Preliminary discussion on the ignition mechanism of exploding foil initiators igniting boron potassium nitrate

Exploding foil initiator(EFI)is a kind of advanced device for initiating explosives,but its function is unstable when it comes to directly igniting pyrotechnics.To solve the problem,this research aims to reveal the ignition mechanism of EFIs directly igniting pyrotechnics.An oscilloscope,a photon Doppler velocimetry,and a plasma spectrum measurement system were employed to obtain information of electric characteristics,impact pressure,and plasma temperature.The results of the electric characteristics and the impact pressure were inconsistent with ignition results.The only thing that the ignition success tests had in common was that their plasma all had a relatively long period of high-temperature duration(HTD).It eventually concludes that the ignition mechanism in this research is the microconvection heat transfer rather than the shock initiation,which differs from that of exploding foil initiators detonating explosives.Furthermore,the methods for evaluating the ignition success of semiconductor bridge initiators are not entirely applicable to the tests mentioned in this paper.The HTD is the critical parameter for judging the ignition success,and it is influenced by two factors:the late time discharge and the energy of the electric explosion.The longer time of the late time discharge and the more energy of the electric explosion,the easier it is to expand the HTD,which improves the probability of the ignition success.

Structures and physical properties of R_2TX_3 compounds

Rare-earth compounds have been an attractive subject based on the unique electronic structures of the rare-earth elements. Novel ternary intermetallic compounds R2TX3 （R = rare-earth element or U, T = transition-metal element, X = Si, Ge, Ga, In） are a significant branch of this research field due to their complex and intriguing physical properties, such as magnetic order at low temperature, spin-glass behavior, Kondo effect, heavy fermion behavior, and so on. The unique physical properties of R2TX3 compounds are related to distinctive electronic structures, crystal structures, micro- interaction, and external environment. Most R2TX3 compounds crystallize in A1B2-type or derived A1B2-type structures and exhibit many similar properties. This paper gives a concise review of the structures and physical properties of these compounds. Spin glass, magnetic susceptibility, resistivity, and specific heat of R2 TX3 compounds are discussed.

Thermal and ignition properties of hexanitrostilbene(HNS) microspheres prepared by droplet microfluidics

HNS-IV(Hexanitrostilbene-IV) is the main charge of the exploding foil initiators(EFI), and the microstructure of the HNS will directly affect its density, flowability, sensitivity, and stability. HNS microspheres were prepared using droplet microfluidics, and the particle size, morphology, specific surface area, thermal performance, and ignition threshold of the HNS microspheres were characterized and tested. The results shown that the prepared HNS microspheres have high sphericity, with an average particle size of 20.52 μm(coefficient of variation less than 0.2), and a specific surface area of 21.62 m^(2)/g(6.87 m^(2)/g higher than the raw material). Without changing the crystal structure and thermal stability of HNS-IV, this method significantly enhances the sensitivity of HNS-IV to short pulses and reduces the ignition threshold of the slapper detonator to below 1000 V. This will contribute to the miniaturization and low cost of EFI.

Preparation and Characterization of Stellera Chamaejasme-Based Carbon Molecular Sieves

The activation effect of boric acid as an activator is good,and we investigate the best activation conditions for the boric acid impregnation method.To represent the structural characteristics and adsorption performance of the Stellera Chamaejasme based carbon molecular sieves,we use Brunner-Emmet-Teller(BET)measurements,scan-ning electron microscope(SEM),Raman spectra(Raman),X-ray diffraction(XRD),and adsorption property measurement.When the loading ratio was 0.68:1,the specific surface area was 532.21 m^(2)/g,the total pore volume was 0.24 cm 3/g,the average pore size was 1.81 nm,the adsorption value of methylene blue was 145.28 mg/g,and the adsorption value of iodine was 713.33 mg/g,the results showed that boric acid had better activation effect.The carbon molecular sieves made from Stellera Chamaejasme and activated with boric acid produce two peaks on the aperture distribution graph that are densely distributed in the micropore range.This indicates that boric acid’s pore-forming tendency is primarily micropore.

