Film Layer Research Articles

Emulsions stabilized by phospholipids

HypothesisPhospholipids are amphiphilic molecules able to adsorb at oil/water interfaces and thus used to stabilize parenteral emulsions. Yet, their low preferred curvature, which sensitively depends on molecular structures and interactions, favors the formation of lamellar phases and sets constraints on the system formulation. Combining phase studies, structural interfacial characterizations, and stability monitoring for different water/phospholipid/oil systems should shine a light on the mechanisms at play and thus tools to optimize formulations. ExperimentsFour phase diagrams were established for ternary aqueous systems containing either DOPC or POPC as the phospholipid and hexadecane or miglyol 812 as the oil. Droplet interfaces were probed using small-angle neutron scattering and the amount of adsorbed lipid was determined using separation and Raman spectroscopy. The metastability of both nano and macro emulsions was systematically assessed over weeks using light scattering. FindingsWe show that nanoemulsion droplets are stabilized by a lipid monolayer and display excellent metastability if the preferred curvature is positive and large enough, even without any added charges or at high ionic strengths. In contrast, macroemulsion droplets are stabilized with a lipid multilayer, which should possess a positive preferred curvature but also a good enough interfacial anchorage, which is lost upon increasing the preferred curvature. Overall, we provide a rationale for understanding the impact of molecular changes in the formulation on emulsion metastability, through the analysis of the lipid film preferred curvature, layering, and interfacial anchorage.

Microfluidic Device with an Oxygen Gradient Generator for Investigating Effects of Specific Hypoxia Conditions on Responses of Tumor Cells.

The oxygen level in the tumor microenvironment (TME) plays a critical role in regulating cell fates such as proliferation, migration, apoptosis, and so forth. To better elucidate how hypoxia affects tumor cell behaviors, a series of microfluidic strategies have been utilized to generate an oxygen gradient covering both hypoxia anions. However, in most studies, some chemicals are introduced into microfluidic chips, causing the potential of their poor biocompatibility. The common oxygen gradient with linear variation does not allow the effects of specific oxygen concentrations on tumor cells to be analyzed accurately. In this paper, based on the physical method of gas diffusion, a microfluidic device integrated with an oxygen gradient generator is proposed for investigating effects of different hypoxia levels on responses of tumor cells. This device consists of three layers, i.e., upper layer, thin film layer, and bottom layer. The upper layer is used for introducing the initial gas and generating an oxygen gradient in the form of gas. The bottom layer is used for introducing cells and culture medium. The thin film layer separates the former two layers, allowing the gas to diffuse from the top to the bottom through it. The oxygen gradient in the bottom layer is finally generated in the form of dissolved oxygen. The device is fabricated using microfabrication technology. The effects of structural and working parameters of the device on the oxygen gradient are evaluated by finite element simulation. The oxygen gradient in cell culture channels is characterized by using oxygen-sensitive fluorescence materials. The proliferation and morphology of HeLa cells under specific oxygen levels are compared after culturing for 48 h. The oxygen gradient with a ladder-like distribution demonstrates that this microfluidic device can provide a prospective experimental platform for in vitro cell studies and revelation of the mechanism of tumor metastasis associated with a specific hypoxic microenvironment.

Electrochemical CO2 Reduction in Acidic Electrolytes: Spectroscopic Evidence for Local pH Gradients.

Inspired by recent advances in electrochemical CO2 reduction (CO2R) under acidic conditions, herein we leverage in situ spectroscopy to inform the optimization of CO2R at low pH. Using attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and fluorescent confocal laser scanning microscopy, we investigate the role that alkali cations (M+) play on electrochemical CO2R. This study hence provides important information related to the local electrode surface pH under bulk acidic conditions for CO2R, both in the presence and absence of an organic film layer, at variable [M+]. We show that in an acidic electrolyte, an appropriate current density can enable CO2R in the absence of metal cations. In situ local pH measurements suggest the local [H+] must be sufficiently depleted to promote H2O reduction as the competing reaction with CO2R. Incrementally incorporating [K+] leads to increases in the local pH that promotes CO2R but only at proton consumption rates sufficient to drive the pH up dramatically. Stark tuning measurements and analysis of surface water structure reveal no change in the electric field with [M+] and a desorption of interfacial water, indicating that improved CO2R performance is driven by suppression of H+ mass transport and modification of the interfacial solvation structure. In situ pH measurements confirm increasing local pH, and therefore decreased local [CO2], with [M+], motivating alternate means of modulating proton transport. We show that an organic film formed via in situ electrodeposition of an organic additive provides a means to achieve selective CO2R (FECO2R ∼ 65%) over hydrogen evolution reaction in the presence of strong acid (pH 1) and low cation concentrations (≤0.1 M) at both low and high current densities.

