Vaporization and Thermodynamic Properties of the NbO2–TiO2 System

Glass Physics and Chemistry - The vaporization and thermodynamic properties of the NbO2–TiO2 system are studied by high-temperature differential mass spectrometry. The samples are evaporated...     

Crystal Structure and Physical Properties of PVDF Films Filled with CuCl2–MnCl2 Mixed Fillers

ABSTRACT

Poly(vinylidene fluoride) (PVDF) films filled with mixed fillers of CuCl₂–MnCl₂ were prepared. The differential thermal analysis (DTA) indicates the existence of two main endothermic peaks and the crystallization exothermic temperature. X-ray diffraction (XRD) evidenced the presence of a semicrystalline structure containing α, β, and γ crystalline phases. The optical absorption spectra depicted two shoulder-like bands as well as a strong valley. The IR spectra confirmed the XRD implications about the presence of α, β, and γ phases. The dc electrical resistivity results are discussed on the basis of Kuivalainen modified interpolaron hopping model. The temperature and filling level dependence of the hopping distance R₀ were studied. The dc magnetic susceptibility data follow the Curie-Weiss law. The electron spin resonance (ESR) investigation suggested the existence of aggregated Mn²⁺ for higher values of x where the spectra were characterized by Lorentzian signal. On the other hand, at lower values of x, the spectra were characterized by two unresolved sharp peaks.     

Influence of Solvent–Evaporation Effect on the Structure and Properties of PVDF-g-PNIPAAm Membranes

Temperature-sensitive poly(vinylidene fluoride)-graft-poly(N-isopropylacrylamide)(PVDF-g-PNIPAAm) copolymer was synthesized and its flat membranes were prepared through phase inversion method with mixture of N,N-dimethylformamide (DMF) and tetrahydrofuran (THF) as solvent in water coagulation bath. The effects of “open time” (solvent–evaporation time) on the structure and performance of membranes were investigated by X-ray photoelectron spectroscopy, field-emission scanning electronic microscopy, contact angle, filtration experiments and static protein adsorption. It was found that the increasing “open time” endowed the membrane with more pores on the surface, higher flux and better hydrophilicity, provided the membrane with lower protein adsorption. Thus, the copolymer membranes showed a good antiprotein fouling.     

The Ionic Liquid Based Synthesis of Polyaniline–MnFe2O4–CTAB Nanocomposite: Electrical Properties

Polyaniline (PANI)–MnFe₂O₄ nanocomposite was successfully synthesized by using 1-butyl-3-methyl-imidazolium bromide as ionic liquid and cetyl trimethylammonium bromide as surfactant via in situ polymerization. Structural, morphological, spectral and magnetic investigation of the product were done by X-ray powder diffractometry, fourier transform infrared spectroscopy, thermal gravimetric analyzer, transmission electron microscopy, vibrating sample magnetometry respectively. Electrical properties of PANI–MnFe₂O₄–CTAB nanocomposite was characterized with a measurement of an impedance spectroscopy, which was evaluated at frequency range varying from 1 Hz to 3 MHz for temperature range of 20–120 °C. In general ac conductivity remained almost unchanged until it reaches up to 160 kHz, and then reduced slightly almost for all temperatures except for some slight fluctuation somehow.     

Relationship Between the Synthesis and Structure of Ceramic Precursors of the TiO2–CeO2–ZrO2 System

Refractories and Industrial Ceramics - Tetragonal solid solutions based on the TiO2–CeO2–ZrO2 system stable up to 1,350°C were obtained. A method of pH titration of the initial...     

The MgO–TiO2–SiO2 system: Experiments and thermodynamic assessment

Phase relations in the MgO–TiO₂–SiO₂ system have been investigated in air over a wide temperature range using the equilibration method. X-ray powder diffraction, scanning electron microscopy combined with wave length X-ray spectroscopy (SEM/EPMA), and differential thermal analysis (DTA) have been used for sample characterization. Based on the obtained experimental results, isothermal sections of the system at 1523, 1673, and 1773 K have been established. The solid-state invariant reaction MgTi₂O₅ + T-SiO₂⇋P-MgSiO₃ + TiO₂ has been detected at 1625 ± 8 K by step-wise heat treatment. A partial liquidus projection has been suggested, and the temperatures and compositions of three eutectic invariant reactions have been experimentally measured by DTA and ex-situ analysis of the sample microstructures after melting using SEM/EPMA. Considering the newly obtained experimental data, thermodynamic parameters describing the system have been thermodynamically evaluated within the CALPHAD approach.     

Structure–Activity Correlations for Au Nanoclusters Supported on TiO2

The catalytic performance of reducible metal-oxide-supported Au nanoclusters displays striking dependencies on several factors such as dispersion, support, pretreatment, and preparation methods. Planar model Au/TiO₂ catalysts have been prepared in ultrahigh vacuum in order to investigate the strong size dependence of low-temperature CO oxidation. It is demonstrated that the experimentally observed structure sensitivity of CO oxidation on Au/TiO₂ may be rationalized by a quantum size effect. Via scanning tunneling microscopy and spectroscopy (STM/STS) and elevated pressure reaction kinetics measurements, we show that a clear correlation exists between the structural, electronic, and reactivity properties of supported Au nanoclusters.     

