Ni Transition Metal Research Articles

Hydrogen binding property of Co- and Ni-based organometallic compounds

The binding property of hydrogen on organometallic compounds consisting of Co, and Ni transition metal atoms bound to CmHm rings (m = 4, 5) is studied through density functional theory calculation. CoCmHm and NiCmHm complexes can store up to 3.49 wt% hydrogen with an average binding energy of about 1.3 eV. The adsorption characteristics of hydrogen to organometallic compounds are investigated by analyzing vibrational spectra of CoC4H4(H2)n and NiC4H4(H2)n (n = 0, 1, 2). The kinetic stability of these hydrogen-covered organometallic complexes is assured by analyzing the energy gap between the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals. It is also discussed the application of 18-electron rule in predicting maximum number of hydrogen molecules that could be adsorbed by these organometallic compounds.

Elemental Concentrations of Eleven New Caledonian Plant Species from Serpentine Soils: Elemental Correlations and Leaf-Age Effects

We investigated accumulation of elements (Ca, Co, Cr, Cu, Fe, K, Mg, Mn, P, Pb, and Zn) in leaves of different ages for 11 evergreen woody plant species from serpentine soils of New Caledonia. Species were classified into four categories of Ni accumulation ability: one species was a non-accumulator (<100 mg Ni/ kg), three were accumulators (100–1000 mg Ni/kg), two were hyperaccumulators (1000–10,000 mg Ni/kg), and five were hypernickelophores (>10,000 mg Ni/kg). We harvested leaves from each species, separating them into three (four in one case) relative age categories based upon their position along branches (younger toward the apex, older far from it). Leaf samples were dried, ground, and dry-ashed, and their elemental concentrations were determined by inductively coupled plasma spectrometry (all elements except Ni) or atomic absorption spectrophotometry (Ni). Great variation was found for most elements both within and among species, but Ni varied most (1050-fold between species for oldest leaves). Correlations between Ni and other transition metals showed no significant relationships within samples of any species, but, we found significant positive correlations between Ni and Pb (correlation coefficient = 0.97) and Ni and Fe (correlation coefficient= 0.87) among species. Leaf Ni concentrations varied significantly with leaf age for two species, the hypernickelophores Geissois pruinosa and Homalium kanaliense. We conclude that Ni concentration varies markedly between species, but generally does not vary with leafage within species. We also suggest that four Ni accumulation category terms— non-accumulator, hemi-accumulator, hyperaccumulator, and hypernickelophore—be used to subdivide the wide variation found in Ni concentrations in plant leaves.

Electronic Structure and Magnetic Properties of Ni2MnGa1-xGexand Disordered Ni2MnSn Heusler Alloys

The physical properties of the Heusler alloys are of great interest for both basic research and technological applications because of their magnetic properties and structural transformation. Due to potential application as magnetic actuators, the Heusler alloys based on Ni and Mn transition metals have been extensively investigated [1–9]. Ni2MnGa is a vastly studied ferromagnetic shape memory alloy with martensitic transformation [5–7]. Here, we focused on electronic properties of Ni2MnGa1−xGex, whose magnetic properties and temperature of martensitic transformation have been experimentally studied earlier [8]. The structural transformation of Ni–Mn–Sn from austenite to martensite phase has been studied by various experimental methods [1]. It was observed that the strength of the exchange interaction in both phases change substantially upon transformation from one phase to another. Attention has been devoted to Ni50Mn34Sn16 in [4] because of its large magnetocaloric effect. Moreover, film samples of Ni50Mn50−xSnx exhibited signs of martensitic transformation [2, 9], too.

Ni-based amorphous alloy membranes for hydrogen separation at 400 °C

Amorphous alloy membranes composed primarily of Ni and early transition metals (ETMs) are an inexpensive alternative to Pd-based alloy membranes, and these materials are therefore of particular interest for the large-scale production of hydrogen from carbon-based fuels. Catalytic membrane reactors can produce hydrogen directly from coal-derived synthesis gas at 400 °C, by combining a commercial water–gas-shift (WGS) catalyst with a hydrogen-selective membrane. In order to explore the suitability of Ni-based amorphous alloys for this application, the thermal stability and hydrogen permeation characteristics of Ni–ETM amorphous alloy membranes has been examined. A fundamental limitation of these materials is that hydrogen permeability is inversely proportional to the thermal stability of the alloy. Alloy design is therefore a compromise between hydrogen production rate and durability. Amorphous Ni 60Nb 40− X Zr X membranes have been tested at 400 °C in pure hydrogen, and in simulated coal-derived gas streams with high steam, CO and CO 2 levels, without severe degradation or corrosion-induced failure. Ni–Nb–Zr amorphous alloys are therefore prospective materials for use in a catalytic membrane reactor for coal-derived syngas.