Research on design and firing performance of Si-based detonator

For the chip integration of MEMS(micro-electromechanical system) safety and arming device, a miniature detonator needs to be developed to reduce the weight and volume of explosive train. A Si-based micro-detonator is designed and fabricated, which meets the requirement of MEMS safety and arming device. The firing sensitivity of micro-detonator is tested according to GJB/z377A-94 sensitivity test methods:Langlie. The function time of micro-detonator is measured using wire probe and photoelectric transducer. The result shows the average firing voltage is 6.4 V when the discharge capacitance of firing electro-circuit is 33 mF. And the average function time is 5.48 ms. The firing energy actually utilized by Si-based micro-detonator is explored.

Enhanced Electromagnetic Wave Absorption Properties of Poly(3,4-ethylenedioxythiophene) Nanofi ber-Decorated Graphene Sheets by Non-covalent Interactions

Graphene sheets(GNs) have high conductivity, but they exhibit weak electromagnetic(EM) wave absorption performance. Here, poly(3,4-ethylenedioxythiophene)(PEDOT) nanofibers were decorated on the surface of GNs in which the residual defects and groups act as the active sites and therefore are beneficial for the deposition of PEDOT nanofibers.The SEM images display that PEDOT nanofibers are successfully decorated on the surface of GNs through in situ polymerization. The diameter of the PEDOT nanofibers were ranged from 15 to 50 nm with hundreds of nanometers in length. The EM wave absorption properties of graphene, PEDOT, and GNs-PEDOT were also investigated. Compared to pure graphene and PEDOT, the EM wave absorption properties of GNs-PEDOT improved significantly. The maximum value of RLwas up to-48.1 d B at 10.5 GHz with a thickness of only 2 mm. Meanwhile, the absorption bandwidth of RL values below-10 d B was 9.4 GHz(5.8–12.3, 12.9–15.8 GHz) in the thickness of 1.5–3 mm. The enhancement is attributed to the modification of PEDOT and the unique structure of nanofibers. On one hand, the deposition of PEDOT nanofibers on the surface of GNs decreases the conductivity of graphene, and makes impedance match better. On the other hand, the unique structure of PEDOT nanofibers results in relatively large specific surfaces areas, providing more active sites for reflection and scattering of EM waves. Therefore, our findings demonstrate that the deposition of conducting polymers on GNs by non-covalent bond is an efficient way to fabricate strong EM wave absorbers.

Research on a MEMS pyrotechnic with a double-layer barrier safety and arming device

As an essential component of ammunition, pyrotechnics can control ignition with high reliability.However, due to limits of fabrication technology, traditional pyrotechnics are bulky. To achieve both functionality and miniaturization, MEMS pyrotechnics integrate initiator, safety-and-arming(S&A) device and lead charge and keep all components within a small size. MEMS S&A devices, as the core component to ensure system safety, are difficult to achieve active and rapid response to control signals with high safety and reliability. In order to overcome the difficulty, we propose the design and characterization of a MEMS pyrotechnic with a double-layer barrier S&A device. The MEMS pyrotechnic is a high-integrated device with an overall size of 13.4 × 8.5 × 5.2 mm^(3). The initiator is a Ni Cr bridge foil covered with an Al/Cu O energetic film, which can generate flame when ignited by an excitation voltage.To match the flame energy, lead styphnate is chosen in this study as the lead charge. The S&A device contains four semi-circular barriers, which are directly driven by V-shape electro-thermal actuators to gain active control of the pyrotechnics’ ignition condition with rapid response. To improve the system’s reliability, the four barriers are axisymmetrically placed in two layers, two barriers for each layer, to constitute a double-layer structure with a thickness of 100 μm. The ignition test results show that the S&A device can prevent the initiator from detonating the lead charge in safety condition. In arming condition, the lead charge will be detonated.

