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1.
Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi ; 34(6): 676-682, 2020 Jun 15.
Artigo em Chinês | MEDLINE | ID: mdl-32538555

RESUMO

Objective: To summarize the effectiveness of nitinol memory alloy two foot fixator with autologous cancellous bone grafting in treating old scaphoid fracture and nonunion. Methods: Between January 2013 and January 2017, 11 patients of old scaphoid fracture and nonunion were treated with nitinol memory alloy two foot fixator and autologous cancellous bone grafting. All patients were male with an average age of 26.1 years (range, 18-42 years). The fractures were caused by sport in 3 cases, falling in 7 cases, and a crashing object in 1 case. The interval between injury and operation was 6-18 months (mean, 8.9 months). Postoperative outcome measures included operation time, fracture healing time, grip strength, range of motion (ROM) of flexion, extension, ulnar deviation, and radial deviation, Mayo score, visual analogue scale (VAS) score, and the Disabilities of the Arm, Shoulder, and Hand (DASH) score. Results: The operation time was 35-63 minutes (mean, 48 minutes). All incisions had primary healing with no infection and loosening or breakage of internal fixator. All patients were followed up 12-30 months (mean, 20.7 months). X-ray films showed that fracture healing was achieved in all patients with an average time of 15 weeks (range, 12-25 weeks). All internal fixators were removed after 10-12 months of operation (mean, 11.2 months). At last follow-up, the grip strength, ROMs of flexion, ulnar deviation, and radial deviation were superior to those before operation ( P<0.05), no significant difference was found in ROM of extension between pre- and post-operation ( t=0.229, P=0.824). There were significant differences in above indexes between affected and normal sides ( P<0.05). At last follow-up, the Mayo, VAS, DASH scores were also significantly superior to those before operation ( P<0.05). Conclusion: For the old scaphoid fracture and nonunion, Ni-Ti arched shape-memory alloy fixator and autologous cancellous bone grafting can obtain good effectiveness, which is an effective treatment.


Assuntos
Ligas , Transplante Ósseo , Osso Esponjoso , Fixação Interna de Fraturas , Fraturas não Consolidadas , Osso Escafoide , Adolescente , Adulto , Ligas/química , Transplante Ósseo/métodos , Osso Esponjoso/cirurgia , Fixação Interna de Fraturas/normas , Fraturas não Consolidadas/cirurgia , Humanos , Masculino , Amplitude de Movimento Articular , Osso Escafoide/cirurgia , Resultado do Tratamento , Adulto Jovem
2.
PLoS One ; 15(6): e0234774, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32569283

RESUMO

We developed and describe a differential scanning calorimetry method for calculating the initial crystallinity, change of crystallinity and crystallinity percentage of amorphous metal alloys as a function of temperature. Using thermodynamic enthalpies of amorphous, crystalline and partially devitrified specimens, our methodology is capable of determining crystallinity percentages as low as a few percent. Moreover, the linear relationship between the set (pre-determined) and calculated crystallinities of experimental samples indicates that there is no need to prepare calibration samples before measuring the crystallinity percentage of target samples. This technique also eliminates the need for expensive in situ accessories, such as those required in electron microscopy. Thus, the technique is highly relevant as a primary technique for characterization of devitrification behavior in amorphous materials.


Assuntos
Ligas/química , Varredura Diferencial de Calorimetria , Cristalografia por Raios X , Temperatura
3.
PLoS One ; 15(6): e0234981, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32574186

RESUMO

The corrosion behavior of an AZ91D magnesium alloy was investigated under a heterogeneous electrolyte layer by using electrochemical methods and surface analysis techniques. Dynamic polarization curves and morphological characterization were obtained at the center and near the edge zones under the electrolyte layer. The influence of the gas/liquid/solid three-phase boundary zone (TPB) on the corrosion behavior of the AZ91D magnesium alloy was discussed. The corrosion rate changed more significantly near the TPB zone than that at the other zones. The AZ91D alloy exhibited the characteristics of filiform corrosion together with shallow pitting corrosion. Different from the randomly distributed shallow pits, the filiform corrosion preferred to initiate near the TPB region and then progressively expanded adjacent to the edge of the electrolyte layer. The TPB zone played a vital role in determining the corrosion location, the corrosion morphologies and the corrosion rate of the magnesium alloy by influencing the mass transport process of carbon dioxide.


