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1.
Materials (Basel) ; 17(6)2024 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-38541451

RESUMO

The effect of extrusion on the microstructure, mechanical property, corrosion behavior, and in vitro biocompatibility of as-cast Mg-1.5Zn-1.2Y-0.1Sr (wt.%) alloy was investigated via tensile tests, electrochemical methods, immersion tests, methylthiazolyl diphenyltetrazolium bromide (MTT), and analytical techniques. Results showed that the as-cast and as-extruded Mg-1.5Zn-1.2Y-0.1Sr alloys comprised an α-Mg matrix and Mg3Y2Zn3 phase (W-phase). In the as-cast alloy, the W-phase was mainly distributed at the grain boundaries, with a small amount of W-phase in the grains. After hot extrusion, the W-phase was broken down into small particles that were dispersed in the alloy, and the grains were refined considerably. The as-extruded alloy exhibited appropriate mechanical properties that were attributed to refinement strengthening, dispersion strengthening, dislocation strengthening, and precipitation strengthening. The as-cast and as-extruded alloys exhibited galvanic corrosion between the W-phase and α-Mg matrix as the main corrosion mechanism. The coarse W-phase directly caused the poor corrosion resistance of the as-cast alloy. The as-extruded alloy obtained via hydrogen evolution and mass loss had corrosion rates of less than 0.5 mm/year. MTT, high-content screening (HCS) analysis, and cell adhesion tests revealed that the as-extruded alloy can improve L929 cell viability and has great potential in the field of biomedical biodegradable implant materials.

2.
Materials (Basel) ; 17(6)2024 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-38541535

RESUMO

The corrosion process under the complex safe-end feedwater line conditions was investigated via experimental lab testing and numerical simulation. The corrosion of safe-end feedwater lines was controlled through the combination of galvanic corrosion, residual stress, and flow velocity. Firstly, galvanic corrosion occurred once the 20 steel was welded with 316L stainless steel. The pitting corrosion could be observed on the 20 steel side of the weld joint. Secondly, a vortex flow was detected around the welding bump and within the pits. The growth of the pits was accelerated in both the vertical and horizontal directions. Finally, under the residual stress condition, the stress intensity factor (K) at the bottom of the pits was easier to reach than the critical stress intensity factor (KISCC). Then, pitting was transformed into stress corrosion cracking which then propagated along the weld line. Therefore, the critical factor inducing the failure of safe-end feedwater lines was the combined action of galvanic corrosion, residual stress, and flow velocity.

3.
Small ; : e2307742, 2024 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-38326101

RESUMO

Biodegradable medical implants promise to benefit patients by eliminating risks and discomfort associated with permanent implantation or surgical removal. The time until full resorption is largely determined by the implant's material composition, geometric design, and surface properties. Implants with a fixed residence time, however, cannot account for the needs of individual patients, thereby imposing limits on personalization. Here, an active Fe-based implant system is reported whose biodegradation is controlled remotely and in situ. This is achieved by incorporating a galvanic cell within the implant. An external and wireless signal is used to activate the on-board electronic circuit that controls the corrosion current between the implant body and an integrated counter electrode. This configuration leads to the accelerated degradation of the implant and allows to harvest electrochemical energy that is naturally released by corrosion. In this study, the electrochemical properties of the Fe-30Mn-1C/Pt galvanic cell model system is first investigated and high-resolution X-ray microcomputed tomography is used to evaluate the galvanic degradation of stent structures. Subsequently, a centimeter-sized active implant prototype is assembled with conventional electronic components and the remotely controlled corrosion is tested in vitro. Furthermore, strategies toward the miniaturization and full biodegradability of this system are presented.

4.
Colloids Surf B Biointerfaces ; 236: 113808, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38422669

RESUMO

In the cardiovascular field, coating containing copper used to catalyze NO (nitric oxide) production on non-degradable metal surfaces have shown unparalleled expected performance, but there are few studies on biodegradable metal surfaces. Magnesium-based biodegradable metals have been applied in cardiovascular field in large-scale because of their excellent properties. In this study, the coating of copper loaded in silk fibroin is fabricated on biodegradable ZE21B alloy. Importantly, the different content of copper is set to investigate the effects of on the degradation performance and cell behavior of magnesium alloy. Through electrochemical and immersion experiments, it is found that high content of copper will accelerate the corrosion of magnesium alloy. The reason is the spontaneous micro-batteries between copper and magnesium with the different standard electrode potentials, that is, the galvanic corrosion accelerates the corrosion of magnesium alloy. Moreover, the coating formed through silk fibroin by the right amount copper not only have a protective effect on the ZE21B alloy substrate, but also promotes the adhesion and proliferation of endothelial cells in blood vessel micro-environment. The production of NO catalyzed by copper ions makes this trend more significant, and inhibits the excessive proliferation of smooth muscle cells. These findings can provide guidance for the amount of copper in the coating on the surface of biodegradable magnesium alloy used for cardiovascular stent purpose.


