA. This study characterized how AEM properties influence the behavior and performance of an electrochemical separating CO2 MEA suitable for high-humidity, low CO2 concentration environments. Pt and IrO2 electrodes were used evaluate the performance of unsupported and supported membranes within a MEA, characterized by electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and constant-current measurements to examine the CO2 electromigration.

Fabrication and Characteristics of Methyl-Modified TiO2-SiO2 Membrane by Sol-Gel Method: Effect of Titania Content

Titania-doped methyl-modified silica membrane was prepared via an acid-catalyzed sol-gel method using tetraethylorthosilicate and methyltriethoxysilane as the silicon source and tetraethylorthosilicate as the titanium source. The influence of titanium/silicon molar ratio (nTi ) on the properties of TiO2-SiO2 sol and microstructure of unsupported TiO2-SiO2 membrane was systematically studied. The gas permeance and vapor stability of TiO2-SiO2 membrane were also tested. The results showed that, as nTi increased, the density, viscosity, refractive index and viscous activation Gibbs free energy of TiO2-SiO2 sol gradually decreased, while the particle size increased. The existence of Si-CH3 and Ti-O-Si bonds in TiO2-SiO2 membrane proved that the hydrophobic modification was successful and that SiO2 was chemically bonded to TiO2, respectively. The titanium element exists in form of Ti-O-Si structure and anatase phase TiO2 in TiO2-SiO2 membrane. When operated at 150 °C and a pressure difference of 0.3 MPa, the H2 permeance and H2/CO2 permselectivity of TiO2-SiO2 membrane with nTi =0.1 is 6.84 × 10−6 mol·m −2·Pa−1·s −1 and 6.96, respectively. After aging in the moist circumstance for 9 d, the H2 permeance of TiO2-SiO2 membrane reduced by 6.86%, while the H2/CO2 permselectivity increased by 2.71%.

Fabricating Ultra-thin Silicon Nitride Membranes Suspended on Silicon Wafer

Ultrathin silicon nitride SiNx membrane suspended on a silicon wafer is a popular two-dimensional platform in MEMS applications. The unsupported membrane has a low thermal conductivity, is electrically insulated, and very robust against mechanical impact. Remarkably thin, it is difficult to fabricate and manipulate. Recently equipped with a dual chamber system for plasma enhanced chemical vapor deposition (PECVD) and reactive ion etching, we calibrate it to deposit silicon nitride Si3N4, silicon dioxide SiO2, and to dry etch these materials. Based on the superb quality of Si3N4, we perform a through-wafer etch that creates suspended Si3N4 membranes. The recipe is reliable and reproducible. We analyze the membrane’s chemical composition and optical properties. Although created by PECVD, the membrane is so robust that it survives multiple lithography steps. It extends our capability to study thermal transport at the submicron scale as well as to fabricate micron size devices for MEMS applicati

Application of green synthesized ZnO nanoparticle coated ceramic ultrafiltration membrane for remediation of pharmaceutical components from synthetic water: Reusability assay of treated water on seed germination

Discharges from pharmaceutical sectors into water bodies are major environmental issue as most of them are persistent in nature and causes endocrine disruption. Treatment processes presently undertaken are not effective in complete removal of these contaminants. Removal study of ibuprofen has been undertaken by adsorption and nanofiltration membrane whereas little knowledge of atenolol separation by membrane has been reported. Ceramic ultrafiltration membrane developed from green synthesized zinc oxide nanoparticles (ZnO NPs) was employed in this present study for removal of atenolol and ibuprofen drugs from synthetic solution. About 96 % and 99 % removal of atenolol and ibuprofen respectively was obtained by single step ultrafiltration process. UF membrane developed had surface area of 21.503 m2/g and pore diameter of 39.8 Å. X-ray diffraction study of unsupported membrane showed pure phase crystalline zinc oxide particles. The effect of different parameters viz., TMP (Transmembrane pressure), time, feed concentration etc. on membrane filtration efficiency was analyzed by RSM (Response Surface Methodology). Germination studies on Vigna mungo was performed using untreated atenolol and ibuprofen solutions and membrane treated permeate to assess the membrane efficiency of producing clean water suitable for reuse. The study revealed higher germination rate in presence of ibuprofen solution but lower germination for atenolol solution. Protein content on the other hand were highly affected in both ibuprofen and atenolol solution. Seeds germinated in membrane permeate showed better germination rate and protein content and comparable to that of control.

