Toughening effects of titanium dioxide nanoparticles on TiO2/epoxy resin nanocomposites

The purpose of this study was to investigate the influence of adding different volume concentrations of titanium dioxide (TiO₂) nanoparticles to an Araldite LY 564 epoxy resin. In order to characterize the nanoparticles toughening effects, compact tension specimens were used to determine the plane strain fracture toughness (K_IC). Additionally, elastic modulus, tensile strength, and maximum sustained strain were measured in mechanical tensile tests. Composites were analyzed by means of electronic microscopy, both TEM and SEM, to check the dispersion quality of the nanoparticles in thepolymer matrix and to study the observed toughening mechanisms of the fillers. Addition of TiO₂ nanoparticles could simultaneously improve the stiffness and the toughness of the epoxy resin. POLYM. COMPOS., 31:1241–1246, 2010. © 2009 Society of Plastics Engineers     

Defect-mediated optical properties of Fe-substituted TiO2 nanoparticles

Here, sol–gel derived Fe–TiO₂ anatase nanoparticles with varying concentrations of Ti_(1–x)Fe_xO₂ (x = 0%, 1%, 5%, 10%) were prepared. The structural, morphological, and optical properties of prepared samples were studied. X-ray diffraction (XRD) patterns show the formation of pure anatase phase. The mean crystallite size of Fe–TiO₂ decreases with increase in the concentration of Fe. Fourier transform infrared spectroscopy (FTIR) spectra confirmed the presence of Ti–O vibrational band for all the samples. In Raman spectrum, peak broadening and red shifting linked with Eg ∼144 cm^–1 divulge the Fe substitution at Ti sites into host lattice structure. Photoluminescence (PL) spectra verified nine peaks related to near band-edge emission and various defect states. The UV–vis diffuse reflectance spectra represent redshift and reduction in the bandgap energy. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigations show that the size of the grains decreases with increase in Fe doping concentration. The study shows that Fe-doped TiO₂ anatase phase nanoparticles are suitable for photocatalytic activity and solar cell applications.     

Morphology and properties of highly filled iPP/TiO2 nanocomposites

Nanocomposites based on isotactic polypropylene (iPP) and titanium dioxide (TiO₂) nanoparticle containing 1–15 vol% (4.6–45.5 wt%) of the nanoparticle were prepared by the melt blending process. The effect of an anhydride‐modified polypropylene as a compatibilizer on dispersion of TiO₂ nanoparticles was assessed using SEM. TGA and DSC analysis were performed to study the thermal properties of the nanocomposites. Crystalline structures of iPP in the presence of TiO₂ were analyzed by XRD. Mechanical properties of the nanoparticles were measured and a micromechanical analysis was applied to quantify interface interaction between the polymer and particle. SEM results revealed improvement of TiO₂ particle dispersion by adding the compatibilizer. It was shown that the thermal stability and crystalline structure of the nanocomposite are significantly affected by the state of particle dispersion. TiO₂ nanoparticles were shown to be strong β‐nucleating agents for iPP, especially at concentrations less than 5 vol%. Presence of the β‐structure crystals reduced the elastic modulus and yield strength of the nanocomposites. Micromechanical analysis showed enhanced interaction between organic and inorganic phases of the compatibilized nanocomposites. POLYM. ENG. SCI., 54:874–886, 2014. © 2013 Society of Plastics Engineers     

The effect of silica nanoparticles on the thermomechanical properties of polystyrene

A series of polystyrene (PS)/SiO₂ nanocomposites were prepared. Silica nanoparticles with an average diameter of 16 nm were used, and treated with dimethyldichlorosilane, while their weight fraction varied from 4 up to 10%. The viscoelastic‐thermomechanical properties of the nanocomposites and their interrelation with the material's structure were studied with various experimental techniques. Scanning electron microscopy, differential scanning calorimetry, dynamic mechanical analysis, and tensile testing at three different temperatures were applied. The stress–strain curves at 85°C, where the material's viscoplastic response is manifested, were simulated through a plasticity model, developed in previous works. The 4% weight fraction was found to be the optimum one for the enhancement of the thermomechanical properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Immobilization of TiO2 nanoparticles on montmorillonite clay and its effect on the morphology of natural rubber nanocomposites

