Optical Determination of Cuprous Oxide at Zinc Oxide—Metal Interface of an Oxidized α-Brass

Preparation of Zinc Oxide Films by a Humid Air Plasma

The surface of zinc metal exposed to a humid air plasma gives rise to an oxide layer which was identified by the linear sweep voltammetry technique. The quantity of zinc oxide (ZnO) layer formed increases with exposure time and the humid air gas flow. The humid air plasma treatment of a zinc surface can be proposed as a new technique to prepare zinc oxide.

Effect of temperature on the visualization by digital color mapping of latent fingerprint deposits on metal

Visualization of fingerprint deposits by digital color mapping of light reflected from the surface of heated brass, copper, aluminum, and tin has been investigated using Adobe® Photoshop®. Metals were heated to a range of temperatures (T) between 50°C and 500°C in 50°C intervals with enhancement being optimal when the metals are heated to 250°C, 350°C, 50°C, and 300°C, respectively, and the hue values adjusted to 247°, 245°, 5°, and 34°, respectively. Fingerprint visualization after color mapping was not degraded by subsequent washing of the metals and color mapping did not compromise the visibility of the fingerprint for all values of T. The optimum value of T for fingerprint visibility is significantly dependent of the standard reduction potential of the metal with Kendall’s Tau (τ) = 0.953 (p < 0.001). For brass, this correlation is obtained when considering the standard reduction potential of zinc rather than copper.

Effect of temperature on rectifying Schottky barriers formed from fingerprint sweat corrosion of brass

Corrosive electrochemical processes of brass, including those resulting from fingerprint sweat, continue to be studied because of the widespread industrial use of brass. Here, we examine how increased temperature affects the relative abundance of fingerprint sweat corrosion products and the rectifying Schottky barrier formed between p-type copper (I) oxide corrosion and brass. X-ray photoelectron spectroscopy confirms increasing dezincification with increasing temperature. This leads to n-type zinc oxide replacing copper (I) oxide as the dominant corrosion product, which then forms a rectifying Schottky barrier with the brass, instead of copper oxide, when the temperature reaches c. 600°C. Using X-ray diffraction, resulting diodes show polycrystalline oxides embedded in amorphous oxidation products that have a lower relative abundance than the diode forming oxide. Conventional current/voltage (I/V) characteristics of these diodes show good rectifying qualities. At temperatures between c. 100 and c. 600°C, when neither oxide dominates, the semiconductor/brass contact displays an absence of rectification.

Note: Measuring dezincification of brass by Schottky barrier diodes formed between semiconductor corrosion products and brass

A newly developed method is presented for measuring dezincification on the surface of brass from a consideration of the forward and reverse bias potential drop across a Schottky barrier diode formed between n-type zinc oxide or p-type copper (I) oxide corrosion products and the brass substrate. Electrical connection to the corrosion product is made with zinc and platinum tipped probes, approximately 1 mm diameter. Comparison with x-ray photoelectron spectroscopy shows the difference between the forward and reverse bias potential drop to be dependent on the relative abundance of the corrosion products and the work function of the metal probe. This difference, for a zinc tipped probe, gives a statistically significant correlation to the surface zinc to copper ratio and the degree of dezincification. Details of the setup, operation, and testing of a portable instrument designed to measure dezincification of brass by this method are given.