Ordered structure powdered mixtures

Ohta KM. Fuji M, Chikazawa M. Effect of geometric structure of flow promoting agents on the flow properties of pharmaceutical powder mixture. Pharm Res 2003 20(5) 804—9. Swaminathan V. Kildsig D. The effect of particle morphology on the physical stability of pharmaceutical powder mixtures The effect of surface tou ness of the carrier on the stability of ordered mixtures. Drug Dev Ind Pharm 2000 26(4) 365. 

The M—O, M—C, M—O shells are determined as previously. If the stoichiometry of the compounds is taken into account, the bridging network shown above is only compatible with a chain structure. The X-ray powder pattern,excludes the presence of copper oxalate and strongly suggests an ordered structure deriving from the structure of nickel oxalate. A 1/1 mixture of the pure microcrystalline powders can also be ruled out. Consequently, a bimetallic chain structure appears to be the most likely (Fig. 19). 

For a non-structured powder randomization is normally the goal of an industrial mixer. An ordered mixture would be very desirable from the point of view of mixture quality but the reality is that segregation Figure 5.1(d)), and a subsequent loss of quality are the most likely outcome of the mixing process. 

A similar development in this direction is the synthesis of a mixed-phase material containing both micro- and mesopores (Ti-MMM-1) (223). This material was synthesized by the addition of organic templates for mesopores (cetyltrimethylammonium bromide, CTABr) and micropores (tetrapropylammo-nium bromide, TPABr) at staggered times and the variation of the temperature of a single reaction mixture. Ti-MMM-1 is more selective (for oxidation of cyclohexane and of n-octane) than either Ti-MCM-41 or TS-1. The powder X-ray diffraction pattern indicates that the material contains both MCM-41 and MFI structures. The mixed phase contains framework Ti species and more atomic order within its walls than Ti-doped MCM-41. 

Although there are many variations on how carbon fibers are made, the typical process starts with the formation of PAN fibers from a conventional suspension or solution polymerization process between a mixture of acrylonitrile plastic powder with another plastic, such as methyl acrylate or methyl methacrylate, and a catalyst. The product is then spun into fibers, with the use of different methods, in order to be able to achieve the internal atomic structure of the fiber. After this, the fibers are washed and stretched to the desired fiber diameter. This step is sometimes called "spinning" and is also vital in order to align the molecules inside the fiber and thus provide a good basis for the formation of firmly bonded carbon crystals after carbonization [7]. 

The interaction between pyridine and organolithium compounds in benzene was first reported by Ziegler and Zeiser129 and was attributed to the formation of 1 1 adducts. Indirect evidence for intermediates of this kind was based on the formation of dihydropyridines by treatment of the reaction mixture with water. More definite evidence was obtained with quinoline, isoquinoline, and acridine.130 Phenyllithium reacts quantitatively with quinoline in ether to yield an adduct as a yellow powder that can be recrystallized. In order to define the site of attachment, the adducts were hydrolyzed to dihydro derivatives and the latter dehydrogenated. Because this treatment leads mainly to 2-phenyIquinoIine and l-phenylisoquinoline from quinoline and isoquinoline, respectively, the related adducts can be assumed to have structures 80 and 81. Isolation and characterization of the dihydro derivatives have been carried out, as well as in the case of the reaction of acridine with phenyllithium. 

---