Temperature of decomposition

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. 

Table 1. Effect of Temperature of Decomposition of the Product of Reaction of Pentafluorophenyllithium with Dimethyl Oxalate on Product Distribution [JJ]...

Instrumental factors. Heating rate. When a substance is heated at a fast rate, the temperature of decomposition will be higher than that obtained at a slower rate of heating. The effect is shown for a single-step reaction in Fig. 11.4. The curve AB represents the decomposition curve at a slow heating rate, whereas the curve CD is that due to the faster heating rate. If TA and Tc are the decomposition temperatures at the start of the reaction and the final temperatures on completion of the decomposition are TB and TD, the following features can be noted ... 

Diverse thermogravimetric results can be obtained from samples with different pre-histories for example, TG and DTG curves showed that magnesium hydroxide prepared by precipitation methods has a different temperature of decomposition from that for the naturally occurring material.32 It follows that the source and/or the method of formation of the sample should be ascertained. 

For applications having only moderate thermal requirements, thermal decomposition may not be an important consideration. However, if the product requires dimensional stability at high temperatures, it is possible that its service temperature or processing temperature may approach its temperature of decomposition (Tj) (Table 7-12). A plastic s decomposition temperature is largely determined by the elements and their bonding within the molecular structures as well as the characteristics of additives, fillers, and reinforcements that may be in them. 

Compound Preparation" Temperature (°C) Time (days) Temperature of decomposition (°C) (g/cm ) Ref... 

The NFPA reactivity code, labour regulations, enthalpy and temperature of decomposition of the compound are all listed in the following table. They help to identify a compound s instability. There are a few compounds used in the explosives industry added to the list. These codes are described in Part I (see p. 119-123). 

A study showed that, if the salt present decomposes at 180°C, its temperature of decomposition reaches 74-80 C when it is in a solution with DMSO. The compounds formed are the ones that are mentioned, but formol is in the form of polymer. There is a substantial gas release during the decomposition. This gas certainly caused the sealed tube to detonate. Another decomposition reaction has been suggested ... 

Thus, the overall reaction may be written as RH + 02 1 ROOH. The G values for hydroperoxide formation at 50°C range from -16 for 2,2,4-trimethylpentene-l to -400 for cyclohexene (Wagner, 1969). Although this temperature is somewhat lower than the temperature of decomposition of the hydroperoxide, in practice the reactions are conducted at elevated temperatures. In such cases, the radition-induced initiation either eliminates the induction period or allows the recations to proceed at somethat lower temperatutes than would be otherwise required. 

The temperature of decomposition of carbonates of the YBCO high-temperature superconductor to oxides [97] ... 

When the melting point of a decomposing substance is to be determined the bath is heated rather rapidly to within 10°-20° of the temperature of decomposition, and from that point onwards the rate of heating is reduced to about 5° per minute. 

After 5 h at room temperature, 6 mol% of chlorine was replaced by the malonate accompanied with ca. 6% of C=C structure to result in a pale brown powdery product (15). Temperature of decomposition of the product, however, fell to ca. 200°C (DTA) compared with that of PVC (270°C). 

After an incident involving the violent decomposition of hot 3-methyl-5-amino-isoxazole, the thermal stability of 7 other isoxazole derivatives was studied by DSC, TGA and ARC. Only 4-amino-3-isoxazolidinone decomposed exothermally in an open crucible, but all did so in sealed capsules, evolving much gas. The results below give isoxazole derivative, ARC onset temperature of decomposition (°C)/adiabatic exotherm (°C)/max. pressure (bar) and DSC heat of decomposition (kJ/g), respectively for all 9 compounds. 

Fig. 1.34 The influence of annealing temperature on onset and peak temperature of decomposition peak obtained by DSC test...

