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Study of the Effect of Additive Particle Size on Non-ideal ExplosivePerformance

Waldemar A. Trzcinski, Stanisław Cudziło, Jozef Paszula

Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland)

James Callaway*

Defence Science and Technology Laboratory, Fort Halstead, Sevenoaks, TN147BP (UK)

Received: January 11, 2008; accepted February 06, 2008

DOI: 10.1002/prep.200800005

Abstract

Detonation performance of non-ideal RDX-based composi-tions was studied. Charges of phlegmatised RDX containing 30%of two types of aluminium powders, coarse aluminium oxide orfine lithium fluoride particles were tested. The research concern-ing influence of inert and reactive additives on the detonationvelocity and quasi-static pressure was carried out. To estimate thedegree of afterburning of the detonation products and reactiveparticles, closed explosions were performed in a chamber filledwith different atmospheres. Explosion residues were also ana-lysed. Gasdynamical and thermochemical calculations were alsoperformed for the tested explosive compositions.

Keywords: Detonation Velocity, Explosion Residue, Non-idealExplosives, Quasi-static Pressure

1 Introduction

RDX-based compositions containing 15 – 60% alumini-um powder were tested in Ref. [1, 2]. In these works,aluminium powder and flaked aluminium were mixed withphlegmatised RDX. Advanced studies involved measure-ments of detonation velocity, shock wave curvature, accel-eration ability, detonation energy and heat, parameters offree field explosion (overpressure history of a blast wave,light output) and characteristics of confined explosion(quasi-static pressure, QSP).This research is a continuation of the study on the

influence of aluminium particle size on the detonationperformance of RDX mixtures.Discrete fine (�5 mm) and coarse (�75 – 90 mm) alumi-

nium were applied. Moreover for comparison, inert addi-tives of similar particle size replaced aluminium in themixtures. RDX-based compositions containing 30% of a

non-explosive component – inert or active – were tested. Tocheck the effect of additives on the detonation process,measurements of detonation velocity for different chargediameters were performed. To evaluate the afterburningdegree of detonation products and aluminium powder,QSPwas determined in a steel chamber of 0.15 m3 volume filledwith air, nitrogen or argon. Analysis of solid residues fromthe chamber for metallic aluminium and alumina contentwas also done. The results of detonation velocity and QSPmeasurements were compared with those obtained fromgasdynamical and thermochemical calculations.

2 Explosive Mixtures

To prepare the tested explosive samples, commercialgrade phlegmatised RDX (RDXph) was used as in theprevious studies. This material contains ca. 94% of pureRDX and 6% of wax (CH2)n. A selection of aluminium andaluminiumalloy powders have been prepared byALPOCO,UK using their M2 low oxide inert gas atomisation plant.The powders produced have been designed to vary insurface passivation, purity and particle size distribution. Forthis comparative study, two powders made from the sameultrapure 99.94% Al feedstock were mixed with RDXph.The first one,marked here asAl5, is a fine particle sized highalumina passivated aluminium powder with an averageparticle size of 5 mm. The second one, marked here as Al90,is low alumina passivated aluminium powder of particle sizein a range of 75 – 90 mm. Both powders were analysedaccording to Polish national standard No. PN-V-04002-5(1997) to evaluate the content of metallic aluminium. Theaccuracy of the applied analytical method was 1%. As maybe predicted, the total content of metallic aluminium in thecoarse powder (Al90) is high and exceeds 99%. The fine Al* Corresponding author; e-mail: [email protected]

227Propellants, Explosives, Pyrotechnics 33, No. 3 (2008)

K 2008 WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim

powder (Al5) contains ca. 96.5%metallic aluminium, whichcorrelates well with the manufacturersN analytical labora-tory test methods using X-Ray fluorescence (XRF) spec-trometry and inductively coupled plasma optical emissionspectrometry (ICP-OEP) to determine alumina and metal-lic aluminium content.To perform a deeper investigation on behaviour of the Al

powders after detonation, the aluminium powders werereplaced with inert controls which have particle grain sizesclose to theAl powders. The controls used were fine lithiumfluoride with a particle size of ca. 5 mm (LiF No. 01140Sigma –Aldrich) and coarse aluminiumoxidewith a particlesize of ca. 75 mm(MerckKGaA,No. 101097). LiFandAl2O3

