Interfacial reactions between solid Ni and liquid Sn-Zn alloys

The limitation of the harmful lead-containing solders used in the electronics and other industry applications change lead with another metals. Interfacial reactions between Sn-Zn alloys and Ni substrate after annealing at 400 and 450°C were studied. Three intermetallic compounds Ni3Sn4, T1, γ-Ni5Zn21 and liquid Sn were observed in the Ni/Sn-Zn diffusion couples. Scanning electron microscope was used for the investigation of the microstructure. The microhardness measurement of the intermetallic layers was also performed

Comparative analyses of thermodynamic properties assessments, performed by geometric models: Application to the Ni-Bi-Zn system

The thermochemical properties of metals and alloys are essential for the chemists to invent and improve metallurgical and materials’ design processes. However, the properties of multicomponent systems are still scarcely known due to experimental difficulties and the large number of related systems. Thus, the modelling of some thermodynamic properties would be advantageous when experimental data are missing. Considering mentioned facts, geometric models to estimate some thermodynamic properties for the liquid phase of the Ni-Bi-Zn systems. The calculations have been performed in a wide temperature range (1000-2000 K). Ternary interaction parameters for the liquid phase allowing molar Gibbs excess energy calculation have been determined

On the synthesis of Bi-based precursors for lead-free solders development

Preliminary studies on the design of lead-free solders precursors by wet chemistry methods are presented. The main objective is to assess the impact of the way of hydroxide precipitates preparation on the metal elements content of the precipitates. Namely, ternary hydroxide mixtures of three systems: a. Cu(II), Bi(III), Sn(II); b. Cu(II), Bi(III), Sb(III); and c. Cu(II), Bi(III), Zn(II) were prepared, firstly, by single-element precipitation and, secondly, by co-precipitation. Thereafter, all mixtures were reduced by using hydrogen gas. Both, the initial mixtures and the reduced samples were studied by X-ray diffraction, optical and scanning electron microscopes. The chemical compositions of the precipitates were determined experimentally and their dependence on the pH was verified. It was found that alloying occurred during the reduction procedure, but in some cases the reduction was not complete (i.e. oxide phases rest in the samples). This might be a huge obstacle to use such an approach for the preparation of lead-free solders. Moreover, the materials obtained after reductions apparently are bulk alloys, thus, the preparation of small-sized metal particles would be a challenge. Another key feature to be addressed in future studies is the correlation between the chemical compositions of the parent solution and these of the corresponding precipitates

Stability of corn and olive oil-in-water emulsions supplemented with ethanol-treated rapeseed meal protein isolate

Rapeseed meal was treated with 70% ethanol to reduce anti-nutrient compounds, and used in the preparation of a protein isolate. The ethanol- treated rapeseed meal protein isolate (ERPI) was produced by alkaline extraction of proteins (pH 12) followed by isoelectric precipitation at pH 4.5. The aim of the present work was to evaluate the potential of ERPI as an emulsifying agent in corn and olive oil-in-water emulsions under slightly acidic conditions (pH 6). A total of nine emulsions for each type of oil were prepared to assess the significant effect of two variables, oil (5, 10, and 15% w/w) and ERPI protein concentrations (0.25, 0.5, and 1.0% w/w), on emulsion stability. The initial stability was evaluated by Gibbs free energy (ΔG) and lipid particle size distribution, while the dynamics of emulsion stability was investigated along 7 d by turbidity measurement. The increase in concentration of both types of oil positively influenced initial stability of the emulsions as indicated by ΔG. At each oil concentration, the three ERPI supplementation levels resulted in significant differences in ΔG. While in all olive oil-in-water emulsions, the highest initial stability was achieved by the addition of 0.25% ERPI; and in corn oil-in-water emulsions, lower ΔG values were achieved by supplementing either with 0.5 or 1.0% ERPI. With a few exceptions, there was an agreement between Gibbs free energy and microstructural characteristics of the emulsions. With a reduction in turbidity not higher than 30% at day 7, all corn oil-in-water emulsions supplemented with 0.5% ERPI demonstrated a better stability than the emulsions prepared with olive oil.info:eu-repo/semantics/publishedVersio

On the synthesis of Bi-based precursors for lead-free solders development

Preliminary studies on the design of leadfree solders precursors by wet chemistry methods are presented. The main objective is to assess the impact of the way of hydroxide precipitates preparation on the metal elements content of the precipitates. Namely, ternary hydroxide mixtures of three systems: a. Cu(II), Bi(III), Sn(II); b. Cu(II), Bi(III), Sb(III); and c. Cu(II), Bi(III), Zn(II) were prepared, firstly, by single-element precipitation and, secondly, by co-precipitation. Thereafter, all mixtures were reduced by using hydrogen gas. Both, the initial mixtures and the reduced samples were studied by Xray diffraction, optical and scanning electron microscopes. The chemical compositions of the precipitates were determined experimentally and their dependence on the pH was verified. It was found that alloying occurred during the reduction procedure, but in some cases the reduction was not complete (i.e. oxide phases rest in the samples). This might be a huge obstacle to use such an approach for the preparation of lead-free solders. Moreover, the materials obtained after reductions apparently are bulk alloys, thus, the preparation of smallsized metal particles would be a challenge. Another key feature to be addressed in future studies is the correlation between the chemical compositions of the parent solution and these of the corresponding precipitates