Decomposition sohd-state

Both zirconium hydride and zirconium metal powders compact to fairly high densities at conventional pressures. During sintering the zirconium hydride decomposes and at the temperature of decomposition, zirconium particles start to bond. Sintered zirconium is ductile and can be worked without difficulty. Pure zirconium is seldom used in reactor engineering, but the powder is used in conjunction with uranium powder to form uranium—zirconium aUoys by soHd-state diffusion. These aUoys are important in reactor design because they change less under irradiation and are more resistant to corrosion. 

Arsenic pentachloride [22441-45-8] (arsenic(V) chloride), AsQ., is produced by irradiation of a solution of AsQ. chlorine at —105°C using ultraviolet light (22). Arsenic pentachloride is a pale yellow soHd (presumably because of an entrained chlorine impurity) which melts with partial decomposition at —50° C. Raman spectra show that it is a trigonal—bipyramidal molecule both in solution and in the soHd state. 

The molecule S12, like Se, is of Dsd symmetry but in the soHd state it occupies sites of the much lower C211 symmetry [163]. Due to the low solubihty and the thermal decomposition on melting only solid state vibrational spectra have been recorded [2,79]. However, from carbon disulfide the compound Si2-CS2 crystallizes in which the S12 molecules occupy sites of the high Sg symmetry which is close to 03a [163]. The spectroscopic investigation of this adduct has resulted in a revision [79] of the earher vibrational assignment [2] and therefore also of the earlier force constants calculation [164]. In Fig. 24 the low-temperature Raman spectra of S12 and Si2-CS2 are shown. 

The theoretical hmit of 5.4% (NaAlH4+2 mol% TiN) for the two subsequent decomposition reactions is in both cases only observed in the first cycle. The reason for the decrease in capacity is stiU unknown and litde is known about the mechanism of alanate activation via titanium dopants in the sohd state. Certainly, the ease of titanium hydride formation and decomposition plays a key role in this process, but whether titanium substitution in the alanate or the formation of a titanium aluminum alloys, i.e., finely dispersed titanium species in the decomposition products is crucial, is stiU under debate [41]. 

A few diazoniiun salts are unstable in solution, and many are in the sohd state. Of these, the azides, chromates, nitrates, perchlorates (outstandingly), picrates, sulfides, triiodides and xanthates are noted as being explosive, and sensitive to friction, shock, heat and radiation. In view of their technical importance, diazo-nium salts are often isolated as their zinc chloride (or other) double salts, and although these are considerably more stable, some incidents involving explosive decomposition have been recorded. 

Carstensen, J.T., and Kothari, R. (1983), Sohd-state decomposition of alkoxyfuroix acids in the presence of microcrystalline cellulose, / Pharm. Sci.,12,1149. 

Cd(OH)2 is precipitated from aqneous Cd + by addition of bases. It is colorless and solnble in acids and aqueons NH4CI, but only slightly in NaOH solutions. Cd(OH)2 is a base stronger than Zn(OH)2 its solnbility product is 10 and log K for the eqnihbrium Cd - - OH = CdOH+ is 6.38. Cd(OH)2 begins to undergo thermal decomposition at about 150 °C (at 200 °C it is complete). Several basic salts are known and may be prepared from alkaline Cd + solutions or by heating CdO with solntions of Cd + salts at 200 °C. Hydroxide halides have been carefully investigated both in solution and in sohd state. Physical properties of Cd(OH)2 are reported in Table 8. 

The anion [AuFe]" has distorted octahedral structure with /(Au F) = 1.85 to 1.90 A. Oxidation of M[AuF4] (where M = K, Cs, or NO) by fluorine also produced [AuFe]. Gold(V) fluoride is formed by the thermal decomposition of [KrF][AuF6] or [02]" [AuF6]A AuFs is a fluorine-bridged polymer in the sohd state. 

The stability of trihydride complex (171) has been fonnd to be a remarkable featnre. Complex (171) is stable under inert atmosphere up to 115 °C in the sohd state and in toluene solution at room temperatnre for months. It was observed that when the toluene solntion was heated at 100 °C, no decomposition occurred until indium(O) traces appeared. In the presence of catalytic amount of indium(0), complex (171) decomposed entirely in a few minutes, freeing the free carbene, IMes (equation 24). 

