柠檬酸盐法制备Na0.5Bi0.5TiO3陶瓷粉体的工艺研究

本实验采用柠檬酸盐法制备（NaBi）0.5TiO3无铅压电陶瓷粉体,系统研究了柠檬酸浓度、溶液pH值、煅烧温度等工艺条件对制备的影响。经研究分析,当柠檬酸浓度C=9%,溶液pH=7.5时,能形成透明、均匀、稳定的溶胶,且形成时间最短;650℃下煅烧2h能够合成单一的钙钛矿结构的钛酸铋钠晶相,比传统固相反应法煅烧温度降低了200℃。     

Effect of the nitrogen heterocyclic compounds on hydrodesulfurization using in situ hydrogen and a dispersed Mo catalyst

The hydrodesulfurization (HDS) of the highly refractory sulfur-containing compounds, dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT), and the effect of the basic and non-basic nitrogen heterocyclic compounds, such as quinoline and carbazole, on HDS using a dispersed unsupported Mo catalyst and in situ generated hydrogen were studied. Experimental results indicated that the dispersed unsupported Mo catalyst was effective for the HDS of 4,6-DMDBT in a mixture containing DBT. The direct desulfurization pathway (DDS) was the preferred pathway for the HDS of DBT while the hydrogenation pathway (HYD) was the preferred pathway for the HDS of 4,6-DMDBT under our experimental conditions. A strong inhibitive effect of the basic quinoline or the non-basic carbazole on the HDS of each of the sulfur-containing compounds was observed. The DDS and HYD pathways in the HDS of the refractory sulfur-containing compounds were affected to a different extent by the nitrogen-containing compounds, suggesting that different active sites were involved in these two reaction pathways.     

Influence of pozzolans and slag on the microstructure of partially carbonated cement paste by means of water vapour and nitrogen sorption experiments and BET calculations

The influence of water-to-binder ratio (0.33 to 0.50) and additions (fly ash, slag, silica fume) on the microstructure of partially carbonated cement pastes was studied by nitrogen sorption and static and dynamic water vapour sorption. The selected technique affects macropore condensation and accessibility of pores, while predrying influences removal of CSH interlayer water. BJH calculations showed the increased amount of capillary pores with higher water-to-cement ratio, and the decrease of micropores (< 2 nm), in pastes with 50% or more fly ash or slag. Paste with 10% SF showed a high amount of gel pores, related to the higher amount of CSH gel, calculated from adsorption at 23% RH. A linear relation was observed between BET specific surface and water-cement ratio. Thermogravimetric analysis illustrated the influence of water-cement ratio and pozzolanic materials on the portlandite content. Introduction of silica fume, increased the specific surface accessible to water, but not to nitrogen molecules.     

Multistability,nonlinear response and wave propagation in self-humidified PEM fuel cells

A simple tanks-in-series model is presented, which allows for the understanding of the basic physics behind complex spatiotemporal behaviors observed in self-humidified polymer electrolyte membrane (PEM) fuel cells. Our approach is focused on how the intrinsically nonlinear dynamics of water formation couples with water transport, leading to multistability, inhomogeneous steady state current profiles through the cell and other nonlinear phenomena. We show in particular how the operating parameters determine the location of high current spots and the subsequent propagation of current waves throughout the cell during the ignition procedure. We also reproduce and explain transient current increases seen during the extinction of the cell and the unusual aspect of the polarization curves. Implications for the efficiency of self-humidified PEM fuel cells are highlighted, and possible ways to improve their performances are discussed on these bases.     

An ideal point method for the design of compromise experiments to simultaneously estimate the parameters of rival mathematical models

When several rival mathematical models are proposed for one and the same process, experimental design techniques are available to design optimal discriminatory experiments. Because these techniques are model-based, it is important that the model predictions are not too uncertain. Therefore, model discrimination may become more efficient and effective if this uncertainty is reduced first. This can be achieved by performing experiments designed to increase the accuracy of the parameter estimates and, thus, the model predictions. However, performing such an additional experiment for each rival model may undermine the overall goal of optimal experimental design, which is to minimize the experimental effort. This paper deals with the design of a so-called compromise experiment, which is an experiment that is not optimal for each of the rival models, but sufficiently informative to improve the overall accuracy of the parameters of all rival models. For this purpose, the problem is approached as a multi-objective optimization problem and the ideal point method is proposed to design the compromise experiment. This method searches for the experiment that is as close as possible to the optimal experiments of the individual rival models. The method is applied to a case study where nine rival models are competing to describe the kinetics of an enzymatic reaction, and the obtained results show that the ideal method is capable of designing a compromise experiment.     

