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Gradient materials can achieve both external strengthening and internal toughening, which has great potential to break the strong plastic tradeoff. Titanium carbide (TiC) particle is conducive to form a wearable surface in biomedical Titanium (Ti) alloy. In this work, gradient TiC/Ti6Al4V composites were successfully prepared by friction stir processing (FSP). Microstructure, texture and mechanical properties of the material were systematically characterized. Scanning electron microscopy (SEM) showed that the equiaxed grains near the machined surface were transformed into elongated grains inside. The results of energy spectrum analysis (EDS) showed that there was element aggregation near TiC particles. X-ray diffraction (XRD) indicated martensitic transformation in the stir zone and in the transition zone. The results of nano indentation showed that the hardness of stir zone was higher. In order to promote recrystallization and improve the hardness of the transition zone, high temperature rapid heat treatment was carried out after FSP. When the sample was heated at 700°C and cooled in the furnace, the hardness increased to the maximum. In the process of rapid heating, the dissolution of elements near TiC particles also led to the increase of hardness. This study provides a new idea for surface modification of gradient titanium alloy by using FSP method to improve its mechanical properties.

Fiber-optic anemometers have attracted an increasing attention over the past decade owing to their high sensitivity, wide dynamic range, low power consumption, and immunity to electromagnetic interference. However, expensive instruments may limit their practical applications. Herein, a new type of airflow sensor based on optical micro/nanofiber (MNF) is proposed and realized. The sensing element is a flexible polydimethylsiloxane (PDMS) cantilever embedded with a U-shaped MNF. Upon exposure to airflow, the induced deflection of the cantilever results in a bending-dependent transmittance variation of the embedded MNF. The performance of the sensor can be engineered by tuning the cantilever thickness and/or the MNF diameter. When four cantilevers are arranged in two orthogonal directions, the transmittance of each cantilever will be dependent on both flow speed and direction. By analysing the output signals of the four cantilevers, omnidirectional airflow with flow speed within 15 m/s were experimentally measured. In addition, a variety of voice and respiratory signals can be monitored and distinguished in real-time using an optimized cantilever with a resolution of 0.012 m/s, presenting great potential for health monitoring applications.

The effect of relative humidity on the surface electric field (SEF) strength and a new non-contact assessment method based on space charge density were studied. The purpose of using space charge was to assess the SEF accurately, particularly after corona occurs. Space charge measurement and SEF evaluation were conducted at a relative humidity of 40% to 90%. The change law of SEF after corona occurs at different relative humidity was obtained. Results showed that under the same relative humidity, the space charge density increases with the applied voltage, while the SEF decreases with voltages after corona occurs. As the humidity condition aggravated, SEF first increases and then decreases, and the turning point is about 70%. The distribution of charge density has an opposite change trend. The variation of charge density and SEF demonstrates that the two have mutual inhibition. Meanwhile, the change formula of SEF shows that the electric field intensity on the wire surface is not constant after corona occurs. The corona discharge experiment and theoretical research can be further carried out based on the results in this paper.

Transition metal sulfides (TMSs)-based materials have been extensively investigated as effective non-noble catalysts for various applications. However, the exploration of TMSs-based catalysts for hydrogenation of nitro compounds is limited. Herein, CoSx/NC catalysts were prepared by solvothermal sulfurization of ZIF-67, followed by high-temperature annealing (300–600 °C) under NH3 atmosphere. It was found that the structures and compositions of the as-prepared CoSx/NC can be readily tuned by varying the annealing temperature. Particularly, CoSx/NC-500, which possesses higher degree of S defects and larger specific surface areas, can achieve high conversion, selectivity and stability for catalytic reduction of nitro compounds into amines under mild reaction conditions.

A subsecond and novel approach of electroshock treatment (EST) is used in this study to repair defects in directed-energy-deposited Ti-5Al-5Mo-5V-3Cr-1Zr near-β titanium alloy. After EST, the porosity of the specimen decreased significantly from 0.81 to 0.1 pct. Large cracks observed at the bottom of the above mentioned near-β titanium alloy became intermittent small cracks and the number of voids decreased. The defects in the top and middle regions of the specimens are repaired. The potential defect repair is attributable to energy concentration, which promoted the coalescence of defect tips, and thermal stresses, which compressed the defects inward and closed them.

Friction stir lap welding (FSLW) was employed to weld dissimilar joints of zirconium and stainless steel for the first time. The microstructure, evolution mechanism of intermetallic compounds (IMCs) and mechanical properties of joint were investigated. Discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) occurred in zirconium, while DDRX occurred in stainless steel during FSLW. The formation sequence of IMCs at the interface was FeZr3, FeZr2, Fe2Zr, and Fe23Zr6. The crack nucleated at the hook zone on the advancing side (HookAS), and IMCs in the Zr/SS mixed zone accelerated crack propagation. The fracture surface exhibited ductile-brittle mixed fracture characteristic.

Friction stir processing (FSP) is a new severe plastic deformation technique where microstructure refinement, homogenization, and densification occur simultaneously. In this study, the microstructure and superplastic deformation behavior of AZ80 magnesium alloy prepared by FSP were investigated. FSP led to remarkable grain refinement and modification of texture for AZ80 magnesium alloy. A maximum elongation of 606% was obtained at 3 × 10−4 s−1 and 350 ℃. When superplastic deformation was conducted at 3 × 10-3 s−1 and 300 ℃, or at 1 × 10-4 s−1 and 400 ℃, the superplasticity was relatively lower, thus exhibiting a lower strain rate sensitivity. The coarsening of both grains and β-Mg17Al12 precipitates deteriorated superplastic elongation. Applied deformation promoted the premature dissolution of β precipitates at 400 ℃ during superplastic deformation. Moreover, superplastic deformation weakened and spread the basal texture. Although the activation of prismatic and pyramidal slips is beneficial for superplastic deformation, grain boundary sliding is the main superplastic deformation mechanism.