The above method can be extended and selectivity increased by use of any analytical technique capable of distinguishing and measuring yields of individual products. Most of the routine methods of gas analysis [71-75] have been used to determine the compositions of gaseous products from sohd state decompositions. The sophistication of the analysis may range from a single determination of the amount and composition of the accumulated gas at the end of reaction, to the continuous or frequent monitoring of individual gaseous products with temperature or with time. These profiles can be used for the determination of kinetic information. 

The review of the decomposition of oxides, given below, focusses attention on those studies which have yielded information on the mechanisms of reactions proceeding in the sohd state. 

For the decompositions of some chromates it has been possible to relate values of to spectroscopically measured charge transfer energies. Such studies could be of value in identifying the bonding situations ("transition state") which arise during the course of sohd state decompositions. The possibility that electron-accommodating energy levels at surfaces or interfaces may be involved has been discussed [119]. 

Ammonium salts have been grouped in a separate chapter to emphasize the similarities of behaviour in reactions involving the NH4 ion, or yielding the volatile NH3 molecule, following a proton transfer step. Detailed kinetic studies have been published for the sohd-state decompositions of many ammonium salts. Comparisons with the metal salts containing the same anion are often useful. The reactions of sohd coordination compounds in which ammonia is present as a ligand are discussed in Chapter 17. 

Thallium(I) nitride is a highly explosive black solid, but the yellow azide TIN3 is more stable the physical properties suggest that there is some covalent T1—bonding in the sohd state. The mechanism of the decomposition has been reviewed. ... 

Reactions of materials in the solid state are strongly influenced by an enormous range of variables, and a complete treatment of this vast subject is beyond the scope of this book or, in fact, any single volume. One factor that becomes apparent immediately when dealing with soHd state reactions is that the rate can generally not be expressed in terms of concentrations. We can illustrate this by means of the following example. The first step in the decomposition of metal oxalates when they are heated normally leads to the loss of carbon monoxide and the formation of a carbonate. In the case of NiC204, the process can be shown as... 

This chapter provides an introduction to the principles underlying the reactions of soHds. Kinetic studies in this area are not as highly accurate or reproducible as those on reactions in solutions or in the gas phase. However, because of the importance of many soHd state reactions, some understanding of how the reactions occur is necessary. Processes such as the drying of solids, crystaUization, and decomposition of a wide range of materials make it clear that this area of chemical kinetics will receive more attention in the future. 

The sodium salt is decomposed in the sohd state by heat and light. It also decomposes slowly in basic or neutral solution and more rapidly in acidic solution. The decomposition in alkaline solution occurs as follows ... 

The thermal decomposition of 2-CEES on nanocrystalhne zeohtes was probed by FTIR spectroscopy. Comparison of the reactivy of nanocrystaUine NaZSM-5, silicalite and NaY indicated that NaZSM-5 was most effective for 2-CEES thermal oxidation and that external surface silanol sites were important to the zeolite reactivity. The adsorption and reaction of DMMP on nanocrystalline NaY was investigated using FTIR and sohd state NMR spectroscopy. External surface silanol and EFAL sites were implicated in the thermal oxidation of DMMP on nanocrystaUine NaY. Thus, the nanocrystalline zeolites can be envisioned as new bifunctional catalyst materials with active sites on the external surface playing an important role in the intrinsic reactivity of the material. Future studies will focus on optimizing the activity of nanocrystaUine zeolites for CWA decontamination apphcations by taUoring the surface properties. 

Price, G. L. Kanazirev, V. and Church, D. F., Formation of Cu-MFI NO decomposition catalyst via reductive sohd-state ion exchange, Journal of Physical Chemistry, 99(3), 864-868 (1995). 

Telluradiazolines are thermally stable crystal compounds, but they are very sensitive to light. When exposed to daylight, telluradiazolines undergo rapid decomposition, even in the sohd state. By heating degassed solutions of telluradiazoline 79a in deuterochloroform or benzene, telluroketone 85 and alkenes 81 and 82 are formed in almost quantitative yield (93JA7019). 

Vyazovkin, S. (2003). Reply to "What is meant by the term variable activation energy when ap>phed in the kinetics analyses of sohd state decompositions (crystolysis reactions) ", Themochimica Acta, Vol. 397, pp. 269-271 ISSN 0040-6031 Vyazovkin, S. (2010). Thermal Analysis, Analytical Chemistry, Vol. 82, pp. 4936-4949 ISSN 0003-2700... 

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