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Properties of hypersonic sprayed nanostructured carbide coatings

100%

Żórawski W. , Trpcevska J.

tom Z. 13

446--450

Nanostructured cermet coating was sprayed from agglomerated nanostructured WC12Co powder feedstock by means of hypersonic spray process (HVOF). Grains of tungsten carbide nanopowder were analyzed by scanning electron microscope (SEM) and transmission electron microscope (TEM). Investigations revealed that grains of powder consist of nanoparticles. Nanostructured sprayed coating was observed by SEM. A denser coating structure with higher hardness compared to conventional coating was observed. Dry abrasive rubber wheel tester was applied to estimate wear resistance. These tests show that nanostructured tungsten carbide have got better wear resistance.

Kinetic study of zinc leaching from sal-ammoniac flux in acidic media

80%

Smincakova E. , Trpcevska J. , Piroskova J. , Blaskova K.

tom R. 61, nr 1

31--36

This paper presents the results of the laboratory investigation of acid leaching of sal-ammoniac flux. Sal-ammoniac is waste product originated during wet hot dip galvanizing process having about 40 % of zinc. Zinc is the most abundant element in the sal-ammoniac flux and in the supplied sample was occurred in the form of following phases: Zn5(OH)8Cl2 H2O in amount of 70.83 %, (NH4)2(ZnCl4) in amount of 24.02 % and ZnCl2(NH3)2 in amount of 5.5 %. Leaching test of sal-ammoniac flux in distilled water and aqueous solution of hydrochloric acid has been carried out kinetically. The experimental parameters of HCl concentration, leaching time and temperature were varied. The results obtained are as follows: The apparent activation energy of leaching reaction by hydrochloric acid solution was Ea = 6.28 kJ mol-1. The apparent order of reaction n = 0.33 was estimated.

W artykule przedstawiono wyniki badań laboratoryjnych kwaśnego ługowania odpadowego salmiaku. Salmiak ten jest produktem powstającym podczas gorącej zanurzeniowej galwanizacji zawierający ok. 40 % mas. cynku. Cynk jest pierwiastkiem występującym w największej ilości, dostarczona (badana) próbka zawierała następujące fazy: Zn5(OH)8Cl2 H2O — 70,83 %, (NH4)2(ZnCl4) — 24,02 % i ZnCl2(NH3)2 — 5,5 %. Testy ługowania prowadzono w wodzie destylowanej i w wodnych roztworach kwasu solnego. W testach zmiennymi parametrami były: stężenie HCl, czas i temperatura ługowania. Uzyskano następujące wyniki: pozorna energia aktywacji ługowania roztworem kwasu solnego Ea = 6,28 kJ mol-1, pozorny rząd reakcji n = 0,33.

The Effects of Microwave-Assisted Leaching on the Treatment of Electric Arc Furnace Dusts (EAFD)

70%

Laubertova M. , Havlik T. , Parilak L. , Derin B. , Trpcevska J.

2020

tom Vol. 65, iss. 1

321--328

In this study, laboratory-scale experiments were carried out to investigate the effects of microwave-assisted alkaline leaching on the treatment of electric arc furnace dusts to recover zinc and lead. Microwave treatment is a new innovative technology in waste treatment and now is an attractive advanced inter-disciplinary field and also environmental friendly. The highest zinc extraction, 50.3% in 60 minutes using 5 M NaOH at 750 W and L:S ratio 20, and lead extraction up to 92.84% was achieved in these same conditions but in 30 minutes. Compared with conventional leaching, the top extraction rate using MW-assisted leaching was higher by 16% (Zn) and 26% (Pb). Zinc presents in the flue dust in the form of franklinite (ZnFe2 O4 ), its leaching in sodium hydroxide does not occur under the examined conditions, because it is enclosed in a matrix of iron.