Investigation of surface modification of rutile TiO2 nanoparticles with SiO2/Al2O3 on the properties of polyacrylic composite coating

Surface modification and characterization of TiO₂ nanoparticles as an additive in a polyacrylic clear coating were investigated. For the improvement of nanoparticles dispersion and the decreasing of photocatalytic activity, the surface of nanoparticles was modified with binary SiO₂/Al₂O₃. The surface treatment of TiO₂ nanoparticles was characterized with FTIR. Microstructural analysis was done by AFM. The size, particle size distribution and zeta potential of TiO₂ nanoparticles in water dispersion was measured by DLS method. For the evaluation of particle size and the stability of nanoparticles in water dispersions with higher solid content the electroacoustic spectroscopy was made. To determine the applicability and evaluate the transmittance of the nano-TiO₂ composite coatings UV–VIS spectroscopy in the wavelength range of 200–800 nm was employed. The results showed that surface treatment of TiO₂ nanoparticles with SiO₂/Al₂O₃ improves nanoparticles dispersion and UV protection of the clear polyacrylic composite coating.     

Tribological properties of Al2O3 nanoparticles as lubricating oil additives

Nano-scale Al₂O₃ spherical particles, prepared via a hydrothermal method and modified by silane coupling agent, can be well-dispersed in lubricating oil. The tribology properties of Al₂O₃ nanoparticles as lubricating oil additives have been studied by four-ball and thrust-ring friction test, which illustrate that the modified Al₂O₃ nanoparticles can effectively improve the lubricating behaviors compared to the base oil. When the added concentration is 0.1 wt%, the friction coefficient and the wear scar diameter are both smallest. The lubrication mechanism is that a self-laminating protective film is formed on the friction surface and the wear behavior changes from sliding friction to rolling friction.     

Performance of polyester and modified polyester coil coatings exposed in different environments with high UV radiation

Coil coating is a continuous strip coating technology, which enjoyed rapid growth. It provides a cost-effective method of applying a coating to a metal substrate with a low solvent emission, and nowadays paints of different nature are applied this way on a range of metal substrates, for a large variety of products and uses.

Coil coatings can be more or less degraded by high UV radiation. However, differences in distribution of light intensity as a function of wavelength between exposure environments, can lead to significant differences in the degradation results, depending on coating nature. In this work, the behaviour of polyester and silicone polyester coatings exposed in three different high UV environments (natural atmosphere and two accelerated UV tests), was studied. Coatings of two different colours (blue and brown) were considered for each paint system. Colour change, gloss and chalking measurements and, visual inspections of coating defects were carried out. In order to explain their corresponding performance, chemical changes on coil coated exposed surfaces were studied by to Fourier transform infrared spectroscopy equipped with a photoacustic detector (PAS/FTIR).     

纳米粒子改性丙烯酸酯制备复合材料

作为分散相的纳米粒子以独立的相态形式通过改性,分散到作为连续相的丙烯酸酯聚合物基体中形成一种既保留无机材料的热稳定性与硬度,又兼具聚合物韧性与介电性能的复合材料,该过程不是无机相与有机相的简单混合,而是在纳米尺度内两相的有机复合。综述了近年来纳米粒子改性丙烯酸酯复合材料,重点介绍了纳米粒子种类、纳米粒子表面改性、复合材料制备方法及其工业应用等方面的研究成果,并对其发展方向进行了分析和展望。     

Preparation of nanosized anatase TiO2-coated kaolin composites and their pigmentary properties

Nanosized anatase TiO₂-coated kaolin composites were prepared by the chemical deposition method starting from calcined kaolin and TiCl₄. The resultant TiO₂ nanoparticles on the kaolin surfaces existed in anatase phase after calcination at 200, 400, and 900 °C for 1 h, respectively. The surfaces of the kaolin powders were uniformly coated by a monolayer of TiO₂ nanoparticles. The higher calcination temperature was beneficial to formation of well crystallized anatase TiO₂ nanoparticles. The light scattering indexes of the TiO₂-coated calcined kaolin composites were two times higher than that of the kaolin substrate. XPS analysis shows that TiO₂ coating layers anchored at the kaolin surfaces via the Ti-O-Si and Ti-O-Al bonds.     

