Advanced Materials Research Vols. 455-456

Abstract: Conductimetry was employed to investigate the precipitation polymerization of acrylamide/methacrylic acid (AAm/MAA) in ethanol (EtOH). The conductivity change vs. temperature of AAm/MAA-EtOH as well as the effects of monomer ratio and monomer concentration was studied. An abrupt decrease of conductivity in AAm/MAA-EtOH was observed at ca 25°C, indicating the phase separation of monomers and EtOH. As the ratios of AAm/MAA increased from 2/1 to 5/1 (wt/wt), the phase separation temperature increased from 22 to 31°C. The higher the monomers concentration, the temperature of phase separation is lower. These results proved that the lyophobicity of methyl group of MAA dominated the phase separation and the precipitation polymerization system of AAm/MAA-EtOH, by which the microspheres were prepared, was heterogeneous prior to the polymerization.

Abstract: The effects of nano-ZrO₂, ZrO₂ fiber and sintering additives on the mechanical properties of Al₂O₃ ceramic composite were investigated by means of orthogonal experimental design. Meanwhile, the effect of environmental temperature on flexural strength of Al₂O₃ ceramic composite was tested. XRD and SEM were used to analyze the microstructure. The results showed that the content of ZrO₂ fiber had the greatest effect on flexural strength and fracture toughness, followed by the content of nano-ZrO₂. Nano-ZrO₂ made the crystalline grains of Al₂O₃ smaller. ZrO₂ fiber pulled out from Al₂O₃ matrix could consume energy of crack and increase the flexual strength and toughness of ceramic composite.

Abstract: The physical and mechanical properties of nanometer ZrO₂-ZrO₂ fiber composite ceramics were studied by introduction of ZrO₂ fiber. ZrO₂ composite ceramics at different sintering temperature was investigated by porosity and water absorption measurements, flexual strength and thermal shock resistance analysis. Results showed that ZrO₂ composite ceramics containing 15 wt% ZrO₂ fiber with sintering temperature of 1650°C exhibited good mechanical properties and thermal shock resistance. The porosity and the water absorption were 8.84% and 1.62%, respectively. The flexual strength was 975 MPa and the thermal shock times reached 31 times. Scanning electron microscope (SEM) was used to analyze the microstructure of ZrO₂ composite ceramics.

Abstract: The carbodiimides 4, obtained from the aza-Wittig reaction of iminophosphorane 3 with aromatic isocyanates, reacted with aliphatic amines or alcohols to give 2-substituted thieno [2,3-d] pyrimidin-4(4H)-ones 6 in the presence of catalytic amount of sodium alkoxide in good yields.

Abstract: Purification of polyether polyols made by double metal cyanide catalysis was studied. The removal effect of residual double metal cyanide in the polyols by the methods of adsorption and precipitation-filtration is characterized by the residual concentration of the zinc and cobalt ions which is measured by Inductively Coupled Plasma Atomic Emission Spectrometry. Compared with precipitation-filtration, the method of adsorption was more practical and efficient for the purification of the polyols. And the optimum kind and amount of the adsorbent were obtained. The results showed that the combination of chelating fiber and attapulgus clay was the most favorable for the removal of zinc and cobalt ions and the appropriate weight ratio of chelating fiber and attapulgus clay was 1:1. The total concentration of zinc and cobalt ions can be reduced to lower than 1×10^-6. And the amount of the adsorbent added was 3.33% by the weight of the polyether polyols. Also through Scanning Electron Spectroscopy the morphology of the chelating fiber was characterized before and after adsorption. The functional groups on the surface of the fiber could be coordinated with the catalyst attached to the polyol polymer chains to form the separable insoluble particles.

Abstract: The initial pathways in the CVD process of preparing silicon carbides with CH₃SiCl₃-H₂ precursors was searched theoretically, which involves 21 well-defined transition states. The geometries of the species were optimized by employing the B3PW91/6-311G(d,p) method. The energy barriers and the reaction energies were evaluated with the accurate model chemistry method at G3(MP2) level after a non-dynamical electronic correlation detection. The heat capacities and entropies were obtained with statistical thermodynamics. The Gibbs free energies at 298.15 K and 1200 K for all the possible elementary reactions, including both direct decomposition and the radical attacking dissociations for MTS were reported. The energies at any temperature could be derived classically by using the analytical heat capacities. It was found that the free radical reactions have clearly kinetic ascendency to be the most efficient decomposition pathway.

