SiO2 Suspension Research Articles

Erratum: Preparation of Poly(pentafluorophenyl acrylate) Functionalized SiO2 Beads for Protein Purification.

Erratum: Preparation of Poly(pentafluorophenyl acrylate) Functionalized SiO2 Beads for Protein Purification.

Effects of abnormal expression of fusion and fission genes on the morphology and function of lung macrophage mitochondria in SiO2-induced silicosis fibrosis in rats in vivo

Silicosis is a serious occupational disease affecting millions of related workers. Many studies showed lung macrophages play an important role in the disease. However, the changes of macrophages are not fully characterized and the mechanisms need further investigations. The objectives of this work were to evaluate the effects of abnormal expression of fusion and fission genes on the morphology and function of lung macrophage mitochondria in SiO2-induced silicosis fibrosis in rats. In this study, the rats were injected with 1 mL of SiO2 suspension (100 mg/mL) into the lungs to establish silicosis models, and killed after 30, 60, and 120 days. The rats which were injected with normal saline (1 mL) into lungs were used as control. The lungs of rats were taken for pathological observation. Lung macrophages were collected to measure the number, activity, level of MDA and SOD, and relative content of fusion (Mfn1, Mfn2) and fission (Fis, DRP) genes. Subsequently, mitochondria were extracted from the macrophages to measure the changes of function, including MDA, SOD, ATP, and ATPase. We found that silica dust inhalation led to the proliferation of collagen fibers in the lung tissue. During this process, the number and activity of macrophages increased, the degree of lipid peroxidation increased, and the expression of mitochondrial fusion and fission genes was abnormal. Moreover, the mitochondrial lipid peroxidation level in macrophages increased, the production of ATP and the activity of ATPase decreased, and the abnormal forms of mitochondria occurred. Our results indicated that the morphology and function of mitochondria in macrophages changed during the progress of silicosis, which were related to the abnormal expression of fusion and fission genes.

Rapid fabrication and characterization of SiO2-Fe2O3 heterogeneous metamaterial via one-step self-assembly process

SiO2-Fe2O3 heterogeneous metamaterial was fabricated by one-step self-assembly process. The micro-morphology and optical properties of the SiO2-Fe2O3 heterogeneous metamaterials were characterized by scanning electron microscope (SEM) and UV/Vis/NIR spectrophotometer respectively. The crystal phase of the calcined Fe2O3 powders was characterized by X-ray diffraction (XRD). The influences of the concentration of SiO2 suspension and voltage on heterogeneous metamaterials are discussed. The model of SiO2-Fe2O3 heterogeneous photonic crystal was established, and the wavelength of the bandgap center was simulated and analyzed. The results show that the ordered SiO2-Fe2O3 heterogeneous metamaterial can be successfully obtained by a one-step self-assembly process with no voltage when the concentration of SiO2 suspension is 3% (in a short time). In the suspension system, the voltage is not beneficial to the self-assembly process, and even destroys the electrode cathode. As can be seen from transmission spectra, the as-prepared samples have three bandgaps, and the absorption peaks are obvious in the near infrared range (1235˜1419 nm). In this paper, we show that the application of this composite system can avoid dependence on the ITO electrode material.

Patterned Flexible Electrochromic Device Based on Monodisperse Silica/Polyaniline Core/Shell Nanospheres

The developments of inexpensive, lightweight, low-power and flexible electrochromic devices have gained considerable attention. In this respect, the flexible, patterned and electrochromic device was successfully assembled. The flexible indium tin oxide/polyethylene terephthalate (ITO/PET) was used as transparent conductive substrates. the spray-coated monodisperse silica/polyaniline (SiO2/PANI) core/shell nanosphere film was used as electrochromic layer, and the monodisperse SiO2/PANI core/shell nanosphere were synthesized by in situ chemical oxidative polymerization of aniline in monodisperse SiO2 suspension. LiClO4/PMMA/PC gel was used as polymeric electrolyte, and spray-coated PEDOT:PSS film electrode was used as counter electrode. The flexible electrochromic device shows large optical contrast, fast response speed, high coloration efficiency and excellent cycling stability. And the flexible electrochromic device retains its excellent electrochromic performance after 500 cycles of bending. Moreover, the high-quality patterns were successfully prepared by spray-coated method. The patterned electrochromic films exhibit multicolor range from colorless, light yellow, green and dark blue. And the patterned electrochromic device also exhibits good flexible, large optical modulation. The patterned flexible electrochromic device has promising application in electronic books, flexible electronic cards, flexible energy efficient display and advertising boards.

