Electroless Deposition of Ni Nanoparticles on Boron Particles: Physicochemical and Oxidation Properties
Authors: SHIN Weon Gyu , Deshmukh Prashant 
Published: August 2024

Elemental boron also has a high volumetric heat of combustion (136 kJ/cm3), the third highest gravimetric heat of combustion (58.5 MJ/kg) and its oxidation is a highly exothermic process. All these features make boron an attractive constituent of propellants, explosives, and high energy density solid fuels for air-breathing propulsion as an energetic material. Given these uses, researchers have worked on the ignition and combustion processes of boron. However, boron has several serious issues that limit its practical use, including large ignition delay, inefficient combustion, and a complex burning process in solid propellants due to the formation of a defensive boron oxide (B2O3) layer on the boron surface. Previous studies have found that the ignition and combustion performance of boron can be improved by coating it with metal particles, metal oxides, or organic materials, as well as by removing the boron oxide layer.

In the literature, there are limited studies on metal particle coating of a boron surface using the electroless Ni plating method. The electroless coating has several impressive advantages over conventional electrolytic coating. The prime advantage is that electroless plating does not require any electricity to operate and is a low-cost process. Among other advantages, it provides a uniform coating and can be used with all kinds of substrates with complex shapes. Conductive and non-conductive materials/powders can be coated with constant thickness with good adhesion.

The present work investigated Ni nanoparticle coating on irregularly shaped/non-spherical boron particles using the electroless Ni-plating method at room temperature to prevent the oxidation of boron particles. This is preferable since it is very difficult to coat large quantities at relatively high temperatures. The four different simple paths were chosen during the electroless Ni plating to coat Ni on boron particles: no rinsing and no drying (Path A), only drying (Path B), both rinsing and drying (Path C) and only rinsing (Path D). Previous studies have explored the effect of bath concentration, pH, and temperature on the Ni coating. However, the influence of the four different paths mentioned above on Ni coating with boron particles or any other materials has rarely been investigated. Surface morphology confirmed the Ni nanoparticles coating on the surface of boron particles. The size of the Ni nanoparticles varied between 10 and 120 nm concerning the chosen paths used for preparation using TEM. XRD characterization results of the Ni coated boron particles showed the formation of crystalline Ni nanoparticles. EDAX and XPS results showed the presence of the primary B and Ni elements in samples synthesized in the present study. Thermogravimetric analysis conducted in air atmosphere found the boron particles coated with Ni nanoparticles had enhanced oxidation resistance compared to bare boron particles. Also, the Ni coated boron particles showed a shift in exothermic peak to a lower temperature and higher heat evolution than the bare boron particles.

Acknowledgements:

This work was supported by the National Research Foundation (NRF) of Korea grant funded by the Korea government (MSIT) No. 2019R1A2C1010862, 2022R1A2C2013508