Novel Coronavirus copper containing stainless steel from antibacterial to antiviral stride

Huang mingxin’s team adopted the production process of powder metallurgy to increase the copper content in stainless steel to 20%, and obtained stainless steel with novel coronavirus resistant characteristics. In this way, the high copper content of stainless steel can not only avoid “copper brittle” phenomenon, but also its copper-rich precipitate can be evenly distributed in the whole metal products, even if the product surface wear will not affect its antiviral effect.

Since the outbreak of COVID-19, “person-to-person” transmission has become one of the important ways of novel Coronavirus transmission. The Novel Coronavirus has been shown to survive on ordinary stainless steel surfaces for up to three days. Therefore, the development of stainless steel materials that can kill novel coronavirus has become a major goal of the industry and academia.

Recently, the university of Hong Kong school of engineering department of mechanical engineering professor Huang Mingxin leadership team and the university of Hong Kong (li ka shing faculty of medicine) immunization and infection research center Pan Liewen professor’s research team, by adjusting the chemical composition and microstructure of stainless steel, success has adhered on the surface of the stainless steel can kill the will of coronavirus, and other common pathogens microorganisms.

The new stainless steel containing 20% copper shows strong novel coronavirus resistance

Since it was invented at the beginning of the 20th century, with excellent performance in hardness, corrosion resistance, machinability and other aspects, from the infrastructure of public places, to the daily decoration of family life, stainless steel has become one of the most commonly contacted materials by the public.

But as the COVID-19 pandemic has swept the world, stainless steel, the basic material available in public places, has become a vehicle for the spread of the Novel Coronavirus — the material on which virus-carrying droplets and respiratory secretions attach, making it a potential vector for viral transmission.

For example, the Chinese Center for Disease Control and Prevention has previously conducted an analysis of a novel coronavirus infection case, suggesting that it is highly likely that the virus could spread among households in the same building by sharing an elevator and touching the stainless steel elevator buttons together.

In the specific study, in order to better compare the antibacterial and antiviral properties of different stainless steel materials, Huang mingxin’s team prepared several samples, which were conventional 316 stainless steel, stainless steel containing 0.3% and 0.6% silver, four stainless steel containing 1%-20% copper and pure silver and pure copper. And in order to highlight its practical value, they have specially prepared it as an elevator button to simulate the novel coronavirus resistance performance of different types of stainless steel in the most common application environment.

Finally, the results showed that conventional 316 stainless steel, sterling silver and silver-containing stainless steel had no significant inhibitory effect on novel Coronavirus and Influenza A (H1N1) viruses. In contrast, pure copper and copper containing stainless steel showed very significant antiviral properties. In particular, the 20% copper content of stainless steel can significantly reduce the living novel Coronavirus on its surface by 99.75% and 99.99% in 3 hours and 6 hours respectively, showing strong novel coronavirus resistance.

Because the high copper content stainless steel is prepared in a powder metallurgical manner, it is not affected by surface wear of the material and can maintain novel coronavirus resistant properties over a long period of time, Huang said.

It is very important to grasp the copper content in stainless steel from antibacterial to antiviral

In fact, long before the development of novel coronavirus resistant stainless steel, antibacterial stainless steel was widely available and industrial production began early, also with the addition of copper and silver.

Yang Ke, a researcher at the Chinese Academy of Sciences’ Institute of Metal Research, pointed out that copper and silver have been recognized as excellent antibacterial materials in the industry, including escherichia coli and other common pathogens have excellent resistance. For example, copper content of only 5% antibacterial stainless steel, it has 99% antibacterial rate. Because dense copper-rich precipitates remain permanently in the stainless steel matrix, they produce long-lasting antibacterial effects. Silver is more antibacterial, as long as 0.3% of silver added to the stainless steel matrix, can produce a strong antibacterial effect. However, for antibacterial stainless steel to achieve novel coronavirus resistant effect, the copper content in it needs to be increased.

