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Explosions involving gaseous fuels, vapors, dust, and condensed phase materials have been discussed in the earlier chapters. The release of fuel gas or vapor into the ambient from leaks in pipelines conveying gaseous fuel and volatile liquid fuels at high pressures and from spills of gaseous and liquid fuels from fuel storages vessels, oil rigs and refineries, and chemical process industries could form explosive gas clouds in the atmosphere.

Gaseous, liquid, and solid substances containing elements such as carbon and hydrogen can chemically react with oxygen in the air and release energy.

The blast wave, generated by a rapid release of energy, disperses and dissipates the energy into the surrounding medium.

The word ‘explosion’ is generally used to describe events associated with a loud noise and sudden disruption of the objects at the site of its occurrence and around it.

Chemical reactions are not to the only means of obtaining rapid release of energy for the occurrence of explosions.

The overpressure and impulse at a distance \(R_s\) from an explosion were determined in Chap. 2 by assuming the energy to be released instantaneously at a point. A length scale for the energy release called as ‘explosion length \(R_0\)’ was defined, and a non-dimensional parameter \(R_s/R_0\) was used to find the values of overpressure and impulse following Sach’s scaling law. In practice, all sources of energy release would have a finite volume and the release of energy cannot be instantaneous.

Gaseous fuels and volatile liquid fuels are used for household and industrial purposes and for propulsion. They are transported by road, rail, and sea in tankers of different sizes.

When the temperature of a reactive medium is increased, chemical reactions take place in it and energy is released.

The rate of energy release from the chemical reaction of a given mass or volume of an explosive was seen to increase as its temperature increases.

In Chap. 5, the conditions for thermal explosion of a reactive substance were determined based on the heat generated and the heat loss from it. Terms like auto-ignition and ignition temperatures were derived using a lumped mass assumption. It is rarely possible for the entire bulk of the substance to get ignited; rather, a flame or a detonation, as described in the last chapter, would get initiated from an ignition or initiation source and it would thereafter propagate. We consider the formation of flames and detonations and the conditions of the gaseous explosive for which the formation and propagation is possible in this chapter.

Blast waves, formed from explosive energy release, would interact with bodies placed in their path of propagation.

Condensed phase explosives contain the fuel and the oxidizer integrated together as a solid or a liquid. The fuel and oxidizer could be combined in the form of a chemical compound (i.e., fuel and oxidizer exist as a single molecule) or could be intimately mixed together as a heterogeneous substance. In the latter, the fuel and oxidizer are mixed well to be qualified as a single substance.

The principles governing explosion of gaseous, dust, and condensed phase substances are discussed in the previous chapters. Confined and unconfined explosions, physical explosions, and explosions of pressure vessels are modeled. Chapman–Jouguet detonations and quasi-detonations are seen to be more destructive than flames in a confined geometry.

In this communication, the influence of solvent (water and mixed solvent) on the structural, surface microstructural, dc-electrical and optical properties of spray deposited cadmium oxide (CdO) thin films doped with different weight percentages (wt%) of boron (B) on microscopic glass substrates at 300 °C is reported. The X-ray diffraction (XRD) analysis suggests that the samples are polycrystalline in nature and the crystallinity is enhanced by B doping concentrations. The average crystallite size of (200) plane is ranging 29–90 and 40–138 nm for water, and mixed solvent of water and methanol (1:1), respectively. Oxidation state of B doped CdO thin film was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The surface microstructures of B doped CdO thin films are effectively modified by solvent and the average particle size varies between 301 and 466 nm for water solvent and 221 and 705 nm for mixed solvent used B doped CdO films. The direct optical band gap energy values varies between 2.11 and 2.35 eV for water and 2.43 and 2.54 eV for mixed solvent used B doped CdO thin films. High average transmittance (80 %) and high mobility of 64.42 cm2/V·s were obtained for 1.0 wt% B doped CdO thin film deposited using mixed solvent. The mixed solvent used 1.0 wt% B doped CdO thin film has high figure of merit (16.2 × 10−3 Ω−1). The variations in electrical resistivity, carrier concentration, mobility and optical transmittance with respect to spray solvents have been discussed.

Potassium niobate (KNbO3 ), a lead free perovskite single crystal , was grown by top seeded solution growth method using K2O as self flux. The synthesized powder and grown crystal of KNbO3 were studied by various characterization techniques. The thermal stability of KNbO3 was determined by Thermo Gravimetric and Differential Thermogram (TG-DTG) analyses. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectral studies reveal the formation of single phase orthorhombic structure of KNbO3 with space group Cm2m. In addition, Rietveld refinement analysis of XRD of KNbO3 confirms that there is no impurity or secondary phase formation in the grown crystal. Energy dispersive X-ray (EDS) analysis confirms the elemental composition and the presence of K, Nb and O. Chemical etching studies on the grown crystal reveal the layer by layer growth behavior.

We report the effect of lanthanum (La3+) substitution on the physical properties of cobalt ferrite (CoFe2O4) magnetic nanoparticles by co-precipitation method. X-ray diffraction analysis reveals the formation of single phase cubic inverse spinel structure of CoFe2O4 and CoFe1.9La0.1O4, and CoFe2−x La x O4 (0.2 < x < 0.5) with a mixed impurity phase, LaFeO3. Fourier transform infrared spectral analysis confirms the presence of Fe-O symmetrical stretching vibration at tetrahedral site. SEM studies reveal that the surface microstructure of CoFe2O4 nanoparticles was effectively modified by La3+ ion substitution. Energy dispersive spectral analysis confirms the presence of elements in the synthesized nanoparticles. Transmission electron microscopy studies reveal that the particle size increases with increasing La3+ ion concentrations. Dielectric properties reveal that the value of dielectric constant (ɛ′) and dielectric loss (ɛ″) are gradually increases with increasing La3+ ion concentration as well as temperature. Magnetic measurement reveals that the saturation magnetization decreases from 61.45 to 25.13 emu/g with increasing La3+ ion concentrations.