Addition Of Silica Particles Research Articles

Synthesis and effect of using silica fume particles on shear properties of basalt fibers‐epoxy composites

AbstractIn this study, the effect of the addition of silica particles modified with silane agent on the mechanical properties of basalt fibers‐epoxy composites were studied with the interlayer shear strength (ILSS) test. In the first stage, silica fume particles were synthesized using the sol‐gel method and surface modified using tri mercaptopropyl trimethoxy silane agent. The results of the characterization showed that the synthesized powder is nanometric scale, amorphous and high purity. The surface‐modified silica fume particles (0, 2, 4, 6 wt.%) were distributed inside the epoxy matrix using a mechanical stirrer and ultrasonic waves. The hand lay‐up method was used to fabricate composite samples, then the effect of adding these particles on the mechanical properties of basalt fibers‐epoxy composites under interlayer shear loads was studied. The results of the research indicated that the addition of silica fume particles has a significant effect on improving the mechanical properties of basalt fibers‐epoxy composites, and the greatest improvement in mechanical properties was achieved by adding 4 wt.% of modified silica fume particles. In the case of composites without SF particles, the shear strength was 34 MPa, which was increased to 40 MPa by adding 4 wt.% of SF particles (about 20% improvement). On the other hand, results demonstrated that the optimal distribution of silica fume particles within the polymer matrix performs an impressive role in improving the mechanical response of composite samples.Highlights The use of silica fume in the polymer composite is one of the research innovations. Silica fume is a super‐fine spherical powder that is collected as a by‐product. The silane is used to better distribute and optimal interaction of the silica fume in epoxy. Sol‐gel is one of the methods to synthesis of silica fume. ILSS test was done to investigate the strength of the interface of basalt fibers and epoxy.

Design of silica coated polyamide fabrics for thermo‐regulating textiles

AbstractEfficient thermal management is essential for the energy balance and thermal comfort. In this context, the design of textiles, which can modulate the infrared radiation emitted by the human body, is attractive. These fabrics will manage the microclimate between the skin and fabric. The proposed textile design consists of the coating of commercial woven fabrics based on polyamide 6–6 by a dip‐coating process. The coating is based on the incorporation of fine spherical silica particles with a submicron size within thermosensitive poly(N‐isopropylacrylamide) hydrogels. Neat commercial fabrics reflect 12% of the radiation, while the addition of silica particles leads to a reflection of 24% of the infrared radiation in the 5–15 μm wavelengths range. The infrared radiation reflection capacity of the coated fabrics can be increased by managing the size and the content of the silica particles, which allows reaching 36% of reflected radiation. Our findings open opportunities for warming up fabrics and thus reduce energy consumption in heating close space.

Environmental impact assessment of nanofluids containing mixtures of surfactants and silica nanoparticles

Due to widespread use of nanoparticles in surfactant-based formulations, their release into the environment and wastewater is unavoidable and toxic for biota and/or wastewater treatment processes. Because of concerns over the environmental impacts of nanofluids, studies of the fate and environmental impacts, hazards, and toxicities of nanoparticles are beginning. However, interactions between nanoparticles and surfactants and the biodegradability of these mixtures have been little studied until now. In this work, the environmental impacts of nanofluids containing mixtures of surfactants and silica nanoparticles were valuated. The systems studied were hydrophilic silica nanoparticles (sizes 7 and 12 nm), a nonionic surfactant (alkyl polyglucoside), an anionic surfactant (ether carboxylic acid), and mixtures of them. The ultimate aerobic biodegradation and the interfacial and adsorption properties of surfactants, nanoparticles, and mixtures during biodegradation were also evaluated. Ultimate biodegradation was studied below and above the CMCs of the individual surfactants. The interfacial and adsorption properties of surfactant solutions containing nanoparticles were influenced by the addition of silica particles. It was determined that silica nanoparticles reduced the capability of the nonionic surfactant alkyl polyglucoside to decrease the surface tension. Thus, silica NPs promoted a considerable increase in the surfactant CMC, whereas the effect was opposite in the case of the anionic surfactant ether carboxylic acid. Increasing concentrations of surfactant and nanoparticles in the test medium caused decreases in the maximum levels of mineralization reached for both types of surfactants. The presence of silica nanoparticles in the medium reduced the biodegradability of binary mixtures containing nonionic and anionic surfactants, and this effect was more pronounced for larger nanoparticles. These results could be useful in modelling the behaviour of nanofluids in aquatic environments and in selecting appropriate nanofluids containing nanoparticles and surfactants with low environmental impact.Graphical abstract

