NiO powder is used in nickel alloys, salts, catalysts, fuel cells and other chemicals as well as ceramic glazes, frits and colorants. Typical impurities include cobalt, copper, iron and sulfur at levels of 1% or less.

Occupational and environmental exposures to green NiO (NiO-g) have been reported in the USA. About 4000 tons of chemical grade NiO are produced annually.

In a 2-year National Toxicology Program study in F344/N rats, some carcinogenicity was reported with chronic inflammation without fibrosis. The most commonly affected tissues were lungs, bronchial lymph nodes and thymus. Changes in these organs were similar in animals exposed to low-level aerosol exposures to NiO-g.

High-resolution XPS spectroscopy confirmed the presence of crystalline NiO with main peaks at 2.41, 2.09, 1.48, 1.26 and 1.21 A (d) values and multiplets for Ni 2p and O 1s. In addition, XRD showed a thin surface oxide for NiO-g that is covered by a defect-rich Ni2O3 or Ni(OH)2 surface oxide.

Release data for the exposed NiO-g powder were determined in synthetic fluids with relevance for the two main exposure routes of nickel toxicity including artificial sweat (ASW) and artificial lysosomal fluid (ALF). After exposure, the released nickel amounts from the Ni metal powders dissolved significantly faster and were lower in ALF than in ASW, indicating that the released nickel was mainly a function of chemical dissolution rather than electrochemical or complexing processes.

Detailed particle and surface oxide characterization, combined with kinetics analysis of the release of nickel from the nickel metal powders compared to a nickel oxide bulk powder, is an important step towards understanding the behavior of micron-sized nickel metal powders. This investigation is also a valuable tool for determining the reactivity of bulk powders as a means of improving their safety.

tags: Semiconductors semiconductor industry