Porous Alloy Research Articles

Strong Bonding of Robust Lubricating Hydrogels to Porous Substrates for Joint Replacement.

Hydrogels with excellent mechanical and lubrication properties have been developed rapidly, laying the foundation for their application in cartilage replacement. However, the combination of robust hydrogels and substrates under different forms of movement is a great challenge. In addition, due to differences in modulus, the stress shielding effect caused by implantable artificial joint metal materials can lead to bone resorption. Here, we proposed to combine a 3D printed porous titanium alloy with a high-strength lubricating hydrogel to construct an integrated joint substitute material. The porous titanium alloy TC4 substrate constructed by 3D printing possesses a modulus similar to that of human bone. The strong bonding of the hydrogel and TC4 was achieved through two strategies: mechanical interlocking and chemical bonding. The combination of the alloy substrate and hydrogel realizes the construction of a bionic lubricating cartilage layer on the surface of traditional artificial joint materials. The hydrogel has excellent bonding properties with the porous substrate under different test conditions. Truly human-like joint sockets were prepared for the first time with soft-soft and soft-hard contact modes. Under conditions simulating human motion, the hydrogel maintains a low friction coefficient and still has excellent substrate adhesion after 100,000 cycles. This study further pushes the application of hydrogels in biolubrication into practice.

Mechanical Properties, Biodegradation, and Biocompatibility of Porous Mg Alloy Scaffolds for Load Bearing Bone Applications

Mechanical Properties, Biodegradation, and Biocompatibility of Porous Mg Alloy Scaffolds for Load Bearing Bone Applications

Facilitating martensitic reorientation via porous structure of Ti-doped Ni–Mn–Ga shape memory alloy

Abstract Porous Ni–Mn–Ga shape memory alloy with the pore size of 20–30 μm was fabricated by the powder metallurgy with the pore-forming agent of NaCl. The prepared alloy has a uniform pore distribution and a complete sintering neck, which reduces the number of grain boundaries. Pores constrain the transmission of stress, leading to stress concentration, which decreases the critical stress of martensitic twin variants reorientation (<10 MPa). Meanwhile, the strength of porous alloys can be tuned by the alloying of Ti. In addition, the porous Ni–Mn–Ga alloy obtained a lower critical stress for martensitic twin boundary motion after cyclic compression, which makes it suitable for devices that require energy absorption under low stress. The microstructure and mechanical properties of Ni–Mn–Ga porous alloy were analyzed, and the effects of pores on the Ni–Mn–Ga alloy were also discussed.

Copper-promoted growth of hierarchical Cu–Co–Ni alloys on copper nanodendrites for enhanced hydrogen evolution in a wide pH range

Efficient and sustainable electrocatalysts for the hydrogen evolution reaction (HER) using earth-abundant elements are crucial for eco-friendly hydrogen production, particularly under neutral and acidic conditions. In metallic alloys, careful selection of alloying elements and control over the composition, morphology, electronic structure, and structural defects are expected to tune electrocatalytic activities. In this work, we introduce a two-step electrodeposition approach to create a 3D porous trimetallic alloy, Cu@Cu–Ni–Co, exhibiting excellent catalytic activity and stability for HER in neutral and acidic environments. The process begins with the electrodeposition of 3D copper dendrites, which was found to be crucial for the catalyst's mechanical stability, followed by the deposition of the trimetallic alloy, where copper's inclusion promotes the controlled growth of the alloy's 3D structure. The Cu@Cu–Ni–Co catalyst outperforms Cu@Ni, Cu@Co, Cu@Ni–Co, and GC@Cu–Ni–Co electrocatalysts in neutral and acidic conditions, highlighting the importance of the developed electrodeposition approach. In 1.0 M phosphate-buffer solution (PBS), Cu@Cu–Ni–Co achieves a current density of 10 mA cm−2 at an overpotential of 275 mV with a Tafel slope of 134 mV dec−1, maintaining remarkable stability in both acidic and neutral conditions at high current densities (48–165 mA cm−2) for up to 50 h without any decline in activity.

