Nickel - a silver-white metal, does not fade in the air. In its pure form, it is very ductile and can be processed by pressure. It is a ferromagnet with a Curie point of 358 ° C. Physical properties of nickel and nickel alloys: Electrical resistivity of 0.0684 μOhm o m. The coefficient of linear thermal expansion α = 13.5 o 10-6 K - 1 at 0 ° C The coefficient of volumetric thermal expansion β = 38–39 o 10-6 K - 1 The elastic modulus is 196–210 GPa. Nickel has a high tensile strength and keeps it to very high temperatures. Nickel processing can be both cold and hot. It lends itself well to machining and can be joined by welding, soldering with hard and soft solders. It has excellent corrosion resistance,
Most often, nickel powder is produced in the following ways:
carbonyl (dissociation of carbonyls);
recovery of nickel compounds.
PNA powder is obtained by the carbonyl method. The starting material is nickel carbonyl - Ni (CO) 4. The process proceeds in two stages. In a first step, nickel-containing feedstocks react with carbon monoxide to form carbonyl. This step is called carbonyl synthesis. In the second stage, upon heating, carbonyl dissociates (decomposes) into nickel and carbon monoxide. This step is called the thermal decomposition of carbonyl.
PNE powder is obtained by electrolytic method. As a result of passing direct current through an aqueous solution of the compound of the metal (nickel) emitted or its molten salt, pure metal is released at the cathode.
It is worth noting that both carbonyl and electrolytic production methods produce pure nickel powder.
During reduction, nickel powder is obtained by removing a non-metallic component from a chemical compound (oxide or nickel salt) by adding a reducing agent. The reducing agent reacts with a non-metallic component (oxygen or saline residue), the metal is released in its pure form. As a reducing agent, as a rule, hydrogen is used.
Particle size depends on the brand. So for xxxx1 ..., xxxx4 and xxxx3, ..., , the particles should be less than 20 microns. The xxxx1 brand should contain grains 71-100 microns, PNK-2K10 - 45-71 microns. Moreover, the number of particles, the size of which differs from the required, should not be more than 20% of the batch mass for heavy and coarse-grained powders and not more than 15% for light. The grain size of the PNE-1 brand should be less than 71 microns, the content of particles less than 45 microns in size should be at least 30% of the batch mass. For PNE-2 powder, the particle size should be less than 250 microns, the content of grains with a size of less than 71 microns should be at least 3% of the batch mass. Moreover, the number of particles, the size of which differs from the required, should not be more than 4% and 3%, respectively.
Grain sizes, bulk density, delivery status of the described products are regulated by standard GOST 9722-97.
A small grain size nickel powder is also called nickel powder.
Nickel powder is widely used in modern industry. There are many alloys, one of the main components of which is nickel (for example, nickel, copper-nickel alloys). This metal has good properties of heat resistance, heat resistance and corrosion resistance. This leads to the addition of nickel as an alloying agent to various steels and alloys. The nickel plating process is also widespread - applying a thin nickel film to metal surfaces, which protects them and gives a beautiful appearance. For these purposes, nickel powder is used, which is sprayed on the surface or deposited on it.
They are used in powder metallurgy as a binder based on nickel, for corrosion-resistant or non-magnetic grades of hard alloys, in the manufacture of magnets, batteries, filter elements, electrical contacts, special coatings, dyes, catalysts, welding electrodes, composite adhesives, ferrites, and also creating wear-resistant coatings on aircraft engine parts.
Nickel electrodes made from the finest powders are also used in fuel cells. The catalytic properties of nickel and its compounds are of particular importance here. Nickel is an excellent catalyst for complex processes occurring in chemical current sources..