Surface Pore Diameter Research Articles

Refined Pore Structure Design and Surface Modification of 3D Porous Copper Achieving Highly Stable Dendrite‐Free Lithium‐Metal Anode

Abstract3D porous copper is anticipated to serve as an ideal current collector for lithium‐metal anodes (LMAs) owing to its excellent conductivity, huge surface area, and cost‐effectiveness. However, most pertinent studies center around commercial copper foams, where their notable large pore size (150–400 µm) is identified as a primary inducement for dendrite formation and ultimate battery failure. Hence, ensuring the appropriate pore structure in 3D porous copper for achieving highly reversible lithium deposition/stripping process plays a pivotal role in stabilizing LMAs. Herein, the hydrogen bubble template method is employed to fabricate five distinct types of 3D porous copper. Among them, the one with an average surface pore diameter of 25.18 µm and the lowest probability of macropores distribution within the pore walls demonstrates optimal electrochemical performance. To further improve the inherent lithiophobicity of copper, Cu2Se/Cu2O heterostructure nanowires are loaded as kinetic enhanced nucleation sites. Benefiting from the synergistic effect of optimized pore structure and heterostructure nanowires, the Cu2Se/Cu2O@3D Cu composite current collector exhibits excellent dendrite‐free characteristics and outstanding electrochemical performance, showcasing an ultra‐long symmetrical‐cell lifespan of 3000 h at 1 mA cm−2 and stability for 300 h even under 20 mA cm−2.

Construction of the biocompatible and pH-sensitive prodrug nanoparticles via the self-assembly for improving tumor therapy

Endosomal pH-responsive micellar nanoparticles were prepared by self-assembly of a macromolecular poly(ethylene glycol)-Schiff-Doxorubicin (PEG-Schiff-DOX) prodrug.. These nanoparticles exhibited excellent storage stability for over 1 week under normal conditions, but disassembled quickly in response to faintly acidic environment. According to the EPR effect, the surface pore diameter of tumor blood vessels can reach hundreds of nanometers, while the surface pore diameter of ordinary blood vessels does not exceed 20 nanometers. Therefore, the chemical assembly of the drug is designed to have a diameter of 20-200 nanometers, thereby greatly improving the selectivity of the drug for tumor cells. Additionally, benefitting from the difference in drug release mechanism and rate between encapsulated DOX and conjugated DOX, a programmed drug release behavior was observed, which may result in higher intracellular drug concentration and longer action time. CCK-8 assays showed that the nanoparticles demonstrated superior antitumor activity than free PTX against both HeLa cells. These nanomedicines, which utilize prodrugs, exhibit immense promise in the advancement of translational DOX formulations for cancer treatment.

Response Surface Optimization of Electro-Spun Polyvinyl Alcohol Nano-Fiber Membrane Process Parameters and its Characterization

An empirical exploration into the effects of time duration, voltage supply, concentration and flow rate on the membrane average fiber diameter and surface pore size distribution were done using response surface methodology (RSM) based on central compact design (CCD). The average fiber diameter and average surface pore diameter of the membrane (i.e. 110 nm and 130 nm, respectively) were obtained at optimum input parameters of 45 min, 10 wt. %, 12 kV and 1.0 mL/h for time duration, concentration, voltage supply, and flow rate, respectively. The optimization study shows that the predicted versus actual values of both membrane fiber diameter and surface pore diameter are at R2 = 0.96. In addition, the effect of glutaraldehyde on membrane crosslinking was also assessed for further studies. The results from FESEM images of the fabricated PVA nanofiber membranes using the optimized parameters revealed that the membranes showed smooth morphological structures without formation of beads. The thermo gravimetric analysis (TGA) results displayed an improvement in thermal stability after membrane crosslinking. From this study we have observed that the membrane average fiber diameter and surface pore diameter can be controlled by varying the electro-spinning parameters and can be utilized for wastewater treatment application.

