Adsorbed states of K on the diamond (100)(2×1) surface

The adsorbed states of K on the C(100)(2×1) surface have been studied by electron energy loss spectroscopy (EELS), work function change (Δφ) measurement and thermal desorption spectroscopy (TDS). In the region where the K coverage is less than one-half of a monolayer (θ_K≤0.5), a loss is observed from ∼1.2 eV (θ_K=0.2) to 1.0 eV (θ_K=0.5); the work function decreases upon K adsorption until reaching a shallow minimum of Δφ=−3.35 eV at θ_K=∼0.5; and a desorption peak (β) is observed from ∼825 K (θ_K=0.05) to 525 K (θ_K=0.5). These results indicate that the K–substrate bond is highly polarized; the 1.2 eV loss is attributed to the electronic transition from the bonding to antibonding states formed at the K–substrate interface. In the region between θ_K=0.5 and 1, two losses are observed at 0.7 and 1.4 eV (θ_K=0.6); there is only a small increase of the work function; and a desorption peak (α) is observed in addition to the β peak. These results indicate that the K regains its electron and becomes, essentially, neutral. The 1.4-eV loss is ascribed to the transition from the 4s to 4p states of K. The origin of the 0.7-eV loss is discussed. The Δφ and TDS results are analyzed by the depolarization model.     

Chemisorption of O2 and CO on the K-modified diamond (100)2×1 surface

The adsorption of O₂ and CO molecules on the K-modified C(100) surface has been studied mainly by electron energy loss spectroscopy (EELS) and additionally by thermal desorption spectroscopy (TDS) and low-energy electron diffraction (LEED) at 300 K. Although O₂ does not react with the clean C(100) surface, it readily reacts with the K-modified surface. The adsorbed species are characterized by the two loss peaks at 150 and 214 meV. The 150 and 214-meV losses are ascribed to the CO stretch of the COC (ether) and >CO (carbonyl) species which are formed by breaking both σ and π bonds of a surface dimer, respectively. In contrast to Si(100), substrate oxidation mainly occurs at the top layer of C(100). The CO molecule also reacts with the K-modified surface, while it does not react with the clean C(100) surface. The adsorbed species are characterized by the loss peaks at 154 meV with a shoulder at 192 meV. The 154-meV loss is tentatively assigned to the CO stretch of the (C₂O₂)²⁻2K⁺ complex formed on the K-modified C(100) surface. The shoulder at 192 meV is ascribed to the CO stretch of either (C₄O₄)²⁻2K⁺ or >CO, in which the π bond is largely perturbed by the K adatoms.     

Study on the chemical synthesis and the performance of V(Ⅲ)-V(Ⅳ) electrolyte

钒电池是一种高效储能装置,钒电池电解液直接影响电池性能。本文以V2O3、V2O5和H2SO4为原料,化学合成了用于钒电池的V(Ⅲ)-V(Ⅳ)电解液,研究了无水乙醇与焦磷酸钠作为添加剂对电解液稳定性和电化学活性的影响。实验结果表明,当V2O3/V2O5质量比为7.2∶1时,可以得到V(Ⅲ)/V(Ⅳ)离子浓度比为1.0的电解液;添加剂的加入能提高电解液的稳定性和电化学反应活性。     

Effect of nano-titania (η-TiO2) content on the mechano-physical properties of a magnesia refractory composite

The mechano-physical properties of a sintered magnesia matrix containing 0–8 wt% nano-titania (η-TiO₂) have been investigated. The crystalline phases and microstructure characteristics of the refractory specimens sintered by solid state at 1500 °C for 4 h in an electric furnace were studied by X-ray diffraction (XRD), and scanning electron microscopy (SEM) with microanalysis (EDS), respectively. The physical properties are reported in terms of density and porosity. The mechanical behavior was evaluated by a cold crushing strength (CCS) test. As a result, it was found that the presence of η-TiO₂ in the magnesia matrix induced titanates formation (Mg₂TiO₄ and CaTiO₃), which improved the sintering process. Nano-titania also produced a fine-grained microstructure with intergranular second phase particles, which remain at the boundary and exert a pinning effect. In general, the addition of 5 wt% of η-TiO₂ contributed to reach a maximum increment in physical and mechanical properties.     

