Preparation and Properties of Polylactide/Poly(ethylene-co-octene)/nano-SiO2 Ternary Composites

Polylactide (PLA)/poly(ethylene-co-octene)(POE) blends with various contents of nano-SiO₂ were prepared via melt mixing. The structure and properties of the PLA/POE/nano-SiO₂ ternary composites were studied by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), rheometry, and tensile testing. The particle size of the dispersed POE phase first decreased with increasing nano-SiO₂ content and then remained constant. Nano-SiO₂ played an important role in the heterogeneous nucleation of PLA, which resulted in an increase of the crystallinity of PLA. The synergistic effect of both POE and nano-SiO₂ can significantly improve the toughness, strength, and modulus of PLA. When the ratio of PLA/POE/nano-SiO₂ was 90/10/0.5, PLA/POE/nano-SiO₂ composite had the best comprehensive properties.     

Mechanochemically conjugated PMHS/nano-SiO2 hybrid and subsequent optimum grafting density study

In this paper, we reported the preparation of poly(methylhydrosiloxane) (PMHS)/SiO₂ hybrid particles by mechanochemical method based on high energy ball milling (HEBM). The obtained hybrid particles were characterized by Fourier transform infrared (FT-IR) spectroscopy, ²⁹Si CP (cross-polarization) MAS NMR, viscosity measurement, particle size distribution, thermal analysis (TGA, DSC and DTG), static contact angle (CA), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). FT-IR and ²⁹Si CP MAS NMR spectra indicate that PMHS is chemically anchored onto the surface of nano-SiO₂. Viscosity measurement, particle size distribution, FE-SEM and TEM demonstrate that an appropriate grafting density optimizes the dispersion of nanoparticles in poly(dimethylsiloxane) (PDMS) matrix, so lower viscosity can be achieved. Too high or too low grafting density may only achieve suboptimal and poor dispersions. The optimum grafting density of PMHS on nano-SiO₂ was determined by thermal analysis, with approximately 0.0531 PMHS/nm². Static contact angle measurement indicates that the water contact angle of hybrid particles is modulated by changing the grafting density of PMHS on nano-SiO₂. The CA value of PMHS/SiO₂ hybrid with optimum grafting density is 139.4°, and the highest CA value of PMHS/SiO₂ hybrid is approximately 158.2°.     

Synthesis and characterization of polyurethane/SiO2 nanocomposites

In order to achieve good dispersion of nano-SiO₂ and increase the interactions between nano-SiO₂ and PU matrix, nano-SiO₂ was firstly modified with poly(propylene glycol) phosphate ester (PPG-P) which was a new polymeric surfactant synthesized through the esterification of poly(propylene glycol) (PPG) and polyphosphoric acid (PPA). Then a series of polyurethane (PU)/SiO₂ nanocomposites were prepared via in situ polymerization. The surface modification of nano-SiO₂, the microstructure and the properties of nanocomposites were investigated by FTIR, SEM, XRD and TGA. It was found that good dispersion of nano-SiO₂ achieved in PU/SiO₂ nanocomposite after the modification with PPG-P. The segmented structures of PU were not interfered by the presence of nano-SiO₂ in these nanocomposites.     

Preparation of Polypropylene/Glycidyl Methacrylate Modified n-TiO2-PMMA Composites via the RAFT Process: Grafting “Through” Surface-Modified Nanoparticles

Glycidyl methacrylate (GMA), a functionalized agent that can chemically link to TiO₂ nanomaterial (n-TiO₂), was used to modify the surface of n-TiO₂ via a Ti-ethereal bond, yielding a GMA-modified n-TiO₂ (mn-TiO₂). Then the GMA bonded to the TiO₂ surface was copolymerized with methyl methacrylate (MMA) via a reversible addition-fragmentation chain transfer (RAFT) polymerization in the presence of the RAFT agent S-1-dodecyl-S′-(α, α′- dimethyl -α″-acetic acid)trithiocarbonate (DDACT) to form mn-TiO₂-PMMA nanoparticles. The resulting mn-TiO₂ nanoparticles and mn-TiO₂-PMMA nanoparticle materials were characterized by using infrared spectroscopy (IR), thermal analysis, and electron microscopy. The mn-TiO₂ nanoparticles demonstrated good dispersive capacity in organic solvents. The results of TGA indicated that the amount of PMMA grafted onto the surface of TiO₂ increased with the polymerization time. Additonally, the effects of mn-TiO₂/PMMA on the thermal and mechanical properties of polypropylene were studied.     

