Brazing is one of the most important techniques known in joining two similar/dissimilar metals/metal–nonmetal combinations for structural, mechanical, and aerospace applications. Brazing joints are formed by melting pure or alloyed foil called braze. Braze is melted in between the two substrates to be joined, and the joint is formed due to inherent adhesion and reactivity between braze and substrate. Copper and nickel are most commonly used brazes in the industry. Copper behavioral studies are mostly aimed at stainless steels (SS), and lot of research is carried out in Cu–SS systems. But, what is the copper behavior with medium carbon steels? What is the grain boundary behavior of copper and its mechanism when the alloying elements in steel are very low? Sandwich experiments were conducted with C45/Cu/C45 systems under an inert gas environment at 1100 °C. Cu was found to be wetting and penetrating the grain boundaries of medium carbon steel such as C45. The depth of penetration varied depending on holding times. The microstructure of the interface was characterized by SEM, and penetration depth was measured by image analysis software for better resolution and accuracy.
The wettability of a copper substrate by Sn–Ni alloy and the interfacial active properties of nickel were investigated. We determined the contact angle as a function of holding time in the Sn–Ni/Cu system at low Ni concentration. The contact angle of Sn can be decreased from 30° to 25° by adding 0.1 wt% Ni to Sn. We observed accumulation of the nickel at the solid–liquid interface. We assume that the nickel accumulation is caused by the interfacial active property of the nickel in an Sn–Ni/Cu system.
Authors:Kanokon Nuilek, Andrea Simon and Peter Baumli
Carbon nanostructured materials, including nanosheets, are being produced from a variety of natural waste materials. The process involves activation and carbonization. Potassium hydroxide (KOH) is a well-known chemical agent used to generate pore structure and to prepare the micro/nanostructure of carbon. This study compares the effect of the state of KOH (solid or solute) on carbon formation in peanut shells. Carbon nanosheets were formed from peanut shell by activation with KOH and heat treatment. The surface microstructure and individual carbon nanosheets of peanut shell were found to be more distinct after treatment with solute KOH compared to treatment with solid KOH. This suggests that solute KOH treatment is a simple, cheap, and effective method for producing carbon nanosheets from peanut shells.