Silica Weight Fraction Research Articles

Effects of fillers on the hydrogen uptake and volume expansion of acrylonitrile butadiene rubber composites exposed to high pressure hydrogen: -Property of polymeric materials for high pressure hydrogen devices (3)-

To develop sealing materials for high-pressure hydrogen devices, the effects of filler type and amount on the hydrogen uptake and volume expansion of rubber composites were evaluated up to 90 MPa. The amount of hydrogen in the rubber matrix and carbon black was elucidated using nuclear magnetic resonance, and the hydrogen elimination behavior of the composites was analyzed by thermal desorption analyses. As hydrogen physically adsorbed on carbon black, the hydrogen uptake of carbon black-filled composites increased. The hydrogen uptake of the composites filled with nonabsorbent silica was smaller, depending on the weight fraction of silica. The ratio of volume expansion to the amount of hydrogen in the matrix of carbon black-filled composites was suppressed by the reinforcement effect of carbon black, which did not expand with hydrogen uptake. The suppression of silica-filled composites was limited by the volume fraction of silica.

Preparation of auxetic warp-knitted spacer fabric impregnated with shear thickening fluid for low-velocity impact resistance

This paper reports the preparation of auxetic warp-knitted spacer fabric impregnated with shear thickening fluid and studied its impact behavior under low-velocity impact loading. The shear thickening fluids have been prepared by mechanically dispersing 12 nm silica particles with weight fraction of 10, 15, 20, and 25% in various carriers (PEG200, PEG400, and PEG600). Rheological results indicate that shear thickening fluid experiences shear thickening transition at a specific shear rate. The critical shear rate reduces, and initial viscosity and maximum viscosity increase with the increase of silica weight fraction. The higher molecular weight of polyethylene glycols can lead to lower critical shear rate. The impact process of composite under impact loading can be divided into three stages. The warp-knitted spacer fabric with different negative Poisson’s ratio has a significant effect on the impact behavior. The warp-knitted spacer fabric with better auxetic performance endows composite better impact resistance, the specific performance is the deformation depth, and energy absorption and peak load increase with the increase of auxetic effect of fabric. The silica weight fraction of shear thickening fluid can increase the energy absorption of composite due to the shear thickening transition of shear thickening fluid. Shear thickening fluid has a synergistic effect with the auxetic warp-knitted spacer fabric on impact resistance of composite. The various carriers have no obvious influence on the overall energy absorption and impact load of composites.

Silica sand modified aluminium composite: an empirical study of the physical, mechanical and morphological properties

This research work explored the properties of a metal matrix composite of aluminum reinforced with silica sand. Silica sand of average particle size −53 μm and weight fractions 3 to 19% in intervals of 4 was used to reinforce pure aluminum using double stir casting technique. XRD analysis of the silica sand used as reinforcement showed the presence of phases like quartz, sodium silicate, suessite among others. SEM analysis of the composite revealed fairly uniform distribution of the particulates in the matrix showcasing the efficacy of the fabricating method. Density was observed to decrease as the weight fraction of silica increased whereas hardness, tensile strength, impact energy and porosity were higher than that of the matrix metal. Overall, Al—Silica sand composite with 11 wt% silica showed the highest tensile strength of 65.64 MPa. This work showcased the possibility of a future use of local content silica sand as reinforcement in the world of metal matrix composites.

Fabrication and characterization of electrospun mats of Nylon 6/Silica nanocomposite fibers

In this article, the electrospinning process for Silica nanoparticles reinforced Nylon 6 nanofiber composite mats is investigated. More specifically, the effect of Nylon 6/Formic Acid concentration and silica weight fraction on the solution viscosity and the properties of the end product is studied. Rheological measurements were conducted to investigate the solutions’ viscosity, and scanning electron microscope was used to characterize the morphology and dimensions of the nanofibers. Energy dispersion X-ray was used to prove that silica nanoparticles are well distributed within the nanofibers. Finally, surface roughness and porosity of the mats were measured. It was found that when Nylon 6/Formic Acid concentration increased from 15 to 20 wt%, solution viscosity increased by 0.63 Pa·s, which leads to the increase in average fiber diameter from 103 to 160 nm. Also, when silica increased by 6%, highest viscosity increase was 0.1 Pa·s, while average fiber diameter increased for around 5 nm. In addition, protuberances or small silica beads are observed when silica weight fraction is increased above a critical value. The porosity remains unchanged while surface roughness increased by increasing silica weight fraction and decreasing Nylon 6 concentration. This study outlines the successful fabrication of bead-free Silica reinforced Nylon 6 nanofibers and their mats via electrospinning. Good control over processing parameters results in tailorability of size, morphology, and surface roughness of the end products.

Effects of mixed micro and nano silica particles on the dynamic compressive performances of epoxy adhesive

Effects of mixed micro and nano silica particles on the dynamic stiffness, stress transmissibility, and energy absorption of the epoxy composite were investigated using the split Hopkinson pressure bars. It was found that the dynamic stiffness significantly increased with silica weight fraction regardless of its sizes and composition ratio. However, the effect became less significant as the temperature approached Tg. It was also found that mixed micro and nano silica particles decreased both the epoxy dynamic stiffness and the stress transmissibility, and increased the energy absorption. The optimum composition ratio was found to maximize the energy absorption while maintaining high stiffness performance of epoxy. The results obtained in the present work can be used to design the performance of epoxy/silica adhesive for appropriate applications.

Effect of silica weight fraction on rheological and quasi-static puncture characteristics of shear thickening fluid-treated Twaron® composite

Intelligent energy shunting fluid/fabric base structure which utilizes well-processed shear thickening fluid has been developed. The shear thickening fluid has been synthesized by a powerful mechanical stirrer to disperse 12 nm silica particles into polyethylene glycol 200 g/mol at three concentration levels from low to near maximum packing as 15, 25 and 35 wt%. Examining the rheological behavior of the shear thickening fluid indicates that the increase of shear thickening fluid concentration leads to significant increase in the suspension’s initial, critical and ultimate (up to 104 Pa.s) viscosities, reduction of the critical shear rate, increase of viscoelastic modulus and instability of the suspension. The quasi-static puncture test results demonstrate with the increase of shear thickening fluid concentration, the maximum bearable load by the 15, 25 and 35 wt% shear thickening fluids-treated Twaron® composites increases by 132, 315 and 362%, and the energy absorption increases by 143, 159 and 209%, respectively, compared to the neat fabric. Regarding penetrator structure and dimension, by using rounded penetrators, windowing and pull-out mechanisms would be expected at low velocities. However, sharp-nosed penetrators most likely cause yarns to push aside that is not taken into account as a perfect criteria for investigation of puncture resistance performance. Also, larger penetrators have a larger presented area of impact and, as a result, break more number of yarns to penetrate the fabric.

Nanocomposites from mesoporous silica and dimethacrylic resin

Mesoporous silica has been considered as fillers to elaborate nanocomposites polymer-silica. The organic part of conventional dental resin mixed with mesoporous silica, has been photopolymerized using visible irradiation and camphorquinone as an initiator. The porosity filling has been followed using differential scanning calorimetry, X-ray diffraction, nitrogen adsorption/desorption isotherms, scanning electronic microscopy (SEM), transmission electron microscopy (TEM), helium density measurements. The silica porous volume is completely filled with the dental resin and composites can be obtained when silica weight fraction is below 25%. Thermo-mechanical analyses have been performed showing a thermal dilatation coefficient around 80·10−6°C−1.

Investigation on Structures and Properties of Shape Memory Polyurethane/Silica Nanocomposites

In this study, high performance shape memory polyurethane (SMPU)/silica nanocomposites with different silica weight fraction including SMPU bulk, 3%, 4.5%, 6%, 7.5%, 10%, were prepared by sol-gel process initiated by the solid acid catalyst of p-toluenesulfonic acid (PTSA). Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) observation show that the silica nanoparticles are dispersed evenly in SMPU/silica nanocomposites. Tensile test and dynamic mechanical analysis (DMA) suggest that the mechanical properties and the glass transition temperature (Tg) of the nanocomposites were significantly influenced by silica weight fraction. Thermogravimetric analysis (TGA) was utilized to evaluate the thermal stability and determine the actual silica weight fraction. The TGA results indicate that the thermal stability can be enhanced with the hybridization of silica nanoparticles. Differential scanning calorimetry (DSC) was conducted to test the melting enthalpy (ΔH) and the results suggest that the ΔH was markedly improved for the SMPU/silica nanocomposites. Thermomechanical test was conducted to investigate the shape memory behavior and the results show that the shape fixity is improved by hybridization of silica and good shape recovery can be obtained with the increasing of cycle number for all the samples.

