Effect of atomic oxygen on corrosion and friction and wear behavior of polyimide composites

Improved Tribological Performance of MOF@MXene/PI under High Temperature

High-temperature-resistant and self-lubricating polymer composites with long life and high reliability are increasingly indispensable in the aerospace field. Herein, ZIF-67 grown on the MXene lamella was successfully prepared, and ZIF-67@MXene/PI composites with a regular layered structure were obtained by a hot-pressing three-dimensional network aerogel. It was revealed that incorporating ZIF-67@MXene into PI dramatically reduced the friction and abrasion with elevated temperatures. Largely, aerogel walls always paralleled the sliding direction by compressing, providing a significant antifriction effect. More notably, the presence of a vigorous tribofilm composed of a PI matrix and a diamond-type lattice MOF-modified MXene provided rolling and sliding interface friction under high temperatures, simultaneously. In addition, the uniform tribofilm with a thickness of about 200 nm can effectively avoid the direct contact of the friction pair during the sliding process. Hence, the combination of the constructed multiscale nanocomposites and nanostructured tribofilm with outstanding tribological performance endow the material potentially useful in reducing energy consumption, thus addressing the energy wastage problem caused by friction.

Mechanically Robust Irradiation, Atomic Oxygen, and Static-Durable CrOx/CuNi Coatings on Kapton Serving as Space Station Solar Cell Arrays

The polymers that served for solar cell arrays are constantly subject to various hazards, such as atomic oxygen (AO), ion irradiation, or electrostatic discharge (ESD) events. To address these issues, we fabricated and sifted CrO_0.16/CuNi-coated Kapton with a gradient structure with the goal of reaching an equilibrium between AO durability and resistance. The resulting material exhibits an impressively low E_y of 6.61 × 10^-26 cm³ atom^-1, 2.20% of which was detected as pristine Kapton. Self-evolution of the CrO_0.16 coating under 525.4 displacement per atom (dpa) Fe⁺ ion irradiation indicated that it can still maintain a good state of ultrafine nanocrystalline in addition to local amorphization. Its AO-based degradation and irradiation evolution are demonstrated by molecular dynamics (MD) simulations. It is mechanically robust enough to endure the cyclic folding treatments attributed to its gradient structure fabrication. Moreover, the CrO_0.16/CuNi-coated Kapton exhibits alleviated electrostatic accumulation capability and sufficient conductivity. Our strategy has promising potential for creating surface protection on flexible polymers operating in the low Earth orbit (LEO).