Palladium mechanical properties

Dentistry. Most casting alloys meet the composition and properties criteria of specification no. 5 of the American Dental Association (37) which prescribes four types of alloy systems constituted of gold—silver—copper with addition of platinum, palladium, and 2inc. Composition ranges are specified, as are mechanical properties and minimum fusion temperatures. Wrought alloys for plates also may include the same constituents. Similarly, specification no. 7 prescribes nickel and two types of alloys for dental wires with the same alloy constituents (see Dental materials). 

Physical and Mechanical Properties. Whereas there are some similarities in the physical and chemical properties between corresponding members of the PGM triads, eg, platinum and palladium, the PGMs taken as a unit exhibit a wide range of properties (2). Some of the most important are summarized in Table 2. 

Thus, changes in the phase composition of a membrane as a result of its operation may substantially alter local mechanical characteristics, a process that should be taken into account and controlled when analyzing experiments in which intense flows of hydrogen pass through a palladium membrane. The model also makes it possible to relate independent experimental data on equilibrium, transport, and mechanical properties of palladium membranes. The estimates obtained are in close agreement with a large numbers of experimental data [200-202] on the behavior of various characteristics of palladium membranes with different prehistories and under different condition of hydrogen transport. 

Not only the permeability, permselectivity and mechanical properties, but also the catalytic properties are affected by the two hydride forms that can exist in palladium. The a phase corresponds to solid solutions with a H/Pd ratio of about 0.1 and the P phase with a H/Pd ratio of about 0.6. The phase change is associated with a large change in lattice constant that often leads to microcracks and distortion in the palladium membrane. As a result, the mechanical properties are reduced. The transformation depends on the operating conditions such as temperature and hydrogen partial pressure. Repeated thermal cycles, for example, between 100 and 250 C under 1 atm of hydrogen pressure can make a 0.1 mm thick Pd foil expand to become 30 times thicker [Armor, 1992]. 

The synthesis of alternating copolymers from carbon monoxide (CO) and olefins using palladium catalysts is currently an area of intense research. In cases where a-olefins are used, the regiochemistry (head/tail orientations) and stereochemistry (tacticity) of olefin insertion have a strong influence on the physical and mechanical properties of the polymers. Unlike regioregular a-olefins homopolymers, these copolymers have a directionality along the polymer backbone due to the incorporation of CO. Therefore isotactic, regioregular CO/a-olefin polymers are chiral by virtue of their main-chain stereochemistry (Scheme 11). 

The palladium-silver alloy membrane system was successfully commercialized in the early 1960s [12], but the reduction of palladium content by the addition of silver would still not be a cost-effective alternative for large-scale processes [42] unless micron-scale films could be prepared, a goal currently being addressed by many researchers. In recent years, the Pd-Cu system has been the most heavily investigated alloy for hydrogen membrane applications due to the high permeability of select alloys [67, 90, 91], enhanced mechanical properties [92] and reported chemical resistance. The elevated permeability identifled for select Pd-Cu alloys is attributed to an increase in both the solubility and diffusivity of the B2 crystalline phase [86-88] as compared to the face-centered-cubic (fee) phase that exhibits permeability values proportional to the Pd-content [89, 91, 93]. 

R. Foley, K. Rebeiz, S. Nesbit, A. Craft, Influence of partial hydride formation/ decomposition on the mechanical properties of palladium, Scr. Mater. 1996, 35(8), 1013-1018. 

F. N. Berseneva, 1. A. Mikhaylova, N. 1. Timofeyev, The influence of hydrogen on the phase composition and physico-mechanical properties of the membrane palladium-based alloy V-1, Phys. Met. Metall. 1992, 72(2), 151-156. 

I. N. Avertseva, M. V. Raevskaya, Hydrogen permeability and mechanical properties of palladium alloyed with ruthenium, samarium, yttrium, and neodymium, Phys. Met. Metall. 1994, 77(5), 518-521. 

Craig and coworkers also used metallopincer complexes to form supramolecular polymer networks [143, 144]. In their work, poly(4-vinylpyridine)s were synthesized and subsequently cross-linked by addition of small-molecule bifunctional palladium(II) or platinum(II) N,C,N-pincevs in dimethyl sulfoxide. With this approach, the authors were able to control the dynamic mechanical properties of the gels, as discussed in detail in the Sect. 2.3. 

INTRODUCTION This data sheet contains optical data for palladium films as well as thermal, physical and mechanical properties for bulk palladium. 

Goods, S.H. Guthrie, S.E. (1992). Mechanical properties of palladium and palladium hydride, Scripta Metallurgica Vol.26(4), pp. 561-566. 

A wide variety of binary zirconium alloys was exposed in autoclaves and in in-pile loops to uranyl-sulfate solutions (see Section 5-5) however, only alloys of zirconium with niobium, palladium, or platinum showed greater corrosion resistance than Zircaloy-2. With the exception of the phase diagrams and a few mechanical property tests on low-niobium alloys [138], no information on any of these systems was available in the open literature. The few results for the mechanical property tests indicated very brittle alloys. 

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