Addition Of SiO2 Nanoparticles Research Articles

Tribological behaviors of epoxy composites under water lubrication conditions

The aim of this work is to investigate the tribological behaviors of epoxy (EP)composites under water lubrication conditions at both varying and constant sliding speeds. In particular, the roles of reinforcing fillers, i.e. carbon and glass fibers, solid lubricants and SiO2 nanoparticles, on the friction and wear properties of EP were investigated. It is demonstrated that both the reinforcing fibers significantly enhance the wear resistance of EP. Under mixed and boundary lubrication conditions, the addition of SiO2 nanoparticles into EP conventional composite filled with carbon fibers and graphite reduces the friction and wear. It is revealed that the tribological performance of the fiber-reinforced EP composites is mainly attributed to the high abrasion resistance of the fibers and the tribofilm formation.

Novel uses of SiO2 nanolubrication in end milling of medium carbon steel for higher compressive residual stress measured by high-energy X-ray diffraction data

Milling is a machining process that removes any desired material from the surface by using relative motion between a work piece and a rotating cutter where the cutting tool intermittently enters and leaves the work piece. The milling process operates in two modes, namely, conventional (up) mode and climb (down) mode. Both modes are known for their significant effects on surface integrity due to the entering movement of the cutting tool and the formation of the chips during cutting process. Use of flood lubrication can improve the residual stress and surface quality of the component. It controls the temperature in cutting zone, reduces the power required, washes away chips, and reduces friction between chips, tools, and workpieces. Moreover, it has a great effect on the environment too. Minimum quantity lubrication can be used as an alternative of lubrication for clean machining. With an addition of nanoparticles into the minimum quantity lubrication, it is expected to enhance the machining performance that meets the environmental friendly purposes. Residual stresses remain in a solid material in the absence of external loading or thermal gradients, which is sometimes undesirable. The presence of compressive residual stresses is beneficial, while the presence of tensile stresses is detrimental. In order to study the residual stress and its relation with the surface quality (after milling process), the effects of reduced oil consumption in minimum quantity lubrication and the addition of SiO2 nanoparticles in minimum quantity lubrication for clean machining are presented in this research. Results indicate that there is an improvement in residual stresses and surface quality especially during conventional (up) milling under minimum quantity lubrication and minimum quantity lubrication–SiO2 nanolubrication condition.

Preparation and characterization of PES/SiO2 composite ultrafiltration membrane for advanced water treatment

Polyethersulfone (PES) is a commonly used polymeric material for the fabrication of ultrafiltration (UF) membranes. However, the hydrophobic nature of PES leads to poor membrane performance with low anti-fouling properties during filtration process. Hence, for this study, the PES-based hollow fiber membrane was modified with inorganic silicon dioxide (SiO2) nanoparticles of various loading (from zero to 4 wt%), aiming to improve the membrane properties for advanced water treatment process. The characterization of the surface morphology, physical and chemical properties of novel PES/SiO2 composite membranes was performed by SEM, FTIR-ATR, TGA and contact angle analyzer. The SEM images show the changes in membrane structure as well as skin layer thickness upon addition of SiO2 nanoparticles. The FTIR-ATR analysis shows the functional group of SiO2 in the polymer matrices. Results further show that the presence of 2 wt% SiO2 in the membrane matrix is the best loading to improve the water flux and bovine serum albumin (BSA) rejection, achieving 87.2 L/m2·h and 94%, respectively. As a comparison, the control PES membrane only exhibits water flux of 44.2 L/m2·h and rejection of 81%. Results also show that the flux recovery percentage of the membrane was improved from 82% in the control membrane to 93% in the membrane incorporated with 2 wt% SiO2, indicating improved membrane anti-fouling property. Furthermore, the PES/SiO2 membrane shows huge potential for advanced water treatment, as the qualities of the permeate samples treated by this membrane could meet the limit set by a local water company.

