Effect of the processing on the production of cordierite–mullite composite

In this study, effect of process on the production of cordierite–mullite composite was studied. For this reason two different processing methods were used in the production of cordierite–mullite composites. In first process, in situ cordierite–mullite composites were produced from cordierite and mullite layers which were formed by using aqueous tape casting method. In second one, composite was produced by addition of pre-produced mullite powders (in different weight percents, 0–30) into cordierite starting powders. The results show that the addition of pre-sintered mullite powders to the cordierite slip has more effect on densification behavior and mechanical properties of composites than layered production method.     

Promotion Effect of FeOx Addition on the Catalytic Activity of Supported Cu Catalysts for the Water–gas Shift Reaction

Among the supported Cu–FeO_x catalysts, Al₂O₃-supported Cu–FeO_x catalyst exhibited the highest activity for WGS reaction. The enhancement of the catalytic activity by adding FeO_x to Cu/Al₂O₃ could be interpreted by the two possibilities; one is the formation of highly dispersed Cu⁰ and the other is the participation of reduced FeO_x in WGS reaction in the presence of Cu⁰.     

Effect of calcium lignosulfonate on the hydration of the tricalcium aluminate–anhydrite system

As a plasticizer and retarder, calcium lignosulfonate (CL) frequently leads to quick set of Portland cement containing anhydrite. For exploring the cause of this problem, the hydration characteristics of the tricalcium aluminate–anhydrite system in the saturated calcium hydroxide solution with and without CL were researched from two aspects: the compositions of liquid phases and the formations of hydration products. Results show that the CL can promote the formation of ettringite, which induces a significant decrease in sulfate ion concentration at the initial time of hydration. The size of ettringite crystals becomes large in the presence of CL, which seems to be related to a decrease in calcium sulfate saturation ratio. It can be deduced that the quick set in the presence of CL is mainly caused by the accelerated reaction between the tricalcium aluminate and the anhydrite at the initial time of hydration.     

Effect of Molecular Additives on the Ignition of Methane–Air Mixtures

Combustion, Explosion, and Shock Waves - The ignition of methane–air mixtures with additives of ClF5, ClF3, OF2, and H2O2 (additive content in the mixtures  $$\le$$ 1%) is studied by...     

Coagulation–bubbling–ultrafiltration: Effect of floc properties on the performance of the hybrid process

A novel hybrid process of coagulation–bubbling–ultrafiltration was proposed to study membrane fouling phenomena by surface water. Relationship of bubbles, flocs and the hollow fibers was explored. When applying less than 20 mL/min gas flow rate, membrane fouling was accelerated with air bubbles introduced. When gas flow rate increased further to 40 mL/min and 60 mL/min, TMP showed a two-stage development trend, which was a fast development in the first few hours followed with a relatively slow development after about 4 h. Unified membrane fouling index (UMFI) increased from 0.00216 (without bubbles) to 0.00274 m²/L (40 mL/min gas flow rate) and 0.00219 m²/L (60 mL/min gas flow rate). As gas flow rate increased, bubble size became bigger, and its distribution range became wider, resulting in higher shear rate in the ultrafiltration column, which led to severe floc breakage. Flocs of small size and compact structure accelerated membrane fouling, resulting in highest UMFI value under 40 mL/min gas flow rate. However, under 60 mL/min gas flow rate, with largest bubbles and highest shear rate examined in this study, concentration polarization was effectively limited. As a result, TMP development slowed down when pore blockage reached equilibrium.     

