A Kinetic Study of Manganese Leaching from Low-Grade Psilomelane Ore by Acetic-Tannic Acid Lixiviant

Kinetic leaching of psilomelane using tannic acid as reductant and acetic acid as an acidic modifier is investigated in terms of tannic acid and acetic acid concentration, solid-liquid ratio, particle size and temperature. Kinetic modelling using three models: shrinking core, shrinking particle, and diffusion-interface transfer model revealed that at room temperature leaching (30 °C), experimental data are best modelled using diffusion-interface transfer model, indicating the dissolution of Mn is more affected by reaction rate among reactants and their concentration in bulk volume rather than by transfer across the boundary layer. At higher temperatures (≥ 50 °C), the shrinking particle model fits the experimental data best, suggesting the prominence of the diffusion process boundary layer. The apparent activation energy obtained at two temperatures were 13.1 and 52.7 kJ/mol for lower and higher temperatures. Plot between rate constant and concentration yields reaction order to be 1.28 for tannic acid and 0.73 for acetic acid. A semi-empirical model for each temperature range is proposed to describe the overall manganese leaching efficiency.

Improved TiN Deposition on the SKD11 with Equally Spaced Multi-Sources of Cathode Arc

The Multi-Sources of Cathode Arc (MSCA) were installed in the vacuum chamber in order to increase the substrate temperature and to provide a plenty of Ti plasmas from titanium plate inside the chamber. The increase rate of the substrate temperature of the SKD11 substrate against the deposition time for two thicknesses of the substrate by operations with both single ion source and MSCA was obtained. It was known that MSCA were useful for the film synthesis for the larger substrate both in size and in number. A wider diffusion interface between TiN film and SKD11 substrate was formed by dissolution of both TiN and Ti2N into the substrate more actively due to plenty Ti ion numbers supplied by MSCA. Due to the thick diffusion interface the adhesion of the film increased and thus the hardness increased up to twice. The peaks of Ti2N(111) and Ti2N(211) which are indicators of high hardness were observed in XRD pattern. The pseudo-diffusion interface between the outer TiN film and substrate formed and it improved the film adhesion. By using MSCA the hardness of SKD11 surface was improved up to 126 from 58 in Rockwell-C scale by the TiN deposition in this study.

Transmission and diffusion: Linguistic change in the regional French of Béarn

ABSTRACTThis article examines the seemingly dichotomous linguistic processes of transmission and diffusion (Labov, 2007) in the regional variety of French spoken in Béarn, southwestern France. Using a sociophonetic apparent time methodology, an analysis of nasal vowel quality provides evidence for the advancement of linguistic changes from below taking place between successive generations during the transmission process, as well as for change from above taking place in the variety as a result of exposure to diffusing non-local varieties of French. The results address Labov's (2007) assertion that it is rare to investigate incremental changes occurring from below in European dialectological studies and shed light on the transmission–diffusion interface by showing the adoption of an individual change from above to instigate a faithfully-transmitted counterclockwise chain shift in the regional French nasal vowel system.

Fracture Surface Analysis in Thixojoined Tool Steels

Thixojoining has been developed for D2 and M2 tool steels. The suitable globular microstructure and excellent bonding quality are obtained through this work. Scanning electron microscopy (SEM) observation along the joint interfaces showed a smooth transition zone with no cracks. In addition, fracture surface of the shear test samples showed that the fracture mode was transgranular. Finally, based on obtained results, this method presented high quality joint with nonequilibrium diffusion interface.