Influence of SiO2 nanoparticles on morphological, thermal, and dielectric properties of PVDF

The morphology, crystalline structure, and thermal stability in a system of SiO2 nanoparticles dispersed in PVDF matrix are investigated. SEM/TEM indicated that SiO2 nanoparticles present in PVDF matrix have been homogeneously dispersed. The spherulite texture of PVDF was significantly disrupted by the presence of SiO2 nanoparticles as observed by optical micrographs. The XRD pattern shows that the intensity decreases, while full width at half maximum increases with the increasing nanoparticles content, which is ascribed to the significant decline in crystallinity. DSC also shows that the crystallinity is influenced by the SiO2 nanoparticles in the PVDF matrix. The thermal properties of nanocomposites directly reflect the morphological and structural changes induced by SiO2 nanoparticles. TG shows that the nanocomposites have higher decomposition temperatures in comparison with the PVDF. The increase in thermal stability with the addition of SiO2 nanoparticles is mainly attributed to interfacial interactions between the organic polymer and inorganic nanoparticles. The investigation of the dielectric properties at different frequencies and temperature revealed that the relaxation mechanism, which controls the movement of the charge carriers in the nanocomposites, is strongly related to the morphology of the system.

Effects of nano-SiO2 particles addition on the microstructure, wettability, joint shear force and the interfacial IMC growth of Sn3.0Ag0.5Cu solder

In the present study, the nano-composite solder with SiO2 nanoparticles into eutectic Sn3.0Ag0.5Cu solder were prepared. The addition concentration of SiO2 nanoparticles ranges from 0 to 1 wt%. The effects of SiO2 on the microstructure, the wettability, joint shear force of the composite solder under different working temperature and the growth of interfacial intermetallics compounds (IMCs) at solder/Cu substrate during thermal cycling were investigated respectively. The results show that appropriate addition of nano-SiO2 particles can refine the β-Sn matrixes and enhance the wettability of nano-SiO2 composite solder. Additionally, slight addition of nano-SiO2 particles can inhibit the formation and the growth of the interfacial IMCs layer between the solder and Cu substrate during reflow and thermal cycling. Moreover, nano-SiO2 can also increase the shear force of composite solder joint. However, excessive addition of SiO2 nanoparticles in the Sn3.0Ag0.5Cu solders degrade the wettability, joint shear force and the inhibition effect on the interfacial IMCs. There is an optimum addition concentration of SiO2 nanoparticles in Sn3.0Ag0.5Cu solder alloys, which is 0.05 wt%, and Sn3.0Ag0.5Cu–0.05 wt% SiO2 solders possess the biggest wetting force, highest shear force and the best inhibition effect on the interfacial IMCs formation and growth.

Microstructural and mechanical properties of Al–SiO2 nanocomposite foams produced by an ultrasonic technique

In this study, nanocomposite foams reinforced with different weight percentages of silicon dioxide nanoparticles (0.25, 0.5, 0.75 and 1.0wt%) were fabricated using the ultrasonic and stir casting techniques. For this purpose heat treated TiH2 was used as foaming agent. Microstructural studies were done by optical microscope and scanning electron microscope. Hardness evaluation of precursor nanocomposites showed that the hardness was significantly increased by the addition of SiO2 nanoparticles and Al–0.75wt% SiO2 nanocomposite makes the highest hardness. Evaluation of compressive behavior of Al–SiO2 nanocomposite foams showed that the plateau stress increases more than 3 times as the foam relative density increases from 0.09 to 0.16. Energy absorption of Al–SiO2 nanocomposite foams has been found to be dependent on both relative density and structural properties.

