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1.
Environ Pollut ; 251: 885-891, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31234254

RESUMO

Guangdong Province, which is located in southern China, has a tropical climate with high temperatures and humidity, making it extremely unfavourable for the corrosion resistance of various materials. Meanwhile, as a quickly developing region in China, Guangdong Province is also facing multi-pollutant conditions, which seriously affect the atmospheric degradation of the materials in this region. It is therefore necessary to identify the key air pollutants that affect the atmospheric corrosivity of Guangdong Province and to propose targets of air pollutant control. An analysis of the environmental data and corrosion rates in Guangdong Province showed that the atmospheric corrosivity of the entire region is closely related to the presence of sulfur dioxide (SO2) and ozone (O3). In addition, a superposition model was utilised to reflect the synergistic effect of SO2 and O3, and a superimposed map of both pollutants was drawn to demonstrate their amount. To control the corrosion rate of carbon steel and avoid exceeding the C2 classification in ISO 9223, the following targets of air pollutant control are proposed: an SO2 concentration of lower than 10 µg m-3 and an O3 level of lower than 85 µg m-3.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/análise , Monitoramento Ambiental/métodos , Ozônio/análise , Dióxido de Enxofre/análise , China , Corrosão , Temperatura Alta , Umidade , Dióxido de Nitrogênio/análise , Material Particulado/análise
2.
Chemosphere ; 233: 744-753, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31200134

RESUMO

In this study, the enhanced effect of pyrite (FeS2) on zero-valent iron (Fe0) corrosion for arsenic (As) removal was investigated in a combined-Fe0/FeS2 system. The effects of different Fe0/FeS2 composition, dosage and initial pH were evaluated by batch experiments. Results showed that the best combination ratio of Fe0:FeS2 (w/w) was 1:1 and the optimal dosage of mixture was 2.0 g/L. The combination of Fe0 and FeS2 in a system significantly enhanced the reactivity of Fe0 for effective As removal within a broad pH range (3.0-9.0). The effective As removal in the combined-Fe0/FeS2 system was primarily ascribed to being enhanced corrosion of Fe0 by addition of FeS2. SEM and XRD characterizations strongly verified this point. Specifically, the mechanism study (the releases of Fe2+ and total Fe ion, variations of pH values as well as XPS characterization) suggested that FeS2 in the combined-Fe0/FeS2 system could alleviate the passivation of Fe0 (pHini 3.0-5.0) and accelerate the dissolution of pristine oxide film that coated on Fe0 surface (pHini 6.8-9.0). Besides, FeS2 in combined-Fe0/FeS2 system could also accelerate the reactions between Fe0 to O2 at pHini 3.0-9.0. These phenomena were well explained by a galvanic couple between Fe0 and FeS2, where FeS2 was a cathode and Fe0 was an anode. Consequently, electrons released from Fe0 that mediated by FeS2 to oxide film, passivation layer and O2 were accelerated in combined-Fe0/FeS2 system and thereby enhanced the corrosion of Fe0 for efficient As removal. Our findings suggest that utilizing FeS2 to enhance the corrosion of Fe0 would be a promising technology for remediation of As-contaminated water.


Assuntos
Arsênico/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Arsênico/química , Corrosão , Ferro/química , Sulfetos/química , Água , Poluentes Químicos da Água/química
3.
Bioelectrochemistry ; 129: 106-115, 2019 Oct.
Artigo em Espanhol | MEDLINE | ID: mdl-31153125