NiTi-Nb porous shape memory scaffold was in-situ sintered by eutectic reaction using NiTi powder, Nb powder and Ti wire at 1180 °C. Ti2Ni and Ni4Ti3 phases are precipitated between the eutectic region and Ti wire, while the R martensite phase and Nb-Rich phases are formed in both eutectic region and the pre-eutectic region. Moreover, the stacking faults and micro-twinning in the eutectic region are beneficial to nucleation of R-phase martensite. All results demonstrate that the eutectic reaction combined with the interaction of Ti wire, NiTi powder and Nb powder contribute to tremendous increase in compressive strength up to 350 MPa.

Electro-shocking treatment (EST) has been investigated as a pathway to optimise the microstructure and mechanical properties of titanium alloys. The thermal conditions introduced by EST resulted in a phase transformation from α to β. The fraction of β phase decreased from 25.27% to 19.47% after EST for 0.02 s, which was possibly caused by the recrystallization of α phase. The application of EST for 0.04 s resulted in an increase in volume fraction of the β phase to 26.95%. The energy introduced by EST resulted in changes to the direction and intensity of texture within the microstructure with the texture intensity of the α phase increasing from 4.94 to 8.52, and that of β both increased from 3.35 to 9.88 after 0.04 s EST. Keywords: Electroshocking treatment (EST), Microstructure, Phase transformation, Phase content, Texture, TC11 alloy

The metallic glasses are known as amorphous and metastable materials. These materials have superior mechanical properties over crystalline materials with the same chemistry. Continuous efforts were made to improve the properties of metallic glass. The severe plastic deformation (SPD) method is used to improve the ductility of the glass. SPD causes the deformation at the atomic level in the disordered structure of the glass. Many methods are reported, such as cryogenic cycling, high-pressure torsion, and equal channel angular pressing, which are used for the SPD. In recent works on nanostructured metallic glasses, it has been evidenced that some properties, for example, mechanical, thermal, and magnetic, have improved compared to the bulk metallic glass. This paper has reviewed the recent progress in the SPD of the bulk and nanostructured metallic glasses. Different methods for the SPD have been addressed here. The effect of SPD on the properties of metallic glass is deliberated in this paper. Moreover, the challenging tasks of deformation occurrence in the glass and its characterization were considered, trying to develop a sound understanding of SPD in bulk and nanostructured metallic glasses.

The exploitation of highly efficient carbon dioxide reduction (CO2RR) electrocatalyst for methane (CH4) electrosynthesis has attracted great attention for the intermittent renewable electricity storage, but remain challenges. Here, N-heterocyclic carbene (NHC)-ligated Copper single atom site (Cu SAS) embedded in metal organic framework is reported (2Bn-Cu@UiO-67), which can achieve an outstanding Faradaic efficiency (FE) of 81% for the CO2 reduction to CH4 at -1.5 V vs RHE with a current density of 420 mA cm-2. Notably, the CH4 FE of our catalyst remains above 70% within a wide potential range, and achieves an unprecedented turnover frequency (TOF) of 16.3 s-1, which almost represents the best molecular catalyst for CH4 electrosynthesis to date. The experimental results show that the σ donation of NHC enriches the surface electron density of Cu SAS and promotes the preferential adsorption of CHO* intermediates. Meanwhile, the porosity of the catalyst facilitates the diffusion of CO2 to 2Bn-Cu, thereby significantly increasing the availability of each catalytic center. This NHC-ligated Cu SAS catalyst design has great advantages in CH4 electrosynthesis and provides ideas for the commercial production of CH4.

Effects of electroshock treatment (EST) on the microstructural evolution and mechanical properties of near-β titanium alloy (Ti-55531) formed by directed energy deposition (DED) was studied in this work. With the increase in EST time, the average hardness of specimen decreased from 426 HV to 316 HV, and the fracture strain increased significantly, which was attributed to the uniform dispersion of α phase along grain boundaries and inside the β grains. After EST, the texture intensity decreased in terms of the orientation distribution function (ODF), which was ascribed to the redistribution of α phase. Moreover, more atomic vacancies and lattice distortion were formed near the α/β interfaces, which were verified by transmission electron microscopy (TEM) observation and ascribed to the migration of atoms near the interface under EST. External loadings facilitated the dislocation motion and lattice distortions near the interfaces, which resulted in the reduction in hardness and the improvement in ductility. The above results indicated that EST can quickly alter the microstructure and mechanical properties of DED titanium alloys as a simple and energy-saving method.

To control the polarization of shallow etched ridge waveguide made of crystalline silicon on insulator (SOI), a non-rectangular section SOI waveguide is proposed. The transmittivity formulas of TE0 and TM0 in the proposed waveguide are deduced, and the finite difference time domain method is used for analysis. It is found that the transmittivity of TE0 and TM0 modes shows great deviation in some parameter range; however, the difference is less than 0.03% in some other parameters, which could be regarded as polarization independent. At the same time, the sensitivity to structure parameters of modes in the non-rectangular waveguide is lower than that of the rectangular. Therefore, the proposed non-rectangular SOI ridge waveguide is expected to improve the polarization independence of the waveguide.