Assuntos
Ligas/química , Eletrólitos/química , Magnésio/química , Corrosão , Técnicas Eletroquímicas/instrumentação , Eletrodos , Propriedades de Superfície , Difração de Raios X
4.
PLoS One ; 15(4): e0231179, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32240256

RESUMO

Site-specific atom probe tomography (APT) from aluminum alloys has been limited by sample preparation issues. Indeed, Ga, which is conventionally used in focused-ion beam (FIB) preparations, has a high affinity for Al grain boundaries and causes their embrittlement. This leads to high concentrations of Ga at grain boundaries after specimen preparation, unreliable compositional analyses and low specimen yield. Here, to tackle this problem, we propose to use cryo-FIB for APT specimen preparation specifically from grain boundaries in a commercial Al-alloy. We demonstrate how this setup, easily implementable on conventional Ga-FIB instruments, is efficient to prevent Ga diffusion to grain boundaries. Specimens were prepared at room temperature and at cryogenic temperature (below approx. 90K) are compared, and we confirm that at room temperature, a compositional enrichment above 15 at.% of Ga is found at the grain boundary, whereas no enrichment could be detected for the cryo-prepared sample. We propose that this is due to the decrease of the diffusion rate of Ga at low temperature. The present results could have a high impact on the understanding of aluminum and Al-alloys.


Assuntos
Ligas/química , Alumínio/química , Tomografia/métodos , Gálio/química , Íons , Temperatura
5.
Biofouling ; 36(3): 276-291, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32338044

RESUMO

Metal release rates were measured from four different copper alloy-based materials used by the aquaculture industry: copper sheet machined into a diamond mesh, copper alloy mesh (CAM), silicon bronze welded wire mesh, and copper sheeting, and compared with conventional nylon aquaculture net treated with a cuprous oxide antifouling (AF) coating. Release rates were measured in situ in San Diego Bay using a Navy-developed Dome enclosure system at nine different time points over one year. As expected, copper was the predominant metal released, followed by zinc and nickel, which were fractional components of the materials tested. Release rates followed a temporal trend similar to those observed with copper AF coatings applied to vessel hulls: an initial spike in copper release was followed by a decline to an asymptotic low. Leachate toxicity was consistent with prior studies and was directly related to the metal concentrations, indicating the alloys tested had no additional toxicity above pure metals.


Assuntos
Ligas/análise , Cobre/análise , Monitoramento Ambiental/métodos , Poluentes Químicos da Água/análise , Ligas/química , Baías/química , California , Níquel/análise , Água do Mar/química , Zinco/análise
6.
Comput Methods Biomech Biomed Engin ; 23(8): 372-383, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32116034

RESUMO

The aim of this study was to assess the stress/strain in dental implant/abutments with alternative materials, in implants with different microgeometry, through finite element analysis (FEA). Three-dimensional models were created to simulate the clinical situation of replacement of a maxillary central incisor with implants, in a type III bone, with a provisional single crown, loaded with 100 N in a perpendicular direction. The FEA parameters studied were: implant materials-titanium, porous titanium, titanium-zirconia, zirconia, reinforced fiberglass composite (RFC), and polyetheretherketone (PEEK); and abutment materials-titanium, zirconia, RFC, and PEEK; implant macrogeometry-tapered of trapezoidal threads (TTT) and cylindrical of triangular threads (CTT) (ø4.3 mm × 11 mm). Microstrain, von Mises, shear, and maximum and minimum principal stresses in the structures and in peri-implant bone were compared. There was increased stress and strain in peri-implant bone tissue caused by implants of materials with lower elastic modulus (mainly for PEEK and RFC). They also presented higher concentration of stresses in the implant itself (especially RFC). Zirconia implants led to lower stress and strains in peri-implant bone tissue. Less rigid abutments (RFC and PEEK) associated with titanium implants led to higher stress in the implant and in peri-implant bone tissue. The TTT macrogeometry showed a higher stress concentration in the implant and peri-implant bone tissue. The stress/strain in peri-implant bone tissue and implant structures were affected by the material used, where reduced values were caused by stiffer materials. Lower stress/strain values were obtained with cylindrical implants of triangular treads.


