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Zinc (Zn)-based composites are promising biodegradable bone-implant materials because of their good biocompatibility, processability, and biodegradability. Nevertheless, the low interfacial bonding strength, coordinated deformation capacity, and mechanical strength of current Zn-based composites hinder their clinical application. In this study, we developed a biodegradable in situ 4Mg2Ge/Zn-0.3Cu-0.05P composite (denoted ZMGCP) via phosphorus (P) modification and hot-rolling for bone-implant applications. The mechanical properties, corrosion behavior, biotribological performance, in vitro cytocompatibility and osteogenic differentiation, and in vivo osteogenesis and osteointegration of the as-cast (AC) and hot-rolled (HR) ZMGCP samples were systematically evaluated and compared to those of 4Mg2Ge/Zn-0.3Cu (denoted ZMGC). The primary and eutectic reinforcement Mg2Ge phases formed during solidification were refined after P modification and hot-rolling. The HR ZMGCP exhibited the best tensile properties among all the samples with an ultimate tensile strength of 288.9 MPa, a yield strength of 194.5 MPa, and an elongation of 17.7 %. The HR ZMGCP showed the lowest corrosion rate of 336 μm/a, 186 μm/a, and 61.7 μm/a as measured by potentiodynamic polarization, electrochemical impedance spectroscopy, and immersion testing, respectively, among all the samples in Hanks’ solution. The HR ZMGCP also showed higher biotribological resistance than its ZMGC counterpart. The HR ZMGCP exhibited the highest in vitro cytocompatibility, the best osteogenesis capability and angiogenesis property among the HR samples of pure Zn, ZMGC, and ZMGCP. Furthermore, the HR ZMGCP displayed complete in vivo biocompatibility, osteogenesis, osteointegration capability, and an appropriate degradation rate, showing significant potential for a biodegradable bone-implant material.

A new nanoindentation approach is developed in this study to determine both indentation size effect (ISE) and continuous apparent activation volume (V) during loading of nanocrystalline nickel (NC Ni) and nanocrystalline nickel-20 wt% iron alloy (NC Ni–Fe alloy). This approach involves conducting nanoindentation tests under loading modes controlled by both constant strain rate (CSR) and constant loading rate (CLR). Firstly, a new empirical expression for the parameter f in the modified Nix-Gao model is established to study the strain rate dependence of the ISEs created in the CSR and CLR tests. Then, continuous V data of each individual sample (indentation) during loading are obtained in the CLR test through the alternative use of continuous stiffness measurement technique. The stress dependence of V is analyzed based on Duhamel et al.’s model, which considers the role of vacancies generated during inhomogeneous dislocation nucleation. Finally, based on the above experimental and theoretical work as well as transmission electron microscopy observation, the influences of loading mode, loading rate, and material properties (stacking fault energy) on resulting intrinsic hardness of NC Ni and NC Ni–Fe alloy are analyzed. The nanoindentation approach developed in this study provides profound insights into the mechanical behaviors during loading and underlying mechanisms of materials.

ABSTRACTPoly(lactic acid)-zinc oxide (PLA-ZnO) nanocomposites for fused filament fabrication have potential applications in the biomedical field as they combine the bio-compatibility of PLA with the antibacterial properties of ZnO. This work investigates the effects of masterbatch mixing strategy, ZnO concentration and ZnO surface treatment (silanisation) on the printability and the mechanical performance of the nanocomposites as a pre-requirement to the wider uptake of these materials. The results showed that the printability decreased as the filler loading increased. However, the surface treatment of the ZnO powder enhanced the matrix-filler interfacial interactions and reduced the thermal degradation of PLA. This ameliorated the printability and the tensile properties of the nanocomposites filled with up to 5 wt.% of ZnO. Moreover, despite the additional thermal treatment, melt-mixing prevented the degradative effect induced by the solvent used for solvent mixing. Future work will focus on assessing the antibacterial properties of the nanocomposite FFF parts.

Three mole percent yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) ceramics are exemplary materials for dental restoration due to their high mechanical strength, fracture toughness, chemical endurance, and biocompatibility. Nevertheless, 3Y-TZP ceramics are opaque and their CAD/CAM manufacturing process may cause micro-cracks in conventional clinical practice. In this study, 3Y-TZP ceramic samples were prepared using vat photopolymerization, pre-sintering, external staining, and final high-temperature sintering. The microstructures, mechanical properties, optical properties, and cytotoxicity of the 3Y-TZP ceramic samples were investigated. The results indicate that with increasing Fe3+ concentration of staining solution from 0.1 mol/L to 0.3 mol/L and increasing staining time from 5 s to 30 min, the 3Y-TZP ceramic samples showed a tetragonal crystal structure of zirconia with densely packed grains and a slight increase in grain size. The flexural strength, Vickers hardness, and fracture toughness of 3Y-TZP ceramic samples stained in 0.1–0.3 mol/L Fe3+ solution for 5 s to 3 min were all greater than 665 MPa, 11.9 GPa, and 5 MPa m1/2, respectively, meeting the mechanical requirements for clinical application. Colorimetric analysis revealed a decrease in L* (black-white index) from 90.4 to 81.3, an increase in a* (green-red index) from −1.5 to 3.2, and an increase in b* (blue-yellow index) from 11.6 to 20.3, approximating the commercial VITA 3D-Master Shade Guide chromaticity. Furthermore, the 3Y-TZP ceramic samples exhibited a cell viability of 90% or higher toward L929 cells.

