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 | Burn Rate Studies of a Titanium Based Pyrotechnic Smoke Composition
Author : Rajendra, A.G.;Kartha, C.B.;Babu, V.V.
Source : Defence Science Journal ; Vol:50(2) ; 2000 ; pp 199-206
Subject : 662.3 Propellants;66 Chemical Technology
Keywords : Pyrotechnic smoke compositions;Burn rate
Abstract : A pyrotechnic smoke composition producing titanium tetrachloride (TiCl/sub 4/) as one of the major reaction products has been studied. The composition consists of titanium metal powder, hexachloroethane (C/sub 2/Cl/sub 6/), potassium perchlorate (KClO/sub 4/) and titanium dioxide (TiO/sub 2/)/zinc oxide (ZnO). Pyrotechnic aluminium was added in small percentages to tailor the burn rate. The effect of percentage variation of KClO/sub 4/, TiO/sub 2/ ZnO, titanium and aluminium on the burn rate has been investigated. While, the burn rate decreases as the percentage of TiO/sub 2/ ZnO increases, it reaches a maximum as the percentage of KClO/sub 4/ is successively increased, but falls off on further increase. This maximum has been first fixed by studying the tricomponent system containing no oxide. It corresponds to 25 percent KClO/sub 4/. Successive additions of C/sub 2/Cl/sub 6/ and ZnO in 1:3 mol ratio or C/sub 2/Cl/sub 6/ and TiO/sub 2/ in 2:3 mol ratio lead to cooler compositions that burn smoothly without much flame and at lower temperatures. Compositions containing less than 5 per cent titanium is difficult to ignite. Similarly, addition of excess titanium or small quantities of aluminium to the composition is found to increase the burn rate. |
| | Addition of RDX/HMX on the Ignition Behaviour of Boron-Potassium Nitrate Pyrotechnic Charge
Author : Rani Krishnan, K.R. ;Anandavally Ammal, R. ;Hariharanath, B. ;Rajendran, A.G.;Kartha, C.B.
Source : Defence Science Journal ; Vol:56(3) ; 2006 ; pp 329-338
Subject : 620.261 Explosives
Keywords : Pyrotechnic compostion;Boron potassium nitrate;Thermal decomposition;Ignition behaviour;Pyrotechnic change;RDX;HMX;Fuel-oxidiser mixture
Abstract : Boron-potassium nitrate (B-KNO3) (25/75) is a well-known pyrotechnic composition which finds application as energy-release system for small-calibre rockets and pyrogen igniters for larger motors. The decomposition of the oxidiser in this composition is endothermic which can be activated by the addition of high explosives, which decompose exothermically. This paper describes the influence of two nitramine explosives, RDX and HMX, on the ignition characteristics of B-KNO3 composition using thermogravimetry, differential scanning calorimetry, heat and pressure output measurements. Different compositions were prepared by varying the amount of RDX/HMX from 10 per cent to 50 per cent. Thermal studies on the B-KNO3/high explosive mixtures reveal that these undergo two-stage decomposition. The first stage corresponds to the decomposition of high explosive and the second stage corresponds to that of the reaction between B and KNO3. Kinetic parameters were calculated for both the stages of TG curves using Coats- Redfern and Mac Callum-Tanner methods. Ignition temperature of B-KNO3 decreases on the addition of RDX/HMX while the onset of RDX or HMX decomposition is not significantly affected by B-KNO3. The pressure output of B-KNO3 increases on adding RDX/HMX. The heat output of B-KNO3 is not much affected by the addition of RDX or HMX, even though the heat of explosion of RDX and HMX are low. This is due to the reaction between the combustion products of RDX/HMX and reaction products of B-KNO3 to form more exothermic products like B2O3, releasing extra heat. The flame temperature of the charge increases while the average molecular weight of the products of combustion decreases as the RDX/HMX content increases. Thus, the charge, on addition of RDX or HMX, produces higher pressure output, maintaining the heat output at comparable levels. |
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