SiO2 Suspension Research Articles

Studi Awal Sintesis ZnO/SiO2 dengan Silika dari Limbah Padat Geothermal dan Uji Performansinya dalam Penghilangan Metilen Biru

Industrial development impacts environmental problems, such as the emergence of wastewater containing methylene blue. In this research, SiO2 was composited with ZnO to remove methylene blue. The steps of this study include SiO2 extraction from geothermal solid waste, ZnO/SiO2 synthesis, and methylene blue removal test. The process of extracting SiO2 from geothermal solid waste used the sol-gel method. The FTIR analysis showed that SiO2 contains siloxane group (Si-OH) and silanol group (Si-O-Si). ZnO/SiO2 synthesis was done by making SiO2 suspension and continued with adding the addition of several Zn(NO3)2.6H2O. The FTIR analysis of ZnO/SiO2 showed no absorption at the wavenumber 960 cm-1 and there is a shoulder around the number 950 cm-1 which indicates the vibration of Si-O-Zn. Meanwhile, methylene blue removal tests were carried out on artificial wastewater. Based on the research results, the highest percent removal (99%) was obtained under operating conditions, including a dose of 500 mg/L, pH 10, and contact time of 30 minutes. Based on box-benkhen analysis, it is known that dose and pH singularly affect the percent removal, while contact time does not affect the percent removal. The optimization results obtained optimum conditions for methylene blue removal at a dose of 581.952 mg/L, pH of 10, and contact time of 30 minutes. Percent removal in conditions without irradiation and with irradiation of UV light were 98.758% and 99.178%. It shows that the adsorption process is the main process in removing methylene blue, while the photocatalytic process has little effect because it is possible that only a small amount of ZnO can attach to the surface of SiO2.

Wetting-and scaling-resistant superhydrophobic hollow fiber membrane with hierarchical surface structure for membrane distillation

In this study, we address the challenge of wetting and scaling in membrane distillation (MD) by developing a robust superhydrophobic poly(vinylidene fluoride) (PVDF) hollow fiber membrane. To achieve this, we utilized co-extrusion technology and subsequent fluorination treatment to create micro-nanoscale surfaces. The fabrication process involved extruding a SiO2 suspension onto the outermost layer of a triple-orifice spinneret to create a hierarchical structure, followed by 1H,1H,2H,2H-perfluorooctyltrichlorosilane (FAS) modification to lower the membrane surface energy. This resulted in a highly water-repellant membrane, as evidenced by contact angle measurements of 153°, 147°, and 141° for water, sodium dodecyl sulfate (SDS) solution (0.4 mM), and saline SDS solution (0.4 Mm SDS and 35 wt% NaCl), respectively, indicating increased resistance to liquid penetration. Through direct contact membrane distillation (DCMD) experiments, we demonstrated that the PVDF/FAS membrane exhibited excellent wetting resistance to seawater (3.5 wt% of NaCl) with SDS at varying concentrations. Furthermore, the membrane effectively hindered the CaSO4 scaling by reducing both heterogeneous nucleation and the tendency of bulk crystal deposition on the membrane outer surface. Overall, the developed approach for fabrication of superhydrophobic PVDF hollow fiber membrane presents a promising solution for facile and scalable manufacturing of anti-wetting and anti-scaling MD membranes. This advancement has significant implications for enhancing the practical application of MD technology.

Lipid characteristics of lung tissue in silicosis rat model were studied based on lipid metabolomics

Silicosis is a common occupational disease caused by the long-term inhalation of large amounts of silica dust. Lipid metabolism plays an important role in the progression of silicosis, but its contributing mechanism remains unclear. The aim of this study was to investigate the differential lipid metabolites and active metabolic pathways in silicosis rat lung tissue. We first constructed a silicosis rat model, and randomly divided 24 male SD rats into control group (C), silicosis group for 1 week (S1W), silicosis group for 2 weeks (S2W) and silicosis group for 4 weeks (S4W) with 6 rats in each group. 1 mL SiO2 suspension (50 mg/mL) or normal saline were injected into the trachea, and the rats were killed at 1 week, 2 weeks and 4 weeks, respectively. The lung tissue pathology of the rats was observed by HE staining and VG staining, and the plasma TC and FC levels were detected by the kit. Western blot was used to detect the expression of lipid-related factors CD36, PGC1α and LXR. In addition, lipidomics analysis of lung tissue samples was performed using UPLC-IMS-QTOF mass spectrometer to screen out potential differential metabolites in silicosis models and analyze lipid enrichment, and verified the expression of differential gene CHPT1 in the metabolic pathway. HE and VG staining showed that the number of nodules and fibrosis increased in a time-dependent manner in the silicosis model group, and the levels of TC, FC and CE in silicosis plasma increased. Western blot results showed that PGC1α and LXR decreased in the silicosis model group, while CD36 expression increased. In addition, metabolomics screened out 28 differential metabolites in the S1W group, 32 in the S2W group, and 22 in the S4W group, and found that the differential metabolites were mainly enriched in metabolic pathways such as glycerophospholipid metabolism and ether lipid metabolism, and the expression of differential gene CHPT1 in the metabolic pathway was decreased in the silicosis model group. These results suggest that there are significant changes in lipid metabolites in lung tissue in silicosis rat models, and glycerophospholipid metabolism was significantly enriched, suggesting that glycerophospholipids play an important role in the progression of silicosis. The differential metabolites and pathways reported in this study may provide new ideas for the pathogenesis of silicosis.