RESUMO

Due to their desirable elastic modulus and density that are similar to natural bone, non-toxic element containing magnesium alloys are regarded as promising bio-degradable materials. A biodegradable HA-particle-reinforced magnesium-matrix composite Mg-3Zn-0.2Ca-1HA (wt%) was fabricated for biomedical application by a combination of high shear solidification (HSS) and hot extrusion technology. The microstructure, mechanical properties, corrosion resistance and cell biocompatibility of the composite were subsequently investigated. In comparison with the matrix alloy, the as-cast Mg-3Zn-0.2Ca-1HA composite obtained by HSS technology exhibited a uniform and fine grained structure, further refined after a hot extrusion ratio of 36:1. The yield strength (0.2%YS), ultimate tensile strength and elongation of the extruded composite were 322 MPa, 341 MPa and 7.6%, respectively. The corrosion rate of the as-extruded Mg-3Zn-0.2Ca-1HA composite was measured to be 1.52 mm/y. Electrochemical and immersion tests showed that the corrosion resistance of the composite is slightly improved comparing to that of the matrix alloy.


Assuntos
Ligas/química , Materiais Biocompatíveis/química , Durapatita/química , Magnésio/química , Zinco/química , Animais , Linhagem Celular , Corrosão , Fibroblastos/citologia , Teste de Materiais , Camundongos , Resistência à Tração
4.
World J Microbiol Biotechnol ; 35(5): 73, 2019 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-31037431

RESUMO

Metal corrosion is a major global concern in many economic sectors. The degradation of metal surfaces is responsible for losses in values that account for about 3% of gross domestic product (GDP) only in the US. Parts of all corrosion processes described in different environments are present mainly in marine environments. The marine environment is characterized as favoring the corrosion processes of several metallic alloys, damaging structures used in the construction of ships, ports, oil pipelines, and others. Despite chemical corrosion being the most frequently described in these environments, studies show the participation of microorganisms in direct corrosion processes or in the acceleration/influence of the corrosive action, through the formation of complex biofilms. These structures create favorable conditions for microorganisms to degrade metal surfaces, causing damage known as pitting and crevices. Currently, diverse technicians are employed in biocorrosion research, e.g. electronic microscopy, and DNA sequencing. These techniques have clarified the dynamic process of the formation of biofilm structures, allowing understanding of the succession of different species during the evolution of the structure. Improving the understanding of how this interaction between biofilm and metallic surface occurs will enable better evaluation of strategies to avoid or decelerate the degradation of metallic structures in marine environments.


Assuntos
Biofilmes/crescimento & desenvolvimento , Água do Mar/microbiologia , Aço/química , Ligas/química , Bactérias/metabolismo , Aderência Bacteriana/fisiologia , Fenômenos Fisiológicos Bacterianos , Corrosão , Eletroquímica , Metais/química , Propriedades de Superfície
5.
J Biomed Nanotechnol ; 15(6): 1172-1184, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-31072426

RESUMO

Magnesium is an attractive candidate for orthopedic implants due to its similar mechanical properties to human bone and biodegradability. However, the high corrosion rate of magnesium accompanying with high pH value and poor osteogenic activity hinder its further application. In this study, we employed micro arc oxidation (MAO) to improve corrosion resistance by introduce nanoporous coating on AZ91 magnesium. Meanwhile, we added lithium, an angiogenic and osteogenic element, to the coating (named as Li-MAO) by reaction in a lithium-containing electrolyte to simultaneously enhance angiogenic and osteogenic activity of AZ91. The favorable corrosion resistance of Li-MAO was verified by electrochemical and immersion test in vitro. Better biocompatibility was observed in Li-MAO samples by cell counting kit-8 (CCK-8) and live/dead assay. The in vitro results of immunofluorescence staining, Alizarin red staining and osteogenic-related genes expression indicated better osteogenic ability of Li-MAO group, which may result from the activation the Wnt/ß-catenin pathway. In vitro angiogenic tests also demonstrated better angiogenesis in Li-MAO group. A bone defect repair model was built to evaluate the in vivo osseointegration of samples. The outcomes of micro-computed tomography (Micro-CT) scanning, sequential fluorochrome labeling and Van Gieson staining suggested better in vivo bone repair ability of Li-MAO than other groups. Our promising results both in vitro and in vivo demonstrated that lithium-containing nanoporous coating can improve corrosion resistance, angiogenesis and osseointegration of magnesium alloy, which may forward the clinic application of Li-MAO magnesium.


