The search for new hard materials is often challenging, but strongly motivated by the vast application potential such materials hold. Ti3Au exhibits high hardness values (about four times those of pure Ti and most steel alloys), reduced coefficient of friction and wear rates, and biocompatibility, all of which are optimal traits for orthopedic, dental, and prosthetic applications. In addition, the ability of this compound to adhere to ceramic parts can reduce both the weight and the cost of medical components. The fourfold increase in the hardness of Ti3Au compared to other Ti-Au alloys and compounds can be attributed to the elevated valence electron density, the reduced bond length, and the pseudogap formation. Understanding the origin of hardness in this intermetallic compound provides an avenue toward designing superior biocompatible, hard materials.
Hexagonal close-packed iron (hcp-Fe) is a main component of Earth’s inner core. The difference in density between hcp-Fe and the inner core in the Preliminary Reference Earth Model (PREM) shows a density deficit, which implies an existence of light elements in the core. Sound velocities then provide an important constraint on the amount and kind of light elements in the core. Although seismological observations provide density-sound velocity data of Earth’s core, there are few measurements in controlled laboratory conditions for comparison. We report the compressional sound velocity (V P) of hcp-Fe up to 163 GPa and 3000 K using inelastic x-ray scattering from a laser-heated sample in a diamond anvil cell. We propose a new high-temperature Birch’s law for hcp-Fe, which gives us the V P of pure hcp-Fe up to core conditions. We find that Earth’s inner core has a 4 to 5% smaller density and a 4 to 10% smaller V P than hcp-Fe. Our results demonstrate that components other than Fe in Earth’s core are required to explain Earth’s core density and velocity deficits compared to hcp-Fe. Assuming that the temperature effects on iron alloys are the same as those on hcp-Fe, we narrow down light elements in the inner core in terms of the velocity deficit. Hydrogen is a good candidate; thus, Earth’s core may be a hidden hydrogen reservoir. Silicon and sulfur are also possible candidates and could show good agreement with PREM if we consider the presence of some melt in the inner core, anelasticity, and/or a premelting effect.
Foliar sprays of iron (Fe) and zinc (Zn) fertilisers are known to be an effective way to improve Fe and Zn concentrations in rice grain. However, results can differ significantly among different rice cultivars and/or types of foliar fertiliser. In this study, several Fe-rich rice cultivars were used to identify an effective foliar fertiliser for optimal Fe and Zn enrichment of rice grain.
In this work, textures measured by electron backscatter diffraction (EBSD) and X-ray diffraction in rolled FePd alloys were compared. The effect of scanning size used for EBSD measurements was investigated. The correlation coefficient was first proposed to quantify the similarity of the orientation density profile along the α- and β-fibers after cold rolling. The correlation coefficient is approximately 1 for a scanning step range of 1-20μm after 50% and 88% reduction. A large scanning step can capture the main components of the macrotexture in EBSD measurements. Thus, the macrotexture measured by EBSD provides another method for the quality control of texture.
Replacing noble metals in heterogeneous catalysts by low-cost substitutes has driven scientific and industrial research for more than 100 years. Cheap and ubiquitous iron is especially desirable, because it does not bear potential health risks like, for example, nickel. To purify the ethylene feed for the production of polyethylene, the semi-hydrogenation of acetylene is applied (80 × 10(6) tons per annum; refs 1-3). The presence of small and separated transition-metal atom ensembles (so-called site-isolation), and the suppression of hydride formation are beneficial for the catalytic performance. Iron catalysts necessitate at least 50 bar and 100 °C for the hydrogenation of unsaturated C-C bonds, showing only limited selectivity towards semi-hydrogenation. Recent innovation in catalytic semi-hydrogenation is based on computational screening of substitutional alloys to identify promising metal combinations using scaling functions and the experimental realization of the site-isolation concept employing structurally well-ordered and in situ stable intermetallic compounds of Ga with Pd (refs 15-19). The stability enables a knowledge-based development by assigning the observed catalytic properties to the crystal and electronic structures of the intermetallic compounds. Following this approach, we identified the low-cost and environmentally benign intermetallic compound Al(13)Fe(4) as an active and selective semi-hydrogenation catalyst. This knowledge-based development might prove applicable to a wide range of heterogeneously catalysed reactions.