Uncovering mechanisms of Baojin Chenfei formula treatment for silicosis by inhibiting inflammation and fibrosis based on serum pharmacochemistry and network analysis

BackgroundBaojin Chenfei formula (BCF), a Chinese herbal formula, has significant effects on improving the clinical symptoms of patients with silicosis. However, its active compounds and the underlying mechanisms have not yet fully been elucidated. PurposeThis study aimed to explore the underlying mechanisms of BCF in treating silicosis. MethodsThe rat model of silicosis was developed via a single intratracheal instillation of SiO2 suspension to examine the therapeutic impacts of BCF on silicosis. Subsequently, the active compounds, targets, and mechanisms of BCF were analyzed based on serum pharmacochemistry and network analysis. Finally, the underlying mechanisms of representative compounds of BCF were validated in vitro experiments. ResultsBCF significantly alleviated SiO2-induced silicosis in rats, evidenced by improved lung function, decreased pathological injury, and reduced inflammatory response and fibrosis. 19 active compounds were identified from the rat serum samples after BCF gavage. Subsequently, 299 targets for these 19 compounds in BCF and 257 genes related to silicosis were collected. 26 overlapping targets, including AKT1, TNF, IL6, MAPK3, EGFR, and others, were obtained from the intersection of the 299 BCF-related targets and 257 silicosis-associated genes. These overlapping targets mainly corresponded to glycyrrhetic acid and paeoniflorin and were mainly associated with positive regulation of smooth muscle cell proliferation, positive regulation of MAP kinase activity, and inflammatory response. In vitro experiments also demonstrated that the representative compounds of BCF (glycyrrhetic acid and paeoniflorin) could suppress inflammatory response by the MAPK pathway, and also inhibited fibroblast activation by the EGFR-PI3K-AKT pathway. ConclusionActive compounds of BCF, such as glycyrrhetic acid and paeoniflorin, could suppress inflammatory response by the MAPK pathway and suppress fibroblast activation by the EGFR-PI3K-AKT pathway. These might be the mechanisms of BCF in treating silicosis.

Discrete amplified sensing of temperature and strain

In this paper, a parallel connected optical fiber interferometer is proposed, aiming to improve the strain and temperature sensitivity by using the Vernier effect (VE). The sensor is fabricated by an optimized 3 × 2 step manufacturing process, and implements simple and cost-effective techniques such as cleaving, splicing and gluing. The sensor consists of two Fabry–Perot interferometers (FPIs) with different propagation media, one is air and the other is a SiO2 suspension core, named C1 and C2 respectively. Separate FPIs are used as sensing units in temperature and strain sensing, and another FPI is used as a reference unit. It is proved that when the fine fringe of FPI is redshifted, the envelope is blueshift when the FPI with a large free spectral range (FSR) is used as the sensing unit, the envelope is redshift when the FPI with a small FSR is used as the sensing unit. The results show that the temperature and strain sensitivities are 188.38pm/°C and 201.18pm/μɛ, with amplification factors of 21.2 and 19.6, respectively. In addition, the sensor has a very low cross-sensitivity because C1 is far from the temperature environment and the free end of C2 cannot be fixed for strain measurement.

