Developing a highly scalable synthetic strategy for 5-amino-4-nitrobenzo[1,2-c:3,4-c']bis([1,2,5]oxadiazole)1,b-dioxide(CL-18)and investigating the influence of crystal engineering and positional isomerization on its safety and laser ignition performance

5-amino-4-nitrobenzo[1,2-c:3,4-c']bis([1,2,5]oxadiazole)1,6-dioxide(CL-18)exhibits significant potential as an initiating explosive.However,its current synthesis process remains non-scalable due to low yields and safety risks.In this study,we have developed a simple and safe synthetic route for CL-18.It was synthesized from 3,5-dihaloanisole in a four-step reaction with an overall yield exceeding 60%,surpassing all reported yields in the literature.Subsequently,recrystallization of CL-18 was successfully achieved by carefully selecting appropriate solvents and antisolvents to reduce its mechanical sensitivity.Ultimately,when DMF-ethanol was employed as the recrystallization solvent system,satisfactory product yield(>90%)and reduced mechanical sensitivity(IS=15 J;FS=216 N)were obtained.Additionally,CL-18 is derived from the rearrangement of oxygen atoms on i-CL-18 furoxan,and a comparative analysis of their physicochemical properties was conducted.The thermal stability of both compounds is similar,with onset decomposition temperatures recorded at 186 and 182℃respectively.Similarly,they exhibit 5 s breaking point temperatures of 236 and 237℃.Additionally,we present novel insights into the positional-isomerization-laser-ignition performance of CL-18 and its isomer i-CL-18 using laser irradiation for the first time.Remarkably,our findings demonstrate that i-CL-18 exhibits enhanced laser sensitivity,as it can be directly ignited by a 1064 nm wavelength laser,whereas CL-18 lacks this characteristic.

Safety control for powder compaction of initiating explosive device

Powder compaction is one of the most crucial processes in initiating explosive device manufacturing. The quality of powder compaction may influence the performances of product directly. Traditional powder compaction mainly makes use of manual gravitational spiral loading machine or lever loading machine. Potential accident by the strike in powder compaction of initiating explosive device could risk life, property and the environment. To prevent this risk, automatic control system and control strategy can be used to guarantee no strike in pressing process. The scope of this paper is to analyze and review the control strategy for powder compact and discuss the experimental results for the application of the proposed strategy.

Numerical simulation of the delay arming process of initiating explosive brakes

The delay arming process of initiating explosive （ IE ） brakes for fuse is complex and hard to be verified. A numerical simulation model of IE brakes was established based on the arbitrary La- grange-Euler method. The model included the structure, the air filed, etc. The simulation boundary conditions were defined, including the contacts, blasting parameters of the explosive and the fluid- solid coupling interface. The simulation results show that the shear pin of the chosen IE can be cut off. When the piston needs to move 0.8 cm, the time set to the delay arming of the IE brakes model is about 40μS. The maximum displacement of the piston is 1. 17 cm. The model provides basis for parameters design and further improvement of IE brakes.

Effect of the Al/O ratio on the Al reaction of aluminized RDX-based explosives

Aluminum（Al） powders are used in composite explosives as a typical reducing agent for improving explosion performance. To understand energy release of aluminum in aluminized RDX-based explosives, a series of thermal measurements and underwater explosion（UNDEX） experiments were conducted. Lithium fluoride（LiF） was added in RDX-based explosives, as a replacement of aluminum, and used in constant temperature calorimeter experiments and UNDEXs. The influence of aluminum powder on explosion heat（Qv） was measured. A rich supply of data about aluminum energy release rate was gained. There are other oxides（CO2, CO, and H2O） in detonation products besides alumina when the content of RDX is maintained at the same levels. Aluminum cannot fully combine with oxygen in the detonation products. To study the relationship between the explosive formulation and energy release, pressure and impulse signals in underwater experiments were recorded and analyzed after charges were initiated underwater. The shock wave energy（Esk）, bubble energy（Eb）, and total energy（Et） monotony increase with the Al/O ratio, while the growth rates of the shock wave energy,bubble energy, and total energy become slow.

Application of equivalent information method to high reliability assessment of initiating explosive devices

The amount of information required for reliability assessment of success/failure products is defined and the formula of equivalent information method is deduced. Based on the formula, a method for assessing reliability of initiating explosive devices with small sample size is established. Compared with the assessment method for devices with large sample size, the new method is correct and feasible and can be used to assess the reliability of initiating explosive devices with high reliability requirements.

