nano-TiO2 Particle Research Articles

Effect of nano-TiO2 size and utilization ratio on the performance of photocatalytic concretes; self-cleaning, fresh, and hardened state properties

In this study, photocatalysis technology was used to reduce water pollution. Decolorization of Reactive Black 5 using nano-TiO2 (NT) as a photocatalyst was investigated by adsorption and degradation experiments. Effects of NT particle size and utilization ratio on the time-dependent flow performance, compressive-flexural strength, and Bohme abrasion resistance of cementitious systems were investigated. In addition to the NT-free control mixture, a total of six photocatalytic self-cleaning mortar mixtures (PSCM) were prepared using NT in two different particle sizes (28 and 38 nm) and three different ratios (0.5%, 1%, and 1.5%). The PSCM sample containing 38 nm NT exhibited superior performance in terms of photocatalytic properties compared to the 28 nm state. It was observed that the flow performance of PSCM mixtures with NT substitution is adversely affected regardless of the NT type. Mixtures containing NT with a lower particle size (28 nm) had higher compressive and flexural strengths.

Combined effects of pentachlorophenol and nano-TiO2 with different sizes on antioxidant, digestive, and immune responses of the swimming crab Portunus trituberculatus

Marine nano-titanium dioxide (nano-TiO2) and pentachlorophenol (PCP) pollution are escalating concerns in coastal areas. This study investigated the combined effects of continuous exposure to nano-TiO2 (25 nm, 100 nm) and PCP (0, 1, 10 μg/L) for 28 days on the antioxidant, digestive, and immune abilities of the swimming crab Portunus trituberculatus. Compared with the control group, the interaction between nano-TiO2 and PCP was significantly higher than exposure to a single stressor, with a pronounced decrease in amylase activity observed due to the reducing nano-TiO2 particle sizes. Resulting in increased MDA and SOD activity. The expression levels of Toll4, CSP3, and SER genes in crab hemolymph showed perturbations following exposure to nano-TiO2 and PCP. In summary, according to the results of CAT, GPX, PES and AMS enzyme activities, it was concluded that compared to the larger particle size (100 nm), the single stress of nano-TiO2 at a smaller particle size (25 nm) and co-stress with PCP have more significant impacts on P. trituberculatus. However, the potential physiological regulation mechanism of the interaction between these pollutants remains elusive and requires further study.

Soy Protein/Polyvinyl-Alcohol (PVA)-Based Packaging Films Reinforced by Nano-TiO2

This work was investigated to prepare a reinforcing composite packaging film composited of soy protein/polyvinyl alcohol (PVA) and nano-TiO2. First, different film compositions were designed by the particle size of nano-TiO2, concentration of nano-TiO2, concentration of polyvinylpyrrolidone (PVP, a dispersing agent for nano-TiO2), and pH of film casting solution. Then, the film composition that yielded the optimal physical properties was identified using orthogonal array design single-factor experiments, considering its physical properties, including tensile strength, elongation, water absorption, water vapor transmission, oxygen permeation, thermal property, and film morphology. The results displayed that the optimal film composition was (1) soy protein/PVA film with 2.5 wt% nano-TiO2, (2) 30 nm nano-TiO2 particle size, (3) 1.5 wt% PVP, and (4) pH 6.0 of film-forming solution. It yielded tensile strength of 6.77 MPa, elongation at break rate of 58.91%, and water absorption of 44.89%. Last, the films were characterized by scanning electron microscope (SEM) and differential scanning calorimetry (DSC). SEM analysis showed that compared with the film without TiO2, the film containing TiO2 has a smoother surface, and DSC determined that adding nano-TiO2 can improve the thermostability of soy protein/PVA film. Therefore, the film prepared in this paper is expected to provide a new theoretical basis for use in the packaging industry.

