Investigation of diffusion kinetics of plasma paste borided AISI 8620 steel using a mixture of B 2 O 3 paste and B 4 C/SiC

In the present study, AISI 8620 steel was plasma paste borided by using various B₂O₃ paste mixture. The plasma paste boriding process was carried out in a dc plasma system at temperatures of 973, 1023 and 1073 K for 2, 5 and 7 h in a gas mixture of 70% H₂ -30% Ar under a constant pressure of 10 mbar. The properties of the boride layer were evaluated by optical microscopy, X-ray diffraction, Vickers micro-hardness tester and the growth kinetics of the boride layers. X-ray diffraction analysis of boride layers on the surface of the steel revealed FeB and Fe₂B phases. Depending on temperature and layer thickness, the activation energies of boron in steel were found to be 124.7 kJ/mol for 100% B₂O₃.     

Inhibition of yeasts isolated from traditional Turkish cheeses by Lactobacillus spp.

Antifungal activity of some Lactobacillus strains was determined. Yeasts were isolated and identified as Saccharomyces cerevisiae (10 of 17) and one each of Candida pseudotropicalis, C. krusei, C. lipolytica, C. lusitaniae, C. ciferrii, Torulopsis glabrata and Rhodotorula rubra . Lactobacillus strains were found to have fairly strong antifungal activity against S. cerevisiae . Of the 19 bacteria tested, L. plantarum Lp 21 seemed to have the most inhibitory effect against all of the S. cerevisiae strains except for S. cerevisiae 13. We suggest that L. plantarum Lp 21 can be used with starter cultures for cheese production.