TiO2 Agglomerates Research Articles

Imprinting on empty hard gelatin capsule shells containing titanium dioxide by application of the UV laser printing technique

The purpose of this study was to examine the application of ultraviolet (UV) laser irradiation to printing hard gelatin capsule shells containing titanium dioxide (TiO2) and to clarify how the color strength of the printing by the laser could be controlled by the power of the irradiated laser. Hard gelatin capsule shells containing 3.5% TiO2 were used in this study. The capsules were irradiated with pulsed UV laser at a wavelength of 355 nm. The color strength of the printed capsule was determined by a spectrophotometer as total color difference (dE). The capsules could be printed gray by the UV laser. The formation of many black particles which were agglomerates of oxygen-defected TiO2 was associated with the printing. In the relationship between laser peak power of a pulse and dE, there were two inflection points. The lower point was the minimal laser peak power to form the black particles and was constant regardless of the dosage forms, for example film-coated tablets, soft gelatin capsules and hard gelatin capsules. The upper point was the minimal laser peak power to form micro-bubbles in the shells and was variable with the formulation. From the lower point to the upper point, the capsules were printed gray and the dE of the printing increased linearly with the laser peak power. Hard gelatin capsule shells containing TiO2 could be printed gray using the UV laser printing technique. The color strength of the printing could be controlled by regulating the laser energy between the two inflection points.

TiO2/clinoptilolite composites for photocatalytic degradation of anionic and cationic contaminants

The present work aims to study the bulk and surface properties of the TiO2/clinoptilolite composite on the crystalline structure, superficial area, bandgap energy, zeta potential, particle size distribution, and chemical composition; in order to analyze the effect of the clinoptilolite proportion in the photocatalytic degradation of pollutants. TiO2/clinoptilolite composites were prepared by adding different mass proportions of clinoptilolite to a sol–gel bath containing TiCl4 as the titania precursor. Surface charge studies explain the larger sensitivity to composite ratio observed in the photocatalytic degradation of anionic pollutants than in cationic dyes. An optimum TiO2/clinoptilolite ratio of 90/10 was found to be the most efficient in terms of lower tendency to agglomeration, largest surface area, and increased crystallite size. Improvement in composite surface area occurs only at low clinoptilolite wt% and seems to be caused by lower agglomeration of nanometric TiO2 and acid-induced porosity in the zeolite.

Preparation and characterization of polypyrrole/TiO2 nanocomposites by reverse microemulsion polymerization and its photocatalytic activity for the degradation of methyl orange under natural light

PPy/TiO2 nanocomposites were successfully prepared by reverse microemulsion polymerization and used as an effective photocatalyst for the degradation of methyl orange. Titanium dioxide (TiO2) was modified by silane coupling agent to improve the dispersity before the polymerization. X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectra were carried out to characterize the morphology and structure of the samples. TEM analysis shows that TiO2 particles are deposited by polypyrrole (PPy) and the existence of PPy mitigates the agglomeration of TiO2. XRD spectra reveal that the deposition of PPy does not change the structure of TiO2 particles. Uv–vis analysis shows that the PPy/TiO2 nanocomposites have a higher photocatalytic activity under natural light than neat TiO2. The highest degradation rate occurs when the mass ratio of PPy to TiO2 is kept at 0.02. POLYM. COMPOS., 34:1076–1080, 2013. © 2013 Society of Plastics Engineers

Deposition behavior of inhaled nanostructured TiO2 in rats: fractions of particle diameter below 100 nm (nanoscale) and the slicing bias of transmission electron microscopy