The antifouling and separation performance of an ultrafiltration membrane derived from a novel amphiphilic copolymer containing a crown ether

Amphiphilic copolymers have attracted extensive attention for the preparation of ultrafiltration (UF) membranes processed with high separation and antifouling performances. Herein, hydrophilic crown ether (dibenzo-18-crown-6-ether, DE) units were introduced into poly(p-terphenyl, isatin) (PDTI) based on a polycondensation reaction via superacid-catalysis. The copolymers showed good thermal stability and membrane-forming properties, and the UF membranes fabricated by NIPS exhibited excellent separation performance. The content of the hydrophilic DE significantly influenced the morphology structure of the UF membranes. The cross-section structure of the membranes gradually converted from finger-like pores to loose sponge pores during delayed phase separation. The water flux of membranes ascended from 130.9 LMH bar−1 to 286.6 LMH bar−1 while the BSA rejection rate decreased from 99.4% to 90.8% as the DE content increased from 10% to 30%. These changes were associated with an enhanced surface porosity, larger surface pore diameter, and thinner top layer. Moreover, increasing the DE content in the copolymer greatly improved the antifouling performance due to greater hydrophilicity. Upon increasing the molar ratio of DE to p-terphenyl from 1: 9 to 3: 7, the flux recovery rate of the membranes surged from 58.5% to 91.5% and remained >80.2% after three fouling-cleaning cycles. In addition, the surface segregation of the hydrophilic DE segment in the copolymer was confirmed by the higher oxygen element content of the UF membrane on the top surface (18.62%) than that of the polymer (13.97%). Therefore, the amphiphilic copolymer containing a crown ether synthesized by a one-pot polycondensation reaction provides an effective way for the preparation and property adjustment of UF membranes.

Production and Characterization of Bilayer Tissue Scaffolds Prepared with Different Alginate-Salts and Fibroin

The presented study aimed to design and characterize bilayer Alginate/Fibroin scaffolds to provide faster and higher quality treatment of skin tissue losses with tissue engineering approach. In this context, it was tried to form the dermis and epidermis layers with alginate salts (sodium and calcium) and fibroin with a biomimetic approach, and it was aimed to determine the most suitable alginate salt-fibroin composite scaffold by trying different production methods. The optimum design was determined by macroscopic measurement and dimensional analysis of the scaffolds produced by four different methods and their chemical structures were controlled with FTIR. Among the produced scaffolds, calcium alginate/fibroin (CaAlg/Fb) scaffolds were determined to have the most suitable morphological and chemical structure. With further characterization, the pore distribution and size were examined by SEM analysis and it was determined that surface pore diameters vary from 30 µm to 300 µm which are suitable for cell settlement. The thermal stability of the structure was determined by thermal gravimetry, and the degradation rate was calculated from the thermograms. According to the TG analysis, decomposition of the CaAlg/Fb scaffolds occurs much faster with temperature than homo-biopolymeric (CaAlg and Fb) structures. As a result, it was found that bilayer CaAlg/Fb scaffolds were capable of forming full-thickness dermal and/or also osteochondral wound dressings both morphologically and structurally. It is recommended to perform the tissue forming ability of this scaffold structure by performing advanced biological analyzes.

Ultrathin DDR Films with Exceptionally High CO2 Flux and Uniformly Adjustable Orientations

AbstractThin and oriented zeolite films are important for advanced separations, catalysis, and sensing. Strategies for tailoring zeolites for applications include controlling their crystal size, shape, and orientation. Here, three siliceous DDR zeolite ultrathin films with different orientations achieved by homoepitaxial growth from 60 nm‐sized seed particles are reported. The 0.5 µm thick membrane shows a separation selectivity of 400 for CO2–CH4 mixtures and CO2 permeance of 25 × 10‐7 mol m‐2 s‐1 Pa‐1 at 20 °C and 1 bar, leading to a record‐high performance among all reported DDR membranes. Furthermore, the seed nanoparticles are grown into mono‐dispersed DDR sub‐micron crystals with trigonal and tabular habits. These crystals are assembled in monolayers for the growth of ultrathin and uniformly (h0h)‐oriented and c‐oriented films with maximum surface pore diameter of 0.365 and 0.263 nm, respectively, by using the 1‐adamantanamine template in fluoride medium. The novel strategy not only provides high‐performance membrane candidates for industrial CO2 separation, but also inspires interfacial engineering, pore size, and orientation controlling for other microporous crystals, and their membranes.

PVDF Composite Membranes with Hydrophobically-Capped CuONPs for Direct-Contact Membrane Distillation.