Additively manufactured porous Ti6Al4V Alloy with excellent mechanical properties, corrosion resistance, in vitro and in vivo biocompatibility

In view of the insufficient bearing capacity of porous Ti6Al4V (TC4) alloy, four kinds of porous TC4 alloys with a wall thickness of 200 μm and a side length ranging from 400 to 700 μm were designed and subsequently prepared by Additive Manufacturing (Selective Laser Melting, SLM). The results indicated that the porous TC4 alloy was primarily comprised of α' phase and a small amount of β phase. As the side length increased, the size and volume of the acicular α' phase increased while the β phase decreased. Besides, the dislocation density also increased with the increase of side length. The porous TC4 alloy with a side length of 700 μm exhibited the maximum dislocation density of 6.07×1014 m2. The yield strength and elastic modulus initially decreased and then increased with the increase of side length. Moreover, the increase in side length induced the decrease of Icorr from 1.807 × 10−6 to 4.777 × 10−7 A/cm2, especially that sample 7–2 presented the best corrosion resistance with the smallest Icorr value (4.777 × 10−7 A/cm2). It was observed by in vitro assessment that the optical density (OD) of the porous TC4 alloys surpassed 75 % on days 1, 4, and 7. It was noteworthy that the OD value of the porous TC4 alloys with a side length of 700 μm surpassed 100 % on day 7. Furthermore, the number of adherent cells displayed an increasing trend with the increase in side length. After implanting into the alveolar bone of rabbits at 12th week, the porous TC4 alloy with a side length of 700 μm induced bone growth due to a higher percentage of bone volume compared to the dental implant. After 12 weeks of in vivo experiments, the results showed that the porous TC4 alloy could reduce the inflammatory response, promote the growth of bone tissue, and have excellent osteogenic properties.

Prompt template-free synthesis of porous PtPb sponge-like nanostructure for electro-oxidation of methanol and carbon monoxide

Porous Pt-based alloys entail earth-abundant and low-cost metal, not only contribute to the rational consumption of expensive and rare Pt metal but also the enhancement of its activity towards the methanol electro-oxidation reaction (MEOR). Herein, a porous sponge-like PtPb alloy was synthesized by using the ice-reduction method driven by the coalescence growth mechanism under the intensive reduction power of borohydride. The presented PtPb sponge nanostructure was prepared using a facile, one-step method without heating or surfactants. Meanwhile, PtPb had a sponge-like shape with accessible active sites, a high surface area, abundant pore volume (0.05 cm3/g), pore size (2–20 nm), Pb loading (13.0 at.%), and an upshifted d-band center of Pt. These inimitable structural and compositional merits endow the electro-oxidation of methanol with a higher mass (specific) activity of 0.907 mA/µgPt (5.7 mA/cm2) compared to those of Pt sponge-like nanostructure and Pt/C catalyst by 1.47 (1.35) and 1.72 (8.51) times, respectively, besides higher durability. Moreover, PtPb had higher activity and durability towards the electro-oxidation of carbon monoxide (CO) than Pt and Pt/C. The proposed study may provide new insights into the simple synthesis of a Pt-based alloy for the electrocatalytic oxidation of small organic molecules.

Preparation and Characterization of Ni-Mn-Ga-Cu Shape Memory Alloy with Micron-Scale Pores

Porous Ni-Mn-Ga shape memory alloys (SMAs) were prepared by powder metallurgy using NaCl as a pore-forming agent with an average pore size of 20–30 μm. The microstructure, phase transformation, superelasticity, and elastocaloric properties of the porous alloys were investigated. The prepared porous alloy had a uniform pore distribution and interconnected microchannels were formed. Cu doping can effectively improve the toughness of a porous alloy, thus improving the superelasticity. It was found that porous Ni-Mn-Ga-Cu SMAs have a flat stress plateau, which exhibits a maximum elongation of 5% with partially recoverable strain and a critical stress for martensite transformation as low as about 160 MPa. In addition, an adiabatic temperature change of 0.6 K was obtained for the prepared porous alloy at a strain of 1.2% at about 150 MPa. This work confirms that the introduction of porous structures into polycrystalline Ni-Mn-Ga SMAs is an effective way to reduce costs and improve performance, and provides opportunities for engineering applications.

