Preparation and phosphorus recovery performance of porous calcium–silicate–hydrate

Porous calcium–silicate–hydrate was synthesized and used to recover phosphorus from wastewater. The principal objective of this study was to explore the phosphorus recovery performance of porous calcium–silicate–hydrate prepared by different Ca/Si molar ratios. Phosphorus recovery mechanism was also investigated via Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectrum (EDS), Brunauer–Emmett–Teller (BET) and X-ray Diffraction (XRD). The law of Ca²⁺ release was the key of phosphorus recovery performance. Different Ca/Si molar ratios resulted in the changes of pore structures. The increase of specific surface area and the increase in concentration of Ca²⁺ release were well agreement together. The Ca/Si molar ratio of 1.6 for porous calcium–silicate–hydrate is more proper to recover phosphorus. The pore structure of porous calcium–silicate–hydrate provided a local condition to maintain a high concentration of Ca²⁺ release. Porous calcium–silicate–hydrate could release a proper concentration of Ca²⁺ and OH^? to maintain the pH values at 8.5–9.5. This condition was beneficial to the formation of hydroxyapatite. Phosphorus content of porous calcium–silicate–hydrate reached 18.64% after phosphorus recovery.     

Preparation and characterisation of titania-supported vanadium–phosphorus oxide catalysts

A series of vanadium–phosphorus oxides (mainly with V P ) supported on pigmentary anatase (10 m² g^-1) has been prepared using aqueous NH₄VO₃ and (NH₄)H₂PO₄ solutions, with loadings up to 11.3 wt%, equivalent to about 12.7 monolayers. Characterisation by X-ray diffraction, laser Raman spectroscopy, X-ray photoelectron spectroscopy and temperature-programmed reduction suggests that the main phase present at loadings below about 10 wt% is an amorphous V–P oxide which exists chiefly as blocks of disordered material. The presence of small amounts of crystalline -VOPO₄ and of V₂O₅ is indicated at the highest loadings, especially when and V P ratios are used. The two materials having the lowest loadings are active for methanol oxidation at 473–533 K, and show high selectivity to formaldehyde. This revised version was published online in June 2006 with corrections to the Cover Date.     

Residual phosphorus effects and nitrogen × phosphorus interactions in soybean–maize rotations on a P-deficient Ferralsol

Legume-cereal rotations are an essential component of integrated soil fertility management in low-input cropping systems, but strategies are needed to increase phosphorus (P) fertilizer use efficiency in such systems. These may include preferential targeting of P to one of the crops in the rotation cycle, the use of P-efficient genotypes, and the optimization of the rates of P fertilizer used. A field trial was conducted to evaluate the effects of increasing P fertilizer rates (0, 11, 22 and 44 kg P ha^?1, added as triple super phosphate) applied to three soybean genotypes grown on a P-deficient Ferralsol, on the nitrogen (N) and P nutrition of a subsequent maize crop. In addition, a greenhouse trial was set up to assess N, P and other rotation effects of three soybean genotypes on a subsequent maize crop relative to a maize–maize rotation at high and low P supply. In the field trial, soybean did not respond to increasing P rates, but residual P effects improved maize grain yields by up to 90 %. Ear leaf (field trial) and shoot (pot trial) P concentrations increased by applying N to maize, demonstrating important N × P interactions. The pot trial did not reveal a positive rotation effect of soybean on maize beyond the mere N-benefit, showing that soybean was not able to improve P availability to maize after correcting for the N-effect. No variation in rotation effects on maize among soybean genotypes was observed. Because of the absence of effects of the soybean crop on P availability to maize, opportunities to increase P fertilizer use efficiency in soybean–maize rotations mainly reside in maximizing P uptake by each crop separately and in matching P fertilizer rates with crop demand.     

Effect of phosphorus–nitrogen compound on flame retardancy and mechanical properties of polylactic acid

A phosphorus-nitrogen flame retardant (PN) was synthesized by using cytosine and diphenylphosphinic chloride. The flame retardancy and thermal stability of polylactic acid (PLA)/PN composites were investigated by the UL-94 vertical burning test, limited oxygen index (LOI), cone calorimeter test, and thermogravimetric analysis. The PN performs efficiently on improving the flame retardancy of PLA. The PLA composite achieves the UL-94 V-0 rating and its LOI increases to 30.4 vol% by adding 0.5 wt% PN. The flame retardant mechanism analysis showed that PN catalyzes the degradation of PLA to improve the flame retardancy by melting-away mode. Meanwhile PN reduces the release of flammable gasses during thermal degradation of PLA by promoting the transesterification of PLA, which is helpful for extinguishing flame. Moreover, triglycidyl isocyanurate (TGIC) was used as a micro-crosslinking agent to reduce the loss of mechanical properties of PLA/PN composites caused by degradation. Adding 0.1 wt% TGIC and 1.0 wt% PN into PLA, the tensile strength and elongation at break of PLA/PN are increased to the same level as that of PLA. Therefore, PLA with excellent comprehensive performance can be obtained.     