Effects of TiO<sub>2</sub>/SiO<sub>2</sub> Reinforced Nanoparticles on the Mechanical Properties of Green Hybrid Coating

Titanium and silica oxides nanoparticles were introduced into hybrid silica sol–gel/epoxy coating to enhance the mechanical properties of coatings. Titanium dioxide (TiO2) and silica oxide (SiO2) were chemically synthesised before adding to the prepared silica sol gel coating. X-ray diffraction (XRD), Energy-dispersive x-ray analysis (EDX) and Transmission Electron microscope (TEM) were used to characterize the prepared nanoparticles. The coating was then applied to 3003 aluminium alloy (AA3003) surface. The adhesion performance of different sol gel coating compositions was investigated using shear test to define the influence of nanoparticles on adhesive strength of the coating. The Rockwell C hardness test was used to study the micro-hardness of different compositions of sol gel coating. Also, contact angel was used to investigate the hydrophobicity of the coatings. The results showed that there was a significant improvement of the adhesion performance of hybrid silica sol gel coating due to addition of TiO2 and the hydrophobicity of sol gel coating was increased due to addition of SiO2 nanoparticles.

Effects of TiO<sub>2</sub>/SiO<sub>2</sub> Reinforced Nanoparticles on the Mechanical Properties of Green Hybrid Coating

Titanium and silica oxides nanoparticles were introduced into hybrid silica sol–gel/epoxy coating to enhance the mechanical properties of coatings. Titanium dioxide (TiO2) and silica oxide (SiO2) were chemically synthesised before adding to the prepared silica sol gel coating. X-ray diffraction (XRD), Energy-dispersive x-ray analysis (EDX) and Transmission Electron microscope (TEM) were used to characterize the prepared nanoparticles. The coating was then applied to 3003 aluminium alloy (AA3003) surface. The adhesion performance of different sol gel coating compositions was investigated using shear test to define the influence of nanoparticles on adhesive strength of the coating. The Rockwell C hardness test was used to study the micro-hardness of different compositions of sol gel coating. Also, contact angel was used to investigate the hydrophobicity of the coatings. The results showed that there was a significant improvement of the adhesion performance of hybrid silica sol gel coating due to addition of TiO2 and the hydrophobicity of sol gel coating was increased due to addition of SiO2 nanoparticles.

Nano-scale modification of polysulfone membrane matrix and the surface for the separation of chromium ions from water

In this study, aiming at hexavalent chromium removal from aqueous solutions, different strategies were proposed for developing hydrophilic and surface functional polysulfone (PSf) membrane. In addition to PSf membrane, three different types of membranes were prepared by addition of SiO2 nano-particles to the dope solution and/or by deposition of polydopamine (PDA) layer on the surface of the membranes. The membranes (i.e. PSf, PSf/PDA, PSf/SiO2 and PSf/SiO2/PDA) were characterized by different techniques. The membranes’ transport properties and the separation performance were studied using a filtration unit operated at a continuous dead-end flow mode. The kinetics and the separation mechanism of Cr(VI) were investigated by tracing the effect of pH, initial chromium concentration and operation time. It was found that the surface and adsorption property of PDA layer is dependent on the substrate (PSf or PSf/SiO2) on which it is grown. Reusability of the membranes was studied by repeating consecutive adsorption/desorption cycles. NaOH (0.05M) showed the highest stripping capability. Among the membranes, PSf/SiO2/PDA membrane with relatively smooth surface and robust structure over the operation time exhibited quite stable water flux (at 13Lm−2h−1) and superior separation performance (94% at pH=3), which is quite encouraging from practical and industrial points of view.

Influence of SiO2 nanoparticles on hardness and corrosion resistance of electroless Ni–P coatings

Nickel–phosphorus (Ni–P) coatings with controllable P content and desirable characteristics can be produced by tuning bath chemistry and processing conditions during the electroless process. Although pure medium- and high-P coatings offer a good combination of mechanical and corrosion properties, their performance attributes can be further enhanced through incorporation of silica (SiO2) nanoparticles. Using 15 and 30g/L of sodium hypophosphite as reducing agent in the plating bath, Ni–P coatings with respective P content of 10.8 and 14.3wt.% were produced. While the surface roughness and grain size increased with an increase in the P content, the average hardness value and corrosion resistance of medium-P coatings were superior to their high-P counterparts. The average hardness of the Ni–P– SiO2 coatings based on medium-P Ni–P matrix was determined to be ~11.0GPa. Electrochemical impedance spectroscopy (EIS) studies of these coatings indicated area-impedance values on the order of 108Ω·cm2, whereas the double-layer capacitance per unit area (Cdl) and charge transfer area-resistance (Rct) values, computed from theoretical fit of the EIS data, were in the range of 1.18×10−10F·cm−2 and 3.14×108Ω·cm2, respectively. The findings confirmed that addition of SiO2 nanoparticles modifies deposit morphology through grain refinement, reduction in the surface roughness and minimization of surface porosity in the nanocomposite coatings.