Interactions between basalts and oil source rocks in rift basins: CO2 generation

Basalts interbedded with oil source rocks are discovered frequently in rift basins of eastern China, where CO2 is found in reservoirs around or within basalts, for example in the Binnan reservoir of the Dongying Depression. In the reservoirs, CO2 with heavy carbon isotopic composition (δ13C>-10‰ PDB) is in most cases accounts for 40% of the total gas reserve, and is believed to have resulted from degassing of basaltic magma from the mantle. In their investigations of the Binnan reservoir, the authors suggested that the CO2 would result from interactions between the source rocks and basalts. As the source rocks around basalts are rich in carbonate minerals, volcanic minerals, transition metals and organic matter, during their burial history some of the transition metals were catalyzed on the thermal degradation of organic matter into hydrocarbons and on the decomposition of carbonate minerals into CO2, which was reproduced in thermal simulations of the source rocks with the transition metals (Ni and Co). This kind of CO2 accounts for 55%–85% of the total gas reserve generated in the process of thermal simulation, and its δ13C values range from-11‰–-7.2‰ PDB, which are very similar to those of CO2 found in the Binnan reservoir. The co-generation of CO2 and hydrocarbon gases makes it possible their accumulation together in one trap. In other words, if the CO2 resulted directly from degassing of basaltic magma or was derived from the mantle, it could not be accumulated with hydrocarbon gases because it came into the basin much earlier than hydrocarbon generation and much earlier than trap formation. Therefore, the source rocks around basalts generated hydrocarbons and CO2 simultaneously through catalysis of Co and Ni transition metals, which is useful for the explanation of co-accumulation of hydrocarbon gases and CO2 in rift basins in eastern China.

Bonding and structural characteristics of Zn-, Cu-, and Ni-encapsulated Si clusters: Density-functional theory calculations

The bonding and structural characteristics of metal $(M)$ embedded silicon clusters $\mathrm{M}@{\mathrm{Si}}_{12}$ and $\mathrm{M}@{\mathrm{Si}}_{10}$, $M=\mathrm{Zn},\mathrm{Cu},\mathrm{Ni}$ have been studied in parallel within the framework of the density functional theory with the hybrid nonlocal exchange and correlation functional of Becke and Lee, Yang and Parr (B3LYP). It is illustrated that for Zn and Cu, which are characterized by filled $d$ shells the bonding and structure are largely characterized by the valence metal electrons, contrary to Ni and other transition metals where the bonding is dominated by the filling of the empty $d$ shells by cage electrons. In $\mathrm{M}@{\mathrm{Si}}_{12}$ clusters there is a strong competition between cubic, icosahedral, and hexagonal prismatic structures. However, with the possible exception of $\mathrm{Zn}@{\mathrm{Si}}_{12}$, the corresponding fully symmetric ${O}_{\mathrm{h}}$, ${I}_{\mathrm{h}}$, and ${D}_{6\mathrm{h}}$ structures for all three metals are statically and/or dynamically unstable due to Jahn-Teller distortions. In addition to $\mathrm{M}@{\mathrm{Si}}_{12}$, hydrogenated $\mathrm{M}@{\mathrm{Si}}_{12}{\mathrm{H}}_{12}$, $M=\mathrm{Ni},\mathrm{Zn}$ clusters have been studied in order to examine the changes in the bonding and structural properties induced by saturating the dangling bonds with surface-hydrogen. In these clusters the effect of hydrogen consists in weakening considerable (up to zero) the metal-cage interactions, enhancing the $s{p}^{3}$ cage interactions. This leads in many cases to empty hydrogenated silicon cages, after the removal of the metal atom, which are very stable and symmetrical with large highest occupied-lowest unoccupied molecular orbital (HOMO-LUMO) energy and optical gaps.