石墨烯柔性导电改性涤纶织物的制备与性能

采用乙二胺（EDA）和氢氧化钠对涤纶织物进行改性，获得氨基化改性涤纶，再将改性涤纶浸渍氧化石墨烯（GO）溶液，涤纶表面的GO还原成还原氧化石墨烯（RGO）后得到具有导电性能的涤纶织物。采用扫描电镜（SEM）对导电涤纶进行表征，并进行耐洗和耐摩擦性能测试。研究结果表明，涤纶织物经EDA改性后对GO的吸附能力增强，织物导电性增加；改性涤纶的最佳导电整理工艺为GO溶液pH值6，5 g/L保险粉在95℃还原60min可使织物上GO较充分还原，改性涤纶织物的导电性随GO浓度的增大、还原温度的增加和还原时间的延长而增强，当GO为2g/L时，改性涤纶的表面电阻值降低至14.575 KΩ/cm。由SEM结果可知未经改性的涤纶织物表面光滑，经导电整理后织物表面覆盖一层石墨烯薄膜。     

Preparation of surface modified nano-Mg(OH)2 via precipitation method

Nano-magnesium hydroxide was prepared via wet precipitation by using the mixture of sodium dodecyl sulfate (SDS) and monoalcohol ether phosphate (MAP) as surface modifiers. The yield of the surface modified nano-Mg(OH)₂ was about 98%. The usage and dosage of surface modifiers were optimized by means of the measurements of suspension volume of the nano-particles in liquid paraffin. As the mass ratio of SDS to MAP was 2:1 and the total of 0.2 wt.% of Mg(OH)₂ theoretical weight (4.35 g) was used, the nano-Mg(OH)₂ with optimized dispersibility was obtained. The volume percent of the surface modified nano-particles suspension in liquid paraffin could reach 96% after 11 h while that of the nano-Mg(OH)₂ without modification would be 62%. The as-prepared samples were characterized through N₂ adsorption, X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetry-differential scanning calorimetry (TGA-DSC). The results show that hexagonal crystal nano-particles with both SDS and MAP molecules on the surfaces were obtained. The LOI value of PP composites is 35.0 at 150 phr (50% by weight) of surface modified nano-Mg(OH)₂.     

改性高岭土/水性聚氨酯复合材料的制备与表征

采用钛酸酯偶联剂干法改性高岭土,配成母液,用此母液乳化中和后的聚氨酯预聚体,制得改性高岭土/水性聚氨酯复合材料(WPUM)。研究了复合材料的乳液粒径、胶膜力学性能、结晶性和热稳定性等性能。结果表明:复合材料乳液粒径随着改性高岭土质量分数的增加,先增加后减小;改性高岭土的加入可以明显提高水性聚氨酯胶膜的力学性能,当改性高岭土质量分数为1.6%时,复合材料的断裂伸长率与纯聚氨酯胶膜相比提高了13%;X射线衍射法(XRD)分析结果显示,改性高岭土促进了聚氨酯的微相分离;热重分析法(TG)、差示热重法(DTG)分析结果表明,水性聚氨酯复合材料胶膜热分解的起始温度无变化,硬段最高热失重温度略有降低。     

Weathering performance of spruce coated with water based acrylic paint modified with TiO2 and clay nanoparticles

This work examines the effect of wood specimens coated with water based acrylic coatings modified with TiO₂ and clay nanoparticles against weathering strain. The long-term durability of the specimens towards climate strain was studied within a relatively short time frame by accelerated climate ageing. The surface changes that occurred as a result of photodegradation of the specimens subjected to accelerated climate exposures were studied using colour measurements and Fourier transform infrared (FTIR) spectroscopy. The results revealed a significant decrease in the intensity of lignin bands attributed to degradation of the lignin component of the wood. However, the intensity of the lignin photodegradation was lower for coated specimens, with slightly lower degradation for the specimens coated with paints modified with TiO₂ and unmodified montmorillonite clay nanoparticles.     