Effect of nano-TiO2 particle size on the bonding performance and film-forming properties of starch-based wood adhesives

The effect of nano-TiO2 particle size on the properties of starch-based wood adhesives was studied in this work. Our findings indicate that a smaller size of nano-TiO2 particles corresponds with a larger specific surface area and more hydroxyl sites on the particle surface that interact with latex molecules, forming a more compact network structure. Therefore, the bonding performance and water resistance of the adhesive were enhanced. In addition, rheology results showed that the adhesive behaves as a pseudoplastic fluid. Small-angle X-ray scattering and energy dispersive spectroscopy confirmed the good compatibility and dispersion of nano-TiO2 in the adhesive films. Diffusing wave spectroscopy and scanning electron microscopy showed that smaller TiO2 particles were more favorable for the formation of smoother and denser films. These results are of great significance for improving the structure and properties of starch-based wood adhesives and preparing high-performance environmentally friendly biobased adhesives.

Ion Transport and Dielectric Studies on [PEO:TiO2]:NH4SCN Nanocomposite Polymer Electrolytes

AbstractAn improvement in ion transport behavior and dielectric properties of polyethylene oxide based polymer electrolytes have been investigated upon the dispersal of TiO2 nanoparticles. TiO2 nanoparticle is synthesized with the help of well‐known sol–gel technique. The different compositions of polymer electrolyte systems are prepared by the solution cast technique. Nanocomposite polymer electrolytes (NCPEs) films are synthesized by loading of nanoTiO2 particle in a pristine polymer electrolyte matrix. The structural and morphological behaviors of nanocomposite polymer electrolytes (NCPEs) have been subsequently characterized by XRD and SEM studies. The ionic behavior of synthesized NCPEs is ascertained by Wagner's polarization technique. AC and DC conductivity of polymer electrolyte films have been carried out using impedance spectroscopic techniques. Dielectric relaxation studies of polymer electrolytes are examined using impedance spectroscopic data. The conductivity relaxation mechanism of NCPEs has been concluded with the help of modulus formalism. DC conductivity of best ion‐conducting NCPEs at room temperature has been found to σ = 2.5 × 10−5 S cm−1. The electrode polarization effect has completely vanished in the dielectric and modulus formalism and the conductivity scaling data show a single master curve observed in ion dynamics. The change in ionic conductivity with frequency and temperature is studied by impedance spectroscopic investigations. The effect of salt on dielectric parameters of NCPEs is also extracted from impedance spectroscopic data to explore underlying ion dynamics.

A Machine Learning Approach to Predict the Performance of Refrigerator and Air Conditioning Using Gaussian Process Regression and Support Vector Methods

Aim: Develop machine learning models for the performance of refrigerator and airconditioning system. Background: The Coefficient Of Performance (COP) of Refrigerator and Air-Conditioning (RAC) is a complex function of evaporative temperature and concentration of nano-particle in lubricants. In recent years, researchers focus on experimental study for improvement of COP. Further, few researchers applied simulation techniques such as fuzzy system, Artificial Neural Network (ANN), simulated annealing, etc. to the Vapour Compression Refrigeration (VCR) cycle. There is a scarcity of modeling research work for the performance of RAC system. Objective: The study aims to develop the machine learning predictive models for the performance of refrigerator and air-conditioning system using experimental data. Methods: The experiment was performed on VCR system to determine COP. Three different concentration of lubricants (added 0.5, 1.0 and 1.5g nano-TiO2 particle on 1 liter of Polyolester (POE) oil) were used. The experimentally calculated COP was used to train and test the machine learning models. Gaussian Process Regression (GPR) and Support Vector Regression (SVR) methods were applied to develop the models. Results: The experimental result reveals that the COP increases with increasing the concentration (of nano particles) at a given temperature. The addition of 0.5 and 1.0g TiO2 in the POE oil shows better rate of increment in the COP in comparison to addition of 1.5g TiO2 in the POE oil. Machine learning models using GPR and SVR with RBF kernel function is the most appropriate machine learning model for the nonlinear relationship between the output parameter (COP) and the input parameter (evaporative temperature and concentration of TiO2). Conclusion: The present study was conducted to investigate the machine learning approaches for performance of RAC system using experimental data sets. The experimental result shows that R134a and TiO2-POE nanolubricant work efficiently and the coefficient of performance of VCR system increases with concentration of nano-particle. The developed model performance is compared using coefficient of correlation and RSME values. After comparison, it is concluded that RBF based GPR model is the best fit machine learning model to predict the COP in the context of any other model for this data set.

