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Lanthanum hexaboride

Uses. In spite of unique properties, there are few commercial appUcations for monolithic shapes of borides. They are used for resistance-heated boats (with boron nitride), for aluminum evaporation, and for sliding electrical contacts. There are a number of potential uses ia the control and handling of molten metals and slags where corrosion and erosion resistance are important. Titanium diboride and zirconium diboride are potential cathodes for the aluminum Hall cells (see Aluminum and aluminum alloys). Lanthanum hexaboride and cerium hexaboride are particularly useful as cathodes ia electronic devices because of their high thermal emissivities, low work functions, and resistance to poisoning. [Pg.219]

XPS spectra were obtained using a Perkin-Elmer Physical Electronics (PHI) 555 electron spectrometer equipped with a double pass cylindrical mirror analyzer (CMA) and 04-500 dual anode x-ray source. The x-ray source used a combination magnesium-silicon anode, with collimation by a shotgun-type collimator (1.). AES/SAM spectra and photomicrographs were obtained with a Perkin-Elmer PHI 610 Scanning Auger Microprobe, which uses a single pass CMA with coaxial lanthanum hexaboride (LaBe) electron gun. [Pg.38]

Tungsten has the necessary high melting temperature (3660 K) to be employed as a thermionic source, and lanthanum hexaboride (LaB6) is also employed because of its low work function. [Pg.132]

Figure 10.7 illustrates the prototype hexaboride crystal structure, that of lanthanum hexaboride. It consists of a simple cubic array of boron octahedra surrounding a metal atom at the body center of each cube. The octahedra are linked by B-B bonds connecting their comers. This makes the overall structure relatively hard with approximately the hardness of boron itself since plastic shear must break B-B bonds. The open volumes surrounded by boron octahedra are occupied by the relatively large lanthanum atoms as the figure shows schematically. [Pg.138]

Figure 10.7 Crystal structure of Lanthanum Hexaboride (prototypre hexaboride). The black circles represent boron octahedra. They form a simple cubic arrangement surrounding the central metal atom. Figure 10.7 Crystal structure of Lanthanum Hexaboride (prototypre hexaboride). The black circles represent boron octahedra. They form a simple cubic arrangement surrounding the central metal atom.
An alternative version of the lanthanum hexaboride crystal structure has the boron octahedra occupying the body centered positions of the cubic array of lanthanum atoms (Figure 10.8). This version makes it clear that in order to plastically shear the structure, the boron octahedra must be sheared. Note that the octahedra are linked together both internally and externally by B-B bonds. [Pg.139]

Figure 10.8 Alternative drawing of the crystal structure of Lanthanum Hexaboride with the metal atoms occupying the cube corners. Figure 10.8 Alternative drawing of the crystal structure of Lanthanum Hexaboride with the metal atoms occupying the cube corners.
The Lanthanum Hexaboride Electron Emission Source and the Vacuum Environment, Amray Technical Bulletin 112-277, Amray, Bedford, Mass., 1986, pp. 11-18. [Pg.155]

Hafnium carbide, 0521 Lanthanum hexaboride, 0193 Magnesium nitride, 4698 Tin(II) sulfide, 4900 Titanium carbide, 0561 Zirconium carbide, 0565 Zirconium nitride, 4733... [Pg.373]

Figure 2. Diffraction camera for single-molecule electron diffraction. A Lanthanum hexaboride electron source is used. The laser and associated optics is rotated after each data readout for a new molecular beam orientation. Organic molecules are picked up within liquid helium droplets to form a molecular beam traversing the electron beam. Figure 2. Diffraction camera for single-molecule electron diffraction. A Lanthanum hexaboride electron source is used. The laser and associated optics is rotated after each data readout for a new molecular beam orientation. Organic molecules are picked up within liquid helium droplets to form a molecular beam traversing the electron beam.
Lanthanum hexaboride sources show brightness in excess of 10 amps... [Pg.69]

Lanthanum hexaboride cathodes fall short of the required brightness for a round beam to compete with a shaped beam only producing lxl06 A/cm2.ster. (25 kV) with adequate reliability for unattended production applications (40). In summary, highest throughput in production is obtained with shaped beams. [Pg.23]

Of a series of powdered refractory compounds examined, only lanthanum hexaboride, hafnium carbide, titanium carbide, zirconium carbide, magnesium nitride, zirconium nitride and tin(II) sulfide were dust explosion hazardous, the 2 latter being comparable with metal dusts. Individual entries are ... [Pg.2568]

Hafnium carbide, 0518 Lanthanum hexaboride, 0193 Magnesium nitride, 4693 Tin(II) sulfide, 4894 Titanium carbide, 0558 Zirconium carbide, 0562 Zirconium nitride, 4728... [Pg.2568]

M. M. Korsukova and V. N. Gurin, Single Crystals of Lanthanum Hexaboride Their Preparation, Properties and Prospective Uses, in Current Topics in Materials Science , ed. E. Kaldis, Elsevier Science, New York, 1984, Vol. 11, p. 389. [Pg.412]


See other pages where Lanthanum hexaboride is mentioned: [Pg.551]    [Pg.219]    [Pg.278]    [Pg.282]    [Pg.283]    [Pg.88]    [Pg.141]    [Pg.218]    [Pg.347]    [Pg.69]    [Pg.219]    [Pg.551]    [Pg.93]    [Pg.2104]    [Pg.81]    [Pg.289]    [Pg.365]    [Pg.6]    [Pg.42]    [Pg.139]    [Pg.82]    [Pg.82]    [Pg.81]    [Pg.2021]   
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See also in sourсe #XX -- [ Pg.138 , Pg.139 , Pg.140 ]

See also in sourсe #XX -- [ Pg.365 ]

See also in sourсe #XX -- [ Pg.6 ]

See also in sourсe #XX -- [ Pg.82 ]

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See also in sourсe #XX -- [ Pg.594 ]




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