Formation Of Multilayer Films Research Articles

On the Formation and Investigation of Multilayer Films of a High-Entropy Alloy Obtained by the Ion-Plasma Method in a Nitrogen Environment

On the Formation and Investigation of Multilayer Films of a High-Entropy Alloy Obtained by the Ion-Plasma Method in a Nitrogen Environment

Enhancing corrosion resistance of Mg-Al-Mn-Ca-Y dilute alloy via novel core-shell structured Al8Mn4Y-Al2Ca and controllable solute segregation

A novel core-shell structured Al8Mn4Y-Al2Ca phase and controllable solute-segregation are elaborately designed in dilute Mg-0.6Al-0.5Mn-0.1Ca-0.1Y alloy (wt.%), via incomplete peritectic transformation during twin-roll casting. When soaked in 3.5 wt.% NaCl solution, Al2Ca shell with a low electrochemical potential prevents direct contact of noble Al8Mn4Y with Mg matrix, mitigating the micro-galvanic corrosion and meanwhile accelerating the formation of uniform corrosion film. Thereafter, solute (Al, Ca)-segregation motivates the formation of heterogeneous multilayered corrosion product films, enhancing corrosion resistance and even achieving self-healing upon long-term corrosion. Notably, the dilute Mg alloy exhibits a corrosion rate as low as 0.22 ± 0.05 mm·y−1.

Controlling the structure of spin-coated multilayer ethylcellulose/hydroxypropylcellulose films for drug release

Porous phase-separated ethylcellulose/hydroxypropylcellulose (EC/HPC) films are used to control drug transport out of pharmaceutical pellets. Water-soluble HPC leaches out and forms a porous structure that controls the drug transport. Industrially, the pellets are coated using a fluidized bed spraying device, and a layered film exhibiting varying porosity and structure after leaching is obtained. A detailed understanding of the formation of the multilayered, phase-separated structure during production is lacking. Here, we have investigated multilayered EC/HPC films produced by sequential spin-coating, which was used to mimic the industrial process. The effects of EC/HPC ratio and spin speed on the multilayer film formation and structure were investigated using advanced microscopy techniques and image analysis. Cahn-Hilliard simulations were performed to analyze the mixing behavior. A gradient with larger structures close to the substrate surface and smaller structures close to the air surface was formed due to coarsening of the layers already coated during successive deposition cycles. The porosity of the multilayer film was found to vary with both EC/HPC ratio and spin speed. Simulation of the mixing behavior and in situ characterization of the structure evolution showed that the origin of the discontinuities and multilayer structure can be explained by the non-mixing of the layers.

Effects of Annealing and Thickness of Co60Fe20Yb20 Nanofilms on Their Structure, Magnetic Properties, Electrical Efficiency, and Nanomechanical Characteristics

X-ray diffraction (XRD) analysis showed that metal oxide peaks appear at 2θ = 47.7°, 54.5°, and 56.3°, corresponding to Yb2O3 (440), Co2O3 (422), and Co2O3 (511). It was found that oxide formation plays an important role in magnetic, electrical, and surface energy. For magnetic and electrical measurements, the highest alternating current magnetic susceptibility (χac) and the lowest resistivity (×10−2 Ω·cm) were 0.213 and 0.42, respectively, and at 50 nm, it annealed at 300 °C due to weak oxide formation. For mechanical measurement, the highest value of hardness was 15.93 GPa at 200 °C in a 50 nm thick film. When the thickness increased from 10 to 50 nm, the hardness and Young’s modulus of the Co60Fe20Yb20 film also showed a saturation trend. After annealing at 300 °C, Co60Fe20Yb20 films of 40 nm thickness showed the highest surface energy. Higher surface energy indicated stronger adhesion, allowing for the formation of multilayer thin films. The optimal condition was found to be 50 nm with annealing at 300 °C due to high χac, strong adhesion, high nano-mechanical properties, and low resistivity.

