SiO2 Filler Research Articles

Pressureless joining of SiC ceramics with magnesia‐alumina‐silica glass ceramics

AbstractLiquid phase sintered SiC ceramics were joined using magnesia‐alumina‐silica (MAS) glass‐ceramic fillers without applied pressure. Four different filler compositions with 9.3–25.2 wt.% MgO, 20.7–33.6 wt.% Al2O3, and 49.2–68.1 wt.% SiO2 were studied. The effects of filler composition and joining temperature (1450–1600°C) on the joint strength were investigated. All compositions exhibited an optimum joining temperature at which the maximum joint strength was obtained. A low joining temperature resulted in poor wetting of the SiC substrate due to the high viscosity of the filler. Whereas a high joining temperature caused dewetting and large unfilled sections in the interlayer due to the deleterious interfacial reactions. The joint strength was inversely proportional to the interlayer thickness, which was a function of filler composition and joining temperature. The SiC ceramic joined at 1525°C with MgO‐25 wt.% Al2O3‐60 wt.% SiO2 filler exhibited a four‐point bending strength of 286 ± 40 MPa.

Hybrid Composite Membrane of Phosphorylated Chitosan/Poly (Vinyl Alcohol)/Silica as a Proton Exchange Membrane.

Chitosan is one of the natural biopolymers that has been studied as an alternative material to replace Nafion membranes as proton change membranes. Nevertheless, unmodified chitosan membranes have limitations including low proton conductivity and mechanical stability. The aim of this work is to study the effect of modifying chitosan through polymer blending with different compositions and the addition of inorganic filler on the microstructure and physical properties of N-methylene phosphonic chitosan/poly (vinyl alcohol) (NMPC/PVA) composite membranes. In this work, the NMPC biopolymer and PVA polymer are used as host polymers to produce NMPC/PVA composite membranes with different compositions (30–70% NMPC content). Increasing NMPC content in the membranes increases their proton conductivity, and as NMPC/PVA-50 composite membrane demonstrates the highest conductivity (8.76 × 10−5 S cm−1 at room temperature), it is chosen to be the base membrane for modification by adding hygroscopic silicon dioxide (SiO2) filler into its membrane matrix. The loading of SiO2 filler is varied (0.5–10 wt.%) to study the influence of filler concentration on temperature-dependent proton conductivity of membranes. NMPC/PVA-SiO2 (4 wt.%) exhibits the highest proton conductivity of 5.08 × 10−4 S cm−1 at 100 °C. In conclusion, the study shows that chitosan can be modified to produce proton exchange membranes that demonstrate enhanced properties and performance with the addition of PVA and SiO2.

Influence of Liquid Type, Filler and Coupling Agent on the Interface Resistivity Between Silicone Rubber and Fiber Reinforced Plastic

The interface between silicone rubber (SR) and fiber reinforced plastic (FRP) is a weak point in composite insulator, which is easy to be affected by moisture. However, the corresponding evaluation methods and detection means are not complete yet. Based on the newly proposed method for measuring the interface resistivity with a four-electrode system, the influence of liquid type, filler and coupling agent on the interface resistivity are studied in this paper. It is found that the interface resistivity reduced by 2-4 orders of magnitude after permeation by deionized water, saline and low concentration nitric acid, but the variation trend of interface resistivity is specific when permeated in high concentration of nitric acid solution (1 mol/L). The experimental results of samples with and without silicone coupling agent (SCA) are compared and it is found that the interface without silane coupling agent is easier to be penetrated by liquid, and the change of interface resistivity is more obvious. Besides, the influence of moisture-sensitive Alumina Tri-hydrate and SiO2 fillers, which could provide paths for water and hydrated ions to permeate, on interface resistivity are analyzed. The experimental results are of great significance for the selection of the appropriate formula system and the prevention of liquid penetration for composite insulators.