Natural rubber/organoclay/titanium dioxide nanocomposites were obtained via mechanical blending using rubber latex, organically modified montmorillonite clay (cloisite 30B) and titanium dioxide (TiO₂). Glycerol was utilized as a dispersant for the inorganic components. Scanning electron microscopy analysis shows that TiO₂ nanoparticles were deposited on the clay surface and that the clay–TiO₂ combination was homogeneously dispersed on the natural rubber. The high aspect ratio and the polar character of the clay layers allowed interactions with individual nanoparticles of TiO₂. The X-ray diffraction patterns reveal an increment of the crystalline character of the NR/C30B/TiO₂ nanocomposites as a consequence of the nanoscale dispersion of the TiO₂ particles. Infrared Spectroscopy spectra indicate compatibility between natural rubber and glycerol due to the formation of hydrogen bonds. A mechanism in particle–natural rubber compatibility, in which glycerol is involved, is proposed. However, nanoscale dispersion was largely dependent on the clay–TiO₂ interactions. This work proposes an easy method to immobilize TiO₂ nanoparticles on clay layers, which allows their dispersion in polymers. Nanocomposites obtained by this method can be used for supports of photocatalyst molecules.     

Effects of size and shape on filtration of TiO2 nanoparticles

Titanium dioxide (TiO₂) is one of the most widely used nanoscale materials to date and could result in human exposures. The main objective of this study was to perform detailed characterization of TiO₂ agglomerate particles and how these properties influence particle penetration in a screen filter. Transmission electron microscope (TEM) photos showed compact agglomerates of nanoscale primary particles. The projected area diameter was close to the mobility diameter, where the length was about 25% larger than the mobility diameter. The mean aspect ratio of TiO₂ agglomerate was constant between 1.39 and 1.55. Using the tandem differential mobility analyzer-aerosol particles mass analyzer (DMA-APM) technique, we were able to measure aerodynamic diameter, mass, and fractal dimension. The value of fractal dimension based on mass and mobility diameter was 2.8. Penetration of classified TiO₂ particles through a screen filter was measured. Penetration increased with increasing mobility diameter and flow rate indicating that diffusion and interception were the main filtration mechanism. The measured physical dimensions, mobility diameter, and aerodynamic diameter were used in a single-fiber filtration theory for the fan model filter to predict the penetration of TiO₂ particles. The interception parameter was the key to estimate the penetration. Experimental penetration data were in best agreement with the model in which the maximum length was used to calculate the interception model. This result was consistent with the assumption that the rotation time of a non-spherical particle of small aspect ratio was much less than the transport time for the particle to pass through the filter fiber.

© 2017 American Association for Aerosol Research     

Hydrothermal effects on the thermomechanical properties of high performance epoxy/clay nanocomposites

The effects of hydrothermal ageing on the thermomechanical properties of high performance epoxy and its nanocomposite were studied. The epoxy–clay nanocomposite was prepared through a recently developed “slurry‐compounding” approach. The cured samples were immersed in distilled water at 60°C for different periods of time before subjecting to characterization. The storage modulus, relaxation behavior, fracture toughness, and tensile properties were investigated. It was found that the storage modulus and α‐relaxation were strongly affected by water uptake, while the fracture toughness and Young's modulus were less influenced. Dependence of tensile strength and strain at break on water uptake was found to be different in neat epoxy and epoxy–clay systems. POLYM. ENG. SCI., 46:215–221, 2006. © 2005 Society of Plastics Engineers     

水热合成二氧化钛纳米颗粒及光致发光性能研究

以价格较为低廉的钛酸丁酯为钛源,不同添加量的十六烷基三甲基溴化铵（CTAB）为模板剂,采用水热合成法制备二氧化钛纳米颗粒。利用氮吸附仪、扫描电子显微镜（SEM）、X射线衍射仪（XRD）、荧光光谱仪（PL）对材料进行结构分析及光致发光性能测试。结果表明,所制备的二氧化钛纳米材料均为锐钛矿结构,粒径较小的纳米颗粒堆积形成介孔结构。样品具有特殊的光致发光特性,由于纳米颗粒粒径大小不同,孔径大小不等使得光致发光特性的强度产生较大差异,发射峰位置产生明显红移。     

