New Energetic Materials - Current Research

Quote: Originally posted by katyushaslab

PETN is regarded as the "boundary" between primary and secondary in the modern literature. Interestingly, impact values do seem to vary lab to lab. https://pubs.acs.org/doi/10.1021/acsomega.1c01115

Quote: Originally posted by Microtek

PETN has an impact sensitivity of 3.6J, mannitol hexanitrate 0.8-1.8 J. I couldn't find data for ETN, but I would guess around 2J. Definitely too sensitive for the military, but I wouldn't worry too much in a laboratory setting.

Quote: Originally posted by Microtek

Well, my charges are rarely more than 1 gram secondary (hence my moniker), so a potential accident would be less catastrophic. Having said that, one of the things I enjoy about this hobby, is the engineering aspect of it. It will be interesting to see how the sensitivity can be modified by adding polymers or other binders, and how that will affect performance. I will post in this thread when I have something to report.

Quote: Originally posted by Microtek

Ok, so I've synthesized what I believe to be urazine. I began from dimethylcarbonate and followed "Green Synthetic Method for1,5-Disubstituted Carbohydrazones" by Li et al. Thus dimethylcarbonate (9g, 0.1 mol) was mixed with hydrazine hydrate (5.5 g, 0.11 mol) in a small two-necked flask fitted with reflux coloumn and thermometer adapter and heated with stirring to 70C. The mix was held at this temp (with constant stirring) for 4 hrs. Then the reflux coloumn was replaced with a distillation head, and a small amount of liquid was distilled off under reduced pressure. I think most of the liberated methanol had probably escaped through the reflux coloumn, or else weren't condensed in the cooler in this step. After cooling down, more hydrazine hydrate (11 g, 0.22 mol) was added, and the mix was stirred at 70C for another 4 hrs (with reflux coloumn). Then the distillation head was attached again, and the mix was concentrated under reduced pressure until a white precipitate began to form. Heating was stopped, and once cooled, the reaction mixture was filtered to recover the crude product, which should be carbohydrazide. The product consisted of large, stocky crystals and after washing with a little water and drying overnight, it weighed 6,77 g, corresponding to ca. 75% yield. To synthesize urazine, the method from "Inorganic Synthesis" (vol 4, p 30-31) was followed. I had the problem that the small amounts of material (6.77 g carbohydrazide and 7 ml HCl, 12M) didn't allow me to effectively monitor the temperature. I used an IR thermometer, but couldn't get very consistent readings. The procedure calls for slowly raising the temp. There should be a plateau around 215C which it should hold for about an hour. Then, when the temp increases to above 220C, heating is stopped and the reaction is allowed to cool. Then water (8 ml) is added, and the reaction is heated to dissolve byproduct hydrazine*HCl. The product, urazine, is not very soluble in water (0.32 g in 100 ml at 0C) so isolation is easy. After washing and drying, 1.878 g crude product was obtained. I recrystallized it from 0.1M HCl as outlined in the litterature, but I'm not sure it was necessary; the melting point didn't seem to change much. Anyway, after recrystallization, I was left with 1.548 g urazine (assuming that is what it is - solubilities and melting point corroborate the assumption, but I haven't tried any other methods of analysis). The total yield is just 26.6 % based on dimethylcarbonate, and less based on hydrazine hydrate. This is still enough for doing some testing since it should give about 2.6 g urazine perchlorate given the yield from the Klapötke paper. However, I don't like this procedure since it is uses quite a lot of hydrazine. I find this problematic, both because of the expense and the potential health effects (I do work in a fume hood, but accidents do happen).

Quote: Originally posted by Microtek

That is a predicted value using the ACDlabs software. ACDlabs is notorious for overestimating the density of organic molecules, so I am quite certain the actual density is somewhat lower. In fact, I would be extremely surprised if urazine isn't less dense than the perchlorate salt. Hydrazine*HCl to sulfate is a simple metathesis reaction, and is driven by the precipitation of low solubility hydrazine bisulfate. I would simply add 50% sulfuric acid (possibly even sodium sulfate) directly to the filtrate after filtering off the urazine, then filtering off the formed HS.

Quote: Originally posted by Microtek

I'm fairly certain that metathesis won't work to produce urazine perchlorate. The urazine is a very weak base, and even with HClO4 the salt is only formed on heating.

