Actinide–lanthanide co-extraction by rigidified diglycolamides

Within the actinide and lanthanide co-extraction strategy, three rigidified diglycolamides, namely 2,6-bis (N-dodecyl-carboxamide)-4-oxo-4H-pyran (1), 2,6-bis-[N-(4-tert-butylphenyl)carboxamide]-4-oxo-4H-pyran (2), 2,6-?bis[(N-docecyl-N-methyl)carboxamide]-?4-methoxy-?tetrahydro-pyran (3), were synthesized. Moreover, the effect of structural rigidification on Am(III) and Eu(III) extraction under different conditions was investigated. The carboxamide extractant 3 resembles the extracting behavior of N,N,N′,N′‐tetraoctyl diglycolamide (TODGA) in terms of efficiency and affinity within the lanthanide family, together with fast kinetics and satisfactory cation back-extraction. The presence of 1-octanol in the diluent mixture strongly affects the ligand stability. Moreover, despite the low extraction efficiency showed by 1 and 2, all the three ligands exhibit a higher affinity for Am with respect to TODGA, resulting in a lower lanthanide/Americium separation factor, of around 4 for ligand 3 and close to 1 for ligands 1 and 2.     

Phosphorus Recovery by Liquid–Liquid Extraction

Abstract

It is acknowledged that phosphorus removal is more crucial in comparison with nitrogen removal for preventing algae glooming and eutrophication. Chemical and biological methods are common methods for the P removal. Excessive sludge production and difficulties of recovering phosphorus are concerns in terms of sustainable waste management. A liquid-liquid extraction (LLE) process is thus considered for the study aiming at recovering phosphorus from wastewater in a sustainable way. The results revealed that the best extractant is a mixture of kerosene and benzyl-di-methyl-amine (BDMA) at a volume ratio of 2:1. Under the study conditions, one part of extractant can react with four parts of wastewater to transfer >97% of P to the organic phase. In addition, in the stripping step, a 1:1 ratio of extract to recycled acid can result in 96% recovered P, implying an overall 93% phosphorus recovery efficiency can be achieved by the LLE process. Most importantly, the extractant can be recycled and reused at least 5 times if the residual P concentration should be less than 4 mg/L vs. the original P concentration of 21 mg/L. A complexion between amine groups in BDMA and phosphates and the positive charge of the micelles surface when the extractant (composed of kerosene and BDMA) mixed with P containing wastewater would contribute to the P recovery and this is a novel approach to recover P from wastewater.     

Investigation of polyethylene–wax blends by CRYSTAF and SEC–FTIR

Summary Oxidized wax blends with respectively HDPE, LDPE and LLDPE were investigated using CRYSTAF and SEC–FTIR in order to determine the possibility and extent of co–crystallization of the wax with each of these polyethylenes. CRYSTAF shows very little or no co–crystallization of wax with HDPE and LDPE, while there is a strong indication of co–crystallization in the case of LLDPE. SEC-FTIR analyses show co–elution of wax with LLDPE, indicating some chemical interaction between the oxidized wax and LLDPE.     

Ultrahydrophobic silica films by sol–gel process

Wettability of solid surfaces is a crucial concern in our daily life as well as in engineering and science. The present research work describes the room temperature (27 °C) synthesis of adherent and water repellent silica films on glass substrates using vinyltrimethoxysilane (VTMS) as a hydrophobic reagent by a single step sol–gel process. The silica sol was prepared by keeping the molar ratio of tetraethoxysilane (TEOS), methanol (MeOH), water (H₂O) constant at 1:14.69:5, respectively, with 0.01 M NH₄F throughout the experiments and the VTMS/TEOS molar ratio (M) was varied from 0 to 0.97. The effects of M on the surface structure and hydrophobicity have been researched. The static water contact angle as high as 144° and water sliding angle as low as 14° was obtained for silica film prepared from M = 0.97. The hydrophobic silica films retained their hydrophobicity up to a temperature of 255 °C and above this temperature the films became superhydrophilic. The prepared silica films were characterized by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier Transform Infrared (FT-IR) spectroscopy, humidity test and static and dynamic water contact angle measurements.     

