Film Formation Process Research Articles

Effect of Speed and Number of Sliding Cycles on the Film Formation Behavior of Fluorine-Based Grease

Grease, a type of lubricant, finds applications in various mechanical components due to advantages such as shape stability and sealing. However, grease is classified as a non-Newtonian fluid, and its film formation behavior is not fully understood to date due to variations in the mechanism related to the film formation behavior of grease based on factors like the base oil, bleed oil, thickener, and additives. In this study, the film formation behavior of fluorine-based grease was analyzed through the 3D profile of the grease after a friction test. In particular, the film formation behavior of the grease during sliding motion was analyzed. The experimental equipment used was a reciprocating-motion-type experimental equipment. Variations in the 3D profile were observed based on the speed and the cycle, indicating differences in the film formation behavior corresponding to changes in viscosity. In contrast to numerous studies that have observed the film formation behavior of grease under rolling motion, investigating the film formation behavior during the initial cycles of sliding motion will provide a profound understanding of the grease’s film formation process.

Preparing a liquid crystalline dispersion of carbon nanotubes with high aspect ratio.

We successfully prepared a surfactant-assisted carbon nanotube (CNT) liquid crystal (LC) dispersion with double-walled CNTs (DWCNTs) having a high aspect ratio (≈1378). Compared to dispersions of single-walled CNTs (SWCNTs) with lower aspect ratio, the transition concentrations from isotropic phase to biphasic state, and from biphasic state to nematic phase are lowered, which is consistent with the predictions of the Onsager theory. An aligned DWCNT film was prepared from the DWCNT dispersion by a simple bar-coating method. Regardless of the higher aspect ratio, the order parameter obtained from the film is comparable to that from SWCNTs with lower aspect ratios. This finding implies that precise control of the film formation process, including a proper selection of substrate and deposition/drying steps, is crucial to maximize the CNT-LC utilization.

Oligothiophene Additive‐Assisted Morphology Control and Recombination Suppression Enable High‐Performance Organic Solar Cells

AbstractTuning the morphology through processing additives represents one of the most promising strategies to boost the performance of organic solar cells (OSCs). However, it remains unclear how oligothiophene‐based solid additives influence the molecular packing and performance of OSCs. Here, two additives namely 2T and 4T, are introduced into state‐of‐the‐art PM6:Y6‐based OSCs to understand how they influence the film formation process, nanoscale morphology, and the photovoltaic performance. It is found that the 2T additive can improve the molecular packing of both donor polymer and non‐fullerene acceptor, resulting in lower Urbach energy and reduced energy loss. Furthermore, the blend film with 2T treatment displays enhanced domain purity and a more favorable distribution of the acceptor and donor materials in the vertical direction, which can enhance charge extraction efficiency while simultaneously suppressing charge recombination. Consequently, OSCs processed with 2T additive realize a promising efficiency of 18.1% for PM6:Y6‐based devices. Furthermore, the general applicability of the additive is demonstrated, and an impressive efficiency of 18.6% for PM6:L8‐BO‐based OSCs is achieved. These findings highlight that the uncomplicated oligothiophenes have excellent potential in fine‐adjustment of the active layer morphology, which is crucial for the future development of OSCs.

Improving the hole mobility of conjugated semiconducting polymer films by fast backbone aggregation during the film formation process

Forming high-performance IDTBT film with large aggregations with tight π–π stacking via fast aggregation between backbones during film formation by adjusting the solubility difference Ra (b–s) of the backbone and side chain in the solvent.

Multi-arm quinoxaline-based acceptors formed by π-conjugation extension for efficient organic solar cells.

Manipulating the conjugated backbone of small molecule acceptors (SMAs) is of particular importance in developing efficient organic solar cells (OSCs). Recently, trimers and other multi-arm SMAs have been found to be able to provide more intermolecular interaction, demonstrating excellent molecular stacking and device performance. However, the synthesis of this type of SMA usually relies on tristin or polystin compounds. Instead, expanding multiple arms in the central cores of SMAs is relatively simple and not restricted by tin compounds. Based on the quinoxaline core, two kinds of multi-arm SMAs, FQx-IC and TQx-IC with 4 and 3 arms, have been developed in this work. Compared to FQx-IC, TQx-IC exhibits an ordered face-on molecular orientation, appropriate film-forming process, and more favorable phase separation morphology and balanced charge transport. When blended with the polymer donor D18, OSCs based on TQx-IC achieve a power conversion efficiency (PCE) of 17.36%, which is superior to the device based on D18:FQx-IC (16.24%). In addition, using the ternary strategy of incorporating the TQx-IC into the D18:Y6 system, an excellent PCE of 18.82% is achieved. Therefore, this multi-arm molecular design strategy has great potential for regulating molecular stacking, absorption, and the corresponding device performance.