Quote: Originally posted by Microtek

My experiments with urazine are on hold, since I have come to doubt the identity (or maybe purity) of the compound I had synthesized. It seems I will have to buy some after all. In the mean time, I have been experimenting with some 4-amino-1,2,4-triazole that I ordered some years ago to test the capability of a supplier. I was searching for candidates for melt castable explosives, and wanted to try some aminotriazole compounds. I had some limited success with the picrate salt IIRC, but in the end I put it on indefinite hold. However, the urazine salts inspired me to make some more tests. The nitrate and perchlorate salts are both energetic as would be expected, but the nitrate is not reliably initiated in my setup. It may possibly be of interest as a less sensitive explosive. The perchlorate salt is much more sensitive, and seems to propagate detonation very effectively. My initial sensitivity tests involve a rapid cook-off test, a hammer test and a friction test. In the cook-off test, 50 mg ATrzP melts, bubbles and finally "pops" with enough force to make a large hole in the Al foil it is held on. It doesn't detonate though. ATrzN just burns with a hissing flame. In the hammer test 50 mg ATrzP is easily set off with moderate hammer blows, and detonates with a loud report and a VERY bright flash. The explosion is reminiscent of a drop of NG on tissue paper, in that it seems to be the entire mass of explosive that detonates (often, these tests will only set off parts of the explosive, and successive blows can achieve more detonations). ATrzN is only set off with difficulty in the hammer test. I wasn't able to initiate either of them by rubbing between hammer and anvil, but AtrzP gave a (very) positive reaction in my oblique impact test, which is a steel pendulum drop hammer which impacts a steel surface at a 25 degree angle from horizontal. The pendulum can be released from varying heights and the sample can be placed directly on the steel anvil or on a small piece of fine grit sand paper. In this test, ATrzP gave a positive test (any sign of chemical decomposition) at a slightly lower height than PETN, but did so more reliably. PETN often does not explode, but decomposition can be detected by smell. ATrzP usually explodes with flame and a clearly audible report. I also tested performance in the manner that I described under the "NHN without hydrazine hydrate" thread. I didn't press it very much because of the insufficiently tested sensitivity, but at a density of only 1.55 g/cc, the dent in aluminum bar stock was on par with that of HMX at >1.8 g/cc. If I can tame the sensitivity of the material (inert binders, perchlorate/nitrate mixes or other methods) it could be an interesting avenue of research. I experimented with two different methods of preparation: One was straight forward reaction of 4-amino-1,2,4-triazole with HClO4 followed by evaporation of the water. The other was reaction of the triazole with hydrochloric acid followed by evaporation. Then the hydrochloride was dissolved in ethanol, and a saturated solution of NaClO4 in ethanol was added at 55 C. NaCl precipitated and the mix was stirred at 55C for 10 minutes. The NaCl was filtered off, and the ethanol was evaporated. The products from the two reactions are not identical. They are both very explosive and react about the same in the hammer and cook-off tests, but the ethanol preparation produces a material that is difficult to dry out, while the HClO4 method makes a non-hygroscopic material (but mine was contaminated with an excess of one of the reactants). There is much work to be done. [Edited on 22-12-2021 by Microtek]

I keep saying that. Perchlorates are an unexplored area. Many discoveries are yet to be made. In the sense of primary and primarily secondary choristans. For easy safely initiation.

Quote: Originally posted by Microtek

In my research into triazoles, I recently stumbled onto a class of coordination complexes known as EMOFs - energetic metal-organic frameworks. In a number of very new papers, the authors are throwing around some quite extraordinary numbers: Substances having measured sensitivities less than TNT coupled with calculated detonation energy of 3.9 kcal/g (that is not an error; about twice ONC or CL-20), Pcj of 50-60 GPa and VOD of 10-11 km/s. In addition, they have measured thermal stabilities of around 300C. Of course, several of these numbers are calculated and it remains to be seen whether the models are any good at predicting performance at these extremes of the spectrum. Still, if they are reasonably close, it is a huge leap in performance, without any compromise with regards to safety. Some of the most energetic EMOFs I have seen are based on coupled furazan-tetrazoles as ligands around metal ions. These form 1-,2- , or 3-D frameworks that can have other ions in the voids in the structure. Some appetizers: https://pubs.acs.org/doi/10.1021/acs.inorgchem.9b01636# Almost 12 km/s Very high densities [Edited on 10-1-2022 by Microtek] [Edited on 10-1-2022 by Microtek]

