Sputter-deposited TaAgB Films And TaCuN Films:Structure,Tribological And Biomedical Properties

With the development and progress of society and the improvement of people’s living standards,more and more people attach importance to teeth,occlusal and facial coordination,and the orthodontic industry is in the stage of rapid development.Fixed orthodontic technique is the main treatment method in orthodontic clinic.The core device is orthodontic bracket and arch wire.Among many orthodontic materials,stainless steel has become a common material for brackets and arch wires in orthodontic treatment because of its advantages of low cost and high stiffness.In most cases of orthodontic treatment,we need the friction between the arch wire and the bracket to be as small as possible,which will be conducive to the tooth moving in the designed direction and rate during the orthodontic process,and ultimately achieve the purpose of efficient and accurate orthodontic.Friction blocks the force needed for directional tooth movement,and about 12 to 60 percent of the force used to move the tooth is dissipated in the form of friction.The high frictional resistance between stainless steel and stainless steel will reduce the efficiency of orthodontic.It is an effective way to coat the bow wire with protective coating.At present,the protective coating on the arch wire in the existing technology mainly includes transition metal nitride,transition metal boride,nano silicon dioxide,titanium compound,nano zinc oxide and nano diamond.The oral cavity is a constant temperature and humid environment for a long time,and the oral microenvironment is complex.In the process of correction,plaque attachment will inevitably form around the orthodontic bracket and arch wire,and the metabolism of bacteria in plaque can cause enamel demineralization and periodontal tissue inflammation.Secondly,patients often face the problem of mucosal rupture caused by orthodontic brackets and arch wire scraping.When the mucosa is traumatized,bacterial colonies adhering to the arch wire and in the mouth can cause oral mucosa infection and inflammation,resulting in ulcers.Moreover,the biocompatibility of stainless steel materials is also poor.The key to solve the above problems is to prevent bacteria from attaching to brackets and orthodontic arch wires,reduce enamel demineralization and periodontal inflammation,and improve the biocompatibility of orthodontic materials and reduce oral mucosa irritation.Studies have proved that both Cu and Ag have obvious bactericidal,antibacterial and anti-inflammatory effects,and both have been widely used in the medical field as antibacterial materials.In summary,it is a simple and effective method to develop a stainless steel coating protective film that can improve the friction performance,corrosion resistance and biocompatibility of stainless steel materials,and has long-term bactericidal and bacteriostatic effects.In this study,the TaAgB solid solution coating was successfully prepared by magnetron sputtering technology with Ag-doping.Compared with the pure Ta B₂coating and the Ta B₂/Ag nanocomposite coating with Ag-precipitation,the solution strengthening effect gives the TaAgB coating a higher mechanical hardness of up to34.3±0.58 GPa.The tribological behaviors of TaAgB in saliva environment reveal that the oxide lubrication phase induced by friction on TaAgB surface and the unique water-based lubrication feature of saliva contribute to the friction reduction,and the corresponding friction coefficient is as low as 0.08.The characteristics of high hardness and smooth surface make TaAgB coating further show excellent wear resistance in the process of low friction,wear rate is only 6.51×10^-18m³/Nm.In addition,subsequent biological experiments confirm that the TaAgB coating owns non-toxic,good biocompatibility and antibacterial ability.The dual optimization of tribological and antibacterial properties was achieved by depositing TaAgB coating with solid solution structure on stainless steel surfaces.In the longer view,the TaAgB coating as a protective coating of orthodontic materials has a great potential for application.Besides,we investigate the mechanical properties and tribological behaviors of pure Ta N film without Cu atoms,TaCuN solid solution film and Ta N/Cu nanocomposite film,respectively.Hardness tests show that the hardness of Ta N and Ta N/Cu is about 15.6 GPa and 7.3 GPa,respectively.In contrast,TaCuN film has the highest hardness of about 17.6 GPa,which contributes to the excellent wear resistance of the films.The hydrolysis reaction of the TaCuN film in the friction process makes saliva environment into a solution containing the oxide colloid particles.Moreover,the existence of Cu₂O induced hydrophobic surface appears.Using the colloidal solution of double electric layer repulsion and saliva lubricating film absorption of hydrophobic surface,the TaCuN film won ultra-low friction and ultra-low wear properties,with friction coefficient and wear rate of 0.045 and 1.18×10^-18m³/Nm,respectively.In addition,the living biological experiments confirm that the TaCuN film is a material with non-toxic and good biocompatibility,and also shows stronger antibacterial ability than stainless steel.This design provides a new idea for the surface modification of orthodontic appliances,and TaCuN film could be potentially applied as protective film in the fields of dental treatment.Comparing the tribological and physicochemical properties of TaAgB film coating and TaCuN film coating,the former has higher hardness,while the latter has lower coefficient of friction and lower wear rate.From the point of view of orthodontic mechanics,TaCuN film coating has more advantages.As inorganic antibacterial materials,silver antibacterial materials have similar antibacterial performance to copper antibacterial materials,but their cost will be higher.Therefore,the solid solution TaCuN film coating has a better clinical application prospect in the future.