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Gostin PF, Addison O, Morrell AP, Zhang Y, Cook AJMC, Liens A, Stoica M, Ignatyev K, Street SR, Wu J, Chiu YL, Davenport AJ. In Situ Synchrotron X-Ray Diffraction Characterization of Corrosion Products of a Ti-Based Metallic Glass for Implant Applications. Adv Healthc Mater 2018; 7:e1800338. [PMID: 30221474 DOI: 10.1002/adhm.201800338] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Revised: 08/03/2018] [Indexed: 11/11/2022]
Abstract
Ti-based bulk metallic glasses are under consideration for implants due to their high yield strength and biocompatibility. In this work, in situ synchrotron X-ray diffraction (XRD) is used to investigate the corrosion products formed from corrosion of Ti40 Zr10 Cu34 Pd14 Sn2 bulk metallic glass in artificial corrosion pits in physiological saline (NaCl). It is found that Pd nanoparticles form in the interior of the pits during electrochemical dissolution. At a low pit growth potential, the change in lattice parameter of the Pd nanoparticles is consistent with the formation of palladium hydride. In addition, a salt layer very close to the dissolving interface is found to contain CuCl, PdCl2 , ZrOCl2 ∙8H2 O, Cu, Cu2 O, and several unidentified phases. The formation of Pd nanoparticles (16 ± 10 nm at 0.7 V vs Ag/AgCl) containing small amounts of the other alloying elements is confirmed by transmission electron microscopy. The addition of albumin and/or H2 O2 does not significantly influence the nature of the corrosion products. When considering the biological compatibility of the alloy, the biological reactivity of the corrosion products identified should be explored.
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Affiliation(s)
- Petre Flaviu Gostin
- School of Metallurgy and Materials; University of Birmingham; Edgbaston Birmingham B15 2TT UK
| | - Owen Addison
- School of Dentistry; University of Birmingham; Edgbaston Birmingham B15 2TT UK
| | | | - Yue Zhang
- School of Metallurgy and Materials; University of Birmingham; Edgbaston Birmingham B15 2TT UK
| | - Angus J. M. C. Cook
- School of Metallurgy and Materials; University of Birmingham; Edgbaston Birmingham B15 2TT UK
| | - Alethea Liens
- Université de Lyon; INSA-Lyon; Laboratoire MATEIS; UMR CNRS 5510; 20 Avenue Albert Einstein 69621 Villeurbanne Cedex France
| | - Mihai Stoica
- Laboratory of Metal Physics and Technology; Department of Materials; ETH Zürich; 8093 Zürich Switzerland
| | - Konstantin Ignatyev
- Diamond Light Source; Harwell Science and Innovation Campus; Didcot Oxfordshire OX11 0DE UK
| | - Steven R. Street
- School of Metallurgy and Materials; University of Birmingham; Edgbaston Birmingham B15 2TT UK
| | - Jing Wu
- School of Metallurgy and Materials; University of Birmingham; Edgbaston Birmingham B15 2TT UK
| | - Yu-Lung Chiu
- School of Metallurgy and Materials; University of Birmingham; Edgbaston Birmingham B15 2TT UK
| | - Alison J. Davenport
- School of Metallurgy and Materials; University of Birmingham; Edgbaston Birmingham B15 2TT UK
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Zhang Y, Davenport AJ, Burke B, Vyas N, Addison O. Effect of Zr Addition on the Corrosion of Ti in Acidic and Reactive Oxygen Species (ROS)-Containing Environments. ACS Biomater Sci Eng 2018; 4:1103-1111. [DOI: 10.1021/acsbiomaterials.7b00882] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Yue Zhang
- School of Metallurgy and Materials, University of Birmingham, Birmingham, B15 2TT, United Kingdom
| | - Alison J. Davenport
- School of Metallurgy and Materials, University of Birmingham, Birmingham, B15 2TT, United Kingdom
| | - Bernard Burke
- Biomaterials Unit, School of Dentistry, University of Birmingham, Birmingham B5 7EG, United Kingdom
- Faculty of Health & Life Sciences, Coventry University, Coventry CV1 5LW, United Kingdom
| | - Nina Vyas
- Biomaterials Unit, School of Dentistry, University of Birmingham, Birmingham B5 7EG, United Kingdom
| | - Owen Addison
- Biomaterials Unit, School of Dentistry, University of Birmingham, Birmingham B5 7EG, United Kingdom
- School of Dentistry, University of Alberta, Edmonton T6G 1C9, Canada
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3
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Bray JM, Davenport AJ, Ryder KS, Britton MM. Quantitative, In Situ Visualization of Metal-Ion Dissolution and Transport Using (1) H Magnetic Resonance Imaging. Angew Chem Int Ed Engl 2016; 55:9394-7. [PMID: 27329307 PMCID: PMC5094501 DOI: 10.1002/anie.201604310] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Indexed: 11/07/2022]
Abstract
Quantitative mapping of metal ions freely diffusing in solution is important across a diverse range of disciplines and is particularly significant for dissolution processes in batteries, metal corrosion, and electroplating/polishing of manufactured components. However, most current techniques are invasive, requiring sample extraction, insertion of an electrode, application of an electric potential or the inclusion of a molecular sensor. Thus, there is a need for techniques to visualize the distribution of metal ions non-invasively, in situ, quantitatively, in three dimensions (3D) and in real time. Here we have used (1) H magnetic resonance imaging (MRI) to make quantitative 3D maps showing evolution of the distribution of Cu(2+) ions, not directly visible by MRI, during the electrodissolution of copper, with high sensitivity and spatial resolution. The images are sensitive to the speciation of copper, the depletion of dissolved O2 in the electrolyte and show the dissolution of Cu(2+) ions is not uniform across the anode.
