Spherical Titanium Dioxide Particles Research Articles

Assessment of particle distribution in particle-containing composite materials using an electron probe microanalyzer

Abstract Numerous filler particles are being developed and applied to improve the properties of conventional composite materials or to develop composite materials with additional functionalities. When filler particles are added to the polymer matrix of a fiber-reinforced composite material, the particles dispersed in the polymer resin can be filtered between fiber strands during the manufacturing process, which leads to a nonuniform particle distribution and material defects. Therefore, understanding and controlling such filtration phenomena has become a critical issue. In the present study, a new microscopic methodology for measuring the distribution of filler particles in fully cured composite parts using an electron probe microanalyzer (EPMA) is proposed. The distributions of spherical titanium dioxide particles and carbon nanotubes conjugated with silver nanoparticles as tracers were visualized by elemental mapping analysis. Furthermore, the concentrations were separately measured in the intratow and intertow regions by quantitative analysis.

Synthesis and properties of titanium dioxide/polydimethylsiloxane hybrid particles

Spherical particles of titanium dioxide and poly(dimethylsiloxane) hybrid have been synthesized from titanium tetraisopropoxide and methoxy-functionalized poly(dimethylsiloxane) by a co-precipitation method. The refractive index of the hybrid particles exhibits a linear relationship with the titanium dioxide content. These hybrid particles have elastic properties. The nano structures of the products were characterized by TEM, XRD, IR, UV-Vis. spectroscopy and HAADF-STEM. The hybrids have an islet-like nano-structure, which consisted of titanium dioxide and PDMS domains in the nanometer size range.

Synthesis of Spherical Titanium Dioxide Particles by Homogeneous Precipitation in Acetone Solution

Titania powders were synthesized by thermal hydrolysis of titanium tetrachloride in a mixed solvent was studied. The dielectric constant was tuned by regulating the acetone/water volume ratio (R/H ratio) and temperature of the solvent. Hydroxypropyl cellulose (HPC) was used as a steric dispersant. The synthesis were carried out at R/H ratios of 0–4, temperatures of 70–90°C, TiCl4 concentrations of 0.05–0.2 M, HPC concentrations of 0–5 × 10−3 g/cm3, and synthesis times of 15–60 min. The TiO2 particles obtained at an R/H ratio of 0, i.e., pure water system, were fine and agglomerated. In contrast, the TiO2 particles prepared at an R/H ratio of 3 were uniform and spherical. The TiO2 particle size increased with increasing TiCl4 concentration. The synthesis temperature did not influence the particle size, but greatly influenced the morphologyof the TiO2. Adding HPC to the solution yielded more uniform and spherical particles. In addition, the synthesis time should be longer than 30 min to obtain the most uniform and spherical particles. The dielectric constant of the acetone-water mixed solvent at 28 gave the most uniform and spherical TiO2 particles. The powders prepared at the condition of 0.1 M TiCl4, R/H ratio of 3, HPC concentration of 0.001 g/cm3, temperature of 70°C, and synthesis time of 1 h exhibited the most uniform and spherical morphology. The as-synthesized powder was anatase and retained the phase below 400°C. It transformed to the rutile phase after calcination at 700°C.

Fabrication of nanoparticles of anatase TiO 2 by oxygen-supplied pulsed laser deposition

Nanoparticles of titanium oxides have been fabricated by ablating a Ti target with pulsed CO 2-laser deposition in Ar-diluted oxygen environments. The pulse energy and repetition rate of the CO 2 laser (wavelength 10.6 μm) are 0.44 J/cm 2 per pulse and 50 Hz, respectively. During the focused laser irradiates the Ti target, Ar and O 2 gases are supplied into the irradiation chamber. The gas pressure is varied in a range of 1×10 3 to 1×10 5 Pa. The flow rates of Ar and O 2 gases are adjusted in ranges of 75–83 and 3.3–8.3 cm 3/s, respectively. Above 3×10 4 Pa, the laser irradiation creates nanosized spherical particles of titanium dioxide. The nanospheres are characterized by transmission electron microscopy (TEM) to be of the anatase type. Each nanoparticle consists of a single crystal or single-crystalline domains. The particle size slightly increased with increasing the gas pressure, irrespective of the flow rate. The results demonstrate that nanoparticles of anatase TiO 2 are created by the reactive pulsed laser deposition (PLD).

