Key Engineering Materials Vol. 967

Abstract: The adhesive strength and degradation behavior of the Al/resin interface was investigated under high temperature and high humidity conditions. The adhesive strength of the joint without aging was approximately 14 MPa. The value is the same as the Cu/resin joint. With progress of aging at 85°C in 85%R. H., the strength decreased rapidly in the early aging stage and decreased gradually by further aging. The strength of the Al/resin joint was inferior to that of the Cu/resin joint after aging. The fracture mainly occurred in the interface of the joint. The result of Fourier transform infrared spectroscopy analysis for the fracture surface showed that water absorption in the Al/resin joint occurs by aging and causes the degradation of the strength.

Abstract: Open-air aerosol-assisted plasma deposition has emerged as an efficient process to deposit innovative composite coatings. In this work, it was used to investigate biodegradable polymeric coatings loaded with carbon dots (CDs) for bioengineering and biomedical applications. The structure, composition, wettability, and biodegradation of these coatings depend on the precursors used, here methacrylic anhydride and ethylene glycol di-methacrylate. The effectiveness of the deposition was confirmed by X-ray photoelectron and Fourier-transformed infrared spectroscopies, i.e., polymerization of vinyl groups and integrity of hydrolysable functions. The latter allow control the CDs release over time, which were homogenously distributed in the coating, as confirmed by electronic and confocal microscopies. Both coatings were found to be non-cytotoxic to human dermal fibroblasts. This one-step open-air acrylate-based plasma deposition strategy has enabled the tuning of the coating release profile and offers new perspectives for drug delivery applications.

Abstract: Current research on biodegradable iron-based alloys mainly focuses at regulating the material degradation rate, as well as its biological behavior, especially from the point of view of the hemocompatibility and cytocompatibility. In fact, fine-tuning of the surface roughness, morphology and chemical composition can improve the functional response of the material. For that purpose, a surface modification strategy, namely plasma immersion ion implantation (PIII), is proposed to perform the selective modification of surface properties without affecting the bulk ones. In this work, the influence of treatment time (t_imp = 15, 60 and 120 min.) and implanted species (O, N or C) on the surface properties of a Fe-13Mn-1.2C resorbable alloy was investigated. The findings demonstrated that varying the process gas and the exposition time led to a variety of topographies, surface energies and chemical compositions. XPS analyses and depth profiles clearly showed the impact of the process parameters on the surface features and element distribution, due to implanted species penetration into the alloy. The implanted samples showed a delayed clotting time, thus a better hemocompatibility. In contrast, nitrogen-treated surfaces displayed a more pronounced hemolytic behavior, whereas oxygen and methane did not. PIII implantation appears to be a versatile solution for fine-tuning surface topography, composition and biological properties, making the process promising for the improvement of metallic biodegradable vascular implants.

Abstract: The excellent biocompatibility of Ti and Zr alloys makes them the best candidates for orthopedic implantations. The design of high Ti and Zr-containing alloys that show low Young's modulus for implant manufacturing is the objective of this work. Here, a feed-forward-back propagation neural network was used to speed up the design process and optimize alloy composition. The β-typeTi₄₅-Zr₃₉-Nb₁₂-Mo₄ alloy is designed and showed promising properties. The alloy showed a low elastic modulus of 78 GPa and a high yield strength of 891 MPa resulting in a high elastic admissible strain that made it suitable for orthopedic applications.

Abstract: Organ models that resemble the original anatomy are needed in the education and training of human and veterinary doctors. The organs should be as close as possible to the original in shape, colour and feel. Furthermore, these organ models must be able to be handled in such a way that they can be examined by palpation and imaging (ultrasound, X-ray, CT and endoscopy). The diagnostic procedures should detect pathologies such as cysts, tumours, ruptures, haemorrhages or air collections. Following the diagnostic measures, it must be possible to initiate a therapy. Possible therapeutic measures are surgery with a scalpel, electrosurgery or puncture. The present work deals with the production of training models by means of a casting process. With this method, the models can be produced quickly and at low cost. Different compositions of hydrogels and other biomaterials are investigated. These gels are examined for the following properties, among others: thermostability, electrical conductivity and dimensional stability under pressure. Other parameters such as pot life, cross-linking time and durability in relation to mould formation will also be considered.

Abstract: A comparative study of the structure and properties of two biodegradable Fe – 27Mn and Fe – 27Mn – C alloys for biomedical use after equal channel angular pressing (ECAP) has been carried out. It is noted that addition of carbon in the alloy leads to a change in the mechanism of plastic deformation from the formation of martensite to deformation twinning in austenite. ECAP improves the strength characteristics of the alloys under study and the corrosion rate by refining the structure and increasing the dislocation density. The presence of a partially twinned structure in the Fe – 27Mn – C alloy results in a lower corrosion rate despite a stronger refinement of the alloy structure after ECAP.