Assuntos
Ligas/química , Dente Suporte , Implantes Dentários , Análise do Estresse Dentário , Análise de Elementos Finitos , Dinâmica não Linear , Estresse Mecânico , Titânio/química , Humanos
7.
PLoS One ; 15(2): e0228593, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32074123

RESUMO

The present investigation devices a novel X-type six-high (X-6h) mill. In addition, parametric models of different roll layouts such as the four-high (4-h), I-type six-high (I-6h), and X-6h mills are established. Three-dimensional (3D) finite element (FE) contact analysis for a strip rolling process is conducted when the mills are subjected to a constant vertical load of 65 kN. Through comparative analysis of von Mises stress, contact stress and elastic deformation displacement in three roll layouts, the rigidity characteristic of each is obtained, and it is found that the proposed X-6h mill has the largest roll gap stiffness. The influence of different roll diameter ratios on the roll gap stiffness of the roll system is investigated, based on which an optimization design model is built. Further, by taking into account the roll gap stiffness of the roll system as the optimization objective, the optimum diameter ratios of backup roll (BUR) to work roll (WR) of the X-6h rolling mill is achieved via the genetic algorithm (GA) optimization method, obtaining the optimum structural parameters of BUR and WR as well. The reliability of the proposed design is verified by manufacturing a prototype mill which produced magnesium alloy and aluminum alloy strips of high quality.


Assuntos
Indústria Manufatureira/instrumentação , Ciência dos Materiais/instrumentação , Aço/química , Ligas/química , Ligas/normas , Análise de Elementos Finitos , Magnésio/química , Indústria Manufatureira/métodos , Ciência dos Materiais/métodos , Fenômenos Mecânicos , Aço/normas
8.
Carbohydr Polym ; 234: 115889, 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-32070509

RESUMO

We report a facile method to prepare a novel composite based on Fe-Cu alloy decorated cellulose nanocrystals (Fe-Cu@CNC) via simple oxidation-reduction reaction. Spherical zero-valent iron nanoparticles (NZVI) and sheet-like copper nanoparticles were serially anchored on the CNC surface, and the generated composite exhibited excellent antibacterial activities and highly efficient Pb2+ removal. The composites had high antibacterial ratios of 95.9 %-99.9 %, because superoxide radicals can cause irreversible damage to the bacteria, eventually leading to apoptosis and bacterial death. Meanwhile, the Fe-Cu@CNC composite showed quick Pb2+ ion removal, reaching a 70.76 % removal within 5 min, a total removal of 93.98 % after 1 h, and excellent reusability (retaining removal efficiency of 80.41 % after six cycles). The adsorption kinetics demonstrated that the adsorption behavior can be described by pseudo-second-order kinetic model (R2>0.99). This study offers a new strategy to prepare a promising composite with advanced antibacterial and heavy metal removal properties for wastewater treatment.


Assuntos
Ligas/farmacologia , Antibacterianos/farmacologia , Celulose/farmacologia , Chumbo/isolamento & purificação , Nanopartículas/química , Poluentes Químicos da Água/isolamento & purificação , Ligas/química , Antibacterianos/síntese química , Antibacterianos/química , Celulose/química , Cobre/química , Cobre/farmacologia , Escherichia coli/efeitos dos fármacos , Ferro/química , Ferro/farmacologia , Chumbo/química , Testes de Sensibilidade Microbiana , Tamanho da Partícula , Espécies Reativas de Oxigênio/antagonistas & inibidores , Espécies Reativas de Oxigênio/metabolismo , Staphylococcus aureus/efeitos dos fármacos , Propriedades de Superfície , Poluentes Químicos da Água/química
9.
Nanotechnology ; 31(23): 235101, 2020 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-32097900

RESUMO

Modifications to the compositional, topographical and morphological aspects of bone implants can lead to improved osseointegration, thus increasing the success of bone implant procedures. This study investigates the creation of dual-scale topography on Ti-5Al-5Mo-5V-3Cr (Ti5553), an alloy not presently used in the biomedical field, and compares it to Ti-6Al-4V (Ti64), the most used Ti alloy for bone implants. Dual-scale surface topography was obtained by combining selective laser melting (SLM) and electrochemical anodization, which resulted in micro- and nanoscale surface features, respectively. Ti5553 and Ti64 samples were manufactured by SLM and showed comparable surface topography. Subsequent electrochemical anodization succeeded in forming titania nanotubes (TNTs) on both alloys, with larger nanotubes obtained with Ti5553 at all investigated anodization voltages. At an anodization voltage of 40 V, a minimum time of 20 min was necessary to have nanotube formation on the surface of either alloy, while only nanopores were evident for shorter times. Seeded Saos-2 cells showed ideal interactions with surface-modified structures, with filopodia extending to both surface microparticles characteristic of SLM and to the interior of TNTs. Attractiveness of Ti5553 lies in its lower elastic modulus (E = 72 GPa) compared to Ti64, which should mitigate stress-shielding phenomena in vivo. This, combined with the analogous results obtained in terms of dual-scale surface topography and cell-substrate interaction, could indicate Ti5553 as a promising alternative to the widely-employed Ti64 for bone implant device manufacturing.