Water scarcity is an imminent problem that humanity is beginning to attempt to solve. Among the several technologies that have been developed to mitigate water scarcity, membrane distillation is of particular note. In the present work, CuO nanoparticles capped with 1-octanethiol (CuONPs@CH) or 1H,1H,2H,2H-perfluorodecanethiol (CuONPs@CF) are prepared. The nanoparticles are characterized by FT-IR and TGA methods. Two weight losses are observed in both cases, with the decomposition of the organic fragments beginning at 158 °C and 230 °C for CuONPs@CF and CuONPs@CH, respectively. Flat sheet PVDF composite membranes containing nanoparticles are prepared by the casting solution method using nanoparticle concentrations that ranged between 2–20% with a non-woven polyester fabric as support. The obtained membranes showed a thickness of 240 ± 40 μm. According to water contact angle (87° for CuONPs@CH and 95° for CuONPs@CF, both at 10% w.t) and roughness (12 pixel for CuONPs@CH and 14 pixels for CuONPs@CF, both at 10% w.t) determinations, the hydrophobicity of membranes changed due to a decrease in surface energy, while, for naked CuONPs, the roughness factor represents the main role. Membranes prepared with capped nanoparticles showed similar porosity (60–64%). SEM micrographs show asymmetric porous membranes with a 200-nm surface pore diameter. The largest finger-like pores in the membranes prepared with CuONPs, CuONPs@CH and CuONPs@CF had values of 63 ± 10 μm, 32 ± 8 μm, and 45 ± 10 μm, respectively. These membranes were submitted to a direct contact membrane distillation module and flux values of 1.8, 2.7, and 3.9 kg(m2·h)−1 at ΔT = 30 °C were obtained for the CuONPs, CuONPs@CH, and CuONPs@CF, respectively. The membranes showed 100% salt rejection during the testing time (240 min).

Modification of polyethylene terephthalate track etched membranes by planar magnetron sputtered Ti/TiO2 thin films

This study investigates the surface modification of polyethylene terephthalate track-etched membranes by planar magnetron sputtering of titanium and titanium dioxide thin films to improve its hydrophilicity and photocatalytic activity. After cold plasma treatment to enhanced adhesion, Ti thin films were deposited by planar magnetron sputtering and TiO2 thin films by reactive magnetron sputtering in an Ar-O2 gas atmosphere. The morphology of the deposited thin films was characterised using atomic force microscopy and scanning electron microscopy. The pores retained a mostly circular shape. However, the modified track membrane's surface pore diameter reduced from 0.2 µm to 0.15 µm for Ti coated samples and 0.08 µm for Ti-TiO2 coated samples. Structural studies using X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy and Raman spectroscopy of Ti and TiO2 thin films revealed the intricate composition of the sputtered thin films which was a result of the complexity of sputtering on top of the porous polymer support. Additional investigations in surface wettability and bandgap showed a significant change in the track membrane surface's hydrophilicity and photocatalytic properties after depositing TiO2-Ti, adding to the self-cleaning properties of the coated TM. The bandgap of the film was 3.1 eV and of the indirect type. Both Ti and TiO2-Ti sputtering over the TM surface significantly reduced the water contact angle from 72° for untreated PET to 43° and 45° for Ti-TM and TiO2-Ti-TM, respectively. This study shows that planar magnetron sputtering is a viable approach to surface modification of a porous polymeric support, such as track-etched membranes. The sputtered coating enhanced membrane hydrophilicity, thereby reducing the chance of surface fouling by organic substances, which leads to improved self-cleaning properties.

The Influence of Water Immersion on the Physical and Chemical Structure of Coal

ABSTRACT In order to reveal the reaction mechanism responsible for the spontaneous combustion of water-immersed coal, this study researched the changes in the physical and chemical structures of coal samples before and after water immersion. The results of the specific surface and pore size analyzer test showed that compared with the original coal sample, the microporous (<10 nm) ratio decreased, but the proportion of macropores (>50 nm) increased obviously in the water-immersed coal sample. Also, as the water immersion time increased, the proportion of micropores decreased from 78.5% to 74.2%, while the proportion of macropores increased from 8.5% to 13.4%. The increase in the number of macropores increased the exposure of coal to oxygen. The scanning electron microscopy (SEM) results showed that the surface pore diameter of the water-immersed coal sample increased obviously, the surface of the coal sample was rougher, and the adsorption and diffusion of oxygen were enhanced. The Fourier transform infrared (FTIR) experiment showed that the contents of hydroxyl and aliphatic groups with higher activity in water-immersed coal samples increased significantly. The content of hydroxyl groups increased in lignite, bituminite, and anthracite by 2.7%, 2.27%, and 0.11% respectively, while the contents of aromatic hydrocarbons and oxygen-containing functional groups showed relative decreases. Compared with the original coal, the physical and chemical structure of water-immersed coal changed obviously. Therefore, it was easier for the water-immersed coal to react with oxygen, and it was also prone to spontaneously ignite.

