Cetyltrimethyl Ammonium Research Articles

The distinct roles of the anaphylatoxin receptors C5aR1, C5aR2 and C3aR during experimental invasive meningococcal disease

In this study, the experimental surface tensions were measured for aqueous solutions of cetyltrimethyl ammonium bromide, 1-propanol, 2-propanol, and 1-butanol with a pendant drop apparatus. The temperature and pressure of all experiments were 298.15 K and 1 bar, respectively. Subsequently, a model based on the equality of the chemical potential of components at the interface and the bulk liquid was used. The results of this part showed that the surface tensions were reproduced well. The average absolute deviation percent of surface tension was 1.11. Then the surface tensions of (cetyltrimethylammonium bromide + alcohols) aqueous mixtures were measured at different concentrations. Moreover, the critical micelle concentrations of the applied systems were determined. The present model was used for aqueous mixtures of (cetyltrimethylammonium bromide + alcohols). The average absolute deviation percent of surface tension was 2.72, so the model successfully predicted the surface tension for aqueous solutions of (cetyltrimethylammonium bromide + alcohols). Furthermore, the results of the model proved that the presence of alcohols decreased the surface coverage of cetyltrimethylammonium bromide and increased the values of the critical micelle concentration.

Voltammetric Quantification of Ibuprofen Using CTAB and Carbon Paste Electrodes Modified with Copper (II) Oxide

Introduction Ibuprofen [2- (p-isobutyl phenyl) propionic acid] is a nonsteroidal anti-inflammatory drug (NSAID) with high analgesic, antipyretic and anti-inflammatory properties. Due to its effectiveness in pain, fever and inflammation treatment, and its easy acquisition by consumers (it does not requires medical prescription), it has become one of the most consumed NSAIDs in the world (Bushra & Aslam, 2010). Recently, Sondergaard et al. (2017) reported heart diseases related to ibuprofen consumption in high and frequent doses; therefore, the quantification of this active compound in medicines has become a matter of great importance. The United States Pharmacopoeia (USP-NF-26) and the European Pharmacopoeia (EP) establish official methodologies to carry out the quantification of these drug, however, these have some disadvantages compared to electroanalytical techniques, such as high analysis times and costs, previous pretreatment of the sample and more complicated procedures. Among the electroanalytical techniques used to quantify drugs, voltammetry with carbon paste electrodes has demonstrated outstanding results, since these electrodes present important advantages compared to others. Carbon paste electrodes can be easily modified, due to the inclusion of nanostructures in order to improve the electrochemical transformation of electroactive molecules (Ramírez, 1996). Metal oxide nanoparticles have been recently widely used for the modification of electrodes, due to its high catalytic activity, in which indirectly improves the analytical signal. Copper oxide nanoparticles have aroused great interest since they can be easily synthesized at a low cost, in addition to having a great catalytic activity, (Male et al., 2004). Taking into account these advantages, this work presents the development of a voltammetric methodology based on a graphite-CuO nanoparticles paste electrode, optimized by the Box-Behnken method, in order to quantify ibuprofen. Cetyl trimethyl ammonium (CTAB) is used to improve the analytical signal of the proposed methodology. Methodology As part of the electrochemical characterization of the system, Cyclic Voltammetries were carried out to determine the electrochemical behavior of ibuprofen, optimize the pH medium, optimize the supporting electrolyte and optimize the working electrode’s composite composition As part of the analytical characterization, Differential Pulse Voltammetry (DPV) was optimized using a Box-Behnken design in order to maximize the analytical signal. Calibration curves are used to determine the analytical parameters of the proposed methodology, the effect of possible interferences in the system is evaluated. The proposed methodology is then used for the quantification of ibuprofen in commercial drugs and validated with the official methodology. Results By means of cyclic voltammetry (CV), a composite mixture 99% graphite - 1% CuO nanoparticles could be established, using for the supporting electrolyte a mixture of 0.1 M phosphate buffer, 0.05 M of CTAB and 0.5 M of sodium sulfate with an optimum pH of 6.2. With CVs at different scan rates, it was possible to establish that the process governing ibuprofen oxidation of is diffusional. Significant changes were observed in the electroanalytical signal for different ibuprofen concentrations in a range of 10-5 to 10-3 M. The resulting calibration curve showed two linear trends, one in the concentration range 10-5 to 10-4 M and the other from 10-4 to 10-3 M. The curve was constructed considering the optimal parameters of the DPV: step potential of 3 mV, pulse amplitude of 100 mV, pulse period of 100 ms and a pulse width of 80 ms, according to the Box Behnken design. References Bushra, R. y Aslam, N. (2010). An overview of clinical pharmacology of ibuprofen. Oman Medical Journal, (25), 3, 155 – 161. Sondergaard, K. B., Weeke, P., Wissenberg, M., Schjerning Olsen, A. M., Fosbol, E. L., Lipper, F. K., Torp-Pedersen C. Gislason G. H., Folke Fredrik (2017). Non-steroidal anti-inflamatory drug use is associated with increased risk of out-of-hospital cardiac arrest: a nationwide case-time-control study. European Heart Journal Cardiovascular Pharmacotherapy, (3), 2, 100-107. Male, K. B., Hrapovic, S., Liu, Y., Wang, D., Luong, J. (2004), Electrochemical detection of carbohydrates using copper nanoparticles and carbon nanotubes. Analytica Chimica Acta 516 35–41. T. Ramírez Silva, Diferentes electrodos composite con matriz de grafito. Estudio comparativo de su funcionamiento y de sus potencialidades, Tesis Doctoral, Universidad Autónoma Metropolitana-Iztapalapa (1996).

