Improved Adhesion Strength Research Articles

Surface Passivation of ITO on Heterojunction Solar Cells with Enhanced Cell Performance and Module Reliability

The indium tin oxide (ITO) thin film plays an important role in the silicon heterojunction (SHJ) solar cells, which acts as not only a carrier transport layer in vertical and lateral directions but an anti-reflection layer as well. Thickness reduction of the expensive ITO is an efficient strategy to reduce the cost of SHJ solar cells. In this work, the simulated antireflection effects of several dielectric capping layers demonstrate that Al2O3 and SiO2 are the suitable candidates for both of the SHJ solar cell and module. Hall effect measurements show that the SiO2 layer is able to passivate the ITO surface and improve the mobility and conductivity of the ITO film, which is beneficial to further reduce the thickness of ITO films. It is also found that the SiO2 capping layer can significantly enhance the adhesion strength between the solar cell and the encapsulating polymer film by 26% in the SHJ module. The improved adhesion strength is attributed to the higher surface energy of SiO2 than ITO, according to the liquid-solid contact angle measurements. These results show that the SiO2 capping layer can not only reduce the consumption of ITO thin films, but also increase the reliability of SHJ module.

Технология обработки углеродных волокон при электромагнитных воздействиях различной природы с целью получения высокопрочных углепластиков

The effect of pretreatment technologies of carbon fibers by different electromagnetic methods on their mechanical characteristics has been examined. The methods of cold plasma and ultraviolet radiation were used. Such a treatment improves adhesion strength of a metal coating with fibers for production of carbon-filled plastics with high interfacial shear durability. By experiments it has been found out that the plasma treatment method is the most effective. The study and experiment results are presented.

Rust Conversion Performance of Phosphoric Acid-Gallic Acid in Vinyl Chloride Acrylic Emulsion

This work studied the application of phosphoric acid-gallic acid in vinyl chloride acrylic emulsion and its rust conversion performance. The increase of phosphoric acid affected the stability of the system, leading to the rapid precipitation of flocculent precipitation. Rust conversion coating (RCC) showed the best synergistic conversion effect when gallic acid (GA) was 0.2 wt.% and phosphoric acid (PA) was 2 wt.%. XRD and FTIR analysis show that the components of adherent rust (AR) are α-FeOOH, γ-FeOOH and Fe3O4. The conversion products are ferric phosphate (FP) and ferric gallate (FG). The RCC can effectively treat the rusted steel (RS) produced by simulated marine atmospheric corrosion. The corrosion current density was reduced by three orders of magnitude, the adhesion reached 2.75 MPa, and the salt spray corrosion resistance was 20 days. The results of Raman, XPS, SEM and EDS show that the ionic dissolution of iron, complexation and further oxidation reactions occur at the interface between the adherent rust and the RCC. After rust conversion treatment, unreacted rust (UR) affects the further improvement of adhesion strength and anti-corrosion performance.

Tribological and Mechanical Properties of Multicomponent CrVTiNbZr(N) Coatings

Multi-element material coating systems have received much attention for improving the mechanical performance in industry. However, they are still focused on ternary systems and seldom beyond quaternary ones. High entropy alloy (HEA) bulk material and thin films are systems that are each comprised of at least five principal metal elements in equally matched proportions, and some of them are found possessing much higher strength than traditional alloys. In this study, CrVTiNbZr high entropy alloy and nitrogen contained CrVTiNbZr(N) nitride coatings were synthesized using high ionization cathodic-arc deposition. A chromium-vanadium alloy target, a titanium-niobium alloy target and a pure zirconium target were used for the deposition. By controlling the nitrogen content and cathode current, the CrNbTiVZr(N) coating with gradient or multilayered composition control possessed different microstructures and mechanical properties. The effect of the nitrogen content on the chemical composition, microstructure and mechanical properties of the CrVTiNbZr(N) coatings was investigated. Compact columnar microstructure was obtained for the synthesized CrVTiNbZr(N) coatings. The CrVTiNbZrN coating (HEAN-N165), which was deposited with nitrogen flow rate of 165 standard cubic centimeters per minute (sccm), exhibited slightly blurred columnar and multilayered structures containing CrVN, TiNbN and ZrN. The design of multilayered CrVTiNbZrN coatings showed good adhesion strength. Improvement of adhesion strength was obtained with composition-gradient interlayers. The CrVTiNbZrN coating with nitrogen content higher than 50 at.% possessed the highest hardness (25.2 GPa) and the resistance to plastic deformation H3/E*2 (0.2 GPa) value, and therefore the lowest wear rate was obtained because of high abrasion wear resistance.