Ti and Ti alloys have charming comprehensive properties (high specific strength, strong corrosion resistance, and excellent biocompatibility) that make them the ideal choice in orthopedic and dental applications, especially in the particular fabrication of orthopedic and dental implants. However, these alloys present some shortcomings, specifically elastic modulus, wear, corrosion, and biological performance. Beta-titanium (β-Ti) alloys have been studied as low elastic modulus and low toxic or non-toxic elements. The present work summarizes the improvements of the properties systematically (elastic modulus, hardness, wear resistance, corrosion resistance, antibacterial property, and bone regeneration) for β-Ti alloys via surface modification to address these shortcomings. Additionally, the shortcomings and prospects of the present research are put forward. β-Ti alloys have potential regarding implants in biomedical fields.

Electronic skin, a class of wearable electronic sensors that mimic the functionalities of human skin, has made remarkable success in applications including health monitoring, human-machine interaction and electronic-biological interfaces. While electronic skin continues to achieve higher sensitivity and faster response, its ultimate performance is fundamentally limited by the nature of low-frequency AC currents. Herein, highly sensitive skin-like wearable optical sensors are demonstrated by embedding glass micro/nanofibers (MNFs) in thin layers of polydimethylsiloxane (PDMS). Enabled by the transition from guided modes into radiation modes of the waveguiding MNFs upon external stimuli, the skin-like optical sensors show ultrahigh sensitivity (1870 kPa-1), low detection limit (7 mPa) and fast response (10 μs) for pressure sensing, significantly exceeding the performance metrics of state-of-the-art electronic skins. Electromagnetic interference (EMI)-free detection of high-frequency vibrations, wrist pulse and human voice are realized. Moreover, a five-sensor optical data glove and a 2×2-MNF tactile sensor are demonstrated. These initial results pave the way toward a new category of optical devices ranging from ultrasensitive wearable sensors to optical skins.

The effects of shot peening (SP) on mechanical behavior and surface morphology of Ti-6Al-4V were investigated in detail. After SP, the uniformity of compressive residual stress (CRS) was analyzed. The CRS decreased as SP intensity increased because of the severe impact of shots. The CRS was enhanced from − 762.7 to − 795.5 MPa with an increase in SP intensity. The fatigue life was increased from 0.46 × 106 cycles to 8.10 × 106 cycles after SP when the loading amplitude was 610 MPa. This increase was mainly attributed to the enhancement of the crack initiation hindering and propagation by the high CRS and refined domain sizes. The results of surface morphology showed that the convexity and concave regions were generated after SP and the improvement in SP intensity aggravated the increase in roughness. Although the roughness increased after SP, it did not hinder the enhancement of fatigue lives, indicating that CRS played a leading role in the improvement in fatigue lives. Thus, the analysis and discussion revealed that SP was beneficial for the improvement of the surface mechanical behavior of titanium alloys.

The strengthening effect of laser remelting on Ti-35Nb-2Ta-3Zr alloy was studied in this study. The surface of the material changed from an equiaxed crystal to a needle-like structure after laser remelting. Dislocations and ω phases were observed during the process, and the orientation relationship between ω phase and β matrix was identified as [11 0]β// [ 11 2 - 0 ] ω . The microhardness of the laser-remelted alloy increased significantly.

In the past two decades, friction stir processing (FSP) technology has received considerable attention. FSP can be used to adjust and control the microstructure of materials, including eliminating defects, destroying dendrites and controlling fractions in the second stage, and is therefore widely used in titanium and its alloys for biomedical, aerospace and automotive applications. This article comprehensively reviews the methods of studying FSP, the microstructure evolution of materials and the summary of material properties. It begins with the introduction of the FSW system, characterization, structure and elemental analysis, and simulation and performance testing methods, and then introduces the microstructure evolution mechanism of various titanium materials and discusses in detail the material properties of titanium alloy, namely hardness and wear resistance, elasticity and plasticity, corrosion resistance and biocompatibility. Finally, this review presents unresolved issues and outstanding challenges in FSP technology and reveals the direction of this emerging field of research.

After high-load spherical indentation treatment, the variations of hardness on the plastic zone of Ti-6Al-4V were investigated via nanoindentation method. The hardness within the center of plastic zone was measured by nanoindenter, and the magnitude decreased gradually along the depth, which were caused by the different extent of plastic deformation under the residual imprint. The microstructure of indentation were observed using scanning electron microscope (SEM) before and after surface etching, and the results showed that the microhardness revealed the average hardness of α and β phases of Ti-6Al-4V. The maximum hardness reached 6.438 GPa in the depth of 132 μm. In addition, the two and three dimensional contour profiles of residual imprint introduced by high-load spherical indentation were measured by the white-light interferometer and the shape of residual imprint was obtained. All results were discussed in detail. Keywords: Nanoindentation, Spherical loading, Hardness, Microstructure, Ti-6Al-4V

The surface microstructure and mechanical properties of Ti-6Al-4V/Ag nanocomposite processed by friction stir processing (FSP) are studied in this work. Scanning electron microscope (SEM) results show the gradient grain size of surface layer. The pile-up and tangle of dislocations and the deformation twins are observed by transmission electron microscopy (TEM). Atom probe tomography (APT) analyses reveal the presence of Ag-enriched nanoparticles in both the interiors and boundaries of α-Ti grains. Severe plastic deformation via FSP is responsible for considerable dislocations pile-up and tangle in the deformation bands. The enhancement in hardness and elastic modulus is attributed to the grain refinement and formation of much more deformation twinning. Moreover, Ag agglomeration could accelerate the recrystallization process and prevent grain coarsening, resulting in the higher hardness and the larger elastic modulus. This study confirms FSP is effective on surface modification of titanium alloys for improving the surface mechanical properties.

