Porous Alumina Membranes Research Articles

(Invited, Digital Presentation) Vertical Heterogeneous Integration of Metal Halide Perovskite Quantum-Wires/Nanowires for Flexible Narrowband Photodetectors

Charge collection narrowing (CCN) has been reported to be an efficient strategy to achieve optical filter-free narrowband photodetection (NPD) with metal halide perovskite (MHP) single crystals. However, the necessity of utilizing thick crystals in CCN limits their applications in large scale, flexible, self-driven, and high-performance optoelectronics. Here, for the first time, we fabricate vertically integrated MHP quantum wire/nanowire (QW/NW) array-based photodetectors in nanoengineered porous alumina membranes (PAMs) showing self-driven broadband photodetection (BPD) and NPD capability simultaneously. Two cutoff detection edges of the NPDs are located at around 770 and 730 nm, with a full-width at half-maxima (fwhm) of around 40 nm. The optical bandgap difference between the NWs and the QWs, in conjunction with the high carrier recombination rate in QWs, contributes to the intriguing NPD performance. Thanks to the excellent mechanical flexibility of the PAMs, a flexible NPD is demonstrated with respectable performance. Our work here opens a new pathway to design and engineer a nanostructured MHP for novel color selective and full color sensing devices. Figure 1

Research on the gas migration trend and mechanism of the transition flow regime in coal based on MRT-LBM simulation

In order to reveal the process and mechanism of gas flow in a low-permeability coal seam, a new multiple-relaxation-time lattice Boltzmann method (MRT-LBM) model of gas migration in coal micro/nanopores based on Langmuir monolayer adsorption theory, the slip boundary scheme and Bosanquet effective viscosity was established. The software MATLAB was used to carry out the simulation study of uniform pore gas flow based on the MRT-LBM model, and the results were compared and verified with the porous anodic alumina membrane gas flow experimental results. On this basis, the gas flow in coal pores with different micro/nanopore sizes considering adsorption was simulated. The results show that the dimensionless permeability coefficient increases with decreasing pore size under the same pressure, which reflects the subsequent enhancement of the microboundary constraint effect and reveals that the pore system becomes the main controlling factor of coal seam permeability within the coal matrix in the middle and late stages of coal seam gas extraction, while the role of the microboundary constraint effect needs to be considered. The gas adsorption layer weakens the pore gas flow capacity, but for pores with a radius greater than 16 nm, the apparent change in permeability caused by the adsorption layer is less than 5%, and the adsorption effect can be ignored. N2, CH4, and CO2 enter the transition flow regime under different pressure conditions; with gas extraction, the gas pressure decreases, and the difference in the gas flow characteristics of the three gases increases.

High-Performance pH Sensor Electrodes Based on a Hexagonal Pt Nanoparticle Array-Coated Nanoporous Alumina Membrane.

Porous anodic alumina membranes coated with Pt nanoparticles (PAAM/Pt) have been employed as pH sensor electrodes for H+ ion detection. The PAAM was designed using a two-step anodization process. Pt nanoparticles were then sputtered onto the membrane at different deposition times. The membrane’s morphological, chemical, and optical characteristics were carefully assessed following the fabrication stage using a variety of analytical techniques. The potential of the PAAM/Pt sensor electrode was investigated by measuring the potential using a simple potentiometric method. The effects of depositing Pt nanoparticles for 3–7 min on sensor electrode sensitivity were examined. The optimal potentiometric Nernstian response slope for the PAAM/Pt sensor electrode with 5 min Pt sputter coating is 56.31 mV/decade in the pH range of 3.0 to 10 at 293 K. Additionally, the PAAM/Pt sensor electrode’s stability and selectivity in various ions solutions were examined. The sensor electrode had a lifetime of more than six weeks and was kept in a normal air environment.

Large-scale perovskite light-emitting diodes enabled by quantum-wire arrays: One step closer to commercialization

Halide perovskite light-emitting diodes (PeLEDs) are enticing candidates for displays and lighting. However, it remains a challenge for devices to upscale to large-area or non-planar structures with high uniformity. Recently, in <i>Nature Photonics</i>, Fan and co-workers developed perovskite quantum-wire arrays templated by porous alumina membranes to achieve highly uniform performance LEDs based on wafer-scale substrates and three-dimensional spherical structures.

