coating materials
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2022 ◽  
Yancheng Meng ◽  
Henggao Xiang ◽  
Jianqiang Zhang ◽  
Zhili Hu ◽  
Jun Yin ◽  

Abstract Stiff membranes on soft substrates may wrinkle and fold during compression1-11, but the strong post-buckling nonlinearity3,12 and the propensity of overall bending of these systems4,9,11 under large compression make the intriguing morphological evolution ill-controlled and less understood. Here, we present a simple peeling strategy that controllably makes stiff nanomembranes on soft microfilms wrinkled, then folded with a preset period, and ultimately fractured into regular ribbons. The fold and fracture periods exhibit a quantized, stepped dependence on the microfilm thickness, with the period doubled per step. The controlled wrinkle-to-fold-to-fractures transitions can be quantified by both computations and a scaling law, showing generality to different forms of compressive loading. This quantized wrinkle evolution deepens our understanding of complex behaviors of such natural and artificial systems as cerebral cortexes, skins, and coating materials, and opens a way to advanced manufacturing by fracturing large-area nanomembranes into uniformly shaped microflakes.

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 107
Vasily Pozdnyakov ◽  
Sören Keller ◽  
Nikolai Kashaev ◽  
Benjamin Klusemann ◽  
Jens Oberrath

Laser shock peening (LSP) is a surface modification technique to improve the mechanical properties of metals and alloys, where physical phenomena are difficult to investigate, due to short time scales and extreme physical values. In this regard, simulations can significantly contribute to understand the underlying physics. In this paper, a coupled simulation approach for LSP is presented. A global model of laser–matter–plasma interaction is applied to determine the plasma pressure, which is used as surface loading in finite element (FE) simulations in order to predict residual stress (RS) profiles in the target material. The coupled model is applied to the LSP of AA2198-T3 with water confinement, 3×3mm2 square focus and 20 ns laser pulse duration. This investigation considers the variation in laser pulse energy (3 J and 5 J) and different protective coatings (none, aluminum and steel foil). A sensitivity analysis is conducted to evaluate the impact of parameter inaccuracies of the global model on the resulting RS. Adjustment of the global model to different laser pulse energies and coating materials allows us to compute the temporal pressure distributions to predict RS with FE simulations, which are in good agreement with the measurements.

Friction ◽  
2022 ◽  
Shuaihang Pan ◽  
Kaiyuan Jin ◽  
Tianlu Wang ◽  
Zhinan Zhang ◽  
Long Zheng ◽  

AbstractMetal matrix nanocomposites (MMNCs) become irreplaceable in tribology industries, due to their supreme mechanical properties and satisfactory tribological behavior. However, due to the dual complexity of MMNC systems and tribological process, the anti-friction and anti-wear mechanisms are unclear, and the subsequent tribological performance prediction and design of MMNCs are not easily possible: A critical up-to-date review is needed for MMNCs in tribology. This review systematically summarized the fabrication, manufacturing, and processing techniques for high-quality MMNC bulk and surface coating materials in tribology. Then, important factors determining the tribological performance (mainly anti-friction evaluation by the coefficient of friction (CoF) and anti-wear assessment with wear rate) in MMNCs have been investigated thoroughly, and the correlations have been analyzed to reveal their potential coupling/synergetic roles of tuning tribological behavior of MMNCs. Most importantly, this review combined the classical metal/alloy friction and wear theories and adapted them to give a (semi-)quantitative description of the detailed mechanisms of improved anti-friction and anti-wear performance in MMNCs. To guarantee the universal applications of these mechanisms, their links with the analyzed influencing factors (e.g., loading forces) and characteristic features like tribo-film have been clarified. This approach forms a solid basis for understanding, predicting, and engineering MMNCs’ tribological behavior, instead of pure phenomenology and experimental observation. Later, the pathway to achieve a broader application for MMNCs in tribo-related fields like smart materials, biomedical devices, energy storage, and electronics has been concisely discussed, with the focus on the potential development of modeling, experimental, and theoretical techniques in MMNCs’ tribological processes. In general, this review tries to elucidate the complex tribo-performances of MMNCs in a fundamentally universal yet straightforward way, and the discussion and summary in this review for the tribological performance in MMNCs could become a useful supplementary to and an insightful guidance for the current MMNC tribology study, research, and engineering innovations.