It is of great allure but still challenging to construct carbon-based metal free electrocatalysts to replace Pt-based ones for efficient ORR in both acidic and alkaline media. In this work, protein-hydrogel networks are demonstrated as a precursor for preparing N, S-codoped, hierarchically porous carbon (NSPC) materials with tunable pore structure. Of note, NSPC-0.2–900 possesses a high pore volume of 0.8552 cm³ g–1 and shows excellent ORR activity in both alkaline (Eonset, ∼0.93 vs. RHE) and acidic (Eoneset, ∼0.89 V vs RHE) media. As a cathode catalyst for zinc-air batteries, NSPC exhibits higher power density and better long-term durability than Pt/C does. The work presents a great potential of using protein as a precursor for preparing heteroatom doped, hierarchically porous carbon materials for energy and environmental applications.

Additive manufacturing (AM) has a substantial capability to produce superior and divergent properties of titanium alloys for biomedical implants, unlike the existing conventional technologies. This work investigated the mechanical properties and microstructure evolution of a β-type Ti-35Nb-2Ta-3Zr alloy prepared by selective laser sintering (SLS) process. The superelastic properties of the resultant specimen were characterized by cyclic loading-unloading tensile testing to evaluate the effect of SLS-process on the β-type Ti alloy specimen. The zigzag and V-shaped formation of {112} β twins, coexisting with stress-induced ω-formation, were observed by the transmission electron microscopy (TEM). The formation of Type I twin martensite along with β-structure is attributed to superelastic recovery and elastic recovery of SLS-produced specimen. High resolution TEM (HRTEM) observation was used to investigate the transition between β and ω phases. Thin layers of ω-formation in weak interfacial stress regions along with the longitudinal twin boundaries were also analyzed. The orientation relationship between ω-structure and parent β-phase involves an overlapping of ω-phase, observed along with longitudinal β-matrix and β-twins. Moreover, dislocation tangles and dislocation pile-ups form along with twin martensite, stress-induced ω-phase, and β-phase.

Hollow porous carbon (HPC) composed of inner voids and outer shells, is receiving increasing attention in constructing supported catalysts for diverse applications. It is of great allure but still ...

Titanium and its alloys are among the widely used materials in the biomedical field, but they have poor wear resistance and antibacterial properties. In the present study, anodization, photo-reduction, and spin-coating technologies were integrated to prepare a hybrid modified coating for bio-inert titanium implants, having excellent comprehensive performance. The surface roughness of Ti–35Nb–2Ta–3Zr was specifically optimized by surface modification leading to improved wear resistance. Ag ions are still detectable after 28 days of submersion in saline. The antibacterial rate of the composite coating group reaches 100% by plate counting due to the antibacterial mechanism of direct and indirect contact. Both bacteria morphology and fluorescence staining experiments confirm these results. Besides, no cytotoxicity was detected in our fabricated implants during the CCK-8 assay. Accordingly, fabrication of hybrid modified coatings on Ti–35Nb–2Ta–3Zr is an effective strategy for infection and cytotoxicity prevention. These hybrid modified coatings can be regarded as promising multifunctional biomaterials.

NiTi alloy has a wide range of applications as a biomaterial due to its high ductility, low corrosion rate, and favorable biocompatibility. Although Young’s modulus of NiTi is relatively low, it still needs to be reduced; one of the promising ways is by introducing porous structure. Traditional manufacturing processes, such as casting, can hardly produce complex porous structures. Additive manufacturing (AM) is one of the most advanced manufacturing technologies that can solve impurity issues, and selective laser melting (SLM) is one of the well-known methods. This paper reviews the developments of AMNiTi with a particular focus on SLM-NiTi utilization in biomedical applications. Correspondingly, this paper aims to describe the three key factors, including powder preparation, processing parameters, and gas atmosphere during the overall process of porous NiTi. The porous structure design is of vital importance, so the unit cell and pore parameters are discussed. The mechanical properties of SLM-NiTi, such as hardness, compressive strength, tensile strength, fatigue behavior, and damping properties and their relationship with design parameters are summarized. In the end, it points out the current challenges. Considering the increasing application of NiTi implants, this review paper may open new frontiers for advanced and modern designs.

Design an implant similar to the human bone is one of the critical problems in bone tissue engineering. Metal porous scaffolds have good prospects in bone tissue replacement due to their matching elastic modulus, better strength, and biocompatibility. However, traditional processing methods are challenging to fabricate scaffolds with a porous structure, limiting the development of porous scaffolds. With the advancement of additive manufacturing (AM) and computer-aided technologies, the development of porous metal scaffolds also ushers in unprecedented opportunities. In recent years, many new metal materials and innovative design methods are used to fabricate porous scaffolds with excellent mechanical properties and biocompatibility. This article reviews the research progress of porous metal scaffolds, and introduces the AM technologies used in porous metal scaffolds. Then the applications of different metal materials in bone scaffolds are summarized, and the advantages and limitations of various scaffold design methods are discussed. Finally, we look forward to the development prospects of AM in porous metal scaffolds.

The main goal of this research is to scrutinize the effect of texture and grain size on the biological response of hierarchical structured pure titanium (Ti), examining the interrelation between grain refinement mechanisms with texture variation. The hierarchical structure was produced using two methods of severe plastic deformation (SPD). The Ti specimens were first processed up to six passes by equal channel angular pressing (ECAP) and subsequently treated at the top surface using surface mechanical attrition treatment (SMAT). Microstructure examination by Electron backscatter diffraction (EBSD) indicates that the SMAT-treated surface was categorized into three distinct microstructural regions based on the type of grain refinement process involved during SPD: twin induced dynamic recrystallization (TDRX) and geometric dynamic recrystallization (GDRX) in the topmost surface, and continuous (CDRX) and discontinuous dynamic recrystallization (DDRX) in the lower regions of the sample. The biological experiments showed meaningful improvement in the cellular response of SMATed and ECAPed samples. It was demonstrated that grain refinement could have the capability of improving the biological response of Ti surface. In this regard, SMATed + 2ECAPed sample showed the best result although it has not the smallest grain size and the highest texture intensity. It was observed that texture and grain orientation of planes have an important impact on the biological response of pure Ti and dominance of prismatic (1010) texture can improve the cell viability, adhesion and its differentiation. Therefore, microstructure and texture tailoring through combined SPD methods could be a promising strategy for the improvement of the next generation of medical implants.