Achieving biomimetic porosity and strength of bone in magnesium scaffolds through binder jet additive manufacturing

Magnesium (Mg) alloys are a promising candidate for synthetic bone tissue substitutes. In bone tissue engineering, achieving a balance between pore characteristics that facilitate biological functions and the essential stiffness required for load-bearing functions is extremely challenging. This study employs binder jet additive manufacturing to fabricate an interconnected porous structure in Mg alloys that mimics the microporosity and mechanical properties of human cortical bone types. Using scanning electron microscopy, micro-computed tomography, and mercury intrusion porosimetry, we found that the binder jet printed and sintered (BJPS) MgZnZr alloys possess an interconnected porous structure, featuring an overall porosity of 13.3 %, a median pore size of 12.7 μm, and pore interconnectivity exceeding 95 %. The BJPS MgZnZr alloy demonstrated a tensile strength of ~130 MPa, a yield strength of ~100 MPa, an elastic modulus of ~21.5 GPa, and an ultimate compressive strength of ~349 MPa. These values align with the ranges observed in human bone types and outperform those of porous Mg alloys produced using the other conventional and additive manufacturing methods. Moreover, the BJPS MgZnZr alloy showed level 0 cytotoxicity with a greater MC3T3-E1 cell viability, attachment, and proliferation when compared to a cast MgZnZr counterpart, since the highly interconnected 3D porous structure provides cells with an additional dimension for infiltration. Finally, we provide evidence for the concept of using binder jet additive manufacturing for fabricating Mg implants tailored for applications in hard tissue engineering, including craniomaxillofacial procedures, bone fixation, and substitutes for bone grafts. The results of this study provide a solid foundation for future advancements in digital manufacturing of Mg alloys for biomedical applications.

Optimization Design and SLM Manufacturing of Porous Titanium Alloy Femoral Stem.

In order to solve the loosening problem caused by stress shielding of femoral stem prostheses in clinical practice, an optimization design method of a personalized porous titanium alloy femoral stem is proposed. According to the stress characteristics of the femur, the porous unit cell structures (TO-C, TO-T, TO-B) under three different loads of compression, torsion, and bending were designed by topology optimization. The mechanical properties and permeability of different structures were studied. Combined with the porous structure optimization, a personalized radial gradient porous titanium alloy femoral stem was designed and manufactured by selective laser melting (SLM) technology. The results show that the TO-B structure has the best comprehensive performance among the three topologically optimized porous types, which is suitable for the porous filling structure of the femoral stem, and the SLM-formed porous femoral stem has good quality. The feasibility of the personalized design and manufacture of porous titanium alloy implants is verified, which can provide a theoretical basis for the optimal design of implants in different parts.

Effect of Cr content on the high temperature oxidation behavior of FeCoNiMnCrx porous high-entropy alloys

FeCoNiMnCr porous high-entropy alloys were prepared using the activation reaction sintering method with Fe, Co, Ni, Mn, and Cr as raw materials. The oxidation behaviors of FeCoNiMnCrx porous high-entropy alloys with different Cr contents, such as pore structure, the surface oxide film phase composition, structure, and morphology, were characterized by X-ray diffraction (XRD), electron probe micro analysis (EPMA), energy dispersive X-ray spectroscopy (EDS), and pore tester after high-temperature oxidation at 800–1000 °C. The results indicate that the initial porous high-entropy alloy comprises a single FCC solid solution phase. With the increase in Cr content, the average pore diameter, average porosity, and air permeability of the porous high-entropy alloy also increase. The oxidation kinetics of the porous high-entropy alloy after exposure to temperatures between 800 °C and 1000 °C follows a single-stage parabolic evolution law. At the same oxidation temperature, With the increase of Cr content, the oxidation gains gradually increased, at the same Cr content at different temperatures, the antioxidant performance of 1000 °C was the weakest, followed by 800 °C, and 900 °C showed excellent antioxidant performance. The oxidation products are mainly Mn2O3, Mn3O4, (Mn, Cr)3O4, Cr2O3and Fe2O3.

