The Experts below are selected from a list of 213 Experts worldwide ranked by ideXlab platform

Francesco Rosalbino - One of the best experts on this subject based on the ideXlab platform.

  • structural characterisation and corrosion resistance of ga Precious Metal Alloys formed by liquid solid reaction at room temperature
    Journal of Alloys and Compounds, 2001
    Co-Authors: M R Pinasco, Emma Paola Maria Virginia Angelini, E Cordano, Francesco Rosalbino
    Abstract:

    Abstract An attempt to eliminate Hg from dental amalgams was made by substituting it with low melting Ga-based Alloys, liquid at room temperature. However more information is needed on the influence of alloy composition and their questioned corrosion resistance. In this paper the reaction of some liquid Ga Alloys and some solid Precious Metal Alloys with different nobility was studied. Structural features, hardness and corrosion resistance of the obtained composite materials were investigated as a function of composition of the starting Alloys, liquid/solid ratio and different mixing methods. Every combination of the solid Precious Metal powders and the liquid Ga-Alloys gives rise to similar composite materials. The structure always consists of unreacted solid alloy particles embedded in a complex matrix composed of many reaction phases. The formation of some phases depends on the composition of the solid alloy, others originate all the time; however their topography and morphology may be different as well as their compositional range. The high porosity generally present in the composite materials markedly affects hardness values; nevertheless some prepared materials reach hardness comparable with the one of commercial amalgams. The nobility of the solid alloy and porosity percentage play a determinant role on the corrosion behaviour. In all cases the low corrosion resistance of the experimented materials may be attributed to a galvanic coupling between the reaction intermediate phases and the unreacted liquid alloy remained inside the pores.

  • Structural characterisation and corrosion resistance of Ga-Precious Metal Alloys formed by liquid–solid reaction at room temperature
    Journal of Alloys and Compounds, 2001
    Co-Authors: M R Pinasco, Emma Paola Maria Virginia Angelini, E Cordano, Francesco Rosalbino
    Abstract:

    Abstract An attempt to eliminate Hg from dental amalgams was made by substituting it with low melting Ga-based Alloys, liquid at room temperature. However more information is needed on the influence of alloy composition and their questioned corrosion resistance. In this paper the reaction of some liquid Ga Alloys and some solid Precious Metal Alloys with different nobility was studied. Structural features, hardness and corrosion resistance of the obtained composite materials were investigated as a function of composition of the starting Alloys, liquid/solid ratio and different mixing methods. Every combination of the solid Precious Metal powders and the liquid Ga-Alloys gives rise to similar composite materials. The structure always consists of unreacted solid alloy particles embedded in a complex matrix composed of many reaction phases. The formation of some phases depends on the composition of the solid alloy, others originate all the time; however their topography and morphology may be different as well as their compositional range. The high porosity generally present in the composite materials markedly affects hardness values; nevertheless some prepared materials reach hardness comparable with the one of commercial amalgams. The nobility of the solid alloy and porosity percentage play a determinant role on the corrosion behaviour. In all cases the low corrosion resistance of the experimented materials may be attributed to a galvanic coupling between the reaction intermediate phases and the unreacted liquid alloy remained inside the pores.

M R Pinasco - One of the best experts on this subject based on the ideXlab platform.

  • structural characterisation and corrosion resistance of ga Precious Metal Alloys formed by liquid solid reaction at room temperature
    Journal of Alloys and Compounds, 2001
    Co-Authors: M R Pinasco, Emma Paola Maria Virginia Angelini, E Cordano, Francesco Rosalbino
    Abstract:

    Abstract An attempt to eliminate Hg from dental amalgams was made by substituting it with low melting Ga-based Alloys, liquid at room temperature. However more information is needed on the influence of alloy composition and their questioned corrosion resistance. In this paper the reaction of some liquid Ga Alloys and some solid Precious Metal Alloys with different nobility was studied. Structural features, hardness and corrosion resistance of the obtained composite materials were investigated as a function of composition of the starting Alloys, liquid/solid ratio and different mixing methods. Every combination of the solid Precious Metal powders and the liquid Ga-Alloys gives rise to similar composite materials. The structure always consists of unreacted solid alloy particles embedded in a complex matrix composed of many reaction phases. The formation of some phases depends on the composition of the solid alloy, others originate all the time; however their topography and morphology may be different as well as their compositional range. The high porosity generally present in the composite materials markedly affects hardness values; nevertheless some prepared materials reach hardness comparable with the one of commercial amalgams. The nobility of the solid alloy and porosity percentage play a determinant role on the corrosion behaviour. In all cases the low corrosion resistance of the experimented materials may be attributed to a galvanic coupling between the reaction intermediate phases and the unreacted liquid alloy remained inside the pores.