The Water–Gas-Shift Reaction on Pd/Ceria–Praseodymia: The Effect of Redox Thermodynamics

Reaction rates for the water–gas-shift (WGS) reaction were measured on catalysts with 1-wt% Pd supported on CeO₂, Ce_0.5Pr_0.5O_2?x and PrO _x in order to determine whether the weakly bound oxygen associated with Pr could enhance reaction rates. However, differential rates in 25 Torr of both CO and H₂O showed that the activity of Pr-containing catalysts were much lower. Measurements of the oxygen content of these samples after reduction in dry H₂ at 873 K, after reoxidation in steam at 873 K, and following exposure of the catalysts to WGS conditions at 873 K demonstrate that ceria is easily reoxidized by steam and remains oxidized under WGS conditions, while the loosely bound oxygen associated with praseodymia or ceria–praseodymia is lost under WGS conditions and cannot be restored by oxidation in steam. These results can be understood by comparing the equilibrium redox properties of the support materials to the typical P(O₂) experienced under WGS conditions.     

Effect of a Gas‐Phase Reaction on the Combustion Performance of a Sandwich Layered System

This paper considers a sandwich layered combustion model (an oxidizer and a fuel) that takes into account condensed and gasphase chemical reactions and transverse heat and mass transfer. Under particular simplifications, algebraic expressions are obtained for the burning rates of the components and the temperature and concentration of gaseous reagents on the burning surface. Calculated dependences of the burning rate on the sandwich size agree with experiments.     

Effect of zinc concentration on the magnetic properties of cobalt–zinc nanoferrite

Nano-cobalt–zinc ferrite (CZFO) Co_(1?x)Zn_xFe₂O₄ with varied quantities of zinc (x = 0.0, 0.1, 0.2, 0.3, 0.4) have been prepared by solution combustion method. X-ray diffraction and transmission electron microscopy confirmed the size, structure and morphology of the nanoferrites. The addition of zinc in cobalt ferrite has been shown to play a crucial role in enhancing the magnetic properties. Ferromagnetic ordering is observed in nano samples at room temperature. Zn substitution shows maximum saturation magnetization for x = 0.1, that is 56.74 emu/g and then decreases for further increase in Zn substitution. The dependence of Mössbauer parameters viz. isomer shift and hyperfine magnetic field with zinc concentration has been studied. Mössbauer results are also supported by magnetization data. The results obtained from this method make these samples suitable for preparing high quality nanocrystalline ferrite for high density data storage applications.     

Effect of surface pre-treatment on the adhesive strength of epoxy–aluminium joints

A detailed study of the effect of pre-treatment applied on the surface characteristics of aluminium substrates and on the adhesive strength of epoxy–aluminium joints is reported. The variation of the density, composition and aspect of the adherends were analysed as a function of the applied pre-treatment. In order to determine the influence of alloying elements, two different aluminium alloys were used, A1050 and A2024. The adhesive strength was measured by the lap shear test, using several epoxy resins to analyse the influence of the adhesive nature.A chromate-free treatment based on the sulphuric acid-ferric sulphate etch provided an improved joint strength compared to dichromate-sulphuric acid etching, alkaline etching or mechanical abrasion. This increase is associated to the porous oxide layer formed, but it depends on the adhesive nature used. The joints with Al–Cu–Mg alloy substrates generally presented higher adhesive strength values than those with pure aluminium adherends, due to the selective etching of some allowing elements and intermetallic compounds, which have different electrochemical potential.     

Study on the Effect between Dynamics of MgO Grain Growth and Additive of Y2O3

1IntroductionAdditive agent plays a great role in changingphysical and chemical properties and microstructure ofmaterials,especially in CaO-riched MgO-CaO refracto-ry system.Rare earth elements[1~6]have high electronlevel and special electronic structure …     

Effect of SiC on the corrosion resistance of electroless Cu–P–SiC composite coating

In this work, Cu–P–SiC composite coatings were deposited via electroless plating with the addition of sodium hypophoshite (NaH₂PO₂) as a reducing agent. The coating compositions deposited were determined by using energy dispersive X-ray spectroscopy (EDX). The surface morphology of the coatings that were analyzed using scanning electron microscopy (SEM) showed that SiC particles were uniformly distributed by virtue of surfactant addition and mechanical stirring. The anti-corrosion properties of Cu–P and Cu–P–SiC coatings in NaCl and HCl solutions were investigated by the weight loss and potentiodynamic polarization techniques. The results showed that the corrosion resistance of Cu–P–SiC coatings was superior to that of electroless Cu–P coatings and carbon steel substrates in various concentrations of NaCl and HCl solutions.     