Increasing lithium extraction performance by adding sulfonated poly (ether ether ketone) into block‐copolymer ethylene vinyl alcohol membrane

AbstractBACKGROUNDHigh efficiency membrane extraction (ME) of lithium from brine has been constrained by membrane mass transfer resistance. We report here a new solvent‐resistant membrane produced from ethylene vinyl alcohol (EVAL) and sulfonated polyether ether ketone (SPEEK).RESULTSThe effect of the SPEEK on the thermodynamics and kinetics of demixing to the membrane morphology was investigated systematically. Addition SPEEK created extra resistance to the movement of the polymer chains in solution which was reflected in the reduced gelation diffusion coefficient. About 0.5 wt% of SPEEK was sufficient to reduce the mass transfer resistance of lithium ions (Li+). Membrane thickness showed linear correlation with Li+ flux, but was limited by its weak mechanical strength. Finally, a composite EVAL/SPEEK membrane supported by a thin loose nonwoven fabric showed a stress of 12.5 MPa, nearly 10‐fold greater than the unsupported membrane, and the highest lithium extraction flux of 4.80 × 10−8 mol cm−2 s−1.CONCLUSIONThe work provides a rationale for developing mechanically stable, high extraction flux membranes for ME. © 2020 Society of Chemical Industry

Collagen-I/silk-fibroin biocomposite exhibits microscalar confinement of cells and induces anisotropic morphology and migration of embedded fibroblasts.

Microstructural anisotropy of tumor-associated matrix correlates with invasion of cancer cells into the surrounding matrix during metastasis. Here, we report the fabrication and characterization of a three-dimensional (3D) silk-fibroin/collagen-I bio-composite based cell-culture model that exhibits microstructural and biochemical anisotropy. Using RGD-deficient silk-fibroin fibers to confine collagen-I gelation, we develop a silk-fibroin/collagen-I (SFC) bio-composite in a one-step process allowing control over the microstructural and biochemical anisotropy and the pore-size. Two forms of the SFC bio-composite are reported: a sandwich (Sfc ) configuration amenable to live-cell microscopy and an unsupported membrane (Mfc ) for use as a scaffold. Both microscalar and macroscalar mechanical properties of the SFC bio-composite are characterized using atomic force microscope (AFM)-based indentation and tensile-testing. We find that the modulus of stiffness of both Sfc and Mfc can be controlled and falls in the physiological range of 5-20 kPa. Furthermore, the modulus of stiffness of Mfc exhibits a ~200% increase in axial direction of microstructure, as compared to lateral direction. This implies a highly anisotropic mechanical stiffness of the microenvironment. Live-cell morphology and migration studies show that both the morphology and the migration of NIH-3 T3 fibroblasts is anisotropic and correlates with microstructural anisotropy. Our results show that SFC bio-composite permits proliferation of cells in both Sfc and Mfc configuration, promotes cell-migration along the major axis of anisotropy and together with morphological and migration data, suggest a potential application of both the composite configurations as a biomimetic scaffold for tissue engineering applications.

The application of 3D printed resorbable polymer membranes in extraction sockets and implant sites

