Viscosity Of Sol Research Articles

Investigation of the Effects of Acid Content and Annealing on the Properties of Nanostructured TiO2 Sol

Titanium dioxide (TiO2) sol was prepared using tetrabutyl titanate as a precursor via an acid catalyzed sol-gel process. Investigation of the effects of acid content and annealing on the properties of nanostructured TiO2 materials. The influence of acid content on the sol density, viscosity, stability and particle size were studied and based on the kinematic viscosity data, Gibbs energies of activation for viscous flow (ΔG*) were also calculated. Furthermore, the prepared samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and ultraviolet-visible (UV-Vis) spectrophotometer. The results showed that the increase of acid content nearly had no obvious influence on the chemical structure of TiO2 sol. With the increase of annealing temperature, titanium dioxide changes from amorphous phase to crystalline phase, anatase coexists with rutile at 600 °C, sample absorbance increases, and the edge of UV-Vis spectra shows red shift. Ti-O-Ti bond is the main structure of TiO2 sol, and the formed TiO2 molecule has linear structure.

Reactivity and Aggregative Stability of Colloidal Silica

The properties of colloidal silica taking into account the reactivity of silica, as well as the kinetics of polycondensation and depolymerization, are analyzed. The breaking of siloxane bonds during depolymerization leads to the appearance of reactive Si–OH and Si–O–Me+ groups, destruction of the silica structure, formation of gel-like layers on the surface and in the volume of particles (at a high level of alkalinity), growth of their hydrophilicity, and the dissolution of silica (limiting depolymerization). The formation of gel-like structures is accompanied by an increase in the hydrodynamic radii of the particles, an increase in the viscosity of aggregative stable sols, a decrease in their turbidity upon transition from acidic to alkaline media, sol dilution, and the introduction of electrolytes. Alkalis affect the solid phase depolymerization process by increasing the cation basicity in the series K+ > Na+ > Li+. The formation of gel-like structures causes an increase in the aggregative stability of the sol at pH> 5.5–6.0. Upon reaching pH 9.0–9.5, the quasi-equilibrium of the polycondensation rates and depolymerization reactions ensures the high aggregative stability of the sol. The further increase in alkalinity (increase in pH, silica modulus) in the aqueous phase increases the concentration of depolymerization products and silicate anions containing ionized and non-ionized silanol groups. Under these conditions, the oligo- and polymeric molecules of silicic acids are formed in the aqueous medium during the secondary polycondensation, and, based on them, linear supramolecular structures, the viscosity of the colloidal system grows, and gels are formed.

Effect of water content on the performance and structure of nanosized TiO2 sol

Titanium dioxide (TiO2) sol was prepared using tetrabutyl titanate as a precursor via an acid catalyzed sol–gel process. The influence of water content on the sol density, viscosity, stability and particle size were studied and based on the kinematic viscosity data, Gibbs energies (ΔG*) of activation of the viscous flow was also calculated. Furthermore, the obtained TiO2 materials were characterized by infrared spectroscopy (IR) and X-ray diffraction (XRD) analysis. The results showed that, with the increase of water content, the sol viscosity and zeta potential were increased and the particle size distribution was narrow. When the molar ratio of H2O/Ti reached 4, the prepared sol was transparent, uniform and stable, and the sol average particle size gets the minimum. Ti–O–Ti bond was the primary structure of TiO2 sol and the formed titanium molecules possessed the line-typed structure. The increase of water content nearly had no obvious influence on the chemical structure of sol. The TiO2 gel material was the amorphous state and it turned into anatase type after calcination at 350°C.

Novel, infection-free, advanced hemostatic material: physical properties and preclinical efficacy

Introduction: Self-assembling peptides are synthetic, amphipathic peptides that may serve as new hemostatic agents. The first-generation hemostat TDM-621 has been used in clinical practice in a limited capacity. The second-generation hemostat TDM-623 was developed for faster gel formation and better tissue-sealing capability. We compared the physical properties and hemostatic effects of TDM-621 and TDM-623.Material and methods: First, we evaluated the physical properties of both materials in a bench test setting, including the external appearance of the gel, rheological properties in sol/gel forms, and local self-weight pressure. We then performed a randomized preclinical trial using swine. Bleeding wounds were created on the liver surface, and randomized application of 1 mL of either TDM-621 or TDM-623 was performed. The hemostatic effects were evaluated two and five minutes after application. Resected specimens were histologically evaluated.Results: In the bench test setting, TDM-623 showed higher gel height, higher sol viscosity, and higher local self-weight pressure than TDM-621. In the preclinical setting, TDM-623 showed significantly greater hemostatic effects at two and five minutes after application than TDM-621. Histological examination showed no inflammatory reaction in either group.Conclusions: TDM-623 has greater hemostatic capability than TDM-621 and is therefore promising as a new hemostatic agent.