Effect of different fillers on the microstructural evolution and high temperature oxidation resistance of Mo-Si-B coatings prepared by pack cementation

Mo-Si-B coatings were prepared on molybdenum by a pack cementation process. The effects of Al2O3, SiO2, and SiC fillers on the microstructural evolution and high temperature oxidation kinetic of Mo-Si-B coatings were studied. All the three Mo-Si-B coatings were composed of a MoSi2 layer and a MoB transitional layer. The thickness of the transitional layers showed no discernable differences in different coatings, but the coating prepared with the SiC filler showed the thickest MoSi2 outer layer owing to the additional silicon source supplied by the SiC pack agent. After oxidation at 1250 °C for 100 h, the oxidized coatings exhibited a three-layer structure consisting of an outer SiO2 film, a middle Mo5Si3 layer and an inner MoSi2 layer. The coating prepared with the SiO2 filler showed the smallest weight gain and consumption of the MoSi2 layer, which may be due to the residual SiO2 pack agent favoring the rapid formation of a dense SiO2 film.

Effect Of Sea Water On Mechanical Properties Of Glass Fiber Reinforced Polymer With Silicon Dioxide & Silicon Oil Fillers

This paper deals the effect of sea water on moisture absorption behavior, tensile and flexural properties of the composite. The composite laminates are prepared using Glass fiber/Vinyl ester mixed with Sio2 and Silicon oil filler by hand layup technique. As per ASTM standard composite specimens prepared and weighted then samples immersed in sea water for 56 days. The composite specimens were removed from the artificial seawater for every week, dated, weighted & recorded to study the moisture absorption behavior. After 56 days aged specimens are tested for Mechanical Properties. The filler Silicon Dioxide and Silicon Oil act as a toughening modifier for vinyl ester resin. The composite with filler Sio2 and Silicon oil gives better result than the unfilled composites after ageing.

A safeguarding and high temperature tolerant organogel electrolyte for flexible solid-state supercapacitors

An organogel electrolyte with anti-impact and high-temperature tolerance properties is developed by dissolving poly(vinyl alcohol) (PVA) in ethylene glycol (EG) and mixing with shear thickening fluid (STF) to fabricate STF reinforced supercapacitor (SSC). Because of the hydrogen bond between EG and PVA and the thermodynamic stability of EG, SSC possesses good environmental stability and can withstand a high temperature of 80 °C with a high potential window of 1.7 V. The capacitance of SSC also increases by 90% due to the better ionic conductivity of the organogel at 80 °C. More importantly, the as-designed SSC can dissipate and reduce hammer impact force from 570 N to 81 N, showing an outstanding anti-impact property. This super safeguarding property results from the synergistic effect of shear thickening (ST) effect of STF, SiO2 fillers, and hydrogen bonds in the matrix. Finally, a three SSCs-based series wearable wristband maintains 95% of capacitance from harsh impact and can protect human beings. Thus, this work opens a new avenue for the development of functional SSC as new power source in wearable electronics and safeguard areas.

The action of fillers in the enhancement of the tribological performance of epoxy composite coatings

The addition of reinforced material (polymer and mineral fillers) to epoxy resin matrices results in the improvement of the overall performance of the composite, allowing the application of these materials as tribo-materials in industrial applications. Enhancement of the tribological properties (low friction coefficient, increased wear resistance and non-stick properties) of epoxy coatings is done by embedding fillers with various particle sizes and with different filler volume fractions. The aim of this work is to determine the factors influencing the wear-reducing mechanisms of the fillers. This was done by wear tests carried out on a pin-on-disc apparatus and on a Taber Abraser device. A significant decrease in the wear rate was recorded with the formulations containing polymer fillers such as polytetrafluoroethylene (PTFE), polyethylene (PE) and fluorinated ethylene propylene (FEP), due to their self-lubricating nature. The particle size of silica (SiO2) fillers was found to play a significant role, coarse particles reducing the wear rate due to the bond at the resin/filler interface. It was shown that not all fillers helped improving the wear resistance; the SiO2 fillers with lower particle size had a negative effect on the wear resistance of the epoxy coating, by causing discontinuities in the material. The worn surfaces were analyzed using light microscopy and scanning electron microscope (SEM), to help better understand the wear mechanisms involved.

