Rutile conductivity

Figure 4.10 Proposed conceptual model of high-activity-mixed phase catalysts. Illumination promotes an electron into the rutile conduction band. This electron is then located sequentially in trapping sites in (1) the rutile lattice, (2) the anatase lattice, and (3) interfacial and surface sites. Reproduced with permission from Elsevier [38].

Charging bv ion bombardment is the technique used in most mineral separations. The conductive-induction (nonionizing) plate types of separators have also been used Application.s of this device in the minerals indiisti v include its use as a final cleaning step when concentrating rutile and zircon,... 

Conductive induction Zircon or rutile concentrate (eastern Aiistraliaj Residual conductor minerals from rutile and zircon upgrading of concentrate from 98.95 to 99..35% zircon at 92% recoveav Plate 50-80 -0.21 + 10.074 0.6-0.7, 5-10... 

Shock-modified rutile is found to exhibit two characteristic resonances, which can be confidently identified as (1) an isotropic resonance characteristic of an electron trapped at a vacancy, and (2) an isotropic resonance characteristic of a Ti" interstitial. The data indicate a concentration of 2 X 10 cm , which is an order of magnitude greater than observed in hydrogen- or vacuum-induced defect studies. At higher pressures the concentration of interstitials is the same as at lower pressure, but more dispersion is observed in the wave shape, indicating higher microwave conductivity. 

Further evidence for the unique nature of the shock-formed point defects is the dispersion in ESR lineshape characteristic of conductivity at temperatures above 30 K. In shock-modified powder the conductivity is constant down to 2 K, indicating that the electrons responsible for the conductivity are not trapped. These observations indicate that shock-modified rutile is in a physical defect state that has not been obtained in more conventional vacuum-reduction defect studies. 

The dioxides of molybdenum (violet) and tungsten (brown) are the final oxide phases produced by reduction of the trioxides with hydrogen they have rutile structures sufficiently distorted to allow the formation of M-M bonds and concomitant metallic conductivity and diamagnetism. Strong heating causes disproportionation ... 

It is a valve metal and when made anodic in a chloride-containing solution it forms an anodic oxide film of TiOj (rutile form), that thickens with an increase in voltage up to 8-12 V, when localised film breakdown occurs with subsequent pitting. The TiOj film has a high electrical resistivity, and this coupled with the fact that breakdown can occur at the e.m.f. s produced by the transformer rectifiers used in cathodic protection makes it unsuitable for use as an anode material. Nevertheless, it forms a most valuable substrate for platinum, which may be applied to titanium in the form of a thin coating. The composite anode is characterised by the fact that the titanium exposed at discontinuities is protected by the anodically formed dielectric Ti02 film. Platinised titanium therefore provides an economical method of utilising the inertness and electronic conductivity of platinum on a relatively inexpensive, yet inert substrate. 

Observing NEMCA, and actually very pronounced one, with Ti0224 and Ce0271 supports was at first surprising since Ti02 (rutile) and Ce02 are n-type semiconductors and their ionic (O2 ) conductivity is rather low so at best they can be considered as mixed electronic-ionic conductors.77... 

The stepwise heating/cooling cycle was conducted on the Ti02 wafer (8H rutile after being heat treated in O2) and a typical correlation of 0/Ti ratio versus temperature is shown in Figure 6 for one particular run. Surface reduction is facilitated by ESD, and additional cycles continually reduced both maximum 0/Ti ratio obtained at high temperature and the minimum 0/Tl ratio observed at room temperature, and a final value of 0.7 was measured at the com-... 

X-ray diffraction conducted on the codeposited powder revealed that the deposit obtained from a suspension of gamma alumina, which had been partially converted to the alpha phase, contained both phases of alumina. Whereas, the powder codeposited from a suspension having a 50 50 mixture of alpha to gamma alumina powder, consisted only of the alpha phase. Using a parallel plate electrode configuration, Chen et al. [31] concluded that only alpha alumina can be codeposited. Chen also observed a difference in codeposition with copper when using two different phases of the titanium oxide particle system rutile readily codeposited but anatase titania did not... 

Technical electrodes usually consist of a mixture of Ru02 and TiC>2 plus a few additives. They are called dimensionally stable anodes because they do not corrode during the process, which was a problem with older materials. These two substances have the same rutile structure with similar lattice constants, but RuC>2 shows metallic conductivity, while pure TiCU is an insulator. The reaction mechanism on these electrodes has not yet been established the experimental results are not compatible with either of the two mechanisms discussed above [4]. 

The sulphosuccinamate collector was extremely effective in flotation of rutile, as well as ilmenite and zircon from a fine sand deposit. Laboratory testing conducted on Wimmera heavy mineral sand from Australia indicated that the use of sulphosuccinamate achieved a high titanium recovery in the bulk cleaner concentrate. Table 25.4 shows the results obtained on the Wimmera heavy mineral sand. The sand was scrubbed and deslimed before flotation. Between 90% and 95% Ti02 was recovered using a 60g/t addition of succina-mate collector. 

Development work conducted over the past 3 years has identified a treatment process that will produce a high-grade rutile concentrate. The initial flowsheet is similar to that used for the Guadalajara ore. However, using this flowsheet, only a portion of the calcite was recovered and an appreciable amount of the rutile was lost in the gangue concentrate. An alternative, effective treatment process has been developed that produces excellent results. 

We have included here, for comparison, the results of a study of zirconolite-rich Synroc nominally composed of 80 wt% Ce- or Pu-doped zirconolite plus 10 wt% hollandite and 10 wt% rutile (Hart et al. 1998). Inclusion of this study in this section is significant because the two additional phases are both highly durable in their own right and the experiments were conducted at two different temperatures (90 and 200 °C) and in three different aqueous solutions (pure water, silicate, and brine). The authors found no major differences in the release rates of Ca, Ce, Hf, Ti, Zr, Pu, and Gd apart from those for Ce and Ti, which appeared to be somewhat higher in the brine. On average, for all elements, the increase in temperature caused the release rates to increase by a factor of approximately seven. Release rates were generally below 10 2 g/m2/d for Ca, 10 3 g/m2/d for Ce and Gd, and 10 4 g/m2/d for Ti, Zr, Hf, and Pu (except for the brine at 200 °C, which gave a Ti release rate of 2 x 10 3g/m2/d). Hart et al. (2000) also determined the release rate of Pu in an LLNL-type zirconolite ceramic. After nearly one year in pure water at 90 °C the release rate of Pu decreased from 2 x 10-3 g/m2/d to less than 10-5 g/m2/d (Fig. 7). 

---