Morphological characterization of shocked porous material

Abstract

Abstract. Morphological measures are introduced to probe the complex procedure of shock wave reaction on porous material. They characterize the geometry and topology of the pixelized map of a state variable like the temperature. Relevance of them to thermodynamical properties of material is revealed and various experimental conditions are simulated. Numerical results indicate that, the shock wave reaction results in a complicated sequence of compressions and rarefactions in porous material. The increasing rate of the total fractional white area A roughly gives the velocity D of a compressive-wave-series. When a velocity D is mentioned, the corresponding threshold contour-level of the state variable, like the temperature, should also be stated. When the threshold contour-level increases, D becomes smaller. The area A increases parabolically with time t during the initial period. The A(t) curve goes back to be linear in the following three cases: (i) when the porosity δ approaches 1, (ii) when the initial shock becomes stronger, (iii) when the contour-level approaches the minimum value of the state variable. The area with high-temperature may continue to increase even after the early compressive-waves have arrived at the downstream free surface and some rarefactive-waves have come back into the target body. In the case of energetic material needing a higher temperature for initiation, a higher porosity is preferred and the material may be initiated after the precursory compressive-waves have scanned all the target body. One may desire the fabrication of a porous body and choose appropriate shock strength according to what needed is scattered or connected hotspots. With the Minkowski measures, the dependence on experimental conditions is reflected simply by a few coefficients. They may be used as order parameters to classify the maps of physical variables in a similar way like thermodynamic phase transitions.Submitted to: J. Phys. D: Appl. Phys.

Preparation of Ag nanoparticles in the presence of low generational poly(ester‐amine) dendrimers

“….0 (OH) 16 and G1.5 (NH 2 ) 8 were prepared according to literature, 15,16 respectively. The structures of G1.0 (OH) 16 and G1.5 (NH 2 ) 8 were given in Scheme 1.…”

“…The structures of G1.0 (OH) 16 and G1.5 (NH 2 ) 8 were given in Scheme 1. Silver nitrate (AgNO 3 ), sodium borohydride (NaBH 4 ), and 50% (mass) hydrazine aqueous were purchased from the Chemical Reagent Company of Shanghai (China) and were used without further purification.…”

“…Dendrimers of lower generation are easily prepared, and tend to exist in relative open forms, which provide reactive sites at the periphery of dendrimer, so, they attract attentions. 13,14 In this work, Ag nanoparticles were formed in the presence of low generational hydroxyl terminated poly(ester-amine) dendrimer G1.0 (OH) 16 and aminoterminated poly(ester-amine) dendrimer G1.5 (NH 2 ) 8 synthesized by ourselves. It has been found that they are good templates and stabilizers for the synthesis of Ag nanoparticles.…”

“…It has been found that they are good templates and stabilizers for the synthesis of Ag nanoparticles. Our approach relies on the coordination between Ag ions and nitrogens of G1.0 (OH) 16 and G1.5 (NH 2 ) 8 dendrimers. Reducing the Ag ions with NaBH 4 produced colloid solutions stabilized by the dendrimers.…”

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ABSTRACT: Stable Ag nanoparticles of 10-20 nm were prepared by reduction of AgNO 3 with NaBH 4 in water solution in the presence of low generational hydroxylterminated poly(ester-amine) dendrimer G1.0 (OH) 16 and amino-terminated poly(ester-amine) dendrimer G1.5 (NH 2 ) 8 by optimizing preparation conditions. UV-vis absorption spectra and transmission electron microscopy were adopted to characterize absorption properties of Ag þ /dendrimer complex, Ag/dendrimer nanocomposite aqueous solutions, and the morphology of the formed Ag nanoparticles, respectively.

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