Quote: Originally posted by Microtek

Most of these have been synthesized and tested with respect to density, heat of formation, stability and sensitivity. Most of the energetic properties are computed via semi-empirical methods such as the Kamlet-Jacobs equations. That is why I say that it remains to be seen whether these equations work for this kind of material. I believe that I can relatively easily prepare the material called ATRZ-1 ([Cu(4,4'-azo-1,2,4-triazole)3(NO3)2]n). It is basically made by mixing boiling aqueous solutions of Cu(NO3)2 and 4,4'-azo-1,2,4-triazole, filtering and allowing the filtrate to slowly evaporate until crystals form. The ligand 4,4'-azo-1,2,4-triazole is prepared by oxidative azo-coupling of 4-amino-1,2,4-triazole using sodium dichloroisocyanurate (pool chemical). As mentioned previously, I possess 4-amino-1,2,4-triazole from an old experiment, and I have prepared 4,4'-azo-1,2,4-triazole (I hope). I will attempt the synthesis of ATRZ-1, and also see what happens if Cu(ClO4)2 is substituted for the nitrate. ATRZ-1 has a heat of detonation of more than 15 kJ/g, but a density of only 1.68 g/cc, so the performance is predicted to be only about the level of HMX, but a perchlorate analogue might be better. On another note, I received my carbohydrazide recently, and have prepared urazine following the procedure from Inorganic Synthesis vol 4. It involves adding concentrated HCl and then slowly heating to 220C. Then water is added to dissolve the byproduct hydrazine*HCl, and the insoluble urazine is filtered off. The yield exactly matched the litterature procedure. I then added a slight excess of sulfuric acid to the recovered filtrate, which caused a large amount of white crystals to precipitate. This should be hydrazine sulfate, and after filtering, washing with cold water and drying, I recovered a yield of about 70%. In total, 23.4 g carbohydrazide was converted to 11.5 g urazine and 15.6 g hydrazine sulfate. The 1.16 g urazine was then reacted with one molar equivalent of 50% HClO4, and stirred for 1 hour at room temp, then 1 hour at 50C. Then the water was evaporated by placing the entire mass in a petri dish and heating to 60C on the hotplate. The product UZP is very dense and extremely energetic (in the hammer test), but moderately hygroscopic. I tried desensitizing it by dissolving 5 parts by weight of bees wax in a minimal amount of detergent gasoline, mixing this with 95 parts of the UZP and evaporating the gasoline while continually agitating the mix. The sensitivity is indeed reduced a little, but the wax does nothing for the hygroscopicity. The powder was pressed into a 7mm ID brass tube and easily achieved a packing density of 2.05 g/cc, however, when this was tested in my usual setup, a very disappointing result of 2.92 mm dent depth in 20 mm Al bar stock was achieved. For comparison: Picric acid: 3.53 mm 5-ATz*NO3: 3.84 mm RDX: 4.13 mm HMX: 4.35 mm It was only at this point I discovered the hygroscopicity issue. I had left weighing boats with both some of the neat crystals and also some of the wax treated powder in my workshop for testing. The relative humidity is slightly higher in my workshop than in my lab, and the samples that were in my lab *looked* fine, but the ones in the workshop had visibly absorbed atmospheric moisture. It may certainly be possible to work around both the sensitivity issue and the hygroscopicity (the right PBX formulation may solve both), but before working on that, I will conduct further tests to see if better performance can't be achieved from the dry product.

Quote: Originally posted by Microtek

Most of these have been synthesized and tested with respect to density, heat of formation, stability and sensitivity. Most of the energetic properties are computed via semi-empirical methods such as the Kamlet-Jacobs equations. That is why I say that it remains to be seen whether these equations work for this kind of material. I believe that I can relatively easily prepare the material called ATRZ-1 ([Cu(4,4'-azo-1,2,4-triazole)3(NO3)2]n). It is basically made by mixing boiling aqueous solutions of Cu(NO3)2 and 4,4'-azo-1,2,4-triazole, filtering and allowing the filtrate to slowly evaporate until crystals form. The ligand 4,4'-azo-1,2,4-triazole is prepared by oxidative azo-coupling of 4-amino-1,2,4-triazole using sodium dichloroisocyanurate (pool chemical). As mentioned previously, I possess 4-amino-1,2,4-triazole from an old experiment, and I have prepared 4,4'-azo-1,2,4-triazole (I hope). I will attempt the synthesis of ATRZ-1, and also see what happens if Cu(ClO4)2 is substituted for the nitrate. ATRZ-1 has a heat of detonation of more than 15 kJ/g, but a density of only 1.68 g/cc, so the performance is predicted to be only about the level of HMX, but a perchlorate analogue might be better. On another note, I received my carbohydrazide recently, and have prepared urazine following the procedure from Inorganic Synthesis vol 4. It involves adding concentrated HCl and then slowly heating to 220C. Then water is added to dissolve the byproduct hydrazine*HCl, and the insoluble urazine is filtered off. The yield exactly matched the litterature procedure. I then added a slight excess of sulfuric acid to the recovered filtrate, which caused a large amount of white crystals to precipitate. This should be hydrazine sulfate, and after filtering, washing with cold water and drying, I recovered a yield of about 70%. In total, 23.4 g carbohydrazide was converted to 11.5 g urazine and 15.6 g hydrazine sulfate. The 1.16 g urazine was then reacted with one molar equivalent of 50% HClO4, and stirred for 1 hour at room temp, then 1 hour at 50C. Then the water was evaporated by placing the entire mass in a petri dish and heating to 60C on the hotplate. The product UZP is very dense and extremely energetic (in the hammer test), but moderately hygroscopic. I tried desensitizing it by dissolving 5 parts by weight of bees wax in a minimal amount of detergent gasoline, mixing this with 95 parts of the UZP and evaporating the gasoline while continually agitating the mix. The sensitivity is indeed reduced a little, but the wax does nothing for the hygroscopicity. The powder was pressed into a 7mm ID brass tube and easily achieved a packing density of 2.05 g/cc, however, when this was tested in my usual setup, a very disappointing result of 2.92 mm dent depth in 20 mm Al bar stock was achieved. For comparison: Picric acid: 3.53 mm 5-ATz*NO3: 3.84 mm RDX: 4.13 mm HMX: 4.35 mm It was only at this point I discovered the hygroscopicity issue. I had left weighing boats with both some of the neat crystals and also some of the wax treated powder in my workshop for testing. The relative humidity is slightly higher in my workshop than in my lab, and the samples that were in my lab *looked* fine, but the ones in the workshop had visibly absorbed atmospheric moisture. It may certainly be possible to work around both the sensitivity issue and the hygroscopicity (the right PBX formulation may solve both), but before working on that, I will conduct further tests to see if better performance can't be achieved from the dry product.