Context: In experimental studies with nanomaterials where translocation to secondary organs was observed, the particle sizes were smaller than 20 nm and were mostly produced by spark generators. Engineered nanostructured materials form microsize aggregates/agglomerates. Thus, it is unclear whether primary nanoparticles or their small aggregates/agglomerates occur in non-negligible concentrations after exposure to real-world materials in the lung.Objective: We dedicated an inhalation study with nanostructured TiO2 to the following research question: Does the particle size distribution in the lung contain a relevant subdistribution of nanoparticles?Methods: Six rats were exposed to 88 mg/m3 TiO2 over 5 days with 20% (count fraction) and <0.5% (mass fraction) of nanoscaled objects. Three animals were sacrificed after cessation of exposure (5 days), others after a recovery period of 14 days. Particle sizes were determined morphometrically by transmission electron microscopy (TEM) of ultra-thin lung slices. Since the particles visible are two-dimensional surrogates of three-dimensional structures we developed a model to estimate expected numbers of particle diameters below 100 nm due to the TEM slicing bias. Observed and expected numbers were contrasted in 2 × 2 tables by odds ratios.Results: Comparisons of observed and expected numbers did not present evidence in favor of the presence of nanoparticles in the rat lungs. In simultaneously exposed satellite animals agglomerates of nanostructured TiO2 were observed in the mediastinal lymph nodes but not in secondary organs.Conclusions: For nanostructured TiO2, the deposition of nanoscaled particles in the lung seem to play a negligible role.

Mechanical and thermal properties of nanosized titanium dioxide filled rigid poly(vinyl chloride)

Nano-sized rod-like titanium dioxide (TiO2) filled rigid poly(vinyl chloride) (PVC) nanocomposites were prepared by using injection-molding method. Vicat, Charpy impact and tensile tests as well as thermogravimetric and dynamic mechanical analyses were used to characterize the structure and properties of the nanocomposites. The results showed that nano-TiO2 could improve Vicat softening temperature and also improve thermal stability of PVC during the stages of dehydrochlorination and formation of carbonaceous conjugated polyene sequences, which can be ascribed to restriction of the nanoparticles on the segmental relaxation as being evidenced by raises in glass transition and β-relaxation temperatures of PVC upon filling TiO2. Addition of TiO2 nanoparticles less than 40 phr (parts per hundreds of resin) could significantly improve impact strength of the composites while the TiO2 agglomeration at high contents leads to a reduction in impact toughness.

Effect of Pt or Pd doping on stability of TiO2 nanoparticle suspension in water

Stability of suspensions of TiO2 nanoparticles synthesized by the flame aerosol reactor (FLAR) could be altered by doping TiO2 nanoparticles with Pt, Pd, or Pt–Pd dopants. It was found that doping of TiO2 with Pd or Pt could contribute to the control of the agglomeration of TiO2 suspended in water. With the change of doping content, the isoelectric point (IEP) of stable TiO2 suspension decreased gradually from 5 to 3.6 while the specific surface area was increased from 43.27 to 60.84m2/g. With pH>6.0, 2wt% Pt–Pd/TiO2 suspension exhibited the lowest agglomeration behavior. The plausible intrinsic structures of Pt, Pd, and Pt–Pd doped TiO2 nanoparticles were proposed and discussed with respect to their IEP based on the DLVO theory.

Preparation and properties of TiO2‐filled poly(acrylonitrile‐butadiene‐styrene)/epoxy hybrid composites

AbstractPoly (acrylonitrile‐butadiene‐styrene) (ABS) was used to modify diglycidyl ether of bisphenol‐A type of epoxy resin, and the modified epoxy resin was used as the matrix for making TiO2 reinforced nanocomposites and were cured with diaminodiphenyl sulfone for superior mechanical and thermal properties. The hybrid nanocomposites were characterized by using thermogravimetric analyzer (TGA), dynamic mechanical analyzer (DMA), universal testing machine (UTM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The bulk morphology was carefully analyzed by SEM and TEM and was supported by other techniques. DMA studies revealed that the DDS‐cured epoxy/ABS/TiO2 hybrid composites systems have two Tgs corresponding to epoxy and ABS rich phases and have better load bearing capacity with the addition of TiO2 particles. The addition of TiO2 induces a significant increase in tensile properties, impact strength, and fracture toughness with respect to neat blend matrix. Tensile toughness reveals a twofold increase with the addition of 0.7 wt % TiO2 filler in the blend matrix with respect to neat blend. SEM micrographs of fractured surfaces establish a synergetic effect of both ABS and TiO2 components in the epoxy matrix. The phenomenon such us cavitation, crack path deflection, crack pinning, ductile tearing of the thermoplastic, and local plastic deformation of the matrix with some minor agglomerates of TiO2 are observed. However, between these agglomerates, the particles are separated well and are distributed homogeneously within the polymer matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Annealed Zn–TiO2 nanocomposites electrodeposited: Effect of the substrate