Effect of filler addition and strain rate on the compressive strength of silica styrene‐butadiene rubber‐filled epoxy composites

AbstractThe compressive failure of nanoparticle silica and styrene‐butadiene rubber (SBR)‐filled epoxy composites has been investigated. Significant increase in compressive strength, compressive modulus, work of yielding, and work of fracture was noted for the cases of composites containing low weight fraction of silica and SBR. The compressive strength is about 4–10 times of the tensile strength for composite material containing different weight percent of SBR. Increase in compressive yield strength and decrease in compressive ultimate strength have been observed with crosshead speed 0.1–100 mm/s over all weight content of SBR and silica. The material shows increased elastic region with increasing crosshead speed. This indicates that the material is expected to behave more elastically and less plastically over all the crosshead speeds. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Morphology studies of poly(ethylene terephthalate)/silica nanocomposites

Poly(ethylene terephthalate)/silica nanocomposites have been prepared through in situ polymerization. The morphology was investigated by atomic force microscopy in the tapping mode and scanning electron microscope. The interface morphological structure of the poly(ethylene terephthalate)/silica nanocomposites strongly depends on the ratio of silica in the matrix. When silica weight fraction is lower than 3 wt%, the system consists of aggregated silica particles dispersed in the organic matrix; beyond this concentration, the structure is co-continuous with that of the organic matrix. Surface of poly(ethylene terephthalate) was smooth; while nanocomposites were rough, there are good interfacial adhesion and compatibility between the polymer matrix and the nanofillers.

Nanoscale and effective mechanical behavior and fracture of silica nanocomposites

An experimental investigation of the composite and local mechanical and fracture behavior of an EPON based epoxy with 12 nm (primary) and 100 nm (secondary) fumed silica particles was carried out. The secondary particles promoted matrix stiffening at small weight fractions, which decreased at larger weight fractions and converged to that of the primary nanoparticles. The elastic modulus of the composites with 12-nm silica particles increased by as much as 30% for 15 wt.% silica loading. Atomic Force Microscopy coupled with Digital Image correlation (AFM/DIC) full-field strain measurements showed matrix strain localization in the vicinity of 100-nm fillers, which controlled the overall composite stiffness. In composites with 5 wt.% secondary particles, neighboring particles located at small proximities to each other behaved as single large particles or resulted in local matrix strain shielding. The tensile strength of all composites was independent of particle size and weight fraction, which was attributed to strong particle bonding and failure initiation in the matrix. The critical mode I stress intensity factor of 12-nm silica composites increased with silica weight fraction, by as much as 35% for 15 wt.% silica. SEM fractographs showed enhanced matrix yielding for 15 wt.% silica compared to significant roughening of the fracture plane and void formation at smaller weight fractions.

Preparation of acrylate polymer/silica nanocomposite particles with high silica encapsulation efficiency via miniemulsion polymerization

Acrylate polymer/silica nanocomposite particles were prepared through miniemulsion polymerization by using methyl methacrylate/butyl acrylate mixture containing the well-dispersed nano-sized silica particles coupling treated with 3-(trimethoxysilyl)propyl methacrylate (MPS). The encapsulation efficiency of silica particles was determined through the elution and hydrofluoride acid etching experiments, and the size distribution and the morphology of the composite latex particles were characterized by dynamic light scattering and transmission electron microscopy. The coupling treatment of silica with MPS can improve the encapsulation efficiency of silica and the degree of grafting of polymer onto silica. When 0.10g MPS/g silica was used to modify silica, the encapsulation efficiency of silica was greater than 95%, and the degree of grafting of acrylate polymer onto silica was about 60%. Although the average size and the size distribution index of the composite latex particles increased as the weight fraction of silica increased, the stable latex containing the ‘guava-like’ composite particles was obtained. The grafting of polymer onto silica particles improved the dispersion of silica particles in the solvents for acrylate polymer and in the polymer matrix.

Effects of hydroxyl groups and architecture of organic polymers on polystyrene/silica nanocomposites

AbstractTransparent polystyrene/silica nanocomposites were synthesized by casting the blend solutions of polystyrene (PS) derivatives and perhydropolysilazane (PHPS) and by calcinating the blend films of PS derivatives and PHPS at 100°C for 3 h under steam. Poly(styrene‐co‐4‐vinyl phenol)s [P(S‐co‐VPh)s], poly(styrene‐co‐hydroxymethyl styrene)s [P(S‐co‐HMS)s], poly(styrene‐co‐4‐vinyl phenol)‐block‐PSs [P(S‐co‐VPh)‐block‐PSs], and poly(styrene‐co‐hydroxymethyl styrene)‐block‐PSs [P(S‐co‐HMS)‐block‐PSs] were used as the PS derivatives. The morphology of the microphase separation, transparency, the degree of grafting of PHPS onto PS derivatives, and surface hardness of the composites were investigated by transmission electron microscopy, UV–vis, FTIR, and nanoindentation, respectively. Degrees of grafting of PHPS onto PS derivatives and transparency of the composites of P(S‐co‐VPh)s and P(S‐co‐VPh)‐block‐PSs were higher than those of P(S‐co‐HMS)s and P(S‐co‐HMS)‐block‐PSs. Surface hardness of the composites of P(S‐co‐VPh)‐block‐PS was drastically increased from 0.22 to 0.55 GPa by increasing the weight fraction of silica to 33.7%. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1835–1847, 2005