Weak shear bond strength (SBS) has always been a challenge for clinical bonding of 3mol% yttria-stabilized tetragonal zirconia (3Y-TZP). With the development of additive manufacturing technology, vat photopolymerization (VPP) is an alternative that allows zirconia to form precise complex structures and achieve bionic structure molding based on the natural advantages of different organisms in relation to biological structure, microstructure, and mechanical behavior. As report goes, the toe structure of tree frog can effectively achieve friction enhancement on humid and flooded surfaces. In this paper, we present a new type of 3Y-TZP material loaded with tree-frog bionic structures via VPP additive manufacturing to improve SBS between resin cement and 3Y-TZP for clinical requirements. And flexural strength, finite element analysis and accuracy analysis of bio-inspired 3Y-TZP is carried out to verify its feasibility of clinical application. The SBS of the bio-inspired group with 250 μm width and 250 μm height reached a maximum of 22.7 ± 1.3 MPa before hydrothermal aging, the flexural strength of the bio-inspired group with 250 μm width and 150 μm height decreased the least, reaching 825 ± 30 MPa, and the accuracy analysis of the central-incisor veneer restoration loaded with the bionic structures showed that the average deviation value was 0.033 ± 0.036 mm. This study has found that these bionic structures can effectively improve the SBS of the interface between zirconia and resin cement, while flexural strength and accuracy can also meet requirements of clinical dental application.

Magnesium (Mg)-based bone implants degrade rapidly in the physiological environment of the human body which affects their structural integrity and biocompatibility before adequate bone repair. Rare earth elements (REEs) have demonstrated their effectiveness in tailoring the corrosion and mechanical behavior of Mg alloys. This study methodically investigated the impacts of scandium (Sc) and terbium (Tb) in tailoring the corrosion resistance, mechanical properties, and biocompatibility of Mg–0.5Zn–0.35Zr–0.15Mn (MZZM) alloys fabricated via casting and hot extrusion. Results indicate that addition of Sc and Tb improved the strength of MZZM alloys via grain size reduction and solid solution strengthening mechanisms. The extruded MZZM–(1–2)Sc–(1–2)Tb (wt.%) alloys exhibit compressive strengths within the range of 336–405 MPa, surpassing the minimum required strength of 200 MPa for bone implants by a significant margin. Potentiodynamic polarization tests revealed low corrosion rates of as–cast MZZM (0.25 mm/y), MZZM–2Tb (0.45 mm/y), MZZM–1Sc–1Tb (0.18 mm/y), and MZZM–1Sc–2Tb (0.64 mm/y), and extruded MZZM (0.17 mm/y), MZZM–1Sc (0.15 mm/y), MZZM-2Sc (0.45 mm/y), MZZM-1Tb (0.17 mm/y), MZZM-2Tb (0.10 mm/y), MZZM–1Sc-1Tb (0.14 mm/y), MZZM-1Sc-2Tb (0.40 mm/y), and MZZM–2Sc–2Tb (0.51 mm/y) alloys, which were found lower compared to corrosion rate of high-purity Mg (∼1.0 mm/y) reported in the literature. Furthermore, addition of Sc, or Tb, or Sc and Tb to MZZM alloys did not adversely affect the viability of SaOS2 cells, but enhanced their initial cell attachment, proliferation, and spreading shown via polygonal shapes and filipodia. This study emphasizes the benefits of incorporating Sc and Tb elements in MZZM alloys, as they effectively enhance corrosion resistance, mechanical properties, and biocompatibility simultaneously.

Abstract Nanostructured surfaces are effective at physically killing bacterial cells, highlighting their prospective application as biomaterials. The benefits of application of mechano‐bactericidal nanostructures as an alternative to chemical functionalisation are well documented, however, the effects of protein adsorption are not well understood. In this work, theoretical and experimental analyses are conducted by studying the adsorption of human serum proteins (HSP) to nanosheet titanium (Ti) and its subsequent effect on the mechano‐bactericidal efficacy toward Staphylococcus aureus and Pseudomonas aeruginosa cells. The nanosheet pattern exhibits enhanced antibiofouling behaviour mantaining high bactericidal efficiency toward both Gram‐negative and Gram‐positive cells in the presence of adsorbed HSP. To ascertain the immunomodulatory response, S. aureus cells are introduced to protein‐conditioned Ti nanosheet surfaces prior to introducing RAW 264.7 macrophages. On the pre‐infected nanostructured surfaces, macrophages exhibit wound healing behaviour with superior activation of M2‐like macrophage polarization and secretion of anti‐inflammatory cytokines. By contrast, macrophages attached to infected smooth surfaces activated the M1‐like polarized phenotype via the high expression of pro‐inflammatory cytokines, indicating persistent inflammation. The outcomes of this work demonstrate the suitability of Ti nanosheets as a potential biomaterial surface whereby the mechano‐bactericidal activity is not compromised by HSP adsorption and, furthermore, positively influenced an anti‐inflammatory immune response.