Stainless steel as an iron based alloy, based on iron, nickel, chromium and other elements will be added in the production process to enhance its performance. If blindly adding a large amount of copper, will make its basic properties change, resulting in it no longer has the characteristics of stainless steel, can not be large-scale application. Yang Ke said that the production of antiviral stainless steel, its biggest challenge lies in how to add a sufficient amount of antiviral elements at the same time, and do not change the core performance of stainless steel.

Although copper is one of the core elements of stainless steel, excessive addition will seriously affect the core properties of stainless steel. Yang Ke told reporters that the hot working and forging process of steel needs to be carried out at a high temperature of about 1200℃, while the melting point of copper itself is about 1080℃. Too much copper will lead to poor forging property of steel during hot working, and the phenomenon of “copper brittleness” in general sense.

In order to avoid “copper brittle” phenomenon, at the same time to ensure that the content of enough anti-virus effect of the copper, researchers switch to physical gas deposition, cold spraying, ion injection and other methods, for stainless steel coated with a layer of anti-virus coating. However, the coating produced by these methods, the thickness is less than 1 mm, and it is easy to be worn leading to a significant decline in its antiviral performance, so this kind of stainless steel material can not achieve long-term antiviral effect, does not have the value of large-scale application.

Huang mingxin’s team adopted the powder metallurgy process to increase the copper content in stainless steel to 20%, and obtained stainless steel with novel coronavirus resistant characteristics. According to Yang ke, THE method of powder metallurgy is to press the metal powder in a mold under high pressure, and then sintering it at a higher temperature. The high copper content stainless steel manufactured by this method not only does not appear “copper brittle” phenomenon, but also its copper-rich precipitate is not only distributed on the surface, but evenly distributed throughout the metal products, so even the surface wear of the products does not affect its antiviral effect.

Market space is still to be excavated to expand the scale of industrialization from two aspects

Yang Ke introduced, although the experimental effect is significant, but antiviral stainless steel to form large-scale, industrialization, there is still a long way to go. Even if the current industrial production has been very mature antibacterial stainless steel, it still has a large market space to be excavated.

“One company we work with produced and sold 5,000 tons of antibacterial stainless steel in 2020.” Yang Ke said that the antibacterial stainless steel industry has a relatively large scale, and the formation of the relevant industry standards. At the end of 2020, the Ministry of Industry and Information Technology has officially released the “copper containing antibacterial stainless steel” industry standard YB/T 4171-2020, covering the ordering content, technical requirements, test methods, inspection rules and other aspects of copper containing antibacterial stainless steel series. But at present antibacterial stainless steel is still mainly used in the production of tableware and kitchenware in the food and beverage field, such as antibacterial stainless steel chopsticks, kitchen knives, and the consumer market is mainly concentrated in Jiangsu, Zhejiang, Guangdong, the application scale is still small, the use of the scene is relatively single.

Yang Ke also pointed out that the powder metallurgy method used in the production of antiviral stainless steel, complicated process, high cost, can not become the mainstream production mode, and too much copper element will also make stainless steel corrosion resistance decline, so that it can not be used to produce high-end products, to a certain extent limited its application scenarios.

Yang Ke believes that although the research results are still some time away from large-scale application, but it opens a new window, so that the role of copper in stainless steel materials is more obvious, and gives new possibilities for stainless steel materials. “Our country’s antibacterial stainless steel production technology is the world’s leading, antibacterial stainless steel can have more applications in the future, among which the application of anti-infection in medical devices is the most promising.”

At present, Yang Ke and others are also working with Shenzhen Metro to develop handles and railings made of antibacterial stainless steel. He believes that in the future, in order to achieve the large-scale application of antibacterial and antiviral stainless steel, we should also make efforts in two aspects. One is to find suitable application scenarios in the application end, such as the construction of a model room with antibacterial stainless steel in the hospital, and play a demonstration effect. On the other hand, basic research should be strengthened. At present, the mechanism of copper ion antibacterial and antiviral action is still not clear, all kinds of theories have their own school, there is no unified, widely persuasive mechanism of action, to a certain extent, restrict the development of antibacterial and antiviral stainless steel.

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