Enhanced Mechanical, Thermal and Antimicrobial Properties of Additively Manufactured Polylactic Acid with Optimized Nano Silica Content.

The scope of this work was to create, with melt mixing compounding process, novel nanocomposite filaments with enhanced properties that industry can benefit from, using commercially available materials, to enhance the performance of three-dimensional (3D) printed structures fabricated via fused filament fabrication (FFF) process. Silicon Dioxide (SiO2) nanoparticles (NPs) were selected as fillers for a polylactic acid (PLA) thermoplastic matrix at various weight % (wt.%) concentrations, namely, 0.5, 1.0, 2.0 and 4.0 wt.%. Tensile, flexural and impact test specimens were 3D printed and tested according to international standards and their Vickers microhardness was also examined. It was proven that SiO2 filler enhanced the overall strength at concentrations up to 1 wt.%, compared to pure PLA. Atomic force microscopy (AFM) was employed to investigate the produced nanocomposite extruded filaments roughness. Raman spectroscopy was performed for the 3D printed nanocomposites to verify the polymer nanocomposite structure, while thermogravimetric analysis (TGA) revealed the 3D printed samples’ thermal stability. Scanning electron microscopy (SEM) was carried out for the interlayer fusion and fractography morphological characterization of the specimens. Finally, the antibacterial properties of the produced nanocomposites were investigated with a screening process, to evaluate their performance against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus).

A high-performance, thermal and electrical conductive elastomer composite based on Ti3C2 MXene

In this study, a single-layered Ti3C2 hybrid SiO2 filler (Ti3C2-h-SiO2) was proposed to fabricate high-performance styrene-butadiene rubber (SBR) elastomer composites. It was found that incorporating SiO2 not only facilitated the uniform dispersion of Ti3C2-h-SiO2 in the SBR matrix but also endowed the surface of Ti3C2-h-SiO2 with nano protuberances for immobilizing more rubber chains, resulting in the improvement of the interfacial interaction between Ti3C2-h-SiO2 and SBR matrix. Thus, the tensile strength of the SBR/Ti3C2-h-SiO2 elastomer composite was reinforced by 174% compared with the unfilled SBR. Moreover, the wet skid resistance and rolling resistance of the SBR/Ti3C2-h-SiO2 elastomer composite were also remarkably improved. Noteworthily, the exceptional thermal conductivity (0.401 W m−1 k−1) and electrical conductivity (4.87 × 10−4 S m−1) of the SBR/Ti3C2-h-SiO2 elastomer composite were comparable to the SBR/reduced graphene oxide (rGO) elastomer composite, implying that the conductivity of Ti3C2-h-SiO2 may be competitive with the rGO.

Improved mechanical and microwave absorption properties of SiCf/SiC composites with SiO2 filler

SLF and KD-S SiC fibers were used to fabricate SiCf/SiC composites by precursor impregnation and pyrolysis (PIP) method. To simultaneously improve both the mechanical and electromagnetic wave absorption properties of SiCf/SiC composites, the SiO2 fillers were mixed into the PSC/xylene precursor solution as inert filler. In this research, the effects of SiO2 filler on the micro morphologies, XRD patterns, mechanical and dielectric property were investigated. The results exhibit that the flexural strength of the SLF and KD-S SiCf/SiC composites was improved from 167.69 MPa to 241.95 MPa and 248.16 MPa–324.87 MPa with SiO2 filler, respectively. The lower complex permittivity and better impedance matching are attributed to a broken conductive network in the SiC matrix, which is caused by SiO2 filler. Therefore, the reflection loss values of SLF SiCf/SiC composites with SiO2 filler were approach at −40 dB, and the KD-S SiCf/SiC composites with SiO2 filler of that over −12 dB. The effective absorption bandwidths of SLF and KD-S SiCf/SiC composites with SiO2 filler are 3.44 GHz and 2.75 GHz, respectively.