Assuntos
Nanoporos , Ligas , Materiais Revestidos Biocompatíveis , Corrosão , Lítio , Magnésio , Osseointegração , Oxirredução , Microtomografia por Raio-X
6.
Orthop Clin North Am ; 50(3): 281-288, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31084829

RESUMO

There has been increased interest in the role of corrosion in early implant failures and adverse local tissue reaction in total hip arthroplasty. We review the relationship between the different types of corrosion in orthopaedic surgery including uniform, pitting, crevice, and fretting or mechanically assisted crevice corrosion (MACC). Passive layer dynamics serves a critical role in each of these processes. The femoral head-neck trunnion creates an optimal environment for corrosion to occur because of the limited fluid diffusion, acidic environment, and increased bending moment.


Assuntos
Artroplastia de Quadril/efeitos adversos , Artroplastia de Quadril/instrumentação , Desenho de Prótese , Falha de Prótese , Corrosão , Humanos , Metais , Óxidos , Complicações Pós-Operatórias , Termodinâmica
7.
Water Sci Technol ; 79(7): 1287-1296, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31123228

RESUMO

Our findings proved that micron-scale zero-valent iron (mZVI) particles with pre-magnetization combined with peroxymonosulfate (PMS) can markedly enhance the removal of acid orange 7 (AO7). Investigation into the mechanism showed that PMS accelerated the corrosion of ZVI to release Fe2+ under acidic conditions, and the in-situ generated Fe2+ further activated PMS to produce SO4•- and •OH, resulting in AO7 removal. Further, the Lorentz force strengthened the convection in the solution and the field gradient force tended to move Fe2+ from a higher to a lower field gradient at the pre-magnetized ZVI (Pre-ZVI) particle surfaces, thus indicating that pre-magnetization promoted the corrosion of ZVI to release Fe2+, which resulted in the enhancement of PMS activation. Nano-scale ZVI (nZVI) was more effective than mZVI in activating PMS to degrade AO7, but the pre-magnetization effect on mZVI was better than on nZVI. AO7 removal increased with higher ZVI and PMS dosage, lower AO7 concentration, and acidic conditions (pH = 2, 3). This study helps to understand the reactive radicals-based oxidation process with application of pre-magnetized ZVI in activating PMS.


Assuntos
Compostos Azo/química , Benzenossulfonatos/química , Peróxidos/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Compostos Azo/análise , Benzenossulfonatos/análise , Catálise , Corrosão , Ferro/química , Poluentes Químicos da Água/análise
8.
Environ Sci Pollut Res Int ; 26(19): 19906-19914, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31090008

RESUMO

Identification of the accumulation mechanism of major elements on pipe surface is essential to investigate the development of corrosion scales and co-occurrence of trace inorganic contaminants. In this study, corrosion scale samples were collected from old, corroded iron pipes made of different materials and exposed to different water qualities and operation conditions. Elemental composition of these scales was determined by energy dispersive X-ray spectroscopy (EDS). Cumulative occurrence analysis, Q-style hierarchical cluster analysis (CA), and principal component analysis (PCA) were conducted to ascertain major elements typical for corrosion scales and to estimate the dominant influencing factor to each elemental constituent. The major elements in the examined scales are Fe, C, Zn, Si, Ca, Al, and S in the descending prevalence. Their occurrences are influenced by an interactive effect. Pipe material imposes a significant effect on the accumulation of Fe, Zn, and Ca in corrosion scales; water composition can account for the presence of Si, Al, and S in this study; hydraulic condition is identified as the primary factor influencing the occurrence of C and Ca. Q-style CA and PCA are verified practicable for data interpretation and identification of dominant factors influencing scale characteristics.