Ultrasound Synthesis of Polyindole–TiO2 Nanocomposite and Evaluation of Antibacterial Activity

The present work reports the synthesis and evaluation of antimicrobial activity of polyindole–TiO₂ nanocomposite. Polyindole–TiO₂ nanocomposite was synthesized by aqueous in situ chemical polymerization of indole using ammonium persulfate as an oxidant under ultrasonic condition. The synthesized polyindole and polyindole–TiO₂ nanocomposites were characterized by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscope, thermogravimetric analysis, and X-ray diffraction techniques. A sharp peak at ～1,402?cm^?1 is due to the stretching vibrations of O?Ti?O bond in polyindole–TiO₂ nanocomposite. The X-ray diffraction pattern shows the major diffraction peaks at 25°C and 48°C, indicating TiO₂ in anatase form. Polyindole–TiO₂ shows maximum activity against gram-positive Staphylococcus aureus and Bacillus subtilis as compared to gram-negative Escherichia coli.     

CO Oxidation over Au/TiO2–Carbon Catalysts: The Effect of Thermal Treatment, Stability and TiO2 Support Structure

The effect of thermal treatment on the catalyst structure and the CO oxidation performance of a Au/TiO₂ catalyst supported on a carbon composite material has been studied. X-ray absorption spectroscopy shows that the carbon composite stabilises the TiO₂ and prevent agglomeration of the particles. The activity measurements show that both Au and TiO₂ need to be present in order to obtain catalytic activity. The catalytic performance was found to be strongly affected by thermal treatments of the active phase prior to the reaction. The thermal treatments have an effect on the ordering of the TiO₂ structure, and on the CO oxidation activity. Heat treatment after Au deposition has a positive effect on the CO oxidation performance. This is attributed to the introduction of a stronger interaction between the oxide and Au which improves the catalytic activity. This also indicates that the TiO₂ support and the Au–TiO₂ interface play important roles in the CO oxidation reaction.     

Electrical Properties and the Structure of Halogen-Containing Lead Borate Glasses: I. The PbF2–2PbO · B2O3 System

The concentration and temperature dependences of the dc electrical conductivity of glasses in the PbF₂–2PbO · B₂O₃ system is investigated. It is found that, at 20–25 mol % PbF₂, the dependences log = f([F]) and E = f([F]) exhibit kinks. The concentration dependence of the true transport number of fluorine ions _F – is studied using the Tubandt method. It is shown that the introduction of 20–25 mol % PbF₂ leads to a crossover from the protonic conductivity to the unipolar fluorine ionic conductivity ( ). The results obtained are discussed in terms of the Myuller theory of the microinhomogeneous glass structure associated with the selective interaction of the components during the synthesis.     

Electrical Properties and the Structure of Halogen-Containing Lead Borate Glasses: II. The PbF2–PbO · B2O3 System

The temperature and concentration dependences of the dc electrical conductivity of glasses in the PbF₂–PbO · B₂O₃ system are investigated. It is found that the dependences log = f([PbF₂]) and E = f([PbF₂]) for glasses containing 20 and 35 mol % PbF₂ exhibit kinks, which are interpreted from the standpoint of the microinhomogeneous structure associated with the selective interaction of the components during the synthesis of glasses. Analysis of the transport numbers has revealed that the unipolar fluorine ionic conductivity is observed upon introduction of more than 35 mol % PbF₂. It is shown that, in the concentration range from 0 to 35 mol % PbF₂, the electric current is provided by both protons and fluorine ions.     

Ethylene Vinyl Acetate and Polycaprolactone–Organoclay Nanocomposite: Thermal,Mechanical and Morphological Properties

Organoclay of the type Cloisite^® 20A (C-20A) with two structurally different but semicrystalline polymer matrices was studied. Polycaprolactone (PCL), a linear, biodegradable polymer, and ethylene vinyl acetate (EVA), a branched copolymer, were chosen to prepare polymer clay nanocomposites via the melt-blending method. The results show that the structure of a polymer matrix plays a significant role towards compatibilization with the silicate layers of the clay. Scanning electron microscopy and X-ray diffraction analyses revealed an exfoliated-intercalated mixed morphology for the PCL matrix. However, for the EVA matrix, silicate layers agglomerated to form tactoids and resulted primarily in an intercalated morphology. Fourier transform infrared spectroscopy was used to determine the nature of the interactions between the polymer and the filler. The thermal properties were investigated using thermogravimetric analysis and indicated that, with an increase in clay loading, the thermal stability was reduced for both matrices. Tensile tests suggested that Young’s modulus improved for the EVA matrix with an increase in clay dosage whereas for PCL the modulus was found to be highest for 8% clay loading.     