Organic-ion-intercalated FeSe-based superconductors

Finding a new derivative structure of FeSe-based superconductors with a high superconducting transition temperature (${T}_{c}$) is of great significance. Here, in this work, an organic-ion-[cetyltrimethyl ammonium (${\mathrm{CTA}}^{+}$)]-intercalated FeSe-based superconductor ${(\mathrm{CTA})}_{0.3}\mathrm{FeSe}$ with ${T}_{c}$ as high as 45 K is synthesized by an electrochemical intercalation method. The as-prepared ${(\mathrm{CTA})}_{0.3}\mathrm{FeSe}$ has a hybrid crystal structure consisting of double layers of ${\mathrm{CTA}}^{+}$ and one layer of FeSe, which is consistent with a lateral-bilayer model. The superconductivity of ${(\mathrm{CTA})}_{0.3}\mathrm{FeSe}$ is confirmed by magnetic susceptibility. Furthermore, a negative pressure effect on superconductivity $d{T}_{c}/dP=\ensuremath{-}5$ K/GPa is observed. This is the first pure organic-ion-intercalated FeSe-based superconductor with a high ${T}_{c}$ and high crystallinity. Our work offers a new method to modify the interface interaction between the FeSe layer and the intercalator, and sheds new light on finding new FeSe-based superconductors with higher ${T}_{c}$.

RNA–CTMA Dielectrics in Organic Field Effect Transistor Memory

In recent years, biopolymers are highly desired for their application in optic electronic devices, because of their unique structure and fantastic characteristics. In this work, a non-volatile memory (NVM) device based on the bio thin-film transistor (TFT) was fabricated through applying a new RNA–CTMA (cetyltrimethylammonium) complex as a gate dielectric. The physicochemical performance, including UV, CD spectral, thermal stability, surface roughness, and microstructure, has been investigated systematically. The RNA–CTMA complex film exhibits strong absorption with a well-defined absorption peak around 260 nm, the RMS roughness is ~2.1 nm, and displayed excellent thermal stability, up to 240 °C. In addition, the RNA–CTMA complex-based memory device shows good electric performance, with a large memory window up to 52 V. This demonstrates that the RNA–CTMA complex is a promising candidate for low cost, low-temperature processes, and as an environmentally friendly electronic device.