Constructing efficient organic solar cells by highly volatile solid additives with controlled phase morphology.

We synthesized two highly volatile and low-cost solid additives, PT and TFT. The inclusion of PT and TFT effectively influences the aggregation behavior of D18: L8-BO during the film-forming process. Consequently, PT and TFT-treated D18: L8-BO-based OSCs achieved power conversion efficiencies of 18.28% and 19.19%, respectively. This study provides a straightforward approach for achieving efficient photovoltaic performance of OSCs.

One-step fabrication of high energy storage polymer films with a wide bandgap and high melting temperature induced by the fluorine effect for high temperature capacitor applications with ultra-high efficiency.

The development of polymer dielectrics with both high energy density and low energy loss is a formidable challenge in the area of high-temperature dielectric energy storage. To address this challenge, a class of polymers (Parylene F) are designed by alternating fluorinated aromatic rings and vinyl groups in the polymer chain to confine the conjugating sequence and broaden the bandgap with the fluorine effect. The target films with desired thickness, ultra-high purity, and a wide bandgap are facilely fabricated by a one-step chemical vapor deposition (CVD) technique from monomers. The symmetric and bulky aromatic structures exhibit high crystalline performance and excellent stability at high temperature. The presence of strongly electronegative fluorine atoms effectively enhances bandgap and electron trapping capability, which effectively reduces the conduction loss as well as the possibility of breakdown at high temperatures. CVD technology avoids the post-processing film-forming process, ensuring the fabrication of thin films with high quality. These benefits allow Parylene F films to effectively store electrical energy at temperature up to 150 °C, exhibiting a record discharged energy density of 2.92 J cm-3 at charge-discharge efficiency exceeding 90%. This work provides a new idea for the design and synthesis of all-organic polymer dielectric films for high temperature applications.

Fabrication and film-forming mechanism of PCTFE films with exceptional water-vapor barrier and mechanical properties via solvent-assisted method

Polychlorotrifluoroethylene (PCTFE) has the outstanding water-vapor barrier performances among thermoplastics, and is with excellent transparency, high cryogenic toughness, and ultralow dielectric constant/loss. It plays an important role in high-performance packaging, electric circuit constructions, anti-corrosion coatings, cryogenic sealing, and so forth. Nevertheless, due to its borderline thermal stability and sensitivity to shearing effect, the melt-processing of PCTFE is rather difficult. Herein, a solvent-assisted method, which contained fabrication, coating, drying, and sintering of PCTFE suspension, was proposed for the fabrication of PCTFE films. The influence of processing parameters, including particle shape, drying temperature, and sintering time on the film-forming process was investigated. The as-prepared PCTFE films exhibited exceptional mechanical properties, with a tensile strength and failure strain of ∼42 MPa and ∼108 %, respectively. The water vapor transmission rate, light transmittance, and haze reached ∼0.02 g/(m2·24 h), ∼91 %, and ∼3 %, respectively. Finally, the potential film-forming mechanism was explained by the densification of PCTFE particles via capillary force, neck formation and particles coalescence driven by surface tension and viscous flow, and co-crystallization across the initial particle interfaces. In summary, the solvent-assisted method opened a new pathway for the processing of PCTFE films and is conducive to broadening their application fields.

A Review of the Developments of the Characteristics and Mechanisms of Airless Spraying on Complex Surfaces

The special surface appearance of complex surfaces restricts the coating film quality of spraying. The study of the atomization and film formation characteristics of typical complex surfaces, as well as the spraying mechanism, is essential for planning the spraying robotic trajectory and improving the spraying efficiency. In this paper, modeling and characteristics of the atomization and film formation process, based on CFD numerical simulations in previous studies, are systematically reviewed, focusing especially on airless spraying. In addition, the advantages and disadvantages of the existing research from the perspective of numerical models and methods are discussed. Finally, a further research direction for spraying on complex surface is prospected. Overall, a comprehensive and up-to-date review of spray atomization and film formation characteristics is considered valuable to practitioners and researchers in these fields, and will facilitate the further application of robotic spraying in the mechanical, automotive, marine, aerospace, petrochemical and other industries.