Biodegradable implants from magnesium (Mg) alloys have emerged in the biomedical field especially in the orthopedic and cardiovascular stent applications owing to their low density, high specific strength, excellent machinability, good biocompatibility, and biodegradability. The primary shortcoming of Mg-based implants is their low corrosion resistance in the physiological environment, which results in premature mechanical integrity loss before adequate healing and the production of excessive hydrogen gas, which is harmful to the body tissues and negatively affects the biocompatibility of the implant. Laser surface modification has recently received attention because it can improve the surface properties such as surface chemistry, roughness, topography, corrosion resistance, wear resistance, hydrophilicity, and thus cell response to the surface of the material. The composition and microstructures including textures and phases of laser-treated surfaces depend largely on the laser processing parameters (input laser power, laser scan velocity, frequency, pulse duration, pressure, gas circulation, working time, spot size, beam focal position, and laser track overlap) and the thermophysical properties of the substrate (solubility, melting point, and boiling point). This review investigates the impacts of various laser surface modification techniques including laser surface melting, laser surface alloying, laser cladding, laser surface texturing, and laser shock peening, and highlights their significance in improving the surface properties of biodegradable Mg alloys for implant applications. Additionally, we explore how different laser process parameters affect its composition, microstructure, and surface properties in each laser surface modification technique.

In this study, extrusion was performed on Mg‒Zr‒Sr‒Dy alloys for improving their mechanical, corrosion, and biocompatibility properties. Effects of extrusion and alloying elements on the microstructural characteristics, tensile and compressive strengths, corrosion behavior, and biocompatibility were investigated. The Mg‒Zr‒Sr‒Dy alloys were composed of an α-Mg matrix containing {101¯2} extension twins and secondary phases of intermetallic compounds Mg17Sr2 and Mg2Dy. Evolution of basal and rare earth (RE) textures was observed in the extruded alloys and an increase in Dy content to 2 wt.% resulted in texture randomization and strengthening of the RE component, mainly due to particle-stimulated nucleation and a change from discontinuous dynamic recrystallization to continuous dynamic recrystallization, which also led to an improved tension–compression yield asymmetry of 0.87. Extrusion of the alloys significantly enhanced their tensile and compressive properties due to improved distribution of alloying elements and formation of textures. Corrosion rates tested by hydrogen evolution testing, potentiodynamic polarization, and electrical impedance spectroscopy showed similar trends for each composition, and the lowest corrosion rate of 3.37 mmy−1 was observed for the Mg-1Zr-0.5Sr-1Dy in the potentiodynamic polarization testing. Dy2O3 was observed in the inner layers of the Mg(OH)2 protective films, whose protective efficacy was confirmed by charge-transfer and film resistances. A comparison among the minimum CRs observed in this study and previously studied as-cast Mg‒Zr‒Sr‒Dy and extruded Mg‒Zr‒Sr alloys, demonstrates that both the extrusion process and addition of Dy in Mg‒Zr‒Sr improved the CR. Similarly, extruded Mg–Zr–Sr–Dy alloys showed improved cell viability and adhesion of human osteoblast–like SaOS2 cells due to increased corrosion resistance and enhanced Sr distribution within the Mg matrix.

Abstract Zinc (Zn)–dysprosium (Dy) binary alloys are promising biodegradable bone fracture fixation implants owing to their attractive biodegradability and mechanical properties. However, their clinical application is a challenge for bone fracture healing, due to the lack of Zn–Dy alloys with tailored proper bio‐mechanical and osteointegration properties for bone regeneration. A Zn‐5Dy alloy with high strength and ductility and a degradation rate aligned with the bone remodeling cycle is developed. Here, mechanical stability is further confirmed, proving that Zn‐5Dy alloy can resist aging in the degradation process, thus meeting the mechanical requirements of fracture fixation. In vitro cellular experiments reveal that the Zn‐5Dy alloy enhances osteogenesis and angiogenesis by elevating SIRT4‐mediated mitochondrial function. In vivo Micro‐CT, SEM‐EDS, and immunohistochemistry analyses further indicate good biosafety, suitable biodegradation rate, and great osteointegration of Zn‐5Dy alloy during bone healing, which also depends on the upregulation of SIRT4‐mediated mitochondrial events. Overall, the study is the first to report a Zn‐5Dy alloy that exerts remarkable osteointegration properties and has a strong potential to promote bone healing. Furthermore, the results highlight the importance of mitochondrial modulation and shall guide the future development of mitochondria‐targeting materials in enhancing bone fracture healing.

Zinc (Zn)-based composites have been received adequate attention lately in the biomedical field as degradable biomaterials owing to their simple preparation process, inherent biodegradability, intrinsic biological activity, and good biocompatibility. Nevertheless, the low mechanical strength and fast corrosion rate of Zn-based composites caused by a large number of coarse reinforcement particles have severely impeded their further clinical application. This work reports a promising method to fabricate an in situ biodegradable Zn–5Mg2Ge composite with high mechanical properties, wear resistance, corrosion resistance, and cytocompatibility via high-intensity ultrasonication and followed by hot-rolling. After hot rolling, the ultrasonicated Zn–5Mg2Ge composite exhibited the best mechanical properties and hardness with a yield strength, an ultimate tensile strength, elongation, Vickers hardness, and Brinell hardness of 142.9 MPa, 253.6 MPa, 8.9%, 109.5 HV, and 104.0 HB, respectively. Further, the ultrasonicated Zn–5Mg2Ge composite after hot-rolling exhibited significantly higher corrosion and wear resistance than its un-ultrasonicated counterpart in Hanks’ solution. The diluted extract (12.5% concentration) of the.