Nano-silica reinforced epoxy resin/nano-rubber composite material with a balance of stiffness and toughness

In the electronics and aerospace industries, epoxy resins are generally regarded as economical and efficient adhesives and have a high status. However, epoxy resins are highly crosslinked polymers and are very brittle adhesives where they are prone to fast crack propagation under dynamic loads. Therefore, it is very necessary to enhance the toughness of epoxy resin adhesives. Nano-rubber has been proved to be an important toughening agent for epoxy resin, which can significantly improve the fracture toughness of epoxy resin. However, increasing the toughness of epoxy resin by adding nanomaterials is often accompanied by decreasing the strength and stiffness of resin. Therefore, in this work, rigid nano-silica particles were added to improve the rigidity and tensile strength reduction caused by the addition of rubber particles. And further increase the toughness of the epoxy resin to obtain an epoxy adhesive with balanced stiffness-toughness. As a result, it can be found that the addition of silica particles can significantly improve the decrease in stiffness caused by the addition of rubber particles. For example, Young’s modulus and tensile strength are increased by 28%, and 23%, respectively, with 4% silica is added based on rubber particles. Through the single lap shear experiment, it is found that the shear strength of the epoxy/RnP/silica composite adhesive has increased, which further proves that the addition of nano-silica particles can increase the stiffness of the epoxy composite. The dynamic mechanical analysis experiment found that after adding nano-silica particles, the storage modulus of epoxy composites increased, which also shows that adding nano-silica particles can improve the stiffness of epoxy composites. Scanning electron microscopy analysis was performed to study the reinforcement mechanism of epoxy/RnP/silica composite materials. The thermal stability of epoxy composites was characterized by Dynamic mechanical analysis and thermogravimetric analysis.

Interfacially-adsorbed particles enhance the self-propulsion of oil droplets in aqueous surfactant.

Understanding the chemo-mechanical mechanisms that direct the motion of self-propulsive colloids is important for the development of active materials and exploration of dynamic, collective phenomena. Here, we demonstrate that the adsorption of solid particles on the surface of solubilizing oil droplets can significantly enhance the droplets' self-propulsion speeds. We investigate the relationship between the self-propulsion of bromodecane oil droplets containing silica particles of varying concentration in Triton X-100 surfactant, noting up to order of magnitude increases in propulsion speeds. Using fluorescently labeled silica, we observe packing of the particles at the oil-water interfaces of the rear pole of the moving droplets. For bromodecane oil droplets in Triton X-100, the highest droplet speeds were achieved at approximately 40% particle surface coverage of the droplet interface. We find particle-assisted propulsion enhancement in ionic surfactants and different oil droplet compositions as well, demonstrating the breadth of this effect. While a precise mechanism for the propulsion enhancement remains unclear, the simple addition of silica particles to droplet oil-water interfaces provides a straightforward route to tune active droplet dynamics.

Molecular Dynamic Investigations on the Adhesion Behaviors of Asphalt Mastic-Aggregate Interface.

