The effect of pH modifier on the flotation of celestite with sodium oleate and sodium metasilicate
Abstract This paper studies the influence of two pH modifiers, namely sodium hydroxide (NaOH) and sodium carbonate (Na 2 CO 3 ), on the flotation of celestite ore using sodium oleate as the collector and sodium silicate (Na 2 SiO 3 ) as the depressant. The use of Na 2 CO 3 provides the best results for the concentration of celestite, under the same experimental conditions.
Contact Angle and Surface Tension in the Celestite + Sodium Oleate Aqueous Solutions + Air System
The contact angles of the ternary system celestite + sodium oleate aqueous solutions + air were measured in the range 7.3 × 10-6 mol·L-1 and 6.2 × 10-4 mol·L-1 of sodium oleate at pH between 4 and 12 and at the temperature 20 °C. The surface tensions of the aqueous solutions of sodium oleate were also measured to obtain the values of the work of adhesion at the solid−liquid interface.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME