Porosity Of Films Research Articles

Vapor Deposited Zeolitic Imidazolate Framework-8 Derived from Porous ZnO Thin Films

In recent years, the vapor deposition of zeolitic imidazolate framework-8 (ZIF-8) has gained high attraction due to its good scalability, conformality, and thickness control. The present study provides new fundamental insights regarding the vapor deposition of ZIF-8 from zinc oxide (ZnO). During synthesis, ZnO thin films with different percentages of open porosity (14.5%–24%) were subjected to a 2-methylimidazole vapor for different conversion times (20 min–24 h). For the first time, the impact of the porosity of ZnO thin films onto the converted ZIF-8 is investigated. Grazing incidence X-ray diffraction reveals randomly oriented crystallites of ZIF-8, which already appear after 20 min of conversion. The thickness, roughness, and average particle height of the ZIF-8 layers increase with the conversion time, reaching values up to (172 ± 20) nm, (29 ± 3) nm, and (113 ± 8) nm, respectively, for ZIF-8 obtained from ZnO with 14.5% open porosity. At long conversion times (i.e., 24 h), the results hint at greater precursor porosities resulting in lower thicknesses of ZIF-8, as the thickness, roughness, and average particle height for ZIF-8 obtained from 24%-porous ZnO show values of (132 ± 20) nm, (25 ± 3) nm and (80 ± 8) nm, respectively. Additionally, the potential of the ZIF-8 layers as a photocatalyst for the degradation of the organic dye methylene blue was studied. The ZIF-8 enhances the degradation by approximately 8% when compared to degradation without a photocatalyst.

Sustainable Dielectric Films with Ultralow Permittivity from Soluble Fluorinated Polyimide.

In the rapidly growing area of high-frequency communications, polyimide films with ultralow dielectric constant and dielectric loss, adequate insulating strength, and recyclability are in high demand. Using a synthesized soluble fluorinated polyimide, a series of recyclable porous dielectric films with varying porosities were fabricated in this study through nonsolvent-induced phase separation. By manipulating the mass ratio of the binary solvent used to dissolve the polyimide, the shape, size, and size distribution of the pores generated throughout the polyimide matrix can be accurately regulated. The porosity and average pore size of the as-prepared porous films were adjustable between 71% and 33% and between 9.31 and 1.00 μm, respectively, which resulted in a variable dielectric constant of 1.51-2.42 (100 kHz) and electrical breakdown strength of 30.3-119.7 kV/mm. The porous sPI film with a porosity rate of 48% displayed a low dielectric constant of 2.48 at 10 GHz. Coupled with their superior thermal stability, mechanical characteristics, and recyclability, these porous polyimide films are highly promising for constructing high-frequency microelectronic devices.

In Situ Synthesis of AIEgen-based Porous Organic Polymer Films by Interfacial Amino-yne Click Polymerization for Efficient Light-Harvesting.

We developed a catalyst-free, atom-economical interfacial amino-yne click polymerization to in situ synthesize new aggregation-induced emission luminogen (AIEgen)-based free-standing porous organic polymer films at room temperature. The crystalline properties of POP films were confirmed by powder X-ray diffraction and high-resolution transmission electron microscopy. The good porosity of these POP films was proved by their N2 uptake experiments. The thickness of POP films can be easily regulated from 16 nm to ≈1 μm by adjusting monomer concentration. More importantly, these AIEgen-based POP films show bright luminescence with high absolute photoluminescent quantum yields up to 37.8 % and good chemical and thermal stability. The AIEgen-based POP film can encapsulate an organic dye (e.g., Nile red) to further form an artificial light-harvesting system with a large red-shift (Δλ=141 nm), highly efficient energy-transfer ability (ΦET =91 %), and high antenna effect (11.3).