Spaceflight Associated Dry Eye Syndrome (SADES): Radiation, Stressors, and Ocular Surface Health

Crewed spaceflight missions require careful scrutinization of the health risks including alterations to the tear film lipid layer in astronauts. We review the current literature and prior published work on tear film lipid layer biophysics and secondary spaceflight-associated dry eye syndrome (SADES). We define the term spaceflight-associated dry eye syndrome to describe the collection of ocular surface signs and symptoms experienced by astronauts during spaceflight. Our review covers the ocular surface and lipidomics in the spaceflight environment. From our literature review, we extrapolate biophysical principles governing the tear film layer to determine the changes that may arise from the harsh conditions of spaceflight and microgravity. Our findings provide vital information for future long-duration spaceflight, including a return to the Moon and potential missions to Mars.

Semiconductive Tendency of the Passive Film Formed on Super Austenitic Stainless Steel SR-50A in Acidic or Alkaline Chloride Solutions

Stainless steel is widely used in various industrial fields due to its excellent corrosion resistance and mechanical properties. The key to this corrosion resistance is the thin passive film that naturally forms on the metal surface. Passive films are characterized by oxide film theory and adsorption theory, each uniquely explaining the structure and mechanism of the protective film on the metal surface. Research on the semiconductive properties of passive films on stainless steel offers diverse viewpoints, classifying theories into the point defect model and the bipolar fixed charge-induced passivity. Specific changes in passive film attributes that lead to degradation, however, are not fully understood. In this study, we analyzed the inner and outer layers of the passive film on super austenitic stainless steel SR-50A under various conditions in acidic and alkaline chloride environments. The interpretations of these results were based on the point defect model and the bipolar model for the passivation mechanism, and correlations between p-type and n-type semiconductor properties and passivation behavior were examined. The surface of the stainless steel forms a passive film comprising two layers with p-type and n-type semiconductive properties, independent of the pH of the solutions. The corrosion resistance increases as the p-type and n-type semiconductive tendencies become more balanced, consequently enhancing the properties of the passive film.

A quantitative theory for heterogeneous combustion of nonvolatile metal particles in the diffusion-limited regime

The paper presents an analytical theory quantitatively describing the heterogeneous combustion of nonvolatile (metal) particles in the diffusion-limited regime. It is assumed that the particle is suspended in an unconfined, isobaric, quiescent gaseous mixture and the chemisorption of the oxygen takes place evenly on the particle surface. The analytical solution of the particle burn time is derived from the conservation equations of the gas-phase described in a spherical coordinate system with the utilization of constant thermophysical properties, evaluated at a reference film layer. This solution inherently takes the Stefan flow into account. The approximate expression of the time-dependent particle temperature is solved from the conservation of the particle enthalpy by neglecting the higher order terms in the Taylor expansion of the product of the transient particle density and diameter squared. Coupling the solutions for the burn time and time-dependent particle temperature provides quantitative results when initial and boundary conditions are specified. The theory is employed to predict the burn time and temperature of 10–100 μm iron particles, which are then compared with measurements, as the first validation case. The theoretical burn time agrees with the experiments almost perfectly at both low and high oxygen levels. The calculated particle temperature matches the measurements fairly well at relatively low oxygen mole fractions, whereas the theory overpredict the particle peak temperature due to the neglect of evaporation and the possible transition of the combustion regime.Novelty and significance statementFor the first time, we present a comprehensive and quantitative analytical theory elucidating the heterogeneous combustion of nonvolatile (metal) particles in the diffusion-limited regime. This novel theoretical model exhibits a remarkable capacity for quantitative prediction, obviating the need for supplementary information from numerical simulations or experimental data. The derivation process of analytical solutions for burn time and time-dependent particle temperature from conservation equations is elaborated, offering transparency and insight into the model’s foundations. To demonstrate the practical utility of the theory, we apply it to analyze the combustion of iron particles, providing valuable mathematical perspectives on the underlying processes. The model’s predictions for burn time and temperature align closely with experimental results, offering a partial validation of the theory within the realm of its applicable assumptions. This pioneering work contributes a robust and versatile analytical framework, advancing our understanding of diffusion-limited combustion phenomena of nonvolatile particles.

