Diffusional behavior of multi-arm star polymers by H pulsed field gradient spin-echo NMR method

The diffusional behavior of multi-arm star-shaped p(tBMA) was investigated in a concentration range from dilute to semidilute region with ¹H pulsed field gradient spin-echo NMR (PFGSE-NMR). An 142-arm star-shaped p(tBMA) showed two diffusional mode, which reflected the coexistence of liquid ordering phase and liquid phase near the ordering transition. On the other hand, for star-shaped p(tBMA) with 55 arms showed a single diffusional relaxation in all concentration ranges during observation time. In the semidilute region, the relationship between the diffusion coefficient against the polymer concentration was affected strongly not only the arm number but also liquid ordering structure.     

Effect of the addition of silver compounds during the pyrolysis of manganese nitrate on tantalum anodic oxide film

A study of the pyrolysis of an aqueous solution of manganese nitrate in the presence of silver compounds has been carried out. Thermal analysis showed that the MnO₂ formation temperature and the transformation temperature from MnO₂ to Mn₂O₃ shifted towards a lower temperature in the presence of silver acetate. A large particle-size and high crystallinity MnO₂ was formed; this may be a useful method of making an excellent tantalum capacitor with high capacitance.     

Inter- and intra-molecular ionic interactions of polyampholyte: Carboxymethyl-2-diethylaminoethylcellulose

Carboxymethyl-2-diethylaminoethylcellulose (CM-DEAE cellulose) was prepared by etherification of carboxymethylcellulose with diethylaminoethyl chloride in a NaOH solution. The behaviour of CM-DEAE cellulose in aqueous solution was studied by viscosity and GPC measurements. The degree of substitution (DS) and existing states of DEAE substituents were examined by the use of proton NMR, and those of the CM substituents were observed with FT-IR. The results reveal that the reduced viscosity and apparent molecular size of CM-DEAE cellulose vary with the concentration of sodium chloride and changes in pH and DS. These phenomena can be explained in terms of inter- and intra-molecular ionic interactions.     

An entropy model for shear deformation of granular materials

A statistical mechanical analogy for characterization of granular materials is discussed by using such notions as the state of the material, the density of states, entropy, canonical distribution and the partition function. The transition law of states during shear deformations of the material is microscopically investigated in the case of two-dimensional model granular materials. The assumption of entropy growth is shown to characterize the dilatancy of the material. A rough proof is given by assuming the measure preserving property of the transition and showing its ergodicity.     

Cooperative behavior of various agents in dynamic environment

The multi-agent model is a model in which agents with limited ability cooperate each other to accomplish a goal. In this paper, we introduce a multi-agent model in which agents are created to imitate real ants. There are two different type of agents, each type of which has a particular task. We designed agents to communicate each other by using pheromone considering noise. On this model, we observed cooperative behavior of agents and evaluated conditions to make an order of behavior in the model.     

Effect of the addition of NH4F on anodic behaviors of DSA-type electrodes in H2SO4-(NH4)2SO4 solutions

The effect of NH₄F addition on the high-anodic behaviors of various DSA-type electrodes was investigated in a mixture of sulfuric acid and ammonium sulfate. The pronounced effect of NH₄ addition was observed on DSA-type Ti/RuO₂, Ti/IrO₂?TiO₂ electrodes, but not observed on the other electrodes studied. The close relationship was found between the increment of the electrode potential caused by the NH₄ addition and the quantity of F^? adsorbed on the electrode surface. The effect of NH₄F addition was considered to be resulted from the adsorption of F^? on the electrode surface, and the presence of adsorbed F^? was directly proved.     

Synthesis of polyethylene oxide end‐capped with perfluoroalkyl groups/polystyrene prototype brushes

Polystyrene (PS)/poly(ethylene oxide) (PEO) prototype brushes were prepared by alternating free‐radical copolymerization of methacryloyl‐terminated PS and α‐vinylbenzyl‐ω‐hydroxy or α‐vinylbenzyl‐ω‐perfluoroalkyl (R_f) PEO macromonomers with the addition of Lewis acid (SnCl₄). It was found from their dilute‐solution properties that PS/PEO end‐capped with R_f (PBR_f), and PS/PEO having OH groups at terminal ends (PBOH) prototype brushes formed a single molecule in benzene and aggregates in chloroform, respectively. However, the brush PBOH formed a single molecule in N,N‐dimethylformamide. Such aggregation behaviors seemed to be caused by the interaction between hydroxy groups of PEO chain ends. The brush PBOH was also converted into PBR_f‐type brush by chemical modification, using corresponding acid chloride. The substitution of R_f groups was ～70% due to slipping of terminal hydroxy groups into PEO internal domains. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 772–778, 2006     

Activation of a Au/TiO2 Catalyst by Loading a Large Amount of Fe–Oxide: Oxidation of CO Enhanced by H2 and H2O

Catalytic activity of a 1 wt% Au/TiO₂ catalyst is markedly improved by loading a large amount of FeO_x, on which the oxidation of CO in excess H₂ is selectively promoted at temperature lower than 60 °C. Oxidation of CO with O₂ on the FeO_x/Au/TiO₂ catalyst is markedly enhanced by H₂, and H₂O moisture also enhances the oxidation of CO but its effect is not so large as the promotion by H₂. We deduced that activation of Au/TiO₂ catalyst by loading FeO_x is not caused by the size effect of Au particles but a new reaction path via hydroxyl carbonyl intermediate is responsible for the superior activity of the FeO_x/Au/TiO₂ catalyst.     

Two-stage pyrolysis of heavy oils. 3. Pyrolysis of tar-sand bitumens. Relation between ethylene yield and structural characteristics of heavy oils

Thermal cracking of tar-sand bitumens has been carried out using a two-stage pyrolysis reactor with temperature zones of 440°C and 750–800°C, respectively. Feedstocks were pyrolysed in the first stage into cracked oils, which were carried to the second stage for subsequent pyrolysis. Only 12–14 wt% of ethylene was obtained from tar-sand bitumens at the residence time of 1.2 s in the second stage, although 27 and 16 wt% were obtained from Taching and Iranian heavy vacuum residues, respectively. The tar-sand bitumens contain shorter paraffinic straight-chains and have more branched molecules than the vacuum residues of petroleum. A straight-chain paraffin index is proposed, with which a good correlation was obtained between ethylene yield and the fraction of straight-chain paraffin carbons in the heavy oil.     

Influence of activated carbon pore structure on oxygen reduction at catalyst layers supported on rotating disk electrodes

Carbon materials are often used as catalyst supports, and for catalysts in electrodes of a polymer electrolyte fuel cell, carbon black has been used. Recently, it was found, however, that activated carbon could replace carbon black and besides, significantly improve the activity of the electrode catalyst layer for oxygen reduction. In the present study, to optimize the pore structure of activated carbon for further activity improvement, the influence of the pore structure on the activity was investigated using activated carbon of various specific surface areas and mean pore diameters. A catalyst layer was formed from activated carbon loaded with platinum and a polymer electrolyte. The activity of the layer was measured in an oxygen-saturated perchloric acid solution, supporting the layer on a rotating glassy carbon disk electrode. We found that increases in the specific surface area and mean pore diameter increased the activity and that the latter was more effective than the former mainly due to the enhanced mass-transfer in the pores; the catalyst layer formed from activated carbon with the largest mean pore diameter was the most active. Unless pores excessively develop and lose connections between particles, a large pore diameter is therefore desired for the fuel cell electrodes.