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.

Ignition of nanothermites by a laser diode pulse

Experimental investigation has been carried out for laser ignition and combustion of nanothermites based on aluminum and oxides of copper,bismuth and molybdenum.Ultrasonic mixing of nanosized powders was used to produce compositions.For thermite ignition,initiating laser pulse with a maximum intensity of 770 W/cm2 was generated by a laser diode with a wavelength of 808 nm.The ignition delay times,the minimum initiation energy density,and the average burning rate at various thermite densities and mass fractions of components were determined by recording the emission of radiation of the reaction products using a multichannel pyrometer jointly with a high-speed video camera.The effect of adding carbon black on the threshold parameters of a laser pulse was also studied.Based on the obtained results,certain assumptions were put forward with regard to the mechanism of nanothermites’ignition by laser radiation and their burning.In particular,the assumptions were made on the two-stage process of the reaction initiation and jet burning mechanism of porous nanothermites.

An efficient light-to-heat conversion coupling photothermal effect and exothermic chemical reaction in Au NRs/V_(2)C MXene membranes for high-performance laser ignition

MXene,a new type of two-dimensional materials,have been demonstrated as one of the best photothermal materials owing to their strong light-matter interaction and high photothermal conversion efficiency in recent years.Herein,we report the intriguing light-to-heat conversion property of vanadium carbide(V_(2)C)MXene under irradiation of millisecond laser pulse.Unlike the typical photothermal materials,the V_(2)C MXene not only converts the incident laser energy to heat by the physical photothermal effect,but also triggers the exothermic oxidation of the V_(2)C MXene.The oxidation could be greatly promoted with addition of plasmonic Au nanorods(Au NRs)for light absorption enhancement.Owing to the unique light-to-heat conversion property,the Au NRs/V_(2)C MXene membrane could serve as high temperature pulse(HTP)generators that is proposed for numerous applications with high demand for immediacy.As a proof-of concept application,Au NRs/V_(2)C MXene membrane was applied for laser ignition of the high energy density materials,such as 2,4,6,8,10,12-(hexanitrohexaaza)cyclododecane(HNIW or CL-20).An improved ignition performance,in terms of lowered laser threshold,is achieved as compared to the state-of-the-art light-to-heat conversion materials.

An effective catalyst carrier SiO_(2):Enhancing catalytic and combustion properties of CuFe_(2)O_(4)on energetic components

To enhance the catalytic activity of copper ferrite(CuFe_(2)O_(4))nanoparticle and promote its application as combustion catalyst,a low-cost silicon dioxide(SiO_(2))carrier was employed to construct a novel CuFe_(2)O_(4)/SiO_(2)binary composites via solvothermal method.The phase structure,morphology and catalytic activity of CuFe_(2)O_(4)/SiO_(2)composites were studied firstly,and thermal decomposition,combustion and safety performance of ammonium perchlorate(AP)and 1,3,5-trinitroperhydro-1,3,5-triazine(RDX)with it affecting were then systematically analyzed.The results show that CuFe_(2)O_(4)/SiO_(2)composite can remarkably either advance the decomposition peak temperature of AP and RDX,or reduce the apparent activation energy at their main decomposition zone.Moreover,the flame propagation rate of RDX was promoted by about 2.73 times with SiO_(2)content of 3 wt%,and safety property of energetic component was also improved greatly,in which depressing the electrostatic discharge sensitivity of pure RDX by about 1.89 times.In addition,the effective range of SiO_(2)carrier content in the binary catalyst is found to be 3 to 5 wt%.Therefore,SiO_(2)opens a new insight on the design of combustion catalyst carrier and will promote the application of CuFe_(2)O_(4)catalyst in solid propellant.

