No abstract

In recent decades, powder metallurgy technology has advanced considerably and been used to manufacture sintered structural components with extremely high dimensional accuracy and excellent surface finish. This process is based on the compression of a mixture of metal powder and sintering in an oven using controlled temperature and atmosphere. This technology meets copper alloys design with excellent mechanical properties at the lowest cost. This prompted us to study the effect of sintering temperature and aluminum concentration on the hardness, microstructure, and density of copper-aluminum (Cu-Al) alloys prepared by using the powder compaction process. In this work, samples of Cu-Al alloy with 5, 11, 14, and 18 wt. % of Al were prepared by mechanical alloying of elemental powders, followed by consolidation under a pressure of 12.5 MPa and sintering at 700-1000 C in vacuum for 90 min. Microstructural constituents were examined using X-ray diffraction. Density and hardness were measured and their changes with the size of the granules and the formed phases were studied. The 2 phase samples showed higher hardness.

In this experimental study, a new solar dryer has been designed and manufactured by combining a concave solar concentrator with a series of convergent lenses whose concentrated radiation are reflected on the same absorber. Our main goal for this combination is to reduce the thermal losses by increasing the receiver bottom temperature. In our dryer, the receiver design uses air and water as the heat transfer fluid; these two fluids are heated and sent a heat exchanger to raise the drying air temperature. Furthermore, in order to improve the thermal performance, our approach is based on some techniques such as; the combination of two types of solar concentrators, simultaneous use of two natural heat transfer fluids, tilting concentrators, the insertion of obstacles at the absorber, and a specific solar tracker for explosive atmosphere. Our dryer has been tested for the first time in gas filling plant in Morocco for drying painted gas cylinders. The experimental results show that compared with flat-plate solar collector, the proposed dryer can significantly improve the performance in terms of air drying temperature. In fact, our solar dryer has reduced the drying time from 420 seconds to just 40 seconds and has improved drying air the temperature from 40 °C to 65 °C. Also, the health risks of workers have been reduced and the number of painted bottles has been increased by more than 43%.