Background Hard tissue augmentation prior to and during dental implantation is one of the greatest areas of potential development. Graft materials and barrier membranes are widely utilised but offer relatively little structural support to the augmented tissue during the healing period. A directly 3D printed bioresorbable membrane has the potential to incorporate structural and design features offering support to the graft during bone formation while maintaining barrier properties. Aim/Hypothesis The aims of this study were to assess the feasibility and hard and soft tissue response of the placement of chair side produced sterile, resorbable polymer barrier membranes in extraction sites and buccal wall defects of dental implant sites. Materials and Methods Ten patients were selected with a mean range of 67 years for each of two groups. Group A required socket augmentation following extraction and the other group (B) buccal augmentation to repair a dehiscence or fenestration at the time of implant placement. Teeth were extracted and scanned as STL files (3-shape). The files were then used to design (Fusion 360 + AutoCAD) a rigid resorbable polymer graft (Polyoss R+ Ossform Pty. Australia). This was printed using a Graftmaker FDM 3D printer (Ossform Pty. Australia) as a sterile device at the chair side and fitted at the time of extraction implantation. Biooss (Geistlich AB, Switzerland) was used to fill any significant voids beneath the grafts. Characteristics of Inflammation+ Contour, Stiffness and Closure were ranked non-parametrically by the surgeon on a scale of 0-5 for each parameter at the time of surgery, 2,4,6 and 12 weeks after. Contour was further evaluated by scanning alginate impressions of each graft at placement and 12 weeks Results The parameters of Inflammation, Contour, Stiffness, Stability and Closure were ranked for each group (A - Socket augmentation, B- Implant placement) at 0, 2,4,6 and 12 weeks. The mean and median values for each parameter were tabulated. Mean values were rounded up or down as appropriate. The mean values for inflammation were (0 = no inflammation - 5 frank inflammation with crusting, breakdown and exudate) 0 for Groups A and B at all time intervals. Median values were 0 for both groups. Graft contour (0 for complete lack of contour - 5 as original anatomy) had a mean value of 3 for Group A and 4 for B.Graft stiffness (0 = no support just as an unsupported membrane - 5 sound bone) had mean values of 4 at all intervals for both groups. Stability (0 = moveable, slidable graft - 5 rigid, immobile graft) had mean values of 4 for Group A and 3 for Group B. Wound closure (0 for open socket - 5 is complete closure no exposure of membrane) had a mean value of 2 for Group A and 4 for Group B. Conclusion and Clinical Implications This preliminary clinical study demonstrates that a rigid resorbable polymer graft can be designed and fabricated at the chair side. It can be successfully placed at surgery with no evidence of inflammation. The graft offers benefits in terms of stiffness and support for the early bone formation whilst retaining the features of a barrier membrane. Further studies will provide a means of comparison with established technologies.

Modification of surface charge characteristics for unsupported nanostructured titania–zirconia UF/NF membrane top layers with calcination temperature

Ceramic membranes are more advantageous alternatives especially for harsh working conditions when compared with the polymeric membranes. The porous multilayer structure of the ceramic membranes (composed of support, intermediate, and top layers) can be prepared via different oxides. Titania and zirconia, having superior properties, are mainly preferred for the top layer formation. The separation properties of the membrane are both dependent on pore morphology and surface charge of the oxide(s) forming the top layer. The effect of surface charge in separation may be very significant in case of filtration of charged species with relatively lower mass as in the ultrafiltration (UF) and nanofiltration (NF). In this study, unsupported membrane top layers were prepared with varying titania/zirconia ratios by sol-gel technique. Their surface charges at different pH conditions after calcination at varying temperatures (400°, 500°, and 600 °C) were determined. The surface charge of the pure titania (full Ti) top layer was decreasing with the increasing calcination temperature. The highest magnitudes of zeta potential for both acidic and basic conditions were measured via Zr rich top layer (TiZr2575) at calcination temperatures ≥ 500 °C, which was composed of anatase, rutile (titania), and tetragonal (zirconia) phases after calcination. The tailor-made top layer can be prepared with modifications during membrane preparation.

Synthesis and Characterization of Mesoporous Hydrotalcite-Alumina Membrane for Carbon Dioxide Enrichment

Hydrotalcite material was incorporated to enhance the carbon dioxide (CO2) affinity of the alumina membrane for CO2 separation from different gas mixtures. The crack free mesoporous HT-alumina (∼10 µm) porous membranes were successfully synthesized on surface of α-Al2O3 disc support using the sol-gel and dip-coating techniques. The unsupported membranes were characterized for the presence of HT, surface functional groups, surface topography and morphology, pore size and CO2 adsorption capacity. These characterizations were done using X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectrometry, scanning electron microscopy (SEM), Brunauer-Emmett-Teller method (BET) and Thermo gravimetric analyser (TGA) techniques. The modification of alumina membrane with HT enhanced CO2 separation performance. The CO2 permeance was higher than that of methane and nitrogen. While the permeance of hydrogen was almost same to that of CO2 even though the hydrogen molecule was smaller than the CO2 molecule. Indicating that the gas transport through the membrane was predominantly surface adsorption. The mesoporous Hydrotalcite-alumina membrane overcame the Knudsen limitation and produced the highest permselectivity of 2.16 for CO2/CH4 system at 30°C temperature and 100 kPa pressure difference.