Possibility for Gaining Nuclear Energy without Radioactivity from Solid Density Hydrogen Boron Using Lasers with Nonlinear Force Driven Plasma Blocks

In addition to the matured ＂Laser Inertial Fusion Energy （LIFE）＂ with spherical compression of deuterium-tritium （DI） for a pure fusion engine or for fusion-fission-hybrid operation, a very new scheme may have now been opened by igniting the neutron-free reaction of proton-boron-11 （p-^11B） using side-on block ignition. Laser pulses of several petawatt power and ps duration led to thc discovery of an anomaly of interaction, if the prepulses are cut off by a factor 108 （contrast ratio） to avoid relativistic self focusing. In this case the Bobin-Chu conditions of side-on ignition of solid fusion fuel can be applied after several improvements leading to energy gains of 10,000 similar to the Nuckolls-Wood ignition with extremely intense 5 MeV electron beams. In contrast to the impossible laser-ignition of p-^11B by the usual spherical compression, the side-on ignition is less than ten times only more difficult of DT ignition. This p-^11B fusion produces less radioactivity per gained energy than burning coal. After encouraging success with computations based on the different nuclear cross sections, next steps are focusing on stability and transport problems.

Experimental and numerical study on ignition and combustion characteristics of boron-magnesium composite powders

A high-pressure laser ignition and combustion system with adjustable oxidizer gas atmosphere is established to investigate the ignition and combustion characteristics of boron-magnesium(BM)com-posite powders.An ignition and combustion model of BM powders is established and validated in the present study.The results show that increasing water content,O_(2) content and Mg content all result in shorter ignition delay time of BM powders,among which the effect of water content is the most obvious.However,ignition delay time increases as pressure increases.The combustion time decreases with increasing Mg content and ambient pressure but increases with water content.With the increase of O_(2) content,combustion time of BM powders first increases and then decreases,which means a critical O_(2) content exists above which combustion time decreases.The results show that there exists a trade-off between ignition and combustion performance of BM composite powders.

Thrust characteristics of nano-carbon/Al/oxygenated salt nanothermites for micro-energetic applications

Combustion within small motors is key in the application-specific development of nanothermite-based micro-energetic systems. This study evaluates the performance of nanothermite mixtures in a converging-diverging nozzle and an open tube. Mixtures were prepared using nano-aluminum(n-Al),potassium perchlorate(KClO_(4)), and different carbon nanomaterials(CNMs) including graphene-oxide(GO), reduced GO, carbon nanotubes(CNTs) and nanofibers(CNFs). The mixtures were packed at different densities and ignited by laser beam. Performance was measured using thrust measurement,high-speed imaging, and computational fluid dynamics modeling, respectively. Thrust, specific impulse(ISP), volumetric impulse(ISV), as well as normalized energy were found to increase notably with CNM content. Two distinctive reaction regimes(fast and slow) were observed in combustion of low and high packing densities(20% and 55%TMD), respectively. Total impulse(IFT) and ISPwere maximized in the 5%GO/Al/KClO_4 mixture, producing 7.95 m N·s and 135.20 s respectively at 20%TMD, an improvement of 57%compared to a GO-free sample(5.05 m N·s and 85.88 s). CFD analysis of the motors over predicts the thrust generated but trends in nozzle layout and packing density agree with those observed experimentally;peak force was maximized by reducing packing density and using an open tube. The numerical force profiles fit better for the nozzle cases than the open tube scenarios due to the rapid nature of combustion. This study reveals the potential of GO in improving oxygenated salt-based nanothermites,and further demonstrates their applicability for micro-propulsion and micro-energetic applications.

Surface Temperature Field of Ti-66Al and Ti-Al and Ti-4848Al AlloysAl Alloys Under Continuous Laser AblationUnder Continuous Laser Ablation

