Low Adhesion Research Articles

Pulse current electroforming of Ni-PTFE nanocomposite mold insert with long-lifetime and anti-adhesive properties

Polymeric micro features tend to deform and break under the demolding force during injection molding process, which becomes a bottleneck problem limiting its precision manufacturing. To reduce the polymer-mold interfacial adhesion, nickel-polytetrafluoroethylene (Ni-PTFE) nanocomposite molds with low surface adhesion and high wear resistance were manufactured via pulse current electroforming. The electrodeposited Ni-PTFE nanocomposite showed a good hydrophobic property and low friction coefficient (between 0.1 and 0.3) than pure nickel (0.78). Compared with direct current, pulse current electrodeposition was beneficial to reduce the crystallite size and internal stress, thus improving the wear resistance and reducing the cracking defects. The hardness of pulse current electrodeposited Ni-PTFE reached 442.3 HV, which was 51.7 % higher than that of pure nickel. Compared to nickel mold, Ni-PTFE nanocomposite mold significantly improved the dimensional accuracy of molded microfluidic chips. This study systematically investigates the Ni-PTFE nanocomposite electroforming process under both direct and pulse currents, which provides a new approach for the manufacturing of high-performance precision injection mold insert.

High-efficiency and low-damage modification of engineering metal materials by oxygen-mixing atmospheric pressure cold plasma jets

Engineering metal materials have been widely developed and applied in aviation, aerospace and biomedicine fields. Wettability improvement of these materials can alleviate problems caused by low adhesion and poor bioactivity, thereby facilitating their practical applications. Compared with other methods, atmospheric pressure cold plasma treatment has better versatility and can efficiently improve wettability without causing serious damages, and has therefore been widely used in polymer hydrophilization. However, when treating metal materials, the cold plasma may induce surface breakdown or have low efficiency. In this paper, we developed a new cold plasma jet by mixing oxygen into working gas to achieve high-efficiency and low-damage modification. When oxygen mixing ratio was 0.4 %, the cold plasma jet could modify TC4 titanium alloy surface to be superhydrophilic within 20 s, which was much more efficient than traditional plasma jet (120 s). We then further investigated the mechanism contributing to higher efficiency, and found that the oxygen-mixing plasma jet did not cause serious damages, while generating more polar groups by higher-concentration active particles, as confirmed by surface energy calculation and optical emission spectra. Besides titanium alloy, the oxygen-mixing plasma jet could also achieve rapid hydrophilization of various engineering metal materials, showing promising application prospects.

Awareness of possible complications associated with direct composite restorations: A multinational survey among dentists from 13 countries with meta-analysis

ObjectivesResin-based composites (RBCs) evolved into favoured materials for teeth restorations, marking a significant change in dental practice. Despite many advantages, RBCs exhibit various limitations in their physical and chemical properties. Therefore, we assessed the dentists' awareness of possible complications after direct composite restorations and their opinions about this material. MethodsThe online questionnaire was created in English in May 2023. A 16-item survey was dedicated to general dentists and specialists. The first section included four questions related to demographic characteristics. The second section comprised twelve questions and focused on awareness of potential side effects of composite restorations, the most crucial advantages and disadvantages of composite resins, and the frequency of experienced clinical complications after the application of composite materials. ResultsA total of 1830 dentists from 13 countries took part in the survey. Dentists most often declared awareness of low adhesion to the dentine (77.5 %) and, most rarely, solubility in oral fluids (42.6 %). Aesthetics was identified as the main advantage of composite fillings (79 %), followed by the possibility of repair (59 %) and adhesion to enamel (57 %). Polymerisation shrinkage was a major disadvantage for most countries (70 % overall). Analysing the declared potential clinical complications for all countries, statistically significant findings were obtained for marginal discolouration (OR=2.982, 95 % CI: 1.321–6.730, p-value=0.009) and borderline significance for secondary caries (OR=1.814, 95 % CI: 0.964–3.415, p-value=0.065). ConclusionsDentists value aesthetics and repairability but are aware of shrinkage and experience discolouration. The issue of toxicity and solubility seems to be the least known to dentists.Clinical significance: Dentists should use RBCs with critical caution due to possible side effects. Despite the undoubted aesthetics of direct composite restorations, it is necessary to remember potential clinical complications such as marginal discolouration or secondary caries.