Interfacial Stability Between Lithium and Fumed Silica-Based Composite Electrolytes

Composite electrolytes consisting of methyl-capped poly(ethylene glycol) oligomer lithium bis(trifluoromethylsulfonyl)imide and fumed silica were investigated. In particular, the effects of fumed silica-surface chemistry and weight percentage in the composite on cycling behavior of Li/electrolyte/Li, Li(Ni)/electrolyte/Li, and Li/electrolyte/metal oxide cells were studied. Four types of fumed silicas with various surface groups were employed, A200 (native hydroxyl groups), R805 (octyl-modified), R974 (methyl-modified), and FS-EG3 (ethylene oxide-modified). The presence of fumed silica enhances lithium cyclability by reducing the interfacial resistance and cell-capacity fading, regardless of surface chemistry. However, the extent of the enhancing effect of fumed silica strongly depends on its surface chemistry, with the largest effect seen with A200 and the least effect seen with FS-EG3. Increasing fumed silica weight fraction intensifies the stabilizing effect. © 2002 The Electrochemical Society. All rights reserved.

Structure of weakly bonded PPG-silica nanocomposites

The structure of silica-polypropyleneglycol (PPG) nanocomposites with weak physical bonds between the organic (PPG) and inorganic (silica) phase, prepared by the sol-gel process, was investigated by small angle X-ray scattering (SAXS). These nanocomposite materials are transparent, flexible, have good chemical stability and exhibit high ionic conductivity when doped with lithium salt. Their structure was studied as a function of silica weight fraction x (0.06 ≤ x ≤ 0.29) and [O]/[Li] ratio (oxygens being of ether-type). The shape of the experimental SAXS curves agrees with that expected for scattering intensity produced by fractal aggregates sized between 30 and 90Å. This result suggests that the structure of the studied hybrids consists of silica fractal aggregates embedded in a matrix of PPG. The correlation length of the fractal aggregates decreases and the fractal dimension increases for increasing silica content. The variations in structural parameters for increasing Li+ doping indicate that lithium ions favor the growth of fractal silica aggregates without modifying their internal structure and promote the densification of the oligomeric PPG matrix.

The behavior of apatite during crustal anatexis: Equilibrium and kinetic considerations

The solubility and dissolution kinetics of apatite in felsic melts at 850°–1500°C have been examined experimentally by allowing apatite crystals to partially dissolve into apatite-undersaturated melts containing 0–10 wt% water. Analysis of P and Ca gradients in the crystal/melt interfacial region enables determination of both the diffusivities and the saturation levels of these components in the melt. Phosphorus diffusion was identified as the rate-limiting factor in apatite dissolution. Results of four experiments at 8 kbar run in the virtual absence of water yield an activation energy ( E) for P diffusion of 143.6 ± 2.8 kcal- mol −1 and frequency factor ( D 0) of 2.23 +2.88 −1.26 × 10 9 cm 2- sec −1. The addition of water causes dramatic and systematic reduction of both E and D 0 such that at 6 wt% H 2O the values are ~25 kcal-mol −1 and 10 −5 cm 2-sec −1, respectively. At 1300°C, the diffusivity of P increases by a factor of 50 over the first 2% of water added to the melt, but rises by a factor of only two between 2 and 6%, perhaps reflecting the effect of a concentration-dependent mechanism of H 2O solution. Calcium diffusion gradients do not conform well to simple diffusion theory because the release of calcium at the dissolving crystal surface is linked to the transport rate of phosphorus in the melt, which is typically two orders of magnitude slower than Ca. Calcium chemical diffusion rates calculated from the observed gradients are about 50 times slower than calcium tracer diffusion. Apatite solubilities obtained from these experiments, together with previous results, can be described as a function of absolute temperature ( T) and melt composition by the expression: In D apatite/ melt P = [(8400 + (( SiO 2 − 0.5)2.64 × 10 4))/ T] − [3.1 + (12.4( SiO 2 − 0.5))] where SiO 2 is the weight fraction of silica in the melt. This model appears to be valid between 45% and 75% SiO 2, 0 and 10% water, and for the range of pressures expected in the crust. The diffusivity information extracted from the experiments can be directly applied to several problems of geochemical interest, including I) dissolution times for apatite during crustal anatexis, and 2) pileup of P, and consequent local saturation in apatite, at the surfaces of growing major-mineral phases.