Multipurpose Solar Photoelectrochemical Hybrid Multilayer Films Based on Porphyrin and Preyssler Type Polyoxometalates for Solar Cell and Ag Nanomaterial Synthesis

Multilayer films with electrostatic interaction between Preyssler,s Polyanions (NH4)14[NaP5W30O110]14- .31H2O and tetracationic free base porphyrin [H2TN+(Me)3PyP]4+ have been alternately deposited on quartz and ITO substrates. and characterized by UV-visible absorption spectroscopy to follow the successive deposition of multilayer film. Solution phase interaction of both components revealed the stiochiometric ratio of the electrostatic complex formed . The morphology and composition of films were studied by atomic force microscopy and X-ray photoelectron spectroscopy (XPS ) .While permeability to cations in aqueous media and redox behavior were studied by cyclic voltametry . The solar photoctalytic activity of hybrid films is identified by TEM images obtained after heterogeneous aqueous photoreduction of Ag2SO4(aq) and KAuCl4 (aq) to yield diversified nanostructures . The study is first and initial report on preyssler type polyanions and porphyrin based heterogenous photocatalysis that provide a green, solar and multiple applications for precious metal recovery as nanoparticle ,sustainable wastewater purification and solar photocurrent generation.Polyoxometalates (POMs) are metal−oxygen framework of early metal elements in their highest oxidation state , able to undergo reversible, stepwise, multielectron-transfer reactions, which are the basis for many catalytic processes[1].These polyanions clusters exhibit applications in catalysis, medicine, materials science [2]. They offer effective photocatalytic properties in oxidation and reduction processes. On photolysis, the high oxidizing ability of excited POMs can lead to the degradation of a variety of organic compounds such as pollutants, leading to a process for water purification [3]. In the presence of a sacrificial electron donor , their photolysis lead to the formation of reduced POMs which can in turn reduce metallic ions. It could be a good alternative for precious metals recovery or synthesis of metal nanoparticles. [4,5]. However, polyoxometalates absorb in the uv part of spectrum, thus they require UV excitation, which cease its large-scale environmental application. One of obvious strategy is to couple it with some chromophore group which can be sensitized by visible light. Metal porphyrins are attractive components in materials because of their appealing chemical and photochemical properties: high stability, intense visible absorption bands, long-lived excited states, and tunability by chemical derivatization [2]. Figure 1.1 R.H.S. Representation of the porphyrin used 5, 10, 15, 20-Tetrakis (4-trimethylammoniophenyl) porphyrin tetra(p-toluenesulfonate), namely [H2TN+(Me)3PyP]4+) used with the Preyssler type (NH4)14[NaP5W30O110]14- .31H2O . L.H.S. UV-visible record on quartz and ITO shows layer by layer absorbance. Formation of Multilayer Films :H2TN+(Me)3PyP4+] / [(NH4)14[NaP5W30O110]14- .31H2O ] The alternate deposition of positively charged porphyrin, H2TN+(Me)3PyP4+, and negatively charged [NaP5W30O110]14-on slides of quartz and Indium tin Oxide (ITO) lectrodes by layer-by-layer were performed.

Effect of inhomogeneous composition on the passive film of AISI 431 coating fabricated by extreme-high-speed laser cladding

The effect of inhomogeneous composition of Cr and Fe on morphology and formation mechanism of passive film was investigated. A bi-layer structure passive film with a Cr2O3 inner layer and a Fe2O3 outer layer obtained on EHLA coating. The passive film is heterogeneous (thickness, compactness) between inter-dendrite and dendrite core due to the element segregation and dislocation. Aspects of the passive film formation mechanism are discussed according to the thermodynamics. It indicates the prior oxidation of chromium resulting in the formation of inner Cr-rich layer, while higher diffusion rate of Fe3+ is the main reason for the formation of outer Fe-rich layer. This provides a new sight on the formation of multilayer oxide films.