Tailoring exfoliated 2D Mo-PDA nanopetals as sustainable intelligent anti-corrosion nanoreservoir for upgrading the self-healing/barrier function of epoxy coatings

The present study unfurled novel route to tailor cutting-edge molybdenum-polydopamine (AHPDA) and molybdenum-polydopamine-Ce3+/4+ nanocarriers (AHPDA@Ce) using in-situ self-nucleophilic polymerization techniques and scrutinized their intelligent anti-corrosion and physicomechanical properties in solution and coating phases. The manageable emancipation of Ce3+/4+,MoO42-, polydopamine (PDA) derivatives from exfoliated AHPDA and AHPDA@Ce nanocarriers at the extract solutions brilliantly reduced the icorr from 5.14 to 2.22 and 1.45 µA/cm2, respectively. Afterward, the derivatives assembled intricate barrier films at the electrochemical active sites, outstandingly restricting the severe corrosion on steel panels immersed in AHPDA@Ce and AHPDA extract solutions. Moreover, even after 48 h immersion, not only did the scratched EAHC (containing AHPDA@Ce nanocarriers) and EAHM (including AHPDA nanocarriers) coatings exhibit superior self-healing protection by 382 % and 327 % promotion in RTotal towards NE coatings (neat epoxy), but also intelligent EAHC and EAHM coatings tolerated the salt spray condition up to 1000 h exposure rather than 400 h of NE coating. Also, the intact EAHC and EAHM coatings after 24 weeks of submersion with noteworthy log|Z|0.01Hz of 10.51 and 9.98 Ω cm2 showcased boosted barrier-passive function lifetime with respect to the NE coatings (5.68 Ω cm2). Furthermore, smart EAHM and EAHC nanocomposites flaunted lower adhesion loss of 2.3 and 5.2 times, respectively, as well as, an incredible 76.11 % and 31.50 % improvement in the reduction of cathodic peel-off area regarding the NE coating. Ultimately, smart EAHC and EAHM coatings could be employed as eco-friendly effective anti-corrosion coatings with terrific self-healing/barrier function and durable service life in strategic knowledge edge applications.

Analysis of Experimental Biaxial Surface Wrinkling Pattern Based on Direct 3D Numerical Simulation.

This paper presents a direct 3D numerical simulation of biaxial surface wrinkling of thin metal film on a compliant substrate. The selected compliant substrate is a commercial Scotch tape on which a gold metal thin film has been transferred by using low adhesion between the thin metal film and polyimide substrate. Compared with the previous fabrication of a cylindrical thin-film wrinkling pattern, an undulated wrinkling pattern has been implemented by increasing the width of the thin metal film in order to create biaxial straining in the thin film. To understand the wrinkling behavior due to biaxial loading, a simple direct numerical simulation based on material imperfections defined in the compliant substrate has been conducted. Through modeling and simulation, it was found that the wrinkling mode is determined by the biaxiality ratio (BR), the ratio between transversal strain and longitudinal strain. Depending on the BR, the wrinkling mode belongs to one of the cylindrical, undulated (or herringbone), checkerboard, or labyrinth modes as a function of applied strain. The cylindrical wrinkling is dominant at the input of BR less than 0.5, while the undulated (or herringbone) ones become dominant just after the onset of the wrinkling pattern at BR greater than 0.9. Through the comparison of the wrinkling patterns between simulation and experiment, the applied BR of the fabricated thin film has been successfully estimated.