Assuntos
Ligas/farmacologia , Osseointegração/efeitos dos fármacos , Titânio/farmacologia , Ligas/síntese química , Ligas/química , Linhagem Celular , Teste de Materiais , Microscopia Eletrônica de Varredura , Nanotubos , Tamanho da Partícula , Próteses e Implantes , Propriedades de Superfície
10.
Environ Sci Pollut Res Int ; 27(8): 7934-7942, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31893362

RESUMO

Nickel-titanium alloys have been used in medical applications for several years; however, biocompatibility of the material remains controversial. In the present study, the human umbilical vein endothelial cells (HUVEC) were cultured in contact with the nitinol used in two different heat treatment  surface modifications-helium and hydrogen. The amount of Ni ions released from these alloys in contact with HUVEC was measured in media and in the cells by ICP-MS. An increased release of Ni ions was detected in He alloy compared with H2 alloy modification with an elevation with the metal exposition duration (24 h vs. 72 h). The cells contained the Ni ions in both selected alloy modifications with the lower levels in H2 alloys. To evaluate the potential of multiple metal applications, similar values were observed in media and in cell suspension for all surface modification combinations. The model analysis of effect of metal ion release on distant cells in the body showed that the concentration is interestingly similar to concentrations in cells in direct contact with the metal alloy. The cells are able to regulate the concentration of Ni ions within the cell. According to our best knowledge, the study for the first time describes the presence of Ni ions released from nitinol directly in the cells. In the case of the H2 modification, the lowest levels of Ni ions were detected both in medium and in the cells, which likely increases the biocompatibility of the nitinol alloy.


Assuntos
Níquel , Titânio , Ligas/química , Células Endoteliais/química , Humanos , Íons/química , Níquel/química , Propriedades de Superfície , Titânio/química
11.
Mater Sci Eng C Mater Biol Appl ; 108: 110433, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31923945

RESUMO

To instill pure Ti with an antibacterial effect, Cu was added by metallurgical alloying to produce Ti-5 wt% Cu alloy (Ti-5Cu alloy). The precipitation of the likes of Ti2Cu in a Ti-Cu alloy is one of the factors that influences its antibacterial property. However, in the present study, Ti-5Cu alloy precipitates with different microstructures were obtained by applying heat treatment at different temperatures and for different durations. After the heat treatment, metallographic, microstructure, and element analyses were performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDS). The antibacterial property of the Ti-5Cu alloy was assessed by the plated-count method using Escherichia coli (E. coli). The microstructure analysis revealed that the solution-treated alloy had no precipitation, while the aged alloy contained precipitations of intermetallic Ti2Cu compound. The aged alloy exhibited better antibacterial performance as the duration of the aging treatment increased. The optimal heat treatment for Ti-5Cu was found to be aging at 700 °C for 4 h, at which point the nucleation formation of the Ti2Cu particles would assume an acicular morphology. These acicular precipitates exhibit a high Cu content which, in turn, influences the antibacterial performance.


Assuntos
Ligas , Escherichia coli/crescimento & desenvolvimento , Ligas/química , Ligas/farmacologia , Antibacterianos/química , Antibacterianos/farmacologia
12.
Nat Commun ; 11(1): 401, 2020 01 21.
Artigo em Inglês | MEDLINE | ID: mdl-31964879

RESUMO

Magnesium-based biodegradable metals (BMs) as bone implants have better mechanical properties than biodegradable polymers, yet their strength is roughly less than 350 MPa. In this work, binary Zn alloys with alloying elements Mg, Ca, Sr, Li, Mn, Fe, Cu, and Ag respectively, are screened systemically by in vitro and in vivo studies. Li exhibits the most effective strengthening role in Zn, followed by Mg. Alloying leads to accelerated degradation, but adequate mechanical integrity can be expected for Zn alloys when considering bone fracture healing. Adding elements Mg, Ca, Sr and Li into Zn can improve the cytocompatibility, osteogenesis, and osseointegration. Further optimization of the ternary Zn-Li alloy system results in Zn-0.8Li-0.4Mg alloy with the ultimate tensile strength 646.69 ± 12.79 MPa and Zn-0.8Li-0.8Mn alloy with elongation 103.27 ± 20%. In summary, biocompatible Zn-based BMs with strength close to pure Ti are promising candidates in orthopedics for load-bearing applications.