There are serious concerns on the toxicity of vanadium in Ti-6Al-4V alloy. In this regard, we describe the biological footprint of Ti-6Al-4V and compare with a viable alternate Ti-6Al-7Nb alloy, in terms of novel experimentation pertaining to cellular activity that include qualitative and quantitative analysis of Feret’s diameter of cells, area, and perimeter, and proteins-actin, vinculin, and fibronectin. Interestingly, Ti-6Al-7Nb was characterized by superior cell attachment, proliferation, viability, morphology, and spread, which were significantly different from Ti-6Al-4V alloy. Additionally, immunofluorescence studies demonstrated stronger vinculin signals associated with actin stress fibers in the outer regions of the cells and cellular extensions in Ti-6Al-7Nb alloy. These striking observations suggest enhanced cell-substrate interaction and activity on the surface of niobium-containing titanium alloy. The significant differences in the cellular response between the two alloys clearly point to the determining role of alloying element (Nb versus V) in a conclusive manner. Based on this study, next generation of titanium alloys is proposed to focus on niobium-containing alloy. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.
Ti-51Ni (at%) alloys including coherent precipitates of Ti3Ni4 exhibits thermally-induced B2-R transformation. If the Ti3Ni4 is formed under tensile stress, it orientates preferentially so that its habit plane becomes perpendicular to the tensile axis. In such specimens, stress-induced reverse R-B2 transformation is reported to occur. In the present study, the stress-induced reverse R-B2 transformation behavior was studied by infrared camera and in situ X-ray analysis. The infrared camera observation revealed that the temperature of the specimen decreases homogeneously by the application of tensile stress within the resolution of the camera. The in situ X-ray analysis revealed that stress-induced reverse R-B2 transformation and rearrangement of variants of the R-phase occurs simultaneously in the specimen.
Mechanical and electrochemical characterisation of new Ti-Mo-Nb-Zr alloys for biomedical applications
- Journal of the mechanical behavior of biomedical materials
- Published over 3 years ago
The development and characterisation of new metallic biomaterials that contain non-toxic and non-allergic elements but possess low elastic modulus and low biodegradation rates, has become a topic of serious investigation in orthopaedic implant application. The lowering of elastic modulus and improving of corrosion resistance can be achieved by specific chemical alloying and super-elasticity effects, associated with a stress-induced phase transformation from the BCC metastable beta phase to the orthorhombic α″ martensite. Using this framework, this paper focuses on the effect of Nb and/or Zr micro-additions on the elastic modulus/yield strength balance and discusses microstructure, and the mechanical and electrochemical behaviour of four new β-Ti-8Mo-xNb-xZr (x=2-5) alloys, using tensile tests, X-ray diffraction, SEM characterisation, ultrasound technique and potentiodynamic polarisation methods. The results reveal that the alloys exhibit a pronounced microstructural sensitivity response, with alloying elements and excellent agreement between β-stability and high mechanical strength, with increasing Nb additions. Although all the alloys possess excellent corrosion resistance and low Young׳s modulus, Ti-8Mo-4Nb-2Zr alloy, which consists of β+α'‘ phases, exhibits a low Young modulus of 35GPa, which is lower than those of the commercial alloys already used in biomedical implantation. The significant corrosion resistance, nontoxicity and better mechanical compatibility are properties pertinent to preventing stress shielding and bone resorption in orthopaedic implant applications.
Athletic centers have been locations for the transmission of community-acquired infections. This study assessed the capacity of copper alloys to reduce the bacterial burden associated with high-touch athletic center equipment. Copper alloy weights and grips were rotated with rubber coated and stainless steel controls in an undergraduate college athletic center over a 16-month period. The athletic center is used by college athletic teams, student body, and local community.
The low performance or high cost of commercially available conductive inks limits the advancement of printed electronics. This article studies the explosion of metal wires in aqueous solutions as a simple, low-cost, and environmentally friendly method to prepare metallic nanoparticles consisting of Cu and Cu alloys for use in affordable, highly conductive inks. Addition of 0.2 M ascorbic acid to an aqueous explosion medium prevented the formation of Cu2O shells around Cu nanoparticles, and allowed for the printing of conductive lines directly from these nanoparticles with no post-treatment. Cu alloy nanoparticles were generated from metal wires that were alloyed as purchased, or from two wires of different metals that were twisted together. Cu nanoparticles alloyed with 1% Sn, 5% Ag, 5% Ni and 30% Ni had electrical conductivities similar to Cu but unlike Cu, remained conductive after 24 hrs at 85 °C and 85% RH.