Dialdehyde cellulose (DAC) and polyethyleneimine (PEI) coated polyvinylidene fluoride (PVDF) membrane for simultaneously removing emulsified oils and anionic dyes

Developing high-efficiency membrane for oil and dye removal is very urgent, because wastewater containing them can cause great damage to human and environment. In this study, a coated membrane was fabricated by applying DAC and PEI onto the commercial PVDF microfiltration membrane for supplying the demand. The coated membrane presents superhydrophlic and superoleophobic properties with a water contact angle of 0o and underwater oil contact angle exceed 150°, as well as excellent low underwater oil adhesion performance. The coated membrane shows high separation efficiency exceeded 99.0% and flux 350.0 L·m−2·h−1 when used for separating for six kinds of oil including pump oil, sunflower oil, n-hexadecane, soybean oil, diesel and kerosene in water emulsions. Additionally, the coated membrane can effectively remove anionic dyes, achieving rejection rates of 94.7%, 93.4%, 92.3%, 90.7% for the CR, MB, RB5, AR66, respectively. More importantly, the membrane was able to simultaneously remove emulsified oil and soluble anionic dyes in wastewater containing both of them. Therefore, this novel coated membrane can be a promising candidate for treating complex wastewater.

Inflammatory, metabolic, and endothelial biomarkers before and after pregnancy complications.

Women with gestational diabetes mellitus (GDM), hypertensive disorders of pregnancy (HDP), and preterm birth (PTB) have excess cardiovascular disease compared with those with uncomplicated births, perhaps related to prepregnancy inflammation, dysmetabolism, or endothelial dysfunction. We included 1238 women in the Coronary Artery Risk Development in Young Adults Study (1985-2011) with 2215 births classified according to outcomes (term, uncomplicated births were the referent). Using repeated measures analysis of variance, we estimated prepregnancy and postpregnancy biomarkers, as well as biomarker change according to pregnancy outcomes, adjusted for confounders. GDM and term HDP groups had higher prepregnancy high-sensitivity C-reactive protein (hsCRP) (+0.37 [95% CI, 0.08-0.65]; +0.29 [95% CI, 0.04-0.55] log mg/L), higher leptin (+0.29 [95% CI, 0.09-0.50]; +0.37 [95% CI, 0.17-0.56] log ng/ml), and lower adiponectin (-0.25 [95% CI, -0.36 to -0.13); -0.11 [95% CI, -0.22 to -0.01] log ng/ml) values than those with uncomplicated births, and these profiles persisted in magnitude postpregnancy. Controlling for body mass index attenuated most profiles, except that lower prepregnancy adiponectin remained associated with GDM. PTB without HDP or GDM was related to lower prepregnancy hsCRP and soluble intercellular adhesion molecule-1 (-0.31 [95% CI, -0.56 to -0.06] log mg/L; -0.05 [95% CI, -0.09 to -0.01] log ng/ml) and a larger leptin increase from before to after pregnancy (+0.20 [95% CI, 0.02-0.37] log ng/ml). Prepregnancy inflammation and metabolic dysfunction contributed to GDM and HDP, perhaps due to higher body mass index. PTB may be related to adverse metabolic changes postpregnancy, although the unexpected endothelial biomarker profile warrants further study.

Influence of Cr + Si content variation on cutting behavior of TiAlCrSiN HPPMS coatings