The asphalt mastic–aggregate interface plays an essential role in determining the service performance of asphalt mixtures. The objective of this paper was to investigate the adhesion behaviors and mechanism between asphalt mastic and aggregate based on molecular dynamic (MD) simulations. First, the asphalt mastic model considering the actual mass ratio of filler to asphalt (F/A) condition was established and validated in terms of thermodynamic properties. Second, the molecular arrangement characteristics of polar components on the aggregate substrate were analyzed by radial distribution function (RDF), relative concentration (RC), and mean square displacement (MSD). Third, the interfacial adhesion ability between asphalt and aggregate was quantitively evaluated based on the work of adhesion. Finally, the coupling effect of moisture and temperature on interfacial adhesion behaviors was investigated to explore the adhesion failure characteristics of the asphalt–aggregate interface. The results demonstrate that the thermodynamic properties could be employed to validate the reliability of the asphalt mastic model. The self-aggregation degree of polar components in base asphalt could be significantly increased with the addition of silica particles, exhibiting a change of configuration from “parallel arrangement” into “stack distribution” due to the high polarity of silica particles. The polar components in asphalt mastic exhibit a more uniform distribution state and lower mobility capability than base asphalt owing to the adsorption effect of silica particles. Silica particles with amounts of residual charges could significantly increase the electrostatic energy of the asphalt mastic–aggregate interface, contributing to an improvement of the adhesion between asphalt mastic and aggregate. The increase of temperature enhances the work of adhesion of the asphalt mastic–aggregate interface, which is opposite to that of the base asphalt–aggregate interface. The asphalt mastic exhibits a greater sensitivity to interfacial moisture damage than base asphalt. The findings would provide insights into a better understanding on the micro adhesion mechanism of the asphalt mastic–aggregate interface.

Strong silica-nanocellulose anisotropic composite foams combine low thermal conductivity and low moisture uptake

We report the fabrication of anisotropic lightweight composite foams based on commercial colloidal silica particles and TEMPO-oxidized cellulose nanofibrils (TOCNF). The unidirectional ice-templating of silica-TOCNF dispersions resulted in anisotropic foams with columnar porous structures in which the inorganic and organic components were homogeneously distributed. The facile addition of silica particles yielded a significant enhancement in mechanical strength, compared to TOCNF-only foams, and a 3.5-fold increase in toughness at a density of 20 kg m−3. The shape of the silica particles had a large effect on the mechanical properties; anisotropic silica particles were found to strengthen the foams more efficiently than spherical particles. The water uptake of the foams and the axial thermal conductivity in humid air were reduced by the addition of silica. The composite foams were super-insulating at dry conditions at room temperature, with a radial thermal conductivity value as low as 24 mW m−1 K−1, and remained lower than 35 mW m−1 K−1 up to 80% relative humidity. The combination of high strength, low thermal conductivity and manageable moisture sensitivity suggests that silica-TOCNF composite foams could be an attractive alternative to the oil-based thermal insulating materials.

Controlling the Thermally Induced Phase Separation of Polymer/Ionic Liquid Blended Films with Concentrated-Polymer-Brush-Decorated Hybrid Particles.

The development of quasi-solid electrolytes for electrical devices operating at high voltages is important for addressing future energy storage requirements. Here, we report a new method to fabricate quasi-solid electrolytes through the thermally induced phase separation of a polymer/ionic liquid (polymer/IL) blend. In a polymer/IL blend that exhibits lower critical solution temperature-type phase separation, we demonstrate that the addition of silica particles decorated with concentrated polymer brushes (CPB-SiPs) can prevent macroscopic phase separation after heating, resulting in a quasi-solid electrolyte with a continuous IL phase. This is due to the adsorption of CPB-SiPs onto the polymer/IL interface in the phase-separated structure. We also reveal a relationship between the molecular weight of the CPB and the phase-separated structure. Namely, a quasi-solid film with a bicontinuous phase-separated structure is formed only when polymers with an appropriate molecular weight are grafted on the CPB-SiPs. The resulting quasi-solid film exhibits a relatively high ionic conductivity, owing to the existence of a continuous ion-conductive phase solely consisting of IL. In addition, we fabricated a quasi-solid electrolyte with the blended film and successfully applied it to an electric double-layer capacitor operating at a high voltage, owing to the wider potential window of the IL employed herein.