Investigation on corrosion and wear behaviors of nanoparticles reinforced Ni-based composite alloying layer

In order to investigate the role of amorphous SiO₂ particles in corrosion and wear resistance of Ni-based metal matrix composite alloying layer, the amorphous nano-SiO₂ particles reinforced Ni-based composite alloying layer has been prepared by double glow plasma alloying on AISI 316L stainless steel surface, where Ni/amorphous nano-SiO₂ was firstly predeposited by brush plating. The composition and microstructure of the nano-SiO₂ particles reinforced Ni-based composite alloying layer were analyzed by using SEM, TEM and XRD. The results indicated that the composite alloying layer consisted of γ-phase and amorphous nano-SiO₂ particles, and under alloying temperature (1000 °C) condition, the nano-SiO₂ particles were uniformly distributed in the alloying layer and still kept the amorphous structure. The corrosion resistance of composite alloying layer was investigated by an electrochemical method in 3.5%NaCl solution. Compared with single alloying layer, the amorphous nano-SiO₂ particles slightly decreased the corrosion resistance of the Ni-Cr-Mo-Cu alloying layer. X-ray photoelectron spectroscopy (XPS) revealed that the passive films formed on the composite alloying consisted of Cr₂O₃, MoO₃, SiO₂ and metallic Ni and Mo. The dry wear test results showed that the composite alloying layer had excellent friction-reduced property, and the wear weight loss of composite alloying layer was less than 60% of that of Ni-Cr-Mo-Cu alloying layer.     

Silica Nanoparticles Induced Embryonic Dysplasia and Apoptosis Via Endoplasmic Reticulum Stress in Zebrafish(Danio Rerio)

The possible detrimental effects of nanomaterials on organisms have become a public concern because of the wide applications of nanomaterials in modern society. This study investigates the effects of silica nanoparticles (nano-SiO₂) on zebrafish development. Fluorescent nano-SiO₂ (FITC-nano-SiO₂) is synthesized with an emission wavelength of 517 nm. Due to similar hydrodynamic size, FITC-nano-SiO₂ is used to simulate the distribution of nano-SiO₂ in zebrafish. Nano-SiO₂ regulated col2a1a, col9a2, lect1, and her12 to delay liver development and regulated prox, wnt2bb, mypt1, and hhex caused spinal curvature. The hand2, mef2a, nkx2.5, and atp1a2a are significantly down-regulated. The whole embryo in situ hybridization revealed amhc and flk1 are also down-regulated. This suggests that nano-SiO₂ affected heart and blood vessels development of zebrafish. Furthermore, it is found that cell apoptosis occurred in the heart. The proapoptotic genes (bax, bid) are upregulated, and the antiapoptotic genes (bcl-2, mcl-1b) are down-regulated. Nano-SiO₂ increases the endoplasmic reticulum (ER) stress-related genes (chop, bip, perk, elF2α), indicating that the ER stress is involved in cell apoptosis. This study provides a toxicological basis for evaluating the possible hazards of nano-SiO₂ to aquatic organisms.     

Efficient fluorescence of dissolved CaF2:Tb and CaF2:Ce, Tb nanoparticles through surface coating sensitization

Oleic acid (OA)-modified CaF₂:Tb³⁺ nanoparticles with various Tb³⁺ concentrations and CaF₂:Ce³⁺, Tb³⁺ nanoparticles were synthesized. The as-prepared nanoparticles were shown to be well dissolved in some common organic solvents, such as chloroform and toluene. The nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-Ray diffraction (XRD) and transmission electron microscopy (TEM). The investigation of fluorescence properties of CaF₂:Tb³⁺ nanoparticles showed that the Tb³⁺ ions could be sensitized efficiently by the surface coating of OA and CaF₂:Tb³⁺ nanoparticles with 10 mol% Tb³⁺ concentrations possess the highest emission intensity. The comparison of emission for CaF₂:Ce³⁺, Tb³⁺ and CaF₂:Tb³⁺ (10 mol%) nanoparticles revealed that the emission intensity of the former is about 4.5 times as strong as that of the latter.     

Study on the Morphological and Mechanical Properties of Nylon 6/ABS/Nano-SiO2 Composites

The mechanical properties and morphology of the composites of nylon 6, acrylonitrile-butadiene-styrene (ABS) rubber, and nano-SiO₂ particles were examined as a function of the nano-SiO₂ content. A mixture with separation and encapsulation microstructures existed in the nylon 6/ABS/nano-SiO₂ at lower nano-SiO₂ content, and ABS and nano-SiO₂ improved the toughness synergistically, while obvious agglomeration appeared at higher nano-SiO₂ content and the impact strength decreased. Moreover, the addition of nano-SiO₂ particles also affected the dispersion of the rubber phase, resulting in the appearance of smaller rubber particles. The deformation and toughening mechanisms of the composites were also investigated; they resulted from rubber voiding, crack forking, and plastic deformation of the matrix.     

