Nanostructure and reactivity of nascent carbon particles from 2,5-dimethylfuran/n-heptane swirling inverse diffusion flames

Carbon particles (Soot) have been the one of primary pollutants inevitably with the combustion of fossil fuels. A better understanding on incipient soot was useful to build the models of soot formation and even control soot emissions. The present work focuses on the nanostructure and oxidation reactivity of nascent carbon particles (soot) formed from 2,5-dimethylfuran (DMF)/n-heptane non-swirling and swirling inverse diffusion flames (IDFs). The nascent soot samples were derived from three different fuels: 100% n-heptane, 50% n-heptane/50% DMF and 100% DMF. In addition, the effects of swirling combustion and collection time on characteristics of nascent soot were investigated in detail using the high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Results demonstrated that nascent soot from pure n-heptane flames presented the film-like morphology and nanostructure of amorphous nature, while the nearly primary particles with more well-organized nanostructure were found in pure DMF soot. Swirling combustion increased the entire flame front areas and diameters due to the existence of tangential velocity at the outlet of burner. Moreover, swirling combustion could enhance the mixability of the oxidizer stream and fuel stream, leading to more young soot within the fuel stream being oxidized in the inception stage. However, the collection time on soot characteristics exhibited quite negligible impacts in comparison to the swirling effects.     

Carbon nanostructure examined by lattice fringe analysis of high-resolution transmission electron microscopy images

The dimensions of graphitic layer planes directly affect the reactivity of soot towards oxidation and growth. Quantification of graphitic structure could be used to develop and test correlations between the soot nanostructure and its reactivity. Based upon transmission electron microscopy images, this paper provides a demonstration of the robustness of a fringe image analysis code for determining the level of graphitic structure within nanoscale carbon, i.e., soot. Results, in the form of histograms of graphitic layer plane lengths, are compared to their determination through Raman analysis.     

Viscosities of nonelectrolyte liquid mixtures. II. Binary and quaternary systems of some n-alkanes

This paper is the second in a series of viscosity and density studies on multicomponent mixtures of n-alkanes from 303 to 338 K. Reported here are the results of binary mixtures of n-tetracosane + n-octane as well as quaternary mixtures of n-tetracosane + n-octane + n-decane + n-hexane at 318.16, 328.16, and 338.16 K. Viscosities were determined using a standard U-tube Ostwald viscometer, and densities were determined using a flask-type pycnometer. Empirical relations tested include the Grunberg and Nissan equation and the method of corresponding states. In addition, comparisons were made regarding the behavior of this quaternary system and homologous binary mixtures of n-hexadecane + n-octane and n-tetracosane + n-octane at the same temperatures.     

Electrical properties of tri-n-butyl tin acrylate-methylmethacrylate copolymers

The copolymerization of tri-n-butyl tin acrylate (TBTA) with methylmethacrylate (MMA) has been investigated in dioxane. The composition of these copolymers was determined quantitatively by ¹H nuclear magnetic resonance (NMR) spectroscopy. The tin contents were estimated by gravimetric as well as thermogravimetric techniques (TGA). The reactivity ratio of such copolymers was estimated by application of the Kelen-Tudos method. The dielectric properties of the copolymers have been studied over a frequency range of 100–50 kHz at different temperatures from 20 to 70°C. The electrical conductivity for such copolymers was also measured. The results are interpreted in terms of the tin content of the copolymers.     

Substrate temperature and water vapour effects on structural and mechanical properties of TiO x N y coatings

