Search

The overview describes the synergy between biological sciences and cellular structures processed by additive manufacturing to elucidate the significance of cellular structured implants in eliminating stress shielding and in meeting the bio-mechanical property requirements of elastic modulus, impact resistance, and fatigue strength in conjunction with the biological functionality. The convergence of additive manufacturing, computer-aided design, and structure-property relationships is envisaged to provide the solution to the current day challenges in the biomedical arena. The traditional methods of fabrication of biomedical devices including casting and mechanical forming have limitations because of the mismatch in micro/microstructure, mechanical, and physical properties with the host site. Additive manufacturing of cellular structured alloys via electron beam melting and laser powder bed fusion has benefits of fabricating patient-specific design that is obtained from the computed tomography scan of the defect site. The discussion in the overview consists of two aspects - the first one describes the underlying reason that motivated 3D printing of implants from the perspective of minimising stress shielding together with the mechanical property requirements, where the mechanical properties of cellular structured implants depend on the cellular architecture and percentage cellular porosity. The second aspect focuses on the biological response of cellular structured devices. [ABSTRACT FROM AUTHOR]

Anodisation with electrochemical cathodic deposition method was employed to modify the surface of Ti implants with a bilayer coating made of Sr- doped titania (Sr-TiO2) and hydroxyapatite doped with magnesium (Mg-HAp). The Mg-HAp/Sr-TiO2 bilayer coating was compared with pure TiO2 and Sr-TiO2 single-layer coating. The Sr incorporation into TiO2 and Mg substitution into HAp strengthened their bioactive properties. The tensile test indicated increase in the mechanical strength of the bilayer coated substrate compared to pure TiO2 substrate. Moreover, the study indicated that the Sr and Mg ions were uniformly incorporated into the Mg-HAp/Sr-TiO2 bilayer coating with significantly higher roughness and hydrophilicity compared to the control. In vitro studies with osteoblasts cells had a superior response to the Mg-HAp/Sr-TiO2 bilayer surface. It was found that a bilayer Mg-HAp/Sr-TiO2 coating on Ti implants promotes bioactivity and has superior adhesion strength necessary for osseointegration and bone healing. [ABSTRACT FROM AUTHOR]

High entropy alloys (HEAs), consisting of five or more elements with nearly equal atomic composition with one another (5–35%), are new-generation alloys that have attracted signifi)cant interest since their advent in 2004 because of their unique structural and mechanical properties and thermodynamic and chemical stability. Some characteristics, including high mechanical strength at elevated temperatures, high ductility and fracture toughness at cryo)genic temperatures and high corrosion, erosion and wear resistance, have been demonstrated for HEAs that outperform traditional alloys and superalloys. Laser-cladding (LC) is an additive manufacturing technique that has good feasibility in designing and processing HEAs for advanced structural components and protective coatings. This overview provides a glimpse of recent advances in LC of HEAs in terms of design fundamentals, metallurgical phase and microstructure, specific properties for advanced coating applications and the effect of ceramic particles reinforcement in LC deposition of HEA coatings. [ABSTRACT FROM AUTHOR]

A Ti3C2 MXene/Ti composite powder was developed through surface modification and powder coating for producing a high-performance titanium matrix composites (TMCs) by laser power bed fusion. Introducing MXene rarely changed the original sphericity and flowability of Ti powder while it slightly enhanced the laser absorption capacity of Ti powder. The printing conditions in turn affected the morphology and distribution of MXene in as-printed composites. At optimised printing parameters, majority of MXene with high structural integrity and uniform distribution remained along the grain boundaries of as-printed composites, and a combination of high surface quality, geometrical accuracy and densification was obtained. The remaining MXene played the synergy of pulling-out effect and load transfer role, which increased the yield strength from 530 to 710 MPa, while retaining good ductility (elongation of 19.8%). Compared with ASTM standard cast Ti64 alloy, our MXene/Ti composites also exhibited superior comprehensive tensile properties and excellent strength-ductility synergy. [ABSTRACT FROM AUTHOR]

Polycrystalline nanoparticles of Al-doped and Ce-co-doped ZnO were processed through sol)gel co-precipitation. Crystallite sizes determined from XRD were in the range of 10.90 to 48.77 nm. FTIR spectra indicated a stretching mode of Zn-O bond. The insertion of Al and Ce at Zn-O site created Al-O and Ce-O bonds. UV-vis spectra favoured the formation of impurity levels by doping and co-doping. Their overlapping with the conduction band edge led to the reduction of band-gap. Blue-green emission which arises from radiative recombination of a photogenerated hole with an electron occupying oxygen vacancy was observed in photo)luminescence spectra. FESEM suggested granular growth in undoped ZnO which changed to diverse structures such as nano-bar and cluster of elongated grains. Significant improvement in room temperature ferromagnetism (RTFM) was noticed by co-doping of Ce in Al-doped ZnO. Formation of bound magnetic polarons (Ce3+-Vo-Ce3+) was the primary mechanism responsible for the improvement in RTFM. [ABSTRACT FROM AUTHOR]