Cover Image, Volume 138, Issue 20

The image of Transmission Electron Microscopy Micrographs by Mayara Pollyane Calderaro and colleagues shows the morphology of nanobiocomposites: PBAT/hybrid nanofiller-montmorilonitte, sepiolite, and nanoTiO2. The nanocomposites with isolated nanoclays present tactoids and some agglomerates, while good dispersion of the nanoTiO2 particle is observed in the polymeric matrix. The hybrid nanocomposites show synergism on mechanical and barrier properties due to the dispersion of nanofillers, mainly for the montmorillonite that presented intercalated and exfoliated structures. Doi: 10.1002/app.50414

An AFM-IR study on surface properties of nano-TiO2 coated polyethylene (PE) thin film as influenced by photocatalytic aging process

Most plastic wastes undergo extensive photo-aging in the environment, and the aged plastics exhibit different surface properties from pristine ones. Here, we investigate the surface properties of a nano-TiO2 coated polyethylene (PE) film as influenced by photocatalytic aging process using an atomic force microscopy coupled with infrared spectroscopy (AFM-IR) technique. Results showed that the height range of the as-prepared samples was about 30 nm, and the equivalent diameter of nano-TiO2 was ~70 nm. The photo-induced oxidation of the CH2 bond occurred on the surface of the PE film. Photo-aging mainly affected the thermal properties of PE film in a local area, especially affecting the components surrounding the nano-TiO2 particle. The glass transition temperature of unaged PE film mainly changed in the range of 93.9–96.5 °C, but after aging the temperature gradually increased with the distance to nano-TiO2 increasing from near to far. The plastic film surrounding the nano-TiO2 particle became stiffer after photo-aging, and the photocatalytic reaction had an effect on the stiffness of the film material. The second characteristic peaks with resonance deviations (i.e., 110, 112, and 115 kHz) were used for Lorentz contact resonance (LCR) measurements. The mechanical properties of PE film after photo-aging were closely related to the distance between nano-TiO2 and film surface. These research findings are conducive for us to understand better the photo-induced aging process of functional plastic film.

Automobile Exhaust Removal Performance of Pervious Concrete with Nano TiO2 under Photocatalysis.

The urban environment is facing serious problems caused by automobile exhaust pollution, which has led to a great impact on human health and climate, and aroused widespread concern of the government and the public. Nano titanium dioxide (TiO2), as a photocatalyst, can be activated by ultraviolet irradiation and then form a strong REDOX potential on the surface of the nano TiO2 particles. The REDOX potential can degrade the automobile exhaust, such as nitrogen oxides (NOx) and hydrocarbons (HC). In this paper, a photocatalytic environmentally friendly pervious concrete (PEFPC) was manufactured by spraying nano TiO2 on the surface of it and the photocatalytic performance of PEFPC was researched. The nano TiO2 particle size, TiO2 dosage, TiO2 spraying amount, and dispersant dosage were selected as factors to investigate the efficiency of photocatalytic degradation of automobile exhaust by PEFPC. Moreover, the environmental scanning electron microscope (ESEM) was used to evaluate the distribution of nano TiO2 on the surface of the pervious concrete, the distribution area of nano TiO2 was obtained through Image-Pro Plus, and the area ratio of nano TiO2 to the surface of the pervious concrete was calculated. The results showed that the recommended nano TiO2 particle size is 25 nm. The optimum TiO2 dosage was 10% and the optimum dispersant dosage was 5.0%. The photocatalytic performance of PEFPC was best when the TiO2 spraying amount was 333.3 g/m2. The change in the photocatalytic ratio of HC and NOx is consistent with the distribution area of nano TiO2 on the surface of the pervious concrete. In addition, the photocatalytic performance of PEFPC under two light sources (ultraviolet light and sunlight) was compared. The results indicated that both light sources were able to stimulate the photocatalytic performance of PEFPC. The research provided a reference for the evaluation of automobile exhaust removal performance of PEFPC.