Assuntos
Fibroínas , Fibroínas/farmacologia , Fibroínas/química , Cobre/farmacologia , Ligas/farmacologia , Ligas/química , Magnésio/farmacologia , Magnésio/química , Células Endoteliais , Materiais Revestidos Biocompatíveis/farmacologia , Materiais Revestidos Biocompatíveis/química , Corrosão
5.
Materials (Basel) ; 16(23)2023 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-38068019

RESUMO

Wire bonding, one of the methods for electrically connecting a semiconductor chip with a substrate, involves attaching thin metal wires to pads. It is the oldest electrical connection method that exhibits high compatibility with other processes. The metal wires used for electrical connection in wire bonding are mainly made of Au, Cu, and Ag. After the wire bonding, molding is performed using the epoxy molding compound (EMC). However, EMC inevitably contains ions such as halogen elements. In addition, it absorbs moisture due to its hydrophilicity, creating a corrosive environment with electrolytes. In this study, we evaluated the influence of hydrochloric acid concentration on corrosion behavior between Au or Cu bonding wires and sputtered Al bond pads. The electrochemical factors such as corrosion potential difference (ΔE), galvanic corrosion current density (ig), and anodic and cathodic Tafel slopes were found to influence galvanic corrosion behavior. Galvanic corrosion tendency in first bond and second bond areas of PCB unit specimen was confirmed.

6.
Materials (Basel) ; 16(23)2023 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-38068169

RESUMO

Hydrogen generation through the hydrolysis of aluminum alloys has attracted significant attention because it generates hydrogen directly from alkaline water without the need for hydrogen storage technology. The hydrogen generation rate from the hydrolysis of aluminum in alkaline water is linearly proportional to its corrosion rate. To accelerate the corrosion rate of the aluminum alloy, we designed Al-Ni alloys by continuously precipitating an electrochemically noble Al3Ni phase along the grain boundaries. The Al-0.5~1 wt.% Ni alloys showed an excellent hydrogen generation rate of 16.6 mL/cm2·min, which is about 6.4 times faster than that of pure Al (2.58 mL/cm2·min). This excellent performance was achieved through the synergistic effects of galvanic and intergranular corrosion on the hydrolysis of Al. By raising the solution temperature to 50 °C, the optimal rate of hydrogen generation of Al-1 wt.% Ni in 10 wt.% NaOH solutions at 30 °C can be further increased to 54.5 mL/cm2·min.

7.
J Funct Biomater ; 14(12)2023 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-38132818

RESUMO

The interaction of different dental alloys with the oral environment may cause severe side effects (e.g., burning sensation, inflammatory reactions, carcinogenesis) as a result of oral galvanism. However, the pathogenesis of side effects associated with oral galvanism is still unclear, and the effects of direct current and alloy corrosion ions are considered potentially contributing factors. Therefore, the aim of this study was to systemically compare the damaging effects of (1) galvanism as a synergistic process (direct current + corrosion ions), (2) direct current separately, and (3) corrosion ions separately on an in vitro mucosa-like model based on a cell line of immortalized human keratinocytes (HaCaTs) to reveal the factors playing a pivotal role in dental alloys side effects. For this, we chose and compared the dental alloys with the highest risk of oral galvanism: Ti64-AgPd and NiCr-AgPd. We showed that galvanic current may be the leading damaging factor in the cytotoxic processes associated with galvanic coupling of metallic intraoral appliances in the oral cavity, especially in the short-term period (28 days). However, the contribution of corrosion ions (Ni2+) to the synergistic toxicity was also shown, and quite possibly, in the long term, it could be no less dangerous.