Magnesium (Mg) and its alloys have attached more and more attention because of their potential as a new type of biodegradable metal materials. In this work, AZ31/ZrO2 nanocomposites with good uniformity were prepared successfully by friction stir processing (FSP). The scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to characterize the microstructure of the composites. The mechanical properties, electrochemical corrosion properties and biological properties were evaluated. In addition, the effect of reinforced particles (ZrO2) on the microstructure and properties of the composite was studied comparing with FSP AZ31 Mg alloy. The results show that compared with the base metal (BM), the AZ31/ZrO2 composite material achieves homogenization, densification, and grain refinement after FSP. The combination of dynamic recrystallization and ZrO2 particles leads to grain refinement of Mg alloy, and the average grain size of AZ31/ZrO2 composites is 3.2 μm. After FSP, the c-axis of grain is deflected under the compression stress of shoulder and the shear stress of pin. The ultimate tensile strength (UTS) and yield strength (YS) of BM were 283 and 137 MPa, respectively, the UTS and YS of AZ31/ZrO2 composites were 427 and 217 MPa, respectively. The grain refinement and Orowan strengthening are the major strengthening mechanisms. Moreover, the corrosion resistance in simulated body fluid of Mg alloy is improved by grain refinement and the barrier effect of ZrO2.

An ideal keratoprosthesis scaffold should have good mechanical property, high biocompatibility, suitable corrosion and wear resistance. Due to limitation of materials, the difference of tenacity between the keratoprosthesis and the cornea often causes the exposure of keratoprosthesis materials, which results in serious complications. The cartilage has the similar biological characteristics to the cornea, no blood vessels and has certain flexibility. Although using the auricular cartilage or rib cartilage to reinforce the keratoprosthesis has been proven greatly successful, it is not possible to be individually designed and idealized. It is urgent to design a biosynthetic material for cartilage replacement to deal with predicament. We prepared and combined the decellularized cartilage extracellular matrix (DCECM) and the decellularized bone matrix (DBM), added the rabbit adipose-derived mesenchymal stem cells (rADMSCs) to construct a biosynthetic keratoprosthesis skirt. We asssessed the mechanical property, cell binding efficiency, safety and cytotoxicity, biocompatability and chondrogenic or osteogenic capacity of the DCECM/DBM-rADMSCs composite scaffold. Tests revealed the DCECM/DBM scaffold has proper elasticity, tenacity, and, is safe to cells. It’s observed that the DCECM/DBM-rADMSCs composite scaffold integrated into the recipient cornea without inflammation and rejection, while transplanted in the recipient cornea for 12 months. In particular, chondrogenesis and osteogenesis are found inside and even around the scaffold. Hence, the DCECM/DBM-rADMSCs composite scaffold coule be a potential biosynthetic skirt for keratoprosthesis or a fixed supportive scaffold to reinforce the keratoprosthesis in the treatment of end-stage corneal blindness.

The CoCrNi and precipitate-hardened (CoCrNi)94Ti3Al3 medium entropy alloys (MEAs) have attracted much attention, due to their exceptional mechanical properties, whereas the hot deformation characteristics have not been revealed. In the present study, we investigated the dynamic recrystallization behavior and microstructure evolutions of the two MEAs hot-compressed at single-phase temperatures. The constitutive equation was obtained, and microstructures were observed. Discontinuous dynamic recrystallization acted as a key mechanism of grain refinement at a relatively higher temperature and lower strain rate, which leads to the formation of a homogeneous grain structure. The addition of Ti and Al promoted dynamic recrystallization due to the solid solution hardening effect. The results provide valuable guidelines for microstructure refinement via thermomechanical processing.

Additive manufacturing (AM) is among the most attractive methods to produce implants, the processes are very swift and it can be precisely controlled to meet patient’s requirement since they can be produced in exact shape, dimension, and even texture of different living tissues. Until now, lots of methods have emerged and used in this field with diverse characteristics. This review aims to comprehensively discuss 3D printing (3DP) technologies to manufacture metallic implants, especially on techniques and procedures. Various technologies based on their main properties are categorized, the effecting parameters are introduced, andthe history of AM technology is briefly analyzed. Subsequently, the utilization of these AM-manufactured components in medicine along with their effectual variables is discussed, and special attention is paid on to the production of porous scaffolds, taking pore size, density, etc., into consideration. Finally, 3DP of the popular metallic systems in medical applications such as titanium, Ti6Al4V, cobalt-chromium alloys, and shape memory alloys are studied. In general, AM manufactured implants need to comply with important requirements such as biocompatibility, suitable mechanical properties (strength and elastic modulus), surface conditions, custom-built designs, fast production, etc. This review aims to introduce the AM technologies in implant applications and find new ways to design more sophisticated methods and compatible implants that mimic the desired tissue functions.

