Papers by Keyword: Nano-SiO₂

Abstract: Using ammonium persulfate as an oxidant and nano-silica as dispersing medium,o-toluidine was oxidized to form a core-shell structure poly (o-toluidine)/nano-SiO₂ particle. Investigation of particle yield by ICP-AES method, the adhesion method was used to study the adhesion between coating and cylinder liner. The cavitation resistance of the coating cylinder was studied by the vibration gas cavitation method. The results showed that poly(o-toluidine) was uniformly coated around the nano-silica particles to which forms stable poly (o-toluidine)/nano-SiO₂ with core-shell structure, when m(SiO₂):m(POT)=1:8，n((NH₄)₂S₂O₃):n(POT)=1:1,and the temperature was controlled from 10 to 15°C, the composite poly(o-toluidine)/nano-SiO₂ particles were prepared and the yield reached 85%. Composite poly(o-toluidine)/nano-SiO₂ particles as a functional component and epoxy resin as a film-forming agent were used to prepare composite poly(o-toluidine)/nano-SiO₂/epoxy resin coated cylinder liner with good cavitation resistance, t₁₀₀=885min.

Abstract: The purpose of this work was to study and further clarify the anti-wear and anti-friction mechanism of ultrafine SiO₂/MoS₂ powders in the complex calcium sulfonate grease. In this paper, 15nm nanoSiO₂, 1μm MoS₂ and commercial NLGI Grade No.2 complex calcium sulfonate grease were used as the research objects, SEM, EDS and XPS were used to study the morphology, composition and film chemical constitution of the long friction wear spots of grease containing single nanoSiO₂ powder, ultrafine MoS₂ powder and the two compound powders, which formed in the process of four ball long friction. The results show that nanoSiO the grease plays a role in filling the undercut, ball bearings and polishing and forming high hardness Ca₃Fe₂(SiO₄)₃ and part of Fe₂O₃ anti-wear films in the process of long friction. The ultrafine MoS₂ powder has a self-repairing effect to fill the grooves,forming the MoS₂, MoO₃ anti-friction films and Fe₂(SO₄)₃ anti-wear film. The two powders in the composite grease have a synergistic effect, acting on the friction pair together, and simultaneously forming self-repairing anti-friction and anti-wear films, thereby further improving the tribological performance of the base grease.

Abstract: For the development of complex calcium sulfonate grease containing ultrafine SiO₂/MoS₂ powders with self-reparing performance. On the basis of the dispersion of the nanoSiO₂ particles, the effects of particle size,addition amount,load and the mass ratio of nanoSiO₂ to ultrafine MoS₂ powders on the tribological properties of commercial No.2 complex calcium sulfonate grease were systematically studied by four ball friction and wear tester. The results show that suitable particle size and addition amount of single SiO₂ and MoS₂ powders can significantly reduce the coefficient of friction (COF) and the wear scar diameter (WSD) of the grease. The composite of nanoSiO₂ and MoS₂ powder can broaden the load range of base grease and further improve the tribological properties of complex calcium sulfonate grease. When the mass ratio of nanoSiO₂ powder to MoS₂ powder is 3:7 and the total addition amount is 0.8wt%, the COF and the WSD of the grease are decreased by 53.64% and 27.08%, respectively, compared with the base grease. The two powders in the composite grease have synergy effect for improving the tribological performance and the friction stability of the grease during the process of long friction.

Abstract: This research was studied the effect of 15 nm SiO₂ on the hydration behavior, hydration process and microstructure of spinel-containing high alumina cement (HAC), which is from high titanium blast furnace slag via smelting reduction method of Ti-Si-Fe making process. The results showed that with the increase of nano-SiO₂, the heat released rate of hydration and the maximum peak were decreased and advanced. Accumulation of hydration heat to release was considerably improved before 16h. Nano-SiO₂ can promote the formation of hydration products or promote the hexagonal phases CaAl₂O₄·10H₂O and Ca₂Al₂O₅·8H₂O change into cubic phase Ca₃Al₂O₆·6H₂O, which has the pozzolanic and filler effects, which The pore size distribution of the hydration products was enhanced by nano-SiO₂. At the same time, the flexural and compressive strength was increased gradually.

