Search

Polyetheretherketone (PEEK) and its fiber-reinforced materials are thermoplastic polymer materials with broad application prospects. Depositing Ni-P alloy on them can improve their poor conductivity and electromagnetic shielding performance, and further expand their application field. The application effect of the plated parts is significantly impacted by the bonding strength between PEEK and coating. The bonding strength between non-metallic substrate and coating is largely influenced by the surface characteristics of the substrate. Therefore, it is significant to study how the surface roughness of PEEK materials and the modified fibers in materials affect the adhesion of the coating. In this study, Ni-P alloy was electroless deposited on PEEK, 30% carbon-fiber-reinforced PEEK (CF30/PEEK), and 30% glass-fiber-reinforced PEEK (GF30/PEEK) with varying surface roughness. The influence of surface roughness and modified fibers on the coating adhesion was studied. Additionally, the effect of the concentrations of nickel sulfate, sodium hypophosphite, pH, and temperature on the deposition rate of the coating was investigated for the three materials. Based on the highest deposition rate, the process parameters were then optimized. The results demonstrated that as surface roughness increased, adhesion between substrate and coating first increased and then decreased. The surface roughness Ra of 0.4 μm produced the highest coating adhesion. Additionally, fiber-reinforced PEEK adhered to coatings more effectively than PEEK did. The mechanism of the difference in bonding strength between different PEEK-modified materials and coatings was revealed. The optimal process parameters were: nickel sulfate: 25 g/L, sodium hypophosphite: 30 g/L, pH: 5.0, and temperature: 70 °C.

Bamboo scrimber refers to a lignocellulosic structural material, which is usually attacked by water, ultraviolet radiation and fungus. Surface coating is an effective way to protect it, and its coating properties depend on surface wettability. In this study, the surface wettability of bamboo scrimbers with varying resin content was investigated via the comprehensive analysis of surface roughness, surface contact angle, surface free energy, surface chemical composition and coating properties. The resultant scrimbers had a similar profile with low roughness. Their surface was hydrophilic, but the hydrophilicity decreased with the increase in resin content. High resin content gave rise to low total free energy, in which the Lifshitz–van der Waals component was dominant and it decreased with the increasing resin content. Meanwhile, the ratio of the electron-accepting component to the electron-donating component becomes higher. This was due to the decreasing hydrophilic groups (e.g., -OH and -COOH groups) and the increasing oxygen-free groups (e.g., C-H and -CH2 groups) on the scrimber surface. The resin content affected the adhesion by decreasing the surface wettability, but the coating adhesion still reached the level of 2 for all bamboo scrimbers. The results will provide a theoretical reference for the surface coating of bamboo scrimbers in the structural application for good coating durability.

Electric vehicles are shaping the future of the automotive industry. The traction battery is one of the most important components of electric cars. To ensure that the battery operates safely, it is essential to physically and electrically separate the cells facing each other. Coating a cell with varnish helps achieve this goal. Current studies use a destructive method on a sampling basis, the cross-cut test, to investigate the coating quality. In this paper, we present a fast, nondestructive and inline alternative based on hyperspectral imaging and artificial intelligence. Therefore, battery cells are measured with hyperspectral cameras in the visible and near-infrared (VNIR and NIR) parts of the electromagnetic spectrum before and after cleaning then coated and finally subjected to cross-cut test to estimate coating adhesion. During the cross-cut test, the cell coating is destroyed. This work aims to replace cross-cut tests with hyperspectral imaging (HSI) and machine learning to achieve continuous quality control, protect the environment, and save costs. Therefore, machine learning models (logistic regression, random forest, and support vector machines) are used to predict cross-cut test results based on hyperspectral data. We show that it is possible to predict with an accuracy of ~75% whether problems with coating adhesion will occur. Hyperspectral measurements in the near-infrared part of the spectrum yielded the best results. The results show that the method is suitable for automated quality control and process control in battery cell coating, but still needs to be improved to achieve higher accuracies.

