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Local defects in coatings allow aggressive electrolytes penetrate to the coating/substrate interface, accelerating the corrosion of the exposed Mg substrate and compromising its biocompatibility. In this work, self-healing calcium hydrogen phosphate dihydrate (DCPD) coating incorporated with 3,5-dinitrosalicylic acid (3,5-D) or 5-amino salicylic acid (5-A) is designed on Mg. The results reveal that the self-healing and corrosion resistance performance of DCPD improves after adding 3,5-D/5-A. Namely, incorporating 3,5-D/5-A into DCPD accelerates the self-healing process and repair the coating at the initial stage. The released 3,5-D/5-A additives could adsorb on the exposed Mg surface and combine with the Ca2+ ions to precipitate. The interfacial adsorption mechanism of 3,5-D/5-A additives is disclosed by quantum chemical calculation. The simultaneously responsive adsorption and deposition of additives during coating degradation increase the thickness and compactness of the deposition layer at the coating defects, further inhibiting corrosion and stabilizing pH. These findings suggest taking biocompatibility recovery into consideration of preparing self-healing coating for biomedical applications.

Aluminum (Al) and its alloys have been widely used in daily life, but the absence of antibacterial properties makes them potential vectors for bacterial transmission. In this study, an Ag-doped TiO2 coating was successfully prepared on the porous surface of etched Al foil using the sol-gel method. The results indicated that the porous layer allowed the gel to permeate through the holes, thereby forming an interface carrying these antibacterial agents with a thickness of about 10 μm. The Ag dopant promoted the transformation of titania from rutile to anatase during the calcination process, with the rutile being absent when the atomic ratio of Ag to Ti reached 0.10. Meanwhile, the doped Ag+ was thermally decomposed into metallic Ag0. As a result, doping Ag enhanced the photocatalytic efficacy of TiO2 coating. Moreover, the antibacterial rate of this coating against Escherichia coli and Staphylococcus aureus under dark conditions could reach more than 99%, and the corrosion resistance of the Al foil was also slightly improved by it.

Mg is a typical biodegradable metal widely used for biomedical applications due to its considerable mechanical properties and bioactivity. Biodegradable polymers have attracted great interest owing to their favorable processability and inclusiveness. However, it is challenging for the degradation rates of Mg or polymers to precisely match tissue repair processes, and the significant changes in local pH during degradation hinder tissue repair. The concept of combining Mg with polymers is proposed to overcome the shortcomings of materials, aiming to meet repair needs from various aspects such as mechanics and biology. Therefore, it is essential to systematically understand the behavior of biodegradable Mg/polymer composite (BMPC) from the design, manufacturing, mechanical properties, degradation, and biological effects. In this review, we elaborate on the design concepts and manufacturing strategies of high-strength BMPC, the “structure-function” relationship between the microstructures and mechanical properties of composites, the variation in the degradation rate due to endogenous and exogenous factors, and the establishment of advanced degradation research platform. Additionally, the interplay among composite components during degradation and the biological function of composites under non-responsive/stimuli-responsive platforms are also discussed. Finally, we hope that this review will benefit future clinical applications of “structure-function” integrated biomaterials.

Abstract Biodegradable porous Mg scaffolds are a promising approach to bone repair. In this work, 3D-spherical porous Mg–1.5Zn–0.2Ca (wt.%) scaffolds were prepared by vacuum infiltration casting technology, and MgF2 and fluorapatite coatings were designed to control the degradation behavior of Mg-based scaffolds. The results showed that the pores in Mg-based scaffolds were composed of the main spherical pores (450–600 μm) and interconnected pores (150–200 μm), and the porosity was up to 74.97%. Mg-based porous scaffolds exhibited sufficient mechanical properties with a compressive yield strength of about 4.04 MPa and elastic modulus of appropriately 0.23 GPa. Besides, both MgF2 coating and fluorapatite coating could effectively improve the corrosion resistance of porous Mg-based scaffolds. In conclusion, this research would provide data support and theoretical guidance for the application of biodegradable porous Mg-based scaffolds in bone tissue engineering. Graphical Abstract