Engineering of Ultra-Violet Reflectors by varying Alternate Layers of Titania/Silica for Harmful UV-Protection

The primary requisite of engineering optical/photonic devices is either for scaling or altering the properties. Here, we present the engineering of ultra-violet (UV) reflectors made up of alternate layers of titania (TiO2) and silica (SiO2) by using the sol-gel spin coating method. The choice of these two materials is appropriate to realize the optical reflectors due to their large refractive index contrast. The formation of multilayer films of TiO2 and SiO2 are studied by field-emission scanning electron microscopy (FESEM), while UV-vis spectroscopy measurement is performed to study the reflectance. By varying the number of TiO2/SiO2 stacks, we have achieved the maximum reflectance within the UV region at center wavelength of 335 nm, 358 nm, and 367 nm corresponding to the 3, 6, and 9 stacks-based reflectors. Finally, we summarize that these reflectors prohibit the propagation of ultraviolet light, and therefore, they are promising as UV protection coating.

Adsorption of arabinogalactan-proteins from Acacia gums (senegal and seyal) and its molecular fractions onto latex particles

Adsorption of Acacia gums (GA) (A. senegal and A. seyal) and A. senegal molecular fractions, made of arabinogalactan-proteins (AGPs) with different molecular weights, onto latex particles, with different sizes and surface charges, was studied using molecular (fluorescence and nanoIR spectroscopies, microscopies including Atomic Force Microscopy) and mesoscopic (Dynamic Light Scattering, zeta potential, Asymmetrical flow field-flow fractionation) methods. Adsorption of GA onto latex particles revealed a complex mechanism of adsorption where the highest adsorption was observed when A. senegal and latex particles were negatively charged. The invert was observed for A. seyal where the maximum of adsorption was observed when gum and latex were oppositely charged. The duality of positive and negative charges on GA macromolecules together with conformational changes certainly explain the complex mechanism of adsorption. A mechanism where either the protein moiety either the sugars blocks adsorb is to be preferred. This mechanism seems to produce differences of behaviour due to viscoelastic properties of adsorbed layers, and differences of hydration due to differences of polarity of AGPs. The consequence of electrostatics in the adsorption process is a water release from the adsorbed layers and important gain in entropy. A fair agreement was found between protein content and adsorbed layer thickness of GA, with the formation of partial coverage, monolayer and multilayer films depending on GA concentration. Structural changes induced by GA adsorption onto latex particles was probed using fluorescence and nanoIR spectroscopies without giving clear evidence of conformational changes induced after GA adsorption. The results of this study highlighted that GA surface adsorption process depend not only on the protein moiety and electrostatic interactions but also on other parameters related to AGP hydration status. The protein structural accessibility, the molecular weight distribution, the AGPs intrinsic viscoelastic properties allowing structural rearrangements on the surface and spreading in order to form a viscoelastic film onto latex particles should also play a pivotal role in the adsorption process.

Annealing Effect on the Contact Angle, Surface Energy, Electric Property, and Nanomechanical Characteristics of Co40Fe40W20 Thin Films

This study investigated Co40Fe40W20 single-layer thin films according to their corresponding structure, grain size, contact angle, and surface energy characteristics. Co40Fe40W20 alloy thin films of different thicknesses, ranging from 10 to 50 nm, were sputtered on Si(100) substrates by DC magnetron sputtering. The thin films were annealed under three conditions: as-deposited, 250 °C, and 350 °C temperatures, respectively. The Scherrer equation was applied to calculate the grain size of Co40Fe40W20 thin films. The results show that the grain size of CoFe(110) increased simultaneously with the increase of post-annealing temperature, suggesting that the crystallinity of Co40Fe40W20 thin films increased with the post-annealing temperature. Moreover, the contact angles of all Co40Fe40W20 thin films were all less than 90°, suggesting that Co40Fe40W20 thin films show changes in the direction of higher hydrophilicity. However, we found that their contact angles decreased as the grain size of CoFe increased. Finally, the Young equation was applied to calculate the surface energy of Co40Fe40W20 thin films. After post-annealing, the surface energy of Co40Fe40W20 thin films increased with the rising post-annealing temperature. This is the highest value of surface energy observed for 350 °C. In addition, the surface energy increased as the contact angle of Co40Fe40W20 thin films decreased. The high surface energy means stronger adhesion, allowing the formation of multilayer thin films with magnetic tunneling junctions (MTJs). The sheet resistance of the as-deposited and thinner CoFeW films is larger than annealed and thicker CoFeW films. When the thickness is from 10 nm to 50 nm, the hardness and Young’s modulus of the CoFeW film also show a saturation trend.

