Herbert Ipser

Experimental Investigation of the Cd-Pr Phase Diagram

The complete Cd-Pr equilibrium phase diagram was investigated with a combination of powder-XRD, SEM and DTA. All intermetallic compounds within this system, already reported in literature, could be confirmed: CdPr, Cd2Pr, Cd3Pr, Cd45Pr11, Cd58Pr13, Cd6Pr and Cd11Pr. The corresponding phase boundaries were determined at distinct temperatures. The homogeneity range of the high-temperature allotropic modification of Pr could be determined precisely and a limited solubility of 22.1 at.% Cd was derived. Additionally, single-crystal X-ray diffraction was employed to investigate structural details of Cd2Pr; it is isotypic to the AlB2-type structure with a z value of the Cd site of 0.5. DTA results of alloys located in the adjacent two-phase fields of Cd2Pr suggested a phase transformation between 893 and 930°C. For the phase Cd3Pr it was found that the lattice parameter a changes linearly with increasing Cd content, following Vegard’s rule. The corresponding defect mechanism could be evaluated from structural data collected with single-crystal XRD. Introduction of a significant amount of vacancies on the Pr site and the reduction in symmetry of one Cd position (8c to 32f) resulted in a noticeable decrease of all R-values.

Sn-Ag-Cu Nanosolders: Solder Joints Integrity and Strength

Although considerable research has been dedicated to the synthesis and characterization of lead-free nanoparticle solder alloys, only very little has been reported on the reliability of the respective joints. In fact, the merit of nanoparticle solders with depressed melting temperatures close to the Sn-Pb eutectic temperature has always been challenged when compared with conventional solder joints, especially in terms of inferior solderability due to the oxide shell commonly present on the nanoparticles, as well as due to compatibility problems with common fluxing agents. Correspondingly, in the current study, Sn-Ag-Cu (SAC) nanoparticle alloys were combined with a proper fluxing vehicle to produce prototype nanosolder pastes. The reliability of the solder joints was successively investigated by means of electron microscopy and mechanical tests. As a result, the optimized condition for employing nanoparticles as a competent nanopaste and a novel procedure for surface treatment of the SAC nanoparticles to diminish the oxide shell prior to soldering are being proposed.

The Enthalpies of Mixing of Liquid Ni-Sn-Zn Alloys.

The partial and integral enthalpies of mixing of liquid ternary Ni-Sn-Zn alloys were determined. The system was investigated along two sections xNi/xSnxa0≈xa01:9, xNi/xSnxa0≈xa01:6 at 1073xa0K and along two sections xSn/xZnxa0≈xa09:1, xSn/xZnxa0≈xa04:1 at 873xa0K. The integral enthalpy of mixing at each temperature is described using the Redlich-Kister-Muggianu model for substitutional ternary solutions. In addition, the experimental results were compared with data calculated according to the Toop extrapolation model. The minimum integral enthalpy of approx. −20000xa0Jxa0mol-1 corresponds to the minimum in the constituent binary Ni-Sn system, the maximum of approx. 3000xa0Jxa0mol-1 is equal to the maximum in the binary Sn-Zn system.

Liquid Co–Sn alloys at high temperatures: structure and physical properties

ABSTRACT The Co–Sn system is an important subsystem for Sn-based anode materials of lithium-ion batteries. Experimental results on the physical–chemical properties of this system in the liquid state, however, are rather sparse. In this work, the atomic structure and structure-sensitive thermophysical properties (viscosity, electrical resistivity, and thermoelectric power) of liquid Co–Sn alloys were investigated in a wide temperature range with special attention to the melting-solidification region. The obtained experimental results were combined with differential thermal analysis (DTA) data in order to verify the liquidus curve in the Sn-rich part of the Co–Sn phase diagram.

Enthalpies of mixing of liquid ternary Co–Li–Sn alloys

The partial and integral molar enthalpies of mixing of liquid Co–Li–Sn alloys were determined using drop calorimetry. The investigations were performed along six sections by the addition of lithium to mixtures with the compositions

A thermodynamic study of the cadmium–neodymium system

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Thermodynamics of liquid Au–Sb–Sn

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