Andreasen et al. [86] also found that ball milling increased the rate constant, k, in the JMAK equation (Sect. 1.4.1), of reaction (Rib) in solid state but virtually had no effect on the rate constant of reaction (R2). They also showed that the reaction constant, k, of reaction (Rib) in solid state increases with decreasing grain size of ball-milled LiAlH within the range 150-50 mn. Andreasen et al. concluded that the reaction (Rib) in solid state is limited by a mass transfer process, e.g., long range atomic diffusion of Al while the reaction (R2) is limited by the intrinsic kinetics (too low a temperature of decomposition). In conclusion, one must say that ball milling alone is not sufficient to improve the kinetics of reaction (R2). A solution to improvement of the kinetics of reaction (R2) could be a suitable catalytic additive. 

TGA analysis shows that polymer degradation starts at about 235°C which corresponds to the temperature of decomposition of the cellobiose monomer (m.p. 239°C with decom.). Torsion Braid analysis and differential scanning calorimetry measurements show that this polymer is very rigid and does not exhibit any transition in the range of -100 to +250 C, e.g. the polymer decomposition occurs below any transition temperature. This result is expected since both of the monomers, cellobiose and MDI, have rigid molecules and because cellobiose units of the polymer form intermolecular hydrogen bondings. Cellobiose polyurethanes based on aliphatic diisocyanates, e.g. HMDI, are expected to be more flexible. 

As in the case of AN, the thermal decomposition process of HNF varies with the temperature of decomposition. Deflagatory decomposition of HNF produces ammonium nitroformate, which decomposes to hydrazine, nitroform, and am-monia.[2 l These products react to generate heat in the gas phase and the final combustion products are formed according to ... 

This test differs from Abel s test in using temperature of decomposition rather than time at constant temperature Ref Daniel (1902), 679... 

Thermal initiation of an explosion as well as the temperature of decomposition of propellants are measured by standard test No. 6 developed by the Joint Army-Navy-Air Force Panel on Liquid Propellants (2). The primary purpose of this test is to determine at what temperature an unstable material will undergo rapid exothermic decomposition. If the rate at which the heat is generated is greater than the rate at which it can be dissipated, an explosion will be likely. This test attempts to predict the result of conditions that can exist in the regenerative heating section of a rocket engine as well as at the propellant injector. Both of these sections experience relatively rapid local temperature rises owing to combustion. 

The temperature of decomposition depends also on steric factors The spiro compound 196 c with the five-membered dithiaphospha ring is much more stable than the spiro compound 196 d with the six-membered hetero ring. Only in the latter compound can a stable 1.2-dithia-cycloalkane be formed by radical cleavage Once again the preparative behaviour is in accord with the results of mass spectroscopy (p. 112). 

Ephraim and Bolle 3 find that the stability of the ammines of general formula [M(NII3) ]R2 depends not only on the central atom but also on the anion. These influences oppose one another, and the stability of the whole molecule is therefore the resultant of the two influences consequently, very little parallelism may appear between analogous compounds. For instance, the temperatures of decomposition of the hexanunino-salts of nickel decrease in the order perchlorate, iodide, bromide, chlorate, nitrate, chloride, sulphate whilst in the ease of the liexammino-salts of zinc, the order for decreasing stability is iodide, bromide, chloride, perchlorate, sulphate, nitrate, chlorate. 

Table I. Starting temperatures of decomposition (T

Table II. Inherent viscosities (tjinh s), glass transition temperatures (Ta s) and starting temperatures of decomposition (T

Thermal properties of the polyesters obtained were studied by TG and DSC. The starting temperature of decomposition (Tfrom Table III, Tpolymer measured in air is lower than that measured in nitrogen. T[Pg.219]

Table III. Starting temperatures of decomposition (T s) of polyesters (XII) with syringyl-type biphenyl units...

The characteristics of this explosive are calculated density (X-ray diffraction) =1.865gem"3, impact sensitivity (h50% for 5 kg weight) =70cm, friction sensitivity = insensitive, temperature of decomposition (DSC) ca. 350°C and VOD = 8200 ms"1. The data confirm that DANTNP is slightly more powerful while its impact insensitivity is of the order of TATB [174]. 

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