Cadmium metal

Cadmium metal particles are a kind of fine particles with metallic lustre and soft texture composed of cadmium element, which is chemically more active and has certain applications in many fields such as industry, but due to the toxicity of cadmium, its use is also subject to many restrictions.

Characteristics

Appearance: silver blue-grey metallic luster

Crystal structure: hexagonal most dense packing (hcp) structure

Density: 8.65g/cm³ at room temperature (20°C), 7.996g/cm³ in liquid state (at melting point).

Hardness: Mohs hardness is 2.0, Brinell hardness in 203-220MPa, relatively soft texture.

Melting point: 594.22K (321.07℃), belongs to the relatively low melting point of the metal.

Boiling point: 1040K (767℃).

Speed of sound: In the fine rod-shaped cadmium metal, the speed of sound at 20 ℃ is about 2310m/s.

Coefficient of thermal expansion: 30.8 µm/(m・K) at 25℃.

Thermal conductivity: The thermal conductivity is relatively high, about 96.6W/(m・K).

Electrical conductivity: relatively low resistivity, resistivity of 72.7nΩ・m at 22℃, good electrical conductivity.

Atomic number: 48

Atomic weight: 112.414

Electronic configuration: (Kr)4d¹⁰5s².

Oxidation state: The common oxidation state is + 2. Oxidation states such as – 2 and +1 also exist.

Chemical properties: stable in dry air, but in humid air the surface will be oxidised gradually to form oxides; can react with mineral acids to form the corresponding cadmium salts; cadmium vapour is dark yellow and monoatomic form.

Application

Nickel-cadmium batteries: formerly cadmium metal is widely used in the field of batteries, commonly used in the manufacture of nickel-cadmium (Ni-Cd) batteries. These batteries have good resistance to electrical abuse, high cycle life, reliability and versatility.

Aviation and railway fields: nickel-cadmium batteries can be used as engine starting power, aircraft circuit backup power and for starting locomotive engines, for passenger cars and track lights to provide electricity.

Pigments and paints: Cadmium metal can be used in the production of pigments that provide bright, long-lasting colours, such as cadmium red and cadmium yellow pigments. These pigments are used for dyeing and colour mixing in plastics, rubber, paints and printing ink industries, which can make products with good colour stability and weather resistance. However, the application of cadmium in the field of pigment has been subject to more and more strict restrictions due to its toxicity which is potentially harmful to the environment and human health.

Electroplating industry: Cadmium metal plating layer has good corrosion resistance, abrasion resistance and decorative appearance, so it can be used for plating certain metal products, such as cadmium plating on the surface of iron and steel can prevent rusting of iron and steel to improve its service life. But also because of environmental and health considerations, the application of cadmium plating is also gradually reduced.

Alloy manufacturing: Cadmium metal can form alloys with other metals, used to improve the performance of alloys. For example, cadmium can improve the strength and corrosion resistance of copper alloys, in some special bearings, springs and other components will be used in the manufacture of cadmium-containing alloy materials.

Semiconductor and electronic components: in semiconductor manufacturing, cadmium can be used as a dopant in the preparation of certain semiconductor materials to change their electrical properties. In addition, cadmium metal or its compounds may also be used in the manufacturing process of some electronic components such as resistors and capacitors.

Nuclear reactors: In nuclear reactors, cadmium can be used as a control rod material for absorbing neutrons and controlling the rate of nuclear reactions.