MECHANISM OF ELECTROCOAGULATION OF CHAMBER PRODUCT AFTER FLOTATION OF CYCLONE DUST OF SILICON PRODUCTION

Spheroidal micro silica has a large specific-surface. This makes it indispensable for the manufacture of composite materials: construction mixtures, paints, rubber, adsorbents, etc. In the process of studying the properties of dust formed in the production of silicon, it was established that practically all of the quartzite carried away in the form of a fine dust phase into the gas removal and gas cleaning system is represented by spheroidized micro- and nanoparticles of SiO2 with a carbon impurity that is invariably present also in the finely dispersed state. One of the ways to extract carbon and amorphous silicon oxide from the dust cyclone is flotation. As a result of flotation, 29% of the sand fraction, 40% of the foam product enrichedcarbon, and 31% of the chamber product enriched SiO2 were obtained. It is shown that the target nanofraction of amorphous silica from the chamber product after flotation can be extracted by electrocoagulation. The dependence of the mass of the coagulum on the current density on aluminum electrodes was obtained during electrocoagulation of the chamber product. It is established that under the action of current on the system under investigation, the metal of the cathode and the anode dissolve. The mechanism of electrocoagulation is shown. The chamber product is a stable finely dispersed SiO2 suspension with a pH of 8-9. Since the surface of the silica is hydrophilic, OH- is adsorbed on it and the surface of the dispersed particle is charged negatively. As a result of electrochemical and chemical dissolution of aluminum electrodes, the aluminum hydroxide formed has a positive charge. The different particles stick together, as a result of which their dimensions increase, coagulation takes place, and then precipitation occurs.Forcitation:Petrovskaya V.N., Kondrat’ev V.V., Petrovskiy A.A. Mechanism of electrocoagulation of chamber product after flotation of cyclone dust of silicon production. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 10. P. 68-74

Al2O3\u2013TiO2/ZrO2\u2013SiO2 based porous ceramics from particle-stabilized wet foam

The porous ceramics based on Al2O3–TiO2/ZrO2–SiO2 from particle-stabilized wet foam by direct foaming were discussed. The initial Al2O3–TiO2 suspension was prepared by adding TiO2 suspension to partially hydrophobized colloidal Al2O3 suspension with equimolar amount, to form Al2TiO5 on sintering. The secondary ZrO2–SiO2 suspension was prepared using the equimolar composition, and to obtain ZrSiO4, ZrTiO4, and mullite phases in the sintered samples, the secondary suspension was blended into the initial suspension at 0, 10, 20, 30, and 50 vol%. The wet foam exhibited an air content up to 87%, Laplace pressure from 1.38 to 2.23 mPa, and higher adsorption free energy at the interface of approximately 5.8×108 to 7.5×108 J resulting an outstanding foam stability of 87%. The final suspension was foamed, and the wet foam was sintered from 1400 to 1600 °C for 1 h. The porous ceramics with pore size from 150 to 400 μm on average were obtained. The phase identification was accomplished using X-ray diffraction (XRD), differential thermal analysis (DTA), and thermogravimetric analysis (TGA), and microstructural analysis was performed using field emission scanning electron microscopy (FESEM).

Rapid in-situ solidification of SiO2 suspension by direct coagulation casting via controlled release of high valence counter ions from calcium iodate and pH shift

Rapid in-situ solidification of SiO2 suspension under the joint action of releasing calcium ions and shifting pH has been proposed. When the suspension was heated up to 60℃, decomposition of calcium iodate which released calcium ions, as well as hydrolysis of diacetate (GDA) which shifted the pH toward the isoelectric point, both contributed to the solidification of suspension. The controlled coagulation of SiO2 suspension could be realized via controlled release of high valence counter ions and pH shift at 60℃ within 30min, which could considerably shorten the coagulation time compared with present reported results (1–3h). Green body prepared by heating the SiO2 suspension with 6.5gL−1 calcium iodate and 2.0vol% GDA at 60℃ for 30min shows uniform microstructure with compressive strength of close to 0.3MPa. SiO2 ceramics sintered at 1275℃ for 3h possess homogeneous microstructure with bulk density of 2.06gcm−3 and flexural strength of 40.3MPa.