Remarkable bactericidal traits of a metal-ceramic composite coating elated by hierarchically structured surface.

SummaryA ceramic-based coating with a hierarchical surface structure was synthesized via solid-state reaction enabled by a double cathode glow discharge technique. This innovative coating comprises two distinct layers, specifically an outer layer with a well-aligned micro-pillar array and a dense inner layer. Both are composed of a face-centered cubic Cu(Co,Ni,Fe) solid solution phase together with a spinel-type Fe(Al,Cr)2O4 oxide. This coating exhibits superhydrophobicity and, yet, a very strong adhesion to water, i.e., the so-called “rose petal effect”. This coating also exhibits highly efficient antibacterial ability against both Staphylococcus aureus and Escherichia coli bacteria under both dark and visible light conditions. The excellent antibacterial property originates from the synergistic effects through the release of Cu ions coupled with photothermal activity upon light activation.

Reversible supramolecular adhesives formed by metallacycle-crosslinked polymer networks via amino‑yne click reaction

Control over the adhesive properties are of great importance for both biological and chemical systems. Herein, we use amino‑yne click reaction to prepare metallacycle-crosslinked supramolecular polymer networks, which are further employed as reversible adhesive materials. The introduction of metallacyclic structures not only gives the formed polymer networks good emission and self-healing properties, but also affords improved adhesion strength and increased glass transition temperature, making them serve as reversible and emissive supramolecular adhesives. This study provides an efficient strategy for the preparation of functional supramolecular polymer networks towards adhesive applications.

Flexibility Enhancements of Hybrid Copper Inks with Cellulose Nanocrystals

Increasingly, copper nanopowders are commonly used in conductive inks due to their cost-efficiency compared to silver or gold and excellent electrical conductivity. One of the challenges associated with copper inks is oxidation and to address, we have developed a hybrid copper-based ink by removing the oxide layer of copper powders and coat the powders with a silver shell to protect from oxidation. Despite the advances, the inks are prone to fatigue failures when the ink films are repeatedly bent or stretched. In order to overcome this challenge, we proposed to integrate cellulose nanocrystals (CNC) with the copper-based ink on a polymer substrate and use a sintering process based on intense pulsed light in an argon atmosphere. Sintering in argon gas environment improved in electrical conductivity that may be the result of the partial carbonization of the CNC rather than combustion. It has also been experimentally determined that CNC improved adhesion strength of the copper ink film. Moreover, the addition of CNC also reduced the damage caused by bending and stretching. The ink film containing 10% CNC increased the electrical resistance by only 3.82 times after 600 bending cycles versus the resistance increased by 34.4 times without CNC. Under the 30% strain of stretching, the change in resistance of the ink film containing 10% CNC was 1.75 times lower than without CNC. It was observed through microscopy techniques that the presence of CNC reduced the formation of cracks by enhancing mechanical strength.

Influence of pulse frequency on microstructure and mechanical properties of Al-Ti-V-Cu-N coatings deposited by HIPIMS

As an important parameter of HIPIMS, pulse frequency has significant influence on the microstructure and mechanical properties of the deposited coatings, especially for the multi-component coatings deposited by using a spliced target with different metal sputtering yields. In this study, a single Al67Ti33-V-Cu spliced target was designed to prepare Al-Ti-V-Cu-N coatings by using high power impulse magnetron sputtering (HIPIMS). The results showed that the peak target current density decreased from 0.75 to 0.24 A∙cm−2 as the pulse frequency increased, along with the microstructure transferred from dense structure to coarse column structure. The pulse frequency has significant influence on chemical compositions of Al-Ti-V-Cu-N coatings, especially for Cu content increasing from 6.2 to 11.7 at.%. All the coatings exhibited a single solid-solution phase of Ti-Al-V-N, and the preferred orientation changed from (111) to (220) when the pulse frequency increased above 200 Hz. The decrease in peak target current density at high pulse frequencies resulted in a sharp decrease in the coating hardness from 35.2 to 16.4 GPa, whereas the relaxation of compressive residual stress contributed to an improvement in adhesion strength from 43.3 to 79.6 N.