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Affiliation(s)
- Joshua M Bray
- School of Chemistry, University of Birmingham, Birmingham, B15 2TT, UK
| | - Alison J Davenport
- School of Metallurgy and Materials, University of Birmingham, Birmingham, B15 2TT, UK
| | - Karl S Ryder
- Materials Centre, Department of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | - Melanie M Britton
- School of Chemistry, University of Birmingham, Birmingham, B15 2TT, UK.
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4
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Bray JM, Davenport AJ, Ryder KS, Britton MM. Quantitative, In Situ Visualization of Metal‐Ion Dissolution and Transport Using
1
H Magnetic Resonance Imaging. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201604310] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Joshua M. Bray
- School of ChemistryUniversity of Birmingham Birmingham B15 2TT UK
| | - Alison J. Davenport
- School of Metallurgy and MaterialsUniversity of Birmingham Birmingham B15 2TT UK
| | - Karl S. Ryder
- Materials CentreDepartment of ChemistryUniversity of Leicester Leicester LE1 7RH UK
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Yu F, Addison O, Davenport AJ. A synergistic effect of albumin and H₂O₂ accelerates corrosion of Ti6Al4V. Acta Biomater 2015; 26:355-65. [PMID: 26238758 DOI: 10.1016/j.actbio.2015.07.046] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 07/22/2015] [Accepted: 07/30/2015] [Indexed: 10/23/2022]
Abstract
The synergistic effect of albumin and H2O2 on corrosion of titanium alloy Ti6Al4V in physiological saline was investigated with long-term immersion tests and electrochemical methods. It was found that in the presence of both albumin and H2O2, the rate of metal release in immersion tests was far higher than in the presence of either species alone. Electrochemical polarisation curves and potentiostatic tests showed that H2O2 increased both the rates of the anodic and cathodic reactions, whilst albumin significantly decreased the rate of the cathodic reaction and slightly decreased the rate of the anodic reaction. The synergistic effect of albumin and H2O2 during immersion tests was attributed to the effect of adsorption of albumin in lowering the rate of the cathodic reaction and thus lowering the open circuit potential into the active region of titanium where complexation by H2O2 increased the corrosion rate. The corrosion attack was found to be greater in the β-phase of the alloy. The findings suggest that current standard tests in physiological or phosphate-buffered saline may underestimate the rate of corrosion in the peri-implant environment, in which albumin is the predominant protein, and reactive oxygen species such as H2O2 can occur as a result of inflammatory reactions in response to surgery, infection, or implant corrosion products. STATEMENT OF SIGNIFICANCE Corrosion of many biomedical implant materials occurs in the body leading to adverse biological responses. Several components of the environment into which a metal implant is placed including proteins and products of cellular physiology, been shown to modify corrosion resistance. Previously all studies on such components including the common protein albumin and the inflammatory product H2O2 have considered the effects of these species in isolation. For the first time we report a synergistic interaction between albumin and H2O2 significantly accelerating corrosion of Ti6Al4V at physiological pH and temperature. This is attributed to an increased rate of the anodic reaction caused by H2O2 complexation of Ti, suppression of cathodic reaction by albumin adsorption shifting OCP to the active region of Ti6Al4V.