had been chosen not only because they are chemically inertbut also because they have similar thermochemical proper-ties to alumina passivated aluminium powders. All thetested RDX-based compositions contained 70% of RDXphand 30% of the chosen active (Al5, Al90) or inert (LiF,Al2O3) additives.Somemicroscopy analyses (SEMandopticalmicroscopy)

were performed to characterise the components of RDX-based compositions. The shape and size of powder particles

were observed with a scanning microscope JEOL 5400 at amagnification from 500 to 2000 times (Figures 1 – 4).SEM images (Figure 1 and 3) revealed that the Al

powders chosen for studying the detonation performanceofRDXph/Almixtures differ significantly from each other inparticle size and shape. Particles of Al5 are sphere shaped,whereas particles of Al90 are much less spherical. Sphere-shaped alumina particles (Al2O3, Figure 4) are composed ofsintered crystals. The porosity of these particles is high andcan influence the density of RDXph/alumina mixtures. Thestability of Al2O3 particles during explosion was verified bySEM observation of explosion residues. LiF particles (Fig-ure 2) are cubic-shaped with rounded wedges and theycorrespond well with Al5 morphology, so that LiF was agood choice to replace Al5 in the mixtures with RDXph.Optical microscopy was applied to determine particlesN

size distribution of Al5, Al90, LiF and Al2O3. The particlesize distributions are presented in Figures 5 – 8. Thequantity of particles with diameters within a choseninterval was used to build the distributionmarked by blackbars. Themass of particles inside the interval was applied toconstruct the dependence indicated by grey bars. The masswas assumed to be directly proportional to cube of theparticle diameter. Additionally, on the basis of sizedistribution of particles, the specific surface area ofinvestigated powders assumed that their particles areroughly sphere shaped. The specific surface area of 2750,

Figure 1. SEM images of Al5 particles.

Figure 2. SEM images of LiF particles.

Figure 3. SEM images of Al90 particles.

Figure 4. SEM images of Al2O3 particles.

228 W. A. Trzcinski, S. Cudziło, J. Paszula, J. Callaway

Propellants, Explos., Pyrotech. 33, No. 3, 227 – 235 www.pep.wiley-vch.de K 2008 WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim

www.pep.wiley-vch.de

1840, 260 and 160 cm2 g�1 was estimated for Al5, LiF, Al90and alumina, respectively.Al5 and LiF powders have, generally, similar particle and

mass distributions. In the case of Al90 powder, a largenumber of small particles are present (Figure 7). They arealso visible in the SEM image (Figure 3). However, the totalmass of small particles is very low and they should notinfluence the detonation performance of RDXph/Al90mixtures.For the manufacturing of pressed explosive charges, a

moulding powder was prepared by granulation of RDXph/additive mixture with chloroform. Firstly, weighed quantityof RDX and chosen powder (LiF, Al2O3, Al5, Al90) weremixed mechanically and after obtaining homogenous com-position chloroform was added to wet the mixture. Theslurry-like mixture was mixed once again. Then, the chloro-form was completely evaporated. That procedure leads to ahomogenous mixture in which additivesN particles arebounded to RDX particles.Pressed charges containingAl additiveswere investigated

using SEM and optical microscopy. It was determined thatAl particles appear larger before pressing than after the

compaction process. Al particles can be partially deformedduring charge preparation; however their observable sizewas probably lower due to merging into the RDX matrix.The porosity of pressed charges, a, was calculated using

the following formula:

a¼1s=1c�1 ð1Þ

where s refers to the solid or matrix material and c to theporous conditions. The following densities of solids (kgm�3)were used: 1Al¼ 2710, 1LiF¼ 2640, 1Al2O3

¼ 4000, 1RDX¼1800, 1WAX¼ 890 to give the porosity of the pressedmixturesas shown in Table 1.

Figure 5. Particle size distribution of Al5.

Figure 6. Particle size distribution of LiF.

Figure 7. Particle size distribution of Al90.

Figure 8. Particle size distribution Al2O3.

Table 1. Density and porosity of tested mixtures.

