Electrochemical Corrosion Behavior of Ta₂N Nanoceramic Coating in Simulated Body Fluid

Chemical Interaction of Hydrogen Radicals (H*) with Transition Metal Nitrides

Transition metal nitrides (TMNs) are reported as protective coatings in reactive hydrogen environments. Although the permeation of H2 through TMN coatings is well reported, their reducibility in H* environments is less investigated. In this work, we categorize the interaction of H* with ambient exposed TiN, ZrN, HfN, VN, NbN, and TaN thin films at 700 °C into three classes. We find that in TiN and VN samples, H*-induced reduction was limited to the surface (≈ top 2 nm). Significant denitridation was observed in ZrN and HfN samples beneath the surface, along with an increase in the transition metal oxide (TMOx) fraction. Denitridation was observed in NbN and TaN samples as well, but the increase in the TMOx content was less than for ZrN and HfN. We propose a model in three steps: hydrogenation, formation of volatile species, and diffusion of subsurface atoms to the surface. We show that the interaction of H* with TiN, ZrN, HfN, VN, NbN, and TaN with partially oxidized surfaces can be explained using the preferred hydrogenation pathway (based on the work functions) and the thermodynamic driver for forming volatile species (NH3 and H2O; based on the change in Gibbs free energy).

Effects of Cold Rolling on the Microstructure and Corrosion Resistance of the Double-Glow Plasma Ni-Cr Alloying Layer on Q235 Steel

A Ni-Cr alloyed layer was prepared on the surface of Q235 steel using double-glow plasma surface alloying (DGPSA) technology and the alloyed layer was cold-rolled with different deformation rates. The microstructure, composition distribution and phase composition of the alloyed layer were characterized using a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and an electrochemical workstation. On this basis, the corrosion resistance of the alloyed layer was analyzed. The results showed that a Ni-Cr alloyed layer formed on the surface of Q235 steel following double-glow plasma nickel-chromium alloying. The alloy elements of Ni and Cr were distributed in a gradient from the outside to the inside and the main phases were FeCr_0.29Ni_0.16C_0.06, Cr₂₃C₆ and γ solid solution. The alloyed layer, once cold-rolled with different deformation rates, underwent synchronous plastic deformation with the substrate, with no fracturing and spalling. The self-corrosion potential of the cold-rolled specimens in 5% H₂SO₄ and 3.5% NaCl solution is close to that of 304L stainless steel, and the corrosion currents are much lower. The corrosion resistance of the cold-rolled specimens is comparable to the original specimens, with no significant changes.

Nanostructured Coatings: Review on Processing Techniques, Corrosion Behaviour and Tribological Performance

Corrosion and tribology are surface phenomena. Modifying surfaces of materials without resorting to altering their bulk properties is an effective route to alleviate corrosion, friction and wear, encountered in engineering applications. With the advancements in the field of nanotechnology, surface protective coatings with nanomaterials can be readily developed to explore their functionality in mitigating chemical/physical damage of surfaces. Surface protection enhances performance and operating lifetimes of industrial machinery components. This review presents insights on various types of recently developed nanostructured coatings, their synthesis routes, corrosion behaviour and tribological performance. It provides the state-of-the-art information on the development of nanostructured coatings, namely, ceramic coatings, metallic coatings and nanocomposite coatings with metal and polymer matrices. Biomimetic approaches in making nanostructured coatings and challenges encountered in the development of nanostructured coatings are highlighted.

A comprehensive review of biological and materials properties of Tantalum and its alloys

Tantalum (Ta) and its alloys have been used for various cardiovascular, orthopedic, fracture fixation, dental, and spinal fusion implants. This review evaluates the biological and material properties of Ta and its alloys. Specifically, the biological properties including hemocompatibility and osseointegration, and material properties including radiopacity, MRI compatibility, corrosion resistance, surface characteristics, semiconductivity, and mechanical properties are covered. This review highlights how the material properties of Ta and its alloys contribute to its excellent biological properties for use in implants and medical devices.

Tantalum boride as a biocompatible coating to improve osteogenesis of the bionano interface

A proper biological microenvironment conducive to tissue repair and regeneration, while the bioimplant interface directly affects the local microenvironment. In this study, to improve the biological microenvironment, a nanosized tantalum boride (Ta-B) was coated on a titanium alloy substrate (Ti6Al4V, TC4) using magnetron cosputtering. The sample surface was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). To investigate the effects of tantalum boride coating on the microenvironment, rabbit bone marrow stromal cells (BMSCs), and RAW 264.7 cells were respectively seeded on the sample surface and relevant experiments were conducted in vitro. The pure tantalum coating (Ta) and naked TC4 were prepared as controls. Our results showed that the Ta-B coating enhanced cell proliferation and adhesion and inhibited the inflammatory response. Findings of alkaline phosphatase (ALP) staining, alizarin red staining and real-time PCR for osteoblastic gene expression indicated that Ta-B and Ta coating improve the osteogenesis, in which Ta-B coating showed higher osteogenesis than Ta coating. Thus, this study suggests that Ta-B coating with excellent biocompatibility could have new applications for wound healing in bone tissue engineering.