Layered double hydroxide (LDH) coatings on magnesium (Mg) alloys shine brightly in the field of corrosion protection because of their special ion-exchange function. State-of-the-art steam coating as a type of LDH film preparation technique has emerged in recent years because only pure water is required as the steam source and its environmentally friendly LDH coating fits the current need for green development. Moreover, this coating can effectively inhibit the corrosion of the Mg alloy substrate due to the chemical bonding between the coating and the Mg alloy substrate. This review systematically explains cutting-edge advancements in the growth mechanism and corrosion behavior of LDH steam coatings, and analyzes the advantages and limitations of the steam-coating method. The influencing factors including pressure, CO2/CO32−, aluminum content of the substrate alloy, solution type, and acid-pickling pretreatment, as well as the post-treatment of steam-coating defects, are comprehensively elucidated, providing new insights into the development of the in situ steam-coating technique. Finally, existing issues and future prospects are discussed to further accelerate the widespread application of Mg alloys.

In this study, the microstructures, mechanical properties, corrosion behaviors, and biocompatibility of extruded magnesium-zirconium-strontium-holmium (Mg-Zr-Sr-Ho) alloys were comprehensively investigated. The effect of different concentrations of Ho on the microstructural characteristics, tensile and compressive properties, corrosion resistance, and biocompatibility were investigated. The microstructures of the extruded Mg-1Zr-0.5Sr-xHo (x = 0.5, 1.5, and 4 wt.%) alloys consisted of α-Mg matrix, fine α-Zr particles, and intermetallic phase particles of Mg17Sr2 and Ho2Mg mainly distributed at the grain boundaries. Extensive {101¯2} tensile twins were observed in the partially recrystallized samples of Mg-1Zr-0.5Sr-0.5Ho and Mg-1Zr-0.5Sr-1.5Ho. Further addition of Ho to 4 wt.% resulted in a complete recrystallization due to activation of the particle stimulated nucleation around the Mg17Sr2 particles. The evolution of a rare earth (RE) texture was observed with the Ho addition, which resulted in the weakened basal and prismatic textures. Furthermore, a drastic increase of 200% in tensile elongation and 89% in compressive strain was observed with Ho addition increased from 0.5 to 4 wt%, respectively. The tension-compression yield asymmetry was significantly decreased from 0.62 for Mg-1Zr-0.5Sr-0.5Ho to 0.98 for Mg-1Zr-0.5Sr-4Ho due to the weakening of textures. Corrosion analysis of the extruded Mg-Zr-Sr-Ho alloys revealed the presence of pitting corrosion. A minimum corrosion rate of 4.98 mm y−1 was observed in Mg-1Zr-0.5Sr-0.5Ho alloy. The enhanced corrosion resistance is observed due to the presence of Ho2O3 in the surface film which reduced galvanic effect. The formation of a stabilized surface film due to the Ho2O3 was confirmed through the electrical impedance spectroscopy and XPS analysis. An in vitro cytotoxicity assessment revealed good biocompatibility and cell adhesion in relation to SaOS2 cells.

Additive manufacturing (AM, also commonly termed 3D printing) is progressing from being a rapid prototyping tool to serving as pillar of the Industry 4.0 revolution. Thanks to their low density and ease of printing, polymers are receiving increasing interest for the fabrication of structural and lightweight parts. Nonetheless, the lack of appropriate standards, specifically conceived to consistently verify the tensile properties of polymer parts and benchmark them against conventional products, is a major obstacle to the wider uptake of polymer AM in industry. After reviewing the standardisation needs in AM with a focus on mechanical testing, the paper closely examines the hurdles that are encountered when existing standards are applied to measure the tensile properties of polymer parts fabricated by fused filament fabrication (FFF, aka fused deposition modeling, FDM), which is presently the most popular material extrusion AM technique. Existing standards are unable to account for the numerous printing parameters that govern the mechanical response of FFF parts. Moreover, the literature suggests that the raster- and layer-induced anisotropic behaviour and the complicated interplay between structural features at different length scales (micro/meso/macro-structure) undermine pre-existing concepts regarding the specimen geometry and classical theories regarding the size effect, and ultimately jeopardise the transferability of conventional tensile test standards to FFF parts. Finally, the statistical analysis of the tensile properties of poly(lactic acid) (PLA) FFF specimens printed according to different standards (ASTM D638 type I and ASTM D3039) and in different sizes provides experimental evidence to confirm the literature-based argumentation. Ultimately, the literature survey, supported by the experimental results, demonstrates that, until dedicated standards become available, existing standards for tensile testing should be applied to FFF with prudence. Whilst not specified in conventional standards, set-up and printing parameters should be fully reported to ensure the repeatability of the results, rectangular geometries should be preferred to dumbbell-like ones in order to avoid premature failure at the fillets, and the size of the specimens should not be changed arbitrarily.

