Friction Stimuli Research Articles

Energetic Azoxy‐Coupled Tetrazoles

ABSTRACTAzoxy coupling of 5‐amino‐1‐methyl‐tetrazole, 5‐amino‐2‐methyl‐tetrazole, and 5‐amino‐1‐methoxy‐tetrazole was performed by reacting each with various oxidants. These reactions revealed aqueous Oxone to be the most facile system for yielding the azoxy couple for the previously mentioned tetrazoles. Chemical and structural characterization of each novel azoxy‐coupled tetrazole was conducted with 1H NMR, 13C NMR, HRMS, and single‐crystal x‐ray diffraction. Energetic characterization was evaluated by analysis of each compounds' single crystal x‐ray diffraction density, impact sensitivity, friction sensitivity, and decomposition temperature. All compounds were found to be very sensitive to impact and friction stimuli.

Thermally stable and insensitive energetic metal-organic frameworks based on two new tetrazole ligands

Two new tetrazole ligands were designed and synthesized using simple methods in this study, namely 1H-tetrazole-5-carbohydrazide (HCHT, 1) and 2-amino-5-(1H-tetrazol-5-yl)-1,3,4-oxadiazole (HAOT, 2). Their solvent-free potassium salts [K(CHT)]n (3) and [K(AOT)]n (4) are new two-dimensional energetic metal-organic frameworks (EMOFs), and their structures were characterized using nuclear magnetic resonance (NMR), infrared spectroscopy (IR), mass spectrometry (MS), elemental analysis (EA), and single-crystal X-ray diffraction (SXRD). Both compounds 3 and 4 exhibit high decomposition temperatures (Td) of 314 ​°C and 310 ​°C, respectively and are highly insensitive to impact and friction stimuli (IS ​> ​40 ​J, FS ​> ​360 ​N). The detonation velocity and pressure of 3 were calculated at 9141 ​m ​s−1 and 29.0 ​GPa, respectively, and those of 4 were determined at 8423 ​m ​s−1 and 24.5 ​GPa, respectively. Furthermore, intermolecular interactions in 3 and 4 were analyzed using 2D fingerprint plots with associated Hirshfeld surfaces. In this manner, two thermally stable and insensitive EMOFs were developed based on two new tetrazole ligands.

RDX crystals with high sphericity prepared by resonance acoustic mixing assisted solvent etching technology

In order to obtain high-quality spherical RDX crystal particles, the RDX crystals were suspended in a mixed solvent of cyclohexanone and cyclohexane, subsequently a solvent etching study was carried out under the action of vibration/acoustic flow coupled flow field, which generated by resonance acoustic mixing. The effects of solvent ratio, temperature, acceleration and experiment time on morphology as well as particle size of RDX crystals were studied. Not only were the morphology, particle size distribution and crystal form of RDX crystals determined, but also the thermal decomposition performance and mechanical sensitivity of spherical RDX were examined and discussed. Results indicated that under the process of solvent/non-solvent volume ratio at 1:2, temperature of 40°C, acceleration of 40 g and experiment time of 4 h, α-type RDX crystal with sphericity of 0.92 can be obtained. Furthermore, the median particle size (D50) of spherical RDX crystals is 215.8 μm with a unimodal particle size distribution (size span 1.34). For one thing, the thermal decomposition peak temperature of spherical RDX is about 2.5°C higher than that of raw RDX, and apparent activation energy reaches 444.68 kJ/mol. For another thing, impact sensitivity and friction sensitivity of spherical RDX are 18.18% and 33.33% lower than that of raw RDX, respectively. It demonstrates that safety of spherical RDX under thermal, impact and friction stimuli has been improved.

The Influence of Potassium Salts Phase Stabilizers and Binder Matrix on the Properties of Novel Composite Rocket Propellants Based on Ammonium Nitrate.

