Adhesion Of Thin Films Research Articles

On the adhesion of diamond‐like carbon coatings deposited by low‐pressure plasma on 316L stainless steel

Diamond‐like carbon (DLC) thin films constitute proven protective coatings due to their outstanding mechanical and tribological properties, combined with a relative chemical inertness and long‐term stability. These make them particularly attractive to protect metallic medical implants from corrosion and erosion. However, lack of adhesion between DLC and metallic surfaces is a recurrent problem due to poor interactions with the native oxide layer. An effective strategy to overcome these adhesion issues consists in building interfacial layers. In this context, in this work, the use of a plasma treatment to generate shallow metallic carbide layers was investigated, to promote DLC adhesion directly on the surface of 316L stainless steel (SS). The metallic carbides presence stabilizes and promotes DLC thin film deposition. The highest adhesion was obtained on samples carburized by methane during 20 min with a bias of −700 V. Furthermore, this led to interface amorphization. In conclusion, this study shows that plasma can provide new insights for overcoming the lack of adhesion of DLC thin films on SS metallic surfaces.

Degree of Conversion of Two Universal Adhesives Incorporated with Ascorbic Acid Coated Superparamagnetic Nanoparticles Assessed by FTIRDegree of conversion, universal adhesives, Superparamagnetic Fe3O4nanoparticles, FTIR analysis

Aims: To prepare and characterize a nano-ferro fluid of ascorbic acid coated superparamagnetic Fe3O4nanoparticles and incorporate them into two universal dental adhesives to test their effect on the immediate and 24-hours post-cure Degree of Conversion (DC) in comparison to their control non-incorporated adhesives. Study design: An invitro study.Methods and Material: A colloidal nano ferro fluid of ascorbic acid coated superparamagnetic nanoparticles was prepared and characterized by transmission electron microscopy and incorporated into two universal adhesives. Thirty-two adhesive samples in PotassiumBromide (KBr) discs were prepared for FTIR analysis, and distributed as following, i.e., GI: Eight adhesive samples of non-incorporated All Bond Universal (Control), GII: Eight adhesive samples of 2%-incorporated All Bond Universal, GIII: Eight adhesive samples of non-incorporated Prime&Bond Universal (Control), GIV: Eight adhesive samples of 2%-incorporated Prime&Bond Universal.Equal amount (25μL) of each adhesive was placed on KBr disc, the solvents was evaporated by a gentle steam of air, and then a second KBr disc was mounted over the first one and pressed softly to form a thin adhesive film. Finally, the KBr discs containing the adhesive were placed in the demountable cell holder and mounted into the sample chamber of the FTIR spectrometer. FTIR spectra was then recorded for each adhesive before, immediately after, and 24-hours post-curing to calculate the degree of conversion.Statistical analysis used: Statistical analysis was conducted using independent variable t-test by the IBM-SPSS software version 22.Results: The study results showed good DC values for the incorporated adhesives with no statistically significant differences in the degree of conversion values (i.e. Immediate and 24-hours post-cure) in comparison to control groups for both adhesives. The Prmie&Bond universal (Both control and incorporated) revealed significantly higher DC than All bond universal.Conclusions: Incorporation of ascorbic acid coated Fe3O4nanoparticles at 2% by mass into the universal adhesives resulted in good degreeof polymerization with no significant difference in comparison to their commercial controls.

Gallium-based liquid metal alloy incorporating oxide-free copper nanoparticle clusters for high-performance thermal interface materials