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Street SR, Mi N, Cook AJMC, Mohammed-Ali HB, Guo L, Rayment T, Davenport AJ. Atmospheric pitting corrosion of 304L stainless steel: the role of highly concentrated chloride solutions. Faraday Discuss 2015; 180:251-65. [DOI: 10.1039/c4fd00246f] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The morphology of atmospheric pitting corrosion in 304L stainless steel plate was analysed using MgCl2 droplets in relation to changes in relative humidity (RH) and chloride deposition density (CDD). It was found that highly reproducible morphologies occur that are distinct at different RH. Pitting at higher concentrations, i.e. lower RH, resulted in satellite pits forming around the perimeter of wide shallow dish regions. At higher RH, these satellite pits did not form and instead spiral attack into the shallow region was observed. Increasing CDD at saturation resulted in a very broad-mouthed pitting attack within the shallow dish region. Large data sets were used to find trends in pit size and morphology in what is essentially a heterogeneous alloy. Electrochemical experiments on 304 stainless steel wires in highly saturated solutions showed that the passive current density increased significantly above 3 M MgCl2 and the breakdown pitting potential dropped as the concentration increased. It is proposed that the shallow dish regions grow via enhanced dissolution of the passive film, whereas satellite pits and a spiral attack take place with active dissolution of bare metal surfaces.
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Affiliation(s)
- Steven R. Street
- University of Birmingham, School of Metallurgy and Materials
- Birmingham
- UK
| | - Na Mi
- University of Birmingham, School of Metallurgy and Materials
- Birmingham
- UK
| | | | | | - Liya Guo
- University of Birmingham, School of Metallurgy and Materials
- Birmingham
- UK
| | - Trevor Rayment
- Diamond Light Source, Harwell Science and Innovation Campus
- Oxford
- UK
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Britton MM, Bayley PM, Howlett PC, Davenport AJ, Forsyth M. In Situ, Real-Time Visualization of Electrochemistry Using Magnetic Resonance Imaging. J Phys Chem Lett 2013; 4:3019-3023. [PMID: 24265861 PMCID: PMC3831549 DOI: 10.1021/jz401415a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 08/22/2013] [Indexed: 05/27/2023]
Abstract
The drive to develop better electrochemical energy storage devices requires the development of not only new materials, but also better understanding of the underpinning chemical and dynamical processes within such devices during operation, for which new analytical techniques are required. Currently, there are few techniques that can probe local composition and transport in the electrolyte during battery operation. In this paper, we report a novel application of magnetic resonance imaging (MRI) for probing electrochemical processes in a model electrochemical cell. Using MRI, the transport and zinc and oxygen electrochemistry in an alkaline electrolyte, typical of that found in zinc-air batteries, are investigated. Magnetic resonance relaxation maps of the electrolyte are used to visualize the chemical composition and electrochemical processes occurring during discharge in this model metal-air battery. Such experiments will be useful in the development of new energy storage/conversion devices, as well as other electrochemical technologies.
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Affiliation(s)
- Melanie M Britton
- School of Chemistry, University of Birmingham , Birmingham, B15 2TT, United Kingdom
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Hammons JA, Davenport AJ, Ghahari SM, Monir M, Tinnes JP, Amri M, Terrill N, Marone F, Mokso R, Stampanoni M, Rayment T. Interfacial Phenomena during Salt Layer Formation under High Rate Dissolution Conditions. J Phys Chem B 2013; 117:6724-32. [DOI: 10.1021/jp311666w] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Joshua A. Hammons
- School of Chemistry, University of Birmingham, B15 2TT, Birmingham,
United Kingdom
| | - Alison J. Davenport
- School of Metallurgy
and Materials, University of Birmingham, B15 2TT, United Kingdom
| | - S. Majid Ghahari
- School of Metallurgy
and Materials, University of Birmingham, B15 2TT, United Kingdom
| | - Mehdi Monir
- School of Metallurgy
and Materials, University of Birmingham, B15 2TT, United Kingdom
| | - Jean-Phillipe Tinnes
- School of Chemistry, University of Birmingham, B15 2TT, Birmingham,
United Kingdom
| | - Mahrez Amri
- School of Chemistry, University of Birmingham, B15 2TT, Birmingham,
United Kingdom
| | - Nick Terrill
- Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation
Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - Federica Marone
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - Rajmund Mokso
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - Marco Stampanoni
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - Trevor Rayment
- Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation
Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