8.
Materials (Basel) ; 16(20)2023 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-37895602

RESUMO

The AZ series of Mg alloys have become promising in several industrial fields thanks to its potential microstructure refinement and the ß-Mg17Al12 eutectic that controls the mechanical behaviour. Simultaneously, the rapid degradation characterizing Mg alloys makes the investigation of their corrosion behaviour necessary. The present work considers high-pressure die cast (HPDC) AZ91 alloy to evaluate its corrosion behaviour in 1M NaCl solution and investigates how different friction stir process parameters can affect the corrosion responses. No studies analyse the effects induced by the friction stir processed zone, reached using high rotational speeds (>2000 rpm), on the unprocessed HPDC AZ91 alloy. In addition, the morphological analysis of the corroded surfaces having a friction stir processed zone, in which the grain refinement was not obtained, is not present in the literature yet. Microstructural features were investigated by optical microscope and X-ray diffraction analysis before and after the friction stir process. These were subsequently correlated to the corrosion responses after the immersion tests. The results show that HPDC samples with a very smooth surface have the best corrosion resistance with a corrosion rate lower than 3 mm/year, evaluated through the weight loss, compared to the rougher ones. Both the amount of ß-Mg17Al12 eutectic and the wt.% Al in the α-Mg matrix, as well as the surface roughness, influence the corrosion behaviour of friction stir processed samples. The best corrosion resistance was obtained with an HPDC alloy processed at 2500 rpm and 50 mm/min.

9.
Maxillofac Plast Reconstr Surg ; 45(1): 36, 2023 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-37801180

RESUMO

BACKGROUND: A range of different chemical interactions can generate an unexpected electronic current in a process called galvanism. Oral galvanism (OG) can also be generated by different chemical actions from diverse intraoral rehabilitated metals, including gold, copper, mercury, titanium, and titanium alloy. The main aim of this manuscript is to review OG, particularly focusing on titanium implants and related metallic materials. We searched the MEDLINE (PubMed), Embase, Scopus, and Google Scholar databases for relevant literature published through December 2019. The keywords included "galvanic current", "galvanism", "galvanic corrosion", "oral galvanism", combined with "oral", "oral cavity", "implant", and "saliva." RESULTS: Out of 343 articles, 126 articles that met the inclusion criteria were reviewed. We examined and summarized research on OG through a division into four categories: definition and symptoms, diagnosis with testing methods, galvanic corrosion, and oral precancerous lesions with OG. CONCLUSIONS: Patients with OG have high oral energy and current, and although this phenomenon may be due to the patient's mental illness, OG due to amalgam or mercury occurs. It is evident that the difference in electron potential caused by different elemental components such as titanium alloy and pure titanium, which are essential for manufacturing the implant fixture and the abutment, and chrome and nickel, which are essential for manufacturing the upper crown, causes OG. Since the oral cavity is equipped with an environment in which electric current can be transmitted easily due to saliva, it is imperative that clinicians review the systemic and local effects of salivation.

10.
Front Chem ; 11: 1090648, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37035119

RESUMO

The corrosion mechanism and kinetics of the silver-coated conductive yarn (SCCY) used for wearable electronics were investigated under a NaCl solution, a main component of sweat. The corrosion occurs according to the mechanism in which silver reacts with chlorine ions to partly form sliver chloride on the surface of the SCCY and then the local silver chloride is detached into the electrolyte, leading to the electrical disconnect of the silver coating. Thus, the electrical conductance of the SCCY goes to zero after 2.7 h. The radial part-coating of gold, which is continuously electrodeposited in the longitudinal direction on the SCCY but is partly electrodeposited in the radial direction, extends the electrical conducting lifetime up to 192 h, despite the corrosion rate increasing from 129 to 196 mpy (mils per year). Results show that the gold partly-coating on the SCCY provides a current path for electrical conduction along the longitudinal direction until all the silver underneath the gold coating is detached from the SCCY strands, which creates the electrical disconnect. Based on the corrosion behavior, i.e., local oxidation and detachment of silver from the SCCY, the gold part-coating is more cost effective than the gold full-coating electrodeposited on the entire surface for electrically conducting SCCY.

