Influence of milling parameters on the preparation of fine tungsten and copper powders by mechanically induced self-propagating reaction

Abstract

Mechanically induced self-propagating reaction in planetary ball mill was realized in three different systems, CaWO4 (scheelite) + Mg, CuO + Ti and CuO + Zr. An influence of a ball diameter (from 5 to 41.2 mm) at three different angular velocities (170, 200 and 230 min" ) on the ignition time (time required for initiating reaction by self-propagating combustion wave) was investigated. A significant influence of mechanochemical treatment parameters to the ignition time was observed. Generally, increasing angular velocity of the supported disc and ball diameter up to 16mm causes shortening of the ignition time to initiate reaction. Further increasing of ball diameter have no significant effect on time needed to initiate the reaction. Ignition time show exponential decay as a function of the kinetic energy of single ball. Changes in chemical composition, structure and morphology was examined by X-ray diffraction and scanning electron microscopy. The tungsten powder was obtained by leaching reaction products of the system CaWO4+Mg. Existence of spherical copper particles in reaction products in either CuO+Ti and CuO+Zr system indicates that reaction temperature exceeds the melting temperature of copper.

Mehanički je inicirana samorasprostiruća reakcija u planetarnom mlinu u tri različita sistema, CaWO4 (šelit) + Mg, CuO + Ti i CuO + Zr. Ispitan je uticaj prečnika kugli (od 5 do 41,2 mm) pri tri različite ugaone brzine osnovnog diska (170, 200 i 230 min" ) na vreme iniciranja reakcije (vreme potrebno da se inicira reakcija samo-rasprosturućeg talasa sagorevanja). Primećen je znatan uticaj parametara mehano-hemijskog tretmana na vreme neophodno za iniciranje reakcije. Generalno, povećanje brzine obrtanja osnovnog diska i prečnika kugli do 16 mm dovodi do skraćenja vremena potrebnog za iniciranje reakcije. Dalje povećanje prečnika kugli nema značajnijeg uticaja na vreme potrebno za iniciranje reakcije. Vreme iniciranja je pokazalo eksponencijalnu opadajuću zavisnost od kinetičke energije pojedinačne kugle. Promene u hemijskom sastavu, strukturi i morfologiji praćene su rentgenskom difrakcijom i skanirajućom elektronskom mikroskopijom. Prah volframa dobijen je luženjem produkata reakcije sistema CaWO4 + Mg. Prisustvo sfernih čestica bakra u produktima reakcija u sistemima CuO + Ti i CuO + Zr ukazuje da reakciona temperatura premašuje temperaturu topljenja bakra.