Osmium alloys

Because of its hard brittle nature, the metal osmium has few uses. However, the powdered form can be sintered under high pressure and temperatures to form some useful products, despite its toxicity and malodor. Its main use is as an alloy to manufacture devices that resist wear and stand up to constant use. As an alloy, osmium loses both its foul odor and toxicity. Some of these products are ballpoint and fountain pen tips, needles for record players, and pivot points for compass needles. Osmium alloys are also used for contact points on special switches and other devices that require reduced frictional wear. 

Osmium isotopes currently provide the strongest case for mineral-to-mineral disequilibrium, and for mineral-melt disequilibrium available from observations on natural rocks. Thus, both osmium alloys and sulfides from ophiolites and mantle xenoliths have yielded strongly heterogeneous osmium isotope ratios (Alard et al., 2002 Meibom et al., 2002). The most remarkable aspect of these results is that these ophiolites were emplaced in Phanerozoic times, yet they contain osmiumbearing phases that have retained model ages in excess of 2 Ga in some cases. The melts that were extracted from these ophiolitic peridotites contained almost certainly much more radiogenic osmium and could, in any case, not have been in osmium-isotopic equilibrium with all of these isotopically diverse residual phases. 

Figure 4 is a scale drawing of a spreading resistance probe tip and the nominal contact size for a 10 gram probe load. The probe tips are a hard tungsten-osmium alloy they have a... 

Steel appears to form valuable alloys with a very small proportion of some other metals. With a little silicon and aluminum, it yields a metal equal to the Indian wootz and with small quantities of silver, platinum, rhodium, palladium, and even iridium and osmium, alloys of prodigious hardness and toughness are obtained. part of silver is sufficient to effect a marked improvement. 

Osmium and Osmium Alloys Applications. Osmium is used as a component in hard, wear- and corrosion-resistant alloys, as surface coatings of W-based filaments of electric bulbs, cathodes of electron tubes, and thermo-ionic sources. Osmium itself. Os alloys, and Os compounds are strong and selective oxidation catalysts. Commercial grades available are powder in 99.6% and 99.95% purity, OSO4, and chemical compounds. 

Phases and Phase Equilibria. Selected phase diagrams are shown in Figs. 3.1-339-3.1-342 [1.216]. Continuous series of solid solution are formed with Re and Ru. Miscibility gaps exist with Ir, Pd and Pt. The solid solubility in the Os—W system are 48.5 at.% for W and 5 at.% for Os. Osmium alloyed to Fe lowers the y-a transition temperature considerably (Fig. 3.1-343 [1.297]). Thermodynamic data are given in Table 3.1-267 [1.216] and molar heat capacities in Table 3.1-190. Table 3.1-268 gives structures and lattice parameters of intermediate compounds with Ir, Ru, Pt, and W [1.216]. 

Iridosmine = Iridium osmium alloy Fe-Cordierite = Sekaninaite Iserine (Nigrine) = Ilmenite + Rutile Isoplatinocopper = Hongshiite Isostannite = Kesterite-Ferrokesterite Jade = Jadeite (Nephrite)... 

Orthite = Allanite Orthose = Orthoclase Osmiridium = Iridium-osmium alloy Outremer = Ultramarine (Lazurite)... 

The element forms an alloy with osmium which is used for tipping pens and compass bearings. 

High Temperature Properties. There are marked differences in the abihty of PGMs to resist high temperature oxidation. Many technological appHcations, particularly in the form of platinum-based alloys, arise from the resistance of platinum, rhodium, and iridium to oxidation at high temperatures. Osmium and mthenium are not used in oxidation-resistant appHcations owing to the formation of volatile oxides. High temperature oxidation behavior is summarized in Table 4. 

Ruthenium, iridium and osmium Baths based on the complex anion (NRu2Clg(H20)2) are best for ruthenium electrodeposition. Being strongly acid, however, they attack the Ni-Fe or Co-Fe-V alloys used in reed switches. Reacting the complex with oxalic acid gives a solution from which ruthenium can be deposited at neutral pH. To maintain stability, it is necessary to operate the bath with an ion-selective membrane between the electrodes . 

Ruthenium nowadays finds many uses in the electronics industry, particularly for making resistor tracks. It is used as an ingredient in various catalysts and, importantly, in electrode materials, e.g. Ru02-coated titanium elements in the chloralkali industry. Osmium tetroxide is a very useful organic oxidant and, classically, is used as a tissue stain. Both elements are employed in making certain platinum alloys. 

Plutonium-noble metal compounds have both technological and theoretical importance. Modeling of nuclear fuel interactions with refractory containers and extension of alloy bonding theories to include actinides require accurate thermodynamic properties of these materials. Plutonium was shown to react with noble metals such as platinum, rhodium, iridium, ruthenium, and osmium to form highly stable intermetallics. 

Because of- the similarity in the backscattering properties of platinum and iridium, we were not able to distinguish between neighboring platinum and iridium atoms in the analysis of the EXAFS associated with either component of platinum-iridium alloys or clusters. In this respect, the situation is very different from that for systems like ruthenium-copper, osmium-copper, or rhodium-copper. Therefore, we concentrated on the determination of interatomic distances. To obtain accurate values of interatomic distances, it is necessary to have precise information on phase shifts. For the platinum-iridium system, there is no problem in this regard, since the phase shifts of platinum and iridium are not very different. Hence the uncertainty in the phase shift of a platinum-iridium atom pair is very small. 

Salomon and Shirley [296] have performed Mossbauer-source experiments on Fe( Os) alloys with less than 0.1 at% osmium against a metallic Ir absorber. Their spectra were well-resolved magnetic eight-line patterns, which the authors could satisfactorily analyze using the Hamiltonian... 

Silvery, shiny, and hard. Unique metal, gives off an odor as it forms volatile 0s04 on the surface (oxidation states 81). Osmium is the densest element (22.6 g cm3 record ). Was replaced in filaments (Osram) by the cheaper tungsten. Used in platinum alloys and as a catalyst. Haber s first catalyst in ammonia synthesis was osmium, which fortunately could be replaced by doped iron. The addition of as little as 1 to 2 % of this expensive metal increases the strength of steel (e.g. fountain-pen tips, early gramophone needles, syringe needles). 

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