Have you heard enough about organic polymer materials—now, how about inorganic ones?

It's the "top-tier" player in the ultra-high-temperature coating industry—polysilazane.

What are the main characteristics of polysilazane?

Its molecular backbone is composed of Si-N bonds, which have small bond angles, causing the molecules to "pull" tightly against each other. This makes it difficult for the molecular chains to coil into rings, and consequently reduces the likelihood of disruptive side reactions, such as rearrangements, during the polymerization process.
The difference in electronegativity between Si and N makes the Si-N bond somewhat akin to an ionic bond, which significantly distinguishes the performance of polysilazanes from that of hydrocarbons with similar structures.

Moreover, the Si-N bond is "weak," with a bond energy of only about 355 kJ/mol, making it highly susceptible to transforming into other chemical bonds.

Moreover, the Si-N, Si-H, and N-H bonds in polysilazanes are particularly "reactive," readily undergoing hydrolysis, condensation, and other reactions with numerous substances such as water and alcohols—demonstrating exceptionally high chemical activity.

However, currently polysilazanes are far less widely used than polysiloxanes. This is mainly due to their preparation methods still being imperfect, resulting in complex molecular structures and generally lower molecular weights in the products. Moreover, polysilazanes are highly reactive, readily interacting with polar molecules in the environment, making storage and transportation particularly challenging.

Its high-temperature range is 400–1300°C, and under high-temperature conditions, it can decompose into SiCN, SiCNO, or silica ceramics, achieving a hardness of 8H or higher after curing.

Moreover, it exhibits excellent chemical stability, maintaining structural integrity even in acidic or alkaline environments, under high-energy radiation, and in salt-spray conditions. Its dielectric strength is ≥10⁵ V/mm, making it suitable for use in the field of electronic insulation.

Since its first synthesis in 1921 via the ammonolysis of chlorosilanes with ammonia, this material has long faced challenges such as difficult storage and transportation, as well as an uneven molecular weight distribution of the product, primarily due to its high reactivity and the inherently hard-to-control preparation process. In the 1990s, a significant breakthrough was achieved by introducing boron into the synthesis process to produce Si-B-C-N ceramics, thereby accelerating research into modified polysilazanes.

The core application areas of polysilazane

1. Insulating Coatings in Semiconductor Manufacturing

In chip manufacturing processes below 5nm, polysilazane serves as an insulating layer material, enabling highly effective electromagnetic shielding at the nanoscale. Currently, high-end products largely rely on suppliers such as Shin-Etsu of Japan and Clariant of Switzerland. Meanwhile, the PSN series products developed by the Institute of Chemistry, Chinese Academy of Sciences, have already achieved mid-to-low-end market substitution and are being utilized in Yangtze Memory Technologies' 3D NAND chip production.

1. Protective Materials for Photovoltaic and Aerospace Applications

Photovoltaic module application: Photovoltaic panels treated with a polysilazane coating remained free from discoloration and cracking even after being exposed to high temperatures of 800°C for 24 consecutive hours, followed by an abrupt water-quenching test. This demonstrates a weathering performance that is more than three times superior to conventional materials.

Aerospace material applications: Their radiation-resistant properties can meet the demands of satellite components for over 20 years of space service. NASA's Mars rover Perseverance utilizes a similar material system for its sensor housing, while Si-C-N ceramic matrix composites have already been employed in the throat liners of SpaceX's Starship rocket engines.

3. High-Temperature Protection for Aircraft Engines

The SiCN ceramic coating, produced by the pyrolysis of polysilazane, can withstand instantaneous high temperatures exceeding 3000℃. It is currently used to protect the surfaces of turbine blades in aeroengines, enabling components to maintain stable operation even under 1200℃ working conditions.

Technological Barriers and Progress in Domestic Substitution

1. The International Landscape of Technological Monopolies

In the global polysilazane market, companies like Clariant from Switzerland and Toray from Japan hold over 90% of the high-end product share. Their core technology is centered on the high-purity synthesis process for polyhydrogenated silazane (PHPS), with purity control requirements exceeding 99.999%. In the hydrogen fuel cell sector, polysilazane-modified proton exchange membranes can raise the operating temperature from 80°C to 180°C. Toyota’s next-generation Mirai model has already begun field testing with these advanced coatings, aiming to boost fuel cell efficiency by up to 15%.

1. Challenges in Synthetic Processes

Reaction conditions are stringent: During polymerization, the temperature must be tightly controlled within ±2°C, and the catalyst ratio error cannot exceed 0.1%; otherwise, Si-N bonds are prone to breakage, leading to degraded product performance. Post-processing is also complex: Since polysilazanes are highly sensitive to moisture and oxygen, the purification process must be carried out under an inert atmosphere, thereby increasing production costs.

1. Domestic technological breakthrough

China Shipbuilding Industry Corporation's 600°C temperature-resistant coating has already been applied to the anti-slip layer on aircraft carrier decks. Meanwhile, domestic researchers have developed a polysilazane coating that can automatically trigger a ceramicization reaction when cracks form—thanks to the introduction of humidity-responsive functional groups. This innovative technology is expected to achieve engineering-scale application for protecting spacecraft exteriors by 2025. Additionally, a Xi'an-based company has successfully produced Si-C-N ceramic fibers with a tensile strength reaching 3.2 GPa, nearly matching the 4.5 GPa level achieved by Japan's Toray. However, there still remains a gap in terms of fiber diameter uniformity and surface finish compared to Toray's advanced standards.

The Strategic Value of Materials Technology

Polymerized silazane, a quintessential "bottleneck" material, represents a technological breakthrough that spans the entire chain—from molecular design and synthesis processes to engineering applications. Currently, China has already achieved domestic substitution in the medium-temperature range; however, aerospace-grade materials capable of withstanding temperatures up to 1,300°C still rely on imports. It is anticipated that, through focused technological efforts over the next 5 to 8 years, China will attain independent control over high-end polymerized silazane materials, providing critical material support for strategic sectors such as chip manufacturing and aerospace engineering.