Abstract: Three novel Eu-complexes based on phenanthroline derivatives as second ligands have been synthesized and characterized by element analysis, ¹H NMR, FT-IR, UV-vis, and PL. The luminescence spectra presented characteristic emission lines of Eu³⁺ ion. The results of luminescence spectra indicated that the Eu³⁺ ion occupied only a single site, and the ligand filed surrounding the Eu³⁺ ion was highly polarizable. Meanwhile, all complexes exhibited relative high luminescence quantum efficiency (η). Among these Eu-complexes, the complex Eu (DBM)₃HPIP exhibited the lowest quantum efficiency due to the presence of O-H oscillators in this complex, the result indicated different phenanthroline derivatives as second ligands can significantly influence the luminescence properties of Eu-complexes.

Abstract: Adsorption of reactive red on Mg/Al-CO₃ layered double hydroxide in a batch stirred system was investigated. Experiments were carried out as function of Mg/Al molar ratio, contact time, initial pH, adsorbent amount and temperature. It was found that the maximum dye removal was at Mg/Al molar ratio of 3. Solution pH ranging from 2-8 had little effect on adsorption rate. Dye removal decreased with increased temperature in studied temperature range. The Langmuir and Freundlich isotherm models were used for modeling the adsorption equilibrium. The adsorption equilibrium data could well interpreted by the Langmuir models with maximum adsorption capacity of 131.58 mg/g (R²=0.9986). The results indicate the possible dye removal from water by using Mg/Al-CO₃ layered double hydroxide.

Abstract: The light-thermal sensitive microcapsule is synthesized by interfacial polymerization method. Photoinitiator sensitometric characteristic effecting on the light-thermal sensitive microcapsule is analyzed from light curing and imaging density. The curing property and imaging density of the light-thermal sensitive microcapsule are studied by FT-IR and thermal imaging technique. Results of the infrared spectra show that the free radicals induce the unsaturated-C=CH bond of encapsulated trimethylol propane triacrylate (TMPTA) crosslinking, when the microcapsules are exposed. But curing rate and degree of photopolymer TMPTA induced by photoinitiators is distinctly difference at the same exposure times. The results also show that the light curing has relations with the light absorption ability of photoinitiator and the exposure light. Thermal imaging results show that the developing density of light-thermal sensitive microcapsule gradually decreases with the exposure time prolonging, because photopolymer curing production forms the parcel role for dye precursor and decreases the combination opportunities of dye precursor and developer. The results of thermal imaging are consistent with that of the infrared spectrum. When microcapsule samples are exposed by high pressure mercury lamp light, the initiation efficiency of Irgacure 907 is more than that of Irgacure 184.

Abstract: Non-adsorption of water dispersible gold nanoparticles (GNPs) is a major concern in its widely labeling applications. This paper presents the investigation of the adsorption properties of GNPs with superficially tethered ferrocene functions to different surfaces. The GNPs were coated with a mixed monolayer of PEG-thiol and progargyl PEG-thiol, and the later was linked with a ferrocene moiety (Fc) through the alkyne-azide click reaction. The adsorption behaviors of the Fc-GNP to glassy carbon, gold and platinum electrodes, in the absence and presence of a self-assembled monolayer (SAM) or protein layer, were studied by cyclic voltammetry (CV). It was found that the bare gold electrode possessed higher adsorption capacity. However, the adsorption was either reduced or completely prevented when the gold electrode was modified with monolayers of 2-mercaptoethanol (ME), dodecanethiolate (DT) and PEG-thiol. The electroactive and water dispersible GNPs with Fc labels allows us to use CV to explore the interaction between these GNP and bovine serum albumin (BSA). The BSA modified electrode resulted in better resistant to adsorption compared to other modifiers coated electrodes. Thus, the study of non-specific interaction by CV was found effective when compared to results obtained by surface plasmon resonance (SPR) and FTIR.