- Статьи
- Science and technology
- Metal installation: scientists will accelerate the creation of equipment resistant to extreme conditions
Metal installation: scientists will accelerate the creation of equipment resistant to extreme conditions
Russian scientists have developed an innovative method of metallization of technical ceramics — applying heavy-duty metal coatings to it. In addition, the authors proposed a mathematical model that predicts the deposition parameters, which allows you to control the thickness of the coating with an accuracy of 95%. The proposed approach will be applied in micro- and radio electronics for the development of devices and sensors operating at extreme temperatures, and in the aerospace industry. For more information about the technology, see the Izvestia article.
Technical ceramics for microelectronics
Scientists from Saratov State Technical University named after Yuri Gagarin (SSTU) have developed a new method for applying heavy-duty metal coatings to technical ceramics. The essence of the approach is that the source metals — niobium and molybdenum — are heated to 2300 ° C by passing a high-frequency current through them (almost like in an induction cooker). In this case, metal atoms evaporate and settle on the unheated ceramic, which forms a coating with a thickness of one to two tens of micrometers on its surface.
As experts explained to Izvestia, ceramic materials, such as aluminum oxide, are widely used in microelectronics, the aerospace industry and the energy industry due to their resistance to high temperatures and chemicals. For example, applying thermal barrier coatings — multilayer heat—resistant ceramic materials - to parts of aircraft and rocket engines reduces their weight, since such coatings have a density several times lower than that of metals. The substrates for microcircuits based on technical ceramics dissipate heat, thereby ensuring temperature regulation. However, the fragility of ceramics and poor adhesion to metals limit their use as structural materials.
To eliminate these disadvantages, protective metal coatings are applied to the ceramic surface — for example, from refractory metals niobium, molybdenum or alternating layers of these metals, which are able to withstand not only high temperatures, but also radiation and mechanical stress.
Traditionally, metals are applied to the surface of ceramics by depositing them from the gas phase at relatively low temperatures. However, this approach requires the creation of a high vacuum — a pressure hundreds of millions or even a billion times lower than atmospheric pressure. This requires expensive equipment and long hours of pumping air out of the spray area. In addition, the deposition itself takes a long time, and after spraying, it is often necessary to additionally heat the finished products for better adhesion between metallization and ceramics.
The new deposition method can be carried out in low vacuum conditions — at a pressure 250-750 times lower than atmospheric pressure. At the same time, the approach ensures fast coating deposition — the process takes only a few minutes. Experiments have shown that the adhesion between metal and ceramics is three to eight times higher than that of coatings obtained by classical methods, even without subsequent high-temperature treatment.
The inductor-target-samples system
— Our approach has advantages over traditional physical and chemical methods: it does not require high vacuum and prolonged additional post-treatment. At the same time, it allows you to control the thickness of the molybdenum metallization layer with an accuracy of 0.3 micrometers," Alexander Fomin, project manager, Doctor of Technical Sciences, Head of the Department of Materials Science and Biomedical Engineering at SSTU, told Izvestia.
This makes the technology promising for industrial implementation. In the future, scientists plan to obtain metallization from refractory metals (niobium, molybdenum and a number of other metals) both on vacuum-tight ceramics of beryllium oxide and aluminum nitride, as well as on titanium and other metal products.
Energy efficient method
The scientists also developed a mathematical model that provides 95 percent accuracy in obtaining a given thickness of the metallization layer. Numerical models make it possible to visualize the nature of the temperature distribution in a metal when eddy currents are passed through it. Such modeling will help predict the rate at which a coating of a certain thickness will form, depending on the source metal.
The authors emphasize that the proposed technology is energy efficient: the power consumed during the spraying process does not exceed 10 kW, which is comparable to four working electric kettles. In addition, the approach requires vacuum pumps, which are ten times cheaper than those used in classical deposition methods.
An annular target, titanium disk samples, and ceramic test plates coated with molybdenum
The developed method simplifies and reduces the cost of ceramic metallization due to operation in low vacuum conditions and the absence of high-temperature post-treatment, Veronika Suvorova, researcher at NUST MISIS Structural Ceramic Materials Research Center, told Izvestia.
"This opens up opportunities for the mass production of heat—resistant ceramic-metal components in microelectronics (chip substrates, sensors), the aerospace industry (engine nozzles, turbine blades) and the energy industry, where materials with high thermal conductivity and resistance to extreme loads are required," the expert emphasized.
However, when scaling the technology to large-sized products, legitimate questions arise related to the design features of the installation, said Lev Logunov, Candidate of Chemical Sciences, researcher at the ITMO Faculty of Physics. An increase in the size of the annular evaporator will lead to the need for a significant increase in current and power, which will negatively affect the efficiency of the process and may impair the uniformity of coating.
"At the same time, for products with small dimensions, such as microelectronics components or sensor elements, this technology looks very promising," he said.
Microstructure (chipping) of molybdenum coating on alumina ceramics
The method must also be tested to ensure quality stability and economic feasibility. For example, in addition to metal bonding to the ceramic surface, it is important to ensure low coating defects, said Evgeny Alexandrov, Director of the NTI Center for Digital Materials Science: New Materials and Substances at Bauman Moscow State Technical University.
The results of the study, supported by a grant from the Russian Science Foundation (RSF), are published in the journal Ceramics International.
Переведено сервисом «Яндекс Переводчик»
