What Is Nickel?

Nickel is a silvery-white, face-centered cubic transition metal with atomic number 28 and the chemical symbol Ni. It is hard, ductile, and moderately magnetic at room temperature, remaining ferromagnetic up to its Curie temperature of 358°C, above which thermal energy disrupts magnetic domain alignment. With a density of approximately 8,902 kg/m³ and a melting point of 1,453°C, nickel combines high-temperature stability with strong resistance to oxidation and corrosion in both acidic and alkaline environments. These properties make it one of the most industrially significant metals, used either in commercially pure form or as an alloying element in thousands of engineering materials.

Nickel is a d-block element in Group 10 of the periodic table, with an electronic configuration of [Ar]3d⁸4s². Its partially filled d-shell gives it versatile chemistry: nickel forms stable compounds in the +2 oxidation state most commonly, along with +3 and higher states in specialized applications. The metal is found naturally in the Earth's crust primarily in sulfide ores (pentlandite) and lateritic deposits, and it is refined by smelting, roasting, and electrorefining to the high-purity grades required for electronics and battery applications.

Physical and Chemical Properties

The AZoM materials database entry for nickel summarizes nickel's engineering properties in detail: electrical conductivity at about 22% IACS, thermal conductivity of approximately 90 W/(m·K), and a Mohs hardness of about 3.8. These values place it between copper and iron on most performance scales. Nickel's face-centered cubic crystal structure confers good formability and toughness, and the metal can be drawn, rolled, and welded without special precautions under standard industrial conditions.

Nickel resists attack by dilute acids at room temperature but dissolves in concentrated nitric acid. It is notably stable in alkalis, a property directly exploited in nickel-cadmium and nickel-metal hydride battery electrodes, where the positive electrode consists of nickel oxide hydroxide (NiOOH) operating within a concentrated potassium hydroxide electrolyte without significant corrosion over thousands of cycles.

Engineering and Industrial Uses

In its commercially pure form, nickel is used where corrosion resistance and moderate strength are required simultaneously. Electroplated nickel coatings protect steel components from atmospheric corrosion and provide a hard, bright surface for decorative and functional applications. Pure nickel foil and powder serve as current collectors and conductive substrates in battery and fuel cell construction.

As an alloying element, nickel is the base metal for an entire family of superalloys, including the Inconel and Hastelloy series, which retain tensile strength above 1,000 MPa at temperatures exceeding 650°C. ScienceDirect's overview of nickel-based superalloys explains how the gamma-prime (γ') precipitate phase, Ni₃(Al,Ti), impedes dislocation motion at high temperatures and is the principal strengthening mechanism in turbine blade alloys.

Nickel also appears extensively in stainless steels: austenitic grades such as Type 304 (18% chromium, 8% nickel) and Type 316 (with added molybdenum) owe their non-magnetic character and superior corrosion resistance to the nickel content stabilizing the face-centered cubic austenite phase. The copper-nickel alloys reference from the International Copper Association illustrates how even relatively small nickel additions to copper dramatically improve seawater corrosion resistance.

Applications

Nickel has applications across many sectors of engineering and manufacturing, including:

• Aerospace turbine blades and combustion hardware in nickel superalloys
• Rechargeable battery electrodes in Ni-Cd, Ni-MH, and lithium-ion systems
• Corrosion-resistant stainless steel for chemical processing and food equipment
• Electroplating and surface finishing for industrial and consumer components
• Catalysis in hydrogenation and petroleum refining processes