Strengthening effect of nano-rutile on Ti–3Zr–2Sn–3Mo–25Nb titanium alloy and mechanism of TiO2 phase transformation

The safety and stability of medical metal materials in the post-implantation period have always needed to be improved. Ti–3Zr–2Sn–3Mo–25Nb (TLM) near-β bio-titanium alloy has suitable biological properties and nontoxicity, by introducing nano-rutile particles in the micro-arc oxidation surface treatment process of TLM titanium alloy, can enhance its strength performance while retaining the original phase and excellent properties. The effects of nano-rutile on the microstructure and strength properties of micro-arc oxidation coating were tested and analyzed. The results showed that the addition of nano-rutile reduced the porosity and roughness of the coating, significantly increased the thickness, density, and especially the hardness. The self-corrosion potential increased from −0.345 to −0.272 V; the corrosion current decreased from 9.639 × 10−7 to 6.793 × 10−9 A/cm2. Furthermore, the friction coefficient decreased from 0.8 to 0.2, and the strength of fatigue wear and adhesive wear both attenuated. In addition, the chemical reactions that might occur during micro-arc oxidation were also speculated through the phase analysis, and the film-forming process and the influence of rutile doping on the oxidation process were also discussed. Moreover, the model of the nucleus in the TiO2 phase transition process was established and the relationship between the nucleation rate and the temperature was derived.

N-Methyl-2-pyrrolidone driven solvent engineering of hybrid perovskite solar cells fabricated under air ambient conditions

The efficiency and stability of perovskite solar cells (PSCs) are highly affected by their morphological properties, including grain size, crystal orientation, and perovskite film coverage. Solvent engineering has been recognized as a key strategy for controlling the film formation process and achieving optimized morphologies. Herein, we have explored solvent engineering using N-Methyl 2-pyrrolidone (NMP) for mixed cation and mixed halide-based PSCs to investigate the impact on device performance. To optimize the NMP concentration, four different precursor solutions with NMP quantities 0 µL (N0), 20 µL (N20), 40 µL (N40), and 60 µL (N60) were prepared by partially replacing DMSO in a triple solvent system (i.e., DMSO, DMF, and NMP). Optimum amount of NMP in the precursor solution leads to the formation of better uniformity, coverage, and compact film with larger grains. By incorporating a modification with the N40 precursor solution, the champion device fabricated under air ambient achieved an efficiency of 21.54 %. The optimized devices exhibited remarkable stability, maintaining an efficiency above 91 % even after 1500 h of storage in the dark under ambient. Thus, this study provides the pathway for improving the device performance and stability of PSCs by utilizing the solvent engineering approach.

Advanced thin films of indium-tin oxide doping with photosensitive polymer via embossing process

We propose a sol-gel thin film formation process involving nanoimprint lithography. First, indium tin oxide was dissolved in 2-methoxyethanol at a ratio of 5:5 and the mixture were mixed with 10 wt% of a UV-curable. Subsequently, a polydimethylsiloxane sheet prepared by covering a silicon wafer with a polydimethylsiloxane mold was attached to a InSnO thin film to duplicate the nanostructure through UV irradiation exposure. The replicated nanostructured thin films formed about morphological and chemical composition changes on the surface, we progressed to x-ray photoelectron spectroscopy and atomic force microscopy analysis. Furthermore, atomic force microscopy image analysis showed superior patterned grooves for a UV exposure time of 3 min. A suitability test involving the measurement of the transmittance was performed for examining the suitability of the thin film for use in display devices.