A novel high corrosion-resistant and superhydrophobic MAO-30/PA/VTES composite coating on Cu[sbnd]15Fe alloy for long-term corrosion protection

The copper (Cu) alloys are prone to severe corrosion in marine environments. In this work, we successfully develop a novel high corrosion-resistant and superhydrophobic MAO-30/PA/VTES composite coating on Cu15Fe alloy for long-term corrosion protection. The composite coating, with a corrosion rate of 0.00001 mm/y and a water contact angle of 152.7°, presents significant advantages over most Cu alloys modification methods to date. Benefiting from the modification with phytic acid (PA) and vinyltriethoxysilane (VTES), the corrosion current density of the composite coating remains 2.14 × 10−10 A·cm−2 even after 168 h of immersion in 0.6 M NaCl, which is four orders of magnitude lower than Cu15Fe substrate (5.68 × 10−6 A·cm−2). The exceptional long-term corrosion resistance of the composite coating is attributed to the physical barrier effect of the micro-arc oxidation (MAO) layer, the superhydrophobic characteristics and sealing effect of the PA/VTES film layer, and the chelating effect of the phytic acid. Developing the composite coating introduces a new approach to protecting Cu alloys from corrosion in marine environments.

Optimizing rotary kiln operations for molybdenite concentrate oxidation roasting to produce molybdic trioxide

The effects of the rotational speed (0–10 rpm) and temperature (550–650 °C) of rotary kiln drums on the oxidation roasting of molybdenite (MoS2) concentrate was investigated in this study. Computational predictions indicated that production of MoO2 was more favorable than that of MoO3 up to a certain stage of the oxidation roasting process, after which MoO3 is produced through the consumption of MoO2. Thus, understanding the MoS2–MoO2–MoO3 relationship and its equilibrium is important. A drum rotational speed > 5 rpm significantly increased the S reduction rate and considerably decreased the S content at 60 min to < approx. 5 %. Additionally, the S content at 60 min decreased with decreasing the temperature from 650 to 550 °C due to the MoS2 concentrate exothermic reaction during oxidation roasting. The MoS2 to MoxOy (≈ MoO2+MoO3) conversion rate (%) was generally proportional to the rotational speed and reaction duration. X-ray diffraction analysis indicated that 5–10 rpm and 550–600 °C yielded a higher experimental conversion rate (97–98 %). Furthermore, the MoO2 and MoO3 conversions were separately quantified. Agglomeration was more pronounced without drum rotation and at higher temperatures. Analysis of the reaction kinetics using the unreacted-core model indicated that diffusion through the gas film layer is supported by the 20.9 kJ/mol activation energy obtained from the Arrhenius plot. Consequently, an appropriate drum rotational speed at a relatively low temperature is a prerequisite for producing MoO3 through the oxidation roasting of MoS2 concentrates in a rotary kiln.

Emergence of critical thickness and multifaceted role of stacking faults in high misfit hexagonal ferrites films

Polarization in improper ferroelectrics is believed to be robust against the depolarizing field. However, this characteristic appears to be disrupted in hexagonal ferrite and manganite, leading to a controversial debate regarding the origin of the critical thickness. In this study, we design hexagonal TbFeO3 (h-TFO) films which exhibits a critical thickness exceeding 5 nm at room temperature and an exceptionally long suppression layer in thicker films. It is explained that the critical thickness effect originates from the synergistic interplay of the interface, strain, and vacancies, which is confirmed by combining scanning transmission electron microscopy (STEM), electron energy-loss spectroscopy (EELS) and density functional theory (DFT). This explanation is equally applicable to the polarization suppression near the stacking fault (SF). Finally, we find that the SF reduces the suppression length to an extent, and contributes to changes in the topological order of the domain in h-TFO film. Our study provides a more comprehensive understanding of the origin of critical thickness and the multifaceted role of the SF in ferroelectrics.

Formation and dissolution of porous magnetite layer in contact with lead-bismuth eutectic: Locally equilibrium thermodynamic model

Locally equilibrium thermodynamic model is developed to describe the formation and dissolution of the outer magnetite layer of an oxide film on the steel surface in contact with lead-bismuth eutectic. The model allows to predict the outer layer growth law as a function of dissolved oxygen and iron concentrations, temperature and coolant flow rate. Comparison with experiments allows to explain the phenomenon of magnetite dissolution in two experimentally observed cases: when oxygen concentration in LBE is above the solid magnetite stability line and under the high values of the coolant flow rate, without the consideration of mechanical erosion.