A smartphone-based ratiometric resonance light scattering device for field analysis of Pb2+ in river water samples and immunoassay of alpha fetoprotein using PbS nanoparticles as signal tag

Herein, we developed a smartphone-based ratiometric resonance light scattering (RLS) device for portable field analysis and immunoassay. The RLS signal was detected by the camera in a smartphone controlled by a user-edited APP software. Except the smartphone, the total cost of the detection system itself is about 60 $, including a laser pointer and battery, a twin cuvette, a collective lens, and outside box. By using the RLS brightness ratio between the sample and reference channels in the twin cuvette as the signal indicator, the baseline drifts due to the variations in incident light intensity, ambient temperature, and shooting parameters of camera, can be eliminated efficiently. A new brightness indictor, (R − R0)/(Rmax − R), was proposed to linearize the calibration curve. Where R and R0 are the rightness ratio in sample and blank, Rmax is the maximum averaged brightness ratio, respectively. The applicability of the portable RLS device was demonstrated by the field analysis for Pb2+ in environmental water samples, using [CTA]2PbI4］(CAT = cetyltrimethyl ammonium) as the luminophore. The limit of detection for Pb2+ is 0.7 μg L−1. By using PbS nanoparticles conjugated second antibody as the signal tag, the RLS method was applied in immunoassay to determine alpha fetoprotein with the limit of detection of 0.1 pg mL−1. This smartphone-based ratiometric RLS device offers the advantages of good portability, low cost, high sensitivity and reliability.

Wavelet analysis on the drag-reducing characteristics of turbulent channel flow with surfactant additive based on experimental data

Two-dimensional velocity fields for turbulent channel flows of water and 50 ppm CTAC/NaSal (cetyltrimethyl ammonium chloride/sodium salicylate) solution were experimentally obtained by particle image velocimetry. Multi-scale decompositions of the fluctuating velocity signals were performed by two-dimensional binary orthogonal discrete wavelet to analyze the influence of surfactant additives on the multi-scale characteristics of turbulent channel flow. From the results of wavelet multi-scale decompositions, it can be observed that the quantity of coherent structures near the wall in CTAC solution flow is decreased obviously. The results of the flatness factor show that the addition of drag-reducing additives inhibits the intermittency in turbulence. By analyzing the distribution of local intermittence measure and local Reynolds shear measure, it is found that the intermittency mainly concentrates near the wall, and the intermittent region distinctly reduces in CTAC solution flow compared with that in water flow. By combining the analysis of the motion of coherent structures in turbulent channel flow, it is shown that surfactant additives mainly and distinctly impact the coherent structures near the wall, especially in the viscous layer.

Experimental and modeling study of the surface tension and interface of aqueous solutions of alcohols, cetyltrimethylammonium bromide (CTAB) and their mixtures

In this study, the experimental surface tensions were measured for aqueous solutions of cetyltrimethyl ammonium bromide, 1-propanol, 2-propanol, and 1-butanol with a pendant drop apparatus. The temperature and pressure of all experiments were 298.15K and 1bar, respectively. Subsequently, a model based on the equality of the chemical potential of components at the interface and the bulk liquid was used. The results of this part showed that the surface tensions were reproduced well. The average absolute deviation percent of surface tension was 1.11. Then the surface tensions of (cetyltrimethylammonium bromide+alcohols) aqueous mixtures were measured at different concentrations. Moreover, the critical micelle concentrations of the applied systems were determined. The present model was used for aqueous mixtures of (cetyltrimethylammonium bromide+alcohols). The average absolute deviation percent of surface tension was 2.72, so the model successfully predicted the surface tension for aqueous solutions of (cetyltrimethylammonium bromide+alcohols). Furthermore, the results of the model proved that the presence of alcohols decreased the surface coverage of cetyltrimethylammonium bromide and increased the values of the critical micelle concentration.