Effect of chromium on the kinetics of the contact melting and the graphite-to-diamond transformation in the Co–Fe–C system

We have studied the effect of chromium concentration in alloys of the Co–Fe system on their interaction with graphite at p, T parameters of thermodynamic stability of diamond. It has been found that addition of chromium to the alloys stabilizes the Me₃C-type carbide, as a result, the structure of a layer of a contact melting at the alloy–graphite interface is identical to a horizontal section of the metastable phase diagram of the Fe–C system. It is shown that addition of chromium to the Co–Fe–C system lowers the eutectic melting temperature by 80–100 K. In this case, the coefficient of carbon diffusion in the melt increases by ∼20–30%. An increased surface activity of a Cr-containing melt with respect to graphite is noted, which is the reason of intensive intrusion of the melt deep into a graphite layer along the grain boundaries. As a result, the number of nucleating diamond crystals and the degree of the graphite→diamond transformation increases.     

Influence of Solvent–Evaporation Effect on the Structure and Properties of PVDF-g-PNIPAAm Membranes

Temperature-sensitive poly(vinylidene fluoride)-graft-poly(N-isopropylacrylamide)(PVDF-g-PNIPAAm) copolymer was synthesized and its flat membranes were prepared through phase inversion method with mixture of N,N-dimethylformamide (DMF) and tetrahydrofuran (THF) as solvent in water coagulation bath. The effects of “open time” (solvent–evaporation time) on the structure and performance of membranes were investigated by X-ray photoelectron spectroscopy, field-emission scanning electronic microscopy, contact angle, filtration experiments and static protein adsorption. It was found that the increasing “open time” endowed the membrane with more pores on the surface, higher flux and better hydrophilicity, provided the membrane with lower protein adsorption. Thus, the copolymer membranes showed a good antiprotein fouling.     

Dynamics Research on the Gelling Course of Silica Sol

Dreipping electrolytes into silica sol ,gelling reaction will occur,The research indicates:this is a complicated physicemistry course,which consists of a pre-reaction and a polymerizaion,The former controls the whole course,and in which electronic layers of the sol‘s particles be-come more and more thiner,but with incresing of the sol concentration,its control force will be diminished ,till the fast-coagulation ,the gelling couse becomes o-controlled,The latter is an in-finite polymeric chani-reaction.The result of gelatination is to produce a very big plymeric molecule-gel,which involves in all space,includes all water ,and its molecular weight is in-definite big.The researh also indicates:the dy-namic course of the gelling could be described quantitaively by an experience formula:lgt=-nlgc B,All of the characteristic values have definite physical meaning,Electronic value of the contrary-inos is the biggest influential factor ,the natures of the contrary-ions and the natures of the same-electronic-inos have a few influential forces on the characteristic values,The temperature increasing makes the gelling reaction fast.     

Effect of the Molecular Structure on the Adsorption Properties of Cationic Surfactants at the Air–Water Interface

The surface activity and thermodynamic properties of adsorption at the air–water interface of two series of cationic surfactants based on isourea: the O-dodecyl-N,N′-diisopropylisourea hydrochloride, hydrobromide, and hydroiodide and the O-tridecafluorooctyl-N,N′-diisopropylisourea hydrochloride and hydrobromide were studied. The effect of structural parameters as the nature of the halide counter ion and the nature of the non-polar chain on the surface activity and thermodynamic properties of adsorption were investigated. The surface parameters, the maximum surface excess concentration (Γ _max), the minimum area per molecule (A _min) at the aqueous solution-air interface, effectiveness of surface tension reduction (π_CMC), and efficiency of surface tension reduction (pC ₂₀) were estimated. The standard Gibbs free energy of adsorption, (ΔG°_ads) change has been calculated at different temperatures.     