Particle Stabilized Wet Foam to Prepare SiO<sub>2</sub>-SiC Porous Ceramics by Colloidal Processing

Porous ceramics with tailored pore size and shape are promising materials for the realization of a number of functional and structural properties. A novel method has been reported for the investigation of the role of SiC in the formation of SiO₂ foams by colloidal wet processing. Within a suitable pH range of 9.9 ~ 10.5 SiO₂, particles were partially hydrophobized using hexylamine as an amphiphile. Different mole ratios of the SiC solution were added to the surface modified SiO₂ suspension. The contact angle was found to be around 73°, with an adsorption free energy 6.8 × 10 −12 J. The Laplace pressure of about 1.25 ~ 1.6 mPa was found to correspond to a wet foam stability of about 80 ~ 85%. The mechanical and thermal properties were analyzed for the sintered ceramics, with the highest compressive load observed at the mole ratio of 1:1.75. Hertzian indentations are used to evaluate the damage behavior under constrained loading conditions of SiO₂–SiC porous ceramics.

Influence of solution pH, supporting electrolyte presence and solid content on the stability of aqueous nanosilica suspension

The effects of solution pH, supporting electrolyte presence and solid content on nanosilica suspension stability were examined. The turbidimetry method was applied to monitor the changes in the system stability in the short (about 2h) and long (about 18 days) periods of time. The stability coefficients and aggregate diameters were calculated numerically to estimate colloidal system properties. The sodium chloride presence (as a supporting electrolyte) improves the stability conditions of SiO2 suspension. The greatest effect of solution pH change is observed in the aqueous medium. The most unstable system occurs at pH 10.6 after 18 days.

Correlation between the Photocatalytic Degradability of PAHs over Pt/TiO2‐SiO2 in Water and Their Quantitative Molecular Structure

The correlation between the photocatalytic degradability of polycyclic aromatic hydrocarbons (PAHs) over Pt/TiO2‐SiO2 in water and their quantitative molecular structure was studied. Six PAHs, namely, naphthalene, fluorene, phenanthrene, pyrene, benzo[a]pyrene, and dibenzo[a,h]anthracene, were tested in Pt/TiO2‐SiO2 suspension under UV irradiation. The results showed that the degradation efficiencies of the higher molecular weight PAHs were enhanced significantly in the presence of Pt/TiO2‐SiO2, while the degradation efficiencies of the lower molecular weight PAHs were decreased in the presence of Pt/TiO2‐SiO2. Both the photolysis and photocatalysis of all PAHs fit the pseudo‐first‐order equation very well, except FL. Quantitative analysis of molecular descriptors of energy of the highest occupied molecular orbital (Ehomo), energy of the lowest unoccupied molecular orbital (Elumo), and the difference between Elumo and Ehomo, GAP (GAP = Elumo − Ehomo), suggested that the GAP was significant for predicting a PAHs’ photocatalytic degradability. Through comparison against the maximum GAP (7.4529 eV) of PAHs (dibenzo[a,h]anthracene) that could be photocatalytically degraded and the minimum GAP (8.2086 eV) of PAHs (pyrene) that could not be photocatalytically degraded in this study, the photocatalytic degradability of 67 PAHs was predicted. The predictions were partly verified by experimental photocatalytic degradation of anthracene and Indeno[1.2.3.cd]pyrene.

Adsorption and thermal properties of the bovine serum albumin–silicon dioxide system

The adsorption, electrokinetic, thermal and stability properties of the silicon dioxide (silica, SiO2)/bovine serum albumin (BSA) system were determined. All measurements were carried out as a function of solution pH value. The highest amount of BSA absorbed on the silica surface was observed at pH 4.6 [the value close to the BSA isoelectric point (pI)], which is primarily related to the packed albumin conformation and the lack of adsorbent–adsorbate electrostatic repulsion. At pH 4.6, largest mass decrease was also noticed (thermogravimetric measurements). At pH 3, 7.6 and 9, the adsorption levels were much lower. This phenomenon is associated with the electrostatic repulsion between the BSA macromolecules and the silica particles as well as the expanded BSA structure. During biopolymer adsorption, the whole solid surface is coated with the albumin macromolecules. Then, the properties of the silica particles become similar to those of the BSA macromolecules. In the presence of albumin, the silica pHiep point is identical to the BSA pI value. It should also be noted that the albumin adsorption affects the SiO2 suspension stability. The greatest change was observed at pH 3. Under these conditions, the BSA addition causes electrosteric system stabilization.

Calcium phosphate coating of biomedical titanium alloys using metal–organic chemical vapour deposition

Metal–organic chemical vapour deposition was used to fabricate hydroxyapatite (HAp) and α-tricalcium phosphate coatings on the surface of representative biomedical titanium alloys: Ti–29Nb–13Ta–4·6Zr, commercially pure Ti, and Ti–6Al–4V ELI. The effect of the substrate surface roughness, alloy composition and precursor temperature was investigated in relation to the type of calcium phosphate formed and the morphology and thickness of the HAp coating. The surface roughness of substrates mechanically polished by SiC paper was found to vary depending on the type of alloy, whereas the roughness of substrates buff polished using a colloidal SiO2 suspension was comparable. The type of calcium phosphate formed could be controlled by the precursor temperature. A coarse, granular microstructure was observed on the surface of the thicker HAp coatings formed on the rough polished substrates, while the thinner HAp coatings formed on the smooth polished substrates had a relatively dense and fine grained microstructure.