Explosive Mixture Densitykg m�3

Porosity%

RDXph/LiF 1750 8.6RDXph/Al2O3 1640 25.0RDXph/Al5 1860 2.7RDXph/Al90 1850 3.3

Study of the effect of additive particle size on non-ideal explosive performance 229

K 2008 WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim www.pep.wiley-vch.de Propellants, Explos., Pyrotech. 33, No. 3, 227 – 235


The porosity of RDXph/Al2O3 is much higher in compar-ison to the rest of themixtures. This feature can influence thedetonation characteristics of that composition.

3 Detonation Velocity

To measure the detonation velocity of unconfined charg-es, the explosives tested were pressed in the form ofcylindrical pellets with diameters of 16, 20, 25, 30, 40 and50 mm. The pellets were ca. 20 mm in length. For eachdiameter, a charge was made from five pellets of the testedexplosive and a booster made of phlegmatised HMX.Detonation velocity was measured using short-circuitsensors (shock collapsible sensors) manufactured fromtwo insulated copper wires. Three measuring distances, ofca. 20 mm in length each, were used. The first sensor wasfixed at a distance of ca. 40 mm from the booster. Two shotswere done for each tested mixture.Dependence of the detonation velocity on charge diam-

eter is presented inFigures 9 and10.The averageddensity ofthe tested explosive is also shown in the figures. For mostcases, the arithmetic average of detonation velocity, calcu-lated from all the experimental results for an explosive,differs from the extreme values less than 1%, which is theultimate precision of the measuring method. Taking intoaccount the fact that the density of small diameter charges isslightly higher than that of large diameter ones, the averageddetonation velocity is practically constant for a chargediameter from the range of 16 – 50 mm.The detonation velocities of the explosivemixtures tested

were calculated assuming the inertness of the additives.From the analysis of the detonation process of explosivescontaining inert admixtures presented in Ref. [3], it followsthat in the reaction zone the temperature of the componentsin the mixture, that is the detonation products and the inertadditive, is not equalised for particles greater than 1 – 2 mmin diameter. Taking into account the particle mass distribu-tion of the additives, the detonation velocity of the tested

mixtures was calculated using the method described in Ref.[3] with the assumption of no heat exchange between thecomponents. In this method, the mixture of explosive withthe additive was described by a model of multicomponent,multiphase medium. Additivity of specific volume andinternal energy of components as well as complete mechan-ical equilibriumwere assumed. The thermodynamic proper-ties of the detonation products were described by the JWL(Jones –Wilkins –Lee [4]) equation of state. As regards theadditives the GrQneisen equation of state, obtained on thegrounds of adiabatic shock [5], was used. Empirical data foradiabatic shock were taken from Ref. [6, 7]; coefficients ofphlegmatisedRDXwere taken fromRef. [8]. The calculatedvalues of the detonation velocity are presented in Figure 11by solid lines. They are compared with the averageddetonation velocities measured for charges of the samediameter.The results presented in Figure 11 show that a quite good

agreement between the experimental results and thecalculated ones is obtained when the neutrality of the

Figure 9. Detonation velocity of RDXph/Al5 and RDXph/LiFmixtures versus charge diameter.

Figure 10. Detonation velocity of RDXph/Al90 and RDXph/Al2O3 mixtures versus charge diameter.

Figure 11. Averaged detonation velocity versus averaged densityof tested compositions.




additives is assumed. Thus, we can draw a conclusion thatboth LiFand Al2O2 as well as reactive aluminium behave inthe reaction zone like chemically inert admixtures.

4 Quasi-Static Pressure (QSP)

QSP tests with explosive charges were performed in asteel chamber of about 0.15 m3 volume. The chamber wasfilled with air, nitrogen or argon under a normal pressure ofabout 0.1 MPa. The ambient temperature was about 5 8C. A50 g charge was hung in the centre of the chamber. Chargesof a 30 mm diameter had the same density as those used indetonation velocity measurements. A standard fuse wasused to initiate the charge. Three tests were performed foreach investigated explosive composition.Exemplary overpressure histories for the mixtures con-

taining 30%Al5,Al90, LiForAl2O3 are shown in Figures 12and 13.Each overpressure history was approximated by using the

following formula:

Dpappr (t)¼Dp0 exp(�at) (2)

whereDp0 and a are constants [9]. The parameterDp0 can betreated as themaximal approximatedoverpressure (QSP) atthe chamber wall.To determine averaged values of the constants, the

approximated overpressure histories for all shots for a giventype of the explosive were taken into account. Evaluatedvalues of the parametersDp0 and a are presented in Table 2.The standard deviation is also given in the table.To estimate the final overpressure in the chamber

theoretically, thermochemical calculations were performedby using CHEETAH code [10]. The set of values of theparameters a¼ 0.5, b¼ 0.298, k¼ 10.5,V¼ 6620 [11] for theBKW equation of state was used in the calculations. Aconstant volume explosion state was determined for anexplosive charge and gas closed in the chamber. It wasassumed that aluminium took part in the chemical reactionsbutLiFandAl2O3 behaved like an inert additive.Apart froman explosive charge and gas filling the chamber, the fuseexplosive was taken into account in the calculations (�1.3 gPETN). The results of the thermochemical calculations areshown in Table 3.The QSP values measured in the chamber are lower than

the calculated ones for all the atmospheres. However, thefact should be taken into consideration that calculationswere carried out under an assumption of thermochemicalequilibrium of the reactive mixture.Whereas, gasdynamicalprocesses like turbulence, mixing, and shock wave rever-berations take place inside the chamber volume and theequilibrium state is attained when a part of released heat istransferred to the chamber wall.

Figure 12. Exemplary overpressure histories recorded in the0.15 m3 chamber filled with air.

Figure 13. Exemplary overpressure histories recorded in the0.15 m3 chamber filled with nitrogen.

Table 2. Estimated parameters of Equation (2) for explosivestested in the chamber of 0.15 m3 volume.

Explosive Gaseous Filler Dp0MPa

a� 103ms�1

RDXph/LiF Nitrogen 0.29� 0.03 3.6� 1.8Air 0.59� 0.03 3.6� 1.5

RDXph/Al2O3 Nitrogen 0.31� 0.01 4.1� 2.1Air 0.64� 0.02 3.4� 1.7

RDXph/Al5 Nitrogen 0.58� 0.03 2.9� 1.6Argon 0.79� 0.02 4.8� 1.2Air 0.95� 0.02 2.8� 0.5

RDXph/Al90 Nitrogen 0.52� 0.03 4.6� 1.1Argon 0.77� 0.02 4.4� 1.4Air 0.92� 0.05 2.4� 1.4

Table 3. Calculated overpressure in the chamber for testedexplosives.

Explosive Gaseous Filler Dp0MPa

RDXph/LiF Nitrogen 0.37Air 0.71

RDXph/Al2O3 Nitrogen 0.38Air 0.75

RDXph/Al Nitrogen 0.74Argon 0.95Air 1.15




From Table 2, it follows that the values of QSP (Dp0) foraluminised RDXph are higher than those for RDXph with aninert additive regardless of gaseous atmosphere in thechamber (nitrogen and air). Estimated QSPs for themixtures with LiFand Al2O3 are about twice as low as thoseof RDXph/aluminium mixtures. This means that aluminiumreactswith oxygen fromdetonationproducts or air. Theheatof the reactions causes an increase in temperature andpressure of gaseous mixture in the chamber.The QSP values obtained from the overpressure histories

measured inside the chamber filled with argon are higher ascompared with the nitrogen atmosphere. This fact is theeffect of different physical properties of both the gases, forexample, the density and heat capacity. Equilibrium ther-mochemical calculations confirm the experimental results ina qualitative manner (Table 2).The QSP measured for the mixtures containing lithium

fluoride is slightly lower than that of compositions withalumina. Similar relation is also observed in the calculateddata. Different physical properties of both additives affectthis correlation. Moreover, a great difference in the specificsurface of both the additives (1840 and 160 cm2 g�1 for LiFand Al2O3, respectively) can influence the heat transferfrom the gaseous detonationproducts to admixture particlesduring the first stage of equilibration and change thepressure inside the chamber.The chemically active additives Al5 and Al90 also differ

significantly in the specific surface – 2750 and 260 cm2 g�1,respectively. High specific surface facilitates the heatexchange and reaction of an admixture with detonationproducts and air. However, an additional heat releasedduring the reaction between fine aluminium powder andoxygen or detonation products increases the temperature ofthe explosion products and consequently the pressure in thechamber. That is why the QSP is higher in the case of finealuminium addition (Al5).

