Simultaneous epoxy grafting on SiO2 nanoparticles during bead milling and their effects on the mechanical properties of epoxy-based composites

Epoxy resin-grafted SiO₂ nanoparticles stabilized in toluene were successfully designed by the simultaneous surface modification of SiO₂ nanoparticles during bead milling which involves the adsorption of polyethyleneimine-oleic acid complex (PEI-OA) and epoxy resin grafting to the free amine groups of PEI-OA (PEI-OA-Epoxy). The effectiveness of epoxy grafting on the properties of the SiO₂/epoxy based nanocomposites were investigated using a bead-milled SiO₂/toluene suspension stabilized with PEI-OA, PEI-OA-Epoxy, and a complex of PEI and an anionic surfactant comprising an epoxy-soluble polyethylene glycol-based chain (PEI-AS). While SiO₂ nanoparticles were pulverized with similar sizes (c.a. 126–171 nm) and stabilized in toluene with any of the three surface modifications, PEI-OA-stabilized SiO₂ nanoparticles aggregated during processing epoxy-based composites. PEI-AS- and PEI-OA-Epoxy-stabilized SiO₂ nanoparticles maintained their dispersion stability, however, the epoxy composites with PEI-OA-Epoxy-stabilized SiO₂ nanoparticles exhibited better material properties, such as increase in the strain at fracture and higher T_g.     

Silicon nanoparticles synthesised through reactive high-energy ball milling: enhancement of optical properties from the removal of iron impurities

Alkyl-terminated silicon nanoparticles (SiNPs) were prepared through reactive high-energy ball milling with contamination of iron from the steel milling materials. Iron impurities in the form of iron nanoparticles cause a decrease of photoluminescence intensity and an increase of the UV absorption. The iron impurities were removed either by gel permeation chromatography separation or by treatment with an aqueous HCl solution. The photoluminescence properties of the SiNPs were enhanced after the removal of iron. Transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and proton nuclear magnetic resonance were used to determine morphology, elemental composition and surface passivation of SiNPs.     

Framework influence of erbium doped oxyfluoride glasses on their optical properties

Glasses of different matrix (phosphate, borate, silicate and lead-silicate) were studied for their optical properties. The effect of Er dopant on transmittance and luminescence properties was presented. The significant “red shift” and “blue shift” of UV edge absorption were discussed based on the changes in the framework of the borate and phosphate glasses, respectively. It was showed that the integral intensity of the two main optical absorption transitions monotonically increases with the order: phosphate < borate < silicate < lead-silicate. Ellipsometric measurement was applied to obtain the refractive index of the glasses. The correlation between the shift of edge absorption and the change of refractive index was presented. Effect of glassy matrix on luminescence of Er³⁺ was discussed.     

载银TiO_2纳米线的制备及其光吸收性能

以纳米TiO2(P25)粉体为原料,采用水热法合成了TiO2纳米线,通过葡萄糖还原Ag(NH3)2+,得到了表面载银(Ag)的TiO2纳米线。利用透射电镜(TEM)、X射线光电子能谱(XPS)和紫外-可见光谱(UV-Vis)对产物进行了表征。结果表明,Ag纳米粒子均匀分散在纳米线表面,并且该Ag/TiO2纳米线在可见光区域表现出较强的吸收性能。     

咔唑和二氰基蒽掺杂纳米粒子的制备及光学性质

以蓝光染料咔唑为电子给体,黄光染料9,10-二氰基蒽为电子受体,采用再沉淀法制备了咔唑和二氰基蒽等摩尔掺杂的纳米粒子。掺杂纳米粒子与纯咔唑聚集体或二氰基蒽聚集体的形貌和发射光颜色明显不同,说明咔唑和二氰基蒽很好的掺杂到一起。吸收光谱表明咔唑和二氰基蒽在掺杂纳米粒子中没有形成电荷转移复合物,荧光发射光谱和荧光寿命表明咔唑和二氰基蒽在掺杂纳米粒子中形成激基复合物,激基复合物的出现使得掺杂纳米粒子的发射光颜色为橙色。     

Preparation and optical properties of titania/epoxy nanocomposite coatings

This work reports the preparation of TiO₂/Epoxy nanocomposites coatings with high refractive index and optical transparency. Highly dispersed titania nanoparticles were synthesized by sol-gel method at room temperature. The TiO₂ nanoparticles can be dispersed directly into the polymer without the use of organic surfactant. Nanocomposite coating with refractive index of 1.668 can be obtained by adding 30 wt% TiO₂ nanoparticles into the polymer matrix. All coatings with different amount of TiO₂ exhibit excellent optical transparency of more than 90%. Although higher refractive index of the nanocomposite can be obtained by increasing the content of TiO₂ nanoparticles, cracks also appear in the surface of the hybrid coating.     