Photocatalytic aging process of Nano-TiO2 coated polypropylene microplastics: Combining atomic force microscopy and infrared spectroscopy (AFM-IR) for nanoscale chemical characterization

Microplastics (MPs) are considered to have greater environmental hazards than large plastics. Most MPs undergo different degrees of aging and aged MPs exhibit different physicochemical properties from pristine ones. This study successfully prepared a nano-TiO2 coated polypropylene MPs, and explored the nanoscale infrared, thermal, and mechanical properties of MPs before and after photo-aging using a combined AFM-IR technique. Surface height range of MPs was ± 25 nm. The signal intensity of the absorption peak at 1654 cm−1 in terms of vinylidene end groups gradually increased as the irradiation time prolonged. The softening temperature of MPs decreased from 126.7 °C to 108.5 °C as the irradiation time increased from 0 h to 4 h. The MPs after photo-aging became stiffer, especially for the components surrounding the nano-TiO2 particle, indicating that photocatalytic reaction accelerated the aging process of MPs. The resonance frequency of MPs surrounding the nano-TiO2 particle was stronger after photo-aging and the stiffer components were uniformly distributed, confirming that the thermal and mechanical properties of MPs changed after photo-aging. These novel findings are essential to better understand the changes in the surface microstructures, physical properties, and chemical compositions of MPs during aging process.

Influence of nano-TiO2 on the wellbore shear bond strength at cement-formation interface

Abstract This research investigates the wellbore shear bond strength of nano-TiO2-containing oil-well cement pastes with particle sizes of 20 and 40 nm. The nanoparticles were picked by the weight of cement at proportions corresponding to 1, 2, 3 and 4%. Test results indicated that nano-TiO2 significantly enhanced the interfacial shear bond strength. The results also revealed that the strength enhancement was reliant on the nano-TiO2 particle sizes. The specimens containing nano-TiO2 40 nm provided greater strength compared to 20 nm, due to effective pozzolanic activity. By fluctuating the nano-TiO2 dosages, the optimal replacement content was 3% for all particle sizes. The particle size did not affect the appropriate dosage of nano-TiO2, it only impacted the bonding strength of the interfaces. With 3% (40 nm) nano-TiO2, the 3, 7, 14 and 28 days strength increased by 557.38, 504.17, 528.57 and 412.04% respectively. The scanning electron microscope, X-ray diffraction and thermogravimetric technique were used to examine the influence of nano-TiO2 on the cement-formation bonding.

Studies on the size effects of nano-TiO2 on Portland cement hydration with different water to solid ratios

The effects of using different sizes of nano-TiO2 (NT) on the hydration characteristics of Portland cement with different water to solid ratios (w/s, solid: cement + NT) were investigated in this study. Cement was partially replaced by NT with two sizes, 5 nm and 25 nm, at weight fractions of 0, 0.5%, 1.0%, 1.5% and 2.0%. The compressive strength, hydration products, hydration degree, pore structures and morphologies of the modified cement pastes were systematically evaluated. The experimental results showed that a suitable NT content effectively enhanced the compressive strength of the cement paste, and this enhancement directly depended on the NT particle size. Cement paste mixed with 5-nm NT resulted in a higher compressive strength than 25-nm NT, irrespective of the w/s ratio. The cement paste with a maximum compressive strength at all the curing ages was obtained using a 0.3 w/s ratio and 0.5 wt% of 5-nm NT (which were therefore identified as the optimal NT parameters). The compressive strength of this cement paste increased by 41.4%, 15.9%, 18.7% and 24.35% at 1, 3, 7 and 28 days, respectively, compared to a control sample. For both NT sizes, the w/s ratio and the NT content controlled the compressive strength development of the paste during the early and late ages, respectively. Compared with 25-nm NT, replacing cement by 5-nm NT within the optimum content range was more effective in accelerating cement hydration, increasing the hydration degree, decreasing the crystal size of Ca(OH)2, refining the pore structure and densifying the cement paste at the microscale, all of which increased the compressive strength at the macroscale.

Effects of nano-TiO2 particle size on microstructure and electrochemical performance of TiO2/PEDOT nanocomposites cathode in lithium-sulphur battery

ABSTRACT The PEDOT/TiO2 nanocomposites with different TiO2 particle sizes were fabricated by a simple soft chemical approach-assisted in situ synthesis route and used as an effective cathode of Li-S batteries. When the TiO2 particle size was 5 nm, the discharge capacity of the cells is the best and the initial discharge capacity is 859.7 mAhg−1, within 300 charge–discharge cycles at 1 C. The improvement on cells electrochemical performance is attributed to the TiO2 particles well dispersed in the PEDOT, and the PEDOT creates integral electronic conductive net-work and prevent soluble long-chain polysulphides diffuse into the liquid electrolyte during the charge–discharge processes.

