Film Formation Research Articles

Preparation of molybdenum disulfide/bentonite nanohybrid and its tribological properties as lubricant for water-based drilling fluids

In recent years, with the increase in energy demand and gradual scarcity of medium and shallow oil and gas resources, oil and gas exploration has shifted to special wells such as deep wells, ultra-deep wells, and extended reach wells. These complex wellbore structures inevitably increase the torque and friction between the casing and the drill pipe during drilling, which aggravates friction and wear, and leads to accidents such as drill sticking and drill breakage in severe cases. In this study, molybdenum disulfide/bentonite (MoS2/Bent) nanohybrids as drilling fluid lubricant were synthesized by hydrothermal method using sodium molybdate (Na2MoO4) and thiourea (CH4N2S) as raw materials and bentonite as carrier. The as-synthesized MoS2/Bent nanohybrid was characterized by X-ray powder diffractometer, transmission electron microscopy, Fourier transform infrared spectroscopy, and the high temperature resistance and tribological properties of MoS2/Bent nanohybrid were evaluated in base slurry. The results show that the friction coefficient of MoS2/Bent nanohybrid drilling fluid before aging is reduced by 74 % and the wear rate is reduced by 97 % compared with the base slurry. After high-temperature aging at 240 °C, the friction coefficient is reduced by 77 % and the wear rate is reduced by 90 %. The excellent friction reducing and antiwear performance is attributed to the formation of low shear strength MoS2 deposition film and oxide tribofilm on the surface of the friction pair during the rubbing process.

Synthesis, crystal structure, characterization and corrosion inhibition studies of a strontium coordination polymer with tartaric acid

The reaction of anhydrous strontium chloride with the proton transfer compound 1-H-Imidazolium Hydrogen- meso-tartrate in water resulted in the formation of polymeric tartrate complex of strontium which is characterised by SXRD, IR, UV-Visible and TG/DTG analyses. The single crystal X-ray diffraction analysis reveals that each strontium atom is eight coordinate with distorted dodecahedral arrangement. The two metal fragments are linked through central four-membered Sr2O2 ring and there is no imidazole moiety in the complex. The compound displays a rare crystallographic feature where a shared hydrogen atom is located between two carboxylic groups. This unusual arrangement of hydrogen atom with an occupancy factor 0.5, located in between two carboxylate groups balances the total charge of the structure. FT- IR study reveals the bidentate coordination mode of the ligand. The thermal behaviour of the compound was studied using TG/DTG analysis. Corrosion inhibition property of the title compound on mild steel in 1.0M HCl has been investigated using weight loss method. The formation of protective film on the mild steel surface is confirmed by Scanning Electron Microscopy images. The inhibition efficiency increases with increase in concentration of inhibitor.

A-C/Au Film with Low Humidity Sensitivity of Friction by Forming Au Transfer Film.

Amorphous carbon is recognized as an excellent lubricating material; however, its tribological properties are significantly influenced by humidity. To elucidate the mechanism underlying this humidity dependence and to propose a novel enhancement method, we investigated and compared the tribological properties of hydrogenated amorphous carbon (a-C:H) and amorphous carbon/gold (a-C/Au) composite films. First, the friction coefficient of these carbon films under different humidity conditions was tested using a rotational ball-on-disk tribometer. Subsequently, we analyzed the morphology and structure of the sliding interface employing optical microscopy (OM), Raman spectroscopy, transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Finally, first-principle calculations were carried out to calculate the adsorption energy of water molecules on different surfaces. The results indicate that the friction coefficient of a-C:H film and the area of transfer film increase with the increase of humidity. This phenomenon can be attributed to the fact that water molecules enhance the interaction between the a-C:H film and steel counterfaces. Notably, in contrast, the friction coefficient of a-C/Au film demonstrates low sensitivity to humidity due to the formation of an Au transfer film that exhibits weak interaction with water molecules. These findings provide a promising strategy for developing environment-adaptive amorphous carbon films and play an important role in promoting the development of intelligent lubricating film.

