Assessing the biocompatibility of NiTi shape memory alloys used for medical applications

The present paper reviews aspects related to the biocompatibility of NiTi shape memory alloys used for medical applications. These smart metallic materials, which are characterised by outstanding mechanical properties, have been gaining increasing importance over the last two decades in many minimal invasive surgery and diagnostic applications, as well as for other uses, such as in orthodontic appliances. Due to the presence of high amounts of Ni, the cytotoxicity of such alloys is under scrutiny. In this review paper we analyse work published on the biocompatibility of NiTi alloys, considering aspects related to: (1) corrosion properties and the different methods used to test them, as well as specimen surface states; (2) biocompatibility tests in vitro and in vivo; (3) the release of Ni ions. It is shown that NiTi shape memory alloys are generally characterised by good corrosion properties, in most cases superior to those of conventional stainless steel or Co–Cr–Mo-based biomedical materials. The majority of biocompatibility studies suggest that these alloys have low cytotoxicity (both in vitro and in vivo) as well as low genotoxicity. The release of Ni ions depends on the surface state and the surface chemistry. Smooth surfaces with well-controlled structures and chemistries of the outermost protective TiO₂ layer lead to negligible release of Ni ions, with concentrations below the normal human daily intake.     

Electrochemical characterisation of dental alloys: its possibilities and limitations

Dental alloys are metallic biomaterials which have a broad variation of composition compared to technical alloys. It is therefore in the interest of patients and technicians to conduct a good assessment of the electrochemical behaviour of dental alloys in order to collect information about their corrosion resistance. The purpose of this work was to demonstrate possibilities and limitations of two electrochemical techniques: the voltammetry of immobilised microparticles (ViMP) onto lead, and cyclic voltammetry measurements with the help of the mini-cell system (MCS). Based on fingerprints obtained from ViMP it was possible to analyse and differentiate the dental alloys. The results obtained by MCS were comparable with ViMP, but give a better understanding of the corrosion behaviour of the materials.     

Chemical short range order in MgPb alloys

Magnesium and its alloys are the ideal materials for the automotive and aerospace applications due to their light weight, excellent physical and mechanical properties. In recent years, great effort is being made to synthesise Mg-alloys which are superior in corrosion performance and endowed with required thermal and mechanical properties. Despite of the growing interest in such alloys, very little studies exist which analyse the microscopic level bonding and the atomic order which are ultimately responsible for their thermal stability and synthesisation. In the present work, we have used the compound formation model (2Mg + Pb?Mg₂Pb) to establish the interconnection between the microscopic interactions to the observed thermodynamic properties. It has been used to compute the concentration and the temperature dependence of the excess free energy, concentration fluctuations and chemical short range order which suggests that a reasonable degree of chemical order exist in the alloys.     

Quantitative analysis of the structure in the fracture zone of silicon carbide

Summary Technical high-temperature ceramics replace metals and alloys in increasing domains because of their special chemical and physical properties. To proof the applicability of ceramics at high temperatures under load it is necessary to analyse the fracture behaviour and to characterize the fracture mechanisms. One possibility is the analysis of the fracture surfaces and the subsequent correlation between structure parameters and geometric parameters of the fracture surface to achieve a quantitative fractography for ceramics. In this paper first steps towards this target will be presented by the example of two SiC qualities. The selected SiC qualities are: one hot isostatically pressed SiC material (SiC-HD) and one quality which is alloyed with 5% AlN.

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Quantitative Gefügeanalyse in der Bruchzone von Siliciumcarbid

     

Vacancy assisted diffusion on single-atom surface alloys

Bimetallic surfaces can exhibit an improved catalytic activity through tailoring the concentration and/or the arrangement of the two metallic components. However, in order to be catalytically active, the active bimetallic surface structure has to be stable under operating conditions. Typically, structural changes in metals occur via vacancy diffusion. Based on the first-principles determination of formation energies and diffusion barriers we have performed kinetic Monte-Carlo (kMC) simulations to analyse the (meta-)stability of PtRu/Ru(0001), AgPd/Pd(111), PtAu/Au(111) and InCu/Cu(100) surface alloys. In a first step, here we consider single-atom alloys together with one vacancy per simulation cell. We will present results of the time evolution of these structures and analyse them in terms of the interaction between the constituents of the bimetallic surface.     

