Ductile metallic solids

The silvery, shiny, ductile metal is passivated with an oxide layer. Chemically very similar to and always found with zirconium (like chemical twins, with almost identical ionic radii) the two are difficult to separate. Used in control rods in nuclear reactors (e.g. in nuclear submarines), as it absorbs electrons more effectively than any other element. Also used in special lamps and flash devices. Alloys with niobium and tantalum are used in the construction of chemical plants. Hafnium dioxide is a better insulator than Si02. Hafnium carbide (HfC) has the highest melting point of all solid substances (3890 °C record ). 

Metallic solids are excellent electrical and thermal conductors. They are ductile and malleable. When a piece of metal is forced to take a different shape, it continues to hold together since its electrons can shift to bond the metallic atoms in their new positions. 

The nature of the bonds between the structural units of crystalline solids impart other physical properties to these solids. Metals are good conductors of electricity because metallic bonds allow a free flow of electrons. Covalent network, molecular, and ionic solids do not conduct electricity because their bonds do not provide for mobile electrons. Remember, however, that ionic solids in a water solution have free electrons and are good conductors of electricity. Metallic solids are malleable and ductile covalent network solids are brittle and hard. These differences in physical properties are caused by the chemical bonds between the units It is all in the bonds ... 

In summary, LME in my view is due to the upsetting of the Ratio of covalent bond to metallic band and resulting in an increased difficulty in the creation of free radicals. This takes away the ductility and results in brittleness. In this context, one can venture to predict that if solid metal is coated with a liquid metal whose electron density is less than that in solid metal, solid metal may become free electrondeficient and may actually facilitate the creation of free radicals. In this case an enductilement may result in lieu of embrittlement. 

Aluminum, a silver-white, malleable, and ductile metal, is the most abundant metallic element in the lithosphere, comprising about 8% of the earth s crust. It is never found free in nature, but occurs combined with other elements, most commonly as aluminosilicates, oxides, and hydroxides in rock, minerals, clays, and soil. It is also present in air, water, and many foods. Bauxite, a weathered rock consisting primarily of aluminum hydroxide minerals, is the primary ore used in aluminum production. Aluminum enters environmental media naturally through the weathering of rocks and minerals. Anthropogenic releases are in the form of air emissions, waste water effluents, and solid waste primarily associated with industrial processes, such as aluminum production. Because of its prominence as a major constituent of the earth s crust, natural weathering processes far exceed the contribution of releases to air, water, and land associated with human activities. 

M.F. Horstemeyer, A.M. Gokhale A void-crack nucleation model for ductile metals. Int. J. Solids Struct. 36, 5029-5055 (1999)... 

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. 

Malleability and ductility These terms refer respectively to how readily a solid can be shaped by pressure (forging, hammering, rolling into a sheet) and by being drawn out into a wire. Metallic solids are known and valued for these qualities, which derive from the non-directional nature of the attractions between the kernel atoms and the electron fluid. The bonding within ionic or covalent solids may be stronger, but it is also directional, making these solids subject to fracture (brittle) when struck with a hammer, for example. A metal, by contrast, is more likely to be simply deformed or dented. 

Vanadium is a silveiy-white, ductile, metallic-looking solid. Ductile means capable of being drawn into thin wires. Its melting point is about 3,500°F (1,900°C) and its boiling point is about 5,400°F (3,000°C). Its density is 6.11 grams per cubic centimeter, more than six times the density of water. 

Metallic solids Recall from Chapter 8 that metallic solids consist of positive metal ions surrounded by a sea of mobile electrons. The strength of the metallic bonds between cations and electrons varies among metals and accounts for their wide range of physical properties. For example, tin melts at 232°C, but nickel melts at 1455°C. The mobile electrons make metals malleable—easily hammered into shapes—and ductile—easily drawn into wires. When force is applied to a metal, the electrons shift and thereby keep the metal ions bonded in their new positions. Read Everyday Chemistry at the end of the chapter to learn about shape-memory metals. Mobile electrons make metals good conductors of heat and electricity. Power lines carry electricity from power plants to homes and businesses and to the electric train shown in Figure 13-21a. 

Physical state Heavy, mobile, liquid metal Solid mercury is ductile, maleable mass which may be cut with a knife Crystals, granules or powder rhombic crystals, crystalline solid0 Heavy amorphous powder, also occurs as black cubic crystals (mercuric sulfide, black) powder, lumps, hexagonal crystals (mercuric sulfide, red) Heavy powder rhombic crystals or crystalline powder 1... 

In general, metallic solids are ductile and malleable, whereas ionic salts are brittle and shatter readily (although they are hard). Explain this observation. 

PHYSICAL PROPERTIES The physical properties of metallic tantalum and tantalum pentoxide are provided for illustrative purposes, (metallic tantalum) steel-blue to gray solid or black powder very hard, malleable, ductile metal can readily be drawn in fine wires odorless insoluble in water insoluble in acids, except hydrofluoric and fuming sulfuric acids soluble in fused alkalies MP (2996"C, 5425"F) BP (5425 C, 9797T) DN/SG (16.65 (metal), 14.40 (powder)) CP (25.4 J/K-mol crystal at 25°C) VD (NA) VP (approximately 0 mmHg at 20 C) TS (130,000 psi) EC (8 x 10" over range 20 - 1500 C). (tantalum pentoxide) white, microcrystalline, infusible powder insoluble in water, acids, and alcohol soluble in hydrogen fluoride MP (1800 C, 3272 F) BP (NA) DN/SG (8.2) CP (135.1 J/K-mol crystal at 25"C) VD (NA) VP (approximately 0 mmHg at 20 C). 

Physical Description Metal White, hard, ductile, malleable solid with a bluish-gray luster. 

Physical Description Metal Silver-white, malleable, ductile, lustrous solid. [Note Weakly radioactive.]... 

Figure 10.4 Schematic engineering stress ngineering strain (

SECTION 12.3 Metallic solids are typically good conductors of electricity and heat, malleable, which means that they can be hammered into thin sheets, and ductile, which means that they can be drawn into wires. Metals tend to form structures where the atoms are closely packed. Two related forms of close packing, cubic ciose packing and hexagonal close packing, are possible. In both, each atom has a coordination number of 12. 

Which of the following properties are typical characteristics of a covalent-network solid, a metallic solid, or both (a) ductility, (b) hardness, (c) high melting point ... 

In the yielding of polyerystalline ductile metals that obey symmetrical 3D yield criteria of von Mises or Tresca type (McClintock and Argon 1966) the plastic shear resistance is nearly independent of pressure and the S-D effect is negligible. In comparison it is very substantial in disordered solids, with the ratio rc/ T being in the range 1.2-1.3. 

---