Nanocrystalline C–BN synthesized by mechanical alloying

Nanocrystalline carbon–boron nitride (C–BN) compounds have been synthesized by solid phase mechanical alloying of C_x(BN)_1−x powder with various carbon fractions x. Ternary mixing within the structures was found to occur after ball milling and hot-pressing. High temperature recrystallization led to a change in structural configuration, specifically, into alternating layers of graphite and BN. The hardness of the C–BN plates increased when the carbon fraction x increased from 0 to 0.5, and then decreased when x increased thereafter. The composite C_0.5(BN)_0.5 possessed the highest hardness equalling twice that of nanocrystalline graphite and three times that of nanocrystalline BN. The lattice parameters c and a were larger and smaller, respectively, than those of graphite and hBN. The property differences between the initial and resultant materials were attributed to the structural transformation of the original substances into heterogeneously layered C_x(BN)_1−x compounds. New additional peaks were also observed and matched those of shock-wave compressed BN.     

Phenol–formaldehyde resins modified by copper nanoparticles

Abstract

Phenol–formaldehyde (PF) resins modified by copper nanoparticles were synthesised by in situ polymerisation process. X-ray diffraction (XRD), transmission electron microscopy (TEM) revealed that nanosized copper particles were well dispersed in the resulting PF resins. The thermal properties of the prepared PF resins were investigated by thermogravimetric analysis (TGA). It was indicated that copper nanoparticles remarkably improved the thermal stability of the PF resins at lower temperature. However, the copper nanoparticles increased the rate of the degradation of the PF resins at the elevated temperature. The toughness and the tribological properties of the friction materials based on the prepared PF resins were also studied. The results showed that copper nanoparticles obviously improved the brittleness and the tribological performances of the friction materials.     

Investigation of Alumina Wetting by Fe–Ti,Fe–P and Fe–Ti–P Alloys

Abstract

The wetting of alumina substrates by Fe–Ti, Fe–P and Fe–Ti–P alloys has been investigated using sessile drop experiments conducted under an inert gas atmosphere in the temperature range of 1550 to 1620°C. The surface and interfacial structures have been explored by scanning electron microscopy and energy dispersive X-ray spectroscopy. Substantial additions of titanium are known to induce steel melts to wet alumina due to the formation of a Ti-rich reaction product at the alloy/ceramic interface, but the present work has shown that even low Ti concentrations can induce a reactive wetting process leading to an improvement of the wettability of alumina by Fe alloys. The contact angle of molten steel containing phosphorus on alumina decreased with increasing P content. The improvement of the wetting behaviour in this system was attributed solely to the adsorption of P onto the surface of the Fe melt. The addition of P as a ternary alloying element to the system Fe–Ti proved to be beneficial to the wetting behaviour. The measured contact angles were much lower than those in the binary systems Fe–Ti and Fe–P. This effect was related to the fact that P enhances the activity of Ti in the Fe melt. According to experimental observations, it turns out that the wettability of liquid Fe-based alloys, when an Al2O3 surface is present, is not only a property of the metal/oxide couple but is also dependent on the oxygen partial pressure, whereas temperature variations bring about a comparatively small effect. This work is of interest in understanding the phenomena pertaining to inclusion engineering and steel– refractory interactions, such as the clogging of submerged entry nozzles by agglomerated alumina particles during the continuous casting process.     