New Concept in Humidity Sensing: Role of Molecular Brownian Energy and Probabilistic Mean Free Path to differentiate RH- and Trace Level Detection.

A break in the traditional pore morphology approach in anodic alumina is presented here to see its niche merit over the conventional sensors for water vapor detection. The cylindrical pore structure was replaced with a normal cone for trace-level and inverse cone for RH-level detection. The normal conical pore was fabricated by sheer manipulation of the reaction rates of electrolytes, anodic polarization, rate and time; the procedure was reversed in the case of the inverse cone structure. A sensor with a normal cone geometry exhibits excellent response at the ppm level and slightly extended to low RH level with a detection range of 120 ppm-30% RH, having response and recovery times of 6 and 255 s, measured at 120 ppm. Lowering of the minimum detection limit further requires alteration of the conical geometric parameters, in tandem with the molecular dynamics of water vapor molecules within the pore. In contrast, a sensor developed from an inverse conical structure shows response only at the RH level, from 20% RH to 90% RH with response and recovery times of less than 60 s over the entire range. Limitations such as nonlinear response, large response-recovery time, and high hysteresis as observed in conventional anodic alumina-based humidity sensors have been removed. The sensor response in conical and inverse conical pore morphologies is compared with that of standard sensors having a cylindrical pore morphology, with a top pore diameter identical with that of the reported sensors. The standard sensors were found to detect in the RH range only, with response and recovery times below 20s. The sensing mechanisms in both structures have been suitably demonstrated and ratified with experimental data. Trace level detection is interpreted with the statistical probabilistic approach in the light of the kinetic theory of gases and Brownian energy. A correlation between top surface pore diameter (through which water molecules enter) and the optimized mean free path of vapor molecule is established, and its effectiveness has been demonstrated for humidity detection at a trace level. The results are encouraging, and the same concept may be tried for the detection of other gaseous stimuli, including organic vapors.

3D Macroporous Catalysts: Impact of Additives on the Morphology and Performance of Cu/Cu2O Foam Prepared by Dynamic Hydrogen Bubble Template Towards Glycerol Electro-Oxidation

Macroporous Cu/Cu2O foam is electrochemically prepared using the dynamic hydrogen bubble template technique (DHBT) where a highly porous honeycomb-like Cu/Cu2O film is obtained. Various additives such as (NH4)2SO4, KBr, and KCl are added into the deposition bath of Cu to study their effect on the formation of Cu/Cu2O macroporous foam and their impact towards glycerol electro-oxidation reaction (GOR). The morphological structure, surface pore diameter, and electro-active surface area are tuned. The electrochemical activity of the foams is improved towards glycerol electro-oxidation reaction in alkaline medium. The macroporous film prepared in the presence of KBr shows the best catalytic performance due to its high electro-active surface area and surface pore diameter. Material and electrochemical characterization (e.g. SEM, XRD, and CV) techniques were used to relate the observed enhancement to the morphology, composition, and structure of the as synthesized Cu/Cu2O foams.

Development of an antibacterial and visible photocatalytic nanocomposite microfiltration membrane incorporated by Ag3PO4/CuZnAl NLDH

Novel microfiltration mixed matrix membranes (MMMs) were successfully prepared by embedding the Ag3PO4/ZnAlCu nanolayerd double hydroxide (NLDH) nanocomposite into the polyethersulfone (PES) matrix. The results demonstrated that adding the Ag3PO4/ZnAlCu-NLDH nanocomposite improved the antifouling properties in the microfiltration process with the increase of hydrophilicity, porosity, surface pore diameter, and antibacterial properties. When the content of the nanocomposite was 0.5 wt%, the pure water flux was increased to 269.5 L m−2 h−1, as compared with the pristine PES membrane (229.2 L m−2 h−1). Surprisingly, it was found that embedding only 0.5 wt% of the Ag3PO4/ZnAlCu-NLDH nanocomposite in the PES matrix could spring up an antibiofouling membrane with the flux recovery ratio (FRR) of 62.3%, as compared to the pristine PES membrane with 50.9% of FRR. As confirmed by the inductively coupled plasma optical emission spectroscopy (ICP-OES), the copper and silver assembly in the PES membranes resulted in controlled leaching, proving that more than 95% of the added nanocomposite remained in the membrane after two months. The fabricated Ag3PO4/ZnAlCu-NLDH nanocomposite membranes also exhibited appreciable antibacterial efficiency against E. coli, Staphylococcus aureus, and B. anthracis. This study, therefore, suggests Ag3PO4/ZnAlCu-NLDH could be an effective additive to modify the PES microfiltration membrane for the development of MBR membranes.