Controllable preparation of methyltriethoxysilane xerogel nanofibers

In recent years, the controllable preparation of silicone xerogel nanofiber without the addition of a carrier polymer is becoming more and more attractive. The methyltriethoxysilane (MTES) sol prepared using MTES/H2O/ethanol in a molar ratio of 1:5:6 under acidic catalysis conditions has excellent spinnability in a long span of spinning time. Further, pure silicone nanofibers with different gelation times were prepared by electrospinning. The influence of gelation time on the colloidal particle morphology and size, cross-linking degree, and viscosity of as-synthesized silicone sols was studied in depth with SEM, DLS, and ATR-FTIR, and the effects on the morphology, hydrophobicity, and thermal stability of as-prepared xerogel nanofibers were also determined. As the gel time increased, there was a higher increase in the colloidal particle size, cross-linking degree, and viscosity of sol. The xerogel nanofibers with long gelation time exhibited higher hydrophobicity and thermal stability due to sufficient hydrolysis and condensation. The optimum gelation time was approximately 200 h, and the optimum viscosity range was in between 300 and 1000 cp, which were obtained for stable fiber jet and for preparing uniform and continuous xerogel nanofibers with excellent physical and chemical properties.

Evaluation of in vitro properties of 3D micro-macro porous zirconia scaffolds coated with 58S bioactive glass using MG-63 osteoblast-like cells

A new family of bioceramic scaffolds consisting of zirconia foam-like structures with 58S bioactive glass (BG) coating was developed. Three open-cell structures fabricated by the foam replica method were coated via immersion in a sol-gel solution. The coating technique was optimised controlling the sol viscosity, condensation time, and the number of immersions in order to increase the coating thickness. The scaffolds chemical and structural characteristics were evaluated before in vitro tests, including the Ca/P ratio, crystalline phase composition, pH change, pore diameter and microporosity of the scaffolds struts. In vitro tests were performed by culturing MG-63 human osteoblast-like cells. An increase in cell proliferation of 100% was found with the decrease in pore size from 700 to 120 μm. Also, with the presence of the 58S-BG coating, an increase of cell proliferation was reached, which indicates the positive effect of the BG coating on the otherwise bioinert ceramic scaffold.

The influence of scattering layer thin film on photoelectric properties of Bi2S3/CdS/TiO2 electrode

We adopt the dip-coating method using the viscosity of TiO2 sol to carry out the experiment aiming at combining both the advantage of morphologies of ordered and disordered nanostructures to select the photo-anode of TiO2. The nanoparticles scattering layer thin film growing at the TiO2 nanotubes (H:TTW) nozzle (H:TTWP) can increase the specific surface area of the top structure as well as can improve the adsorption of the quantum dots. Meanwhile, this nanostructure can keep the advantage of the direct electronic channel and the less vertical structure interface at the bottom of nanotubes. We use the method of successive ionic layer adsorption and reaction (SILAR) to conduct the quantum dot co-sensitization on the H:TTWP with CdS and Bi2S3. We found that the number of dip-coating with TiO2 nanoparticles was 6, it exhibited the best performance and reached a high photocurrent density of 9.34 mA/cm2, which is 2.1-times as many as Bi2S3/CdS/H:TTW system. What's more, the photoconversion efficiency is 6.13%. The improvement of the performance is mainly due to the enhancement of light absorption and the amount of heterojunctions of Bi2S3/CdS/TiO2, the ladder-like energy level structure and the novel morphology structure.

Partial removal of acetyl groups in konjac glucomannan significantly improved the rheological properties and texture of konjac glucomannan and κ-carrageenan blends

The main aim of the current study was to research the effect of the degree of konjac deacetylation on the rheological and textural properties of konjac glucomannan (KGM) and κ-carrageenan blends. A series of deacetylated konjac glucomannan (Da-KGM) with different degrees of deacetylation (0, 20.35%, 35.62%, 57.19%, and 74.01%) was prepared by a heterogeneous deacetylation method. The rheological and textural properties of mixed sols and gels of Da-KGM with different degrees of deacetylation and κ-carrageenan were determined. The results showed that the viscosities of mixed sols of Da-KGM and κ-carrageenan decreased with increasing degree of deacetylation. The partial removal of acetyl groups from konjac glucomannan could significantly improve the hardness and springiness of mixed gels of KGM and κ-carrageenan. Meanwhile, decreasing the acetyl content could decrease the syneresis of mixed gels. By regulating the deacetylation degree of konjac, gels with high gel strength could be prepared, which provides a new idea for the production of high-strength gelatin food.