Novel Na–Li–SiAlPON glasses prepared by melt synthesis using AlN

Amorphous alumino–silicophosphate materials containing up to 1.70 wt.% nitrogen have been successfully prepared by aluminium nitride solution in Na–Li–Si–Al–P–O melts at 850 °C thus preventing phosphorus volatilisation. Although the solubility limit for nitrogen in these glasses was limited to 8.31 wt.%, the presence of nitrogen in the materials greatly increases their glass transition temperatures, suppresses the devitrification and has a significant effect on their melting behaviour. Comparative analysis of Raman spectra for the oxide and oxynitride glasses shows the substitution of P–O–P linkages by PN–P linkages while tri-coordinated nitrogen bridges were not detected. The attendant increase in network connectivity arising from such a substitution is responsible for the increase in glass transition temperature when nitrogen substitutes for oxygen.     

Asymmetrical modification of Wells–Dawson POMs by Cu–phnz coordination polymers

A new asymmetrically modifying Wells–Dawson polyoxometalates (POMs), {[Cu₃(C₁₂N₂H₈)₅](H₂P₂W₁₈O₆₂)}·0.5[Cu₂(C₁₂N₂H₈)₃]·(C₁₂N₂H₈), have been synthesized and structurally characterized. X-ray diffraction analysis reveals that the Wells–Dawson POMs are asymmetrically functionalized by [Cu (C₁₂N₂H₈)₂] monomers and [Cu₂(C₁₂N₂H₈)₃] dimers, and the asymmetrical coordination mode to stabilize the Wells–Dawson POMs has never been found in the POM chemistry hitherto. In the crystal engineering point of view, the bigger steric hindrance, the polycyclic aromatic bridging and conjugated action of the phnz molecules facilitate the formation of asymmetrical coordination mode of the Wells–Dawson POMs. Additionally, the electrochemical behavior of the title compound modifying CPE (1-CPE) has been studied.     

Toughened carbon nanotube–iron–mullite composites prepared by spark plasma sintering

Carbon nanotube–iron–mullite nanocomposite powders were prepared by a direct method involving a reduction in H₂–CH₄ and without any mechanical mixing step. The carbon nanotubes are mostly double- and few-walled (3–6 walls). Some carbon nanofibers are also observed. The materials were consolidated by spark plasma sintering. Their electrical conductivity is 2.4 S/cm whereas pure mullite is insulating. There is no increase in fracture strength, but the SENB toughness is twice than the one for unreinforced mullite (3.3 vs. 1.6 MPa m^1/2). The mechanisms of carbon nanotube bundle pullout and large-scale crack-bridging have been evidenced.     

Zirconia toughening of mullite–zirconia–zircon composites obtained by direct sintering

Although multi-phase ceramic materials were always used, nowadays composite materials have an important industrial and technological role, because they enlarge the design capability of the manufacturer in properties and behaviors.Some mullite–zirconia–zircon composites were recently processed and characterized which presented satisfactory properties for structural applications under severe chemical and thermomechanical conditions. The objective of the present work is to study the influence of the starting composition in the mechanical and fracture properties of mullite–zirconia–zircon composites, with different microstructures, obtained by direct sintering of binary mixtures of electrofused mullite–zirconia (MZ) and micronized zircon. The materials were consolidated by slip casting of concentrated aqueous suspensions in plaster molds from a wide range of powder compositions (between 15–85 wt% and 85–15 wt% of the two raw materials used).Flexural strength (σ_f), dynamic elastic modulus (E), toughness (K_IC) and fracture surface energy (γ_NBT) were evaluated. The results were explained by microstructure and the XRD-Rietveld analysis.At low proportion, the zircon was thermally dissociated. The ZrO₂ was a product of this reaction and also influenced the mechanical and fracture properties of these materials through several combined mechanisms, principally as a result of the development of microcracks due to the volume change of the zirconia grains caused by the martensitic transformation during the cooling of these composites from sintering temperature.Composites prepared with higher MZ in the starting powders showed a higher fracture toughness and initiation energy. Microstructure consisting of mullite as a continuous predominant phase in which zircon and zirconia grains were distributed showed better mechanical and fracture properties.     

