Hollandite

Hog fat Hohlraum H-Oil process Holding furnaces Hole mobilities Hollander beater Hollandite [12008-99-0]... 

Figure 7. Crystal structures of (a) hollandite, (b) romanechite (psilomelane), and (c) todorokite. The structures arc shown as three-dimensional arrangements of the MnO() octahedra (the tunnel-tilling cations and water molecules, respectively, are not shown in these plots) and as projections along the short axis. Small, medium, and large circles represenl the manganese atoms, oxygen atoms, and the foreign cations or water molecules, respectively. Open circles, height z. = 0 fdled circles, height z = Vi.

Parker, R.B. and Toots, H. 1972 Hollandite-coronadite in fossil bone. American Mineralogist 57 1527-1530. 

Figure 2. In this low-symmetry, metal-metal bonded adaptation of the well-known hollandite structure the chains forming the four sides of each tunnel are related in pairs by P 1 symmetry.

Figure 4.15 Hollandite structure. The shaded diamonds represent chains of edge-shared MnC>6 octahedra and the shaded circles Ba2+. The light and heavy shading represent octahedra and atoms at two different heights. The unit cell is outlined.

A hollandite structure phase containing Ba, Ti, Al, and O is fabricated with the aim of immobilizing radioactive nuclides, (a) What is the formula of the hollandite (b) It is desired to replace 10% of the Ba with radioactive K. What would the formula of the new phase be (c) It is desired to replace 35% of the Ba with radioactive Sr. What would the formula of the new phase be (d) It is desired to replace 17% of the Ba with radioactive La. What would the formula of the new phase be ... 

The use of framework structures to minimize AH for alkali-ion electrolytes has been demonstrated to provide a means of opening up the bottlenecks to cation motion in a number of oxides (Goodenough, Hong and Kafalas, 1976). Framework structures may provide one-dimensional tunnels as in hollandite, two-dimensional transport in planes as in the )S-aluminas, or three-dimensional transport as in NASICON and LISICON. Since one-dimensional tunnels are readily blocked, the two-and three-dimensional conductors are the more interesting. 

Fig. 7.4 Tunnel structures based on rutiles, (a) Rutile-like chains, showing alternately short and long metal-metal distances, as in MoOj. (h)-(

Hollandite Mn02nH20 Mn02nH20-m(R20, RO, R2O3) where R = Na, Ca, Co, Fe, Mn (Ba,K)i 2Mn8Ci6 XH2C (MnCe) octahedra Cpen tunnels permit large cation incorporation... 

Turgite = hematite + water PBF 1 532 Hollandite Ba(Mn, Mn )80i6 PBF 1 743 (cryptomelane group) Kermesite 862820 PBF 1 279 Plattnerite Pb02 PBF 1 581 (rutile group)... 

Akaganeite, P-FeOOH, is named after the Akagane mine in Japan where it was first discovered (Mackay, 1962). It occurs rarely in nature and is found mainly in Cl-rich environments such as hot brines and in rust in marine environments. Unlike the other FeOOH polymorphs, it has a structure based on body centered cubic packing of anions (bcp) (hollandite structure) and contains a low level of either chloride or fluoride ions. It has a brown to bright yellow colour. 

Furthermore, specific mineral matrices for use in conditioning separated radio nuclides are also elaborated and studied on the basis of mineral structures, known in nature for their selective-insertion capabihties with respect to certain radio nuclides and their stabihty over time. Among those phases, hollandite, zirconoUte, apatite and monazite are particularly studied. 

The hosts for ACT and REE immobilization are phases with a fluorite-derived structure (cubic zirconia-based solid solutions, pyrochlore, zirco-nolite, murataite), and zircon. The REEs and minor ACTs may be incorporated in perovskite, monazite, apatite-britholite, and titanite. Perovskite and titanite are also hosts for Sr, whereas hollandite is a host phase for Cs and corrosion products. None of these ceramics is truly a single-phase material, and other phases such as silicates (pyroxene, nepheliiie, plagioclase), oxides (spinel, hibonite/loveringite, crichtonite), or phosphates may be present and incorporate some radionuclides and process contaminants. A brief description of the most important phases suitable for immobilization of ACTs and REEs is given below. 

Hollandite does not contain long-lived ACTs and, therefore, it is undergoing p-y-irradiation from fission and corrosion products, but in multiphase ceramics it can also be a-irradiated from neighbouring ACT-bearing phases. Irradiation by a-particles from external 238PuOz sources and heavy ions results in a volume expansion of 2-2.5% and transformation of tetragonal to monoclinic symmetry. 

Smith, K. L. Lumpkin, G. R. 1993. Structural features of zirconolite, hollandite and perovskite, the major waste-bearing phases in Synroc. In Boland, J. N. Fitz Gerald, J. D. (eds) Defects and Processes in the Solid State Geoscience Applications. The McLaren Volume. Elsevier Science Publishers, B.V., 401-422. 

Pyrochlore. perovskite, uraninite + hollandite Pyrochlore + branncritc. baddeleyite, rutile Zirconolite + baddeleyite. rutile Ba-Cs-hollandite + rutile... 

The crystal stmcture of hollandite, A i i 7B8Oi6, is similar to that of rutile and consists of edge-... 

Fig. 6. Plots of the cumulative alteration depth versus time for Synroc-C in deionized water at 70 °C (a) and 150 °C (b). These plots use Al, Ca, Mo, and Ba as indicator elements for the alteration depth of Al-rich oxide phases, perovskite, intermetallic phases, and hollandite, respectively.

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