Assuntos
Corrosão , Poluentes Químicos da Água/análise , Abastecimento de Água , Água/química , Ferro/química
9.
Microsc Res Tech ; 82(9): 1384-1391, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31111992

RESUMO

The aims of this study were: (a) to determine if the presence of probiotic bacteria in an aging medium, that is, artificial saliva in this study, has relevant effects on the surface roughness and the chemical composition of two main alloys used in dentistry (NiTi and stainless steel [SS]) and (b) in the case of NiTi, if these effects are influenced by the coating of the alloy (rhodium and titanium nitride). Atomic force microscopy and Raman spectroscopy were used to study the surface morphology and identify metal oxides formed on the surface of the alloys. Experiments demonstrated that the probiotic bacteria Lactobacillus reuteri can induce processes that alter some features of the surface such as roughness and chemical composition. The effect is dependent on the type of alloy and coating. The bacteria increased roughness in the case of uncoated NiTi more than saliva alone (pH = 4.8). Probiotic bacteria tend to decrease the corrosive influence of saliva on NiTi when the alloy is coated with rhodium or titanium nitride and this effect was also evidenced on SS. Raman spectroscopy confirmed that only SS samples are prone to oxidation processes, predominantly associated with exposure to saliva rather than probiotic bacteria.


Assuntos
Ligas Dentárias/química , Lactobacillus reuteri/crescimento & desenvolvimento , Lactobacillus reuteri/metabolismo , Probióticos/metabolismo , Saliva/microbiologia , Propriedades de Superfície , Corrosão , Microscopia de Força Atômica , Óxidos/análise , Análise Espectral Raman
10.
Waste Manag ; 87: 407-416, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31109541

RESUMO

In this work, the leaching pattern, chemical speciation, and environmental risks of various heavy metals (Pb, Zn, Cu, Cd, Cr, and Ni) were investigated synchronously under different acid corrosion conditions through end-point pH leaching experiments. The heavy metals were present in raw, stabilized (phosphoric acid; chelating agent), and solidified (Portland cement) municipal solid waste incineration (MSWI) fly ash. The results showed that the stabilization and solidification pre-treatment could effectively decrease the leaching of most heavy metals. However, phosphoric acid stabilization and Portland cement solidification increased the solubility of Ni and Pb/Cu/Cd under low end-point pH conditions, while that of Cr and Pb increased under high end-point pH conditions. Overall, the leaching pattern of heavy metals was not affected by the addition of binders/additives. The results from speciation analysis showed that the bioavailable fractions (exchangeable and carbonate-bound) were leached out from initial raw or solidified/stabilized fly ash after distilled water leaching. However, with the decrease in end-point pH levels, the bioavailable fractions increased again due to the increase in acid corrosion on metal-bearing mineral matrixes. The risk assessment results indicated that, after exposing the raw or solidified/stabilized fly ash to highly acidic conditions, not only the high-content Pb/Zn/Cu, but also some low-content Cd posed potential risks to the environment. During the leaching process, under extremely acidic conditions, the increased environmental risks posed by Pb/Zn/Cu/Cd in residual fly ash solids were greatly ascribed to the increase in bioavailable fractions, which might result in the re-leaching of some heavy metals to the environment.


Assuntos
Incineração , Metais Pesados , Carbono , Cinza de Carvão , Corrosão , Material Particulado , Resíduos Sólidos
11.
Chemosphere ; 230: 230-238, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31103869