Structural and phase transformations in Fe-Pd-Ag layered thin films by grain boundary diffusion

The influence of the stacking order and of an additional Ag layer on the formation of ordered phases in thin (< 50 nm) layered Fe/Pd and Fe/Ag/Pd films was investigated at 460 °C. The samples were prepared by magnetron sputtering at room temperature on Si/SiO2 substrate and were post-annealed in vacuum. Composition depth profiling and x-ray diffraction were used to characterize the processes. It has been shown, that the stacking order strongly influences the formation of ordered phases both in Fe/Pd bilayered and Fe/Ag/Pd trilayered films. In bilayered Fe/Pd films for both stacking orders the FePd3 phase appeared and it also showed L12 ordering for one stacking order. Addition of Ag layer between the Fe and Pd layers found to promote the formation of FePd phase which showed L10 ordering or A1 disordered structure depending on stacking order. Based on the analysis of the chemical depth profiles and XRD patterns the transformations were interpreted by grainboundary diffusion mechanisms including grainboundary diffusion induced grainboundary migration and solid state reaction.

Comparative study of the sensitivity of H2S and NO2 in CuInSe2 gas sensors that are fabricated using screen printing and MEMS Integration

This study compares the gas response efficiency of a gas sensor substrate that is produced using screen-printing (SP) and micro-electro-mechanical systems (MEMS) technology, followed by deposition of CuInSe2 (CIS) film layers by radio-frequency (RF) sputtering and hyperthermal annealing for gas sensing applications. The SP substrates are used for CIS film deposition for RF sputtering, followed by various hyperthermal annealing treatments. SEM observations of the CIS film surfaces after annealing show surface particles with a size distribution of 155 to 30 nm, which demonstrate a phenomenon that is similar to Ostwald ripening and which creates structural variation and unevenness after annealing. The CIS film/MEMS substrates (MEMSs) gas sensor substrates are evaluated using a NIR thermal camera to determine the optimal operating temperature for direct annealing, which is 203.2 °C. Gas sensing response tests show that only H2S or NO2 gas rapidly and significantly elicit a response but a CIS film/SPs gas sensor exhibits significant resistance signal noise. The CIS film/MEMSs gas sensor is more stable than CIS film/SPs (after annealing) so it is more suitable for gas sensing. SEM images confirm that the film remains intact, so it is suitable for gas sensing applications.

Highly efficient halogen-free rigid and flexible binary organic solar cells using new solid indacene additive

Flexible Organic solar cells (OSCs) have garnered widespread attention due to the increased popularity of wearable electronic devices. To enhance the efficiency and stability of the device we have prepared (2E,2′E)-3,3'-(4,4,9,9-tetrahexadecyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b'] dithiophene-2,7-diyl)bis(2-cyanoacrylic acid) (IDT) based dopant by reacting the aldehyde precursor with cyanoacetic acid in the presence of piperdine. Here, we investigate the effect of IDT on the performance of OSCs by adding IDT to star active layers PM6:Y6 and PM6:BTP-eC9 to improve OSCs' performance through morphology optimization. The addition of 5 wt% IDT significantly improved the device performance, achieving a remarkable PCE of 16.08 % for PM6:Y6 devices. The charge transport and recombination dynamics analysis showed that the appropriate concentration of IDT can provide better channels for carrier transport, promoting effective charge generation and extraction in OSCs. It is observed that the addition of IDT promotes effective generation and dissociation of excitons, thus improving OSC performance. The flexible ITO-free OSC was fabricated using PM6:Y6:IDT as the active layer film, achieving a high PCE of 12.59 % with VOC, JSC, and FF of 0.83 V, 23.21 mA/cm2 and 68.63 %, respectively. Hence, the findings indicate a reliable approach which could potentially deliver rigid and flexible OSCs with excellent performance and commercial viability.