Thermal interface materials (TIMs) with high thermal conductivity, fluidic characteristics, and surface wettability are crucial for the effective thermal management of high-power electronics. Gallium-based liquid metal (LM) can be a candidate for obtaining the purposes due to their thermo-physical properties. Several studies attempted to further increase the thermal conductivity of composites by adding conductive fillers. However, these efforts have been limited due to the oxidation and solidification issues at high vol% of fillers. In this work, we apply three strategies to obtain the enhanced thermal conductivity while maintaining the fluidity: 1) suppressing Ga-induced oxidation, 2) reducing the matrix-fillers interfacial resistance, and 3) forming additional heat-pathways within the LM matrix. An oxide-free ultrasonication-assisted particle internalization method has been developed, in which the copper nanoparticles (Cu NPs) are incorporated into the gallium-indium-tin (GaInSn) LM matrix. The fabricated composite shows ~180% enhancement of thermal conductivity (~64.8 Wm−1K−1) with only 4 vol% of nano-fillers compared to the untreated GaInSn. In the droplet impacting test, the synthesized GaInSn/Cu NPs composite presents almost identical spreading diameters with the untreated one, which confirms the maintained fluidity. The predicted thermal conductivity using the theoretical model, calculating the measured cluster fraction, is well-matched to the experimental data, which clarifies that the nanoparticle clusters created effective heat-pathways. A high-quality interface with a silicon substrate is confirmed by the X-ray photoelectron spectroscopy, demonstrating the presence of a thin-film Ga2O3 adhesion layer. In the cooling performance test, the developed TIM provides over 20% lower hot-spot temperature than that of the grease-type TIM at high heat flux regime (>150 W/cm2), showing excellent thermal stability over 230 cycles of acceleration test. This work will help develop high-performance TIMs, especially for high power density semiconductor applications.

A comparison of qualitative and quantitative adhesion analysis for a composite thin film system

The adhesion strength of a thin film to the substrate determines the life cycle of the thin film system. Analyzing techniques for this adhesion strength are categorized into two types, 1. Qualitative and 2. Quantitative. Both types of techniques are established and standardized for metallic, polymeric, and compound thin films. However, there are very few works available that give credibility to the qualitative analyzing techniques for a metallic composite thin film. In this study, by the magnetron deposition process, composite Tungsten-Tantalum thin films on a steel substrate are deposited. Both qualitative and quantitative techniques implemented to analyze thin films adhesion. Indentation technique selected as the qualitative process and Nano scratch technique selected as the quantitative process in this study. Simple Rockwell indentation, according to VDI 3198 standard, is used to qualitatively categorize the films into acceptable adhesion and not acceptable adhesion films. Nano scratch with a Nano indenter assessed the adhesion strength of the thin films quantitatively. The films categorised as not acceptable adhesion in Rockwell micro indentation test have fared poorly in the Nano scratch test, and the films which emerged as acceptable adhesion have better adhesion strength registered in the Nano scratch test. This study concludes that the qualitative indentation results produced using Rockwell indenter are similar to the results produced by the quantitative Nano scratch test.

Preparation techniques of thin cyanoacrylate adhesive films for interface analysis

ABSTRACT For understanding the interactions between adhesives and different surfaces, the in-situ characterization of the interface is essential. Especially for highly reactive cyanoacrylates, better known as super glues, the adhesion mechanism is poorly understood because, among other things, the characterization of the interface is difficult. The aim of this work is to evaluate methods to produce nm-thin, homogeneous films of cyanoacrylate to enable spectroscopic analysis of the interface in the future. Two deposition techniques, thermal evaporation and spin coating, of ethyl-cyanoacrylate, are compared. Thickness and composition of the cured films are investigated by atomic force microscopy, laser scanning microscopy and x-ray photoelectron spectroscopy. Thermal evaporation in ultra-high vacuum leads to cluster-like depositions and is therefore not suitable for interface analysis. Spin coating is strongly dependent on solvent and concentration. While the solvent tetrahydrofuran leads to porous and inhomogeneous films, spin coating with anisole as solvent provides homogeneous films of cyanoacrylate with a thickness of only 4 nm. This allows surface-sensitive analytical methods to access the interface and possible interactions can be characterized in-situ.

Development of adhesion force evaluation equipment for nano diamond coated tool using shear method

In this study, we have developed a thin film adhesion evaluation system for diamond coating tool, which is mainly used for CFRP processing. CFRP is widely used in aviation and automobile industries. Because of the high surface hardness of the diamond coating tool, it is difficult to evaluate the adhesive strength of the tool, and it is difficult to quantitatively evaluate the existing adhesion force evaluation method and it is costly. This study has developed an evaluation method to measure the adhesive force based on the data of the grinding process using a low-cost polishing pad. When the frictional force and the shearing force are applied to the specimen by the sanding belt, friction is continuously generated between the coating layer and the belt, and peeling occurs at the moment when a specific load is applied. Acceleration, load, and torque values that occur during each experiment are collected through acceleration sensors, load cells, and torque sensors. The data obtained through the experiments are subjected to FFT processing and analysis. As a result, the peeling point and the critical load value at this point are identified and referred to as the adhesion force of the coating layer.

