Lithium molten

In general, only low-carbon steel (5)y niobium, tantalum, and molybdenum are desirable materials of construction for molten lithium. Molten lithium will attack quartz, glass, and silicates in general, and the lithium oxide often present in molten lithium at high temperatures is an excellent flux for most oxides and silicates. 

Regarding the lithium molten salt FeS2 battery, I am well aware of this work. But I did not discuss it as it falls outside the scope of the Summer School. However, I believe that many of the technical engineering and operational problems are common to the two systems. 

Gallium, molten Hydrochloric acid, 10% (140 F) Hydrochloric acid, over 5% (RT) Hydrogen sulfide, moist Indium, molten Lead, molten Lithium, molten Nitric acid... 

These are halides formed by highly electropositive elements (for example those of Groups I and II, except for beryllium and lithium). They have ionic lattices, are non-volatile solids, and conduct when molten they are usually soluble in polar solvents in which they produce conducting solutions, indicating the presence of ions. 

Molten lithium fluoride is used in salt mixtures for an electrolyte in high temperature batteries (qv) (FLINAK) (20), and as a carrier in breeder reactors (FLIBE) (21) (see Nuclear reactors). 

Economic Aspects. Lithium metal is available commercially in ingots, special shapes, shot, and dispersions. Ingots are sold in 0.11-, 0.23-, 0.45-, and 0.91-kg sizes. Special shapes include foil, wire, and rod. Lithium is available in hermetically sealed copper cartridges and in sealed copper tubes for use in treating molten copper and copper-base alloys. Shot is sold in 1.19—4.76 mm (16—4 mesh) sizes. Lithium dispersions (30% in mineral oil) of 10—50-p.m particle size are used primarily in organic chemical reactions. Dispersions in other solvents and of other size fractions can be suppHed. 

Lithium is used in metallurgical operations for degassing and impurity removal (see Metallurgy). In copper (qv) refining, lithium metal reacts with hydrogen to form lithium hydride which subsequendy reacts, along with further lithium metal, with cuprous oxide to form copper and lithium hydroxide and lithium oxide. The lithium salts are then removed from the surface of the molten copper. 

An emerging electrochemical appHcation of lithium compounds is in molten carbonate fuel ceUs (qv) for high efficiency, low poUuting electrical power generation. The electrolyte for these fuel ceUs is a potassium carbonate—hthium carbonate eutectic contained within a lithium aluminate matrix. The cathode is a Hthiated metal oxide such as lithium nickel oxide. 

The molten carbonate fuel ceU uses eutectic blends of Hthium and potassium carbonates as the electrolyte. A special grade of Hthium carbonate is used in treatment of affective mental (mood) disorders, including clinical depression and bipolar disorders. Lithium has also been evaluated in treatment of schizophrenia, schizoaffective disorders, alcoholism, and periodic aggressive behavior (56). 

Lithium Chloride. Lithium chloride [7447- 1-8], LiCl, is produced from the reaction of Hthium carbonate or hydroxide with hydrochloric acid. The salt melts at 608°C and bods at 1382°C. The 41-mol % LiCl—59-mol % KCl eutectic (melting point, 352°C) is employed as the electrolyte in the molten salt electrolysis production of Hthium metal. It is also used, often with other alkaH haHdes, in brazing flux eutectics and other molten salt appHcations such as electrolytes for high temperature Hthium batteries. 

Lithium Iodide. Lithium iodide [10377-51 -2/, Lil, is the most difficult lithium halide to prepare and has few appHcations. Aqueous solutions of the salt can be prepared by carehil neutralization of hydroiodic acid with lithium carbonate or lithium hydroxide. Concentration of the aqueous solution leads successively to the trihydrate [7790-22-9] dihydrate [17023-25-5] and monohydrate [17023-24 ] which melt congmendy at 75, 79, and 130°C, respectively. The anhydrous salt can be obtained by carehil removal of water under vacuum, but because of the strong tendency to oxidize and eliminate iodine which occurs on heating the salt ia air, it is often prepared from reactions of lithium metal or lithium hydride with iodine ia organic solvents. The salt is extremely soluble ia water (62.6 wt % at 25°C) (59) and the solutions have extremely low vapor pressures (60). Lithium iodide is used as an electrolyte ia selected lithium battery appHcations, where it is formed in situ from reaction of lithium metal with iodine. It can also be a component of low melting molten salts and as a catalyst ia aldol condensations. 

Other Metals. AH the sodium metal produced comes from electrolysis of sodium chloride melts in Downs ceUs. The ceU consists of a cylindrical steel cathode separated from the graphite anode by a perforated steel diaphragm. Lithium is also produced by electrolysis of the chloride in a process similar to that used for sodium. The other alkaH and alkaHne-earth metals can be electrowon from molten chlorides, but thermochemical reduction is preferred commercially. The rare earths can also be electrowon but only the mixture known as mischmetal is prepared in tonnage quantity by electrochemical means. In addition, beryIHum and boron are produced by electrolysis on a commercial scale in the order of a few hundred t/yr. Processes have been developed for electrowinning titanium, tantalum, and niobium from molten salts. These metals, however, are obtained as a powdery deposit which is not easily separated from the electrolyte so that further purification is required. 

