Single Step Process for Crystalline Ni-B Compounds

Abstract

Crystalline Ni2B, Ni3B, and Ni4B3 are synthesized by a single-step method using autogenous pressure from the reaction of NaBH4 and Ni precursors. The effect of reaction temperature, pressure, time, and starting materials on the composition of synthesized products, particle morphologies, and magnetic properties is demonstrated. High yields of Ni2B (>98%) are achieved at 2.3–3.4 MPa and ~670 °C over five hours. Crystalline Ni3B or Ni4B3 form in conjunction with Ni2B at higher temperature or higher autogenous pressure in proportions influenced by the ratios of initial reactants. For the same starting ratios of reactants, a longer reaction time or higher pressure shifts equilibria to lower yields of Ni2B. Using this approach, yields of ~88% Ni4B3 (single phase orthorhombic) and ~72% Ni3B are obtained for conditions 1.9 MPa < Pmax < 4.9 MPa and 670 °C < Tmax < 725 °C. Gas-solid reaction is the dominant transformation mechanism that results in formation of Ni2B at lower temperatures than conventional solid-state methods.

Stoichiometry of tetragonal and hexagonal FexSe: phase relations

“…Molar ratios of iron powder (99.9% purity, particle size ∼10 µm) supplied by Alfa Aesar and selenium powder (99.9% purity; particle size ∼149 µm) supplied by Sigma-Aldrich are weighed, ground in an agate mortar and pressed into a pellet of ∼1 g. The pellet is placed into a boron nitride crucible housed within the reactor and filled with Ar. Further details of the reactor configuration and methods of use are provided in earlier publications [15,16]. The tightly sealed reactor is removed from the glove box, placed onto the heating element and filled with Ar gas to pressures ranging between 0.56 MPa to 1 MPa at room temperature (∼25 • C).…”

Nickel Boride (NixB) Nanocrystals: From Solid-State Synthesis to Highly Colloidally Stable Inks

“…For example, reducing the metal halides by borohydrides − yielded amorphous mixed borides, which can be post-treated at high temperatures (400–580 °C) to crystallize the obtained amorphous metal borides. Another strategy was the reaction performed at similar temperatures between the elemental boron and the metal precursor with and without the addition of secondary metal (Mg or Na). − Nickel and cobalt boride thin films have been prepared by physical-vapor deposition, rapid quenching, − chemical reduction, , electrodeposition, chemical-vapor deposition, − and pulsed laser deposition using metal halide and sodium borohydride as precursors. , …”

Synthesis of Ni–B Compounds by High-Pressure and High-Temperature Method

“…Nickel borides are promising functional materials, because of their potential high hardness, high melting point, high thermal stability, and excellent catalytic performance. − The superior properties are from Ni and B atoms that can construct abundant subunits, which contribute to form rich Ni–B compounds. − However, there are rarely reports of single phases of Ni–B compounds which have good crystallization, especially the bulk samples of Ni–B compounds. There is still a lack of data on the intrinsic properties of Ni–B compounds, such as conductivity and hardness.…”

“…Nanoscale Ni−B compounds can be synthesized by NiCl 2 and NaBH 4 which heat at 750 °C for 1.5 h. 13 However, there are many defects and stacking faults appearing in the nanoparticles. Another problem is that the mixed phases are easily generated in the synthesis of Ni−B compounds, such as Ni, 7 Ni 3 B, 10 and Ni 4 B 3 . 8 The reason for mixtures is that the substructures of Ni−B compounds are very close and all of the Gibbs free energies of NiB compounds are negative at temperature of 0− 1200 K, which means all the Ni−B compounds can be spontaneously reacted by elements Ni and B.…”