The effect of TiO2 particle size on the characteristics of Au–Pd/TiO2 catalysts

The nanocrystalline TiO₂ materials with average crystallite sizes of 9 and 15 nm were synthesized by the solvothermal method and employed as the supports for preparation of bimetallic Au/Pd/TiO₂ catalysts. The average size of Au–Pd alloy particles increased slightly from sub-nano (< 1 nm) to 2–3 nm with increasing TiO₂ crystallite size from 9 to 15 nm. The catalyst performances were evaluated in the liquid-phase selective hydrogenation of 1-heptyne under mild reaction conditions (H₂ 1 bar, 30 °C). The exertion of electronic modification of Pd by Au–Pd alloy formation depended on the TiO₂ crystallite size in which it was more pronounced for Au/Pd on the larger TiO₂ (15 nm) than on the smaller one (9 nm), resulting in higher hydrogenation activity and lower selectivity to 1-heptene on the former catalyst.     

Citrate-Nitrate Synthesis and the Electrophysical Properties of Ceramics in the K2O–TiO2–Fe2O3 System

Glass Physics and Chemistry - This paper presents a study of the electrically conductive properties of ceramics based on phases crystallizing in the K2O–Fe2O3–TiO2 system, when using...     

Cellulose–Polyvinyl Alcohol–Nano-TiO2 Hybrid Nanocomposite: Thermal,Optical, and Antimicrobial Properties against Pathogenic Bacteria

Cellulose fiber-reinforced composite has received great attention due to the high strength, stiffness, biodegradability, and renewability of the excellent natural biomaterials. Cellulose nanofibers for the development of organic–inorganic hybrid composite is relatively new filed of research. Cellulose macro and nanofibers can be used as reinforcement in the hybrid composite because of improved mechanical, thermal, optical, electrical, morphological, and biological properties. The hybrid nanocomposites were synthesized by an in situ sol–gel process in the presence of coupling agent. The sol–gel process has definitely proven its potential by providing the synthesis of various functional organic–inorganic hybrid nanocomposites through an in situ sol–gel process. The hybrid nanocomposites have been prompted by the ability to control the morphology of final materials. The photoluminescence spectral studies indicate that the emission shifts toward higher wavelength (326–532?nm) accompanied by a reduction in impurity centers with increasing concentration of poly(vinyl alcohol)–TiO₂ and hybrid nanocomposite. The final nanostructured TiO₂ hybrid nanocomposites with particle size ranging from 0.32 to 20?nm were characterized by Field -emission transmission electron microscopy (FE-TEM) analysis. Furthermore, cellulose–poly(vinyl alcohol)–nano-TiO₂ hybrid composite was characterized by Fourier transform infrared, X-ray diffraction, UV, Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC), FE-SEM–EDX, Field-emission scanning electron microscopy (FE-SEM), and FE-TEM analysis. The different analysis results of the hybrid composite indicate the optical transparency, optical properties, T_g, crystallinity, thermal stability, and controlled morphology of hybrid nanocrystalline composites. Finally, the cellulose–poly(vinyl alcohol)—nano-TiO₂ hybrid nanocomposites were tested against pathogens such as Gram-positive Bacteria Bacillus cereus and Gram-negative Escherichia coli for antimicrobial activity. These results show that the hybrid composite exhibited excellent antimicrobial properties against pathogens.     

A New 2D Porous Pb-MOF Based on Ribbon‐Shaped SBU and 2-Nitroimidazole: Structure and Properties

A new porous metal-organic framework, [Pb₅(OAc)₇(nIm)₃]_n (1), has been successfully synthesized by employing 2-nitroimidazole ligand and Pb²⁺ ion. 1 contains novel the ribbon-shaped Pb-O SBU and reveals a 2D porous framework with a 1D tubular channel. Due to the existence of the electronegative O atom of nitro group and Lewis acid metal ion in the channel, 1 shows moderate CO₂ adsorption uptake of 25.8 cm³ cm^??1 at 298 K and 760 mmHg, and adsorption sites are also confirmed by GCMC simulations. Moreover, the electronic structures and luminescence properties of 1 was investigated. This work displays an effective approach to enrich multifunctional porous Pb-MOFs.

     

Synthesis and Properties of Lipoamino Acid–Fatty Acid Mixtures: Influence of the Amphiphilic Structure

The acylation of amino acids by acid chlorides with from 8 to 12 carbon atoms in alkaline aqueous medium following Schotten–Baumann reaction results in sodium salts of a N ^α-acylamino acid and fatty acid mixture. The latter are present in a proportion from 40 to 60%. These compositions represent mixtures of amphiphilic anionic surfactants. Together they contribute to the properties of the formulation. Measurements of the surface-active properties of these formulations, such as critical micelle concentration (CMC), surface tension at the CMC (ST), foaming capacity (FC) and foaming stability (FS), show that surfactant mixtures with the longest chain have the most desirable properties. They are comparable to commercial petroleum-based surfactants. Thus, the CMC, ST and CM values of the formulation obtained starting from leucine and dodecanoyl chloride (310 mg/l, 30.1 mN/m and 200%, respectively) are similar to, and even better than, sodium dodecylsulfate (290 mg/l, 39.1 mN/m and 230%, respectively).