LL: My standard test setup is as follows:

A 3D-printed holder is glued to the 20mm thick aluminum bar stock. Then the brass tube (7mm ID, 8mm OD, 40mm length, and the end is cut on my lathe to ensure that it is completely perpendicular to the axis of the tube) is inserted and glued into the holder.
The brass tube contains 1.000 +- 0.002 g of the substance to be tested and 0.300 +- 0.002 g PETN. It is initiated by aminoguanidinium nickel perchlorate.



MineMan
UZP is quite sensitive when dry, about on the level of ETN. With wax desensitization, maybe on par with PETN.
I just did another test with a fresh batch of UZP. Thia time I stored the powder in a dessicator, then prepared a PBX consisting of 6 parts PIB/5w40 oil (both dissolved in detergent gasoline) and 94 parts UZP. After mixing the components, most of the gasoline was evaporated, and the almost dry composite was placed in the dessicator overnight. Then it was pressed into the brass tube at a quite moderate pressure, to eliminate potential dead pressing as an issue. The density of the charge was still right around 2.00 g/cc, and the assembled charge was placed back into the dessicator until just before firing.
Despite all this, the result was only 2.934 mm dent depth. I therefore conclude that either it is impractical to keep the material dry enough, or else the problem lies elsewhere. Perhaps UZP loses more performance at this scale than some other energetics like RDX and HMX, or perhaps the model simply overestimates the performance of this material. Perhaps it is very easily dead pressed.

Great measurement, hat off. I finally see someone doing accurate tests. Thanks.....
And not like some who wrote "I heard it exploded", sure it works...

[Edited on 17-1-2022 by Laboratory of Liptakov]

Quote: Originally posted by Microtek

LL: My standard test setup is as follows: A 3D-printed holder is glued to the 20mm thick aluminum bar stock. Then the brass tube (7mm ID, 8mm OD, 40mm length, and the end is cut on my lathe to ensure that it is completely perpendicular to the axis of the tube) is inserted and glued into the holder. The brass tube contains 1.000 +- 0.002 g of the substance to be tested and 0.300 +- 0.002 g PETN. It is initiated by aminoguanidinium nickel perchlorate. MineMan UZP is quite sensitive when dry, about on the level of ETN. With wax desensitization, maybe on par with PETN. I just did another test with a fresh batch of UZP. Thia time I stored the powder in a dessicator, then prepared a PBX consisting of 6 parts PIB/5w40 oil (both dissolved in detergent gasoline) and 94 parts UZP. After mixing the components, most of the gasoline was evaporated, and the almost dry composite was placed in the dessicator overnight. Then it was pressed into the brass tube at a quite moderate pressure, to eliminate potential dead pressing as an issue. The density of the charge was still right around 2.00 g/cc, and the assembled charge was placed back into the dessicator until just before firing. Despite all this, the result was only 2.934 mm dent depth. I therefore conclude that either it is impractical to keep the material dry enough, or else the problem lies elsewhere. Perhaps UZP loses more performance at this scale than some other energetics like RDX and HMX, or perhaps the model simply overestimates the performance of this material. Perhaps it is very easily dead pressed.

Quote: Originally posted by Microtek

In my research into triazoles, I recently stumbled onto a class of coordination complexes known as EMOFs - energetic metal-organic frameworks. In a number of very new papers, the authors are throwing around some quite extraordinary numbers: Substances having measured sensitivities less than TNT coupled with calculated detonation energy of 3.9 kcal/g (that is not an error; about twice ONC or CL-20), Pcj of 50-60 GPa and VOD of 10-11 km/s. In addition, they have measured thermal stabilities of around 300C. Of course, several of these numbers are calculated and it remains to be seen whether the models are any good at predicting performance at these extremes of the spectrum. Still, if they are reasonably close, it is a huge leap in performance, without any compromise with regards to safety. Some of the most energetic EMOFs I have seen are based on coupled furazan-tetrazoles as ligands around metal ions. These form 1-,2- , or 3-D frameworks that can have other ions in the voids in the structure. Some appetizers: https://pubs.acs.org/doi/10.1021/acs.inorgchem.9b01636# Almost 12 km/s Very high densities [Edited on 10-1-2022 by Microtek] [Edited on 10-1-2022 by Microtek]

