Addition Of SiO2 Particles Research Articles

Structure and Properties of Ti-Si Composite Ceramic Coatings by Laser Cracking with SiO<sub>2</sub> Particles

Ti-Si composite ceramic coating containing SiO2 particles was prepared on 45 steel substrate by in-situ laser pyrolysis with laser power of 600W and laser wavelength of 980nm. The density and wear resistance of the composite ceramic coating were improved. By means of scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), reciprocating friction and wear tester, the element composition, existing forms, surface morphology and friction and wear properties of Ti-Si composite ceramic coatings with different mass fraction of SiO2 particles were analyzed. The results show that the addition of SiO2 particles can improve the surface density and inorganic degree of the composite ceramic coating. When the mass fraction of SiO2 is 1% and the load is 1N, the friction coefficient of the composite ceramic coating is 61% lower than that of 45 steel. When the mass fraction of SiO2 is 5% and the load is 3N, the friction coefficient of the composite ceramic coating is 51% lower than that of 45 steel. The composite ceramic coatings show good antifriction performance and wear resistance.

Preparation of PMMA/SiO2 PCM microcapsules and its thermal regulation performance on denim fabric

PurposeThis study aims to evaluate the thermal performance of phase change materials (PCMs) microcapsules (MCs) attached using SiO2 microspheres and investigate the thermal regulation effect on the coated denim fabric.Design/methodology/approachThe PCM microcapsule was prepared by in situ polymerization using a mixture of solid paraffin and butyl stearate as core material (CM) and methyl methacrylate as a monomer. The SiO2 microparticles were attached to the outer layer of the membrane to enhance the thermal performance of MCs. The morphology, chemical structure, latent heat storage and thermal resistance of MCs were characterized. PCM MCs were coated on the denim fabric and thermo-gravimetric analysis was conducted; thermal insulation and thermal infrared imaging performance of the coated fabrics were also investigated.FindingsThe diameters of SiO2 particles and PCMs MCs were 300-500 nm and 1 μm, respectively. SiO2 was wrapped on single-wall PCMs MCs with the mass ratio of 1:5. With the addition of SiO2, the phase transition temperature range of MCs increased from 34°C to 39°C, and the endothermic and exothermic latent heat decreased by 5.35 J/g and 10.07 J/g, respectively. The degradation rate of MCs was significantly slowed down at high temperature. The denim fabric coated with MCs revealed thermal regulation property. After absorbing heat, the MCs slowed down the rate of heat loss and extended the heat release time.Research limitations/implicationsThe phase transition temperature of the composite CM was wide, and the latent heat storage was reduced. The addition of SiO2 particles can significantly slow down the rate of heat loss, but it further reduces the latent heat storage performance.Practical implicationsThe method developed provided a simple and practical solution to improve the thermal regulation performance of fabrics.Originality/valueThe method of adjusting the phase transition temperature range of the composite CM is novel and many applications could be found in preparation of PCMs and thermal management.

Compressive Behavior of 7075 Al-SiO2 Waste Particle Composite Foams Produced with Recycled Aluminum Cans

7075 Al-SiO2 composite foams were successfully produced by using low-cost materials, including as-received pressed blocks of recycled beverage aluminum cans and silica waste particles as a reinforcement and thickening agent. The composite foams were produced by using direct foaming of melt method. Different percentages of foaming agent and SiO2 particles were used to optimize the properties of the produced foams. The compressive behavior at different strain rates of the composite foams was investigated. At all strain rates studied in the present work, the addition of SiO2 particles into 7075 Al foam considerably enhanced the compressive properties of the composite foams, including the compressive plastic stress, plateau stress, modulus of elasticity, normalized modulus, energy absorption and energy absorbing efficiency without increasing in the relative density of the foams. The compressive properties of the composite foam produced by using low-cost materials, in the present work, are comparable or higher than those of the aluminum alloy foams reported in the literature. The composite foams exhibited higher strain hardening exponents in comparison with those of the 7075 Al foams, indicating that a strong interfacial bond between 7075 Al alloy and SiO2 particles was developed. The compressive plastic stress and plateau stress of the investigated foams exhibited a significant sensitivity to altering the strain rate, even at low and narrow range of strain rate used in the present work.

