Adding TiO2 Nanoparticles Research Articles

Structural stability of photodegradable poly(l-lactic acid)/PE/TiO2 nanocomposites through TiO2 nanospheres and TiO2 nanotubes incorporation

Photodegradation of PLA/PE, PLA/PE/TiO2 nanospheres and PLA/PE/TiO2 nanotubes was obtained under simulated sunlight. The nanocomposites were analyzed by infrared spectroscopy, scanning electron microscopy and tensile-deformation measurements. TiO2 nanospheres and TiO2 nanotubes were found to present different effects on the crystallinity of PLA and a straight correlation between structural organization and photostability was observed. According to the results, TiO2 promotes the degradation of PLA and PE, affecting the organizational level of the polymers. By adding TiO2 nanoparticles to the PLA/PE films, vibration modes characteristic of degradation products were promptly observed and the lifetime of the polymer decreased when compared to the PLA/PE without TiO2 nanoparticles. Mechanical measurements showed an improvement of the mechanical properties when adding the TiO2 nanoparticles.

Effects of continuous sonication on laminar convective heat transfer inside a tube using water–TiO2 nanofluid

In this research, an experimental study is carried out to investigate the effect of adding TiO2 nanoparticles to the distilled water on convective heat transfer and pressure drop with and without continuous induced ultrasonic field in the nanofluid’s reservoir under constant heat flux. Experiments are done for laminar flow regime with volume concentration, up to 0.25%. It is observed that adding nanoparticles to the base liquid enhances Nusselt number, and more particle concentration leads to more enhancements in Nusselt number except for 0.25% volume concentration. Results also show that the Nusselt number of the nanofluids at the volume concentration of 0.25vol.% was approximately the same as base fluids for the given conditions. In addition, the achievements demonstrate that inducing ultrasonic field increases Nusselt numbers dramatically compared with those results obtained with no sonication. Finally, no significant increase occurs in pressure drop in the range of studied volume fractions.

Shear bond strength and antibacterial effects of orthodontic composite containing TiO2 nanoparticles

Nanofillers can reduce enamel demineralization without compromising physical properties of the composite. The aim of this study was to evaluate shear bond strength (SBS) and antibacterial effects of an orthodontic composite after adding titanium oxide (TiO2) nanoparticles. Light cure orthodontic composite paste (Transbond XT) was blended with TiO2 nanoparticles. A total of 30 extracted premolars were randomly allocated into two groups of 15. In order to bond brackets, Transbond XT adhesive and nanocomposite were used in each group, respectively. SBS of two groups were determined, and the adhesive remnant index (ARI) scores were assessed. A total of 45 composite discs specimen were prepared. Of the 45 discs, 30 discs were made from nanocomposite and tested for antibacterial properties immediately and 30 days after curing by direct contact test. The antibacterial properties of the remaining 15 discs that were made from the conventional composite were tested immediately after curing as control group. Student's t-test and chi-square tests were used to analyse the data with the significance level of 0.05. No significant difference was found between SBS of conventional and nanocomposites, 24 hours after curing (P = 0.58). Chi-square test showed that ARI scores of two groups were not significantly different after debonding (P = 0.69). Comparison of antibacterial effects between conventional and nanocomposite demonstrated significant difference between two groups, with nanocomposites having a higher antibacterial activity (P = 0.03). Colony count revealed no significant difference in bacterial growth immediately and 30 days after curing in nanocomposite group. Adding TiO2 nanoparticles to orthodontic composite enhances its antibacterial effects without compromising the SBS.

Coated wooden claddings and the influence of nanoparticles on the weathering performance

Accelerated climate aging experiments and cup measurements have been performed to investigate the effect of adding TiO2 nanoparticles and nanoclay to acrylic stain coatings against the influence of weathering. The coated specimens resistance toward solar radiation and water spray was evaluated by the discoloration rate from visual assessment and color analysis and by the chemical changes observed by Fourier transform infrared spectroscopy. Furthermore water vapor resistance was examined by the cup measurements. The nanomaterial containing coatings provided in general better protection against the artificial aging than the unmodified coating, showing the nanomaterials may have a natural place in coatings for protection of wood.

Preparation of mixed-matrix membranes for micellar enhanced ultrafiltration based on response surface methodology

The response surface methodology (RSM) was used in this work to develop an optimum membrane for micellar-enhanced ultrafiltration (MEUF). The mixed-matrix membranes were prepared by adding TiO2 nanoparticles into polyvinylidene fluoride (PVDF) solution and cast at different thicknesses. Flat-sheet PVDF membranes were prepared via the phase inversion technique on the basis of central composite design (CCD). The objective function of the optimization is to prepare membrane with high rejection and flux for micellar enhanced methylene blue (MB-SDS) ultrafiltration. The interactive effects of the various parameters, namely polymer concentration, membrane casting thickness and TiO2 concentration towards rejection of MB-SDS and permeation flux were evaluated. CCD was employed to obtain the mutual interaction between the various parameters. The optimum membrane could be prepared under polymer concentration of 18wt.%, casting thickness of 400μm and TiO2 concentration of 1.62wt.%. The experimental value of permeation flux and rejection was 53.28±2.75L/h.m2 and 99.02±0.55%, respectively. These values were found to be in good agreement and very close to the optimized value predicted from CCD, which were 57.68L/h.m2 and 98.77%. The results show that process optimization using CCD was reliable to produce membrane with desired performance.