As high power pulse magnetron sputtering (HPPMS) technology is becoming popular in cutting tool industry, the development of nanocomposite coating systems such as TiAlCrSiN with this technology presents a new research avenue. Here, the combined effect of Cr and Si contents on properties and cutting behavior of high Al content TiAlCrSiN HPPMS coatings needs further investigation. For this purpose, three HPPMS coatings with Al/Ti ratio x = 1.4–1.5 and varying Cr + Si content, namely (Ti28Al40Cr16Si16)N, (Ti30Al43Cr17Si10)N and (Ti36Al54Cr5Si5)N, were deposited on cemented carbide substrates. In addition to basic characterization, the fracture behavior of the coatings was characterized by scratch tests. The cutting behavior of the coated inserts was exemplarily investigated during dry cutting of normalized medium carbon steel C45 with cutting speed vc = 80 m/min, feed rate f = 0.12 mm and cutting depth ap = 0.8 mm. The tool damage over the cutting time of tc = 35–40 min, as per the tool condition, was observed using light microscopy. Moreover, the damage mechanisms were analyzed in detail at the end of the cutting test using scanning electron microscopy. All coatings showed comparable indentation hardness HIT and indentation modulus EIT. However, an increased Cr + Si content amplified the brittle fracture of the coating under sliding load of scratch test. Moreover, the workpiece material C45 showed a higher adhesion tendency to cutting insert with high Cr + Si content TiAlCrSiN coatings during cutting tests. The tool wear and built-up edge formation increased due to the combined effect of workpiece adhesions and amplified brittle fracture of the coating at considered cutting speed. On the other hand, the inserts with low Cr + Si content coating exhibited better cutting performance and reduced built-up edge formation based on the improved fracture behavior of the coating and lower adhesion tendency of workpiece material to the corresponding coated insert.

Reducing Ice Adhesion to Polyelectrolyte Surfaces by Counterion-Mediated Nonfrozen Hydration Water.

Hydrophilic anti-icing coatings can be energy-effective passive solutions for combating ice accretion and reducing ice adhesion. However, their underlying mechanisms of action remain inferential and are ill-defined from a molecular perspective. Here, we systematically investigate the influence of the counterion identity on the shear ice adhesion strength to cationic polymer coatings having quaternary alkyl ammonium moieties as chargeable groups. Temperature-dependent molecular information on the hydrated polymer films is obtained using total internal reflection (TIR) Raman spectroscopy, complemented with differential scanning calorimetry (DSC) and ellipsometry. Ice adhesion measurements show a pronounced counterion-specific behavior with a sharp increase in adhesion at temperatures that depend on the anion identity, following the order Cl- < F- < SCN- < Br- < I-. Linked to the freezing of hydration water, the specific ordering results from differences in ion pairing and the amount of water present within the polymer film. Moreover, similar effects can be promoted by varying the cross-linking density in the coating while keeping the anion identity fixed. These findings shed new light on low ice adhesion mechanisms and may inspire novel approaches for improved anti-icing coatings.

Preparation of Durable Superhydrophobic Coatings Based on Discrete Adhesives

Due to the low adhesion observed at the interface between solid and liquid, superhydrophobic coatings hold significant promise for various applications, such as self-cleaning, anti-corrosion, anti-icing, and drag reduction. However, a notable challenge hindering their widespread adoption in these domains lies in their delicate durability. In this study, we propose a straightforward method for preparation. The fluorosilicone resin is initially discretized through a gradual introduction of nonsolvent into its solution, followed by thorough mixing and stirring with silica nanoparticles. The resulting mixture is then sprayed onto the substrate surface after drying, forming a self-similar, porous, and rough structure extending from top to bottom. This process yields a coating exhibiting excellent chemical and mechanical durability simultaneously. Using this approach, we achieved a superhydrophobic coating with a contact angle of 156° and a roll angle of 2.2°, with water droplet adhesion of only 10.8 ± 0.4 µN. Remarkably, the coating maintained excellent superhydrophobicity even after undergoing sandpaper abrasion (10 m), tape peeling (30 times), and prolonged water impact (60 min), showing its robust mechanical stability. Furthermore, following exposure to acid, alkali, and aqueous solutions (7 days), UV irradiation (10 days), and extreme temperature variations (–20 °C to 80 °C), the coatings retained their superhydrophobic properties and exhibited good chemical durability. This method offers a novel approach to enhance the durability and practicality of superhydrophobic coatings.

Thermal Properties' Enhancement of PLA-Starch-Based Polymer Composite Using Sucrose.

