Gallium alloys

Alloys. Gallium has complete miscibility in the liquid state with aluminum, indium, tin, and zinc. No compounds are formed. However, these binary systems form simple eutectics having the following properties ... 

Aluminum alloys also are embrittled by tin-zinc and lead-tin alloys. The embrittlement susceptibility is related to heat treatment and the strength level of the alloy. Gallium in contact with aluminum severely disintegrates unstressed aluminum alloys into individual grains. Therefore, grain-boundary penetration of gallium is sometimes used to separate grains and to study... 

Intermetallic compounds with gallium are used as semiconductors. Indium is used to coat other metals to protect against corrosion, especially in engine bearings it is also a constituent of low-metal alloys used in safety sprinklers. The toxicity of thallium compounds has limited the use of the metal, but it does find use as a constituent of high-endurance alloys for bearings. 

Chemical Reduction. Reduction of galHum by aluminum has been developed in the former Soviet Union. This method is in operation (ca 1994). The Bayer Hquor is contacted using a gallium—aluminum alloy named GaHam, and the galHum is deposited. 

The first semiconductor lasers, fabricated from gallium arsenide material, were formed from a simple junction (called a homojunction because the composition of the material was the same on each side of the junction) between the type and n-ty e materials. Those devices required high electrical current density, which produced damage ia the region of the junction so that the lasers were short-Hved. To reduce this problem, a heterojunction stmcture was developed. This junction is formed by growing a number of layers of different composition epitaxially. This is shown ia Figure 12. There are a number of layers of material having different composition is this ternary alloy system, which may be denoted Al Ga his notation, x is a composition... 

A low melting (5°C) gallium—indium—tin alloy has been the choice for small spiral-groove bearings in vacuum for x-ray tubes at speeds up to 7000 rpm (71). Surface tension 30 times that of oil avoids leakage of the gallium alloy from the ends of the bearings. 

The toxicity of vanadium alloys may depend on other components in the alloy. For example, the V Ga alloy requires precautions related to both vanadium and gaUium, and gallium is highly toxic. Similarly, alloys with chromium may require precautions associated with that metal. 

Arsine is used for the preparation of gallium arsenide [1303-00-0] GaAs, (17), and there are numerous patents covering this subject (see Arsenic and ARSENIC alloys). The conversion of a monomeric arsinogaHane to gallium arsenide has also been described (18). GaUium arsenide has important appHcations in the field of optoelectronic and microwave devices (see Lasers Microwave technology Photodetectors). 

Because bismuth expands on solidification and because it alloys with certain other metals to give low melting point alloys, bismuth is particularly weU suited for a number of uses. Alloys of bismuth can be made that expand, shrink, or remain dimensionally stable on solidification. AH other metals except gallium and antimony contract on solidification. Bismuth aHoys and uses are summarized in Table 5. 

Gallium-Based Alloys. A gaUium-based alloy has been kitroduced commercially ki Japan as a substitute for dental amalgam, but similar alloy types have previously been associated with abnormal cellular reactions and are not much used elsewhere nickel— gallium alloys have produced carckiomas ki rats (139). The corrosion resistance of the gallium alloys is also marginal. 

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. 

Arsenic and antimony are metalloids. They have been known in the pure state since ancient times because they are easily obtained from their ores (Fig. 15.3). In the elemental state, they are used primarily in the semiconductor industry and in the lead alloys used as electrodes in storage batteries. Gallium arsenide is used in lasers, including the lasers used in CD players. Metallic bismuth, with its large, weakly bonded atoms, has a low melting point and is used in alloys that serve as fire detectors in sprinkler systems the alloy melts when a fire breaks out nearby, and the sprinkler system is activated. Like ice, solid bismuth is less dense than the liquid. As a result, molten bismuth does not shrink when it solidifies in molds, and so it is used to make low-temperature castings. 

Obviously this method is limited to liquid metals like mercury and gallium and their amalgams respectively alloys. Modifications of this method have been reported [86FIor]. At elevated temperatures with molten salt electrolytes alloys with an appropriately low melting point can be investigated, too. 

This equation was hrst obtained by Gabriel Lippmann in 1875. The Lippmann equation is of basic importance for electrochemistry. It shows that surface charge can be calculated thermodynamically from data obtained when measuring ESE. The values of ESE can be measured with high accuracy on liquid metals [e.g., on mercury (tf= -39°C)] and on certain alloys of mercury, gallium, and other metals that are liquid at room temperature. 

Portland cement Isobutyl alcohol Liquid metal alloy of gallium, indium, and tin of melting point Water 63.4-65.0 0.13-0.17 0.13-0.17 up to 100... 

A liquid metal alloy [36] containing gallium, indium, and tin has been proposed as an additive to Portland cement. A formulation is shown in Table 18-10. The liquid metal alloy has a melting point of 11° C. Its presence does not cause corrosion of stainless steel up to 250° C but causes corrosion of steel alloys at temperature above 35° C, and it dissolves aluminum at room temperature. The alloy is harmless to skin and mucous membranes. 

R. A. Allakhverdiev, B. Khydyrkuliev, and N. V. Reznikov. Plugging solution for repairing oil and gas wells-contains plugging Portland cement, isobutanol, water and liquid metal alloy of gallium, indium and tin, to increase strength of cement stone. Patent SU 1802082-A, 1993. 

Figure 26. Activation and superactivation of an aluminum-gallium (0.2%) alloy at different current densities.128...

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