Transmission electron microscopy and x-ray diffraction studies of the detonation soot of high explosives

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1 Journl of Physics: Conference Series PAPER OPEN ACCESS Trnsmission electron microscopy nd x-ry diffrction studies of the detontion soot of high explosives To cite this rticle: A O Kshkrov et l 2016 J. Phys.: Conf. Ser Relted content - The effect of soot modeling on therml rdition in uoynt turulent diffusion flmes A Snegirev, E. Kokovin, A. Tsoy et l. - Multiwll cron nnotues Christin Schönenerger nd Lszlo Forró - Numericl Investigtion on Scttering of n Aritrrily Incident Bessel Bem y Frctl Soot Aggregtes Cui Zhi-Wei, Hn Yi-Ping nd Yu Mei-Ping View the rticle online for updtes nd enhncements. This content ws downloded from IP ddress on 05/03/2018 t 18:21

2 Trnsmission electron microscopy nd x-ry diffrction studies of the detontion soot of high explosives A O Kshkrov 1,3, E R Pruuel 1,3, K A Ten 1, I A Rutsov 1,3, E Yu Gersimov 2,3 nd P I Zukov 1 1 Lvrentyev Institute of Hydrodynmics of the Sierin Brnch of the Russin Acdemy of Sciences, Lvrentyev Avenue 15, Novosiirsk , Russi 2 Boreskov Institute of Ctlysis of the Sierin Brnch of the Russin Acdemy of Sciences, Lvrentyev Avenue 5, Novosiirsk , Russi 3 Novosiirsk Stte University, Pirogov Street 2, Novosiirsk , Russi E-mil: kshkrov@hydro.nsc.ru Astrct. This pper presents the results of electron microscopy nd x-ry diffrction studies of the recovered cronceous residue (soot) from the detontion of some high explosives: TNT, mixture of TNT nd RDX (50/50), enzotrifuroxne, nd triminotrinitroenzene. The use of the sme experimentl setup llowed qulittive nd quntittive comprison of the detontion products formed under similr conditions. The results clerly show differences in the morphology of grphite-like nd dimond inclusions nd in the quntittive content of nnodimonds for the explosives used in this study. 1. Introduction The detontion products of vrious explosives with negtive oxygen lnce contin wide morphologicl nd phse diversity of cron forms. It is lso known tht the forms of condensed cron in detontion products depend on the explosion conditions. The development of detontion methods for the synthesis of vrious forms of nnodimonds is primrily motivted y their commercil nd dvnced pplictions. Wide use hs een mde of dimond-contining products consisting of qusi-sphericl prticles out 5 nm in dimeter produced y detontion of mixture of TNT nd RDX under vrious conditions nd the products contining lrge (up to hundreds of microns) polycrystlline prticles synthesized y detontion of mixture of RDX nd grphite. Commercil methods for the production of nnodimonds differ in the mss of the chrges used nd explosion conditions: the chrge is enclosed in wter or ice shell, the explosion chmer is filled with different inert gses or just mient ir, etc. Tht is, the properties of the product cn e controlled y choosing synthesis conditions. However, for reserchers, the inverse prolem is of greter interest. The form nd mount of nnodimonds nd other cron inclusions in explosion products provide informtion on the thermodynmic conditions in the region of their formtion. In ddition, condensed cron forms re certinly involved in the kinetics of formtion of detontion products nd the flow ehind the detontion front. Content from this work my e used under the terms of the Cretive Commons Attriution 3.0 licence. Any further distriution of this work must mintin ttriution to the uthor(s) nd the title of the work, journl cittion nd DOI. Pulished under licence y Ltd 1