The effect of the nature of the gas phase on the surface properties of liquid tin in contact with the (100) face of solid electrolyte ZrO2Y2O3

Using the method of measuring the electrolytic conductivity G between the electrode being investigated and the auxiliary electrode as a function of the potential φ, a study has been made of the surface properties of liquid tin in contact with solid electrolyte 0.90 ZrO₂0.10 Y₂O₃ in an atmosphere of COCO₂ as well as in helium. The G-φ curves obtained exibit two free surface energy (FSE) maxima in the gas mixture COCO₂ at 900°C and only one FSE maximum in the helium atmosphere. In the COCO₂ atmosphere the transition from the (100) face of the solid electrolyte 0.90 ZrO₂0.10 Y₂O₃ single crystal to the sintered material displaces the potential of the first maximum by 0.07 V towards the negative region, that of the second maximum by 0.06 V. It has been found that the change of the gas phase COCO₂ for the gas phase H₂H₂O (hydrogen with an insignificant admixture of water) affects very largely the magnitude of the potentials that correspond to the FSE maximum. The latter circumstance is a demonstration that the adsorption phenomena play a significant part.     

Study on the crystal structure of (Gd2−xCex)Ti2O7 (0 ≤ x ≤ 0.8) pyrochlore

Synthesis, characterisation and crystal structure analysis studies of oxides in (Gd_2?x Ce_x)Ti₂O₇ series have been reported, Ce³⁺ used as a surrogate for Pu³⁺ because they have similar physical and chemical properties. In the present report, a series of pyrochlore-type crystal with composition (Gd_2?x Ce_x)Ti₂O₇ (0?≤?x?≤?0.8) were successfully synthesised by the solution combustion followed by high temperature calcining. The phase purity and crystal structure of samples were investigated by X-ray diffraction analysis as well as Rietveld refinement. It was observed that the solubility of Ce³⁺ in the lattice of Gd₂Ti₂O₇ pyrochlore is 39.62?mol.-%. The calculated lattice parameters and the simulated XRD patterns of (Gd_2?x Ce_x)Ti₂O₇ (x?=?0, 0.5, 1) were obtained based on the density functional theory. The results of theoretical calculation are quite consistent with the results of the experiment. Additionally, the grain size and the visual information about the microscopic structure of the (Gd_2?x Ce_x)Ti₂O₇ crystals were obtained by transmission electron microscopy.     

Effect of the reductant nature on the catalytic removal of N2O on Fe-zeolite-β catalysts

The catalytic reduction of N₂O by H₂, NH₃, CO, propene and n-decane, in the presence of O₂, has been studied on two Fe-zeolite-β (Fe-BEA) catalysts. In the following experimental conditions (GHSV=35 000 h⁻¹, 2000 ppm N₂O, 3% O₂), CO starts to reduce N₂O from 473 K and is the most efficient reductant in the low temperature domain. The absence of strong adsorption and the ability to reduce Fe^III oxo-cations can be put forward to explain this behaviour. At medium temperature range n-decane become very reactive to reduce N₂O. Finally, in the absence of NH₃ slip, this reductant can be considered as an excellent candidate owing to the harmless of its reduction products.     

Effect of Incorporation of Butyl Acrylate–Iron Chelate Resin on the Flammability Properties of Mg(OH)2-LDPE Compositions

Abstract

Butyl acrylate resin–iron chelate was prepared by cross-linking with divinyl benzene and complexation with ferric chloride. The prepared resin was incorporated in different amounts into low-density polyethylene samples filled with magnesium hydroxide. Flammability properties were evaluated by cone calorimetry and thermogravimetric analysis. It was found that the resin–iron chelate has a remarkable effect on the flammability properties of low-density polythylene (LDPE) compositions. Five phr of the new resin decreased the maximum rate of heat release into 835.6 Kw/m² by more that 50%. It was also found that the LDPE composition, sample M3, which contains 15 part per hundred of the prepared resin complied with the category FV2 of the ISO standard 1210. In general the thermal stability of most of LDPE composition was improved.     