Preparation, characterization and photocatalytic performance of Nd-doped titania nanoparticles with mesostructure

Nd³⁺-doped titania nanoparticles with mesostructures were synthesized via hydrothermal process by using cetyltrimethylammonium bromide (CTAB) as directing and pore-forming agent. The obtained materials were characterized by XRD, nitrogen adsorption-desorption, TEM and DRS. The existence of neodymium ion affect significantly the phase transition of the amorphous to anatase, and the band-gap energy was reduced because of the defect energy level induced by the 4f atomic orbital of Nd³⁺ with the optimal content of 1.5 at.% Nd. Density functional theory calculations can explain the band-gap narrowing. The maximum photocatalytic activity corresponds to the 0.5 at.% Nd³⁺-doped anatase nanopowders with mesostructures, which is higher than that of undoped samples.     

Hazard reduction for the application of titania nanoparticles in environmental technology

Photocatalytically active titania (TiO2) nanoparticles are applied, and considered for application, in the degradation of hazardous substances. However, these nanoparticles are also hazardous by themselves. High efficiency immobilization of TiO2 nanoparticles on large inorganic supports that are not vulnerable to photocatalytic degradation is conducive to hazard reduction. Immobilization should also aim at minimizing the release of TiO2 nanoparticles from such supports due to attrition. In doing so there may be a trade off between hazard and photocatalytic activity.     

Preparation and photocatalytic properties of mixed-phase titania nanospheres by laser ablation

Laser ablation technique was adopted to prepare titania nanospheres; scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM) were employed to characterize the morphology and structure of the product. The results demonstrate that TiO₂ nanospheres with mixed-phase (rutile and anatase) structure were successfully fabricated by laser ablation of titanium target in water. We proposed that changed temperature and pressure after the laser ablation is responsible for the co-existence of the rutile phase and the anatase phase. The mixed-phase titania nanospheres (MTNSs) show superior photocatalytic properties compared with commercial titania powder, which is ascribed to the mixed-phase structure.     

Dispersion of amorphous silica nanoparticles via beads milling process and their particle size analysis,hydrophobicity and anti-bacterial activity

In this present work, amorphous silica is synthesized by simple solution method using sodium silicate (Na₂SiO₃) as raw material. The synthesized silica is dispersed in various dispersing agent obtained from local paint industry and used for painting application. XRD analysis revealed the existence of amorphous silica with a peak at 2θ value of 23° and the SEM analysis exemplified silica nanoparticles demonstrating spherical morphology with agglomeration. Different dispersing agents (as indicated by the codes given by paint industry) were used for the dispersion of SiO₂ by beads milling process and its effects were studied. Among the several dispersing agents used amorphous silica dispersed in SND 504 (Sodium salt of polymeric carboxylic acid with water) dispersing agent exhibit better dispersion compared to the other dispersing agents. Further, 10 wt% of SND 504 dispersing agent was optimized with the particle size to 384 nm and zeta potential value of −24.69 mV. The contact angle measurement of the dispersed silica reveals the superior hydrophobic behaviour of SiO_2, especially with 10 wt% SND 504 dispersing agent. The critical surface tension of SiO₂ with 10 wt% SND 504 dispersing agent reveal low value compared to other concentration of dispersant. Thus, the dispersed silica nanoparticles with enhanced hydrophobicity can be effectively used for painting applications as fillers. Silica dispersed in 10 wt% SND 504 dispersing agent show superior anti-bacterial activity compared to the bare silica which is also reported.     