Biomolecules adsorption to trigger the self-assembly of nanospheres and nanorods

HypothesisThe self-assembly (SA) of nanostructures triggered by the adsorption of biomolecules (BSA) is investigated as a platform to develop diagnostics and functional applications. Mixing nanostructures of different morphologies; SiO2 nanospheres (NS) to a cellulose nanorod crystals (CNC) leads to the formation of short range ordered domains in the dried film. Adding biomolecules-treated SiO2 NS into the CNC develop the long range ordered assembly in the composite film. ExperimentsThe CNC-SiO2 composite films were prepared by mixing CNC suspension (3 wt%) with the SiO2 NS of different concentration (0.5–5 mg/mL) followed by drying at the ambient conditions. The CNC-SiO2 @BSA films are prepared by first mixing the BSA (1 mg/mL) with the SiO2 suspension of different concentrations. Later the SiO2 @BSA suspension was mixed with the CNC and left for drying at the ambient conditions. The self-assembly mechanisms of CNC, SiO2 and BSA are studied by combining SEM, DLS, UV-Vis, QCM-D and SAXS analysis. FindingsThe SA mechanism of aqueous suspensions of CNC blended with SiO2 NS pre-treated with BSA (by adsorption) is studied by a combination of small angle X-ray scattering (SAXS), scanning electron microscopy (SEM), UV-Vis spectroscopy (UV-Vis), dynamic light scattering (DLS) and quartz crystal microbalance with dissipation (QCM-D). Both CNC and SiO2 NS are negatively charged and have demonstrated self-assembly ability driven from a combination of long- and short- range order arrangement. Adding SiO2 NS to a CNC suspension disrupts the original SA of both CNC and SiO2, which leads to the formation of small, short- range ordered domains of large polydispersity. Surprisingly, adding BSA-treated SiO2 NS into the CNC network enhances the arrangement of CNC and NS towards a new system with long range ordered assembly. The SA mechanisms of cellulose-SiO2 composites result from the balance of electrostatic repulsion and van der Waal attraction in the structure factor, radial distance distribution and potential of mean force. Understanding the effect of biomolecule adsorption on the self-assembling mechanisms of CNC nanorods with SiO2 nanospheres enables the efficient engineering of catalysis, biosensors and diagnostics.

Abiotic transformation of synthetic progestins in representative soil mineral suspensions

Altrenogest (ALT), drospirenone (DRO), and melengestrol acetate (MLA) are three highly potent synthetic progestins that can be released into agricultural soils, while their fate in soil minerals remains unclear. This study explored the transformation of these progestins in MnO2, SiO2, and ferrihydrite suspensions and identified their transformation products (TPs) via high resolution mass spectrometry and density functional theory calculations. Transformations were only observed for DRO and MLA in SiO2 suspension and ALT in MnO2 suspension (half-lives = 0.86 min – 9.90 day). ALT transformation was facilitated at higher MnO2 loadings, while DRO and MLA transformations were inhibited at higher SiO2 loadings. These data indicated that hydrophobic partitioning interaction was dominant at higher SiO2 loadings rather than specific interaction, which limited subsequent surface-catalyzed transformation. ALT transformation rate decreased with increasing pH because MnO2 reduction requires proton participation. In contrast, relatively high pH facilitated MLA and DRO transformation, indicating that base-catalyzed hydrolysis occurred in SiO2 suspension. The clustermap demonstrated the formation of abundant TPs. Lactone ring and acetoxy group hydrolysis was the major transformation pathway for DRO and MLA, with estimated yields of 57.7% and 173.2% at 6 day, respectively. ALT experienced C12 hydroxylation and formed the major TP 326g (yield of 15.4% at 8 hr). ALT also experienced allyl group oxidation and subsequent C5 hydroxylation, forming the major TP 344a (yield of 14.1% at 8 hr). This study demonstrates that TPs of metastable progestins are likely the main species in soils and that TP identification is a particular priority for risk assessment.

Low-temperature welded PAN/TPU composite nanofiber membranes for water filtration

Nanofiber membranes have attracted considerable interest in water filtration owing to their unique structure and excellent performance, but large pore size and wide pore size distribution combined with weak inter-fiber strength are major limitations for practical applications. This work describes a facile and efficient method for nanofiber membrane fabrication with stable mechanical properties, high separation and excellent antifouling performance. The nanofiber membranes are prepared from a mixture of a low melting point polymer (thermoplastic polyurethane, TPU, Tm = 52 °C) and a structural skeleton-forming polymer (polyacrylonitrile, PAN, Tm = 317 °C) that undergoes electrospinning and hot-pressing. Hot-pressing treatment at 50–80 °C and 2 MPa melts the TPU phase to create inter-fiber connections, thereby reducing the nanofiber membrane pore size and improving its dimensional stability and mechanical properties. The connectivity of the nanofiber membrane can be controlled by adjusting the ratio of TPU and PAN in the nanofiber and the hot-pressing temperature. The tensile strength and Young's modulus of the hot-pressed membrane are 24.5 MPa and 630.6 MPa, which are 4.8 times and 6.0 times higher than the nascent membrane, respectively. The membrane pressed at 80 °C shows excellent filtration performance, with a high pure water flux of 8490 L m−2 h−1 and active sludge and 100 nm SiO2 suspension retention efficiency of 99.99%. In addition, the hot-pressed membranes exhibited excellent antifouling performance and mechanical properties, meet the reusability and long-term service demand. Therefore, hot-pressed composite nanofiber membranes made of low melting point thermoplastic polymer and a skeleton polymer provide a facile and economical approach for the development of high-performance separation media.