Spectroscopic properties and photophysics of the synthesized compound 5-nitro-benzo[b]thiophene-2-carboxylic acid in non-polar/polar media and in the presence of TiO2 nanoparticles

The present work investigates by electrochemical and steady-state and time-resolved spectroscopic methods a synthesized compound 5-nitro-benzo[b]thiophene-2-carboxylic acid (5NBTC), both in normal solvents and in the presence of TiO₂ nanoparticles to reveal the nature of the photophysical processes involved. From the present experimental observations it is inferred that both in the ground state and the excited electronic state S₁, there exists a strong binding between -COOH functionality of 5NBTC and TiO₂ nanoparticles. However, the rupture of this binding in the presence of excess TiO₂, as apparent from the steady-state and time-resolved spectroscopic measurements, is responsible for the increase in radiative transitions. Formations of aggregations of TiO₂ nanoparticles at higher concentrations appear the cause of such rupturing. The redox potential measurements by cyclic voltammetry and theoretical computations by time-dependent density functional theory (TD-DFT) with B3LYP/6-311 G(d, p) basis function implemented in the Gaussian package confirm the electron accepting nature of 5NBTC and hence no electron transfer is possible between the organic compound and TiO₂ nanoparticles. It is most likely that the interaction model between 5NBTC and TiO₂ nanoparticles should be that the -COOH group of 5NBTC molecule coordinates either directly or through a hydrogen bond to the TiO₂ surface.     

Correlation between interfacial interactions and mechanical properties of PA-6 doped with surface-capped nano-silica

The polyamide-6 pellets were mixed with nano-SiO₂ particles surface-capped by 3-aminopropyltriethoxysilane (APS) via a melt blending route. PA-6 composites doped with surface-capped nano-SiO₂ (designated as PAMNS, where AMNS refers to APS surface-capped nano-SiO₂). AMNS and the silica samples (designated as EAMNS) extracted by acid etching from various PAMNS samples containing different concentration of amino functional groups on surface-capped nano-silica surfaces were characterized by means of Fourier transformation infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). This aims at revealing the interfacial interaction between AMNS and PA-6 matrix and its effect on the mechanical properties of the filled PA-6 composites. The chemical features and microstructures of the PAMNS composites were analyzed by means of FTIR and transmission electron microscopy (TEM), respectively, while their mechanical properties were evaluated using standardized test rigs. Results demonstrate that the surface-modified nano-SiO₂ particles were uniformly dispersed in PA-6 matrix. The residue silica extracted from various PAMNS samples showed characteristic FTIR absorbance peak of PA-6 and had larger weight losses than AMNS, implying that the polymeric matrix was chemically bonded with the nanofiller particles. The interfacial interactions are closely related to the concentration of functional groups in AMNS, and there might exist a critical concentration at which the strongest interfacial interactions could be reached. Beyond the critical concentration of the functional groups in AMNS, the mechanical properties of the filled PA-6 composites tended to decrease to some extent.     

Synthesis of Co-Cu-Zn doped Fe3O4 nanoparticles with tunable morphology and magnetic properties

Co-Cu-Zn doped Fe₃O₄ nanoparticles can be successfully synthesized using a simple method. The particles in the size range 20−400 nm with different regular shapes i.e. sphere-like, regular hexane and tetrahedron are controllably achieved by changing the metal ion concentration. Compared to pure Fe₃O₄ without dopants, Co-Cu-Zn doped Fe₃O₄ nanoparticles exhibit better microwave absorbing properties at 2−18 GHz. Among three Co-Cu-Zn doped Fe₃O₄ nanoparticles with different morphologies, tetrahedral Co-Cu-Zn doped Fe₃O₄ nanoparticles represent a better dielectric loss in high frequency range. This work is believed the first known report of Co-Cu-Zn doped Fe₃O₄ nanoparticles with tunable morphology and magnetic properties through the hydrothermal process without using any organic solvents, organic metal salts or surfactants.     