Influence of base pressure prior to deposition on the adhesion behaviour of carbon thin films on steel

The poor adhesion of carbon thin films was the main restriction for its massive application in recent years. Physicochemical interaction improvement at the adhesion interface between substrate and thin film is one of the most important fields of research to overcome such problem. From a chemical point of view, oxygen seems to be a major issue in the adhesion control. In this work, the influence of base pressure prior to deposition process on the carbon thin film tribological behaviour was studied. Rockwell C and scratch tests were performed to qualify the thin film failures and adhesion. Chemical mapping was performed by energy-dispersive spectroscopy to characterise the chemical elements after thin film failure. The carbon thin films show better adhesion at lower base deposition pressures. The tribological behaviour is associated with the oxygen content in the chamber atmosphere as well as to the higher thin film adhesion achieved at lower base pressures.

Preparation of Thin Frozen Sections from Nonfixed and Undecalcified Hard Tissues Using Kawamoto's Film Method (2020).

A method for preparing frozen sections with an adhesive film is described. In order to observe fine structures and weak fluorescence of samples, new types of adhesive films [Cryofilm type 3C(16UF) and 4D(16UF)] are used. The adhesive film is made with very clear and very low autofluorescence. For gene analysis, a very thin adhesive film (LMD film) is used to cut by means of the laser microdissection (LMD). For MALDI mass spectrometry imaging (MALDI-MSI), a conductive adhesive film (Cryofilm type MS) is used to avoid electric charge of the sample. A biological sample is frozen quickly and freeze-embedded. The frozen sample is cut with a very sharp disposable blade made from fine tungsten carbide. The combination of the adhesive films and the blade can generate 3 micrometer thick sections from samples including bone, while it is also possible to generate 1μm thick sections. The morphology of bone and soft tissues are preserved using this method. Cells such as osteoblasts, fibroblasts, and osteoclasts are clearly observed with an oil immersion lens at high magnification. Sections generated using the Cryofilm type 3C(16UF) shows weak fluorescent signals more clearly than sections generated with the previously reported adhesive films [Cryofilm type 2C(9) and 2C(10)]. Furthermore fluorescence of the fine structures in cells is clearly shown using a super-high-resolution microscope. Several staining and experimental methods such as histology, histochemistry, enzyme histochemistry, immunohistochemistry, and in situ hybridization can be performed on these sections. This method is also useful for preparing frozen sections of large sample such as a whole-body mouse and rat. In gene analysis, gene quality of sample collected from the section made with the LMD film is superior to that of sample made by a conventional method. The Cryofilm type MS makes almost complete section from tissues including hard tissues and large samples. The satisfactory signals are detected from the section with MALDI-MSI.

Mechanical characteristics of metal nanoparticle thin film on flexible substrate exposed to saline solution

The robust and reliable mechanical characteristics of metal nanoparticle (NP) thin films on flexible substrates are important because they operate under tensile, bending, and twisting loads. Furthermore, in wearable printed electronics applications, salty solutions such as sweat and seawater can affect the mechanical reliabilities of devices. In this paper, we investigated the effect of sodium chloride (NaCl) solutions on silver (Ag) NP thin films on flexible polymer substrate. After exposure to NaCl solution of Ag NP thin film, we observed the aggregation behavior between Ag NPs and formation of larger pores in the film due to the removal of organic capping layer from the surface of Ag NPs. The average porosity and 5% deviation strains of Ag NP thin films on the polyimide substrate were dramatically increased and decreased from 2.99% to 9.64% and from 3.94% to 0.87%, respectively, after exposure to NaCl solution for 1 h. Also, we verified a drastic deterioration of the surface adhesion of the Ag NP thin film to the substrate by exposure to NaCl solution. We could observe crack propagation and delamination by in-situ scanning electron microscope imaging. In addition, passivation effect by a parylene layer for preventing the permeation of the saline solution was investigated.

