Nanomaterials with high specific surface area and high absorption capacity are attracting increased interest aimed at imparting the desired magnetic properties. This work is devoted to the study of the effect of heat treatment in a hydrogen atmosphere on the microstructure, adsorption and magnetic properties of heterogeneous FePt/h-BN nanomaterials. Obtained via the polyol process, FePt nanoparticles (NPs) had a size < 2 nm and were uniformly distributed over the surface of hexagonal boron nitride (h-BN) nanosheets. The temperature-activated fcc→fct phase transformation in ultrafine FePt NPs has been well documented. FePt NPs act as active centers dissociating H₂ molecules and transfer adsorbed hydrogen atoms to the h-BN. Density functional theory (DFT) calculations also indicate that the h-BN substrate can absorb hydrogen adsorbed on the FePt NPs. This hydrogen circulation in the FePt/h-BN system promoted the fcc→fct phase transformation and allowed to control the magnetic properties. FePt/h-BN nanomaterials also exhibited a high adsorption capacity with respect to various organic dyes.

High-purity straight and discrete multiwalled boron nitride nanotubes (BNNTs) were grown via a boron oxide vapor reaction with ammonia using LiNO₃ as a promoter. Only a trace amount of boron oxide was detected as an impurity in the BNNTs by energy-dispersive X-ray (EDX) and Raman spectroscopies. Boron oxide vapor was generated from a mixture of B, FeO, and MgO powders heated to 1, 150 ℃, and it was transported to the reaction zone by flowing ammonia. Lithium nitrate was applied to the upper side of a BN bar from a water solution. The bar was placed along a temperature gradient zone in a horizontal tubular furnace. BNNTs with average diameters of 30-50 nm were mostly observed in a temperature range of 1, 280-1, 320 ℃. At higher temperatures, curled polycrystalline BN fibers appeared. Above 1, 320 ℃, the number of BNNTs drastically decreased, whereas the quantity and diameter of the fibers increased. The mechanism of BNNT and fiber growth is proposed and discussed.