Sensitivity Test and Data Analysis for Storage Reliability Assessment of Explosive Initiator

The explosive initiator is one kind of sensitivity products with long life and high reliability.In order to improve the storage reliability assessment,the method of storage reliability assessment for explosive initiator was proposed based on time series model using the sensitivity test data.In the method,the up and down test was used to estimate the distribution parameters of threshold.And an approach to design the up and down test was present to draw better estimations.Furthermore,the method of shrinkage estimation was introduced to get a better estimation of scale parameter by combining the sample information with prior information.The simulation result shows that the shrinkage estimation is better than traditional estimation under certain conditions.With the distribution parameters estimations,the time series models were used to describe the changing trends of distribution parameters along with storage time.Then for a fixed storage time,the distribution parameters were predicted based on the models.Finally,the confidence interval of storage reliability was obtained by fiducial inference.The illustrative example shows that the method is available for storage reliability assessment of the explosive initiator with high reliability.

The role of tangential velocity in explosive initiation by fragment impact

An initiation study is presented in which we examine the effect of the normal and the tangential velocity components of a fragment that impacts a covered and a bare Comp-B explosive. The study is based on calibrated numerical Lagrangian simulations using the LS-Dyna hydrocode. A special procedure was developed to present the estimated initiation point and the shock wave transition into detonation for various impact angles. The influence of the fragment strength and the steel cover thickness on the detonation threshold were also examined. The velocity threshold results are presented and used to modify the Jacobs-Roslund initiation model.

Design of multi-channel equivalent system for IED based on Gigabit Ethernet transmission

To test the pulse signal of initiating explosive device (IED) in an aircraft,a multi-channel equivalent system for IED based on Gigabit Ethernet transmission is designed according to its electrical parameters. The output voltage of multi-channel equivalent circuit is converted by analog-to-digital converter (ADC). Then the validity of the converted signal is judged by field programmable gate array (FPGA). Finally,it is transmitted the host computer through Gigabit Ethernet for waveform displaying. Compared with the traditional equivalent equipment of IED,the designed system here can not only test the validity of the pulse signal and normal operation of equivalent circuit,but also realize fast and reliable analysis of pulse signal by means of Gigabit Ethernet. It solves the problems of low speed and lag of response of traditional equivalent equipment.

Method for high reliability evaluation of explosive initiator based on sensitivity distribution order restricted theory

Based on the hypothesis testing theory and sampling inspection, and utilizing the distribution parameters obtained by order restricted method, the matter of reliability index verification is transformed into testing the scale parameters of distribution. Thus, a lower stimulus level is selected, and small sample size specimens are tested to verify the high reliability at required stimulus level. Analysis for mean square error of verification test stimulus level is taken, and the result demonstrates that it is reasonable to confirm the test scheme using the order restricted estimation. The new method is used for reliability verification of the stab detonator comparing with run-down method. The result shows that it is available for verification of high reliability explosive initiator by small sample size.

Neural Networks Combined with Importance Sampling Techniques for Reliability Evaluation of Explosive Initiating Device

Concerning the issue of high-dimensions and low-failure probabilities including implicit and highly nonlinear limit state function, reliability analysis based on the directional importance sampling in combination with the radial basis function （RBF） neural network is used, and the RBF neural network based on first-order reliability method （FORM） is to approximate the unknown implicit limit state functions and calculate the most probable point （MPP） with iterative algorithm. For good efficiency, based on the ideas that directional sampling reduces dimensionality and importance sampling focuses on the domain contributing to failure probability, the joint probability density function of importance sampling is constructed, and the sampling center is moved to MPP to ensure that more random sample points draw belong to the failure domain and the simulation efficiency is improved. Then the numerical example of initiating explosive devices for rocket booster explosive bolts demonstrates the applicability, versatility and accuracy of the approach compared with other reliability simulation algorithm.

Metal-organic framework templated synthesis of copper azide as the primary explosive with low electrostatic sensitivity and excellent initiation ability

Subject Code:F05With the support by the State Key Laboratory of Explosion Science and Technology,the research team led by Prof.Yang Li(杨利)and Prof.Wang Bo(王博)of Beijing Institute of Technology,applied MOFderived porous carbon materials with well-distributed metal source in the in-situ synthesis of primary explosive(MOFT-CA),which was published in Advanced Materials(2016,28:5837—5843).