Lattice Model of Multilayer Adsorption of Particles with Orientation Dependent Interactions at Solid Surfaces.

A simple lattice model has been used to study the formation of multilayer films by fluids with orientation-dependent interactions on solid surfaces. The particles, composed of two halves (A and B) were allowed to take on one of six different orientations. The interaction between a pair of differently oriented neighboring particles was assumed to depend on the degrees to which their A and B parts overlap. Here, we have assumed that the AA interaction was strongly attractive, the AB interaction was set to zero, while the BB interaction was varied between 0 and . The ground state properties of the model have been determined for the systems being in contact with non-selective and selective walls over the entire range of BB interaction energies between 0 and . It has been demonstrated that the structure of multilayer films depends on the strengths of surface potential felt by differently oriented particles and the interaction between the B halves of fluid particles. Finite temperature behavior has been studied by Monte Carlo simulation methods. It has been shown that the bulk phase phase diagram is qualitatively independent of the BB interaction energy, and has the swan neck shape, since the high stability of the dense ordered phase suppresses the possibility of the formation of disordered liquid-like phase. Only one class of non-uniform systems with the BB interaction set to zero has been considered. The results have been found to be consistent with the predictions stemming form the ground state considerations. In particular, we have found that a complete wetting occurs at any temperature, down to zero. Furthermore, the sequences of layering transitions, and the structure of multilayer films, have been found to be the same as observed in the ground state.

Evaluation of anti-corrosion performance of poly(maleic acid-co-N‐[3‐(dimethylamino)propyl]‐methacrylamide) as novel copolymer inhibitor for carbon steel in neutral medium

Polymer corrosion inhibitors have many advantages in comparison with small organic molecule inhibitors, such as easier formation of multilayer films on metal surface, more adsorption sites and better temperature resistance. Poly(maleic acid-co-N‐[3‐(dimethylamino)propyl]‐methacrylamide) (PMD) was synthesized via aqueous solution polymerization and its structure and molecular weight were confirmed. The anti-corrosion performance of PMD for Q235 carbon steel in neutral medium was evaluated by several methods like gravimetric and electrochemical tests, surface analysis and theoretical calculation. Results indicated that polymer corrosion inhibitor PMD exhibited high corrosion inhibition efficiency of 90.1% at a dosage of 200 mg/L, and acted as anodic-type inhibitor that inhibited anodic reactions by forming adsorption polymer film. The adsorption model conformed to Langmuir adsorption isotherm involving both physisorption and chemisorption fitted by electrochemical data. The outcomes of surface morphology investigation including contact angle analysis, AFM and SEM were consistent with experimental results. Moreover, Theoretical calculation including quantum chemical computation and molecular dynamics (MD) simulation further reveal the corrosion inhibition mechanism of PMD.

Adsorbed protein film on pump surfaces leads to particle formation during fill-finish manufacturing.

During fill-finish manufacturing, therapeutic proteins may aggregate or form subvisible particles in response to the physical stresses encountered within filling pumps. Understanding and quantitating this risk is important since filling may be the last unit operation before the patient receives their dose. We studied particle formation from lab-scale to manufacturing-scale using sensitive and robust protein formulations. Filling experiments with a ceramic rotary piston pump were integrated with a rinse-stripping method to investigate the relationship between protein adsorption and particle formation. For a sensitive protein, multilayer film formation on the piston surface correlated with high levels of subvisible particles in solution. For a robust protein formulation, adsorption and subvisible particle formation were minimal. These results support an aggregation mechanism that is initiated by adsorption to pump surfaces and propagated by mechanical and/or hydrodynamic disruption of the film. The elemental analysis confirmed that ceramic wear debris remained at trace levels and did not contribute appreciably to protein aggregation.

