M. Bouchear - Academia.edu (original) (raw)

Papers by M. Bouchear

Materials Chemistry and Physics, 1998

Materials Chemistry and Physics, 2004

The analysis of dilatometric and calorimetric curves, completed by optical microscopy observation... more The analysis of dilatometric and calorimetric curves, completed by optical microscopy observations, permitted to follow the kinetics and the morphology changes of ␤-phase particles during ageing of Al-12 wt.% Mg alloy. It is now well established that ␤-phase particles, which are semi-coherent and metastable, appear initially in a globular shape, transform into thin needles, then into particles of the equilibrium ␤-phase after a long ageing time, as predicted by the phase diagram. In addition, ␤ and ␤-phases are formed and dissolved successively and independently one of the other, during non-isothermal ageing.

Materials Chemistry and Physics, 2008

The ordering iron aluminide alloys such as Fe 3 Al and FeAl which exhibit D0 3 and B2 ordered str... more The ordering iron aluminide alloys such as Fe 3 Al and FeAl which exhibit D0 3 and B2 ordered structures have received considerable attention for their unique properties and wide range of applications. It is well-known that the mechanical properties are a function of the order degree of the materials; therefore, it is important to know the effect of ternary additions on the ordering behaviour of these materials for improving the mechanical properties by alloying elements. The aim of the present study was to investigate the chromium addition effect on B2 → D0 3 order transition utilizing differential scanning calorimetry (DSC), dilatometric analysis and microhardeness measurements and to estimate the activation energy and the Avrami exponent n of D0 3 phase. The thermal analysis and the determination of kinetics parameters of Fe-28 at.% Al-2 at.% Cr and Fe-28 at.% Al-5 at.% Cr alloys have shown that the effects of chromium addition are to stabilize the B2 ordered phase and to make the B2 → D0 3 transition slower than in the binary Fe-28 at.% Al alloy.

Journal of Alloys and Compounds, 2001

Philosophical Magazine A, 1996

ABSTRACT

Un nouveau systeme tout ceramique a base de disilicate de lithium, l’IPS Empress 2 a recemment et... more Un nouveau systeme tout ceramique a base de disilicate de lithium, l’IPS Empress 2 a recemment ete developpe pour repondre aux besoins cliniques, tout en se rapprochant davantage de l’aspect des dents naturelles. L'objectif de ce travail est de presenter les etapes cliniques et de laboratoire qui ont permis chez des patients, la realisation dans le secteur anterieur des incisives, des restaurations prothetiques fixees avec cette nouvelle technique.

Notre etude a porte sur des echantillons de l'alliage Al-4,5(% masse) Cu homogeneises, trempe... more Notre etude a porte sur des echantillons de l'alliage Al-4,5(% masse) Cu homogeneises, trempes puis soumis a differents traitements thermiques de vieillissement apres bombardement avec des rayons γ. Nous montrons l'effet du rayonnement sur l'apparition des phases precipitees, en utilisant differentes methodes experimentales, essentiellement la diffraction des rayons X (DRX), l'analyse calorimetrique differentielle (DSC), les mesures de micro-durete et la microscopie optique. Les resultats obtenus par l'analyse calorimetrique differentielle (DSC), nous ont permis de constater l'effet du rayonnement y seulement pour le vieillissement inferieur a 300°C ou la phase presente est coherente avec la matrice, et de separer les pics de dissolution des zones G.P.1 et G.P.2. Cependant les vieillissements a hautes temperatures, ou les phases precipitees sont semi-coherentes ou incoherentes, ne permettent de detecter aucun effet de rayonnement. L'examen microscopique m...

International Journal of Materials Research, 1996

The autocatalytical continuous reaction in Al-8 wt. % Mg alloy, due to heterogeneous nucleation a... more The autocatalytical continuous reaction in Al-8 wt. % Mg alloy, due to heterogeneous nucleation and growth into grains, is a reversible phenomenon because the dissolution of precipitated particles is also a heterogeneous reaction. The study of the defect called rosette which leads to these heterogeneous precipitation and heterogeneous dissolution reactions has shown that it is difficult to confirm precisely its origin. It is not the concentration of a given element because microanalysis (line scan, point counting and X-ray image) has not shown any enrichment in this element, and microhardness measurements give the same value in different regions of the matrix (with and without rosettes). However, the observation of a complex network of dislocations confirm the idea that rosettes are probably a steady structure defect of this type.

The north-east area of Constantine has a very complex geological setting. The variety of sediment... more The north-east area of Constantine has a very complex geological setting. The variety of sedimentary rocks such as sandstone and clay in abundance, represent a big importance in the industry and road infrastructure. The X-ray diffraction (XRD) analysis, Scanning Electron Microscopy SEM/EDS, FTIR spectroscopy of sandstone and clay are required for qualitative and quantitative analysis of the existing phases. In addition, chemical analysis of the same samples is required to confirm the XRD, EDS (Energy Dispersive X ray Spectroscopy) and FTIR spectroscopy results. The results of this multidisciplinary study, obtained by various analytical techniques, show a good agreement on the existing phases.

