Showing papers on "Rutile published in 1970"

Thermal Expansion of Rutile and Anatase

Abstract: Lattice parameters of rutile and anatase were determined from 30° to 650°C and from 28° to 712°C, respectively, using a high-temperature powder camera These data were used to evaluate the coefficients of thermal expansion of rutile and anatase The temperature dependence of the coefficients, α11 and α1, parallel and perpendicular to the principal axis, respectively, are represented by the equations: Rutile: Anatase: The relative magnitudes of the coefficients of thermal expansion of these polymorphs are explained in terms of the interionic distances

Titanium as Free Oxide and Substituted Forms in Kaolinites and Other Soil Minerals

Abstract: Titanium in TiO2 minerals was differentiated from that isomorphously substituted into minerals by the use of dihydrogen hexafluorotitanate (hydrofluotitanic acid, H2TiF6), which selectively dissolved minerals containing substituted Ti4+, leaving free crystalline TiO2 minerals in the residue. Titanium analyses on the original samples and the residues remaining after H2TiF6 treatment, by both wet chemical (Tiron) and neutron activation methods, indicated that an average of 86 per cent of the titanium in seven kaolinite samples was present in the residual TiO2 form (largely anatase), whereas only 28 per cent in two bentonites was present in the TiO2 form. Residual Ti accounted for 100 per cent of the Ti in synthetic anatase and for 92 per cent of the Ti in coarse clay sized rutile, the latter value suggesting that about 8 per cent amorphous TiO2 was removed from the mechanically dry ground rutile by the H2TiF6 reagent. The Ti present as residual TiO2 in a variety of other samples ranged from 0 to 100 per cent.

The Catalytic Oxidation of Carbon Monoxide on Titanium Dioxide; Anatase and Rutile

Abstract: For the purpose of investigating the correlation between the crystal structure of titanium dioxide and its catalytic activity, the catalytic oxidation rate of carbon monoxide and the desorption rate of oxygen from the sample surface have been measured on anatase, rutile, and an anatase-rutile mixture. The oxidation of carbon monoxide was investigated by a static method at temperatures of 250–550°C and under gas pressures of 10−2–150 mmHg. The desorption of oxygen was carried out at 600–750°C. The reaction rate was proportional to PCO and did not depend on either PCO2 or PCO2 The activation energy was 16.0 kcal/mol for anatase and 6.7 kcal/mol for rutile. The catalytic activity per unit of the surface area of rutile was 3—6 times as much as that of anatase. The reaction rate almost coincided with the rate of the reduction of titanium dioxide by carbon monoxide. The electric resistance of the sample was little affected by the PO2. The following reaction mechanism is proposed to explain the results. The rate...

New Ordered Phases of Slightly Reduced Rutile and Their Sharp Dielectric Absorptions at Low Temperature

Abstract: The temperature dependence of the complex dielectric constant of single-crystal rutile has been studied at different frequencies and as a function of reduction. The results suggest the existence of two new ordered phases in slightly reduced rutile. Sharp dielectric absorptions have been observed in these phases. This is attributed to the hopping of low-mobility charge carriers between two ion sites. The nature of the charge carriers introduced by reduction is discussed. It is proposed that the room-temperature conductivity alone may not characterize the state of a slightly reduced rutile sample.

Electrical conductivity of slightly reduced rutile between 2° and 370°K

Abstract: The electrical resistivity and the Hall coefficient of slightly reduced rutile crystals were measured in the temperature range between about 2 °K and 370 °K. The time of reduction treatments between 900 °C and 1300 °C was usually as long as 300 hrs, which assures the homogeneous reduction of crystals, The conduction mechanisms in three temperature ranges, i. e. 1. 9∼3°K, 3∼100°K and 100∼250°K, were discussed in terms of lattice defects evidenced by ESR studies.

Heat of immersion of modified rutile pigments in water

Abstract: A series of rutile pigments modified by surface treatment with silica and/or alumina have been studied by heat of immersion and adsorption techniques. The results clearly indicate that these surface treatments markedly alter the measured properties of the pigments, and that silica and alumina treatments behave quite differently. The results are explained in terms of the varying surface hydroxyl concentration with treatment variations.

Vapor Deposited Titanium Dioxide Thin Films: Some Properties as a Function of Crystalline Phase.

Abstract: : Thin films of TiO2 are grown in a low temperature (150C) vapor deposition process by hydrolyzing tetraisopropyl titanate at the substrate. These films can be made uniform over a 1-1/4 in substrate to within 100 A and are found to be amorphous in the 'as grown' condition. Films in the amorphous state have an index of refraction of 2.0 and can be etched easily (50 A/sec) in 0.5% HF. Annealing in air at 350C converts the film to the anatase tetragonal crystalline form and at 700C to a mixture of anatase and rutile. Both forms are quite etch resistant, but the anatase can be etched by HF and warm H2SO4. At 1000C, the film is completely rutile with an index of refraction of 2.5. This form is extremely etch resistant even in 120C H2SO4 (1000 A/hour). The conversion from amorphous to rutile is accompanied by a thickness decrease of 36%. (Author)

Preparation of fibrous titanium dioxide

Abstract: A process is described for producing rutile fibers of unusual dimensional uniformity. Titanium trichloride is reacted at 960*990* C. with humidified oxygen followed by dry oxygen in the presence of molten sodium and potassium chloride mixtures containing preformed titanium dioxide of pigmentary size.

