Contribution of components from volume defect in natural pyrite and quartz to solution chemistry of flotation pulp

The volume defects in pure pyrite and quartz from a classical Cu-Pb-Zn-Fe sulfide deposit were investigated.The results indicate that a large number of volume defects exist in natural pyrite and quartz.The volume defects assume a variety of shapes,including long strips,oval shapes and irregular shapes,with sizes ranging from a few microns to dozens of microns.These volume defects are rich in metallogenic elements as a result of the capture of metallogenic and mineralizing fluid during the defect-forming process.The volume defects are fractured during the grinding process,and their chemical components are released into the solution,as confirmed by the abundant presence of various metal and non-metal components in the cleaning water and EDS results.Under the experimental conditions of 10 g pyrite or quartz with grinding fineness of d90=37 μm,which was cleaned in 40 m L of pure deionised water under an inert atmosphere,the total average concentrations of Cu,Pb,Zn,Fe,Ca,Mg and Cl-in the aqueous solution are 32.09×10^-7,16.51×10^-7,19.45×10^-7,516.52×10^-7,129.50×10^-7,35.30×10^-7 and 433.80×10^-7 mol/L,respectively,for pyrite and 19.20×10^-7,8.88×10^-7,8.31×10^-7,82.71×10^-7,16.21×10^-7,4.28×10^-7 and 731.26×10^-7 mol/L,respectively,for quartz.These values are significantly greater than those from the experimental non-oxidative dissolution of the pyrite or quartz,respectively.Therefore,the metallogenic fluid in volume defects of mineral crystal is concluded to represent the dominant contribution to the solution chemistry of sulfide flotation pulp.The present investigation will help to deeply understand the flotation theory of sulfide minerals.

VOLUME DEFECT FATIGUE FAILURE OF CERAMIC BALLS UNDER ROLLING CONDITION

A newly developed pure rolling fatigue test rig with three contact points is used to test the rolling contact fatigue properties of silicon nitride ceramic balls. Ball surfaces are examined after failure with optical microscopy and scanning electron microscopy. The failure cause, fatigue phenomenon and mechanics are analyzed. The research shows that subsurface cracks play a dominant role in the formation of spalling failure. These cracks originated from volume defects of the material and propagate, to form elliptical fatigue spalls under the action of principal tensile stresses. The principal tensile stress increases with increasing contact load, causing spall formation and reduction of rolling contact life. The greater the principal tensile stress is, the more severe the peeling of near surface is. Under the same condition, the closer volume defects are to the surface, the more likely failure occurs, the shorter the rolling contact life is.