The repair of critical-sized bone defects (CSBD) remains a significant challenge in clinical practice. Personalized 3D porous scaffolding is generally considered an ideal approach for directed regeneration of CSBD, which usually has irregular and complex 3D geometry. In this study, we designed a customized porous scaffold rabbit radius based on a body-centered cubic unit. Borate bioactive glass/polycaprolactone (BBG/PCL) composite scaffolds with different BBG contents (0%, 5%, 10%, 20%, and 40%) were fabricated using selective laser sintering. The pore geometry, porosity, mechanical strength, hydrophilicity, protein absorption, degradation behavior, in vitro cytocompatibility, and osteogenesis differentiation of the composite scaffolds were systematically characterized. The in vivo biological properties of the BBG/PCL composite scaffold for CSBD repair were assessed using a rabbit foreleg radius defect model. The results indicate that the BBG/PCL composite scaffold with 20% BBG content effectively promoted the proliferation of osteoblasts and repaired the rabbit radius defects. The mechanical strength of the scaffold was sufficient to maintain the integrity of the scaffold structure during a relatively long CSBD repair. Our results indicate that the BBG/PCL composite scaffold can be anticipated to be a promising biomaterial for CSBD repair.

Efficiently obtaining ideal superhydrophobic metallic surfaces through traditional laser ablation is still a challenge. Meanwhile, revealing the mechanism of the transition from superhydrophilic to superhydrophobic of laser-ablated metallic surfaces is required. Inspired by the lotus leaf, we fabricated the arrays of micro-protrusions on aluminum substrates by nanosecond laser ablation. A layer of hydrophobic species was formed on the micro-protrusions after organic adsorption process, which promoted the surface to obtain superior superhydrophobic, anti-wetting and self-cleaning properties. The principle of the transition from superhydrophilic to superhydrophobic during heat treatment process was revealed, and how organic adsorption temperature and time affect water contact angle and slide angle was clarified. We found that nano-particles can drastically reduce the solid–liquid fraction of the surface after analysis. The parameters including laser scanning space, organic adsorption time and heat treatment temperature were optimized to realize high-efficient and energy-saving production. Furthermore, superior wetting resistance to various solutions and the self-cleaning property for solid powders were experimentally indicated. Superhydrophobic aluminum surfaces could be efficiently fabricated in several hours without any expensive equipment, complicated process, strict environment and environmentally harmful chemical reagent by the proposed two-step method.

Novel ternary Zn–Ca–Cu alloys were studied for the development of absorbable wound closure device material due to Ca and Cu's therapeutic values to wound healing. The influence of Ca and Cu on the microstructure, mechanical and degradation properties of Zn were investigated in the as-cast state to establish the fundamental understanding on the Zn–Ca–Cu alloy system. The microstructure of Zn-0.5Ca-0.5Cu, Zn-1.0Ca-0.5Cu, and Zn0.5Ca-1.0Cu is composed of intermetallic phase CaZn13 distributed within the Zn–Cu solid solution. The presence of CaZn13 phase and Cu as solute within the Zn matrix, on the one hand, exhibited a synergistic effect on the grain refinement of Zn, reducing the grain size of pure Zn by 96%; on the other hand, improved the mechanical properties of the ternary alloys through solid solution strengthening, second phase strengthening, and grain refinement. The degradation properties of Zn–Ca–Cu alloys are primarily influenced by the micro-galvanic corrosion between Zn–Cu matrix and CaZn13 phase, where the 0.5% and 1.0% Ca addition increased the corrosion rate of Zn from 11.5 μm/y to 19.8 μm/y and 29.6 μm/y during 4 weeks immersion test.

The corrosion resistance and wear resistance of metallic biomaterials are critically important for orthopedic hard-tissue replacement applications because the lack of such properties not only adversely affects their mechanical integrity but also allows the release of wear debris into the human body. In this study, the potential of zirconium (Zr) as an alloying element and graphene nanoplatelets (GNPs) as a nano-reinforcement material were investigated in relation to improving the tribological performance of pure magnesium (Mg). The GNPs–reinforced Mg matrix nanocomposites (MNCs) were fabricated using powder metallurgy. Results indicate that additions of 0.5 wt.% Zr and 0.1 wt.% GNPs to Mg matrices significantly improved the wear resistance by 89% and 92% at 200 µN load, 60% and 80% at 100 µN load, and 94% and 93% at 50 µN load, respectively, as compared to the wear resistance of pure Mg. The wear depth and coefficient of friction of the MNC containing 0.5 wt.% Zr and 0.1 wt.% GNPs (Mg0.5Zr0.1GNPs MNC) were considerably reduced as compared to pure Mg and Mg0.5Zr. Our results demonstrate that the Mg0.5Zr0.1GNPs MNC is promising for orthopedic applications in relation to its excellent tribological performance.

This study combines self-prepared NaTi2(PO4)3 (NTP) with commercial vapor-grown carbon fiber (VGCF) using a solid state calcination, then coats it with carbon to synthesize the composite anode material NaTi2(PO4)3/VGCF@C (NTP/VGCF@C). The microstructure and electrochemical properties of the composite material were then analyzed using microstructure analysis and electrochemical testing equipment. Single phase NTP shows nanoparticles with a polyhedral structure, and there is good contact at the interface between the nanoparticles and the VGCFs. The carbon coating formed on the NTP particles displays a nearly 6.5 nm thick layer of amorphous carbon. From the coin-cell battery performance measurements, after 850 cycles, the composite material NTP/VGCF@C exhibits an excellent retention rate of 96.3% compared to that of the pure NTP material when the current density is 200 mA/g. As a result, the composite material and lithium manganate (denoted as LMO) were assembled into an LMO-NTP/VGCF@C aqueous sodium-ion soft pack full battery system. The full battery shows an initial capacity of 31.07 mAh at a rate of 0.5C, and a reversible discharge capacity retention rate of 95.8% after 480 cycles, exhibiting a good long-cycle stability performance.

