Dissertation (PhD)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: This study comprises the preparation and characterisation of various novel organometallic species of gold(I) by employing a range of anionic group 6 metal Fischer-type carbene complexes and group 6 metal-acyl complexes as synthons of the organic moieties introduced to the gold(I) electrophiles. The main objectives of this work are to develop the use of Fischer-type carbene complexes as synthons in the preparation of novel organometallic species along unusual reaction pathways and, in doing so, to expand the organometallic chemistry of gold(I), especially Au-C bond formation reactions. By reacting various β-CH acidic Fischer-type alkoxy/dialkylamino/ alkthio(methyl)carbene complexes, first with a base, and then with a gold(I) electrophile (Ph3PAu+), easy access to vinyl ether/dialkylamine/thioether complexes of gold(I) coordinated to M(CO)5 (M = Cr, Mo, W) fragments, is obtained. When methyl alkoxy- or dialkylaminocarbene complexes are employed, coordination of the novel alkoxyvinyl-gold(I)PPh3 and dialkylaminovinyl-gold(I)PPh3 species to the M(CO)5 fragments occurs in an asymmetrical fashion through the vinyl functionalities of the novel gold(I) species. This usually unstable coordination mode for vinyl ethers is stabilised by delocalisation of partial positive charges from the α-gold vinyl carbon atoms to either the gold(I)PPh3 fragment [for η2-{alkoxyvinyl-gold(I)PPh3}M(CO)5 complexes] or the nitogen atoms of the vinyl amine group [for η2-{dialkylaminovinylgold( I)PPh3}M(CO)5 complexes]. In the latter complexes this delocalisation occurs to such an extent that these complexes are best described as zwitterions. The corresponding negative charges in the bimetallic complexes reside on the M(CO)5 fragments. As a representative example, uncoordinated ethoxyvinyl-gold(I)PPh3 was isolated in high yield via a ligand replacement reaction with PPh3. When Fischer-type alkthio(methyl)carbene complexes are employed in this conversion, novel sulphur coordinated {alkthiovinyl-gold(I)PPh3}Cr(CO)5 complexes are formed.The reaction mechanism involved in these conversions is believed to be the gold(I) analogue of the hydrolysis of Fischer-type carbene complexes. In this mechanism the bimetallic η2-vinyl ether coordinated {alkoxyvinyl-gold(I)PPh3}M(CO)5 complexes represent stabilised gold(I) analogues of postulated transition states in the hydrolytic decomposition of Fischer-type alkoxycarbene complexes. The term aurolysis is conceived to describe the conversion when Ph3PAu+ is employed as electrophile instead of H+. The formation of the bimetallic η2-vinyl ether coordinated complexes in the current conversion, furthermore, strongly supports the existence of similar transition states in the hydrolytic decomposition of Fischer-type alkoxycarbene complexes. This mechanism is also accepted for the formation of analogous η2-{dialkylaminovinyl-gold(I)PPh3}M(CO)5 and {alkthiovinyl-gold(I)PPh3}-S Cr(CO)5 complexes when β-CH deprotonated Fischer-type dialkylamino- and alkthiocarbene complexes are employed in this reaction. The reaction of anionic group 6 metal-acyl complexes and their nitrogen analogues, N-deprotonated Fischer-type aminocarbene complexes, leads to the formation of acylgold(I) and novel imidoylgold(I) complexes coordinated to M(CO)5 (M = Cr, W) fragments. In the previous complexes poor stabilisation of the M(CO)5 fragments allows halide anions to readily form ionic adducts with these groups. This characteristic of these products provides a useful reaction pathway to the first example of a free acylgold(I) complex, benzoyl-AuPPh3. Coordination of the imine nitrogen atom to the M(CO)5 fragments