The Effects of Nano-SiO<sub>2</sub> on the Chemical Composition of Layers on Aluminum Alloy by Micro-Arc Oxidation

In this article, a nano-SiO2/micro-arc oxide composite coating layer was prepared on the surface of 7A52 Aluminum alloy by addition of SiO2 nanoparticles into the micro-arc oxidation electrolyte to enhance the performance of the formed oxidative layer. Then, the composite oxidative layer was characterized by X-ray Photoelectron Spectroscopy (XPS) to investigate its elemental and chemical compositions, as well as their respective distributions. The results revealed that at elevated temperatures resulted from micro-arc discharge, the SiO2 in the composite reacted with Al2O3 (the major content of the micro-arc oxidative layer) to form a new compound known as mullite. In addition, the contents of SiO2 and γ-Al2O3 in the inner layer of the oxidative layer were lower than those in the surface layer. This can be explained by the higher temperature in the inner layer which motivated the formation of mullite and α-Al2O3 from SiO2 and γ-Al2O3 respectively during the micro-arc oxidation process.

Corrosion Resistance Enhancement of AZ91D Magnesium Alloy by Electroless Ni-Co-P Coating and Ni-Co-P-SiO2 Nanocomposite

Electroless Ni-Co-P coating and Ni-Co-P-SiO2 nanocomposites were successfully applied on AZ91D magnesium alloy via environmentally friendly cerium-lanthanum-permanganate treatment and their properties were compared with traditionally binary Ni-P coating. The prepared coatings were analyzed using scanning electron microscopy, x-ray diffraction, and energy dispersive x-ray spectroscopy. Moreover, the corrosion behavior of the coatings in 3.5 wt.% NaCl was evaluated by two electrochemical methods. It is found that the Ni-Co-P coating possesses more uniform and compact structure and better corrosion protection characteristics in comparison with the Ni-P coating. The plating rate of Ni-Co-P bath is relatively lower than the Ni-P bath, but it significantly increases after addition of SiO2 nanoparticles more probably due to adsorption of silica nanoparticles on alloy surface. The corrosion resistance of Ni-Co-P-SiO2 composite coatings was superior with respect to Ni-P and Ni-Co-P coatings due to formation of thick and compact coating with tortuous grain boundaries.

Role of nanoparticles in controlling arsenic mobilization from sediments near a realgar tailing.

Microcosm experiments were conducted to investigate the mechanism of microbial-mediated As mobilization from high arsenic tailing sediments amended with nanoparticles (NPs). The addition of SiO2 NPs could substantially stimulate arsenic mobilization in the sodium acetate amendment sediments. However, the addition of Fe2O3 and Fe3O4 NPs restrained arsenic release because these NPs resulted in Fe-As coprecipiate. Moreover, NP additions in sediments amended with sodium acetate as the electron donor clearly promoted microbial dissimilatory iron reduction. Nearly 4 times the Fe(II) (11.67-12.87 mg·L(-1)) from sediments amended with NPs and sodium acetate was released compared to sediments amended with only sodium acetate (3.49 mg·L(-1)). Based on molecular fingerprinting and sequencing analyses, the NP additions could potentially change the sediment bacterial community composition and increase the abundance of Fe(III) and As(V) reduction bacteria. Several potential NP-stimulated bacteria were related to Geobacter, Anaeromyxobacter, Clostridium, and Alicyclobacillus. The findings offer a relatively comprehensive assessment of NP (e.g., Fe2O3, Fe3O4, and SiO2) effects on sediment bacterial communities and As mobilization.