The environmental impact and availability of ingredients are vital for the new generation of rocket propellants. In this context, several novel composite propellants were prepared based on the "greener" oxidizer phase-stabilized ammonium nitrate (PSAN), a micronized aluminum-magnesium alloy fuel, iron oxide powder burn rate modifier, triethylene glycol dinitrate (TEGDN) energetic plasticizer and a polyurethane (PU) binder. The novelty of this study is brought by the innovative procedure of synthesizing and combining the constituents of these heterogeneous compositions to obtain high-performance "eco-friendly" rocket propellants. The polymorphism shortcomings brought by ammonium nitrate in these energetic formulations have been solved by its co-crystallization with potassium salts (potassium nitrate, potassium chromate, potassium dichromate, potassium sulphate, potassium chlorate and potassium perchlorate). Polyester-polyol blends, resulting from recycled post-consumer polyethylene terephthalate (PET) glycolysis, were utilized for the synthesis of the polyurethane binder, especially designed for this type of application. To adjust the energetic output and tailor the mechanical properties of the propellant, the energetic plasticizer TEGDN was also involved. The performance and safety characteristics of the novel composites were evaluated through various analytical techniques (TGA, DTA, XRD) and specific tests (rate of combustion, heat of combustion, specific volume, chemical stability, sensitivity to thermal, impact and friction stimuli), according to NATO standards, providing promising preliminary results for further ballistics investigations.

Spun of improvised cis‐1,3,4,6‐tetranitrooctahydroimidazo‐[4,5‐d]-Imidazole (BCHMX) in polystyrene nanofibrous membrane by electrospinning techniques

Development of ultra-fine fiber technology and nano-sized materials are widely taking place to enhance the characteristic of different materials. In our study, a newly developed technique was used to produce improvised nano energetic fibers with the exploitation of cis‐1,3,4,6‐Tetranitrooctahydroimidazo‐[4,5‐d] imidazole (BCHMX) to spin in a polystyrene nanofiber membrane. Scanning electron microscopy (SEM) showed the synthesized nanofibrous polystyrene (PS)/BCHMX sheets with clear and continual fiber were imaged with scanning electron microscopy (SEM). Characterization of the produced nanofiber was examined by Fourier Transform Infrared (FTIR), and X-ray diffractometer (XRD). Explosive sensitivity was also evaluated by both BAM impact and friction apparatus. Thermal behavior for the synthesized PS/BCHMX fiber and the pure materials were also investigated by thermal gravimetric analysis (TGA). The results show enhancement in the fabrication of nano energetic fibers with a size of 200–460 nm. The TG confirms the high weight percentage of BCHMX which reaches 60% of the total mass. PS/BCHMX fiber was confirmed with the XRD, FTIR spectrum. Interestingly, XRD sharp peaks showed the conversion of amorphous PS via electrospinning into crystalline shape regarding the applied high voltage. The synthesized PS/BCHMX nanofiber was considered insensitive to the mechanical external stimuli; more than 100 J impact energy and > 360 N initiation force as friction stimuli. PS/BCHMX is considering a candidate tool to deal with highly sensitive explosives safely and securely for explosives detection training purposes.

Study on Indium (III) Oxide/Aluminum Thermite Energetic Composites

Thermites or composite energetic materials are mixtures made of fuel and oxidizer particles at micron-scale. Thermite reactions are characterized by high adiabatic flame temperatures (>1000 °C) and high heats of reaction (>kJ/cm3), sometimes combined with gas generation. These properties strongly depend on the chemical nature of the couple of components implemented. The present work focuses on the use of indium (III) oxide nanoparticles as oxidizer in the elaboration of nanothermites. Mixed with an aluminum nanopowder, heat of reaction of the resulting Al/In2O3 energetic nanocomposite was calculated and its reactive performance (sensitivity thresholds regarding different stimuli (impact, friction, and electrostatic discharge) and combustion velocity examined. The Al/In2O3 nanothermite, whose heat of reaction was determined of about 11.75 kJ/cm3, was defined as insensitive and moderately sensitive to impact and friction stimuli and extreme sensitive to spark with values >100 N, 324 N, and 0.31 mJ, respectively. The spark sensitivity was decreased by increasing In2O3 oxidizer (27.71 mJ). The combustion speed in confined geometries experiments was established near 500 m/s. The nature of the oxidizer implemented herein within a thermite formulation is reported for the first time.