The Interrelation of Synthesis Conditions and Wettability Properties of the Porous Anodic Alumina Membranes.

The results of studies on the wettability properties and preparation of porous anodic alumina (PAA) membranes with a 3.3 ± 0.2 μm thickness and a variety of pore sizes are presented in this article. The wettability feature results, as well as the fabrication processing characteristics and morphology, are presented. The microstructure effect of these surfaces on wettability properties is analyzed in comparison to outer PAA surfaces. The interfacial contact angle was measured for amorphous PAA membranes as-fabricated and after a modification technique (pore widening), with pore sizes ranging from 20 to 130 nm. Different surface morphologies of such alumina can be obtained by adjusting synthesis conditions, which allows the surface properties to change from hydrophilic (contact angle is approximately 13°) to hydrophobic (contact angle is 100°). This research could propose a new method for designing functional surfaces with tunable wettability. The potential applications of ordinary alumina as multifunctional films are demonstrated.

(Invited, Digital Presentation) Nanostructured Perovskite Resistive RAM for Next Generation Data Storage

Resistive RAMs (Re-RAMs) have emerged as a propitious candidate among next generation non volatile memories because of their strikingly fast speed, prolonged data retention ability and high storage density. Herein, we developed an electrochemical metallization (ECM) based Re-RAM with three-dimensionally integrated single-crystalline perovskite (methyl ammonium lead halide or MAPbX3 where X=I, Br and Cl) quantum wire (PQW)/ nanowire (PNW) array embedded in a nano-engineered porous alumina membrane (PAM) serving as the switching medium. The PQWs and PNWs were grown inside the PAM template by a vapor-solid-solid-reaction (VSSR) process and were clubbed between silver (Ag) and aluminum (Al) contacts. The nanostructured perovskite Re-RAM exhibited 100 ps switching speed which is a record for perovskite Re-RAMs and also among the fastest for all types of Re-RAMs reported. The fast switching was attributed to the increased ionic (Ag+) and electronic mobility and subsequent accelerated filament formation within the body of the monocrystalline PQWs/PNWs. The PAM scaffolding imparted material and electrical stability to the environmentally delicate perovskite. As a consequence, we were able to obtain a record long (among perovskite Re-RAMs) estimated retention time > 28 years and record-high (among perovskite Re-RAMs) uninhibited cyclic endurance of 6×106 cycles. Also, utilizing the ultra-high density (2×1011/cm2) of the PQWs, a 14 nm lateral dimension ultra-small memory cell was built. In conjunction with multi-bit switching, an effective device footprint of 76.5 nm2 was achieved for a single bit storage. Further, as a concept proof, an 8×8 Re-RAM crossbar array device was fabricated which demonstrated temporally robust alphabetic data storage, with a unique metal-semiconductor-insulator-metal (MSIM) architecture to alleviate the sneaky path problem. The MSIM scheme based on quasi-self-selecting elements, demonstrated a strong potential for unhindered scalability in the future, a problem often encountered with integrating external selecting diodes and transistors. The PQW/PNW Re-RAMs also responded to light stimuli, exhibiting optical programmability among the low resistance states. In summary, these intriguing results propel perovskite Re-RAMs to the state-of-the-art standard and demonstrate an attractive potency for PQW/PNW devices to be used as an alternative technology in future storage and computing modules.

Vertical Heterogeneous Integration of Metal Halide Perovskite Quantum-Wires/Nanowires for Flexible Narrowband Photodetectors

Charge collection narrowing (CCN) has been reported to be an efficient strategy to achieve optical filter-free narrowband photodetection (NPD) with metal halide perovskite (MHP) single crystals. However, the necessity of utilizing thick crystals in CCN limits their applications in large scale, flexible, self-driven, and high-performance optoelectronics. Here, for the first time, we fabricate vertically integrated MHP quantum wire/nanowire (QW/NW) array based photodetectors in nanoengineered porous alumina membranes (PAMs) showing self-driven broadband photodetection (BPD) and NPD capability simultaneously. Two cutoff detection edges of the NPDs are located at around 770 and 730 nm, with a full-width at half-maxima (fwhm) of around 40 nm. The optical bandgap difference between the NWs and the QWs, in conjunction with the high carrier recombination rate in QWs, contributes to the intriguing NPD performance. Thanks to the excellent mechanical flexibility of the PAMs, a flexible NPD is demonstrated with respectable performance. Our work here opens a new pathway to design and engineer a nanostructured MHP for novel color selective and full color sensing devices.