Evaluation of imidazole blocking layers for perovskite stability

The prevention of AgI formation is critical for ensuring long term stability of perovskite solar cells. While sputtered metal oxide films are known for uniform dense film formation, solution phase nanoparticle coatings of metal oxides are prone to pinholes through which free iodide can migrate leading to AgI formation at the back contact. Iodide migration can be prevented through the addition of passivator or blocking layers at the perovskite/charge transport or charge transport/Ag interfaces. In this paper we evaluated a series of imidazoles as interfacial layers to prevent iodide migration from the perovskite to the Ag back contact through solution phase deposited Y:SnO2. We identified structural features of the imidazoles that contribute to an effective blocking layer. Specifically, it was found that imidazoles with conjugated planer systems and hydrogen bonding heteroatoms were able to prevent ion migration while retaining device performance. Of the materials evaluated 4-(Imidazol-1-yl)phenol had the best performance with a 60 % increase in stability verse the control under illumination at short circuit conditions.

Effects of varying pH on the passive film formation in high-strength anti-seismic rebar

ABSTRACT In this paper, electrochemical measurements (CV, PDP, M-S and EIS) and surface characterisation techniques (SEM, EDS, AFM, TEM and XPS) were used to study the passivation phenomenon in high-strength anti-seismic rebar under varying pH conditions. The results show that a passive film with a polycrystalline structure with a certain roughness is formed on the surface of the rebar. The passive film is mainly composed of Fe oxides and hydroxides, and there are also oxides of Nb, Mn, Si and Cr. The existence of these oxides builds a dense and stable passive film. The passive film is basically stable at 7d, but the early growth of the passive film at higher alkalinity show instability. After 10 days of passivation, with the decrease of pH, the passive film gradually densifies, the pitting potential increased by about 0.03–0.14 V, the carrier density decreased by 30% on average, the phase angle increased slightly, and the ratios of Fe2+/Fe3+ and O2−/OH− increased, resulting in a passive film thickness of 6.2 nm.

Unraveling the Formation Process of an Organic Photovoltaic Active Layer During High‐Speed Coating Via a Synergistic Concentration‐Temperature Gradient Control Strategy

AbstractThe Layer‐by‐Layer (LbL) strategy has emerged as a highly effective approach for enhancing the performance of organic photovoltaics (OPVs), notably boosting light harvesting and fill factor through spectral complementarity and morphology optimization. Crucially, the LbL processing strategy has been found to mitigate or overcome the decline in power conversion efficiency (PCE) during high‐speed blade coating. Despite these advancements, there remains a scarcity of research into the film‐formation process and the corresponding control strategies in high‐speed printing. A novel synergistic concentration‐temperature gradient control (SCTGC) strategy aimed at achieving high‐performance LbL‐type active layers at ultra‐fast coating speeds. This investigation reveals that both baseplate temperature and solution concentration exert a nonmonotonic regulatory influence on PCEs. Fine‐tuning the concentration gradient proves instrumental in balancing microfluidic competition within the wet film, thereby facilitating stable mass transport during the film formation process, and enhancing the high‐speed processability of the relevant OPV system. Additionally, the variations in crystallization kinetics under different temperatures are monitored. This work sheds light on the coating mechanism and film formation in high‐speed coating, highlighting the efficiency of the SCTGC method.

Enhancing the anti-wear performance of graphene sheets embedded carbon films through interface nanotexture fabricated on the substrate

The effect and mechanism of surface texture on friction have been extensively explored, such as storing the abrasive and reducing the real contact area. However, studying the impact of the interface texture remains crucial, especially as the texture size approaches the nanoscale. In the present work, the silicon substrate with different parameters nanotexture was fabricated using a metal-assisted chemical etching process, and the graphene sheets embedded carbon (GSEC) film was deposited on the nanotextured substrate via a low-energy electron irradiation process to produce the interface nanotextured carbon films. After the addition of the interface nanotexture, the tribological performance of carbon films exhibited significant enhancement, with the degree of improvement being influenced by the parameters of the interface nanotexture. A super-low wear rate was achieved, with a value of 6.54 ± 0.70 × 10−8 mm3/N m. The improved tribological performance is due to the enhancement of film-substrate adhesion strength facilitated by interface nanotexture, and its role in promoting the rapid formation of a stable transfer film on the counter-grinding ball. The carbon film with nanotexture displays a small size of the abrasive particles, which contributes to the stabilization of the friction process.

