Low-melting-point metals

Steels and austenitic stainless steels are susceptible to molten zinc, copper, lead and other metals. Molten mercury, zinc and lead attack aluminum and copper alloys. Mercury, zinc, silver and others attack nickel alloys. Other low-melting-point metals that can attack common constructional materials include tin, cadmium, lithium, indium, sodium and gallium. 

Nickel and nickel-rich alloys must be considered as having generally poor resistance to molten metals. Eldred has made a systematic investigation of the attack of liquid metals on solid metals and alloys, and his results for nickel, and nickel-chromium and nickel-copper alloys, are summarised in Table 7.35. These are for tests at up to 500 C and apart from potassium and sodium all the low-melting-point metals investigated produced moderate to severe attack on the nickel-rich materials. Furthermore, the values for many of the combinations given in the table indicate a marked tendency to preferential intergranular attack. 

Porous refractory (tungsten) infiltrated with a low melting point metal (silver) Hot-pressed refractory metal containing an oxide filler... 

Evaporation is used extensively for the deposition of aluminum and other low melting-point metals as well as hard coatings such as TiN for cutting tools, decorative coatings (jewelry), and for the metallization of paper and fibers. It is also a major coating... 

In earlier work with pure metals, it was generally accepted that the area of films deposited at, say, 0°C was proportional to their weight (with the exception of group IB and low melting-point metals). Information was available on the surface areas of films of Ni, Pt, Pd, Rh, etc. (71), and hence absolute reaction rates could be calculated. It would be a considerable undertaking to establish similar data for alloy systems, bearing in mind that various compositions would have to be examined and also a method for preparing exact compositions would be required. However, for sintered alloy films, approximate methods can be proposed. 

Pressure Atomization 50-500 Standard deviation 1.4 Sn, Pb, Sb, Bi, In, Mg, Al, Zn — -17 — Narrow size distribution High EE Limited to low melting point metals... 

For low melting-point metals (for example, solder materials), the liquid metal and the atomization gas may be mixed internally inside the atomizer for both low and high melting point materials, the two fluids can be mixed externally outside the atomizer in the nearnozzle region. 

How do we make a contact with an optically transparent electrode or a low-melting-point metal such as lead ... 

If the solid product sinters together under the conditions of the reacion, as for instance low melting point metals produced by the reduction of much higher melting point oxides, then the possibility must be considered of the product choking the reaction, even though the volume ratio if satisfactory. 

A practical application coming out of field ion emission is the liquid metal ion source. Ion sources of a wide variety of chemical elements, most of them low melting point metals, can be produced by using either liquid metals131,132 or liquid alloys.133 The idea of extracting charged droplets out of liquid by application of an electrostatic field is perhaps older than field ion microscopy. But the development of liquid metal ion sources from liquid capillaries, from slit shaped emitter modules and from wetted field emission tips, etc., as well as the understanding of the mechanisms of ion formation in terms of field evaporation and field ionization theories,... 

In low melting point metal dispersed systems, the Al203/Ni system has been studied to obtain the desired microstructure and improvement of mechanical properties by modification of the microstructure. Moreover, considering the magnetic properties of the composites, it was expected to improve both mechanical and magnetic properties by incorporating merely nanometer-sized Ni, Co, and Fe into an A1203 matrix. 

Fig. 12. XRD patterns of some low-melting-point metals supported on y-Al20) of a specific surface (170 m2/g). (a) Mixture of 0.10 g Sn/g y-Al203. (a ) Sample a after a heat...

Liquid metal-induced embrittlement (LMIE), particularly solid metal-induced failure result in accelerated brittle failure on normally ductile metals under applied or residual stresses when in contact with liquid or solid low-melting point metal. SMIE was first noted as the delayed failure of steels in solid Cd environments. 

The methods already described have illustrated the wide applicability of flame atomisation techniques to the analysis of non-ferrous alloys. The introduction of electrothermal atomisation has enabled the direct determination of sub-part per million levels of impurities. The presence of very low levels of lead, bismuth and other low melting point metals is known to have a deleterious effect on the metallurgical properties of nickel alloys. 

Sea disposal could be carried out in the following way, similar to the approach used during the Soviet period as discussed in section 2. The reactor vessels and the primary circuits are drained for water and filled with a material like furfurol or a low melting point metallic alloy to fix the damaged fuel and the control rod and to decrease the release of activity to the environment. If need be, additional material, e.g. concrete may be added to the reactor compartment to reduce the radiation level around the submarine. At the same time the floatability of the submarine must be ensured. After these preparations the submarine is transported out to the sea to a proper place, where the submarine is disposed of by sinking. Depending on the state of the submarine, it may by towed to the disposal area or it may have to be transported in a floating dock or by some other means. 

By varying parameters such as jet design, pressure and volume of the atomizing fluid, and density of the liquid metal stream, it is possible to control the overall particle size and shape. In principle, atomization is applicable to all metals that can be melted, and is commercially used for the production of iron, steels, alloy steels, copper, brass, bronze, and other low-melting-point metals such as aluminium, tin, lead, zinc, and cadmium. 

Low-melting-point metals are of particular concern. Molten copper, zinc, or aluminum will attack the grain boundaries of austenitic alloys preferentially. Copper alloy clamps or fixtures used to hold work, whereas welding has been known to leave smears of metal that have subsequently caused cracking. Zinc from galvanized steel or paint primers has also been known to contaminate weld joints. 

For high impedance electrodes, e.g., liquid membrane ion-selective tips (39), another method is essential. Using techniques borrowed from electrophysiology, it is possible to construct dual tips from theta glass (Chapter 3). One barrel of the double tip can be used for the liquid membrane, and the other may be filled with a low melting point metal such as gallium to make a voltammetric sensor (41). 

Die For complex shapes with thin walls in low melting point metals such as aluminum and zinc... 

Aluminum is a low melting point metal, therefore microstructural stability (and consequently creep) is an important issue even for near ambient temperature. Many common structural aluminum alloys are precipitation strengthened at heat treatment temperatures on the order of 423 K, implying that the service temperature must be considerably lower. There are a few aluminum alloys designed for high-temperature applications however, creep makes them unacceptable as materials of construction for contaimnent of pressurized gas at elevated temperature. On the other hand, aluminum alloys are commonly employed at cryogenic temperatures. 

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