in U.S. Patent 7,645,439, Mexican Petroleum Institute (IMP) researchers reveal a new nanofabrication process to produce a novel type of nanostructured titanium oxide material. The new phase of nano-titanium is nicknamed "JT Phase" and it has never been observed before. The materials feature orthorhombic symmetry.
The positions of the atoms, their surroundings, the crystal parameters and space groups in the crystalline materials do not match any of the known phases of titanium dioxide (anatase, brookite, rutile) or any of the not so well known phases (beta and others).
That's according to Instituto Mexicano del Petroleo researchers Jose Antonio Toledo Antonio, Carlos Angeles Chavez, Maria Antonia Cortes Jacome, Fernando Alvarez Ramirez, Yosadara Ruiz Morales, Gerardo Ferrat Torres, Luis Francisco Flores Ortiz, Esteban Lopez Salinas and Marcelo Lozada y Cassou.
The nanomaterials are useful mainly as a support for catalysts and/or as catalysts, as photocatalysts, as adsorbents, as semiconductors in the construction of electronic devices, in photoelectric cells, in pigments and cosmetics, among other applications.
The new crystalline structure forms the basic unit of construction of nanomaterials which are nanofibers, nanowires, nanorods, nanoscrolls and/or nanotubes. The nanomaterials are obtained from a precursor that is isostructural to the new crystalline structure and is a hydrogen titanate and/or a mixed sodium and hydrogen titanate.
These titanates are the hydrogenated, protonated, hydrated and/or the alkalinized phases of the new crystalline structure. The new crystalline structure is named the "JT phase of TiO2-x." The term "JT phase" means a crystalline structure or crystalline phase with an orthorhombic symmetry having the formula TiO2-x, and has at least one of the space groups 59 Pmmn, 63 Amma, 71 Immm or 63 Bmmb.
Also, this discovery further involves the synthesis process of the nanomaterials, which have as a building block the new JT phase. The new nanomaterials after being subjected to dynamic thermal treatment in an inert, oxidizing or reducing atmosphere have a stable nanotubular structure that is preserved intact without collapse, thus maintaining their fibrilar morphology and high specific area.
Also, this discovery further involves the synthesis process of the nanomaterials, which have as a building block the new JT phase. The new nanomaterials after being subjected to dynamic thermal treatment in an inert, oxidizing or reducing atmosphere have a stable nanotubular structure that is preserved intact without collapse, thus maintaining their fibrilar morphology and high specific area.
FIGS. 1a, 1b and 1c are scanning electron microscopy images (SEM) of a nanofibrilar and nanotubular morphology of the hydrogen titanate, of the mixed sodium and hydrogen titanate and of the TiO2-x JT phase,
It has been discovered that the hydrogen titanate and mixed sodium and hydrogen titanate nanotubes, that are unstable when heated higher than 300.degree. C. in air in an oven can be stabilized by heating in a dynamic oxidizing, inert or reducing flowing atmosphere, which transforms the titanate nanotubes into the stable, oxygen deficient JT phase nanotubes.
FIG. 1a shows nanofibers and/or nanotubes obtained at low temperature, from 50 to 130.degree. C., FIG. 1b shows nanofibers and/or nanotubes obtained at medium temperature, from 130 to 160.degree. C.
FIG. 1c shows nanofibers and/or nanotubes of TiO2-x JT phase, obtained after dynamic thermal treatment of the hydrogen titanates, or the mixed sodium and hydrogen titanates synthesized at high temperature, between 160 and 180.degree. C.;
FIG. 1a shows nanofibers and/or nanotubes obtained at low temperature, from 50 to 130.degree. C., FIG. 1b shows nanofibers and/or nanotubes obtained at medium temperature, from 130 to 160.degree. C.
FIG. 1c shows nanofibers and/or nanotubes of TiO2-x JT phase, obtained after dynamic thermal treatment of the hydrogen titanates, or the mixed sodium and hydrogen titanates synthesized at high temperature, between 160 and 180.degree. C.;
FIGS. 3a-3f show transmission electron microscopy (TEM) images where FIGS. 3a, 3b and 3c correspond to nanotubes of hydrogen titanates and mixed sodium and hydrogen titanates, and
FIGS. 3d-3f correspond to nanotubes of TiO2-x JT phase. FIGS. 3a-3f are illustrative examples of the typical transmission electron microscopy images obtained for the present hydrogen titanate and mixed sodium and hydrogen titanate and the TiO2-x JT phase.