Effects of suspension processing conditions on the multi-scale structural changes of photocured SiO2 bodies during sintering process: An operando observation using optical coherence tomography

The relationships between the processing methods of photocurable SiO2 suspensions, powder dispersion states, material processability, and the structural changes of photocured SiO2 bodies during their sintering into transparent glass components were investigated. Using an inter-particle photo-cross-linkable SiO2 suspension as the model system, three series of suspensions with different dispersion states but the same compositions were designed via different powder processing routes. The effects of the differences in the particle dispersion states on the real-time multi-scaled structural changes of photocured bodies during sintering were elucidated via operando observation using an optical coherence tomography (OCT) system equipped with an infrared image furnace. The photocured body prepared using the well-dispersed suspension starts to gradually densify from the outside, finally reaching a fully densified state. Furthermore, during the densification process, the photocured body warped, and then the structure recovered owing to the earlier densification at the bottom region of the sample, where the infrared light was focused for heating. Contrastingly, when the suspension contained agglomerates, an un-densified area was observed in the sintering material in the form of microstructures, which remained in the material after sintering. The in-line transparency of the sintered SiO2 material was consistent with those of the microstructures observed using OCT.

Microfluidic Study of the Effect of Nanosuspensions on Enhanced Oil Recovery.

The essential advantages of microfluidic studies are the excellent visualization of the processes of oil displacement from the porous medium model, simple cleaning, and the possibility of the repeated use of the microfluidic chip. The present article deals with the process of oil displacement by suspension flooding using a microfluidic chip, simulating a porous medium, and the suspensions of silicon dioxide nanoparticles (22 nm). The mass concentration of nanoparticles in suspensions ranged from 0.1 to 2 wt%. Five mass concentrations (0.125 wt%, 0.25 wt%, 0.5 wt%, 1 wt% and 2 wt%) were considered. The article presents the experimental photographs of the oil displacement process by water and SiO2 suspension. It is shown that, with the increasing concentration of nanoparticles, the oil recovery factor increases. A significant effect is observed at 0.5 wt% concentration of nanoparticles. It is shown that the increase in oil recovery during flooding by SiO2 suspension with the maximum concentration was 16%.

Photocatalytic and Superhydrophilic TiO2‐SiO2 Coatings on Marble for Self‐Cleaning Applications

AbstractThe application of photocatalytic and self‐cleaning titanium dioxide (TiO2) nanomaterials coating on the stone of architectural heritage (particularly on marble) can be used to preserve their aesthetic qualities. The present work describes the effect of dipping time on the wetting property of coatings and the effect of UV irradiation on the coating in terms of hydrophilicity. The suspension of TiO2‐SiO2 is prepared by adding 30–50 nm in size TiO2 particles in the sol–gel processed SiO2 solution. The water contact angle (WCA) decreases with increasing dipping time of piece of marble in TiO2 – SiO2 suspension. Also the hydrophilicity of coating increases with increasing UV illumination time. The 2D and 3D laser microscope analysis revealed surface structure and stable surface roughness of 1.0 µm. Such type of superhydrophilic TiO2 – SiO2 coating may be used to protect architectural heritage and buildings.