The process of hydrocarbon accumulation in polycyclic superimposed basins often involves multistage crude oil charging, but not every stage of crude oil charging plays a significant role in the current hydrocarbon accumulation. Fluid inclusion methods can only provide constraints on the stages and time of crude oil charging, but cannot determine the contribution of each stage of crude oil charging for hydrocarbon accumulation. To study the contributions of different stages of crude oil charging for the reservoirs, the Ordovician carbonate reservoirs in the subsalt area, Tahe oilfield (Tahe subsalt area) were taken as an example. This study employed crude oil geochemistry, fluid inclusion analysis, fluorescence spectrum, and single well simulation analysis methods to systematically reveal the fluorescence characteristics of crude oil and hydrocarbon accumulation stages and time of the study area. The analysis of crude oil biomarker parameters indicates that the crude oil has the same parent material and was deposited in a marine weak reducing environment. By comparing the crude oil with the study area's source rocks, it was determined that all the crude oil was derived from the source rocks of the Lower Cambrian Yuertusi Formation. The aromatic methylphenanthrene index and methyldibenzothiophene parameters of crude oil serve as effective indicators for the quantitative evaluation of crude oil maturity. The calculated crude oil maturity (Ro) in the Tahe subsalt area ranges from 0.90% to 1.47%, and this may correspond to multiple stages of oil and gas charging. Based on fluorescence spectrum analysis of oil inclusions and homogeneity temperature and salinity measurements of associated saline inclusions in the Ordovician reservoirs in the Tahe subsalt area and the study area's burial history of single well burial history and thermal history simulation, it was determined that the oil reservoirs in the Tahe subsalt area experienced three stages of crude oil charging during the stages of middle Caledonian (420 Ma), middle Hercynian (318 Ma) and late Himalayan (10 Ma). By comparing the fluorescence spectrum parameters of crude oil and oil inclusions in these three stages, it is concluded that the late Himalayan is the primary stage of hydrocarbon accumulation in the Tahe subsalt area, making the largest contribution for the Ordovician reservoirs in the Tahe subsalt area.

Staplers have been widely used in the clinical treatment of gastrointestinal reconstruction. However, the current titanium (Ti) staple will remain in the human body permanently, resulting in some adverse effects. In this study, we developed a type of biodegradable staple for colonic anastomosis using 0.3 mm diameter magnesium (Mg) alloy wires. The wire surface was modified by micro-arc oxidation treatment (MAO) and then coated with poly-l-lactic acid (PLLA) to achieve a moderate degradation rate matching the tissue healing process. The results of tensile tests on isolated porcine colon tissue anastomosed by Mg and Ti staples showed that the anastomotic property of Mg staples was almost equal to that of Ti staples. The in vitro degradation tests indicated the dual-layer coating effectively enhanced the corrosion resistance and maintained the tensile force of the coated staple stable after 14-day immersion in the simulated colonic fluid (SCF). Furthermore, 24 beagle dogs were employed to conduct a comparison experiment using Mg-based and clinical Ti staples for 90-day implantation by ent-to-side anastomosis of the colon. The integrated structure of Mg-based staples was observed after 7 days and completely degraded after 90 days. All animals did not have anastomotic leakage and stenosis, and 12 dogs with Mg-based staples fully recovered after 90 days without differences in visceral ion levels and other side effects. The favorable performance makes this Mg-based anastomotic staple an ideal candidate for colon reconstruction.

Biomedical degradable materials would be subjected to different degrees and forms of static stress after being implanted in the human body. In this work, the biocorrosion behaviors of AZ31B magnesium alloy under different stress forms with different magnitudes (20 ∼ 150 MPa) were studied. It was found that the corrosion behaviors at stressed conditions were severer than those at unstressed conditions and corrosion rates were obviously accelerated. The biocorrosion behaviors are more sensitive to the effects of tensile loads than to compressive loads. A biocorrosion numerical model on the degradation process of Mg alloy under static loads was established. The corrosion current density (icorr) of Mg alloy and the applied static stress (σ) matches a linear relationship of ln icorr ∼ σ well during the early stage (within 24 hrs) while deviated gradually in the latter period of corrosion. This work could provide a guidance and theoretical reference for further researches on the biocorrosion behaviors and practical clinical applications of the biomedical materials subjected to physiological loads.