储氢合金抗气体杂质毒化的研究进展

本文综述了氢气中的不同杂质气体对储氢合金吸放氢性能的影响。主要评价了LaNi4.7Al0.3、LaNi5、Fe-Ti、ZrCr2-xFex、Ti(Fe,Mn)等合金及它们的氢化物被CO、CO2、H2S等气体毒化的情况,并通过分析目前提升储氢合金抗毒化能力的主要方法及其使用效果,总结了合金抗毒化研究进展,为今后的发展提出了一些新思路。     

缺陷对混合稀土贮氢合金性能的影响

贮氢合金是一种重要的功能材料。在多种贮氢合金中,AB~5型稀土系贮氢合金的应用最为广泛。本文用正电子湮没技术(PAT)对AB~5型混合稀土贮氢合金的缺陷进行了研究,并结合X射线衍射(XRD)测试、循环伏安(CV)测试以及合金容量的测定,对合金的结构及性能进行了研究。结果表明,合金微观缺陷的存在能大幅度提高金的性能。     

Electrodeposition of cobalt–tungsten alloys and their application for surface engineering

Applying electrochemically deposited coatings is a convenient way to improve surface properties of a substrate metal. Today materials for applications are frequently selected according to their functional properties. Nowadays theoretical and practical studies of the co-deposition of tungsten with iron group metals are conducted worldwide, and interest for these studies increases. Tungsten alloys of iron group metals have a high melting point and are often considered high-performance alloys, and the attractiveness in those has been driven by their outstanding properties and multiple possible applications. That research is encouraged by the pronounced mechanical, tribological, and magnetic properties as well as the corrosion resistance of tungsten alloys. The magnetic properties of electrodeposited Co–W alloys are of interest in recording media and remotely-actuated micro-/nano-electromechanical systems. The given research presents an overview of versatile possibilities of Co–W alloys as multiscale materials obtained by electrodeposition from citrate solutions at pH 5–8 and temperatures 20–60°C. The paper discusses electrodeposited tungsten alloys as suitable candidates to meet many technological demands at macro-, micro- and nano-scale as coating films, microbumps and nanowires.     

Second Generation Lead-free Solder Alloys – A Challenge to Thermodynamics

Summary. For environmental reasons, lead has to be removed from solder alloys used for interconnection purposes in electronics equipment. A new series of alloys, mainly based upon tin, and often containing copper and silver, has been evolved by empirical reasoning. A more theoretical approach is now being pursued, using thermodynamic principles, to produce the second generation of solder alloys. The paper outlines the soldering process, the requirements of solder alloys, and the various mechanisms (such as overload, fatigue, creep, and thermomechanical fatigue) that are potential causes of failure in service. It also describes from the manufacturing and the performance perspectives, the physical and mechanical properties necessary for reliable solder joints. These include conductivity, melting point, strength, ductility, and thermal stability of microstructure. The challenging question is posed as to how can thermodynamics contribute to prescribing and developing an improved series of alloys?     

Second Generation Lead-free Solder Alloys – A Challenge to Thermodynamics

For environmental reasons, lead has to be removed from solder alloys used for interconnection purposes in electronics equipment. A new series of alloys, mainly based upon tin, and often containing copper and silver, has been evolved by empirical reasoning. A more theoretical approach is now being pursued, using thermodynamic principles, to produce the second generation of solder alloys. The paper outlines the soldering process, the requirements of solder alloys, and the various mechanisms (such as overload, fatigue, creep, and thermomechanical fatigue) that are potential causes of failure in service. It also describes from the manufacturing and the performance perspectives, the physical and mechanical properties necessary for reliable solder joints. These include conductivity, melting point, strength, ductility, and thermal stability of microstructure. The challenging question is posed as to how can thermodynamics contribute to prescribing and developing an improved series of alloys?     