Protonated g-C3N4/Ti3+ self-doped TiO2 nanocomposite films: Room-temperature preparation, hydrophilicity, and application for photocatalytic NOx removal

Fabrication of photocatalysis films with good adhesion, hydrophilicity, and high activity on substrates at room temperature is essential for their application in air pollution control. Herein, functionalized transparent composite films containing ultrathin protonated g-C3N4 (pCN) nanosheets and Ti3+ self-doped TiO2 nanoparticles (pCN/TiO2) were fabricated on glass at room temperature. Thickness of the films measures 80 nm with surface roughness of 7.16 nm. The adhesion ability was attributed to the viscosity of TiO2 sol, which served as “chemical glue” in the films. The high photo-induced hydrophilicity demonstrated their self-cleaning potential. pCN/TiO2 films showed remarkably high visible-light-driven activity in terms of NO removal in a continuous-flow mode. Photoelectrochemical tests demonstrated the superior charge separation efficiency of pCN/TiO2 films compared with that of pristine TiO2. As identified by electron spin resonance spectra, O2− and OH radicals were the key reactive species involved in NO removal. The possible mechanism for photocatalytic NO oxidation was proposed. Potential cytotoxicity of pCN/TiO2 films was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay to ensure the biosecurity. This work provides a facile route to fabricate nanocomposite films under ambient temperature. The nanocomposite films were characterized by photo-induced hydrophilicity, high NO removal efficiency, and good biocompatibility, showing its potential in large-scale application.

Influence of spinning parameters on synthesis of alumina fibres by centrifugal spinning

The present study investigates the synthesis of alumina fibres of 5–15 µm dia. by sol-gel process through centrifugal spinning. Among various spinning parameters such as rpm, viscosity, humidity, chamber temperature etc., effect of rpm and viscosity on quality of spun fibres was examined in order to spin less defective (less shots) fibres. From the rpm vs viscosity experiments, it was concluded that viscosity between 13 and 42 Pa.s with 3000 rpm was favourable for obtaining fibres containing less shots. It was shown that besides viscosity, refractive index and percent weight loss of the aged sol can be used as indicator for determining spinnability of alumina precursor sols. Influence of only preheating and continuous heating of the chamber during spinning were also investigated and it was found that only preheating did not help in producing fibres. Besides this, influence of hot air blower (HAB) aligned in different directions with respect to the spinnerette, on fibre quality was tested. It was observed that the quality of fibres did not change due to change in HAB direction.

Inorganic Effect Pigment-Binder System following Sol-Gel Process –Application for Optical Textile Functionalization

100% cotton plain-weaved woven fabric has been treated with inorganic effect pigment-binder system in water following solgel process. Thickener has been added to maintain the viscosity of the sol. Dispersing agent has been included where necessary to even distribution of sol on textile. Complete process was done ensuring inorganic chemicals such as pigment, binder, thickener and dispersing agent. After drying, the reflection and transmission characteristics were measured using spectrophotometry. It gives the quantitative measurements (wavelength 220 nm to 1400 nm) of the reflection and transmission properties of the coating as a function of wavelength. These values are then used to discuss the developed optical protection (against IR, visual and UV light) of coated cotton textile by inorganic effect pigment and binder system.

Characteristics of unsupported alumina membrane prepared using sol-gel technique

A laboratory scale alumina membrane was prepared using sol-gel technique. Results from the experiment demonstrate that the addition of PVA is important for viscosity adjustment to determine the appropriate coating time if the membrane is required for coating on the porous support. The effects of varying PVA content and sintering temperature on the characteristics of the sintered membrane are discussed. In this work, a 2 volume % of PVA solution containing 4g of PVA in lOOml of water was discovered to be adequate to achieve appropriate porosity level and avoid cracks in the gel layer. It was also discovered that the sol viscosity essentially increased as the PVA addition was increased. On the contrary, the coating time decreased as PVA content in the sol was increased. Generally, the pore size of the membrane increased with the increase in PVA addition. The density of the membrane increased with increase in sintering temperature. The porosity level however, decreased as the temperature was increased. The pore size became greater and pore size distribution wider at higher sintering temperatures.

