Titanium Dioxide Dispersions Research Articles

Coefficient of thermal expansion of TiO2 filled EVA based nanocomposites. A new insight about the influence of filler particle size in composites

The effect of uniformly dispersed titanium dioxide (TiO2) nanoparticles on the coefficient of thermal expansion (CTE) of films of Poly (ethylene-co-vinyl acetate) (EVA) based nanocomposites was investigated. High energy ball cryomilling was initially used to achieve a uniform dispersion of nanoparticles within the thermoplastic polymer to subsequently obtain films of composites by hot pressing. A method based on the use of an atomic force microscope (AFM) was used for measuring nano-thermal expansion of nanocomposite films to finally obtain their CTEs. The addition of TiO2 nanoparticles considerable decreases the CTE of EVA (only a 5% by weight or 1.3% by volume implies a 63% of decrement). To estimate CTEs, different theoretical proposals were used, being subsequently compared with a simple and intuitive one to understand the influence of the addition of fillers in EVA polymer in general and, the influence of the particle size in particular. It was concluded that the creation of an interphase, the amount and the size of the particles in the composites are the main factors to change the CTE of the polymer used as the matrix.

The effect of titanium dioxide on the tribological properties of carbon fiber-reinforced polyimide composites

This study examined the effect of titanium dioxide (TiO2) dispersion on the tribological properties of carbon fiber (CF)-reinforced–polyimide (PI) matrix (CF/PI) composites. Nanocomposites were prepared through compression molding as milled CF/PI mixtures without further melt mixing. The incorporation of TiO2 leads to a significant improvement in friction and wear properties of the CF/PI composite. The scratches on the worn surface of the CF/PI composite filled with TiO2 are considerably reduced. We can see a relatively smooth, uniform, and compact worn surface, which is in good agreement with the considerably increased wear resistance of the CF/PI composite.

Influence of anions stabilizing the sols in synthesis of powders of highly dispersed titanium dioxide and three-dimensional nanocomposites based on SiO2/TiO2

This paper reports on the results of investigations into the influence of anions (Cl−, SO42−,NO3−), which stabilize the sol-gel synthesis of highly dispersed titanium dioxide, on the crystallization and phase transition of TiO2 upon dehydration. The effect of the size factor on the phase composition of TiO2 in SiO2/TiO2 nanocomposites has been investigated using a three-dimensional opal matrix as a set of nanoreactors for the sol-gel synthesis of TiO2 · nH2O. It has been shown that there is a possibility of extending the region of the existence of a thermodynamically metastable modification of TiO2 (anatase) to the temperature of 1100°C due to the changes in the conditions of the sol-gel synthesis of TiO2 · nH2O.

Dispersion Stabilization of Titania Nanoparticles for Textile: Aggregation Behavior and Self-Cleaning Activity

The effect of various dispersion stabilization parameters on particle size, stability, and self-cleaning activity of titania aqueous dispersion was investigated with a focus on stability during preparation, storage, and introduction of fabric in the dispersion. Effect of parameters such as sonication, high-speed mixing, pH, and addition of ionic and nonionic dispersants was studied. The degree of surface charge on titania influences its stability and depends on the type of pH and dispersant. The stability of titania dispersion with the immersion of cotton, was also found to be a strong function of pH, dispersants and their combination. With the immersion of cotton in the dispersion ξ potential was >40 mV in the pH range of 1–3, and then gradually becomes close to zero in the pH range 4–7, then decreased further with the increase in pH. In the study of combined effect of pH and dispersants, influence of pH on ξ potential was independent in case of ionic dispersants and addition of nonionic dispersant has significant pH dependence. Self-cleaning activity (SCA) of titania-treated cotton fabric was quantitatively assessed by a standard method known as stain degradation assessment (SDA) method. SCA was highest at pH 2 followed by that at pH 10 and 12. In the presence of cationic dispersant, CTAB, ξ potential was >50 mV before and after cotton immersion and high SCA was obtained, however, in the presence of sodium salt of PAA, stable dispersion was obtained, but SCA reduced.

Effects of Beating of Cotton Linter Pulps with Titanium Dioxide on Paper Properties

To improve the physical properties, such as swelling and flexibility, of the cotton fiber, sodium hydroxide or cellulase was used for pretreatment before the beating process. Titanium dioxide was blended during beating process to improve the fibrillation of cotton fibers and even distribution of fillers to cotton fibers. Blending with titanium dioxide during beating process, led to improve the tensile strength and beating degree This treatment also improved the opacity, resulted by well dispersed titanium dioxide during blending. By the blending of titanium dioxide during beating process, similar impact of cotton fiber with cellulase or sodium hydroxide pretreatment was achieved. To improve the tensile strength and opacity of cotton paper simultaneously, titanium dioxide blending in during beating process was found as effective treatment.

