•Cu-doped TiO2 coating was synthesized by micro-arc oxidation.•Cu nanoparticles were successfully incorporated into the coating.•The Cu-doped coating exhibited excellent antibacterial activities.
...Infection associated with titanium implants remains the most common serious complication after surgery. In this work, Cu-doped antibacterial TiO2 coating was synthesized by micro-arc oxidation of titanium in an electrolyte bearing Cu nanoparticles. Surface morphology and structure of the coating were characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicated that Cu nanoparticles were not only distributed on the surface and inside the pores but also embedded in the coating. Cu mainly exists in the Cu2+ state in the TiO2 coating. The Cu-doped coating exhibited excellent antibacterial activities against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus).
Incorporation of antibacterial agents (e.g. Ag and Cu) at the surface of biomedical materials has evolved as a potentially effective method for preventing the bacterial infections. However, the ...antibacterial efficacy of medical device implants must necessarily be balanced by good corrosion resistance and the corrosion behavior of the antibacterial coatings has seldom been reported. In this work, Zn-incorporated antibacterial TiO2 coating was produced on pure titanium (Ti) by micro-arc oxidization (MAO) and the electrochemical behavior was assessed. The results obtained from the antibacterial studies suggest that the Zn-incorporated TiO2 coating provides bactericidal activity against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) over 90%. The corrosion behavior of Zn-incorporated TiO2 coating were investigated using a combination of complementary electrochemical measurement techniques such as open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy. The results show that the Zn-incorporated TiO2 coating move the OCP to the positive direction and increase the polarization resistance, thereby enhances the corrosion resistance of pure Ti. Collectively, the Zn-incorporated TiO2 coating with both antibacterial ability and anti-corrosive properties might be more suitable for biomedical surfaces.
Electrochemical anodization has become a prevalent surface modification method for biomaterials nowadays. In this study we prepared Ni2O3-doped TiO2 nanotubes (NTs) on NiTi alloy using ...electrochemical anodization method and explored its suitability for biomedical applications. Morphology, composition and microstructure of NT films were found to depend on preparation conditions. NT film prepared at 35V, 45°C and 10min had well-defined nanotubular architecture and were composed of TiO2 and a small amount of Ni2O3. Annealing at 450°C, the film remained amorphous structure, with excellent corrosion resistance. At annealing temperatures of 600°C, rutile crystalline was formed thus enhanced the bioactivity of the film. Formation of NT film on the surface of NiTi alloy also increased its wettability, especially for 600°C annealed sample, so the biological response is expected to be improved. Our results indicate that annealing the NT film coated NiTi alloy at 450°C is desirable for cardiovascular applications. This attributes to its advantages such as the eliminated toxic F species, enhanced corrosion resistance and reduced risk of calcification. For orthopedic applications, annealing at 600°C is preferred due to its enhanced corrosion resistance and bioactivity.
The Gd-Fe-Al amorphous/nanocrystalline composites were successfully designed and obtained with both high Curie temperature (Tc) and large magnetic entropy change (ΔSM). The Tc can be tuned from 172 ...to 280 K and refrigeration capacity (RC) has a value between 690 and 867 J/kg under a field change of 0–5 T by changing the Gd contents and the formation of Gd nanocrystallites. And, ΔSM in Gd-Fe-Al amorphous/nanocrystalline composites reached a value of 7.2 J kg−1 K−1 under a field change of 0–5 T. The high RC in Gd-Fe-Al system were ascribed to the widening full width at half maximum (δFWHM) up to 240 K of the magnetic entropy change (ΔSM
max) peak because of the combination contribution of amorphous matrix and the precipitated Gd-riched nanocrystalline. Our research would shed light on how to design attractive candidates for magnetic refrigeration materials with high performance at near room temperature.
Laser powder bed fusion (LPBF) is capable to process complex flow field structures on 316L stainless steel (316L SS) bipolar plates, which is promising to improve the performance of proton exchange ...membrane fuel cell (PEMFC). However, insufficient corrosion resistance and relatively high interfacial contact resistance (ICR) hinder the widespread of LPBF-processed 316L SS bipolar plates. In this work, active screen plasma nitriding (ASPN) was used to modify 316L SSs fabricated by the LPBF process and forging, respectively. Results showed that the nitrided layer of LPBF-processed 316L SS (2000 mm/s, 300 W) exhibited the highest surface nitrogen concentration, thickest nitrided layer and highest average hardness. The ICR values decreased significantly after ASPN treatment. The corrosion current of nitrided LPBF-processed 316L SS (2000 mm/s, 300 W) was much lower than that of the nitrided forged 316L SS. By comparing multiscale microstructures between LPBF-processed and forged 316L SS, the ASPN mechanism of LPBF-processed 316L SS was proposed.