Polylactic-acid-starch-based polymer composite (PLA/TPS) has good thermal stability for biocomposites. However, the physical and mechanical properties of PLA/TPS do not meet the standards. It needed additives to enhance its physical and mechanical properties. The aim was to improve the physical and mechanical properties of PLA/thermoplastic starch using sucrose. In addition, this study evaluated the enhancement of thermal properties of PLA/thermoplastic starch using sucrose. This study used sucrose as an additive to enhance the PLA/TPS composite. The addition of sucrose inhibits the degradation of biocomposites. This means that thermal stability increases. The thermal stability increased because the degree of crystallinity increased with the addition of sucrose, which was also proven in the XRD result. The addition of sucrose caused the morphology of the biocomposite to have pores. The FESEM results showed that biocomposites with the addition of sucrose had pores and gaps. These gaps result from low adhesion between polymers, causing a decrease in the mechanical and physical properties of the sample. Based on the FTIR spectra, biocomposite PLA/TPS blends with the addition of sucrose still have many hydroxyl groups that will lead to attracting other molecules or ions, such as oxygen or water. This phenomenon affects the physical and mechanical properties of materials. The physical and mechanical properties increased with sucrose addition. The best composite was prepared using 3% sucrose. This is because sucrose has a crystalline structure that affects the properties of biocomposites. However, the addition of 3% sucrose was not as effective as that of neat PLA.

Preparation and physicochemical properties: a new extruded rice using cassava starch and broken rice flour

With the increasing demand for nutrition and health, many researchers are trying to develop a rice product with lower aging rate and convenient nutrient fortification. Being composed of high amylopectin content, cassava starch (CS) shows a lower retrogradation tendency compared to rice starch. So, it has a broad application prospect to partially replace rice starch with CS in rice by extrusion technology. In this study, a new extruded rice (ER) was prepared by broken rice flour and CS using single-screw extruder through “improved extrusion cooking technology,” and the maximum addition level of CS in ER was 30%. Color parameters and texture profile analysis showed that ER was a little darker in appearance with lower hardness, adhesiveness and chewiness. Rapid visco analysis demonstrated that the viscosity of ER paste appeared earlier during the initial heating phase and displayed a lower retrogradation trend than normal rice in the cooling process. The gelatinization temperature and gelatinization enthalpy decreased with the increasing CS in ER, while the degree of gelatinization increased to 76.36% when the content of CS was 30% after extrusion. The X-ray diffraction patterns of control was typical A-type structure, while ER changed to V-type structure with a lower degree of crystallinity. The microstructure observation showed that ER exhibited a looser and more porous structure with increasing the content of CS, which facilitated easier cooking and nutritional enhancement.

Effect of fat on physicochemical, rheological, textural and sensory properties of Ricotta cheese spreads

SummaryThe effect of different fat contents of milk and cheese whey mixture (20:80) on physicochemical, rheological and sensory properties of Ricotta cheese spread (RCS) was evaluated. Four types of product such as no‐fat milk (NFM)‐RCS, low‐fat milk (LFM)‐RCS, medium‐fat milk (MFM)‐RCS and full‐fat milk (FFM)‐RCS were prepared from Ricotta cheese curd added with salt (1.5%) and guar gum (0.4%). The NFM‐RCS had higher (P &lt; 0.05) protein, ash, acidity, dynamic modulus (G' and G"), critical stress, firmness, work of shear, stickiness, work of adhesion values and lower fat, and pH, L*, a*, b* values when compared with LFM‐, MFM‐ and FFM‐RCS. Except spreadability, highest sensory scores for all other attributes were found in MFM‐RCS when compared with other experimental samples. This study indicated that increase in fat content or decrease in protein content of RCS samples produced lower viscoelastic modulus values, firmness, stickiness, adhesiveness and higher spreadability, yield, solids recovery and highly acceptable sensory characteristics.