3 Therefore, in developing models for the detontion trnsformtion of explosives, it is necessry to ccount for the condensed phse chrcteristic of the selected explosive nd the explosion conditions. At the sme time, there is lck of dt from direct mesurements of the nucletion nd dynmics of cron prticles ehind the detontion front. This necessittes the ddition of vrious hypotheses to numericl models. The development of reserch methods using synchrotron rdition hs mde it possile to exmine the dynmics of formtion of nnodimonds nd their growth ehind the detontion front [1 3], ut the introduction of numer of ssumptions is lso required. In solving the inverse prolem of reproducing the formtion of nnodimonds from smll-ngle x-ry scttering dt, one ssumes sphericl prticle shpe nd typiclly monodisperse size distriution. Investigtion of the condensed residue, though not providing informtion on the stte of cron during the pssge of the detontion front, provides detiled informtion on the finl forms of cron. In this work, the experimentl setup ws s nerly the sme s possile to compre dt on the recovered detontion products of vrious explosives. The chrges used were identicl to those investigted in [1, 4] using synchrotron rdition. 2. Experimentl conditions Detontors sed on ulk PETN in n icy ody were mde to reduce the content of impurities. Initition ws performed y n uxiliry chrge of PETN nd HMX s they give n insignificnt mount of condensed residue. The entire experimentl ssemly ws frozen in ice with totl mss of out 1 kg. Detontion ws crried out in n ir-filled 50-liter explosion chmer of stinless steel. For the experiments, cylindricl chrges of 20 mm dimeter weighing out 20 g were prepred. Cst chrges of TNT nd 50/50 TNT/RDX mixture, commonly used for commercil production of nnodimonds, nd pressed chrges of TATB nd BTF were investigted. Condensed detontion products mixed with wter nd crushed ice were collected nd dried. The resulting smples were further purified (if necessry) y wshing with cid to remove impurity metls or y nneling in ir flow to remove morphous cron nd grphite. 3. TEM studies Trnsmission electron microscopy (TEM) microgrphs were otined with use of JEM-2010 instrument (lttice resolution 1.4 Å, ccelertion voltge 200 kv). Anlysis of the locl elementl composition ws crried out using n energy dispersive x-ry (EDX) spectrometer equipped with Si(Li) detector (energy resolution 130 ev). TEM dt llow one to qulittively estlish the specific forms of cron in the detontion products of the explosives studied nd determine the typicl liner size of inclusions, ut it is worth noting tht the resulting size will not e the men one ecuse of the complex form of cron structures nd ecuse of the sujective preferences of the resercher. For the 50/50 TNT/RDX mixture, widely used in commercil production of nnodimonds, the results re presented in figure 1. The condensed products contin lrge mount of seprte qusi-sphericl nnodimonds (the mesured interplnr spcings corresponding to the dimond form of cron re shown in the figure) with typicl size of out 5 nm, cron fiers up to severl tens of nnometers nd onion-like cron prticles few nnometers in dimeter. The results re in good greement with literture dt, e.g., [5 7]. TEM imges show (figure 2) tht the detontion products of TNT contin cron fiers (up to tens of nnometers) nd non-sphericl nnodimond prticles which re lrger thn those for the TNT/RDX mixture nd hve size of out 10 nm or more. The mount of the dimond phse in the unpurified detontion products is sustntilly less thn expected [8]. It should e noted tht the lrger dimond prticles chrcteristic of TNT re lso rre in the detontion products of the 50/50 TNT/RDX mixture. This is oviously due to the inhomogeneity of the mixture, which ws lso mentioned in [7, 9]. 2

XXXI Interntionl Conference on Equtions of Stte for Mtter (ELBRUS2016) Figure 1.

dimeter) nd cron fiers (tens of nnometers in length). Figure 2. TEM microgrphs of TNT: nnodimonds (few nnometers in dimeter); cron fiers (tens of nnometers in length).

tens of nnometers. TEM imges do not revel the presence of nnodimond prticles.

4 XXXI Interntionl Conference on Equtions of Stte for Mtter (ELBRUS2016) Figure 1. TEM microgrphs of 50/50 TNT/RDX: nnodimonds (few nnometers in dimeter), the numers re the mesured interplnr spcing of the dimond lttice for different prticles; onion-like cron (few nnometers in dimeter) nd cron fiers (tens of nnometers in length). Figure 2. TEM microgrphs of TNT: nnodimonds (few nnometers in dimeter); cron fiers (tens of nnometers in length). The smples otined y detontion of TATB chrges (figure 3) re chrcterized y the presence of minly cron fiers up to tens of nnometers nd rre morphous cron structures with liner sizes up to severl tens of nnometers. TEM imges do not revel the presence of nnodimond prticles. Similr results on the sence of nnodimonds in the detontion products of identicl chrges were otined in study [4] of the dynmics of cron condenstion ehind the detontion front using smll-ngle x-ry scttering of synchrotron rdition. The integrted intensity of smll-ngle x-ry scttering on detonting TATB chrges ws lower thn tht in TNT detontion nd significntly lower (y more thn 2-fold) thn for 50/50TNT/RDX chrges. In the cited pper, the verge dimeter of the scttering centers ehind the detontion front for TATB chrges is reported to e 2.6 nm (for comprison, for TNT/RDX chrges, 4.6 nm in the sme work), nd it is concluded tht these regions of density fluctutions hve nondimond cron structure. The presence of nnodimonds is ssumed, ut their mount nd chrcteristic sizes re lower (less thn 2 nm) thn the resolution of the experimentl setup. 3

XXXI Interntionl Conference on Equtions of Stte for Mtter (ELBRUS2016) Figure 3.