The concept of the contact angle in the process of oil film formation in internal combustion piston engines

In internal combustion piston engines, the process of oil film formation differs from that in industrial machines. The adhesive strength of the molecules at the interface between the coating of engine parts and the lubricating oil affects the load carrying capacity and the ability to form a lubricated film. The geometry of the lubricating wedge between the surfaces of the piston rings and the cylinder wall is determined by the thickness of the oil film and the amount of oil coverage of the ring. This state is modified by many parameters describing the operation of the engine and the physical and chemical parameters of the coatings of the cooperating pairs. For lubricating molecules reaching energies greater than the energy barrier of adhesion at the boundary, sliding occurs. Therefore, the value of the contact angle of the liquid on the surface of the coating depends on the value of the intermolecular force of attraction. According to the author, there is a strong correlation between the contact angle and the lubrication effect. Research indicates that the potential barrier is a function of the contact angle and the contact angle hysteresis (CAH). The innovation of the work consists in the study of the contact angle and CAH in the conditions of thin layers of lubricating oil in cooperation with hydrophilic and hydrophobic coatings. The thickness of the lubricating film was measured under various speed and load conditions using optical interferometry. The study proves that CAH is a better interface parameter to correlate with the effect of hydrodynamic lubrication.

Emulsion polymerization of super-hydrophobic acrylate enabled by a novel “ferrying” strategy for developing waterborne coatings with reduced surface tension and glossiness

The emulsion polymerization of high-alcohol acrylates with extreme hydrophobicity while achieving high monomer conversion has been posed significant challenges. In this study, the emulsion copolymerization of super-hydrophobic stearyl acrylate (SA) with an 18-carbon alkyl group has been successfully conducted by a novel “ferrying” strategy. Specifically, an emulsifier with a 23-carbon alkyl group (hydrophobic) and a 20-oxethyl group (hydrophilic) simultaneously was designed to facilitate the efficient transfer of SA through hydrophobic interaction from monomer drops to micelles, leading to a remarkable improvement in monomer conversion. The self-migration of the 18-carbon alkyl groups grafted onto the copolymer chains, which moved from the inner matrix to the coating surface, resulted in the creation of the waterborne coating with low surface tension during the film formation process. Moreover, it was confirmed that the self-crystallization of the 18-carbon alkyl groups caused the coating to exhibit a self-matting effect with low glossiness. Using an industrial formula, the effects of different types and dosages of emulsifiers, as well as the dosage of SA, on the total monomer conversion, SA conversion, and coating properties were extensively investigated. This work not only broadens the monomer range for emulsion polymerization to highly hydrophobic species, but also provides a variety of industrial waterborne products with low surface tension and low glossiness derived from high-alcohol acrylates, contributing to the development of environmentally friendly chemical industries.

Central Core Substitutions and Film-Formation Process Optimization Enable Approaching 19% Efficiency All-Polymer Solar Cells.

Molecular interactions and film-formation processes greatly impact the blend film morphology and device performances of all-polymer solar cells (all-PSCs). Molecular structure, such as the central cores of polymer acceptors, would significantly influence this process. Herein, the central core substitutions of polymer acceptors are adjusted and three quinoxaline (Qx)-fused-core-based materials, PQx1, PQx2, and PQx3 are synthesized. The molecular aggregation ability and intermolecular interaction are systematically regulated, which subsequently influence the film-formation process and determine the resulting blend film morphology. As a result, PQx3, with favorable aggregation ability and moderate interaction with polymer donor PM6, achieves efficient all-PSCs with a high power conversion efficiency (PCE) of 17.60%, which could be further improved to 18.06% after carefully optimizing device annealing and interface layer. This impressive PCE is one of the highest values for binary all-PSCs based on the classical polymer donor PM6. PYF-T-o is also involved in promoting light utilization, and the resulting ternary device shows an impressive PCE of 18.82%. In addition, PM6:PQx3-based devices exhibit high film-thickness tolerance, superior stability, and considerable potential for large-scale devices (16.23% in 1 cm2 device). These results highlight the importance of structure optimization of polymer acceptors and film-formation process control for obtaining efficient and stable all-PSCs.

Corrosion product film formation mechanism of 110H-13Cr casing steel in simulated ultra-high-temperature gas environment for shale oil production

This study investigated the corrosion film formation mechanism of 110H-13Cr at 350 °C in the coexistence of four gases, including H2, H2S, CO2 and H2O, by using techniques such as SEM, EDS, XRD and RAMAN, along with thermodynamic calculations. The results indicate that the average corrosion rate of 110H-13Cr is only 0.0573 mm/a. In this environment, the 110H-13Cr steel spontaneously reacts with H2S and H2O. The corrosion products consist of an easily removable outer Fe(1-x) S film and a dense inner Fe-Cr oxide film. The corrosion film formation process comprises an interfacial reaction stage and an element diffusion stage.