Effect of the volume ratio of zirconia and alumina on the mechanical properties of fibrous zirconia/alumina bi-phase composites prepared by co-extrusion

Fibrous zirconia/alumina composites with different composition were fabricated by piston co-extrusion. After a 3rd extrusion step and sintering at 1600 °C, crack-free composites with a fibre width of 50 μm were obtained for all compositions. The effect of the volume ratio of secondary phase on the mechanical properties was investigated. The Young's modulus of the composites decreased linearly with increasing the zirconia content. The fracture toughness of the composites was improved by introducing fine second phase filaments into the matrix. The maximum fracture toughness of 6.2 MPa m^1/2 was attained in the 3rd co-extruded 47/53 vol% zirconia/alumina composite. The improvement in toughness was attributed to both “stress-induced” transformation of zirconia and a crack deflection mechanism due to thermal expansion mismatch between the two phases. Bending strength of the composites was almost the same as that of the monolithic alumina regardless of the composition.     

Immobilization of pamidronic acids on the nanotube surface of titanium discs and their interaction with bone cells

Self-assembled layers of vertically aligned titanium nanotubes were fabricated on a Ti disc by anodization. Pamidronic acids (PDAs) were then immobilized on the nanotube surface to improve osseointegration. Wide-angle X-ray diffraction, X-ray photoelectron microscopy, and scanning electron microscopy were employed to characterize the structure and morphology of the PDA-immobilized TiO₂ nanotubes. The in vitro behavior of osteoblast and osteoclast cells cultured on an unmodified and surface-modified Ti disc was examined in terms of cell adhesion, proliferation, and differentiation. Osteoblast adhesion, proliferation, and differentiation were improved substantially by the topography of the TiO₂ nanotubes, producing an interlocked cell structure. PDA immobilized on the TiO₂ nanotube surface suppressed the viability of the osteoclasts and reduced their bone resorption activity.     

Health effects of exposure to nano-TiO2: a meta-analysis of experimental studies

The paper is aimed to investigate the toxicity of nano-TiO₂ and its potential harmful impact on human health using meta-analysis of in vitro and short-time animal studies. Data were retrieved according to included and excluded criteria from 1994 to 2011. The combined toxic effects of nano-TiO₂ were calculated by the different endpoints by cell and animal models. From analysis of the experimental studies, more than 50% showed positive statistical significance except the apoptosis group, and the cytotoxicity was in a dose-dependent but was not clear in size-dependent manner. Nano-TiO₂ was detained in several important organs including the liver, spleen, kidney, and brain after entering the blood through different exposure routes, but the coefficient of the target organs was altered slightly from animal models. It is possible that nano-TiO₂ can induce cell damage related to exposure size and dose. Further studies will be needed to demonstrate that nanoparticles have toxic effects on human body, especially in epidemiological studies.     

Interfacial microstructure and properties of carbon fiber-reinforced unsaturated polyester composites modified with carbon nanotubes

To improve the interfacial properties in carbon fiber (CF)-reinforced unsaturated polyester (UP) composites, we directly introduced functionalized carbon nanotubes dispersed in the fiber sizing onto the fiber surface. For comparing the influence of polymer type on sizing effect, two different polymers (UP MR13006 and water-soluble epoxy (EP)) were used to prepare sizing agent. Morphology and surface energy of CFs were examined by scanning electron microscopy and dynamic contact angle analysis test. Tensile strength was investigated in accordance with ASTM standards. Mechanical properties of the composites were investigated by interlaminar shear strength (ILSS) and impact toughness. Test results indicate that TS, ILSS, and impact toughness were enhanced simultaneously. For UP matrix, the sizing agent containing UP has better reinforcing and toughening effect than the sizing agent containing water-soluble EP.     