TEM microgrphs of BTF: lrge sphericl prticles (hundreds of nnometers). The sence of nnodimonds in the TATB detontion products is not consistent with the literture dt we re wre of.

High content of nnodimonds ws lso detected in TATB/HMX mixtures [11]. However, the conditions of the experiments in these studies were different.

At the sme time, synchrotron rdition studies of cron condenstion in TATB/HMX chrges of 20 mm dimeter showed no significnt difference in cron condenstion for different proportions of the

5 XXXI Interntionl Conference on Equtions of Stte for Mtter (ELBRUS2016) Figure 3. TEM microgrphs of TATB: cron fiers (tens of nnometers in length); morphous cron prticles (tens of nnometers in dimeter). Figure 4. TEM microgrphs of BTF: lrge sphericl prticles (hundreds of nnometers). The sence of nnodimonds in the TATB detontion products is not consistent with the literture dt we re wre of. Thus, in [10], the mesured percentge yield of nnodimonds for pressed chrges of TATB ws 2.08% of the initil weight of the explosive. High content of nnodimonds ws lso detected in TATB/HMX mixtures [11]. However, the conditions of the experiments in these studies were different. In [10], the dimeter of TATB chrges (40 mm) ws two times greter, nd in [11], the weight of the initil chrge (310 g) ws more thn ten times higher. At the sme time, synchrotron rdition studies of cron condenstion in TATB/HMX chrges of 20 mm dimeter showed no significnt difference in cron condenstion for different proportions of the components [1] The condensed products of detontion of enzotrifuroxne re minly lrge round prticles up to few hundred nnometers in dimeter (figure 4). According to TEM nlysis, these prticles hve heterogeneous internl structure (figure 4). Detection of nnodimonds in the unpurified products is difficult, since the dimond core cnnot e seen due to the thick lyer of non-dimond cron on the surfce. In the literture, there re dt on the detection of nnodimonds in the detontion products of BTF using vrious methods. Thus, in study [12] of detontion of BTF chrges weighing 4

XXXI Interntionl Conference on Equtions of Stte for Mtter (ELBRUS2016) Figure 5. TEM microgrph of semi-purified BTF soot. Some lrge sphericl prticles hve complex structure. Figure 6.

1000 g, x-ry structurl nlysis indictes the presence of the dimond phse, nd in [13], the presence of nnodimonds in the detontion products of BTF chrges weighing 100 g is confirmed y TEM.

To confirm the presence of nnodimonds y TEM, the initil smples were purified from other cron phses y nneling in ir flow.

6 XXXI Interntionl Conference on Equtions of Stte for Mtter (ELBRUS2016) Figure 5. TEM microgrph of semi-purified BTF soot. Some lrge sphericl prticles hve complex structure. Figure 6. TEM microgrphs of purified BTF soot: complex-shped nnodimonds; single-crystl nnodimond (up to 100 nnometers) g, x-ry structurl nlysis indictes the presence of the dimond phse, nd in [13], the presence of nnodimonds in the detontion products of BTF chrges weighing 100 g is confirmed y TEM. The presence of significnt mounts of the dimond phse of cron ehind the detontion front ws lso confirmed y synchrotron rdition study [1]of detonting BTF chrges of 20 mm dimeter. To confirm the presence of nnodimonds y TEM, the initil smples were purified from other cron phses y nneling in ir flow. An intermedite result of nneling t temperture of 460 C is presented in figure 5. In the TEM microgrph, one cn see tht the lrge prticles hve complex internl structure nd, fter removl of prt of the morphous nd grphite phses of cron, their shpe remins sphericl. Further increse in the nneling temperture to 515 C results in nerly complete disppernce of the non-dimond phse. TEM oservtions show complex-shped dimond prticles, some of which hve single-crystl structure with liner sizes up to 100 nm (figure 6). In the center of the imge (figure 6) there is polycrystlline dimond prticle with dimeter of more thn 100 nm which retins its sphericl shpe. This confirms the conclusion of [12] tht 5

Figure 7. TEM microgrphs of BTF soot. Lrge sphericl prticles with n onion-like structure: with homogeneous internl structure; with lrge numer of inhomogeneities.

