What Materials Can Be Used to Create Black Films?

There is a wide variety of materials available for producing black films, ranging from traditional inorganic substances to cutting-edge nanomaterials.

Carbon-Based Materials

Carbon-based materials are widely recognized as some of the blackest substances available and are a primary choice for creating black films. Their effectiveness is mainly due to the material's inherent strong light absorption and unique structural traps that enhance this property.

Diamond-like Carbon (DLC) is an amorphous carbon film composed of a mixture of diamond structure (sp(3) bonds) and graphite structure (sp(2) bonds). It not only achieves a high degree of blackness, with a visible light absorption rate of 95-98%, but also boasts extremely high hardness, wear resistance, and chemical stability. This is the material commonly used for the black films found on high-end watch casings, precision machinery guides, and automotive engine parts.

Carbon nanotube array films are among the blackest man-made materials known, with an absorption rate exceeding 99.965%. Vantablack is a famous example of this material. Its microstructure resembles a nanoscale forest--light entering the structure gets repeatedly reflected between the tube walls until its energy is completely dissipated, achieving an astonishing absorption rate of over 99.965%. An object coated with this material appears to lose all contour and detail to the naked eye, resembling a two-dimensional black hole. This technology finds application in space telescopes, helping to capture faint starlight from the depths of the universe.

Metal Compounds

Metal compounds impart additional functionalities to black films beyond just color.

Titanium nitride typically has a golden-yellow color, but by adjusting its nitrogen content, a range of hues from dark gray to pure black can be achieved while maintaining its ultra-high hardness. This makes it a common choice for smartphone frames and cutting tools. Black titanium oxide, created by introducing oxygen vacancies into white titanium dioxide, achieves high light absorption while maintaining chemical stability.

Black silicon is produced by etching to form micro/nano-conical structures on its surface. This results in an absorption rate exceeding 98% and offers compatibility with semiconductor processes, making it widely used in high-efficiency solar cells.

Conversion Coatings for Metals

Generating black conversion coatings directly on metal surfaces represents a well-established family of solutions.

Platinum black is formed through electrodeposition, creating a porous structure with a huge specific surface area. This reduces electrode impedance, making it an ideal choice for neural electrode coatings.

Black gold is produced by evaporating gold in a residual argon atmosphere, causing the gold atoms to randomly stack into a porous structure. This structure provides a good sensing response to gases like NO??.

For aluminum and its alloys, a porous oxide film created through anodization can subsequently absorb black dyes. The blackening treatment for steel involves creating a magnetite (black iron oxide) layer through chemical oxidation, a process that is simple and cost-effective.

Organic and Composite Materials

When flexibility or smart responsiveness is required in a black film, organic materials take center stage.

Polyimide itself is dark-colored and can withstand high temperatures exceeding 400C. By adding carbon black, various functional black films can be produced, used in applications like flexible circuit boards and aerospace thermal insulation blankets.

Scientists have also incorporated carbon black into liquid crystal elastomers, developing smart films that possess both structural color and photothermal response. Under near-infrared light irradiation, this material heats up rapidly, enabling actions like bionic crawling or flower petal opening/closing, while also offering potential for information encryption.

Conclusion

As technology continues to advance, the range of materials used for black films keeps expanding. From the ultra-black carbon nanotube arrays used in space exploration to the durable coatings on everyday consumer goods and the smart, responsive organic films of the future, each material brings a unique set of properties to the table. Whether the goal is extreme light absorption, wear resistance, chemical stability, or intelligent functionality, there is likely a black film material engineered to meet the need.

COMTEX_474712028/2891/2026-03-05T12:12:58

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