RESUMO

There have been many studies on TCE degradation by synthesized nanoscale zero-valent iron (nZVIB) and commercial nanoscale zero-valent iron (nZVIH), but the effect of anaerobic corrosion on the dechlorination pathways and speciation distribution of chlorine is still unclear. Compared with nZVIH, nZVIB has a faster degradation rate of TCE and formation rate of Cl-(aq) (kSA, TCE = 3.67 ±â€¯0.85 × 10-4 & 2.17 ±â€¯0.13 × 10-4 L·h-1·m-2 and kobs, Cl- = 0.344 ±â€¯0.027 & 0.166 ±â€¯0.010 µM·h-1 for nZVIB & nZVIH, respectively). Based on the characterization of XRD, XPS and TEM during the anaerobic corrosion, the corrosion of nZVIB was dramatic under the dissolution-reprecipitation mechanism; but that of nZVIH was moderate and inward by maintaining the core-shell structure and shaping slightly rough and lumpy surface. Due to the different corrosion products (FeOOH for nZVIB and Fe3O4/γ-Fe2O3 for nZVIH) and the catalysis of boron on the nZVIB surface, the preferential dechlorination pathway of TCE was not identical by hydrogenolysis (nZVIB) vs. reductive ß-elimination (nZVIH). Meanwhile, the dechlorination pathway of nZVIH was similar to that of ZVI and the reductive pathway to acetylene bypassed the formation of more toxic VC. This study shows that the high reactivity of nZVIB results in rapid corrosion with the side effect of enhanced adsorption of VC while nZVIH has a stable core-shell structure and less sorbed chlorine, which provides a new sight to access the ecological risk of nZVI due to the overlooked effect of non-identical corrosion.


Assuntos
Cloro/análise , Poluentes Ambientais/análise , Recuperação e Remediação Ambiental/métodos , Ferro/química , Nanopartículas/química , Tricloroetileno/análise , Adsorção , Cloro/química , Corrosão , Poluentes Ambientais/química , Halogenação , Modelos Teóricos , Oxirredução , Propriedades de Superfície , Tricloroetileno/química
12.
Environ Sci Pollut Res Int ; 26(18): 18256-18266, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31041705

RESUMO

Landfill leachate is generally transferred to in situ facilities for advanced treatment by using a pipe system. Because of its harmful and complex compounds, leachate may react with pipe materials, leading to corrosion and scaling. This experimental study uses typical PVC pipe material and investigates its anti-corrosion performance by placing the material samples into different aged leachates. By evaluating the changes in different experimental parameters, including calcium, magnesium, and chloride ion concentration, oxidation-reduction potential, dissolved oxygen, and pH, combined with a characterization of the material properties, we infer the main causes of pipe scaling-corrosion. Results show that the scaling is more intense in the younger leachate, and the concentration of calcium ions is the dominant influencing factor. The scaling might be resulted from joint actions of chemical precipitation and microbial metabolic activities. It is expected the study to provide useful insights into taking effective actions on anti-clogging, and enhance pipes design by selection of appropriate materials for future modification.


Assuntos
Cloreto de Polivinila/química , Poluentes Químicos da Água/química , Precipitação Química , Corrosão , Oxigênio , Microbiologia do Solo
13.
Bioelectrochemistry ; 129: 10-17, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31075534

RESUMO

In this study, the corrosion behavior of 7075-T6 aluminum alloy in a high salinity environment containing Aspergillus niger was investigated using high-performance liquid chromatography tandem mass spectrometry, gas chromatography, surface analysis and electrochemical measurement. Results demonstrated that uniform and localized corrosion rates of the alloy in the presence of A. niger were approximately 3.7 and 22.4 times, respectively, of that in the absence A. niger. This higher corrosion rate was attributed to accelerated anode and cathode reactions from the actions of A. niger biofilm. Additionally, organic acid corrosion caused by the presence of A. niger was confirmed to be the main cause for the corrosion of aluminum alloy.


Assuntos
Ligas/química , Alumínio/química , Aspergillus niger/fisiologia , Biofilmes/crescimento & desenvolvimento , Corrosão , Técnicas Eletroquímicas , Eletrodos/microbiologia , Salinidade , Propriedades de Superfície
14.
Bioelectrochemistry ; 129: 42-53, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31103846

RESUMO

Electrochemical, anticorrosion and adsorption behaviour of bio-based melatonin (MEL) in 5% HCl solution was investigated by experimental and theoretical approaches. MEL was found to possess high adsorptive capacity for steel surface and inhibits the acid corrosion. With a concentration of 10 mM, inhibition efficiency of 98.3% and 88.6% were obtained at 30 °C and 60 °C respectively. Langmuir associative and dissociative models describe simultaneous physisorption and chemisorption. FTIR, SEM/EDS and quantum molecular dynamics simulations using DFT provide evidences that MEL forms adsorbed surface complex film (in the protonated form) coordinated mainly by indole ring, N(9) and O(10). The biomolecule is a promising alternative anticorrosion additive for acid wash solutions.