Effect of the reaction conditions on the properties of poly(4,4′-diphenylether-1,3,4-oxadiazole)s

Summary Poly(4,4-diphenylether-1,3,4-oxadiazole)s have been prepared by polycondensation of 4,4-diphenylether dicarboxylic acid and hydrazine sulphate, HS, in poly(phosphoric acid), PPA, under different reaction condictions. The products were characterized by viscometry, gel permeation chromatography, ¹H-NMR spectrometry and thermogravimetric analysis. Dense membranes have been prepared and submitted to gas transport and wide angle X-ray diffraction, WAXD, experiments. The differences found in permeability and selectivity parameters, as well as in density and WAXD results, are discussed in terms of their solution viscosities and hydrazide repeat unit contents.     

Effect of Polysaccharides on the Properties of the Mucoadhesive Poly(Vinyl Alcohol) Multicore–Shell Microparticles

This study discusses about the effect of polysaccharides (agar, gum tragacanth, and guar gum) on the properties of the core (organogel)–shell [poly(vinyl alcohol)] microparticles. The size, swelling, and mucoadhesive properties of the poly(vinyl alcohol) microparticles were altered in the presence of the polysaccharides. Thermal analysis confirmed the presence of organogels within the microparticles. Fourier transform infrared spectroscopy confirmed the presence of the polysaccharides within the microparticles. The microparticles were biocompatible in nature. Drug release indicated that an alteration in the shell composition can be used for altering drug release. Ciprofloxacin-loaded microparticles showed sufficient antimicrobial efficiency.     

Effect of Processing Variables on the Solution Characteristics of γ-Glycidoxypropyltrimethoxysilane (γ-GPS)

The effects of the hydrolysis and condensation processes on the molecular structure of γ-glycidoxypropyltrimethoxysilane (γ-GPS) in aqueous solutions were investigated using Fourier-transform nuclear magnetic resonance (FT-NMR) spectroscopy and FT-Raman spectroscopy. Hydrolysis was characterized by monitoring the production of methanol and the decrease in concentration of SiOCH₃ groups in 1% solutions of deuterium oxide using proton NMR. The production of methanol and loss of methoxy groups in 25% solutions of γ-GPS in water was characterized using Raman spectroscopy. Hydrolysis was found to be a very rapid process, whose rate could be increased or decreased by altering the pH of the solution. NMR spectroscopy showed that hydrolysis was complete in a 1% γ-GPS solution in deuterium oxide after 34 minutes. Raman spectroscopy also showed hydrolysis to be rapid and complete in a 25% solution of γ-GPS in water after 1 hour. Condensation, on the other hand, took a relatively long time to occur. In the NMR spectra, condensation was observed by the broadening of peaks due to the protons on the carbon atom adjacent to the silicon atom. In the Raman spectra, condensation was characterized by the disappearance of the SiOH band near 725 cm^?1 and the development of an SiOSi band near 600 cm^?1. In addition to the proton NMR, Si-29 NMR was used to characterize the silane in 10% solutions of γ-GPS in water. The Si-29 NMR showed oligomer growth with respect to time. The oligomer growth was correlated with mechanical test results.     

Effect of nucleating agents on the crystallization behaviour and microstructure of SiO2–CaO–MgO (Na2O) glass-ceramics

The crystallization behaviour of the ternary SiO₂–MgO–CaO system comprising different nucleating agents was investigated using DTA and XRD techniques. The effect of compositional changes on bulk crystallization and growth morphology were also studied. After a two-stage heat treatment, the phases such as wollastonite, diopside and in some cases, cristobalite, were identified. The microstructures were investigated by SEM. It was found that the pairs of V₂O₅+MoO₃ and CaF₂+MoO₃ are more effective nucleants compared with that of Fe₂O₃+WO₃. The coarse fibrous morphology with directional surface crystallization was observed for some specimens containing Fe₂O₃+WO₃ as nucleants     

Optimization of Enzymatic Synthesis of n-Propyl Acetate (Fruit Flavor Ester) – Effect of the Support on the Properties of Biocatalysts