Quote: Originally posted by Microtek

No, I haven't given completely up on it, and I do have some left of my first batch of urazine. I was thinking that I would see if the nitrate is useful, and I could also try a PETN mix and maybe a very lightly pressed charge. I tried making the picrate, but adding urazine to molten picric acid did not produce anything other than the starting materials. My UZP crystals were smaller than the ones reported in the paper, but still relatively large. They are not uniform and they don't crystallize cleanly. Since the material is produced by heating the mix of HClO4 and urazine, I agitate it regularly to avoid a solid lump of highly sensitive and energetic HE that I then need to break down mechanically. When I triturate the crystals under detergent gasoline, they are easily reduced in size without applying too much force. I would like to try a charge without any additives, but am leery of pressing such a sensitive HE (especially as the crystals "creak" as they are pressed, somewhat like snow when it is compacted). On another note, I did some more experiments with 4-amino-1,2,4-triazolium perchlorate. I prepared some from equimolar (10 mmol) amounts of perchloric acid and the parent triazole. Then I evaporated the water by heating in a petri dish on a hotplate. I let it coodown with agitation and then placed it in a dessicator. After sitting ca. 24 hours, I ground it in a motar and pestle, about 30 mg at a time. Then I placed it in the dessicator again. 1.000 g of the, now much finer, powder was pressed uneventfully to 1.75 g/cc which corresponds to more than 96 % TMD according to a paper that I found (attached). On detonation, the dent produced was 4.38 mm deep, which is on par with HMX (4.35 mm). In the paper, they find a sensitivity of 30 kg*cm (HMX 34 kg*cm), but in my own tests, my impression is that it is more sensitive than that (perhaps it is more sensitive to friction which plays a part in most non-ideal impacts). Anyway, I also discovered that it melts below 100C. In the paper they say 84C, my own melting point determination says 78C at 12 degrees per minute, but this may be due to included water. When I let the temp continue to rise, no visible sign of decomposition could be detected up to 225C. This long molten temperature range makes it a candidate for melt casting, possibly in conjunction with other materials such as the nitrate or maybe urazine perchlorate. I would still like to lower the sensitivity a little, though. [Edited on 18-1-2022 by Microtek] [Edited on 18-1-2022 by Microtek]

Excellent work! Is that the compound that has twice the energy of a regular explosive? Considering it made the same dent as HMX, but at a lower density, and melt cast! Impressive . Are there any denser more powerful ones you can do… well if you decide to after reading dorniers post

In my opinion, the detonation pressure is more important than the detonation velocity VoD. For this reason, the dent plate method is the most convincing. It's cheap, fast and shows the most important things. That is, the mechanical effect on the pad. The speed of light is the highest of all. But it moves the spacecraft only slightly. Therefore, is best aluminum brick and 1 gram EM. In a column of material that is taller than wider. The so-called supra-square. In a cavity of 7 mm, for example 15 mm, in a cavity of 8 mm, for example 12 mm. The crater from ETN (or PETN) then serves as a reference depth. VoD measurement (electrically or optically) has a very laborious preparation, much more grams is used. And the test is loud. Not to mention the price of the measuring device. In amateur conditions is it luxury. // Let's make things as simple as is possible. But not simplier // Albert Einstein......

Quote: Originally posted by Microtek

N2O5 won't help matters. We don't need the nitronium ion, and the problem is that urazine is so weakly basic that it can't hold on to the nitrate ion. It doesn't stay protonated, especially since nitric acid is relatively volatile which pushes the UZ*HNO3 <--> UZ + HNO3 equilibrium towards the right as it evaporates. The same behavior is seen with aminonitroguanidinium nitrate, but to a lesser degree (so it takes longer for ANQN to lose all the nitrate). I'm going to try to measure VOD with an oscilloscope, but it is an experimental procedure I haven't tried before (I don't know much about electronics - I only barely know how to operate an oscilloscope), but I've found some papers that describe different methods. The simplest method uses ionization probes, which can be made from coaxial cables. It is based on using the conductivity of the reaction zone just behind the detonation front to act as a switch to close an electrical circuit. This can then be detected with an oscilloscope. Another option that looks attractive is based on detecting the arrival of the detonation front based on capturing the emitted light, and guiding it to fast photodiodes using fiberoptic cable. The optical detectors they used in the paper were quite expensive (ca. 500 dollars a piece and I need at least two - more preferably a few more), but I've found some much more affordable ones that I'm hoping are good enough.