Molecular dynamics study of the groove-forming mechanism of mechanically scratched grating multilayer aluminum films

For a long time, the forming quality of large area diffraction gratings is restricted by the one-time coating quality and uniformity of large thickness and large area aluminum films. Large thickness coatings, low accuracy of large depth grooves and diamond tool wear problems were the main reasons for the failure of the test to inscribe large area diffraction gratings. Therefore, the use of layered coating process can effectively ensure the uniformity and consistency of large-area and large-thickness grating blanks coated with aluminum film, and improve the high precision of large depth diffraction grating slot type. In order to reveal the mechanism of the groove-forming process of multilayer aluminum films, the microstructure and mechanical properties of different aluminum films were observed. In this article, the removal behavior and mechanism of nanomechanically scratched multilayer aluminum film materials are investigated using a molecular dynamics approach, and the characteristics of multilayer aluminum films scratched into grooves are analyzed in terms of surface morphology, scratching force, structural evolution, dislocation distribution, von Mises stress and shear strain. The results indicate that in the scratching simulation process, multilayer aluminum film has a higher number of removed atoms and a larger atomic displacement compared to single layer aluminum film, which is conducive to precise shape control of the groove. The average tangential force and normal force of multilayer aluminum film show a decreasing trend compared to single layer aluminum film, which helps to scratch grooves and reduce tool wear. The total length of the dislocation lines of the multilayer aluminum film is large, and the distribution area is large, which improves the precision of scratching the grooves. Therefore, an appropriate increase in the number of aluminum film layers has a precise control effect on the groove shape. This study has certain reference significance for analyzing the complex grooving deformation law of grating aluminum film, improving the diffraction efficiency of grating aluminum film, and further improving the manufacturing process of grating aluminum film.

Significantly enhanced energy storage performance in multi-layer polyimide films with nano dielectric layer

Polymer-based composites with multilayer structure were emerging as an effective way to solve the contradiction between high breakdown strength and large permittivity in past decades. However, the incorporating layers in conventional multilayer composite films are usually inorganic thick films, which is not beneficial for the retention of excellent mechanical properties of the polymer matrix. In this work, the multilayer films consisting of micrometer polyimide (PI) and nanoscale TiO2 layer were prepared by spin-coating and atomic layer deposition (ALD), respectively. Carrier migration in PI-TiO2 multilayer films was hindered effectively by the interfacial barrier, as indicated by the results of the Pulsed Electro-Acoustic (PEA) tests. Compared to pure PI, both the permittivity, dielectric loss and breakdown strength were optimized in the PI-TiO2 multilayer films. A satisfactory discharge energy density of 6.77 J cm−3 (efficiency >90 %) was obtained in the multilayer films, which is about 5 times higher than that of pure PI. The strategy of constructing heterogeneous interfaces by incorporated nanoscale TiO2 layers is promising for designing high performance capacitors in practical application.

Optical properties of transparent TiO2 films by sintering anatase nanoparticles with a CO2 laser

A novel CO2 laser additive manufacturing technique is reported in this paper for depositing transparent TiO2 films on quartz substrates using anatase TiO2 nanoparticles (NPs). Single- and double-layers of TiO2 films were prepared in two stages: (i) wet deposition using the spin-coating technique, and (ii) laser-assisted both drying of the wet layer and then sintering of the dried NPs to form a film. A theoretical model is presented to select and optimize the laser processing parameters. Scanning electron microscopy (SEM) revealed that the laser heating induces necking and coalescence of TiO2 NPs without cracking the sintered films or damaging the quartz substrate. An anti-reflection coating (ARC) model is utilized to select the film material and film thickness, aiming to reduce the reflectance and enhance the transmittance at certain wavelengths. UV/Vis spectrophotometry showed transmittance above ∼90% in the visible (Vis) range. The effect of laser power on the enhancement of transmittance is presented in this paper. Different concentrations of TiO2 NPs were used to optimize the film thickness. Single layer (∼110nm thick) and double layer films of the same total thickness as the single layer were analyzed to infer the effects of interface on the transmittance of TiO2 films. The transmittance of the single layer is higher, same as that of the double layer. Therefore, the difference in the transmittance of the single- and double-layer may be due to the effect of interface. The optical properties of the anti-reflection TiO2 coating in the UV–Vis ranges were investigated. X-ray diffraction (XRD) analysis showed that the thickness affects the crystallinity of the sintered TiO2 films.

Effect of deposition rate and annealing on Nb thin film growth on Cu substrate: Molecular dynamics simulation

Molecular dynamics (MD) simulations are performed to study the growth mechanisms of Nb thin film on Cu substrate. In this investigation, we provide insights and information about the quality of the deposited Nb thin film by analyzing the growth mode, stress, and evolution of its microstructural and morphological properties by considering different deposition rates and thermal annealing processes. The results show that the growth of Nb atoms on the Cu substrate follows the island mode. The interface analysis reveals the presence of a nucleation phenomenon, moreover, the results indicate that the first layer of Nb film remains incomplete until approximately the amount of 4 monolayers of Nb is deposited. The analysis of interdiffusion indicates that Nb penetration is initially limited to the first Cu layer. However, after annealing, there is a significant increase in Nb atom penetration and a clear rearrangement of Nb within each layer of the film. The film adopts a BCC structure, with crystallinity rates varying based on the deposition rate. The highest crystallinity rate is observed at 5 atoms/ps, and annealing further increases these percentages. Deposition at different rates leads to different levels of compressive normal and biaxial stress.