Modulating layer-by-layer assembled sodium alginate-chitosan film properties through incorporation of cellulose nanocrystals with different surface charge densities

In this work, 2,2,6,6-tetramethylpiperidine-1-oxyl-oxidized cellulose nanocrystals (TOCNs) were loaded into sodium alginate/chitosan multilayer film as nanofillers to investigate the modulation of the surface charge density of TOCNs on the film properties. First, the surface charge density of TOCNs was controlled by adjusting the carboxyl content and morphological size by varying the oxidant dosage. After oxidation, TOCN with higher surface charge density was observed to display a higher crystallinity, a more open internal structure, a better dispersibility and a slightly weaker thermal stability. In addition, a 15-layer film composed of sodium alginate and chitosan, called (SA/CH)15, was constructed by layer-by-layer assembly. Both in situ deposition monitoring and free-standing multilayer film formation indicated that TOCNs relied on strong electrostatic interactions and hydrogen bonding to achieve a compact and uniform interlayer and a thinner thickness of (SA/CH)15, which was more evident at a high surface charge density. The addition of TOCNs also enhanced the mechanical properties, thermal stability, hydrophobicity, and barrier properties of (SA/CH)15. In particular, the resulting sodium alginate/chitosan multilayer film exhibited an improved packaging performance when nanocomposite was performed using TOCN with a surface charge density of 3.22 ± 0.11 e nm−2.

Analytical strategy for studying the formation and stability of multilayered films containing gold nanoparticles.

The design of layer-by-layer (LbL) polyelectrolyte films including nanoparticles is a growing field of innovation in a wide range of biomedical applications. Gold nanoparticles (AuNPs) are very attractive for further biomolecule coupling to induce a pharmacological effect. Nanostructured LbL films coupled with such metallic species show properties that depend on the conditions of construction, i.e. the polymer nature and dissolution buffer. Tripartite LbL films (polycation, AuNP, and polyanion) were evaluated using two different polycationic polymers (poly(allylamine hydrochloride) (PAH), poly(ethylene imine) (PEI)) and various medium conditions (salts, i.e. phosphate, Tris or Tris-NaCl buffers, and concentration). AuNP incorporation and film stability were analysed by visible spectrophotometry, capillary zone electrophoresis, a quartz crystal microbalance, and high-performance liquid chromatography. The ideal compromise between AuNP loading and film stability was obtained using PAH prepared in Tris-NaCl buffer (0.01-0.15M). This condition allowed the formation of a LbL film that was more stable than the film with PEI and provided an AuNP quantity that was 4.8 times greater than that of the PAH-PBS-built film. In conclusion, this work presents an analytical strategy for the characterization of nanostructured multilayer films and optimization of LbL films enriched with AuNPs to design biomedical device coatings.

Revealing the anti-corrosion mechanism of fluconazole by experimental and theoretical studies

Through techniques such as electrochemical impedance spectroscopy and open circuit potential, the protective behavior of fluconazole against the mild steel corrosion process in neutral medium was evaluated. Best-fitted adsorption isotherm was the Frumkin model respect to Langmuir, which implies a multilayer protective film formation with lateral attraction between the adsorbed inhibitor molecules on mild steel surface. To document the protective mechanism, DFT computations and QTAIM analysis were carried out. The results, showed that the stability of the protection film is attributed to the flu-flu and flu-water clusters formation which, are stabilized by OH⋯N, OH⋯O, CH⋯N, CH⋯O, CH⋯F hydrogen bonds, as well as π-stacking. Altogether, the results reported here suggest that the fluconazole is adsorbed on the metal surface demonstrating that electrostatic interactions are the most relevant in the corrosion process.

Strategies for the Formation of Monolayers From Diazonium Salts: Unconventional Grafting Media, Unconventional Building Blocks.