Assuntos
Ácido Clorídrico/química , Melatonina/química , Aço/química , Adsorção , Corrosão , Técnicas Eletroquímicas , Cinética , Simulação de Dinâmica Molecular , Propriedades de Superfície
15.
MBio ; 10(3)2019 05 14.
Artigo em Inglês | MEDLINE | ID: mdl-31088920

RESUMO

The concept that anaerobic microorganisms can directly accept electrons from Fe(0) has been controversial because direct metal-microbe electron transfer has previously only been indirectly inferred. Fe(0) oxidation was studied with Geobacter sulfurreducens strain ACL, an autotrophic strain that was previously shown to grow with electrons derived from a graphite cathode as the sole electron donor. Strain ACL grew with Fe(0) as the sole electron donor and fumarate as the electron acceptor. However, it appeared that at least a portion of the electron transfer was via H2 produced nonenzymatically from the oxidation of Fe(0) to Fe(II). H2, which accumulated in abiotic controls, was consumed during the growth of strain ACL, the cells were predominately planktonic, and genes for the uptake hydrogenase were highly expressed. Strain ACLHF was constructed to prevent growth on H2 or formate by deleting the genes for the uptake of hydrogenase and formate dehydrogenases from strain ACL. Strain ACLHF also grew with Fe(0) as the sole electron donor, but H2 accumulated in the culture, and cells heavily colonized Fe(0) surfaces with no visible planktonic growth. Transcriptomics suggested that the outer surface c-type cytochromes OmcS and OmcZ were important during growth of strain ACLHF on Fe(0). Strain ACLHF did not grow on Fe(0) if the gene for either of these cytochromes was deleted. The specific attachment of strain ACLHF to Fe(0), coupled with requirements for known extracellular electrical contacts, suggest that direct metal-microbe electron transfer is the most likely option for Fe(0) serving as an electron donor.IMPORTANCE The anaerobic corrosion of iron structures is expensive to repair and can be a safety and environmental concern. It has been known for over 100 years that the presence of anaerobic respiratory microorganisms can accelerate iron corrosion. Multiple studies have suggested that there are sulfate reducers, methanogens, and acetogens that can directly accept electrons from Fe(0) to support sulfate or carbon dioxide reduction. However, all of the strains studied can also use H2 as an electron donor for growth, which is known to be abiotically produced from Fe(0). Furthermore, no proteins definitely shown to function as extracellular electrical contacts with Fe(0) were identified. The studies described here demonstrate that direct electron transfer from Fe(0) can support anaerobic respiration. They also map out a simple genetic approach to the study of iron corrosion mechanisms in other microorganisms. A better understanding of how microorganisms promote iron corrosion is expected to lead to the development of strategies that can help reduce adverse impacts from this process.


Assuntos
Geobacter/genética , Geobacter/metabolismo , Ferro/metabolismo , Anaerobiose , Corrosão , Citocromos/genética , Transporte de Elétrons , Formiato Desidrogenases/genética , Oxirredução , Oxirredutases/genética , Transcriptoma
16.
Bioelectrochemistry ; 128: 252-262, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31048108

RESUMO

Biocorrosion is an important type of corrosion which leads to economic losses across oil and gas industries, due to increased monitoring, maintenance, and a reduction in platform availability. Ideally, a chemical compound engineered to mitigate against biocorrosion would possess both antimicrobial properties, as well as efficient corrosion inhibition. Gemini surfactants have shown efficacy in both of these properties, however there still remains a lack of electrochemical information regarding biocorrosion inhibition. The inhibition of corrosion and biocorrosion, by cationic gemini surfactants, of carbon steel was investigated. The results showed that the inhibition efficiency of the gemini surfactants was high (consistently >95%), even at low concentrations. Gemini surfactants also showed strong antimicrobial activity, with a minimum inhibitory concentration (0.018 mM). Corrosion inhibition was investigated by electrochemical impedance spectroscopy (EIS) and linear polarisation resistance (LPR), with biocorrosion experiments carried out in an anaerobic environment. Surface morphology was analysed using scanning electron microscopy (SEM).


