ELABORATION AND TESTING OF MATERIALS USING CONCENTRATED SOLAR ENERGY
1. Brief history of the use of solar energy to transform matter 2. Main characteristics of solar furnaces 3. Elaboration of materials using concentrated solar energy 3.1 Surface treatments 3.2 Melting and purification of bulk materials 3.3 Production of chemical commodities and ceramics 3.4 Elaboration of carbon molecules, nanomaterials and thin films 4. Testing of materials using concentrated solar energy 4.1 Original devices at the focus of solar furnaces 4.2 Test of materials for aerospace applications 4.2.1 Atmopsheric re-entry (oxidation and catalycity) 4.2.2 Solar probe mission 4.3 Test of materials for future system of energy production 5. Conclusion Bibliography Biographical Sketches
Metals, nitrides, and carbides via solar carbothermal reduction of metal oxides
We have examined the thermodynamics of the carbothermic reduction of metal oxides in either nitrogen or argon atmospheres. The reaction, which is given generally by (where the M denotes metal) MxOy + C (+ N2;) → {Mx′Ny′, Mx″Cy″, M} + CO, is highly endothermic and proceeds at temperatures from 1300 to 2350 K for the systems considered. Exploratory experimental studies were conducted in a solar furnace using concentrated solar radiation. The nature of the solid-phase products was determined by X-ray powder diffraction. Nitrides (AlN, TiN, Si3N4, ZrN) were formed for systems run in N2; carbides (Al4C3, TiC, SiC, CaC2) were formed for runs in Ar; and metals (Mg, Zn) were obtained from their oxides in an Ar atmosphere. The use of solar energy as the source of high-temperature process heat offers the possibility of reducing emissions of greenhouse gases and other pollutants to the environment when it replaces the burning of a fuel for process heat. Furthermore, the availability of process heat at very high temperatures may make alternative processes economically feasible.
Joint strength of aluminum ultrasonic soldered under liquidus temperature of Sn–Zn hypereutectic solder
Abstract In order to obtain high-strength aluminum joints, ultrasonic soldering of 1070 aluminum was conducted under liquidus temperature of Sn–Zn hypereutectic solder. A device for ultrasonic soldering was assembled, which propagated ultrasonic vibrations in a direction perpendicular to joining surfaces. This device joined 1070-Al using quasi-melting Sn–Zn hypereutectic solder without using any artificial spacers. The strength of the solder joints was evaluated by tensile tests. The optimum joining conditions were determined, and the effects of solder compositions and soldering temperature on the joint strength and the solder layer thickness were examined. In this ultrasonic soldering process, the highest tensile strength was obtained for the solder joints fabricated at 220 °C for the Sn–23Zn and Sn–40Zn solder compositions. The joint strength was equivalent to that of 1070-Al heat treated at 220 °C. The sound joints were obtained at 300 °C using Sn–82Zn solder, the liquid phase volume fraction of which was theoretically only 0.24. The present work also revealed that the thickness of retained solder layer in the joint after ultrasonic soldering could be estimated. Accordingly, ultrasonic soldering under the liquidus temperature of Sn–Zn hypereutectic solder could be a spacer-free soldering method to obtain high-strength aluminum joints.