Wear behavior of metal bond diamond composite with hollow spherical silica particles as pore former

To obtain the high grinding efficiency and good self-dressing performance for the metal bond diamond grinding tools, hollow spherical silica particles with different contents were introduced into Fe-based diamond composites as pore former. A pin-on-disc wear test was performed to assess the wear properties and grinding performance of the fabricated specimens, and the morphological properties of the worn surface were evaluated. Results show that the porosity of the Fe-based diamond composite was positively correlated with the content of silica particles. These pores provided chip-storage spaces and an appropriate ratio between wear of the matrix and diamond grits in the grinding process. Therefore, as the porosity of the specimens increased, the wear of the Fe-based diamond composites increased. However, the maximum disc/pin wear ratio with a value of 47 was obtained at the specimen with 0.5 wt% silica particle addition, of which porosity is 3.5%. At this addition amount, the bending strength also reached the maximum value of 1127 MPa.

Influence of Blend Composition and Silica Nanoparticles on the Morphology and Gas Separation Performance of PU/PVA Blend Membranes.

Polymer blending and mixed-matrix membranes are well-known modification techniques for tuning the gas separation properties of polymer membranes. Here, we studied the gas separation performance of mixed-matrix membranes (MMMs) based on the polyurethane/poly(vinyl alcohol) (PU/PVA) blend containing silica nanoparticles. Pure (CO2, CH4, N2, O2) and mixed-gas (CO2/N2 and CO2/CH4) permeability experiments were carried out at 10 bar and 35 °C. Poly(vinyl alcohol) (PVA) with a molecular weight of 200 kDa (PVA200) was blended with polyurethane (PU) to increase the CO2 solubility, while the addition of silica particles to the PU/PVA blend membranes augmented the CO2 separation performance. The SEM images of the membranes showed that the miscibility of the blend improved by increasing the PVA contents. The membrane containing 10 wt % of PVA200 (PU/PVA200–10) exhibited the highest CO2/N2~32.6 and CO2/CH4~9.5 selectivities among other blend compositions, which increased to 45.1 and 15.2 by incorporating 20 wt % nano-silica particles.

Air Templated Macroporous Epoxy Foams with Silica Particles as Property-Defining Additive.

Nonaqueous foams were successfully produced by mechanically beating air into liquid epoxy resin, surfactant, and silica particle mixtures and used as templates to produce macroporous polymers. The air bubbles introduced into the epoxy formulations served as templates for the pores of the cured epoxy foams. The addition of silica particles into the resin mixture resulted in an increased viscosity of the formulation, thus enhancing the stability of the liquid epoxy froths, which could then be thermally cured at 60 °C. Increasing the silica loading in the formulation resulted in an increase of the foam density and decrease of the average pore size of the epoxy foams. The epoxy foams containing silica exhibited a hierarchical pore structure, where large pores were surrounded by smaller pores, and enhanced stiffness as compared to the control epoxy foams with a monomodal pore size distribution.

Lowering of Water Absorption for Epoxy Resin by The Addition of Silica Particles and Silane Coupling Agent

Lowering of Water Absorption for Epoxy Resin by The Addition of Silica Particles and Silane Coupling Agent

Effect of filler on thermodynamic and mechanical behaviour of asphalt mastic: a MD simulation study

ABSTRACT To fully understand the filler reinforcement mechanism in asphalt mastic, molecular dynamic (MD) simulation was adopted to explore the effect of mineral filler on the structural, thermodynamic and mechanical properties of asphalt mastic. An asphalt/silica nanoparticle composite system that consisted of silica nanoparticles and a 12-components combined asphalt model was generated to represent asphalt mastic. The asphalt molecular model was validated in terms of thermodynamic properties such as density, glass transition temperature (T g) and cohesive energy density (CED). The structural properties, in the form of free volume and radial distribution function (RDF) of asphalt mastic were calculated. Thermodynamic properties including density, T g and CED of asphalt mastic were further investigated. Mechanical properties such as Young’s, bulk and shear moduli were also estimated. Results show that the addition of silica particles to neat asphalt binder decreased the interaction between asphalt molecules and increased free volumes in the configuration. T g decreased as the increasing concentration of the silica particle. Furthermore, the effects of the filler particle size and concentration on the thermodynamic and mechanical properties of asphalt mastic were discussed. This fundamental level simulation results reported here provide a platform for potentially accounting for the effect of fillers on the properties of asphalt mastic.