Assuntos
Antibacterianos/farmacologia , Biofilmes , Corrosão , Compostos de Amônio Quaternário/farmacologia , Aço/química , Tensoativos/farmacologia , Espectroscopia Dielétrica , Microscopia Eletrônica de Varredura
17.
Mater Sci Eng C Mater Biol Appl ; 101: 292-305, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31029323

RESUMO

A novel implant coating material containing graphene oxide (GO) and collagen (COL), and hydroxyapatite (HA) was fabricated with the aid of tannic acid by electrodeposition. The surface of Ti16Nb alloy was subjected to anodic oxidation, and then HA-GO coating was applied to Ti16Nb surface by cathodic method. Then, COL was deposited on the surface of the HA-GO coating by the biomimetic method. HA, HA-GO, HA-GO-COL coatings on the surface of the Ti16Nb alloy have increased the corrosion resistance by the formation of a barrier layer on the surface. For HA-GO-COL coating, the highest corrosion resistance is obtained due to the compactness and homogeneity of the coating structure. The contact angle of the bare Ti16Nb is approximately 65°, while the contact angle of the coated samples is close to 0°. Herein, the increased surface wettability is important for cell adhesion. The surface roughness of the uncoated Ti16Nb alloy was between 1 and 3 µm, while the surface roughness of the coated surfaces was measured between 20 and 110 µm. The contact between the bone and the implant has been improved. Graphene oxide-containing coatings have improved the antibacterial properties compared to the GO-free coating using S. aureus. The hardness and elastic modulus of the coatings were measured by the nanoindentation test, and the addition of GO and collagen to the HA coating resulted in an increase in strength. The addition of GO to the HA coating reduced the viability of 3 T3 fibroblast cells, whereas the addition of collagen to HA-GO coat increased the cell adhesion and viability.


Assuntos
Ligas/farmacologia , Materiais Revestidos Biocompatíveis/farmacologia , Colágeno/farmacologia , Durapatita/farmacologia , Galvanoplastia/métodos , Grafite/farmacologia , Compostos de Estanho/química , Células 3T3 , Animais , Corrosão , Fibroblastos/citologia , Fibroblastos/efeitos dos fármacos , Fibroblastos/ultraestrutura , Camundongos , Testes de Sensibilidade Microbiana , Nanotubos/química , Nanotubos/ultraestrutura , Staphylococcus aureus/efeitos dos fármacos , Propriedades de Superfície , Compostos de Estanho/farmacologia , Difração de Raios X
18.
Mater Sci Eng C Mater Biol Appl ; 101: 92-102, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31029368

RESUMO

In this work, microstructures and corrosion behaviors of novel ZrTiAl-χV (χ = 0, 1, 3, 5, 7 wt%) alloys have been investigated. Phase composition and microstructures of the specimens are characterized using X-ray diffraction, optical microscopy, scanning electron microscopy, and transmission electron microscopy. The results show that phase composition of the alloys change by α' → α″ → α″ + ßâ€¯â†’â€¯ß as V is added gradually. Meanwhile, the mean size of the α' phase, α″ martensite and ß phase decreases as V content increases. In order to test the corrosion performance of the specimens, potentiodynamic polarization tests in NaCl and HCl solutions and immersion tests in HCl solution are performed. Analysis of potentiodynamic potential curves indicates that corrosion potential increases and corrosion current density decreases with adding V content in the examined alloys. From the results of weight loss tests, it can be observed that the weight loss of the examined alloys decreases along with the increase of V content. In addition, when the content of V is added from 3 to 7 wt%, the metastable corrosion pits are replaced with the stable corrosion pits. The phase composition as well as the grain size can be identified as the main factor affecting the corrosion performance of the alloys.


