TiAl grains

Fig. 17. Structuie of U-700 after piecipitation hardening temperature of 1168 C/4 h + 1079" C/4 h + 843 C/24 h + TGO C/IG h with air cooling from each temperature. A grain boundary with precipitated carbides is passing through the center of the electron micrograph. Matrix precipitates are y -Nij(TiAl).

The next point to realize is that the best emitter is a metal. Many forms of carbon initially studied are semiconductors or even insulators, including nanodiamond [8-11] and diamond-like carbon (DLC) [12-13,4]. Combine this with local field enhancement means that there is never uniform emission from a flat carbon surface, it emits from local regions of field enhancement, such as grain boundaries [8-11] or conductive tracks burnt across the film in a forming process akin to electrical breakdown [13]. Any conductive track is near-metallic and is able to form an internal tip, which provides the field enhancement within the solid state [4]. Figure 13.2 shows the equipoten-tials around an internal tip due to grain boundaries or tracks inside a less conductive region. 

Aluminum nitride is most commonly used for its high thermal conductivity. Recently, a poreless composite material, TiAl-TiB2-AlN, was obtained by reacting a Ti-F(0.7-0.95)A1+(0.05-0.50)8 mixture at 30- to 100-atm nitrogen pressure (Yamada, 1994). The use of high-pressure nitrogen gas was found to be effective for simultaneous synthesis and consolidation of nitride ceramics with dispersed intermetallic compounds (e.g., TiAl). Dense, crack-free products with uniform grains (approximately 10 mm in size) were obtained. 

One of the peculiarities of the natural diamond is a considerably lower content of admixtures Ni, Mn, oth. as compared to the synthetic diamond. It is this feature that determines its raised resistance to the action of high temperature in the combustion wave. Figure 3 shows the dependencies of the recuperated synthetic and natural diamond strength on the mass proportion of the charge layers mi/m2 with diamond concentration equal to 25 % vol. on the example of the bi-layered composite with the ceramic binder (Ti,Mo)Ca. The strength of diamond grains is also affected by mi/m is the composites with the binder of NiAl, TiB+Ti, TiC-l-TiAl, TiB2+Si. 

Trousseau s H tial Aerated Water. Fotassio-tartrate of iron, 10 grains artificial Seltzer water, 1 pint. 

The striking features after oxidation of Ti35A15Nb for 4h at 900°C are the slight enrichment of aluminium in the metal subsurface zone instead of aluminium depletion, the preferred formation of AlON in wide parts of the metal/oxide interface and the development of a rather dense, coarse-grained partial layer consisting of titania in the oxide scale. Several reasons for the beneficial effect of niobium addition on the oxidation behaviour are discussed in the literature [5,10,11]. Beside the influence of niobium on the aTl/aAI ratio and expansion of the 7-TiAl phase field the effect of doping of titania by niobium is often discussed. By doping of titania with niobium the concentra-... 

Kg.3. Bright field TEM cross section of y-TiAl oxidized for 100 h.The SAD pattern reveals the cubic structure of the A1 depleted grains. 

Cardamom Seed. Grains of paradise. Dried ripe seeds of Elettaria cardamomum Maton, Zingiheraceac. Habit Malabar, cultivated in India. Coyjon. Guatemala. Constit Resin 2-8% essential oil. 1 -2% fixed oil. The essen tial oil contains eucalyptol (cineol) sabinene. d,a terpineol and acetate bomeol. limonene. terpinene, 1 -terpinen -4-ol and its formate and acetate. The fixed oil consists of the... 

There are many examples which show that the strength and hardness of an alloy can be increased by a factor of 4-7 if the grain size is decreased into the nanometer range. One such example is the rapidly solidified Al96Cr3Ce]COjc x = 1-2%) alloy containing as a main component a nanosized quasicrystalline icosahedral phase [35]. A similar strengthening is found in many metals such as TiAl [36], Cu [37], and other... 

Tntermetallic materials in the Ti-AI system were used as a precursors for synthesis of TijAlN powders. In the first stage of the experiment TiAl powder was synthesized by SHS method Titanium hydride powder, TiHj, and metallic aluminium powder with grain sizes below 10 pm were used as... 

---