Compatibilization of silicone/fluorosilicone blends by dynamic crosslinking and fumed silica addition

The aim of this work is to study the compatibility of silicone/fluorosilicone blends by exploring two compatibilization strategies. First, the crosslinking of the blend under shearing conditions leads to a reduction in the size of the fluorosilicone domain and hence to an effective stabilization of the morphology under shear and long time annealing. The refinement of the morphology in the dynamic crosslinking step is most likely due to a decrease in the viscosity ratio coming from preferential crosslinking of the fluorosilicone phase. However, the formation of a copolymer between silicone and fluorosilicone at the blend interface cannot be totally excluded. Secondly, the silicone/fluorosilicone blend was compatibilized by the addition of silica particles whose surface is hydrophilic or hydrophobic. Fumed hydrophilic silica allows to reduce the size of the fluorosilicone phase up to 500 nm while its hydrophobic counterpart is ineffective. This observation has been attributed to the specific hydrogen and dipolar interactions of the silicone and the CF3 group with the silanol present on the surface of the hydrophilic silica. The compatibilization mechanism is supposed to be due to a decrease in the interfacial tension and to a reduction of the coalescence phenomenon.

Influence of silica nanoparticles combined with zinc phosphinate on flame retardant properties of PET

Zinc phosphinate (Exolit OP950), nanosilica particles and polyethylene terephthalate (PET) have been blended and thereafter melt‐spinned to develop a new flame retardant (FR) system for PET textiles. The effects of the two types of nanosilica fillers on the wettability, dispersibility and thermal properties were studied to determine how the degree of hydrophilicity affects the PET matrix. The influence of the blends on thermal transitions has been investigated by differential scanning calorimetry (DSC), the thermal stability of the polymer/FR blend composites has been assessed by thermogravimetric analysis (TGA) and cone calorimetry has been used to study the fire reaction. It was noticed that the nanoparticles have a limited influence on the thermal transitions of the PET matrix, but zinc phosphinate acted as a plasticizer and a compatibilizer for the more hydrophobic particles. Thermogravimetric analysis results showed that the addition of silica particles and FR compound improves slightly the thermal stability of the PET systems under nitrogen and air atmospheres. Furthermore, it was noticed that the incorporation of nanoparticles gives almost no improvement in the PET fire reaction from cone calorimeter experiments. However, in the presence of Exolit OP950, the systems acted as FR in PET films and knitted structures. The heat release rate during the combustion decreased, and the thermal behaviors of these structures were closed to those with 10% wt of Exolit OP950. Copyright © 2017 John Wiley & Sons, Ltd.

Controlling the length of short electrospun polymer nanofibers via the addition of micro-spherical silica particles

Short electrospun nanofibers were fabricated by adding 1.2 µm micro-spherical silica particles with concentrations that varied from 0 to 10 wt% in a 13 wt% polymer solution. The addition of these silica particles resulted in four types of nanofibers: short, short-beaded, short aggregated-beaded, and continuous-beaded. The flow rate to fabricate short nanofibers was increased to 1 µL min−1 by the addition of 1–10 wt% silica particles, compared with the maximum flow rate of a plain polymer solution at 0.48 µL min−1. Short-beaded nanofibers were fabricated at 20 µL min−1 by the addition of 4 wt% silica particles not fabricated from the plain polymer solution. Nanofibers were cut at the edges of the micro silica particles, and the lengths were nearly in inverse proportion to the concentration of the silica particles. The lengths of the short nanofibers calculated by a cutting model, wherein the nanofibers were cut to match the portion of each micro silica particle, were consistent with the experimental results. This indicates that the lengths of short nanofibers can be simply controlled by the number of micro-spherical silica particles.