Extended Hückel Molecular Orbital Calculations II. The Sigma and Pi Overlap Populations in Titanium Oxides

Abstract: A method for analysis of separate sigma and pi overlap populations in a system of very low symmetry has been proposed. The calculations are performed in Ti3O3, rutile, anatase, brookite and tetragonal barium titanate. The examination of the various bond overlap populations has led to reasonable explanation on the infrared absorption spectra of CO and CO3 chemisorption on rutile and anatase and the relative heats of formation of anatase, rutile and brookite.

Preparation of alkali metal tetratitanate

Abstract: Alkali metal titanates are produced substantially exclusively in the tetratitanate form in a process in which mineral rutile is the titanium dioxide source by particular control of reaction parameters including particle size of reaction mixture components to influence the titanate form obtained.

High bandwidth - time product spin echo system

Abstract: A system for the generation of a spin-echo signal utilizing a paramagnetic sample of titanium dioxide (rutile) selectively doped with nickel wherein the crystalline electric field of the rutile doped with nickel splits the energy level of the nickel at a predetermined frequency (8.25GHz) and spin-echo signals are produced without the requirement of an external magnetic field.

Nitrous oxide decomposition and low temperature parahydrogen enrichment on pure and doped rutile

Abstract: Doping with 0.1 mol % Cr2O3, Fe2O3, NiO, Nb2O5 or WO3 has little effect on the catalytic properties of rutile for the decomposition of nitrous oxide in the temperature range 450–590°C. For all six catalysts, first-order kinetics with respect to initial nitrous oxide pressure were obeyed. Relatively small differences in the activation energies were observed, but an apparent compensation effect resulted in the absolute rates at 550°C and 1.33 × 104 N m–2 lying between 1.2 and 2.2 × 1012 molecules cm–2 s–1. Parahydrogen enrichment has been investigated at 77 and 90 K over the pressure range 1.33 × 102 to 2.66 × 104 N m–2 on the six catalysts used in nitrous oxide decomposition. The reaction proceeds by the paramagnetic vibrational mechanism on a small active fraction of the oxide surface. Results obtained for other samples of doped rutile, and analytical measurements on progressively dissolved material, show the existence of a surface excess concentration of dopent both at a nominal concentration of 0.1 mol % and at 100 p.p.m. Inhomogeneity in doped titanium dioxide, which has not been reported previously, is of importance in the catalytic properties of such material.

Rutile titanium dioxide pigment for paper laminates

Abstract: IN A PROCESS OF TREATING RUTILE TITANIUM DIOXIDE PIGMENT BY (A) MIXING TITANIUM DIOXIDE AND A SILICATE IN WATER FORMING A SLURRY; (B) NEUTRALIZING THE SLURRY TO OBTAIN A PH VALUE OF ABOUT 5-8, AT A TEMPERATURE OF ABOUT 50-70* C.; (C) ADDING A SOLUBLE ZINC SALT TO THE MIXTURE AND ADJUSTING THE PH OF THE MIXTURE TO A LEVEL OF ABOUT 6.5-7.5; (D) ISOLATING THE TREATED PIGMENT FROM THE MIXTURE; (E) CALCINING THE ISOLATED PIGMENT; AND (F) DRY-GRINDING THE CALCINED PIGMENT, THE LIGHT STABILITY OF THE PIGMENT AND THE ABILITY OF THE PIGMENT TO BE RETAINED BY PAPER PULP IN THE MANUFACTURE OF PAPER IS IMPROVED BY RAPIDLY ADDING SULFURIC ACID HAVING A CONCENTRATION OF 50-96 PERCENT TO THE SLURRY OF PIGMENT AND SILICATE, REDUCING THE PH OF THE SLURRY TO A VALUE OF 5 OR LESS AND EFFECTING RAPID PRECIPITATION OF SILICA.

X-Ray Line Profile Analysis of Rutile Powder Subjected to Impact

Abstract: グリセリン液中爆発による粉体の衝撃圧縮実験法を述べ, ルチルの微細構造に及ぼす衝撃加工の効果を論じた。衝撃加工されたルチル粉末のみかけ粒度を電子顕微鏡観察し, 格子面 {110} に垂直方向の結晶子の大きさおよび平均2乗平方格歪を, Warren-Avervach の解析法により計算した。格子不整の熱処理による回復をもまた調べて, 次のような結果を得た。1) みかけ粒度 1μ以下のルチル粉末を, 衝撃圧縮すると, 圧搾粉体が得られ, 粉末粒子は破砕されない。2) 格子歪成分は, 短距離では不均一であるようにみえるが, 距離100Åにわたって平均されると, ほぼ一定になり, その値は, 約0.4×10-2 である。結晶子の大きさは, 衝撃加工により加工前の約1000Åに対して約 100Å に減少する。3) 衝撃加工により生じた格子不整は, 1000℃, 1時間の熱処理により除かれる。