Research on honeycomb structure explosives and double sided explosive cladding

In order to resolve the current issues about the backward method of charge and low energy efficiency of explosives, honeycomb structure explosives and double sided explosive cladding were used in the present study. Honeycomb structure explosives are used to ensure the quality of charge. Double sided explosive cladding can clad two composite plates simultaneously. Honeycomb structure explosives and double sided explosive cladding, which significantly reduce the critical thickness of stable detonation of explosives, are used to increase the energy efficiency of explosives and save the amount of explosives. Emulsion explosives with the thickness of 5 mm can be stable detonation. In this paper, the experiment of double sided explosive cladding for two groups of steel of No. 45 with the thickness of 2 mm to steel of Q235 with the thickness of 16 mm and two groups of stainless steel with the thickness of 3 mm to steel of Q235 with the thickness of 16 mm were successfully investigated. Without constraints, the critical diameter of emulsion explosives is 14–16 mm. Compared to the existing explosive cladding method, the consumption of explosives for steel of No. 45 to steel of Q235 and stainless steel to steel of Q235 are reduced by 83% and 77% in the case of cladding the same number of composite plates. The explosive cladding windows and collision velocity of flyer plate were calculated before experiment. It shows that the calculation prefigures exactly the explosive cladding for steel of No. 45 to steel of Q235 and stainless steel to steel of Q235.     

爆轰合成用的乳化炸药制备工艺与爆轰特性

制备了一种用于爆轰合成纳米MnFe2O4颗粒的新型乳化炸药,并对其制备工艺及爆轰特性进行探讨,确定了其制备工艺参数,通过爆速测量实验及爆轰产物检测,获得了该炸药的爆速,并研究了其爆轰状态.结果表明,该乳化炸药的制备工艺比传统炸药要求更加严格.纯净乳化基质不具备爆轰感度,添加RDX后,其爆轰参数与传统乳化炸药相近(或略低...     

Combustion characteristics of the heat pellet prepared from the Fe powders obtained by spray pyrolysis

Fe powders for thermal batteries were prepared by reduction of iron oxide powders obtained by spray pyrolysis. The iron oxide powders prepared by spray pyrolysis had fine size, spherical shape and high surface area. The morphologies of the Fe powders were affected by the preparation temperatures of the iron oxide powders. The Fe powders obtained from the iron oxide powders prepared by spray pyrolysis at 900 and 1000 °C had slightly aggregated structure of the primary powders with several microns sizes. The powders had pure Fe phases at reducing temperatures between 600 and 800 °C. The heat pellets with diameter of 18.2 mm were prepared using Fe powders and potassium perchlorate (KClO₄). The porosity of the prepared heat pellet was about 40%. The break strength of the heat pellet was 0.9 kgf. The ignition sensitivity of the heat pellet was 4 W. The maximum burn rate of the heat pellet obtained from the Fe powders were 8.6 cm s^?1.     

Measurement of microemulsion zone and preparation of monodispersed cerium oxide nanoparticles by W/O microemulsion method

In the W/O microemulsion system of cetyltrim ethylamine bromide (CTAB) + butanol / cyclohexane / water solution, the microemulsion area was measured and cerium oxide nanoparticles were prepared according to the principle by two-phase liquid–liquid method. The samples were analyzed by means of transmission electron microscope, X-ray diffraction, thermogravimetric-differential scanning calorimetry, and infrared. And their morphology, phase, components were investigated. The results made clear that nanometer cerium oxide could be prepared in the measured area of microemulsion and it is an effective way to gain the well dispersed and uniformly distributed nanometer cerium oxide grains with the size of about 3 nm.     

Synthesis and photoluminescence of zinc sulfide nanowires by simple thermal chemical vapor deposition

We present a synthetic method of zinc sulfide nanowires by a simple and safe reaction of zinc oxide and iron sulfide powders on a gold-coated silicon substrate through chemical vapor transport and condensation. High quality ZnS nanowires with single crystalline wurtzite structures are grown along [0 0 1] direction with diameters in the range of 10–30 nm and lengths up to tens of micrometers. Photoluminescence spectrum shows strong emission near 339 nm. These nanowires with cleaved ends could be a prominent candidate material for a nanoscale cavity as a ultra-violet nanolaser.     