Fabrication of porous Ni-Ti shape memory alloy via binder jet additive manufacturing and solid-state sintering

This paper explores the additive manufacturing of nickel-titanium (Ni-Ti) shape memory alloys (SMAs) using binder jetting and subsequent solid-state sintering under an Ar atmosphere. The consolidated 3D-printed Ni-Ti parts exhibit a correlation between pore morphology, pore fraction, and phase formation at different solid-state sintering temperatures. At a sintering temperature of 1175 °C, NiTi grains with TiC precipitates along grain boundaries are observed, accompanied by irregular, interconnected pores constituting ∼15 % of the volume. Increasing the sintering temperature to 1185 °C leads to the formation of a minor phase of Ni4Ti3 within NiTi grains, along with grain boundary TiC precipitates, and isolated pores with a volume fraction of ∼5 %. The higher sintering temperature corresponds to a higher average nanohardness value (8.1 GPa or 763 Hv compared to 6.9 GPa or 654 Hv), indicating the presence of a greater abundance of secondary phases and higher densification at the elevated sintering temperature. While the transformation temperatures (TTs) were undetectable in the bulk-printed samples, a different structure featuring designed channels and thin struts, sintered under similar conditions, exhibited detectable TTs, with a martensite start temperature of 34 °C. Biocompatibility tests demonstrated cell spreading and attachment on both sintered Ni-Ti samples. These findings offer valuable insights into the potential use of binder jetted Ni-Ti for medical implants and tissue engineering applications.

Harmonious balance of strength and toughness: Carbon-modified effusive-rock-like Fe-Sn alloy for stable Li storage

For the integrated electrodes of lithium-ion batteries, a strong substrate is crucial to maintain stable electrochemical performance. Therefore, this work proposes a concept to achieve a harmonious balance between strength and toughness in an integrated electrode by combining the Sn-based alloy, which introduces a strengthening phase, and amorphous carbon. Three-dimensional hierarchical porous FeSn/FeSn2 integrated anodes are prepared based on Fe45Sn55 alloys using a simple dealloying method to verify the concept. FeSn2, as a strengthening phase within the FeSn porous alloy, enhances the structural stability of the porous structure under mechanical stress. An amorphous carbon layer with excellent toughness is coated on the surface of the porous alloy, which buffers the volume expansion of Sn and slows down the accumulation rate of stress in the porous structure. Additionally, Fe and Sn produced as electrochemical reaction products act as the inert-active system, uniformly distributing throughout the porous structure, which further buffers the volume expansion of Sn and improves the conductivity of the electrode, allowing it to maintain a reversible capacity of 1.43 mAh cm−2 after 300 cycles at 1 mA cm−2.

Corrigendum to “Additively manufactured porous Ti6Al4V Alloy with excellent mechanical properties, corrosion resistance, in vitro and in vivo biocompatibility” [J. Alloy. Compd. 1009 (2024) 176982]

Corrigendum to “Additively manufactured porous Ti6Al4V Alloy with excellent mechanical properties, corrosion resistance, in vitro and in vivo biocompatibility” [J. Alloy. Compd. 1009 (2024) 176982]

Microstructure, Mechanical Properties, and Corrosion Resistance of Porous Bio Mg Alloy Scaffolds Prepared via a Novel Method

Mg alloy scaffolds can be used as repair materials for human bone defects. Herein, porous Mg–1Zn–1Ca–0.5Mn alloy scaffolds with different pore sizes of the primitive model are prepared by combining 3D‐printed pure Ti templates and infiltration casting Mg alloy method. The results exhibit that the scaffold porosity ranges from 58.8 ± 1.4% to 63.3 ± 5.3% and the surface quality is good. Complete connectivity inside the scaffolds and the precise control of the pore structure are realized simultaneously. The mechanical properties of the scaffolds increase with increasing pore size; therefore, the LP scaffold displays the best mechanical performance with a yield strength of 9.88 ± 0.33 MPa. The simulation results are in good consistent with the experimental results. The reticular second phase provides a barrier to the Mg matrix during corrosion, which improves the corrosion resistance of the scaffolds as the increase of pore size. Therefore, the corrosion rate of the LP scaffolds is only 2.35 ± 1.28 mm year−1 after 200 h of immersion. Furthermore, MC‐3T3 cells adhere on the surface of Mg–1Zn–1Ca–0.5Mn alloy scaffolds, indicating that Mg–1Zn–1Ca–0.5Mn alloy scaffolds have excellent biocompatibility.