Influence of the interaction of calcium carbonate particles with surfactants on the degree of water pollution in small rivers

IntroductionThe influence of the interaction of calcium carbonate (CaCO3) and surface-active substances (SAS; surfactants) with different chain lengths and cationic and anionic hydrophilic centers has been analyzed.ResultsLaboratory simulations indicate reduced negative influences on cationic SAS nitrification/self-purification processes in the presence of anionic species. This suggests the role of complex ionic formation [anionic SAS * cationic SAS] as a cause of this effect. UV-Vis spectra of lauryl sulfate (LS) and of cetyltrimethylammonium (CTMA), as well as of their mixtures in ratios of 2:1 and 1:1, treated by fine particles of CaCO3, display decreased amounts of SAS in analyzed solutions and their presence on the surface of CaCO3 nanoparticles. UV-Vis spectra reveal the decomposition of the complex [anionic SAS (SAS-An) * cationic SAS (SAS-Ct)] in solutions when CaCO3 is added. CTMA can be bonded by LS through hydrophobic chains, on the surface of CaCO3 particles. Therefore, CaCO3 modifies the nature of LS and CTMA interactions. This leads to an increased degree of toxicity of cationic SAS in aquatic environment. The amounts of CTMA in aqueous solutions are diminished in the presence of ammonium ion NH4+ (2 mg/L). In the presence of two orders higher concentration of ammonium ion, this effect strongly increases, making the association obvious. The structure of cationic SAS does not influence this effect. The obtained results have been confirmed both by timed natural aquatic sample analysis and laboratory simulations using water from Moldovan small rivers (Isnovat, Raut, and Bic).ConclusionsUV-Vis spectra and laboratory simulations demonstrate the change due to the addition of calcium carbonate. Simulations and laboratory tests of water samples from Isnovat, Bic, and Raut Rivers, establish the cationic SAS negative influence on treatment and self-purification processes.

Electrosynthesis of Layered Organo-Manganese Dioxide Framework-Doped with Cobalt for Iodide Sensing.

Aqueous Mn2+ ions were anodized at 70 °C with Co2+ in the presence of cationic surfactant, cetyltrimethylammonium (CTA). X-ray diffraction (XRD) analysis revealed that the deposited film possesses a layered structure of MnO2, the interlayer of which is occupied with the assembled CTA molecules. Inclusion of Co ions in the MnO2 film was evidenced by X-ray photoelectron spectroscopy (XPS). They were located in the MnO2 framework, not in the interlayer. The thus-obtained film, CTA-intercalated Co-framework-doped layered MnO2 (CTA/Co-MnO2), was applied as an electrochemical sensor toward iodide (I-), a hydrophobic anion. The organic phase between MnO2 layers could extract I- ions from solution, providing a better sensitivity than a film consisting of layered MnO2 with hydrated alkali metals. On the other hand, the Co-doped layers of MnO2 achieved faster electron transfer kinetics for the oxidation of I-, which resulted in a drastic reduction in response time compared to the nondoped CTA/MnO2.

One-Step Synthesis of Hierarchical ZSM-5 Using Cetyltrimethylammonium as Mesoporogen and Structure-Directing Agent.

Hierarchical ZSM-5 zeolite is hydrothermally synthesized in a single step with cetyltrimethylammonium (CTA) hydroxide acting as mesoporogen and structure-directing agent. Essential to this synthesis is the replacement of NaOH with KOH. An in-depth solid-state NMR study reveals that, after early electrostatic interaction between condensed silica and the head group of CTA, ZSM-5 crystallizes around the structure-directing agent. The crucial aspect of using KOH instead of NaOH lies in the faster dissolution of silica, thereby providing sufficient nutrients for zeolite nucleation. The hierarchical ZSM-5 zeolite contains mesopores and shows excellent catalytic performance in the methanol-to-hydrocarbons reaction.

Cooperative interactions among CTA+, Br– and Ag+ during seeded growth of gold nanorods

We have carried out a comprehensive study on the formation mechanism of Au nanorods (AuNRs) in binary surfactant mixtures composed of quaternary ammonium halide and sodium oleate (NaOL). We identify the cetyltrimethyl ammonium (CTA)-Br-Ag+ complex as the key ingredient in directing the anisotropic growth of AuNRs. Based on the improved understanding of the cooperative interactions among CTA+, Br– and Ag+, we further demonstrate that AgBr, which is readily solubilized by the cetyltrimethyl ammonium bromide (CTAB) or cetyltrimethyl ammonium chloride (CTAC) micelles, can be employed as the combined source of Ag+ and Br– for the preparation of AuNRs. The growth of high-quality AuNRs can be completed within 15 min under extremely low bromide content (0.1 mM).

