Simplified LIBS-based intensity-ratio approach for concentration estimation (SLICE): an approach for elemental analysis using laser induced breakdown spectroscopy.

We propose what we believe to be a new approach for elemental analysis using laser induced breakdown spectroscopy (LIBS). This method offers enhanced convenience and simplicity for elemental analysis as it eliminates the necessity of Boltzmann/ Saha-Boltzmann plot. It is an intensity-ratio based approach that provides several notable advantages. One of the key benefits is its ability to perform comprehensive elemental analysis using only a few spectral lines; specifically, only n + 1 emission lines are sufficient for a sample containing n elemental species. This offers a great flexibility in the choice of emission lines which do not suffer from self-absorption. Further, high accuracy can be obtained as many repeated estimations from a single measurement are possible. We demonstrate the theory and working procedure of this technique by experimentally recording the data of two samples (binary and ternary copper alloys). A nanosecond Nd:YAG pulsed laser of ∼7 ns pulse duration and 532 nm incident wavelength is used. The results are in good agreement with CF-LIBS and Energy-dispersive X-ray spectroscopy (EDS).

Time-Dependent Intensity Ratio-Based Approach for Estimating the Temperature of Laser Produced Plasma.

Reported here is a rapid and simplified approach for modeling the temporal evolution of the plasma temperature. The use of only two emission lines makes this technique simple, accurate, and fast. Usually, multiple emission lines are required for estimating plasma temperature using Boltzmann/Saha-Boltzmann plots. But, in several cases, either multiple emission lines are not available for every element and/or sufficient lines are not free from self-absorption effect. The proposed method greatly increases the possibility of plasma temperature estimation as it requires only two lines. A brass target was used to generate the plasma, using a conventional single-pulse nanosecond laser of ∼7 ns pulse duration at an excitation wavelength of 532 nm. The initial temperature of plasma and the radiation decay constant were estimated using a proposed intensity ratio model. The results were estimated using various combinations of emission lines, which show an excellent agreement with the values obtained using the previously reported method.

Discrete model of gas-free spin combustion of a powder mixture.

We propose a discrete model of gas-free combustion of a cylindrical sample which reproduces in detail a spin combustion mode. It is shown that a spin combustion, in its classical sense as a continuous spiral motion of heat release zones on the surface of the sample, does not exist. Such a concept has arisen due to the misinterpretation of the experimental data. This study shows that in fact a spinlike combustion is realized, at which two energy release zones appear on the lateral surface of the sample and propagate circumferentially in the opposite directions. After some time two new heat release zones are formed on the next layer of the cylinder surface and make the same counter-circular motion. This process continues periodically and from a certain angle it looks like a spiral movement of the luminous zone along the lateral surface of the sample. The model shows that on approaching the combustion limit the process becomes more complicated and the spinlike combustion mode shifts to a more complex mode with multiple zones of heat release moving in different directions along the lateral surface. It is shown that the spin combustion mode appears due to asymmetry of initial conditions and always transforms into a layer-by-layer combustion mode with time.

Dynamical and statistical behavior of discrete combustion waves: a theoretical and numerical study.

We present a detailed theoretical and numerical study of combustion waves in a discrete one-dimensional disordered system. The distances between neighboring reaction cells were modeled with a gamma distribution. The results show that the random structure of the microheterogeneous system plays a crucial role in the dynamical and statistical behavior of the system. This is a consequence of the nonlinear interaction of the random structure of the system with the thermal wave. An analysis of the experimental data on the combustion of a gasless system (Ti + xSi) and a wide range of thermite systems was performed in view of the developed model. We have shown that the burning rate of the powder system sensitively depends on its internal structure. The present model allows for reproducing theoretically the experimental data for a wide range of pyrotechnic mixtures. We show that Arrhenius' macrokinetics at combustion of disperse systems can take place even in the absence of Arrhenius' microkinetics; it can have a purely thermal nature and be related to their heterogeneity and to the existence of threshold temperature. It is also observed that the combustion of disperse systems always occurs in the microheterogeneous mode according to the relay-race mechanism.