The propose of this review was to summarize the advances in multi-scale surface technology of titanium implants to accelerate the osseointegration process. The several multi-scaled methods used for improving wettability, roughness, and bioactivity of implant surfaces are reviewed. In addition, macro-scale methods (e.g., 3D printing (3DP) and laser surface texturing (LST)), micro-scale (e.g., grit-blasting, acid-etching, and Sand-blasted, Large-grit, and Acid-etching (SLA)) and nano-scale methods (e.g., plasma-spraying and anodization) are also discussed, and these surfaces are known to have favorable properties in clinical applications. Functionalized coatings with organic and non-organic loadings suggest good prospects for the future of modern biotechnology. Nevertheless, because of high cost and low clinical validation, these partial coatings have not been commercially available so far. A large number of in vitro and in vivo investigations are necessary in order to obtain in-depth exploration about the efficiency of functional implant surfaces. The prospective titanium implants should possess the optimum chemistry, bionic characteristics, and standardized modern topographies to achieve rapid osseointegration.

Decreasing elastic modulus and simultaneously improving biological compatibility has been a major challenge in developing biomedical alloy. In this study, Ti6Al4V/Zn composite with surface nano crystallization is successfully fabricated by friction stir processing (FSP) with simultaneous addition of beneficial Zn element. Nanoscale microstructures in surface region include nanoscaled Zn rich particles (including TiZn2), α nanograins, nanotwins and nano α + β lamellae. Dislocations slip and grain boundary sliding contribute much to the transformation of α-Ti nanograin, while dynamic overlapping of two partial dislocations is the main deformation mechanism for nanotwins. Interestingly, these nanoscale microstructures reduce the elastic modulus of this region.

A simulation model based on the finite-element method (FEM) and transfer matrix method (TMM) is developed for analyzing mechanical long-period fiber gratings (MLPFGs). The anisotropic characteristics of the cross section of a fiber are obtained using FEM and the non-rectangular distribution of refractive index of the stressed area is accounted for to analyze band-rejection filtering characteristics using TMM, both of which are neglected in the conventional coupled-mode method (CMM). The overall attenuation in the entire spectral range is successfully simulated by the proposed method. The deviations of the transmittance at resonance wavelength between theoretical values and the actual conditions are 11.39 dB and 1.18 dB for CMM and FEM-TMM, respectively, for a high-birefringence case under a high applied force such as F = 60 N.

A reflection-type liquid-level sensor based on mechanically induced long-period fiber grating (MLPFG) is proposed and experimentally demonstrated. The sensor, acting as a Michelson interferometer, includes MLPFG with double-cladding fiber (DCF) whose end-face is coated with a silver film. DCF is used here in order to be more conducive for interference-spectrum generation. The liquid level can be measured by monitoring the shift of the interference fringes. By theoretical and experimental analysis of the interference characteristics, it is concluded that there are certain relationships between the interference-fringe spacing and the distance from the grating to the reflector, and that the fringe contrast ratio is influenced either by the stress or the position of the MLPFG. After the appropriate parameters are selected for the liquid-level sensor, the sensor sensitivity of 0.03136 nm/mm is obtained, which is considerably superior to that of conventional interferometric liquid-level sensors. In addition, the device has advantages, such as low cost and structural simplicity.

Friction stir processing (FSP) was successfully employed to produce gradient multi-phase structured Ti–6Al–4V/Ag nanocomposite surface layer. Microstructural evolution of amorphous/nanocrystalline/nano-twin in the surface layer was characterized by TEM in detail. The formation of amorphous phase in the upper surface of stir zone (SZ) was attributed to mechanically driven amorphization caused by dislocation gliding plastic deformation and elements mixing process. The dislocation activities played a dominant role in causing the distortion of lattices and nanocrystallization. The plastic deformation via FSP was responsible for considerable dislocations pile-up and tangle in the potential deformation bands.

Corrosion fatigue is one of the major forms for nickel‑aluminum bronze alloy used in marine propeller. It is greatly important to understand the corrosion fatigue behavior of nickel‑aluminum bronze alloy in seawater for the purpose of improving the service life of marine equipment. In this study, corrosion fatigue crack growth rate of nickel‑aluminum bronze alloy in 3.5% NaCl solution was tested under various stress intensity factors, stress ratios and loading frequencies to reveal its corrosion fatigue mechanism. The results show that corrosion environment significantly accelerates the crack growth and decreases the corrosion fatigue threshold, which is attributed to the corrosion reactions between the metals of crack tip and corrosive medium. Among the various factors, loading frequency has more predominant influence on the corrosion fatigue crack growth rate of nickel‑aluminum bronze alloy, which can be rationally explained by the hydrogen embrittlement mechanism. Additionally, in the process of corrosion fatigue crack growth, the acidification and the dealumination would occur at the crack tip, resulting in the corrosion dissolution of κ phases and the deterioration in mechanical properties of crack tip.

In this study, coarse-grained Nickel-Aluminum bronze (NAB) alloy is subjected to shot-peening (SP) treatment, and the grain refinement mechanisms of various phases in shot-peened NAB alloy are investigated separately. The results show that severe deformation layers are produced on the surface. Meanwhile, refined grains with the average size below 100 nm are induced through SP treatment indicated by the results of X-ray diffraction (XRD) patterns. Various phases in NAB alloy including α, β' and three intermetallic phases (κii, κiii and κiv) display different grain refinement mechanisms. The grain refinement in the α phase involves dislocation segmentation in the precipitation-free zone and the twinning intersection in the precipitation zone. The formation of nanotwins by emitting partial dislocations at the grain boundary is found to be responsible for the grain refinement in the β' phase. As for the κ phases, the strip-shaped κiii phases are fragmented after severe deformation, and the κiv and κii phases exhibit the twinning and dislocation deformation modes, respectively. Also, the microhardness is significantly enhanced after SP treatment, which is mainly attributed to the work hardening effect and grain refinement.