Effective removal of surface-bound cetyltrimethylammonium ions from thiol-monolayer-protected Au nanorods by treatment with dimethyl sulfoxide/citric acid

A simple and effective strategy for removing surface-bound cetyltrimethylammonium (CTA) cations from poly(ethylene glycol)thiolate-protected AuNRs (PEG-AuNRs) by treatment with dimethyl sulfoxide/citric acid (DMSO/Cit).

Heparin Isomeric Oligosaccharide Separation Using Volatile Salt Strong Anion Exchange Chromatography.

The complexity of heparin and heparan sulfate saccharides makes their purification, including many isomeric structures, very challenging and is a bottleneck for structure-activity studies. High-resolution separations have been achieved by strong anion exchange (SAX) chromatography on Propac PA1 and cetyltrimethylammonium (CTA)-C18 silica columns; however, these entail subsequent desalting methodologies and consequent sample losses and are incompatible with orthogonal chromatography methodologies and, in particular, mass spectrometry. Here, we present the CTA-SAX purification of heparin oligosaccharides using volatile salt (VS) buffer. In VSCTA-SAX, the use of ammonium bicarbonate buffer for elution improves resolution through both weaker dissociation and conformational coordination of the ammonium across the sulfate groups. Using ion mobility mass spectrometry, we demonstrate that isomeric structures have different structural conformations, which makes chromatographic separation achievable. Resolution of such structures is improved compared to standard SAX methods, and in addition, VSCTA-SAX provides an orthogonal method to isolate saccharides with higher purity. Because ammonium bicarbonate is used, the samples can be evaporated rather than desalted, preventing substantial sample loss and allowing more effective subsequent analysis by electrospray mass spectrometry. We conclude that VSCTA-SAX is a powerful new tool that helps address the difficult challenge of heparin/heparan sulfate saccharide separation and will enhance structure-activity studies.

Synergistic Effect of Clay Platelets and Carbon Nanotubes in Styrene–Butadiene Rubber Nanocomposites

Nanoscale materials have provided a big advantage for enhancing the performance of rubber composites through leading the synergy effects in the physical and chemical properties. Here, the authors prepare hybrid fillers using a simple solution‐based method, based on electrostatic interactive assembly, of hydroxyl‐functionalized exfoliated montmorillonite (FE‐MMT) and cetyl trimethylammonium bromide‐modified multiwall nanotube (MWNT). The driving force of hybridization is due to specific interaction between the positive charge on the MWNT and the negative charge of hydroxyl group on MMT. To improve their dispersion, the obtained hybrid fillers are then co‐coagulated with styrene–butadiene rubber (SBR) latex to prepare elastomeric composites. Homogenous dispersion of the hybrid nanofillers in the SBR matrix results in a remarkable improvement in mechanical properties such as modulus (0.31 MPa) and tensile strength (75 MPa) at low loadings. Moreover, the prepared composite of hybrid nanofillers and rubber in the SBR matrix exhibits outstanding thermal (0.3779 W m−1 K−1) and electrical conductivities (15 kΩ) and gas barrier performance (9.16 × 10−45 m4 s−1 N−1). The synergistic reinforcement of SBR achieved by the combined incorporation of MWNT and MMT makes it ideal for use in conscious tires. This research opens up a wealth of new opportunities to prepare high performance rubber composites for future engineering applications. image

Bright luminescence from pure DNA-curcumin-based phosphors for bio hybrid light-emitting diodes.