Preparation and Characterization of Hybrid Nanocomposites Containing Polyethylene Oxide Segments and SiO2 Through a Dual-curing Process

Hybrid organic–inorganic nanocomposites containing SiO₂ and polyethylene oxide (PEO) segments linked to an epoxy acrylate (EA) network were prepared through a dual-cure process involving photopolymerization and subsequent condensation of alkoxysilane groups using 3-isocyanatopropyltriethoxysilane-terminated PEO (PEO-[Si(OC₂H₅)₃]₂) and tetraethoxysilane (TEOS) as precursors, 3-methacryloxypropy ltrimethoxysilane (MEMO) as coupling agent, and EA as prepolymer. The chemical structures of the products were characterized by Fourier transform infrared (FTIR) spectroscopy. Transmission electron microscopy (TEM), atomic force microscopy (AFM), and X-ray diffractometry (XRD) showed that the in situ generated nano-SiO₂ dispersed uniformly in the EA matrix and the organic and inorganic phase interacted strongly. Dynamic mechanical analysis (DMA) and mechanical properties results indicated that the glass transition temperature (Tg) and the impact strength of the hybrid nanocomposites increased simultaneously with increase of the SiO₂ content.     

Effect of the particle size on the electrochemical performance of nano-Li2FeSiO4/C composites

Nano-Li₂FeSiO₄/C composites were prepared from three kinds of nano-SiO₂ (their particle sizes are 15?±?5, 30?±?5, and 50?±?5 nm, respectively) by a traditional solid-state reaction method. The as-prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), elementary analyzer, Brunauer–Emmett–Teller (BET) analysis, galvanostatic charge–discharge test, and electrochemical impedance spectroscopy. XRD results reveal that nano-Li₂FeSiO₄ composites fabricated from nano-SiO₂ (smaller than 30 nm) have less impurity. SEM results indicate that the particle size of nano-Li₂FeSiO₄ composites is nearly accord with the particle size of nano-SiO₂. BET analysis indicates that the specific surface areas of LFS15, LFS30, and LFS50 are 35.10, 35.27, and 26.68 m² g, respectively, and the main pore size distribution of LFS15, LFS30, and LFS50 are 1.5, 5.5, and 10 nm, respectively. Electrochemical measurements indicate that nano-Li₂FeSiO₄ composites prepared from nano-SiO₂ of 30?±?5 nm have the best electrochemical performance among the three samples.     

Friction and wear properties of ZrO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> composite nanoparticles

In this article, the lubrication properties of ZrO₂/SiO₂ composite nanoparticles modified with aluminum zirconium coupling agent as additives in lubricating oil under variable applied load and concentration fraction were reported. It was demonstrated that the modified nanoparticles as additives in lubrication can effectively improve the lubricating properties. Under an optimized concentration of 0.1 wt%, the average friction coefficient was reduced by 16.24%. This was because the nanoparticles go into the friction zone with the flow of lubricant, and then the sliding friction changed to rolling friction with a result of the reduction of the friction coefficient.     

Performance enforcement of gel polymer electrolyte for lithium ion battery with co-doping silicon dioxide and zirconium dioxide nanoparticles

In this work, we report a new method to enforce the comprehensive performances of gel polymer electrolyte (GPE) for lithium ion battery. Poly(methyl methacrylate-acrylonitrile-vinyl acetate) [P(MMA-AN-VAc)] is synthesized as polymer matrix. The physical and electrochemical performances of the matrix and the corresponding GPEs, doped with nano-SiO₂ and nano-ZrO₂ particles individually or simultaneously, are investigated by scanning electron microscopy, thermogravimetry, electrochemical impedance spectroscopy, and charge/discharge test. It is found that the membrane co-doped with 5 wt.% nano-SiO₂?+?5 wt.% nano-ZrO₂ and the corresponding GPE combine the advantages of those doped individually with 10 wt.% nano-SiO₂ or 10 wt.% nano-ZrO₂. Accordingly, the comprehensive performances of the membrane and the corresponding GPE, in terms of thermal stability, ionic conductivity, and electrochemical stability on the anode and cathode of lithium ion battery, is enforced by co-doping 5 wt.% nano-SiO₂ and 5 wt.% nano-ZrO₂.     

Composite electroplating of Cu-SiO2 nano particles on carbon fiber reinforced epoxy composites

The main purpose of this work is to co-deposit nano-SiO₂ particles into the copper coatings on carbon fiber reinforced epoxy (C/EP) composite surface by electrodeposition method in order to improve the micro hardness of coatings. C/EP composites are copper plated with sulfuric acid based solution, and the effects of nano-SiO₂ and C₆H₁₂O₆ in the electrolyte contents on the copper coatings are investigated. It is found that crystalline grains of coatings are markedly refined by nano-SiO₂ in the acidic sulfate copper plating bath and the ceramic particles cause an increase in hardness of coatings though nano-SiO₂ results in a decline of deposition rate and a decrease in electrical conductivity of electroplating layers. Otherwise, C₆H₁₂O₆ in the plating bath is indispensable to the layer formation even though nano-SiO₂ added. These results demonstrate that the hardness of coatings will be increased with appropriate contents of co-deposited SiO₂ and C₆H₁₂O₆ in the plating bath.     