Abstract: Nanocomposites of polyamide-6 with nanoSiO₂ surface modified by 3-aminopropyltrimethoxysilane (3-APTMS) were prepared by melt blending in torque rheometer. Chemical modification of nanoparticles surface with 3-APTMS were observed by FTIR. Prior to nanocomposites processing, neat polyamide-6 (PA-6) was processed in a torque rheometer with varying processing parameters: polymer residence time in the chamber, rollers rotational speed, and polymer filling volume in the chamber. Two levels for each parameter were fixed. The influence of these parameters on degradation of PA-6 was determined by dilute solution viscosity and capillary rheometry. Results indicate that the best condition was achieved with the higher polymer residence time in the chamber, the higher rollers rotational speed, and the higher polymer filling volume in the chamber. With this information, PA-6 pellets were mixed with nanosilica particles unmodified and surface-capped by 3-APTMS via melt blending in torque rheometer, obtaining PA-6 composites with 1 wt.% of nanofillers. Mechanical and thermal properties of nanocomposites were evaluated by means of tensile test and differential scanning calorimetry (DSC).

Abstract: Polyvinylidene fluoride (PVDF) membranes were prepared with different compositions of SiO2 nanoparticles. PVDF is one of the most widely used in membrane technology. The molecular structure of PVDF fluoropolymer provides high chemical resistance, good mechanical properties and thermal stability. It also can be used as composites with inorganic nanoparticles such as SiO₂ to improve the performance and properties of the membrane. In this study, Dimethylacetamide (DMAc) was used as solvent. The prepared membranes were characterized using contact angle measurements with water, atomic force microscope (AFM) and scanning electron microscope (SEM) for the structures of the membranes and mechanical strength. The experimental results showed that additional of nanoSiO₂ will exhibit different characteristic on the microstructure and mechanical strength of the membrane.

Abstract: Ultra High Toughness Cementitous Composites (UHTCC) is a unique class of the ultra-ductile fiber reinforced cementitious composites. To meet the increasingly high requirements for materials in the construction, nanoSiO₂, polyvinyl alcohol (PVA) and steel (ST) fibers were added into UHTCC to improve the mechanical property and control the crack width. Multiple effects of nanosilica and hybrid fibers on the flexural properties of UHTCC under three-point bending are evaluated. The results show that nanoSiO₂ can increase flexural strength of UHTCC while equivalent deformability is guaranteed. When the addition of nanoSiO₂ is 5%, the highest flexural strength is 15.77MPa. Moreover, hybrid steel-PVA fibers effectively mitigate negative influence from nanoSiO₂ which induce the wider cracks of UHTCC as the stronger matrix. Comparing with mono fiber composites, hybrid fibers composites exhibit remarkably higher flexural strength and slightly lower deformation. The best performance are 24.85MPa and 2.34% at maximum volume of hybrid fibers.

Abstract: Surface modification of nanoSiO₂ was carried out in ethanol solution with two different silane coupling agents, 3-aminopropyltriethoxysilane (KH-550) and 3-methacryloxypropyltrimethoxysilane (KH-570), respectively. The structure and performance of modified nanoSiO₂ were analyzed by infrared spectroscopy, surface hydroxyl number and conductivity. The influence factors as stirring time, temperature and modifier amount on modified performance have been discussed. The results shown that optimal modification conditions with KH-550 and KH-570 were as follow: temperature 75 ^oC, stirring time 4 h and the modifier 5% (w/w). Surface hydroxyl numbers were 0.7826×10²⁰/g and 0.7525×10²⁰ /g, conductivity were 32μs/cm and 92μs/cm, respectively. The modification effect of nanoSiO₂ with KH-550 was better than KH-570.

Abstract: A nanoSiO2/polyacrylamide (PAM) organic–inorganic nanocomposite system was prepared using acrylamide as the monomer, nanoSiO2 as the modifier, and ammonium persulfate as the initiator. The system was then used to investigate the impact of various factors, including amount of modifier and concentration of monomer, thereby determining the conditions for optimal reaction. Infrared spectroscopy was then used for structural characterization. Measurements using the viscosity method indicated that the viscosity average molecular weight of the product exceeded 1 million. Electron microscopy images showed that a good organic coating layer formed on the surface of the microspheres.

Abstract: With the study of permeability of plain concrete and concrete mixing with fly-ash and concrete mixing with fly-ash and nanoSiO₂ as admixture for resistance to chloride ion, the outcome of the test goes that the permeability of concrete with nanoSiO₂ for resistance to chloride ion will be increased considerably.