Recently, significant advances have occurred in the development of phosphors for bio hybrid light-emitting diodes (Bio-HLEDs), which have created brighter, metal-free, rare-earth phosphor-free, eco-friendly, and cost-competitive features for visible light emission. Here, we demonstrate an original approach using bioinspired phosphors in Bio-HLEDs based on natural deoxyribonucleic acid (DNA)-curcumin complexes with cetyltrimethylammonium (CTMA) in bio-crystalline form. The curcumin chromophore was bound to the DNA double helix structure as observed using field emission tunnelling electron microscopy (FE-TEM). Efficient luminescence occurred due to tightly bound curcumin chromophore to DNA duplex. Bio-HLED shows low luminous drop rate of 0.0551 s−1. Moreover, the solid bio-crystals confined the activating bright luminescence with a quantum yield of 62%, thereby overcoming aggregation-induced quenching effect. The results of this study herald the development of commercially viable large-scale hybrid light applications that are environmentally benign.

Detoxification of Steam-Exploded Corn Stover Prehydrolyzate with Organobentonite Enhances Ethanol Fermentation by Pichia stipitis

The inhibitors derived from degradation of lignocellulose have adverse impacts on fermentation, which is considered to be a fundamental problem in bioethanol production. Fermentation of steam-exploded corn stover prehydrolyzate by Pichia stipitis showed that phenolic compounds had much higher inhibitory effects than weak acids and furan at high fermentation pH. Two types of organobentonite (cetyltrimethylammonium (CTMA)- and benzyltrimethylammonium (BTMA)-modified bentonite) were used to remove phenolic compounds in prehydrolyzate. The effectiveness of organobentonite treatment was evaluated by ethanol fermentation, which indicated that the organobentonite treatment improved the fermentability substantially, even though a noticeable difference was found in the phenol removal by the two organobentonites. Without organobentonite treatment, the sugar utilization ratio was only 68.1%, and the produced ethanol was 15.36 g/L. After CTMA- and BTMA-bentonite treatment, the sugar utilization ratios were beyond 95%; meanwhile, the ethanol production increased by 45.5% and 42.8%, respectively. This indicated that organobentonite treatment was a potential detoxification method.

Hybrid silica with bimodal mesopore system: Synthesis and catalytic evaluation

As-synthesized CTA–MCM-41 silica possesses basic siloxy (SiO-) catalytic sites, enabling it to be used in reactions such as transesterification and Knoevenagel condensation. Its application in basic catalysis has shown promising results, but attempts to reuse it in more than one cycle has revealed rapid loss of activity due to the removal of cetyltrimethylammonium (CTA) cations from the interior of the channels. The present work describes the encapsulation of nanoparticulate methacrylic polymers during the conventional synthesis of MCM-41, resulting in hybrid silicas containing polymers in the interior of the inorganic and organic matrix. Aqueous dispersions containing surfactant and monomers were characterized by small-angle X-ray scattering (SAXS), which confirmed the expansion of the micelles due to the presence of the encapsulated monomers. Transmission electron microscopy (TEM) was used to observe the formation of polymer nanoparticles stabilized by the surfactant (cetyltrimethy lammonium bromide). Infrared absorption spectroscopy and chemical analysis showed that these particles were present in the material after the synthesis. Analysis of the silicas using SAXS and nitrogen physisorption showed the expansion of the channels of the CTA–MCM-41 and the formation of two mesopore systems in the silica. Catalytic evaluation demonstrated that the silicas synthesized in the presence of the emulsified polymers possessed better catalytic stability when low monomer contents and monomers with larger alkyl chains were used. The encapsulation of nanoparticles of methacrylic polymer in the interior of the CTA–MCM-41 channels helped to avoid leaching of the CTA cations during the reaction.