With an upsurge of biodegradable metal implants, the research and application of Mg alloys in the gastrointestinal environment of the digestive tract have been of great interest. Digestive enzymes, mainly pepsin in the stomach and pancreatin in the small intestine, are widespread in the gastrointestinal tract, but their effect on the degradation of Mg alloys has not been well understood. In this study, we investigated the impacts of pepsin and pancreatin on the degradation of Mg-2Zn alloy wires. The results showed that the pepsin and pancreatin had completely different even the opposite effects on the degradation of Mg, although they both affected the degradation product layer. The degradation rate of Mg wire declined with the addition of pepsin in simulated gastric fluid (SGF) but rose with the addition of pancreatin in simulated intestinal fluid (SIF). The opposite trends in degradation rate also resulted in completely different degradation morphologies in wires surface, where the pitting corrosion in SGF was inhibited because of the physical barrier effect of pepsin adsorption. In contrast, the adsorption of pancreatin affected the integrity of magnesium hydrogen phosphate film, causing a relatively uneven degraded surface. These results may help us to understand the role of different digestive enzymes in the degradation of magnesium and facilitate the development and clinical application of magnesium alloy implanted devices for the digestive tract.

The real physiological environment of human body is complicated with different degrees and forms of dynamic loads applied to implanted medical devices due to the daily activities of the patients, which would have impacts on the degradation behaviors of magnesium alloy implants. In this work, the bio-corrosion behaviors of AZ31B magnesium alloy under alternating cyclic dynamic loads with different low frequencies (0.1–2.5 Hz) were specially investigated. It was found that the bio-degradation performances under external dynamic stressed conditions were much severer than those under unstressed conditions and static loads. The corrosion rates were generally accelerated as the rise of cyclic frequency. Hereby a numerical model for the degradation process of Mg alloy was established. The corrosion current density icorr of Mg alloy and the applied loading frequency f matches a linear relationship of ln icorr ∝ f, which is the result of interactions between the cyclic alternating load and corrosive environment. This work could provide a theoretical reference and an experimental basis for further researches on the biodegradation behaviors of biomedical materials under dynamic conditions.

Mg-based porous materials, as potential bone tissue engineering scaffolds, are considered an attractive strategy for bone repair owing to favorable biodegradability, good biocompatibility and suitable mechanical properties. In this work, 3D-cubic interconnected porous Mg–xZn–0.3Ca (x = 0,3,6) scaffolds were prepared to obtain desirable pore structures with a mean porosity up to 73% and main pore size of 400–500 µm, which pore structures were close to the human cancellous bone. The structure–property relationships in the present scaffolds were analyzed by experiments and theoretical models of generalized method of cells (GMC). Mg–xZn–0.3Ca scaffolds exhibited good compression properties with a maximum above 5 MPa in yield strength and about 0.4 GPa in elastic modulus. This was attributed to not only the alloy strengthening but also the large minimum solid area. On the other hand, the scaffolds showed undesirable and relatively serious degradation behavior in Hank's solution, resulting from Zn addition in Mg-based scaffolds and the high surface area ratio in the pore structure. Therefore, surface modifications are worth studying for controlled degradation in the future. In conclusion, this research would explore a novel attempt to introduce 3D-cubic pore structure for Mg-based scaffolds, and provide new insights into the preparations of Mg-based scaffolds with good service performances for bone repair.