5 Analysis of the Chamber Residue

The solid residues after detonation of 50 g charges of theRDXph/Al90 and RDXph/Al5 mixtures in the 0.15 m

3 cham-ber filled with air, nitrogen and argon were analysed todetermine their composition. In each case, the residueextracted from the chamber was first sieved (to removefragments of detonator and its electric leads) and then driedfor 24 h at 100 8C.Detonation of the charges in air producedgrey powder with high bulk density, whereas products ofdetonation in an inert atmosphere (N2 orAr)were black anddusty, like soot.Obviously, detonation products of RDX contain carbon

oxides, water as well as free carbon and nitrogen in quitelarge amounts. Therefore, detonationofRDXph/Almixturesmay result not only in the formation of aluminium oxide butalso its nitrides and carbides (especially when the detona-tion takes place in nitrogen or argon [12]). Some amount ofunreacted aluminium should be expected, as well. Thissuggestion is supported by the note in Ref. [13] that only up

to 40% of aluminium (particles below 1 mm in diameter)oxidises during detonation of HMX/TNT/Al¼ 60 :30 :10mixtures in a chamber filled with nitrogen at an initialpressure of 0.2 – 0.3 MPa.Taking this into consideration, we started the analyses

from TG/DTA measurements using Labsys TG/DTA/DSCanalyser. A powdery sample of the residues (60 – 80 mg inmass) was heated up from 20 to 1000 8C, at a 2.5 8C min�1

heating rate, with an oxygen dynamic atmosphere (flow rateof 50 cm3 h�1). The sample was placed in an open platinumcrucible. Under these conditions, all the expected detona-tion products should be completely oxidised – soot at ca.400 8C, Al at ca. 600 8C and AlN above 900 8C.The obtained thermograms are presented in Figures 14 –

16. Chamber residue after detonation of the charges in aircontains entirely aluminium oxide Al2O3, because the massof the samples does not practically change while heating upto 1000 8C, in the presence of oxygen (Figure 14). Thismeans that carbon and aluminium, that have not reacted indetonation wave, fully oxidise in expanding and reshockeddetonation products, consuming oxygen from the atmos-phere.The composition of residues produced by detonation in

nitrogen or argon atmosphere is much more complicated.Nonetheless, the TG/DTA thermogramsmake it possible toidentify all the expected components (Figures 15 and 16). Inboth the cases DTA curves indicate three stages ofoxidation.First amorphous carbon (soot) oxidises. The process starts

at ca. 200 8C, and is accompanied by a weight loss of 1.5 –1.8% (out of the initial sample mass). At 500 8C, aluminiumbegins to oxidise. The sample mass increases becauseoxygen is fixed by aluminium giving Al2O3. Still anendothermic peak, corresponding to aluminium melting(at ca. 653 8C), can be seen on the descending slope ofaluminium oxidation peak. At around 700 8C, next broadexothermic peak commences that can be attributed tooxidation of aluminium nitride. Again, the sample mass

Figure 14. Thermogravimetric (TG) curves for residues extract-ed from the chamber after detonation of RDXph/Al charges in air.




increases, as AlN (ca. 41 gmol�1) is replaced withAl2O3 (ca.102 g mol�1).From the thermal analyses, it follows that aluminium

nitride appears irrespective of whether the initial chamberatmosphere includes nitrogen or not. Thus, AlN is formedjust in the detonation wave or in reactions betweenexpanding detonation products. This, rather unexpectedresult induced us to perform a phase analysis of chosendetonation products.To this end X-ray diffraction (XRD) spectra were

measured (D500 Diffractometer, Siemens, CuKa radiation)in the range of 2V from 10 to 708. The recorded patterns forsamples collected after detonation of RDXph/Al90 mixturein nitrogen and RDXph/Al5 mixture in argon are presentedin Figures 17 and 18.Results of the phase analyses unambiguously confirm that

both of the tested samples contain aluminium nitride in theform of intermediate 2Al2O3 ·AlN phase. Moreover com-

plex aluminium-oxide-carbide (Al2OC) and aluminium-oxide-carbide-nitride (Al28C6N6O21) systems are also pres-ent. Pure aluminium phase was identified in the products ofRDXph/Al90 detonation in nitrogen, Figure 17.The composition of the residues extracted from the

chamber after detonation of RDXph/Al charges in nitrogenwas determined as follows. First the content of free carbonwas calculated using results of the thermogravimetricanalyses. In three consecutive runs, the mass variations ina temperature range of 200 – 400 8C (carbon oxidation)werefound to be (average values from three experimentalresults): 1.8� 0.2% for RDXph/Al90 and 1.5� 0.3% forRDXph/Al5.Next the content of metallic aluminium was determined

applying volumetric analysis. Results of the analyseswere asfollows: 3.1� 0.1% for RDXph/Al90 and 1.4� 0.2% forRDXph/Al5.

