New carbide ceramics have become the ＂new favorite＂ of supersonic aircraft coatings?

1. Research status of supersonic aircraft

(1) The "calorie" problem

We know that the high temperature environment experienced by the aircraft is caused by aerodynamic heating, engine gas, and the sun's radiation in space. However, due to aircraft flying in the air for a long time, and some flying speeds are as high as 3 times the speed of sound, the high-temperature materials used must have good high-temperature durability, creep strength, and thermal fatigue strength, and high in air and corrosive media. Oxidation resistance and thermal corrosion resistance, and should have long-term structural stability at high temperatures. Therefore, the high-temperature environment involved in the aviation technology field often includes both high-temperature high-speed airflow and particle erosion.

For example, we know that when an airplane flies at a high altitude at Mach 5, an ultra-high temperature of 2000-3000°C is generated on the surface of the airplane. At this time, the coating material of the airplane is easily destroyed and decomposed at this high temperature. The development of supersonic aircraft must solve the problem of heat accumulation on the surface of the aircraft. At present, scientists have discovered a new carbide ceramic coating that will help supersonic aircraft speed up.

(2) The "dilemma" of aircraft coating materials

In order for the aircraft to fly at supersonic speeds, its surface components must be protected from air damage caused by high pressure and structural components caused by friction. At present, ultra-high temperature ceramics (UHTC) are used to cover the surface of the aircraft. Down can remain stable. These traditional ceramic coating materials are effective in heat resistance, but are very easily deteriorated.

In addition,zirconium diboride is widely used in high-temperature coating materials for aircraft because it can resist oxidation at high temperatures, and has low density and low cost. But the fatal disadvantage is that when boron atoms are oxidized, the boron in zirconium diboride will further promote ablation, which may cause catastrophic consequences.

2. New carbide ceramics help supersonic aircraft flight

Studies have shown that if any material is exposed to a sufficiently high temperature, its molecular chain will loosen and fall off. If it is washed by high-speed particles, it will produce "ablation"; it will also react with oxygen to produce changes in molecular structure. Easily oxidized.

We know that carbide is currently the most high temperature resistant material, represented by the general formula MxCy. According to the different properties of M, carbides are roughly divided into metal carbides and non-metallic metal carbides. Carbide ceramics are the most commonly used high temperature resistant structural ceramics. Common high temperature resistant ceramics include: silicon carbide, zirconium carbide, boron carbide, tungsten carbide, etc. These ceramic materials generally have properties such as high melting point, high hardness and good chemical stability, and are used in many areas of the national economy.

The newly developed carbide coating material can give the coating a super strong and oxidation-resistant structure, which can resist problems such as ablation and oxidation in a high-temperature environment. Studies have shown that introducing this kind of ceramics into carbon fiber reinforced carbon-based composites may be an effective way to improve thermal shock resistance.

The new coating is a ternary alloy mixture made of zirconium, titanium, carbon and boron, which is deposited into a carbon composite by a method called reactive melt infiltration, although it has the same properties as other carbide ceramics Similar, but the relatively low concentration of boron makes it less likely to be ablated, and the carbon structure helps prevent the material from tearing under thermal shock. The experimental results show that the carbide coating shows better ablation resistance at 2000-3000°C.

3. Application prospects of new carbide ceramic coatings

At present, the new coating is widely used in aerospace, because the spacecraft will encounter extreme temperature hazards during the process of passing through the atmosphere. The use of this new carbide ceramic coating will be safer!

Boeing CEO Dennis once said that new supersonic passenger planes may appear in the sky within the next ten years. These planes will shorten travel time by as much as 700%, which means that the flight from Shanghai to New York will be reduced from 15%. Hours reduced to 2 hours!

At present, civil aviation aircraft generally fly at subsonic speeds. Once the civil supersonic aircraft is realized, it will greatly reduce the global travel time and make people's communication more convenient. Although supersonic passenger aircraft has not been widely used in our lives, the discovery of this coating material will undoubtedly help supersonic aircraft to be commercialized as soon as possible!

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