Fabrication of WS2/C composite coatings via electrohydrodynamic atomization and their tribology behaviours

WS2 coatings were prepared by electrohydrodynamic atomization method, and graphite was introduced in order to improve their mechanical properties and oxidation resistance. The influence of graphite on the microstructure, anti-oxidation capability, mechanical performances and tribological properties of the composite coatings were systematically analysed. The sharkskin-like biomimetic textures were fabricated on the substrates by laser machining. The results showed that the sharkskin-like biomimetic textures increased the compressive stresses and surface energies of substrates, resulting in improved adhesion strength between deposited coatings and substrates. The improved adhesion strength and oxidation resistance of the WS2/C coatings as well as the antifriction capability of micro/nano-textures aided in keeping a low stabilized friction coefficient down to 0.05 for a long sliding time. The WS2/C (4:1) composite coatings deposited on the sharkskin-like biomimetic textured substrates presented the longest wear life of ~2800 s, which was ~2.3 times longer than that of the pure WS2 coatings on the polished substrates. The wear rate of WS2/C (4: 1) coating deposited on the textured substrate was ~3.1 × 10−7 mm3/N mm, which was about three-fifths of that of the pure WS2 coating deposited on the polished substrate. The micro/nano-grooves, which acted as reservoirs for WS2 lubricating material, could support the formation of the low-friction tribo-films.

Optimization of plasma treatment parameters to improve the wood-coating adhesion strength using Taguchi integrated desirability function approach

The aim of this study is to enhance the coating adhesion strength by optimizing the air plasma application parameters. Air-plasma treatment parameters were selected as working distance, treatment speed and pressure, while material type parameters were determined as low mean density fiberboard (MDF-1) and high-density mean fiberboard (MDF-2). Due to the low adhesion strength in water-based paint applications compared to other types of paint, water-based paint was applied to these samples. Taguchi orthogonal design and analysis of variance (ANOVA) were applied to investigate the significant parameters on the adhesion strength. Desirability function was used to determine the optimum factor levels. According to experimental design results, working distance, treatment speed, and pressure values of 8.82 mm, 60 mm/s, and 1.10 bar were determined as optimum plasma treatment parameters for MDF-1, respectively. Corresponding values for MDF-2 were 9.19 mm, 60 mm/s, and 1.06 bar. The improvement in adhesion strength was evaluated as 22% increase for MDF-1 and 16% increase for MDF-2.

Effect of TiN/Ti coating combined with laser shock peening pre-treatment on the fatigue strength of Ti-6Al-4V titanium alloy

The multilayer gradient TiN/Ti coating was deposited by using filtered cathodic vacuum arc (FCVA) deposition method. The laser shock peening (LSP) process was carried out before deposition. The surface morphology, mechanical properties were measured by atomic force microscope (AFM), nanoindentation and scratch tester. The fatigue strength was investigated on a vibration test platform and the fracture morphologies were observed by scanning electron microscope (SEM). The results showed that the compound process has little negative influence on the roughness. A hardened layer with high hardness and compressive residual stress was formed by the LSP pre-treatment. This layer can also suppress plastic deformation, making the adhesion strength between the coating and substrate increased from 54.9 N to 79.1 N. The TiN/Ti coating and the compound process improve the fatigue strength of TC4 alloy by 58.1% and 98.8%, respectively. The coating can restrain crack initiation on the surface and slow its propagation. The crack initiation location of the compound process sample moved into the deeper site and the improved adhesion strength further reduces the crack propagation rate. Thus, the compound process of TiN/Ti coating combined with laser shock peening pre-treatment greatly improves the fatigue strength of TC4 alloy.

Fouling resistant silicone coating with self-healing induced by metal coordination

Silicone based fouling release coatings with eco-friendliness have received growing interest. Yet, their poor fouling resistance and self-repairing inability restrict their applications. Here, we report a new poly(dimethylsiloxane) (PDMS) coating cross-linked via coordination bonds between 2-(2-benzimidazolyl)ethanethiol (BET) and zinc ions. Such modified PDMS still has low surface energy but improved adhesion strength in comparison with PDMS elastomer. The metal coordination makes its cross-linking reversible, so it exhibits good self-healing in air or artificial seawater at room temperature. Moreover, the presence of zinc-imidazole complexes with antifouling function significantly improves the fouling resistance against the marine bacteria Pseudomonas sp. and the diatom Navicula incerta. The study provides an approach to develop high performance antifouling coating.

