Silver azide properties

Property Mercury fiihninate Lead azide Silver azide Normal lead styphnate DDNP Tetrazene... 

Similar in properties to lead or silver azide, it explodes on heating or impact. 

Gray and Waddington [57,120] examined the physico-chemical properties of silver azide and state that its melting point is 300°C. On the basis of the latest opinion that the explosive decomposition of azides results from processes involving ions and electrons caused by imperfection and deficiencies in the crystal lattice (Jacobs and Tompkins [22]), the authors incorporated silver cyanide, Ag2(CN)2,... 

Thus migration of the cation is possible, and the authors presume that this is the cause of the initiating property of silver azide. 

There are some indications that silver perchlorate has initiating properties since in some unexplained cases, the large crystals detonate on slight friction in a way similar to the detonation of crystals of lead azide or silver azide (Hein [127]). 

A correction should be made to the description in Vol. Ill of some properties of silver azide it is tron-hygroscopic, accordUig to C. A. Taylor and Rinkenbach [133] and Costain [3, (Vol. 2, p. 51)]. The hygroscopicity described previously was probably due to impurities. 

Tire above figures and Fig. 78 throw some light on the problem (p. 475) of why lead and silver azides possess marked initiating properties when the others do not. 

The trend in detonator and explosive-train design, which has continued into the 1970s, has been to smaller components, requiring decreased amounts and diameters of more efficient explosives. This trend itself has tended to emphasize the technological importance first of lead and then silver azide and to assure the continued modification of their properties by process development and control. 

Properties Lead azide Silver Azide Experimental preparation ... 

Minute amounts (0.01% to 2%) of impurities significantly affect the rate of thermal decomposition of lead and silver azides (Chapter 6, Volume 1). For example, the ionic impurities Ag, Fe IFeNs], and [BiN,] increase [59-61] and Cif decreases [100] the rate of thermal decomposition of lead azide Cu increases the rate for silver azide. In contrast to ionic unpurities incorporated in the azide lattice, semiconductors [62,63] in contact with the surface and proton- or electron-donor vapor adsorbed on the surface of azide (Chapter 4. Volume 2) affect its decomposition properties. 

The sensitivity of azides to heat is one of their properties which can be most precisely determined. The more practically useful substances, such as lead and silver azides, do not detonate until temperatures close to or at their melting points are attained. Among technologically important sohd explosives such as TNT, tetryl, and RDX, the relatively high melting points of lead and silver azides (<300°C) and the good vacuum stability in standard tests are perhaps not representative of their overall sensitivity. Once a threshold temperature has been attained in the azides, the transition from slow decomposition to detonation is... 

The disorder produced by irradiation has been studied in only a limited number of the explosive azides. The selection of the azides for investigation has undoubtedly been determined by their usefulness for civilian and military applications. Hence silver azide, and, in particular, lead azide, have been studied. Other factors, such as ease of preparation, ease of handling, similarities in properties to azides of practical importance, and purely fundamental considerations have played a roll in the selection of materials. In addition to lead and silver azide only thallium and barium azides have Keen studied to any extent, and this section is devoted almost exclusively to these four materials. All results are for a-Pb(N3)2 unless otherwise stated. 

Because colloidal metal (color) is produced by irradiation of small band gap azides, they may be useful as photographic materials. In fact, silver azide emulsions have been made and their properties compared with emulsions of silver halides [208,209]. No attempt is made here to review in detail the photographic properties of emulsions. Instead a few characteristics of crystalline material are discussed briefly. 

Silver azide has similarities to lead azide in its photodecomposition properties, although the rate of gas evolution is about an order of magnitude greater than for lead azide [234]. The intensity dependence of the rate for both materials varies approximately linearly, although departures have been observed for both solids as a function of the magnitude of the intensity and of the total amount of decomposition. Zakharov et al, reported that the intensity depen-... 

Silver azide is slightly hygroscopic and is a very vigorous initiator, almost as cllicient as lead azide, Like lead azide, silver azide decomposes under the influence of ultra-violet irradiation. If the intensity of radiation is suflicicntly high the crystals may explode by photochemical decomposition. The ignition temperature and sensitiveness to impact of silver azide are lower than that of lead azide. Some of its properties are presented in Table 2.5. 

Impact sensitivity significantly depends on many aspects. Let us look at some of these properties starting with crystal size of the material under test. Colloidal silver azide prepared from concentrated solutions exhibits significantly lower sensitivity (0.5 kg from 77.7 cm) than coarser crystals prepared from diluted solutions, which required less than half the energy (0.5 kg fi om 28.5 cm). MF measured under the same conditions for comparison required 12.7 cm with the 0.5 kg hammer [20]. It is interesting to note that the impact sensitivity of S A (in fine powdery form), which is considered very sensitive, is lower than that of MF. Similar investigations have... 

The main historical obstacle for the practical use of pure silver azide (apart from its price) was its unsuitable form— unsuitable free flowing properties for volumetric loading and pressing into detonators. This problem was successfully solved by the development of a process for production of granular silver azide. An example of commercially manufactured spherical shaped crystals of silver azide is presented in Fig. 4.10 [22]. 

All heavy metal azides run very quickly into detonation. This spedlic property has estabhshed the use of silver azide and lead azide as primary explosives in detonators. 

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