Influence of Clay Modification on the Properties of Resol Nanocomposites

Two organically modified (Cloisite® 30B and 10A) and one unmodified clay (Cloisite® Na) were added to a resol‐type phenolic prepolymer. The modified montmorillonites showed a better dispersion in the prepolymer. The dispersion of the clay, the chemical structure as well as the thermal degradation behavior of the cured polymer and nanocomposites were studied. It was observed that the addition of Cloisite® Na leads to enhanced crosslinking of the cured polymer, leading to a higher activation energy for thermal degradation. The resol with Cloisite® 10A contained a higher percentage of voids, which seems to be one of the major factors that reduce hardness and adhesive strength when the nanocomposite was applied to a metal substrate.

     

Lactobacillus assisted synthesis of titanium nanoparticles

An eco-friendly lactobacillus sp. (microbe) assisted synthesis of titanium nanoparticles is reported. The synthesis is performed at room temperature. X-ray and transmission electron microscopy analyses are performed to ascertain the formation of Ti nanoparticles. Individual nanoparticles as well as a number of aggregates almost spherical in shape having a size of 40–60 nm are found.     

Production of bacterial nanocellulose from wine industry residues: Importance of fermentation time on pellicle characteristics

Bacterial nanocellulose (BNC) was produced by Gluconacetobacter xylinus under static conditions using grape pomace extract (the most abundant residue of the wine industry) as a carbon source and corn steep liquor (a byproduct of corn wet‐milling) as the main nitrogen source. Carbon and nitrogen source concentrations, as well as inocula size, fermentation time, and temperature, were all considered in order to maximize BNC production by the use of statistically designed experiments and the response surface methodology. At optimum production conditions, the effect of fermentation time on morphology, solids content, chemical structure, crystallinity, thermal decomposition pattern, and storage modulus of dried BNC pellicles was analyzed. The results evidenced that dried BNC pellicles that were incubated for longer times showed higher thermal stability, higher crystallinity, and higher storage modulus, resulting from a denser nanoribbons network. All of these characteristics will certainly play a role in the performance of BNC in practical applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43109.     

Structure,dielectric and optical properties of Nd3+-doped LiTaO3 transparent ferroelectric glass–ceramic nanocomposites

Here, we present the structural, dielectric and optical properties of neodymium ion (Nd³⁺) doped novel transparent glass-ceramics containing LiTaO₃ nanocrystals in the Li₂O–Ta₂O₅–SiO₂–Al₂O₃ (LTSA) glass system prepared by the melt-quenching technique. The precursor glasses were isothermally crystallized at 680 °C for 3–100 h, following the differential thermal analysis (DTA) data, to obtain nanostructured glass-ceramics. They were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), Fourier transform infrared reflection spectra (FTIRRS), optical absorption and luminescence spectroscopy along with dielectric constant measurements. XRD, FESEM, TEM and FTIRRS confirm the nanocrystallization of LiTaO₃ (14–36 nm) in the LTSA glass matrix. A steep increase in dielectric constant (?_r) of glass-ceramics with heat-treatment time is observed due to high dielectric constant ferroelectric LiTaO₃ formation. The measured NIR photoluminescence spectra have exhibited emission transitions of ⁴F_3/2 → ⁴I_J (J = 9/2, 11/2 and 13/2) from Nd³⁺ ions upon excitation at 809 nm. It is observed that the photoluminescent intensity and excited state (⁴F_3/2) lifetime of Nd³⁺ ions decrease with increase in heat-treatment time due to concentration quenching effect. The absorption spectra and fluorescence measurements reveal that the incorporation of Nd³⁺ ions in the LiTaO₃ crystal lattice in the oxide glassy matrix is important for obtaining desirable fluorescence performance of the material.     

Processing and Properties of Eu3+‐Doped Barium Bismuth Titanate (BaBi4Ti4O15) Glass–Ceramic Nanocomposites

Precursor glasses for the ferroelectric barium bismuth titanate (BaBi₄Ti₄O₁₅) (BBiT) have been prepared by the melt‐quench technique in the SiO₂–K₂O–BaO–Bi₂O₃–TiO₂ (SKBBT) glass system with and without Eu₂O₃ doping. BBiT glass–ceramic (GC) nanocomposites have been derived from these glasses by controlled heat treatment. The structural properties of the GCs have been investigated using X‐ray diffraction (XRD), electron microscopy (FE‐SEM, TEM), and FT‐IR reflectance spectroscopy. FE‐SEM images show the formation of randomly oriented hexagonal rod‐shaped crystals of 200–400 nm and TEM images show 10–20 nm crystallites. FT‐IR spectra exhibit the characteristic bands of BBiT at 480, 585, and 680 cm^?1. The activation energy of crystallization (E_c) varies from 295 to 307 kJ/mol. The dielectric constants (ε_r) of glass and GC nanocomposites increase with an increase in frequency up to 3.0 MHz and then decrease up to 5.0 MHz. Heat‐treated GCs show higher ε_r values, in the range 25–55, compared to the precursor glasses (20–37). Dielectric losses (tan δ) for all the samples increase from 0.005 to 1.0 with an increase in frequency from 100 Hz to 5.0 MHz. Excitation spectra were recorded by monitoring emission at 613 nm corresponding to the ⁵D₀ → ⁷F₂ transition. An intense 466 nm excitation band corresponding to the ⁷F₀ → ⁵D₂ transition was observed. Emission spectra were then recorded by exciting the glass samples at 466 nm. Longer heat‐treatment times led to a 15‐fold increase in the intensity of the red emission at 612 nm, attributed to the segregation of Eu³⁺ ions into the low phonon energy BBiT crystallites. The hardness (3.8–5.1 GPa) and fracture toughness (1.8–3.5 MPam^0.5) values obtained in the GCs are high and suitable for structural applications.     