In Situ Synthesis of AIEgen‐based Porous Organic Polymer Films by Interfacial Amino‐yne Click Polymerization for Efficient Light‐Harvesting

AbstractWe developed a catalyst‐free, atom‐economical interfacial amino‐yne click polymerization to in situ synthesize new aggregation‐induced emission luminogen (AIEgen)‐based free‐standing porous organic polymer films at room temperature. The crystalline properties of POP films were confirmed by powder X‐ray diffraction and high‐resolution transmission electron microscopy. The good porosity of these POP films was proved by their N2 uptake experiments. The thickness of POP films can be easily regulated from 16 nm to ≈1 μm by adjusting monomer concentration. More importantly, these AIEgen‐based POP films show bright luminescence with high absolute photoluminescent quantum yields up to 37.8 % and good chemical and thermal stability. The AIEgen‐based POP film can encapsulate an organic dye (e.g., Nile red) to further form an artificial light‐harvesting system with a large red‐shift (Δλ=141 nm), highly efficient energy‐transfer ability (ΦET=91 %), and high antenna effect (11.3).

The inhibitive action of 2-mercaptobenzothiazole on the porosity of corrosion film formed on aluminum and aluminum–titanium alloys in hydrochloric acid solution

2-Mercaptobenzothiazole (2-MBT) in a solution of 0.5 M HCl is an effective corrosion inhibitor for aluminum and aluminum–titanium alloys. Tafel polarization and electrochemical impedance spectroscopy (EIS) were employed to assess this heterocyclic compound’s anticorrosive potential and complementary by scanning electron microscope (SEM) and calculating porosity percentage in the absence and presence of various inhibitor concentrations. Inhibition efficiency (IE%) was strongly related to concentration (10–6–10–3 M). Temperature’s effect on corrosion behavior was investigated. The data exhibited that the IE% decreases as the temperature increases. An increase in activation energy (Ea) with increasing the inhibitor concentration and the decrease in the IE% value of the mentioned compound with raising the temperature indicates that the inhibitor molecules are adsorbed physically on the surface. Thermodynamic activation parameters for Al and Al–Ti alloy dissolution in both 0.5 M HCl and the inhibited solution were calculated and discussed. According to Langmuir’s adsorption isotherm, the inhibitor molecules were adsorbed. The evaluated standard values of the enthalpy (Delta {H}_{ads.}^{o}), entropy (Delta {S}_{ads.}^{o}) and free energy changes (Delta {G}_{ads.}^{o}) showed that Delta {H}_{ads.}^{o} and Delta {G}_{ads.}^{o} are negative, while Delta {S}_{ads.}^{o} was positive. The formation of a protective layer adsorbed on the surfaces of the substrates was confirmed with the surface analysis (SEM). The porosity percentage is significantly reduced in the inhibitor presence and gradually decreased with increasing concentration. Furthermore, the density functional theory (DFT) and Monte Carlo (MC) simulations were employed to explain the variance in protecting the Al surface from corrosion. Interestingly, the theoretical findings align with their experimental counterparts. The planarity of 2-MBT and the presence of heteroatoms are the playmakers in the adsorption process.

Highly conductive copper films prepared by multilayer sintering of nanoparticles synthesized via arc discharge

The major challenges in producing highly electrically conductive copper films are the oxide content and the porosity of the sintered films. This study developed a multilayer sintering method to remove the copper oxides and reduce copper film porosity. We used a self-built arc discharge reactor to produce copper nanoparticles. Copper nanoparticles produced by arc discharge synthesis have many advantages, such as low cost and a high production rate. Conductive inks were prepared from copper nanoparticles to obtain thin copper films on glass substrates. As demonstrated by scanning electron microscopy analyses and electrical resistivity measurements, the copper film porosity and electrical resistivity cannot be significantly reduced by prolonged sintering time or increasing single film thickness. Instead, by applying the multilayer sintering method, where the coating and sintering process was repeated up to four times in this study, the porosity of copper films could be effectively reduced from 33.6% after one-layer sintering to 3.7% after four-layer sintering. Copper films with an electrical resistivity of 3.49 ± 0.35 μΩ·cm (two times of the bulk copper) have been achieved after four-layer sintering, while one-layer sintered copper films were measured to possess resistivity of 11.17 ± 2.17 μΩ·cm.