Deposition of Tungsten – Tantalum composite coating on RAFM steel by sputtering deposition process

Tungsten – Tantalum composite coatings on Reduced Activation Ferritic Martensitic Steel (RAFM) for plasma-facing applications in a Tokamak, are prepared by magnetron sputtering deposition in this study, and the parameters that influence thin-film adhesion are analysed. Thin film adhesion as the objective, the suitable interlayer selection and process parameters were optimized using Taguchi orthogonal array. Tungsten was used to establish the process parameters and suitable interlayer material initially. The optimized parameters and interlayer material were subsequently used for depositing W-Ta composite film varying the Ta percentage from 5% to 20 %. Deposition rate of maximum 18 nm/min and 16 nm/min were achieved for W and W-Ta thin films respectively in this study. It is concluded that 5% Ta composite film, when deposited with Cr interlayer at 350 °C, has the best adhesion and morphological properties compared to other coatings. Adhesion, morphological features, and chemical analysis of W and W-Ta composite thin films studied by scratch test, Rockwell Indentation test, FESEM, and EDS analysis.

Synthesis and characterization of Poly (ortho-aminophenol-co-para-toluidine) and its application as semiconductor thin film

Hydrochloric acid doped poly (ortho-aminophenol–co-para-toluidine) as a conjugated semiconducting copolymer is synthesized in acidic medium via the oxidative polymerization method. The spin coating technique is applied to deposit with appropriate adhesion of doped copolymer thin film. The resulting doped poly (ortho-aminophenol–co-para-toluidine) (POAPT) thin film is characterized by the various techniques to explore its structural, morphological, and optical properties. Density-functional theory (DFT) calculations were implemented utilizing Cambridge Serial Total Energy Package (CASTEP) from Accelrys based on a plane-wave pseudopotential. The optical dispersion of poly (ortho-aminophenol–co-para-toluidine) thin film is expressed in the single oscillator terms of Wemple–Didomenico (WD) model. The parameters Eg is 2.02 eV, n and k (at 2.36 eV) are 1.73 and 3.27×10-8, respectively, n∞ is 1.633, λo is 172.65 nm and So is 2.126 nm-2. Based on the resulting data of optical analysis and conductivity the doped poly (ortho-aminophenol–co-para-toluidine) thin film was found to have promising applications in optoelectronic devices area.

Facile separation of optically transparent adhesive films by heat-triggered gas generation of vaporizable core–shell nanocapsules embedded with benzenesulfonyl hydrazide

A simple and effective separation methodology for separating optically transparent adhesive films without damaging the substrate is presented here. Evaporable core–shell nanocapsules embedded with benzenesulfonyl hydrazide were introduced into acrylic films, and could generate nitrogen gas by thermal treatment, inducing the facile separation of the adhesive thin films from the substrate. The heat-triggered gas generation of surface-confined vaporizable nanocapsules created the interfacial openings between the thin film and substrate, and thus accelerated the selective and clear detachment of thin films. In addition, the nanocapsule-embedded adhesive films exhibited the high optical clarity for display applications.

Interfacial adhesion of alumina thin films over the full compositional range of ternary fcc alloy films: A combinatorial nanoindentation study

Combinatorial materials design of thin films allows one to investigate fundamental mechanic relationships and optimize films for engineering applications. Using a newly integrated shutter controller, specifically developed for precise control over coating design, ternary alloys with full compositional range can be deposited onto single wafers. Programmable shutters allow one to create multilayered thickness gradients of two or three different materials, which can then be annealed to create films with large compositional gradients. Two 50 nm fcc alloys (AlCuAu, AuAgPd) were magnetron sputtered onto (0001) sapphire wafers. The changing chemical composition across the wafer was investigated with energy dispersive x-ray spectroscopy and transmission electron microscopy. AlCuAu showed multiple phases and intermetallics across the wafer, whereas for AuAgPd a solid-solution was observed. Both alloys were coated with 400 nm Al2O3 (atomic layer deposition, ALD), to investigate their potential as adhesion layers for ALD coatings. Adhesion of the bilayers across the wafer was measured with instrumented nanoindentation, producing well-defined delamination-blisters. Small arrays of indents placed over the surface, each location corresponding to different adhesion layer compositions, illustrate adhesion-promoting properties of numerous interface compositions in single samples. For the two bilayer systems, adhesion mapping revealed the areas of optimum adhesion layer composition for best adhesion properties.

