Palladium alloy alternatives

In dentistry, palladium alloys are widely used as alternatives to base metal alloys in the manufacture of crowns and bridges as weU as the replacement of lost or damaged teeth (see Dental materials). Such alloys contain over 80% palladium, and hence offer significant cost benefits over alloys containing a high proportion of gold. 

Due to these problems, research on the development of alternative PEM has been carried out to minimize the shortcomings. Developments in preparing new membranes can be classified into three different branches such as (1) synthesizing new polymers based on nonfluorinated backbones [7,8] (2) incorporating inorganic fillers such as montmorillonite (MMT) [9], palladium alloy [10], silicon [11], titanium oxide [12], and zeolite [13] into parent polymer matrices and (3) sulfonated polymers [14,15]. 

Type III alloys are still used today for full cast crowns. This type of alloy has the most metallurgical alternatives because of economic concerns. Initially alloys were developed with ever-lowering gold content and then silver-palladium alloys were introduced having no gold at all. The challenge has been to reduce the cost of the material without sacrificing the functional and fabrication characteristics of the alloy. 

Electronic Applications. The PGMs have a number of important and diverse appHcations in the electronics industry (30). The most widely used are palladium and mthenium. Palladium or palladium—silver thick-film pastes are used in multilayer ceramic capacitors and conductor inks for hybrid integrated circuits (qv). In multilayer ceramic capacitors, the termination electrodes are silver or a silver-rich Pd—Ag alloy. The internal electrodes use a palladium-rich Pd—Ag alloy. Palladium salts are increasingly used to plate edge connectors and lead frames of semiconductors (qv), as a cost-effective alternative to gold. In 1994, 45% of total mthenium demand was for use in mthenium oxide resistor pastes (see Electrical connectors). 

The development of new alloys in new fields for example the development of molybdenum and tungsten with iron, cobalt or nickel for coating of dies and nozzles, or the development of palladium-nickel alloy as an alternative to gold for connectors. 

Alternatively, it may be possible to demonstrate for the pure metals that the catalytic activity is independent of film weight in a certain weight range. For example, rates of ethylene oxidation were constant over pure palladium films, deposited and annealed at 400°C and weighing between 4 and 40 mg (73). Then, if electron micrographs show that the crystallite size is relatively independent of composition, a satisfactory comparison of catalytic activity can be made at the various alloy compositions. Finally, surface area measurements are less urgently needed when activity varies by orders of magnitude, or where the main interest lies outside the determination of absolute reaction rates. 

The Wacker PdCl2-CuCl2 catalyst is a highly corrosive one, and its use requires special vessels and apparatus, such as titanium or tantalum alloys. Heteropolyacids have been used as alternative noncorrosive reoxidants of palladium for a variety of organic transformations,410 for example in reaction (155).411... 

The lithium is in the form of an alloy with magnesium or aluminium which retains much of the tritium until it is released by treatment with acid. Alternatively the tritium can be produced by neutron irradiation of enriched LiF at 450° in a vacuum and then recovered from the gaseous products by diffusion through a palladium barrier. As a result of the massive production of tritium for thermonuclear devices and research into energy production by fusion reactions, tritium is available cheaply on the megacurie scale for peaceful purposes. The most convenient way of storing the gas is to react it with finely divided uranium... 

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