Assuntos
Implantes Absorvíveis , Ligas/química , Fixadores Internos , Desenho de Prótese , Zinco/química , Animais , Interface Osso-Implante/diagnóstico por imagem , Linhagem Celular , Fêmur/diagnóstico por imagem , Fêmur/cirurgia , Fixação Interna de Fraturas/instrumentação , Células Endoteliais da Veia Umbilical Humana , Humanos , Teste de Materiais , Microscopia Eletrônica de Varredura , Osteoblastos , Ratos , Resistência à Tração , Suporte de Carga , Microtomografia por Raio-X
13.
J Nanobiotechnology ; 18(1): 18, 2020 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-31964403

RESUMO

BACKGROUND: Although accumulating evidence suggests that the crosstalk between malignant cells and cancer-associated fibroblasts (CAFs) actively contributes to tumour growth and metastatic dissemination, therapeutic strategies targeting tumour stroma are still not common in the clinical practice. Metal-based nanomaterials have been shown to exert excellent cytotoxic and anti-cancerous activities, however, their effects on the reactive stroma have never been investigated in details. Thus, using feasible in vitro and in vivo systems to model tumour microenvironment, we tested whether the presence of gold, silver or gold-core silver-shell nanoparticles exerts anti-tumour and metastasis suppressing activities by influencing the tumour-supporting activity of stromal fibroblasts. RESULTS: We found that the presence of gold-core silver-shell hybrid nanomaterials in the tumour microenvironment attenuated the tumour cell-promoting behaviour of CAFs, and this phenomenon led to a prominent attenuation of metastatic dissemination in vivo as well. Mechanistically, transcriptome analysis on tumour-promoting CAFs revealed that silver-based nanomaterials trigger expressional changes in genes related to cancer invasion and tumour metastasis. CONCLUSIONS: Here we report that metal nanoparticles can influence the cancer-promoting activity of tumour stroma by affecting the gene expressional and secretory profiles of stromal fibroblasts and thereby altering their intrinsic crosstalk with malignant cells. This potential of metal nanomaterials should be exploited in multimodal treatment approaches and translated into improved therapeutic outcomes.


Assuntos
Antineoplásicos/química , Fibroblastos Associados a Câncer/efeitos dos fármacos , Nanopartículas Metálicas/química , Metástase Neoplásica/tratamento farmacológico , Ligas/química , Animais , Antineoplásicos/uso terapêutico , Fibroblastos Associados a Câncer/patologia , Linhagem Celular Tumoral , Movimento Celular , Sobrevivência Celular , Progressão da Doença , Doxorrubicina/química , Doxorrubicina/uso terapêutico , Feminino , Fibroblastos/citologia , Fibroblastos/efeitos dos fármacos , Regulação Neoplásica da Expressão Gênica , Ouro/química , Humanos , Nanopartículas Metálicas/uso terapêutico , Camundongos Endogâmicos BALB C , Metástase Neoplásica/patologia , Transplante de Neoplasias , Prata/química , Microambiente Tumoral/efeitos dos fármacos
14.
Mater Sci Eng C Mater Biol Appl ; 108: 110208, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31924034

RESUMO

Zinc (Zn) and its alloys are proposed as promising resorbable materials for osteosynthesis implants. Detailed studies should be undertaken to clarify their properties in terms of degradability, biocompatibility and osteoinductivity. Degradation products of Zn alloys might affect directly adjacent cellular and tissue responses. Periosteal stem cells are responsible for participating in intramembranous ossification during fracture healing. The present study aims at examining possible effects emanating from Zn or Zn-4Ag (wt%) alloy degradation products on cell viability and osteogenic differentiation of a human immortalized cranial periosteal cell line (TAg cells). Therefore, a modified extraction method was used to investigate the degradation behavior of Zn and Zn-4Ag alloys under cell culture conditions. Compared with pure Zn, Zn-4Ag alloy showed almost fourfold higher degradation rates under cell culture conditions, while the associated degradation products had no adverse effects on cell viability. Osteogenic induction of TAg cells revealed that high concentration extracts significantly reduced calcium deposition of TAg cells, while low concentration extracts enhanced calcium deposition, indicating a dose-dependent effect of Zn ions. Our results give evidence that the observed cytotoxicity effects were determined by the released degradation products of Zn and Zn-4Ag alloys, rather than by degradation rates calculated by weight loss. Extracellular Zn ion concentration was found to modulate osteogenic differentiation of TAg cells. These findings provide significant implications and guidance for the development of Zn-based alloys with an optimized degradation behavior for Zn-based osteosynthesis implants.


