Aluminum/carbon elemental ratios

The Elements Beryllium (Be), Magnesium (Mg), and Calcium (Ca) all formed oxides in fhe ratio of one afom per oxygen atom RO Boron (B) and Aluminum (Al) formed R2O3 Carbon (C) and Silicon (Si) formed RO2... 

As reinforcement material for all matrix materials - ceramics, metals, and plastics -SiC platelets offer a similar potential as whiskers, but at lower cost and without any health hazard. Platelets are single-crystal, plate-like a-SiC particles with an aspect ratio of about 8-15. SiC platelets typically range in size from about 5-100 pm in diameter and 1-5 pm in thickness (see Table 4.2). They are produced commercially from inexpensive raw materials (silica and carbon, micron-sized 3-SiC powders) at temperatures of 1900-2100 °C under an inert atmosphere [100]. Due to the presence of the boron and aluminum dopants added, platelet-shaped crystals are formed. Aluminum enhances the growth in the [0001] direction and decelerates the growth perpendicular to the [0001] direction. Boron enhances the growth notoriously perpendicular to the [0001] direction [101]. Aluminum (0.04—0.45 wt%), boron and nickel (each 0.4-0.8 wt%), and free silicon (0.3-3.6 wt%) were identified as impurity elements in SiC platelets produced by Millenium Materials [102]. 

Similarly, reaction of 992 with the homologous sulfinylimine (+)-996 afforded a mixture of (+)-997 and (+)-998 (70%) in a ratio of 13 1. The sul-finyl substituents, having served their purpose as control elements, were removed from 994 and 997 by hydrolysis with hydrochloric acid, after which double cyclization was easily accomplished by treating the corresponding iodides (formed in situ) with potassium carbonate in acetonitrile to give (—)-999 ( = 1) and (+)-1000 (n = 2) in moderate yields. Standard reduction of the esters with hthium aluminum hydride completed the syntheses of (—)-tashiromine (ent-929) and (—)-epilupinine (e <-921). As a rider to this synthesis, a similar sequence of transformations on the minor diaste-reomer (- -)-998 yielded (+)-lupinine (ent-926). 

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