Effect of TiO2 nanoparticles on the long-term hydrolytic degradation behavior of PLA

The longer-than-one-year hydrolytic degradation of poly (lactic acid) (PLA)/TiO2 nanocomposites was investigated in phosphate buffer solution of pH 7.4 at 37 °C so as to elucidate the effect of nanofillers on the degradation characteristics of PLA. The temporal changes in appearance, water absorption, number-average molecular weight (Mn), glass transition temperature, melting temperature, and crystallinity of the samples were traced. The results showed that the heterogeneous degradation and bulk-erosion were general mechanisms for PLA and its TiO2 nanocomposites. The change in surface morphology and molecular weight after hydrolysis revealed that the hydrolysis of nanocomposites occurred at the interface of PLA matrix and nanofillers, and the degradation rate was accelerated by the addition of the TiO2 nanofillers. The dispersion of nanofillers in polymer matrix affected the water absorption and degradation rate. The rapid increase of crystallinity also affected the degradation rate of nanocomposites. The present study suggested that the hydrolyzability of PLA could be controlled by adding TiO2 nanoparticles.

Enhanced thermoelectric properties of Mg2Si by addition of TiO2 nanoparticles

The effects on the thermoelectric properties of Mg2Si when adding TiO2 nanoparticles have been evaluated experimentally. A batch of Mg2Si was prepared through direct solid state reaction and divided into portions which were mechanically mixed with different amounts of TiO2 nanoparticles ranging from 0.5 to 3 vol% and subsequently sintered to disks. All materials showed n-type conduction and the absolute value of the Seebeck coefficient was reduced with increasing amount of TiO2 added, while the electrical resistivity was greatly reduced. The thermal conductivity was surprisingly little affected by the addition of the nanoparticles. An optimum value of the thermoelectric figure-of-merit ZT = TS2σ/k was found for the addition of 1 vol% TiO2, showing almost three times higher ZT value than that of the pure Mg2Si. Larger TiO2 additions resulted in lower ZT values and with 3 vol% added TiO2 the ZT was comparable to the pure Mg2Si. The sintering process resulted in reduction or chemical reaction of all TiO2 to TiSi2 and possibly elemental titanium as well as reduced TiOx. The increased electrical conductivity and the decreased Seebeck coefficient were found due to an increased charge carrier concentration, likely caused by the included compounds or titanium-doping of the Mg2Si matrix. The low observed effect on the thermal conductivity of the composites may be explained by the relatively higher thermal conductivity of the included compounds, counter-balancing the expected increased grain boundary scattering. Alternatively, the introduction of compounds does not significantly increase the concentration of scattering grain boundaries.

Direct application of commercial fountain pen ink to efficient dye-sensitized solar cells

Fountain pen ink possesses a well-dispersed nature and a relatively large specific surface area of carbon nanoparticles. In the present study, fountain pen ink was systematically studied and developed as cost-efficient counter electrodes (CEs) for planar dye-sensitized solar cells and fiber-shaped DSSCs (FDSSCs), which showed power conversion efficiencies above 6% under AM1.5G (100 mW cm−2). For ink-based planar solar cells, electrochemical impedance spectroscopy (EIS) confirmed that ink CEs had a slightly lower charge-transfer resistance than platinum CEs. EIS also proved that adding TiO2 nanoparticles into the ink could reduce the device's series resistance and the diffusion impedance of the electrolyte through electrode pores. For ink-based FDSSCs, the effects of film thickness, light intensities, and a comparative research of CE catalytic activities toward various electrolytes were discussed.

An Innovative Design of a Measuring Equipment and Using TiO<sub>2</sub> Nanogrease to Reduction of Friction Force for Pneumatic Cylinder

The purpose of the study is to measure the maximum static friction and dynamic friction in the actuation process of pneumatic cylinder after TiO2 nanoparticles are added to grease. The study makes an innovative design of a new measuring equipment of friction force, which can measure the friction force between the piston seal in pneumatic cylinder and the cylinder bore. The friction force of pneumatic cylinder bore directly affects the output dynamic property of pneumatic cylinder motion. Friction force measuring system can measure the change of friction force of pneumatic cylinder bore under the condition with different operating speeds, and can analyze the relationship between friction force of pneumatic cylinder and output dynamic property of pneumatic cylinder. Such a friction force measuring equipment takes pneumatic cylinder as an output of motive force to drive the measurement of pneumatic cylinder, and uses load cell and draw-line encoder to measure the friction force of pneumatic cylinder bore and the motion speed. In the experiment, the friction forces of pneumatic cylinder given with oil and without oil are measured respectively, achieving the friction force property of pneumatic cylinder bore when being lubricated by nanogrease added with nanoparticles of different weight percentages (wt.%). The experimental results show that adding TiO2 nanoparticles to grease can effectively decrease the friction force produced in the actuation process of pneumatic cylinder.

