Production and characterization of activated carbon from barley straw by physical activation with carbon dioxide and steam

In recent years, the growth of environmental protection policies has generated an increase in the global demand for activated carbon, the most widely used adsorbent in many industrial sectors, and with good prospects of implementation in others such as energy storage (electrodes in supercapacitors) and agriculture (fertilizer production). This demand is driving by the search for renewable, abundant and low-cost precursor materials, as an alternative to traditional fossil sources. This study investigates the production of activated carbon from barley straw using physical activation method with two different activating agents, carbon dioxide and steam. Experimental tests under different conditions at each stage of the process, carbonization and activation, have been conducted in order to maximize the BET surface area and microporosity of the final product. During the carbonization stage, temperature and heating rate have been found to be the most relevant factors, while activation temperature and hold time played this role during activation. Optimal conditions for the activation stage were obtained at 800 °C and a hold time of 1 h in the case of activation with carbon dioxide and at 700 °C and a hold time of 1 h in the case of activation with steam. The maximum BET surface area and micropore volume achieved by carbon dioxide activation were of 789 m2/g and 0.3268 cm3/g while for steam activation were 552 m2/g and 0.2304 cm3/g, which represent respectively an increase of more than 43% and 42% for the case of activation with carbon dioxide

Unveiling the Complex Magnetization Reversal Process in 3D Nickel Nanowire Networks

Understanding the interactions among magnetic nanostructures is one of the key factors to predict and control the advanced functionalities of Three-Dimensional (3D) integrated magnetic nanostructures. In this work, we focus on different interconnected Ni nanowires forming an intricate, but controlled, and ordered magnetic system: Ni 3D Nanowire Networks. These self-ordered systems present striking anisotropic magnetic responses, depending on the interconnections' position between nanowires. To understand their collective magnetic behavior, we studied the magnetization reversal processes within different Ni 3D Nanowire Networks compared to the 1D nanowire array counterparts. We characterized the systems at different angles using first magnetization curves, hysteresis loops, and First Order Reversal Curves techniques, which provided information about the key features that enable macroscopic tuning of the magnetic properties of the 3D nanostructures. In addition, micromagnetic simulations endorsed the experiments, providing an accurate modeling of their magnetic behavior. The results revealed a plethora of magnetic interactions, neither evident nor intuitive, which are the main role players controlling the collective response of the system. The results pave the way for the design and realization of 3D novel metamaterials and devices based on the nucleation and propagation of ferromagnetic domain walls both in 3D self-ordered systems and future nano-lithographied devices