Industrial-grade electrocatalytic synthesis of glycine from oxalic acid and nitrate using a porous PbSnBi catalyst

Electrochemical transformation of oxalic acid and nitrate into glycine is an appealing way for valuable chemical synthesis and waste nitrate treatment. Currently, strategies to electrosynthesis of amino acid through catalyst design have been successfully developed, but it is still of huge challenge to realize industrial grade electrocatalytic synthesis of amino acid. Here, we develope an innovative electrochemical method to synthesize glycine from harnessing nitrate (NO3-) and oxalic acid in an aqueous electrolyte with a porous PbSnBi alloy catalyst. By means of construction the multiple catalytic sites and regulation electrode surface microenvironment, this strategy produces glycine with high Faraday efficiencies of 57.2 %, high yield rates of 1.125 mmol h−1 cm−2cat, and average current density up to 1 A cm−2 at −1.5 V vs. SCE potential after 2 h electrolysis. The recycled electrolysis experiment confirms its good stability and practical potential.

Enhanced osseointegration and antimicrobial properties of 3D-Printed porous titanium alloys with copper-strontium doped calcium silicate coatings.

The 3D printing of porous titanium scaffolds reduces the elastic modulus of titanium alloys and promotes osteogenic integration. However, due to the biological inertness of titanium alloy materials, the implant-bone tissue interface is weakly bonded. A calcium silicate (CS) coating doped with polymetallic ions can impart various biological properties to titanium alloy materials. In this study, CuO and SrO binary-doped CS coatings were prepared on the surface of 3D-printed porous titanium alloy scaffolds using atmospheric plasma spraying and characterized by SEM, EDS, and XRD. Both CuO and SrO were successfully incorporated into the CS coating. The in vivo osseointegration evaluation of the composite coating-modified 3D-printed porous titanium alloy scaffolds was conducted using a rabbit bone defect model, showing that the in vivo osseointegration of 2% CuO-10% SrO-CS-modified 3D-printed porous titanium alloy was improved. The in vitro antimicrobial properties of the 2% CuO-10% SrO-CS-modified 3D-printed porous titanium alloy were evaluated through bacterial platform coating, co-culture liquid absorbance detection, and crystal violet staining experiments, demonstrating that the composite coating exhibited good antimicrobial properties. In conclusion, the composite scaffold possesses both osteointegration-promoting and antimicrobial properties, indicating a broad potential for clinical applications.

Individualized C1-2 intra-articular three-dimensional printed porous titanium alloy cage for craniovertebral deformity

BackgroundCongenital craniovertebral deformity, including basilar invagination (BI) and atlantoaxial instability (AAI), are often associated with three-dimensional (3D) deformity, such as C1-2 rotational deformity, craniocervical kyphosis, C1 lateral inclination, among other abnormalities. Effective management of these conditions requires the restoration of the 3D alignment to achieve optimal reduction. Recently, 3D printing technology has emerged as a valuable tool in spine surgery, offering the significant advantage of allowing surgeons to customize the prosthesis design. This innovation provides an ideal solution for precise 3D reduction in the treatment of craniovertebral deformities.ObjectiveThis study aims to describe our approach to individualized computer-simulated reduction and the design of C1-2 intra-articular 3D printed porous titanium alloy cages for the quantitative correction of craniovertebral junction deformities.MethodsA retrospective analysis was conducted on patients with craniovertebral deformities treated at our institution using individualized 3D-printed porous titanium alloy cages. Preoperative CT data were used to construct models for 3D realignment simulations. Cage designs were tailored to the simulated joint morphology following computer-assisted realignment. Preoperative and postoperative parameters were statistically analyzed.ResultsFourteen patients were included in the study, with a total of 28 3D-printed porous titanium alloy cages implanted. There were no cases of C2 nerve root resection or vertebral artery injury. All patients experienced symptom relief and stable implant fixation achieved in all cases. No implant-related complications were reported.ConclusionThe use of individualized computer-simulated reduction and the design of C1-2 intra-articular 3D printed porous titanium alloy cage facilitates precise 3D realignment in patients with craniovertebral deformities, demonstrating effectiveness in symptom relief and stability.