in the analogous bimetallic imidoylgold(I)-M(CO)5 complexes is much stronger. These complexes are remarkably stable and could even be effectively isolated by means of low temperature silica gel chromatography. As a preliminary reaction mechanism for this conversion we propose a mechanism that is closely related to the aurolysis mechanism described above. The only difference is that, instead of formal reductive elimination of vinyl ethers/amine/thioether complexes of gold(I) from the M(CO)5 fragments, acyl and imidoyl complexes of gold(I) are produced in this step. Furthermore, the (Z)- stereoisomers of the bimetallic imidoylgold(I)-M(CO)5 complexes generated in this conversion are exclusively obtained.A second N-deprotonation-auration reaction sequence performed on suitable examples of the bimetallic imidoylgold(I)-M(CO)5 complexes yields, as the only isolable product, a novel triangular Au2Cr cluster complex, cis-{η2-(Ph3PAu)2} PPh3Cr(CO)4. This complex is the isolobal equivalent for the unstable molecular hydrogen complex, (η2-H2)PPh3Cr(CO)4, and exhibits the shortest known Au-Au separation between two gold atoms in cluster complexes of the type Au2M. Finally, two novel and vastly different molecular structures of closely related anionic benzoylpentacarbonyl tungstates, one with Li+ as counterion and another in which exactly half the Li+-cations have been replaced by protons, highlight the importance of hydrogen bonding and ion-dipole interactions in determining the solid state structure of such complexes. / AFRIKAANSE OPSOMMING: Hierdie studie behels die bereiding en karakterisering van verskeie nuwe organometaalkomplekse van goud(I). Hierdie komplekse is berei deur gebruik te maak van n wye reeks anioniese groep 6 metaal Fischer-tipe karbeenkomplekse asook anioniese groep 6 metaal asielkomplekse as sintetiese ekwivalente vir die organiese fragmente wat gedurende die sintese aan die goud atoom gebind word. Die hoofdoel van hierdie studie is om die gebruik van Fischer-tipe karbeenkomplekse as sintetiese voorgangers in die bereiding van nuwe organometaalverbindings te ontwikkel en om sodoende ook die organometaalchemie van goud verder uit te bou. Veral die ontwikkeling van nuwe sintetiese metodologieë vir die bereiding van Au-C bindings is hier van belang. Verskeie Fischer-tipe alkoksie-/dialkielamino-/alktio-(metiel)karbeenkomplekse met suuragtige waterstofatome geleë op die β-metallo-koolstofatoom is eers onomkeerbaar gedeprotoneer. Byvoeging van die goud(I) elektrofiel, Ph3PAu+, lei - volgens n ongewone reaksiemeganisme - tot die vorming van onderskeie vinieleter-, dialkielvinielamien- en vinieltioeterkomplekse van goud(I). Hierdie komplekse is verder ook op verskillende wyses aan M(CO)5 fragmente (M = Cr, Mo, W) gekoördineer. Die vinieleter- en vinielamienkomplekse van goud(I), wat vorm wanneer alkoksie- en dialkielaminokarbeenkomplekse onderskeidelik in hierdie sintese aangewend word, koördineer onsimmetries deur hulle viniel dubbelbindings aan die vrygestelde M(CO)5-groepe. Hierdie normaalweg onstabiele vorm van vinieleterkoördinasie, word gestabiliseer deur delokalisering van positiewe lading vanaf die α-goud viniel koolstofatoom na die AuPPh3-fragment [vir die η2-{alkoksievinielgoud( I)PPh3}M(CO)5 komplekse] óf na die stikstofatoom van die dialkielvinielamien groep [vir die η2-{dialkielaminoviniel-goud(I)PPh3}M(CO)5 komplekse]. Laasgenoemde komplekse kan as zwitterione beskryf word. Die onderskeie negatiewe ladings in hierdie komplekse bevind hulle hoofsaaklik op die M(CO)5 groepe. Sterk koördinerende ligande (bv. PPh3) verplaas die onsimmetriese viniel eter vanaf die M(CO)5-fragment. Só kon, as n voorbeeld, die vrye etoksievinielgoud( I)PPh3-kompleks