Effect of calcination conditions on the species formed and the reduction behavior of the cobalt–magnesia catalysts

The structural characteristics and the reduction behavior of the Co/MgO catalysts were investigated using temperature‐programmed reduction (TPR) and X‐ray diffraction (XRD). The variables investigated included the preparation method and the heat treatment conditions (calcination temperature and time). Depending on these factors, one, two or three of the following Co‐containing species, Co₃O₄, MgCo₂O₄ and (Co, Mg)O (solid solution of CoO and MgO) were identified. The extent of solid solution formation increased as the calcination temperature and calcination time increased. A much lower calcination temperature was needed to form a solid solution in the impregnated catalysts than in the physically mixed ones. The formation of a solid solution rendered the catalyst less reducible. Finally, the decomposition of CH₄, as a probe reaction, was performed and it was found that the amount of carbon deposited decreased with increasing extent of solid solution formation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of Molybdenum on the Sulfur-Tolerance of Cerium–Cobalt Mixed Oxide Water–Gas Shift Catalysts

As traditional sources of energy become depleted, significant research interest has gone into conversion of biomass into renewable fuels. Biomass-derived synthesis gas typically contains concentrations ranging from ~30 to 600 ppm H₂S. H₂S is a catalyst poison which adversely impacts downstream processing of hydrogen for gas-to-liquid plants and the deactivation of water–gas shift catalysts by sulfur is typical. Novel catalysts are needed to remain active in the presence of sulfur in order to boost efficiency and mitigate costs. Previous studies have shown molybdenum to be active in concentrations of sulfur >300 ppm. Cobalt has been shown to be active as a spinel in concentrations of sulfur <240 ppm. Ceria has received attention as a catalyst due to its oxygen donating properties. In this study, mixed oxide catalysts were synthesized via Pechini’s method into various blends of metal oxide solutions. Activity testing at low steam-to-carbon ratios (1:1) produced near equilibrium conversions at a GHSV of 6,300 h^?1 and over a temperature range of 350–400 °C for a Ce–Co mixed oxide even after an 800 ppm sulfur treatment. The addition of molybdenum to the Ce–Co base had little effect on sulfur tolerance, but it did lead to a reduction in selectivity for methanation. Specific surface areas generally increased following the sulfur treatments and X-ray diffraction patterns confirmed that bulk sulfiding did not occur.     

Effect of Oxygen Pressure on Phase Equilibria in the Lu–Mn–O System

The heterogeneous equilibria attained during thermal dissociation and hydrogen reduction of LuMnO₃ and LuMn₂O₅ are investigated using the static method (vacuum circulation setup) and X-ray powder diffraction analysis of quenched solid phases. It is found that the dissociation of LuMn₂O₅ proceeds in three stages. At the low-oxygen boundary of the homogeneity region of LuMn₂O₅, this compound dissociates into LuMnO₃ and Mn₃O₄ with the liberation of oxygen. Upon reduction, LuMnO₃ dissociates with the formation of Lu₂O₃ and MnO and the liberation of oxygen. Equations for the dissociation and reduction reactions of LuMn₂O₅ and LuMnO₃ are derived, and mass balance equations for these processes are written. A fragment of the isothermal section of the phase diagram of the Lu–Mn–O system at a temperature of 900°C is constructed in the composition–oxygen pressure coordinates.     

Effect of the Mesostructuration of the Beta Zeolite Support on the Properties of Cobalt Catalysts for Fischer–Tropsch Synthesis

The effect of mesostructuration of beta zeolite and of metal loading on the properties of cobalt-based catalysts for Fischer–Tropsch synthesis was studied in this work. The most active catalyst was the mesostructured beta zeolite-supported cobalt (10%), which also showed a low selectivity to methane and the lowest olefin/paraffin ratio.