Figure 16. TG/DTA curves for residues extracted from thechamber after detonation of RDXph/Al charges in argon.

Figure 17. XRD pattern of residue extracted from the chamberafter detonation of RDXph/Al90 mixture in nitrogen.

Figure 18. XRD pattern of residue extracted from the chamberafter detonation of RDXph/Al5 charges in argon.

Figure 15. TG/DTA curves for residues extracted from thechamber after detonation of RDXph/Al charges in nitrogen.




The content of the other two components (AlN andAl2O3) was found after solution of the equation systemresulting from the law of conservation of mass and massincrease during heating. The mass of aluminium nitride wasas follows: 15.5� 0.2 and 24.3� 0.3% for RDXph/Al90 andRDXph/Al5, respectively. Similarly, the mass of aluminiumoxide was found to be: 79.6� 0.2% for RDXph/Al90 and71.8� 0.3% for RDXph/Al5.Finally, from the results of the thermal analysis it can be

calculated that 5.6%of the aluminiumAl90 powder remainsunreacted, 18.2% forms AlN, and 76.2% is oxidised toAl2O3. For Al5 powder the values are: 2.5% of Al remainsunreacted, 28.9% reacts to AlN and 68.6% reacts to Al2O3.For comparison, 60% aluminium forms AlN and 40% isoxidised to Al2O3 under the conditions of thermochemicalequilibrium state was calculated for an explosion inside the0.15 m3 chamber filled with nitrogen using CHEETAH [10].This means that the real conditions in the chamber differfrom the predicted equilibrium ones.As it was expected, a reduction in Al particle sizes

increases aluminium reactivity. The solid residue afterdetonation of RDXph/Al5 mixture includes less metallicaluminium than in the case of RDXph/Al90 explosive. Theunreacted aluminium content is quite low, 2.5 – 5.6%. Thisresult is inconsistent with that of published by Gilev andAnisichkin [13] – who reported that only 7 – 42% Altransforms into Al2O3 when aluminised explosives aredetonated in nitrogen atmosphere (0.2 – 0.3 MPa). How-ever, they used explosives with much lower oxygen balance(30% of TNT) and performed experiments under differentconditions. Moreover, they assumed that detonation prod-ucts include only carbon, aluminium and aluminium oxide.Our analyses show that unexpectedly large amounts ofaluminium react with nitrogen producing complex AlNcontaining phases – its content was found to be in the rangeof 15 – 24%. More AlN is formed when fine Al particles areused. It should be underlined that thermochemical calcu-lations suggest that substantial amounts of AlN can beobtained under the experimental conditions.To characterise the shape and microstructure of the

alumina particles in the chamber residue, the scanningelectron microscopy was applied. SEM photographs ofalumina particles recovered from the chamber after deto-nation of the RDXph/Al2O3 and RDXph/Al90 charges areshown in Figures 19 and 20. The chamber was filled with air.The original shape and size of Al90 and inert control Al2O3

particles are shown in Figures 3 and 4. From comparison ofSEMphotographs of particles before andafter a shot it followsthat the particle shape and size of original and oxidised Al90are similar. However, post-explosion alumina particles havemuch smaller size than that before explosion. This means thatalumina particles disintegrate during the explosion process.

6 Conclusion

Themost important conclusions from the results obtainedare:

* The averaged detonation velocity of the compositiontested is practically constant for a charge diameter fromthe range of 16 – 50 mm. The different porosities of thepressed mixtures investigated are the main reason for thedifference in detonation velocity.

* A quite good agreement between the experimentalresults and the calculated ones is obtained when theneutrality of the additives is assumed. Thus, aluminiumpowders behave in the reaction zone like chemically inertadmixtures.

