Metal powders play a crucial role in advancing manufacturing technologies and enhancing the performance of products across various industries. Nano nickel powder is a really good example. 

Nano nickel powder exhibits excellent oxidation resistance at high temperatures, maintains strength and ductility at low temperatures, demonstrates good compatibility with various alloying elements, and possesses catalytic properties suitable for chemical reactions. High quality nano nickel powder demonstrates precise control over parameters such as particle size, shape, purity, and chemical composition. Its unique properties, including a high surface area-to-volume ratio and enhanced reactivity, make it highly valuable in numerous sectors including aerospace, automotive, electronics, and clean energy.

In recent years, the continuous development of the new energy industry, electronics industry, and aerospace sector has led to a sharp increase in demand for nano nickel powder. The preparation of high quality nano nickel powder requires resolving the trade-off between particle size, dispersion, and high-temperature sintering. Methods for producing nano nickel powder include physical vapor deposition, chemical vapor deposition, electrical explosion of wire, plasma method, liquid phase chemical reduction method, spray pyrolysis, sol-gel method, mechanochemical method, and so on.

Method for Preparing Nano Nickel Powder

1️⃣ Physical Vapor Deposition (PVD)

Physical Vapor Deposition is a preparation technique that forms ultrafine powders through metal vaporization and condensation in a vacuum environment. Its core principle involves using high-temperature evaporation, sputtering, arc discharge, or other methods to detach nickel atoms from a solid surface into the gas phase within a high-vacuum or inert atmosphere. These atoms then condense into nano- to submicron-sized particles in a low-temperature region.

This method involves preparation under high temperatures in an inert gas atmosphere, so the resulting nano nickel powder exhibits controllable particle size and morphology, high purity, excellent crystallinity, and a clean surface requiring no post-processing. Furthermore, the production process is environmentally friendly. However, this method necessitates complex production equipment, demands high technical expertise, incurs high production costs, and suffers from low efficiency.

2️⃣ Chemical Vapor Deposition (CVD)

Chemical vapor deposition, also known as gas-phase hydrogen reduction, is a preparation method by reducing gaseous metal compounds with hydrogen gas. At elevated temperatures, nickel precursors are vaporized and subsequently reduced to elemental nickel atoms in a hydrogen atmosphere. These atoms then undergo nucleation, growth, and condensation to form ultrafine nano nickel powder. The preparation temperature reaches as high as 900–1000°C, and the nickel powder exhibits excellent oxidation resistance.

This method enables the preparation of nano nickel powder with uniform particle size and high crystallinity at relatively low production costs. However, it imposes extremely high demands on the corrosion resistance of equipment, and the required apparatus is also relatively expensive.

3️⃣ Electrical Explosion of Wire (EEW) 

The electrical explosion of wire method (EEW) is an advanced technique for preparing nano-sized metal, alloy, and metal compound powder materials. Within a reaction chamber filled with inert gas, a high direct current voltage is applied along the axial direction of metal or alloy raw material wires, which generates an extremely high current density within the wire, causing it to explode and produce spherical nano powder materials with internal lattice defects, self-igniting properties, and high reactivity.

This method offers high production capacity and superior product quality. By adjusting specific production parameters, it can yield nano powder materials with varying particle sizes and morphologies for diverse applications. The method generates no harmful substances and causes no environmental damage, making it a green approach for preparing nano powders.

4️⃣ Plasma Method

The plasma method utilizes an electric arc to ionize gas, forming a stable high-temperature plasma that melts and vaporizes metal. Metal vapor particles rapidly cool, nucleate, and grow, ultimately depositing onto the surface of a cooled collection chamber. After undergoing inert gas stabilization and passivation treatment, loose nanoscale powder can be obtained.

The nano nickel powder prepared by this method exhibits high purity, small average particle size, uniform size distribution, controllable shape and dimensions, and an environmentally friendly preparation process. However, it imposes stringent requirements on production equipment.

5️⃣ Liquid Phase Chemical Reduction Method

The liquid phase chemical reduction method is currently one of the most widely applied techniques for producing nano nickel powder. This solution-based chemical process utilizes aqueous solutions of NiSO₄, NiCl₂, Ni(OH)₂, and other compounds as raw materials. Reduction agents such as hydrazine hydrate (N₂H₄·H₂O), polyols, NaBH₄, and KBH₄ are employed to catalyze redox reactions, synthesizing metallic nickel.

The production process is as follows: Using nickel salts (such as nickel sulfate or nickel chloride) as precursors, dissolve them in water or organic solvents to form a uniform solution. Subsequently, strong reducing agents such as sodium borohydride, hydrazine hydrate, or sodium hypophosphite are added. Under alkaline conditions at a pH of 8–12, the reduction reaction converts nickel ions (Ni²⁺) into metallic nickel particles. Temperature must be precisely controlled (50-90°C) during the reaction, and surfactants (such as polyvinylpyrrolidone, namely PVP) are added to prevent nanoparticle agglomeration. The final nano nickel powder is obtained through centrifugation, ethanol washing, and vacuum drying.

This preparation process and equipment are simple, with readily available raw materials. The resulting nano nickel powder exhibits a narrow particle size distribution and excellent dispersion properties.

6️⃣Spray Pyrolysis

As a process method for preparing nanopowders, spray pyrolysis involves atomizing a metal salt solution and spraying it into a high-temperature reaction environment, where the solvent evaporates and the solute undergoes thermal decomposition to directly produce the desired material.

The production process is primarily divided into three stages: melting, atomization, and cooling. First, high-purity metallic nickel (≥99.9%) is heated to 1450-1600°C in an inert atmosphere to melt into a liquid state. Subsequently, high-pressure gas (such as nitrogen or argon, at 5-20 MPa) or centrifugal force (rotation speed >20,000 rpm) breaks the liquid nickel into micron-sized droplets. During rapid cooling, these droplets solidify into spherical or near-spherical powder particles. The final target nano nickel powder is obtained through sieving.

The equipment employs combustion heating or electric heating methods, requiring high temperatures (reaction temperature range: 400-900°C) and vacuum conditions. It imposes stringent demands on both equipment and operation. When integrated with a high-speed centrifugal atomization device, it enables large-scale production.

7️⃣ Sol-Gel Method

The sol-gel method generally refers to the preparation of precursors using metal salts in solvents, where the solute undergoes hydrolysis or alcoholysis under specific conditions to yield particles approximately 1 nm in size, forming a sol. This sol is then evaporated and dried to remove the solvent, transforming it into a gel. The gel is subsequently processed through drying, calcination, and other techniques to produce the final product.

This preparation method holds significant research value due to its high initial reaction activity, molecular-level uniform mixing of reaction components, low synthesis temperature, minimal energy consumption, fine product particle size, and high purity.

8️⃣ Mechano-Chemical Process

The mechanochemical method combines chemical reactions with mechanical comminution. Through various mechanical forces such as mechanical balls and ultrasonic grinding, it mechanically comminutes the nickel (Ni) produced by the reduction reaction of raw materials (e.g., NiCl).

Nano nickel powder features small particle size and large specific surface area, offering performance advantages such as highly efficient photocatalysis, high conductivity, and magnetic properties. 

Its application replaces more expensive precious metal materials, significantly reducing production costs. In fields such as MLCCs, conductive coatings, chemical catalysis, and new energy batteries, the required nano nickel powder must exhibit a regular spherical structure, small size with uniform particle size distribution, excellent dispersibility, high tap density, and strong oxidation resistance. The preparation process for nano nickel powder is continuously upgraded and improved, enhancing its performance and unlocking new application areas.