Influence of BaTiO3 morphology on BaTiO3/P(VDF-HFP) electrolyte for self-charging sodium-ion batteries

The coming era of the Internet of Things urgently demands self-charging power systems with the ability of low-power energy harvesting and energy storage. In this work, we design BaTiO3 with different morphologies (nanoparticles, nanoplates, and nanowires) to be filled in the P(VDF-HFP) composite. The introduction of NaCl crystal as a template can increase the porosity of the polymer film. A series of flexible self-charging sodium-ion batteries have been assembled using the porous BaTiO3-P(VDF-HFP)-NaClO4 film as a piezo-electrolyte. Among those piezo-electrolytes with different morphologies BaTiO3 filler, self-charging sodium-ion batteries (Na0.71Co0.96O2||Na) with BaTiO3 nanoplates-P(VDF-HFP) - NaClO4 as electrolyte exhibit superior self-charging performance with the increased capacity of 1.132 mAh in 100 h under static pressure of 5 N. In addition, the flexible battery was subjected to bending pressure and tapping tests. There is little work investigating the morphology effects of filler on self-charging batteries. This work provides an optimization method for piezo-electrolyte of self-charging sodium-ion batteries.

Cobalt Electrodeposition in Nanoporous Anodic Aluminium Oxide Films with Different Oxidation Time

The anodic aluminum oxide films with different oxidation times were investigated using electrochemical techniques including electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and open-circuit potential versus time. The stable open-circuit potential versus time indicates that the longer anodization time provides a larger block for cobalt electrodeposition. The EIS monitoring revealed the capacitance characteristics of the barrier layer. When the oxidation time is 4 h, the thickness and porosity of AAO film are 1517 nm and 16.4 % corespondingly, and the radius of the capacitive reactance arc is the smallest. The reduction peak current of CV is attributed to the change in diffusion coefficient of cobalt when oxidation time changes.

Steering carbon dioxide reduction toward C–C coupling using copper electrodes modified with porous molecular films

Copper offers unique capability as catalyst for multicarbon compounds production in the electrochemical carbon dioxide reduction reaction. In lieu of conventional catalysis alloying with other elements, copper can be modified with organic molecules to regulate product distribution. Here, we systematically study to which extent the carbon dioxide reduction is affected by film thickness and porosity. On a polycrystalline copper electrode, immobilization of porous bipyridine-based films of varying thicknesses is shown to result in almost an order of magnitude enhancement of the intrinsic current density pertaining to ethylene formation while multicarbon products selectivity increases from 9.7 to 61.9%. In contrast, the total current density remains mostly unaffected by the modification once it is normalized with respect to the electrochemical active surface area. Supported by a microkinetic model, we propose that porous and thick films increase both local carbon monoxide partial pressure and the carbon monoxide surface coverage by retaining in situ generated carbon monoxide. This reroutes the reaction pathway toward multicarbon products by enhancing carbon–carbon coupling. Our study highlights the significance of customizing the molecular film structure to improve the selectivity of copper catalysts for carbon dioxide reduction reaction.

Effects of pre-emulsion prepared using sucrose esters with different hydrophile-lipophile balances on characteristics of soy protein isolate emulsion films

The preparation of emulsion films using pre-emulsification has received extensive attention due to the enhancement of oil binding capacity. However, the different effects of water in oil (W/O) and oil in water (O/W) pre-emulsions on the physicochemical properties of films are still unclear. Therefore, the soy protein isolate (SPI) based emulsion films were prepared by W/O or O/W pre-emulsion using sucrose esters with different hydrophile-lipophile balances to investigate the properties of SPI emulsion (SPIE) films. The viscosity, storage moduli, and loss moduli of film-forming solutions (FFSs) with O/W pre-emulsion were higher than those of FFSs with W/O pre-emulsion. The oil droplets of FFSs with W/O pre-emulsion were large and uneven, and the oil droplet size increased after drying. Phase separation and macroporous network appeared in cross-sectional of SPIE films with W/O pre-emulsion according to scanning electron microscope images. Meanwhile, the SPIE films with W/O pre-emulsion demonstrated higher oil concentration and hydrophobicity on the upper surface compared with the SPIE films with O/W pre-emulsion. Low tensile strength, glass transition temperature, and high elongation at break and transparency value of SPIE films with O/W pre-emulsions were founded. The water vapor permeability of SPIE films with W/O pre-emulsion increased with the addition of oil, whereas the opposite trend appeared in that with O/W pre-emulsion. In conclusion, the structure and porosity of emulsion films could be affected by the pre-emulsion types, which can determine the application ranges.