The present study deals with the optimization of the enzymatic synthesis of n-propyl acetate using response surface methodology (RSM). The biocatalysts were prepared by physical adsorption of lipase from Thermomyces lanuginosus (TLL) on mesoporous hydrophobic supports – poly-hydroxybutyrate (PHB) and poly-methacrylate (PMA) particles. Their catalytic properties were also assayed in the hydrolysis of olive oil emulsion. The biocatalyst TLL–PMA presented the highest immobilization yield (IY, 90.6 ± 2.8%), immobilized protein concentration (36.5 ± 0.4 mg/g of PMA), and catalytic activity in esterification reaction. TLL–PHB was more active in the hydrolysis of olive oil emulsion by a four-fold factor (1240.5 ± 29.2 IU/g of PHB). Maximum acid consumption percentage of 84.3% was observed after 50 min of reaction catalyzed by TLL–PMA using 2000 mM of each reactant (n-propanol and acetic acid) in heptane medium. The purified ester was confirmed by gas chromatography mass spectrometry (GC–MS) analysis. After six consecutive cycles of esterification reaction, the biocatalyst retained around 50% of its initial activity. The results show that PMA may be an interesting support to prepare active biocatalysts in the synthesis of fruit flavor ester by esterification reaction.     

Study on the effect of Ti,Al, Cu,and Ag doping on the bonding properties of soldered β-Sn(100)/ZrO2(111) interface

Selecting active elements for filler metal is very important in soldering of ZrO₂ ceramics. In this paper, the effects of Ti, Al, Cu, and Ag active elements on the bonding strength and electronic structures of soldered β-Sn(100)/ZrO₂(111) interface were studied via the method of first principle calculation. The work of adhesion (W_ad) results show that the O₂-terminated interface is more stable than other kinds of interfaces. Then, the atoms of Ti, Al, Cu, and Ag were doped into the interface by replacing the Sn atom in situ. It is found that additions of Ti, Al, and Cu atoms can increase the W_ad, and Ag atom has the opposite effect. From the results of heat of segregation, doping Ti and Al into the interface is stable in thermodynamics and doping Cu and Ag is not stable. The forming of strong ionic-covalent Ti-O and Al-O bonding contributes to the increase of the interfacial adhesion strength. The calculation results indicate that Ti and Al can act as active elements in Sn to solder ZrO₂. The Ti-O and Al-O compounds formed at interface can improve the wetting and bonding between Sn-based solder and ZrO₂ ceramics.     

Influence of Cu(II) on the electronic conductivity in γ-CuI

The hole conductivity of CuI is affected by the presence of Cu(II) ions arising from the synthesis process. By treating these ions as aliovalent impurities, the value of the hole migration energy is obtained.     

Investigation of the effect of minor ions on the stability of β-C2S and the mechanism of stabilization

In this paper the effect of minor ions on the stability of β-C₂S has been studied. It is discovered that the effect of minor ions on the stability of β-C₂S is closely related to the polarization ability of the ions. According to this the authors propose a new judgement, the ion polarization ability judgement, by which we can determine if minor ions have the stabilizing affect on β-C₂S. The judgement is that those ions, either having smaller polarization ability than that of calcium ion or greater than that of silicon ion, all have the ability to effect the stability of β-C₂S. This judgement is more practical than those made by other authors. In this paper a new mechanism about the stabilization has been described on the basis of applying the principles of thermodynamics and dynamics of the transformation of solid phases in accordance with the above judgement.     

A study on the crystallization behavior of poly(β-hydroxybutyrate) thin films on Si wafers

The exact molecular chain orientation of poly(β-hydroxybutyrate) (PHB) in ultrathin films was successfully probed using surface-sensitive, grazing incidence X-ray diffraction techniques. The crystal orientation of spin-coated PHB films was very sensitive to free surface and thermal annealing. In pristine films, the free surface easily exerted its influence on PHB crystallization and caused lamellar orientation with the b-axis perpendicular to the film surface. The effect of the buried interface increased with temperature. With the increase in thermal annealing temperature, the lamellar orientation changed from the b-axis being perpendicular to the film surface to the c-axis becoming perpendicular to the film surface. As film thickness increased, the temperature, at which the lamellae with the b-axes oriented normal to the film surface disappeared, increased. The thickness and temperature dependence of the crystallization behavior of PHB in an ultrathin film could be attributed to the competition between the effects of the free surface and the buried interface.     