11.
Entropy (Basel) ; 25(2)2023 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-36832663

RESUMO

Dual-phase high entropy alloys have recently attracted widespread attention as advanced structural materials due to their unique microstructure, excellent mechanical properties, and corrosion resistance. However, their molten salt corrosion behavior has not been reported, which is critical in evaluating their application merit in the areas of concentrating solar power and nuclear energy. Here, the molten salt corrosion behavior of AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) was evaluated in molten NaCl-KCl-MgCl2 salt at 450 °C and 650 °C in comparison to conventional duplex stainless steel 2205 (DS2205). The EHEA showed a significantly lower corrosion rate of ~1 mm/year at 450 °C compared to ~8 mm/year for DS2205. Similarly, EHEA showed a lower corrosion rate of ~9 mm/year at 650 °C compared to ~20 mm/year for DS2205. There was selective dissolution of the body-centered cubic phase in both the alloys, B2 in AlCoCrFeNi2.1 and α-Ferrite in DS2205. This was attributed to micro-galvanic coupling between the two phases in each alloy that was measured in terms of Volta potential difference using a scanning kelvin probe. Additionally, the work function increased with increasing temperature for AlCoCrFeNi2.1, indicating that the FCC-L12 phase acted as a barrier against further oxidation and protected the underlying BCC-B2 phase with enrichment of noble elements in the protective surface layer.

12.
Materials (Basel) ; 16(3)2023 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-36769928

RESUMO

A mechanistic model of atmospheric bimetallic corrosion with a simplified empirical approach to the onset of localized corrosion attacks is presented. The model was built for a typical bimetallic sample containing aluminum alloy 1050 and stainless steel 316L sheets. A strategy was developed that allowed the model to be calibrated against the measured galvanic current, geometrical corrosion attack properties, and corrosion products. The pitting-onset simplification sets all pits to be formed at a position near the nobler metal and treated all pits as being of the same shape and size. The position was based on the location of the highest pitting events and the pit attributes on an average of the deepest pits. For 5 h exposure at controlled RH (85%, 91%, and 97%) and salt load (86 µg NaCl/cm2), the model was shown to be promising: both for analysis of local bimetallic corrosion chemistry, such as pH and corrosion products, and for efficient assessment of pitting damage by computing a single largest pit depth. Parametric studies indicated that the pitting-onset approximation deviated the most at the beginning of exposure and when RH was below 91%.

13.
Materials (Basel) ; 16(3)2023 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-36770072

RESUMO

Chloride ions contained in the sealing compound currently used in the electronic packaging industry not only interact with intermetallic compounds but also have a serious impact on silver alloy wires. A 15 µm ultrafine quaternary silver-palladium-gold-platinum alloy wire was used in this study. The wire and its bonding were immersed in a 60 °C saturated sodium chloride solution (chlorination experiment), and the strength and elongation before and after chlorination were measured. Finally, the fracture surface and cross-section characteristics were observed using a scanning electron microscope and focused ion microscope. The results revealed that chloride ions invade the wire along the grain boundary, and chlorides have been generated inside the cracks to weaken the strength and elongation of the wire. In addition, chloride ions invade the interface of the wire bonding to erode the aluminum substrate after immersing it for enough long time, causing galvanic corrosion, which in turn causes the bonding joint to separate from the aluminum substrate.

14.
ACS Biomater Sci Eng ; 9(1): 153-164, 2023 01 09.
Artigo em Inglês | MEDLINE | ID: mdl-36571764

RESUMO

Fe has immense potential for biodegradable orthopedic applications, but it degrades slowly in the physiological environment. Inducing galvanic couple by alloying Cu to Fe using ball milling is a promising approach. However, the ductile nature of Cu leads to the cold welding of a large amount of Cu powder during ball milling, which makes it difficult to disperse uniformly in the Fe matrix. Here, a Fe-CuO implant with highly dispersed Cu particles in the matrix was developed by shift-speed ball milling and selective laser melting. Specifically, copper oxide (CuO) particles were selected as precursors and dispersed in Fe powders by ball milling since they were brittle and would not be cold-welded during ball milling. After further milling in higher energy, it was found that CuO particles reacted with Fe and generated Cu particles through a stress-activated redox reaction. Subsequently, the obtained powders were prepared into a Fe-CuO implant using selective laser melting. Microstructure examination revealed that the Cu phases in the implant were dispersed evenly in the Fe matrix, which was considered to establish a large number of galvanic couples and aggravated the galvanic corrosion tendency. Electrochemical tests indicated that the implant had improved performance in degradation behavior in terms of high corrosion current density (22.4 µA/cm2), low corrosion resistance (1319 Ω cm2), and good degradation stability. In addition, it presented antibacterial effects against Escherichia coli and Staphylococcus aureus by diffusion mechanisms with killing rates of 90.7 and 96.7%, respectively, as well as good cytocompatibility.