The microstructures, mechanical properties, and corrosion behaviors of Mg-4Gd-xY-1Zn-0.5Ca-1Zr (x = 1, 3, and 5 wt.%) alloys under as-cast condition were studied. The results indicate that all the alloys are composed of α-Mg matrix, eutectic phase, and lamellar stacking faults (SFs) located at the outer edge of the α-Mg grains. The plate-like long period stacking ordered (LPSO) structures are found in the alloys with higher Y content. The nano hardness of different phases obeys the following order: eutectic phase > SFs/LPSO structure > α-Mg matrix. Higher Y concentration leads to the nano hardness enhancement of the α-Mg matrix and more uniform hardness distribution. Tensile tests at ambient temperature indicate that Y addition plays a crucial role in improving the yield strength of the as-cast alloys. The corrosion properties of the as-cast alloys after immersion in 3.5 wt.% NaCl solution for 60 h reveal that Mg-4Gd-3Y-1Zn-0.5Ca-1Zr alloy shows a more uniform corrosion morphology and better corrosion resistance than the other two alloys.

The Neoproterozoic Binggounan Formation mud shale in the Hongliugou Ⅰ section on the northwestern margin of the Altyn Tagh fault was deposited in a passive continental margin. They are shelf sediments about 60 m thick, interbedded with siliceous rocks, undergone a low temperature thermodynamic metamorphism, and had hydrocarbon generation potential. The tectonic background, provenance, weathering and sedimentary environment of the mud shale were discussed with regard to stratigraphic sections, mineralogy and geochemical analyses. The mud shale was mainly composed of silica-rich clay rock and mud-rich siliceous shale, followed by mud-silica mixed shale. They have simila-rities in Si, Mg, K, P, Sc, Y, Hf, Th Sc contents compared with the Post Archaean Australian shale (PAAS). The Ti, Mn, Fe, Ta contents and δEun, δCen, ΣREE values are higher, while the Al, Ca, Na, Nb and Zr contents are lower. The primitive sediment sources of the Binggounan mud shale were recycled sedimentary clasts, intermediate mafic and acid intrusive rocks, similar to a normal shale and arenites argillites and ensialic of continental upper crust in composition. The shale has undergone moderate chemical weathering in warm and humid conditions. The formation was divided into three sedimentary cycles from bottom to top, mainly anaerobic and anoxic, and occasionally oxidized. Hydrothermal alteration also occured in the lower section. The mud shale with a clay content of about 40% is rich in trace elements (REE) and organic matter, which was deposited in a suboxic to anoxic section on the shelf, showing a high productivity and hydrocarbon-generation potential.

Self-healing coatings have been developed as smart surface coatings for Mg and its alloys to retain local corrosion from the coating damages. In this study, we prepared dicalcium phosphate dihydrate (DCPD) coating on biomedical Mg, and found that the artificial scratches in DCPD coating can be efficiently sealed by anti-corrosive products in both Hank's and normal saline (NS) solutions. Besides, the in-depth study revealed that DCPD was served as not only a physical barrier but also a self-healing agent, demonstrating an autonomous self-healing coating without embedded extra corrosion inhibitors. Moreover, Hank's solution provided foreign-aid film-forming ions to promote self-healing behavior. The findings might offer new opportunities for further studies and applications of efficient self-healing coatings on biodegradable Mg implants.

In this work, a facile direct current atmospheric pressure micro-plasma (APM) technology was deployed for the synthesis of functional gold nanoparticle/chitosan (AuNP/CS) nanocomposites for the first time. Different experimental parameters, such as metal salt precursor concentration and chitosan viscosity, have been investigated to understand their effects on the resulting nanocomposite structures and properties. The nanocomposites were fully characterized using a wide range of material characterization techniques such as UV–vis, transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectra and X-ray photoelectron spectroscopy (XPS) analyses. Potential reaction pathways have been proposed for the nanocomposite synthesis process. Finally, potential of the synthesized nanocomposites towards photothermal conversion and bacteria eradiation applications has been demonstrated. The results show that APM is a facile, rapid and versatile technique for the synthesis of AuNP/CS functional nanocomposites. Through this work, a more in-depth understanding of the multi-phase system (consisting of gas, plasma, liquid and solid) has been established and such understanding could shine a light on the future design and fabrication of new functional nanocomposites deploying the APM technique.