Assuntos
Implantes Absorvíveis , Ligas , Materiais Biocompatíveis , Teste de Materiais , Osteogênese/efeitos dos fármacos , Periósteo/metabolismo , Zinco , Ligas/química , Ligas/farmacologia , Materiais Biocompatíveis/química , Materiais Biocompatíveis/farmacologia , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Corrosão , Humanos , Periósteo/citologia , Zinco/química , Zinco/farmacologia
15.
Carbohydr Polym ; 230: 115466, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31887965

RESUMO

Seven natural polymers namely, chitosan (CHI), dextran (Dex), carboxymethyl cellulose (CMC), sodium alginate (ALG), pectin (PEC), hydroxylethyl cellulose (HEC), and Gum Arabic (GA) were screened for anticorrosion property towards AZ31 Mg alloy in 3.5 wt.% NaCl solution. CHI, Dex, CMC, PEC, and GA accelerated the corrosion while ALG and HEC moderately inhibited the corrosion of the alloy. HEC and ALG (1 g/L) protected the alloy by 64.13 % and 58.27 %, respectively. Two inhibitor cocktails consisting of either HEC or ALG, KI, and Date palm seed oil have been formulated. HEC- and ALG-formulations inhibited the alloy corrosion by 80.56 % and 77.43 %, respectively from EIS technique. Surface observation studies using SECM, AFM, SEM, and EDX agreed with other experimental results revealing effective corrosion inhibition by the formulations. X-ray photoelectron spectroscopy, FTIR, and UV-vis results disclose that Mg(OH)2 co-existed with adsorbed inhibitor complexes.


Assuntos
Ligas/química , Materiais Revestidos Biocompatíveis/química , Corrosão , Polímeros/química , Adsorção/efeitos dos fármacos , Alginatos/química , Carboximetilcelulose Sódica/química , Quitosana/química , Goma Arábica/química , Magnésio/química , Teste de Materiais , Propriedades de Superfície
16.
Bioelectrochemistry ; 132: 107408, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31816577

RESUMO

Metallic materials can be easily corroded in marine environments, in which pitting corrosion is very common. In this study, we investigated the effect of Bacillus subtilis, isolated from the South China Sea on the corrosion behavior of 2A14 aluminum alloy in seawater. Surface analysis of the alloy in the presence of the bacteria was used to observe corrosion morphology and the corrosion products studied. Electrochemical method was used to analyze the corrosion susceptibility of the alloy in seawater in the presence of the bacteria. Surface analysis suggested that a protective film with CaMg(CO3)2 was gradually formed on the surface of the alloy in the presence of the bacteria. The electrochemical results showed that the radius of the impedance arc of the alloy immersed in seawater with bacteria increased gradually with time. The bacteria promoted the formation of the CaMg(CO3)2 film, which blocked seawater from the alloy and consequently, inhibited pitting corrosion.


Assuntos
Ligas/farmacologia , Alumínio/farmacologia , Bacillus subtilis/efeitos dos fármacos , Biofilmes , Corrosão , Água do Mar , Ligas/química , Alumínio/química , Microscopia Eletrônica de Varredura , Espectrometria por Raios X , Difração de Raios X
17.
Mater Sci Eng C Mater Biol Appl ; 106: 110164, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31753353

RESUMO

This paper investigates the effect of microstructure modification by heat treatment on stress corrosion cracking (SCC) behavior of Mg4Zn alloy in simulated body fluid (SBF). Mg4Zn alloy in as cast, solution heat treated and peak aged conditions was susceptible to SCC in SBF when strained at 3.6 × 10-6 s-1. SCC index based on fracture energy is least for solutionized alloy (0.84), while 0.88 for as cast and peak aged alloys. Fractographic analysis indicates predominantly intergranular SCC for solution treated alloy initiated by anodic dissolution near grain boundaries. As cast and peak aged alloy shows mainly transgranular failure due to hydrogen embrittlement adjacent to secondary phase particles.