Effect of Peptizing Agent Concentration on Morphology of Unsupported Alumina Membrane

Ceramic membranes have received significant attention from both academia and industry, as they show the great potential in several important applications such as H2 separation, recovery of CO2 from natural gas and reduction of green-house gas emission from flue gas. The aim of the present study was to evaluate the effect of peptizing agent concentration on morphology of unsupported alumina membranes that are suitable for gas separation. The unsupported alumina membranes were prepared by the sol-gel method using aluminum-tri-sec-butoxide as a precursor and acetic acid as a peptizing agent. The particle size distributions of produced boehmite sols, as measured by dynamic light scattering technique, range from 10 to 600 nm. The increase in the concentration of acetic acid results in formation of particles of smaller median diameter. The pore volume and size distribution of unsupported alumina membranes were characterized by the Brunauer–Emmett–Teller (BET) method of adsorption of nitrogen gas. The pore size distributions of membranes were rather narrow in the range of 3 to 6 nm. The average diameter and volume of pores increase and the surface area decreases while the concentration of acetic acid increased.

Novel high flux nanofibrous composite membrane based on polyphenylsulfone thin barrier layer on nanofibrous support

A novel thin film nanofibrous composite (TFNC) polyphenylsulfone (PPSU) membrane was fabricated by casting a thin PPSU barrier layer on the surface of the electrospun nanofibrous PPSU support. Polyethylene glycol (PEG) 400 was applied in the electrospinning solution to prevent the penetration of coating solution into the support. The membrane morphology and filtration performance were investigated via scanning electron microscopy (SEM), and filtration of canned beans production wastewater, respectively. Atomic force microscopy (AFM) was utilized to evaluate the surface roughness of the membranes. Furthermore, the mechanical strength and thermal stability of the membranes were determined via tensile test and thermogravimetric analysis (TGA). Comparison of the TFNC membrane and the unsupported membrane prepared through the wet phase inversion method with almost equal rejection values indicated a 2.3 fold higher PWF using the former.

The mouse cortical meninges are the site of immune responses to many different pathogens, and are accessible to intravital imaging.

A wide range of viral and microbial infections are known to cause meningitis, and there is evidence that the meninges are the gateway to pathogenic invasion of the brain parenchyma. Hence observation of these regions has wide application to understanding host-pathogen interactions. Interactions between pathogens and cells of the immune response can be modified by changes in their environment, such as suppression of the flow of blood and lymph, and, particularly in the case of the meninges, with their unsupported membranes, invasive dissection can alter the tissue architecture. For these reasons, intravital imaging through the unperforated skull is the method of choice. We give a protocol for a simple method of two-photon microscopy through the thinned cortical skull of the anesthetized mouse to enable real-time imaging with sub-micron resolution through the meninges and into the superficial brain parenchyma. In reporter mice in which selected cell types express fluorescent proteins, imaging after infection with fluorescent pathogens (lymphocytic choriomeningitis virus, Trypanosoma brucei or Plasmodium berghei) has shown strong recruitment to the cortical meninges of immune cells, including neutrophils, T cells, and putative dendritic cells and macrophages. Without special labeling, the boundaries between the dura mater, the leptomeninx, and the parenchyma are not directly visualized in intravital two-photon microscopy, but other landmarks and characteristics, which we illustrate, allow the researcher to identify the compartment being imaged. While most infectious meningitides are localized mainly in the dura mater, others involve recruitment of immune cells to the leptomeninx.

Novelties in Synthesis of Unsupported and Crack-Free Titania Membranes from Metal Alkoxides Using Two-Way Controllable Sol–Gel Method

A novel approach has been developed to synthesize unsupported titania membranes by two-way controllable sol–gel method wherein polyvinyl alcohol (PVA) was used as a cost effective additive. Defect-free unsupported titania membranes were prepared using controlled hydrolysis by precursor modification and controlled gelation by addition of an organic binder. A suitable concentration of PVA was determined to produce minimum stress and form stable unsupported titania membrane. The optimized concentration of PVA (11.52 wt%) resulted in the formation of self-supported membrane with stable and reproducible textural properties like surface uniformity, larger surface area (118 m2/g) and smaller pore size (9.9 nm). Addition of PVA leads to the deceleration of transformation from anatase to rutile phase and formation of crack-free titania membrane having higher crystallinity. The membranes are fully characterized and will find many applications.

