Investigation on the Tribology of Co Implanted Stainless Steel Using Metal Vapor Vacuum Arc Ion Source

AISI 304 stainless steel was ion implanted with Co, and the tribological property on the surface of the stainless steelwas investigated. The Co ion implantation was carried out using a metal vapor vacuum arc (Mevva) broad-beam ionsource with an extraction voltage of 40 kV, implantation doses of 3×10^(17)/cm^2 and 5×10^(17)/cm^2, and ion currentdensities of 13, 22 and 32μA/cm^2. The results showed that the near-surface hardness of Co-implanted stainless steelsample was increased by 50% or more, and it increased with increasing ion current density at first and then declined.The friction coefficient decreased from 0.74 to 0.20 after Co implantation. The wear rate after Co implantationreduced by 25% or more as compared to the unimplanted sample. The wear rate initially decreased with increasingion current density and then an increase was observed. Within the range of experimental parameters, there existsa critical ion current density for the Co-implanted stainless steel, at which the wear rate decreased with increasingretained dose, going through a minimum and then increased. The critical ion current density in this paper is about22μA/cm^2.

Comparison of Vacuum Metal Deposition and 1,2-lndandione/Ninhydrin Reagent Method for the Development of Fingerprints on Renminbi

It is extremely difficult to develop fingerprints from the surface of currency.There are studies reporting that the high vacuum metal deposition(VMD)method can be used to detect fingerprints on certain types of currency notes.Both VMD and 1,2-indandione/ninhydrin techniques are employed to visualize latent fingermarks on porous surfaces,such as paper.The current study explores whether the VMD method or 1,2-indandione/ninhydrin reagent method is more effective in the development of fingerprints on remninbi(RMB).Uncirculated,circulated,and water-exposed RMB was utilized in this study,along with five donors who ranged in their age and potential to leave fingermarks.Samples were aged for a determined period(for uncirculated and circulated RMB,times were 1,3,5,10,and 35 days;for watei^exposed RMB,exposure time was 1 day)and then treated with VMD and 1,2-indandione/ninhydrin.The results suggested that the 1,2-indandione/ninhydrin reagent yielded a better effect for both circulated and uncirculated RMB.For the RMB exposed to water,VMD performed better and gave limited results in terms of fingerprint development,which could serve as a reference for actual forensic cases.