OG-POSS synergistically enhances the corrosion resistance and adhesion property of primer for silicone resin thermal protective coating

Octaglycidyldimethylsilyl polyhydric silsesquioxane (OG-POSS) in coordination with tetraethyl orthosilicate, tetrapropyl orthosilicate and tetrabutyl orthosilicate mixed solution was applied to the bonding of metal substrate and silicone resin thermal protective coating. The influence of OG-POSS addition on the interface of primer was systematically investigated by means of scanning electron microscope (SEM), salt spray test, thermogravimetric infrared spectroscopy (TGA-IR) and back temperature test. Results showed that the addition of OG-POSS favored the formation of a silane film of the primer, resulting in a more compact and continuous film. At the same time, the silane film had excellent corrosion resistance and adhesion, with a maximum adhesion strength of about 1.42 MPa. In addition, OG-POSS provided a unique Si-O-Si cage structure in the primer, which improved the ablation resistance of the interface layer, preventing the degradation and peeling of the coating in harsh environments.

A straight-forward fabrication of yuba films with controllable mechanical properties by oil-in-water emulsion model system rather than soymilk

The traditional process of producing yuba films from soybeans strictly limits the development of its industrial production due to the numerous processes and intricate procedures involved. In this study, a straight-forward and effective strategy was proposed to substitute soymilk with an emulsion made from soybean protein isolate and soybean oil for the formation of yuba films. It was found that the mechanical properties of yuba films formed through this method were controlled by the concentrations of proteins and oils. As the protein concentrations increased, a higher ratio of adsorbed proteins adhered to the surface of oil droplets, which in turn facilitated the recombination of proteins and the formation of larger aggregates during heat incubation. The rheological properties and interfacial adsorption behavior suggested that larger protein aggregates exhibited a greater diffusion rate and were more prone to unfolding and re-crosslinking at the interface through heat induction, resulting in the formation of stronger protein networks. Confocal laser scanning microscope images revealed a notable increase in the density of oil distribution within the yuba films as the oil concentrations in the pre-emulsion rose. Combined with the dense protein network formed at high protein concentrations, the elongation of yuba films was significantly increased.

SAW-driven directional clearance of bacteria on submerged surfaces

The process of bacterial film formation on submerged surfaces commences with the attachment of bacteria to the substrate. Appropriate combinations of topology and surface chemistry have been explored to prevent biofilm anchoring at the solid–liquid interface. However, the failure to actively remove bacteria from solid surfaces within a fluid in a directional manner results in bacterial backflow onto those surfaces, thus leading to secondary contaminations. Herein, inspired by the biology broom of the ciliary beating system, we propose an active surface sweeper mechanism assisted by charged particles and surface acoustic waves (SAW) to facilitate the directional clearance of bacteria. Through the synergistic effect of charge trapping and acoustic propelling, the sweeper system demonstrates an effective inhibition of bacterial adhesion in the initial stage of biofilm formation. Utilizing SAW for twenty seconds yields a remarkable 94.8% efficiency in bacterial clearance, with antibacterial adhesion efficiency up to 92.4% and 98.8% for Escherichia coli and Staphylococcus aureus, respectively. Moreover, the accompanying theoretical force modeling offers a comprehensive mechanistic insight into the relationship between acoustic streaming and bacteria repelling. The motion analysis of bacteria-loaded particles suggests that the acoustic radiation force, rather than the Strokes force, determines the clearance direction of bacteria.

Synthesis, structure, I–V characteristics, and optical properties of chromium oxide thin films for optoelectronic applications