Effect of cation nature on vacuum tribo-degradation and lubrication performances of two tetrafluoroborate ionic liquids

Vacuum lubrication and tribo-degradation performance investigations of two imidazolium tetrafluoroborate ionic liquids (ILs, LAB103 and LB104), were systematically conducted by the VFBT-4000 vacuum four-ball tribometer equipped with a quadrupole mass spectrometer. They both have quite wide liquid range with high thermostability and good fluidity at low temperature. Results of vacuum tribological tests show that LAB103 present better lubricity and lower corrosivity as compared with that of LB104, due to its strong adsorption layers and robust tribofilms on worn surfaces. Tribo-degradation test results exhibit that the decomposition of ILs is mainly caused by frictional stimulus. The decomposition products partially diffuse to vacuum chamber, being captured by mass spectrometer detector and others participate in the tribochemical reactions.

Computational simulation of safety parameters concerning friction and impact sensitivity of tested civil use explosives

The paper presents the results of the theoretical and practical researches regarding the development of conceptual and experimental models specific to the determination of the safety parameters regarding the friction and impact sensitivity, whose plausibility be guaranteed through a whole range of scientific solutions characterized by validated results through numerical modeling and simulations. Designing these types of processes requires consideration, with a relative approximation, the degree of danger due to the design of fragments resulting from detonation, vibrations, pressures, tensions created in the space affected by the explosion, explosion gas generation etc. Estimating the peak values of induced requests is an essential for implementing IT solutions of previous experimentation allows the study of a large number of scenarios, the limit being mainly dependent on the time spent on computer simulations. In this context, safety research into the handling of explosives, the acquisition of experience and knowledge as well as the validation of results by comparison with previous practical experiments and those specified in the literature, become relevant and necessary requirements. Methods used to determine security parameters, analyzed by classical and IT means are relevant to the interpretation of the nature of the explosive matter in terms of their effect in terms of the effect they may have on the environment of use in the event of an explosion in accordance with the legislation in force an important indicator of classification, handling, storage and transport in the assessment and the management of the risks associated with these operations. The paper presents a series of results regarding computer numerical simulations, safety parameters (friction and impact sensitivity). The similarity of the results obtained in the case of physical experiments to determine the susceptibility of explosive substances tested to friction and impact stimuli in relation to those provided by computerized numerical simulations demonstrate the usefulness of these IT science solutions that through the ANSYS Multiphysics package provide the prerequisites for determining the safety features in the field of explosives for civilian use.

Nanometer Ammonium Perchlorate and Ammonium Nitrate Prepared with 2D Network Structure via Rapid Freezing Technology.

Nanometer (nano) ammonium perchlorate (AP) and ammonium nitrate (AN) were prepared with 2D network structures by the ultra-low temperature spray method. Scanning electron microscopy (SEM), X-ray diffractometry (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis/infrared spectrometry (TG-IR) were employed to probe the micron structure, crystal phase, and thermal decomposition of nano AP and nano AN. SEM images revealed that the sizes of nano AP and AN were in the nanometer scale (<100 nm) in one dimension. XRD patterns showed that the crystal phases of nano AP and AN were in accordance with those of raw AP and raw AN, respectively. DSC traces indicated that the thermal decomposition process of AP depended on its particle size, while the thermolysis of AN was independent of the particle size of AN. TG-IR analyses illustrated that the decomposition products of nano AP were NO2, N2O, HCl and H2O, with a small amount of NOCl, and the main decomposition products of nano AN were N2O and H2O, with a small amount of NH3. The results of mechanical sensitivity tests indicated that nano AP was more sensitive than raw AP and both nano AN and raw AN were very insensitive to impact and friction stimuli.

Tactile Texture Display with Vibrotactile and Electrostatic Friction Stimuli Mixed at Appropriate Ratio Presents Better Roughness Textures

Vibrotactile and friction texture displays are good options for artificially presenting the roughness and frictional properties of textures, respectively. These two types of displays are compatible with touch panels and exhibit complementary characteristics. We combine vibrotactile and electrostatic friction texture displays to improve the quality of virtual textures, considering that actual textured surfaces are composed of both properties. We investigate their composition ratios when displaying roughness textures. Grating roughness scales with one of the six surface wavelengths are generated under 11 display conditions, and in 9 of which, vibrotactile and friction stimuli are combined with different composition ratios. A forced-choice experiment regarding subjective realism indicates that a vibrotactile stimulus with a slight variable-friction stimulus is effective for presenting quality textures for surface wavelengths greater than or equal to 1.0mm.

