Grain boundary grooving

The diameter of the wire along the bottoms of the grain boundary grooves,... 

Fig. 12. A grain-boundary groove. The hypothetical tensions OM and ON balance the hypothetical tension acting along the grain boundary OK. The space above the line MON is occupied by a gas (vacuum)...

The approximation of a constant G was dropped later130 and different heat conductivities of ice and water were used to calculate the temperatures of the interface at various distances y the convection in the liquid was, however, not taken into account. Moreover, the function y =f(x) was believed to depend on the distance between two nearest grain-boundary grooves. 

Grain-boundary grooves can develop during thermal annealing by mass transport arising from vapor transport, surface diffusion, or surface-to-surface transport by means of volume diffusion. 

Equation 14.17 can be used to model grain-boundary grooving kinetics when vapor transport is the dominant mechanism. The normal velocity dh/dt is related... 

For the grain-boundary grooving problem, the initial and boundary conditions derive from the initial shape of the surface and Young s equation at the groove notch ... 

W.W. Mullins. Grain boundary grooving by volume diffusion. Trans. AIME, 218(4) 354—361, 1960. 

W.M. Robertson. Grain-boundary grooving by surface diffusion for finite surface slopes. J. Appl. Phys., 42(1) 463-467, 1971. 

In 1902 Rosenhain (7) reported that grain boundary grooves form on platinum following high-temperature treatment. Later, Rosenhain and Humphrey (8) noted the same phenomenon for steel heated in air at elevated temperatures. The first report of striations came from Rosenhain and Ewen in 1912 (9) for silver heated in air (Fig. 1). 

Figure 1.13. Formation of a wetting ridge at the triple line (a) by a mechanism similar to grain-boundary grooving (b).

Figure 3.2. Grain-boundary grooves formed on polycrystalline Ni surface (grain diameter of the order of 100 /mi) in two hours at 900CC. For wetting liquids, these grooves can act as capillaries. The profile was obtained by high-resolution optical profilometry.

Figure 4.8. Definition of the dihedral angles i/> and formed at grain-boundary grooves in the...

To determine the surface energy of the solid A in equilibrium with its own vapour, dihedral angle ]/° of grain boundary grooves in vacuum or a neutral gas. Then, assuming that the grain boundary energy of solid A in contact with liquid B is not affected by adsorption of B, (jgV is obtained from the equation ... 

Figure H.2. a) Infiltration of pre-existing grain boundary grooves at S/V surface, b) Extension of the...

Samples B (obtained from condensation of water vapour). The AFM investigations of the samples formed from condensation of water vapour at 10-, 20- an 30% of relative humidity at -30°C show a poly crystal line ice structure (Fig.6). The ice crystals have diameters of approximately 5-15 pm and are easily identified by grain boundary grooves between 50-500 nm depth, (see Section 2.2.1). The thickness of the sample is 3-10 pm (measured by AFM via complete melting of the sample after investigation). 

We modified a commercial AFM to image ice surfaces in situ under various experimental conditions of temperature and relative humidity. The ice surfaces showed different structures (e.g. grain boundary grooves, defects of ice surface, frost crystals) depending on thickness of the ice sample, temperature and humidity. 

An accelerated rate of grain boundary grooving (thermal etching) has been observed in alumina ceramics (Fig. 9), where the etching rate was especially enhanced as the level of impurities increased. The microwave enhancement of the grain boundary etching... 

Lee, K.Y. Case, E.D. A comparison of theoretical and experimental profiles for thermally-induced grain-boundary grooving. Eur. Phys. J., Appl. Phys. 1999, 5 (3), 197-214. 

Cracking, zero creep, and field emission microscopy yield equal values for y and a. By inert gas bubble precipitation, grain boundary grooving, and scratch relaxation rate studies CT can be determined, and y by contact angle and multiphase equilibrium studies. 

Figure 24.17 Munoz, N., Gilliss, S.R. CBC. See also Munoz, N.E., Gilliss, S.R., and Carter, C.B. (2004) The monitoring of grain-boundary grooves in alumina, Phil. Mag. Lett., 84,21, http //www.tandf.co.uk/journals Munoz,...

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