Selective Extraction of Trace Arsenite Ions Using a Highly Porous Aluminum Oxide Membrane with Ordered Nanopores.

Metal ion extraction and determination at trace level concentration are challenging due to sample complexity or spectral interferences. Herein, we prepared a through-hole aluminum oxide membrane (AOM) by electrochemical anodization of aluminum substrates. The prepared AOM was characterized by scanning electron microscopy, surface area analysis, porosity measurements, and X-ray photoelectron spectroscopy. The AOM with ordered nanopores was highly porous and possess inherent binding sites for selective arsenite sorption. The AOM was used as a novel sorbent for solid-phase microextraction and preconcentration of arsenite ions in water samples. The AOM’s sub-micrometer thickness allows water molecules to flow freely across the pores. Before instrumental determination, the suggested microextraction approach removes spectral interferents and improves the analyte ion concentration, with a detection limit of 0.02 μg L–1. Analyzing a standard reference material was used to validate the procedure. Student’s t-test value was less than critical Student’s t-value of 4.303 at a 95% confidence level. With coefficients of variation of 3.25%, good precision was achieved.

Fast and Miniaturized Phase Shifter With Excellent Figure of Merit Based on Liquid Crystal and Nanowire-Filled Membrane Technologies

This paper presents a highly miniaturized tuneable microstrip line phase shifter for 5 GHz to 67 GHz. The design takes advantage of the microstrip topology by substituting the ground plane by a metallic-nanowire-filled porous alumina membrane (NaM). This leads to a slow-wave (SW) effect of the transmission line; thus, the transmission line can be physically compact while maintaining its electric length. By applying a liquid crystal (LC) with its anisotropic permittivity as substrate between the transmission line and the NaM, a tuneable microstrip line phase shifter is realized. Three demonstrators are identically fabricated filled with different types of high-performance microwave LCs from three generations (GT3-23001, GT5-26001 and GT7-29001). The measurement results show good matching in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$50\ \Omega$</tex-math></inline-formula> system with reflection less than −10 dB over a wide frequency range. These demonstrators are able to reach a maximum figure of merit (FoM) of 41 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> /dB, 48 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> /dB, and 70 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> /dB for different LCs (GT3-23001, GT5-26001 and GT7-29001, respectively). In addition, experiments show that all three LCs should be biased with square wave voltage at approximately 1 kHz to achieve maximum tuneability and response speed. The achieved response times with GT3-23001, GT5-26001 and GT7-29001 are 116 ms, 613 ms, and 125 ms, respectively, which are much faster than other reported LC phase shifter implementations. Large-signal analysis shows that these implementations have high linearity with third-order interception (IP3) points of approximately 60 dBm and a power handling capability of 25 dBm.

Self-biased coplanar circulator based on electrochemically grown ferrimagnetic nanowires

This paper is about a self-biased coplanar circulator. The design approach is based on the use of magnetic composite substrates self-polarized made from ferrimagnetic nanowires. It consists of integrating and orienting cobalt ferrite (CoFe2O4) nanocrystallites in porous alumina membrane using the magneto-electrodeposition technique. XRD, SEM and EDX analysis confirmed the formation of the spinel phase of cobalt ferrite with a good distribution of Co, Fe and O elements in the unit cell of CoFe2O4 nanowires. The performed SQUID-VSM measurements have revealed that the nano-composite electrodeposited and cooled under a magnetic field of 0.6 T has the best magnetic properties, i.e. a large anisotropy field (Ha), moderate coercive field (Hc), and partial squareness ratio (Mr/Ms). This nano-composite has been selected as an interesting candidate for the fabrication of a miniaturized self-biased circulator. The study has started with the implementation of an analytical dimensioning process based on Bosma's theory. Based on interesting HFSS simulation results, a first prototype was fabricated in the clean room and characterized at high frequencies. The measurements of the S parameters have highlighted a circulation phenomenon of 3 dB.

Tunable Low Crystallinity Carbon Nanotubes/Silicon Schottky Junction Arrays and Their Potential Application for Gas Sensing.