Electrical impedance characterization and modelling of Ti-Β implants.

Commercially pure titanium (c.p. Ti) and Ti6Al4V alloys are the most widely used metallic biomaterials in the biomedical sector. However, their high rigidity and the controversial toxicity of their alloying elements often compromise their clinical success. The use of porous β-Titanium alloys is proposed as a solution to these issues. In this regard, it is necessary to implement economic, repetitive, and non-destructive measurement techniques that allow for the semi-quantitative evaluation of the chemical nature of the implant, its microstructural characteristics, and/or surface changes. This study proposes the use of simple measurement protocols based on electrical impedance measurements, correlating them with the porosity inherent to processing conditions (pressure and temperature), as well as the chemical composition of the implant. Results revealed a clear direct relationship between porosity and electrical impedance. The percentage and/or size of the porosity decrease with an increase in compaction pressure and temperature. Moreover, there is a notable influence of the frequency used in the measurements obtained. Additionally, the sensitivity of this measurement technique has enabled the evaluation of differences in chemical composition and the detection of intermetallics in the implants. For the first time in the literature, this research establishes relationships between stiffness and electrical impedance, using approximations and models for the observed trends. All the results obtained corroborate the appropriateness of the technique to achieve the real-time characterization of Titanium implants, in an efficient and non-invasive way.

High oxidation state on porous Ga-Ag9In4 catalyst enhance CO2 electroreduction to CO

The oxidation state of Ga, In and Ag active sites for the selective electrochemical conversion of CO2 to CO has been successfully modulated through the construction of a porous Ga-Ag9In4 liquid alloy catalyst. X-ray photoelectron spectroscopy measurements confirmed the formation of a higher amount of oxidized states on the high-performing Ga-Ag9In4 electrode surface during the CO2 reduction reaction process. Based on density functional theory calculations, the Ga-Ag9In4 catalyst with a high oxidized species exhibits an electronic-rich surface that promotes CO2 adsorption and activation. In a H-type electrolysis cell, the porous Ga-Ag9In4 catalyst exhibits a maximum Faradaic efficiency of 88 % for CO production, with current densities of 30.2 mA·cm−2. This strategy of porous liquid alloy engineering and oxidation state modulation in multicomponent systems has good application prospect and research value for enhancing electrocatalytic performance.

Preparation and Wear Resistance of Porous TC4 Titanium Alloy Micro‐arc Oxidation Coating Produced by Selective Laser Melting

The porous TC4 titanium alloy prepared by selective laser melting (SLM) is modified by micro‐arc oxidation (MAO) technology. By introducing active elements such as calcium (Ca) and phosphorus (P) into the electrolyte, a wear‐resistant active coating is constructed on the surface of porous TC4. The effects of MAO process parameters on the surface morphology and wear resistance of the coating are discussed. The results show that the thickness and adhesion of the coating increase with the increase of the first‐stage oxidation time, and decrease with the increase of the second‐stage oxidation time. In all processes, the MAO‐2 coating has better surface morphology and performance, with a median pore size of 0.51 μm and a binding force of 18 N. XPS analysis confirms that the coating is mainly composed of TiO2, Ca2P2O7, and Ca(PO3)2 phases. The study of tribological behavior shows that the wear form of the substrate is abrasive wear, while the wear form of the coating is adhesive wear. The friction coefficient of the coating is significantly lower than that of the substrate, and the wear resistance is better. This study provides an effective way to optimize the surface properties of porous TC4 titanium alloy.