Construction of 0D/2D M/rGO@EuMOF Multiscale Heterostructures for Integrated High-Efficiency Microwave Absorption and Corrosion Protection

In the complex world of modern defense and marine engineering, materials face a dual threat that is difficult to solve simultaneously. On one side, advanced radar systems can detect objects from vast distances, making stealth a critical requirement for ships and aircraft. To hide, these vessels need coatings that can swallow radar waves rather than bouncing them back. On the other side, the ocean itself is a relentless enemy. Saltwater and humidity constantly attack metal surfaces, causing rust and structural decay that can eventually destroy a vessel. For decades, scientists have struggled to create a single material that can do both jobs: absorb electromagnetic energy to remain invisible and form a tough barrier to stop corrosion. Usually, materials good at one task fail at the other, or they degrade quickly in harsh environments.

A team of researchers from AVIC Chengdu Aircraft Industrial Group and Southwest Jiaotong University has developed a new approach to this problem by building a composite material that combines two distinct types of structures. They created a hybrid system where tiny, spherical particles are anchored onto flat, sheet-like layers. This design allows the material to act as a sophisticated shield against both radar waves and the corrosive elements of the sea. By carefully balancing the amount of these particles, the team achieved a coating that not only absorbs radar signals with high efficiency but also protects steel from rusting for weeks in salty water, offering a promising path toward more durable and stealthy marine equipment.

The researchers started with a material known as MBene, which is a type of two-dimensional sheet made from iron, aluminum, and boron. These sheets are naturally magnetic and conductive, properties that are useful for interacting with electromagnetic waves. To make them even more effective, the team attached a layer of reduced graphene oxide, a conductive carbon material, to the surface of the MBene sheets. This created a conductive, magnetic foundation. The next step involved growing a third component directly onto this foundation: tiny spheres made from a metal-organic framework containing the element europium. These spheres were grown in place using a hydrothermal process, meaning they were formed in a heated water-based solution. The result was a structure where the flat sheets served as a scaffold for the three-dimensional spheres, creating a multiscale interface where the two materials met.

The team tested how different amounts of these europium spheres affected the performance of the material. They found that the amount of spheres was critical. If there were too few, the material did not absorb radar waves as well as it could. If there were too many, the spheres clumped together and blocked the conductive pathways, causing the material to reflect waves instead of absorbing them. The best balance was found in a specific sample, which they named MG@E3. This sample achieved a minimum reflection loss of -54.02 decibels at a thickness of 2.1 millimeters. In practical terms, this means that when radar waves hit this coating, almost all of the energy is absorbed and dissipated as heat rather than bouncing back to the radar receiver. The material also maintained a wide range of frequencies where it was effective, absorbing waves across a bandwidth of 4.5 gigahertz at a thickness of just 1.4 millimeters.

The mechanism behind this success relies on the unique interaction between the flat sheets and the spheres. When radar waves enter the material, the conductive network of the sheets and the magnetic properties of the MBene help to slow down and trap the waves. The interface between the flat sheets and the spherical particles creates a zone where electrical charges build up and oscillate, a process known as interfacial polarization. This oscillation converts the energy of the radar wave into heat. Additionally, the organic molecules within the spheres act as centers that further disrupt the waves. The researchers confirmed through computer simulations that this specific arrangement allows the waves to enter the material smoothly without being reflected off the surface, and then get trapped and destroyed inside.

Beyond its ability to hide from radar, the material also proved to be an excellent protector against corrosion. The researchers coated steel plates with their composite material and submerged them in a saltwater solution for 21 days. They measured how well the coating prevented the steel from rusting by testing its electrical resistance. The best performing sample in this category, MG@E2, maintained a protection efficiency of 94.8 percent after three weeks in the saltwater. This high level of protection comes from the physical structure of the coating. The flat sheets create a long, winding path that corrosive salt and water must travel to reach the metal underneath, a phenomenon often called a maze effect. The spherical particles fill in the tiny gaps and holes between the sheets, making the barrier even tighter and harder for the corrosive agents to penetrate.

The study also looked at how the material would perform in a real-world scenario by simulating the radar cross-section, which is a measure of how visible an object is to radar. The simulations showed that the coating could reduce the radar signature of a target by approximately 31.85 decibels. This significant reduction means that a ship or aircraft coated with this material would appear much smaller to a radar system, effectively making it harder to detect. The researchers noted that the performance of the material is highly dependent on the precise balance of its components. Too much of the spherical component disrupts the conductive network, while too little fails to provide enough polarization centers to absorb the waves.

This work demonstrates that it is possible to engineer a single material that addresses two of the most challenging problems in marine defense: stealth and durability. By growing spherical particles directly onto conductive magnetic sheets, the researchers created a stable interface that enhances both electromagnetic absorption and physical barrier properties. The findings suggest that with careful control of the material's composition, it is possible to create coatings that are not only effective at hiding objects from radar but also robust enough to withstand the harsh conditions of the ocean for extended periods. The study provides a clear experimental basis for designing future protective systems that can operate reliably in complex environments without sacrificing one function for the other.