Morphology and thermomechanical properties of recycled PET–organoclay nanocomposites

Recycled PET/organoclay nanocomposites were prepared by melt intercalation process with several amounts (1, 3, and 5 wt %) of clay modified with quaternary ammonium salt (DELLITE 67G) dispersed in a recycled poly(ethylene terephthalate) (rPET) matrix. The resultant mechanical properties (modulus and yield strength) of the nanocomposites were found to be different from those of rPET. Wide angle X‐ray scattering (WAXS) and Transmission Electron Microscopy (TEM) measurements have shown that although complete exfoliation was not achieved, delaminated clay platelets could be observed. Thermal analysis did not show significant changes in the thermal properties from those of recycled PET. Mechanical testing showed that nanocomposite properties were superior to the recycled PET in terms of strength and elasticity modulus. This improvement was attributed to nanoscale effects and strong interaction between the rPET matrix and the clay interface, as revealed by WAXS and TEM. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1839–1844, 2007     

核-壳结构ZnO/TiO2复合材料的制备及其光催化性能研究

采用电化学阳极氧化法制得结构规则、有序的TiO2纳米管,以TiO2纳米管为基质,在一定水热条件下合成核-壳结构的TiO2/ZnO复合纳米材料。利用X射线衍射(XRD)、扫描电镜(SEM)、紫外-可见光谱(UV-VIS DRS)等分析手段对所得材料的结构、形貌及光催化性能进行分析和表征。实验结果表明:TiO2/ZnO复合纳米材料的光催化性能较单一TiO2、ZnO纳米材料有所提高。当前驱体溶液加入量为20 mL,甲基橙溶液初始pH为3时,TiO2/ZnO复合纳米材料的光催化效率最高。     

Preparation of TiO2 epoxy nanocomposites by ultrasonic dispersion and resulting properties

Nanocomposites gained more and more importance in the last few years because of their improved performance over the neat polymer matrix, that is, toughness and stiffness can be enhanced simultaneously by the addition of nanoparticles. However, the dispersion of these particles in the matrix remains a big challenge. In this study, two types of TiO₂ nanoparticles were dispersed in two different epoxy resins by means of ultrasound. The particle size development in dependence on the dispersion time was investigated by dynamic light scattering for the different material systems. Furthermore, the influence of the viscosity on the sonication process' efficiency was analyzed. The resulting nanocomposites were tested for fracture and Charpy toughness. SEM images revealed that the improved fracture toughness properties are correlated to a rougher fracture surface, whose formation dissipates more energy. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Magnetic and optical properties of Nd/TiO2- rGO nanocomposites

Graphene, the thinnest 2-dimensional atomic material, is successively used as a composite material has it significantly improves optical, thermal, mechanical and electrical properties. Neodymium being a strong paramagnetic substance is capable of storing large amount of magnetic energy because of their greater number of unpaired electrons in their electron orbital structure. This paper focuses on the influence of graphene on the structural, optical and magnetic properties of rare earth neodymium (Nd) doped TiO₂ nanoparticles. Nd doped TiO₂ nanoparticles are deposited on reduced graphene oxide (rGO) sheets forming the nanocomposites by hydrothermal treatment. The nano size, structure and phase of the composites are analysed by X-ray diffraction and Raman spectra. Dispersion of pure TiO₂ and Nd/TiO₂ nanoparticles on the rGO sheets is studied with FESEM and HRTEM micrographs alongside the elemental composition confirmed by EDAX. Increased surface area and pore size analysis is revealed by BET isotherms and BJH data. Absorption edges are blue shifted owing to particle size and experimental conditions. PL and EPR spectra confirm the presence of paramagnetic defect centres in the nanocomposites. The M − H hysteresis curves of the composites reveal the ferromagnetic behaviour at room temperature.     