Dc reactive sputtering was successfully implemented to deposit titanium oxynitride thin films using a titanium metallic target, argon, nitrogen and water vapour as reactive gases. The nitrogen partial pressure was kept constant during every deposition whereas that of the water vapour was systematically changed from 0 to 0.1 Pa. The study aims at comparing the structural and mechanical properties of the coatings deposited at room temperature (293 K) and at 673 K. Surface morphology of the film was examined by atomic force microscopy and showed different aspects according to the growth temperature. Topography mainly depends on the amount of water vapour introduced during the deposition process. Some significant changes of the crystallographic structure, due to the high substrate temperature were correlated with the evolution of the surface aspect and roughness parameters. Determination of the phase occurrence by X-ray diffraction was also carried out and appeared to be a significant parameter in understanding the evolution of mechanical properties like nanohardness (H _n) and Young’s modulus (E). H _n and E values obtained by nanoindentation ranged from 16.5 to 7 GPa and from 240 to 100 GPa, respectively. For both temperatures, mechanical properties of titanium oxynitride thin films were notably reduced as a function of the water vapour supply, especially for partial pressures higher than 4 × 10⁻² Pa. These mechanical behaviours were correlated and discussed with the phase occurrence and the amorphous structure of titanium oxynitride thin films.     

Synthesis of ZrO<Subscript>2</Subscript> nanoparticles during zirconium oxidation by supercritical water

We have discovered that massive samples of solid zirconium (Zr)_s are completely oxidized by supercritical water (SCW, T > 647 K, P > 22.1 MPa) with the formation of zirconium oxide nanoparticles (ZrO₂) _n . The particle size distribution, morphology, and features of the nanostructure formation depend on the process conditions. The kinetics of H₂ production and zirconium oxidation has been determined using the method of SCW injection into a reactor with (Zr)_s at various temperatures. The dependence of the oxidation induction time on the SCW parameters has been studied.     

Effect of solvents on the preparation of lithium aluminate by sol–gel method

γ-Lithium aluminate was prepared by sol–gel method using lithium methoxide and aluminum-sec-butoxide precursors in i-propanol, n- and tert-butanol. Clear gels could be obtained due to the addition of ethylacetoacetate and the dried solids were calcined at 550 and 900 °C. The resulting solids were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermo-gravimetric analysis/differential thermal analysis (TGA/DTA). γ-Lithium aluminate with the highest purity was obtained with t-butanol solvent and LiAl₅O₈ was the second major phase.     

Thermodynamic properties of n-pentane

Specific volumes and isobaric heat capacity measurements are reported for n-pentane. The measurements were made in the liquid and vapor phases at temperatures ranging from the triple point (173 K) to the onset of dissociation temperature (700 K) and pressures up to 100 MPa including a wide region around the critical point. We are able to fit our data, as well as those of a number of other authors, to a single equation of state with 30 constants. This equation yields the density of n-pentane in the temperature range from 280 to 650 K at pressures up to 80 MPa and the caloric properties up to 500 K. Additional experimental investigations of the thermodynamic properties are required for temperatures above 500 K. Interpolating equations for the caloric properties on the saturated line and in the critical region are also presented.     

Reactions of microcrystalline fullerene C60 with amino and aza macrocyclic ligands under solvent-free conditions

We evaluated the reactivity under solvent-free conditions of 2-aminomethyl-15-crown-5 (AM15C5), 2-aminomethyl-18-crown-6 (AM18C6), 1,4,8,12-tetraazacyclopentadecane (TACPD) and rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (tet b) with microcrystalline fullerene C₆₀. The reactions of nucleophilic addition were carried out at temperatures of about 160°C for 5 h in the case of crown ethers and TACPD, and at 180–190°C for 24 h in the case of tet b. Characterization of the products obtained was performed by using Fourier-transform infrared (FTIR) and Raman spectroscopy, laser desorption/ionization time-of-flight (LDI-TOF) mass spectroscopy, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). To provide an additional insight into the reactivity of macrocyclic compounds with C₆₀ molecules, we employed theoretical calculations in the frame of density functional theory (DFT). According to the results of SEM imaging, macrocyclic reagents are generally unable to deeply penetrate into the bulk of fullerene microcrystals (with a possible exception of TACPD). According to TGA measurements, the reaction efficiency is very low for tet b, whereas the average content of organic fraction in C₆₀-AM15C5 and C₆₀-AM18C6 reaches about 29%, and in C₆₀-TACPD, almost 40%. According to LDI-TOF mass spectral analysis, the products of TACPD, tet b and AM15C5 reactions with fullerene have oligomeric or polymeric structure. By using DFT theoretical calculations, the latter observation was explained by enhanced reactivity of secondary amino groups toward nucleophilic addition onto fullerene cage.     