Plasma Arc Coatings Produced from Powder-Cored Wires with Steel Sheaths

Plasma arc coatings produced from powder-cored wires developed at the Paton Electric Welding Institute that were deposited onto a low-carbon steel substrate were characterized. Interaction between the steel sheath (constituting at least 80 wt.% of the wire) and powder cores, such as B4C, B4C + ZrO2(nano), B4C + (Cr, Fe)7C3, and B4C + (Cr, Fe)7C3 + Al, in the arc plasma spraying process was analyzed. The resultant coatings were free of defects and had low porosity (to 2.5%) and lamellar structure. The core carbide components were found to dope the coating ferritic matrix and strengthen it with carbide, carboboride, and boride precipitates. An addition of 0.5% ZrO2 nanopowder refined the coating structure and participated in the formation of Fe2B and Fe3B precipitates. An aluminum addition within 10 wt.% did not led to iron aluminides but, being easily melted, activated the interaction between components, reduced porosity, and improved adhesion strength of the coatings. The coatings reached a microhardness of 6.25–8.59 GPa, being 4 to 5.5 times higher than the microhardness of the steel wire sheath. The development and use of such powder-cored wires expanded the application of plasma arc spraying, particularly for the protection of equipment against abrasive gas wear in chemical engineering, in the production of parts for pumps, compressors, and other components, and for the recovery of worn parts.

Effect of Hybridization on the Functional Properties of AgMF–MWCNT-Filled Electrically Conductive Adhesive

A combination of metal and non-metal filler in an epoxy resin, called a hybrid electrically conductive adhesive (ECA), is an important development in the field of highly conductive electronic interconnect materials. Carbon nanotubes (CNTs) are well known for contributing strength and stiffness to ECA and silver (Ag) has been widely used as a conductive metal. This study presents the characterization of a hybrid silver micro-flake (AgMF) with multiwalled carbon nanotubes (MWCNT) in an epoxy matrix ECA, in terms of electrical and mechanical properties. The weight percentage of AgMF used was varied, from 1 wt.% to 10 wt.%, whereas the weight percentage of MWCNT filler loading was maintained at 5 wt.%. The properties of the hybrid ECA were characterized using a four-point probe and a universal testing machine for lap shear tests. It was found that the filler hybridization lowered the performance of the ECA in terms of both electrical and mechanical properties, as compared with non-hybrid MWCNT-filled ECA. This may be attributed to the weak interaction between micro- and nano-filler particle sizes and agglomeration of the MWCNT in the epoxy matrix in the hybrid ECA system. The hybrid ECA electrical conductivity was successfully enhanced when a low ratio of AgMF and MWCNT was considered. In addition, failure analysis confirmed that the hybrid ECA with less AgMF filler loading exhibits improved adhesion strength, suggesting a superior epoxy-to-substrate bonding interface.

Polydopamine nanoparticles modified nanofiber supported thin film composite membrane with enhanced adhesion strength for forward osmosis

To minimize the internal polarization concentration (ICP) in FO process and improve the structural stability of thin film composite (TFC) forward osmosis (FO) membrane, a reactable hydrophilic nanofiber substrate was prepared by vacuum filtrating an interlayer composed of polydopamine nanoparticles (PDA NPs) onto an electrospun polyacrylonitrile nanofiber substrate. Then a TFC FO membrane with dense selective layer, low structure parameter, high water permeability and low salt permeability was prepared by the interfacial polymerization thereon. According to the T-peel test, the resulting TFC FO membrane showed greatly improved adhesion strength between selective layer and substrate due to the chemical bonding and entanglement between polyamides and the PDA NPs, and the strong adhesion between PDA NPs and the nanofibers. The ICP in FO process for the resulting membranes were minimized due to the application of the nanofiber substrates with low structure parameter (in the range of 290 ± 36 μm–354 ± 20 μm). These FO membranes performed well in the heavy metal ions contained water treatment, showed 1–2 times higher water flux (29.2 ± 0.3 L/m2h) compared with commercial TFC membrane (HTI-TFC) and high heavy metal ions rejection (99.5% ± 0.4%, 99.1% ± 0.5%, 98.1% ± 0.7% for Cr3+, Cu2+ and Ni2+, respectively) when using 2.0 M NaCl as draw solution. The findings provide the pathway for the design of nanofiber based FO membrane with improved structure stability and high performance by interfacial polymerization.

Highly Stretchable Dry Electrode Composited with Carbon Nanofiber (CNF) for Wearable Device.

In this work, we present a highly stretchable dry electrode composited with carbon nanofiber (CNF) for wearable device by simple method. The fabricated electrodes were assembled with snap connector for connect with electric circuit and sticky polymer for improving adhesion strength on the skin. We evaluated the electrical and mechanical properties depending on the weight % (wt%) and thickness of CNF/elastomer composited stretchable electrode. From the results, the electrical characteristic was improved as increasing concentrations of CNF and their dropping volume. And we evaluated a stretchability and electromechanical property using with cycling test. Through these tests, we have demonstrated that fabricated dry electrode has outstanding stretchability and durability under stretching condition. Finally, electrocardiogram (ECG) was measured with these electrodes. The results of ECG measurement showed similar or larger signal that of commercial wet electrode. Consequently, these results are expected to apply as a wearable device such as a bio-signal measurement and strain sensors.