Nitrogen-rich salts of 5,5′-bistetrazole-1,1′-diolate: Syntheses, structures and properties

A series of new nitrogen-rich energetic salts containing 1H,1′H-[5,5′-bitetrazole]-1,1′-diol (BTO) anion and ethane-1,2-diaminium (1), 1-amino-1H-1,2,3-triazol-3-ium (2), 4-amino-4H-1,2,4-triazol-1-ium (3) and 4,5-diamino-4H-1,2,4-triazol-1-ium (4) cations were synthesized by direct salt formation or by metathesis strategy. The structures of energetic salts 1-4 were comprehensively characterized by elemental analysis, mass spectrometry, IR and NMR spectroscopies and by X-ray crystallography. DSC and TGA methods were used to study thermal properties of these salts. Additionally, the non-isothermal kinetic parameters and thermodynamic parameters were calculated by utilizing the Kissinger's and Ozawa-Doyle's methods. The enthalpies of formation for all target compounds in this study were calculated, and their sensitivity to mechanical impact and friction was tested according to BAM guidelines. We found these new energetic salts exhibit good thermal stability and have typical decomposition temperatures above 230 °C, except for the salt 2. All our salts have highly-positive enthalpies of formation (311.1–473.6 kJ mol−1) and are insensitive to impact and friction stimuli (>40 J, 120 N). With a high nitrogen-rich content, high enthalpy of formation, good thermostability and very low sensitivity to impact, some of these new salts may have a potential for application in the field of environmentally friendly insensitive energetic materials.

Evaluation of the Detonation Performance of Insensitive Explosive Formulations Based on 3,3ʹ Diamino-4,4ʹ-Azoxyfurazan (DAAF) and 3-Nitro-1,2,4-Triazol-5-One (NTO)

ABSTRACTTwo energetic materials identified for relatively high energy, but little to no response to impact, spark or friction stimuli are 3-nitro-1,2,4-triazole-5-one (NTO), and 3,3ʹ diamino-4,4ʹ-azoxyfurazan (DAAF). More of an outlier in performance versus sensitivity, DAAF illustrates insensitivity by small-scale sensitivity tests, yet has a failure diameter estimated to be 1.25 mm and a short run length to detonation. Because of this unusual behavior, DAAF is an ideal material to formulate with NTO to obtain tailored shock sensitivity and critical diameter, with detonation velocities and pressures higher than PBX 9502. Here, we present detonation properties of Kel-F® bonded formulations with ratios of 20–70 wt.-% DAAF added to NTO. All formulations were evaluated for detonation velocity, aluminum flyer acceleration at jump-off, and via the cylinder expansion test.

Axial substitution of a precursor resulted in two high-energy copper(ii) complexes with superior detonation performances.

The design and synthesis of explosives with high performance, good thermal stability, and low sensitivity is an important subject for the development of energetic materials. Energetic complexes have recently emerged as a promising energetic material form. As one of the representatives, [Cu(Htztr)2(H2O)2]n (H2tztr = 3-(1H-tetrazol-5-yl)-1H-triazole) was previously reported with good energetic performance, outstanding thermostability (Tdec = 345 °C) and low sensitivity to impact and friction stimuli. However, due to the existence of water molecules, its effective energy density is remarkably decreased, resulting in a diminished detonation performance. In order to further improve the detonation performance, using [Cu(Htztr)2(H2O)2]n as a precursor, {[Cu(Htztr)(H2O)]NO3}n (1) and [Cu(H2tztr)2(HCOO)2]n (2) were synthesized by the axial substitution reaction with NO3- and HCOO-. The structures of 1 and 2 were characterized by single crystal X-ray diffraction. Both of them exhibit high thermal stabilities and insensitivities to impact and friction. Moreover, the same DFT calculation methodology shows that the heat of detonation of 2 (3.5663 kcal g-1) is significantly higher than that of the precursor [Cu(Htztr)2(H2O)2]n (2.1281 kcal g-1). Meanwhile, the empirical Kamlet-Jacobs equations were used to theoretically predict the detonation properties of the title complexes, and the results show that 1 and 2 have excellent detonation velocity (D) and detonation pressure (P).