* From the tests performed in the 0.15 m3 chamber filledwith nitrogen and air it follows that the values of QSP foraluminised RDXph are higher than those for RDXphcontaining inert additives. This means that the reactionof aluminium additive with oxygen from detonationproducts and air takes place in the chamber.

* The QSP measured in the chamber for the mixturescontaining fine particle size aluminium (Al5) is slightlyhigher than that of compositions with coarse aluminium(Al90). Higher specific surface of Al5 powder facilitatesthe heat exchange and reaction of it with detonationproducts and air. QSP measured for the mixtures

Figure 19. SEM photographs of the Al2O3 particles recoveredafter detonation of RDXph/Al90 explosive.

Figure 20. SEM photographs of the Al2O3 particles recoveredafter detonation of RDXph/Al2O3 explosive.




containing lithium fluoride is slightly lower than that ofcompositions with alumina.

* The QSP values measured for the chamber filled withargon are higher as compared with the nitrogen atmos-phere. This fact is the effect of different physical proper-ties of both the gases.

* Thermogravimetric curves indicate that chamber resi-dues after detonation of the RDXph/Al charges in aircontain entirely aluminiumoxide. Thismeans that carbonand aluminium, that have not reacted in detonation wave,fully oxidise in expanding and reshocked detonationproducts, consuming oxygen from the atmosphere. Whendetonation takes place in nitrogen and argon atmospherechamber residues contain aluminium oxide, aluminiumnitride, carbon and metallic aluminium (four maincomponents). This was confirmed also by XRD analyses.

7 References

[1] W. A. Trzcinski, S. Cudziło, L. Szymanczyk, Studies of Deto-nation Characteristics of Aluminium Enriched RDX Compo-sitions, Propellants, Explos., Pyrotech. 2007, 32, 392.

[2] W. A. Trzcinski, S. Cudziło, J. Paszula, Studies of Free Field andConfined Explosions of Aluminium Enriched RDX Compo-sitions, Propellants, Explos., Pyrotech. 2007, 32, 502.

[3] R. Trebinski, W. Trzcinski, E. Włodarczyk, On a Method ofDetermining the Detonation Adiabates of Mixtures of Ex-plosives with Inert Additions, J. Tech. Phys. 1990, 31, 35.

[4] E. L. Lee,D. Breithaupt, C.McMillan, N. L. Parker, J. W.Kury,C. M. Tarver, W. Quirk, J. Walton, The Motion of Thin Metal

Walls and the Equation of State of Detonation Products, 8thSymposium (International) on Detonation, Albuquerque, NewMexico, USA, July 15 – 19, 1985, p. 613.

[5] R. C. Queen, On Equation of State of Solids, in: R. Kinslow(Ed.),High-velocity Impact Phenomena, Academia Press, NewYork, London, 1970.

[6] S. P. Marsh, LASL Shock Hugoniot Data, University ofCalifornia Press, 1980.

[7] M. A. Meyers, L. E. Murr, Shock Waves and High-strain-ratePhenomena inMetals, PlenumPress, NewYork, London, 1980.

[8] W. A. Trzcinski, S. Cudziło, Characterisation of High Explo-sives Obtained from Cylinder Test Data,Chin. J. Energ. Mater.2006, 14, 1.

[9] W. A. Trzcinski, J. Paszula, Confined Explosions of HighExplosives, J. Tech. Phys. 2000, 41, 453.

[10] L. E. Fried,CHEETAH 1.39UsersManual, UCRL-MA-11754Rev. 3, LLNL, Livermore, CA, 1996.

[11] M. L. Hobs, M. R. Baer, Nonideal Thermoequilibrium Calcu-lationsUsing a Large Product SpeciesData Base, ShockWaves1992, 2, 177.

[12] S. Cudziło, A. Maranda, J. Nowaczewski, R. Trebinski, W. A.Trzcinski, Detonative Synthesis of Inorganic Compounds, J.Mater. Sci. Lett. 2000, 19, 1997.

[13] S. D. Gilev, W. F. Anisichkin, Interaction of Aluminium withDetonation Products, Combust., Explos. Shock Waves, 2006,42, 107.

Acknowledgement

This work was carried out for MoD RAO and DSTL throughQinetiQ Ltd. under sub-contract CDMCL-01492.




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