Molecular Deposition Film Research Articles

Experimental Study on Improving the Recovery Rate of Low-Pressure Tight Oil Reservoirs Using Molecular Deposition Film Technology

The intricate geological characteristics of tight oil reservoirs, characterized by extremely low porosity and permeability as well as pronounced heterogeneity, have led to a decline in reservoir pressure, substantial gas expulsion, an accelerated decrease in oil production rates, and the inadequacy of traditional water injection methods for enhancing oil recovery. As a result, operators encounter heightened operational costs and prolonged timelines necessary to achieve optimal production levels. This situation underscores the increasing demand for advanced techniques specifically designed for tight oil reservoirs. An internal evaluation is presented, focusing on the application of molecular deposition film techniques for enhanced oil recovery from tight oil reservoirs, with the aim of elucidating the underlying mechanisms of this approach. The research addresses fluid flow resistance by employing aqueous solutions as transmission media and leverages electrostatic interactions to generate nanometer-thin films that enhance the surface properties of the reservoir while modifying the interaction dynamics between oil and rock. This facilitates the more efficient displacement of injected fluids to replace oil during pore flushing processes, thereby achieving enhanced oil recovery objectives. The experimental results indicate that an improvement in oil displacement efficiency is attained by increasing the concentration of the molecular deposition film agent, with 400 mg/L identified as the optimal concentration from an economic perspective. It is advisable to commence with a concentration of 500 mg/L before transitioning to 400 mg/L, considering the adsorption effects near the well zone and dilution phenomena within the reservoir. Molecular deposition films can effectively reduce injection pressure, enhance injection capacity, and lower initiation pressure. These improvements significantly optimize flow conditions within the reservoir and increase core permeability, resulting in a 7.82% enhancement in oil recovery. This molecular deposition film oil recovery technology presents a promising innovative approach for enhanced oil recovery, serving as a viable alternative to conventional water flooding methods.

Characterization of polyamide thin films by atomic force microscopy

This study directly compares the mechanical behavior of novel molecular layer deposition (MLD) and analogous interfacial polymerization (IP) polyamide thin films in environments relevant to reverse osmosis (RO) membrane operation. The elastic modulus of the films was determined using atomic force microscopy (AFM) in dry, hydrated, and chlorinated states. Surface roughness characteristics were also obtained given their potential influence on AFM modulus measurements. The much smoother MLD films demonstrated a statistically higher modulus in all states as compared to their IP counterparts. The MLD films maintained a modulus ∼3X and ∼5X greater than that of IP films after hydration and chlorination, respectively. Such differences in behavior may be due to the higher density and correspondingly lower void content of the MLD films. Results from this study provide a rationale for future development of MLD for fabrication of polyamide films for incorporation in RO membranes.

Experimental Investigation on a Novel Polyelectrolyte Molecular Deposition Film for Improved Injectivity in Low-Permeability Reservoirs.

Acrylamide and dimethyl diallyl ammonium chloride were used as monomers to synthesize a polyelectrolyte molecular deposition film (PMDF) injection agent for solving the problem of high injection pressure of water wells in low-permeability reservoirs. The structure of the PMDF injection agent was determined through IR and 1H nuclear magnetic resonance (NMR). The performance evaluation results show a change of wettability from hydrophilic to neutral wetting with the contact angle changing from 22.32 to 73.31° because of agent injection. It can also change the negative ζ-potential on the surface of the sand to a positive value. For comparison, core displacement experiments involving the commercial Gemini surfactant DF-G reveal that the effects of the depressurization of PMDF are more obvious than those of DF-G. The adsorption stability of the former is better than that of the latter. Especially, under a high-speed water flow of 30 pore volume (PV) injection, the depressurization rate of PMDF is still as high as 43.59%. Finally, the oil–water relative permeability curves and core nuclear magnetic resonance (NMR) experiments demonstrate that the PMDF treatment can reduce the irreducible water saturation, which indicated that the porosity of the flowable part of the core increased and the swept volume was increased. The suitable range of PMDF according to NMR pore-radius distribution within a low-permeability reservoir: the flowable partial pore required the throat radius greater than 0.01 μm.