Abstract Improving coating technology and thin film formation by optimizing the experimental parameters has become essential for various industrial and technological fields. This work aims to study the influence of the precursor materials on the physical and electro-optical properties of Cr2O3 thin films. The solutions were prepared using the sol–gel route and deposited on glass slides using the spin coating technique. The structure and morphology of the films were studied using XRD, FT-infrared (IR), and field-emission scan-electron microscope. The results indicated the formation of a high-purity Cr2O3 (Eskolaite) phase in the form of spherical nanoparticles with sizes of 17–25 nm. Three bands appear at 490, 765, and 889 cm − 1 {{\rm{cm}}}^{-1} in the FTIR spectra, which are attributed to Cr – O {\rm{Cr}}{\rm{\mbox{--}}}{\rm{O}} / Cr ═ O {\rm{Cr}}{\rm{═}}{\rm{O}} vibrations. The I–V curves showed linear behavior and good ohmic features. Ultraviolet-visible-near infrared spectra showed that the films are highly transparent, with band gaps in the range of 2.60–2.90 eV, and refractive indices in the range of 1.92–2.25. The sheet resistances, the new figure of merit, the real and fictional dielectric constants, and the optical conductivity were discussed. The Cr2O3 thin films are the best candidates for various utilizations, including solar cells, sensors in the IR region, and energy storage.

Efficient sealing of cemented sheath: An oil-responsive self-healing latex with toughness enhancement for cement composites

The integrity of the cemented sheath is important to the safe exploration of oil and gas resources. Sealing failure of cement sheath will result in formation fluid channeling and pressure carryover in the annulus. The both toughening and oil-responsive self-healing latex (TOS) was prepared to achieve efficient sealing of cemented sheath, and prolong its service life. The structure and oil swelling behavior of TOS, its toughening and self-healing effects on hardened cement paste (HCP) were analyzed by comprehensive characterizations. Results demonstrated that TOS possessed excellent stability and an oil swelling rate of 1235 %. Cement specimens by curing 28d containing 8 % TOS exhibited a 27.8 % increase in flexural strength, a 48.7 % reduction in elasticity modulus and a 33.8 % reduction in brittleness coefficient. The addition of TOS can effectively improve the toughness of cement. The average pore size of specimens containing 8 % TOS admixture decreased to 9.17 nm. This indicates that TOS enhanced the structural density of cement materials. The crack about 103μm in the cracking specimens with 8 % TOS was almost healed, and the corresponding permeability was reduced 99.1 % after curing in oil. Adsorption and film formation of TOS can resist the cracking of cement sheath, and the oil swelling expansion of film in cement matrix can repair the cracked structure.

Effects of chemical etching on surface structure and tribological behavior of silicate substrates

Abstract This study investigated the effect of chemical etching on the surface structure and tribological behavior of silicate substrates. Silicate surfaces were etched using a mixture of nitric acid (HNO3) and ammonium bifluoride (NH4HF2) for durations ranging from 1 to 60 min. The etched surfaces were characterized using optical microscopy, scanning electron microscopy, surface profilometry, water contact angle measurements, and UV–vis spectroscopy to evaluate the changes in surface morphology, roughness, wettability, and optical properties. Tribological performance was assessed using reciprocating ball-on-plate friction tests. The results showed that increasing the etching time resulted in the formation of microscale surface features, increased surface roughness, enhanced hydrophilicity, and reduced optical transmittance. The average friction coefficient decreased with an increase in the etching time up to 30 min, beyond which a slight increase was observed. The 1-minute etched specimen exhibited the best wear resistance with the narrowest wear track and the least material removal. The improved tribological performance was attributed to the formation of a stable transfer film, reduced real contact area, and entrapment of wear debris. This study highlights the potential of chemical etching as a technique to tailor the surface structure and tribological properties of silicate materials for various applications.

On-demand performance optimization of AlGaN/GaN high electron mobility transistors using stoichiometric variation of dielectric alloy AlxTayO