Improvement of impact toughness of AWS E6010 weld metal by adding TiO2 nanoparticles to the electrode coating

Abstract The effect of TiO 2 nanoparticles in the electrode coating on the impact toughness of three weld metals prepared by the shielded metal arc welding process was investigated and the main factors affecting the impact toughness were discussed. The microstructure, mechanical properties and fracture surface morphology of the weld metals have been evaluated and the results are compared. When the content of TiO 2 nanoparticles in the composition of electrode coating is increased, the morphology of ferrite in the microstructure of columnar zone will change from Widmanstatten ferrite to acicular ferrite. This finally changes to allotriomorphic ferrite when the amount of TiO 2 nanoparticles in the electrode coating goes relatively high. Furthermore, the addition of TiO 2 nanoparticles is effective in refining the ferrite grain size of the reheated microstructures of weld metals. This effect is attributed to the increased number of nucleation sites on the oxide nanoparticles. The impact toughness of the weld metal was improved by adding TiO 2 nanoparticles, especially when a medium TiO 2 nanoparticle content was used in the electrode coating. A significant increase in the impact toughness of weld metal was shown to be due to the increased percentage of acicular ferrite and refinement of microstructure.

The effect of TiO2 nanoparticle codeposition on microstructure and corrosion resistance of electroless NiP coating

AbstractNiPTiO2 nanocomposite coatings with various contents of TiO2 nanoparticles were synthesized by adding TiO2 nanoparticles to NiP electroless plating solution. The effects of pH and anionic surfactant sodium dodecyl sulfate (SDS) on the chemical composition of Ni, P, and TiO2 in the coatings were investigated. Scanning electron microscope (SEM), energy dispersive spectrometer (EDX), and X‐ray diffractometer (XRD) were used to characterize the morphology, composition, and crystal structure of deposited coatings, respectively. The hardness of nanocomposite coatings was improved greatly compared to NiP coating especially after heat treatment. After heat treatment at 400 °C for 1 h, an increase in microhardness was observed for heat‐treated NiP coatings. The hardness was increased from 805 to 1050 Hv for NiPTiO2 coating deposited at 9 g/LTiO2 concentration in the bath. The corrosion resistance of NiPTiO2 coating was significantly increased compared to NiP coatings by incorporation of TiO2 nanoparticle.

Impact and mechanism of TiO2 nanoparticles on DNA synthesis in vitro

The impact of TiO2 nanoparticles on DNA synthesis in vitro in the dark and the molecular mechanism of such impact were studied. The impact of TiO2 nanoparticles on DNA synthesis was investigated by adding TiO2 nanoparticles in different sizes and at various concentrations into the polymerase chain reaction (PCR) system. TiO2 nanoparticles were premixed with the DNA polymerase, the primer or the template, respectively and then the supernatant and the precipitation of each mixture were added into the PCR system separately to observe the impact on DNA synthesis. Sequentially the interaction between TiO2 nanoparticles and the DNA polymerase, the primer or the template was further analyzed by using UV-visible spectroscopy and polyacrylamide gel electrophoresis (PAGE). The results suggest that TiO2 nanoparticles inhibit DNA synthesis in the PCR system in the dark more severely than microscale TiO2 particles at the equivalent concentration and the inhibition effect of TiO2 nanoparticles is concentration dependent. The molecular mechanism of such inhibition is that in the dark, TiO2 nanoparticles interact with the DNA polymerase through physical adsorption while TiO2 nanoparticles do with the primer or the template in a chemical adsorption manner. The disfunction levels of the bio-molecules under the impact of TiO2 nanoparticles are in the following order: the primer > the template > the DNA polymerase.

P(VDF-HFP)-based micro-porous composite polymer electrolyte prepared by in situ hydrolysis of titanium tetrabutoxide

A micro-porous composite polymer electrolyte (MCPE) was prepared in situ by adding TiO2 nanoparticles from the hydrolysis of titanium tetrabutoxide to a solution of poly(vinylidenefluoride-co-hexafluoropropylene) [P(VDF-HFP)] copolymer. The prepared microporous polymer films (MCPFs) were characterized by scanning electronic microscopy, X-ray diffraction, thermogravimetric analysis, FT-IR and electrochemical interface resistance. After the addition of TiO2 nanoparticles the polarity of CF2 groups in the polymer chains and the crystallinity of the MCPFs decreased. When the composite polymer film contained 8.5 wt% of TiO2 nanoparticles the MCPE exhibited excellent electrochemical properties such as high ionic conductivity, up to 2.40 × 10−3 S cm−1 at room temperature.