The heat and mass transfer of vacuum membrane distillation: Effect of active layer morphology with and without support material

Abstract The aim of this research was the analysis of heat and mass transfer in vacuum membrane distillation (VMD), specifically for a dead-end feed set-up. The influence of support material on the supported membranes VMD performance was identified. A mathematical model was proposed to evaluate the membrane/feed interface temperature, membrane tortuosity, membrane mass transfer coefficient, and temperature polarization coefficient (TPC). The model was solved by an excel solver based on experimental results of feed temperature, system pressure and the evaporative fluxes. The SEM images showed that the thickness of unsupported membrane was reduced by 42% after the VMD test. Pore shrinkage and tortuosity increase were also expected during this pore collapsing process. On the other hand, the cross-sectional views of the supported membranes did not show significant changes. These results show that the support material can help prevent the membrane pore channel structure from collapsing during the VMD experiment. TPC is close to unity at low feed temperatures. However, it decreases with an increase in evaporation flux as the feed temperature increases, or when a high flux supported membrane is applied.

Shrinkage, defect and membrane distillation performance of composite PVDF membranes

This study addresses the importance of non-woven support (NWS) during the preparation of polyvinylidene fluoride (PVDF) membranes for membrane distillation (MD). Five different NWSs were investigated as substrate materials for composite membranes. Additionally, a series of unsupported membranes were also tested. Unsupported membranes were found vulnerable to shrinkage that constricted and diminished their pores, rendering them unsuitable for MD. The NWS provides sufficient strength for a composite membrane, thanks to its stiffness, thus limiting membrane shrinkage which occurred severely in unsupported membranes. However, some composite membranes were also found vulnerable to shrinkage and defect when cast on a weak NWS. Shrinkage level worsened at higher casting thicknesses, higher polymer concentrations and when the NWS was pre-wetted before casting. Overall, our findings emphasize the importance of NWS selection and casting thickness optimization. High elastic modulus is the first criteria for NWS selection to avoid membrane shrinkage and defects. Optimizing the casting thickness is also vital for obtaining defect free composite membranes with high MD flux. Since MD flux is inversely proportional to net membrane thickness, low casting thickness increases the flux. However, thin casting imposes vulnerability with respect to membrane defect which can lead to membrane wetting.

Preparation and characterization of TiO<sub>2</sub> membrane on porous 316 L stainless steel substrate with high mechanical strength

In this work the preparation and characterization of a membrane containing a uniform mesoporous Titanium oxide top layer on a porous stainless steel substrate has been studied. The 316 L stainless steel substrate was prepared by powder metallurgy technique and modified by soaking-rolling and fast drying method. The mesoporous titania membrane was fabricated via the sol-gel method. Morphological studies were performed on both supported and unsupported membranes using scanning electron microscope (SEM) and field emission scanning microscope (FESEM). The membranes were also characterized using X-ray diffraction (XRD) and N₂ - adsorption / desorption measurement (BET analyses)- It was revealed that a defect-free anatase membrane with a thickness of 1.6 <i>μ</i>m and 4.3 nm average pore size can be produced. In order to evaluate the performance of the supported membrane, single - gas permeation experiments were carried out at room temperature with nitrogen gas. The permeability coefficient of the fabricated membrane was 4 × 10^-8 lit s^-1 Pa^-1 cm^-1.

Micro-porous silica–yttria membrane by sol–gel method: Preparation and characterization

Micro-porous yttria doped silica membrane, fabricated on alpha-alumina substrate and gamma-alumina interlayer, has been prepared via the polymeric sol–gel method. In order to investigate the hydrothermal stability of the membrane, silica sols with different amounts of 5, 15 and 25wt% yttria were prepared. These sols showed particle size distributions in the range of 0.6–3nm. It was found that the hydrothermal stability of the unsupported silica–15% yttria membrane heat treated at 500°C is the highest according to the results of FTIR analysis showing the formation of Si–O–Y bonds. XRD data showed thermal stability up to around 800°C for the unsupported silica membrane with 15% yttria. N2 adsorption–desorption isotherm confirmed the existence of micro-porous structure for this membrane as BET surface area and average pore size of the unsupported membrane was 286m2g−1 and 1.9nm, respectively. Modified substrate surface reduced average roughness and a layer with similar roughness and pore size was achieved. Cross sectional images by FESEM showed the thickness of 680nm for the obtained membrane.