Experimental research on the tactile perception from fingertip skin friction

Skin friction is a main perception channel for humankind to recognize object surface properties. However, the relationship between tactile perception and skin friction is a typical bio-tribology interdisciplinary problem, which is rarely studied both in biology and tribology fields. In order to study the brain stimulation response to the fingertips sliding friction, cognitive related fingertip friction testing was carried out, and the tactile perception evoked by the friction and vibration of various surface textures was investigated in this paper, human subjective tactile experiments was carried out through twenty volunteers testing for the tactile perception of surface properties, focused on three fabric samples (cotton, linen and silk) and three paper samples (photo paper, kraft paper and normal paper). The friction coefficient and frictional vibration signals were measured, and the brain response signals stimulated by the fingertip friction were simultaneously recorded and analyzed. The research works in this paper are beneficial for the deep understanding of tactile perception mechanism by fingertips, and building up a biomimetic model for smart robotic fingers.The research results indicate that the cerebral cortex responds sensitively to the variations in fingertips frictional force and vibration amplitudes. The human tactile perception is very sensitive to the fabric texture properties, which are described by the dimensions such as rough-smooth, coarse-fine and complex-uniform. The higher values of the fabric texture dimensions, the lower values in friction coefficient, and the more sensitive of tactile perception for the surface textures. Furthermore, it is noticed that the amplitude and distribution of brain signals response, i.e. ERPs (event related potentials) evoked by fingertip friction, is affected by the surface texture or friction coefficient. It is found that the response sensibility shown on the beginning peaks of ERP waveform has strong relation to the frictional stimulus on fingertip friction. The parameter of P3 latency (i.e. the third positive peak of ERP) is the distinct identifying information for the tactile perception of surface textures.

An Improved and Scalable Synthesis of Insensitive High Explosive 4,10-Dinitro-2,6,8,12-tetraoxa-4,10-diazaisowurtzitane (TEX)

4,10-Dinitro-2,6,8,12-tetraoxa-4,10-diazaisowurtzitane (TEX), a well-known nitramine category explosive, is much less sensitive to impact and friction stimuli as compared to the familiar explosives, RDX and HMX. TEX is currently produced on pilot plant scale and is being pursued as an insensitive explosive. Herein a newer, improved, efficient, and high yielding protocol is developed for the synthesis of TEX by using solid acidic silica sulfuric acid as an efficient and recyclable catalyst. Sequentially for process parameters optimization, a study was carried out with variation of catalyst loading, nitric acid, and mole ratio of reactants. The process scale-up is also achieved successfully.

Relationship between Activation Energy of Thermolysis and Friction Sensitivity of Cyclic and Acyclic Nitramines

AbstractThe knowledge of sensitiveness of an energetic compound to friction stimuli is important to ensure the safety of people and protection of property during shipment. The information on sensitivity to friction is considered very valuable for nitramines, which show relatively higher sensitivity with respect to the other classes of secondary explosives. This study presents a novel general simple model for prediction of the relationship between friction sensitivity and activation energy of thermolysis of cyclic and acyclic nitramines on the basis of their molecular structures. This methodology assumes that friction sensitivity of an energetic compound with general formula CaHbNcOd can be expressed as a function of activation energy of thermolysis and the contribution of specific molecular structural parameters. For 21 nitramines with different molecular structures, the new correlation has the root mean square and the average standard deviations of 14.2 and 17.8 N, respectively, as compared to experimental values. The proposed new method is also tested for further 8 nitramines containing complex molecular structures, which gives good predictions.

Solid state synthesis, thermodynamics and catalytic combustion effect of a high energy nickel(II) coordination compound