Zn–TiO2 coatings were successfully prepared by the co-deposition method on titanium and steel substrates using an acidic zinc sulphate solution with TiO2 nanoparticles in suspension. The film's surface is rough and the TiO2 agglomerates are randomly distributed on the metallic matrix formed by staked hexagonal plates oriented in different directions. From the structural study it was concluded that although some Tc values are slightly above 1, this may not be indicative of the preferred orientations because the crystals grow randomly, as observed by scanning electron microscopy (SEM). After electrodeposition, samples were heated in air at 450°C for 3h. The X-ray diffraction analysis of the deposits points to the metal matrix modification from Zn to ZnO, and the formation of intermetallic phases. In addition, the SEM results indicate that the films have a high surface area, with a rich morphology, due to the appearance of ZnO hollow structures, porous microdiscs, porous flaky nanosheets and needle-shaped grains. These are highly dependent on the characteristics of as-deposited films, which are tightly correlated to the substrate nature/type.

Novel antibifouling nanofiltration polyethersulfone membrane fabricated from embedding TiO2 coated multiwalled carbon nanotubes

Multiwalled carbon nanotubes (MWCNTs) coated by anatase titanium dioxide (TiO2) nanoparticles were synthesized via the precipitation of TiCl4 precursor on the acid oxidized MWCNTs and used in preparation of nanocomposite polyethersulfone (PES) membranes. In this work, the effect of embedding TiO2 coated MWCNTs in PES matrix on membrane morphology, properties and antibiofouling was presented and the obtained results were compared with the prepared oxidized MWCNTs and TiO2 blended PES membranes. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses showed that the formed TiO2 on the surface of MWCNTs had anatase nanostructure with size in the range of 10–20nm. The scanning electron microscopy (SEM) images displayed a finger-like and porous structure for all NF membranes and showed that agglomeration of TiO2 coated MWCNTs is very low. Contact angle measurements indicated that coating of TiO2 nanoparticles on the surface of oxidized MWCNTs improved the hydrophilicity of the obtained membranes. The pure water flux of the blend membranes increased with the content of TiO2 coated MWCNTs. Fouling resistances of membranes evaluated by whey solution filtration revealed that 0.1wt.% TiO2 coated MWCNTs membrane had the best antibiofouling properties due to its lowest surface roughness and synergistic photocatalytic activity induced by incorporated nanoparticles.

Effects of nano-TiO2 dispersion on thermoelectric properties of Co4Sb11.7Te0.3 composites

Nano-TiO2/Co4Sb11.7Te0.3 composites were prepared by mechanical alloying (MA) and cold isostatic pressing (CIP) process. The phase composition, microstructure, and thermoelectric properties were characterized. The diffraction spectra of all samples well corresponds to CoSb3 skutterudite diffraction plane. TiO2 agglomerates into irregular clusters. They locate at the grain boundaries or some are distributed on the surface of Co4Sb11.7Te0.3 particles. For composites with high TiO2 content (0.6% and 1.0% TiO2), the phonon scattering by TiO2 particle, pores, and small size grains can result in a remarkable reduction in thermal conductivity. The maximum value of ZT is 0.79 for sample with 0.6 wt.% TiO2 at 700 K, which is 11% higher than that of non-dispersed sample.

Comparison of nanoparticle measurement instruments for occupational health applications

Nanoparticles are used in many applications because of their novel properties compared to bulk material. A growing number of employees are working with nanomaterials and their exposure to nanoparticles trough inhalation must be evaluated and monitored continuously. However, there is an ongoing debate in the scientific literature about what are the relevant parameters to measure to evaluate exposure to level. In this study, three types of nanoparticles (ammonium sulphate, synthesised TiO2 agglomerates and aerosolised TiO2 powder, modes in a range of 30–140 nm mobility size) were measured with commonly used aerosol measurement instruments: scanning and fast mobility particle sizers (SMPS, FMPS), electrical low pressure impactor (ELPI), condensation particle counter (CPC) together with nanoparticle surface area monitor (NSAM) to achieve information about the interrelations of the outputs of the instruments. In addition, the ease of use of these instruments was evaluated. Differences between the results of different instruments can mainly be attributed to the nature of test particles. For spherical ammonium sulphate nanoparticles, the data from the instruments were in good agreement while larger differences were observed for particles with more complex morphology, the TiO2 agglomerates and powder. For instance, the FMPS showed a smaller particle size, a higher number concentration and a narrower size distribution compared with the SMPS for TiO2 particles. Thus, the type of the nanoparticle was observed to influence the data obtained from these different instruments. Therefore, care and expertise are essential when interpreting results from aerosol measurement instruments to estimate nanoparticle concentrations and properties.