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Mittal S, Revell M, Barone F, Hardie DL, Matharu GS, Davenport AJ, Martin RA, Grant M, Mosselmans F, Pynsent P, Sumathi VP, Addison O, Revell PA, Buckley CD. Lymphoid aggregates that resemble tertiary lymphoid organs define a specific pathological subset in metal-on-metal hip replacements. PLoS One 2013; 8:e63470. [PMID: 23723985 PMCID: PMC3665779 DOI: 10.1371/journal.pone.0063470] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Accepted: 04/02/2013] [Indexed: 12/12/2022] Open
Abstract
Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) has been used to describe the histological lesion associated with metal-on-metal (M-M) bearings. We tested the hypothesis that the lymphoid aggregates, associated with ALVAL lesions resemble tertiary lymphoid organs (TLOs). Histopathological changes were examined in the periprosthetic tissue of 62 M-M hip replacements requiring revision surgery, with particular emphasis on the characteristics and pattern of the lymphocytic infiltrate. Immunofluorescence and immunohistochemistry were used to study the classical features of TLOs in cases where large organized lymphoid follicles were present. Synchrotron X-ray fluorescence (XRF) measurements were undertaken to detect localisation of implant derived ions/particles within the samples. Based on type of lymphocytic infiltrates, three different categories were recognised; diffuse aggregates (51%), T cell aggregates (20%), and organised lymphoid aggregates (29%). Further investigation of tissues with organised lymphoid aggregates showed that these tissues recapitulate many of the features of TLOs with T cells and B cells organised into discrete areas, the presence of follicular dendritic cells, acquisition of high endothelial venule like phenotype by blood vessels, expression of lymphoid chemokines and the presence of plasma cells. Co-localisation of implant-derived metals with lymphoid aggregates was observed. These findings suggest that in addition to the well described general foreign body reaction mediated by macrophages and a T cell mediated type IV hypersensitivity response, an under-recognized immunological reaction to metal wear debris involving B cells and the formation of tertiary lymphoid organs occurs in a distinct subset of patients with M-M implants.
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Affiliation(s)
- Saloni Mittal
- Rheumatology Research Group, Institute of Biomedical Research, MRC Centre for Immune Regulation, University of Birmingham, Birmingham, United Kingdom
- Royal Orthopedic Hospital, Birmingham, United Kingdom
| | | | - Francesca Barone
- Rheumatology Research Group, Institute of Biomedical Research, MRC Centre for Immune Regulation, University of Birmingham, Birmingham, United Kingdom
| | - Debbie L. Hardie
- Rheumatology Research Group, Institute of Biomedical Research, MRC Centre for Immune Regulation, University of Birmingham, Birmingham, United Kingdom
| | | | - Alison J. Davenport
- School of Metallurgy and Materials, University of Birmingham, Birmingham, United Kingdom
| | - Richard A. Martin
- School of Engineering and Applied Sciences & Aston Research Centre for Healthy Ageing, University of Aston, Birmingham, United Kingdom
| | - Melissa Grant
- Biomaterials Unit, School of Dentistry, University of Birmingham, Birmingham, United Kingdom
| | | | - Paul Pynsent
- Royal Orthopedic Hospital, Birmingham, United Kingdom
| | | | - Owen Addison
- Biomaterials Unit, School of Dentistry, University of Birmingham, Birmingham, United Kingdom
| | | | - Christopher D. Buckley
- Rheumatology Research Group, Institute of Biomedical Research, MRC Centre for Immune Regulation, University of Birmingham, Birmingham, United Kingdom
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Addison O, Davenport AJ, Newport RJ, Kalra S, Monir M, Mosselmans JFW, Proops D, Martin RA. Do 'passive' medical titanium surfaces deteriorate in service in the absence of wear? J R Soc Interface 2012; 9:3161-4. [PMID: 22832360 DOI: 10.1098/rsif.2012.0438] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Globally, more than 1000 tonnes of titanium (Ti) is implanted into patients in the form of biomedical devices on an annual basis. Ti is perceived to be 'biocompatible' owing to the presence of a robust passive oxide film (approx. 4 nm thick) at the metal surface. However, surface deterioration can lead to the release of Ti ions, and particles can arise as the result of wear and/or corrosion processes. This surface deterioration can result in peri-implant inflammation, leading to the premature loss of the implanted device or the requirement for surgical revision. Soft tissues surrounding commercially pure cranial anchorage devices (bone-anchored hearing aid) were investigated using synchrotron X-ray micro-fluorescence spectroscopy and X-ray absorption near edge structure. Here, we present the first experimental evidence that minimal load-bearing Ti implants, which are not subjected to macroscopic wear processes, can release Ti debris into the surrounding soft tissue. As such debris has been shown to be pro-inflammatory, we propose that such distributions of Ti are likely to effect to the service life of the device.
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Affiliation(s)
- O Addison
- Biomaterials Unit, School of Dentistry, University of Birmingham, Birmingham, UK.