Nano-TiO2 reinforced CoCr matrix wear resistant composites and high-temperature tribological behaviors under unlubricated condition

The CoCrMo matrix composites with nano-TiO2 particle (2 wt.%, 4 wt.% and 6 wt.%) were fabricated by using a powder metallurgy technique (P/M), and the nano-TiO2 content was optimized in matrix. The microstructures, mechanical and high-temperature tribological properties of the synthesized composites were systematically studied. Friction and wear behaviors were studied by using a disk-on-ball tribo-tester sliding against Si3N4 ceramic ball from room temperature (23 oC) to 1000 oC in air. TiO2 obviously strengthened the hardness and high-temperature wear resistance of composites. It was attributed to the high load-carrying capacity of matrix, in-situ formed high-temperature solid lubricants and stable oxides film on the wear tracks. 4 wt.% TiO2 was the critical threshold at which there was a transition of tribological properties over a broad temperature range. The composite containing 4 wt.% nano-TiO2 exhibited the most reasonable high-temperature friction coefficient and wear rate at all testing temperatures. At different testing temperatures, the composites showed different wear mechanisms.

The Performance Changes and Migration Behavior of PLA/Nano-TiO2 Composite Film by High-Pressure Treatment in Ethanol Solution.

To study the relationship between performance changes and nanoparticles migration of the composite film at different migration stages, the poly (lactic acid) (PLA)/nano-TiO2 composite film treated by high pressure was immersed in 50% (v/v) ethanol solution for 45 days at 40 °C, and the film characteristics and migration behavior were analyzed. The results showed that the migration of the composite film with the highest loading of nano-TiO2 (20 wt. %) in alcoholic food simulated solution was far less than 10 mg/kg during the 45-day migration process. Although with the increase of migration time, the micro-morphology of composite film became rougher, the crystallinity decreased and the gas permeability increased, but the internal crystal structure of the composite film remained basically unchanged. The PLA/nano-TiO2 composite films treated by high pressure treatment were relatively stable, and had good performance and migration behavior in alcoholic food simulated solution, the nanocomposite film after high pressure treatment could be used to reduce nano-TiO2 particle migration and subsequently reduce human exposure as the packaging film for the packaging of alcoholic food, which provide a theoretical basis for the applications of high pressure treatment of PLA/nano-TiO2 composite films in food packaging material and broaden its application prospects.

Effects of particle size, crystal phase and surface treatment of nano-TiO2 on the rheological parameters of cement paste

In this study, two sizes of rutile nano-TiO2 (NT) (20 nm and 50 nm), three crystal phases of NTs (anatase NT, rutile NT and polymorphic NT, a hybrid of 80% anatase NT and 20% rutile NT) and two surface-treated NTs (SiO2-coated NT and SiO2/Al2O3-coated NT) were employed to their effect on rheological behaviors of cement pastes. The water-to-cement ratio was fixed at 0.24, and the NTs were added to the paste at contents of 0, 0.1%, 0.3%, 0.5%, 0.7% and 1.4 vol% of cement, respectively. The rheological behaviors of cement pastes were characterized using two rheological parameters including yield stress and minimum viscosity. The H-B model was chosen to calculate the yield stress and the minimum viscosity was selected as the smallest apparent viscosity in the apparent viscosity-shear rate curve. Experimental results show that NTs have a significant effect on the rheological parameters of the cement pastes when the NT content exceeds 0.5 vol%. The yield stress and minimum viscosity of the cement pastes varies with NT particle size by changing the total surface area of the system. The rutile NT with smaller particle size produces larger yield stress and the minimum viscosity. Cement pastes with three different crystal phases of NTs show distinct rheological behaviors. The cement paste with the rutile NT has the largest yield stress and minimum viscosity, while cement paste with the polymorphic NT has the smallest yield stress and minimum viscosity. The yield stress and the minimum viscosity of the cement paste with SiO2/Al2O3-coated NTs are larger than those of the cement paste with SiO2-coated NTs owing to a smaller electrostatic repulsion.

