The study aimed to investigate the effect of surface pretreatment on the corrosion protection of aluminum alloy 7075-T6 in sodium chloride solution using cerium acetate as a corrosion inhibitor. Different surface pretreatments were tested: (i) mechanical grinding, (ii) mechanical grinding and non-water diamond polishing, (iii) mechanical grinding, alkaline etching with NaOH and acid desmutting, and (iv) mechanical grinding, alkaline cleaning with a commercial SurTec cleaner and acid desmutting. Topography, composition, and morphology of inhibited surface during immersion were investigated using optical microscopy, 3-D profilometry, scanning electron microscopy/energy-dispersive X-ray analysis and Fourier transform infrared spectrometry. The corrosion properties were determined by potentiodynamic measurements and electrochemical impedance spectroscopy in sodium chloride solution without and with the addition of cerium acetate. A change in the composition and morphology of the inhibited surface was noticed as a function of surface pretreatment and immersion time. Appropriate surface treatment resulted in improved protection against localized corrosion even after long-term immersion up to 1 month. Among mechanical pretreatments, polishing gave better results than grinding. Among chemical pretreatments, alkaline cleaning in SurTec/HNO3 was more appropriate as a preceding step to acid desmutting than alkaline etching with NaOH.
Establishing the correlation between the topography and the bactericidal performance is the key to improve the mechano-bactericidal activity. However, due to the complexity of the mechano-bactericidal mechanism, the correlation between density and bactericidal performance is still not clear. Based on this, a series of nanoblades (NBs) with various density but similar thickness and height were prepared on the chemically strengthened glass (CSG) substrate by a simple alkaline etching method. The mechano-bactericidal properties of NBs on CSG (NBs@CSG) surfaces exposed to Escherichia coli were evaluated. The results show that with the NB density increasing, the mechano-bactericidal performance of the surface increased first and then decreased. Besides, the bactericidal performance of NBs@CSG is not affected after four consecutive ultrasonic cleaning bactericidal experiments. This article can provide guidance for the design of the new generation of mechano-bactericidal surfaces. In addition, this technology is expected to be applied to the civil aviation cabin window lining.
The tetramethylammonium hydroxide (TMAH)-controlled alkaline etching of nickel hexacyanoferrate (NiHCF) mesocrystals is explored. The alkaline etching enables the formation of hollow framework structures with an increased surface area, the exposure of active Ni and Fe sites and the retention of morphology. The ambient reaction conditions enable the establishment of a sustainable production. Our work reveals novel perspectives on the eco-friendly synthesis of hollow and colloidal superstructures for the efficient degradation of the organic contaminants rhodamine-B and bisphenol-A. In the case of peroxomonosulfate (PMS)-mediated bisphenol-A degradation, the rate constant of the etched mesoframes was 10,000 times higher indicating their significant catalytic activity.
Our objective in this study was to promote the growth of bone cells on biomedical titanium (Ti) implant surfaces via surface modification involving sandblasting, alkaline etching, and type I collagen immobilization using the natural cross-linker genipin. The resulting surface was characterized in terms topography, roughness, wettability, and functional groups, respectively using field emission scanning electron microscopy, 3D profilometry, and attenuated total reflection-Fourier transform infrared spectroscopy. We then evaluated the adhesion, proliferation, initial differentiation, and mineralization of human bone marrow mesenchymal stem cells (hMSCs). Results show that sandblasting treatment greatly enhanced surface roughness to promote cell adhesion and proliferation and that the immobilization of type I collagen using genipin enhanced initial cell differentiation as well as mineralization in the extracellular matrix of hMSCs. Interestingly, the nano/submicro-scale pore network and/or hydrophilic features on sandblasted rough Ti surfaces were insufficient to promote cell growth. However, the combination of all proposed surface treatments produced ideal surface characteristics suited to Ti implant applications.
Marine mussel-inspired polydopamine (PDA) coatings show excellent hydrophilicity and substrate-independent adhesion ability, but low stability, especially in a harsh environment such as strong acid or strong base, significantly restricts their applications. In this work, we prepare a novel superhydrophilic and underwater superoleophobic coating based on a modified PDA. Diglycidyl resorcinol ether (DGRE) polyethyleneimine (PEI) and iron ions were incorporated into PDA to strengthen the cross-linking and coating durability. By using three chemically inert hydrophobic membranes, polytetrafluoroethylene (PTFE), poly(vinylidene fluoride), and polypropylene, as substrates, we showed that PDA/PEI/DGRE-coated membranes had a water contact angle (CA) of 0° and underwater oil CA above 157°, and their underwater oil SAs were <7°. The coating is durable against both physical and chemical damages including ultrasound and heat treatments, as well as acid/alkaline etching. After ultrasound treatment in water for 60 min, and heating treatment for 3 h, or acid/alkaline etching for 3 h, the coated PTFE membrane still showed water CAs of ∼0° in air and underwater oil CAs of ∼150°. The coated membranes can efficiently separate oil-in-water emulsions, even in strong acid and base environments. The water flux was above 1500 L m−2 h−1, and the oil rejection was above 99%.