Explosive consolidation of 316L stainless steel powder – Effect of phase composition

Two stainless steel (SS) AISI 316L powders have been processed by explosive consolidation using a cylindrical configuration. Powders with d₅₀ of 9 and 5 μm and a phasic structure consisting of fcc and bcc are used. After shock processing (3.5 up to 4.9 mm/μs) hardness was evaluated. Powders with the lowest particle size and processed with the highest detonation velocities (4.9 and 4.1 mm/μs) gave rise to a bulk material where in the centre occurred a phase transformation of bcc to fcc phase. Nevertheless, the hardness values were dissimilar along the cross section depending on the macrodefects (centre hole and cracks) produced by detonation. After a pre-heating treatment (900 °C), this powder was full austenitic (fcc) and when submitted to explosive consolidation, it led a monolithic solid without cracks, with a density of 99% TMD (theoretical maximum density) and a hardness of 3.1 GPa. This value is lower than others measured, particularly when a centre hole is not present, revealing hardening by plastic deformation. Concerning powder with higher particle size (d₅₀ = 9 μm), the presence of mainly austenite induces after shock processing function of detonation parameters and localisation hardness values from 3.9 up to 5.0 GPa. The homogeneity of hardness reflex of absence of defects and low stress are almost achieved only for low particle size powders, using the lowest detonation velocities (3.4 GPa).     

Effect of aluminum oxide doping on the structural,electrical, and optical properties of zinc oxide (AOZO) nanofibers synthesized by electrospinning

Zinc oxide nanofibers doped with aluminum oxide were prepared by sol–gel processing and electrospinning techniques using polyvinylpyrrolidone (PVP), zinc acetate and aluminum acetate as precursors. The resulting nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–Vis spectroscopy, and current–voltage (I–V) properties. The nanofibers had diameters in the range of 60–150 nm. The incorporation of aluminum oxide resulted in a decrease in the crystallite sizes of the zinc oxide nanofibers. Aluminum oxide doped zinc oxide (AOZO) nanofibers exhibited lower bandgap energies compared to undoped zinc oxide nanofibers. However, as the aluminum content (Al/(Al + Zn) × 100%) was increased from 1.70 at.% to 3.20 at.% in the electrospinning solution, the bandgap energy increased resulting in lower conductivity. The electrical conductivity of the AOZO samples was found to depend on the amount of aluminum dopant in the matrix as reflected in the changes in oxidation state elucidated from XPS data. Electrospinning was found to be a productive, simple, and easy method for tuning the bandgap energy and conductivity of zinc oxide semiconducting nanofibers.     

Synthesis and characterization of nanosized ceria powders by microwave–hydrothermal method

Nanocrystalline ceria powders (CeO₂) have been prepared by adding NaOH to a cerium ammonium nitrate aqueous solution under microwave–hydrothermal conditions. In particular the effect of the synthesis conditions (time, pressure and concentration of both the precursor and the precipitant agent solutions) on the physical properties of the crystals have been evaluated. Microwave–hydrothermal treatment of 5 min at 13.4 atm allows to obtain almost crystallized powders (amorphous phase 4%) as underlined by Rietveld-reference intensity ratio (RIR) results.     

Synthesis and electrical conductivity of La0.6Sr0.4Ru1−xMgxO3−δ (x = 0–0.6) perovskite solid solution

Sr and Mg were doped at La- and Ru-sites of perovskite oxide LaRuO₃, respectively, to enhance electrical conductivity and catalytic property as a cathode material for a low temperature solid oxide fuel cell. Crystal structure and particle morphology of La_0.6Sr_0.4Ru_1?xMg_xO_3?δ powders (shorten as LSRM) and electrical conductivity of sintered LSRM were studied. LSRM powders (x = 0–0.6) were prepared by co-precipitation method using metal nitrate solutions and ammonium carbonate solution. The freeze-dried powders were heated at 1273 K in air to form LSRM solid solution of orthorhombic structure. The true densities and particle sizes of LSRM solid solution, where valence of Ru was estimated to be 3+, decreased with increasing Mg content. The electrical conductivity of LSRM at x = 0–0.3 was almost independent of temperature and was in a range of 19–360 S cm^?1 at 1073 K. Hole conduction contributed to the high electrical conductivities. LSRM at x = 0.4 and 0.5 was a mixed conductor of oxide ions and holes, and showed a conductivity of 11 S cm^?1 at 1073 K in air. This conductivity decreased at a lower oxygen pressure and reached a constant value below 10 Pa of oxygen pressure.     

Microwave-induced combustion synthesis of Li0.5Fe2.5−xCrxO4 powder and their characterization

Li_0.5Fe_2.5−xCr_xO₄ (0 ≦ x ≦ 1.0) powders with small and uniformly sized particles were successfully synthesized by microwave-induced combustion, using lithium nitrate, iron nitrate, chromium nitrate, and carbohydrazide as the starting materials. The process takes only a few minutes to obtain as-received Cr-substituted lithium ferrite powders. The resultant powders annealed at 650 °C for 2 h and were investigated by thermogravimeter/differential thermal analyzer (TG/DTA), X-ray diffractometer (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and thermomagnetic analysis (TMA). The results revealed that the lattice constant decreases linearly with increasing of Cr content in Li_0.5Fe_2.5−xCr_xO₄ specimens. Moreover, the magnetic properties of Cr-substituted lithium ferrite were also strongly affected by Cr content. The saturation magnetization, remanent magnetization, and coercive force decrease monotonously with increasing of Cr content.     