Study on preparation and properties of polyimide lithium battery separator

Soluble polyimide was synthesized from 4, 4’-(4, 4’-Isopropylidenediphenyl-1, 1’-diyldioxy) dianiline (BAPP), 4, 4’-Diaminodiphenyl ether (ODA) and 4, 4’-Oxydiphthalic anhydride (ODPA) in a certain proportion. The porous polyimide (PI) membranes were prepared by phase transfer method. The molecular structure, pore size, contact angle and thermal stability were characterized by fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), contact angle measuring instrument. The results show that the prepared porous polyimide membranes have three-dimensional network of microporous structure with a surface pore diameter of 0.5-1 μm; The porosity increases with the increasing quality ratio of anhydrous ethanol and acetone in the solution, which reaches more than twice of the conventional Celgard 2400 membrane;The contact angles of the porous polyimide membranes are smaller than that of separator of the Celgard 2400 membrane and showing better lyophilicity, which were all take distilled water as the test solution. The porous polyimide membranes have better heat resistance, and the size does not change significantly after heat treatment at a maximum of 180°C for 0.5 h.

電界誘起気泡による穿孔とインジェクションの研究

For this study we have evaluated pore formation and injection performance of electrically-induced bubbles for minimally-invasive injection technology. It is important to note that this device use synergy effect of shock wave and micro-jet of cavitation to process the object. Hence, we have evaluated the contribution of shock wave and micro-jet to pore formation and injection of bubble injector. Agarose gel is employed to be injected by bubble injector, and evaluated the depth and surface pore diameter by visualizing with fluorescent beads. It was observed that the depth and diameter of pore is increase with increase input power. Also, it was confirmed that the invasiveness by shock wave is more dominant than micro-jet contribution. The size of shock wave and the distance between the injector and processing object can be the important parameter to discriminate the invasiveness of injection.

Thin film nanocomposite forward osmosis membranes based on layered double hydroxide nanoparticles blended substrates

One of the biggest challenges for the practical application of forward osmosis (FO) is lack of high-performance FO membranes. In this study, a novel thin film nanocomposite (TFNC) FO membrane was fabricated based on a layered double hydroxide nanoparticles (LDH-NPs) blended ultrafiltration substrate. The influence of the LDH-NPs addition on the physicochemical properties of the ultrafiltration substrate and the resultant FO membrane was systematically investigated. The addition of LDH-NPs endowed the ultrafiltration substrate with increased porosity, surface hydrophilicity, surface pore diameter, mechanical strength and thermal stability. Consequently, all the resultant TFNC FO membranes obtained increased water permeability as compared with pristine FO membrane. Specifically, the TFNC membrane with a 2wt% LDH-NPs dosage exhibited a water flux of 18.1Lm−2h−1 (~42.5% higher than that of the pristine FO membrane) with little compromise in reverse salt flux. Moreover, this membrane reached a higher water flux of 26.9Lm−2h−1 when 2M NaCl was used as draw solution. The water-flux increase could be attributed to the decrease of the structural parameter (S value) of the LDH-NPs blended ultrafiltration substrate. The loaded LDH-NPs facilitated the development of a considerable amount of finger-liked macrovoids, which decreased the support layer tortuosity thus favoring the inhibition of internal concentration polarization. As a result, a moderate water flux was obtained. To the best of our knowledge, this is the first reported TFNC membrane using LDH-NPs blended substrates for FO applications.

Effects of coagulation bath temperature on polyurethane-based hollow fiber membrane morphology

Polyurethane-based hollow fiber membranes were prepared via melt-spinning method. Effects of coagulation bath temperature (CBT) on membrane outer surface and inner surface morphology were studied in detail by image analysis software. Based on the SEM images, membrane surface pore diameter and porosity were calculated, whereas the interconnected pore size and its distribution were determined using capillary flow porometer. Results show that increasing CBT could improve the membrane outer surface porosity at least twice. Thinner hollow fiber membrane with larger inward water flux could be prepared at higher CB-I (the first coagulation bath) temperature. Higher CB-II temperature (the second coagulation bath) could cause pore contraction and reduce the average diameter of outer surface pore. CBT in the early stage controlled the obtained membrane pore size and its distribution.

