A Chinese scientific research team recently proposed a new automotive coating solution that mixes nanotechnology and traditional pigments, which is expected to achieve an "extreme black" appearance close to a "black hole" on mass-produced models. This new hybrid coating combines an advanced vertically aligned carbon nanotube (VACNT) ultra-black coating with a conventional water-based carbon black pigment spraying process. It greatly improves the durability and industrial sprayability of the coating while maintaining ultra-high light absorption capabilities. The coating's absorption rate in the visible light band is as high as 99.90%, and it hardly reflects any light, creating a strong visual immersion effect.
Behind this technology is the rapidly rising demand for black car paint in the Chinese automobile market. In the past, white once accounted for about two-thirds of China's new car market, but now black has jumped to nearly a quarter. It is expected that about 7.5 million new black cars will hit the roads in China this year, which is even more than the major markets of Europe and North America combined. In the minds of consumers, deep black has become a symbol of status and luxury, and market preferences are shifting from "any color will do, as long as it is white" to "the darker, the better."
As early as 2019, BMW used a nano-scale "super black" coating on an X6 concept car, which was called the "blackest car in the world" at the time. Its core principle is to trap incident light in the porous structure by building a "nano forest" composed of carbon nanotubes on the surface, thereby achieving absorption of 98% to 99.9% of light across the ultraviolet, visible and far-infrared bands. However, this type of coating has complex processes, high costs, and fragile mechanical properties. It has been difficult to meet the requirements of mass-produced vehicles in terms of spraying, weather resistance, and wear resistance.
The focus of the hybrid ultra-black coating developed by the Chinese team this time is to introduce traditional carbon black pigments while retaining or even enhancing the "light trap" effect of the nanotube array. The researchers made the carbon black pigment particles spontaneously arrange along the carbon nanotube array to form a rough surface composed of microscopic "peaks and valleys". This structure can also scatter and trap incident light multiple times, making the coating's total absorption rate in the visible light region exceed 99%. Compared with the previous fragile pure nanotube coatings, this hybrid material greatly improves the mechanical strength and adhesion properties, and is closer to the automotive industry's requirements for mass production coatings.
Liu Zhiwei, a chemical researcher from the color technology team of Nippon Paint Group's core R&D center in Shanghai, said that in the Chinese market, body color has become one of the key selling points. Deep black car paint has long been the iconic color of luxury cars and is widely favored for its elegant appearance, strong visual impact and luxurious temperament. He pointed out that vehicle manufacturers are actively looking for ultra-black coating solutions that can be mass-produced and have extreme blackness to strengthen their brand image in the fierce competition.
In terms of process adaptation, one of the highlights of this new hybrid coating is that it can be applied through a traditional automotive spray production line without the need to completely reconstruct the existing coating process. In tests exposed to moisture and high-humidity environments, the research team found that the coating performed well in terms of long-term stability and passed key tests such as humidity, water resistance, and adhesion, showing good potential for industrial application. The Shanghai team has completed the spray painting display on a model car. The car body presents a deep black that is almost non-reflective, and the curved surface details of the car body are almost invisible under the light.
From the perspective of technical principles, the vertically aligned carbon nanotube array (VACNT) coating itself is one of the "blackest" materials known to the scientific community. Its nanoscale tubular structure is perpendicular to the substrate surface, forming extremely high porosity and multiple scattering channels. After the incident light enters the "nano forest", it is continuously scattered and absorbed, making it extremely difficult to escape, thus achieving extremely high light absorption. As early as 2014, Vantablack, developed by the British company Surrey NanoSystems, attracted widespread attention based on similar principles and has been applied in fields such as art and internal extinction of space telescopes.
However, when it comes to demanding application scenarios such as automobiles, how to balance the ultimate optical performance with mechanical and process performance has always been the biggest problem in engineering implementation. The hybrid carbon black-carbon nanotube (CB-CNT) solution proposed by the Chinese team this time synergizes the two types of carbon materials at the micro level. It not only takes advantage of the super light-absorbing ability of the nanotube array, but also relies on the mature process route and physical strength of the conventional carbon black system, providing the possibility for large-scale mass production.
The researchers also said that in the future, they are expected to further introduce Gradient Refractive Index Technology (GRIT) into this hybrid system, that is, building a structure with gradually changing refractive index from top to bottom inside the coating to further reduce surface reflection and allow light to have "nowhere to escape" after entering the coating. In the field of ultra-black materials, some of the latest achievements have approached the so-called "four nines" (99.99%) absorption level, but in this extreme range, how to accurately measure it is a challenge in itself.
Relevant results have been published in the academic journal "Matter & Light" and released through Cell Press and EurekAlert. Industry observers believe that as the demand for black high-end models in China's local market continues to grow, once this type of ultra-black coating with mass production feasibility is truly introduced into OEMs, it is expected to bring new competitive focus in multiple dimensions such as visual design, brand recognition, and functional matting. Whether it can truly win the title of "the world's blackest automotive coating" may still be difficult to determine before the further development of measurement technology, but a technical and aesthetic competition surrounding "extreme black" has obviously begun in the Chinese market.