Biodegradable metals (BMs) gradually degrade in vivo by releasing corrosion products once exposed to the physiological environment in the body. Complete dissolution of biodegradable implants assists tissue healing, with no implant residues in the surrounding tissues. In recent years, three classes of BMs have been extensively investigated, including magnesium (Mg)-based, iron (Fe)-based, and zinc (Zn)-based BMs. Among these three BMs, Mg-based materials have undergone the most clinical trials. However, Mg-based BMs generally exhibit faster degradation rates, which may not match the healing periods for bone tissue, whereas Fe-based BMs exhibit slower and less complete in vivo degradation. Zn-based BMs are now considered a new class of BMs due to their intermediate degradation rates, which fall between those of Mg-based BMs and Fe-based BMs, thus requiring extensive research to validate their suitability for biomedical applications. In the present study, recent research and development on Zn-based BMs are reviewed in conjunction with discussion of their advantages and limitations in relation to existing BMs. The underlying roles of alloy composition, microstructure, and processing technique on the mechanical and corrosion properties of Zn-based BMs are also discussed.

Gyroid polylactic acid (PLA) scaffolds with different unit cell sizes of 2 ​mm (G2), 2.5 ​mm (G25), and 3 ​mm (G3) were fabricated via fused deposition modeling for bone tissue engineering applications. The porosity of the PLA scaffolds ranged from 86% to 90%. The structural anisotropy value of the scaffolds was 3.80, 2.00, and 1.04 for G2, G25, and G3, respectively. Compressive test results indicated that both the dense PLA and porous PLA scaffolds showed elastic-plastic deformation behavior in both building and transverse directions. The compressive elastic modulus and yield strength of the scaffolds were 118–180 ​MPa and 2–8 ​MPa in the building direction and 106–138 ​MPa and 2.5–6.0 ​MPa in the transverse direction, respectively. The tensile elastic modulus and yield strength were 51–63 ​MPa and 1.5–4.5 ​MPa in the building direction and 11–17 ​MPa and 1–5 ​MPa in the transverse direction, respectively. The gyroid PLA scaffolds showed significantly higher values for compressive strength (up to three times) compared to other gyroid structures reported in the literature. The PLA scaffolds can be anticipated as promising scaffold biomaterials for bone tissue engineering applications by virtue of their bone-mimicking porous structure and good mechanical properties.

Magnesium (Mg) alloys are receiving increasing attention as biodegradable implant materials in recent years. However, their low corrosion resistance and fast degradation in the physiological environment remain challenges for a widespread application. Hydroxyapatite (HA) coating on Mg alloys can enhance their corrosion resistance, biocompatibility, and bioactivity of the Mg alloy substrates since the compositions of HA are similar to those of the hard tissue of natural bone. This review analyzes the challenges of Mg alloys for biomedical applications, the fundamental requirements for biodegradable metals, and the corrosion mechanisms of Mg alloys in the physiological environment. The benefits of HA coatings on Mg alloys, the most commonly used surface coating techniques and their advantages and limitations, and the in vitro and in vivo performance of Mg alloys with and without surface coatings are comprehensively elucidated. Multistep processes such as alkali treatment and then HA coating by electrochemical deposition on Mg alloys appear to be necessary to achieve a satisfactory surface coating on Mg alloys, which has been demonstrated to have the potential to improve the degrading behavior, bioactivity and biocompatibility. Multifunctional coatings are most effective in achieving safe and bioactive Mg alloy surfaces for promising biodegradable implant applications.

In this study, the microstructures and mechanical properties of a newly developed β-type Ti–34Nb–25Zr (TNZ) alloy after cold rolling at different reduction ratios and recrystallization annealing were investigated by optical microscopy, XRD, SEM, EBSD, hardness and tensile tests. The tensile strength of the TNZ alloys reached 1071 MPa after cold rolling, which is 1.4 times the tensile strength of the solution-treated alloy. The deformation mechanisms of the TNZ alloys were significantly affected by the cold rolling reduction ratio (CRRR). The dominant deformation mechanisms for the TNZ alloys cold rolled at 20% and 56% CRRR were the formation of kink bands and of stress-induced α” martensite. With increases in CRRR to 76%, the TNZ alloys showed a combination of deformation mechanisms including the formation of shear bands and stress-induced α” martensite, and {332} β mechanical twinning. The TNZ alloy after cold rolling at 86% CRRR followed by annealing exhibited elongation at rupture of 18%, tensile strength of 810 MPa, Young’s modulus of 66 GPa, and toughness of 132 MJ/m3, making it attractive for biomedical applications. Keywords: Ti-Nb-Zr alloy, Mechanical properties, Recrystallization annealing, Cold rolling, Deformation mechanism