Gas-phase oxidation of propylene using oxygen in the presence of a molten nitrate salt such as sodium nitrate, potassium nitrate, or lithium nitrate and a co-catalyst such as sodium hydroxide results in propylene oxide selectivities greater than 50%. The principal by-products are acetaldehyde, carbon monoxide, carbon dioxide, and acrolein (206—207). This same catalyst system oxidizes propane to propylene oxide and a host of other by-products (208). 

Development of practical and low cost separators has been an active area of ceU development. CeU separators must be compatible with molten lithium, restricting the choice to ceramic materials. Early work employed boron nitride [10043-11-5] BN, but a more desirable separator has been developed using magnesium oxide [1309-48-4], MgO, or a composite ofMgO powder—BN fibers. Corrosion studies have shown that low carbon steel or... 

The cubic 2inc blende form of boron nitride is usually prepared from the hexagonal or rhombohedral form at high (4—6 GPa (40—60 kbar)) pressures and temperatures (1400—1700°C). The reaction is accelerated by lithium or alkaline-earth nitrides or amides, which are the best catalysts, and form intermediate Hquid compounds with BN, which are molten under synthesis conditions (11,16). Many other substances can aid the transformation. At higher pressures (6—13 GPa) the cubic or wurt2itic forms are obtained without catalysts (17). 

Interest in the synthesis of diamond [7782-40-3] was first stimulated by Lavoisier s discovery that diamond was simply carbon it was also observed that diamond, when heated at 1500—2000°C, converted into graphite [7782-42-5]. In 1880, the British scientist Haimay reported (1) that he made diamond from hydrocarbons, bone oil, and lithium, but no one has been able to repeat this feat (2). About the same time, Moissan beheved (3) that he made diamond from hot molten mixtures of iron and carbon, but his experiments could not be repeated (4,5). 

The Group 1 elements are soft, low-melting metals which crystallize with bee lattices. All are silvery-white except caesium which is golden yellow "- in fact, caesium is one of only three metallic elements which are intensely coloured, the other two being copper and gold (see also pp. 112, 1177, 1232). Lithium is harder than sodium but softer than lead. Atomic properties are summarized in Table 4.1 and general physical properties are in Table 4.2. Further physical properties of the alkali metals, together with a review of the chemical properties and industrial applications of the metals in the molten state are in ref. 11. 

The small size of lithium frequently confers special properties on its compounds and for this reason the element is sometimes termed anomalous . For example, it is miscible with Na only above 380° and is immiscible with molten K, Rb and Cs, whereas all other pairs of alkali metals are miscible with each other in all proportions. (The ternary alloy containing 12% Na, 47% K and 41% Cs has the lowest known mp, —78°C, of any metallic system.) Li shows many similarities to Mg. This so-called diagonal relationship stems from the similarity in ionic size of the two elements / (Li ) 76pm, / (Mg ) 72pm, compared with / (Na ) 102pm. Thus, as first noted by Arfvedson in establishing lithium as a new element, LiOH and LiiCOs are much less soluble than the corresponding... 

The poor efficiencies of coal-fired power plants in 1896 (2.6 percent on average compared with over forty percent one hundred years later) prompted W. W. Jacques to invent the high temperature (500°C to 600°C [900°F to 1100°F]) fuel cell, and then build a lOO-cell battery to produce electricity from coal combustion. The battery operated intermittently for six months, but with diminishing performance, the carbon dioxide generated and present in the air reacted with and consumed its molten potassium hydroxide electrolyte. In 1910, E. Bauer substituted molten salts (e.g., carbonates, silicates, and borates) and used molten silver as the oxygen electrode. Numerous molten salt batteiy systems have since evolved to handle peak loads in electric power plants, and for electric vehicle propulsion. Of particular note is the sodium and nickel chloride couple in a molten chloroalumi-nate salt electrolyte for electric vehicle propulsion. One special feature is the use of a semi-permeable aluminum oxide ceramic separator to prevent lithium ions from diffusing to the sodium electrode, but still allow the opposing flow of sodium ions. 

The PAFC is, however, suitable for stationary power generation, but faces several direct fuel cell competitors. One is the molten carbonate fuel cell (MCFC), which operates at "650°C and uses an electrolyte made from molten potassium and lithium carbonate salts. Fligh-teinperature operation is ideal for stationary applications because the waste heat can enable co-generation it also allows fossil fuels to be reformed directly within the cells, and this reduces system size and complexity. Systems providing up to 2 MW have been demonstrated. 

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. 

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