This work addresses the susceptibility to stress corrosion cracking in 3.5% NaCl solution (simulating seawater) of three differently obtained microstructures of a nickel-aluminum bronze alloy using slow strain rate tensile tests. The results showed that the stress corrosion cracking susceptibility of annealed and normalized alloys increased with the decrease of the strain rate as the metal became more severely corroded and dissolved at the crack tips. The continuous or semi-continuous α + κⅢ eutectoid structure is sensitive to stress corrosion cracking, resulting in the highest susceptibility of annealed alloy. The thin and overlapped Widmanstatten α grain hinders extension of the cracks and thus decreases the stress corrosion cracking susceptibility of normalized alloy to some degree. The quenched/aged alloy with homogeneous microstructure without α + κⅢ eutectoid structure and the β’ phase exhibits the lowest susceptibility. The stress corrosion cracking process of nickel-aluminum bronze alloys was revealed and is properly explained by the oxide film rupture and anodic dissolution mechanism as well as the hydrogen induced cracking mechanism.

This work studied the formation of the α″ martensite and amorphous phases of TiNbTaZr alloy incorporated with TiO2 particles during friction stir processing. Formation of the amorphous phase in the top surface mainly results from the dissolution of oxygen, rearrangement of the lattice structure, and dislocations. High-stress stemming caused by dislocations and high-stress concentrations at crystal–amorphous interfaces promote the formation of α″ martensite. Meanwhile, an α″ martensitic transformation is hindered by oxygen diffusion from TiO2 to the matrix, thereby increasing resistance to shear.

Chenyuan Zhu,1,2,* Yuting Lv,3,4,* Chao Qian,1,2,* Zihao Ding,3,5 Ting Jiao,1,2 Xiaoyu Gu,1,2 Eryi Lu,6 Liqiang Wang,3 Fuqiang Zhang1,2 1Department of Prosthodontics, Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, 2Shanghai Key Laboratory of Stomatology, Shanghai Research Institute of Stomatology, National Clinical Research Center of Stomatology, 3State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, 4College of Mechanical and Electronic Engineering, Shandong University of Science and Technology, Qingdao, People’s Republic of China; 5Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA, USA; 6Department of Stomatology, Ren Ji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People’s Republic of China *These authors contributed equally to this work Background: The interaction between the material and the organism affects the survival rate of the orthopedic or dental implant in vivo. Friction stir processing (FSP) is considered a new solid-state processing technology for surface modification. Purpose: This study aims to strengthen the surface mechanical properties and promote the osteogenic capacity of the biomaterial by constructing a Ti-6Al-4V (TC4)/zinc (Zn) surface nanocomposites through FSP. Methods: FSP was used to modify the surface of TC4. The microstructures and mechanical properties were analyzed by scanning electron microscopy, transmission electron microscopy, nanoindentation and Vickers hardness. The biological properties of the modified surface were evaluated by the in vitro and in vivo study. Results: The results showed that nanocrystalline and numerous β regions, grain boundary a phase, coarser acicular α phase and finer acicular martensite α' appeared because of the severe plastic deformation caused by FSP, resulting in a decreased elastic modulus and an increased surface hardness. With the addition of Zn particles and the enhancement of hydrophilicity, the biocompatibility was greatly improved in terms of cell adhesion and proliferation. The in vitro osteogenic differentiation of rat bone marrow stromal cells and rapid in vivo osseointegration were enhanced on the novel TC4/Zn metal matrix nanocomposite surface. Conclusion: These findings suggest that this novel TC4/Zn surface nanocomposite achieved by FSP has significantly improved mechanical properties and biocompatibility, in addition to promoting osseointegration and thus has potential for dental and orthopedic applications. Keywords: nanocomposite, friction stir processing, nanocrystalline/ultrafine grained, bone marrow stromal cells, cell proliferation, osteogenic differentiation

Metallic Co4N catalysts have been considered as one of the most promising non-noble materials for heterogeneous catalysis because of their high electrical conductivity, great magnetic property, and high intrinsic activity. However, the metastable properties seriously limit their applications for heterogeneous water phase catalysis. In this work, a novel Co-metal–organic framework (MOF)-derived hollow porous nanocages (PNCs) composed of metallic Co4N and N-doped carbon (NC) were synthesized for the first time. This hollow three-dimensional (3D) PNC catalyst was synthesized by taking advantage of Co-MOF as a precursor for fabricating 3D hollow Co3O4@C PNCs, along with the NH3 treatment of Co-oxide frames to promote the in situ conversion of Co-MOF to Co4N@NC PNCs, benefiting from the high intrinsic activity and electron conductivity of the metallic Co4N phase and the good permeability of the hollow porous nanostructure as well as the efficient doping of N into the carbon layer. Besides, the covalent bridge ...

Low modulus β-type Ti-35Nb-2Ta-3Zr alloy scaffold was fabricated by laser powder bed fusion ( L -PBF). The complex microstructure and mechanical properties were characterized systematically. The martensitic interstitial complex transitions (ICTs) from β to α" (β→α"), α" to ω (α"─ω), and β to α" and ω (β→α''─ω) phases are accompanied by dislocation pile-ups and twins in a heterogeneous manner. A homaloidal transition was observed with astraddle ω and α"M nanolayers and partial nanolayers along the boundaries of the α"T martensitic twin. Crystallographic characterization confirmed that {332}〈113〉 and {112}〈111〉 twinning and shear stress assisted the α─ω and β→α" transitions at the interface of the β region. Both the αꞌꞌ martensitic twin and ω formation were observed adjacent to the {332}〈113〉 type twinning mode. The [332] twinning were instigated and nucleated through ω-phase formation. The secondary [112] twins amid the primary [332] twinning were instigated and nucleated through ω-phase formation. Multiple slip bands were identified on the surface of the micropillar after the microcompression testing. Moreover, high-density dislocations and dislocation pile-ups were found alongside the twins and grain boundaries. In addition, {112}〈111〉 twinning was identified amongst dislocation pile-ups. This work reveals a novel complex phase transformation that could play a significant role in applications such as biomedical implants.