Magnesium (Mg) metal matrix composites (MMCs) reinforced with graphene nanoplatelets (GNPs) have been developed by powder metallurgy (PM). GNPs with different concentrations (0.1, 0.2, and 0.3 wt.%), layer thicknesses (5 nm and 9 nm), and particle sizes (15 µm and 5 µm) were dispersed into Mg powder by high-energy ball-milling processes. The microstructure and mechanical properties of the fabricated composites were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman spectroscopy (RS), and compression tests. The corrosion resistance was evaluated by electrochemical tests and hydrogen evolution measurements. The cytotoxicity of Mg-GNPs composites was assessed using osteoblast-like SaOS2 cells. The results indicate that GNPs are excellent candidates as reinforcements in Mg matrices for the manufacture of biodegradable Mg-based composite implants. GNP addition improved the mechanical properties of Mg via synergetic strengthening modes. Moreover, retaining the structural integrity of GNPs during processing improved the ductility, compressive strength, and corrosion resistance of the Mg-GNP composites. Cytotoxicity assessments did not reveal any significant toxicity with the addition of GNPs to Mg matrices. This study demonstrates that Mg-xGNPs with x

The application of various materials in biomedical procedures has recently experienced rapid growth. One area that is currently receiving significant attention from the scientific community is the treatment of a number of different types of bone-related diseases and disorders by using biodegradable polymer-ceramic composites. Biomaterials, the most common materials used to repair or replace damaged parts of the human body, can be categorized into three major groups: metals, ceramics, and polymers. Composites can be manufactured by combining two or more materials to achieve enhanced biocompatibility and biomechanical properties for specific applications. Biomaterials must display suitable properties for their applications, about strength, durability, and biological influence. Metals and their alloys such as titanium, stainless steel, and cobalt-based alloys have been widely investigated for implant-device applications because of their excellent mechanical properties. However, these materials may also manifest biological issues such as toxicity, poor tissue adhesion and stress shielding effect due to their high elastic modulus. To mitigate these issues, hydroxyapatite (HA) coatings have been used on metals because their chemical composition is similar to that of bone and teeth. Recently, a wide range of synthetic polymers such as poly (l-lactic acid) and poly (l-lactide-co-glycolide) have been studied for different biomedical applications, owing to their promising biocompatibility and biodegradability. This article gives an overview of synthetic polymer-ceramic composites with a particular emphasis on calcium phosphate group and their potential applications in tissue engineering. It is hoped that synthetic polymer-ceramic composites such as PLLA/HA and PCL/HA will provide advantages such as eliminating the stress shielding effect and the consequent need for revision surgery. Keywords: Synthetic polymers, Hydroxyapatite, Magnetron sputtering, 3D printing

In this study, the microstructural evolution and mechanical properties of a newly developed Ti-40.7Zr–24.8Nb (TZN) alloy after different thermomechanical processes were examined. As-cast TZN alloy plates were solution-treated at 890 °C for 1 h, after which the thickness of the alloy plates was reduced by cold rolling at reduction ratios of 20%, 56%, 76%, and 86%. Stress-induced α” formation, {332} β mechanical twinning, and kink band formation were observed in the cold-rolled TZN alloy samples. In the TZN sample after cold rolling at the 86% reduction ratio plus a recrystallization annealing at 890 °C for 1 h, the deformation products of a stress-induced α” phase, {332} β mechanical twinning, and kink bands disappeared, resulting in a fine, equiaxed single β phase. The alloy samples exhibited elongation at rupture ranging from 7% to 20%, Young's modulus ranging from 63 to 72 GPa and tensile strength ranging from 753 to 1158 MPa. The TZN alloy sample after cold rolling and recrystallization annealing showed a yield strength of 803 MPa, a tensile strength of 848 MPa, an elongation at rupture of 20%, and an elastic admissible strain of 1.22%, along with the most ductile fractures during tensile testing. Keywords: TZN (Ti–Nb–Zr) alloy, Orthopedic implants, Thermomechanical process, Deformation mechanism, Mechanical properties

Recently, the fabrication methods of orthopedic implants and devices have been greatly developed. Additive manufacturing technology allows the production of complex structures with bio-mimicry features, and has the potential to overcome the limitations of conventional fabrication methods. This review explores open-cellular structural design for porous metal implant applications, in relation to the mechanical properties, biocompatibility, and biodegradability. Several types of additive manufacturing techniques including selective laser sintering, selective laser melting, and electron beam melting, are discussed for different applications. Additive manufacturing through powder bed fusion shows great potential for the fabrication of high-quality porous metal implants. However, the powder bed fusion technique still faces two major challenges: it is high cost and time-consuming. In addition, triply periodic minimal surface (TPMS) structures are also analyzed in this paper, targeting the design of metal implants with an enhanced biomorphic environment. Keywords: Additive manufacturing, Powder bed fusion, Porosity, TPMS structures