Structure-property relationships in polyimide molecular composites

Rigid rod-like polyimide (PI_R) / flexible-chain polyimide (PI_F) molecular composites, with 20, 40, 50, 60 and 80 wt. % of the rigid component, were prepared and their structure and molecular dynamics were investigated, in relation to those in pure PI_R and PI_F. SAXS, DSC, DMA, TSDC and laser-interferometric creep rate spectroscopy (CRS) techniques were used for characterization of nanostructure, glass transition and sub-T _g relaxations at temperatures from 100 to 600–650 K. All the experiments indicated pronounced deviations from additivity in both nanostructure and dynamics of molecular composites. Mixing of the PI_R and PI_F components led in particular to a smaller nanostructure, down to formation of the nanoscale-homogeneous composite. Changes of the dynamic characteristics in two opposite directions and arising of large dynamic heterogeneity around T _g were observed as a result of confinement/constraining effects. Received: 19 November 2001 / Reviewed/Accepted: 7 December 2001     

Solubility measurement,Hansen solubility parameters and solution thermodynamics of gemfibrozil in different pharmaceutically used solvents

Gemfibrozil (GEM) is cholesterol-lowering agent which is being proposed as poorly water soluble drug (PWSD). Temperature based solubility values of GEM are not yet available in literature or any pharmacopoeia/monograph. Hence, the present studies were carried out to determine the solubility of PWSD GEM (as mole fraction) in various pharmaceutically used solvents such as water (H₂O), methanol (MeOH), ethanol (EtOH), isopropanol (IPA), 1-butanol (1-BuOH), 2-butanol (2-BuOH), ethylene glycol (EG), propylene glycol (PG), polyethylene glycol-400 (PEG-400), ethyl acetate (EA), dimethyl sulfoxide (DMSO) and Transcutol^® (THP) at the temperatures ranging from T?=?298.2 K–318.2?K under atmospheric pressure P?=?0.1?MPa. Equilibrium/experimental solubilities of GEM were recorded by applying a saturation shake flask methodology and regressed using ‘van’t Hoff and Apelblat models’. Hansen solubility parameters for GEM and various pharmaceutically used solvents were estimated using HSPiP software. The solid states of GEM (both in pure and equilibrated states) were studied by ‘Differential Scanning Calorimetry’ which confirmed no transformation of GEM after equilibrium. Experimental solubilities of GEM in mole fraction were observed maximum in THP (1.81?×?10^?1) followed by DMSO, PEG-400, EA, 1-BuOH, 2-BuOH, IPA, EtOH, PG, MeOH, EG and H₂O (3.24?×?10^?6) at T?=?318.2 K and similar tendencies were also recorded at T?=?298.2 K, T?=?303.2 K, T?=?308.2 K and T?=?313.2 K. ‘Apparent thermodynamic analysis’ on experimental solubilities furnished ‘endothermic and entropy-driven dissolution’ of GEM in each pharmaceutically used solvent.     

Zirconium recovery from zircaloy shavings

A chlorination process for recovering Zr from zircaloy scrap has been studied. Zircaloy chlorination was possible at temperatures as low as 220 °C. The scale microstructure and its effect on the zircaloy reactivity was analysed using Thermogravimetric analysis (TGA), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS) and scanning electron microscopy (SEM) techniques. A solid-solid phase transformation took place into the oxide scale during the zircaloy chlorination. Zirconium, as ZrCl₄(g), was separated from the oxide scale and chlorides of Cr and Fe. The effect of the reaction temperature was also analysed.     