Metallurgia Italiana, 2008

The effect of plastic deformation by wire drawing on structure and properties of an industrial el... more The effect of plastic deformation by wire drawing on structure and properties of an industrial electric aluminum wire has been studied. Some heat treatments were applied on the drawn wires. For this investigation, different techniques were used: optical microscopy, transmission electron microscopy, hardness measurements and differential scanning calorimetry. We have observed texture structure along axis wire after the wire drawing process. This cold plastic deformation causes a phenomenon of material consolidation. However, the heat treatments applied on drawn wires lead to recrystallization phenomenon. We have found that in low temperature, the recrystallization reaction is observed only for reduction by wire drawing greater than 30 %.

Journal of Electronic Materials, 2016

The aim of this paper is a comparative study of structural stability and mechanical and optical p... more The aim of this paper is a comparative study of structural stability and mechanical and optical properties of fluorapatite (FA) (Ca5(PO4)3F) and lithium disilicate (LD) (Li2Si2O5), using the first principles pseudopotential method based on density functional theory (DFT) within the generalized gradient approximation (GGA). The stability of fluorapatite and lithium disilicate compounds has been evaluated on the basis of their formation enthalpies. The results show that fluorapatite is more energetically stable than lithium disilicate. The independent elastic constants and related mechanical properties, including bulk modulus (B), shear modulus (G), Young’s modulus (E) and Poisson’s ratio (ν) as well as the Vickers hardness (Hv), have been calculated for fluorapatite compound and compared with other theoretical and experimental results. The obtained values of the shear modulus, Young’s modulus and Vickers hardness are smaller in comparison with those of lithium disilicate compound, implying that lithium disilicate is more rigid than fluorapatite. The brittle and ductile properties were also discussed using B/G ratio and Poisson’s ratio. Optical properties such as refractive index n(ω), extinction coefficient k(ω), absorption coefficient α(ω) and optical reflectivity R(ω) have been determined from the calculations of the complex dielectric function ε(ω), and interpreted on the basis of the electronic structures of both compounds. The calculated values of static dielectric constant ε1(0) and static refractive index n(0) show that the Li2Si2O5 compound has larger values compared to those of the Ca5(PO4)3F compound. The results of the extinction coefficient show that Li2Si2O5 compound exhibits a much stronger ultraviolet absorption. According to the absorption and reflectivity spectra, we inferred that both compounds are theoretically the best visible and infrared transparent materials.

International Journal of Modern Physics B, 2012

Philosophical Magazine A, 1996

ABSTRACT

Materials Chemistry and Physics, 1998

Materials Chemistry and Physics, 2004

Journal of Alloys and Compounds, 2001

Materials Chemistry and Physics, 2008

Materials Chemistry and Physics, 1998

Materials Chemistry and Physics, 2004

The analysis of dilatometric and calorimetric curves, completed by optical microscopy observation... more The analysis of dilatometric and calorimetric curves, completed by optical microscopy observations, permitted to follow the kinetics and the morphology changes of ␤-phase particles during ageing of Al-12 wt.% Mg alloy. It is now well established that ␤-phase particles, which are semi-coherent and metastable, appear initially in a globular shape, transform into thin needles, then into particles of the equilibrium ␤-phase after a long ageing time, as predicted by the phase diagram. In addition, ␤ and ␤-phases are formed and dissolved successively and independently one of the other, during non-isothermal ageing.

Materials Chemistry and Physics, 2008

The ordering iron aluminide alloys such as Fe 3 Al and FeAl which exhibit D0 3 and B2 ordered str... more The ordering iron aluminide alloys such as Fe 3 Al and FeAl which exhibit D0 3 and B2 ordered structures have received considerable attention for their unique properties and wide range of applications. It is well-known that the mechanical properties are a function of the order degree of the materials; therefore, it is important to know the effect of ternary additions on the ordering behaviour of these materials for improving the mechanical properties by alloying elements. The aim of the present study was to investigate the chromium addition effect on B2 → D0 3 order transition utilizing differential scanning calorimetry (DSC), dilatometric analysis and microhardeness measurements and to estimate the activation energy and the Avrami exponent n of D0 3 phase. The thermal analysis and the determination of kinetics parameters of Fe-28 at.% Al-2 at.% Cr and Fe-28 at.% Al-5 at.% Cr alloys have shown that the effects of chromium addition are to stabilize the B2 ordered phase and to make the B2 → D0 3 transition slower than in the binary Fe-28 at.% Al alloy.

Journal of Alloys and Compounds, 2001

Philosophical Magazine A, 1996

ABSTRACT

Un nouveau systeme tout ceramique a base de disilicate de lithium, l’IPS Empress 2 a recemment et... more Un nouveau systeme tout ceramique a base de disilicate de lithium, l’IPS Empress 2 a recemment ete developpe pour repondre aux besoins cliniques, tout en se rapprochant davantage de l’aspect des dents naturelles. L'objectif de ce travail est de presenter les etapes cliniques et de laboratoire qui ont permis chez des patients, la realisation dans le secteur anterieur des incisives, des restaurations prothetiques fixees avec cette nouvelle technique.