Characteristics of unsupported alumina membrane prepared using sol-gel technique

A laboratory scale alumina membrane was prepared using sol-gel technique. Results from the experiment demonstrate that the addition of PVA is important for viscosity adjustment to determine the appropriate coating time if the membrane is required for coating on the porous support. The effects of varying PVA content and sintering temperature on the characteristics of the sintered membrane are discussed. In this work, a 2 volume % of PVA solution containing 4g of PVA in lOOml of water was discovered to be adequate to achieve appropriate porosity level and avoid cracks in the gel layer. It was also discovered that the sol viscosity essentially increased as the PVA addition was increased. On the contrary, the coating time decreased as PVA content in the sol was increased. Generally, the pore size of the membrane increased with the increase in PVA addition. The density of the membrane increased with increase in sintering temperature. The porosity level however, decreased as the temperature was increased. The pore size became greater and pore size distribution wider at higher sintering temperatures.

FORMULATION AND EVALUATION OF ORAL SUSTAINED IN SITU GELLING SYSTEM OF ROXATIDINE

Gel dosage forms are successfully used as drug delivery systems to control drug release and protect the medicaments from a hostile environment. The main objective of this present work is to formulate and evaluate in situ gels of roxatidine for the treatment of peptic ulcer. This system utilizes polymers that exhibit sol-to-gel phase transition due to change in specific physico-chemical parameters. In the present work in situ gels have been developed by using gellan gum and sodium alginate based on the concept of ion activated systems. Sol-to-gel transformation occurred in the presence of monovalent/divalent cations. Formulations were evaluated for clarity, drug content, in vitro gelling capacity, determination of pH, in situ release study, viscosity, gel strength, ex vivo gelation and stability study. All the results found to be satisfactory. Experimental part showed that viscosity of sols and gel strength was increased with increase in the concentration of polymers, also drug release gets sustaining. The formulations were therapeutically efficacious, sterile and provided sustained release of the drug over a period of time. These results demonstrated that the developed system is an alternative to conventional drug delivery systems and can improve patient compliance. Key words: In situ gels, Roxatidine, Peptic ulcer.

Synthesis of thorium sol for fabricating fuel kernels

To fabricate thorium-based fuel kernel for solid fuel molten salt reactor, a component of tri-structural isotropic fuel particles is mostly based on sol–gel method. The preparation of thorium sol is an important step for fabrication of thorium-based fuel kernels, such as thorium carbide and thorium oxide. The gel quality affects the gel particle dispersion and the final products. In this work, thorium sols were prepared using Th(NO3)4 and NH3·H2O by sol–gel method. The effects of thorium concentration, mole ratio of NH4 +/NO3 −and reaction temperature on the pH, viscosity, turbidity, particle size and the thorium sol distribution were investigated. The results show that the viscosity and turbidity increased with the NH4 +/NO3 − ratio; the turbidity and colloidal particle size increased with the reaction temperature, which affected little the sol viscosity; the sol viscosity increased with the thorium concentration, which virtually did not change the turbidity; and the particle size decreased and the size distribution narrowed with increasing thorium concentration. The sol could be stored at room temperature for one day without significant property changes. Thorium gel spheres of good quality were prepared at 60 °C with the NH4 +/NO3 − ratio of 75–85% and the thorium concentration of 1.2–1.4 mol/L.

CATALYTIC SURFACE MODIFICATION OF ALUMINA MEMBRANE FOR OXYGEN SEPARATION

Two types of alumina ceramic membrane in hollow fibre shape was used in this study. Both alumina hollow fibres (AHF) were sintered at different temperatures; (a) 1350oC and (b) 1450oC. In order to improve the catalytic activity of the alumina membrane for oxygen separation purposes, surface modification of the membranes was carried out using La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) perovskite catalyst. LSCF was synthesised using simple Pechini sol-gel method. The evaporation time and temperature of the LSCF-sol were varied to obtain various viscosity of catalytic sol. From XRD analysis, pure LSCF perovskite structure formed at temperature at 850oC. The morphological of unmodified and surface-modified alumina hollow fibre membranes (AHF) were studied using FESEM. The effect of LSCF catalytic sol viscosity was studied and it was found that as the viscosity of the sol increases, the amount of catalyst deposited on the alumina hollow fibre were increased. Besides, the amount of catalyst deposited on 1350 AHF was found to be higher than 1450 AHF. This result is supported by the result of pore distribution data whereby 1350 AHF was observed to be more porous than 1450 AHF, with porosity percentage of 40.38% and 28.80%, respectively. Although higher viscosity of catalytic sol could lead to a high amount of catalyst deposited on the AHF substrate, there is a tendency for micro-cracks to develop. Thus, the viscosity of the catalytic sol is important to control in order to have higher oxygen permeation flux.