Structure—Functional property relationship of aliphatic polyurethane-silica hybrid films

The novel aliphatic polyurethane-silica hybrid films were prepared using prepolymerization method in the presence of spherical, submicron amorphous SiO2 Sidistar T120 particles (0, 1, 2, 5 and 10 wt%). The study of the influence of silica distribution on the structure–functional property relationship of polyurethane (PU) composites was performed using FT-IR, SEM, AFM, TGA, DSC, DMTA, tensile testing and immersion test. It was found that the presence of low SiO2 content is acting as dispersing agent between soft- and hard-segments. Achieved uniform distribution of 1 and 2 wt% of silica caused the formation of additional hydrogen bonds between organic matrix and inorganic filler, and remarkably improved thermal stability, thermal and mechanical properties of obtained polyurethane composites. The agglomerates, formed at higher SiO2 loading (5 and 10 wt%), caused the change of thermal degradation mechanism as well as the change of physical crosslinking disruption mechanism. Despite significantly deteriorated mechanical properties of polyurethanes with heterogeneously incorporated silica particles, the onset temperature of elastomers and the starting of melting of hard domains were registered at higher temperature compared to pure PU. Optimal thermal characteristics (onset, decomposition and melting temperatures) and remarkable tensile properties (especially high elongation-at-break and tensile strength, and extraordinary energy-to-break) compared to pure polyurethane have been determined for the polycarbonate-based polyurethanes containing 1 wt% and especially 2 wt% of SiO2. It allows them to be utilized as mechanically strong and durable coatings or films in biomedical applications or as packaging materials. The solvent-resistance data are well described using novel proposed model covering two swelling and dissolution phenomena. The presence of silica decreased the rate and the amount of swelling in water, acetone, toluene and hexane. The rate and mass reduction of swollen sample in acetone, toluene and hexane also decreased by the addition of SiO2 particles.

Effect of Artificial Aging on Fracture Behavior of Al6061-Silica (SiO<sub>2</sub>) Composites

In the present work improvement in mechanical properties due to the presence of silicon oxide (SiO2) reinforced particles with an average size of 50μm and various weight percentage of (3, 6 and 9) on the hardness and fracture behaviour of Al6061-SiO2 composite is investigated. The influence of artificial aging with different aging temperatures on the mechanical properties was also assessed. Macro hardness and mechanism of fracture behaviour during tensile test have been discussed. Failure mode of fracture surface is studied to determine the parameters which influence the crack growth characteristics. Addition of SiO2 particles and artificially aging at 100°C for Al6061-SiO2 composite shows improvement in hardness by 140% and tensile strength by 60% due to the precipitation of finer secondary intermetallic phases of alloying elements. Fracture surface analysis for composite shows particle interface fracture and void nucleation growth failure.

Plasma electrolytic oxidation coatings on Mg alloy with addition of SiO2 particles

The addition of particles into plasma electrolytic oxidation (PEO) electrolyte provides a possibility to produce functionalized coatings with a wider range of compositions and new phases. In this study, nano- and micro-sized SiO2 particles were in-situ incorporated into phosphate-based coatings and the effect of these particles on the microstructure, composition and properties of the coatings was investigated. It was observed that the size and the melting point of the particles have a synergistic effect on the uptake and incorporation mode. The uptake of the nanoparticles occurred mainly via discharge channels and open pores, while micro-sized particles were mainly absorbed via the coating surface. Different particle properties result in reactive and inert incorporation for the nano- and micro-sized SiO2 particles, respectively. The results show that particle additions improve the wear resistance of PEO coating, although corrosion resistance is slightly reduced. Due to superior wear performance and degradability, PEO coatings with reactively incorporated nanoparticles on Mg alloy might be suitable for bio-medical application.