The high temperature fire retardancy of titanium alloy is an important factor restricting its application in aero-engine,and the laser ignition method can accurately reflect the fire retardancy of titanium alloy under local heating.Due to the limitations of laser ignition experiments on the microscopic boundary and the transient propagation mechanism of the temperature field,molecular dynamics(MD)simulations and JMatPro calculation were applied to study the temperature field of Ti-6Al and Ti-48Al alloys.The results show that a molten pool is formed on the surface of Ti-Al alloys under continuous laser irradiation,and the temperature field of the molten pool is normally distributed from the center to the edge.When the center temperature reaches the critical point of ignition,the extended combustion occurs,and the extended combustion path advances along the direction of the air flow.Compared with Ti-6Al alloy,Ti-48Al alloy has higher fire retardancy under laser ablation.This is due to the better heat transfer performance of Ti-48Al,which leads to the weakening of the heat concentration effect near the boundary of the spot temperature field.So it is necessary to increase the partial pressure of oxygen,and thus to reduce the ignition point of the alloy in order to achieve the ignition boundary condition of Ti-48Al alloy under the same laser heat source.In the aspect of extended combustion path,the boundary heat collection effect of specimens shown by MD models reveals another mechanism affecting combustion expansion path besides the direction of air flow.That is,the heat generated by the laser spot is interrupted when it is transmitted to the boundary of the specimen along the short side direction,resulting in a concentration of heat near the boundary.So the combustion path also tends to expand along this direction.

Review: laser ignition for aerospace propulsion

Renewed interest in the use of high-speed ramjets and scramjets and more efficient lean burning engines has led to many subsequent developments in the field of laser ignition for aerospace use and application.Demands for newer,more advanced forms of ignition,are increasing as individuals strive to meet regulations that seek to reduce the level of pollutants in the atmosphere,such as CH_(x),NO_(x),and SO_(2).Many aviation gas turbine manufacturers are interested in increasing combustion efficiency in engines,all the while reducing the aforementioned pollutants.There is also a desire for a new generation of aircraft and spacecraft,utilizing technologies such as scramjet propulsion,which will never realize their fullest potential without the use of advanced ignition processes.These scenarios are all limited by the use of conventional spark ignition methods,thus leading to the desire to find new,alternative methods of ignition.This paper aims to provide the reader an overview of advanced ignition methods,with an emphasis on laser ignition and its applications to aerospace propulsion.A comprehensive review of advanced ignition systems in aerospace applications is performed.This includes studies on gas turbine applications,ramjet and scramjet systems,and space and rocket applications.A brief overview of ignition and laser ignition phenomena is also provided in earlier sections of the report.Throughout the reading,research papers,which were presented at the 2nd Laser Ignition Conference in April 2014,are mentioned to indicate the vast array of projects that are currenty being pursued.

Goldilocks focal zone in femtosecond laser ignition of lean fuels

Laser ignition of lean fuels offers a promising route for green combustion with high combustion efficiency and low exhaust emissions. The fundamental limitations which apply to femtosecond laser ignition(fs-LI) of lean fuels are the inferior energy deposition and low thermodynamic temperature. However, it was discovered recently that the fs laser filamentation can induce 100% success rate of fs-LI with ultralow sub-m J minimum ignition energy, exhibiting distinct contrast to the general understanding that it is hard to achieve fs-LI. The present contribution examines the extent to which the minimum ignition energies depend on filamentation formation, and explores the key factors for the success of fs-LI. We perform fs-LI of a lean-fuel CH;/air mixture using a femtosecond near-infrared(~40 fs, 800 nm) pulse at different external focal conditions, and find a Goldilocks focal zone to facilitate fs-LI. In this special zone, a crucial balance between the length of igniting “line” kernel and the plasma density of the fs laser filament is achieved, which determines not only the total amount of resultant OH radicals, but also their distribution along the plasma filament. Our finding provides a viable strategy with clear guidelines for fs-LI, and also opens up an avenue of exploring unprecedented ultrafast ignition dynamics after fs-laser-fuel interactions towards gaining deeper insights into reaction intermediates and combustion processes.

Generation of Preformed Plasma Channel for GeV-Scaled Electron Accelerator by Ablative Capillary Discharges

Generation of plasma channels by gated experimentally in details. A time-resolved low jitter ablative capillary discharges is investi- evolution and radial distributions of the electron density are measured, and proof-of-principle optical guiding experiment is conducted. A proper time window for optical guiding of a femtoseeond laser pulse is found. The generated low density, long plasma channel is believed to be useful in the applications as GeV-class channel-guided laser wakefield accelerators and compact X-ray femetoseeond coherent radiation sources.