Super strong ceramics for mechanical engineering and dental prosthetics created by UNN physicists
Scientists at the UNN Physics and Technology Research Institute (PTRI) have obtained high impact and abrasion resistance materials. They are made of aluminium oxide powders by using the spark plasma sintering method.
The new materials can be used in mechanical engineering and metal processing, in the defence industry to produce protective materials, as well as in dental prosthetics and as elements of integrated circuits.
According to researchers, spark plasma sintering is a process when the powder is heated at high speed in vacuum by pulsed electric current at constant pressure. The resulting materials have a homogeneous and fine-grained structure, which significantly increases the strength and wear resistance of the obtained ceramics. Thus, such materials can better withstand higher loads.
"We have been researching spark plasma sintering technologies since 2008. The powder material is heated to sintering temperature at a controlled rate (10 to 2500 °C/min). High heating rates reduce sintering time and limit the growth of powder particles during consolidation, which results in a high-density submicrocrystalline structure and significantly improves the mechanical properties of the ceramics," explains Maxim Boldin, Head of the Ceramics Technology Laboratory at the UNN PTRI, member of the Russian Ceramic Society.
Scientists from Nizhny Novgorod studied three types of ceramic materials based on aluminium oxides: submicron and fine-dispersed Al₂O₃ powders, as well as submicron aluminium oxide powder with an amorphous layer of the same oxide on the particle surface. The densification (shrinkage) occurring during the sintering of the starting substance was investigated by means of mathematical models.
In their experiments, the researchers found that powder particles coated with amorphous aluminium oxide form grains at an unusually fast rate in the alloy at lower activation energies. The UNN scientists attribute the anomalously fast grain growth to defects on their boundaries that increase microhardness, thereby increasing the strength of ceramics produced from the powder with an amorphous layer of aluminium oxide by one and a half times.
It should be noted that the R&D results of PTRI scientists are already being used at Nizhny Novgorod enterprises to manufacture metalworking tools and ceramic bearings. The research is performed within the framework of the grant of the Russian Science Foundation "Design and production of new ceramic and functionally graded materials based on aluminium oxide with high ballistic resistance for composite protection elements".
The results of the research were published in the journal Materials in 2022.