Effect of TiO2 nanoparticles on the antibacterial and physical properties of polyethylene-based film

TiO₂ nanoparticles and their application in packaging systems have attracted a lot of attention because of its antimicrobial activity. In this work, effect of TiO₂ nanoparticles on the antibacterial and physical properties of polyethylene (PE)-based film was investigated. Results indicated that the antibacterial activity of TiO₂-incorporated PE films should be due to the killing effect property of TiO₂ nanoparticles against microorganisms. The TiO₂-incorporated PE film exhibited more effective antibacterial activity for Staphylococcus aureus. The antibacterial activity to inactivate Escherichia coli or S. aureus was improved by UV irradiation. The inhibition ratio of TiO₂-incorporated PE films sample irradiated for 60 min by UV light was improved significantly, which were 89.3% for E. coli and 95.2% for S. aureus, respectively, compared to that of TiO₂-PE film without UV irradiation. The analysis of physical properties revealed that TiO₂ nanoparticles increased the tensile strength and elongation at break of PE-based film. The climate resistance of nano-TiO₂ films is greatly enhanced, compared to that of the blank PE film. Water vapor transmission increased from 18.1 to 24.6 g/m²·24 h with the incorporation of TiO₂ nanoparticles. Results revealed that PE based film incorporating with TiO₂ nanoparticles have a good potential to be used as active food packaging system.     

The effect of TiO2 nanoparticles on the properties of sulfonated block copolymers

Block copolymers composed of styrene and different elastomeric blocks were sulfonated to high ion exchange capacities (IECs). Titanium dioxide (TiO₂) nanoparticles were added to these polymers to improve their mechanical and thermal stabilities, while influencing their transport properties for direct methanol fuel cell (DMFC) applications. Materials properties as proton exchange membranes (PEMs) were analyzed using: FT‐IR, water absorption, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), IEC, methanol permeability, and proton conductivity studies. Although there was no effect of TiO₂ nanoparticles on the thermal stability of the membranes, significant changes were observed in the mechanical properties of both sulfonated block copolymers studied. Water absorption increased at low TiO₂ content, but was then reduced with the incorporation of more nanoparticles. To enhance the interaction between the inorganic fillers and the polymers, sulfonic and amino groups were attached to the surface of the titania nanoparticles. The effect of sulfonated nanoparticles on the properties of the materials was more significant than the effect of the amino functionalized nanoparticles on all the properties evaluated, suggesting enhanced chemical interactions with the ionic domains of the polymer membranes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42651.     

Study of the effect of rutile/anatase TiO2 nanoparticles synthesized by hydrothermal route in electrospun PVA/TiO2 nanocomposites

Mixed rutile–anatase TiO₂ nanoparticles were synthesized by hydrothermal treatment under acidic conditions and incorporated into poly(vinyl alcohol) (PVA). These nanocomposites were electrospun to produce nanofibers of PVA/TiO₂, which were characterized by scanning electron microscopy, transmission electron microscopy, X‐ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The photocatalytic degradation of Rhodamine B and degradation of the polymer by UV‐C lamps were also investigated. The results showed that TiO₂ nanoparticles did not change the morphology and thermal behavior of the nanofiber polymer, but were effective in modifying the UV absorption of PVA without reducing its stability. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Transparent and flexible films of new segmented polyurethane nanocomposites incorporated by NH2-functionalized TiO2 nanoparticles

In this work, TiO₂ nanoparticles are surface modified by NH₂-terminated organic moieties arised from 4,4′-methylene diphenyl diisocyanate (MDI). These nanoparticles are incorporated into ether-based segmented polyurethane (SPU) matrix. MDI is utilized as monomer together with poly(tetramethylene oxide) (PTMO) comonomer for preparing the final polymer as well. The NH₂-functionalized TiO₂ nanoparticles are covalently linked to the NCO terminals of the resulting SPU macromolecules during film preparation stage. Therefore, in addition to butylene glycol, these surface modified nanoparticles with enhanced organophilicity could play the role of the second chain extender of NCO-capped SPU macromolecules through formation of urea linkages. Optical and thermal behaviors of the transparent and flexible film (SPU/TiO₂–MDI) is compared with those of unmodified TiO₂ (SPU/TiO₂) and TiO₂-unloaded SPU films. Though the particle loading is only 5 wt.%, incorporation of TiO₂ and TiO₂–MDI nanoparticles into the SPU polymer enhances significantly the light absorption in UV region at 300–400 nm. SEM images of the prepared films clearly show a considerable decrease in particle aggregation for TiO₂–MDI into SPU matrix compared to that of unmodified TiO₂. TG analyses indicate a one-step decomposition pattern with onset temperatures of about 360 and 380 °C for neat SPU and SPU/TiO₂–MDI, respectively. Moreover, DTA thermograms of both nanocomposites show obviously two exothermic phase transitions in the thermal range of 330–440 °C.     

