Investigations on Bi25FeO40 powders synthesized by hydrothermal and combustion-like processes

The syntheses of phase−pure and stoichiometric iron sillenite (Bi25FeO40) powdersby a hydrothermal (at ambient pressure) and a combustion−like process are described.Phase−pure samples were obtained in the hydrothermal reaction at 100 °C (1), whereas thecombustion−like process leads to pure Bi25FeO40 after calcination at 750 °C for 2 h (2a). Theactivation energy of the crystallite growth process of hydrothermally synthesized Bi25FeO40was calculated as 48(9) kJ mol−1. The peritectic point was determined as 797(1) °C. Theoptical band gaps of the samples are between 2.70(7) eV and 2.81(6) eV. Temperature andfield−depending magnetization measurements (5−300 K) show a paramagnetic behaviour with a Curie constant of 55.66·10−6 m3·K·mol−1 for sample 1 and C = 57.82·10−6 m3·K·mol−1for sample 2a resulting in magnetic moments of μmag = 5.95(8) μB·mol−1 and μmag = 6.07(4)μB·mol−1. The influence of amorphous iron−oxide as a result of non-stoichiometric Bi/Feratios in hydrothermal syntheses on the magnetic behaviour was additionally investigated.

Thermodynamic Assessment of Sn-Co-Cu Lead-Free Solder Alloy

To select a lead-free solder system, factors such as eutectic/peritectic point, electron negativity, abundance, cost, toxicity of elements, world production capacity, segregation during solidification, possibility to form low melting phases with Pb, among others must be carefully considered. On the basis of thorough analysis of binary phase diagrams of Sn-X-systems (X represents other elements) and the properties of the element X, the Sn-Co-Cu eutectic ternary alloy system has been chosen as a new lead-free solder candidate. In order to find the eutectic point for the Sn-Co-Cu system, the Sn-Co binary system was thoroughly assessed with CALPHAD (CALculation of PHAse Diagram) methods. The ternary phase diagram of Sn-Co-Cu system was extrapolated with the assessed thermodynamic parameters of Sn-Co, Sn-Cu, and Co-Cu system. The eutectic point for L–Sn2Co+(Sn)+Cu6Sn5 is 224.4°C and 0.37%Co and 0.68%Cu and 98.95%Sn.

Phase Diagram of the System LaCl3-CaCl2-NaCl

The phase diagram of ternary system LaCl3-CaCl2-NaCl has been constructed from the phase diagrams of the three binary systems and of thirteen quasi-binary systems determined by DTA. For the binaries LaCl3-CaCl2 and CaCl2-NaCl eutectic points were observed at 651 °C , 35.1 mol% LaCl3 and at 508 °C , 49.9 mol% NaCl, respectively. For LaCl3-NaCl, a peritectic point besides the eutectic point at 545 °C , 36.1 mol% LaCl3 was found at 690 °C , 57.5 mol%, which is attributable to the formation of the peritectic compound 3 LaCl3 · NaCl. The phase diagram of the ternary system has a ternary eutetic point and a ternary peritectic point due to 3 LaCl3-NaCl, the form er at 462 °C and 12.1 - 3 9 .7 - 4 8 .2 mol% (LaCl3-CaCl2-NaCl) and the latter at 612 °C and 26.9 - 55.1 - 18.0 mol%.

THE SYSTEM LITHIUM NITRATE–ETHANOL–WATER AND ITS COMPONENT BINARY SYSTEMS

The system lithium nitrate–water has been investigated by thermal analysis and by X-ray powder diffraction studies. No trace of the hemihydrate reported by Donnan and Burt was found. The X-ray powder diffraction pattern of LiNO3.3H2O has been obtained.The equilibrium diagram of the system ethanol–water shows an inflection at –30 °C, corresponding to 40 weight per cent ethanol. This is almost certainly a true peritectic point. The formula of the hydrate formed (if there is one) is uncertain but it may be C2H5OH.5H2O.The system lithium nitrate–ethanol could only be studied in dilute solution (of lithium nitrate) and at temperatures near room temperature, because of high viscosity and extreme supercooling. No evidence for the existence of a solid alcoholate has been obtained.The system lithium nitrate–ethanol–water has been investigated in the form of a series of pseudobinary systems containing water and alcohol in fixed ratios. No solid alcoholate of lithium nitrate has been found in solutions containing less than 50 weight per cent ethanol. The investigation could not be pushed beyond this alcohol content because of high viscosity and supercooling.

THE TERNARY ALLOY SYSTEM: ALUMINIUM–LEAD–SILVER

1. The area of partial miscibility for the ternary system, aluminium–lead–silver, has been determined by thermal and chemical analysis. It is found to extend from the binary system aluminium–lead to alloys containing a maximum of 85.58% silver and 4.71% lead by weight.2. The temperatures of separation of solid phase, bounding this area, have been found to fall at first with addition of silver to the system aluminium–lead, until a temperature of 548.5 °C. is reached. This is the temperature of solidification of the alloy that contains silver and aluminium in their eutectic proportions, plus saturation with lead. The temperature then increases to a maximum of about 736° in the alloy containing about 80% silver and 14% lead. This temperature maximum does not coincide with the summit of the mutual solubility curve but lies well to the right of it.3. No ternary compounds have been found.4. The ternary eutectic practically coincides with the binary eutectic of the system silver–lead.5. As far as can be determined by thermal analysis alone, it appears that there is no solid solution of lead in the α, β, or γ phases of the silver–aluminium system.6. The first peritectic line formed by the addition of lead to the high temperature peritectic point of the silver–aluminium system intersects the partial miscibility curve at 7.90% Al, 7.60% Pb, and 84.50% Ag. The temperature drops from 779.0° to 727.0°.7. The second peritectic line intersects the partial miscibility curve at 10.30% Al, 4.10% Pb, and 85.60% Ag. The temperature drops from 729.0° to 708.0°.8. If the partial miscibility curve had not intervened, the two lines would have intersected at 11.00% Al, 15.50% Pb, and 73.50% Ag.