Formation of quasiperiodic and related periodic intermetallics in alloy systems of aluminum with transition metals

Quasiperiodic phases (quasicrystals) have been found in numerous alloy systems of aluminum with transition metals (TM) between about 60 and 85 at.% Al. In binary Al–TM systems only metastable quasicrystals were observed, while in several ternary systems containing Cu, Ni or Pd the quasicrystals are stable. Many stable and metastable periodic phases formed in these compositional ranges exhibit structural relations to quasicrystals. Studies of these phenomenona have stimulated extensive investigation or revision of the high-Al regions of the ternary alloy systems belonging to the Al–Cu–TM, Al–Ni–TM and Al–Pd–TM groups. These studies are reviewed here.

Rhombohedral ilmenite group nickel titanates with Zn, Mg, and Mn: synthesis and crystal structures

Binary, ternary, and quaternary rhombohedral ordered titanates, Ni1/2Mn1/2TiO3, Ni1/2Mg1/2TiO3, Ni1/3Zn1/3Mg1/3TiO3, and Ni1/4Zn1/4Mg1/4Mn1/4TiO3, were obtained by solid-state synthesis at 1095°C at ambient pressure in a nitrogen atmosphere. All of the compounds adopt ATiO3 (A = Ni, Mn, Zn, and Mg) stoichiometry. Crystal structures were refined by the Rietveld method from powder X-ray diffraction data. Unit cell parameters and unit cell volumes decrease with decreasing average radius of the viA2+ cation. All the synthetic titanates adopt the space group \(R\bar 3\) and the ilmenite structure consisting of distorted AO6 and TiO6 octahedra. The divalent cations and Ti4+ are distributed in layers of octahedra alternating along c with no evidence for disorder. In common with pyrophanite, NiTiO3, and ilmenite sensu stricto, the distortion of the AO6 octahedra is less than that of the TiO6 octahedra. The Ti4+ and A-site cations in the titanates are off-centred within the coordination polyhedra. Deviation of the z positional parameters from their theoretical values for the A and Ti atoms indicate that in the titanates with the larger A2+ cations and Goldschmidt tolerance factors, t ≥ 0.745, the AO6 octahedral layer is more “puckered” above and below planes parallel to (001) than that of the TiO6 octahedra, and vice versa in the titanates with smaller RA2+ for which t≤0.745. Data are given for the volumes and distortion indices of all the coordination polyhedra. This study confirms the existence and stability of complex solid solutions between ordered rhombohedral titanates of Ni and first-row transition metals at ambient conditions over a range of t from 0.786 to 0.737. These experimental data suggest that the formation of ilmenite-type titanates enriched in Ni is possible in exotic mineral-forming systems at low pressure and/or in extraterrestrial rocks.

Pressure effect on phonon frequencies in some transition metals: A molecular dynamics study

It is important to determine the atomic lattice vibrations of metallic materials, under high-pressure conditions, due to its effects on material properties such as thermal, electrical and optical conductions. In this work, we have investigated the changes of acoustic phonon frequencies with hydrostatic pressure for Cu, Ni, Al, Ag and Au transition metals, using molecular dynamics (MD) simulations based on embedded atom method (EAM). For this aim, we have adopted the embedded atom potential proposed by Sutton and Chen. The phonon frequencies have been calculated from the dynamical matrix for [1 0 0], [1 1 0] and [1 1 1] high symmetry directions of the Brillouin zone. The obtained results show that the hydrostatic pressure causes an increment in phonon frequencies, and this rising do not depend linearly on the increasing pressure.

Adsorption of Divalent Transition Metal Ions with a Chelating Agent on Octadecyl Silica Gel

This investigation looked at the extraction ability of divalent transition metal ions onto an octadecyl silica gel (C18g) with a 4,4-trifluoro-1-(2-thienyl)-1,3-butadione (TTA) chelating agent. A method of retaining TTA onto C18g (TTA-C18g) was developed in order to adsorb the metal ions. The difference in the half-adsorption and half-extraction pH values between transition metals Ni2+-Co2+ was found to be 0.7 in this system. This is better than previously published results of 0.3 for the conventional extraction method using TTA in nitrobenzene. More than 96% of the metal ions in aqueous solution could be adsorbed onto TTA-C18g. Our system, which has no organic phase, can achieve a better removal or separation of transition metal ions than the conventional solvent-extraction methods using TTA in toluene or nitrobenzene.

