Honghao Yan

Effect of Initial Hardness on Interfacial Features in Underwater Explosive Welding of Tool Steel SKS3

This paper aims at investigating effects of initial hardness on interfacial features for identical compositional materials under identical welding conditions. Two underwater explosive welding experiments on tool steel SKS3 with copper foil were carried out: one as-received and the other heat-treated. The welding process was simulated using the commercially available software package LS-DYNA. Numerical simulation gave deformation of the flyer/base plate and pressure distribution during the welding process. Microstructure and hardness at interface of the welded metals were evaluated. The results indicate that decreasing impact energy is accompanied by a shift from wavy to linear interface. Moreover, a comparison of the two experiments allows the conclusion that high initial hardness results in a decrease of wavelength and amplitude under identical welding conditions. Hardness profiles of as-received tool steel-copper welding reveal the hardening effect of impact in the vicinity of the interface. However, of interest is that a decrease in hardness was seen in the case of heat-treated martensitic tool steel with copper, fundamentally differing from previous explosive welding research; phase transition is proposed to discuss the relation between the effects of impact and heat, and those of work hardening and softening.

Using ethanol for preparation of nanosized TiO2 by gaseous detonation

A method of preparing nanosized titanium dioxide by gaseous detonation by using ethanol, hydrogen, and oxygen as an explosion source and titanium tetrachloride as a precursor is described. The results indicate that the rutile phase content of the obtained products is high, and the pure rutile phase can be produced by adding a small amount of hydrogen. Most of the particles obtained under the two different synthesis conditions are spherical (or sphere-like) with small and even particle sizes, generally about 30 nm, and has a very good size dispersion.

Hydrogen and air detonation (deflagration) synthesis of carbon-encapsulated iron nanoparticles

With ferrocene as a precursor, carbon-encapsulated iron nanoparticles are synthesized through detonation of a gas mixture of hydrogen and air in a titanium detonation tube. XRD and TEM characterization shows that a downward trend in the size of particles can be observed with increasing amounts of the precursor. However, no further decrease occurs when the size of nanoparticles reaches approximately ≈40 nm, after which they remain in the range of 30–50 nm. The initial temperature of the detonation tube at 353 K is the optimal initial temperature for the synthesis. The average grain size of the synthesized products becomes larger as the temperature of detonation increases.

Experimental Study of Bilinear Initiating System Based on Hard Rock Pile Blasting

It is difficult to use industrial explosives to excavate hard rock and achieve suitable blasting effect due to the low energy utilization rate resulting in large rocks and short blasting footage. Thus, improving the utilization ratio of the explosive energy is important. In this study, a novel bilinear initiation system based on hard rock blasting was proposed to improve the blasting effects. Furthermore, on the basis of the detonation wave collision theory, frontal collision, oblique reflection, and Mach reflection during detonation wave propagation were studied. The results show that the maximum detonation pressure at the Mach reflection point where the incident angle is 46.9° is three times larger than the value of the explosive complete detonation. Then, in order to analyze the crack propagation in different initiation forms, a rock fracture test slot was designed, and the results show that bilinear initiating system can change the energy distribution of explosives. Finally, field experiment was implemented at the hard rock pile blasting engineering, and experimental results show that the present system possesses high explosive energy utilization ratio and low rock fragments size. The results of this study can be used to improve the efficiency in hard rock blasting.

Phase transition rate of anatase during detonation synthesis of TiO2

ABSTRACT TiO2 powders were synthesized by two types of mixed explosives in a sealed reaction kettle. The phase and morphology of TiO2 powders were obtained by X-ray diffractometry and transmission electron microscopy. Results indicate that powders obtained from metatitanic acid contained mixed explosive are mixed crystal of anatase and rutile. The phase transition rate of anatase increases from 22.9% to 93.3% with the rise of mass ratio of hexogen, and the grain size also enlarges gradually. The powder obtained from anatase contained mixed explosive is rutile, and the phase transition rate of anatase is 100%. Compared with that before detonation, the grain size of anatase after detonation significantly changes, from nanoscale to micronscale. Based on the calculation of detonation parameters, the phase transition process and grain growth during the synthesis of TiO2 by means of detonation method are analyzed, and the nucleating collision–growth model is proposed.

Experimental investigations of the controlled explosive synthesis of ultrafine Al2O3

The relation between the parameters of mixed explosives [combinations of Al(NO3)3·9H2O powder, RDX powder, and/or polyethylene foaming particles] and the phase and dimension of ultrafine Al2O3 is studied in this paper. Experimental results indicate that mixed explosives with a high density of 1.8 g/cm3 are adapted to prepare high-temperature α-Al2O3. Ultrafine (α + γ)-Al2O3 with α-phase dominance is synthesized by the detonation of charges with a medium-high density of 1.3 g/cm3. Explosives with a medium-low density of 0.8 g/cm3 synthesize low-temperature pure λ-Al2O3.

Investigation on explosive compaction of W-Cu nanocomposite powders

The technique of explosive powder compaction is used to prepare W-Cu nanocomposites. The nanocrystalline W-Cu powders are produced by mechanical alloying and then analyzed by x-ray diffraction. The compacted specimens are found to have the largest density when the detonation velocity is 5300 m/s. The composition and distribution of the elements in the compacted specimens are uniform and have a Vickers hardness equal to 320 and a density equal to 99.1% of the theoretical density.

Selective synthesis of TiO2 nanopowders

Nanosized anatase, rutile, brookite, and mixtures of these materials taken in different ratios are synthesized using the detonation method with variations in the densities and ratios of explosives composed of the TiO2 precursor, NH4NO3, and C3H6N3(NO2)3. It is shown that the phase composition, the phase content, and the average particle size of TiO2 nanopowders depend on the composition of the explosive mixtures and their densities. When the weight ratio between the C3H6N3(NO2)3 compound and the TiO2 precursor lies in the range 0.695–1.270, the average size of rutile particles is larger than that of anatase particles by a factor of approximately two.

Study of continuous velocity probe method for the determination of the detonation pressure of commercial explosives

ABSTRACT A novel velocity probe, which permits recording the continuous velocities of detonations and shock waves, has been developed based on the transition of operation principle from ionization to pressure-conduction. Using the new probe and the impedance matching method, a series of measuring devices were set up to obtain the shock wave velocities in different inert materials, i.e., water, Plexiglas and paraffin wax. Two test types of powder ammonium nitrate/fuel oil (ANFO), exposed on the ground and tamped in the blast hole, were performed, from which we calculated their detonation pressures, with a density of approximately 0.86 g·cm−3, ranged from 3.52 GPa to 3.65 GPa, and the adiabatic exponents from 2.24 to 2.30. The results show that the present velocity probe-based method can be used to determine the detonation pressure of commercial explosives conveniently and reliably, which is an important supplement for the testing techniques of explosive performance.

Underwater explosive compaction-sintering of tungsten–copper coating on a copper surface

ABSTRACT This study investigated underwater explosive compaction-sintering for coating a high-density tungsten–copper composite on a copper surface. First, 50% W–50% Cu tungsten–copper composite powder was prepared by mechanical alloying. The composite powder was pre-compacted and sintered by hydrogen. Underwater explosive compaction was carried out. Finally, a high-density tungsten–copper coating was obtained by diffusion sintering of the specimen after explosive compaction. A simulation of the underwater explosive compaction process showed that the peak value of the pressure in the coating was between 3.0 and 4.8 GPa. The hardness values of the tungsten–copper layer and the copper substrate were in the range of 87–133 and 49 HV, respectively. The bonding strength between the coating and the substrate was approximately 100–105 MPa.