Carbonates solid-state reactions with

Common routes for the synthesis of selenates and tellurates(IV and VI) are the reactions of metal oxides or carbonates with the repsective acids (see Section 4). The disadvantage of this procedure is, that one usually obtains hydrates or, at higher acid concentrations, acidic compounds. Because the oxides E03 and E02 (E=Se, Te) are solids under ambient conditions, solid-state reactions with the respective metal oxides are an alternative route to prepare the anhydrous compounds. 

Ba-Mn-substituted hexaaluminate Solid state reaction with ball milling Oxides and carbonates 1100-1300 Ba-P-Al203 Catalytic combustion 11... 

Polyacrylonitrile (PAN) has pendant nitrile groups and therefore was selected as a prime candidate for modification by organotitanium complexes, PAN also can be easily fabricated into fibers and processed at elevated temperatures to produce "carbon" which can simultaneously undergo a "solid state" reaction with titanium. Under appropriate processing conditions it was envisaged that Ti-C would be the main constituent of the end product. 

Arc-melting Well mixed (in some cases partially pre-reacted) compacts of carbon and the metal may be reacted by melting arc-melting may be especially suitable. An advantage of melting in comparison with solid-state reactions may be related to the fact that arc-melted pieces have a smooth surface less susceptible to contamination. This method was found especially effective for refining and for the preparation of solid solutions mainly of the 4th and 5th carbides groups. 

The compound Ba5[Ru2(0)n] has been synthesized by solid-state reactions of barium carbonate with ruthenium oxide. The X-ray structure shows that it contains peroxide ions and the ruthenium is in the +5 oxidation state, i.e., Ba5[Ru2(02)0g]. The novel mixed-valence Ru — Ru triple perovskites, Ba3M[Ru2(0)9] (M = Li, Na), have been grown from reactive hydroxide fluxes. ... 

A series of solid-state reactions has been explored by Kaupp et al., in which gaseous amines were reacted with aldehydes to give imines. Analogous reactions with solid anhydrides, imides, lactones or carbonates, and isothiocyanates were used to give, respectively, diamides or amidic carboxylic salts or imides, diamides, carbamic acids, and thioureas [24]. In general the yields were found to be quantitative. Ammonia and other gaseous amines, in particular methyl-amine, have also been shown to aminolyse thermoplastic polycarbonates [25]. 

Most important are quantitative solid-state reactions of cyclic carbonic acid derivatives with gaseous or solid amines. These give open-chain amides that can be recyclized in various cases to new products of preparative interest. 

In the crystal structure of the polymer phase (Fig. 17a), the polymer chains are aligned along the c-axis and the distance (3.71 A) between the centres of adjacent cyclobutane and pyrazine rings corresponds to half the c-axis repeat of the unit cell. For comparison between the monomer and polymer structures, an overlay plot of these structures is shown in Fig. 17b. It is clear that the solid-state reaction is associated with only very small atomic displacements at the site of the [2-1-2] photocyclization reaction (the displacement of the carbon atoms of the C=C double bonds of monomer molecules on forming the cyclobutane ring of the polymer is only ca. 0.8 A for one pair of carbon atoms and ca. 1.6 A for the other pair). Such small displacements are completely in accord with the assignment of this solid-state reaction as a topochemical transformation [124—127] (in which the crystal structure of the reactant monomer phase imposes geometric control on the pathway of the... 

On exposure to moisture, the crystalline anhydrides undergo an auto-accelerated polymerisation with evolution of carbon dioxide. This solid-state reaction proceeds without any observable change in the form of the crystal, and its effect on the X-ray pattern has been briefly investigated by Miller, Fankuchen and Mark (5). The probable mechanism of this process will be discussed later. 

The methods of synthesis of fluorapatite have been widely dis cussed (J ). It is for example possible to obtain fluorapatite by substituting the hydroxyl ion for the fluoride ion, either in a-queous solution at room temperature, or through a solid state reaction at 800°C. It can also be prepared by the action of 6-tricalcium phosphate on calcium fluoride at about 800°C. Its solubility and thermal stability have already been established. While much is known about fluorapatite, many questions still exist concerning the mechanism of their formation, their composition and the structure of some of them. Two of these problems are dealt with here. First, we discuss the formation mechanism of fluorapatite by a solid state reaction between calcium fluoride and apa-titic tricalcium phosphate. Then we present the preparation and the structure of a carbonated apatite rich in fluoride ions. 

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