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11
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Rayment T, Davenport AJ, Dent AJ, Tinnes JP, Wiltshire RJ, Martin C, Clark G, Quinn P, Mosselmans JFW. Characterisation of salt films on dissolving metal surfaces in artificial corrosion pits via in situ synchrotron X-ray diffraction. Electrochem commun 2008. [DOI: 10.1016/j.elecom.2008.03.018] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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12
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Wylie CM, Shelton RM, Fleming GJP, Davenport AJ. Corrosion of nickel-based dental casting alloys. Dent Mater 2007; 23:714-23. [PMID: 16949144 DOI: 10.1016/j.dental.2006.06.011] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2005] [Revised: 03/31/2006] [Accepted: 06/20/2006] [Indexed: 10/24/2022]
Abstract
OBJECTIVES To study the microstructure, corrosion behaviour and cell culture response of two nickel-based dental casting alloys before and after a heat treatment to simulate porcelain firing. METHODS The microstructure was studied using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). Corrosion behaviour was evaluated by electrochemical measurements in artificial saliva at different values of pH in the presence of a crevice. 3T3 mouse fibroblasts were exposed indirectly to alloy specimens and the number of viable cells counted after 3 and 6 days compared to a control culture. RESULTS Small changes in microstructure were observed after heat treatment but had a negligible effect on the corrosion properties in the conditions tested. The alloy with a lower bulk level of Cr (12.6 wt.%) showed lower corrosion resistance, indicated by an increased passive current density and this stability was greatly reduced at pH 2.5, where crevice corrosion was observed. Selective dissolution occurred at regions within the microstructure containing lower levels of Cr and Mo. Furthermore, the proliferation of 3T3 mouse fibroblasts was reduced (p<0.05) when exposed indirectly to this alloy. The alloy containing a higher level of Cr (25 wt.%) showed superior corrosion resistance, which was associated with a more uniform distribution of Cr in the alloy microstructure. SIGNIFICANCE The presence of crevices combined with an inhomogeneous distribution of Cr in the microstructure can lead to accelerated corrosion of Ni-based alloys with lower Cr contents. This effect can be avoided by increasing the Cr content of the alloy.
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Affiliation(s)
- Christopher M Wylie
- Department of Metallurgy and Materials, University of Birmingham, Birmingham B15 2TT, UK
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Davenport AJ, Gurnell AM, Armitage PD. Classifying urban rivers. Water Sci Technol 2001; 43:147-155. [PMID: 11419122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Classification systems have been developed over the last century as a tool to aid managers in the preservation, conservation, enhancement and management of rivers. The classification systems developed to date have been designed to differentiate between relatively unimpacted, mainly rural rivers. Urban rivers typically show poor water quality and biological diversity, and so most current classification systems tend to group urban rivers into a single "poor" category. In this paper we describe a hierarchical framework for recording information about urban rivers that allows a more sensitive description of these rivers enabling subdivision into several classes according to the purpose of the classification. The different levels in the hierarchy, the types of attributes that are to be recorded at each level, and the relational database structure for storing the data are described. The 100-500 m river stretch level in the hierarchy relates to the engineered modification of urban rivers and is the key to their classification. An example classification at this scale illustrates a link between engineering modification, bank and bed materials and the number and diversity of physical habitats present. This classification underlines the importance of adopting a hierarchy of nested spatial scales for data collection, classification and interpretation since it illustrates a clear link between characteristics at the stretch scale and at the finer habitat scale. The classification also illustrates the varied nature of urban rivers and the fact that even quite heavily engineered stretches can contain a diversity of habitat types.
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Affiliation(s)
- A J Davenport
- University of Birmingham, School of Geography and Environmental Sciences, Edgbaston, Birmingham, B15 2TT, UK
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15
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Wang J, Ocko BM, Davenport AJ, Isaacs HS. In situ x-ray-diffraction and -reflectivity studies of the Au(111)/electrolyte interface: Reconstruction and anion adsorption. Phys Rev B Condens Matter 1992; 46:10321-10338. [PMID: 10002877 DOI: 10.1103/physrevb.46.10321] [Citation(s) in RCA: 124] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Abstract
Synchrotron surface x-ray scattering (SXS) studies have been carried out at the Au(lll)/electrolyte interface to determine the influence of surface charge on the microscopic arrangement of gold surface atoms. At the electrochemical interface, the surface charge density can be continuously varied by controlling the applied potential. The top layer of gold atoms undergoes a reversible phase transition between the (1 x 1) bulk termination and a (23 x radical3) reconstructed phase on changing the electrode potential. In order to differentiate the respective roles of surface charge and adsorbates, studies were carried out in 0.1 M NaF, NaCl, and NaBr solutions. The phase transition occurs at an induced surface charge density of 0.07 +/- 0.02 electron per atom in all three solutions.
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