Cloning,Expression and Purification of Cindoxin,an Unusual Fmn‐Containing Cytochrome P450 Redox Partner

Cytochromes P450 (P450s) belong to a superfamily of haemoproteins that catalyse a remarkable variety of oxidative transformations. P450 catalysis generally requires that cognate redox proteins transfer electrons, derived ultimately from NAD(P)H, to the P450 for oxygen activation. P450_cin (CYP176A1) is a bacterial P450 that is postulated to allow Citrobacter braakii to live on cineole as its sole carbon source by initiating cineole biodegradation. Here we report the cloning, expression, purification and characterisation of one of its postulated redox partners, cindoxin (Cdx), which has strong similarity to the FMN domain of cytochrome P450 reductase. Cindoxin reductase (CdR), which displays strong similarity to NADPH‐dependent ferredoxin reductases, was unable to be expressed in a functional form. Mass spectrometric and HPLC analyses confirmed that the flavin cofactor of cindoxin was FMN. Redox potentiometric titrations were performed with cindoxin within the range 6<pH<8; this enabled the quinone/semiquinone (E₁) and semiquinone/hydroquinone (E₂) redox potentials to be determined. Our results show that cindoxin might be somewhat different to other flavodoxins that interact with P450s, in which generally only one couple is important. Both redox states of cindoxin could be catalytically relevant. A catalytically active system was reconstituted in vitro with E. coli flavodoxin reductase (Fpr) acting as the terminal redox partner in the absence of CdR. Our results show that Cdx and Fpr support regio‐ and stereoselective P450_cin‐catalysed cineole oxidation to (1R)‐6β‐hydroxycineole with turnover rates up to 1500 min^?1. This system is tightly coupled with 80 % of NADPH reducing equivalents funnelled into substrate oxidation.     

Influence of chemical structure of hardener on mechanical and adhesive properties of epoxy polymers

The mechanical and adhesive properties of epoxy formulations based on diglycidyl ether of bisphenol A cured with various aliphatic amines were evaluated in the glass state. Impact and uniaxial compression tests were used to determine the impact energy, elastic modulus and yield stress, respectively. The adhesion tests were carried out in steel–steel joints using single‐lap shear, T‐peel, and impact adhesive joints geometry. The better mechanical and adhesive behavior of the networks is obtained when exists high flexibility of chain between crosslink and/or high elastic modulus. The 1‐(2‐aminoethyl)piperazine epoxy network presents the best adhesive properties, high flexibility, and the largest impact energy. However, it possesses low elastic modulus and yield stress. Also, exhibits increases in peel strength and impact energy while reductions in lap shear strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A novel organophosphorus flame retardant: Synthesis and durable finishing of poly(ethylene terephthalate)/cotton blends

A novel, hydroxy‐functional, organophosphorus flame retardant (FR), 2,2‐dihydroxymethylpropane‐1,3‐diolylbis(hydrogen phenylphosphonate) (DHDBP), was synthesized and characterized by Fourier transform infrared (FTIR) spectroscopy, ¹H‐NMR, ¹³C‐NMR, ³¹P‐NMR, and elemental analysis. Subsequently, poly(ethylene terephthalate) (PET)/cotton (T/C; 70/30) blends were treated via pad‐dry‐thermosol finishing with DHDBP, citric acid, and a catalyst. Its flame retardancy, durability effect, and thermal decomposition behaviors were investigated by limited oxygen index, vertical burning test, thermogravimetric analysis, FTIR spectroscopy, and scanning electron microscopy. The results show that DHDBP was not only a reactive FR with a high efficiency but also a good char‐forming agent for the T/C blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Comparison between wet deposition and plasma deposition of silane coatings on aluminium

Silane coatings are applied to metal surfaces for various purposes, e.g., to form a protective layer against corrosion or to act as a primer for subsequent coating. In this work bis-1,2-(triethoxysilyl) ethane (BTSE) was used as a precursor to deposit coatings on Al 99.99% substrates with three different techniques: dipcoating (water based solution), vacuum plasma and atmospheric plasma. Infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS) and field emission gun-scanning electron microscope (FE-SEM) were used to characterise the structure, composition and surface morphology of the silane coatings. The aim of this investigation is to compare the surface and bulk characteristics of the films prepared with the three different methods, in order to get information on how the BTSE molecule is modified by the deposition technique.