Metal-selective DNA-binding response of Escherichia coli NikR.

The NikR transcription factor from Escherichia coli is a Ni(II)-dependent repressor that regulates production of the nickel ion transporter encoded by the nik operon. In the previous paper in this issue (Wang, S. C., Dias, A., Bloom, S. L., and Zamble, D. B. (2004) Selectivity of Metal Binding and Metal-Induced Stability of Escherichia coli NikR, Biochemistry 43, 10018-10028) we demonstrated that NikR can bind 1 equiv of Ni(II) or several other divalent transition metals with similar affinities, but that the Ni(II)-loaded protein is less susceptible to thermal or chemical denaturation than other divalent metal complexes. Here, we investigate the metal selectivity of the DNA-binding activity of NikR. Stoichiometric nickel induces binding of nanomolar NikR to the recognition sequence in the nik promoter, but single equivalents of other divalent metals such as Cd(II), Co(II), and Cu(II) also induce a similar DNA-binding affinity. In the presence of excess nickel, DNA-binding experiments indicate that NikR binds to the nik promoter as a tetramer with much higher affinity (20 pM), and it is this response that is selective for nickel. The DNA binding induced by an excess of other divalent metals is weaker, and is enhanced by the addition of stoichiometric nickel. Nickel titrations into a DNA-binding assay reveal a nickel affinity of 30 nM for a second metal-binding site, and in the presence of 30 nM metal only nickel induces detectable DNA binding by Ni(II)-NikR. These experiments support the hypothesis that there are two metal-binding sites and that both contribute to the nickel-selective DNA-binding response. A model for the in vivo activity of NikR is discussed.

Nickel sequestration in a kaolinite-humic acid complex.

Incorporation of first row transition metals into stable surface precipitates can play an important role in reducing the bioavailability of these metals in neutral and alkaline soils. Organic coatings may interfere with this sorption mechanism by changing the surface characteristics and by masking the mineral surface from metal sorptives. In this study, kinetic sorption and desorption experiments were combined with extended X-ray absorption fine structure (EXAFS) spectroscopy to elucidate the effect of humic acid (HA) coatings on the formation and stabilization of nickel precipitates at the kaolinite-water interface. Initial Ni uptake (pH 7.5, [Ni]i = 3 mM, and I = 0.02 M NaNO3) increased with greater amounts of HA coated onto the kaolinite surface. Ni uptake continued over an extended period of time without reaching an apparent equilibrium. EXAFS analysis of the Ni sorption complex structures formed over time (up to 7 months) revealed the formation of a Ni-Al layered double hydroxide (LDH) precipitate at the kaolinite surface in the absence of HA. HA alone formed an inner-sphere complex with Ni (with 2 carbon atoms at an average radial distance of 2.85 A). A Ni-Al LDH precipitate phase was formed at the kaolinite surface in the presence of a 1 wt % HA coating. However, with 5 wt % HA coated at the kaolinite surface, the formation of a surface precipitate was slowed significantly, and the precipitate formed was similar in structure to Ni(OH)2(s). The Ni(OH)2 precipitate was not resistant to proton dissolution, while the Ni-Al LDH precipitate was. These results augment earlier findings that the incorporation of Ni and other first row transition metals into stable surface precipitates is an important sequestration pathway for toxic metals in the environment, despite the presence of ubiquitous coating materials such as humic acids.