Laser speckle suppression due to dynamic multiple scattering scheme introduced by oblique incidence

Speckle suppression has been the research focus in laser display technology. In the present paper, the relation between multiple scattering and the size of speckle grains is established by analyzing the properties of speckle generated by the laser beam through SiO2 suspension. Combined with dynamic light scattering theory, laser speckle suppression due to dynamic multiple scattering scheme introduced by oblique incidence is proposed. A speckle suppression element consists of a static diffuser and a light pipe containing the water suspension of SiO2 microspheres with a diameter of 300 nm and a molar concentration of 3.0 x 10(-4) μm3, which is integrated with the laser display system. The laser beam with different incident angles into the SiO2 suspension affecting the contrast of the speckle images is analyzed by the experiments. The results demonstrate that the contrast of the speckle image can be reduced to 0.067 from 0.43 when the beam with the incident angle of approximately 8 degrees illuminates into the SiO2 suspension. The spatial average of speckle granules and the temporal average of speckle images were achieved by the proposed method, which improved the effect of speckle suppression. The proposed element for speckle suppression improved the reliability and reduced the cost of laser projection system, since no mechanical vibration is needed and it is convenient to integrate the element with the existing projection system.

Autophagy in lung tissue of rats exposed to silica dust

To investigate the autophagy of effector cells in lung tissue at different time points when rats were exposed to free SiO2 dust. Sixty Wistar rats (220∼230 g) were selected and allocated to experimental group (n = 30) and control group (n = 30). In the experimental group, a rat silicosis model was established by infusing SiO2 suspension into the trachea of rats. Six rats in each group were sacrificed on days 1, 7, 14, 21, or 28 of dust exposure. Lung tissue samples were collected to prepare lung tissue sections. The pulmonary inflammation and fibrosis were observed by HE staining. The proautophagosome, autophagosome, and autophagolysosome in lung tissue sections were observed under a transmission electron microscope. On day 1 of dust exposure, many proautophagosomes and autophagosomes were seen in both experimental group and control group. On day 7 of dust exposure, the experimental group had more autophagosomes in lung tissue than the control group. On day 14 of dust exposure, the experimental group had fewer autophagosomes than the control group. On days 21 and 28, autophagolysosomes were seen in macrophage plasma in both experimental group and control group; the autophagolysosomes in experimental group showed cloudy swelling and expansion, and some were vacuolated, and these changes were more significant on day 28. Free SiO2 dust can induce autophagy in the lung tissue of rats, with varying degrees at different time points of dust exposure.

Study on Measurement of Laser Induced Dynamic Stress in the Suspension: The Influences of Powder Materials on Induced Dynamic Stress

In this paper, the measurement of dynamic stress generated in the suspension using TiO2, SiO2 and ZrO2 powder induced by Nd:YAG laser beam irradiation is proposed. The dynamic stress generated in the suspension by using elastic wave propagation in the cylindrical long bar is measured. As a result, the dynamic stress induced by laser beam irradiation was depended on laser power, powder materials and particle diameter. The dynamic stress generated in the TiO2 suspension was larger than that in ZrO2 and SiO2 suspension. The dynamic stress increased with the decrease of the particle diameter.

Stability of Colloidal Silica Modified by Macromolecular Polyacrylic Acid (PAA) – Application of Turbidymetry Method

The effect of anionic polyacrlic acid (PAA) adsorption on fumed silica (SiO2) surface on suspension stability was studied. The turbidymetry method was applied to monitor the changes in the suspension stability (using apparatus Turbiscan LabExpert with cooling module TLAb Cooler). PAA macromolecules contain dissociable carboxyl groups, therefore, all measurements were carried out at three pH values: 3, 6 and 9. Analysis of obtained transmission and backscattering curves and Turbiscan Stability Indexes (TSI) allowed determination of the most probable mechanism of the stability of the studied systems. The PAA adsorption has the greatest impact on the silica suspension stability at pH 3 (significant improvement of its stability). On the other hand, the presence of polyacrylic acid at pH 6 causes a noticeable deterioration of system stability conditions. At pH 9, polymer minimally influences the stability of SiO2 suspension.