A study on structure and properties of poly(p-phenylene terephthamide) hybrid porous membranes

Poly(p-phenylene terephthamide) (PPTA) hybrid porous membrane has been fabricated via a solution phase inversion method for the first time. The mixtures of PPTA/PEG/PVP/SiO2/H2SO4 were used in this study. Membranes’ corresponding ultrafiltration performances were characterized in terms of pure water flux, porosity, contact angle, mechanical strength, thermogravimetric analysis (TGA), and rejection rate. The morphologies of PPTA hybrid porous membranes were observed by a field emission scanning electron microscope (FESEM). The results showed that the PPTA hybrid porous membrane was a kind of asymmetrical membrane. The dissolved pore-creating agents brought about the fibrillar micro-void structure on the lower surface. The performances of PPTA hybrid porous membrane were obviously affected by the addition of SiO2 particles. It was found that the permeability, hydrophilicity, mechanical strength and rejection substantially increased with the promotion of the appropriate contents of SiO2. The rejection rate of ovalbumin reached more than 90%, while the oil/water emulsion reached more than 80%. What is more, the flux recovery ratio of them could also reach above 90%, which shows excellent anti-fouling property.

Optimization of Test Parameters That Influence Erosive Wear Behaviors of Glass Fiber-Reinforced Epoxy Composites by Using the Taguchi Method

This study describes the development of a multicomponent composite system consisting of thermoplastic epoxy resin reinforced with E-glass fiber and silicon dioxide (SiO2) particles and investigates its erosion behavior under different operating conditions. Due to the increasing importance of composites in engineering applications and the need to tackle solid particle erosion in various industrial sectors, the study aims at finding how these composites behave in such type of wear. The composite specimens used for the tests were classified into three types; pure glass fiber (GF)–epoxy, those with addition of SiO2 particles at an amount of 15% and the last group had SiO2 particles added at 30% of the resin used for the materials. The experiments were carried out by selecting three different impact velocities, three different impingement angles, and angular alumina abrasive particles having approximate sizes of 200 μm. The fiber directions used were 0/90/0 and 45/ − 45/45. SEM views belonging to the specimens were taken before and after the tests in order to investigate the differences and the causes of the surface damages. Moreover, it is found that the Taguchi's robust orthogonal array method provides a simple, systematic, and efficient methodology for the optimization of the erosion wear parameters. At the end of the tests, the most significant factor in affecting the erosion rate is found to be the impingement angle, followed by the impact velocity, fiber direction, and filler material.

Polyethylene and polypropylene hybrid composites based on nano silicon dioxide and different flax structures

Hybrid composites composed of polypropylene (PP) or high-density polyethylene (HDPE), different flax fibers (unidirectional, biaxial, and twill2 × 2), and silicon dioxide (SiO2) were produced by hot-press technique. The ternary polymer composite was effectively fabricated by spraying SiO2 solvents onto the surface of flax fiber. The dispersion of SiO2 particles and flax in the composites was studied by scanning electron microscopy. The related PP- and HDPE-based composites were subjected to instrumented falling weight impact test. The thermal and mechanical properties of the composites were determined by thermogravimetric analysis, dynamic mechanical thermal analysis, creep and stress relaxation tests, respectively. It was found that thermal decomposition temperature of the PP or HDPE/flax composites increased by the addition of SiO2 particles. The impact energy, stiffness, creep resistance, and relaxation modulus value of all flax composites increased markedly compared with the PP and HDPE matrix. Time–temperature superposition was applied to estimate the creep and relaxation modulus of the composites as a function of time in the form of a master curve. The activation energies for all the PP and HDPE composites systems studied were also calculated using the Arrhenius equation. The generalized Maxwell model was fairly applicable to the stress relaxation results.