Pyrolysis of Alucone Molecular Layer Deposition Films Studied Using In Situ Transmission Fourier Transform Infrared Spectroscopy

The pyrolysis of alucone molecular layer deposition (MLD) films was studied in vacuum using in situ transmission Fourier transform infrared spectroscopy. The initial alucone MLD films were grown using trimethylaluminum (TMA) and either ethylene glycol (EG) (HO–(CH2)2–OH) or hydroquinone (HQ) (HO–C6H4–OH) at 150 °C. The alucone MLD films were then pyrolyzed in vacuum at temperatures ranging from 400 to 750 °C. The absorbance features for the C–H, C–C, and C–O stretching vibrations were observed to be lost at pyrolysis temperatures from 350 to 500 °C. For the alucone films grown using TMA and EG, the loss of these absorbance features was coupled to an increase in carboxylate (R-COO–) absorbance features. The carboxylate absorbance features reached their peak at a pyrolysis temperature of 450 °C and then decreased slowly with higher pyrolysis temperatures. The carboxylate absorbance features are consistent with an Al2O3/carbon composite material with Al3+/COO– species at the interface. In addition, the prese...

Caprolactone Ring-Opening Molecular Layer Deposition of Organic-Aluminum Oxide Polymer Films

New hybrid organic-inorganic thin films are finding use in electronics, biomedical, chemical protection, and energy storage systems applications. In a unique vapor-source molecular layer deposition film formation reaction, we find that cyclic ɛ-caprolactone reacts with surface-adsorbed methyl-aluminum species to build a metal-organic hybrid coordination polymer thin film at substrate temperatures between 60 and 120°C. Infrared and X-ray photoelectron spectroscopy analysis confirms (–Al–O–(C8H16)–O–)n bonding, expected from the a Lewis acid catalyzed surface ring-opening reaction. In-situ IR analysis confirms the surface reaction sequence. The materials show good stability and maintain their physical structure in ambient. This surface acid-catalyzed vapor process could extend to other metal organics and vapor/surface ring opening reactions to yield new organic-inorganic film materials for use in gas diffusion barriers, separation membranes and chemical resistance coatings.

Shear of molecular deposition films on glass substrates determined by tribometer

The ultrathin polyelectrolyte molecular deposition films and polyelectrolyte composite nanoparticles molecular deposition films were prepared using layer-by-layer molecular deposition method and in situ growth method. A micro-tribometer has been developed to measure the shear response of those ultrathin molecular deposition films. By using a smooth steel sphere in a ball-on-flat configuration, the shear force was determined for molecular deposition films on glass substrate for different layers. The results indicate that the shear behaviors of molecular deposition film were mainly determined with the contact area and film layers. Moreover, the composite molecular deposition film with nanoparticles has better shear behaviors than the polyelectrolyte molecular deposition film. The shear force of polyelectrolyte molecular deposition film is more dependent on the speed than that of composite nanoparticle molecular deposition film.

Investigation of tribological behavior of lanthanum hybrid polyelectrolyte molecular deposition films

Poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonic acid) sodium salt (PSS) polyelectrolyte molecular deposition films were prepared on quartz substrate by the layer-by-layer method. Lanthanum was deposited in the polyelectrolyte molecular deposition film, making use of the chemisorption ability of –SO 3 − group of PSS, and heating for 2 h at 120 °C to make the lanthanum element chemically bond with PSS. Atomic force microscopy (AFM), ultraviolet–visible (UV–vis) light spectroscope, X-ray photoelectron spectroscopy (XPS), and contact angle measurements were used to characterize the thin films. The tribological behaviors of the polyelectrolyte molecular deposition film and lanthanum hybrid polyelectrolyte molecular deposition film were evaluated on a micro-tribometer by sliding against a steel ball. Tribological experiments show that the friction coefficient of polyelectrolyte molecular deposition film decreases from 0.19 to 0.08 after the rare-earth (RE) self-assembled in the polyelectrolyte molecular deposition film. The lanthanum hybrid polyelectrolyte molecular deposition films have a longer wear life than that for the pure polyelectrolyte molecular deposition film. It is demonstrated that the lanthanum hybrid polyelectrolyte molecular deposition film exhibits a good wear-resistant property.