2022 ◽  
pp. 289-310
Alexandre Jerónimo ◽  
Barroso Aguiar ◽  
Célia Soares ◽  
Nelson Lima

Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 151
Monica Boffito ◽  
Lucia Servello ◽  
Marcela Arango-Ospina ◽  
Serena Miglietta ◽  
Martina Tortorici ◽  

The replication method is a widely used technique to produce bioactive glass (BG) scaffolds mimicking trabecular bone. However, these scaffolds usually exhibit poor mechanical reliability and fast degradation, which can be improved by coating them with a polymer. In this work, we proposed the use of custom-made poly(urethane)s (PURs) as coating materials for 45S5 Bioglass®-based scaffolds. In detail, BG scaffolds were dip-coated with two PURs differing in their soft segment (poly(ε-caprolactone) or poly(ε-caprolactone)/poly(ethylene glycol) 70/30 w/w) (PCL-PUR and PCL/PEG-PUR) or PCL (control). PUR-coated scaffolds exhibited biocompatibility, high porosity (ca. 91%), and improved mechanical properties compared to BG scaffolds (2–3 fold higher compressive strength). Interestingly, in the case of PCL-PUR, compressive strength significantly increased by coating BG scaffolds with an amount of polymer approx. 40% lower compared to PCL/PEG-PUR- and PCL-coated scaffolds. On the other hand, PEG presence within PCL/PEG-PUR resulted in a fast decrease in mechanical reliability in an aqueous environment. PURs represent promising coating materials for BG scaffolds, with the additional pros of being ad-hoc customized in their physico-chemical properties. Moreover, PUR-based coatings exhibited high adherence to the BG surface, probably because of the formation of hydrogen bonds between PUR N-H groups and BG surface functionalities, which were not formed when PCL was used.

2021 ◽  
Vol 9 (3) ◽  
pp. 953-960
Widya Dwi Rukmi Putri ◽  
Syarifa Ramadhani Nurbaya ◽  
Erni Sofia Murtini

The aim of this research was evaluated the effect of type and ratio of coating materials on characteristics of betacyanin extract microencapsulated by freeze drying. The combination was consisted of maltodextrin+gum arabic (MD+GA), maltodextrin+carboxymethyl cellulose (MD+CMC), maltodextrin+carrageenan (MD+C), and maltodextrin (MD) with ratio 3:1 and 4:1 (w/v) to the extract. Betacyanin microcapsules was analyzed for its characteristics, including encapsulation efficiency and microstructure. The result showed type and ratio of coating materials significantly influenced moisture content, color, and bulk density of the microcapsules (p<0,05). MD+GA coating material had the highest value of encapsulation efficiency (99.41 %). Microstructure analysis of the microcapsules showed it had amorphous shape. Betacyanin microcapsules from red dragon peel was potential to be natural food colorant.

2021 ◽  
Ding Lou ◽  
Hammad Younes ◽  
Jack Yang ◽  
Bharat Jasthi ◽  
George Hong ◽  

Abstract Carbon nanotubes (CNTs) and nanofibers (CNFs) are well-known nano additives that produce coating materials with high electrical and thermal conductivity and corrosion resistance. In this paper, coating materials incorporating hydrogen bonding offered significantly lower electrical resistance. The hydrogen bonding formed between functionalized carbon nanotubes and ethanol helped create a well-dispersed carbon nanotube network as the electron pathways. Electrical resistivity as low as 6.8 Ω⋅cm has been achieved by adding 4.5 wt.% functionalized multiwalled carbon nanotubes (MWNT-OH) to 75%Polyurethane/25%Ethanol. Moreover, the thermal conductivity of Polyurethane was improved by 332% with 10 wt.% addition of CNF. Electrochemical methods were used to evaluate the anti-corrosion properties of the fabricated coating materials. Polyurethane with the addition of 3 wt.% of MWNT-OH showed an excellent corrosion rate of 5.105×10-3 mm/year, with a protection efficiency of 99.5% against corrosive environments. The adhesion properties of the coating materials were measured following ASTM standard test methods. Polyurethane with 3 wt.% of MWNT-OH belonged to class 5 (ASTM D3359), indicating the outstanding adhesion of the coating to the substrate. These nano coatings with enhanced electrical, thermal, and anti-corrosion properties consist of a choice of traditional coating materials, such as Polyurethane, yielding coating durability with the ability to tailor the electrical and thermal properties to fit the desired application.

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