Aluminothermic Production of Titanium Alloys (Part 2): Impact of Activated Rutile on Process Sustainability

The aluminothermic process provides a cost-reduced production method for titanium and titanium alloys by reduction of TiO2 with subsequent refining by electroslag remelting The aluminothermy involves high heating rates, high temperatures and short reactions times combined with a self-propagating behaviour of the reaction. By co-reduction of TiO2 and oxides of alloying elements such as vanadium pentoxide, direct synthesis of a titanium alloy is possible. The use of rutile ore concentrates causes a further reduction of process steps. In order to charge rutile ore complex thermodynamic calculations are required taking enthalpy input of various bycomponents into account. The aluminothermic reduction is conventionally enhanced by a highly heatproviding reaction based on the reduction of KClO4. In order to minimize the use of chlorine-based products extensive studies are made to investigate the feasibility of using mechanically activated rutile as input material for the aluminothermic process. Due to the mechanical activation the intrinsic enthalpy of the reaction is increased thus facilitates a process with reduced amount of KClO4. A major challenge represents the determination of a compromise between low activation duration and reduced KClO4 amount. In order to define the process window parameters like intrinsic chemical energy (enthalpy of the reaction mixture), equilibrium temperature and physical properties (particle size and mixing degree) were optimized. After adjusting the process parameters it is possible to save up to 42 % KClO4 for the ATR reaction with 2h activated input material. This reduction of KClO4 material affects a decrease of the produced gaseous compounds and the subsequent off-gas cleaning system

Hallmarks of mechanochemistry: from nanoparticles to technology

Équipe 401 : Nanomatériaux pour la vie et développement durableInternational audienceThe aim of this review article on recent developments of mechanochemistry (nowadays established as a part of chemistry) is to provide a comprehensive overview of advances achieved in the field of atomistic processes, phase transformations, simple and multicomponent nanosystems and peculiarities of mechanochemical reactions. Industrial aspects with successful penetration into fields like materials engineering, heterogeneous catalysis and extractive metallurgy are also reviewed. The hallmarks of mechanochemistry include influencing reactivity of solids by the presence of solid-state defects, interphases and relaxation phenomena, enabling processes to take place under non-equilibrium conditions, creating a well-crystallized core of nanoparticles with disordered near-surface shell regions and performing simple dry time-convenient one-step syntheses. Underlying these hallmarks are technological consequences like preparing new nanomaterials with the desired properties or producing these materials in a reproducible way with high yield and under simple and easy operating conditions. The last but not least hallmark is enabling work under environmentally friendly and essentially waste-free conditions (822 references)