Hydrogen peroxide sensor based on modified vitreous carbon with multiwall carbon nanotubes and composites of Pt nanoparticles-dopamine

Sensors using nanostructured materials have been under development in the last decade due to their selectivity for the detection and quantification of different compounds. The physical and chemical characteristics of carbon nanotubes provide significant advantages when used as electrodes for electronic devices, fuel cells and electrochemical sensors. This paper presents preliminary results on the modification of vitreous carbon electrodes with Multiwall Carbon Nanotubes (MWCNTs) and composites of Pt nanoparticles-dopamine (DA) as electro-catalytic materials for the hydrogen peroxide (H₂O₂) reaction. Chemical pre-treatment and consequent functionalization of MWCNTs with carboxylic groups was necessary to increase the distribution of the composites. In addition, the presence of DA was important to protect the active sites and eliminate the pasivation of the surface after the electro-oxidation of H₂O₂ takes place. The proposed H₂O₂ sensor exhibited a linear response in the 0-5 mM range, with detection and quantification limits of 0.3441 mM and 1.1472 mM, respectively.     

Fe effect on the optical properties of TiO2:Fe2O3 nanostructured composites supported on SiO2 microsphere assemblies

The effect of Fe ion concentration on the morphological, structural, and optical properties of TiO₂ films supported on silica (SiO₂) opals has been studied. TiO₂:Fe₂O₃ films were prepared by the sol-gel method in combination with a vertical dip coating procedure; precursor solutions of Ti and Fe were deposited on a monolayer of SiO₂ opals previously deposited on a glass substrate by the same procedure. After the dip coating process has been carried out, the samples were thermally treated to obtain the TiO₂:Fe₂O₃/SiO₂ composites at the Fe ion concentrations of 1, 3, and 5 wt%. Scanning electron microscopy (SEM) micrographs show the formation of colloidal silica microspheres of about 50 nm diameter autoensembled in a hexagonal close-packed fashion. Although the X-ray diffractograms show no significant effect of Fe ion concentration on the crystal structure of TiO₂, the μ-Raman and reflectance spectra do show that the intensity of a phonon vibration mode and the energy bandgap of TiO₂ decrease as the Fe⁺³ ion concentration increases.     

Dielectric,magnetoelectric and magnetodielectric properties in CMFO-SBN composites

The paper reports synthesis of Sr_0.5Ba_0.5Nb₂O₆ (SBN) and Co_1.2−xMn_xFe_1.8O₄ (CMFO) via ceramic and hydroxide co-precipitation routes respectively. The nanopowders of SBN-CMFO0.1 (MSBN0.1) and SBN-CMFO0.3 (MSBN0.3) are compacted to form the desired magnetoelectric (ME)/magnetodielectric (MD) composites. The Bi₂O₃ is used as a sintering aid. The Bi₂O₃ at three weight percent is observed to cause agglomeration of SBN and CMFO particles and improve the magneto-mechanical coupling. The composites are investigated for their ferroelectric, ferromagnetic, dielectric, magnetoelectric (ME) and magnetodielectric (MD) properties. The results on the magnetocapacitance (M_c) are observed interesting and could be correctly understood in terms of the stress induced variation in the dielectric constant. The MC is observed to remain fairly constant between 10 to 500 kHz and possess a useful magnitude of M_c nearly 4%.     

Study on cerium-doped nano-TiO2 coatings for corrosion protection of 316?L stainless steel

Many methods have been reported on improving the photogenerated cathodic protection of nano-TiO₂ coatings for metals. In this work, nano-TiO₂ coatings doped with cerium nitrate have been developed by sol–gel method for corrosion protection of 316 L stainless steel. Surface morphology, structure, and properties of the prepared coatings were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The corrosion protection performance of the prepared coatings was evaluated in 3 wt% NaCl solution by using electrochemical techniques in the presence and absence of simulated sunlight illumination. The results indicated that the 1.2% Ce-TiO₂ coating with three layers exhibited an excellent photogenerated cathodic protection under illumination attributed to the higher separation efficiency of electron–hole pairs and higher photoelectric conversion efficiency. The results also showed that after doping with an appropriate concentration of cerium nitrate, the anti-corrosion performance of the TiO₂ coating was improved even without irradiation due to the self-healing property of cerium ions.     