Oxidation protective coating of Y2O3-Na2SixO2x+1 composite on graphite crucible for high temperature applications

Oxidation and corrosion protective coatings on graphite are essential for its high temperature applications. In the present work, oxidation protective coating on graphite was achieved with a combination of Y2O3 and SiO2 suspension with NaOH in methanol. Study showed that the optimized composition of the desired coating was Y2O3–15 wt% SiO2 (i.e., 2 g mixture of Y2O3 and SiO2 powder containing 0.3 g of SiO2 which is 15% of the total powder content if expressed in weight) with 5 M NaOH in 10 mL methanol. This protective coating on graphite was stable up to 1473 K for 30 min in Ar ambient before visible cracks appeared. The compositions of SiO2: NaOH were varied (5 mmol:5 M, 10 mmol:5 M and 5 mmol:10 M) to examine the roles of these two components in the overall adhesiveness of the coating. SiO2 and NaOH acted as inorganic binders and formed in-situ intermediate layers during sintering which held Y2O3 layer with the graphite surface. The coated graphite blocks and crucibles were characterized by X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDS), differential thermal analysis and thermogravimetric analysis (DTA/TGA) and Fourier transform infrared spectroscopy (FTIR). The oxidation protective nature of the coating was tested by heating the coated crucible at 1273 K for 1-15 h in air atmosphere. The effective adhesion of oxidative coating on graphite was explained.

High coercivity SmCo5 synthesized with assistance of colloidal SiO2

SmCo5 is one of the most promising candidates for achieving a hard magnet with a high coercivity. Usually, composition, morphology, and size determine the coercivity of a magnet, however, it is challenging to synthesize phase pure SmCo5 with optimal size and high coercivity. In this paper, we report on the successful synthesis of phase pure SmCo5 with spherical/prolate spheroids shape. Size control is obtained by utilizing colloidal SiO2 as a template preventing aggregation and growth of the precursor. The amount of SiO2 nanoparticles (NPs) in the precursor tunes the average particle size (APS) of the synthesized SmCo5 with particle dimension from 740 to 504 nm. As-prepared pure SmCo5 fine powder obtained from using 2 ml SiO2 suspension possesses an APS of 625 nm and exhibits an excellent coercivity of 2986 kA m−1 (37.5 kOe) without alignment of the particles prior to magnetisation measurements. Comparing with a reference sample prepared without adding any SiO2 NPs, an enhancement of 35% of the coercivity was achieved. The improvement is due to phase purity, stable single-domain (SSD) size, and shape anisotropy originating from the prolate spheroid particles.

Wet Mixing with Organic Solvent for Synthesized cis-1,4-Polyisoprene-Based Rubber Composites.

In this work, well-dispersed fumed SiO2/cis-1,4-polyisoprene rubber (IR) masterbatch was first obtained through an effective wet mixing method, and the properties of the corresponding vulcanizate were studied. Before curing with activator and sulfur, IR solution was blended and co-coagulated with SiO2 suspension modified by bis(3-trimethoxysilypropyl) tetrasulfide in n-hexane. The modification of TESPT imparted evenly distributed SiO2 particles in IR and improved interfacial binding among SiO2 and IR. Hence, the prepared compound presented better processability and the corresponding vulcanizate presented higher physical performance, including higher tensile strength, lower heat buildup, and better fatigue resistance than that prepared in the dry mixing method. Additionally, higher wet skid resistance and lower rolling resistance could be observed in fabricated SiO2/IR vulcanizate. The employed wet mixing method is economical and efficient, which is promising in preparing rubber composites with comprehensive performance.

Low-Frequency Shear Elasticity of a Colloid Nanosuspension

The paper presents the experimental results of an acoustic impedance study of low-frequency (105 Hz) shear elasticity of a colloidal SiO2 suspension of differently sized particles in polyethylene siloxane liquid PES-2. The agreement of the experimental results obtained by different variants of the acoustic resonance method confirms that the low-frequency shear elasticity of colloidal nanoparticle suspensions is a bulk property.

The preparation and study of multilayer structured SiO2–TiO2 film: the effects of photonic crystals on enhanced photocatalytic properties

Herein, SiO2-photonic crystal/TiO2 composite film (STF) with multilayer structure was designed and fabricated via self-assembly method and spin coating method. The micro-morphology and optical properties of the STF were characterized by scanning electron microscope (SEM) and UV/Vis/NIR spectrophotometer respectively. The photocatalytic activity of the STF was tested via the degradation rate of rhodamine B. The characterization results indicate that the STF has a regular ordered structure when the amount of ammonia is 3 mL and the concentration of SiO2 suspension is 1%, and SiO2 can be effectively combined with TiO2, so the STF has the best photocatalytic performance. The double-layer SiO2-photonic crystal/TiO2 composite film (DSTF) was further prepared and compared with the single-layer SiO2-photonic crystal/TiO2 composite film (SSTF). The photocatalytic properties of the DSTF are better than that of the SSTF. Finally, the mechanism of STF with enhanced photocatalytic performance is discussed, indicating that photonic crystal can effectively enhance the utilization of light which are near the wavelength of the center band gap, and then improve the photocatalytic performance of the photocatalyst.