Adsorption of Cr (VI) on synthetic hematite (α-Fe2O3) nanoparticles of different morphologies

The adsorption of Cr (VI) from aqueous solution onto nanoparticles hematite (α-Fe₂O₃) of different morphologies synthesized by acid hydrolysis, transformation of ferrihydrite, sol gel methods has been investigated. The hematite particle sizes were in the range 15.69-85.84 nm and exhibiting different morphologies such as hexagonal, plate-like, nano-cubes, sub-rounded and spherical. The maximum adsorption capacity of Cr (VI) was found to be in the range 6.33–200 mgg^?1 for all hematite samples. The kinetics of sorption was rapid, reaching equilibrium at 45–240 minutes. Sorption kinetics and equilibria followed pseudo-second order and Langmuir adsorption isotherm models. The rate constants were in the range 0.996–2.37×10^?2 g/mg/min for all samples. The maximum adsorption was attained at pH 3.0, while adsorption decreased as the pH increased from pH 3.0 to 10.0. The study revealed that the hematite with plate-like morphology has the highest adsorption capacity. The sorption process has been found to be feasible following a chemisorption process, and adsorption of Cr (VI) onto hematite nanoparticles was by inner sphere surface complexation due to low desorption efficiency in the range 9.54–53.4%. However, the result of ionic strength revealed that the reaction was by outer sphere complexation. This study showed that morphologies play a vital role in the adsorption capacities of samples of hematite in the removal of Cr (VI) from aqueous solution.     

Mechanism of the Formation of Ba2Ti9O20-Based Phases in the Course of Solid-Phase Interaction in the BaO–TiO2(ZrO2) and Cs2O–BaO–TiO2(ZrO2) Systems

The mechanism of solid-phase interaction in the BaO–TiO₂(ZrO₂) and Cs₂O–BaO–TiO₂(ZrO₂) systems is investigated. It is established that the formation of the Ba₂Ti₉O₂₀ compound and Ba₂Ti₉O₂₀-based solid solutions is a multistage process proceeding through the formation of intermediate phases. The solid-phase interaction in the BaO–TiO₂(ZrO₂) system occurs through the formation of the BaTi₄O₉ intermediate compound. The Ba₂Ti₉O₂₀ single-phase product is formed only in the presence of ZrO₂ (0.82 mol %) upon heat treatment at a temperature of 1250°C for 5 h. In the Cs₂O–BaO–TiO₂(ZrO₂) system, the BaTi₅O₁₁ metastable intermediate phase is formed at the first stage of the solid-phase interaction. The Cs _x Ba_{2 – x/2}Ti_{9 – y} Zr _y O₂₀ single-phase solid solutions are prepared upon heat treatment at 1100°C for 1 h. It is demonstrated that, in the Ba₂Ti₉O₂₀ structure, cesium can isomorphously substitute for barium with the formation of Cs _x Ba_{2 – x/2}Ti_{9 – y} Zr _y O₂₀ solid solutions (0 x 0.8, y = 0 and 0.09).     

Effects of the lamination temperature on the properties of poly(ethylene terephthalate-co-isophthalate) in polyester-laminated tin-free steel can — I. Characterization of poly(ethylene terephthalate-co-isophthalate)

The effects of lamination temperature on the properties of poly(ethylene terephthalate-coisophthalate) (co-PET), such as thermal, mechanical, and barrier properties, have been investigated in co-PET laminated steel. The variation of the degree of crystallinity and the orientation of the co-PET film during the lamination process was examined using DSC, X-ray diffraction, and birefringence, and water vapor permeability was also measured with varying lamination temperature. Both the degree of crystallinity and the orientation of the co-PET film decreased and water vapor permeability increased with increasing lamination temperature. The stress-strain curves of the co-PET films were different, depending on the lamination temperature. The stress in the co-PET film laminated at higher temperature was lower at a given strain, due to the increase of the amorphous region. The effects of annealing temperature and the extent of drawing on the residual stress in co-PET/tin-free steel (TFS) joints were investigated by examining the stress relaxation behavior of co-PET. It was necessary to heat co-PET/TFS joints at more than 150°C in order to eliminate the residual stress.