Role In Formation Of Films Research Articles

Effects of Oil and Solid Body Temperatures on Elastohydrodynamic Lubrication Film Formation

The present study focuses on investigating the influence of oil and solid body temperatures on elastohydrodynamic lubrication (EHL) film formation. Experimental and numerical simulation methods are employed to examine three heating methods: oil and ball heating, disc heating, and entire system heating. A preliminary comparison between the measured results and numerical simulations confirms the impact of heating methods on film formation while validating the availability of the numerical models. Further numerical analysis reveals that in the case of oil and ball heating, the temperature gradient induced by differences in solid body temperatures plays a more significant role in film formation compared to the conventional thermal-viscosity wedge effect caused by EHL film shear. This effect is further amplified at large sliding–rolling ratios and in steel–steel contacts. The overall film formation is primarily governed by the oil inlet temperature, whereas local film formation characterized by a dimple shape is influenced by both thermal gradient effects and thermal-viscosity wedge effects. This study provides valuable insights for selecting appropriate heating methods in experiments as well as understanding how temperature differences affect film formation in practical engineering.

Efficient modeling of organic adsorbates on oxygen-intercalated graphene on Ir(111)

Organic charge transfer complexes (CTCs) can be grown as thin films on intercalated graphene (Gr). Deciphering their precise film morphologies requires global ab initio structure search, where configurational sampling is computationally intractable unless we reconsider the model for the complex substrate. In this study, we employ charged freestanding Gr to approximate an intercalated Gr/O/Ir(111) substrate, without altering the adsoption properties of deposited molecules. We compare different methods of charging Gr and select the most appropriate substitute model for Gr/O/Ir(111) that maintains the adsorption properties of fluorinated tetracyanoquinodimethane (${\mathrm{F}}_{4}\mathrm{TCNQ}$) and tetrathiafulvalene (TTF), prototypical electron acceptor/donor molecules in CTCs. Next, we apply our model in the Bayesian optimization structure search method and density-functional theory to identify the stable structures of ${\mathrm{F}}_{4}\mathrm{TCNQ}$ and TTF on supported Gr. We find that both molecules physisorb to Gr in various configurations. The narrow range of adsorption energies indicates that the molecules may diffuse easily on the surface and molecule-molecule interactions likely have a central role in film formation. Our study shows that complex intercalated substrates may be approximated with charged freestanding Gr, which can facilitate exhaustive structure search of CTCs.

Hydrolysis and Condensation of n-BuSnCl3: Enabling Deposition of Smooth Metal Oxide Photoresist Thin Films.

Herein, we report hydrolysis and condensation chemistries of C4H9SnCl3 to molecular clusters and gel films. Precursor speciation plays a key role in film formation and quality toward realization of atomically smooth surfaces. Density functional theory investigations of C4H9SnCl3 and its reactions show that hydrolysis of the dimer (C4H9Sn)2(OH)2Cl4(H2O)2 has a high energetic penalty in the gas phase and when using a polarizable continuum solvation model based on density. These computations support our observed stability of the dimeric cluster in air, in various solvents, and through initial film deposition. It hydrolyzes and condenses to the [(C4H9Sn)12O14(OH)6]2+ dodecamer on-chip after a post film-deposition bake at 80 °C. Consequently, film surface smoothness is uniquely retained through on-wafer condensation.

Fabrication of black aluminium thin films by magnetron sputtering.

Black aluminium thin films were prepared by direct current (DC) pulsed magnetron sputtering. The N2 concentration in the Ar–N2 mixture that was used as the deposition atmosphere was varied from 0 to 10%, and its impact on the film growth and optical properties was studied. A strong change in the film growth process was observed as a function of the N2 concentration. At a specific N2 concentration of ∼6%, the Al film growth process favoured the formation of a moth-eye-like antireflective surface. This surface morphology, which was similar to the structure of a cauliflower, is known to trap incident light, resulting in films with a very low reflectivity. A diffuse reflectivity lower than 4% was reached in the ultraviolet-visible-near infrared (UV-VIS-NIR) spectral range that corresponds to a value observed for an ultrahigh absorber. We found that for the preparation of black aluminium, the nitrogen content plays an important role in film formation and the resulting film morphology.