Laser-induced periodic surface structures (LIPSS) on biomedical stainless steel in air and water were systematically studied. The LIPSS exhibit in-plane curves near the ripple centres in the individual tracks of laser scan and the curving was opposite to the laser scan direction. The collective in-plane curving of LIPSS, a hitherto unknown feature for single train pulsed laser processing, is attributed to the accumulative effect of laser ablation and redeposition, which modifies the interference between the surface scattered wave and the incident laser beam. Combinations of media, scan-speed, and laser fluence, showed that the roughness can be increased by slowing the scan-speed. Ripples fabricated in the flowing water with slow scan-speed and high laser power are helpful for the hydrophilicity of biomaterials. A contact angle as low as 47.00 ± 9.35° is obtained towards high surface hydrophilicity. The results provide new insights on LIPSS about their formation and biomedical applications. [ABSTRACT FROM AUTHOR]

The development of robust nano‐ and microstructured catalysts on highly conductive substrates is an effective approach to produce highly active binder‐free electrodes for energy conversion and storage applications. As a result, nanostructured electrodes with binder‐free designs have abundant advantages that provide superior electrocatalytic performance; these include more exposed active sites, large surface area, strong adhesion to substrates, facile charge transfer, high conductivity, high intrinsic catalytic activity, and fine‐tuning of its electronic nature through nanostructure modification. Notably, the interface chemistry of an electrocatalyst plays a significant role in their optimized electrocatalytic activity and stability. This review provides an overview of recent progress in nano‐ and microstructured catalysts, such as one, two, and 3D catalysts as binder‐free electrodes for electrocatalytic water splitting via the hydrogen evolution reaction and oxygen evolution reaction, and beyond. Furthermore, this review focuses on the current challenges and synthesis strategies of binder‐free electrodes, with a focus on the impact of nanostructure on their functional property relationships and enhanced bifunctional electrocatalytic performance. Finally, an outlook for their future advances in energy conversion and storage is provided. [ABSTRACT FROM AUTHOR]

To increase the service life of mechanical parts under severe wear environment, composite coatings with wear resistance are required. Fe‐based/B4C composite coating is fabricated on the surface of ASTM 1045 steel by vacuum cladding and the microstructure, hardness, and wear behavior of the coating are investigated. The results show that the coating is mainly composed of the coating matrix of α‐Fe, [Fe, Ni] solid solution, and the strengthening phases of eutectic borides M2B and carboborides M23(C, B)6 with irregular block distribution. The dispersion strengthening and solution strengthening of the coating microstructures improve the overall hardness distribution of the coating, the microhardness, and macrohardness of the coating are greatly improved, which are better than that of quenched and tempered ASTM 1045 steel (QT45 steel) and NM400 steel. The results of abrasive wear test under different loads (130 N/45 N) indicate that wear scar of the coating become shorter and shallower due to the antiabrasive grinding effect of strengthening phases, and wear resistance is significantly greater than that of QT45 steel and NM400 steel. The main wear mechanisms associate with QT45 steel and NM400 steel involve plastic deformation and microcutting, whereas the coating is mainly a mix mode of plastic cutting and fatigue spalling. [ABSTRACT FROM AUTHOR]

The improvement of recrystallization texture and magnetic properties in grain-oriented electrical steel with trace Bi addition processed by strip casting process was studied in this study. Low casting temperature and sufficient liquid steel flow during strip casting process enabled relatively homogeneous distribution of Bi in the as-cast strip, which accelerated the precipitation during solidification and cooling process. As a result, relatively high density of duplex MnS + AlN, MnS and AlN was formed at grain boundaries and inside grain. Due to the synergistic effect of continuous precipitation and fragmentation of coarse precipitates during cold rolling, the number density of precipitates was increased and mean size was decreased along the processing route. High density of precipitates is attributed to severe inhomogeneous plastic deformation, which promoted the formation of high density in-grain shear bands during cold rolling and recrystallization Goss texture during annealing. Homogeneous microstructure with average grain size of ~ 11.6 μm, strong Goss texture with intensity of 2.5 multiples of random distribution, fine precipitates with number density of ~ 1.9 × 109 /cm2 and mean size of ~ 49 nm were formed after primary recrystallization annealing. Furthermore, grain-oriented electrical steel with Bi addition experienced complete secondary recrystallization of exact Goss grains during high-temperature annealing, which is attributed to beneficial optimization of Goss texture and strong inhibition effect, and superior magnetic induction B8 of 1.91 T was obtained. It is expected that this study paves a new way for fabrication of high-performance grain-oriented electrical steel. [ABSTRACT FROM AUTHOR]

The wide application of magnesium alloys as biodegradable implant materials is limited because of their fast degradation rate. Hydroxyapatite (HA) coating can reduce the degradation rate of Mg alloys and improve the biological activity of Mg alloys, and has the ability of bone induction and bone conduction. The preparation of HA coating on the surface of degradable Mg alloys can improve the existing problems, to a certain extent. This paper reviewed different preparation methods of HA coatings on biodegradable Mg alloys, and their effects on magnesium alloys' degradation, biocompatibility, and osteogenic properties. However, no coating prepared can meet the above requirements. There was a lack of systematic research on the degradation of coating samples in vivo, and the osteogenic performance. Therefore, future research can focus on combining existing coating preparation technology and complementary advantages to develop new coating preparation techniques, to obtain more balanced coatings. Second, further study on the metabolic mechanism of HA-coated Mg alloys in vivo can help to predict its degradation behavior, and finally achieve controllable degradation, and further promote the study of the osteogenic effect of HA-coated Mg alloys in vivo. [ABSTRACT FROM AUTHOR]