Ignition of a Ti–Al–C System by an Electron Beam

This paper describes the optimal modes of initiation of self-propagating hightemperature synthesis with the help of an electron beam on the example of a Ti–Al–C powder mixture. A pulsed electron beam with a particle energy of tens of kiloelectronvolts and a duration of hundreds of microseconds is used. Morphology, structure, and elemental composition of formed products in the form of Ti₃AlC₂ and TiC are studied.     

Microstructure and properties of CaO–ZrO2–SiO2 glass–ceramics prepared by sintering

For the development of a new wear resistant and chemically stable glass-ceramic glaze, the CaO–ZrO₂–SiO₂ system was studied. Compositions consisting of CaO, ZrO₂, and SiO₂ were used for frit, which formed a glass-ceramic under a single stage heat treatment in electric furnace. In the sintered glass-ceramic, wollastonite (CaSiO₃) and calcium zirconium silicate (Ca₂ZrSi₄O₁₂) were crystalline phases composed of surface and internal crystals in the microstructure. The internal crystal formed with nuclei having a composition of Ca_1.2Si_4.3Zr_0.2O₈. The CaO–ZrO₂–SiO₂ system showed good properties in wear and chemical resistance because the Ca₂ZrSi₄O₁₂ crystals positively affected physical and mechanical properties.     

Propane Selective Oxidation Over Monophasic Mo–V–Te–O Catalysts Prepared by Hydrothermal Synthesis

Two distinct phases, orthorhombic and hexagonal, of Mo–V–Te–O mixed oxide catalysts were prepared separately by the hydrothermal synthetic method and solid-state reaction, and these catalysts were tested for propane selective oxidation to acrylic acid. The hydrothermally synthesized orthorhombic phase of the Mo–V–Te–O catalyst showed high activity and selectivity for the oxidation of propane into acrylic acid. This catalyst also showed extremely high catalytic performance in the propene oxidation, producing acrylic acid in a high yield. The hexagonal Mo–V–Te–O catalyst was formed via the solid-state reaction between the orthorhombic Mo–V–Te–O and -TeVO₄. This phase showed poor activity to both propane and propene oxidations, although the hexagonal phase was constructed with the octahedra of Mo and V similar to the orthorhombic phase. Reaction kinetics study over the catalyst with orthorhombic structure revealed that propane oxidation was of first order with respect to propane and nearly zero order with respect to oxygen, suggesting that the rate-determining step of the reaction is C–H bond breaking of propane to form propene. Structural effects on the catalytic oxidation performance were discussed.     

Highly Site-Selective Epoxidation of Polyene Catalyzed by Metal–Organic Frameworks Assisted by Polyoxometalate

Ectropis obliqua Prout is one of the most severe defoliator insects of tea plants. Sex pheromones method has been widely used for monitoring and controlling the insect pest of E. obliqua Prout due to their relative safety, low cost, and environmental friendliness. However, conventional preparing sex pheromones of E. obliqua Prout has been criticized by the costly and/or low efficiency procedure. Herein, we report a series of Fe-based metal–organic frameworks (MOFs) as efficient heterogeneous catalysts for the site-selective epoxidation of 3Z,6Z,9Z-octadecatriene to its monoepoxides. Particularly, MIL-100(Fe) combined with polyoxometalate (POM) as cocatalyst appears as the best catalyst for the oxidation of 3Z,6Z,9Z-octadecatriene to a high site selectivity to the corresponding 6,7-epoxide with good yields. 3Z,6Z,9Z-octadecatriene and its corresponding 6,7-epoxide are the primary sex pheromone components of the E. obliqua Prout. Significantly, the field bioassay experiments showed that the mixed products were highly effective in attracting E. obliqua Prout male moths. This work provides a general method to fast and clean synthesis of sex pheromones and opens new avenues for the application of Fe-based MOFs in the pest control with environmental friendliness.     