Preparation of superhydrophobic asymmetric vitrimer coating with high porosity and the key role of hierarchical pocket structure on long freeze delay time and high durability

AbstractIt is still a big challenge to prepare superhydrophobic anti‐icing coatings with long freeze delay performance and high durability. In this work, in different with conventional flexible porous coating, we prepared an asymmetric coating with hierarchical pocket structure by a facile hot‐pressing/salt‐leaching (BHS) method on a polyacrylate vitrimer polymer with mellability. The asymmetric architecture endowed porous coating with low density and high adhesion strength. The in‐situ growth of silica nanoparticles in above porous coating and surface modification generated a superhydrophobic hierarchical pocket structure. As a result, the freezing delay time was drastically increased to 14,400 s at −10°C. Furthermore, owing to hierarchical pocket structure, the coating could maintain its superhydrophobicity and anti‐icing performance under water flow impacting at 10 kPa pressure, 30 cycles of sandpaper abrasion, 50 cycles of tape peeling, showing advantageous high durability. By employing the hierarchical porous coating on heat exchangers, the energy consumption was drastically reduced by 93%.

Self-regulated secretory materials for long-term icephobicity

Passive icephobic coatings attract increasing attention due to their harmless strategy for preventing undesirable ice accumulation. Slippery liquid-infused surfaces display extremely low ice adhesion (τice) but are argued for their poor stabilities and longevities due to inevitable liquid consumption. Herein we reported a class of lubricated polysiloxane coatings that can maintain low τice (∼2.2 kPa) for a long time (>800 icing/deicing cycle). The coatings have slippery lubricated surfaces and switchable porous matrices loading a large amount of liquid in isolated porevoids. Such droplet-embedded structure allows the surfaces to continuously maintain highly swelling states in a self-adaptive manner, i.e., only in the conditions icing or oil consumption occur dose oil is released, and thus show excellent long-term icephobicity. Besides, these materials exhibit good mechanical properties, antifatigue, and substrate adhesion. Because the coatings can be prepared via facile and green method from cheap starting materials, we foresee their broad application prospect in many fields.

Preparation of a long-lasting tablet of spinosad microspheres and its residual insecticidal efficacy against the yellow fever mosquito, Aedes aegypti (Diptera: Culicidae) larvae.

In order to provide a long-lasting formulation for spinosad (SP) targeting larval stages of Aedes aegypti (Linnaeus) and others alike, a SP tablet was developed based on microspheres, using polylactic acid as inside coating material. The microspheres were encapsulated using polyethylene glycol and 1-hexadecanol to form a sustained-release SP tablet. Micromorphology, active ingredient loading, structure identification, photolysis resistance and biological activity were evaluated in this report. (i) The SP microspheres had an average particle size of 6.16 ± 2.28 μm, low adhesion and good dispersion as evaluated by scanning electron microscopy and morphology. (ii) The average active ingredient loading and encapsulation of SP microspheres were 32.80 ± 0.74% and 78.41 ± 2.22%, respectively. (iii) The chemical structure of encapsulated SP was confirmed by Fourier transform infrared and 1H-nuclear magnetic resonance. (iv) The photostability of the microspheres and the tablets were evaluated. The results showed that DT50 (time required to dissipate 50% of the mass originally present) of SP was 0.95 days in microspheres and 6.94 days in tablets. (v) The long-term insecticidal activity of SP tablets was investigated, and the tablet had a long-lasting activity against the mosquito larvae, showing 100% larval mortality for 63 days. The study provided a new long-lasting formulation of SP, which displayed good efficacy in the control of Ae. aegypti larvae. © 2024 Society of Chemical Industry.

Pesticide loaded nanohydrogel based on attapulgite and gelatin with improved foliar adhesion.