Dielectric polymer based electrolytes for high-performance all-solid-state lithium metal batteries

Solid polymer electrolytes (SPEs) are urgently required for achieving practical all-solid-state lithium metal batteries (ASSLMBs) but remain plagued by low ionic conductivity.Herein,we propose a strategy of salt polarization to fabricate a highly ion-conductive SPE by employing a high-dielectric polymer that can interact strongly with lithium salts.Such a polymer with large dipole moments can guide lithium cations (Li^(+)) to be arranged along the chain,forming a continuous pathway for Li^(+) hopping within the SPE.The as-fabricated SPE,poly(vinylidene difluoride)(PVDF)-LiN(SO_(2)F)_(2)(LiFSI),has an extraordinarily high dielectric constant (up to 10^(8)) and ultrahigh ionic conductivity (0.77×10^(-3)S cm^(-1)).Based on the PVDF–LiFSI SPE,the assembled Li metal symmetrical cell shows excellent Li plating/stripping reversibility at 0.1 m A cm^(-2),0.1 m Ah cm^(-2)over 1500 h^(-1) the ASS LiFePO_(4) batteries deliver long-term cycling stability at 1 C over 350 cycles (2.74 mg cm^(-2)) and an ultralong cycling lifespan of over 2600 h(100 cycles) with high loading (11.5 mg cm^(-2)) at 28°C.First-principles calculations further reveal the ion-dipole interactions-controlled conduction of Li^(+) in PVDF–LiFSI SPE along the PVDF chain.This work highlights the critical role of dielectric permittivity in SPE,and provides a promising path towards high-energy,long-cycling lifespan ASSLMBs.

High-pressure phonon dispersion of copper by using the modified analytic embedded atom method

By using the Born-von Kfirmfin theory of lattice dynamics and the modified analytic embedded atom method, we reproduce the experimental results of the phonon dispersion in fcc metal Cu at zero pressure along three high symmetry directions and four oft-symmetry directions, and then simulate the phonon dispersion curves of Cu at high pressures of 50, 100, and 150 GPa. The results show that the shapes of dispersion curves at high pressures are very similar to that at zero pressure. All the vibration frequencies of Cu in all vibration branches at high pressures are larger than the results at zero pressure, and increase correspondingly as pressure reaches 50, 100, and 150 GPa sequentially. Moreover, on the basis of phonon dispersion, we calculate the values of specific heat of Cu at different pressures. The prediction of thermodynamic quantities lays a significant foundation for guiding and judging experiments of thermodynamic properties of solids under high pressures.

Influence of Structural Variations on Electrical Conductivity and Solubility of 1-Vinyl-3-alkylimidazole Halogen Ionic Liquids

Several 1-vinyl-3-alkylimidazolium halogens [VRIM]X, which are functional materials with ethylenic bonds, were synthesized using the microwave-assisted synthesis method. Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy were carded out to analyze the resultant structures. The electrochemical properties and solubility of [VRIM]Br were investigated and discussed in detail. The temperature dependence of pure [VRIM]Br over a wide temperature range of 298.15-323.15 K fitted the Arrhanius equation well. At certain low concentrations, the electrical conductivity of the [VRIM]Br solution significantly increased with increasing solution concentration. The electrical conductivities of the [VRIM]Br observed in water, methanol, and ethanol showed the trend σwater〉 σmethanol 〉σethanol Conductometry showed that the critical miceUe concentrations of the bromines in water, methanol, and ethanol were 6.8-6.9 × 10-6, 1.4-1.5 × 10-5, and 1.9-2.0×10-5 mol.L-1, respectively; these results indicate that [VRIM]Br is an excellent surfactant. The solubility of [VRIM]X in common solvents was determined at 293.15 K, and results indicated that a decrease in solubility could be observed with decreasing dielectric constant of the solvent, elongation of the alkyl chain of the cation, and increasing anion size. Solubility parameters were also determined according to the Hildebrand-Scoff equation.

Synthesis and Physicochemical Properties of L-(+)-a-(Positive Butyl)-Leucine Ethyl Ester Chiral Ionic Liquids

L-（＋）-α-（positive butyl）-leucine ethyl ester bromide chiral ionic liquid was synthesized by using microwave-assisted synthesis method and L-（＋）-α-（positive butyl）-leucine ethyl ester terafluoroborate and hexafluorophosphate chiral ionic liquids were synthesized by the anion exchange reaction. The structures were characterized by IR, ~1HNMR and structure optimization calculation. The results of studies on physicochemical properties show that they possess better thermal stability, solubility, bio-solubility and high conductivity. They can serve as effective reaction media as well as chiral catalysts. They are presently being investigated as dispersion agents in molecular imprinting ployer.