Photoluminescence optimization of BCNO phosphors synthesized using citric acid as a carbon source

Citric acid was used as carbon source for the optimization of the photoluminescence (PL) performance of boron carbon oxynitride (BCNO) phosphor. Citric acid was chosen as an alternative carbon source because of its simple molecular structure, low decomposition temperature, relative inexpensiveness, and environmental friendliness. The prepared sample exhibited a single, homogeneous, and broad photoluminescence emission band whose peak varied from near-UV (400nm) to yellow-visible (500nm) upon excitation at 365nm. The effects of varying the synthesis temperature, molar ratio of the carbon/boron and nitrogen/boron sources, and addition of SiO2 nanoparticles on the PL properties were also studied. The optimized BCNO phosphors may find potential use in white LED applications.

The study on SiO2 nanoparticles and nanowires added YBCuO: Microstructure and normal state electrical properties

The effects of nanosized silicon oxide nanoparticles and nanowires additions on the microstructure and the normal state transport properties of polycrystalline YBa2Cu3Oy (YBCO, or Y-123) were systematically studied. Samples were synthesized in air using a standard solid state reaction technique by adding nanosized entities up to 3wt.%. Phases, microstructure, superconductivity, have been systematically investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrical measurements. When nanosized SiO2 entities are added to the YBCO the orthorhombic structure is maintained. SEM results reveal that the grain size is reduced with increasing the content of SiO2. TEM investigation shows the presence of inhomogeneities embedded in the superconducting matrix along with the presence of columnar defects in the case of SiO2 nanoparticles added samples. Nanowires tend to agglomerate by entangling with each other in the intergrain regions. To analyze the normal state properties of the samples, the percolation theory based on localized states is applied. A change from Coulomb gap to variable-range hopping mechanisms is observed as a result of increasing the nano-entities concentration. The SiO2 nanowires addition modifies the electrical behavior of samples from metallic to insulating with a much lower concentration comparatively to SiO2 nanoparticles addition. The localization length d and the range hopping R of samples are estimated.

Combination of silica nanoparticles with hydroxyapatite reinforces poly (l-lactide acid) scaffolds without loss of bioactivity

Composite scaffolds of poly(l-lactide acid) and hydroxyapatite are of great interest in bone tissue engineering, but their mechanical properties are typically inferior to scaffolds of pure poly(l-lactide acid) due to agglomeration of the particles and weak interfacial component interaction. Fabrication strategies like double sonication of hydroxyapatite or increasing the amount of this inorganic filler do not effectively enhance the mechanical performance. In this study, poly(l-lactide acid) composites combining two types of fillers, mesoporous silica (SiO2) nanoparticles and hydroxyapatite, were developed to reinforce the poly(l-lactide acid) scaffold without any loss of bioactivity. A 5% addition of SiO2 nanoparticles to hydroxyapatite nanopowder and subjecting the scaffold formulation to double sonication increased the Young’s modulus from 5 MPa (pure poly(l-lactide acid) scaffold) to almost 7 MPa (poly(l-lactide acid)/hydroxyapatite/SiO2 scaffold). In addition, the composite was able to deposit a layer of biomimetic hydroxyapatite both on the surface and interior of the scaffold after 21 days of immersion in a simulated body fluid. The manufacturing method was straightforward and economically viable and does not require any chemical modification of the particles’ surfaces.

SiO2 nanoparticles addition effect on microstructure and pinning properties in YBa2Cu3Oy

A series of YBa2Cu3Oy (YBCO, Y-123) samples with small amounts (0–1wt%) of nanosized SiO2 particles (30nm) are synthesized in air using a solid-state reaction route. The microstructure has been characterized by transmission and scanning electron microscopy (TEM and SEM) techniques and the magnetic field and temperature dependences of the critical current density (Jc) was calculated from the magnetization measurements and by the standard four-probe method at various temperatures. Flux pinning force density (Fp) is calculated and possibility of the pinning mechanisms prevalent in type II superconductors are investigated. X-ray diffraction analysis shows that the orthorhombic structure of YBCO is maintained. Morphology examination by SEM revealed decreases of grain size with SiO2 addition. High zero resistance temperature Tco value of about 90K was maintained in YBCO with SiO2 concentration ≤0.2wt%. Compared to free added-sample, higher critical current densities were obtained for the YBCO sintered with low concentration SiO2 (≤0.1wt%) in applied magnetic field. TEM observations show the presence of columnar defects (2–3nm in diameter) along the c-axis of YBCO and Si-rich nanophase embedded in the superconducting matrix. These defects are responsible for critical current densities improvement in the magnetic field of YBCO.