In situ gelation properties of a collagen–genipin sol with a potential for the treatment of gastrointestinal ulcers

We investigated the potential of collagen–genipin sols as biomaterials for treating artificial ulcers following endoscopic submucosal dissection. Collagen sol viscosity increased with condensation, allowing retention on tilted ulcers before gelation and resulting in collagen gel deposition on whole ulcers. The 1.44% collagen sols containing genipin as a crosslinker retained sol fluidity at 23°C for >20 min, facilitating endoscopic use. Collagen sols formed gel depositions on artificial ulcers in response to body temperature, and high temperature responsiveness of gelation because of increased neutral phosphate buffer concentration allowed for thick gel deposition on tilted ulcers. Finally, histological observations showed infiltration of gels into submucosal layers. Taken together, the present data show that genipin-induced crosslinking significantly improves the mechanical properties of collagen gels even at low genipin concentrations of 0.2–1 mM, warranting the use of in situ gelling collagen–genipin sols for endoscopic treatments of gastrointestinal ulcers.

Fabrication of flexible and amphiphobic alumina mats by electrospinning

Flexible and amphiphobic alumina mats were fabricated by (heptadecafluoro-1, 1, 2, 2-tetradecyl)trimethoxysilane (FAS) modification of electrospun alumina mats. The alumina mats were obtained by the sol–gel method combined with an electrospinning process using aluminum nitrate nonahydrate (Al(NO3)3·9H2O) and aluminum isopropoxide (Al(C3H7O)3) as raw materials, nitric acid and acetic acid as catalysts, water as the solvent, and polyvinylpyrrolidone (PVP) was applied to tune sol viscosity. When the content of PVP was 1.3 wt%, the alumina mat after modification had higher water contact angle of 134° and oil contact angle of 122° than those with other concentrations. In addition, the alumina mat exhibited a hydrophobic property in the pH range from 1 to 14. The good stability of the prepared fiber mat in weak acidic and alkaline solution may extend its application in many industrial fields. Flexible and amphiphobic alumina mat was fabricated by modification of electrospun alumina mat, which was prepared by the sol–gel method combined with an electrospinning process.

Synthesis and Characterization of Silver-containing Sol-gel Derived Bioactive Glass Coating

Silver doped-bioactive glass coatings offer the possibility of bioactivation, corrosion protection and infection prevention of metallic implants. A certain composition of glass (54SiO2–36CaO–8P2O5–2Ag2O (wt %)) was coated on titanium substrate using dip coating method by 1 cm/min withdrawal rate with controlling the effective factors like viscosity of sol, matching thermal expansion coefficient (a), heating rate and etc., then heated at 700°C for 1h at the rate of 3°C/min. Scanning electron microscopy (SEM) depicted a crack-free and homogeneous coating. The energy dispersive X-ray spectroscopy corresponding to the SEM image affirmed the presence of Si, P, Ca and Ag as main elements of Ag-BG coating. Contact angle measurement confirmed positive effect of silver on the wettability and adhesion of Ag-BG on the Ti surface. X-ray Diffraction analysis confirmed the amorphous nature of Ag-BG. Fourier transform infrared spectroscopy confirmed successful inclusion of silver in glass structure. X-ray Fluorescence Spectroscopy demonstrated that composition of Ag-BG was very close to the designed composition. Results of acellular in vitro bioactivity test showed formation of ball-like particles including a layer of entangled rough apatite crystals on the surface.

Preparation of activated aluminum-coated basalt fiber mat for defluoridation from drinking water

Alumina/basalt fiber mat composite (ABFMC) was fabricated by loading activated alumina (AA) on basalt fiber mat (BFM) via sol–gel method for fluoride removal. ABFMC and AA were characterized, and their performance for fluoride removal from aqueous solution was evaluated at different initial fluoride concentration and contact time. The loading capacity of AA on BFM increased with the increase in the sol viscosity, and the sol viscosity was optimized at 3.9 mPa s, whose corresponding loading percentage was 60.25 %. The results from the present study exhibit that ABFMC has shown good adsorption capacity for fluoride removal from aqueous solution. Experimental data revealed that the fluoride sorption on ABFMC was rapid, and 98.7 % fluoride removal was achieved within 30 min, whereas they were 96.8 % and 60 min in case of AA, respectively. The fluoride absorbed of ABFMC is well compared with that of most conventional materials and AA. The maximum of fluoride adsorbed on ABFMC was 1.872 mg/g. Adsorption isotherm analyses indicate that the adsorption of fluoride on ABFMC could be best described with the Langmuir isotherm, which suggested that the fluoride may create a monolayer layer on ABFMC. The adsorption kinetics was best described by the pseudo-second-order kinetic model followed by both intraparticle diffusion and film diffusion as the rate-controlling rate step.