Preparation of Micropowder by a Combination of Jet-Milling and Electrostatic Dispersion

We develop a new method to prepare micropowders with a combination of jet-milling and electrostatic dispersion techniques.The dispersiveness of the powder can be obviously improved by charging the particles during the process of jet-milling.Calcium carbonate(CaCO_(3))powders with high dispersion are prepared by using this method from two different initial particle sizes(10.93 and 25.43𝜈m).The experimental studies and theoretical analysis about the effects of preparation parameter on dispersiveness of the powder are investigated,showing that the jet-milling/electrostatic dispersion(𝐾J/E𝐹)is a considerably effective way to prepare micropowder in ambient atmosphere.It is found that the strength of electrostatic field and particle radius of the raw powder strongly affect the dispersion.The average particle size of both powders decreases with the increase in charging voltage while the reduction of particle size is more obvious in the powder with larger initial particle size.

High Conduction Band Inorganic Layers for Distinct Enhancement of Electrical Energy Storage in Polymer Nanocomposites

Dielectric polymer nanocomposites are considered as one of the most promising candidates for high-power-density electrical energy storage applications.Inorganic nanofillers with high insulation property are frequently introduced into fluoropolymer to improve its breakdown strength and energy storage capability.Normally,inorganic nanofillers are thought to introducing traps into polymer matrix to suppress leakage current.However,how these nanofillers effect the leakage current is still unclear.Meanwhile,high dopant(>5 vol%)is prerequisite for distinctly improved energy storage performance,which severely deteriorates the processing and mechanical property of polymer nanocomposites,hence brings high technical complication and cost.Herein,boron nitride nanosheet(BNNS)layers are utilized for substantially improving the electrical energy storage capability of polyvinylidene fluoride(PVDF)nanocomposite.Results reveal that the high conduction band minimum of BNNS produces energy barrier at the interface of adjacent layers,preventing the electron in PVDF from passing through inorganic layers,leading to suppressed leakage current and superior breakdown strength.Accompanied by improved Young’s modulus(from 1.2 GPa of PVDF to 1.6 GPa of nanocomposite),significantly boosted discharged energy density(14.3 J cm^(-3)) and charge-discharge efficiency(75%)are realized in multilayered nanocomposites,which are 340 and 300% of PVDF(4.2 J cm^(-3),25%).More importantly,thus remarkably boosted energy storage performance is accomplished by marginal BNNS.This work offers a new paradigm for developing dielectric nanocomposites with advanced energy storage performance.

Ultrathin Metal Silicate Hydroxide Nanosheets with Moderate Metal-Oxygen Covalency Enables Efficient Oxygen Evolution

Exploring efficient,cost-effective,and durable electrocatalysts for electrochemical oxygen evolution reaction(OER)is pivotal for the large-scale application of water electrolysis.Recent advance has demonstrated that the activity of electrocatalysts exhibits a strong dependence on the surface electronic structure.Herein,a series of ultrathin metal silicate hydroxide nanosheets(UMSHNs)M_(3)Si_(2)O_(5)(OH)_(4)(M=Fe,Co,and Ni)synthesized without surfactant are introduced as highly active OER electrocatalysts.Cobalt silicate hydroxide nanosheets show an optimal OER activity with overpotentials of 287 and 358 m V at 1 and 10 m A cm^(-2),respectively.Combining experimental and theoretical studies,it is found that the OER activity of UMSHNs is dominated by the metal-oxygen covalency(MOC).High OER activity can be achieved by having a moderate MOC as reflected by aσ^(*)-orbital(e_(g))filling near unity and moderate[3d]/[2p]ratio.Moreover,the UMSHNs exhibit favorable chemical stability under oxidation potential.This contribution provides a scientific guidance for further development of active metal silicate hydroxide catalysts.