Self-assembly of Ni(II) with 3,5-diamino-1,2,4-triazole resulted in a 3D supramolecular compound [Ni3(Hdatrz)6(fma)2(H2O)4]fma·11H2O (1) in the presence of coligand fumaric acid (Hdatrz=3,5-diamino-1,2,4-triazole, H2fma=fumaric acid). X-ray structural analysis reveals that three nickel ions are bridged by six neutral Hdatrz ligands, and abundant lattice water molecules exist in 1. Based on the structural framework and TG curve of 1, a new energetic compound [Ni3(Hdatrz)6(fma)2(H2O)4]fma (2) with 35.5% of nitrogen content was readily prepared through dehydration of 1 at 398K under N2 atmosphere. The enthalpy change of the reaction of formation for 1 was determined to be (−23.24±0.05)kJmol−1 by microcalorimetry at (298.15±0.01)K. Thermodynamic and thermokinetic parameters k, E, n, ΔS≠θ, ΔH≠θ and ΔG≠θ of the reaction of formation for 1 were obtained. Thermoanalytical kinetics of the reaction of formation for 2 was further investigated. The sensitivity experiment results indicated that 2 was more sensitive to impact and friction stimuli that 1. As an additive, 2 effectively promoted the thermal decomposition of ammonium perchlorate (AP), which projected the potential application of the compound 2 as combustion modifier in solid propellants.

How to identify water from thickener aqueous solutions by touch

Water detection is one of the most crucial psychological processes for many animals. However, nobody knows the perception mechanism of water through our tactile sense. In the present study, we found that a characteristic frictional stimulus with large acceleration is one of the cues to differentiate water from water contaminated with thickener. When subjects applied small amounts of water to a glass plate, strong stick-slip phenomena with a friction force of 0.46 ± 0.30 N and a vertical force of 0.57 ± 0.36 N were observed at the skin surface, as shown in previous studies. Surprisingly, periodic shears with acceleration seven times greater than gravitational acceleration occurred during the application process. Finite-element analyses predicted that these strong stimuli could activate tactile receptors: Meissner's corpuscle and Pacinians. When such stimuli were applied to the fingertips by an ultrasonic vibrator, a water-like tactile texture was perceived by some subjects, even though no liquid was present between the fingertip and the vibrator surface. These findings could potentially be applied in the following areas: materials science, information technology, medical treatment and entertainment.

Closed-Vessel and Thermal Studies on Triple-Base Gun Propellants Containing CL-20

This study was undertaken to see the effect of the replacement of picrite by 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) (5, 10, and 15%) in triple-base gun propellants. Experimental results of a closed-vessel test at a loading density of 0.2 g/cm 3 indicate improvement in energetics of the CL-20-incorporated compositions. The force-constant values obtained were 1046, 1071, and 1095 J/g for 5, 10, and 15% CL-20-based formulations, compared with 1028 J/g for conventional picrite composition as the control. Similar trends were observed for linear burning-rate coefficient β 1 values. The selected energetic plasticizers N-(n-butyl)-N-(2-nitroxyethyl) nitramine (Bu-NENA) and bis-2,2 dinitro propyl formal/acetal (BDNPF/A) were also evaluated for their effectiveness in CL-20-containing gun-propellant compositions. Thermal analysis was carried out using differential scanning calorimeter and thermogravimetric analyzer. Replacement of picrite by CL-20 resulted in an increase in AH values (by differential scanning calorimeter) compared with that of control composition. Weight-loss data (from thermogravimetric analyzer) showed a similar trend. The CL-20-based compositions were found relatively more sensitive to friction stimuli (12-17 kg) compared with control composition (19.2 kg).

Low Vulnerable Sheet Explosive Based on 3-Nitro-1,2,4-triazol-5-one

3and tensile strength, 0.5 MPa) was taken as reference and the effect of replacement of RDX by nitrotriazolone to the extent of 5–25% was studied. Inclusion of nitrotriazolone led to a remarkable increase in density (1:23 ! 1:41 g=cm 3 ) and mechanical properties (tensile strength: 0:46 ! 1:08 MPa). The major finding was increase in velocity of detonation by about an average 700 m=s over the reference composition. Velocity of detonation realized ranged from 6800 to 6900 m=s for RDX/nitrotriazolone/ Estane compositions. As regards sensitivity, nitrotriazolone-based compositions were relatively less vulnerable to impact and friction stimuli. Shock sensitivity of RDX/nitrotriazolone/Estane composition was also found to be of the order of 98–110 kbar as against 77 kbar for reference. The armor protection capability of nitrotriazolone-based composition against shaped charge was found to be at par with the corresponding RDX-based sheet explosive. Thermal studies revealed that nitrotriazolone and RDX incorporated sheet explosives with Estane binder decomposed as a unified composite, despite their widely differing decomposition/ignition temperatures.