Rapid three-dimensional structuring of transparent SiO2 glass using interparticle photo-cross-linkable suspensions

Photo-curable suspensions are important materials for shaping complex-structured ceramic and glass components. However, most systems undergo slow debinding and sintering so to avoid structural collapse by rapid gas generation from polymers. Here, we propose a new strategy to fabricate interparticle photo-cross-linkable suspensions for rapid three-dimensional structuring with short debinding and sintering times. SiO2 particles modified with polyethyleneimine complexed with oleic acid (PEI-OA) are dispersed into a refractive-index-tuned solvent, where a photo-radical initiator and a lower-than-typical amount of multifunctional acrylates (MAs) were dissolved. The SiO2 suspension is cured by the photo-radical polymerization of MA and the Michael additive reaction between polymerized MA and amino groups of PEI-OA on SiO2 particles. These photo-curable suspensions can be employed in various shaping processes, from micro-scale stereolithography to centimeter-scale silicone molding. The SiO2 green compacts with complex structures are also debinded and sintered into transparent glass components by rapid heating.

Hydrophilic nano-SiO2/PVA-based coating with durable antifogging properties

Hydrophilic SiO2/poly(vinyl alcohol) (PVA) coating prepared by solution blended method showed high light transmittance and durable antifogging performance. The effects of SiO2 content and pH value of SiO2 suspension on the morphology and properties of hydrophilic coating were studied by Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, contact angle test, ultraviolet visible light spectrophotometer, and antifogging test. Results showed that the PVA had good compatibility with nano-SiO2 because of the formation of Si–O–C chemical bond at the interface between nano-SiO2 and PVA. When prepared at pH = 7, SiO2/PVA coatings (SiO2/PVA mass ratio of 0.8) were hydrophilic, with a water contact angle of 22.9°, and exhibited papilla-like surface features (RMS = 7.6 nm). Polyethylene (PE) samples coated with this SiO2/PVA film exhibited a light transmittance of up to 90%, between 560 and 700 nm, and remained fog-free for more than 1 month after exposure to water at 60°C (QB/T 4475-2013 standard). Water-resisting and wear-resisting tests revealed that antifogging coatings demonstrated excellent mechanical properties.

Alumina particle surface interaction in copolymer of isobutylene and maleic anhydride aqueous solution characterized by colloidal probe atomic force microscopy

ABSTRACT By the addition of isobutylene-maleic anhydride copolymer, Al2O3 aqueous suspensions retain fluidity for approximately 1 h and then gelation occurs. The bi-functionality mechanism as dispersant and gelling-agent of the copolymer was investigated by colloidal probe atomic force microscopy. The time-dependent surface interaction between Al2O3 particles and sapphire substrates were compared to those of SiO2, the suspension of which did not appear experience gelation. After 40 min, repulsive forces increased slightly and attractive forces decreased dramatically with short-range character, corresponding to the dispersant action of the copolymer in aqueous Al2O3. As aging time increased to 2 h, a large repulsive force and long-range attractive force developed. With the aging time going to 3 h, the repulsive force disappeared and only long-range attractive forces remained. On the contrary, in the case of SiO2, long-range repulsive force was only observed after the addition of ISOBAM, and long-range attractive interactions were not observed with increased of aging time. However, no time-dependent long-range attractive interaction was observed in the SiO2 suspension. Therefore, it seems gelation of the Al2O3 aqueous suspension was correlated to the long-range attractive interaction between Al2O3 surfaces.

A free-standing superhydrophobic film for highly efficient removal of water from turbine oil

A free-standing superhydrophobic film is prepared by sequentially dip-coating a commercially available filter paper with nano SiO2 suspension, epoxy emulsion, and octyltrimethoxysilane solution. A surface with micro- or nano-roughness is formed because SiO2 nanoparticles are uniformly and firmly adhered on the backbone of the filter paper by the cured epoxy resin. Furthermore, the surface energy is significantly reduced because of introducing octytrimethoxysilane. Such a surface structure makes the prepared film a superhydrophobic material. Due to its free-standing nature, this superhydrophobic film can be used to remove water from turbine oil by filtration. The efficiency of water removal is high (up to 94.1%), and the filtration process is driven solely by gravity without extra energy consumption. Because of the facile fabrication process and the high efficiency of water removal, this free-standing superhydrophobic film may find application in power industry.