Quote: Originally posted by Microtek

Lithium (or another metal ion) would be the coordination center, and AQ would be the ligand. This kind of complex is what I use for my primary, though using nickel instead of lithium. I don't think alkali metals make for very good coordination centers, but coordination chemistry isn't my specialty. Generally, metal ions do not contribute to the explosive performance (as Dornier pointed out earlier, it's like mixing your wood with ashes before lighting the fire), but can benefit other parameters such as stability, DDT ability, etc. It might be possible to make a complex with urazine as a ligand and perchlorate anions around a (transition) metal center. It could then be hoped that this would make it less sensitive, but more willing to go high order. Then it would be nice if the performance didn't drop too much because of the metal content. With regards to my planned VOD measurement, take a look at the paper I'm attaching. They use probe spacings of 1-4mm on a (strongly confined) charge with rectangular cross section and a width of 0.5 mm. They get measurements with a standard deviation of 13 - 60 m/s, corresponding to an error on the order of 0.5%. So charge size is not an issue. It is true that detonation pressure is very important, but there is a very strong correlation between VOD and Pcj, so measuring VOD will give a very good estimate of Pcj. Additionally, by using several probes, the acceleration of the detonation front could be mapped and this would make it possible to model things like critical diameter and non-ideal behaviour. In the attached paper, they use an oscilloscope with 500MHz bandwidth and 2.5 GSa/s, and that kind of specification costs upwards of 10000 dollars, but if you drop to 200 MHz and 1 GSa/s you can get a very decent one (I'm told) for about 400 dollars. Since 200 MHz should be enough to record 200 oscillations in the time it takes the detonation front to move 10 mm (at 10 km/s), I'm betting on this being sufficient time resolution.

The attached link explains everything. In the last century, a distance between sensors of 10 cm was used. There were no such fast devices for measurement....

Measuring VOD

Synchronising measuring instruments such as oscilloscopes with such fast phenomena is not easy. Here is an example:

During my engineering studies, I did an internship in an explosives research centre, where I worked on measuring the particle velocity behind the wavefront, which is of course lower than the VOD, but is nevertheless expressed in km/s. I used the magnetodynamic method, which consists of measuring the current induced in a metal strip immersed in a magnetic field and entrained by the products of the detonation. The explosive was 200 ml Astrolite A. Both oscilloscopes were triggered by a probe located a few centimetres upstream of the metal tape, but only one worked, and gave a null image. Either it was triggered too early or too late, or its calibration was not good. And I didn't get a second chance...





[Edited on 9-2-22 by pdb]

It are very good results. Powerful than picric acid. Aluminium usually decrease brisancion, but here is it conversely. And the UZP works in your cavity as primary - secondary ?.......... Was tested? I know, you use for start aminoguanidine some perchlorate + PETN 300 mg for maximal kick of examined compoud. 300 mg PETN is too much. This can affect the result. It's a huge blow to the test substance. It would make a small dent in aluminum, even if the place of the substance under investigation was pressed sand. Just my opinion, nothing more.

[Edited on 10-2-2022 by Laboratory of Liptakov]

Quote: Originally posted by Laboratory of Liptakov

Of course, that bigger amount will give more exact results and exact measurement of density. I estimate that 5g will enough. Diameter of high pressed EM of cylinder should by in this cause 12 - 15 mm at 5 g. However alu brick must be a lot bigger. Which can be expensive. For 5g I reccomend using lead block of diameter 70 mm and 60 mm high. Which is possible use repeatedly after casting. And measurement can be on 0,1 mm. Not on 0,01 mm. Lead block is possible use also for measurement longer charge in cavity 7 mm / 5g. With less exact results. Advantage of lead is his huge dynamic resistance of entire block. But 5g require testing chamber minimal 70 x 70 x 70 cm with wet sawdust. [Edited on 12-2-2022 by Laboratory of Liptakov]

Lead is heavy. Test not need any solid pad for same repeatedly results. Lead block can be in any position at the test in chamber or sand pit. And "swim" there. Other on picture. For funny is there production special spoon for slow eating of soup.....

Quote: Originally posted by Laboratory of Liptakov

Lead is heavy. Test not need any solid pad for same repeatedly results. Lead block can be in any position at the test in chamber or sand pit. And "swim" there. Other on picture. For funny is there production special spoon for slow eating of soup.....

Feel free to patent the hole spoon . By your advice (for UZP) was tested Lithex with 10% aluminium powder bright. Interesting is, the deep is exact same as without aluminium. 7,5 mm exactly. Complete energy of detonation was bigger according flying sawdust and other flying parts of testing chamber. Aluminium can provide advantage used less amount of Lithex for a same brizancion. And also for somes application, where is total energy importantly, than maximal brizantion. For example EFP not require maximal brizantion, there is more importatly maximal energy for better shaping of slug. Was observed also more easy filling - pressing behavior, resoectively pull of rod. If is Aluminium not critical compound, he provide clear advantage in mixture Lithex. Interestling...

Quote: Originally posted by Laboratory of Liptakov

Feel free to patent the hole spoon . By your advice (for UZP) was tested Lithex with 10% aluminium powder bright. Interesting is, the deep is exact same as without aluminium. 7,5 mm exactly. Complete energy of detonation was bigger according flying sawdust and other flying parts of testing chamber. Aluminium can provide advantage used less amount of Lithex for a same brizancion. And also for somes application, where is total energy importantly, than maximal brizantion. For example EFP not require maximal brizantion, there is more importatly maximal energy for better shaping of slug. Was observed also more easy filling - pressing behavior, resoectively pull of rod. If is Aluminium not critical compound, he provide clear advantage in mixture Lithex. Interestling...

