In this study, spray deposition technology was used for in situ preparation of silver (Ag) particles on additively manufactured Ti6Al4V alloy surfaces. An amount of silver particles (200 nm) was uniformly achieved on pristine or acid-etched titanium (Ti) alloy surfaces by designing the spraying passes. Energy-dispersive X-ray spectroscopy and X-ray diffraction were used to confirm their composition and crystal structure. The antibacterial activity of the prepared silver particles was investigated against Staphylococcus aureus and Escherichia coli bacteria. Thereafter, the antibacterial activity of silver particles on Ti6Al4V alloy surfaces against S. aureus and E. coli bacteria was investigated by utilizing the bacterial counting method. The damaged cell membranes around the silver particles revealed excellent antibacterial properties, indicating the possibility of harnessing the spray deposition method to take advantage of the in-situ-produced antibacterial silver coatings on additively manufactured metallic materials. The excellent antibacterial activity of the surfaces suggests that silver particles prepared by spray deposition are potential candidates for future dental implant applications.
The technology of high-density electropulsing has been applied to increase the performance of metallic materials since the 1990s and has shown significant advantages over traditional heat treatment in many aspects. However, the microstructure changes in electropulsing treatment (EPT) metals and alloys have not been fully explored, and the effects vary significantly on different material. When high-density electrical pulses are applied to metals and alloys, the input of electric energy and thermal energy generally leads to structural rearrangements, such as dynamic recrystallization, dislocation movements and grain refinement. The enhanced mechanical properties of the metals and alloys after high-density electropulsing treatment are reflected by the significant improvement of elongation. As a result, this technology holds great promise in improving the deformation limit and repairing cracks and defects in the plastic processing of metals. This review summarizes the effect of high-density electropulsing treatment on microstructural properties and, thus, the enhancement in mechanical strength, hardness and corrosion performance of metallic materials. It is noteworthy that the change of some properties can be related to the structure state before EPT (quenched, annealed, deformed or others). The mechanisms for the microstructural evolution, grain refinement and formation of oriented microstructures of different metals and alloys are presented. Future research trends of high-density electrical pulse technology for specific metals and alloys are highlighted.
Zinc (Zn) alloys are promising alternatives to magnesium (Mg)- and iron (Fe)-based alloys because of their moderate corrosion rate and superior biocompatibility. To reduce the mass release of Zn2+ and improve the biocompatibility of Zn implants, the biomimetic zwitterionic polymer layer (phosphorylcholine chitosan—PCCs) was immobilized on the plasma-treated Zn1Mg surface. It is the chemical bonds between the −NH2 groups of the PCCs chain and O–C═O (C═O) groups on the plasma-treated Zn1Mg (Zn1Mg-PP) that contributes to the strong bonding strength between the film and the substrate, by which the PCCs (approx. 200 nm thick) layer can bear a 5.93 N normal load. The electrochemical impedance spectroscopy (EIS) results showed that the PCCs layer remarkably increased the resistance against corrosion attack, protecting substrates from over-quick degradation, and the protective effect of the layer with a thickness of 200 nm lasts for about 24 h. The corrosion products of Zn1Mg-PP-PCC in NaCl solution were determined as Zn5(OH)8Cl2·H2O and Zn3(PO4)2. Besides, the bulk Zn1Mg can trigger more aggressive macrophage activity, while the surface of Zn1Mg-PP and Zn1Mg-PP-PCC and their corrosion products (Zn3(PO4)2) tend to promote the differentiation of macrophages into the M2 phenotype, which is beneficial for implant applications.
A superhydrophobic coating was prepared on copper (Cu) foam by a one-step chemical deposition technique. The as-prepared coated copper foam displayed excellent superhydrophobicity (water contact angle of ∼153.5° and water sliding angle of ∼1°) with a typical surface micro–nano rough structure at a deposition temperature of 60°C and a deposition time of 20 min. The film was composed of cuprous sulfide (Cu 2 S) and copper tetradecanoate, which revealed the reaction mechanism. The as-prepared superhydrophobic copper foam maintained its superhydrophobicity under harsh environmental conditions (alkaline, weakly acidic, salty, long-term storage and mechanical abrasion). The as-prepared surface was still superhydrophobic after 600 mm abrasion, with a contact angle above 150.2 ± 0.2° and a sliding angle below 10°. Through the method of heat treatment and the modification of myristic acid, the surface achieved a rapid transition in wettability, with the contact angle maintaining stability for 20 cycles. The superhydrophobic film was repeatedly soaked in a mud–water mixture 20 times, and it remained silt-free, indicating excellent self-cleaning and antifouling features. More importantly, the modified copper foam can effectively separate a series of oil–water mixtures with high efficiency (>94%) even after five cycles. Thus, the presented superhydrophobic material with dual functionality is a promising candidate for application in efficient oil–water separation.
Ag and its alloys, when prepared by a selective laser melting (SLM) process, have a low density and poor overall performance due to their high reflectivity when the most commonly used laser (λ = 1060 nm) is used, and they have exorbitant thermal conductivity. These characteristics lead to the insufficient melting of the powders and severely limit the applications of additive manufactured silver alloys. To improve the absorption of the laser, as well as for better mechanical properties and higher resistance to sulfidation, Ag-Cu alloys with different La2O3 contents were prepared in this work using the SLM process, via the mechanical mixing of La2O3 nanoparticles with Ag-Cu alloy powders. A series of analyses and tests were conducted to study the effects of La2O3 in Ag-Cu alloys on their density, microstructure, mechanical properties, and corrosion resistance. The results revealed that the addition of La2O3 particles to Ag-Cu alloy powders improved the laser absorptivity and reduced defects during the SLM process, leading to a significant rise from 7.76 g/cm3 to 9.16 g/cm3 in the density of the Ag-Cu alloys. The phase composition of the Ag-Cu alloys prepared by SLM was Silver-3C. La2O3 addition had no influence on the phase composition, but refined the grains of the Ag-Cu alloys by inhibiting the growth of columnar grains during the SLM process. No remarkable preferred orientation existed in all the samples prepared with or without La2O3. An upwards trend was achieved in the hardness of the Ag-Cu alloy by increasing the contents of La2O3 from 0 to 1.2%, and the average hardness was enhanced significantly, from 0.97 GPa to 2.88 GPa when the alloy contained 1.2% La2O3 due to the reduced pore defects and the refined grains resulting from the effects of the La2O3. EIS and PD tests of the samples in 1% Na2S solution proved that La2O3 addition improved the corrosion resistance of the Ag-Cu alloys practically and efficaciously. The samples containing La2O3 exhibited higher impedance values and lower corrosion current densities.
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