Modeling and Simulation of Microwave Heating of Foods Under Different Process Schedules

This paper describes the development of a simulation model for heating of foods in microwave ovens and its uses to optimize food heating strategies. The solution of the coupled energy and mass microscopic balances considers the electromagnetic energy absorption as well as temperature-dependent thermal, transport, and dielectric properties. The microscopic balances are highly nonlinear coupled differential equations, which were solved using finite element software (Comsol Multiphysics). Maxwell equations were employed in order to describe the interaction between electromagnetic radiation and food. The mathematical model allowed the evaluation of the effect of product size and composition in the temperature profiles that developed inside the food that was radiated either on one or both sides. In order to improve the nonuniform temperature profiles that occurred within foods under continuous operation, different operation schemes were evaluated: intermittent cycles, joint action of microwaves with air impingement, and the effect of interference of electromagnetic waves.     

Emulsifiers: Effects on Quality of Fibre-Enriched Wheat Bread

Resistant starch (RS) is a nutritional ingredient commonly used in bread products as dietary fibre (DF). This ingredient presents similar physiological functions than those imparted by DF, promoting beneficial effects such as the reduction of cholesterol and/or glucose levels on blood. Quality improvement of bread containing RS, with an optimized combination of emulsifiers, will be useful in the development of new and healthy bakery products. The objective of this research was to analyse the effects of different emulsifiers on several quality parameters of dough and bread prepared with wheat flour partially substituted with resistant starch as a dietary fibre. A blend of wheat flour/maize-resistant starch (MRS; 87.5:12.5) with sodium chloride, ascorbic acid, α-amylase, compressed yeast and water was utilized. Emulsifiers were incorporated to formulations in different levels according to a simplex centroid design. The viscoelastic, textural and extensional properties of dough were analysed. Bread quality was evaluated throughout the gelatinization and retrogradation of starch, specific volume of loaves, and texture and firmness of bread crumb. The incorporation of 12.5% (w/w) of MRS to wheat flour caused an increase of 5% in water absorption. Stability decreases markedly (from 9.9 to 2.2 min) and the mixing tolerance index increased (from 79 to 35 UF). The sodium stearoyl lactylate (SSL)–diacetyl tartaric acid esters of monoglycerides (DATEM) mixture increased hardness and resistance to extension on dough, whilst dough containing Polysorbate 80 (PS80) was softer; nevertheless, both types of dough retained less CO₂. An optimized concentration of the three emulsifiers (0.24% SSL, 0.18% PS80, 0.08% DATEM, w/w) was obtained by surface response methodology. The bread prepared with this combination of emulsifiers presented a considerable specific volume with a very soft crumb.     

Synthesis and characterization of nanocomposites based on a furan resin

Formaldehyde emissions are nowadays trying to be reduced because of its atmospheric pollutant character. Besides, it is encouraged the use of polymeric materials synthesized from biomass wastes as row materials. For this reason, furan resins would be an alternative to phenolic resins, where formaldehyde is replaced by furfural as a reactant. Regarding, the addition of nanoparticles to the furan resin should enhance their performance as metal coatings with good thermal and oxidative resistance. The aim of this article is to study the influence of the in situ addition of different type of nanoparticles on the chemical reactions involved in the synthesis of a furan resin. From the viscosity measurements it was observed that the addition of the nanoreinforcements led to a higher resin reaction rate. Differences in the final chemical structure among the materials were also observed by infrared spectroscopy analyses. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Prebiotic emulsions stabilised by whey protein and kefiran

The goal of this work has been to assess the influence of a health-promoting hydrocolloid, such as kefiran, in oil-in-water emulsions (O/W: 50/50) containing whey protein isolate (1.0% wt.). Different kefiran concentration levels (0%, 0.25%, 0.5%, 1% wt.) were studied, observing a shift from a fluid-like to a solid-like behaviour and higher viscosities when kefiran content increased. A pseudoplastic behaviour was detected for all systems studied. The observed evolution is attributed to the thickening effect exerted by kefiran, which promoted stability, in spite of observing a certain flocculation degree within the emulsion systems, demonstrated through the addition of sodium dodecyl sulphate (1% wt.). Furthermore, short-term stability of these pseudoplastic emulsions has been verified by laser-scattering techniques. Thus, a Sauter diameter around 1 µm remained unaltered up to 7 days since preparation. The addition of kefiran in the formulation would benefit from their well-known health-promoting effects.