Melting point eutectic

In multi-component liquids, stabilization of the liquid is revealed by the formation of eutectics where the freezing temperature is suppressed. In such liquids, the atomic species (say A and B) are not distributed at random. There are more associated AB pairs (or other clusters) than expected for a random distribution. As a result in binary metal-metalloid alloys, such as Fe-B, the low melting-point eutectics occur at preferential compositions. The most common of these is at about 17 at. % B, or an atom ratio of one B for five Fe atoms (Gilman, 1978). This suggests that clusters of metal atoms surrounding metalloid atoms form (trigonal bipyramids). These probably share corners, edges, and faces. 

Figure 1. Cerium-iron phase diagram showing complete solubility in the liquid phase, zero solubility in the solid phases and one, single, low-melting point eutectic 92.5% Ce.

Cadmium (Cd) is a transition metal widely used in industry. Workers are exposed to cadmium in the manufacture of nickel cadmium batteries, pigments, low-melting-point eutectic materials, in solder, television phosphors, and in plating operations. 

Bismaleimides are produced by the condensation reaction of a diamine, such as methylenedianiline, with maleic anhydride. The reaction product tends to be crystalline with a high melting point. Eutectic blends of different bismaleimides reduce the melting point. However, a coreactant generally is required to improve the processing properties of the material. Bismaleimides owe their reactivity to the double bonds on each end of the molecule, which can react with themselves or with other compounds containing functional groups (vinyls, allyls. or amines). A typical bismaleimide structure is shown by ... 

The major technical barrier associated with biomass combustion systems is the formation of tenacious deposits on heat transfer surfaces caused by the unique high-temperature chemistry of biomass ash. Many types of biomass used in combustion systems contain alkali metal species sodium, potassium, and calcium. The ash content of woody biomass is quite low and not a problem. The ash content of agricultural residues such as wheat straw, rice straw, com stover, and alfalfa stems can be quite high, on the order of 5 percent or up to 20 percent for rice straw and rice husks. The presence of alkali metals in conjunction with the high silica content of some biomass ashes can lead to molten ash at combustion temperatures.553-658 In some cases, the K, Si, and A1 contents are such that very low melting-point eutectic mixtures can form. The materials can be fluid at combustion temperatures, but form glasslike deposits on colder downstream surfaces such as heat exchanger tubes. 

Low melting point and high V205 solubility are obtained by choosing a low melting point eutectic mixture of V205 and K, Na, Cs pyrosulfates. 

Despite their interesting properties wide application of borides is not possible, because they cannot be processed with bonding metals to hard metal alloys and the more expensive hot press process must be used. Furthermore, borides form low melting point eutectics with ferrous metals. 

Several molten salts are volatile under the applied conditions. Chlorides for example are known for their high vapom pressure. Nitrates, usually forming low melting point eutectic mixtures, are unstable and will decompose. Another point of interest is the reaction of the origineil salts into, for example, carbonates and sulfates with components in the exhaust gas, eg. carbon dioxide or sulfirr dioxide, respectively. This could influence the composition of the melt and, thereby, increase the melting point and subsequently reduce or even destroy the activity. 

The Sr-Al and Ba-Al phase diagrams have been examined by thermal micrographic and X-ray methods. The compounds which were observed are shown in Table 6, together with their lattice parameters, derived from several sources, and their melting points. Eutectics were observed at 81.75 mol% Sr (590 °C) and... 

Du] Du, H., Morral, J.E., Prediction of the Lowest Melting Point Eutectic in the Fe-Cr-Mo-V-C System , J. Alloys Compd., 247, 122-127 (1997) (Phase Relations, Experimental, Calculation, Review, 20)... 

Magnesium has a density lower than Al, but is more susceptible to corrosion and like Al, requires a protective treatment. Katzman [59] examined suitable treatments for the fabrication of graphite reinforced Mg composites. The tensile properties of coated carbon fiber reinforced Mg composites have been determined by Zhang and co-workers [90]. A study of the compatibility between PAN based carbon fibers and MggLi alloy during the pressure infiltration process was undertaken [91] and Chen and co-workers [92] examined the interface in Mg matrix composites reinforced with carbon fiber. A Ni coated carbon fiber in a Mg matrix will form Mg-Ni compounds and a low melting point eutectic (508°C) [93]. 

Polymers P olytetrafluoroethylene (PIPE) Suitable below 280 C but avoid the presence or formation of any trace of free alkali-metal. Perfect for the low melting point eutectic NaOH-KOH (lyO C). 

Although the mechanisms of sulfidation and oxidation are fundamentally similar, they differ both in complexity and in rate of attack. Sulfidation is more complex than oxidation because of the occurrence of a larger number of stable sulfides compared with oxides. The complexity is further enhanced because of the low-melting-point eutectics formed in many of the metal-sulfide systems. Examples of such eutectic temperatures are 985 °C for iron 880 °C for cobalt and 645 °C for nickel. 

The rapid heating is one of the characteristics of microwave heating. But if the temperature rising is too fast, there are some low melting point eutectics to be produced in the process of decomposition meanwhile, it could produce some black power material. 

From the Table II, it can be found that it can only produce the black impurity in the product, if the heating rate exceeded 14 C/min. But when the heating rate exceeded 18 C /min, there are both the black impurity and the low melting point eutectics in the product. The black impurity was detected by XRD. The results were shown in Fig. 4. 

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