Electrochemical impedance spectroscopy analysis of plasma-treated, spray-coated single-walled carbon-nanotube film electrodes for chemical and electrochemical devices

In this study, carbon-nanotube (CNT) surfaces were treated with oxygen plasma, and the improvement in surface inertness was analyzed using electrochemical impedance spectroscopy (EIS). Among nanomaterials, CNTs are the most attractive owing to their outstanding properties. However, the chemical inertness of CNT surfaces hinders the widespread implementation of CNTs in bioanalytical applications. Therefore, we present in detail the electrochemical properties of CNTs treated in various plasma conditions. The single-walled carbon nanotube (SWCNT) films were spray-coated onto working electrodes with a three-electrode configuration fabricated on a glass substrate and activated at various plasma conditions. The EIS spectra of the SWCNT film revealed typical porous structure characteristics. As the thickness of the SWCNT film increased by spray coating, the charge-transfer resistance sharply increased owing to the reduction of the effective electrode area caused by the decreased roughness and porosity of the SWCNT film. The Nyquist plots of the plasma-treated SWCNT electrodes featured two semicircular regions at high and intermediate frequencies, as well as one straight line at low frequencies. The plasma-treated SWCNT electrode had a less distinct separation of the second arc and straight line than the untreated SWCNT electrode because the time constant was lowered owing to the diffusion process generated where the charge-transfer reaction occurred. We analyzed the change in the electrodes through EIS, which can identify individual contributions to the total impedance of an electrochemical system.

A broad-spectrum solar energy power system by hybridizing stirling-like thermocapacitive cycles to dye-sensitized solar cells

To maximally utilize inlet sunlight, a novel dye-sensitized solar cell-based hybrid system containing a solar selective absorber and a Stirling-like thermocapacitive cycle is theoretically put forward. Energy efficiencies and output powers of dye-sensitized solar cell, Stirling-like thermocapacitive cycle and hybrid system are deduced. Feasibility as well as competitiveness of hybrid system are expounded through comprehensive comparisons. Numerical results show that output power density and energy efficiency of hybrid system are, respectively, 148.96 Wm-2 and 14.90%, which are, respectively, 93.58% and 204.70% superior to that of standalone dye-sensitized solar cell. Moreover, ponderable parametric studies are performed to examine how key variables affect the hybrid system performance. It is found that greater operating temperature of dye-sensitized solar cell, charging endpoint voltage of Stirling-like thermocapacitive cycle or thermal conductance coefficients between Stirling-like thermocapacitive cycle and dye-sensitized solar cell/solar selective absorber subsystems as well as environment are favorable to the hybrid system performance, while higher environment temperature and discharging endpoint voltage of Stirling-like thermocapacitive cycle are unfavorable variables. In addition, the thickness and porosity of nano porous TiO2 semiconductive film can be structurally optimized to improve the hybrid system performance.

Nanostructured ZnxMn3‒xO4 thin films by pulsed laser deposition: A spectroscopic and electrochemical study towards the application in aqueous Zn-ion batteries

Aqueous Zn-ion batteries (AZIBs) represent a safe and sustainable technology amongst the post-lithium systems, though the poor understanding of the material behaviour at the cathode prevents the full development of efficient AZIBs. ZnMn2O4 (ZMO) has been considered one of the cathode candidates owing to its analogy to the well-established LiMn2O4 cathode for lithium-ion batteries, however its electrochemical mechanism in the presence of Zn ions in aqueous environment is unclear and still debated. In this work, we synthesised nanostructured ZMO thin films by Pulsed Laser Deposition (PLD) and we evaluated, through extensive characterization by microscopic, spectroscopic, and diffraction techniques, how the deposition and annealing conditions affect the film properties. The self-supported nature and the high degree of control down to the nanoscale make a thin film an ideal model system to study the electrochemistry of the material in aqueous solution and to emphasize the impact of the film properties on its electrochemical response. We highlighted the crucial role of the oxygen pressure in the modulation of the film porosity and the combined effect of deposition pressure and annealing temperature to produce a film with tailored properties in terms of morphology, crystallinity, and Zn stoichiometry. A complex redox mechanism involving multiple concurrent reactions and the formation of zinc hydroxide sulphate hydrate (ZHS) was reported, as well as the influence of the film porosity on the voltammetric behaviour of the film at higher scan rate. Our results confirm the intricate electrochemical mechanism of the ZMO material, which does not merely involve the Zn2+ insertion/extraction but also the crucial participation of Mn2+ from the electrolyte, and pave the way for the nanoscale design of engineered ZMO-based electrodes.