Recently, I have devoted my spare time to developing test methodology for measuring VOD using an oscilloscope. I can now report my preliminary findings:





This is a screencapture from a test on pure PETN with probe placement 15 mm apart. The probes are ionisation probes, with each probe simply consisting of two square cut copper leads inserted (the picture shows a single probe point):



The test sleeve is resin 3d printed and the flaring base is just to have a secure attachment to the print plate. It also allows me to glue it onto a witness plate if I want to test brisance along with VOD (the axial hole goes all the way through). The picture doesn't do it justice, but the probe holes are very cleanly printed at exactly 5mm center distance.
The principle of this testing method is that the reaction zone just behind the detonation front is conductive since it is a high density plasma. Therefore, it can act as a switch to close a circuit. I have then constructed a simple circuit with the probes acting as switches in parallel and included a voltage divider setup to allow the change in signal to be detected, even if the conduction zone hasn't completely faded at one probe before triggering the next. The circuit is powered by a 9V battery, which provides the signal.

In the screen capture above, you can clearly see the very sharp rise in the signal as the detonation reaches the probe, followed by a gradual fall as the conductive zone attenuates. The time between the leading edges is very close to 2.5 us which, with probes 15mm apart, corresponds to a VOD of 6.0 km/s. It is difficult to assess this value since I don't know the exact density of the charge. Also, litterature values are often the result of tests on much larger charges, so even if I did know the density, the VOD of my charge would be less than most litterature values at the same value.
Nevertheless, I find the results encouraging.

I still have much work to do, examining the reproducibility of the setup and trying more than two probes to see if I can map the velocity profile. I also have to examine many different explosives to see if the detonation zone is similarly conductive for others.

[Edited on 8-3-2022 by Microtek]

Quote: Originally posted by Microtek

Take a look at this paper. The perchlorate salt is especially interesting IMO: d=1.99 (measured), VOD=9500 m/s and Pcj=45.7 GPa (Explo 5), Tdec=275C, IS=24J, FS=90N. The friction sensitivity is perhaps a little high, but other than that, it is almost perfect. The question is if it is hygroscopic like so many other promising perchlorate salts.

Quote: Originally posted by Microtek

Interesting, but IMO the decomposition temperature of 65C is a deal breaker (also the extremely high sensitivity).

Quote: Originally posted by Microtek

The UZP crystals were about 0.1 mm (but of course a distribution of sizes), and the sensitivity of my NAP is much lower - I have trouble setting the NAP off with steel on steel hammer blows, whereas UZP detonates with firm taps under these conditions. My comments above were directed at trinitroaminotrinitrobenzene.

Quote: Originally posted by Microtek

Well, I don't think the sensitivity issues are insurmountable - nitroglycerine is much more sensitive than UZP and has found quite a bit of use. I think the hygroscopicity is a bigger issue since the semi solvated UZP is VERY corrosive and might well be quite incompatible with other HEDMs or binders. Perhaps if we can find a suitably insensitive and non-hygroscopic perchlorate salt that might co-crystallize with UZP, or one that is melt-castable and forms a non-porous structure. This is only really worth pursuing if the calculated performance can be realized, so I need to analyze what is going on with the low performance. For this, I need to fully develop my test setup for VOD and that requires a series of carefully identical tests to determine the reproducibility and accuracy of the measurements. Also, I need to see how my setup works with more than two probes, since this will be required to map the acceleration of the shock wave. That is what I'm working on at the moment.

Here is the result of my first attempt with more than two probe points. The spacing is 10 mm between each pair. As can be seen from the screen shot, the time between the two first points is 1.45 us and between the second pair it is 1.60 us. This corresponds to VODs of 6897 m/s and 6250 m/s respectively. These values are reasonable for hand pressed charges of PETN with a small diameter (and with weak containment), but the fact that the second measurement is lower than the first is unexpected. Some possible explanations could be uneven charge density due to hand pressing, overdriven detonation from the primary, strange transient effects from reflection of shockwaves or maybe measurement error. Of these, I think the first is the most likely, since I didn't put much effort into consistent pressing.

Quote: Originally posted by dettoo456

Sorry since I’m not the best at understanding explanations without diagrams, but in your last post regarding the testing circuit, were the two probes set opposite of the charge on both ends (like a probe <-> charge <-> probe)? Or were they one probe behind the other, both being parallel to the charge (probe <-> probe <-> charge)? You may want to use piezos too; although they are more finicky and expensive but are used more often for this sort of VOD/pressure testing as they’ll ignore variability that can come with detonation products causing differences in plasma/heat formation. If my advice is retarded just ignore it (I’m no energetics wiz let alone electronics or sensitive circuit testing genius so a grain of salt is recommended as such) but good luck either way. Also in regards to the hygroscopicity, core-shell-explosive design can be interesting regarding primaries and in this case the high VOD of UZP can overcome any small problems with polymer coatings such as n-methylpyrrolidone or poly-dopamine which can be easy to apply with just heat, solvent, and maybe some ultrasonic stimulation.