Synergistic modulation of chitosan on the mechanical and disintegration properties of pre-gelatinized waxy corn starch orally disintegrating film

The inconsistency between good mechanical properties and rapid disintegration characteristic is a challenge for starch-based orally disintegrating films (ODF). In order to improve the mechanical and disintegration performances of the films, chitosan/pre-gelatinized waxy corn starch (PWCS) ODF was fabricated and investigated for physical properties, surface micromorphology and crystallinity. The results showed that the mechanical properties of the composite films were improved (6.55 MPa ± 1.22 MPa, 18.11% ± 2.34%) while the fast disintegration characteristic (<30 s) was still maintained. During the film-forming process, the retrogradation of PWCS chains was hindered by chitosan molecules and the polar groups were exposed, enhancing the plasticity and hydrophilicity of the composite films. There was a synergistic effect between chitosan and PWCS. In addition, the microscopic images indicated that the high compatibility of chitosan and PWCS caused a homogeneous surface for the composite films. However, PWCS aggregated when the concentration of chitosan exceeded 20%, which increased the short-range order and crystallinity of PWCS in the composite films. The study provided a theoretical feasibility for the development of novel oral carrier platform.

Multi-functionally ferroelectric polymer promotes highly-efficient large-area organic solar cells with excellent comprehensive performance

Developing high-performance active layer with excellent comprehensive performance is very crucial for the commercialization of organic solar cells (OSCs). Here, we demonstrate the multi-function of ferroelectric polymer polyvinylidene fluoride (PVDF) in improving the device comprehensive performance including device efficiency, stability, green-solvent large-area printing and mechanical property. Addition of PVDF not only enhances the build-in field to promote charge kinetics, but also develops robust network through strong interaction and chain entanglement between polymer donor and PVDF. Importantly, such robust network effectively protects the active layer from excessive flushing/swelling between D/A component to optimize layer-by-layer (LBL) deposition, induce a favorable vertical phase distribution and prolong the film-forming process, consequently facilitating green-solvent blade-coating printing, improving device efficiency and stability, and enhancing device mechanical flexibility. Due to the multiple advantages of PVDF, the PM6/BTP-eC9 obtains an excellent efficiency of 18.35% for BTP-eC9-based LBL devices. By blade-coating printing with green solvent, one of the highest efficiencies of 16.40% is achieved for large-area (1.21 cm2) binary device. Particularly, toughness is used to comprehensively evaluate mechanical property of OSCs, showing significant improvement with simultaneously enhanced fracture strength and tensile strain, and enabling small molecule-based system even have comparable mechanical flexibility and comprehensive performance to the all-polymer system.

Concretized structural evolution supported assembly-controlled film-forming kinetics in slot-die coated organic photovoltaics

Bulk-heterojunction structured small-area organic solar cells are approaching 20% power conversion efficiency, but the blurred film-forming kinetics in the fabrication of large-area devices causes significant PCE loss and restrains the potential of commercialization. Such blurring came from insufficient knowledge of structural evolution during the film-forming process. Here, we concretize the evolution process with structures detailed to the submolecular level by comprehensive investigations of in-situ UV-vis spectroscopy, Atomic Force Microscope, Grazing Incident Wide Angle X-ray Scattering, and molecular dynamic simulation. With such hierarchical structural knowledge, assembly-controlled film-forming kinetics is proposed to explain the whole picture. Such assembly is determined by molecule configuration and can be tuned via external conditions. Understanding this kinetics will contribute to screening large-area device fabrication conditions, and the detailed structural knowledge could inspire the future design of novel photovoltaic materials that are intrinsically excellent in large-area device fabrications.

Monitoring Polymeric Fouling in a Continuous Reactor by Electrochemical Impedance Spectroscopy

AbstractMonitoring early stages of polymeric deposit formation and its prevention were studied by in‐situ electrochemical impedance spectroscopy (EIS) in a continuously operating reactor employed for polymer production. An EIS flow cell was designed and employed during the emulsion polymerization of vinyl acetate. The electrochemical analysis of the complex impedance at the solution/reactor interface allows the time‐resolved detection of film formation processes. In comparison to oxide‐covered stainless steel, an anti‐adhesive sol‐gel coated alloy showed a significant inhibition of poly(vinyl acetate) fouling. The EIS‐based approach proved to be a valuable tool for monitoring both thin barrier film performance and fouling processes under harsh process conditions.