Low temperature dielectric studies of zinc oxide (ZnO) nanoparticles prepared by precipitation method

Using zinc nitrate as a precursor and NaOH starch as a stabilizing agent, hexagonal zinc oxide (ZnO) nanoparticles has been synthesized by precipitation method. The transmission electron microscopy (TEM) images show particles of nearly uniform spherical size of around 40 nm. The infrared spectroscopy (FT-IR) measurement reveals the peak at 500 cm^?1, corresponding to the Zn–O bond. Dielectric studies of ZnO nanoparticles show frequency dependence dielectric anomaly at low temperature (85–300 K). Results reveal that the capacitance and loss tangent decrease with the frequency while these parameters improve with the increasing of temperature. The increase of a.c. conductivity with the temperature indicates that the mobility of charge carriers is responsible for hopping and electronic polarization in ZnO nanoparticles.     

The explosion of a ship,loaded with black powder,in Leiden in 1807

In 1807 a ship containing 37,000 pounds of black powder exploded in the centre of Leiden. The effects were devastating, resulting in a large number of casualties and an area of 5.5 ha (5.5×10⁴ m²) completely destroyed. The effects of the explosion were calculated, based on an equivalent amount of 9000 kg of TNT, making use of formulas and knowledge derived from detonation tests with conventional explosives. Within a radius of 168 m all houses are collapsed completely or non-repairable. Smaller damage occurred up to 485 m from the explosion point and in the whole city of Leiden glass windows ruptured. The calculated damage areas correspond well with the actual damage after the explosion.     

Synthesis of nanosized spherical cobalt powder by ultrasonic spray pyrolysis

The ultrasonic spray pyrolysis (USP) method has been used to prepare nanosized powders of metallic, intermetallic compounds and ceramic materials. Spherical nanosized cobalt powders were obtained by USP of aqueous solutions of cobalt nitrate followed by thermal decomposition of generated aerosols in hydrogen atmosphere. Particle sizes of the produced cobalt powder can be controlled by the change of the concentration of an initial solution. Non-agglomerated spherical nanosized cobalt particles in the range of 158–1001 nm were obtained at 800 °C. A decrease of the concentration of cobalt nitrate decreases the mean particle diameter from 596 to 480 nm. The discrepancy between the experimentally and theoretically obtained values indicates that the partial coalescence of the droplets occur during the formation of aerosol.     

Synthesis of ZnO nanopowders by DC thermal plasma for dye-sensitized solar cells

Zinc oxide (ZnO) nanopowders were synthesized from commercially available micro-sized zinc powders (Aldrich Co., 98%, 10 μm) by a DC thermal plasma process at atmospheric pressure. The micro-sized zinc powders were vaporized in the plasma region, after which the plasma processing equipment was rapidly quenched, resulting in the formation of ZnO nanopowders with a size of less than 300 nm. Two different reaction gases of oxygen and carbon dioxide were used as the oxygen source and each gas flow rate was controlled as a process variable. The obtained ZnO nanopowders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). All synthesized ZnO nanopowders showed high crystalline wurtzite structures and the differences in their morphologies were strongly dependent on the operating variables. The photocurrent–voltage (J–V) curve of the ZnO nanopowders with a dye of ruthenium (II) 535 bis-TBA (N719, Solaronix) in redox electrolyte showed an overall energy conversion efficiency (η) of 2.54%, demonstrating that the application of the mass-producible ZnO nanopowders by thermal plasma processing to DSSC was feasible.     

乳化炸药密度与纳米MnFe_2O_4颗粒爆炸合成

研究了乳化炸药密度与爆炸合成纳米MnFe2O4颗粒的关系,分别从爆炸产物的外观、XRD图谱、TEM照片、DSC曲线等4个方面,考察了不同密度的乳化炸药爆炸合成的纳米MnFe2O4的相结构、形貌以及热分解特性。结果表明,乳化炸药密度对爆炸产物的成分有较大影响,高密度炸药得到的爆炸产物相对于低密度炸药得到的爆炸产物相对纯净,具有相对较好的颗粒分散性和均匀性;聚苯乙烯球添加剂严重影响乳化炸药的爆轰反应结构。     

Synthesis of titanium carbide and TiC–SiO2 nanocomposite powder using rutile and Si by mechanically activated sintering

High-energy ball milling was applied with subsequent heat treatment for synthesizing nanoparticles of TiC powders by the carbothermic and carbosilisisothermic reduction of titanium oxide (rutile type). The milling procedure involved milling of TiO₂/C and TiO₂/Si/C powders at room temperature in an argon atmosphere. The progress of the mechanically induced solid state reaction was monitored using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results showed that TiC nanoparticles were duly synthesized in the TiO₂/C system at 1700 °C in 60-h milled samples. In the non-milled samples, although heated at the same temperature, only a minor amount of a lower degree of titanium oxide (Ti₃O₅) was observed to form. Further, in other non-milled samples, but with Si initially present, despite heating to 1550 °C no TiC phase was detected. However, using Si as a reducing agent accompanied by graphite, after 60 h ball milling, only Si remained as a distinguishable crystalline phase. Further, heat treatment of activated powders by forming the interphase compounds (such as Ti₃Si₅ and Ti₅Si₃) remarkably decreased the synthesis temperature to 900 °C for the 60 h milled samples.     