Preparation of a Novel Nanocomposite of Polyaniline Core Decorated with Anatase‐TiO2 Nanoparticles in Ionic Liquid/Water Microemulsion

Polyaniline core decorated with TiO2 (PANI‐TiO2) nanocomposite particles was successfully synthesized in ionic liquid/water (IL/water) microemulsion in the presence of anatase TiO2 nanoparticles. The TiO2 nanoparticles had been dispersed beforehand in OP‐10 and n‐butanol to weaken the strong particles agglomeration of TiO2. The PANI‐TiO2 nanocomposites were characterized by fourier transform infrared spectroscopy (FTIR), ultraviolet visible spectroscopy (UV‐Vis), scanning electron microscopy (SEM), and transmission electron microscope (TEM), and their electrochemical behavior was estimated by the electrochemical workstation. SEM micrographs showed that the nanocomposites exhibited spherical morphology with particle sizes about 70 nm. The TEM result showed that the PANI‐TiO2 nanocomposites had a novel structure and that nanocrystalline TiO2 deposited onto the surface of PANI, which was different from the reported structure of TiO2‐PANI nanocomposites. Both FTIR and UV‐Vis spectra indicate that polyaniline and nano‐TiO2 particles are not simply blended or mixed up. A possible reaction mechanism for this nanocomposite preparation is suggested and analyzed.

Cost reduction studies of decorative laminates

Barrier paper, which is made of bleached absorbent kraft pulp, is a significant layer of decorative laminates, since it controls the see-through of brown color of saturating kraft paper and its opacifying effect usually is achieved by a heavy loading of TiO2. The TiO2, due to its very small particle size, passes between the cellulosic fibers and drains into the white water. To overcome this problem, papermakers try to use various retention aids for improving overall retention of TiO2, but agglomeration of TiO2 causes a decrease in light scattering efficiency of TiO2. During the subsequent saturation operation, the air in the voids is replaced by melamine formaldehyde, which has a refractive index close to that of cellulose. As a result, the sheet becomes translucent and poses ‘see through’ problem. Keeping this in view, anhydrous magnesium silicate is used as an extender with TiO2 because it effectively increases the overall filler retention, sheet brightness, opacity. The dispersed aqueous slurry of anhydrous magnesium silicate forms fine gel that entraps TiO2 in the wet web and prevents removal of fines and fillers. The addition of 25% TiO2, 7% micronized soapstone powder, 8% anhydrous magnesium silicate, 1% melamine formaldehyde, and 0.1% sodium hexameta-phosphate was found to improve the overall retention by 65.25% and to cut the manufacturing cost by US$ 546.00 per tonne of pulp without affecting the product quality.

Composite polymer electrolytes of sulfonated poly-ether-ether-ketone (SPEEK) with organically functionalized TiO 2

Synthesis and properties of proton-conducting composites of SPEEK with organically functionalized TiO 2 are described. Composites with hydrophilic titania particles present an inhomogeneous microstructure with agglomeration of TiO 2 particles, high strength and low ductility, high water uptake and proton conductivity. Composites with hydrophobic titania particles have a very homogeneous microstructure, very reproducible mechanical properties, lower water uptake and proton conductivity.

Role of the Solvent Employed for the Cathodic Electrophoretic Deposition (EPD) of ITO/TiO2 Films, over its Morphology, Electronic Properties and Photoelectrochemical Behavior

The role played by solvent during cathodic EPD of TiO2 film was investigated. The differences in film morphology are attributed to the dissimilar surface excess charge of the TiO2 agglomerates in each solvent and to the secondary reactions occurring during the EPD. For the films obtained in aqueous medium an augmentation of donor density and a change toward less negative values of the flat band potential were measured. Furthermore, a decrease in photocurrents and photovoltages was provoked by increasing the electric field used to form the film. Meanwhile, for the films formed in organic medium, the semiconductive properties did not change with the electric field employed to grow the films, and the photoelectrochemical behavior of these films showed completely different trends. The dissimilarities found were attributed to the ability of the solvent to be reduced earlier than TiO2, avoiding the generation of species Ti3+ that acts like trap states.