Effect of processing methods on physicochemical properties of titania nanoparticles produced from natural rutile sand

Titania (TiO₂) nanoparticles were produced from natural rutile sand using different approaches such as sol–gel, sonication and spray pyrolysis. The inexpensive titanium sulphate precursor was extracted from rutile sand by employing simple chemical method and used for the production of TiO₂ nanoparticles. Particle size, crystalline structure, surface area, morphology and band gap of the produced nanoparticles are discussed and compared with the different production methods such as sol–gel, sonication and spray pyrolysis. Mean size distribution (d₅₀) of obtained particles is 76 ± 3, 68 ± 3 and 38 ± 3 nm, respectively, for sol–gel, sonication and spray pyrolysis techniques. The band gap (3.168 < 3.215 < 3.240 eV) and surface area (36 < 60 < 103 m² g^?1) of particles are increased with decreasing particle size (76 > 68 > 38 nm), when the process methodology is changed from sol–gel to sonication and sonication to the spray pyrolysis. Among the three methods, spray pyrolysis yields high-surface particles with active semiconductor bandgap energy. The effects of concentration of the precursor, pressure and working temperature are less significant for large-scale production of TiO₂ nanoparticles from natural minerals.     

Study on crystallinity and morphology controlling of titania using acrylamide gel method and their photocatalytic properties

In this study, polyacrylamide gel method was used for preparation of pure and mixed phase TiO₂ nanoparticles. The influence of synthesis conditions on the physicochemical properties of products was investigated. It was found that the type of acid, which was used for acidifying the precursor solution together with calcination temperature can affect the phase structure, crystalline size, morphology and thereby photocatalytic activity of obtained TiO₂ nanoparticles. Different trends were observed during the phase transformation, particle growth, shift in energy of band gap with the change in tensile strain to compressive strain of the prepared TiO₂ nanomaterial. X-ray diffraction (XRD) showed that prepared nanocrystals, which were calcined at 450 °C have pure anatase and anatase–rutile mixed structures. The prepared samples having crystallite size between 5 nm and 60 nm were observed at different calcination temperatures. In addition, the photocatalytic activities of the prepared samples were evaluated by monitoring the degradation of Cresol Red (CR). The results show that the photocatalyst (TEC_I), exhibits the highest photocatalytic efficiency where 94.7% of CR can be decomposed after UV exposure for 75 min.     

Fabrication and properties of meso-macroporous electrodes screen-printed from mesoporous titania nanoparticles for dye-sensitized solar cells

A meso-macroporous TiO₂ film electrode was fabricated by using mesoporous TiO₂ (m-TiO₂) nanoparticles through a screen-printing technique in order to efficiently control the main fabrication step of dye-sensitized solar cells (DSSCs). The qualities of the screen-printed m-TiO₂ films were characterized by means of spectroscopy, electron microscopy, nitrogen adsorption–desorption and photoelectrochemical measurements. Under the optimal paste composition and printing conditions, the DSSC based on the meso-macroporous m-TiO₂ film electrode exhibits an energy conversion efficiency of 4.14%, which is improved by 1.70% in comparison with DSSC made with commercially available nonporous TiO₂ nanoparticles (P25, Degussa) electrode printed with a similar paste composition. The meso-macroporous structure within the m-TiO₂ film is of great benefit to the dye adsorption, light absorption and the electrolyte transportation, and then to the improvement of the overall energy conversion efficiency of DSSC.     

聚合物包覆纳米铁粒子的结构及其磁性能研究进展

纳米铁粒子具有极大的反应活性而被氧化.本文简要综述了聚合物包覆的纳米铁及其磁性能的研究进展.     

Influence of W5+ ions on the optical properties of doped Bi12TiO20

There have been studied single crystals of undoped and doped Bi₁₂TiO₂₀ with two concentrations of W⁵⁺ (2.62 × 10¹⁷ cm⁻³ and 2.62 × 10¹⁸ cm⁻³). There have been obtained absorption spectra in the energy range of 10,482–15,408 cm⁻¹ by classical measurements. There have been determined the cross-section (σ_a) of the impurity absorption and the oscillator strength of d–d transitions. There have been calculated the refractive index of doped crystals and the concentration of Ti³⁺ ions in an undoped sample through an experiment.     

Aerosol-assisted synthesis of nanoporous silica/titania nanoparticles composites and investigation of their photocatalytic properties

Nanoporous silica/titania nanoparticles composites with relatively large TiO2 content are successfully synthesized by aerosol-assisted co-assembly. By the hybridization of titania with nanoporous silica having high surface area, both the adsorption capability and the reaction rates for the photocatalytic decomposition of methylene blue (MB) are dramatically improved in comparison with unmodified titania nanoparticles without nanoporous silica. Through the quantitative evaluation of the amount of adsorbed and photo-decomposed organic molecule throughout the reaction process, the role of nanoporous silica layers on titania surface is clarified. Rational design of future hybrid photocatalyst with precisely controlled nanostructure will be possible by optimization of our synthetic procedure and careful study of the adsorption and photocatalytic properties.     