Structure of nanoparticle aggregate films built using pulsed-mode electrospray atomization

Thin continuous films with tailored micro- and nano-structure were built from nanoparticle aggregates using pulsed-mode electrospray atomization. The aggregates were assembled in-flight and delivered to a target substrate in a dry state. We report on the processing–structure relationship for an individual aggregate and reveal how their assembly determines the structure of the film. Titanium dioxide nanoparticles (P25, ~ 21 nm) were used as a model system given their importance in a wide range of applications. We describe how properties such as nanoparticle concentration, Taylor cone pulsation frequency, solvent volatility, suspension conductivity, and substrate electrical properties govern the size distribution and morphology of the aggregates. We then further report how the aggregate characteristics govern the structure of the film. Aggregates formed using electrospray possess an excess electric charge that can be maintained after they are deposited on the target substrate. This charge accumulation and its dissipation rate play a significant role in film formation. Films are thicker and exhibit a more significant periodic island structure if the dissipation rate of the accumulated charge is enhanced using a conductive substrate or by periodically deactivating the electrospray. Decreasing the separation distance increases the film thickness and island size by limiting the plume dispersion.

Surface properties of Ti-6Al-4V alloy part I: Surface roughness and apparent surface free energy

Titanium (Ti) and its alloys are the most often used implants material in dental treatment and orthopedics. Topography and wettability of its surface play important role in film formation, protein adhesion, following osseointegration and even duration of inserted implant. In this paper, we prepared Ti-6Al-4V alloy samples using different smoothing and polishing materials as well the air plasma treatment, on which contact angles of water, formamide and diiodomethane were measured. Then the apparent surface free energy was calculated using four different approaches (CAH, LWAB, O-W and Neumann's Equation of State). From LWAB approach the components of surface free energy were obtained, which shed more light on the wetting properties of samples surface. The surface roughness of the prepared samples was investigated with the help of optical profilometer and AFM. It was interesting whether the surface roughness affects the apparent surface free energy. It was found that both polar interactions the electron donor parameter of the energy and the work of water adhesion increased with decreasing roughness of the surfaces. Moreover, short time plasma treatment (1min) caused decrease in the surface hydrophilic character, while longer time (10min) treatment caused significant increase in the polar interactions and the work of water adhesion. Although Ti-6Al-4V alloy has been investigated many times, to our knowledge, so far no paper has been published in which surface roughness and changes in the surface free energy of the alloy were compared in the quantitative way in such large extent. This novel approach deliver better knowledge about the surface properties of differently smoothed and polished samples which may be helpful to facilitate cell adhesion, proliferation and mineralization. Therefore the results obtained present also potentially practical meaning.

An Empirical Rate Constant Based Model to Study Capacity Fading in Lithium Ion Batteries

A one-dimensional model based on solvent diffusion and kinetics to study the formation of the SEI (solid electrolyte interphase) layer and its impact on the capacity of a lithium ion battery is developed. The model uses the earlier work on silicon oxidation but studies the kinetic limitations of the SEI growth process. The rate constant of the SEI formation reaction at the anode is seen to play a major role in film formation. The kinetics of the reactions for capacity fading for various battery systems are studied and the rate constants are evaluated. The model is used to fit the capacity fade in different battery systems.

The effect of adsorption kinetics on film formation of silica/PVA suspension

Particle/binder/solvent systems are widely used in many applications and have long been studied. Understanding and controlling polymer adsorption in these complex material systems are important to achieve successful final performance. In this study, the effect of polymer adsorption on film formation and the relation between the microstructures of the suspension and film have been investigated by measuring the amount of polymer adsorption and the stress development during drying. In terms of mixing (or dispersion) time ( t m ), the adsorption amount ( Γ PVA), characteristic stress ( σ ch ) and dried film density ( ρ) showed a similar behavior in the form of 1 - e t m / τ with a single characteristic time τ = 45 h, which implies that the drying process is determined by this single time constant. The porous and non-uniform microstructure of the dried film at short t m became close-packed and uniform with longer t m . The polymer adsorption was found to play a key role in film formation as it introduces steric repulsion in suspension and suppresses the flocculation during solvent evaporation. It was also pointed out that enough mixing time for the saturated polymer adsorption is critical to acquire the consolidated and uniform film microstructure.