Thermal, structural and morphological properties of High Density Polyethylene matrix composites reinforced with submicron agro silica particles and Titania particles

HDPE—based composites samples filled with 2, 4, 6, 8 and 10wt.% submicron agro-waste silica particles extracted from rice husk ash (RHA) at constant 0.3wt.% Titania loading were prepared using rapra single screw extruder at temperature of 200–230°C. The extrudates were compressed with a laboratory carver press at a temperature of 230°C for 10min under applied pressure of 0.2kPa and water cooled at 20°Cmin−1. Thermal, structural and morphological properties of the composites were studied. The results of the thermogravimetric analysis (TGA) revealed that the composites with 10wt.% SiO2 have the best maximum thermal degradation temperature of 438.73°C. The crystal structure of neat HDPE, and the siliceous composites developed revealed two obvious diffractive peaks of about 21.3° and 23.7° corresponding to typical crystal plane (110) and (200) of orthorhombic phase respectively. The diffractive peaks do not shift with the addition of silica particles; this clearly indicates that the addition of silica particles did not exert much effect on the crystalline structure of HDPE. There is no much difference in the interplanar distance (d-value). Lamellar thickness (L) of HDPE increases with the addition of silica particles, which implies that silica particles aid the formation of more perfect crystals. Scanning electron microscopy studies indicated that there were chains inter diffusion and entanglement between HDPE matrix and the silica particles at lower weight fraction (2–4wt.%) of submicron silica particles which resulted into homogeneous dispersion of the particles within the matrix.

Surface behavior of hydrophilic silica nanoparticle-SDS surfactant solutions: I. Effect of nanoparticle concentration on foamability and foam stability

Hydrophilic silica nanoparticles have no tendency to adsorb at the water/air interface and they do not affect the surface behavior of pure water. In this paper, we show that this tendency remains unaltered by addition of anionic sodium dodecyl sulfate (SDS) surfactant, although the surface behavior of SDS solutions considerably changes with the addition of silica particles. Employing dynamic tensiometry, surface rheology, foamability, and foam stability experiments in presence of variable amounts of silica particles, we found that the surface activity of SDS molecules is significantly increased in the presence of nanoparticles and equivalently behaved as if higher concentrations of SDS are used. The so-called equivalent concentration values (EC) were separately measured using the tensiometry and foamability. The consistency of measured EC trends is discussed, and a new predictive tool for the foaming behavior of surfactant solutions is proposed based on the calculated EC trends from tensiometry and surface dilational rheology.The adsorption process and surface structuring of nanoparticles at the water/air interface were investigated by analyzing the surface pressure values as a function of drop surface area. We measured the standard deviation, STD, of drop shapes from their Laplacian profile during the drop compression process. It was found that STD-values abruptly change when particles form closely-packed surface structures. The STD trend is explained in detail and is shown it can be a very powerful tool for analyzing the surface adsorption and surface structuring of nanoparticles.

دراسة تاثير اضافة دقائق السليكا (SiO2)على مقاومة البلى لمواد متراكبة ذات اساس من سبيكة الالمنيوم (Al-6061 و Al-5086)