met n hoë opbrengs berei word. Wanneer β-gedeprotoneerdeFischer-tipe tiokarbeenkomplekse met Ph3PAu+ reageer, vorm swawel gekoördineerde {tioviniel-goud(I)PPh3}Cr(CO)5 bimetalliese komplekse in stede van die π-komplekse. Dit word voorgestel dat in die bogenoemde reaksies die goud(I)elektrofiel dieselfde rol vervul as die proton gedurende die hidrolise van Fischer-tipe alkoksiekarbeenkomplekse. Die bimetalliese, η2-vinieleter-gekoördineerde {alkoksieviniel-goud(I)PPh3}M(CO)5-komplekse hier berei verteenwoordig dus stabiele goud(I) analoë van voorgestelde tusseprodukte in so ’n meganisme. Die term aurolise word voorgestel om die geval waar Ph3PAu+ in stede van H+ as elektrofiel aangewend word te beskryf. Die vorming van bimetalliese, η2-vinieletergeko ördineerde komplekse in die huidige reaksie ondersteun die moontlike vorming van die voorgestelde tussenprodukte tydens die hidrolise van Fischer-tipe alkoksie(metiel)karbeenkomplekse. ’n Soortgelyke meganisme kan ook gebruik word om die vorming van die η2-{dialkiellamienviniel-goud(I)PPh3}M(CO)5- en {alktioviniel-goud(I)PPh3}-S Cr(CO)5-komplekse vanuit β-CH gedeprotoneerde Fischer-tipe dialkielamino- en tiokarbeenkomplekse en Ph3PAuCl te interpreteer. Die reaksie van anioniese groep 6 oorgangsmetaal metaal-asielkomplekse en hulle stikstofanaloë, N-gedeprotoneerde Fischer-tipe aminokarbeenkomplekse, lewer onderskeidelik asiel- en imidoielkomplekse van goud(I) wat aan M(CO)5 fragmente (M = Cr, W) koördineer. Die goud(I)asiel-M(CO)5 koördinasie deur die asielsuurstofatoom is baie swak en die M(CO)5-eenheid in hierdie komplekse word maklik deur haliedanione en sekere oplosmiddel molekules verplaas. Die haliedanione vorm anioniese addukte met the M(CO)5 fragmente. Hierdie eienskap van die bimetalliese komplekse verskaf sodoende n gerieflike sintetiese roete na die eerste voorbeeld van n vrye asielgoud(I)-kompleks, bensoiel-AuPPh3. Koördinasie van die imienstikstofatoom aan M(CO)5-groepe in die bg. imidoielkomplekse is egter veel sterker. Die bimetalliese {imidoielgoud(I)}M(CO)5-komplekse is verbasend stabiel en kan selfs effektief deur middel van lae temperatuur SiO2-kolomkromatografie geïsoleer word. n Soortgelyke reaksie meganisme as wat voorgestel word vir die aurolise van Fischer-tipe karbeenkomplekse word voorgestel vir hierdie reaksie. Die enigste verskil is dat die formele reduktiewe eliminasie van n viniel-eter, -amien of -tioeter vervang word met die vorming van asiel- of imidoielkomplekse van goud(I). Verder word die (Z)-isomere van die bimetalliese {imidoielgoud(I)}M(CO)5-komplekse uitsluitlik in hierdie reaksie verkry. Wanneer geskikte voorbeelde van bimetalliese {imidoielgoud(I)}M(CO)5-komplekse n tweede keer gedeprotoneer word en gereageer word met Ph3PAuCl, is die enigste isoleerbare produk van die reaksie n driehoekige Au2Cr troskompleks, nl. cis-{η2- (Ph3PAu)2}PPh3Cr(CO)4. Hierdie verbinding dien as n isolobale model vir die onstabiele molekulêre waterstof kompleks , (η2-H2)PPh3Cr(CO)4, en besit verder die kortste Au-Au afstand tussen twee goud atome in driehoekige troskomplekse wat nog tot dusvêr gerapporteer is. Laastens is die kristalstrukture van twee nou verwante anioniese {bensoiel}W(CO)5- komplekse bepaal. Die enigste verskil tussen die hierdie twee verbindings is dat die een slegs Li+ as teenioon bevat terwyl presies die helfte van die Li+-teenione in die tweede struktuur deur protone verplaas is. Hierdie klein verskil in samestelling veroorsaak egter drastiese verskille in die kristalstrukture van hierdie verbindings. Die belangrikheid van waterstof bindings en ioon-dipool interaksies in die bepaling van die vastetoestandstrukture van sulke verbindings word hierdeur beklemtoon.

Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: Please refer to fulltext for abstract / AFRIKAANSE OPSOMMING: Sien volteks vir opsomming

An exploration of some early transition metal (oxy) fluoride systems using solvothermal techniques has been carried out. 30 novel materials have been synthesised, which fall into three classes based on different metal centres; vanadium (21), molybdenum (5) and niobium (4). Some of these also contain secondary metal centres, namely copper (22) and zinc (1). Simultaneously, the relationship between the SHG values and the crystal structures of the hilgardites family members Pb₂B₅O₉Cl, Pb₂B₅O₉Br, Sr₂B₅O₉Cl and Ba₂B₅O₉Cl was investigated. In particular, the Pb–containing members of the hilgardite family of borate halides exhibit an abnormally large non–linear optical response, which was analysed based on neutron powder diffraction. Using solvothermal synthesis in HF–containing media, 21 novel vanadium oxyfluorides containing interesting structural features, were synthesised at 160˚C using a range of organo-amine compounds as a ligand, template, linker or structure directing agent. The architectures of the crystal structures may be categorised into; four clusters including monomeric vanadium units, five clusters including vanadium dimers, eight 1–D chains, two 2–D layers and two 3–D networks. ‘Composition–space’ diagrams with three components were used to study the effect of stoichiometry changes of reactants and to map out the crystallisation fields. The combination of early (Nb⁵⁺, Mo⁶⁺) and late (Cu²⁺) transition metals with different organo-amines produced nine novel compounds incorporating monomers, chains and 2– D interpenetrated networks. The chains and layers were synthesised from a systematic series of reactions at 160˚C and can be subdivided into four pairs, the topologies of which are essentially unique to each ligand, containing in each case a Cu–based cationic species, but alternately either [MoO₂F₄]²⁻ or [NbOF₅]²⁻, in an isomorphous manner, as the anionic moiety. The overall structures of these materials reflect the influence of the organo–amine ligands. The materials have been studied for their magnetic properties and characterised by thermogravimetric analysis, Rietveld refinement and elemental analysis where relevant.

In this thesis, new approaches to direct trace metals analysis of solid samples by inductively coupled plasma spectroscopy were investigated using laser ablation and thermal vaporization systems for solid sample introduction of biological, environmental, and pharmaceutical samples. / Laser ablation with inductively coupled plasma atomic emission spectroscopy (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS) was applied to pharmaceutical tablets. Precision of analysis depended on laser parameters and could be improved using signal ratios. The feasibility of using laser ablation-ICP-MS for detecting natural levels of mercury along a single human hair strand was also demonstrated. / As well, the use of an induction-heating electrothermal vaporizer (IH-ETV) coupled to an ICP-MS was successful in determining mercury concentrations in a single human hair strand. Methodologies for multielement analysis of powdered hair were also explored using IH-ETV-ICP-MS. While calibration by reference hair materials showed promise, calibration methods by liquid standards were not suitable for any element. Detection limits achieved for most elements were below natural levels found in human hair. / IH-ETV-ICP-AES was also applied to the analysis of analyze-laden chromatographic powder. This study showed potential problems that may arise due to the methodology taken to analyze such materials. Finally, recommendations for future investigations and methodologies for laser ablation and thermal vaporization are discussed.

The scope of these studies was two-fold: to evaluate high pressure homogenized slurries as a rapid means of screening wood pulps for their Cu, Mn and Fe content and to evaluate the high pressure homogenization in combination with chelating agents or enzymatic digestion for the liberation/extraction of metal ions from this matrix. / Cu, Mn and Fe were determined successfully in pulp samples using high-pressure homogenization prior to slurry introduction-GF-AAS. The analysis time of the method from sample acquisition to determination was of the order of a few minutes per sample. / Different cellulose swelling/dissolution agents were evaluated for the generation of quasi-stable pulp suspensions, rich in cellulose. High-pressure homogenization alone or in combination with chelating agents or enzymatic digestion was also investigated as a means of quantitatively releasing these metal ions into the liquid phases. / A new model of homogenizer equipped with ceramic homogenizing valve with a few modifications was evaluated in terms of metal contamination levels within the final sample dispersion. (Abstract shortened by UMI.)