Investigation of the Tribological Behaviors of Polymer Molecular Deposition Films by Tribometer Based on Interferometer

The polymer molecular deposition films including polyelectrolyte molecular deposition (PEMD) film and nanoparticles composite molecular deposition (NPs/MD) film have been prepared using the molecular deposition method and the in situ synthesize method. The polymer molecular deposition films were characterized by atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). The tribological behaviors of the substrate and polymer molecular deposition films were investigated by a tribometer based on interferometer. It is found that the NPs/MD film has a lower friction force and a better anti-wear property than the PEMD film under the dry friction. The poly alpha olefin (PAO2) and water films confined between samples and steel ball surfaces have been investigated using thin film interferometry. The friction force of substrate was lower than the polymer molecular deposition films under PAO2 lubrication. The friction forces alteration of PEMD film and NPs/MD film were similar and consistent, and lower than that for substrate under water lubrication.

Nanotribological behaviors of in situ nanoparticles doped molecular deposition films

The molecular deposition films of poly (diallyl dimethylammonium chloride) (PDDA) and poly (acrylicacid) (PAA) with Cu2+ on quartz and glass substrates were prepared in laboratory first, then different bilayers films were dipped into fresh Na2S aqueous solution. As a result, CuS nanoparticles were fabricated in multilayer molecular deposition films in situ. The structure and nanotribological properties of the composite films were analyzed by ultraviolet-visible (UV-visible) spectroscopy, XPS and atomic force microscope (AFM). It was found that the CuS nanoparticles were homogeneously distributed throughout the whole film. And these films had a much smaller friction force than their substrates and higher antiwear life than pristine PDDA/PAA molecular deposition films. The fluctuation and variation trend of the topography, hardness, and friction with the AFM indentation length were also investigated.

Tribological behavior of in situ Ag nanoparticles/polyelectrolyte composite molecular deposition films

Multilayer polyelectrolyte films containing silver ions were obtained by molecular deposition method on a glass plate or a quartz substrate. The in situ Ag nanoparticles were synthesized in the multilayer polyelectrolyte films which were put into fresh NaBH 4 aqueous solution. The structure and surface morphology of composite molecular deposition films were observed by UV–vis spectrophotometer, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Tribological characteristic was investigated by AFM and micro-tribometer. It was found that the in situ Ag nanoparticles/polyelectrolyte composite molecular deposition films have lower coefficient of friction and higher anti-wear life than pure polyelectrolyte molecular deposition films.

Advances in studies of the tribological behavior of molecular deposition films

An overview of the advances in studies on tribology of molecular deposition (MD) films is presented here to summarize the studies of nanofrictional properties, adhesion, wear and mechanical behavior, as well as the molecular dynamics simulation of nanotribological properties of the film in the last decade. Some key research topics which need to be investigate further are addressed.

Tribological behaviors of composite molecular deposition films

Polyallylamine hydrochloride (PAH)/graphite oxides (GO) ultrathin film and the multilayer film of PAH incorporated with TiO 2 enwrapped by polyacrylic acid (PAA), namely PAH/PAA(TiO 2) composite film, were prepared by molecular deposition (MD) method in laboratory. Both of them were heated to change the film forming dynamic force from electrostatic force to covalent bond so as to increase the bonding strength of the films. The structure and nanotribological properties of the films were analyzed by atomic force microscope (AFM) and ultraviolet-visible (UV) spectroscopy. It was found that these films had a much smaller friction force than their substrates and the friction force was dependent on the morphology and/or hardness of the films.

Nanomechanical properties of molecular deposition film

Two nanomechanical properties of the molecular deposition (MD) film deposited on the Au substrate were studied. The first is its nanotribological property investigated by an atomic force microscope, which indicates that the deposition of the MD film could reduce the frictional force. The second is its nano-indent property studied by a nano-indenter. The results show that, after the MD film is deposited on the Au substrate, the elastic modulus, hardness and load decreased all, moreover, the elastic deformation increased and the plastic deformation decreased, which indicates that the MD film can improve the nanomechanical properties of the Au substrate.