تعد المواد المت ا ركبة ذات اساس المنيوم من اهم المواد التي تدخل في مختلف الصناعات بسبب ماتملكه من خصائص جيدة مثل مقاومة البلى, الكثافة الواطئة, والمقاومة العالية نسبة الى الوزن. تم في هذا البحث تحضير مواد مت ا ركبة ذات اساس من سبيكة المنيوم ) 6061-Al ( و ) 5086-Al ( مقواة بدقائق السليكا ) 2SiO ،% ( وبنسبة وزنية ) 3.1 %2.1 ( وبحجم حبيبي مقداره ) 311 مايكرون(. المواد ،%1 المت ا ركبة حضرت بطريقة الدوامة ) Vortex method ،) حيث تم اضافة دقائق السليكا ) 2SiO ( الى المنصهر ثم الخلط بواسطة خلاط كهربائي لعمل الدوامة ثم صب الخليط المنصهر في قالب معدني اسطواني, بعد ذلك تم تقطيع وتحضير العينات لاج ا رء فحص واختبار البلى, الصلادة، الكثافة ود ا رسة التركيب المجهري للنماذج والمقارنة بينهما. تبين من النتائج التي تم الحصول عليها من خلال هذه الد ا رسة ان مقاومة البلى للمواد المت ا ركبة قد تحسنت نتيجة إضافة دقائق السليكا ) 2SiO ( مقارنة مع السبيكة الاساس وكانت مقاومة البلى للمواد المت ا ركبة ذات اساس ) 5086-Al ) اعلى من مقاومة البلى للمواد المت ا ركبة ذات اساس ) Al-6061 (. وقد تم الحصول على اعلى مقاومة بلى عند نسبة اضافة 2.1 % من دقائق السليكا ) 2SiO (. ان اضافة دقائق السليكا بالنسب اعلاه قد ساهم في تحسن قيم الصلادة مما انعكس على تحسن مقاومة البلى، وان هذا التحسن في الخواص يزداد بزيادة نسبة إضافة دقائق السليكا للسبيكة الاساس . اما بالنسبة الى خاصية الكثافة, فقد قلت قيمها للمواد المت ا ركبة بالنسبة الى السبيكة الاساس وبنسبة قليلة عند اضافة دقائقالتقوية السليكا ) 2SiO .) Aluminum matrix composite is most important materials used in various industries because of its good properties such as wear resistance, low density, and high resistance to weight ratio. In this paper, Metal matrix composites (MMCs) of the base alloy (Al-6061) and (Al-5086) reinforced by silica particles (SiO2) (1.5, 3, and 4.5 wt%) with particles size (150 µm) was prepared by stir casting using vortex technique, silica particles (SiO2) are added to the molten and then stirred the melt by electrical mixer stir to work the vortex and then pour the mixture molten into cylindrical mold and then was cutting and preparation of samples for examination and testing of wear, hardness, density and study the microstructure of the samples and the comparison between them. Results show from this study that the wear resistance of Al matrix composite its improvement due to addition of silica particles (SiO2) as compared with basis alloys, (Al-5086) matrix composite has higher wear resistance rather than (Al-6061) matrix composite. The higher wear resistance at added the 4.5 wt.% of silica (SiO2). The addition of silica particles in proportions above has contributed to the improvement of hardness which is reflected in improved wear resistance, and that this improvement in properties increases with the proportion of silica particles added to alloys base. As for the properties of density, decreases the density of Al-matrix composites as compared with base alloys with low proportion when added the silica particles (SiO2).

Highly efficient enzymatic biodiesel production promoted by particle-induced emulsification.

BackgroundAt present, the conversion of oils to biodiesel is predominantly carried out using chemical catalysts. However, the corresponding lipase-catalysed process has important advantages, which include mild reaction conditions and the possibility of using cheap, low quality feedstocks with a high free fatty acid content. Further increases in the efficiency of the enzymatic process are desired to make it even more attractive and suitable for large-scale applications.ResultsHerein, we present a simple and efficient two-phase lipase-catalysed system for the preparation of biodiesel in which different parameters (biocatalyst composition, ethanol concentration and the presence of additives) were optimised in order to obtain the maximum productivity starting from triolein with a high free oleic acid content. In the two-phase system, the enzyme tolerated high-ethanol concentrations, which made it possible to reach high conversions. The addition of silica particles increased the reaction rate substantially. It was suggested that such particles can catalyse acyl migration as a step to the full conversion to glycerol and biodiesel. However, in the system studied here, the effect of the particles was shown to be due to the formation of smaller and more uniform emulsion droplets leading to better mass transfer between the two phases. Particles of widely different size had positive effects, and the highest rate was obtained with silica particles derivatised with phenyl groups. The optimal conditions were applied to the solvent-free ethanolysis of rapeseed oil, and a yield of 96% was reached in 5 h. Under the mild conditions used, chemical catalysts were inefficient.ConclusionsTriacylglycerol oils with a high free fatty acid content can be efficiently converted to ethyl esters using Thermomyces lanuginosus lipase as the catalyst in an aqueous/organic two-phase system. Fast mass transfer can be achieved using silica particles, which helped to decrease the size of the emulsion droplets and thus led to a more efficient process. The high-ethanol concentration tolerated by the lipase in this system made it possible to reach almost quantitative yields.