Shear rate-dependent structure of polymer-stabilized TiO2 dispersions

Opacity, gloss, stability, color acceptance, and other paint properties depend on the quality of pigment dispersion. We measured the shear rate-dependent structure of titanium dioxide (TiO2) dispersions stabilized with commercial polymer dispersants in water. Two different MW polyacid dispersants and two different MW acrylate copolymers were used in this study. The experiments were conducted at the NIST Center for Neutron Research on the perfect crystal diffractometer for ultra-high resolution small-angle neutron scattering (USANS) measurements. The results for TiO2 scattering and rheology show that shear induced dissociation occurs for certain dispersants and shear induced association of TiO2 clusters is observed for other dispersants. The results suggest new ways to consider dispersant selection for paints and the quality of pigment dispersions.

Synthesis of highly dispersed titanium dioxide nanoclusters on reduced graphene oxide for increased glucose sensing

Highly dispersed titanium dioxide nanocluster (TDN) was synthesized on reduced graphene oxide (RGO) in a toluene–water system under microwave irradiation. The prepared RGO–TDN hybrids were used to modify glassy carbon electrode for loading glucose oxidase. The fabricated glucose biosensor exhibits excellent performance for glucose sensing including low work potential (−0.7V), high sensitivity (35.8μAmM−1cm−2), low detection limit (4.8μM), wide linear range from 0.032 to 1.67mM, small Michaelis–Menten constant (Km) (0.81mM), and short response time (10s).

TiO2and ZnO Nanoparticles in Photocatalytic and Hygienic Coatings

Antimicrobial paints were based on the aqueous acrylic dispersion and various nanoparticles of zinc oxide and titanium dioxide. Antimicrobial ability and photoactivity were assumed in these paints. It was possible to observe the photoactivity thanks to change of organic dyes due to oxidative-reductive reaction. The best photocatalytic effect showed the coating containing the mixture of the first type of TiO2and nano-ZnO despite the fact that the first type of TiO2was not better in the photocatalytic test than the other types of TiO2. The agar dilution method was used to test antimicrobial ability. TheEscherichia coli,Pseudomonas aeruginosa,andStaphylococcus aureuswere chosen as test bacteria andPenicillium chrysogenumandAspergillus nigeras test molds. The antimicrobial effect of coatings with the mixture of the first type of TiO2and nano-ZnO was the best of all the tested samples.

Photoelectrochemical Studies of Dye-Sensitized TiO<sub>2</sub> Nanoporous Electrodes

The nanoporous titania dispersion system are prepared under hydrothermal conditions by employing various amount β-cyclodextrin(CD) as the porogent.Then, different microsructure nanoporous TiO2 electrodes are fabricated by Doctor-blade mehod, using the above synthesis of titanium dioxide materials.The photoelectrochemical properties of dye-sensitized nanoporous TiO2 electrodes are studied with transient photocurrent spectrum ,electrochemical impedence spectra (EIS) and photocurrent action spectra. The results indicate that the current response signals of dye-sensitized porous TiO2 electrodes are stable. In addition,the impedence arc radius decreases gradually and light current increases gradually with the addition of β–CD. Meanwhile, the dye-sensitized porous electrodes with β-CD/TiO2 ＝40 wt% showes the best photoelectrochemical properties.

Preparation of Aqueous Dispersion of Titanium Dioxide Nanoparticles using Plasma on Liquid Surface

A method for preparing an aqueous dispersion of titanium dioxide (TiO2) nanoparticles by generating plasma on the liquid surface was developed. The plasma was generated between the tip of a needle electrode in the gas phase and the liquid surface. A 0.01 wt % aqueous dispersion of TiO2 was prepared by plasma treatment with ultrasonication. Dynamic light scattering measurements indicated that the average TiO2 nanoparticle sizes in the dispersions with plasma treatment in air and Ar atmosphere were approximately 150 and 180 nm, respectively. Although the pH of the dispersion prepared by Ar plasma treatment was fairly close to the isoelectric point of TiO2, the dispersion maintained a finely dispersed state. The surface potentials of TiO2 nanoparticles in the dispersions treated with plasma were confirmed to be positively charged. This suggests that the dispersions formed by plasma treatment were stabilized by electrostatic repulsion between the particles.