Highly ordered nanostructure arrays have attracted wide attention due to their wide range of applicability, particularly in fabricating devices containing scalable and controllable junctions. In this work, highly ordered carbon nanotube (CNT) arrays grown directly on Si substrates were fabricated, and their electronic transport properties as a function of wall thickness were explored. The CNTs were synthesized by chemical vapor deposition inside porous alumina membranes, previously fabricated on n-type Si substrates. The morphology of the CNTs, controlled by the synthesis parameters, was characterized by electron microscopies and Raman spectroscopy, revealing that CNTs exhibit low crystallinity (LC). A study of conductance as a function of temperature indicated that the dominant electric transport mechanism is the 3D variable range hopping. The electrical transport explored by I–V curves was approached by an equivalent circuit based on a Schottky diode and resistances related to the morphology of the nanotubes. These junction arrays can be applied in several fields, particularly in this work we explored their performance in gas sensing mode and found a fast and reliable resistive response at room temperature in devices containing LC-CNTs with wall thickness between 0.4 nm and 1.1 nm.

Morphological Characterization of Porous Anodic Alumina Membranes Prepared in Sulphuric, Oxalic, Chromic and Phosphoric Acids

Porous Anodic Alumina membranes (PAAM) have a significant role in nanoscale devices due to their easily tunable structural aspects and variety of applications in nanotechnology. The variable process parameters in the synthesis of PAAM were anodization potential, temperature, duration and nature of electrolyte concentration. Pores of different sizes and geometry were obtained by varying these anodization parameters. In the present work, PAAM were prepared in 0.3 M of sulphuric, oxalic, chromic and phosphoric acids as electrolyte and with anodization potentials (20, 40, 50 and 90 V) at a temperature of 8 °C. Field-emission Scanning Electron Microscopy investigations confirm the pore formation in PAAM layers. Pore ordering was calculated using the Fast Fourier transform (FFT) of top view SEM micrographs. Pore arrangement analysis of PAAM was studied using Image-J and WSxM software. Morphological features of PAAM such as pore diameter, interpore distance, porosity and pore density were calculated in all electrolytes. Results show that, PAAM formed in oxalic acid having high regularity ratio and circularity compared with other cases.

Features of colloidal silica deposits dip coated onto porous alumina membranes from aqueous suspensions

The present work is directed towards understanding the development of coating morphologies and the accompanying hydrodynamics of suspension flows during dip coating on porous substrates. Colloidal silica particles are deposited from aqueous suspension onto nanoporous alumina membranes. The choice of colloidal silica as the model system is motivated by its popularity in fabrication of antireflection coatings, and as nanostructured material templates for electrochemical and catalytic applications. Nanoporous alumina as substrate is notable for its chemical and thermal stability, and its ability to form self-organized pore structures. The objective here is to characterize the dependence of coating morphologies on membrane pore size, wettability, dip coating speed, and size of colloidal particles in suspension. A coating regime map is formulated based on different morphologies obtained for coatings deposited under different operating parameter spaces. The map indicates existence of two perceptibly distinct regimes which emanate from particle-induced interfacial deformation of the meniscus: Scarcely populated particulate deposition regime and densely packed coating regime having significant amount of particle deposition. The experimental results are analysed and explained using numerical results from earlier mathematical models in literature which cater to modified Landau-Levich formulation for porous substrates, as well as the hydrodynamics of colloidal assembly on moving substrates.

The Magnetic Properties of Fe/Cu Multilayered Nanowires: The Role of the Number of Fe Layers and Their Thickness.

Multi-segmented bilayered Fe/Cu nanowires have been fabricated through the electrodeposition in porous anodic alumina membranes. We have assessed, with the support of micromagnetic simulations, the dependence of fabricated nanostructures’ magnetic properties either on the number of Fe/Cu bilayers or on the length of the magnetic layers, by fixing both the nonmagnetic segment length and the wire diameter. The magnetic reversal, in the segmented Fe nanowires (NWs) with a 300 nm length, occurs through the nucleation and propagation of a vortex domain wall (V-DW) from the extremities of each segment. By increasing the number of bilayers, the coercive field progressively increases due to the small magnetostatic coupling between Fe segments, but the coercivity found in an Fe continuous nanowire is not reached, since the interactions between layers is limited by the Cu separation. On the other hand, Fe segments 30 nm in length have exhibited a vortex configuration, with around 60% of the magnetization pointing parallel to the wires’ long axis, which is equivalent to an isolated Fe nanodisc. By increasing the Fe segment length, a magnetic reversal occurred through the nucleation and propagation of a V-DW from the extremities of each segment, similar to what happens in a long cylindrical Fe nanowire. The particular case of the Fe/Cu bilayered nanowires with Fe segments 20 nm in length revealed a magnetization oriented in opposite directions, forming a synthetic antiferromagnetic system with coercivity and remanence values close to zero.