Stabilisierung niedervalenter Ni(CO)-Bausteine durch [Ti](CCR) 2; Reaktionsverhalten von {[Ti](CCR) 2}Ni(CO) gegenüber Triphenylphosphan und Phosphiten

The preparation of heterobimetallic transition metal complexes of the type {[Ti](CCR) 2}Ni(CO) {R=SiMe 3: 3a, [Ti]=(η 5-C 5H 5) 2Ti; 3b: [Ti]=(η 5-C 5H 5)(η 5-C 5H 4SiMe 3)Ti; 3c, [Ti]=(η 5-C 5H 4SiMe 3) 2Ti; R= t Bu: 3d, [Ti]=(η 5-C 5H 4SiMe 3) 2Ti; R=Ph: 3e, [Ti]=(η 5-C 5H 4SiMe 3) 2Ti}, in which next to an early (Ti) a late (Ni) transition metal is present, is described. Additionally, the reaction chemistry of 3a and 3c towards P(OR′) 3 ( 4a, R′=CH 3; 4b, R′=C 6H 5; 4c, R′=C 6H 4Me-2; 4d, R′=C 6H 4 t Bu-2) is reported. In these reactions the nickel-bound carbonyl ligand is replaced by P(OR′) 3 producing {[Ti](CCSiMe 3) 2}Ni[P(OR′) 3] {[Ti]=(η 5-C 5H 5) 2Ti: 5a, R′=CH 3; 5b, R′=C 6H 5; 5c, R′=C 6H 4Me-2; [Ti]=(η 5-C 5H 4SiMe 3) 2Ti: 5d, R′=CH 3; 5e, R′=C 6H 5} along with Ni(CO) 2[P(OR′) 3] 2 ( 6a, R′=C 6H 5; 6b, R′=C 6H 4Me-2; 6c, R′=C 6H 4 t Bu-2). It appeared that the latter reaction strongly depends on the sterical demand, Tolman cone angle, of the respective phosphites used: while, in the reaction of 3a or 3c with 4a selectively 5a and 5d is formed, with more bulky substituents R′, e.g. R′=C 6H 5 and C 6H 4Me-2, complexes 5b and 5c along with 6a and 6b are produced. Changing to even more sterical demanding groups such as R′=C 6H 4 t Bu-2 than exclusively 6c is formed. The dynamic behaviour of 5 in solution is discussed. When 3a is treated with equimolar amounts of PPh 3 ( 7) the titanium–nickel alkynyl species [Ti](μ-η 1:η 2-CCSiMe 3)Ni(PPh 3)(μ-η 1:η 2-CCSiMe 3) { 8a, [Ti]=(η 5-C 5H 5) 2Ti} is accessible via an alkynyl-transfer reaction from titanium to nickel. However, on treatment of 3c with 7 no reaction occurs. Arguments for the different behaviour of 3a– 3c towards 4 and 7 will be presented. The result of the X-ray structure analysis of complexes 5d and 5e are reported. Both complex crystallize in the monoclinic space group P2 1/ n. Cell parameters for 5d: a=10.9390(10), b=15.585(4), c=22.950(3) Å, β=92.861(7)°, V=3907.7(14) Å 3, Z=4 and δ=1.189 g mol −1. 5e: a=17.694(9), b=22.620(10), c=24.510(10) Å, β=103.90(4)°, V=9523(8) Å 3, Z=8 and δ=1.236 g mol −1. In both complexes a low-valent Ni[P(OR′) 3] building block ( 5d, R′=CH 3; 5e, R′=C 6H 5) is stabilised by the chelating effect of the organometallic π-tweezer [Ti](CCSiMe 3) 2, giving rise to a trigonal-planar environment at the nickel atom. The early (Ti) and late (Ni) transition metal centers are thereby bridged via the σ- and π-bound alkynyl groups Me 3SiCC. The influence of the different sterical demanding phosphites onto the [Ti](CCSiMe 3) 2 framework will be discussed.

Bis-bipyridine hexa-aza-macrocycle complexes of zinc(II) and nickel(II) and the catalytic reduction of carbon dioxide

Aza-macrocyclic complexes have gained importance in catalysis for the activation of small molecules, like carbon dioxide. Bis-bipyridine hexa-aza-macrocycles efficiently co-ordinate as a tetradentate ligand, to give complexes of Zn(II), Ni(II) and other transition metal ions that are essentially planar. Spectroscopic, electrochemical and chemical characterizations of these systems are presented in this article. Electrochemical studies performed in a carbon dioxide atmosphere render preliminary information about its electrocatalytical reduction. Quantum chemical calculations are used to understand the origin of the manifested properties of both the ligands and the metal complexes. They show, in this case, the importance of delocalized π interactions, which are responsible for their different structural and electronic characteristics in protic and non-protic media.