Electrostatically driven adsorption of silica nanoparticles on functionalized surfaces

Adsorption of nanoparticles on solid supports is a scientifically interesting and technologically important phenomenon that has been attracting ever-increasing attention. Formation of particle-based films onto surfaces from stable suspensions is at the center of the development of new devices that utilize the plethora of newly synthesized nanoparticles with exciting properties. In this study we exploit the attractive electrostatic interactions between silica (SiO2) nanoparticles and functionalized substrates that display an amine termination in order to devise a simple method for the fabrication of SiO2 nanoparticle films. Electrostatically controlled adsorption allows for uniform coverage of nanoparticles over large areas. The Stöber method (a sol–gel approach) was employed to prepare uniformly sized SiO2 nanoparticles with a diameter of 50–80nm. Native oxide-covered silicon wafer substrates were amino-functionalized utilizing the self-assembled monolayer of 3-aminopropyltrimethoxysilane (APS). The adsorption of SiO2 nanoparticle film onto the silicon wafer substrate was controlled by modulation of the electrostatic interaction between nanoparticles and the substrate. Modification of surface charge of either the SiO2 NP or the substrate is a crucial step in the process. Thus the effect of APS adsorption time on the surface energy of the substrate was investigated. Also, process parameters such as NP concentration and solvent composition were varied in order to investigate the extent of NP adsorption. Moreover, NaCl was introduced to the SiO2 suspension as a charge-screening agent to reduce the inter-particle repulsion in the suspension as well as interaction of the particles with the surface. This resulted in denser/thicker films.

Corrosion behavior of Cu–SiO2 nanocomposite coatings obtained by electrodeposition in the presence of cetyl trimethyl ammonium bromide

Copper silica composite coatings are an attractive alternative to chromium and nickel coatings in order to avoid environmental problems and for application in electrical devices. However, co-deposition of SiO2 particles with metals occurs to a rather limited extent, generally under 1%, due to the hydrophilicity of SiO2, which makes the incorporation of particles in a metallic matrix difficult. To overcome this drawback, the influence of cetyl trimethyl ammonium bromide (CTAB) on the deposition and corrosion behavior of Cu–SiO2 coatings on steel has been studied. It was established that CTAB plays a beneficial role in SiO2 suspension stabilization, promotes the co-deposition of nanoparticles in the copper matrix and improves the deposit morphology and structure. Consequently, a higher corrosion resistance of Cu–SiO2 deposits obtained in the presence of CTAB was noticed. The most important effect was observed in the case when CTAB was used in concentration of 10−3 M in the electroplating bath.

Autophagy and silica‐induced pulmonary fibrosis

The aim of this study was to investigate the potential role of autophagy in the pathogenesis of pulmonary fibrosis. Pulmonary fibrosis was induced by infusing 1 ml SiO2 (100 mg/ml) suspension to rat trachea. Rats were sacrificed 2, 7, 14, 21, and 28 days after the treatment to detect pulmonary fibrosis and autophagy. Autophagy was assessed by measuring the ratio of LC3II/LC3I, an established marker of autophagy, with Western blot and by detecting autophagic vacuoles with electron microscopy. Pulmonary inflammation and fibrosis were detected with H.E. staining. Pulmonary inflammation was evident early after the exposure to SiO2, which was followed by a marked increase in fibrosis. Compared to the control, LC3II/LC3I ratio and autophagosome in the experimental group were significantly increased 7 days after the treatment, indicating that silica can induce autophagy in the early stage of pneumoconiosis. However, the autophagic indexes were markedly lower in the experimental group than that of the control 14, 21, and 28 days after the treatment, implying that autophagy was suppressed in the late stage of pneumoconiosis. Taken together, these data suggest that autophagy may play different roles in the early and late stages of pneumoconiosis. These findings may provide important new insights into the mechanism underlying the pathogenesis of silica‐induced pulmonary fibrosis.

Out-Coupling Efficiency Enhancement of Organic Light Emitting Diode Device by SiO2-UV Hardener Composite Layer

The enhancement of out-coupling efficiency of organic light emitting diode (OLED) using SiO2-polymer composite layers was investigated. The SiO2-polymer composite was made from a SiO2 nanopowder and commercial UV-hardeners. The composite layer was coated on glass by dip-coating method in a SiO2 suspension, followed by spin-coating of 1 microm thick UV-hardener of was found that the optical properties were depend on the quantity of SiO2 nanopowder in the composite layer and dispersion of SiO2 suspension. 194/440 nm size of SiO2 nanopowders were added to the composite layer to enhance the light scattering effect. The OLED device which the SiO2-polymer composite layer was applied showed enhanced out-coupling efficiency around 30%.