Notre etude a porte sur des echantillons de l'alliage Al-4,5(% masse) Cu homogeneises, trempe... more Notre etude a porte sur des echantillons de l'alliage Al-4,5(% masse) Cu homogeneises, trempes puis soumis a differents traitements thermiques de vieillissement apres bombardement avec des rayons γ. Nous montrons l'effet du rayonnement sur l'apparition des phases precipitees, en utilisant differentes methodes experimentales, essentiellement la diffraction des rayons X (DRX), l'analyse calorimetrique differentielle (DSC), les mesures de micro-durete et la microscopie optique. Les resultats obtenus par l'analyse calorimetrique differentielle (DSC), nous ont permis de constater l'effet du rayonnement y seulement pour le vieillissement inferieur a 300°C ou la phase presente est coherente avec la matrice, et de separer les pics de dissolution des zones G.P.1 et G.P.2. Cependant les vieillissements a hautes temperatures, ou les phases precipitees sont semi-coherentes ou incoherentes, ne permettent de detecter aucun effet de rayonnement. L'examen microscopique m...

International Journal of Materials Research, 1996

The autocatalytical continuous reaction in Al-8 wt. % Mg alloy, due to heterogeneous nucleation a... more The autocatalytical continuous reaction in Al-8 wt. % Mg alloy, due to heterogeneous nucleation and growth into grains, is a reversible phenomenon because the dissolution of precipitated particles is also a heterogeneous reaction. The study of the defect called rosette which leads to these heterogeneous precipitation and heterogeneous dissolution reactions has shown that it is difficult to confirm precisely its origin. It is not the concentration of a given element because microanalysis (line scan, point counting and X-ray image) has not shown any enrichment in this element, and microhardness measurements give the same value in different regions of the matrix (with and without rosettes). However, the observation of a complex network of dislocations confirm the idea that rosettes are probably a steady structure defect of this type.

The north-east area of Constantine has a very complex geological setting. The variety of sediment... more The north-east area of Constantine has a very complex geological setting. The variety of sedimentary rocks such as sandstone and clay in abundance, represent a big importance in the industry and road infrastructure. The X-ray diffraction (XRD) analysis, Scanning Electron Microscopy SEM/EDS, FTIR spectroscopy of sandstone and clay are required for qualitative and quantitative analysis of the existing phases. In addition, chemical analysis of the same samples is required to confirm the XRD, EDS (Energy Dispersive X ray Spectroscopy) and FTIR spectroscopy results. The results of this multidisciplinary study, obtained by various analytical techniques, show a good agreement on the existing phases.

Metallurgia Italiana, 2008

The effect of plastic deformation by wire drawing on structure and properties of an industrial el... more The effect of plastic deformation by wire drawing on structure and properties of an industrial electric aluminum wire has been studied. Some heat treatments were applied on the drawn wires. For this investigation, different techniques were used: optical microscopy, transmission electron microscopy, hardness measurements and differential scanning calorimetry. We have observed texture structure along axis wire after the wire drawing process. This cold plastic deformation causes a phenomenon of material consolidation. However, the heat treatments applied on drawn wires lead to recrystallization phenomenon. We have found that in low temperature, the recrystallization reaction is observed only for reduction by wire drawing greater than 30 %.

Journal of Electronic Materials, 2016

The aim of this paper is a comparative study of structural stability and mechanical and optical p... more The aim of this paper is a comparative study of structural stability and mechanical and optical properties of fluorapatite (FA) (Ca5(PO4)3F) and lithium disilicate (LD) (Li2Si2O5), using the first principles pseudopotential method based on density functional theory (DFT) within the generalized gradient approximation (GGA). The stability of fluorapatite and lithium disilicate compounds has been evaluated on the basis of their formation enthalpies. The results show that fluorapatite is more energetically stable than lithium disilicate. The independent elastic constants and related mechanical properties, including bulk modulus (B), shear modulus (G), Young’s modulus (E) and Poisson’s ratio (ν) as well as the Vickers hardness (Hv), have been calculated for fluorapatite compound and compared with other theoretical and experimental results. The obtained values of the shear modulus, Young’s modulus and Vickers hardness are smaller in comparison with those of lithium disilicate compound, implying that lithium disilicate is more rigid than fluorapatite. The brittle and ductile properties were also discussed using B/G ratio and Poisson’s ratio. Optical properties such as refractive index n(ω), extinction coefficient k(ω), absorption coefficient α(ω) and optical reflectivity R(ω) have been determined from the calculations of the complex dielectric function ε(ω), and interpreted on the basis of the electronic structures of both compounds. The calculated values of static dielectric constant ε1(0) and static refractive index n(0) show that the Li2Si2O5 compound has larger values compared to those of the Ca5(PO4)3F compound. The results of the extinction coefficient show that Li2Si2O5 compound exhibits a much stronger ultraviolet absorption. According to the absorption and reflectivity spectra, we inferred that both compounds are theoretically the best visible and infrared transparent materials.

International Journal of Modern Physics B, 2012

Philosophical Magazine A, 1996

ABSTRACT

Materials Chemistry and Physics, 1998

Materials Chemistry and Physics, 2004

Journal of Alloys and Compounds, 2001

Materials Chemistry and Physics, 2008