Improvement of Nb/Cu adhesion and increase of Nb crystal size by laser radiation

Adhesion of Nb thin film to Cu substrate and size of Nb crystal grains for RF cavities were studied depending on laser intensity and dose. Structures of Nb/Cu, obtained by magnetron sputtering with 500 ˚C (Nr.1) and 700 ˚C (Nr.2) deposition temperature, were irradiated by pulsed Nd:YAG laser. Four areas, irradiated with doses D1 = 5.6x1020, D2 = 8.8x1020, D3 = 1.76x1021 and D4 = 1.76x1022 phot/cm2, were studied. Delamination was investigated by scratching method using conical diamond indenter with force increased from 10 mN to 3.0 N. Characterization of the structure before and after the irradiation was performed using an optical microscope, AFM, SEM and XRD. Comparing with the non-irradiated area, the critical delamination force increased by 10% for sample Nr.2 and by 36% for sample Nr.1 at laser doses D2 and D4, respectively. It means that Nb coating layer of sample Nr. 1 is better than that of sample Nr.2. The decrease of average roughness of Nb layer by an order of magnitude was observed after the laser irradiation. The improvement of the structure adhesion was also observed and explained by the diffusion of Nb atoms into Cu through dislocations. The increase of Nb crystallites size from 20 to 35 nm was calculated using XRD data.

Standardization of the method of magnetostriction measurement of grain-oriented electrical steel strip and sheet

Standardization of the method of measurement of AC magnetostriction characteristics of grain-oriented electrical steel strip and sheet by means of a single sheet tester and an optical sensor, i.e. IEC 60404-17 Ed.1 [1], has been promoted in the IEC/TC68/WG2 to meet the demand of transformer industry. The relationship between the magnetostriction characteristics of grain-oriented electrical steel and transformer noise is complicated and yet not fully understood. One of basic problems has been the lack of a standard for the magnetostriction measurements. The measurement requires detection of slight vibration of the test specimen at a resolution of 0.01 μm/m or better. In order to ensure this resolution, not only magnetic aspects but also mechanical aspects of the test apparatus, e.g. the influence of friction and external vibrations, have to be specified. The size of test specimen is restricted to 100 mm × 500 mm. The flux closer is a vertical single yoke or a horizontal double yoke. In order to avoid the influence of friction and vibration, no weight is put on the test specimen except an optical target and a clamp to fix the test specimen to the test apparatus. Also, no weight is connected to the end of test specimen to prevent additional vibration modes. The optical target is low mass and made of non-magnetic and non-conductive materials. The optical target and the clamp are placed between opposite pole faces of the yoke. In order to realize a low and constant friction coefficient, an insertion sheet with a thin fluorine resin-impregnated glass cloth adhesive film on its upper surface is placed under the test specimen. A round robin comparison using different test setups in accordance with the draft of standard was carried out.

Effects of interfacial modification for vapor phase polymerized PEDOT on glass substrate

Optically transparent and highly conductive poly(3,4-ethylenedioxythiophene) (PEDOT) thin films were grown through vapor phase polymerization on (3-Mercaptopropyl)trimethoxysilane functionalized 3,4-Ethylenedioxythiophene (MPTMS functionalized EDOT) grafted glass substrates. Compared to bare glass, the EDOT grafted surface led to enhancements in both electrical conductivity and adhesion of PEDOT thin films. A quinoid-rich structure with increased crystallinity and a further enhanced conductivity was induced by post-deposition sulfuric acid doping. X-ray diffraction showed different orientations of the PEDOT crystals grown on substrates with and without EDOT grafting. The highest conductivity of 2690 S/cm, with an average optical transmittance of 95.4 % in the visible range, was achieved when PEDOT was vapor phase polymerized on EDOT grafted substrates and doped with 98 % sulfuric acid. Photostability was tested using a xenon arc light source and characterized by attenuated total reflection Fourier-transform infrared spectroscopy, showing that photo-induced degradation is associated with a decrease in CC double bond content.