Assuntos
Próteses e Implantes , Estresse Mecânico , Corrosão , Oxirredução
15.
Front Bioeng Biotechnol ; 10: 996195, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36159687

RESUMO

Titanium-magnesium composites have gained increasing attention as a partially degradable biomaterial recently. The titanium-magnesium composite combines the bioactivity of magnesium and the good mechanical properties of titanium. Here, we discuss the limitations of conventional mechanically alloyed titanium-magnesium alloys for bioimplants, in addition we summarize three suitable methods for the preparation of titanium-magnesium composites for bioimplants by melt: infiltration casting, powder metallurgy and hot rotary swaging, with a description of the advantages and disadvantages of all three methods. The titanium-magnesium composites were comprehensively evaluated in terms of mechanical properties and degradation behavior. The feasibility of titanium-magnesium composites as bio-implants was reviewed. In addition, the possible future development of titanium-magnesium composites was discussed. Thus, this review aims to build a conceptual and practical toolkit for the design of titanium-magnesium composites capable of local biodegradation.

16.
Biomater Res ; 26(1): 41, 2022 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-36064494

RESUMO

BACKGROUND: Although several studies on the Mg-Zn-Ca system have focused on alloy compositions that are restricted to solid solutions, the influence of the solid solution component of Ca on Mg-Zn alloys is unknown. Therefore, to broaden its utility in orthopedic applications, studies on the influence of the addition of Ca on the microstructural, mechanical, and corrosion properties of Mg-Zn alloys should be conducted. In this study, an in-depth investigation of the effect of Ca on the mechanical and bio-corrosion characteristics of the Mg-Zn alloy was performed for the optimization of a clinically approved Mg alloy system comprising Ca and Zn. METHODS: The Mg alloy was fabricated by gravitational melting of high purity Mg, Ca, and Zn metal grains under an Ar gas environment. The surface and cross-section were observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to analyze their crystallographic structures. Electrochemical and immersion tests in Hank's balanced salt solution were used to analyze their corrosion resistance. Tensile testing was performed with universal testing equipment to investigate the impact of Ca addition. The examination of cytotoxicity for biometric determination was in line with the ISO10993 standard. RESULTS: In this study, the 0.1% Ca alloy had significantly retarded grain growth due to the formation of the tiny and well-dispersed Ca2Mg6Zn3 phase. In addition, the yield strength and elongation of the 0.1% Ca alloy were more than 50% greater than the 2% Zn alloy. The limited cell viability of the 0.3% Ca alloy could be attributed to its high corrosion rate, whereas the 0.1% Ca alloy demonstrated cell viability of greater than 80% during the entire experimental period. CONCLUSION: The effect of the addition of Ca on the microstructure, mechanical, and corrosion characteristics of Mg-Zn alloys was analyzed in this work. The findings imply that the Mg-Zn alloy system could be optimized by adding a small amount of Ca, improving mechanical properties while maintaining corrosion rate, thus opening the door to a wide range of applications in orthopedic surgery.

17.
J Hazard Mater ; 436: 129169, 2022 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-35739706

RESUMO

Galvanic corrosion is one of the main reasons for pipe degradation and lead contamination in drinking water systems. The electrical connection of dissimilar metals in corrosive tap water accelerates the dissolution rate of lead from leaded materials. This paper reports an electrochemistry based model to predict lead leaching from a copper pipe fitted with leaded connections. The corrosion of lead at the metal-electrolyte interface depends on the charge transfer and the electric field across the interface. The electric potential field and the mass transport process are dynamically coupled for corrosion propagation in stagnant water; they are respectively governed by the conservation of charge and reactant mass. Using polarization parameters for the electrodes as a function of concentration of oxidizing agents, a dynamic electrochemical model is developed to predict lead leaching from galvanic corrosion. The predicted lead and copper leaching curves are in good agreement with the experimental data for a lead-soldered coupled copper pipe, a brass valve coupled copper pipe, and a pure copper pipe. The findings offer a quantitative understanding on galvanic corrosion in drinking water supply systems and a practical modeling framework for prediction of lead leaching in tap water as a function of stagnation time.