Catanionic surfactant systems—thermodynamic and structural conditions revisited

In this work, we review shortly the current state of knowledge about catanionic surfactant systems with a focus on the detailed understanding based on the molecular buildup of such systems and of the electrostatic interaction that controls their amphiphilic monolayer and bilayer. Particularly relevant here is the extent of hydrophobicity of the oppositely charged partners, which can range from just having a more or less hydrophobic counterion until a real surfactant of opposite charge. Based on this discussion, we then investigate different systems based on cetyltrimethylammonium (CTA) combined with either laurate (L) as an oppositely charged surfactant or naphthalenesulfonate (NS) as a strongly hydrophobic counterion. Both systems were studied for the case of having salt present by combining the two amphiphilic salts but also the salt-free situation which arises from combining the hydroxide with the acid. The phase behavior was determined as well as the mesoscopic structures present, as obtained by small-angle neutron scattering (SANS) and light scattering, which allow to discern formation of wormlike micelles and vesicles. Their presence was then further confirmed by rheological measurements, where in particular normal forces allow to distinguish the two types of aggregates, and control of rheology is a key property in such systems. In addition, the thermodynamic conditions in these systems were determined by means of differential scanning calorimetry (DSC). Based on these results, a consistent understanding of the formed structures and their macroscopic properties that arise from the molecular conditions in these systems is presented.

Experimental study on the characteristics of ventilated cavitation around an underwater navigating body influenced by turbulent drag-reducing additives

In this study, a new control strategy for turbulent drag reduction involving ventilated cavitation is proposed. The configurational and hydrodynamic characteristics of ventilated cavities influenced by turbulent drag-reducing additives were experimentally studied in water tunnel. The test model was fixed in the water tunnel by a strut in the aft-part. Aqueous solutions of CTAC/NaSal (cetyltrimethyl ammonium chloride/sodium salicylate) with weight concentrations of 100, 200, 400 and 600 ppm (part per million), respectively, were injected into the ventilated air cavity from the edge of the cavitator with accurate control by an injection pump. The cavity configurations were recorded by a high-speed CCD camera. The hydrodynamic characteristics of the test model were measured by a six-component balance. Experimental results show that, within the presently tested cases, the lengths of cavity influenced by drag-reducing solution are smaller than normal condition (ventilated cavity) in water, but the asymmetry of the cavity is improved. The drag resisted by the test model is reduced dramatically (the maximum drag reduction can reach to 80%) and the re-entrant jet is more complex after the CTAC solution is injected into the cavity. Turbulent drag-reducing additives have the potential in enhancement of supercavitating asymmetry and further drag reduction.

Effects of montmorillonite on phase transition and size of TiO2 nanoparticles in TiO2/montmorillonite nanocomposites

Nanostructured TiO2/montmorillonite (TiO2/Mt) materials have many applications in a variety of fields such as plastic degradation, photocatalysis, antibacterial agent development and water purification. In order to homogeneously disperse TiO2 nanoparticles within the interlayer space of montmorillonite, an in-situ interlayer reaction method was developed to prepare nanostructured TiO2/Mt materials. Briefly, cetyl trimethylammonium (CTA+) was first intercalated into the interlayer of the montmorillonite structure. Then tetrabutyl orthotitanate (TBOT) was introduced into the interlayer space of the CTA+/montmorillonite (CTA+/Mt) nanocomposites by solvation. TBOT in the nanocomposites underwent in-situ hydrolysis, de-hydroxylation and annealed at different temperatures. During annealing, CTA+ was burnt off and TiO2 formed in the interlayer space of montmorillonite. The average crystal size of TiO2 in TiO2/Mt was compared with that of both the pure TiO2 nanoparticles and the mixture of pure TiO2 and montmorillonite. The intermediate and final products were characterized by X-ray diffraction, FT-Raman spectroscopy and transmission electron microscopy. The results showed that the phase-change temperature for transformation of TiO2 nanoparticles in TiO2/Mt nanocomposites from anatase to rutile phase was higher than that for pure TiO2 nanoparticles and the mixture of pure TiO2 and montmorillonite. Pure TiO2 nanoparticles were all converted to rutile when the annealing temperature was increased to over 800°C. However, the anatase-TiO2 still existed in TiO2/Mt, even though the annealing temperature reached a much higher temperature of 1200°C. In addition, at the same annealing temperature, the average crystal size of TiO2 in TiO2/Mt nanocomposites was smaller than that of either the pure TiO2 or the mixture of pure TiO2 and montmorillonite.