Sonochemical synthesis and characterization of magnetic separable Fe3O4–TiO2 nanocomposites and their catalytic properties

A novel sonochemical method is described for the preparation of Fe3O4–TiO2 photocatalysts in which nanocrystalline titanium dioxide particles are directly coated onto a magnetic core. The Fe3O4 nanoparticles were partially embedded in TiO2 agglomerates. TiO2 nanocrystallites were obtained by hydrolysis and condensation of titanium tetraisopropyl in the presence of ethanol and water under high-intensity ultrasound irradiation. This method is attractive since it eliminated the high-temperature heat treatment required in the conventional sol–gel method, which is important in transforming amorphous titanium dioxide into a photoactive crystalline phase. In comparison to other methods, the developed method is simple, mild, green and efficient. The magnetization hysteresis loop for Fe3O4–TiO2 nanocomposites indicates that the hybrid catalyst shows superparamagnetic characteristics at room temperature. Photocatalytic activity studies confirmed that the as-prepared nanocomposites have high photocatalytic ability toward the photodegradation of RhB solution. Furthermore, the photodecomposition rate decreases only slightly after six cycles of the photocatalysis experiment. Thus, these Fe3O4–TiO2 nanocomposites can be served as an effective and conveniently recyclable photocatalyst.

Photocatalytic Degradation of Methylene Blue Using Immobilized Nanoparticles of TiO&lt;sub&gt;2&lt;/sub&gt; Supported by SBA-15 Surface

TiO2-SBA-15 surface (TSS) composites were prepared by the supercritical pretreatment and then sol-gel process with using paraffin used as a clogging agent. The as-grown materials were characterized by using X-ray diffraction, UV-VIS spectroscopy and nitrogen absorption. The photocatalytic activities of TSS were evaluated by quantifying the degradation of methylene blue solution under UV light. Compared with TiO2-SBA-15 (TS) composites prepared only by the sol–gel method, TSS composites remain in mesostructure with high surface areas due to clogging effect of paraffin on SBA-15 cavity. Additionally, the small crystalline size of TiO2 in TSS is attributed to the fact that silica support baffles the agglomeration ofTiO2 nanoparticles. In comparison of TS composites and pure TiO2, higher photocatalytic activity of TSS is obtained and mainly attributed to larger surface areas and greater band-gap energy.

Optimized Method for Preparation of TiO&lt;SUB&gt;2&lt;/SUB&gt; Nanoparticles Dispersion for Biological Study

The objective of the present study was to develop a practical method to prepare a stable dispersion of TiO2 nanoparticles for biological studies. To address this matter a variety of different approaches for suspension of nanoparticles were conducted. TiO2 (rutile/anatase) dispersions were prepared in distilled water following by treated with different ultrasound energies and various dispersion stabilizers (1.0% carboxymethyl cellulose, 0.5% hydroxypropyl methyl cellulose K4M, 100% fetal bovine serum, and 2.5% bovine serum albumin). The average size of dispersed TiO2 (rutile/anatase) nanoparticles was measured by dynamic light scattering device. Agglomerate sizes of TiO2 in distilled water and 100% FBS were estimated using TEM analysis. Sedimentation rate of TiO2 (rutile/anatase) nanoparticles in dispersion was monitored by optical absorbance detection. In vitro cytotoxicity of various stabilizers in 16-HBE cells was measured using MTT assay. The optimized process for preparation of TiO2 (rutile/anatase) nanoparticles dispersion was first to vibrate the nanoparticles by vortex and disperse particles by ultrasonic vibration in distilled water, then to add dispersion stabilizers to the dispersion, and finally to sonicate the nanoparticles in dispersion. TiO2 (rutile/anatase) nanoparticles were disaggregated sufficiently with an ultrasound energy of 33 W for 10 min. The formation of TiO2 (rutile/anatase) agglomerates in distilled water was decreased obviously by addition of 1.0% CMC, 0.5% HPMC K4M, 100% FBS and 2.5% BSA. For the benefit of cell growth, FBS is the most suitable stabilizer for preparation of TiO2 (rutile/anatase) particle dispersions and subsequent investigation of the in vivo and in vitro behavior of TiO2 (rutile/anatase) nanoparticles. This method is practicable to prepare a stable dispersion of TiO2 (rutile/anatase) nanoparticles for at least 120 h.