The availability of casting Ni–Fe alloy as inert anode for direct electro-reduction of V2O3 in molten Na3AlF6-K3AlF6-AlF3 was investigated. The electrochemical oxidation behavior of anode as well as microstructural evolutions of formed oxide scale were systematically studied. The electrochemical characterization and reaction mechanism of the cathode oxide were also investigated to evaluate the influence of alloy anode on cathodic reduction process. The in situ formed three-layered oxide scale is compact and coherent, which is composed of an outermost Fe2O3 + FeAl2O4 skin layer, a Fe2O3 middle layer and a FeAl2O4 inner layer. The skin layer has a continuous, smooth structure and shows electrochemical activity. The Fe2O3 layer with a compact structure prevents inward diffusion of electrolyte and outward migration of metal cations. The innermost FeAl2O4 layer shows a loose structure and functions as a buffer layer to improve the peeling resistance of oxide scale. With the continuous extension of polarization time, the inner FeAl2O4 layer is slowly oxidized and becomes thinner, simultaneously, the dense Fe2O3 layer becomes thicker. Ultimately, metal vanadium product with fine rod-like particles can be obtained and the oxygen content in the metal vanadium is below 0.3 mass% within electrolyzing time of 2 h. The corresponding current efficiency is around 63%.

This work combines several techniques into a novel method to manufacture NiTi Nb layer-like porous structures with 3D interconnected channels, which are of vital importance in the biomedical field. NiTi wires and Nb foils are used herein to prepare NiTi Nb layer-like porous materials via in situ eutectic reaction. Microstructure, phase transformation and superelasticity of the resultant NiTi Nb layer-like porous material are analyzed and discussed, and the interface between NiTi wires and the solidified NiTi Nb eutectic region are also studied. Dislocations and stacking faults occurring at interfaces accelerate the eutectic phase transformation. Meanwhile, rod-like eutectic phase pins the motion of screw dislocations, which is beneficial for stress-induced R martensite nucleation. It is believed that much more superelastic recovery and elastic recovery for such a layer-like porous structure are attributed to formation of more martensites during deformation. Furthermore, both reorientation and subsequent de-twinning of type II twins result in the observed stress-plateau, thereby promoting the superelastic recovery.

With black phosphorus (BP) as an example, the first two-dimensional (2D) semiconductor based sonosensitizer (Au@BP nanohybrids) was fabricated. Under ultrasound irradiation, Au@BP nanohybrids can generate 1O2 in deep tissues and eradicate tumors with high efficacy. This platform paves the way for the application of 2D semiconductors in sonodynamic cancer therapy.

This work uses a novel method of electroshock treatment (EST) to refine the TiB reinforcement to nanometer in TiB/Ti-2Al-6Sn titanium matrix composite (TMC), with an aim to shed insights into improve the deformation coordination between reinforcements and matrix of TMCs. The resistivity of TiB/Ti-2Al-6Sn before and after EST was investigated, and the resistivity increased first and then decreased with the increase of EST time. The variation in resistivity was attributed to the generation of cracks in the reinforcement/matrix interfaces during EST. Microstructural characterization indicates that the TiB whiskers fractured into small particles with 50–312 nm in diameter under the thermal stress and extrusion of matrix during EST. The deformation of matrix could not yield to the deformation of TiB in a very short time and cracks were generated in TiB/matrix interfaces. In order to repair the cracks at TiB/matrix interfaces, external loading was adopted during EST. After EST with external loading, the TiB underwent refinement and cracks in the nano-TiB/matrix interfaces were repaired when the load was 0.3 MPa, due to the thermal and athermal effects of EST as well as the compressive stress of external loading. Combing EST and the external loading, the fracture strain of TiB/Ti-2Al-6Sn increased along with a small slight variation in yield strength. The variation in mechanical properties is attributed to the refinement of TiB and the repairing of cracks. All results indicate that EST is a valuable method to manipulate the size of TiB from micrometer to nanometer, realizing the refinement of TiB and providing a novel idea for improving the deformation coordination of TMCs.

Shot peening (SP) was employed to modify the surface microstructure and mechanical properties of (TiB+TiC)/Ti-6Al-4V titanium matrix composite (TMC). And the microstructure evolution and mechanical properties were characterized and analyzed in detail. Transmission electron microscopy (TEM) results illustrated that the surface nanograins were introduced by the effect of SP and the hindering of reinforcements to the matrix deformation. The nanograins were formed near the reinforcement/matrix interface because the matrix was squeezed by both the shots and the reinforcements. Moreover, with increasing the volume fraction of reinforcements, the smaller nanograins were introduced near the interfaces due to the severe deformation between the matrix and reinforcements, which were caused by the decrease in average distance between two reinforcements. Under the same intensity of SP, the deformation of TiC was more severe than that of TiB, and more dislocations were introduced around TiC. The results were influenced by both the different shapes and distribution of reinforcements, and the impact direction of shots. After SP, the compressive residual stress (CRS) and the hardness in the peened surface layer were improved, which was due to the surface deformation, nanograins and high dislocation density in the nanocrystal layer.