Assuntos
Líquidos Corporais/química , Magnésio/química , Ligas/química , Animais , Corrosão , Humanos , Hidrogênio/química
18.
Mater Sci Eng C Mater Biol Appl ; 106: 110165, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31753354

RESUMO

ß-Titanium alloys have been widely used in medical and surgical implants. However, the present titanium alloys are facing challenges from implant-associated infections and the requirements for highly stressed applications. To overcome these problems, by taking advantage of the ß-phase stabilizing element Mo and the antimicrobial element Ag, we fabricated bulk fine-grained Ti-5Mo-5Ag alloys by a combination of mechanical alloying and spark plasma sintering. The alloy sintered at 900 °C showed a network microstructure consisting of 89% ß-phase with average grain size of 8.1 (± 3.2) µm as the matrix and 11% α-phase with micron/submicron-scale precipitates at the grain boundaries/triple junctions. Such network structure offered excellent mechanical properties with compressive yield strength of up to 1694 (± 8.4) MPa and fracture strain of 23%. In comparison with pure titanium, the fabricated Ti-5Mo-5Ag alloys also demonstrated enhanced corrosion resistance and exceptional antibacterial activity (with antibacterial rate up to ~95% against S. aureus). A combination of excellent mechanical properties, corrosion resistance and biological functions enables the fabricated Ti-5Mo-5Ag alloy a promising candidate for load-bearing implant applications.


Assuntos
Ligas/química , Antibacterianos/química , Antibacterianos/farmacologia , Materiais Biocompatíveis/química , Titânio/química , Força Compressiva , Corrosão , Teste de Materiais , Staphylococcus aureus/efeitos dos fármacos
19.
Mater Sci Eng C Mater Biol Appl ; 107: 110213, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31761172

RESUMO

We produced bifurcated bone-like shape memory implant (BL-SMI) with desirable tooth-root fixation capability by compact-sintering of TiH2-Ni-urea mixture. The primary constituents of the porous product were Ni and Ti. We could adjust the pores' shape, size, and interconnectivity for favorite bone ingrowth by using urea as a space holder. Without urea, we obtained an average porosity of 0.30, and a mean void size of 100 µm. With 70 vol % urea, we got 62% interconnected pores of 400 µm average size. Aging allowed us to tune the austenite-martensite transformation temperatures towards the needed body tissue arouse. Differential scanning calorimetry measured the transformation temperatures. Their austenite start, austenite peak, and austenite finish values were As = 4, Ap = 22, and Af = 34 °C, respectively. They retained functional shape recovery and superelastic effect at the body temperature. Mechanical properties, including Young's modulus of the specimens, matched well to maxilla and mandible bone tissue. The measured Young's modulus of the NiTi specimens was as low as 3.5 GPa, which decreased to ∼2.1 GPa with further porosity increase at higher space holder percentages. Superelasticity regime and low Young's modulus of the implant could potentially prevent stress-shielding from the surrounding bone tissues and give rise to secure fixation of the implant into the bone socket. Bending tests showed 0.9 mm recoverable deflection for specimens which assisted immediate self-fixation of the implant into the jaw bone cavity.


Assuntos
Ligas/química , Implantes Dentários , Níquel/química , Titânio/química , Ureia/química , Módulo de Elasticidade , Teste de Materiais , Microscopia Eletrônica de Varredura , Transição de Fase , Porosidade , Temperatura de Transição
20.
Mater Sci Eng C Mater Biol Appl ; 106: 110013, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31753338

RESUMO

The degradation behavior of Mg-4 wt% Zn alloy with three different microstructures was examined in Hank's solution at 37 °C by electrochemical measurements and immersion tests in this study. The results show that the sample with cellular structure exhibits a more positive corrosion potential, lower corrosion current density, larger impedance and more protective film than samples with columnar dendritic and equiaxed dendritic structure. The higher corrosion resistance is attributed to the preferred orientation, eliminating susceptible grain boundaries and reduced secondary phases.


Assuntos
Ligas/metabolismo , Soluções Isotônicas/química , Ligas/química , Corrosão , Espectroscopia Dielétrica , Hidrogênio/química , Hidrogênio/metabolismo , Magnésio/química , Teste de Materiais , Microscopia Eletrônica de Varredura , Temperatura , Zinco/química
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