Reduced graphene oxide/strontium titanate heterostructured nanocomposite as sunlight driven photocatalyst for degradation of organic dye pollutants

Reduced graphene oxide/Strontium titanate (RGO/SrTiO₃) heterostructured nanocomposite was synthesized by coupling Hummer's synthesized graphene oxide (GO) with hydrothermally synthesized SrTiO₃ nanoparticles (SrTiO₃) through a facile and unique high energy ultrasonication technique using triple solvents. XRD result confirmed the successful formation of pure, single phase and primitive cubic crystal structure RGO/SrTiO₃ heterostructured nanocomposite. SEM result confirmed the successful intercalation of SrTiO₃ nanoparticles over the two dimensional networks of RGO nanosheets. The synergistic and beneficial interactions between SrTiO₃ and RGO resulted in smaller crystallite size (53 nm), reduced band gap (2.87 eV) and larger specific surface area (31 m²/g) than that of as prepared pure SrTiO₃ nanoparticles. RGO strongly influenced the photocatalytic activity of SrTiO₃ and hence RGO/SrTiO₃ heterostructured nanocomposite exhibited greater efficiency in degrading Rhodamine B (RhB) and Rose Bengal (RB) organic dye pollutants under natural sunlight irradiation than that of pure SrTiO₃ nanoparticles.     

Hybrid magnetic nanoparticles derived from wüstite disproportionation reactions at the nanoscale

We present Mössbauer studies of hybrid iron-oxide nanoparticles obtained by the disproportionation of oleic acid stabilized wüstite (Fe_xO) nanoparticles produced by selective oxidation of iron pentacarbonyl in high boiling temperature organic solvents. The results support X-ray diffraction and Transmission Electron Microscope studies of the presence of mixed Fe_xO and Fe₃O₄ phases within the nanoparticles whose relative content can be altered through heat treatment in nitrogen atmosphere. Furthermore, the Mössbauer study gives evidence of the presence of an amorphous, spin-glass like phase due to spin frustration at the Fe_xO/Fe₃O₄ interface.     

氦等离子体处理对纳米二氧化硅溶胶涂覆T300碳纤维拉伸性能的影响

氦等离子体处理纳米二氧化硅溶胶涂覆T300碳纤维能构造出特定空间结构形态的纳米涂覆层.扫描电子显微镜照片显示,经氦等离子体处理后纳米二氧化硅溶胶涂覆T300碳纤维的纳米涂覆层在纤维表面分布均匀,起到填补纤维表面微观缺陷的功能.X射线光电子能谱及傅里叶变换红外光谱显示,纤维表面被引入了活性官能团,纳米二氧化硅涂覆层与碳纤维间有表面激活反应.形成纳米界面结构的T300碳纤维表面与纳米二氧化硅涂覆层间的相互作用符合艾琳方程,利用热激活体积可以对其相互作用进行定量分析.拉伸试验表明,屈服塑性变形导致纳米界面结构热激活,纳米微粒阻碍碳纤维表面大分子链形貌变化的热激活体积是纳米界面结构性能的重要表征. 关键词： 激活体积 溶胶涂覆 氦等离子体 纳米界面结构     

Facile synthesis and phase control of copper chalcogenides with different morphologies

A series of stoichiometric and nonstoichiometric copper–chalcogenide nanocrystallines with different morphologies, e.g., extremely high aspect ratio nanofibers (Cu₉S₈), tubular structure (Cu _x S (x=∼1.86–1.96), nanorods (CuS, Cu₃₁S₁₆), platelets (β-CuSe, Cu₃Se₂), rope-like Cu₃Se₂, as well as spherical nanoparticles (Cu₇Se₄, Cu_2−x Se), have been successfully synthesized in 20 vol% water and 80 vol% organic solvents mixture under mild conditions. The products were characterized by various techniques, including X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electronic diffraction (ED), and high-resolution transmission electron microscopy (HRTEM). The studies of the optical properties revealed that the copper chalcogenides have a wide absorption in the range of about 400–700 nm, with accessional IR band. Systematic studies showed that the mixture of 20 vol% water and 80 vol% organic solvents played a key role in controlling the copper chalcogenides with different morphologies and phases.