Assuntos
Ligas/química , Corrosão , Eletroquímica , Fatores de Tempo , Difração de Raios X
19.
Molecules ; 24(7)2019 Apr 09.
Artigo em Inglês | MEDLINE | ID: mdl-30970539

RESUMO

Thermal energy storage systems work in conjunction with solar technologies with the aim of increasing their dispatchability and competitiveness in the energy market. Among others, latent heat thermal energy storage systems have become an appealing research subject and many efforts have therefore been invested in selecting the best phase change material (PCM) to fit the final application. In this study, an extended corrosion characterization was performed for two PCM candidates, solar salt (40 wt.% KNO3/60 wt.% NaNO3) and myo-inositol (C6H12O6), to be applied in Fresnel solar plants. Corrosion rates were determined in aluminium, stainless steel (AISI 304), carbon steel (AISI 1090), and copper by gravimetric tests, gauging the weight loss after 2000 h of immersion at 250 °C. The corrosion products were characterized by scanning electron microscopy (SEM) and x-ray diffraction (XRD). The corrosion tests carried out with myo-inositol did not show accurate enough results to draw conclusions regarding corrosion on the metals. However, it was observed that this sugar alcohol strongly sticks to the metal specimens, making myo-inositol extremely difficult to manage as an energy storage material. Therefore, the present paper discourages the use of myo-inositol as a PCM beyond its corrosion rate.


Assuntos
Inositol/química , Aço Inoxidável/química , Álcoois Açúcares/química , Corrosão , Energia Solar
20.
Mater Sci Eng C Mater Biol Appl ; 100: 396-410, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30948076

RESUMO

Stainless steel (SS) has been widely applied as one of the most efficient implant metal materials, although corrosion and infection in body environment are still challenging. Herein, an antibacterial passivation method was employed to enhance the antibacterial performance and corrosion resistance of the medical 316L SS. The result proved that the antibacterial-passivated 316L SS exhibited stable antibacterial activity and effectively inhibited the formation of bacterial biofilm. Electrochemical measurements combined with X-ray photoelectron spectroscopy technique were used to study the corrosion resistance and semiconductor behavior of passivated 316L SS immersed in simulated physiological environment. The results indicated that the 316L SS after antibacterial passivation treatment for 1 h, soaking in the medium for 10 days, showed satisfactory corrosion resistance attributing to proper Cu deposition in the passive film. The anodic stripping voltammetry measurement further confirmed that the Cu-bearing passive film could continuously release Cu ions into medium. The zebrafish test demonstrated an excellent in vivo biocompatibility for the 316L SS with antibacterial passivation for 0.5 and 1 h, respectively. In addition, changes of surface roughness, contact angle and chemical composition after antibacterial passivation played an important role in explaining the antibacterial mechanism, which could be clearly divided into contact killing and ionic release killing. Hence, the antibacterial passivation treatment was preliminarily proved as a potential way for enhancing the persistent antibacterial activity and corrosion resistance of 316L SS.


Assuntos
Antibacterianos/farmacologia , Materiais Biocompatíveis/farmacologia , Aço Inoxidável/farmacologia , Animais , Biofilmes/efeitos dos fármacos , Morte Celular/efeitos dos fármacos , Cobre/análise , Corrosão , Espectroscopia Dielétrica , Eletroquímica , Eletrodos , Embrião não Mamífero/citologia , Embrião não Mamífero/efeitos dos fármacos , Viabilidade Microbiana/efeitos dos fármacos , Microscopia de Força Atômica , Espectroscopia Fotoeletrônica , Propriedades de Superfície , Água/química , Peixe-Zebra/embriologia
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