Introduction: The macroporous Amberlite XAD resins were coated with LIX-64N and examined for the rate of uptake of copper . XAD-7 was by far the best support and gave a satisfactory rate of uptake up to loadings of 60% (w/w). The specific surface area of XAD-7 was measured by the adsorption of methylene blue from aqueous solution. The area of the wetted resin was five times less than that of the dry resin. LIX-65N was purified and the anti isomer characterised using spectroscopic techniques . The rate of uptake of copper was not improved by use of purified LIX-65N or by addition of LIX-63. XAD-7 coated with LIX-65N was used in columns. Elution curves for copper showed negligible tailing, and rapid separations of copper from iron (111), nickel, cobalt and magnesium by selective absorption were achieved. Copper was concentrated from very dilute solution at a flow rate of 50 ml min -1 ,and a 99% recovery was obtained. The method was applied to the rapid determination of copper in brass and bronze. A series of long-chain hydroxamic acids were synthesised and tested for suitability as stationary phase on XAD-7. Oleohydroxamic acid and naphthenohydroxamic acid were the most promising. The r ate of uptake of copper was reduced by the use of nonylphenol or amyl alcohol as a diluent. The capacities for copper of the hydroxamic acids were less when supported on XAD-7 than when used as liquid ionexchangers. The distribution coefficients of cobalt, nickel, zinc, lead, vanadium, uranium, iron (111) and copper were measured as a function of pH. XAD-7 coated with oleohydroxamic acid was used in columns for the rapid separation of iron (111) from copper and of copper from nickel, cobalt, lead and zinc. Copper was concentrated from very dilute solution at a flow rate of 45 ml min -1 and a 100,8% recovery was obtained. Copper was successfully separated from nickel by selective elution. The elution curves obtained show negligible tailing. The resin loaded with oleohydroxamic acid lost capacity due to chemical instability. Naphthenohydroxamic acid supported on XAD-7 was not suitable for use in columns, because it was physically unstable.

No description available.

No description available.

Transition metal containing zeolites (zeolite A and ZSM-5) were prepared by addition of various transition metal containing substrates to zeolite synthesis gels. Crystal growth data were recorded in order to determine the influence of the transition metal species on the rate of crystal growth. X-ray diffraction, oxygen adsorption, FTIR and SEM were utilized to evaluate crystal purity. X-ray photoelectron spectroscopy (XPS), chemical analysis and electron microprobe analysis were performed in order to ascertain the position (intrazeolitic versus surface) and homogeneity of the transition metal. It was concluded that intrazeolitic transition metals were produced by the novel procedure presented in this work. 1-Hexene hydroformylation by rhodium zeolite A showed intrazeolitic rhodium to migrate to the external surface of the zeolite. However, in the presence of a solution and surface rhodium poison, intrazeolitic rhodium was found to hydroformylate 1-hexene exclusively to heptanal. Ruthenium containing zeolite A was evaluated under CO-hydrogenation conditions. No migration of intrazeolitic ruthenium to the external surface of the zeolite was observed over the course of the reaction. The product distribution obtained for this catalyst did not follow a log normal behavior. Also, loss of zeolite crystallinity was observed following the reaction. Cobalt ZSM-5 was evaluated under CO-hydrogenation conditions. No migration of cobalt to the external surface of the zeolite occurred. XPS analysis of the catalyst following various stages of the reaction indicated that intrazeolitic cobalt was not reduced to the zero valent state. Consequently, the non-zero valent cobalt was not capable of hydrogenating carbon monoxide. / Ph. D.

Les procédés de mise en forme des tôles métalliques sont largement utilisés dans l’industrie mécanique. La simulation numérique des opérations de mise en forme nécessite une caractérisation précise des modèles de comportement rhéologique des matériaux. Dans de nombreuses opérations de mise en forme des tôles métalliques telle que l’emboutissage, l’hydroformage, …, de grandes déformations et des vitesses de déformations dites intermédiaires peuvent être atteintes sous des états biaxiaux de déformation ou de contrainte. L’objectif de ce travail est de montrer le potentiel de l’essai de traction bi-axiale pour caractériser l’écrouissage des tôles métalliques pour de grandes déformations et dans une gamme de vitesse de déformation dite intermédiaire. A partir de simulations numériques, une forme optimale d’éprouvette en croix, permettant d’atteindre 30% de déformation plastique équivalente dans la zone centrale de l’éprouvette sous un chargement équibiaxial, a été proposée. Par la suite, des essais quasi-statiques et dynamiques de traction bi-axiale ont été réalisés sur la forme d’éprouvette proposée à partir d’une machine dédiée d’essais servo-hydraulique à quatre vérins. Dans un premier temps, le