Assuntos
Água Potável , Poluentes Químicos da Água , Cobre/análise , Corrosão , Chumbo , Poluentes Químicos da Água/análise , Abastecimento de Água
18.
Acta Biomater ; 146: 506-521, 2022 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-35523413

RESUMO

Zinc (Zn)-based metals and alloys are emerging as promising biodegradable implant materials due to their inherent biodegradability and good biocompatibility. However, this class of materials exhibits low mechanical strength and a slow degradation rate, which hinders their clinical application. Here we report the development of a new biodegradable Fe/Zn-3Cu composite fabricated by infiltration casting of a Zn-3Cu alloy into an Fe foam followed by hot-rolling. Our results indicate that the hot-rolled (HR) Fe/Zn-3Cu composite exhibited an α-Zn matrix phase, a secondary CuZn5 phase, and an α-Fe phase. The HR Fe/Zn-3Cu composite exhibited an ultimate tensile strength of 269 MPa, a tensile yield strength of 210 MPa, and an elongation of 27%. The HR Fe/Zn-3Cu composite showed a degradation rate of 228 µm/year after immersion in Hanks' solution for 30 d The diluted extract of the HR Fe/Zn-3Cu composite exhibited a higher cell viability than that of the HR Zn-3Cu alloy in relation to MC3T3-E1 and MG-63 cells. Furthermore, the HR Fe/Zn-3Cu composite showed significantly better antibacterial ability than that of the HR Zn-3Cu alloy in relation to S. aureus. Overall, the HR Fe/Zn-3Cu composite can be anticipated to be a promising biodegradable implant material for bone-fixation applications. STATEMENT OF SIGNIFICANCE: This work reports a new biodegradable Fe/Zn-3Cu composite fabricated by infiltration casting and followed by hot-rolling for biodegradable bone-fixation application. Our findings demonstrated that the hot-rolled (HR) Fe/Zn-3Cu composite exhibited an ultimate tensile strength of 269.1 MPa, a tensile yield strength of 210.3 MPa, and an elongation of 26.7%. HR Fe/Zn-3Cu composite showed a degradation rate of 227.6 µm/a, higher than HR Zn-3Cu alloy after immersion in Hanks' solution for 30 d The diluted extracts of the HR Fe/Zn-3Cu composite exhibited a higher cell viability than HR Zn-3Cu alloy toward MC3T3-E1 cells. Furthermore, the HR Fe/Zn-3Cu composite showed significantly better antibacterial ability than the HR Zn-3Cu alloy toward S. aureus.


Assuntos
Staphylococcus aureus , Zinco , Implantes Absorvíveis , Ligas/farmacologia , Antibacterianos , Materiais Biocompatíveis , Corrosão , Teste de Materiais , Zinco/farmacologia
19.
ACS Biomater Sci Eng ; 8(5): 1841-1851, 2022 05 09.
Artigo em Inglês | MEDLINE | ID: mdl-35442637

RESUMO

Fe is considered as a potential candidate for implant materials, but its application is impeded by the low degradation rate. Herein, a dual-phase Fe30Mn6Si alloy was prepared by mechanical alloying (MA). During MA, the motion of dislocations driven by the impact stress promoted the solid solution of Mn in Fe, which transformed α-ferrite into γ-austenite since Mn was an austenite-stabilizing element. Meanwhile, the incorporation of Si decreased the stacking fault energy inside austenite grains, which tangled dislocations into stacking faults and acted as nucleation sites for ε-martensite. Resultantly, Fe30Mn6Si powder had a dual-phase structure composed of 53% γ-austenite and 47% ε-martensite. Afterward, the powders were prepared into implants by selective laser melting. The Fe30Mn6Si alloy had a more negative corrosion potential of -0.76 ± 0.09 V and a higher corrosion current of 30.61 ± 0.41 µA/cm2 than Fe and Fe30Mn. Besides, the long-term weight loss tests also proved that Fe30Mn6Si had the optimal degradation rate (0.25 ± 0.02 mm/year).


Assuntos
Ligas , Materiais Biocompatíveis , Ligas/química , Corrosão , Próteses e Implantes
20.
Front Chem ; 10: 820379, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35321477

RESUMO

This work investigates the previously unexplored impact of tensile stress on oxygen reduction reaction (ORR) kinetics of a precipitation-hardened, stainless-steel fastener material, UNS S13800. ORR is known to drive localized and galvanic corrosion in aircraft assemblies and greater understanding of this reaction on structural alloys is important in forecasting component lifetime and service requirements. The mechano-electrochemical behavior of UNSS13800 was examined using amperometry to measure the reduction current response to tensile stress. Mechanical load cycles within the elastic regime demonstrated reversible electrochemical current shifts under chloride electrolyte droplets that exhibited a clear potential dependence. Strain ramping produced current peaks with a strain rate dependence, which was distinct from the chronoamperometric shifts during static tensile load conditions. Finally, mechanistic insight into the dynamic and static responses was obtained by deoxygenation, which demonstrated ORR contributions that were distinct from other reductive processes.

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