Investigation of Lithium Transference Number in PMMA Composite Polymer Electrolytes Using Monte Carlo (MC) Simulation and Recurrence Relation

In this study, Monte Carlo (MC) simulation is conducted with recurrence relation to study the effect of SiO2 with different particle size and their roles in enhancing the ionic conductivity and lithium transference number of PMMA composite polymer electrolytes (CPEs). The MC simulated ionic conductivity is verified with the measurements from Electrochemical Impedance Spectroscopy (EIS). Then, the lithium transference number of CPEs is calculated using recurrence relation with the MC simulated current density and the reference transference number obtained. Incorporation of micron-size SiO2 (≤10 μm) fillers into the mixture improves the ionic conductivity from 8.60×10−5 S/cm to 2.35×10−4 S/cm. The improvement is also observed on the lithium transference number, where it increases from 0.088 to 0.3757. Furthermore, the addition of nano-sized SiO2 (≤12 nm) fillers further increases the ionic conductivity up towards 3.79×10−4 S/cm and lithium transference number of 0.4105. The large effective surface area of SiO2 fillers is responsible for the improvement in ionic conductivity and the transference number in PMMA composite polymer electrolytes. Keywords: Solid Polymer Electrolytes, Monte Carlo Simulation, Transference Number, Recurrence Relation, Ionic Conductivity

Study of the Complex Permittivity of a Polyurethane Matrix Modified by Nanoparticles

This study presents the influence of various types of nanoparticle (NP) fillers incorporated into a polyurethane (PU) (VUKOL 022) matrix and its subsequent changes in complex permittivity. Two types of surface modification of SiO2 fillers were investigated. The frequency dependence of the real and imaginary parts of complex permittivity was measured within the frequency range of 1 mHz to 1 MHz using the capacitance method. The 1 wt.% NPs in PU caused an increase (MgO, TiO2, n-SiO2, and f-SiO2) or a decrease (d-SiO2) in the real permittivity. The $\alpha $ -relaxation and intermediate dipolar effect were observed at the temperature dependence of the imaginary permittivity. The change in permittivity by various surface modifications of SiO2 and other nanofillers was discussed based on the multi-core model. Moreover, the NPs caused a shift in the local maximum of the permittivity, which was a result of the interfacial polarisation and a charge multiplication of the $\alpha $ -relaxation process.

Temperature-Triggered/Switchable Thermal Conductivity of Epoxy Resins.

The pronouncedly low thermal conductivity of polymers in the range of 0.1–0.2 W m−1 K−1 is a limiting factor for their application as an insulating layer in microelectronics that exhibit continuously higher power-to-volume ratios. Two strategies can be applied to increase the thermal conductivity of polymers; that is, compounding with thermally conductive inorganic materials as well as blending with aromatic units arranged by the principle of π-π stacking. In this study, both strategies were investigated and compared on the example of epoxy-amine resins of bisphenol A diglycidyl ether (BADGE) and 1,2,7,8-diepoxyoctane (DEO), respectively. These two diepoxy compounds were cured with mixtures of the diamines isophorone diamine (IPDA) and o-dianisidine (DAN). The epoxy-amine resins were cured without filler and with 5 wt.-% of SiO2 nanoparticles. Enhanced thermal conductivity in the range of 0.4 W·m−1·K−1 was observed exclusively in DEO-based polymer networks that were cured with DAN (and do not contain SiO2 fillers). This observation is argued to originate from π-π stacking of the aromatic units of DAN enabled by the higher flexibility of the aliphatic carbon chain of DEO compared with that of BADGE. The enhanced thermal conductivity occurs only at temperatures above the glass-transition point and only if no inorganic fillers, which disrupt the π-π stacking of the aromatic groups, are present. In summary, it can be argued that the bisphenol-free epoxy-amine resin with an epoxy compound derivable from natural resources shows favorably higher thermal conductivity in comparison with the petrol-based bisphenol-based epoxy/amine resins.

