Are Large Particles of Iron Detrimental to Properties of Powder Metallurgy Steels?

It is experimentally shown that a removal of particles exceeding 100 microns in size from iron powders typically used in the fabrication of medium density powder metallurgy steels has a weak effect on apparent density, flowability and compressibility of blends as well as on density and strength of green bodies. An elimination of such particles, i.e., cutting off a heavy tail of a size distribution histogram at the 100 μm threshold, improves a compositional uniformity of sintered materials, but has no noticeable beneficial effect upon the strength of a final product, which is likely be determined by a fraction of pores and their shapes. A presence of soft pearlitic inclusions hardly matters unless their number density becomes so large that a 3D continuity (integrity) of a hard martensitic matrix is lost. This finding suggests that such an expensive preparatory step as sieving away large particles from as-received mixtures would bear no technological advantages. It was experimentally found that an attempt to lower the threshold below 100 μm noticeably worsened apparent density, flowability and compressibility.

Green Synthesis of Silver Nanoparticles by Sonicated Method Using Pulicha Indeca Stem Extract: Characterization and Study of Antibacterial Activity, Anticancer Activity and Cell Viability Test

In the present work, green synthesized silver nanoparticles by sonofication method using pulicha extract, which can act as reducing as well as stabilizing agent. The silver nanoparticles were characterized by UV-VIS spectra, FTIR, XRD, SEM and TEM analysis. The UV –VIS SPR peak was observed at 440 nm, which represents the characteristic plasmon resonance of nanostructures. The fcc crystalline structure of silver nanoparticles is evident from XRD studies. The shape and size of synthesized AgNPs were studied by TEM. The synthesized AgNPs, were mostly mono-dispersed and spherical in shape. The particles are well separated from each other and did not exhibit any aggregation. This indicates the effective capping nature of pulchea indeca extract. The AgNPs size distribution histogram and the average size of AgNPs was found to be 14 ± 2 nm. The effect of silver ion concentration range from 1mm to 10mm and extract concentration 1% to 8% has been studied on the formation of silver nano particles. The AgNPs shows positive antibacterial acivity against stayphylococusaureoous , klebisellapneumonia, basilusbtilis and negative antibacterial activity against protious mirabilis bacteria studied. The anticancer activity of AgNps shows positive activity on HeLa cell.