Fabrication of a nanoscale 2D PEDOT pattern via the combination of colloidal lithography and vapor phase polymerization for application in transparent, highly sensitive bending sensors.

Recent advances in flexible, stretchable, and wearable electronics have necessitated the development of more diverse and complex device structures; high-resolution patterning strategies for conducting polymers are therefore urgently required to enable the fabrication of these devices. In this study, we report a nanoscale patterning strategy for conductive polymer films that utilizes a combination of vapor phase polymerization (VPP) and colloidal lithography. Here, hemispherical non-close-packed colloidal crystals are used as an effective lithographic mask for patterning oxidants on a substrate; subsequently, two-dimensional honeycomb-structured porous poly(3,4-ethylenedioxythiophene) (PEDOT) films are fabricated via VPP using the prepatterned oxidant. The resulting films closely resemble the morphology of the preceding oxidant structure; furthermore, the film porosity can be altered by adjusting the polymerization time. These patterned PEDOT films exhibit high transparency owing to the presence of voids, and high electrical sensitivity to bending stresses, which were concentrated in the narrow-patterned area. As the described fabrication methods are facile and reliable, this approach therefore provides an effective route for the fabrication of various conducting polymer frameworks in the micro- to nanoscale range.

Design of cryogel based CNTs-anchored polyacrylonitrile honeycomb film with ultra-high S-NZVI incorporation for enhanced synergistic reduction of Cr(VI).

An ultra-high NZVI-loaded PAN film (S-CPN) with a unique 3D honeycomb structure was designed based on the cryogel method of green solvent-induced pores and confinement of the spatially free conformation of films by anchoring carbon nanotubes (CNTs), supplemented sulfidation for removing hexavalent chromium (Cr(VI)), and characterized by SEM, AFM, BET, XRD, XPS, and electrochemical corrosion. The doping amounts of the compounds for S-CPN synthesis were optimized to be 0.075g CNTs, 0.25g Na2S, and 0.3M FeSO4. S-CPN possessed a 175.247m2/g specific surface area, -0.365V reduction potential, and 46.54mg/g ultra-high NZVI-loading. S-CPN had the strong activity of Cr(VI) removal and tolerance to coexisting ions. The removal efficiency remained at 80 % after age for 30 days or 5 cycles. The pseudo-first-order kinetics and Langmuir model were more favorable to simulate the adsorption of Cr(VI) on S-CPN. The thermodynamics show that S-CPN removing Cr(VI) was a spontaneous exothermic reaction. The reasons for these excellent properties were that CNTs improve the film porosity and ultra-high NZVI-loading, and synergistic the FeSX layer to chelates-reduces Cr(VI). This was the first time that honeycomb film with 3D structure and potential applications in heavy metal removal was developed via an eco-friendly strategy.

Impact of the acetone/DMSO binary solvent on porosity of epoxy polymer films

Impact of the acetone/DMSO binary solvent on porosity of epoxy polymer films

Microwave Plasma Assisted Aerosol Deposition (μ-PAD) for Ceramic Coating Applications

To improve plasma and chemical resistance on various vacuum components used for semiconductor manufacturing equipment, various ceramic coating techniques have been applied. Among these methods for ceramic coating, the well-known atmospheric plasma spray (APS) is advantageous for providing thick film (100 µm or more) deposition. However, there are problems associated with the phase transition of the coating film and poor film quality due to formation of voids. To solve these problems, the aerosol deposition (AD) method has been developed. This method provides nice ceramic film quality. However, the coating rate is quite slow and has difficulty producing thick films (>30 µm). To overcome these limitations, microwave plasma-assisted aerosol deposition (μ-PAD) is applied at low vacuum conditions without the AD nozzle. This method uses a microwave plasma source during the AD process. After enduring a long-term durability test, as a trial run, μ-PAD has been applied on the actual process site. With the Al2O3 powder, μ-PAD shows a coating rate that is 12 times higher than the AD method. In addition, the formation of a thicker film (96 µm) deposition has been demonstrated. On the other hand, the coating film hardness, porosity, adhesion, and withstand voltage characteristics were confirmed to be less than the AD method.