Synthesis and Characterization of Poly(ether‐block‐amide) Membranes

AbstractPoly(ether‐block‐amide) membranes were made via casting a solution on a nonsolvent (water) surface. In this research, effects of different parameters such as ratio of solvent mixture (n‐butanol/isopropanol), temperature, composition of coagulation bath (water) and polymer concentration, on quality of the thin film membranes were studied. The mechanism of membrane formation involves solution spreading, solvent–nonsolvent exchange, and partial evaporation of the solvent steps. Solvent‐ nonsolvent exchange is the main step in membrane formation and determines membrane morphology. However, at higher temperature of polymeric solution greater portion of solvent evaporates. The results showed that type of demixing process (mutual affinity between solvent and nonsolvent) has important role in film formation. Also, addition of solvent to the nonsolvent bath is effective on membrane morphology. The film quality enhances with increasing isopropanol ratio in the solvent mixture. This behavior can be related to increasing of solution surface tension, reduction of interfacial tension between solution and nonsolvent and delayed solvent‐nonsolvent demixing. Uniform films were made at a temperature rang of 60–80 °C and a polymer concentration of 4–7 wt%. Morphology of the membranes was investigated with scanning electron micrograph (SEM). Pervaporation of ethyl butyrate/water mixtures was studied using these membranes and high separation performance was achieved. For ethyl butyrate/water mixtures, It was observed that both permeation flux and separation factor increase with increasing ethyl butyrate content in the feed. Increasing temperature in limited range studied resulted in decreasing separation factor and increasing permeation flux.

47.3: Role of Film Formation on Disorder States in Alq

AbstractThe carrier transport properties for organic light emitting devices are dominated by energetic disorder and trap states. In this work, we will present our recent results on disorder state spectroscopy in Alq3 and NPB using thermally stimulated luminescence. We show that fluorescent dopants and film formation influence the disorder states.

Study of ion beam assisted deposition of Al/AlN multilayers by comparison of computer simulation and experiment

Nanoscale Al/AlN multilayers have been fabricated by ion beam assisted deposition at various nitrogen ion energies, fluxes and ion-to-atom arrival rate ratios. Computer simulations are performed to describe the deposition process and for comparison with the experimental results. At lower ion energies, fluxes and ion-to-atom ratios, the calculated results are in good agreement with the experimental data. Under this condition film formation is dominated by ballistic processes. For higher ion energies, fluxes and ion-to-atom ratios, comparison of the simulations with experiments reveals that, in addition to ballistic processes, diffusional and chemical processes may play a significant role in film formation.

Reactive Ion Etching of Silicon and Silicon Dioxide in CF 4 Plasmas Containing H 2 or C 2 F 4 Additives

Silicon dioxide to silicon reactive ion etch selectivities in plasmas containing either or additives were measured as a function of additive gas concentration. X‐ray photoelectron spectroscopy showed the presence of a fluorocarbon film on etched silicon surfaces that slows the silicon etch rate and is responsible for the selectivities attained in both cases ( etch rate ratio: >30 for , 4–6 for ). The poor selectivity attained using plasmas is due to a significantly lower etch rate relative to the case and is attributed to less energetic ion bombardment of the surface. A slightly higher etch rate of silicon in the plasma was attributed to a higher fluorine concentration in the plasma and a thinner, more fluorinated residue on the surface that allowed etching to continue even at high additive concentrations (>50% additive). The thinner film, despite a higher concentration of polymerizing species in the gas phase, indicates that plasma‐surface interactions play an important role in film formation.

Structure of Films Formed During the Deposition of Lubrication Molecules on Iron and Silicon Carbide

The structure of films formed on iron foil and silicon carbide wafers during high temperature (700 degrees C) deposition of two lubricants, tricresol phosphate (TCP) and poly phenyl ether (PPE), were studied using scanning and transmission electron microscopy, energy dispersive x-ray analysis, x-ray diffraction, and rate measurements. It was found that on iron foils, TCP decomposes and some of the molecular fragments which remain interact chemically with the iron. A two-layer structure forms. The bottom layer apparently consists of fairly large oriented cementite (Fe3C) crystals. The top layer contains particles of iron phosphide structures. In thicker films, other iron carbides, iron phosphides, and iron-phosphate crystals are also present. The size, chemical content, and degree of crystallinity of the particle structures was found to change with depth of deposit. The rate of deposition declined with time, and this correlated with a decline in the iron concentration near the surface, suggesting that iron plays a catalytic role in film formation. In contrast, the deposition of PPE resulted in the formation of cone-shaped structures, which were primarily carbonaceous but had some iron-containing crystals on their outer surfaces along with evidence of Fe5C2. The rate of deposition remained constant. Finally, on silicon carbide it was found that the rate of deposition was slow (non-catalytic), and that only amorphous particles, rich in phosphorus, formed.

