High-temperature Behavior of a Pd-Ag Alloy for Porcelain

Mackert, J. Rodway; Ringle, Robert D.; Fairhurst, Carl W.

doi:10.1177/00220345830620121201

Cited by 91 publications

(49 citation statements)

References 23 publications

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“…Before reduction, it appeared as if some of the surface was covered with a thin layer and, where this had peeled off, a few intergranular cracks could be seen and nodules of pure Pd were detected and verified by EDAX. Such nodules are apparent for internally oxidized Pd-Al alloys [5] which is consistent with the occurrence of internal oxidation [3]. Extensive and large intergranular cracks were apparent after reduction as seen in Figure 1.…”

Section: Optical Microscopic Observations Sem Edax Sanssupporting

confidence: 79%

The interaction of dissolved H with internally oxidized Pd–Rh alloys

et al. 2002

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Homogeneous fcc Pd-Rh alloys have been internally oxidized in the atmosphere at several temperatures from 1023 to 1123 K forming oxide precipitates within a Pd matrix. As shown from electron diffraction patterns of the internally oxidized Pd 0.97 Rh 0.03 alloy, the oxide that forms is a mixed oxide, PdRhO 2 . Internally oxidized Pd-Rh alloys can be reduced with H 2 (573 to 623 K) forming PdRh precipitates within a Pd matrix. This represents a way of segregating components of a substitutional solid solution binary alloy. The segregated alloy can be returned to the homogeneous Pd-Rh alloy by annealing at an elevated temperature and thus, in contrast to the internal oxidation of, e.g., Pd-Al alloys, the process can be readily reversed. The oxidation and (reduction + H 2 O loss) were monitored from weight changes.After internal oxidation/reduction "diagnostic" hydrogen isotherms (323 K) were measured to follow the extent of oxidation and to determine the extent of trapped H from the positive intercepts along the H/Pd axis in the dilute phase. The H capacities in the steeply rising hydride region of the H 2 isotherms for the internally oxidized alloys are smaller than for Pd unless the Pd in the PdRh precipitates is considered to be inactive for H 2 absorption for the calculation of H/Pd values.In the two-phase region the absorption plateau pressures were significantly greater than for Pd-H, however, they were much closer to the Pd plateau p H2 than to the unoxidized Pd-Rh alloys. The desorption plateaux were very close to that of Pd-H for X Rh =0.01 to 0.05 alloys and therefore it can be concluded that the matrix is pure Pd whose plateaux are affected by the presence of the precipitates.The techniques of TEM, SEM and SANS (small angle neutron scattering) were employed to examine the alloys after internal oxidation and both before and after reduction. SANS confirmed directly that internal precipitates form from the internal oxidation and that they are rather large with an appreciable fraction having diameters greater than 100 nm.

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Section: Optical Microscopic Observations Sem Edax Sanssupporting

confidence: 79%

The interaction of dissolved H with internally oxidized Pd–Rh alloys

et al. 2002

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“…It may be observed that the relationship between time for full oxidation and (1/milling time) 2 is followed linear law. This result is coincident with Equation (12). So the experimental result (Fig.…”

Section: Effect Of Ball-milling On Full Oxidation Time Of Ag-zn Alloysupporting

confidence: 87%

“…The formation of spheric Ag on the surface may be attributed to the external diffusion of silver. Mackert et al [12] studied the internal oxidation dynamics and microstructure of Ag-In alloy. They found that the formation of pure silver on the surface is due to external diffusion of silver.…”

Section: The Effect Of Ball-milling On Oxidation Kineticsmentioning

confidence: 99%

Influence of ball‐milling on the oxidation behavior of Ag–Zn alloy powders

Goto

et al. 2010

Materials & Corrosion

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The gas atomized Ag-15.2 at% Zn alloy powders were treated using ball-milling. The effect of ball-milling on surface morphology, microstructure, and oxidation behavior of the alloy powders was investigated. The results showed that ballmilling treatment enhanced the oxidation rate of Ag-Zn alloy powders due to the increase of dislocation density and the decrease of the diffusion distance of oxygen during internal oxidation. The fully oxidized time of Ag-Zn alloy powders decreases with the ball-milling time. In addition, the ball-milling treatment not only changes the oxidation mechanism but also improves microstructure and properties of the Ag-ZnO materials fabricated by internal oxidation.

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“…Noble alloys for bonding to dental porcelain contain small amounts of secondary elements, such as tin, indium and iron, which form the native oxide and also increase the alloy strength. However, Mackert et al [9] found that during initial oxidation heat treatment, metallic Pd-Ag nodules formed on the surface of a palladium-silver alloy for metal-ceramic restorations and only internal oxidation occurred for the tin and indium present in the alloy composition. They concluded that porcelain bonding arose predominantly from mechanical interlocking with the nodules.…”

Section: Alloys For Fixed Prosthodontics (Metal-ceramic Restorations)mentioning

confidence: 99%