Effects of cropping history and phosphorus source on yield and nitrogen fixation in sole and intercropped cowpea–maize systems

Symbiotic N₂-fixation, N uptake efficiency, biomass- and crop production of cowpea and maize as affected by P source, sole- and intercropped, and introduction of break crops were studied on a farmer’s fields in semi-arid Tanzania. Cowpea fixed around 60% of its N from the atmosphere amounting to 70 kg N ha⁻¹ under sole and 36 kg N ha⁻¹ under intercropping as estimated by the ¹⁵N isotope dilution method around peak biomass production. The amount of N₂-fixed was 30–40% higher when P was applied as either TSP or MRP whereas cowpea yield were unaffected. Intercropped maize with 19,000 plant ha⁻¹ accumulated the same amount of N as 38,000 sole cropped maize plants although intercropping reduced the dry matter accumulation by 25%. The N uptake efficiency of the applied ¹⁵N labelled fertiliser was 26%, which equal a total pool of early available plant N of 158 kg N ha⁻¹. Under the N deficient conditions, P application did not increase the grain yield of maize. The LER indicate that sole cropping required 18% more area than intercropping in order to produce the same grain yield, and 35% more land when LER was based on N uptakes. Introduction of break crops in the maize systems, more than doubled accumulation of dry matter and N in the grain compared to continuous maize cropping. During maturation sole crop cowpea shedded leaves containing 41 kg N ha⁻¹. The current findings underline the importance of crop diversity in Sub Saharan Africa agriculture and emphasise the need for including all residues, including shedded leaves, in nutrient balance studies.     

Preparation of highly dispersed palladium–phosphorus nanoparticles and its electrocatalytic performance for formic acid electrooxidation

Highly dispersed and ultrafine palladium–phosphorus (Pd–P) nanoparticles (NPs) are prepared with a novel phosphorus reduction method. The structural and electronic properties of Pd–P NPs are characterized using Fourier transform infrared (FT-IR), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The electrooxidation of formic acid on Pd–P NPs are investigated by using cyclic voltammetry, chronoamperometry and CO-stripping measurements. The physical characterizations indicate the doped P element can enhance the content of Pd⁰ species in Pd NPs, decrease the particle size and improve the dispersion of Pd–P NPs. The electrochemical measurements show the Pd–P NPs have a better catalytic performance for formic acid electrooxidation than Pd NPs.     

Effect of heat treatment on electroless ternary nickel–cobalt–phosphorus alloy

Ternary Ni–Co–P and binary Ni–P alloy coatings were deposited on mild steel panels from an alkaline bath in the presence and absence of cobalt sulfate using an electroless process. The effects of heat treatment on surface topography and crystal orientation of Ni–Co(11.17%)–P(3.49%) alloy coatings were studied in contrast to that of Ni–P ones. It was found that the as plated Ni–Co–P alloy is a supersaturated solid solution of P and Co dissolved in a microcrystalline Ni matrix with 111 preferred direction. Heat treatment induces structural changes. The formation of Ni₃P phase precipitates and recrystallization of nickel occur when the sample is treated at > 400 °C for one hour. It is observed that the Ni diffraction lines of treated Ni–Co–P alloy at > 400 °C are shifted to lower angles as compared to those of treated Ni–P or as plated Ni–Co–P alloys. The surface topography of Ni–Co–P alloy also changes with heat treatment temperature. The surface topography and crystal orientation were characterized by means of scanning electron microscopy and X-ray diffraction, respectively. The hardness and corrosion resistance, in 5 wt % NaCl solution, of heat treated Ni–Co–P samples were studied.     