Bactericidal Activity of Bulk Nanobubbles through Active Oxygen Species Generation.

We investigated the bactericidal activity of bulk nanobubbles (NBs) using E. coli, a model bacterium. Bulk NBs were produced by forcing gas through a porous alumina membrane with an ordered arrangement of nanoscale straight holes in contact with water. NBs with different gas contents, including CO2, O2, and N2, were generated and evaluated for their bactericidal effects. The survival rate of E. coli was significantly reduced in a suspension of CO2-containing NB (CO2-NB water). The N2-NB water demonstrated a small amount of bactericidal behavior, but its impact was not as significant as that of CO2-NB water. When E. coli was retained in O2-NB water, the survival rate was even higher than that in pure water (PW). We investigated the generation of reactive oxygen species (ROS) in NB suspensions by electron spin resonance spectroscopy. The main ROS generated in the NB water were hydroxyl radicals and OH·, and the production of ROS was the strongest in CO2-NB water, which was consistent with the results of the bactericidal effect measurements. We assumed that NB mediated by ROS would exhibit bactericidal behavior and proposed a kinetic model to explain the retention time variation of the survival rate. The results calculated based on the proposed model matched closely with the experimental results.

Effect of nanoscale dielectric environments on concentration quenching

Abstract We have studied the dependence of concentration quenching of luminescence (donor–acceptor energy transfer) on the thickness d of dye-doped polymeric films (HITC:PMMA) and found its strong inhibition at small values of d. This phenomenon is tentatively explained by a limited number of acceptors, which donors’ excitation can reach in thin samples, if the film’s thickness is comparable to the diffusion length of the energy transfer. The latter mechanism, along with effective reduction of the dye concentration, is responsible for an inhibition of the concentration quenching of dye molecules impregnating porous alumina membranes. The elongation of emission kinetics in thick (≥3 μm) HITC:PMMA films is cautiously attributed to the samples’ crystallinity.

Magnetic Properties of the Densely Packed Ultra-Long Ni Nanowires Encapsulated in Alumina Membrane.

High-quality and compact arrays of Ni nanowires with a high ratio (up to 700) were obtained by DC electrochemical deposition into porous anodic alumina membranes with a distance between pores equal to 105 nm. The nanowire arrays were examined using scanning electron microscopy, X-ray diffraction analysis and vibration magnetometry at 300 K and 4.2 K. Microscopic and X-ray diffraction results showed that Ni nanowires are homogeneous, with smooth walls and mostly single-crystalline materials with a 220-oriented growth direction. The magnetic properties of the samples (coercivity and squareness) depend more on the length of the nanowires and the packing factor (the volume fraction of the nanowires in the membrane). It is shown that the dipolar interaction changes the demagnetizing field during a reversal magnetization of the Ni nanowires, and the general effective field of magnetostatic uniaxial shape anisotropy. The effect of magnetostatic interaction between ultra-long nanowires (with an aspect ratio of >500) in samples with a packing factor of ≥37% leads to a reversal magnetization state, in which a “curling”-type model of nanowire behavior is realized.

Study of long-term changes in visible-light transmittance of porous alumina membranes

The paper presents a study of the optical properties of porous alumina membranes obtained by electrochemical anodizing in electrolytes based on sulfuric and orthophosphoric acids. The pore size was analyzed by SEM. The degradation of transmittance of membranes after one year and six years storage was studied. The change one year later in optical properties was explained by the adsorption of water molecules. Six years later, an increase in throughput is observed for all membranes. At present, there are no theoretical models that can explain obtained experimental results and additional studies in this area are necessary.