Changes in the texture as well as mechanical properties of CoNiFeV0.5Mo0.2 medium entropy alloy wire rods during loading–unloading are investigated. The intensity of the recrystallization texture {001} component and fraction of low angle grains increase with the loading–unloading cycles and the alloy strength increases (934 MPa to 1083 MPa) due to dislocation increment in the loading–unloading cycles. The loading modulus (El) and average modulus (Esecant) for a hysteresis loop decrease slightly, whereas the unloading modulus (Eun) increases, the Eun increment of 5-TC-UTand 10-TC-UT are 22 and 137 GPa.

Aluminum (Al) alloy products are widely used in people’s lives, while the existence and breeding of microorganisms on their surface cannot meet the health criteria and even may harm human health. In the present study, we successfully prepared the antibacterial oxide film on the 6063 Al alloy specimens by direct-current anodizing followed by Ag element depositing and the hole sealing process. The results suggested that compared with the Al substrate, the wear resistance of the obtained film was increased to 0.79, and the corrosion resistance was significantly improved. The antibacterial rate against Escherichia coli could be achieved as 94.38 ± 3.23%, and the adhesion force between the film and substrate was about 11 N. With the increase of the deposition time, the surface color of samples was gradually darkened, and meanwhile, the surface became uniform again without particles eventually. Energy dispersive spectroscopy (EDS) results showed the silver element was deposited on the surface and at the bottom of the porous oxide layer, and the amount of silver also increased with prolonging the deposition time. Moreover, x-ray photoelectron spectroscopy (XPS) analysis results on the surface showed the deposited silver element existed in the form of the ion and elemental substance, which indicated that reduction reaction of Ag ^+ appeared on the oxide film surface.

Biodegradable orthopedic materials (BOMs) are used in rehabilitation and reconstruction of fractured tissues. The response of BOMs to the combined action of physiological stress and corrosion is an important issue in vivo since stress-assisted degradation and cracking are common. Although the degradation behavior and kinetics of BOMs have been investigated under static conditions, stress effects can be very serious and even fatal in the dynamic physiological environment. Since stress is unavoidable in biomedical applications of BOMs, recent work has focused on the evaluation and prediction of the properties of BOMs under stress in corrosive media. This article reviews recent progress in this important area focusing on biodegradable metals, polymers, and ceramics.

This paper offers a method to grow corundum structure thin films of α -(Al,Cr) _2 O _3 in a High Power Pulsed Magnetron Sputtering (HPPMS) system. The films were characterized by grazing incidence x-ray diffraction (GIXRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and nanoindentation. The results indicate that stoichiometric α -(Al,Cr) _2 O _3 film could be deposited at 540 °C without the formation of other metastable phases. The stable process of the magnetron sputtering ensures the smooth and compact surface of the film composed of nano-scale particles. The Cr in films can induce the formation of solid solution and enhance the mechanical property of the films. The hardness of the α -(Al,Cr) _2 O _3 was calculated as ∼25.6 GPa, which is much higher than that of the film deposited using the Al target. These results are considered have positive effect on the low-cost depositing α -phase alumina films on high speed steel substrates as cutting tools.

The corundum-structured seeds have been introduced into alumina films using Al + α -Al _2 O _3 composite and Al _100−x Cr _x (x = 10, 20, 30) alloy as targets by reactive magnetron sputtering. The effects of the seeds on the elemental composition, phase composition, structure characteristic, surface morphology and nano-hardness of the alumina-based films have been investigated. The Al target has also been sputtered to prepare the alumina film as reference. The film is composed of single-phase α -Al _2 O _3 by sputtering the Al + α -Al _2 O _3 composite target at 550 °C, while the solid solution α -type (Al _0.7 Cr _0.3 ) _2 O _3 was detected in the film prepared with the Al _70 Cr _30 target at the same temperature. The nano-hardness of the pure α -Al _2 O _3 film and the α -(Al _0.7 Cr _0.3 ) _2 O _3 film were measured as ∼23.5 GPa and ∼28.5 GPa, respectively, which are much higher than that of the film deposited from Al target (∼16.3 GPa).