Novel strategy to prepare polyaniline—Modified SiO2/TiO2 composite particles

The most commonly used method to deposit polyaniline on TiO2 particles begins with the adsorption of surfactants on TiO2 particles followed by deposition of polyaniline. To avoid the use of surfactants, we propose a novel strategy that employs SiO2 nanoparticles during deposition of polyaniline on TiO2 particles. Thus, polyaniline/SiO2/TiO2 composite particles were successfully prepared during chemical oxidative polymerisation of aniline in a weakly acidic aqueous medium. Polymerisation of aniline in the presence of TiO2 and SiO2 was initiated at pH=3.5 by ammonium peroxydisulphate. Prior to polymerisation, dispersed phases exhibited negative electrophoretic mobility after addition of SiO2 particles into the dispersion of TiO2 particles at pH=3.5. pH measurements conducted during preparation implied that polymerisation was not altered by TiO2 and SiO2 particles. The electrophoretic mobility was modified due to deposition of the polyaniline onto TiO2 and SiO2 particles. The electrophoretic mobility of the composite particles was negative when the amount of TiO2 and SiO2 was high. It gradually turned to positive with increasing proportion of polyaniline to TiO2 and SiO2 in the composite. Particle size measurements and scanning electron microscopy studies showed that agglomeration of the particles occurred during polymerisation. Agglomerate size did not depend on the concentrations of TiO2 and SiO2. Infrared spectroscopy studies indicated that emeraldine salt form of polyaniline was obtained during preparation of the composite particles.

Effect of SiO2 and PTFE additives on dry sliding of NiP electroless coating

The aim of the present work is to study the effect of silicon dioxide and polytetrafluoroethylene (PTFE) additives on NiP coating performance under dry (unlubricated) conditions in unidirectional and reciprocating sliding modes in Ball-on-Flat configuration. Yttria-stabilized zirconia and chrome steel balls were used as counterbodies. Microstructural examination of specimens was conducted by a SEM with EDS. It was found that in contact with steel ball both additives were beneficial, while addition of SiO2 particles was detrimental for contact against ceramic ball. The highest improvement of tribological performance was obtained for NiP coated samples having PTFE or mixed additives.

Mechanical and crystalline properties of monomer casting Nylon‐6/Sio2 composites prepared via in situ polymerization

AbstractA series of monomer casting (MC) nylon‐6/SiO2 composites were prepared via in situ polymerization. It was found that the tensile strength, storage modulus, and notched charpy impact strength of the composites were improved and reached maximum at 3–5 wt% loading of SiO2. The α relaxation peak corresponding to the glass transition temperature (Tg) shifted to high temperature with increasing SiO2 content. Addition of SiO2 led to an increase of the melting and crystallization temperatures, and crystallinity. It also reduced the induction time of crystallization, advance the crystallization process of MC nylon‐6, and improve the crystal growth rate. The self‐nucleation crystallization analysis indicated that SiO2 particles played the role of facilitating the crystallization of the matrix mainly via accelerating the generation of crystal nucleus. By addition of SiO2 particles, the fracture surface of MC nylon‐6 changed to distant striations with many yield folds accompanied by a large number of stress whitening, displaying much obvious character of tough fracture. SiO2 particles can be pulled‐out under stress by being covered with MC nylon‐6 resin due to strong interfacial interaction and presented a skin–core structure. © 2012 Society of Plastics Engineers.

Effective method for dispersing SiO2 nanoparticles into polyethylene

AbstractAn effective solution mixing method starting from a synthesis solution of SiO2 nanoparticles was developed for dispersing nanoparticles into high‐density polyethylene (HDPE). Spherical SiO2 nanoparticles with narrow size distribution (50–100 nm) were prepared by Stöber method, and solvents of the synthesis solution (EtOH/NH4OH) were gradually replaced with toluene by evaporation under reduced pressure. The SiO2 nanodispersion, in toluene and residual ethanol, was mixed and refluxed with dissolved maleic anhydride grafted polyethylene (PEgMA) at a relatively high SiO2 content (17.8 wt %). The PEgMA‐SiO2 masterbatch was filtered, dried under vacuum, and mixed with HDPE by melt compounding. SiO2 contents in the final HDPE nanocomposites were 3 and 5 wt %. SEM images of the masterbatch and final composites showed the SiO2 nanoparticles to be well dispersed in HDPE. No agglomerates were observed. FTIR results suggest that the interactions between the maleic anhydride group of PEgMA and hydroxyl groups of SiO2 surface involve ester and/or hydrogen bonding. Addition of SiO2 particles and PEgMA to HDPE slightly increased Young's modulus, tensile strength, breaking strength, and elongation at break, indicating enhanced toughness of the nanocomposites. The measured Young's moduli of HDPE‐PEgMA‐SiO2 composites agreed well with Young's moduli predicted by Mori‐Tanaka composite theory. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010