Preparation of Aqueous Dispersion of Titanium Dioxide Nanoparticles using Plasma on Liquid Surface

A method for preparing an aqueous dispersion of titanium dioxide (TiO2) nanoparticles by generating plasma on the liquid surface was developed. The plasma was generated between the tip of a needle electrode in the gas phase and the liquid surface. A 0.01 wt % aqueous dispersion of TiO2 was prepared by plasma treatment with ultrasonication. Dynamic light scattering measurements indicated that the average TiO2 nanoparticle sizes in the dispersions with plasma treatment in air and Ar atmosphere were approximately 150 and 180 nm, respectively. Although the pH of the dispersion prepared by Ar plasma treatment was fairly close to the isoelectric point of TiO2, the dispersion maintained a finely dispersed state. The surface potentials of TiO2 nanoparticles in the dispersions treated with plasma were confirmed to be positively charged. This suggests that the dispersions formed by plasma treatment were stabilized by electrostatic repulsion between the particles.

Mechanical and Morphological Properties of Films Based on Ultrasound Treated Titanium Dioxide Dispersion/Natural Rubber Latex

Titanium dioxide dispersion was sonicated as an attempt to reduce its particle sizes and thereafter used as fillers in making natural rubber (NR) composite films. Fillers of reduced particle sizes, owing to enhanced surface areas and aspect ratios, usually result in unique property improvements. The reinforcing effects of untreated and sonicated samples of the fillers were, therefore, compared through the measurement of tensile properties of the dry films. Results, however, indicated a monotonic decrease in moduli with filler content, contrary to behaviour due to conventional fillers, but showed improve- ment in both elongation at break and tensile strength data at low filler concentration (2phr), and thereafter a decrease in the trend. The affinity between the filler and matrix was examined using the composite theory of Einstein. Theoretical prediction of Young's moduli from this was compared against experimental data and it was found that there was certain level of inter- facial interaction.

Verification of a Dispersion Model to Describe the Dispersion of Nanoparticle Agglomerates in Epoxy Resin with a Stirred Bead Mill

In the presented study, the dispersion of titanium dioxide (TiO2) nanoparticle agglomerates in an epoxy resin by the use of a stirred bead mill was investigated. Therefore, systematic dispersion experiments were carried out and the achieved particle sizes were determinated according to the principle of dynamic light scattering. Based on these dispersion experiments a grinding model by Becker[ 1 ] for the description of the milling process in stirred bead mills was constructed and transferred to the dispersion of nanoparticle agglomerates. Afterward, the dispersion model was applied to simulate the particle size distributions of TiO2 nanoparticles for dispersion in the stirred bead mill and, in addition, checked experimentally.

Self-assembled nanometric spacer on surface of natural rubber composited with TiO2

The dispersion of titanium dioxide (TiO2) was mixed with natural rubber latex (NRL) and other additives before casting on glass slide. The dispersion of TiO2 (75% by wt.) were prepared using high pressure homogenizer by varying the concentration of stabilizer, poly (ethylene glycol) (PEG). The results were found that PEG can disperse TiO2 in water phase and the mechanical properties of NRL film composited with TiO2 dispersion is enhancement with increasing the PEG concentration. The effects of the stabilizer and NRL compounding on composited films properties were discussed using surface morphology. The morphology of TiO2 dispersion and composited NRL films were investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM).

Synthesis and characterization of comb polycarboxylic acid dispersants for coatings

AbstractComb polycarboxylic acid dispersants (CPCADs) graft acrylic copolymers which consist of hanging methoxy polyethylene glycol chains and carboxylic acid groups on main acrylic chain. The CPCADs have been synthesized by radical polymerization of methacrylic acid and methoxy polyethylene glycol methacrylate as a nonionic unsaturated hydrophilic macromonomer. The CPCADs are polymeric surfactants that can be used as anionic dispersant. Methoxy polyethylene glycol methacrylate has been synthesized by esterification of methacrylic acid and methoxy polyethylene glycol in the presence of methanesulfonic acid as catalyst. These have been characterized with 1H‐NMR and GPC. Acid values of CPCA dispersants have been determined. The dispersion of CPCA dispersants depends on their molecular weights, length mPEG, and acid values. Dispersion of titanium dioxide in typical solvent‐based paint formulation has been investigated. The physicochemical and mechanical properties of surface coatings having CPCADs such as gloss, hardness, and contrast ratio have been investigated. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Structural characterisation and antibacterial activity of PP/TiO2 nanocomposites prepared by an in situ sol–gel method

Polypropylene/titanium dioxide (PP/TiO2) nanocomposites can be prepared using a novel method based on the hydrolysis–condensation reactions (sol–gel method) of titanium alkoxide inorganic precursors that have been premixed with polypropylene under molten conditions. The resultant nanocomposites were characterised by transmission electronic microscopy (TEM), X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). These techniques showed the formation of the titanium oxi-hydroxide chemical structure (TixOy(OH)z) with a diameter of approximately 10nm in the polymer matrix. Furthermore, a condensation degree of around 17% was determined using XPS analysis. The antibacterial activity was tested according to the JIS Z 2801:2000 standard with Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in the absence of light. Correlations between the microstructure and the chemical composition of PP/TiO2 nanocomposites and the antibacterial properties of these nanocomposites were discussed. The structure of titanium oxi-hydroxide derivative particles (TixOy(OH)z) within the polypropylene matrix has been shown to impact strongly on the antibacterial properties in comparison with the results obtained with a dispersion of anatase titanium dioxide into the PP.