Observations of Liquid Droplet Behavior and Oil Film Formation in O/W Type Emulsion Lubrication

The behavior of liquid droplets in O/W type emulsions flowing between a flat glass plate and a metal roller was observed by means of a microscope. The behavior of the droplets introduced into the EHL film was found to be related to the streamlines of the continuous water phase in the vicinity of the inlet zone. It was observed that the oil droplets which penetrated into the EHL zone formed an oily pool (an oily film zone) containing water droplets in the inlet zone close to the EHL zone. This oily pool was a W/O emulsion rich in oil caused by phase inversion. The effects of oil concentration, emulsifier content and rolling speed on the area of the oily pool were investigated, and it was found that the extent of the oily pool was influenced by the rolling speed as well as oil concentration. The EHD film thickness was measured by means of optical interferometry with use of two wavelengths, and the measured results were compared with the calculated ones employing the starvation theory of Wolveridge et al. and the empirical equation of Wymer and Cameron for the region of the oil pool. It was found that course droplets play an important role in film formation by causing the formation of the oily pool in the low speed range. In the high speed range, however, a fine O/W emulsion forms the film.

The kinetics of anodic and cathodic polarization of aluminium and its alloys

The relatively complex corrosion mechanism of aluminium has been studied by several authors. Corrosion of aluminium occurs only when the metal protective oxide layer is damaged and when the repair mechanism is prevented by chemical dissolution. Polarization methods have been extensively used to investigate the mechanism of localised corrosion and processes that lead to localised corrosion. The potential‐pH diagrams are shown in Fig. 1A. In using potentiostatic techniques, the potential is controlled and current is determined as the independent variable. Potentiostatic and potentiody‐namic techniques have been applied by several authors to study the corrosion of aluminium in different environment. Both anodic and cathodic polarization curves have been used to interpret the kinetics of pitting corrosion of aluminium in chloride containing environments. Both the anodic and cathodic process are complex and the interpretation of the anodic and cathodic polarization curves of aluminium is often tedious. The situation arises partly from the fact that the role of film formation on the kinetics of corrosion is not clearly understood. Previously there is not established mechanisms of initiation and propagation of pits in aluminium and its alloys. Several parameters such as pitting potential, breakdown potential, active passive transition potential, related to the pitting process of aluminium, are full of controversy. Numerous references on the above can be found in literature).

Rheological properties of coatings during drying processes

AbstractCoatings such as paints and printing inks transferred on substrates change from viscous liquids to viscoelastic solids during drying processes and finally become a hardened film. In order to investigate more precisely the viscoelastic properties of coatings during liquid‐to‐solid conversion, we developed the same type of ultrasonic rheometer as employed by Mason et al., in which the reflection coefficient technique is utilized. The complex modulus can be determined by the reflection coefficient and the phase shift. Using this rheometer, we can obtain the viscoelastic properties of coatings at various stages of drying at infinitesimal shear strain at the frequency of 3 MHz.The viscoelastic properties of a commercial offset litho ink which was dried by oxidative polymerization were measured at various temperatures. From the results of viscoelastic measurements, the drying of ink seems to be accelerated remarkably with increasing temperature. As the drying processes progress, a three‐dimensional network structure may be formed in the ink film with the aid of oxidative polymerization. The drying‐time dependence of G′ is different from that of G″. From the drying‐time dependences of G′ and G″, we can quantitatively deduce the internal structure of printing ink films during drying processes and provide a physical explanation for various drying stages. The dispersed pigments in a coating seem to play an important role in film formation and affect the mechanical properties of the drying film.

Protein-Lipid Interactions in Soy Films

The protein and lipid components of a surface film formed from soy-milk were investigated in an attempt to elucidate their interaction. Results indicated that although fluorescent Schiff bases are formed in both soymilk and soymilk film systems, products of lipid oxidation probably do not play a major role in film formation. Microscopic studies showed that protein-protein interactions may occur to form a continuous matrix in which lipid droplets are dispersed. Protein extractability and electrophoresis data indicated that the 2S and 11S fractions were the main extractable protein components involved in film formation. Protein to lipid ratios in the film were independent of processing variables and were reflective of the original soymilk.