WC/TiO2纳米复合材料晶相形成机理及电催化性能

以金红石相纳米TiO₂为载体,偏钨酸铵为钨源,采用表面修饰技术制备了纳米复合材料的前体,将前体在甲烷/氢气气氛下还原碳化并采用XRD对其进行表征,研究了还原碳化温度、时间对纳米复合材料晶相组成的影响,并探讨了WC/TiO₂纳米复合材料的形成机理。通过扫描电子显微镜、热重-差热分析等手段对WC/TiO₂纳米复合材料的形态结构和热稳定性进行了表征。采用循环伏安法研究了纳米复合材料物相组成与电催化性能之间的关系,结果表明由WC和TiO₂两相组成的WC/TiO₂纳米复合材料对对硝基苯酚电还原反应的电催化性能最佳。     

Photocatalytic properties of mesoporous TiO2 nanocomposites modified with carbon nanotubes and copper

The photocatalytic activity of mesoporous TiO₂ modified by the addition of carbon nanotubes (CNTs) and Cu is reported. Nanocomposites of carbon nanotubes (CNTs) containing varying amounts of Cu were formed by treatment with Cu²⁺ then reduced to Cu⁰ using NaBH₄ as the reducing agent. The mesoporous TiO₂, synthesized by a sol-gel method from titanium isopropoxide, was combined with the CNT/Cu nanocomposites to form the photocatalysts which were characterized by XRD, SEM, TEM, FTIR, XPS and BET surface area analysis. The photocatalytic properties of the mesoporous TiO₂ composites were studied by measuring the degradation of methyl orange (MO) which was optimal in the sample containing 20 wt% of the Cu-CNT nanocomposite. The degradation efficiency for MO was a synergistic effect of photo-degradation of TiO₂ and may be due to improvement of the electrical conductivity of the system by the presence of the CNT/Cu networks, since the photodegradation of MO and the photocatalytic activity of the photoactive systems increased with increasing copper content.     

苄基接枝海藻酸衍生物对TiO2纳米粒分散稳定性的影响

以溴化苄为疏水改性剂,采用双分子亲核取代反应(SN2)制得苄基接枝海藻酸衍生物(BAD)。通过动态光散射技术,考察了在不同p H和离子强度下BAD对Ti O_2纳米粒水悬浮液分散稳定性的影响。并采用红外光谱和扫描电镜对BAD/Ti O_2纳米粒复合物的官能团和表面形貌进行了测试。结果表明,通过SN2反应成功地合成了具有胶体性能的BAD。BAD胶束的平均水动力学粒径(dH)大小为423.4 nm,Zeta电位值为-27.4 m V,表现出较好的胶体性能。在不同p H下,BAD的吸附可提高Ti O_2纳米粒的带电性,使其Zeta电位均低于-30 m V,而且其dH相比单一的Ti O_2纳米粒显著减小。在不同离子强度下,BAD可明显削弱反离子对Ti O_2纳米粒静电屏蔽作用的影响,使Ti O_2纳米粒的团聚行为大大降低,dH显著减小。BAD分子链不仅能够提高Ti O_2颗粒间的静电斥力,而且还能提供有效的空间位阻,提高Ti O_2纳米粒在不同p H和离子强度下的分散稳定性。红外和扫描电镜分析结果表明,BAD和Ti O_2纳米粒主要通过氢键作用来实现BAD在Ti O_2纳米颗粒上的吸附,从而提高Ti O_2纳米颗粒间的空间位阻作用使其稳定分散。