Cesium applications

Ion conducting glasses, 12 585-586 Ion-cut process, 14 448-449 Ion cyclotron (ICR) analyzers, 15 663-664 Ion cyclotron resonance instrument, 15 664 Ion-dipole interactions, 14 411-418 Ion doping, in photocatalysis, 19 94-95 Ion doses, measuring, 14 444—445 Ion engines, cesium application, 5 705 Ion exchange, 14 380-426... 

Magnetocrystalline anisotropy constant, of M-type ferrites, 11 67, 68 Magnetohydrodynamic (MHD) convection, in microfluidic mixers, 26 967 Magnetohydrodynamic power generation, cesium application, 5 704 Magnetometers, SQUID, 23 871... 

Photoelectrons, trapping site for, 19 187 Photoemission current, 20 661 Photoemissive devices, cesium applications, 5 702-703 Photoemulsions, sensitizing dyes added to, 20 514... 

The metal has recently found application in ion propulsion systems. Cesium is used in atomic clocks, which are accurate to 5 s in 300 years. Its chief compounds are the chloride and the nitrate. 

Electronic Applications. Electronic appHcations make up a significant sector of the cesium market. The main appHcations are in vacuum tubes, photoemissive devices, and scintillation counters (see Electronic materials). 

Chemical Applications. Cesium metal is used in carbon dioxide purification as an adsorbent of impurities in ferrous and nonferrous metallurgy (qv) it can be used as a scavenger of gases and other impurities. 

Energy Related Applications. Much research, with regard to the use of cesium in energy related processes, has resulted in Httle commercial apphcation. The heightened awareness of the environmental degradation caused by fossil fuel power stations has resulted in increased research both into efficiency improvements for existing plants and into alternative power generation (qv) methods. 

Other Applications. The refractive index of siUcate or borosiUcate glass can be modified by the addition of cesium oxide, introduced as cesium nitrate or carbonate. Glass surfaces can be made resistant to corrosion or breakage by surface ion exchange with cesium compound melts or solutions. This process can also be used for the production of optical wave guides (61). 

Flow boiling of other alkali metals CHF data for other alkali metals were reported by Fisher et al. (1964, 1965), who tested rubidium and cesium in axial and swirl flow and potassium in swirl flow. The data were correlated by postulating a mist or fog flow model for the hydrodynamic situation in the heated section in which CHF occurs. These investigations were motivated by the potential use of alkali metals as Rankine cycle working media in space applications and have not been pursued further, because there is no longer interest in such concepts. 

The participation of cations in redox reactions of metal hexacyanoferrates provides a unique opportunity for the development of chemical sensors for non-electroactive ions. The development of sensors for thallium (Tl+) [15], cesium (Cs+) [34], and potassium (K+) [35, 36] pioneered analytical applications of metal hexacyanoferrates (Table 13.1). Later, a number of cationic analytes were enlarged, including ammonium (NH4+) [37], rubidium (Rb+) [38], and even other mono- and divalent cations [39], In most cases the electrochemical techniques used were potentiometry and amperometry either under constant potential or in cyclic voltammetric regime. More recently, sensors for silver [29] and arsenite [40] on the basis of transition metal hexacyanoferrates were proposed. An apparent list of sensors for non-electroactive ions is presented in Table 13.1. 

Except for sensor applications, the intercalation of alkali metal ions in metal hexacyanoferrates was used for adsorption and separation of cesium ions from different aqueous solutions with Prussian blue [43,44] and cupric hexacyanoferrate [45,46],... 

Although the upper limits of DH° (A-B) - /)//,) (A-B), set by the equipartition principle, must be regarded with caution (see table 5.1), they are indeed applicable to many molecules because, as stated, the vibrational degrees of freedom are not totally frozen at 298.15 K. For instance, when A and B are heavy atoms, like cesium, the vibration frequency is small enough to ensure that the vibration mode is considerably excited, for example, DH° Cs-Cs) -DH Cs-Cs) is only 1.4 kJ mol-1 [17]. 

Aston EW (1932) The isotopic constitution and atomic weights of cesium, strontium, lithium, rubidium, barium, scandium and thallium. Proc Roy Soc A 134 571 Bach RO (ed) (1985) Lithium—Current Applications in Science, Medicine, and Technology. Wiley-Interscience, New York... 

Another application for adsorption of metal impurities is in the nuclear power industry. Radioactive cesium is one of the compounds that is difficult to remove from radioactive waste. This is because ordinary resins and zeolites do not effectively adsorb radioactive cesium. In 1997, lONSlV lE-911 crystalline silicotitan-ate (CST) ion exchangers were developed and effectively used to clean up radioactive wastes in the Melton Valley tanks at Oak Ridge [268, 269], CST was discovered [270] by researchers at Sandia National Laboratories and Texas A M University, with commercial manufacture carried out by UOP. 

Cesium is used as a getter in electron tubes. Other applications are in photoelectric cells ion propulsion systems heat transfer fluid in power generators and atomic clocks. The radioactive Cs-37 has prospective applications in sterilization of wheat, flour, and potatoes. 

The tungstophosphoric acid shows high activity, close to H2SO4 used as a benchmark. Regrettably, this acid is soluble in water and hence not usable as a solid catalyst. However, the corresponding cesium salt (Cs2.5) is also super acidic and its mesoporous structure has no limitations on the diffusion of the reactants. Cs2.5 exhibits low activity per weight, hence it is not suitable for industrial applications. 

Metals generally have face-centred cubic (fee), body-centred cubic (bee) or hexagonal structures. The simplest is fee. In the bee structure, if the central atom is different, the lattice is known as a CsCl (cesium chloride) structure. A bee structure can be considered as two interpenetrating cubic lattices. These are shown schematically in figure 1.3. In catalysis, nanoscopic metallic particles supported on ceramic supports or carbon are employed in many catalytic applications as we show in chapter 5. Increasingly, a combination of two metals (bimetallic) or alloys of two or more metals with special properties are used for specific catalytic applications. 

Haverlock, T. J., Bonnesen, F. V., Sachleben, R. A., Moyer, B. A., Applicability of a calixarene-crown compound for the removal of cesium from alkaline tank waste, Radiochim Acta, 76,103-108,1997. 

The most widely used radioactive isotopes in medical and industrial applications are cobalt 60 ( C), cesium 137 ( Cs), and iridium 192 ( lr). The half-life of is 5.3 years, that of Cs is 30 years, and the half-life of Ir is 74 days. When used for irradiation the isotope is generally in the form of a pellet size, 1.5 x 1.5 mm, loaded into a stainless steel capsule and sealed. Unlike electron beam or x-rays, gamma rays cannot be turned off. 

---