@Dettoo:

This test setup is like this: The charge is a coloumn of PETN or other substance. Down the side of the coloumn, two rows of holes are made at precise intervals (so two holes at the base of the charge, two holes 5 mm above this, two more holes above this and so on. See the photo for clarity). One probe consists of two copper wires inserted in a pair of holes at the same height. a 9V battery is connected along with a resistor to the wires (so one wire is positive, the other is negative, but because of the spacing between the two holes, the circuit is open). When the CJ-zone reaches the probe (remember that's a pair of holes), the conductive plasma closes the circuit and the voltage across the resistor increases. It is this rise in the voltage that is recorded by the oscilloscope.
I did consider piezo sensors (and also fiber optics), but seeing the crisp and clear signal from the ionisation probes, I don't see the need. I think that the micro scale I'm working at gives me an advantage because I can have the oscilloscope placed within one meter of the test. This means that I don't need long wires and problems with induced currents and lots of electronic noise.

I'm attaching another test, this time with 4 probes at 5 mm spacing. I have now figured out how to export the raw data from the scope, so I can make more precise calculations on the VOD. This time I used a 2.5 kg weight to compress the charge at small intervals to get as uniform a density as possible. This means that I only get 0.6 MPa of loading pressure, so the VOD is obviously going to be quite low. The average VOD between probe points are as follows:

5988 m/s between 1 and 2
5181 m/s between 2 and 3
4854 m/s between 3 and 4

(the first peak is quite small, but that is probably because the probe wire were not as firmly imbedded in the charge).
I think this indicates that the VOD actually does decrease down the charge, probably as a result of the weak containment, but I need some more tests to be certain.




[Edited on 5-4-2022 by Microtek]

Quote: Originally posted by Microtek

Reading through some papers and encyclopedias, I found that the critical diameter of any explosive is strongly dependent on particle size. Since mechanical sensitivity is also dependent on particle size, producing an ultra fine UZP batch may prove to improve both the dissapointing performance and address some of the sensitivity issues of UZP. The problem is that it is not easy to do a particle size reduction based on crash precipitation (since dissolving UZP would freebase the urazine and UZP would only reform if all the water was removed). There is of course mechanical grinding, but that is not something I relish with a highly sensitive explosive. Maybe UZP can be ground safely under a non-polar solvent. I think I'll experiment a little at the milligram scale and see if I can make it explode under gasoline (with appropriate precautions obviously). As an aside, particle size effects may also explain the observations on PETN, since a coarse grained charge that is weakly confined would be relatively close to its critical diameter (especially at low density, since critical diameter is also inversely dependent on charge density). [Edited on 9-4-2022 by Microtek]

The only way to get the higher density required to achieve the stated properties is most likely melt casting (although most melt cast energetics can be suceptible to acid decomposition and on top of that melt casting primaries is a death wish) or something similar to anti-solvent recryst that might work for primaries or energetics in the booster range (think PETN, NHN-although insoluble, and tetryl). Basically, you might be able to use a dissolved energetic in a TLC sprayer under high N2 or Argon flow and spray onto a vertical or diagonal facing PTFE sheet. —> Like scraping spray paint particles off of a non stick surface to yield very small particulate. The sheet would have to be allowed to dry and hopefully the HClO4 would evaporate and the UZP would stick to the PTFE sheet. Scraping would also have to be very careful and use of a PTFE scraper could help tremendously. Good luck with whatever you try though and good luck trying to achieve those lofty m/s’s Don’t get yourself burned or scalded though

Quote: Originally posted by Microtek

That synth is easy, but requires a quite exotic pyrimidine to make one of the precursors. They describe it as "commercially available", but I don't think you will find it other places than in lab supply shops. I think I'll be sticking to AGNiP. In other news, it seems my hypothesis about the critical diameter of the rather coarse UZP was correct. I ground up a little more than one gram of it under detergent gasoline. I did it in small portions to reduce the seriousness of any accidental initiation from the grinding, but nothing untoward happened. After drying in a dessicator, I was left with a fine white powder. Previously, I had designed and CNC machined a couple of fixtures for supporting the brass tubes that I'm doing my brisance tests in (and another for the VOD test charge holders). This was necessary because the unsupported brass tubes expand under pressure, making the density of the charge difficult to calculate. These new holders are very solid, and fit the tubes in a light interference fit, meaning that the brass tubes can only expand a few micrometers. Anyway, I pressed the powdered UZP into the tube at a quite high pressure, and easily got it well above 2 g/cc. When detonated, it produced a dent of 4.64 mm depth. The coarse UZP at a similar density made a 2.91 mm dent, so the simple act of pulverizing increased the performance by almost 60%. This dent depth is greater than for any of the other explosives I have tested, so the question is now if I can overcome the hygroscopicity.

Quote: Originally posted by Laboratory of Liptakov

Great results, Microtek. 4.64 mm is incredible the depth. How much provide ETN ? My ETN 1g give at density 1.69g/cc depth 5,34 mm. In alu block. But diameter is 8 mm. (Against your 7?) Lithex gived depth 4.17 / 1.4g/cc. Lithex is also very hygroscopic. But is not crucial problem, because after filling is isolated in metal cavity. For main charge it can be problem. For detonator less.