Design of an Adhesive Film-Based Microfluidic Device for Alginate Hydrogel-Based Cell Encapsulation.

To support the increasing translational use of transplanted cells, there is a need for high-throughput cell encapsulation technologies. Microfluidics is a particularly promising candidate technology to address this need, but conventional polydimethylsiloxane devices have encountered challenges that have limited their utility, including clogging, leaking, material swelling, high cost, and limited scalability. Here, we use a rapid prototyping approach incorporating patterned adhesive thin films to develop a reusable microfluidic device that can produce alginate hydrogel microbeads with high-throughput potential for microencapsulation applications. We show that beads formed in our device have high sphericity and monodispersity. We use the system to demonstrate effective cell encapsulation of mesenchymal stem cells and show that they can be maintained in culture for at least 28days with no measurable reduction in viability. Our approach is highly scalable and will support diverse translational applications of microencapsulated cells.

Design of Thin-Film Interlayer between Silicon Electrode and Current Collector Using a Chemo-Mechanical Degradation Model

To enhance delamination limitations in silicon electrode, a thin-film interlayer between silicon electrode and copper current collector is designed using a chemo-mechanical degradation model. The chemo-mechanical degradation model considers the formation of the solid electrolyte interphase on the surface and within the cracks of the silicon electrode, the physical isolation of active materials and the resistance due to loss of contact between the silicon composite electrode and the copper foil as the main capacity fading mechanisms. The model is validated with experimental data collected from coin cells made of silicon electrode with a bare and an adhesive thin film laminated copper foil. The reduction in the delamination limitations depends on the interplay of the adhesion strength, conductivity, coverage and thickness of adhesive thin film on the surface of the copper foil.

Structures and adhesion of hcp thin film coating interfaces on a single-crystal bcc substrate by PVD: Ti/Mo and Zr/Mo

Polycrystalline hcp Ti and Zr thin films were developed on single-crystal bcc-Mo (110) substrate using PVD method. XRD analysis suggests the preferred facet relation of (0001)hcp//(110)bcc. Sandwich supercell models were then constructed to evaluate the interface energy, adhesion strength and bonding nature from the first principles. The Burgers and Pitsch-Schrader orientation relation (OR) were predicted as the most energy-favored for the PVD Ti and Zr thin film interfaces on the Mo (110), respectively. Interface adhesion was predicted to be fairly strong for both interfaces. The d-d orbital interaction between Ti/Zr and Mo is found closely associated with the spatial redistribution of Bader valence charges. The resulting new bonds across the interfaces are rather delocalized, showing a mixed covalent and weak ionic bond character. These results strongly suggest that single-crystal Mo (110) is a promising substrate for developing high quality hcp Ti or Zr thin films through PVD.

Adhesion of Single-Walled Carbon Nanotube Thin Films with Different Materials.

Single-walled carbon nanotubes (SWCNTs) possess extraordinary physical and chemical properties. Thin films of randomly oriented SWCNTs have great potential in many opto-electro-mechanical applications. However, good adhesion of SWCNT films with a substrate material is pivotal for their practical use. Here, for the first time, we systematically investigate the adhesion properties of SWCNT thin films with commonly used substrates such as glass (SiO2), indium tin oxide (ITO), crystalline silicon (C-Si), amorphous silicon (a-Si:H), zirconium oxide (ZrO2), platinum (Pt), polydimethylsiloxane (PDMS), and SWCNTs for self-adhesion using atomic force microscopy. By comparing the results obtained in air and inert Ar atmospheres, we observed that the surface state of the materials greatly contributes to their adhesion properties. We found that the SWCNT thin films have stronger adhesion in an inert atmosphere. The adhesion in the air can be greatly improved by a fluorination process. Experimental and theoretical analyses suggest that adhesion depends on the atmospheric conditions and surface functionalization.