Structures and properties of titania thin films annealed under different atmosphere

The effects of crystallinity, phase and oxygen vacancies on optical and photocatalytic properties of titania (TiO₂) thin films were systematically studied. The as-deposited amorphous titania films were prepared by reactive sputtering titanium metal targets in argon–oxygen plasma at 100 °C and subsequently annealed at various temperatures of 400–800 °C in air, vacuum and H₂ atmosphere. The results indicate that in general the crystallinity of the annealed films is enhanced with the increasing annealing temperature. At the same temperature, the H₂ annealed films achieve better crystallinity but containing more oxygen vacancies than the films annealed in air and in vacuum. In H₂ or in vacuum, the concentration of oxygen vacancies in the annealed films increases with increasing temperature, while in air it remains constant. Oxygen vacancies in titania film not only facilitate phase transformation but also lower the band gap of titania, and make the film visible-light responsive. Photocatalytic properties of the TiO₂ films were characterized in UV and visible light irradiation by following the Ag reduction and degradation of methylene blue. The films annealed at 600–700 °C in H₂ possess the best film crystallinity and the proper concentration of oxygen vacancies and exhibit the best photocatalytic performance under both UV and visible light.     

Annealing effect on the structural and optical properties of embedded Au nanoparticles in silicon suboxide films

Au/SiO_x nanocomposite films have been fabricated by co-sputtering Au wires and SiO₂ target using an RF magnetron co-sputtering system before the thermal annealing process at different temperatures. The structural and optical properties of the samples were characterized using X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), optical transmission, and reflection spectroscopy. XPS analysis confirms that the as-prepared SiO_x films are silicon-rich suboxide films. FESEM images reveal that with an increase in annealing temperature, the embedded Au NPs tend to diffuse toward the surface of the SiO_x films. In IR spectra, the intensity of the Si-O-Si absorption band increases with the annealing temperature. Optical spectra reveal that the position and intensity of the surface plasmon resonance (SPR) peak are dominated by the effect of the inter-particle distance and size of the Au NPs embedded in the SiO_x films, respectively. The SPR absorption peak shows the blue-shift from 672 to 600 nm with an increase in annealing temperature. The growth of silica nanowires (SiO_x NWs) is observed in the film prepared on a c-Si substrate instead of a quartz substrate and annealed at temperatures of 1000 °C.     

Effect of Ti defects on electrochemical properties of highly-ordered titania nanotube arrays

In this paper, highly-ordered TiO₂ nanotube (TNT) electrodes fabricated by anodization at 20 V in 0.1 M F⁻-based solution were annealed in O₂, N₂ and CO respectively. The surface properties of the TiO₂ electrodes after annealing treatment by different gases were studied by means of photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of the TNT electrodes were investigated by cyclic voltammetry, steady-state polarization and photocurrent response measurements. The results showed that Tiⁿ⁺ (n = 0-3) cations and oxygen vacancies existed in the TNT electrode after annealing in CO, leading to a very efficient electron transfer rate of 1.34 × 10^− 3 cm/s. Steady-state polarization measurement and photocurrent response demonstrated that the electrode potential of oxygen evolution reaction (OER) reduced by 20% and the photocurrent response increased by 50% for CO-annealed TNT electrode compared with O₂-annealed TNT electrode.     

Media milling process optimization for manufacture of drug nanoparticles using design of experiments (DOE)

Design of experiments (DOE), a component of Quality by Design (QbD), is systematic and simultaneous evaluation of process variables to develop a product with predetermined quality attributes. This article presents a case study to understand the effects of process variables in a bead milling process used for manufacture of drug nanoparticles. Experiments were designed and results were computed according to a 3-factor, 3-level face-centered central composite design (CCD). The factors investigated were motor speed, pump speed and bead volume. Responses analyzed for evaluating these effects and interactions were milling time, particle size and process yield. Process validation batches were executed using the optimum process conditions obtained from software Design-Expert® to evaluate both the repeatability and reproducibility of bead milling technique. Milling time was optimized to <5?h to obtain the desired particle size (d90?相似文献