Characterisation and nano‐friction behaviour of molecular deposition films

AbstractThe structure and the nano‐friction behaviour of a new kind of ultrathin film, a molecular deposition (MD) film, on an Au substrate were studied. The MD film is formed by the electrostatic attraction between opposite charges of cationic and anionic compounds, and a multilayer film can be built through alternating deposition of bipolar cationic and anionic compounds. Monolayer, bilayer, trilayer, and tetralayer MD films on Au substrates were examined. MD films with an alkyl terminal group were also investigated. It was found that while the MD film on an Au substrate reduced the friction, its nano‐friction behaviour was unstable because of the active terminal group. However, if the MD film was formed with an alkyl terminal group, its nano‐friction behaviour became stable and its friction decreased markedly. Therefore, this film termination method could contribute to the nano‐tribological application of MD films.

Computer Simulations on Mechanical Properties of Molecular Deposition Film

The mechanical properties of the molecular deposition film deposited on an Au substrate are studied in the theory for the first time. Firstly, the quantum mechanics have been used to calculate the structure parameters and potential parameters of the molecular deposition film. Secondly, molecular dynamics simulations have been used to study indent process of the molecular deposition film with the action of Au tip. The results showed that an obvious jump to contact appears during the Au tip approaches the molecular deposition film; furthermore, the tilt angle and load of the molecules near the tip have the same tendency of hysteresis, which may be caused by the adhesive force between the tip and the molecular deposition film.

Simulations on nanotribological properties of molecular deposition films

The nanotribological properties of molecular deposition films deposited on an Au substrate are studied theoretically for the first time. First, the structure and potential parameters of the molecular deposition film are calculated using quantum mechanics. Second, the film deposited on the Au (111) substrate after interaction with an Au tip is simulated by molecular dynamics simulations. It is found that in the process of compression the tilt angle and the potential energy of the molecules in the film near the tip both increase as the distance between the tip and film decreases. In the scan process, first a continuous slip and afterwards regular stick–slip occur; this is in agreement with the spatial structure.

Molecular dynamics simulation on nanotribological properties of molecular deposition film during the scan process

In this paper, a molecular dynamics simulation has been used to study the nanotribological properties of the molecular deposition film deposited on the Au (111) substrate during the scan process with an Au tip. The results show that the tilt angle and the potential energy of the molecules near the tip are both increased with decreasing distance between the tip and monolayer. Continuous slip also occurs during the slip stage. Furthermore, the regular stick-slip is in agreement with the spatial structure.

Preparation and nanotribological behavior of PAH/graphite oxide molecular deposition film

Polyallylamine hydrochloride/graphite oxides ultra thin film (coded as PAH/GO ultra thin film) was prepared by molecular deposition (MD) in laboratory. The resulting PAH/GO ultra thin film was heated to convert the electrostatic force towards covalent bond so as to increase the bonding strength of the film. The structure and nanotribological properties of the film were analyzed by means of atomic force microscopy and ultraviolet-visible spectroscopy. It was found that the PAH/GO ultra thin film had a much smaller friction force than the glass substrate and the friction force was dependent on the hardness and appearance of the glass substrate.

Nano‐scratch study of molecular deposition films on silicon wafers using nano‐indentation

AbstractExperiments on molecular deposition (MD) films with and without alkyl terminal groups deposited on silicon wafers were conducted using nano‐indentation. It was found that MD films and alkyl‐terminated MD films exhibit a higher critical load and a lower coefficient of friction than the silicon substrate. The critical load increases with the number of layers, and the coefficients of friction of MD films with alkyl terminal groups are lower than those of the corresponding MD films with the same number of layers but without alkyl terminal groups.

Developments in tribological research on ultrathin films

A review of studies of the tribology of ultrathin films is presented, which focuses primarily on the tribological properties of the Langmuir–Blodgett (LB) films, self-assembled monolayers, and the molecular deposition films investigated by the authors and their co-workers. The emergence of the atomic force microscope has helped the development of studies of ultrathin films; particularly LB films which have been studied extensively. Firstly, the results of research into the various factors affecting the tribological properties of LB films and progress in the application of molecular dynamics simulations to study the mechanisms of friction and lubrication are introduced. Then a review of the experimental and theoretical research into self-assembled monolayers is given. Finally, recent advances in the investigation of tribological properties of molecular deposition films on different substrates (Au, Si and silica rock surfaces) are presented and the prospects for the tribological applications of such ultrathin films are addressed.