Bi–Sb Solid Solutions: Potential Materials for High-Efficiency Thermoelectric Cooling to below 180 K

The potential of Bi–Sb solid solutions for use in the n-legs of high-efficiency thermoelectric coolers operating below 180 K was discussed. A magnetothermoelectric miniature cooler comprising a two-stage thermopile and permanent magnets was fabricated. The p-legs of the thermopile were made of doped Sb₂Te₃–Bi₂Te₃crystals, and the n-legs were made of Bi–Sb crystals. The cooler showed a high mechanical strength and high efficiency at temperatures between 120 and 180 K. It was tested at hot-junction temperatures between 140 and 200 K in vacuum. At a hot-junction temperature of 180 K, current of 1.9 A, and applied voltage of 0.52 V, the cooler showed a maximum temperature difference of 48 K and a maximum refrigerating capacity of 0.085 W.     

Characterization and properties of antimony doped Bi1.6Pb0.3Sr2Ca3Cu4O x ceramics

The influence of Sb₂O₃ dopant on the superconductivity and the phase formation of the Bi(Pb)-Sr-Ca-Cu-O system was studied using differential thermal analysis/thermogravimetric analysis (DTA/TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), a.c. susceptibility and resistance measurements. It was found that the solubility of Sb³⁺ in the 110 K superconducting phase is limited; instead Sb³⁺ readily combines with other elements to form one or more unknown second phase(s), which melt at lower temperatures and accelerates the formation of the 110 K phase. Resistance measurements show the transition initiation temperature of the 110 K superconducting phase is unchanged but thatT _c (zero) was found to decrease from 107 K to 98 K. TEM examination generating lattice images from antimony-doped crystals, showed the structure to be inhomogeneous and to contain many defects.     

Functional Barrier Performance of a Polyamide‐6 Membrane Towards n‐Alkanes and 1‐Alcohols

Polymeric barrier membranes are widely used in the food packaging area. So‐called functional barriers prevent the packed food from contamination of permeants from the environment or from other packaging components. Aim of the study was to determine barrier properties of non‐polar n‐alkanes (n‐pentane up to n‐tetradecane) and polar 1‐alcohols (1‐propanol to 1‐octanol) of a 12 µm biaxially oriented PA6 film at temperatures between 70°C and 100°C. From the experimentally determined lag times, the diffusion coefficients D_P as well as the partition coefficients K of the investigated permeants were calculated. From the correlation between the molecular volume V and the diffusion coefficients D_P, the lag times for lower temperatures can be predicted for temperatures between 20°C and 70°C. In conclusion, the investigated 12 µm PA6 film is a sufficient barrier towards organic compounds. The permeation of substances with molecular volumes above 200 ų is negligible for a shelf life of three years and temperatures below of 60°C. These storage conditions are sufficient for nearly all kinds of food packaging applications. Copyright © 2016 John Wiley & Sons, Ltd.     

Flow behaviour and microstructural evolution in cold worked 70∶30 α-brass

Abstract

Deformation behaviour and microstructures at failure were investigated in a mill cold worked 70∶30 α-brass over the test temperature range of 298–973 K and strain rate range of 10^?5–5×10^?3 s^?1. Tensile properties as a function of temperature revealed three distinct regions, with their temperature sensitivity being maximum at intermediate temperatures (553–673 K) and much less towards the lower and higher temperature ranges. Two values of activation energy for high temperature deformation Q were obtained to be 117·5 kJ mol^?1 below 623 K and 196·4 kJ mol^?1 above this critical temperature. In the respective temperature range the values of stress exponent n were 5·6 and 3·8. Based on the values of Q and n, the deformation mechanism was suggested to be dislocation climb creep with a probable contribution from dislocation pipe diffusion on lowering the temperature. Both grain size and cavity size were found to increase with increasing test temperature, suggesting them to be interrelated and act as an alternative steps for accommodating grain boundary sliding. Static grain growth study, over the temperature range of 773 to 1073 K, led to activation energy for grain growth to be 71 kJ mol^?1, with the time exponent of 0·37.     