Preparation of organic–inorganic intumescent flame retardant with phosphorus,nitrogen and silicon and its flame retardant effect for epoxy resin

According to the requirement of fire life cycle assessment (LCA), chitosan ethoxyl urea phosphate (CEUP), an organic–inorganic intumescent flame retardant (IFR) containing phosphorus, nitrogen, and silicon, was synthesized by the reaction of chitosan, phosphorus pentoxide, and urea. FTIR, ¹H NMR, SEM, and XRD were employed to characterize the compounds. As a result, CEUP was successfully prepared with higher thermal stability, favorable to enhance fire resistance. Combined with OMMT, the organic/inorganic IFR was applied as EP flame-retardant agents. The combustion behavior of EP composite was investigated by LOI, UL-94, CCT, SEM, TGA, and TG-IR. It was observed that using 15% CEUP and 3% OMMT (EP3), LOI value reached 34.8% and passed the UL-94 V-0 rating, while THR and TSP of EP composite reduced 65 and 72% compared with pure EP. The char residue of EP composite was up to 22.4%. The thermal decomposition mechanism was traced from 100 to 600°C by TG-IR. It was suggestive that CEUP decomposition commenced at 100°C to create phosphoric acid and sublimation of urea occurred at 300°C. EP3 exhibited a strong thermal stability, namely even at 600°C, the volatile substances were detectable. Dense and expanded carbon layer was confirmed in SEM images.     

Characterisation and modelling of CNT–epoxy and CNT–fibre–epoxy composites

Abstract

This research presents an experimental and theoretical investigation on the effects of carbon nanotube (CNT) integration within neat epoxy resin (nanocomposites) and a carbon fabric–epoxy composite (multiscale composites). An approach is presented for the prediction of mechanical properties of multiscale composites. This approach combines woven fibre micromechanics (MESOTEX) with the Mori-Tanaka model which was used for the prediction of mechanical properties of nanocomposites in this research. Nanocomposite and multiscale composite samples were manufactured using cast moulding, resin infusion, and hand lay-up process. The CNT concentrations in the composite samples were from 0 to 5 wt-%. The samples were characterised using tensile, shear and flexural tests. The discrepancy between the theoretical predictions and the experimental observations was hypothesised to be due to dispersion and bonding issues and SEM images are presented in support of the hypothesis.     

Flame-retardant epoxy resin with good smoke-suppression endowed by chitosan–cobalt/phosphorus complex

Chitosan-based flame-retardant CS–Co–DOPA (CCD) was synthesized by the neutralization reaction of 10-hydroxy-9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide (DOPA) with chitosan-cobalt complex and fully characterized by scanning electron microscopy (SEM), energy-dispersive spectrometer, x-ray diffraction, X-ray photoelectron spectroscopy (XPS), optical emission spectrometer, and Fourier transform infrared (FTIR) characterizations. The epoxy resin (EP) modified with CCD exhibited good flame retardancy. With the addition of 5 wt% CCD, the EP/CCD achieved UL-94 V-1 rating and possessed limiting oxygen index (LOI) value of 30%. Cone calorimetry (CC) test demonstrated that EP/CCD resulted in a remarkable reduction of peak smoke production rate (pSPR) and total smoke production (TSP) by 63% and 40%, respectively, showing an outstanding smoke suppression. The char residue obtained from the CC test was further characterized using SEM, FTIR, Raman, and XPS techniques. The results revealed that CCD facilitated the formation of a dense and compact char layer on EP during combustion, thereby impeding gas and heat transfer. In addition, TG-IR was employed to investigate the gas-phase flame-retardant effect of EP/CCD composites, which revealed that CCD promotes the release of water, CO_2, and other incombustible gases, altering the decomposition path of EP.     

Oxidation of butane over vanadium–phosphorus oxides of P/V≥2

Two mixed oxides of vanadium and phosphorus, with phosphorus to vanadium atomic ratio (P/V) about 2 and 2.4, were studied as catalysts for selective oxidation of butane to maleic anhydride. The sample with P/V about 2 was poorly crystalline, contained a small amount of V(V), and oxidized butane to maleic anhydride with about 50% selectivity. The sample with P/V about 2.4 contained well crystalline VO(PO₃)₂ phase, but it deactivated with time-on-stream with the formation of V(PO₃)₃. The results suggested that the two samples differed greatly in their rates of oxidation of the vanadium ions.     

Synthesis and characterizations of BNT–BT and BNT–BT–KNN ceramics for actuator and energy storage applications

Dielectric and ferroelectric properties of 0.93Bi_0.5Na_0.5TiO₃–0.07BaTiO₃ (BNT–BT) and 0.93Bi_0.5Na_0.5TiO₃–0.06BaTiO₃–0.01K_0.5Na_0.5NbO₃ (BNT–BT–KNN) ceramics were studied in detail. An XRD analysis confirmed the single perovskite phase formation in both the samples. Room temperature (RT) dielectric constant (ε_r) ~1020 and 1370, respectively at 1 kHz frequency were obtained in the BNT–BT and BNT–BT–KNN ceramics. Temperature dependent dielectric and the polarization vs. electric field (P–E) studies confirmed the coexistence of ferroelectric (FE) and anti-ferroelectric (AFE) phases in the BNT–BT and BNT–BT–KNN ceramics. Substitution of KNN into the BNT–BT system decreased the remnant polarization, coercive field and the maximum strain percentage. The energy storage density values ~0.485 J/cm³ and 0.598 J/cm³ were obtained in the BNT–BT and BNT–BT–KNN ceramics, respectively. High induced strain% in the BNT–BT ceramics and the high energy storage density in the BNT–BT–KNN ceramics suggested about the usefulness of these systems for the actuator and the energy storage applications, respectively.     