Pioneered by J. Pinson and coll. in 1990s, the reductive grafting of aryldiazonium salts has become a powerful method for surface functionalization. Highly robust interfaces result from this surface attachment, resistant to heat, chemical degradation and ultrasonication. Importantly, this approach can be applied to many materials, ranging from conducting, semi-conducting, oxides to insulating substrates. In addition, either massive, flat surfaces or nanomaterials can be functionalized. The method is easy to process and fast. The grafting process involves the formation of highly reactive aryl radicals able to attack the substrate. However, the generated radicals can also react with already-grafted aryl species, leading to the formation of loosely-packed polyaryl multilayer films, typically of 10–15 nm thick. It is thus highly challenging to control the vertical extension of the deposited layer and to form well-ordered monolayers from aryldiazonium salts. In this mini review, we briefly describe the different strategies that have been developed to prepare well-ordered monolayers. We especially focus on two strategies successfully used in our laboratories, namely the use of unconventional solvents, i.e., room temperature ionic liquids (RTILs), as grafting media and the use of calixarene macrocycles by taking benefit of their pre-organized structure. These strategies give large possibilities for the structuring of interfaces with the widest choice of materials and highlight the potential of aryldiazonium grafting as a competitive alternative to self-assembled monolayers (SAMs) of alkyl thiols.

Retraction Note to: formation of polyelectrolyte multilayer films with controlled wettability via layer-by-layer electric-assembly

The editors have retracted this article [1] because after publication concerns were raised regarding the validity of the conclusions drawn.

The effect of duty cycle on the mechanical and electrochemical corrosion properties of multilayer CrN/CrAlN coatings produced by cathodic arc evaporation

ABSTRACT Multilayer CrN/CrAlN coatings were deposited on the 420-SS by the cathodic arc evaporation system with different duty cycles of bias-voltage. The deposited films were characterized by XRD and FESEM techniques. Mechanical, electrochemical, and surface properties of deposited films were studied by nano-indentation, electrochemical, and AFM analysis. Microstructure investigation confirmed the formation of adhesive and dense nanostructure multilayer film. Increasing the duty cycle led to the decrease in the coating grain size and promoted the hardness to 34.1 ± 4 GPa. A clear reduction of size and distribution of macroparticles was observed by using large repulsive force at a high duty cycle. By increasing the duty cycle, the coating deposition rate was increased from 1.23 to 1.38 µm/h and the surface roughness was decreased from 155 to 70 nm. The lower corrosion current density was obtained for the film applied at the 40% duty cycle (0.59 µA cm−2), which was about 10-order of magnitude less than the substrate.

Controlled Formation of Multilayer Films of Discrete Molecular Catalysts for the Oxygen Reduction Reaction Using a Layer-by-Layer Growth Mechanism Based on Sequential Click Chemistry

Molecular electrocatalysts show promise for energy-relevant multi-electron transformations due to their rationally-tunable activity and selectivity from systematic ligand modifications. However, su...

Pulmonary surfactant protein SP-B nanorings induce the multilamellar organization of surfactant complexes

Surfactant protein SP-B is absolutely required for the generation of functional pulmonary surfactant, a unique network of multilayered membranes, which stabilizes the respiratory air-liquid interface. It has been proposed that SP-B assembles into hydrophobic rings and tubes that facilitate the rapid transfer of phospholipids from membrane stores into the interface and the formation of multilayered films, ensuring the stability of the alveoli against physical forces leading to their collapse. To elucidate the molecular organization of SP-B-promoted multilamellar membrane structures, time-resolved Förster Resonance Energy Transfer (FRET) experiments between BODIPY-PC or BODIPY-derivatized SP-B (BODIPY/SP-B), as donor probes, and octadecylrhodamine B, as acceptor probe, were performed in liposomes containing SP-B or BODIPY/SP-B. Our results show that both SP-B and fluorescently labeled SP-B oligomers mediate the connection of adjacent bilayers. Furthermore, by applying rational models to the FRET data, we have been able to provide quantitative details of the structure of SP-B-induced multilayered membrane arrays at the nanometer scale, defining interactions between SP-B rings as key elements for connecting surfactant membranes. The data sustain the structural model and the mechanism of action of SP-B assemblies to sustain the crucial surfactant function.