Laboratory, optical and precision equipments (excl. glasses)

Description

The University of Birmingham invites tenders for the supply of a high specification vertical Bridgman-Stockbarger furnace, with a maximum operating temperature of 1700oC or greater, for the solidification and growth of single crystals of 12 mm diameter over a wide range of growth rates, including quenching capability. A warranty period of reasonable duration is required to ensure the full upkeep and efficiency of the product, as well as the provision of initial training. In addition, the supplier may provide a maintenance/service contract for an extended duration (e.g. 5 years) after installation. The University of Birmingham invites tenders for the supply of a high specification vertical Bridgman-Stockbarger furnace, with a maximum operating temperature of 1700oC or greater, for the solidification and growth of single crystals of 12 mm diameter over a wide range of growth rates, including quenching capability. The specification below outlines the requirements for a Bridgman-Stockbarger furnace that will be used to solidify samples for academic research. The core uses are twofold: 1) The production of high-purity, homogeneous single crystals across a wide spectrum of materials systems, from tin alloys and aluminium alloys to MnSi, FeGa alloys and rare-earth transition metals (e.g. DyFe2). The furnace must therefore allow different crucible materials and types, and operate over a wide range of growth temperatures, with controlled, slow withdrawal rates of typically 0.03 mm min-1. The supplier should detail which crucible materials are possible and indicate the costs of crucibles and their suppliers. To produce single crystals in non-equilibrium structures, the furnace must be capable of rapidly quenching its charge. To achieve high-purity, the sample chamber should be leak-tight under vacuum and have a gas-handling system for backfilling of inert gas atmospheres. 2) The study of dendritic growth and solidification kinetics in selected systems e.g. nickel superalloys. Here high withdrawal rates (typically 3 mm min-1) and large thermal gradients (200oC cm-1 or greater) are required, with a long charge length (45 cm or greater). Quenching is necessary to freeze in dendrite structures. Different technical solutions are evidently possible to realise the quenching requirement e.g. among others, dropping into a liquid metal bath or through a rapid motion into a snug-fit cooled jacket. If the supplier opts for the latter, it should be noted that this must be optimised for at least 2 charge (i.e. inner crucible) diameters: 6 mm and 12 mm. This could be achieved with, for example, a removable copper insert in the quench zone. As the furnace is to be used for research purposes, we expect to vary the parameters (growth rates, temperatures, temperature gradients) substantially. Likewise, the furnace software must permit full and flexible programmable control of the heat zone(s), accompanied with recording of temperature data. It should allow the integration and collection of data from optional measurements e.g. further thermometry for subsequent analysis. Similarly, a thorough understanding of the thermal profiles in the heat zone(s) is desirable. The supplier must be prepared to characterise the thermal profiles in detail, or otherwise provide drawings in sufficient detail to enable finite-element model analysis (e.g. using ProCast). Desirable, but not mandatory, requirements include: (i) fully controllable rotation of the crucible and charge so as to implement the Accelerated Crucible Rotation Technique (ACRT); (ii) the optimisation of the furnace for a third charge diameter of 8 mm, in addition to the two diameters of 6 mm and 12 mm given above; (iii) the ability to reverse the temperature gradient i.e. allow upside-down Bridgman operation; (iv) in conjunction with (iii), the ability to quench into the top of the furnace in situations where it is used in upside-down operation. If they are deemed technically feasible, suppliers are invited to provide separate costs for the options above. The furnace will be located in the foundry area of the school of metallurgy and materials at the University of Birmingham. This space provides 3-phase 400 V electrical power and a high ceiling of 6,5 m. Cooling water, on the other hand, cannot be guaranteed, so the furnace must include a water recirculation and cooling system.