Condensation and morphology of magnesium particles in vapour plumes

A plume chamber study of condensation in magnesium vapour was performed in flowing argon at atmospheric pressure and source temperatures (T ₀) up to 1213 K. The wall temperature (T ) was at 300 K. Sampled particles closely resembled those from zinc and cadmium aerosols and included spheres and prisms, indicative of vapour-liquid and vapour-solid nucleation. The spheres solidify from single rafts, and in addition to the hexagonal prisms that grow from dendrites, flatter and elongated forms occur as twins. The presence or absence of either spheres or prisms was found to depend on the setting ofT ₀, in agreement with theory, which predicts thatT ₀ will determine the position of the nucleation threshold temperature (T _n) relative to the melting point (T _f). The occurrence of particles condensed as solid as well as liquid nuclei whenT _n was higher thanT _f showed that supersaturated vapour states can persist as the vapour cools belowT _n. The twinned particles observed with magnesium do not occur with zinc or cadmium at atmospheric pressure. It is suggested that the presence of hydrodynamic stresses causes twinning in magnesium whereas in zinc and cadmium it results in malformed hexagonal prisms.     

Disproportionation in Hydrogen and Recombination of the Laves Phases of Zirconium with Chromium

By the methods of differential thermal, X-ray phase diffraction, and metallographic analyses, we study the processes of conventional and solid HDDR (hydrogenation-disproportionation-desorption-recombination) in ZrCr₂ compound with C14- and C15-type structures under initial pressures of hydrogen of 3 and 5 MPa at temperatures of up to 1243°K. The ZrCr₂ compound with C15-type structure disproportionates at 1048 and 1093°K for P _H2 = 5 and 3 MPa into ZrH _x and Cr and recombines in a vacuum. The temperature of disproportionation of the Laves phase with C15-type structure is lower than for the C14 phase by 120°K. As the pressure of hydrogen increases, the temperature of disproportionation decreases. The application of HDDR to the reconstruction of the C14-type structure of the Laves phase in ZrCr₂ into the C15-type structure makes it possible to decrease the temperature of treatment and its duration as compared with the case of annealing in vacuum. The procedure of HDDR forms a nanostructure in ZrCr₂. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 3, pp. 101–108, May–June, 2005.     

Al2O3-SiO2纤维增强ZL108合金复合材料的强度特性

用低成本的Al₂O₃-SiO₂系纤维作为增强相,通过加压铸造法制作ZL108合金复合材料,并对该复合材料和ZL108合金进行不同温度下的时效处理和压缩试验。通过DSC、EPMA和TEM分析认为:经488K、0.5h时效处理(T6处理)的V_f 20%的复合材料在573K以下的压缩屈服强度低于ZL108合金,是由于基体中的Mg与Al₂O₃-SiO₂纤维在加压铸造过程中起化学反应而生成MgAl₂O₄,损耗了基体中的大量Mg,导致基体铝合金时效硬化效果很差,所以压缩屈服强度低下。623K、720h保温后的V_f 20%的复合材料的压缩屈服强度比ZL108合金要高得多,是由于在这种温度环境下对ZL108合金来说是过时效,所以纤维的增强怍用显得明显。在高温(673K)下V_f 20%的复合材料的屈服强度比ZL108台金高一倍左右。不论在什么温度场合下V_f5%的复合材料的屈服强度比V_f 20%的复合材料都低。     

The stability and a.c. electrical characteristics of composites containing YBa2Cu3O7−x and alumina at elevated temperatures

Samples of a high-temperature superconductor YBa₂Cu₃O_7–x (orthorhombic phase) showed no significant weight loss in nitrogen up to 1173 K; however, differential thermal analysis measurements show that restructuring/decomposition begins around 1121 K. No reaction with alumina was found after prolonged heating at 1073 K. Electrical properties between 100 Hz and 1 MHz were generally stable at high temperatures, with little variation in properties at 1 MHz in inert and oxidizing atmospheres. Surface oxygen can be removed at high temperatures in flowing argon causing erratic electrical behaviour at lower frequencies and lower temperatures, which can be associated with changes in the oxygen content, x, and partial quenching to the high-temperature tetragonal phase. Stability and electrical tests after pretreatment of YBCO-alumina composites at 933 K in CO₂ or steam showed partial decomposition to BaCO₃, CuO and Y₂Cu₂O₅ and a phase transition from orthorhombic to tetragonal in the YBa₂Cu₃O_7–x . The original state could be retrieved by calcination in air at73 K.