Colloidal Stability and Sintering of Yttria–Silica and Yttria–Silica–Alumina aqueous suspensions

The aim of this work was to produce dense yttrium silicate materials by slip casting, with more than 90% of Y₂SiO₅ phase. The rheological behaviour of concentrated aqueous slips was studied considering the effect of the dispersing additives, solids content and pH. The densification kinetics was examined as a function of temperature and time, and the reactions were analysed in the light of the equilibrium phase diagrams. Deflocculation of the slips was achieved by either an electrostatic mechanism using tetraethylammonium hydroxide, thus requiring a high concentration of base, and by a polyelectrolyte through an electrosteric mechanism, which provided more reliable results. In the binary system Y₂O₃–SiO₂, a very low grade of sintering was obtained at 1600°C. The use of alumina allows sintering through a liquid phase, reaching 90% theoretical density.     

The preparation and properties of zirconia-doped Y–Si–Al–O–N oxynitride glasses and glass-ceramics

Two series (N-9 and N-18 series) of zirconia-doped Y–Si–Al–O–N oxynitride glasses and glass-ceramics were designed. Nominal compositions of the glass samples in equivalent percent (eq%) are xZr: (24–0.25x)Y: (15–0.25x)Al: (61–0.5x)Si: 91O: 9 N and xZr: (24–0.25x)Y: (15–0.25x)Al: (61–0.5x)Si: 82O: 18 N (x=0, 2, 4, 6), respectively. The obtained samples were characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Densities, Vickers hardness, fracture toughness, glass transition temperature, and thermal expansion coefficient data were established for each sample. Effect of Zr and N content on glass network structure, thermal and mechanical properties was investigated. It was found that the addition of zirconia is effective in preparing Y–Si–Al–O–N oxynitride glasses with lower glass transition temperature and higher hardness.     

Crystal growth of diamond from a phosphorus solvent under high pressure–high temperature conditions

Crystal growth of diamond in a phosphorus solvent was studied on a seed of natural octahedral diamond at high pressures and high temperatures of 6.2–6.5 GPa and 1600–1700°C for 5–23 h. Although new growth layers of diamond up to 30 μm in thickness were observed on {111} faces of a seed, growth almost stopped within the first 5 h caused by the following occurrence of spontaneous nucleation. The growth layer was usually gray or bluish gray in color and the surface became undulated with dense triangular growth hillocks and growth steps of 〈110〉 directions. On the grown surface were observed two other characteristic features: one is a circular depression with various size particularly observed in the beginning of the growth and the other is a peculiar growth step with the direction indexed as 〈321〉.     

Unique and contrasting mixed-metal lithium–calcium and lithium–barium hexamethyldisilazide complexes

Addition of lithium hexamethyldisilazide to calcium or barium bis(hexamethyldisilazide) in THF resulted in the synthesis of two unique but very different mixed-metal complexes: X-ray crystallography shows these to be, respectively, the heterobimetallic complex [Ca{N(SiMe₃)₂}₃Li(THF)] (1), containing two calcium–lithium bridging amide ligands and the remarkable co-crystalline compound [Ba{N(SiMe₃)₂}₂(THF)₃][Li₂{N(SiMe₃)₂}₂(THF)₂] (2).     

Synthesis and Characterization of Linear and Tri-Block PLLA–PEG–PLLA Blends

This study was conducted to synthesize poly(L-lactide)–poly(ethylene glycol)–poly(L-lactide) triblock copolymer (PEGLA) with different poly(L-lactide) block length, and explore its applicability in a blend with linear poly(L-lactide) (3051D NatureWorks) with the intention of improving heat seal and adhesion properties at extrusion coating on paperboard. Poly(L-lactide)–poly(ethylene glycol)–poly(L-lactide) was obtained by ring opening polymerization of L-lactide using poly(ethylene glycol) (molecular weight 6000 g mol^?1) as an initiator and stannous octoate as catalyst. The structures of the PEGLAs were characterized by proton nuclear magnetic resonance spectroscopy. The melt flow and thermal properties of all PEGLAs and their blends were evaluated using dynamic rheology and differential scanning calorimeter. All blends containing 10 wt% of PEGLAs displayed similar zero shear viscosities to neat poly(L-lactide), while blends containing 30 wt% of PEGLAs showed slightly higher zero shear viscosity. However, all blends displayed higher shear thinning and increased melt elasticity (based on tan δ). No major changes in thermal properties were distinguished from differential scanning calorimetric studies. High molecular weight PEGLAs could be used in extrusion coating with 3051D without problems.     