De-agglomeration mechanisms of TiO2 aerosol agglomerates in PWR steam generator tube rupture conditions

A steam generator tube rupture (SGTR) in a pressurized water reactor (PWR) might be a major source of accidental release of radioactive aerosols into the environment during severe accident due to its potential to by-pass the reactor containment. In the ARTIST program, tests were carried out at flow conditions typical to SGTR events to determine the retention of dry aerosol particles inside a steam generator tube. The experiments with TiO2 agglomerates showed that for high velocities in the range of 100–350 m/s, the average particle size at the outlet of the tube was significantly smaller than at the inlet due to particle de-agglomeration. Earlier, particle de-agglomeration has not been considered significant in nuclear reactor severe accidents. However, the tests in ARTIST program have shown that there is a possibility that TiO2 aerosol particles de-agglomerate inside a tube and in the expansion zone after the tube exit under SGTR conditions. In this investigation, we measured TiO2 aerosol de-agglomeration in the tube with very high flow velocities with two different TiO2 aerosols. The de-agglomeration was determined by measuring the size of the agglomerates at the inlet and outlet of the test section. The test section was composed of tubes with three different lengths, 0.20, 2.0 and 4.0 m, followed by an expansion zone. The main results were: (i) the de-agglomerate process was relatively insensitive to the initial particle size distribution, (ii) the agglomerates were observed to de-agglomerate in all the tubes, and the resulting particle size distributions were similar for both TiO2 aerosols, (iii) at high flow rates, increasing the gas mass flow rate did not produce further de-agglomeration, and (iv) the agglomerates did not de-agglomerate to primary particles. Instead, after de-agglomeration the particles had a median outer diameter Dc = 1.1 μm. Based on analysis using computational fluid dynamics (CFDs), the de-agglomeration was caused by the turbulent shear stresses due to the fluid velocity difference across the agglomerates in the viscous subrange of turbulence. It has to be noted that the particles used in this investigation were TiO2 agglomerates, and not prototypical nuclear aerosols with significantly different characteristics. Therefore, the results of this investigation cannot be directly used to determine whether the nuclear aerosol particles may de-agglomerate in SGTR sequences. However, this investigation highlights the possibility of particle de-agglomeration under SGTR conditions, and identifies the mechanism of the de-agglomeration inside the broken tube and when the aerosol is discharged to an open space.

Preparation of TiO2/activated carbon with Fe ions doping photocatalyst and its application to photocatalytic degradation of reactive brilliant red K2G

Titanium dioxide coated on activated carbon (AC) with Fe ions doping (Fe-TiO2/AC) composite was prepared by an improved sol-gel method. The photocatalytic activities were tested by photocatalytic degradation of reactive brilliant red K2G in solution. The results show that in comparison with the agglomeration of pure TiO2, the TiO2 nanoparticles are well dispersed in the AC matrix, of which sizes are decreased with Fe ions doping. Additionally, the iron species on TiO2 of composite are Fe2O3 and FeO, which do not affect the crystalline structures of TiO2 nanoparticles. The AC matrix and iron doping content influence the fluorescence intensity of composite due to their effects on recombination probability of hole-electron pairs. Compared with TiO2, 0.3% Fe-TiO2, TiO2/AC, 0.5% Fe-TiO2/AC and 0.1% Fe-TiO2/AC, the 0.3% Fe-TiO2/AC shows the highest photoactivity with the complete mineralization of K2G for finite time due to the optimum Fe ions content and AC matrix. Furthermore, the kinetic constant (k = 0.0229 min−1) of 0.3% Fe-TiO2/AC composite is more than the sum of both TiO2/AC (0.0154 min−1) and 0.3% Fe-TiO2 (0.0057 min−1) because coexistence of the AC and Fe ions has an enlarging effect on improving the photoactivity of TiO2.