Microwave absorption and mechanical properties of SiCf/SiOC composites with SiO2 fillers

Owing to the polysiloxane (PSO) characteristic of cheap, healthy, available and low free carbon content, in this research the SiCf/SiOC composites were manufactured by polymer infiltration and pyrolysis (PIP) method with various content of SiO2 fillers. It can be concluded from the DSC-TGA and XRD analysis that SiOC ceramic was formed from PSO when pyrolysis temperature exceeded 800 °C and after pyrolysis at 1000 °C the PSO mainly composed by amorphous SiO2. The effects of SiO2 fillers on morphology of SiOC matrix, flexural strength, complex permittivity, and microwave absorption property of SiCf/SiOC composites were investigated. The results indicated that the SiO2 fillers can enhance the density and reduce the microcracks of matrix. Therefore, the maximum flexural strength 201.09 MPa can be obtained by adding 5 g SiO2 filler into PSO precursor solution. The complex permittivity and flexural strength of composites first increased when content of SiO2 filler enhanced from 0 to 5 g. Nevertheless, with the content of SiO2 filler increased from 5 g to 10 g and 15 g, the complex permittivity and flexural strength of composites decreased. In summary, the SiCf/SiOC composites with 10 g SiO2 fillers not only possess the reflection loss as low as -26.02 dB and the effective absorption bandwidth (EAB) below -10dB up to 3.21 GHz at the thickness of 3.0 mm but also own the flexural strength of 171.71 MPa.

Synthesis of Core/Shell Structured Zinc Borate/Silica and Its Surface Charring for Enhanced Flame Retardant Properties

An efficient zinc borate/silica composite flame retardant (CFR), with accumulating nano-silica (SiO2) on the surface of grown zinc borate (ZnB) flakes to form a core/shell structure, was synthesized via a facile precipitation route. When mixed with methyl vinyl silicone rubber (VMQ), this combined structure of CFR brought advantages in both flame retardancy and mechanical properties. During a process of combustion, these CFR particles migrated and assembled on the surface of combustion zone, increasing the local concentration and generating a tight and intumescent surface char layer even at a lower loading amount. In comparison with the VMQ/physical mixture (PM, with the same proportion of SiO2 and ZnB), the EVA/CFR formulation passed a UL94 V–0 rating and got a LOI value of 29.5, when used as an alternative of SiO2 filler. Meanwhile, CFR played an effective role in inhibiting the spread of fire; VMQ/CFR showed a fire growth index (FGI) of 0.56 much lower than 0.92 of VMQ/PM. In this case, the heat release rate (HRR), total heat released (THR) and smoke production rate (SPR) were considerably reduced. Moreover, the mechanical properties of VMQ/CFR blends, including both tensile strength (TS) and elongation at break (EAB), were significantly enhanced.

Effects of SiO2 Filler in the Shell and Wood Fiber in the Core on the Thermal Expansion of Core-Shell Wood/Polyethylene Composites.

The influence of nano-silica (nSiO2) and micro-silica (mSiO2) in the shell and wood fiber filler in the core on the thermal expansion behavior of co-extruded wood/polyethylene composites (Co-WPCs) was investigated to optimize the thermal expansion resistance. The cut Co-WPCs samples showed anisotropic thermal expansion, and the thermal expansion strain and linear coefficient of thermal expansion (LCTE) decreased by filling the shell layer with rigid silica, especially nSiO2. Finite element analysis indicated that the polymer-filled shell was mainly responsible for the thermal expansion. The entire Co-WPCs samples exhibited a lower thermal expansion strain than the cut Co-WPCs samples due to protection by the shell. Increasing the wood fiber content in the core significantly decreased the thermal expansion strain and LCTE of the Co-WPCs. The Co-WPCs whose core layer was filled with 70% wood fiber exhibited the greatest anisotropic thermal expansion.

The influences of different size SiO2 nanoparticles on dielectric properties and corona resistance of epoxy composites

In order to optimize the dispersion structure of the filler in polymer composites, 15 nm SiO2 (HL‐150) and 6 nm SiO2 (HL‐380) are added to epoxy (EP). The total content of silica filler is fixed at 15 wt%, and the mass ratio of HL‐380 to HL‐150 in silica filler is adjusted. SiO2/EP nanocomposites are prepared by the sand milling and heat curing process. Transmission electron microscopy results show that the mixed SiO2 fillers are well dispersed in EP. With the increase of HL‐380 filler, the relative permittivity of the SiO2/EP nanocomposites with mixed SiO2 nano‐fillers increases, compared with the nanocomposites added HL‐150 filler alone. The electrical aging threshold and dielectric strength increases, and the inhibiting effect on space charge accumulation is enhanced. When the mass ratio of HL‐380 to HL‐150 is 1/6.89, the corona resistance life are the longest, with the value of 13.23 hours, which is 1.47 times than that of the composites with HL‐150 filler alone.