Surface plasmon resonance microscopy for optical EHL measurement systems

This study investigates the suitability and limitations of surface plasmon resonance (SPR) microscopy for optical elastohydrodynamic lubrication (EHL) measurement systems. SPR microscopy developed in this study can quantify the lubricant density distribution in contact region with high spatial-temporal resolution using simple total reflection optical systems. It means that, if either the temperature or pressure distribution can be estimated, the other can be calculated. To examine the practicalities, we determined specific optical setting conditions such as the incident angle and thickness of each film layer for surface plasmon excitations under EHL conditions based on numerical calculations and demonstration experiments.

New Hybrid Materials Based on N-Doping Copolymers of Thiophene Derivatives for Electrochemical Energy Storage

Over the past decade, electroactive conducting polymers (ECPs) are among the most potential pseudocapacitive materials for the electrodes of microsupercapacitors. ECPs exhibit several advantages, such as good conductivity (up to 103 S cm-1), flexibility, high specific capacitance (values ranging from 300 to 800 F.g-1 depending on synthesis and electrochemical performance conditions), relatively cheap and ease of synthesis [4]. Therefore, the electrochemical deposition of ECPs revealed a new strategy to design a great variety of various polymer morphologies as an innovative pseudocapacitive materials. Based on the different storage mechanism, electrochemical supercapacitors can be divided into three types, namely electrochemical double layer capacitors (EDLCs), pseudosupercapacitors and hybrid supercapacitors in which ECPs and other pseudocapacitive materials such as carbon materials, transition metal oxides, nitride complexes allow to store higher amount of capacitance per gram (faradic reactions) than EDLCs (pure capacitive energy storage reaction).In this work, we have elaborated new n-doped conducting polymers Poly[3,6-bis(2-thienyl)pyridazine] and Poly[3,6-bis(2-(3-n-hexylthienyl))pyridazine] by making electropolymerization on Pt disk electrode and 3 nm alumina coated silicon nanowires in acetonitrile organic electrolyte. The comonomers 3,6-bis(thienyl)pyridazine and (3,6-bis(2-(3-nhexylthienyl))pyridazine) have been successively synthesized. The produced polymeric materials Poly[3,6-bis(2-thienyl)pyridazine] and Poly[3,6-bis(2-(3-n-hexylthienyl))pyridazine] during n-doping process on Pt working electrode in acetonitrile solution of TBAPF6 (0.1 M) expose very low potential value of -2.23 V and -2.19 V at current density of -0.25 mA.cm-2 and -0.06 mA.cm-2, respectively. The elctropolymerization of synthesized comonomer 3,6-bis(thienyl)pyridazine has been done on Al2O3@SiNWs and resulted in thin layer of polymer film with micropores. The experimental results are compared to electropolymerization study of thiophene monomer on Pt disk and Al2O3@SiNWs electrodes to highlight the similarities and electrochemical advancements.

Mono-axial stretching-induced growth of crystalline phase of melt-processed perfluoroalkoxy alkane (PFA) films for protecting inner layer of battery pouch films

Cast polypropylene (CPP) is employed as an inner layer of pouch films; however, CPP shows poor electrolyte, mechanical, and electrical stability, which can lead to instability during cell operation. In this study, we pioneered the use of perfluoroalkoxy alkanes (PFA) in the melt extrusion process to fabricate films based on their high melting flow index, establishing optimal conditions for producing uniform films. We further enhanced the functionality of these films by controlling the crystalline phase orientation through high-temperature uniaxial stretching, which is aimed at applications in battery pouch films. The stretched PFA films exhibited dramatically improved mechanical and insulation properties compared to traditional CPP films, 307.4% increase in tensile strength and 1,748.8% increase in breakdown strength, respectively. Based on these findings, we proposed that stretched PFA films, with their superior performance, are viable substitutes for CPP as the inner layer in battery pouch films. This research not only advances the material science of polymer films but also contributes to the development of safer and more efficient battery technologies.