Colorimetric determination of iron in titanium alloys

There is need for an improved method for the determination of iron in titanium alloys. In this paper a colorimetric method using o-phenanthroline is proposed. The method is applicable to the range of 0.02 to 9 per cent. iron. Two modifications of a basic procedure are described. One modification, applicable to ordinary titanium alloys, is a direct method. A second modification, applicable to alloys containing large amounts of certain alloying elements, calls for a prior separation of the iron by an ether extraction. In a direct method a one gram sample is dissolved in hydrochloric acid and an aliquot of the solution taken. Hydroxylamine and ammonium tartrate are added, the pH of the solution is adjusted by the addition of sodium acetate, and o-phenanthroline added. A study was made to find the best pH and optimum amount of o-phenanthroline for the development of the color.     

Comments on the paper: “Accurate quantitative analysis of gold alloys using multi-pulse laser-induced breakdown spectroscopy and a correlation-based calibration method”

The problem of finding new methods for the analysis of precious alloys has stimulated, in recent years, a number of different proposals for improving the analytical procedures introducing more robust calibration (or calibration-free) methods. In the paper “Accurate quantitative analysis of gold alloys using multi-pulse laser-induced breakdown spectroscopy and a correlation-based calibration method” by G. Galbács, N.Jedinski, G.Cseh, Z. Galbács and L. Túri [Spectrochimica Acta Part B, Volume 63, Issue 5, 591–597 (May 2008)] the authors proposed the use of multiple-pulse LIBS and a correlation-based method for building calibration curves for quantitative analysis of gold alloys. The method is proposed for gold alloys prepared using a fixed proportion of the alloying element. The general case where the relative concentration of the elements of the matrix is not a priori known is not discussed in the paper. In this communication, we will demonstrate that the method proposed is extremely fragile against matrix effects, and therefore cannot be usefully applied for the purpose of actual analytical measurements on gold alloys without a previous knowledge of the matrix composition.     

Determination of tin in titanium alloys

Tin-titanium alloys are becoming increasingly important; consequently a good method is needed for the determination of tin in this type of material. In this paper an accurate iodometric procedure is proposed for the determination. The sample is dissolved in sulfuric acid and the titanium oxidized with potassium permanganate. Tartaric acid is added and the tin precipitated with hydrogen, sulfide. The sulfide precipitate is dissolved in a mixture of sulfuric, perchloric and nitric acids and the solution evaporated to fumes of sulfuric acid. Water and hydrochloric acid are added, and the tin is reduced with lead and antimony trichloride and titrated with iodine. A study was made of the interfering elements that might be found in titanium alloys. The effect of antimony trichloride in reducing interference from copper was investigated. The method is recommended for titanium alloys containing 0.05 to 5.0 per cent. tin.     

熔盐电解法制备稀土合金研究进展

熔盐电解法制备稀土合金具有成本低、成份均匀且容易控制、质量较好、易实现连续化生产等优势.本文结合稀土合金在金属结构材料、磁性材料和贮氢材料中的应用,在介绍熔盐电解的知识进展的基础上,综述了稀土分别与镁、铝、铁、钴、镍、铜等组成的合金的熔盐电解制备研究进展,并对以后的研究工作进行展望.     