Polystyrenes with Hydrophilic End Groups: Synthesis, Characterization, and Effects on the Self-Assembly of Breath Figure Arrays

We report the synthesis and characterization of a series of hydroxyl-end-functionalized polystyrenes (PS-OH) and the formation of patterned porous films. The polymers were synthesized by chain end reaction of polystyrene having a bromide end group (PS-Br) with hydramines including ethanolamine, diethanol amine, 2-amino-1,3-propanediol, and 2-(2-aminoethoxy) ethanol. The polymers were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), and differential scanning calorimetry (DSC). It was found that the end groups can influence the glass transition temperature (T(g)) of the polystyrenes. The polymers with different end groups were then used to prepare honeycomb-patterned porous films by the breath figure method. Results reveal that the subtle chain-end modification leads to a dramatic change in the morphology of the films. Honeycomb films with large area ordered structure can be easily prepared from PS-OH. Effects of the end groups as well as blending PS-OH with PS-Br on the surface pore diameter, pore center distance, and the hierarchical structure were studied in detail. As supported by the results of polymer hydrophilicity, in situ observation of the film formation process, as well as the chain mobility, the film structure is supposed to be mainly determined by the precipitation of polystyrene at the solution/water droplet interface and the interfacial activity enhanced by the end groups.

Facile surface glycosylation of PVDF microporous membrane via direct surface-initiated AGET ATRP and improvement of antifouling property and biocompatibility

This paper describes a facile and novel approach for the surface glycosylation of poly(vinylidene difluoride) (PVDF) microporous membrane. A glycopolymer poly(d-gluconamidoethyl methacrylate) (PGAMA) was tethered onto the membrane surface via activators generated by electron transfer atom transfer radical polymerization (AGET ATRP) directly initiated from the PVDF surface. Chemical changes of membrane surface were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). It was revealed that PGAMA was successfully grafted onto the membrane surface and its grafting density can be modulated in a wide range up to 2.4μmol/cm2. The effects of glycosylation on membrane morphology, flux and surface hydrophilicity were investigated. Field emission scanning electron microscopy (FESEM) results indicated shrinkage of the surface pore diameters and the growth of the glycopolymer layer on the membrane surface. The static water contact angle (WCA) of the membrane surface decreased from 110° to 30.4° with the increase of grafting density, indicating that the PGAMA grafts dramatically improved the surface hydrophilicity. The protein adsorption and platelets adhesion experiments indicated that the grafted PGAMA could effectively improve the membrane antifouling property and biocompatibility.

Taguchi design of experiments approach to the manufacture of one-step alumina microfilter/membrane supports by the centrifugal casting technique

The Taguchi design of experiments method was implemented for the optimization of the manufacture of sintered one-step alumina microfilter/membrane supports by the centrifugal casting technique for the first time. A 10 wt.% alumina aqueous slip containing Tiron (0.001 g/g alumina) as dispersant and PVA as binder were used. Acceleration (3 levels), slip volume (3 levels), binder content (3 levels) and pH (2 levels) were selected as controlling parameters (saturated L-9 array). The use of three different target functions has been discussed: (1) the product of top-layer surface porosity times the reciprocal of top-layer surface pore diameter; (2) the product of permeability times thickness; and (3) membrane curvature. It is deduced that the first target function is the most appropriate as far as the membrane characteristics of the sintered compact are concerned. Using this target function a distinct optimum configuration for the controlling parameter levels could be obtained.

Zeta potential measurements of zeolite Y: Application in homogeneous deposition of particle coatings

Zeolite membranes are typically grown from thin coatings of sub-μm size zeolite particles on porous supports. The particles have the function of seeds in forming a dense zeolite membrane by a secondary growth process. This study focuses on how seed layer coatings can be optimally produced, crack- and agglomerate-free, by dip coating from stable dispersions of nano-crystalline zeolite Y. Surface charge and colloidal charge stabilization were optimized by adjusting the pH to 11.5 at a low ionic strength. The coatings were formed in a combination of film and slip coating on quasi-homogeneous flat porous α-Al 2O 3 supports with a typical surface pore diameter of 40 nm. The optimum pH was established with zeta potential measurements of the dispersion. Optimum conditions resulted in excellent homogeneity, <500 nm thickness of the seed layers with a deposition technique that makes it possible to coat large areas. This makes this process suitable for the production of thin, defect-free, and stable supported zeolite Y membranes by subsequent secondary growth.