Alkoxide process

The seven processing steps shown schematically in Figure 1 are involved to various degrees in making sol—gel-derived siUca monoliths by methods 1, 2, and 3. The emphasis herein is primarily on net-shape sol—gel-derived siUca monoliths made by the alkoxide process (method 3) prepared under ambient pressures. 

The coupling and protection-deprotection reactions to yield Taxol were fully licensed by BMS from FSU as part of the original licensing agreement (Scheme 7.3). This so-called metal alkoxide process was patented by Holton in 1992 [13]. 

Fig. II. Chemical reactions involved in sol-gel alkoxide processing of silica gel-glass...

The alkoxide process allows close control over important physical properties and guarantees a consistent product quality at high purity level. 

The high resolution image was obtained for the crystal from the alkoxides process (Figure 7). The layered structure was obvious from the high resolution image taken from... 

A few varieties of nonsilicate oxide ceramic powders synthesized through alkoxide processing are presented here. These oxide powders were developed for the use of electronic, optical, and high-temperature structural applications. For each material, we start with a brief description of the synthesis, which is followed by powder characteristics (e.g., particle sizes, morphologies, and size distributions) and densification behavior and some properties of dense material. 

A few multicomponent electronic ceramics, fabricated through metal alkoxide processing, are described in this section. 

Numerous reports [53-62] regarding the synthesis of YAG have appeared in the literature, and in most cases the final product was either a mixture of various yttrium aluminate phases or stoichiometric YAG of undesirably large particle size. The phase inhomogeneity in the final product, through alkoxide processing, was caused by the formation of a Y-Al double alkoxide, which is a very stable compound and, hence, extremely resistant to hydrolysis [63]. For the Y and A1 isopropoxides, the two react to form a stable Y-Al double iso-propoxide according to the reaction... 

Figure 4 Scanning electron micrographs of dielectric powder prepared by (a) an alkoxide process and (b) a conventional process. (From Ref. 34.)...

With the improved properties demonstrated for this composite, a comprehensive study was initiated to systematically investigate this composite system. Materials were prepared in situ by the alkoxide process to exploit the full potential of this promising material. A range of SiC whisker additions and Zr02 with different kinds and amounts of stabilizer were employed. An original study was accomplished at the Air Force Research Laboratory," which was complemented by a number of cooperative studies by experts in different disciplines. In the final analysis impressive properties were demonstrated, but some disappointing results were also obtained. 

The so-called alkoxide process is convenient because it is generally applicable to a large number of oxidic compounds and because the microstructure and properties of the product are in general easily changed with the process conditions. 

Hoch, M., Preparation of A1p0o-TlC Ceramic Bodies by the Alkoxide Process. J. de Physique 47 C1-37 (1986). 

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