Synthesis of titanium dioxide particles in supercritical CO 2

Spherical particles of titanium dioxide, anatase, were prepared in a supercritical carbon dioxide medium from titanium alkoxides and water. The dissolution of the alkoxide and stabilization of water dispersions in supercritical CO 2 were found to be required for the formation of spherical particles. An anionic fluorinated surfactant was used to stabilize water dispersions in supercritical CO 2. This could not be realized with hydrocarbon-based surfactants. The solubility of titanium alkoxides in CO 2 appears to parallel their vapor pressure which is dependent on the oligomerization of the unhydrolyzed alkoxides. The polydispersity in particle sizes is due to nucleation occurring simultaneously with particle growth, owing to changes in the degree of supersaturation during the transition from the liquid to the supercritical state.

In situ steric stabilization of titanium dioxide particles synthesized by a sol—gel process

Spherical titanium dioxide particles were synthesized via the hydrolysis of tetraethylorthotitanate (TEOT) in ethanol in the presence of hydroxypropyl cellulose (HPC) which served as an in situ steric stabilizer. This work focused on the effect that water concentration had on the HPCTiO 2 interactions leading to steric stabilization. The water concentration varied in the range [H 2O]/[TEOT] = 5.3–60. The amount of adsorbed HPC increased threefold over this water concentration range. This correlates with measurements of the preferential adsorption of water on TiO 2 in ethanol. The particle size decreased fivefold in the presence of HPC over the range of water concentrations studied owing to the combined effects of increased HPC adsorption and increased nucleation rates. Mean particle diameters as small as 70 nm were obtained.

Spherical particles and their surface properties: II. Preparation of spherical particles of titanium dioxide

The formation of larger spheres of TiO 2 prepared by fusion of five kinds of fine Ti02powder particles in the O 2 H 2 flame was investigated. Each TiO 2 particle formed contains both anatase and rutile structures; the former constitutes mainly the outer part and the latter the inner part of the particle. Smaller particles, collected at a position far from the flame, are richer in anatase content than the larger ones, collected at a position near the flame. Apparently, crystallization of molten TiO 2 drops on quick cooling at lower temperatures yields the anatase structure, while crystallization on slow cooling at higher temperature gives rutile.

Preparation of uniform colloidal dispersions by chemical reactions in aerosols. I. Spherical particles of titanium dioxide

Spherical titanium dioxide particles were prepared by hydrolysis of aerosols consisting of liquid titanium(IV) compounds. The droplets of the latter were nucleated with AgCl in a falling film generator and subsequently hydrolyzed in specially designed chambers kept at different temperatures. When titanium(IV) ethoxide was used as starting material, TiO 2 spheres of narrow size distribution were obtained with modal diameters ranging between 0.06 and 0.6 μm. The size of the particles could be altered by changing the temperature of the falling film generator, the flow rate of the carrier gas, and the AgCl nuclei concentration. The titanium dioxide particles so prepared were essentially amorphous. Titanium tetrachloride was also used as the liquid aerosol material. Owing to the vapor pressure characteristics of this compound, much higher concentration of the droplets was obtained in the same equipment. However, the titanium dioxide powder, resulting from the hydrolysis of TiCl 4 aerosols, consisted of spheres of broader size distributions. The crystallinity of the solid particles could be changed by heating of the solid aerosol stream at different temperatures. The titanium dioxide powders, prepared by the aerosol technique, could be readily dispersed in water. The particle charge was pH dependent and showed an electrophoretic isoelectric point between pH 4.5 and 5.5.

The role of chemical complexing in the formation and stability of colloidal dispersions

The role of chemical complexing in the preparation of monodispersed metal hydrous oxides of iron, aluminum, and titanium is discussed. Specifically, the effect of anions on the size, shape, and composition of the colloidal particles is emphasized. A reaction mechanism is offered which explains the nucleation and growth process involved in the formation of uniform spherical particles of titanium dioxide in acidic solutions containing sulfate ions. To illustrate the influence of chemical complexing in the solution and at the interface on the stability of colloidal dispersions, the interactions of hydrolyzed metal ions and of chelates with latexes and silver halide sols are described. Finally, new data on the adhesion of monodispersed chromium hydroxide particles on glass are given.