In the unpurified cron residue of BTF, there re cron prticles of regulr sphericl shpe consisting of cron lyers covering ech other (figure 7).

7 Figure 7. TEM microgrphs of BTF soot. Lrge sphericl prticles with n onion-like structure: with homogeneous internl structure; with lrge numer of inhomogeneities. in BTF detontion, nnodimonds re formed from liquid cron phse; the porous structure of the products suggests the presence of severl points of growth of the dimond phse. In the unpurified cron residue of BTF, there re cron prticles of regulr sphericl shpe consisting of cron lyers covering ech other (figure 7). The lyered shpe of the prticles is similr to the onion-like structures oserved for the TNT/RDX mixture, ut the size of the prticles is much lrger up to 100 nm. Some prticles contin mny inhomogeneities nd the cron lyers re roken nd entngled (figure 7). 4. X-ry diffrction dt X-ry diffrction (XRD) ptterns were otined with HZG-4S (Germny) using Co K α rdition in 2Θ scnning rnge of The recovered detontion products contin lrge numer of components. Metl impurities resulting from shock wve impct on the wlls of the explosion chmer nd from other cuses re present in ddition to vrious forms of cron. As result, the XRD pttern of the initil detontion products hs mny peks (including overlpping ones) corresponding to vrious sustnces nd their modifictions, which hinders ccurte interprettion of the results. Metl impurities were removed from the detontion products y wshing with cid stndrd method which llows the recovery of primrily dimond prticles due to their low rectivity. Acid tretment of the detontion products t elevted pressure nd temperture lso reduces the content of the non-dimond cron phse; in this cse, this ws not required. The resulting XRD ptterns re presented in figures 8 nd 9, where the rrows indicte the ngles 2Θ for the dimond modifiction of cron. The reltive height of the peks llows qulittive determintion of the percentge of the dimond phse in the smples. Thus, in the smples otined y detontion of 50/50 TNT/RDX, the yield of the dimond phse is sustntilly higher thn tht for pure TNT, whose unpurified detontion products lso contin nnodimonds, s confirmed y TEM oservtions. For TATB, this pek is lmost indistinguishle from noise, indicting the possile presence of only trce mounts of nnodimonds or their smll (less thn 2 nm) size, which is not sufficient to collect sttistics on lttice scttering. According to XRD dt, the detontion products of BTF contin significnt mount of the dimond phse of cron, lthough, ccording to TEM, it is lmost sent from the unpurified products. Given the overll morphology of the condensed residue of BTF, dimond structures should e present in lrge mounts in lrge sphericl prticles. 6

8 Figure 8. XRD pttern of the purified detontion soot of 50/50 TNT/RDX (on the left-hnd side) nd TNT (on the right-hnd side): peks corresponding to nnodimonds re mrked y lck rrows. Figure 9. XRD pttern of the purified detontion soot of TATB (on the left-hnd side) nd BTF (on the right-hnd side): peks corresponding to nnodimonds re mrked y lck rrows. For ll soot smples, except for TATB, there is rodening of the diffrction peks corresponding to the dimond phse of cron. As rule, this is due only to the smll sizes of the regions of coherent scttering (RCS). RCS sizes were estimted y the Willimson Hll method [14]. Given qusi-sphericl prticle shpe, it cn e ssumed tht the RCS size corresponds to the verge prticle size. For TNT nd the TNT/RDX mixture, this ssumption seems quite resonle. For BTF, such n ssumption cnnot e mde. The estimted liner sizes of the RCS nd those oserved from TEM dt re shown in tle 1. For TNT/RDX nd TNT, commonly used for the synthesis of nnodimonds, the otined vlues re in good greement with literture dt. Although the oserved typicl size of dimond prticles is significntly lrger for pure TNT thn for the TNT/RDX mixture, the RCS sizes for these smples re the sme, which is explined y the non-sphericl shpe of nnodimonds in the TNT detontion products. In the detontion of TATB chrges of 20 mm dimeter, nnodimonds with sizes lrger thn 2 nm were not oserved; the detection of dimond prticles of smller sizes is eyond the ccurcy of the equipment, so tht their 7

