Chemical synthesis of crystalline and nanoscale cobalt-iron metal boride powders was studied using hydrous metal chlorides and NaBH ₄. The effects of precursor concentration and optimized synthesis conditions on the phase formation, microstructure, and magnetic properties were investigated. After applying a reaction of CoCl ₂·6H ₂O-FeCl ₃·6H ₂O-NaBH ₄ at 850 °C, (CoFe)B ₂, (CoFe)B, Co ₂B, Fe ₃B, and Fe _0.71Co _0.29 boride phases were obtained from different synthesis conditions applied under autogenic pressure or Ar flow atmosphere. Oxychloride impurities were the reason for the reduced magnetization values. The highest saturation magnetization of 183 emu/g belongs to obtained nanoparticles containing (CoFe)B ₂ and (CoFe)B pure phases. High temperature magnetic measurements marked synthesized powders as soft magnetic materials up to 795 K while no T _c was reached for the obtained phases.

Due to promising mechanical and chemical properties, transition metal borides have attracted attention, and numerous studies have investigated various combinations of transition elements in hopes of acquiring a final product with desired properties combined. In this study, novel low-temperature approach was adopted for the synthesis of cobalt-titanium-boron based crystalline powders. The method was based on the single-step direct reaction of CoCl _2(s), TiCl _4(l) and NaBH _4(s) in a sealed reactor under autogenic pressure. After the reaction of the precursors at 850 °C by using the molar ratios of metal chlorides to NaBH ₄ as 1:3, CoB and TiB ₂ phases were formed in-situ. The subsequent annealing process at 1100 °C achieved a full conversion of metal chlorides to CoB-TiB ₂ composite nanostructures. It was concluded that the binary forms of the borides tend to form as separate phases, which is illustrated in the SEM/EDS analyses with different morphologies. Amorphous boron layer surrounded TiB ₂ particles with an average particle size of 60 nm, whereas the CoB particles formed agglomerates with an average size of 450 nm. The use of synthesized composite powders as reinforcement in metal matrices resulted in enhanced hardness (506 HV) and compressive strength (1682 MPa) of the Ti6Al4V bulk samples.

A new approach for in-situ synthesis of crystalline Co–Fe–B nanoparticles was presented in which low temperature methods were developed by using metal chlorides and NaBH ₄ in an inorganic molten salt environment. Effects of different reaction systems/conditions on the phase formation, thermal behavior and microstructure were investigated. The melting point of reactants and impurities in final powders were reduced by the use of molten salt technique. After a reaction of CoCl ₂, FeCl ₃ and NaBH ₄ at 850 °C in sealed tubes, CoB and Fe ₃B phases formed separately. After a reaction under Ar flow; however, CoFeB ₂ solid solution nano powders were obtained in one step at 850 °C with an average size of 60 nm. After annealing at 1100 °C, stable and highly crystalline (CoFe)B ₂ solid solution phase with a Co:Fe molar ratio of 1:1 was achieved. As-synthesized particles exhibited ferromagnetic property, and possessed a narrow hysteresis curve characteristic of soft magnetic materials. Extended reaction temperature from 650 to 850 °C is seen to produce coercivity enhancement up to 500 Oe without significant reduction in saturation magnetization. On the other hand, after an annealing process and subsequent phase and chemical change, crystalline (CoFe)B ₂ particles exhibited superparamagnetic property.