The current research investigates the potential advantages of optimally combining wide bandgap Al2O3 with high dielectric constant (high-κ) Ta2O5 for gate dielectric applications. Various compositions of 10 nm AlxTayO oxide films are grown on the Al0.3Ga0.7N/GaN heterostructure by co-sputtering Al and Ta metals, followed by thermal oxidation at 500 °C. The average root-mean-square roughness of the grown oxide films is ∼1.2–1.4 nm compared to 0.4 nm for as-deposited metal. X-ray photoelectron spectroscopy and transmission electron microscopyconfirm the formation and thickness of the grown oxide films. The bandgap (Eg) of the oxide films calculated from O1s electron energy loss spectra show a linear increase from 4.85 eV for pure Ta2O5 to 6.4 eV for pure Al2O3. The dielectric constant (εox) calculated from capacitance–voltage (CG−VG) measurements decreases linearly from 25.7 for Ta2O5 to 7.9 for Al2O3. The interface trap density (Dit) is estimated from the frequency dispersion of capacitance–voltage (CG−VG) characteristics. The DC and radio frequency (RF) characteristics of AlxTayO/Al0.3Ga0.7N/GaN high electron mobility transistor (HEMT) devices are measured and compared with the Schottky HEMT devices (without any gate oxide). Compared to Schottky HEMT devices, AlxTayO/Al0.3Ga0.7N/GaN HEMT devices show superior DC characteristics, which helps us achieve maximum RF output power. Furthermore, the OFF-state measurements show that the AlxTayO/Al0.3Ga0.7N/GaN HEMT devices can sustain higher source-to-drain voltages, from a minimum of 88 V on pure Ta2O5 metal-oxide-semiconductor (MOS)-HEMTs to a maximum of 138 V on pure Al2O3 MOS-HEMTs before the dielectric breakdown happens, compared to a 57 V breakdown voltage on Schottky HEMT devices. An oxide variation of AlxTayO, with Al composition ratio of 0.34, shows an exceptional ION/IOFF ratio of 4 × 1011, a gate leakage current of 8 × 10−12 A/mm, a near-ideal subthreshold slope of 63.8 mV/dec, and the unity current gain frequency (fT) of 25.6 GHz.

Study on superhydrophobicity and corrosion resistance of the micro-nano structure prepared by femtosecond laser

The wettability as well as the corrosion resistance of metal is closely related to the surface microstructure. A surface structure with micro protrusion and nano ripple was designed and constructed on 316L stainless steel by femtosecond pulse laser. Superhydrophobic surfaces with a great contact angle over 150° were obtained by surface modifications of heat treatment or fluorination treatment. The corrosion resistance of the superhydrophobic micro-nano structured surfaces was studied through electrochemical testing. The result of polarization curve revealed that the superhydrophobic micro-nano structured surfaces possessed a higher corrosion potential, signifying the susceptibility to corrosion was reduced. Besides, the results of impedance indicated that the superhydrophobic micro-nano structured surfaces exhibited greater total resistance when compared to the original surface, demonstrating the corrosion resistance was enhanced. According to the results, the superhydrophobic surface, characterized by its micro-nanostructure, facilitates the formation of a protective gas film. Additionally, the intricate micro-nano rough structure, in conjunction with the gas film, effectively shields the underlying surface from infiltrative processes, thereby mitigating the potential exacerbation of corrosion phenomena.

Optimizing deposition parameters and characterizing TiO2 thin films for future memristor applications

Titanium dioxide (TiO2) thin films were deposited on glass substrates using Spray Pyrolysis technique, with variations in multiple deposition parameters. The molarity of the precursor was altered within a small range from 0.09 M–0.15 M. The deposition temperature was systematically adjusted from 200 °C to 400 °C while the ratio between precursor and chelating agent varied between 1:1,1:2 and 1:3. The thickness of TiO2 films were found to be in the range of 216 nm to 14.9 μm. Structural analysis conducted by XRD confirmed the formation of anatase TiO2 thin films. Optical studies using UV-Visible spectrophotometer determined the absorption and indirect bandgap ranging from 299 nm to 326 nm and 3.08 eV to 3.44 eV respectively. Electrical studies carried out evaluated the leakage currents and DC resistivity for all individual films with the input voltage applied from ± 0.5 V to ± 5V. Impedance studies were conducted by varying input voltages from 0.2V–3V for each film, so as to examine the resultant impedance, dielectric constant, dielectric loss, conductivity, admittance and modulus spectra. The obtained results were analysed to optimise the deposition parameters for designing future memristors with specific individual or combined characteristics, such as high ON/OFF, switching speed, endurance and retention.

