Ahmed Hassen Galmed

As the demand for a quick and remote way of hardness estimation increases, the attention to use LIBS for such application increases. Most of the studies of hardness estimation that have been done used nanosecond laser sources for LIBS while using femtosecond laser has not been studied yet. In this work, a group of five samples with different hardness were analyzed using nanosecond and femtosecond LIBS for relative hardness estimation. Almost the same wavelength was used to decrease the effect of wavelength as much as possible. Considering that the laser produced plasma is in a state of local thermodynamic equilibrium (LTE), the Boltzmann plot method was adopted to calculate the plasma excitation temperature (Te) which is closely correlated to the samples’ hardness. It was found that in case of nanosecond LIBS as the sample hardness increases the excitation temperature Te increases, while for the femtosecond LIBS the behavior was opposite and Te was found to be decreasing as the hardness of the target increases. This result may be attributed to the different plasma plume creation processes and its expansion for both nano- and femto- second lasers.

Rock’s hardness is one of the most investigated and important parameters which describes the strength properties of a rock mass. Laser-induced breakdown spectroscopy (LIBS) is a developing spectrochemical elemental analysis technique that is recently investigated to be used for metal hardness measurements. In this work, LIBS has been used to study the surface hardness of selected geological samples. The relationship between sample rebound test hardness, sample density and the LIBS plasma excitation temperature (Te) was investigated. It was observed that there is a linear relationship between the hardness and the density of the samples. Also, it was observed that there is a linear relation between Te and the hardness of the samples. The estimation of the surface hardness of the geological samples by measuring the Te shows the feasibility of LIBS as an easy and reliable method for geological samples’ application.

This contribution reports on the thermal conductivity enhancement of MoO3–H2O nano-sheets based nano-fluid. The MoO3–H2O based nano-fluid consists of a set of 2D type nano-sheets with a basal size, approximately ranging from 108 × 200 nm2 to 415 × 631 nm2. A Higher Resolution Transmission Electron Microscopy (HRTEM) observation indicated that the nano-sheets consist of a collection of nano-crystallites (Ø∼7 nm) with various crystallographic orientations with 15 nm in average diameter. The Molybdenum is mainly in 6+ electronic valence. Their thermal conductivity measured via standard Pt wire exhibited an enhancement of about 36%.