A novel phenoxazine-based hole transport material for efficient perovskite solar cell

Based on the previous research work in our laboratory, we have designed and synthesized a small-molecule, hole transport material （HTM） POZ6-2 using phenoxazine （POZ） as central unit and dicyanovinyl units as electron-withdrawing terminal groups. Through the introduction ofa 2-ethyl-hexyl bulky chain into the POZ core unit, POZ6-2 exhibits good solubility in organic solvents. In addition, POZ6-2 possesses appropriate energy levels in combination with a high hole mobility and conductivity in its pristine form. Therefore, it can readily be used as a dopant-flee HTM in perovskite solar cells （PSCs） and a conversion efficiency of 10.3% was obtained. The conductivity of the POZ6-2 layer can be markedly enhanced via doping in combination with typical additives, such as 4-tert-butylpyridine （TBP） and lithium bis（trifluoromethanesulfonyl） imide （LiTFS1）. Correspondingly, the efficiency of the PSCs was further improved to 12.3% using doping strategies. Under the same conditions, reference devices based on the well-known HTM Spiro-OMeTAD show an efficiency of 12.8%.

Temperature Dependence of Raman Scattering in 4H-SiC Films under Different Growth Conditions

The microRaman scattering of 4H-SiC films, fabricated by low pressure chemical vapor deposition under different growth conditions, is investigated at temperatures ranging from 80 K to 550K. The effects of growth conditions on E2 （TO）, E1 （TO） and A1 （LO） phonon mode frequencies are negligible. The temperature dependences of phonon linewidth and lifetime of E2 （TO） modes are analyzed in terms of an anharmonic damping effect induced by thermal and growth conditions. The results show that the lifetime of E2 （TO） mode increases when the quality of the sample improves. Unlike other phone modes, Raman shift of A1 （longitudinal optical plasma coupling （LOPC）） mode does not decrease monotonously when the temperature increases, but tends to blueshift at low temperatures and to redshift at relatively high temperatures. Theoretical analyses are given for the abnormal phenomena of A1 （LOPC） mode in 4H-SiC.

Thermal Expansion of Ni_3A1 Intermetallic Compound:Experiment and Simulation

The thermal expansion of Ni3A1 intermetailic compound is determined by a thermal dilatometer and simulated by the molecular dynamics method. The results of the linear thermal expansion coefficients are presented from 200 K up to the maximum temperature of 1600 K. The single phase of NiaA1 intermetailie compound is confirmed by x-ray diffraction together with DSC melting and solidification peaks, from which the solidus and the liquidus temperatures are obtained to be 1660 and 1695 K, respectively. The measured linear thermal expansion coefficient increases from 1.5 × 10-5 to 2.7 × 10-5 K-1 in the experimental temperature range, in good agreement with the data obtained by the molecular dynamics simulation, just a slight difference from the temperature dependence coefficient. Furthermore, the atomic structure and position are presented to reveal the atom distribution change during thermal expansion of NiaA1 compound.

Measuring Topological Charges of Optical Vortices with Multi-Singularity Using a Cylindrical Lens

我们在场与多重奇特测量光旋涡的拓扑的费用的一个简单方法。用一个圆柱的透镜，一根旋涡横梁能与多重分开的黑暗的洞腐烂进轻地分布，谁的数，就等于输入横梁的拓扑的费用。这个结论然后与多重奇特经由实验和旋涡横梁的繁殖的数字模拟被验证。这个方法也是可靠的与奇特的不同分布测量宽带旋涡横梁的拓扑的费用，它不诉诸多重横梁 interferometric 实验。

MOLECULAR DESIGN OF FUNCTIONAL POLYMERS BASED ON UNIQUE PROPERTIES OF POLYMER CHAINS

The inclusion complex formation of α-CD, β-CD, and γ-CD with various water-soluble polymers has beeninvestigated, and the relationship between the chain cross-sectional areas of the polymers and the diameters of the cavities ofcyclodextrins (molecular recognition) was found. Polyrotaxanes and tubular polymers were prepared on the basis ofmolecular recognition. Several kinds of polymers having tetraphenylporphyrin (TPP) and paramagnetic metallotetraphenyl-porphyrin (AgTPP, CuTPP, VOTPP or ZnTPP) have been prepared by radical polymerization of the correspondingmonomers. Visible spectra of these polymers show hypochromism in the Sorer bands of TPP moieties as compared withthose of monomers. Polymer effects were observed in the magnetic behavior and oxygen adsorption of paramagneticmetallotetraphenylporphyrin moieties. Moreover, polymer effects on photophysical and photochemical behavior were foundin the amphiphilic polymers covalently tethered with small amounts of zinc(Ⅱ)-tetraphenylporphyrin (ZnTPP).