1,721,031 research outputs found
Design of Composites by Infiltration Process: A Case Study of Liquid Ir-Si Alloy/SiC Systems
No full textThe design of processing routes involving the presence of the liquid phase is mainly associated with the knowledge of its surface and transport properties. Despite this need, due to experimental difficulties related to high temperature measurements of metallic melts, for many alloy systems neither thermodynamic nor thermophysical properties data are available. A good example of a system lacking these datasets is the Ir-Si system, although over the last fifty years, the structures and properties of its solid phases have been widely investigated. To compensate the missing data, the Gibbs free energy of mixing of the Ir-Si liquid phase was calculated combining the model predicted values for the enthalpy and entropy of mixing using Miedema's model and the free volume theory, respectively. Subsequently, in the framework of statistical mechanics and thermodynamics, the surface properties were calculated using the quasi-chemical approximation (QCA) for the regular solution, while to obtain the viscosity, the Moelwyn-Hughes (MH) and Terzieff models were applied. Subsequently, the predicted values of the abovementioned thermophysical properties were used to model the non-reactive infiltration isotherm of Ir-Si (eutectic)/SiC system
Experimental Thermodynamics and Surface Properties of Ag-Cu-Ge Solder/Braze Alloys
No full textAg-based alloys have industrial importance in relation to their use as high-temperature solders in jewellery or braze alloys for thermoelectric modules. Good wetting properties and a tarnish-resistance of Ag-Ge and Ag-Cu-Ge alloys together with appropriate mechanical properties make them good candidates for bonding sterling silver (Ag-7.5Cu, in wt.%). The melting temperature and the heat of melting of Ag-Cu, Ag-Ge and Ag-Cu-Ge eutectic alloys have been measured by differential scanning calorimetry. From a technological point of view, particular attention should be paid to the surface tension, a key property of the joining processes. The aim of this study is to correlate the thermodynamic properties of the Ag-Cu-Ge system and its subsystems with their surface properties and to compare the model predicted property values to the data available in the literature
Effect of weak uniaxial loads on creep strain rate in high-porosity MgO compacts during early sintering stages
No full textNew Insights into Phase Equilibria of the Sb-Sn System
No full textA new experimental investigation of the Sb-Sn phase diagram has been performed. Special attention was focused on the phase equilibria within SbSn-Sb3Sn4 composition range. Phase equilibria have been investigated by DSC measurements combined with a thorough optical and electronic microscopy examination with a special attention to the SbSn-Sb3Sn4 phase transformation. Both DSC and metallographic results have been critically evaluated and debated. The presence of two peritectic reactions L + Sb3Sn4 ⇌ (βSn) at 243 ± 1 °C and L + (Sb) ⇌ (SbSn) at 420 ± 1 °C have been confirmed. The invariant reaction at 321 ± 1 °C has been observed and an additional small effect at about 330-340 °C was systematically recorded. These results have been extensively discussed
Transport of oxygen at the surface of liquid metals: models and experiments in Advances in Science and Tecnology
No full textSurface and transport properties of liquid Ag–Sn alloys and a case study of Ag–Sn eutectic solder
No full textThis review represents the state of the art in the thermophysical properties of liquid Ag-Sn alloys highlighting the surface and wetting properties of Ag-Sn eutectic solder. It includes an atomistic approach developed within the framework of statistical mechanical theory in conjunction with a Quasi Lattice Theory that, through a rigorous mathematical formalism, provides exact relationships between the properties in terms of classical thermodynamics. The model predicted property values are substantiated by available experimental data. Based on the phase diagram evidence about the existence of epsilon-Ag3Sn intermetallic compound, the surface (surface tension and surface composition), transport (viscosity and diffusivity) properties and microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) have been studied using the Compound Formation Model in a weak interaction approximation and Quasi Chemical Approximation for regular solutions. A case study of Ag-Sn eutectic alloy is presented. Taking into account its importance for design and development of lead free solder alternatives, the literature data on the wettability and the phases formed at the interface between Ag-Sn eutectic alloy and different substrates (Cu, Ni, Au, Pd) have also been analysed
Phase Relations of the Sm–Ni–Al Ternary System at 800 °C in the 30–100 at.% Al Region
No full textThe Sm–Ni–Al phase relationships at 800 °C have been investigated by using several well–focused experimental techniques such as X–Ray Powder Diffraction (XRPD), Light Optical Microscopy (LOM) and Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Microprobe Analysis (EPMA). The isothermal section of the Sm–Ni–Al system at 800 °C was constructed according to the present experimental results. More than 50 alloys have been synthesized and characterized in the 30–100 at.% Al region. At 800 °C, 9 intermetallic phases have been confirmed, characterized and their relationships have been established. In the Al-rich corner, the presence of two ternary invariant reactions have been postulated whilst along the 16.67 at.% Sm isopleth, the presence of two structurally related extended solid solutions have been observed. The determined phase equilibria at 800 °C are discussed and compared with the isothermal section at 500 °C already reported in literature
Study of dynamic surface tension of molten silicon: development of experiments and models
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