Container washing wastewater treatment by combined electrocoagulation–electrooxidation

Treatment of container washing wastewater (CWW) by using combined electrocoagulation (EC)–electrooxidation (EO) process was studied. CWW contains many organic compounds such as surfactants used in cleaning agents. Wastewater was first treated by EC with iron (Fe) and aluminum (Al) electrodes. The process performance was measured according to the removal efficiencies of soluble chemical oxygen demand (sCOD) and color. Maximum sCOD removal efficiency was found 82% and color removal efficiencies were 95%, 95% and 98% at 436, 525 and 620 nm, respectively, with Fe electrodes under 25 mA/cm² current density, initial pH of 5 and 120-min operation time. Because of the low sCOD removal efficiency, EO was used as post-treatment process by using boron doped diamond electrode (BDD). sCOD removal efficiency was increased to 89% and color removal efficiencies decreased to 72%, 64%, 71% at 436, 525 and 620 nm, respectively, under 25 mA/cm² current density, initial pH of 3 and 300-min operation time. This study showed that electrochemical processes caused new complex molecules formation in the CWW, which caused deterioration of water color and limited the process efficiency.     

Natural rubber–cassava starch foam by compression moulding

Abstract

The foaming processes of mixtures of cassava starch–water and cassava starch–natural rubber latex blends have been carried out by compression moulding. The appropriate conditions under which to produce expanded foam are as follows: a temperature of 150°C, 10·8 MPa pressure, and a 2 min moulding time. For the foam from the cassava starch with water as a blowing agent, it was found that water levels in the range of 150–200% by weight of the dry starch gave good conditions for foaming. The resulting foamed material has a uniform closed cell structure. Regarding blending of cassava starch with natural rubber, the natural rubber could not be dispersed in the gelatinised starch when blended at a temperature of 70°C. To stabilise and prevent the coagulation of natural rubber in the blending process, Nonidet P40, a nonionic surfactant, was used. A suitable amount of Nonidet P40 was 1·5% by weight of natural rubber latex. The compressive stress and the storage modulus of the foam obtained increased (42–233%) with increasing natural rubber content owing to the high elasticity of the natural rubber and its promotion of more elasticity to the foams. When 2–5% of benzoyl peroxide by weight of natural rubber was added to the rubber latex, the compressive stress of the foam was further increased (20–118%) owing to vulcanisation of the natural rubber. Furthermore, an addition of 15–30% of calcium carbonate by weight of the dry starch of the blends was found to increase the compressive stress and storage modulus of the foams (69–148%) and the hardness and brittleness of the foams.     

Epoxidation of olefins catalyzed by molybdenum–siloxane compounds

The triphenylsiloxy complex MoO₂(OSiPh₃)₂ and a related polyhedral metallasiloxane formulated as [MoO₂(O₂SiPh₂)]_n have been tested as catalysts for the liquid phase epoxidation of cyclic olefins by tert-butylhydroperoxide at 55 °C. The initial activities increased in the order 1-octene < trans-2-octene < cyclododecene < cyclooctene and the corresponding epoxides were the only observed products. The best results were obtained without the addition of any co-solvents (other than decane), forming solid–liquid systems. Cyclooctene oxide was obtained in quantitative yield within 7.5 h of reaction, and the solid catalysts could be recycled without measurable loss of activity.     

Filamentous alumina–chitosan porous structures produced by gelcasting

Porous filamentous macroelements with tunable properties were developed using alumina–chitosan fibers produced by gelcasting extrusion. The initial suspension was prepared as a dilute aqueous acetic acid solution containing 13 vol% of alumina particles and 1.3 vol% of dissolved chitosan. After extrusion, coagulation in an NaOH bath and drying, 300 μm diameter continuous fibers (9 vol% of chitosan) were compacted and sintered at different temperatures (1100–1500 °C) to produce 40×40 mm² cylindrical macroelements. The effects of the thermal treatment temperature on the porosity, specific surface area, mechanical strength and microstructure of the macroelements were evaluated. It was verified that these properties can be controllably modified in a wide range, depending on the sintering conditions.