The present work was aimed at developing the antibacterial Ag-containing TiO2 coatings on titanium by combining magnetron sputtering with micro-arc oxidation (MAO). The surface morphology, ...microstructure, chemical composition and chemical state of the Ag-containing TiO2 layers were characterized using scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The concentration of Ag in the sputtering-deposited AgTi layer on pure titanium was 13.9wt.%. The MAO coatings were prepared on the AgTi layers under different oxidation duration of 2, 5 and 8min. The size of the well-separated pores increased by increasing the oxidation duration. Metal Ag existed as Ag0 state was mainly distributed homogeneously inside the pores and the concentrations were 2.36, 2.05 and 1.50wt.%, respectively. The main TiO2 phases bearing Ca and P species appeared within the structure of the coatings were rutile and anatase. The Ag-containing coating oxidation for 5min showed excellent antibacterial activity of Escherichia coli (E.coli) within 24h and the antibacterial rate gradually raised with increasing contact time.
•Porous Ag-containing TiO2 coatings were prepared by a duplex-treatment.•The duplex-treatment consisted of magnetron sputtering and micro-arc oxidation.•Metal Ag existed as Ag0 state was mainly distributed inside the pores.•The main TiO2 phases that appeared in the coatings were rutile and anatase.•The duplex-treated coatings exhibited excellent antibacterial activity to E.coli.
CrAlN coatings were deposited on silicon and AISI H13 steel substrates using a modified ion beam enhanced magnetron sputtering system. The effect of substrate negative bias voltages on the impact ...property of the CrAlN coatings was studied. The X-ray diffraction (XRD) data show that all CrAlN coatings were crystallized in the cubic NaCl B1 structure, with the (1
1
1), (2
0
0) (2
2
0) and (2
2
2) diffraction peaks observed. Two-dimensional surface morphologies of CrAlN coatings were investigated by atomic force microscope (AFM). The results show that with increasing substrate bias voltage the coatings became more compact and denser, and the microhardness and fracture toughness of the coatings increased correspondingly. In the dynamic impact resistance tests, the CrAlN coatings displayed better impact resistance with the increase of bias voltage, due to the reduced emergence and propagation of the cracks in coatings with a very dense structure and the increase of hardness and fracture toughness in coatings.
A lean duplex stainless steel, LDX2404, was DC plasma nitrided under a range of treatment conditions. The microstructure characterisation evaluation of the treated samples revealed that a dense, ...super-hard surface layer can be produced by low-temperature (<450 °C) plasma treatments. The original austenite phase became S-phase and the ferrite phase was supersaturated with nitrogen and ε-Fe3N nitride precipitated from it. When plasma nitriding was carried out at above 450 °C, chromium nitrides precipitated in the surface nitrided layer. Compared to the untreated samples, the surface hardness of the lean duplex stainless steel (DSS) is increased up to four times. The dry wear resistance increased when increasing the treatment temperature. In contrast, the low-temperature treated samples showed the best performance in the electrochemical corrosion and corrosion-wear tests; the performance of the high temperature (>450 °C) plasma nitrided samples was found to be significantly worse than that of the untreated material.
In this work, Ti6Al4V alloy was treated by a duplex treatment of double glow plasma surface molybdenizing-laser surface texturing (LST) aiming to realize surface strengthening and manipulate its ...tribological behavior. The double glow plasma surface alloying (DGPSA) with molybdenum (Mo) was firstly conducted on the Ti6Al4V alloy and followed by LST to prepare round dimple-shape texture with a density of 5%, 7%, 11%. The results showed that Mo and Mo/Ti solid solution phases were detected in the Mo-layer by X-ray diffraction (XRD), the received Mo-layer with a thickness of about 13μm was uniform and compact. Double glow plasma surface molybdenizing significantly improved the surface hardness and elastic modulus of Ti6Al4V alloy by nanoindentation test. The gradient distributed Mo-layer was tightly adhered to the Ti6Al4V alloy matrix through scratching and indentation tests. Duplex treated Ti6Al4V alloy with a 5% texture density suggested better wear resistance in comparison to the untreated Ti6Al4V alloy, which was confirmed by a 48.7% lower specific wear rate than that of Ti6Al4V alloy. Taking advantages of DGPSA and LST, duplex treatment of double glow plasma surface molybdenizing-laser surface texturing was established to create on the working surface of Ti6Al4V alloy with promisingly improved tribological behavior.
Multilayer hard coatings of TiCN/TiC/TiN on high speed steel substrates were deposited using a chemical vapor deposition system. Evaluations of microstructure, wear morphology of coatings were ...characterized by scanning electron microscopy, and optical microscopy. Friction coefficient and wear rates of coatings were investigated using ball-on-disk tester sliding against a WC ball at a constant load of 20
N. Tribological behavior of the coatings at room and elevated temperature were discussed. Different changing tendency of friction coefficient were observed from ball-on-disc experiments. Results showed that the friction coefficient of coatings increased gradually to a highest value, then to a relatively constant value at room temperature dry sliding wear. The friction coefficient exhibited a reverse variation tendency at temperature of 550
°C. It got a higher value at the first sliding friction cycles. Then the value of friction coefficient decreased, suffered irregular oscillations and kept a relatively lower value with increasing sliding time. Reasons of the variation of friction coefficient with sliding time and wear mechanism were analyzed and discussed at room and elevated temperatures, respectively.
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