  • Structural characterisation and corrosion resistance of Ga-Precious Metal Alloys formed by liquid–solid reaction at room temperature
    Journal of Alloys and Compounds, 2001
    Co-Authors: M R Pinasco, Emma Paola Maria Virginia Angelini, E Cordano, Francesco Rosalbino
    Abstract:

    Abstract An attempt to eliminate Hg from dental amalgams was made by substituting it with low melting Ga-based Alloys, liquid at room temperature. However more information is needed on the influence of alloy composition and their questioned corrosion resistance. In this paper the reaction of some liquid Ga Alloys and some solid Precious Metal Alloys with different nobility was studied. Structural features, hardness and corrosion resistance of the obtained composite materials were investigated as a function of composition of the starting Alloys, liquid/solid ratio and different mixing methods. Every combination of the solid Precious Metal powders and the liquid Ga-Alloys gives rise to similar composite materials. The structure always consists of unreacted solid alloy particles embedded in a complex matrix composed of many reaction phases. The formation of some phases depends on the composition of the solid alloy, others originate all the time; however their topography and morphology may be different as well as their compositional range. The high porosity generally present in the composite materials markedly affects hardness values; nevertheless some prepared materials reach hardness comparable with the one of commercial amalgams. The nobility of the solid alloy and porosity percentage play a determinant role on the corrosion behaviour. In all cases the low corrosion resistance of the experimented materials may be attributed to a galvanic coupling between the reaction intermediate phases and the unreacted liquid alloy remained inside the pores.

Shelley D. Minteer - One of the best experts on this subject based on the ideXlab platform.

  • Growth of Phthalocyanine Doped and Undoped Nanotubes Using Mild Synthesis Conditions for Development of Novel Oxygen Reduction Catalysts
    2016
    Co-Authors: Robert L. Arechederra, Kateryna Artyushkova, Plamen Atanassov, Shelley D. Minteer
    Abstract:

    ABSTRACT Precious Metal Alloys have been the predominant electrocatalyst used for oxygen reduction in fuel cells since the 1960s. Although performance of these catalysts is high, they do have drawbacks. The two main problems with Precious Metal Alloys are catalyst passivation and cost. This is why new novel catalysts are being developed and employed for oxygen reduction. This paper details the low temperature solvothermal synthesis and characterization of carbon nanotubes that have been doped with both iron and cobalt centered phthalocyanine. The synthesis is a novel low-temperature, supercritical solvent synthesis that reduces halocarbons to form a Metal chloride byproduct and carbon nanotubes. Perchlorinated phthalocyanine was added to the nanotube synthesis to incorporate the phthalocyanine structure into the graphene sheets of the nanotubes to produce doped nanotubes that have the catalytic oxygen reduction capabilities of the Metallo-phthalocyanine and the advantageous material qualities of carbon nanotubes. The cobalt phthalocyanine doped carbon nanotubes showed a half wave oxygen reduction potential of-0.050 ( 0.005 V vs Hg\HgO, in comparison to platinum’s half wave oxygen reduction potential of-0.197 ( 0.002 V vs Hg\HgO

  • Growth of phthalocyanine doped and undoped nanotubes using mild synthesis conditions for development of novel oxygen reduction catalysts.
    ACS applied materials & interfaces, 2010
    Co-Authors: Robert L. Arechederra, Kateryna Artyushkova, Plamen Atanassov, Shelley D. Minteer
    Abstract:

    Precious Metal Alloys have been the predominant electrocatalyst used for oxygen reduction in fuel cells since the 1960s. Although performance of these catalysts is high, they do have drawbacks. The two main problems with Precious Metal Alloys are catalyst passivation and cost. This is why new novel catalysts are being developed and employed for oxygen reduction. This paper details the low temperature solvothermal synthesis and characterization of carbon nanotubes that have been doped with both iron and cobalt centered phthalocyanine. The synthesis is a novel low-temperature, supercritical solvent synthesis that reduces halocarbons to form a Metal chloride byproduct and carbon nanotubes. Perchlorinated phthalocyanine was added to the nanotube synthesis to incorporate the phthalocyanine structure into the graphene sheets of the nanotubes to produce doped nanotubes that have the catalytic oxygen reduction capabilities of the Metallo-phthalocyanine and the advantageous material qualities of carbon nanotubes. ...

Samir Abou-ayash - One of the best experts on this subject based on the ideXlab platform.

  • Retention forces between primary and secondary CAD/CAM manufactured telescopic crowns: an in vitro comparison of common material combinations
    Clinical Oral Investigations, 2021
    Co-Authors: Martin Schimmel, Moritz Walther, Nadin Al-haj Husain, Kensuke Igarashi, Julia Wittneben, Samir Abou-ayash
    Abstract:

    Objectives To analyze the retention forces between primary and secondary telescopic crowns milled from various materials and to compare them with the retention forces between cast telescopic crowns made of Precious Metal Alloys. Materials and methods Primary and secondary crowns ( N = 60; n = 10 per group) were fabricated using various material combinations (1: zirconia [ZIR]/polyether ether ketone [PEEK]; 2: titanium grade IV [TI]/PEEK; 3: PEEK/PEEK; 4: non-Precious alloy [NPA]/PEEK; 5:NPA/NPA), while Precious alloy (PA) was used for the control group (6: PA/PA). The retention forces at 10, 1000, 5000, and 10,000 connection and disconnection cycles and the relative weights were analyzed, applying nonparametric repeated measures ANOVA and post hoc Mann–Whitney and Wilcoxon signed-rank tests ( α < 0.05). Results Globally, significant differences in the retention forces among the materials ( p < 0.0001), time points ( p < 0.0001), and wear resistance for the various materials ( p < 0.0001) were observed. No significant changes in retention forces compared to baseline were observed in groups 2, 4, 5, and 6. A significantly higher weight loss for both primary and secondary crowns was observed in groups 4 and 6. Conclusions The material combination in telescopic attachments influences retention forces and wear. Interactions between materials and time were evident, indicating that the change in retention forces differs among the materials. The combinations of milled TI/PEEK and NPA/NPA qualify for further preclinical testing in a more clinically realistic setup, determining a material-specific double-crown design. Clinical relevance The design of Precious alloy telescopic crowns cannot be directly transferred to other milled material combinations due to different retention behaviors.

Jean-pierre Lorand - One of the best experts on this subject based on the ideXlab platform.

  • Metal‐saturated sulfide assemblages in NWA 2737: Evidence for impact‐related sulfur devolatilization in Martian meteorites
    Meteoritics & Planetary Science, 2012
    Co-Authors: Jean-pierre Lorand, Jean-alix Barrat, Vincent Chevrier, Violaine Sautter, Sylvain Courrech Du Pont
    Abstract:

    – NWA 2737, a Martian meteorite from the Chassignite subclass, contains minute amounts (0.010 ± 0.005 vol%) of Metal-saturated Fe-Ni sulfides. These latter bear evidence of the strong shock effects documented by abundant Fe nanoparticles and planar defects in Northwest Africa (NWA) 2737 olivine. A Ni-poor troilite (Fe/S = 1.0 ± 0.01), sometimes Cr-bearing (up to 1 wt%), coexists with micrometer-sized taenite/tetrataenite-type native Ni-Fe Alloys (Ni/Fe = 1) and Fe-Os-Ir-(Ru) Alloys a few hundreds of nanometers across. The troilite has exsolved flame-like pentlandite (Fe/Fe + Ni = 0.5–0.6). Chalcopyrite is almost lacking, and no pyrite has been found. As a hot desert find, NWA 2737 shows astonishingly fresh sulfides. The composition of troilite coexisting with Ni-Fe Alloys is completely at odds with Chassigny and Nahkla sulfides (pyrite + Metal-deficient monoclinic-type pyrrhotite). It indicates strongly reducing crystallization conditions (close to IW), several log units below the fO2 conditions inferred from chromites compositions and accepted for Chassignites (FMQ-1 log unit). It is proposed that reduction in sulfides into base and Precious Metal Alloys is operated via sulfur degassing, which is supported by the highly resorbed and denticulated shape of sulfide blebs and their spongy textures. Shock-related S degassing may be responsible for considerable damages in magmatic sulfide structures and sulfide assemblages, with concomitant loss of magnetic properties as documented in some other Martian meteorites.

  • Metal-saturated sulfide assemblages in NWA 2737: Evidence for impact-related sulfur devolatilization in Martian meteorites
    Meteoritics and Planetary Science, 2012
    Co-Authors: Jean-pierre Lorand, Jean-alix Barrat, Vincent Chevrier, Violaine Sautter, Sylvain Pont
    Abstract:

    NWA 2737, a Martian meteorite from the Chassignite subclass, contains minute amounts (0.010 ± 0.005 vol%) of Metal-saturated Fe-Ni sulfides. These latter bear evidence of the strong shock effects documented by abundant Fe nanoparticles and planar defects in Northwest Africa (NWA) 2737 olivine. A Ni-poor troilite (Fe/S = 1.0 ± 0.01), sometimes Cr-bearing (up to 1 wt%), coexists with micrometer-sized taenite/tetrataenite-type native Ni-Fe Alloys (Ni/Fe = 1) and Fe-Os-Ir-(Ru) Alloys a few hundreds of nanometers across. The troilite has exsolved flame-like pentlandite (Fe/Fe + Ni = 0.5-0.6). Chalcopyrite is almost lacking, and no pyrite has been found. As a hot desert find, NWA 2737 shows astonishingly fresh sulfides. The composition of troilite coexisting with Ni-Fe Alloys is completely at odds with Chassigny and Nahkla sulfides (pyrite + Metal-deficient monoclinic-type pyrrhotite). It indicates strongly reducing crystallization conditions (close to IW), several log units below the fO2 conditions inferred from chromites compositions and accepted for Chassignites (FMQ-1 log unit). It is proposed that reduction in sulfides into base and Precious Metal Alloys is operated via sulfur degassing, which is supported by the highly resorbed and denticulated shape of sulfide blebs and their spongy textures. Shock-related S degassing may be responsible for considerable damages in magmatic sulfide structures and sulfide assemblages, with concomitant loss of magnetic properties as documented in some other Martian meteorites.