Combustion synthesis of WC powder in the presence of alkali salts

This paper deals with the formation of tungsten carbide sub-micrometer powders from WO₃ + Mg + C + sodium salts (NaCl, Na₂CO₃) system by combustion synthesis technique. The powders were characterized by XRD and FESEM. X-ray data demonstrate the superiority of the NaCl + Na₂CO₃ combined mixture in the WC formation process. Single phase, sub-micrometer WC powders were synthesized at temperatures as low as 1600 °C. The roles of sodium salts in combustion process were discussed and chemical mechanism of WC formation was proposed. WC powder produced by salt-assisted combustion synthesis technique has a size 0.2–3 μm, crystalline shape and low agglomeration degree.     

Preparation of spherical silica in emulsion systems using the co-precipitation technique

Silica powders with particles of spherical shape and a low tendency to agglomeration of primary particles have been prepared by precipitation from sodium metasilicate and hydrochloric acid via the emulsion technique. The organic phase of the emulsion system was cyclohexane while a non-ionic surfactant was applied as an emulsifier. In the course of silica precipitation three alternative ways of dispersion induction were applied: the top stirrer, homogenization and ultrasounds. The precipitation was performed at three temperatures (25 °C, 40 °C and 60 °C), using different variants of dosing schemes of the emulsion and the aqueous solutions of substrates. Homogenization of the reactive system yielded silica of spherical particles of the lowest mean particle diameter and the most uniform character. The only appropriate mode of dosing the reagents to the emulsion was the introduction of alkaline emulsion to acidic emulsion. A decreased tendency for silica particles agglomeration could be achieved by increasing the volume of the organic phase in the emulsions prepared. The optimum temperature for the precipitation reaction was 25 °C. The procedure permitted obtaining in SiO₂ particles of the optimum diameter (<1 μm) and particles of spherical shape. Moreover, the silica adsorbents obtained manifested high activity. Their surface area reached values in the 340–390 m² g^?1 range.     

ZnO films and nanorod/shell arrays electrodeposited on PET-ITO electrodes

In this work, ZnO films, nanorod and nanorod/shell arrays were synthesized on the surface of PET-ITO electrodes by electrochemical methods. ZnO films with high optical transmittance were prepared from a zinc nitrate solution using a pulsed current technique with a reduced pulse time (3 s). The X-ray diffraction pattern of ZnO film deposited on PET-ITO electrode showed that it has a polycrystalline structure with preferred orientations in the directions [0 0 2] and [1 0 3]. ZnO nanorods were synthesized on electrochemical seeded substrate in an aqueous solution containing zinc nitrate and hexamethylenetetramine. In order to increase the stability of PET-ITO electrode to electrochemical and chemical stresses during ZnO nanorods deposition the surface of the electrode was treated with a 17 wt% NH₄F aqueous solution. Electrochemical stability of PET-ITO electrode was evaluated in a solution containing nitrate ions and hexamethylenetetramine. ZnO nanorod/shell arrays were fabricated using eosin Y as nanostructuring agent. Photoluminescence spectra of ZnO nanorod and ZnO nanorod/shell arrays prepared on the surface of PET-ITO electrode were discussed comparatively. By employing the 1.5 μm-length ZnO nanorod/shell array covered with a Cu₂O film a photovoltaic device was fabricated on the PET-ITO substrate.     

Sol-hydrothermal synthesis and characterization of lead zirconate titanate fine particles

A novel sol-hydrothermal route to prepare lead zirconate titanate (PZT) fine particles is presented, which combined the conventional sol–gel process and the hydrothermal method. The effects of experimental parameters including sol/(sol + water) ratio, reaction temperature and reaction time on the product powders were investigated. The prepared PZT powders were characterized by XRD, SEM/EDS, and Raman techniques. The results indicated that the optimal synthesis conditions were sol/(sol + water) = 20%, 200 °C, 8 h. The obtained powders with an average particle size of 700 nm, were phase pure perovskite PZT with cubic-shaped morphology, and the reaction temperature was as low as 150 °C, which was comparatively lower than that synthesized by the normal sol–gel route. It was supposed that the sol precursor and hydrothermal environment played important roles in the formation of the PZT fine powders at low temperature and low mineralizer concentration.