Three-Dimensional Open-Framework Nickel Aluminophosphate [NiAlP2O8][C2N2H9]: Assembly of One-Dimensional AlP2O83- Chains through [NiO5N] Octahedra

A 3-D open-framework nickel aluminophosphate [NiAlP2O8][C2N2H9] has been solvothermally synthesized using ethylene glycol as the solvent and ethylenediamine as the template. Its structure is assembled through 1-D AlP2O83- chains with corner-sharing 4-MRs via transition metal Ni2+ ions. The 1-D AlP2O83- chains are connected through octahedral Ni atoms, which are coordinated to the terminal oxygens of 1-D AlP2O83- chains and the amino groups of the template. Infinite Ni−O−Ni chains are formed along the [001] direction.

Photoionization of methylphenothiazine in transition metal containing silicoaluminophosphates

Photoionization of methylphenothiazine was studied in different pore size silicoaluminophosphate microporous materials at room temperature. The photoyield of methylphenothiazine cation radical was enhanced by an order of magnitude or more by incorporation of Ni, Co and Cu transition metal ions as electron acceptors into framework sites or ion exchange sites of the microporous materials. Nickel ions had stronger effects on the photoyield than the others. The photoyield also increased with the silicoaluminophosphate pore size.

Surface reaction kinetics on the atomic scale: studies by means of pulsed field desorption mass spectrometry

This paper reviews the development of pulsed field desorption mass spectrometry (PFDMS) towards a quantitative analytical tool for kinetic studies of elemental steps in surface chemical reactions. After a short introduction into the methodical approach, with emphasis on time-resolved studies both in the presence and in the absence of an electric field, case studies are presented including (i) the thermal equilibration of nitric oxide adsorption on Pt(111), (ii) the decomposition of methanol on Rh surfaces, and (iii) the formation of Ni–carbonyls by reaction of carbon monoxide with Ni and other transition metals. It will be demonstrated that insight into relevant mechanisms is obtained by detection of reactive intermediates and that reliable kinetic data is accessible from measurements of characteristic relaxation times.

Infrared Multiphoton Dissociation of Transition Metal Containing Ions: MCnH2n+ (M = Fe, Co, Ni; n = 2−5)

The infrared multiphoton dissociation (IRMPD) processes of groups 8−10 (Fe, Co, Ni) transition metal ion complexes containing acetylene and alkenes were investigated. Of the 30 ions studied, all but four were found to be photoactive at 944 cm-1, the wavelength of the CO2 infrared laser employed. Most of the ions were observed to yield one photodissociation product, as is typical for IRMPD. Ironacyclopentane, nickelacyclopentane, Co(isobutene)+, and Ni(isobutene)+, however, were observed to give multiple products. This observation is a result of kinetic and thermodynamic factors, and it gives information about the potential energy surface of the dissociating ion. More specifically, activation barrier heights leading to the product ions can be probed. Sustained off-resonance irradiation, an experiment designed to mimic infrared activation, was also performed on these ions, yielding results in good agreement with the infrared results.

Formula omitted] X-ray intensity ratios of Fe, Co, Ni, Cu, Mo, Ru, Rh and Pd in equiatomic aluminides

K β K α X-ray intensity ratios of Fe, Co, Ni, Cu, Mo, Ru, Rh and Pd transition metals in equiatomic aluminides have been measured following excitation by 59.54 keV γ-rays from a 200mCi 241Am point-source. In the case of 3 d metal aluminides we find significant deviation in the K β K α ratio from the pure metal value. The maximum deviation observed in the case of cobalt can be accounted by the transfer of 2.48 ± 0.19 electrons both from the (4 s, 4 p) states of the transition metal as well as (3 s, 3 p) states of aluminium to the 3 d state of cobalt. For Fe, Ni and Cu the charge transfer amounts to 1.58 ± 0.20, 0.79 ± 0.21 and 1.08 ± 0.33 respectively. For the 4 d metal aluminides we find an increase in the K β K α ratio by about 4% for Mo and Ru whereas for Rh and Pd almost no difference from the pure metal value is observed. Fresh calculations are needed for explaining the observed increase in the K β K α ratios of Mo and Ru.

Formation of Nanostructural Materials Induced by Mechanical Processings (&lt;I&gt;Overview&lt;/I&gt;)

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).