Helical Nanostructure Formation By Nanoconfinement of Spatiotemporal Patterns in Electrochemical Reactions

Spatiotemporal pattern formation in anodization and electrodeposition is of interest since the patterns can be encoded as structures. Such materials having unique periodic structures can show a variety of properties, and thus the strategy of materials production based on dynamic self-organization has become one of the hot topics. Among the production of materials based on spatiotemporal pattern formation, we have recently focused on spatial symmetry breaking which leads to the formation of chiral materials such as nanohelices. In the present paper, we will show two examples of helical nanostructure formation based on spatiotemporal pattern formation in electrochemical reactions. As the first example, we discuss the helical nanopore formation in a silicon wafer by platinum(Pt)-assisted chemical etching (PacEtch). When a silicon wafer modified with metallic nanoparticles is immersed in an etchant containing HF and H2O2, the local corrosion of silicon is highly enhanced at the interface between metal and silicon. This local corrosion results in the formation of track-pores, the diameter of which is determined by the size of the metallic nanoparticles. The track-pores are generally cylindrical, but they show helical shapes especially when using Pt nanoparticles for local corrosion. Since the etching of silicon is local corrosion, the oxidation reaction must be balanced with the reduction reaction which is the reduction of H2O2. We measured the corrosion potential during PacEtch and found that it is located in the potential region where a negative differential resistance is observed in the reduction of H2O2 on a Pt electrode. We have also confirmed that the reduction of H2O2 spontaneously oscillates when we apply the same potential as the corrosion potential using both a Pt disk electrode and the etchant. These results suggest that the periodic shapes of helical nanopores formed by PacEtch originate from the periodic reduction of H2O2 on the Pt nanoparticles.As another example, we show the co-electrodeposition of palladium (Pd) and copper (Cu). When the co-electrodeposition of Pd-Cu was conducted in an aqueous solution containing PdCl2 and CuCl2, a 2-dimensional target micropattern was spontaneously formed. The spatial pattern formation resulted in the spontaneous formation of a multilayer of Pd-rich and Cu-rich layers. The characteristic size of the target micropattern is ~2 µm. As the next step, we utilized a porous alumina membrane with 200 nm in diameter, whose one of the top surfaces were covered with a gold thin film to be utilized as the working electrode. When Pd-Cu was deposited within the nanopores of the membrane, Pd-Cu rods were obtained. Interestingly, the Pd-rich region grew helically in the rod, which was clearly observed by selective chemical dissolution of the Cu-rich region. This result suggests that spontaneous helical pattern formation is achieved by confining the 2-dimensional spatiotemporal pattern within cylindrical nanopores which is much smaller than the characteristic 2-dimensional pattern. These two examples strongly suggest that the nanoconfinement of spatiotemporal pattern formation leads to spatial symmetry breaking and results in spontaneous helical pattern formation. We believe that the production of helical materials by nanoconfinement of spatiotemporal patterns is a new class of materials science in chirality.

Growth of carbon nanotubes inside porous anodic alumina membranes: Simulation and experiment

Porous anodic alumina (PAA) membranes represent a widely used and extensively studied template for production of carbon nanotubes (CNT). The PAA–CNT membranes possess a number of unique properties, such as controllable nanotube geometry, size– and chemically–based selectivity as well as high water permeability. In this work, we first propose a combination of gas phase and surface reaction models to quantitatively describe the growth of carbon nanotubes in PAA membranes in a commercial CVD reactor. A complimentary experimental study of CNT formation from ethanol precursor with argon as a carrier gas is performed. A new method for characterizing carbon nanotubes geometry by SEM and TEM image processing of membrane cross–sections is proposed. The simulations show that the carbon growth rate (in nm/min) averaged over the membrane remains constant during the deposition process until the pore diameter becomes relatively small, and rapidly falls to zero after that. The carbon nanotube thickness near the membrane surface is slightly higher than that in the membrane center. The carbon growth rate increases with synthesis temperature and pressure, while it decreases with the argon flow rate. The dependence of carbon growth rate on the ethanol/water flow rate reaches maximum at some intermediate value. These results are supported by the experimental data obtained from SEM/TEM image processing. It is found that the SEM data provide overestimated values of nanotube diameter and thickness in comparison with the TEM data. The obtained results provide new insights into the CNT growth kinetics in nanoporous media, and develop quantitative guidelines for synthesis of CNT–PAA membranes with precisely controlled nanopore geometry. It also validates the combined homogenous / heterogeneous reaction model by comparison with carbon deposition kinetics on a nanometer scale.