matériau choisi est un alliage d’aluminium AA5086 ne présentant pas de dépendance à la vitesse de déformation. Les déformations expérimentales sont déterminées à partir de la technique de corrélation d’images. L’écrouissage isotrope de différents modèles est identifié à partir d’une procédure inverse basée sur une modélisation éléments finis de l’essai de traction biaxiale. Trois critères de plasticité (Mises, Hill 48 et Bron et Besson) ont été successivement utilisés pour l’identification des paramètres des lois d’écrouissage. Les résultats obtenus montrent d’une part que la modélisation est très sensible au critère de plasticité choisi, et d’autre part que le critère de Bron et Besson permet d’obtenir une très bonne corrélation entre les courbes d’écrouissage identifiées à partir de l’essai bi-axial et de l’essai uni-axial. Pour les tests dynamiques bi-axiaux, les phénomènes de résonance du dispositif mécanique, générés à l’impact initial de début d’essai et matérialisés par de fortes oscillations du signal d’effort, sont atténués par l’interposition d’un élément en élastomère dans le système d’ancrage de chaque bras de l’éprouvette. Pour finir, la méthodologie d’identification proposée est appliquée à la caractérisation du comportement viscoplastique d’un acier dual phase DP600. Les courbes d’écrouissage identifiées à partir des essais bi-axiaux ont été comparées à celles obtenues par des essais uni-axiaux pour une gamme de vitesse de déformation allant de 10- 3s-1 à 101s-1. Le DP600 présente une même sensibilité à la vitesse de déformation quelque soit la sollicitation, uni-axiale ou bi-axiale. Les lois d’écrouissage de Ludwick et de Voce, identifiées jusqu’à 30% de déformation plastique équivalente sur la base de données expérimentales constituées des essais bi-axiaux, sont relativement proches. Les différences observées entre ces courbes d’écrouissage et celles identifiées à partir des essais de traction uni-axiaux montrent tout l’intérêt de l’essai de traction bi-axiale sur éprouvette en croix. / Sheet metal forming processes are widely adopted to produce panels, tubes, profiled parts in manufacturing industry. The numerical simulation of the forming processes requires accurate constitutive models of material. In many sheet metal working operations such as stamping, hydroforming, …, large strains and intermediate strain rates can be reached under biaxial strain or stress states. The objective of this work is to show the potential of the biaxial in-plane tensile test to characterize the hardening behaviour of metal sheets up to large strain levels. By numerical investigation, an optimal cruciform shape is designed to obtain large equivalent plastic strain, up to 30%, at the central zone under equi-biaxial strain path. As expected, the initial cracks of tested specimens are always observed at the central zone. Then, quasi-static and dynamic biaxial tensile tests on in-plane cross specimens have been performed on a dedicated servo-hydraulic machine. These biaxial tensile tests have been carried out on aluminium alloy AA5086 to validate the identification methodology of hardening behaviour under biaxial loading. This alloy has been chosen since its hardening behaviour is not dependent on the strain rate. Digital Image Correlation (DIC) technique is used for strain measurement. The parameters of isotropic hardening models are identified by inverse analysis based on the finite element model of the biaxial tensile test. Three yield criteria of Mises, Hill48 and Bron and Besson are compared for the parameter identification of different hardening laws. It is shown that the hardening law identified by biaxial test is precise only if an appropriate yield function is preliminarily determined. The biaxial flow stress curve identified with Bron and Besson yield function have been found in good agreement with the experimental flow stress curve obtained from uniaxial tensile tests. For biaxial tests at intermediate strain rates, damping layers are adopted to reduce oscillations on force versus time curves. The comparison of flow stress curves, identified from quasi-static and dynamic biaxial in-plane tensile tests on the non strain rate-dependent material AA5086, validates the identification methodology of strain-rate dependent hardening models. Finally, the proposed methodology is applied to the hardening characterization of a strain-rate dependent Dual Phase steel DP600 at room temperature. Identified biaxial flow stress curves have been compared with uniaxial ones for different strain rates ( . = 10-3s-1, 10-1s-1 and 101s-1). DP600 steel exhibits the same positive strain rate sensitivity for uniaxial and biaxial strain states. The biaxial flow stress curves identified on the basis of Ludwick and Voce hardening models are close, up to equivalent plastic strains of 30%. The benefits of the proposed methodology, based on a biaxial in-plane tensile test carried out on cross specimen, are clearly shown since the hardening behaviour identified in this case for large strains (up to 30%) is very different from the one identified from uniaxial tensile test on a smaller strain range.