9 Tle 1. Nnodimonds in detontion products. Explosive XRD d, nm TEM d, nm TNT/RDX 50/ TNT 3 10 TATB < 2? < 2? BTF 15 up to 100 presence is possile. The porous form of nnodimonds in the detontion products of BTF is responsile for the significnt difference etween the XRD dt nd TEM oservtions. In ddition, it is worth noting tht in [12], the verge RCS size for the detontion products of BTF chrge weighing 1000 g is 31 nm, which is twice tht otined in our study for chrge weighing out 20 g. 5. Conclusions The condensed detontion products (soot) of the investigted explosives contin lrge mount of vrious forms of cron. In ddition, ech of the soot smples hs distinguishing fetures. The detontion soot of pure TNT is chrcterized y the presence of nnodimonds of polyhedrl shpe with size of out 10 nm nd cron fiers up to tens of nnometers which, sed on the mesured interplnr spcing, correspond to the grphite modifiction of cron. The detontion products of the 50/50 TNT/RDX mixture contin smller nnodimonds of qusisphericl shpe with dimeter of few nnometers, onion-like cron of the sme size, nd cron fiers up to severl tens of nnometers long. The TATB detontion cron consists minly of cron fiers up to tens of nnometers long nd slightly seprted prticles of morphous cron with sizes up to tens of nnometers. The BTF chrges re chrcterized y the presence of lrge sphericl cron prticles up to severl hundred nnometers in dimeter. These prticles were initilly composed of liquid cron phse, ut their condenstion followed different pthwys, resulting in oth perfect nd considerly inhomogeneous onion-like prticles up to 100 nm in dimeter nd porous dimonds. The vriety of cron forms in the detontion products of vrious explosives nd their dissimilrity indictes significnt vritions in the detontion process. A comprison with pulished dt shows tht for the sme explosive, the detontion products cn e significntly different in different experimentl setups. The originl TEM dt re ville online [15]. Acknowledgments This work ws supported y the Russin Foundtion for Bsic Reserch (grnt No ). References [1] Ten K A, Titov V M, Pruuel E R, Kshkrov A O, Tolochko B P, Aminov Yu A, Looyko B G, Muzyry A K nd Smirnov E B 2015 Proc. 15th Interntionl Symposium on Detontion. Puliction No. ONR (Sn Frncisco, Cliforni) pp [2] Rmos K J, Jensen B J, Iverson A J, Yeger J D, Crlson C A, Montgomery D S, Thompson D G, Fezz K nd Hooks D E 2014 J. Phys.: Conf. Ser [3] Bgge-Hnsen M, Luderch L, Hodgin R, Bste S, Fried L, Jones A, vn Buuren T, Hnsen D, Benterou J, My C, Grer T, Jensen B J, Ilvsky J nd Willey T M 2015 J. Appl. Phys [4] Ten K A, Titov V M, Pruuel E R, Lukynchikov L A, Tolochko B P, Zhogin I L, Aminov Yu A, Filin V P, Looyko B G, Muzyry A K nd Smirnov E B 2010 Proc. 14th Interntionl Symposium on Detontion. Puliction No. ONR (Coeur d Alene, Idho) pp

10 [5] Greiner N R, Phillips D S, Johnson J D nd Volk F 1988 Nture [6] Kuznetsov V L, Chuvilin A L, Butenko Yu V, Ml kov I Yu nd Titov V M 1994 Chem. Phys. Lett [7] To X, Kng X nd Jizheng Z 1996 Mter. Sci. Eng. B 38 L1 L4 [8] Titov V M, Anisichkin V F nd Ml kov I Yu 1989 Comust., Explos. Shock Wves [9] Chen P, Hung F nd Yun S 2003 Cron [10] Petrov E A, Broshkin K S, Bychin N V, Lrionov B V nd Byrmin I V 2012 Proc. Ultrfine Powders, Nnostructures nd Sustnces: Production, Properties nd Applictions. VI Stvers s Redings (Krsnoyrsk, Russi) pp [11] Anisichkin V F, Ml kov I Yu nd Sgdiev F A 1991 Proc. V-th All-Union Meeting on Detontion vol 1 (Krsnoyrsk, Russi) pp [12] Ml kov I Yu, Filtov L I, Titov V M, Litvinov B V, Chuvilin A L nd Teslenko T S 1993 Comust., Explos. Shock Wves [13] Btsnov S S, Osvchuk A N, Numov S P, Efimov A E, Mendis B G, Apperley D C nd Btsnov A S 2015 Propellnts, Explos., Pyrotech [14] Willimson G K nd Hll W M 1953 Act Metll [15] Kshkrov A O, Pruuel E R, Ten K A nd Zukov P I 2016 Trnsmission electron microscopy of detontion cron. Photo lum. Tnt/rdx, tf, tnt, tt 9

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