Impact of adhesive ingredients on adhesion between rubber and brass‐plated steel wire in tire

AbstractProficiency on underlying mechanism of rubber‐metal adhesion has been increased significantly in the last few decades. Researchers have investigated the effect of various ingredients, such as hexamethoxymethyl melamine, resorcinol, cobalt stearate, and silica, on rubber‐metal interface. The role of each ingredient on rubber‐metal interfacial adhesion is still a subject of scrutiny. In this article, a typical belt skim compound of truck radial tire is selected and the effect of each adhesive ingredient on adhesion strength is explored. Out of these ingredients, the effect of cobalt stearate is found noteworthy. It has improved adhesion strength by 12% (without aging) and by 11% (humid‐aged), respectively, over control compound. For detailed understanding of the effect of cobalt stearate on adhesion, scanning electron microscopy and energy dispersive spectroscopy are utilized to ascertain the rubber coverage and distribution of elements. X‐ray photoelectron spectroscopy results helped us to understand the impact of CuXS layer depth on rubber‐metal adhesion. The depth profile of the CuXS layer was found to be one of the dominant factors of rubber‐metal adhesion retention. Thus, this study has made an attempt to find the impact of different adhesive ingredients on the formation of CuXS layer depth at rubber‐metal interface and establish a correlation with adhesion strength simultaneously.

Study on the Improvement of Adhesion Strength between Composite Solid Propellant, Liner, and Heat‐Resistant Material

AbstractThis study was conducted to improve the adhesion strength between a propellant, liner, and heat‐resistant material. As the drying time of the heat‐resistant material increased, the adhesion strength between the propellant, liner, and heat‐resistant material improved. Further, the surface of the heat‐resistant material was subjected to buffing treatment to improve the adhesion strength. In addition, as the thickness of the heat‐resistant material increased, the adhesion strength degraded. Moreover, the adhesion strength was improved by increasing the thickness of the liner on the heat‐resistant material. Besides, the adhesion strength slightly reduced with an increase in the plasticizer content. The liner curing time was an important factor affecting the adhesion strength, and an optimum liner curing time was obtained. In this study, the adhesion strength was improved by applying a barrier coat between the heat‐resistant material and liner. The adhesion was further improved when the heat‐resistant material was buffed.

Improving adhesion and moisture permeability of UV/heat dual-curable adhesives using organic-inorganic hybrid resin

Seamless displays have attracted considerable attention because they simultaneously offer an immersive experience and one virtual screen. In this study, we prepared new UV/heat dual-curable adhesives containing organic–inorganic hybrid resin for narrow bezel display. The silane coupling groups contained in the organic–inorganic hybrid resin react with substrates, thereby improving adhesion strength and reducing moisture permeability of adhesives. The UV/heat curing ratio, adhesive strength, moisture permeability, and internal contamination of new adhesive were compared with those of conventional sealant. The proposed adhesive offered high adhesion, reduced moisture permeability, and low internal contamination level for a full screen display application.

Effect of sp3 Content on Adhesion and Tribological Properties of Non-Hydrogenated DLC Films.

Non-hydrogenated diamond-like carbon (DLC) films with various ratios of sp3/sp2 were prepared on cemented carbide YG8 with DC magnetron sputtering technology. A pure graphite target was selected as the carbon source. Before DLC deposition, a surface etching pretreatment was carried out by mid-frequency magnetron sputtering method, using Ti atoms to improve adhesion strength. The ratios of sp3/sp2 were adjusted by bias voltages. In order to investigate the effect of the ratio of sp3/sp2 on adhesion and tribological properties, Raman spectra, XPS spectra, adhesion scratch test and ball-on-disk dry friction tests were applied. The results indicated that the ratio of sp3/sp2 fluctuated with bias voltage, increasing in the range of 0.74 to 0.98. The adhesion strength decreased from 31.5 to 18.4 N with the increasing ratio of sp3/sp2, while the friction coefficient rose in DLC-Si3N4 and dropped in DLC-Ti6Al4V. For DLC-Ti6Al4V, the oxidation of Ti6Al4V had a greater influence than graphitization of DLC. The hard oxides of Ti6Al4V broke the graphite transfer layer leading to a high friction coefficient. The wear rate was approximately linearly related to bias voltage. The coefficients of the linear regression equation were influenced by different friction materials. The adhesion strength and the friction coefficient were fitted as a function of the ratio of sp3/sp2.