Pesticides have been widely applied to promote plant growth due to their high insecticidal efficiency. However, most pesticides easily slip from the leaf surface due to the low foliar adhesion, leading to significant damage to the environment and human health. Increasing foliar adhesion of pesticides has been a major challenge. Nanomaterial technology, which can deliver pesticide active ingredients, offers a new opportunity to increase pesticides efficacy with higher foliar adhesion. In this study, we prepared the pesticide loaded nanohydrogel ALP@Ge-g-P(AA-co-AM)/ATP by grafting attapulgite and gelatin onto P(AA-co-AM), and loading the pesticide alphacypermethrin synchronously via the emulsion solvent evaporation method. The size of the new nanohydrogel was 20.5 nm and the pesticide loading capacity was 21.5%. Compared to P(AA-co-AM), the water absorbency of Ge-g-P(AA-co-AM)/ATP increased by 54.3% in 120 min, while the water retention increased from 4.27% to 38.7% after 48 h. Washout experiments and contact angle results suggested that the nanohydrogel, with a contact angle of 44.8° indicating good wettability, can resist rain flush and increase foliar adhesion naturally. Overall, the preparation of pesticide loaded nanohydrogel is simple. Experiments demonstrated the pesticide loaded nanohydrogel has high efficiency and strong foliar adhesion. This makes it a promising candidate for spraying application and reducing pollution levels. © 2024 Society of Chemical Industry.

Enhancing wear resistance and mechanical property of epoxy coating via “roller wheel” liquid metal‐MXene

AbstractThis work presents a design of a unique “roller wheel” structure combining rigid MXene and flexible liquid metal (LM), aiming to construct an epoxy composite coating with simultaneous advanced mechanical strength and lubrication properties. The antiwear property of the epoxy composites is improved by 72.8% when the LM is 0.5 wt% and MXene is 0.03 wt%. The incorporation of LM‐MXene improved the mechanical properties of the epoxy composite coating, resulting in an approximately 136.6% increase in elastic modulus. The unique “roller wheel” structure provides additional mechanical support and leads to lower adhesion between the MXene layers and LM. As a result, LM reduces the stripping and sliding of the interface between MXene layers during the friction process, further enhancing the lubrication performance of the epoxy composite coating.

Alginate-based water-soluble adhesives: effect of incorporated phenolic hydroxy groups on adhesiveness

Abstract Alginic acid (Alg) was modified with tyramine (TA), homoveratrylamine (HVTA), and 2-phenylethylamine (PA) to obtain Alg-based adhesives, AlgTA, AlgHVTA, and AlgPA. The adhesiveness of the modified Algs were evaluated and compared with previously reported catechol-modified alginate, AlgDA. AlgTA showed adhesion tendency differently from AlgDA, depending on the incorporation ratios of TA. AlgHVTA with protected phenolic hydroxy groups showed lower adhesiveness than AlgDA for mica surfaces, but higher for polymethyl methacrylate surfaces. AlgPA without a phenolic hydroxy group also exhibited moderate adhesiveness for mica.

Solid lubrication performance of hybrid Ti3C2Tx/MoS2 coatings

MXenes have gained notable attention in tribology due to their excellent wear resistance based on the formation of beneficial tribofilms. However, studies using MXenes as solid lubricants have mainly focused on multi-layer Ti3C2Tx coatings, while little is known about the tribological performance of MXene composites. Therefore, our study aims at scrutinizing and understanding the tribological behavior of MXenes and MXene composites as solid lubricants under reciprocating sliding conditions. Theoretical predictions regarding the resulting interlayer adhesion and coating-substrate adhesion helped to design the hybrid coatings. Multi-layer Ti3C2Tx, molybdenum disulfide (MoS2) and two hybrid coatings using Ti3C2Tx and MoS2 (random mixture and sandwich-like) were spray-coated onto steel substrates with a coating thickness of about 800 nm. Dry sliding tests using a steel ball as counter-body were carried out at room temperature. The coatings’ morphology and formed tribofilms were holistically characterized by scanning and transmission electron microscopy (SEM, TEM) as well as X-ray photoelectron spectroscopy (XPS). Our results demonstrate that both hybrid coatings notably reduce friction and wear, outperforming their respective pure coatings (Ti3C2Tx and MoS2). This is attributed to synergistic effects between Ti3C2Tx and MoS2, with adhesion forces appearing to be the governing mechanism in enhancing the formation of stable tribofilms. Numerical calculations validate our experimental results, verifying that hybrid coatings exhibit low interlayer friction and high adhesion to ferrous substrates. Consequently, our work reveals the potential of Ti3C2Tx/MoS2 hybrid coatings to further optimize friction and wear.