Rational Doping Strategy to Build the First Solution‐Processed p‐n Homojunction Architecture toward Silicon Quantum Dot Photodetectors

Semiconductor p‐n homojunction is a requisite building block of operating transistors and diodes which make up the modern electronic circuits and optoelectronic applications. However, it has been so far limited to bulk form of single crystals such as silicon (Si) or gallium arsenide. Herein, a brand‐new method of constructing p‐n homojunction architectures that breaks through the limitation is presented. Colloidal inks of p‐type and n‐type Si quantum dots (QDs) are synthesized by thermal disproportionation of (HSiO1.5)n doped with boron or phosphorus, followed by surface ligand engineering. Analysis combining UV photoelectron spectroscopy, electron spin resonance, and current–voltage characteristics confirms that an orthogonal solvent trick makes clean interfaces between n‐type and p‐type SiQD layers without disruption on film formation. The forward and reverse current–voltage characteristics of the diode, along with various spectroscopic characterizations, demonstrate the formation of the first p‐n homojunction of SiQDs. The self‐powered photodiode provides a tunable response specific to the wavelength.

Microcrystalline and nanocrystalline structure of diamond films grown by MPCVD with nitrogen additions: Study of transitional synthesis conditions

This research explores the complex influence of nitrogen concentration and substrate temperature on the resultant properties of polycrystalline diamond (PCD) films grown by microwave plasma chemical vapor deposition (CVD). In particular, we investigated the growth parameters to find the exact conditions for changing the morphology of the resulting film from microcrystalline (MCD) to nanocrystalline (NCD). A series of 2 µm-thick polycrystalline diamond films was grown on Si substrates in methane-hydrogen–nitrogen gas mixtures with varied: (i) nitrogen concentration (0–2 %) and (ii) substrate temperature (700–1050 °C). Comprehensive characterization techniques, including scanning electron microscopy (SEM), micro-Raman spectroscopy, and X-ray diffraction, were employed to assess the morphological, structural, and spectroscopic properties of the films. The study reveals that even minor additions of nitrogen significantly modulate secondary nucleation, impacting both film morphology and phase composition. Furthermore, substrate temperature emerges as another critical parameter, influencing the growth kinetics and crystallite size. The comparison of the characteristics of grown PCD films allowed us to find conditions for the formation of NCD films with minimal surface roughness and maximal growth rate: nitrogen concentration [N2] ≈ 0.2–0.5 % and temperature T ≈ 850–900 °C. These findings can be used to optimize the CVD synthesis parameters of PCD films for applications as protective or friction-reducing layers, as well as for superhard cutting tools and optical devices.

Reusable and non-invasive TiO2-based photodynamic transdermal patch (RPT) for treating MDR-negative bacteria strain and promote wound healing through a synergistic approach of ROS-induced RNS

Wound healing is delayed due to the infection and biofilm formation of antibiotic-resistant species of gram-negative bacteria especially Pseudomonas aeruginosa and Escherichia coli. Antibacterial photodynamic therapy provides an efficient therapeutic strategy for overcoming drug resistance by producing reactive oxygen species (ROS) and reactive nitrogen species (RNS). Here, we have designed a low-cost light emitting diode (LED) based reusable and non-invasive titanium dioxide nanoparticles patch which is sandwiched between the thin polymer layers. The light-induced pore formation in the polymeric film due to the free radical, in turn, passes through the system and kills the bacteria rather than nanoparticles entering the system resulting in the reusability nature of the patch. The patch's in vitro antibacterial and antibiofilm activity and their mechanism (synergic ROS-induced RNS) were studied. In addition, the reusable antibacterial properties, biocompatibility and wound-healing properties of the patch were also successfully elucidated.

Novel Understanding of the Formation and Protectiveness of Corrosion Product Film on Ca–Sb–Cr Weathering Steel

The addition of Ca and Sb in Cr‐bearing steel presents improved corrosion resistance during the field exposure test in a marine atmosphere environment. Through local hydrolysis reactions, Ca and Sb can form CaO, Sb2O3, and Sb2O5 to prevent the intrusion Cl− into the corrosion product film, which improves the protectiveness of the corrosion product film and reduces the corrosion rate. The formation of CaCl2 decreases the relative content of β‐FeOOH and makes the corrosion product film more stable. Due to the inhibition of Sb on the local acidification of corrosion product film, Ca and Cr are able to bond with more hydroxide for generating the corresponding oxides and improving the corrosion resistance of Cr‐bearing steel.