Determination of bismuth in nickel-base alloys by atomic absorption spectrometry with introduction of solid samples into an induction furnace

Atomic absorption spectrometry with an induction furnace is applicable'to the determination of bismuth at 0.02–10 μg g^-1 levels in 1–30-mg samples of nickel-base alloys dropped into the furnace. Calibration graphs of peak absorbance versus mass of bismuth are constructed by use of standardised alloys. Samples of alloys can be added to the furnace at 2.5-min intervals. Calibration graphs, accuracy, precision and limits of detection of the method are discussed for 26 alloys. Accuracy is assessed by comparing the induction furnace results with results supplied with the alloys, and with results obtained for solutions of the alloys by atomic absorption spectrometry in association with hydride generation or a mini-Massmann furnace. With alloys containing more than 0.1 μg Bi g^-1, relative standard deviations by the induction furnace method are usually < 15%. The limit of detection for bismuth is 0.02 μg g^-1     

A new approach to limit the coordination number in alloys I: Binary alloys of vanadium with IIIb and IVb elements

The present paper is a trial to limit the coordination sphere and hence the coordination number of atoms in alloys. This study shows that the average weighted coordination number of binary alloys as a whole lies in between those of the component atoms. This result seems to be encouraging. The coordination numbers of different atoms in the known 26 binary alloys of vanadium are determined using two different methods, compared and discussed.With 1 Figure     

The polarographic determination of indium in zinc-base alloys : The determination of indium in mazak alloys

In this paper, the development of a co-precipitation method for the separation of indium from zinc alloys is described and a method for the determination of indium down to 0.5 p.p.m. in mazak alloys is presented. Results obtained in trials of this method are given and the final conclusions regarding this and previously developed methods are included.     

硼和铈对Cu-Fe-P合金显微组织和性能的影响

Cu-Fe-P系合金是广泛应用的制造集成电路引线框架的材料。本文通过对Cu-0．22Fe-0．06P，Cu-0．22Fe-0．06P-0．05Ce，Cu-0．22Fe-O．06P-0．02B和Cu-0．22Fe-0．06P-0．05Ce-0．02B（％，质量分数）这4种合金的杂质元素含量、显微组织、力学性能和导电率进行测试分析，研究了添加铈和硼对Cu-Fe-P合金纯净度、组织和性能的影响。结果表明，添加微量的铈和硼，一方面具有显著的脱S，Bi，Pb等杂质元素作用；另一方面显著地提高合金的再结晶温度，使合金经冷轧加工＋时效处理后可以获得加工硬化和时效强化的效果，而对导电性的影响微小，从而使合金获得高强度和高导电率的良好结合。     

体外电化学测试对镁合金体内降解行为的预测

可生物降解镁合金因同时具有优良的生物相容性和力学性能,在生物医学界显示出其作为新型骨科内植入物的巨大潜在优势和市场前景。目前,作为制约镁合金医用产业化的关键因素,即过快的降解速率已经成为研究重点。本文回顾了体外电化学测试技术对镁合金抗腐蚀性能的研究,并分析了模拟腐蚀体系对镁合金腐蚀行为的影响;同时评估了电化学测试方法作为快速有效预测镁合金体内降解性能前期分析手段的可行性与局限性。最后,对如何发展更合理的体外电化学测试技术来预测镁合金体内降解提出了可能的解决方法及构思。     

Electrograining of aluminium in HCl: effect of the alloy for high‐speed processing lines

Electrograining of aluminium in hydrochloric acid is one of the most commonly used processes for manufacturing printing lithographic plates. Two of the main features to be taken into account are the final morphology of the electrograined surface and the susceptibility of the alloy to be processed or, more specifically, the speed of the processing line. Both issues determine the efficiency of the production in terms of quality and time. In this work, a widely used commercial aluminium alloy (1050) is compared with a new experimental one (1050 modified with Zn) and with a higher strength alloy (namely 1020). In order to analyse their response to a.c. graining in HCl for high‐speed lines, some techniques such as image analysis or interferometry have been used. In general, the alloys doped with Zn and Mg present a better response to litho processing in terms of graining activity and reduction of streakiness when treatment of lower time periods is applied due to their influence as pitting initiators. Copyright © 2010 John Wiley & Sons, Ltd.