New manufacturing technologies, such as Sheet-Bulk Metal Forming, are facing the challenges of highly stressed tool surfaces which are limiting their service life. For this reason, the load-adapted design of surfaces and the subsurface region as well as the application of wear-resistant coatings for forming dies and molds made of high-speed steel has been subject to many research activities. Existing approaches in the form of grinding and conventional milling processes do not achieve the surface quality desired for the forming operations and therefore often require manual polishing strategies afterward. This might lead to an unfavorable constitution for subsequent PVD coating processes causing delamination effects or poor adhesion of the wear-resistant coatings. To overcome these restrictions, meso- and micromilling are presented as promising approaches to polishing strategies with varying grain sizes. The processed topographies are correlated with the tribological properties determined in an adapted ring compression test using the deep drawing steel DC04. Additionally, the influence of the roughness profile as well as the induced residual stresses in the subsurface region are examined with respect to their influence on the adhesion of a wear-resistant CrAlN PVD coating. The results prove the benefits of micromilling in terms of a reduced friction factor in the load spectrum of Sheet-Bulk Metal Forming as well as an improved coating adhesion in comparison to metallographic finishing strategies, which can be correlated to the processed roughness profile and induced compressive residual stresses in the subsurface region.

Polymethyl methacrylate (PMMA) is an attractive optical plastic that is widely used in augmented reality, virtual reality devices, display, wearable devices, portable optical equipment, and lightweight optics. Thin film prepared by physical vapor deposition (PVD) is the primary choice of coating on PMMA. However, it faces problems with coating adhesion and stress. In this paper, we analyze the problems existing in the current PMMA high-reflection (HR) coating in detail and propose a way to effectively solve issues with bonding force and stress. Based on the current research background, the bonding force was enhanced by introducing a special hard coating as the connection layer between the dielectric film and the substrate. After comparing the stresses of different coating materials and material combinations, the optimal combination of Nb2O5 and SiO2 was determined, and the requirements were successfully prepared. An HR coating that satisfies requirements, with low stress and excellent environmental adaptability, was successfully prepared. Based on this, a broadband HR coating from 750 to 1550 nm was formed on the surface of PMMA by adjusting the partial pressure of oxygen.

In this study, Ni&ndash, P/Ni&ndash, P&ndash, SiC coatings were prepared on pretreated 45 steel substrates by scanning electrodeposition. Prior to the electrodeposition, the substrates were subjected to two types of pretreatments: polishing and sandblasting. The 3D morphology of the pretreated substrates was characterized by laser scanning confocal microscopy. The micromorphology and section morphology of the coating surface were characterized by field emission scanning electron microscopy. The section element composition was characterized using an EDS energy spectrum analyzer. The adhesion and corrosion resistance of 15 coatings were analyzed using an automatic scratch tester and CS350 electrochemical workstation. The results showed the presence of an element penetration region between the coating and the substrate. The sandblasting pretreatment and SiC nanoparticle addition helped widen the penetration region of the elements. The Ni&ndash, SiC coating prepared by scanning electrodeposition on the sandblasted substrate exhibited the thickest penetration region, up to 28.39 &micro, m. A scratch test conducted on this coating showed that it exhibits the best adhesion force, up to 36.5 N. In electrochemical corrosion experiments, its corrosion potential was found to be the highest, reaching &minus, 0.30 V, and the corrosion current density was the lowest, reaching 8.45 &times, 10&minus, 7 A&middot, cm&minus, 2. The presence of the element penetration region increased the coating adhesion and improved the corrosion resistance.

The reactive cathodic arc deposition technique was used to produce Ti nitride and oxynitride coatings on 304 stainless steel substrates (SS). Both mono (SS/TiN, SS/TiNO) and bilayer coatings (SS/TiN/TiNO and SS/TiNO/TiN) were investigated in terms of elemental and phase composition, microstructure, grain size, morphology, and roughness. The corrosion behavior in a solution consisting of 0.10 M NaCl + 1.96 M H2O2 was evaluated, aiming for biomedical applications. The results showed that the coatings were compact, homogeneously deposited on the substrate, and displaying rough surfaces. The XRD analysis indicated that both mono and bilayer coatings showed only cubic phases with (111) and (222) preferred orientations. The highest crystallinity was shown by the SS/TiN coating, as indicated also by the largest grain size of 23.8 nm, which progressively decreased to 16.3 nm for the SS/TiNO monolayer. The oxynitride layers exhibited the best in vitro corrosion resistance either as a monolayer or as a top layer in the bilayer structure, making them a good candidate for implant applications.