Fabrication and characterization of SiO2/PVDF composite nanofiber‐coated PP nonwoven separators for lithium‐ion batteries

ABSTRACTSiO2/polyvinylidene fluoride (PVDF) composite nanofiber‐coated polypropylene (PP) nonwoven membranes were prepared by electrospinning of SiO2/PVDF dispersions onto both sides of PP nonwovens. The goal of this study was to combine the good mechanical strength of PP nonwoven with the excellent electrochemical properties of SiO2/PVDF composite nanofibers to obtain a new high‐performance separator. It was found that the addition of SiO2 nanoparticles played an important role in improving the overall performance of these nanofiber‐coated nonwoven membranes. Among the membranes with various SiO2 contents, 15% SiO2/PVDF composite nanofiber‐coated PP nonwoven membranes provided the highest ionic conductivity of 2.6 × 10−3 S cm−1 after being immersed in a liquid electrolyte, 1 mol L−1 lithium hexafluorophosphate in ethylene carbonate, dimethyl carbonate and diethyl carbonate. Compared with pure PVDF nanofiber‐coated PP nonwoven membranes, SiO2/PVDF composite fiber‐coated PP nonwoven membranes had greater liquid electrolyte uptake, higher electrochemical oxidation limit, and lower interfacial resistance with lithium. SiO2/PVDF composite fiber‐coated PP nonwoven membrane separators were assembled into lithium/lithium iron phosphate cells and demonstrated high cell capacities and good cycling performance at room temperature. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1719–1726

Preparation and Corrosion Resistance Property of Molybdate Conversion Coatings Containing SiO2 Nanoparticles

In this paper, molybdate conversion coatings containing SiO2 nanoparticles were successfully prepared on AZ31 magnesium alloy. The effect of SiO2 nanoparticles on the weight of molybdate conversion coatings was investigated. The surface morphology of molybdate conversion coatings containing SiO2 nanoparticles was examined by scanning electron microscopy (SEM). The polarization curves, electrochemical impedance spectroscopy (EIS) and weight loss measurements were employed to evaluate the corrosion resistance of molybdate conversion coatings containing SiO2 nanoparticles in 3.5 wt% NaCl solution. The results demonstrate that the weight of molybdate conversion coatings reaches a maximum value when the concentration of SiO2 nanoparticles is 4 g L−1. The SiO2 nanoparticles are uniformly distributed in the molybdate conversion coatings. The results of weight loss measurements and electrochemical methods show that the addition of SiO2 nanoparticles in the conversion treatment has significantly improved the corrosion resistance property of molybdate conversion coatings.

Effect of Silica Nanoparticle Content on the Structure and Electrostatic Bonding of PEDOT:PSS

Conducting poly(3,4-ethylenedioxythiophene):poly(styrene-4-sulfonate) (PEDOT:PSS) containing hydroxyl surface rich SiO2 nanoparticles were investigated. Rearrangement and bonding of PEDOT:PSS were affected by the content of SiO2 nanoparticles, which resulted in the modification of an electronic band structure and electrical characteristics. A slight decrease in work function and a shift of the highly occupied molecular orbital edge to the Fermi level were induced by SiO2 nanoparticle addition. The current path was also tuned by SiO2 nanoparticles and resistance of the composite film was diminished. SiO2 nanoparticles affect electrostatic bonding between PEDOT:PSS and doping of PEDOT as well as increase the packing density of PEDOT:PSS.