Surface modification of TiO2 nano-particles with silane coupling agent and investigation of its effect on the properties of polyurethane composite coating

Surface modification and characterization of TiO₂ nano-particles as an additive in a polyurethane clear coat were investigated. For the improvement of nano-particles dispersion and increasing possible interactions between nano-particles and polymeric matrix, the surface of the nano-particles was modified with amino propyl trimethoxy silane (APS). Equivalent amount of APS for monolayer formation on the nano-particles surface was determined by means of elemental analysis (CHN). The grafting of APS on the TiO₂ nano-particles surface was characterized with TGA and FTIR techniques. Mechanical properties of coatings containing various amount of TiO₂ nano-particles were evaluated with DMA technique and tensile strength measurement. UV–vis spectroscopy was employed to evaluate the absorbance and transmittance of the nano-TiO₂ composite coatings in the wavelength range of 230–700 nm.     

Application of EIS and salt spray tests for investigation of the anticorrosion properties of polyurethane-based nanocomposites containing Cr2O3 nanoparticles modified with 3-amino propyl trimethoxy silane

The Cr₂O₃ nanoparticles were modified with 3-amino propyl trimethoxy silane in order to obtain proper dispersion and increment compatibility with the polyurethane coating matrix. The nanocomposites prepared were applied on the St-37 steel substrates. The existence of 3-amino propyl trimethoxy silane on the surface of the nanoparticles was investigated by Fourier transform infrared (FTIR) spectroscopy and thermal gravimetric analysis (TGA). Dispersion of the surface modified particles in the polyurethane coating matrix was studied by a field emission-scanning electron microscope (FE-SEM). The electrochemical impedance spectroscopy (EIS) and salt spray tests were employed in order to evaluate the corrosion resistance of the polyurethane coatings. Polarization test was done in order to investigate the corrosion inhibition properties of the Cr₂O₃ nanoparticle on the steel surface in 3.5 wt.% NaCl solution. The adhesion strengths of the coatings were evaluated by pull-off adhesion tester before and after 120 days immersion in 3.5 wt.% NaCl solution. FT-IR and TGA analyses revealed that surface modification of the nanoparticles with 0.43 silane/5 g pigment resulted in the greatest amount of silane grafting on the surface of particles. Results obtained from FE-SEM analysis showed that the surface modified nanoparticles dispersed in the coating matrix properly. Results obtained from EIS and salt spray analyses revealed that the surface modified particles enhanced the corrosion protection performance of the polyurethane coating considerably. The improvement was more pronounced for the coating reinforced with 0.43 g silane/5 g pigment. Moreover, the adhesion loss decreased in the presence of surface modified nanoparticles with 0.43 silane/5 g pigment.     

Processing and physical properties of Al2O3/aluminum alloy composites

Porous aluminum oxide (Al₂O₃) preforms were formed by sintering in air at 1200 °C for 2 h. A356, 6061, and 1050 aluminum alloys were infiltrated into the preforms by squeeze casting in order to fabricate Al₂O₃/A356, Al₂O₃/6061, and Al₂O₃/1050 composites, respectively, with different volumes of aluminum alloy content. The content of aluminum alloy in the composites was 10–40% by volume. The resistivity of Al₂O₃/A356, Al₂O₃/6061, and Al₂O₃/1050 composites decreased dramatically from 6.41 × 10¹² to 9.77 × 10⁻⁴, 7.28 × 10⁻⁴, and 6.24 × 10⁻⁴ Ω m, respectively, the four-points bending strength increased from 397 to 443, 435.1, 407.2 MPa, respectively, and the deviations were smaller than 2%. From SEM microstructural analysis and TEM bright field images, the pore volume fraction and the relative density of the composites were the most important factors that affected the physical and mechanical properties. The ceramic phase and alloy phase in Al₂O₃/aluminum alloy composites were found to be homogenized and uniformly distributed using electrical and mechanical properties analysis, microstructure analysis, and image analysis.