Structure–dynamic properties relationships in poly(ethylene oxide)/silicon dioxide nanocomposites: dielectric relaxation study

Films of polyethylene oxide (PEO) filled with silicon dioxide (SiO2) were synthesized via casting method. The formation of the PEO/SiO2 nanocomposites was characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) measurements. The XRD patterns confirmed that increasing SiO2 in semicrystalline PEO enhances the amorphousity and causes a disturbance in the crystalline phase. The influence of the SiO2 on the dielectric relaxation spectra of PEO in wide temperature and frequency ranges was investigated. Two molecular relaxation processes are observed: main (α-) and secondary (β-) relaxations. For the α-process, the process slowed down with adding SiO2 fillers reflecting an increase in the glass transition temperature, Tg. This trend was also verified by differential scanning calorimetry (DSC). The findings indicated that adding SiO2 restricted the motion of PEO segments, while such changes were not observed in the glassy state. Further, the attenuation of the electric field of the terahertz waves passed through PEO/SiO2 samples was evaluated. In the terahertz range, the resonant peaks of PEO originated from lattice vibration feature the complex dielectric function. These peaks were weakened broadened and red-shifted by increasing of SiO2 concentrations.

Effect of Size and Content of SiO2 Nanoparticle on Corona Resistance of Silicon–Boron Composite Oxide/SiO2/Epoxy Composite

Corona discharge always threatens the safe and long-term operation of electrical equipment. Therefore, it is imperative to improve the corona resistance of electrical insulation materials. In this research work, fumed silica (SiO2) with different particle sizes and self-made organic silicon–boron composite oxide (Si–B) are used to modify epoxy resin (EP) for enhancing the corona resistance. Si–B/SiO2/EP nanocomposites with different SiO2 content series and 4 kinds of SiO2 particle size series are prepared by grinding machine dispersing and thermal curing. A strong dependence of the corona resistance on SiO2 filler size in nano-scale and content is revealed experimentally. The filler combination of Si–B and nano-SiO2 can reduce the relative permittivity of the Si–B/SiO2/EP nanocomposites and inhibit the increase of dielectric loss. With the particle size of SiO2 filler increases, the space charge suppression effect and the thermal stability are reduced, but corona resistance life is improved.When the 15-nm SiO2 content is 15 wt%, the corona resistance life of the Si–B/SiO2/EP nanocomposites can reach 8.99 h under 90 °C and 80 kV/mm electric field strength, while pure epoxy is only 0.86 h. The degradation path through the material is the more important factor affecting corona resistance performance–large particle size and well dispersion state can effectively extend the degradation path through the material.

Effect of lanthanum‐modified magnesium silicate on isotactic polypropylene crystallization in composite materials during shear flow

AbstractThe activity of isotactic polypropylene (iPP) nucleating additives during shear flow of composite materials is still not entirely explained. In current work the sol‐gel method was employed to synthesize MgO·SiO2 filler, surface‐modified with trivalent lanthanum. The crystallization of commercial iPP in the presence of 0.5% by weight La3+ modified or unmodified silicates was analyzed. The wide angle X‐ray scattering analysis proved that the presence of even small amount of filler influences significantly on supermolecular structure of iPP. The results of microscope observations confirmed that the lanthanum‐modified filler shows the nucleating ability for iPP. In that case a significant reduction of crystallization induction time was noticed. The investigation of iPP crystallization in composites after shear treatment confirmed that the increase of shear rate reduces the nucleating ability of additives. Moreover, the flow of filler particles during shearing may impede the shear‐induced crystallization phenomenon.