Mohieddine Abdellaoui

Bio: Mohieddine Abdellaoui is an academic researcher from SIDI. The author has contributed to research in topics: Ball mill & Nanocrystalline material. The author has an hindex of 18, co-authored 57 publications receiving 1568 citations. Previous affiliations of Mohieddine Abdellaoui include Carthage University & Centre national de la recherche scientifique.

The physics of mechanical alloying in a planetary ball mill: Mathematical treatment

Abstract: Based on a kinematic modeling of the planetary ball mill, the kinematic equations giving the velocity and the acceleration of a ball in a vial in a planetary ball mill are given. The kinetic energy transferred at the collision event, the shock frequency, and the injected shock power are also calculated. The confrontation of the calculated to some experimental results documented in the material literature, show that neither the shock energy nor the shock frequency separately taken into account, govern the end product but only the injected shock power is responsible for the ball milled end product.

Formation of Nanostructural Materials Induced by Mechanical Processings ( Overview )

Abstract: Mechanical alloying (MA) was firstly developed to synthesize metallic matrix composite by mechanically incorporating preformed oxide and or carbide particles into a metallic matrix. A consecutive compaction process is applied to obtain bulk materials. During MA, powders are repeatedly welded, fractured and rewelded in a high energy mill leading to an intimate mixing on a nano/micro-scale with the possible formation of far from equilibrium phases. The versatility of MA is well known ; high volume, low energy mills can be used to commercially produced dispersion strengthened Al, Ni and other transition metal alloys. Various intermetallics and inorganic compounds (amorphous and/or nanocrystalline) have been synthesized by using higher energy mills which have been specially developed in some cases. Mechanical alloying, it appears, as suggested by T. H. Courtney et al., is the Alladin's lamp of powder processing. All the published works have shown that the reaction and end products of the MA process strongly depend on the milling conditions. As a consequence, it is obvious that an improved understanding of the dynamics of MA process is required to gain a full appreciation of the industrial potential of the technique for synthesizing materials. Recently, M. Abdellaoui and E. Gaffet have shown that the crystal to amorphous phase transition (at least in the case of the model Ni 10 Zr 7 ) only depends on the injected mechanically power, allowing a direct comparison among experiments performed using distinct type of milling apparatus (planetary milling machine, horizontal apparatus). An alternative method has been recently proposed by N. Malhouroux-Gaffet and E. Gaffet, for the solid state synthesis of disilicide powders exhibiting a wide contamination during the direct MA preparation : the mechanically activated annealing process (M2AP). Such a M2AP method has been applied to the synthesis of FeSi 2 , MoSi 2 , WSi 2 compounds. Such a method appears as being a well suitable one for the low temperature synthesis of refractory nanomaterials. Recent applications have been successfully performed to mechanically activated sintering (MAS).

Mechanical Alloying And Milling

Abstract: Mechanical alloying (MA) is a solid-state powder processng technique involving repeated welding, fracturing, and rewelding of powder particles in a high-energy ball mill. Originally developed to produce oxide-dispersion strengthened (ODS) nickel- and iron-base superalloys for applications in the aerospace industry, MA has now been shown to be capable of synthesizing a variety of equilibrium and non-equilibrium alloy phases starting from blended elemental or prealloyed powders. The non-equilibrium phases synthesized include supersaturated solid solutions, metastable crystalline and quasicrystalline phases, nanostructures, and amorphous alloys. Recent advances in these areas and also on disordering of ordered intermetallics and mechanochemical synthesis of materials have been critically reviewed after discussing the process and process variables involved in MA. The often vexing problem of powder contamination has been analyzed and methods have been suggested to avoid/minimize it. The present understanding of the modeling of the MA process has also been discussed. The present and potential applications of MA are described. Wherever possible, comparisons have been made on the product phases obtained by MA with those of rapid solidification processing, another non-equilibrium processing technique.

Hallmarks of mechanochemistry: From nanoparticles to technology

Abstract: The aim of this review article on recent developments of mechanochemistry (nowadays established as a part of chemistry) is to provide a comprehensive overview of advances achieved in the field of atomistic processes, phase transformations, simple and multicomponent nanosystems and peculiarities of mechanochemical reactions. Industrial aspects with successful penetration into fields like materials engineering, heterogeneous catalysis and extractive metallurgy are also reviewed. The hallmarks of mechanochemistry include influencing reactivity of solids by the presence of solid-state defects, interphases and relaxation phenomena, enabling processes to take place under non-equilibrium conditions, creating a well-crystallized core of nanoparticles with disordered near-surface shell regions and performing simple dry time-convenient one-step syntheses. Underlying these hallmarks are technological consequences like preparing new nanomaterials with the desired properties or producing these materials in a reproducible way with high yield and under simple and easy operating conditions. The last but not least hallmark is enabling work under environmentally friendly and essentially waste-free conditions (822 references).

Enhancement of Thermoelectric Figure-of-Merit by a Bulk Nanostructuring Approach

Abstract: Recently a significant figure-of-merit (ZT) improvement in the most-studied existing thermoelectric materials has been achieved by creating nanograins and nanostructures in the grains using the combination of high-energy ball milling and a direct-current-induced hot-press process. Thermoelectric transport measurements, coupled with microstructure studies and theoretical modeling, show that the ZT improvement is the result of low lattice thermal conductivity due to the increased phonon scattering by grain boundaries and structural defects. In this article, the synthesis process and the relationship between the microstructures and the thermoelectric properties of the nanostructured thermoelectric bulk materials with an enhanced ZT value are reviewed. It is expected that the nanostructured materials described here will be useful for a variety of applications such as waste heat recovery, solar energy conversion, and environmentally friendly refrigeration.