Abstract: The article presents the results of the study of microstructure, mechanical properties, corrosion resistance and fatigue strength of the Zn-1%Mg and Zn-1%Mg-0.1%Ca alloys, processed by rotary swaging (RS). It is shown that the grain refinement leads to an increase in the strength of the alloys up to 196 ± 4 and 218 ± 6 MPa for the Zn-1%Mg and Zn-1%Mg-0.1%Ca alloys, respectively. The ductility of the Zn-1%Mg and Zn-1%Mg-0.1%Ca alloys also increases up to 5.7 ± 2.2 and 7.0 ± 0.7%, respectively. The structure caused by RS does not affect the corrosion potential of both investigated alloys, but changes the corrosion current density, decreasing it for the Zn-1%Mg alloy and increasing it for Zn-1%Mg-0.1%Ca. The fatigue limit of the Zn-1%Mg and Zn-1%Mg-0.1%Ca alloys after RS is equal to 115 MPa and 130 MPa, respectively.

Abstract: The Co-20Cr-15W-10Ni (CCWN, mass%) alloy, registered as American society of testing and materials (ASTM) F90, has been widely used as a balloon-expandable stent because of its excellent balance between its mechanical properties and corrosion resistance. To realize a less invasive stent placement, the stent diameter must be reduced, which implies that the stent strut thickness must be reduced. As such, the CCWN alloy must be high in strength and ductility while maintaining a low yield stress to facilitate the expansion and suppression of stent recoil. In this study, we focus on the effects of the adding Mn/Fe on the microstructure, mechanical properties, and corrosive properties of CCWN alloys. A 6 mass% Mn-added CCWN alloy with a grain size of approximately 20 μm prepared in this study exhibits excellent balance between tensile strength and ductility. In addition, it exhibits a lower yield stress while maintaining a high tensile strength compared with the ASTM F90 alloy. Meanwhile, a 6 mass% Fe-added CCWN alloy exhibits a higher ductility compared with the ASTM F90 alloy. The addition of Mn or Fe to the CCWN alloy increases the stacking fault energy of the alloy and suppresses strain-induced martensitic transformation during plastic deformation, thus improving the ductility of the alloy. Results of polarization tests show that the 6 mass% Mn-or Fe-added CCWN alloys exhibit the same corrosion current density as the ASTM F90 alloy. Mn-added Co-Cr-W-Ni alloys are suitable for use in balloon-expandable stents.

Abstract: This work briefly discusses the applications of Layered Double Hydroxides (LDHs) to medicine and presents a study regarding the growth of LDHs on the biodegradable AZ31 alloy foreseen to manufacture a rib-fixator. Mg is one of the most investigated metallic materials for biomedical applications owing to its high biocompatibility and osteointegration, as well as a value of the elastic modulus close to that of human bone. Since Mg is essential for metabolism, when it degrades forming Mg²⁺ ions, it promotes healing and growth of bone tissue. Experiments have been carried out to grow LDHs on the alloy surface in view to retard corrosion in human body and intercalate drugs to be released in-situ, with anti-inflammatory, analgesic, and antimicrobial action.

Abstract: Ca-Mg-Zn bulk metallic glasses (BMGs) are promising biomaterials for orthopaedic applications because when they get reabsorbed, a retrieval surgery is not needed. In this study, Ca-Mg-Zn metallic glasses with different compositions, Ca_56.02Mg_20.26Zn_23.72 and Zn_50.72Mg_23.44Ca_25.84, were fabricated by induction melting followed by copper mould casting. Their degree of crystallinity was modified by annealing, obtaining exemplar specimens of fully amorphous, partially amorphous (i.e., a BMG composite (BMGC)) and fully crystalline alloys. The microstructure, thermodynamic and corrosion performance of these alloys were evaluated as well as their electrochemical behaviour. The results of polarisation tests demonstrate that the corrosion resistance of the Zn-rich alloy is markedly better than the Ca-rich BMG. Corrosion rates of these Ca-and Zn-rich alloys with different degrees of crystallinity illustrate that the corrosion behaviours of alloys strongly depend on their microstructure, which shows a positive correlation between the corrosion current density and the crystallised volume fraction of the alloy. This study aims to shed light on the impact of the amorphicity-to-crystallinity ratio on the multifunctional properties of BMGs/BMGCs, and to assess how feasible it is to fine-tune those properties by controlling the percentage of crystallinity.