Ni-Based Multiphase Alloy for Non-Consumable Anodes
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Solution Overview
Problem
The aluminum process industry faces challenges in replacing consumable carbon anodes with non-consumable materials that do not emit CO2 or CF4 during electrolysis, requiring materials with long-term resistance against oxidation and fluoridation, high electrical conductivity, thermal shock resistance, and creep resistance at elevated temperatures.
Innovation Solution
A conductive multicomponent multiphase metal alloy with a composition of at least three elements selected from Sn, Nb, Ta, B, Cr, Ce, Fe, La, Nd, Sm, Gd, Ti, Zr, Mn, Hf, Si, P, Al, Y, and V, with Ni making up at least 35 atom-%, which forms an intrinsic and self-healing mineral coating when submerged in a molten salt bath, providing excellent adherence and resistance to cryolite corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If non-consumable anode materials (metals, ceramics, cermets) are used to replace carbon anodes, then CO2 and CF4 emissions are eliminated, but the materials suffer from cryolite corrosion leading to cracking, spalling, flaking, pulverisation, pore formation and dissolution
Solution Approach 1:
The invention uses a composite material consisting of a metallic matrix (Ni-based alloy) combined with ceramic particles (oxides, fluorides, or oxyfluorides) to create a cermet anode. This composite structure allows the material to benefit from both the conductivity of metals and the corrosion resistance of ceramics, eliminating CO2 and CF4 emissions while maintaining reliability in cryolite environment
Solution Approach 2:
The invention applies local quality by creating a surface layer with specific ceramic coating on the metallic anode substrate. The ceramic layer (containing oxides, fluorides, or oxyfluorides) provides localized corrosion resistance at the surface where cryolite contact occurs, while the bulk metallic matrix maintains electrical conductivity and structural integrity
2Reliability
If all-ceramic anode materials are used, then resistance against cryolite corrosion is improved, but electrical conductivity decreases and thermal shock resistance becomes poor
Solution Approach 1:
The Ni-based metallic matrix provides high electrical conductivity (maintaining power requirements), while the embedded ceramic particles (oxides, fluorides, or oxyfluorides) provide corrosion resistance. This composite structure resolves the contradiction by combining materials with complementary properties in a single anode system
Solution Approach 2:
The ceramic phase is distributed locally within the metallic matrix or forms a surface layer, providing corrosion resistance only where needed (at the cryolite interface), while the bulk metallic material maintains electrical conductivity throughout the anode structure
3Reliability
If extrinsic ceramic coatings are applied on the surface of another object, then resistance against cryolite corrosion is improved, but the coatings spall and crack off with time
Solution Approach 1:
The invention merges the ceramic coating and metallic substrate into a unified composite structure where ceramic particles are embedded within or bonded to the metallic matrix. This integration eliminates the interface between separate coating and substrate that causes spalling and cracking, creating a durable anode that maintains coating adhesion under thermal and mechanical stress
Solution Approach 2:
The composite cermet structure creates a unified material system where ceramic and metallic phases are intimately combined at the microstructural level, eliminating the coating-substrate interface that leads to spalling and cracking in conventional coated anodes
4Power
If anodes made by consolidating ceramic and metallic powders into a solid composite are used, then electrical conductivity increases, but cryolite corrosion degrades the metallic binder holding the composite together
Solution Approach 1:
The invention changes the chemical composition parameters of the metallic binder by using a Ni-based alloy with specific compositional ranges (Fe: 0.1-5%, Cr: 1-10%, Mn: 0.1-5%, and other alloying elements) that provide both conductivity and corrosion resistance. This parameter optimization allows the binder to withstand cryolite corrosion while maintaining electrical conductivity
Solution Approach 2:
The composite structure uses a corrosion-resistant Ni-based metallic matrix to bind ceramic particles, where the matrix composition is specifically designed to resist cryolite attack. The ceramic phase (oxides, fluorides, or oxyfluorides) provides corrosion resistance, while the optimized metallic binder maintains conductivity and structural integrity in the corrosive environment
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The metal alloy achieves high bulk electrical conductivity, thermal shock resistance, and creep resistance, forming a stable and adherent mineral coating that self-heals, making it suitable for use as an anode material in the Hall-Heroult process without emitting harmful gases.
Implementation Method 1
the inventors have realized that the inventive metal alloy is capable of forming an intrinsic and highly adherent mineral coating, upon contact with oxygen gas and molten salt solution
Implementation Method 2
One of the most important criteria for new materials is the long-term resistance against excessive oxidation and fluoridation, since the anode needs to survive at ≈975° C. immersed in molten cryolite salt
Data Source
AI summary
The present invention relates to conductive multicomponent multiphase metal alloy. The metal alloy has the following (in atom-%):Ni, in a total amount of 35-70; wherein the remaining 30-65 comprises at least three elements selected from the list consisting of Sn, Nb, Ta, B, Cr, Ce, Fe, La, Nd, Sm, Gd, Ti, Zr, Mn, Hf, Si, P, Al, Y and V in a total amount of at least 30. The metal alloy comprises at least three distinct crystalline phases, at least one phase being an intermetallic phase. The present invention also relates to an electrode material comprising said alloy, to a method for forming a coating on said alloy, and to a method for manufacturing said alloy.