Highly Aligned Graphene Oxide for Lithium Storage in Lithium‐Ion Battery Through A Novel Microfluidic Process: The Pulse Freezing

AbstractThe modification of carbon‐based lithium‐ion batteries electrodes is required for the growing need of more reliable electric vehicles. Herein, a new method is introduced to fabricate vertically aligned graphene oxide (GO) films as free‐standing carbon lithium hosts for lithium‐ion batteries with enhanced performance. Vertical alignments are induced of GO in a microfluidic channel by controlling flow rates and patterns of GO suspensions. The vertical alignments are preserved and spontaneously form porous microstructures by Pulse Freezing the GO solutions inside the channel. This combined process results in the increase of levels of microstructure porosity and vertical alignment of GO films. The alignment and porous microstructures increase both electron and ion transfer capabilities across the prepared film. The half‐cell performance of aligned GO films shows a specific capacity of 440 mAh g−1 at a current density of 0.5 A g−1 after 150 cycles. This is a 190% specific capacity increase compared to the performance of a half‐cell prepared with GO without the high level of vertical alignment and microporosity. The significant increase in the value and stability of specific capacity and higher rates of charge transfer favor the promising application of carbon‐based lithium‐ion batteries for electric transportation industries.

Research on wet gas separation method based on swirl and ejection cycle technology

Gas-liquid co-production often occurs in the middle and late stages of natural gas production. Efficient wet gas separation is very important in natural gas transportation and measurement. The traditional separation device has a relatively low separation efficiency due to the flow patterns, a new type of pipe separator was designed based on the swirl and ejection cycle technology. A new systematical separation procedure with three main steps was proposed simultaneously. The wet gas was forced to form an annular flow by a swirler. Then, the liquid film flows into the annular gap. The wave layer was introduced into the swirl separation again with the self-circulating ejection system for fine separation finally. Laboratory experiments and Computational Fluid Dynamics (CFD) simulations show that the additional swirl process can decrease the flow pattern influence effectively, and the separation efficiency can increase to more than 90%. The separation efficiency is mainly determined by the gas superficial velocity, and while the velocity of the inlet gas is less than 21 m/s, the separation efficiency is up to 93%. The separation efficiency prediction model was established based on liquid film porosity, and the prediction relative error is less than 10%. The new device, the separation procedure, and the test results can provide constructive technical reference for the real-world pipe separator application.

Chemical Structure, Optical and Dielectric Properties of PECVD SiCN Films Obtained from Novel Precursor

A phenyl derivative of hexamethyldisilazane—bis(trimethylsilyl)phenylamine—was first examined as a single-source precursor for SiCN film preparation by plasma enhanced chemical vapor deposition. The use of mild plasma (20 W) conditions allowed the preparation of highly hydrogenated polymeric-like films. The synthesis was carried out under an inert He atmosphere or under that of NH3 with the deposition temperature range from 100 to 400 °C. The chemical bonding structure and elemental composition were characterized by Fourier-transform infrared spectroscopy, energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy. The surface morphology was investigated by scanning electron microscopy. Ellipsometric porosimetry, a unique high-precision technique to investigate the porosity of thin films, was applied to examine the porosity of SiCN samples. The films were found to possess a morphologically homogenous dense defect-free structure with a porosity of 2–3 vol.%. SiCN films were studied in terms of their optical and dielectric properties. Depending on the deposition conditions the refractive index ranged from 1.53 to 1.78. The optical bandgap obtained using UV-Vis spectroscopy data varied from 2.7 eV for highly hydrogenated polymeric-like film to 4.7 eV for cross-linked nitrogen-rich film. The dielectric constant was found to decrease from 3.51 to 2.99 with the rise of hydrocarbon groups’ content. The results obtained in this study were compared to the literature data to understand the influence of precursor design to the optical and electrical properties of the films.