Static recrystallization plays a key role in the fabrication of thin Mg wires as well as the mechanical properties of the final wires. The effect of annealing parameters on the evolution of the microstructures, textures and mechanical properties of cold-drawn pure Mg wire was studied by means of optical microscopy (OM), electron backscatter diffraction (EBSD), a tensile test and a hardness test. This study shows that the mechanical properties of as-annealed pure thin Mg wire is affected not only by the average grain size, but also the uniformity of the recrystallization grains, including the uniformity of grain size and crystal orientation distribution (more random texture component). With increasing annealing temperature and time, the uniformity of recrystallization grain size first improved and then declined after obvious grain growth. At the same time, the randomness of the basal texture component declined with the development of recrystallization. Annealing at 300 °C for 30 min caused the most uniform grain size and orientation distribution in the microstructures, thus contributing to the best plasticity among all experimental wires. It is reasonable to conclude that more uniform and regular recrystallized grains and a more randomly distributed crystal orientation would be benefit for the mechanical properties of Mg wires.

Immobilization of gold nanoparticles (AuNPs) on the surface of zeolite has received a great interest due to Au@zeolite’s unique characteristics and high performance for catalysis. In this work we studied the grafting of two different functional molecules; one having an amine group (3-aminopropyl)triethoxysilane (APTES) and the second having a thiol group (3-mercaptopropyl)trimethoxysilane (MPTES) on the surface of zeolite using the same wet chemistry method. The modified zeolite surfaces were characterized using zeta potential measurements; diffuse reflectance infrared fourier transform (DRIFT) and X-ray photoelectron spectroscopy (XPS). The results confirmed a successful deposition of both functional groups at the topmost surface of the zeolite. Furthermore; transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) spectroscopy and XPS results clearly evidenced that APTES provided a better AuNPs immobilization than MPTES as a result of; (1) less active functions obtained after MPTES deposition, and (2) the better attaching ability of thiol to the gold surface.

Subsphaeroidal SiC/polymer composite granules with good flowability for additive manufacturing/3D printing of SiC were prepared by ball milling with surface modification using polyvinyl butyral (PVB). PVB adheres to the particle surface of SiC to form a crosslinked network structure and keeps them combined with each other into light aggregates. The effects of PVB on the shape, size, phase composition, distribution and flowability of the polymer-ceramic composite powder were investigated in detail. Results show that the composite powder material has good laser absorptivity at wavelengths of lower than 500 nm.

We performed multiple-pass cold drawing for pure Mg wire which showed excellent formability (~138% accumulative true strain) at room temperature. Different from the continuous work hardening occurring during cold drawing of Mg alloy wires, for pure Mg, an initially rapid increase in hardness and strength was followed by significant work softening and finally reached a steady-state level, approximately 40~45 HV. The work softening can be attributed to the dynamic recovery and recrystallization of pure Mg at room temperature. Meanwhile, an abrupt change in texture component also was detected with the transition from work hardening to softening in the strain range of 28~34%. During the whole drawing, the strongest texture component gradually transformed from as-extruded basal to fiber (~28% accumulative true strain), and then rapidly returned to the weak basal texture.

With promising mechanical property and biodegradability, magnesium (Mg) alloys are considered as the potential candidates in biomedical application. Rapid degradation of Mg alloys compromises the mechanical performance and interfacial bioactivity, hindering clinical adoption. Deposition of a surface coating is an effective technique to improve the corrosion protection and bio-efficacy of Mg biomedical implants. Because of the natural degradability and corrosion, the surface is inevitably damaged in the complex physiological environment. Therefore, it is essential to form a self-healing coating that can repair damage to restore the stable mechanical structure and functions of biomedical Mg alloys. This paper reviews the recent advances in coating technology and the related properties including biodegradation behavior, self-repairing activity, biocompatibility, and other biological effects, and the healing mechanism is discussed. Self-healing coatings suitable for Mg alloys include conversion coatings, encapsulation coatings, and multilayered coatings, and their properties in vitro and in vivo are reviewed by focusing on drug-controlled and prolonged release, sterilization, cytocompatibility, osteogenesis, hemocompatibility, and angiogenesis. This review aims at providing guidance for the future research and development of practical healing coatings for biomedical Mg implants. [ABSTRACT FROM AUTHOR]