Experimental Study on Photocatalytic Effect of Nano TiO2 Epoxy Emulsified Asphalt Mixture

The two major problems that have plagued urban underground roads since their introduction are the harmful emissions caused by hot mix paving and vehicle exhaust accumulation during operation. In order to solve these two problems at the same time, a new asphalt mixture degrading automobile exhaust, which has the advantage of cold mix and cold-application, was presented and studied. A considerable amount of research shows that the use of titanium dioxide (TiO2) for pavements has received considerable attention in recent years to improve air quality near large metropolitan areas. However, the proper method of applying TiO2 to asphalt pavements is still unclear. The new mixture presented in this article contains epoxy emulsified asphalt as the binder; therefore, how to apply TiO2 in the special asphalt mixture proves to be the main focus. By experimental design, four influence factors on the photocatalytic effect, which are the nano-TiO2 particle sizes, dosage, degradation time, and light intensity, have been investigated. The experimental results showed that the 5-nm particle size of TiO2 is better than 10–15 nm for exhaust gas degradation, especially for HC and NO; with an increase in the amount of photocatalytic material, the degradation of CO and CO2 in the exhaust gas did not increase obviously, while the degradation effects of HC and NO were remarkable; in the 4-h time extended degradation test, the experimental data show that the extended time has little effect on the degradation rate of CO2 and CO, and the general trend is that the degradation of exhaust became significant with the extension of time; while setting a 2-h NO degradation rate as an indicator, to make the index more than 50% or 25%, the average illumination of the road surface cannot be less than 60 lx or 40 lx.

Erosion Wear and Hardness of Glass Fiber / Epoxy with Nano and Micro TiO2 Hybride Composites

The objective of this research is to prepare and study (Glass Fiber / Epoxy) with nano and micro Titanium dioxide (TiO2) composites with different volume percentage of nano and micro TiO2 powder of 2%, 4%, and 6% volume fraction. Atomic force microscopy techniques was used to measure the grain size of nano TiO2 powder (average diameter was 46 nm) and particle size analyzer techniques was used. Erosive wear behavior of this composite under three different impingement angles of 30°, 60° and 90° and three angular silica sand abrasive particle sizes approximately 425, 600 and 850 μm and hardness (shore D) were studied. In general the erosion wear of micro composites have lower erosion resistance than other nano-based compounds. Erosion resistance increase as the volume fraction increase. Nano composites of GF / EP with TiO2 have many advantages over micro composites from the view point of wear and hardness tests. The worn surface features of unfilled and filled G-E composites were examined using scanning electron microscopy (SEM) and results indicates more severe damage to matrix and glass fiber in unfilled composite system as compared to TiO2 filled composites.

Synthesis and Characterization of Mechanical Properties of Nano TiO2 Particle Reinforced AL-MMC

Synthesis and Characterization of Mechanical Properties of Nano TiO2 Particle Reinforced AL-MMC

Development of multifunctional plaster using nano-TiO2 and distinct particle size cellulose fibers

The present study reports on the development of multifunctional plaster showing superior thermal insulation, ability to control the indoor RH and NOx photocatalytic degradation. The plaster contains TiO2 nanoparticles (1wt.%) and 0–4wt.% fibers of two distinct sizes: 1mm<d<2mm (Fb1-2mm) and 2mm<d<4mm (Fb2-4mm). The formulations were adjusted based on flow table and rheometer tests, aiming to assure a desirable workability. Plasters with similar workability (spread on table) showed distinct yield stress values over time and Fb(1-2mm) plays an important role on the workability control. Rheological behaviour was governed by Fb(2-4mm). Binary mixture 2.0Fb1-2mm + 2.0Fb2-4mm2·0Fb2-4mm required less water amount to show the same workability of the single formulation 4.0Fb1-2mm. However, the control of the rheological behavior over time was found difficult. The apparent porosity, water absorption and capillary index were strongly incremented with the rise of cellulose fiber concentration. Singular and binary samples present similar results and no significant differences were observed by changing the fibers size. Plaster’s buffering capacity and NOx uptake was considerably improved by using cellulose fibers, being this increment primarily governed by the fiber concentration. Formulation containing 4.0wt.% Fb(2-4mm) revealed the optimal performance.