Direct Metallization Technology

In continuation of his extraordinarily versatile and efficient directed-metalation technology, Snieckus employed indole 87 to selectively lithiate C-4 and to effect a Negishi coupling with 3-bromopyridine to give 88 in 90% yield [110]. In contrast, a Suzuki protocol gave 88 in only 19% yield (with loss of the TBS group). 

Posner and Canella used the directed metalation technology for phenol C-alkylation (equation 35) phenol was dimetalated at both the hydroxy group and the < -position with t-butyllithium, and treatment with methyl iodide gave o-cresol . Brandsma and coworkers employed a complex reagent of butyllithium, Af,Af,A, A -tetramethylethylenediamine, and potassium t-butoxide for the metalation . Bates and Siahaan metalated cresols with butyl-lithium and potassium f-butoxide, and the o- and m-isomers gave the organometallic intermediate in good yield, while the yield was fair for the p-isomer . The Simmons-Smith... 

Direct Metallization Technologies Common Elements. There are two elements common to aU DMT ... 

Finally, it may be pointed out that none of the rare metals can be smelted directly from the ore. The concentrate must first be converted to a pure chemical compound which is utilized as the raw material for the production of the metal. The refractory rare metals are often obtained in the form of a powder or sponge. They are consolidated and refined by powder metallurgy techniques or by arc melting or by electron beam melting. In fact, the current refractory rare metals technology has been crucially dependent on the development of vacuum metallurgical techniques and processes. 

Apart from direct metallization of substrates as described above, transfer metallization is also possible. In this technology the metal layer is deposited on to a carrier film on which the metal adheres only very weakly, or which is coated in such a way that it is subsequently separable. The metallized side of the film is then laminated... 

In the following, a snrvey of the principal types of alloys in current use is provided, with emphasis on those alloys designed for advanced metals technology, as well as the directions of current development. An excellent introductory source on these alloys and on further developments in this area is Smith, from whom much in this section is drawn. 

M. Orme, J. Coulter, Q. Liu, J. Zhu, R. Smith Charged molten metal droplet deposition as a direct write technology. Mater. Res. Soc. Symp. Proc. 624, 17-22 (2000b). 

Directed Vapor Technologies International USA. Custom metal coatings (www.directedvapor.com)... 

The returns on investment indicated would not normally be regarded as sufficiently attractive to justify investment, and smelter costs need to be substantially reduced, or returns by way of treatment charges need to be substantially increased. New direct smelting technologies offer improved economics but returns have been insufficient to justify new greenfields smelters at prevailing metal prices. 

However, VDF-IDT-CRPs always require a free radical source (e.g., butyl peroxide (TBPO)), as direct metal catalyzed initiation from perfluoroiodides or any other halides is not available. This is a serious drawback with respect to the precise synthesis of block or graft copolymers based on FMs, as such systems would inevitably lead to mixtures of homo- and copolymers with the current technology. Therefore, the availability of an initiation method directly from halides, most likely mediated by transition metal catalysis, would be highly valuable. 

Carbon Suspensions. Black Hole, the second direct metallization techniqne, was patented by Dr. Carl Minten in 1988 and pioneered by Olin Hnnt, who sold their technology to MacDermid in 1991. MacDermid improved the process considerably and called it Black Hole II. Instead of palladium activator. Black Hole II uses carbon suspensions as its conductive medium. Polyelectrolyte conditioned nonconductive surfaces absorb carbon sites, and they line up after heating. To ensure sufficient conductivity, the carbon treatment is performed twice. Residues of carbon sites must be removed from the copper foil surface by a... 

Kennedy, C. R. 1991. Directed metal oxidation and pressureless metal infiltration New technologies for the fabrication of reinforced ceramics and metals. Mater. Sci. Monogr. 68 691-700. 

As environmental pressures intensify, so ever more sophisticated and costly investments will be required to satisfy them, which metal prices might fail to justify. Some plants which caimot achieve compliance may be forced to close. Increasingly, the balance seems likely to be tipped in favour of the newer direct smelting technologies. 

The advent of RP/SFF technology, adapted to meet the needs of the jewelry industry, is having a substantial impact. It has also developed into a RM (Rapid Manufacturing) approach, for example, by use of direct metal laser sintering (DMLS) of powders (see later) [83,84]. 

---