Preparation and Properties of Transparent SEBS/Titania Nanocomposite Films via Functionalization of SEBS and Sol–Gel Process

Transparent nanocomposite films based on a thermoplastic elastomer, poly[styrene- b-(ethylene- co-butylene)- b-styrene] triblock copolymer (SEBS), and titania sol-gel precursors are fabricated. The SEBS grafted with maleic anhydride (SEBS-g-MAH) can enhance the dispersion of titania in the SEBS matrix. The SEBS- g-MAH/titania nanocomposite films are transparent and exhibit excellent mechanical properties, including increased modulus and tensile strength, with only a slight loss of stretchability. Moreover, the uniformly dispersed titania nanoparticles in the SEBS-g-MAH matrix can enhance thermal stability of the nanocomposites.

Effect of titanium dioxide on the thermal ageing of polypropylene

Titanium dioxide nanoparticles were prepared by wet synthesis method and the particle size was calculated by transmission electron microscopic technique. Polypropylene/titanium dioxide nanocomposites were prepared using 0–3 wt% of titanium dioxide by melt mixing. It was then compression moulded in to films at 180 °C. Thermal ageing was carried out in an air oven at 100 °C for 24 h. Mechanical properties of the samples were determined before and after thermal ageing. Infrared spectroscopy was used to study the degradation products. Morphology of the tensile fractured surfaces was analysed using scanning electron microscope showed stability of polypropylene/titanium dioxide nanocomposites after thermal ageing. Good dispersion of titanium dioxide in the PP matrix was evident from SEM images. Change in torque with mixing time was noted out using Thermo Haake Rheocord 600 mixing chamber. Thermogravimetric analysis of the samples indicated that thermal stability of PP was increased by the addition of titanium dioxide.

Preparation and characterization of spinel Li4Ti5O12 nanoparticles anode materials for lithium ion battery

Spinel Li4Ti5O12 nanoparticles were prepared via a high-temperature solid-state reaction by adding the prepared cellulose to an aqueous dispersion of lithium salts and titanium dioxide. The precursors of Li4Ti5O12 were characterized by thermogravimetry and differential scanning calorimetry. The obtained Li4Ti5O12 nanoparticles were characterized using X-ray diffraction, transmission electron microscopy (TEM) and electrochemical measurements. The TEM revealed that the Li4Ti5O12 prepared with cellulose is composed of nanoparticles with an average particle diameter of 20–30 nm. Galvanostatic battery testing showed that nano-sized Li4Ti5O12 exhibit better electrochemical properties than submicro-sized Li4Ti5O12 do especially at high current rates, which can deliver a reversible discharge capacity of 131 mAh g−1 at the rate of 10 C, whereas that of the submicro-sized sample decreases to 25 mAh g−1 at the same rate (10 C). Its reversible capacity is maintained at ~172.2 mAh g−1 with the voltage range 1.0–3.0 V (vs. Li) at the current rate of 0.5 C for over 80 cycles.

An Unconventional Route to High-Efficiency Dye-Sensitized Solar Cells via Embedding Graphitic Thin Films into TiO2 Nanoparticle Photoanode

Graphitic thin films embedded with highly dispersed titanium dioxide (TiO(2)) nanoparticles were incorporated for the first time into the conventional dye-sensitized solar cells (DSSCs), resulting in a remarkably improved cell efficiency due to its superior electron conductivity. Massively ordered arrays of TiO(2) dots embedded in carbon matrix were fabricated via UV-stabilization of polystyrene-block-poly(4-vinylpyridine) films containing TiO(2) precursors followed by direct carbonization. For dye-sensitized TiO(2) based solar cells containing carbon/TiO(2) thin layers at both sides of pristine TiO(2) layer, an increase of 62.3% [corrected] in overall power conversion efficiency was achieved compared with neat TiO(2)-based DSSCs. Such a remarkably improved cell efficiency was ascribed to the superior electron conductivity and extended electron lifetime elucidated by cyclic voltammetry and impedance spectroscopy.