Selected Bond Coats

An ideal bond coat should have several characteristics that include uncompromised biocompatibility, good adhesion to both the metal substrate and the osseoconductive top coat, and a well-defined melting point to allow application of thermal spray technology. The adhesive function of the bond coat has been loosely compared to the action of a double-sided adhesive tape. 

---

The stationary phase in LC is a fine granular solid such as silica gel. It can be used as such (mainly for nonpolar compounds), or the granules can be modified by a surface-bonded coating that changes (reverses) the polarity of the gel. A very small selection of stationary phases is listed in Table 35.2. 

Table 7.11 Plasma spray parameters selected to deposit the bioconductive hydroxyapatite top coat and the bioinert titania bond coat (Heimann, Schurmann and Muller, 2004).

Two strategies are currently in use to improve the sensitivity and selectivity of SAW sensor systems. One involves the selection of coatings that exhibit a unique chemical selectivity for the analyte vapor. It is often observed that for a particular vapor/coating interaction, the specificity and reversibility of the interaction are inversely related. That is, highly specific interactions often involve large bonding energies that are not spontaneously reversible. Such... 

Under normal conditions on repair sites it seems likely that a more reliable bond can be achieved by using a bond coat rather than by relying on any natural bond between fresh and hardened Portland cement concretes(2). However, bonding agents for use on site must be tolerant of site conditions, be reliable and cannot be selected solely on the basis of slant shear results. The bonding performance of carefully applied SBR and acrylic latex/cement slurry coats appears to be similar to that of epoxy resin bonding aids(14). However, other factors such as open time, barrier coat effects and cost may affect the final choice. 

Sprayed ceramic coatings can be made chemically active by selection of the spray parameters, which result in metastable phases within the coating. Ceramic bond coats are useful for difficult to bond materials such as ceramic components, including carbide-containing parts and refractory metals. These materials may be used in combination with a metallic bond coat on metallic substrates to mitigate stress differentials between the metallic substrate and the ceramic bond coat due to thermal or mechanical stress. 

Figure 10 The Ni-Al pseudo-binary phase diagram illustrating the compositional range of the P-NiAl phase and the direction of the change in composition as the A1 the in bond coat is depleted by interdiffusion and selective oxidation [10],...

Liu Z, Gao W, Dahm K L, Wang F, The effect of coating grain size on the selective oxidation hehaviour of Ni-Cr-Al alloy , Scripta Mater, 37 (1997) 1551-1558 Strauss D, Muller G, Schumacher G, Engelko V, Stamm W, Clemens D, Quadakkers W J, Oxide scale growth on MCrAlY bond coatings after pulsed electron beam treatment and deposition of EBPVD-TBC , Surf Coat Technol, 2001, 135(2—3), 196-201... 

The hydrogenolyaia of cyclopropane rings (C—C bond cleavage) has been described on p, 105. In syntheses of complex molecules reductive cleavage of alcohols, epoxides, and enol ethers of 5-keto esters are the most important examples, and some selectivity rules will be given. Primary alcohols are converted into tosylates much faster than secondary alcohols. The tosylate group is substituted by hydrogen upon treatment with LiAlH (W. Zorbach, 1961). Epoxides are also easily opened by LiAlH. The hydride ion attacks the less hindered carbon atom of the epoxide (H.B. Henhest, 1956). The reduction of sterically hindered enol ethers of 9-keto esters with lithium in ammonia leads to the a,/S-unsaturated ester and subsequently to the saturated ester in reasonable yields (R.M. Coates, 1970). Tributyltin hydride reduces halides to hydrocarbons stereoselectively in a free-radical chain reaction (L.W. Menapace, 1964) and reacts only slowly with C 0 and C—C double bonds (W.T. Brady, 1970 H.G. Kuivila, 1968). 

Hz for thick coatings such as reinforced coal tar enamel, being selected to minimise interference from commonly occurring frequencies while maximising the distance the signal will travel, some 5-10 km on a reasonably well-coated pipeline. For thin film, coatings, such as a fusion-bonded epoxy, a frequency of 200 Hz has been found more appropriate. 

MIBK is a valuable industrial solvent used primarily in the paint and coating industry and in metallurgical extraction processes. It is also used as a precursor in the production of specialty chemicals such as pesticides, rubber anti-oxidants as well as antibiotics and pharmaceuticals (1). Historically, MIBK has been produced commercially from acetone and hydrogen feedstock in three stages. First, acetone is dimerized to produce diacetone alcohol (DAA). Second, DAA is dehydrated to produce MO and water. Finally, the carbon-carbon double bond of MO is selectively hydrogenated to produce MIBK. These consecutive reactions are outlined in equations (1-3). 

---