Synthesis and Structural Analysis of Co–Zn–Cd Ferrite by Williamson–Hall and Size–Strain Plot Methods

The work aimed at studying the structural properties of Cd-doped cobalt zinc ferrite (Co_0.5Zn_0.5Cd_0.2Fe_1.8O₄) prepared by simple, low-cost solid-state reaction method and characterized by XRD techniques. The X-ray analysis confirms the formation of ferrite particles with a cubic spinel structure. Crystallite size D, lattice constant a, micro strain ε, X-ray density Δ_X, dislocation density ρ _D , hopping lengths (L_A and L_B), bond lengths (A–O and B–O), ionic radii (r_A and r_B), texture coefficients [TC(hkl)], and mechanical properties are also reported.     

Critical plant and soil phosphorus for wheat,maize, and rapeseed after 44 years of P fertilization

Phosphorus (P) crop fertilization requires optimal management to avoid the waste of a non-renewable resource and water pollution, but current methods for assessing soil phyto-available P and plant P requirements are not sufficiently precise to meet this goal. The objectives of the present study were to (1) evaluate the effect of long-term P fertilization on the grain yield of winter wheat, maize, and rapeseed, (2) validate or establish models of critical shoot P concentration (P_C) based on relationships of shoot P concentration with either shoot biomass or shoot nitrogen (N) concentration, and (3) assess both plant-based and soil-based diagnostic tools for managing P fertilization. A long-term field experiment with contrasted P fertilizer treatments, established in 1971 by Agroscope in Changins (Switzerland), was used to measure the shoot biomass and P concentration of winter wheat in 2011, maize in 2012, and rapeseed in 2014 weekly during the growing period and the grain yield at harvest. Soil available P in the 0–0.20 m soil layer was assessed by three chemical extractions: ammonium acetate EDTA (P-AAE), sodium bicarbonate (P-NaHCO₃), and CO₂-saturated water (P-CO₂). Long-term P fertilization increased soil available P extracted by P-CO₂ (+?24%), P-AAE (+?200%), and P-NaHCO₃ (+?155%), shoot growth and grain yield by 8.4% and 26.2% for winter wheat and rapeseed respectively but had no effect on maize. The relationships between P_C and shoot biomass or N concentration were described respectively by allometric and linear models (R²?>?0.85, n?=?21, 28 and 32 for winter wheat, maize and rapeseed respectively; slope P values for linear models <?0.05). The P_C–shoot N concentration model (slope: 0.083, intercept: 0.88) for winter wheat confirmed results from previous studies and can be used for calculating the P nutrition index. For the three soil available P indicators, threshold values needed to achieve 95% of the maximum yield for the three crops were less than those currently used in the official fertilization guidelines in Switzerland. Our results obtained after 44 years of contrasted P fertilization confirm the relationship between P_C and shoot N concentration for grain crops and the need to revise P fertilizer recommendations based on currently used soil P tests.     

Electrocaloric and pyroelectric properties of PZT and PMN–PNN–PZT thin films

The electrocaloric effects (EC) of PZT and PMN–PNN–PZT films were evaluated. PZT and PMN–PNN–PZT thin films with a thickness of 500 nm were fabricated by state-of-the-art chemical solution deposition from a precursor solution with PZT and (PMN?PNN)/PZT=30/70. The polarization hysteresis loop was found to be slim and nonlinear, with smaller hysteretic behavior compared with PZT. The pyroelectric properties evaluated from polarization change and current measurement show that the properties of PMN–PNN–PZT films are superior to those of non-doped PZT films. The electrocaloric temperature changes ΔT due to applied ΔE were calculated. PZT and PMN–PNN–PZT films exhibited ΔT of 2.1 K and 3.6 K at 237.5 °C under a field of 500 kV/cm, respectively. Thermal-electrical energy converters based on pyroelectric effects were investigated for energy harvesting and possible use in ultralow-power sensor modules. The possibilities of pyroelectric energy harvesting using these PZT films were also investigated.