A newly developed porous Ti35Zr28Nb scaffold was manufactured via powder metallurgy (PM) using space-holder (NH4HCO3) sintering from pre-alloyed powder. The pore features, compression and anti-corrosion properties of the manufactured porous scaffolds were systematically studied. The results show that all the manufactured porous Ti35Zr28Nb scaffolds consisted of a single β phase. The porosity of the porous Ti35Zr28Nb scaffolds increased from 50% to 65% with in increasing the NH4HCO3 from 63% to 79% (volume ratio), and the average pore size (d50) was in the range of 230–430 μm. The yield strength in compression and the elastic modulus of the porous Ti35Zr28Nb scaffolds both decreased gradually with an increase in porosity, varying from 230.5 MPa to 79.7 MPa and 6.9 GPa to 1.8 GPa, respectively. The corrosion rate of the porous Ti35Zr28Nb scaffolds in the phosphate buffer saline (PBS) solution increased from 0.91 × 10−3 mm/yr to 4.18 × 10−3 mm/yr with an increase in porosity from 51.4% to 64.9%. In comparison with unalloyed Ti scaffolds with almost the same porosity, the porous Ti35Zr28Nb scaffolds showed a significantly higher compressive yield strength and a lower corrosion rate. These results suggest that porous Ti35Zr28Nb scaffolds fabricated by PM have substantial potential for hard-tissue engineering applications. Additionally, the relationship of porosity, mechanical and anti-corrosion properties of these Ti35Zr28Nb scaffolds has now been confirmed, and could be used in the process of material selection for their specific applications. Keywords: Corrosion resistance, Mechanical property, Porous Ti35Zr28Nb scaffold, Powder metallurgy, Pore characterization

Nanocrystalline (NC) metallic materials have better mechanical properties, corrosion behavior and biocompatibility compared with their coarse-grained (CG) counterparts. Recently, nanocrystalline metallic materials are receiving increasing attention for biomedical applications. In this review, we have summarized the mechanical properties, corrosion behavior, biocompatibility, and clinical applications of different types of NC metallic materials. Nanocrystalline materials, such as Ti and Ti alloys, shape memory alloys (SMAs), stainless steels (SS), and biodegradable Fe and Mg alloys prepared by high-pressure torsion, equiangular extrusion techniques, etc., have better mechanical properties, superior corrosion resistance and biocompatibility properties due to their special nanostructures. Moreover, future research directions of NC metallic materials are elaborated. This review can provide guidance and reference for future research on nanocrystalline metallic materials for biomedical applications.

To optimize both the mechanical and biological properties of titanium for biomedical implants, a highly flexible powder metallurgy approach is proposed to generate porous scaffolds with graded porosities and pore sizes. Sugar pellets acting as space holders were compacted with titanium powder and then removed by dissolution in water before sintering. The morphology, pore structure, porosity and pore interconnectivity were observed by optical microscopy and SEM. The results show that the porous titanium has porosity levels and pore size gradients consistent with their design with gradual and smooth transitions at the interfaces between regions of differing porosities and/or pore sizes. Meanwhile, the porous titanium has high interconnectivity between pores and highly spherical pore shapes. In this article we show that this powder metallurgy processing technique, employing the novel sugar pellets as space-holders, can generate porous titanium foams with well-controlled graded porosities and pore sizes. This method has excellent potential for producing porous titanium structures for hard tissue engineering applications.

The strength of titanium scaffolds with the introduction of high porosity decreases dramatically and may become inadequate for load bearing in biomedical applications. To simultaneously meet the requirements of biocompatibility, low elastic modulus and appropriate strength for orthopedic implant materials, it is highly desirable to develop new biocompatible titanium based materials with enhanced strength. In this study, we developed a niobium pentoxide (Nb2O5) reinforced titanium composite via powder metallurgy for biomedical applications. The strength of the Nb2O5 reinforced titanium composites (Ti-Nb2O5) is significantly higher than that of pure titanium. Cell culture results revealed that the Ti-Nb2O5 composite exhibits excellent biocompatibility and cell adhesion. Human osteoblast-like cells grew and spread healthily on the surface of the Ti-Nb2O5 composite. Our study demonstrated that Nb2O5 reinforced titanium composite is a promising implant material by virtue of its high mechanical strength and excellent biocompatibility.

Valve metals such as titanium (Ti), zirconium (Zr), niobium (Nb) and tantalum (Ta) that confer a stable oxide layer on their surfaces are commonly used as implant materials or alloying elements for titanium-based implants, due to their exceptional high corrosion resistance and excellent biocompatibility. The aim of this study was to investigate the bioactivity of the nanostructures of tantala (Ta2O5), niobia (Nb2O5), zirconia (ZrO2) and titania (TiO2) in accordance to their roughness and wettability. Therefore, four kinds of metal oxide nanoporous and nanotubular Ta2O5, Nb2O5, ZrO2 and TiO2 were fabricated via anodization. The nanosize distribution, morphology and the physical and chemical properties of the nanolayers and their surface energies and bioactivities were investigated using SEM-EDS, X-ray diffraction (XRD) analysis and 3D profilometer. It was found that the nanoporous Ta2O5 exhibited an irregular porous structure, high roughness and high surface energy as compared to bare tantalum metal; and exhibited the most superior bioactivity after annealing among the four kinds of nanoporous structures. The nanoporous Nb2O5 showed a uniform porous structure and low roughness, but no bioactivity before annealing. Overall, the nanoporous and nanotubular layers of Ta2O5, Nb2O5, ZrO2 and TiO2 demonstrated promising potential for enhanced bioactivity to improve their biomedical application alone or to improve the usage in other biocompatible metal implants.