Tungsten single crystals

Figure Al.7.10. STM image (1000 A x 1000 A) of the (111) surface of a tungsten single crystal, after it had been coated with a very thin film of palladium and heated to about 800 K (courtesy of Ted Madey).

Willis, R. F., and Feuerbacher, B. (1975). Angular-resolved secondary-eleetron-emission spectroscopy of clean and adsorbate covered tungsten single-crystal surfaces. Surf. Sci. 53, 144-155. 

Fig. 33. Sticking probability for nitrogen on tungsten single crystal planes. T = 300 K. (From Ref. )...

Muller E.W., (1955) Work function of tungsten single crystal planes measured by the field emission microscope. J. Appl. Phys. 26 732. 

Chemisorption-induced metal atom reorganization at low temperatures had been discovered in the 1960s by field ion microscopy in chemisorption studies of nitrogen and carbon monoxide on a tungsten single-crystal tip (55-58). Likewise, surfece reconstruction was concluded from research of chemisorption on metal and bimetal films (59-61). This surface reconstruction was observed particularly on open crystal faces the more closely packed faces are often corroded from their edges with the former faces. Surface reconstruction is of particular relevance to alloy surfaces, where it leads to chemisorption-induced segregation of one alloy component to the... 

Slip or gliding. Slip is the basic mechanism in the plastic deformation of tungsten single crystals. Slip occurs in the most densely packed [111] direction and either in (110 or in (122) planes. At elevated temperatiue also (111) occurs in addition. 

FIGURE 1.12. Critical flow stress (a) vs. tempeiatuie of a high-purity tungsten single crystal ((110)) [1.48] tensile deformation rate, 1.6 x 10 s . 

TABLE 1.11. Effect of Orientation and Temperature on the Critical Resolved Shear Stresses for Slip of Tungsten Single Crystals in Tension [1.50]... 

FIGURE 1.13. Stress-strain curves of tungsten single crystals with various orientations, tested at room temperature [1.50]. 

Armstrong 78) studied, in the same system, the work function changes caused by CO adsorption on two tungsten single crystals, one exposing the W(IOO) surface, the other the W(112) surface. These experiments confirmed the results obtained by field emission 44) that the W(112) plane is more active in CO adsorption than the W(IOO) plane. Armstrong measured an initial sticking probability for CO at 300°K of about... 

King and co-workers [45—48] have examined the applicability of these kinetic models to the adsorption of nitrogen on tungsten single crystal planes. 

Singh-Boparai et al. [47] studied the adsorption kinetics and surface coverages for N2 on a variety of tungsten single-crystal planes. A... 

Van Liempt (54) made a study of the diffusion of molybdenum in tungsten single crystals and poly crystals, and found once again a dependence upon the size of the individual crystallites. His data for the two cases may be expressed by... 

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