Sliding wear properties of HVOF sprayed WC-20%Cr3C2-7%Ni cermet coatings

WC-20 mass%Cr₃C₂-7 mass%Ni powder was sprayed onto low-carbon steel substrates by a commercial high velocity oxygen-fuel (HVOF) spray process as well as by an improved HVOF process equipped with a gas shroud attachment. The latter process utilizes a nitrogen gas flow to shield the region between the spray gun and the substrate in order to suppress the material's degradation caused by reaction with air such as oxidation and decarburization. Some coatings were further heat-treated in air at 773 K for 30 h to form a thin oxide film on the surface. The sliding wear properties of these coatings against an iron pin were evaluated by using a pin-on-disk wear tester. The specific wear rate of the as-sprayed cermet coatings prepared under the conventional spray condition was about three times higher than that of the chrome plating but by using the gas shroud, the wear rate was reduced to the same level with the chrome plating. The specific wear rate could be further decreased by the oxidation heat-treatment. It was found that a proper amount of oxides existing on the surface or within the coatings have a great beneficial effects on the wear properties such as to promote the transition from severe wear to mild wear and thus to reduce the wear rate remarkably. XPS analysis of the transfer particles collected from the wear track revealed a shift in the oxidation state of iron depending on the wear condition.     

Synthesis and processing of hydroxyapatite ceramic tapes with controlled porosity

Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) ceramic sheets with a wide range of porosities (up to 62%) have been prepared. The process is based on the reaction between dicalcium phosphate (CaHPO₄) and calcium carbonate (CaCO₃). When mixed with the appropriate Ca/P ratio, this proves to be a reliable new method for obtaining hydroxyapatite. Moreover, CaCO₃ serves as a gas-forming agent (due to the evolution of carbon dioxide and water during the reaction), which leads to the development of highly porous microstructures. Alternatively, CaHPO₄ and CaCO₃ can be reacted by calcining at 1000°C to produce pure hydroxyapatite powders. When processed in a similar way, a dense ceramic results. By mixing 50 vol% of CaCO₃ and CaHPO₄ with precalcined powders, hydroxyapatite with an intermediate porosity was obtained. Moreover, it should be possible to achieve porosity control by mixing different amounts of uncalcined and precalcined powders. All of these powders are colloidally processed using tape casting to produce thin sheets 150–200 m thick. This technique can be used to make laminates, with or without porosity gradients, up to several millimetres thick.Currently enrolled in the CICESE PhD programme.     

ALife approach to eco-evo-devo using evolution of virtual creatures

Evolutionary developmental biology, evo-devo, emerged to integrate evolution and development in the 1980s, in which evolution is conceptualized as heritable changes in development. Recently, the field is moving to a new synthesis: ecological evolutionary developmental biology, eco-evo-devo. We believe that artificial life (ALife) approach will provide new insights into the field, and also contribute to the field of robotics through the emergence perspective and the constructive methodology. This paper explores the potential of such an artificial life approach based on the evolution of virtual creatures by presenting our ongoing studies with three models: (1) metamorphosis model, (2) exaptation model and (3) Prey-predator model.     

Production of MAG of CLA in a solvent-free system at low temperature with <Emphasis Type="Italic">Candida rugosa</Emphasis> lipase

We attempted to produce MAG of CLA through lipase-catalyzed esterification of a FFA mixture containing CLA (referred to as FFA-CLA) with glycerol. Screening of lipases showed that MAG-CLA was produced efficiently at 5°C with Penicillium camembertii, Rhizopus oryzae, and Candida rugosa lipases. Among them, C. rugosa lipase was selected because the lipase is widely used as a catalyst for oils and fats processing. The reaction was conducted with agitation of a 300-g mixture of FFA-CLA/glycerol (1∶5, mol/mol), a 200-U/g mixture of C. rugosa lipase, and 2% water. When the reaction was conducted at 30°C, the esterification scarcely proceeded, owing to inhibition of the reaction by glycerol. But the reaction at 5°C eliminated the inhibition and produced MAG efficiently: The degree of esterification reached 93.8% after 58 h, and MAG content in the reaction mixture was 88.4 wt%. To reduce the reaction time, the reactor was connected with a vacuum pump after 24 h, and the reaction was continued with dehydration at 5 mm Hg. The degree of esterification reached 94.7% after 24 h of dehydration (48 h in total), and MAG content increased to 93.0 wt%. Candida rugosa lipase acted a little more strongly on cis-9, trans-11 CLA than on trans-10,cis-12 CLA, but the contents of the two isomers in MAG obtained from a 48-h reaction were the same as the contents in FFA-CLA.     

The effect of some foam boosters on the foamability and foam stability of anionic systems

The foaming properties of anionic surfactant solutions containing a nonionic surfactant, fatty acid N-methyl-ethanolamide (NMEA), were investigated. Foamability, which is the foam-generating power at the initial stage of foaming, was measured by a laboratory-built foam-testing apparatus, and also by the conventional Ross-Miles test NMEA synergistically increased the foamability of anionic surfactant solutions, particularly when small amounts of NMEA were added. Shorter hydrocarbon chain lengths of NMEA, such as N-octanoyl-N-methylethanol (NMEA-08) and N-decanoyl-N-methylethanol (NMEA-10), showed better performance in the laboratory-built foam tester. The results of the Ross-Miles evaluation, however, were completely opposite. Compared with commercial nonionic boosters, such as fatty acid monoethanolamide, fatty acid diethanolamide, and lauramidopropyldimethylbetaine (LPB), NMEA was the most effective for increasing foamability of the solution at the initial stage. The most popular amphoteric foam booster, LPB, did not increase foamability but likely generated the initial foam volume on the Ross-Miles test as a result of foam film stabilization. From these results, a foam-boosting mechanism of NMEA different from that of LPB is suggested.     

The effect of γ‐irradiation on thermal strain of high strength polyethylene fiber at low temperature

To understand the contribution to negative thermal expansion by the length of the molecular chains in high‐strength ultra‐high‐molecular‐weight polyethylene (UHMW‐PE) fiber, the thermal expansion coefficient in the range of low temperature was investigated for high‐strength UHMW‐PE fiber (Toyobo, Dyneema®; hereinafter abbreviated to DF), irradiated by γ‐rays (γ‐rays treatment) that induce the molecular scission. The molecular weight of DF decreased by γ‐ray treatment. X‐ray diffraction behavior did not change by γ‐ray treatment. The melting behavior observed by DSC showed the main chain scission of DF by γ‐ray treatment. The DFs, with and without γ‐ray treatment, expand by cooling down (negative thermal expansion). The change of negative thermal expansion of DF by γ‐ray treatment was small. It is suggested that negative thermal expansion does not change by only the molecular chain scission. These results suggested that the effect of negative thermal expansion of DF in the temperature range from 213 to 303 K by the molecular chain scissions is small and that the length of extended molecular chains contributes to a negative thermal expansion a little. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 204–209, 2006     

Enzyme electrode based on gold-plated polyester cloth

Summary Diaphorase is immobilized on electrodes derived from metal-plated polyester cloth by entrapment method and coupled with an electron mediator. Cyclic voltammogram depended on the existence of the substrate NADH (for oxidation) or NAD⁺ (for reduction) and the flavo-enzyme was shown to exchange electron(s) with the cloth electrode by mediation of the ferrocene derivative (for oxidation cycle) or the viologen derivative (for reduction cycle), even in the immobilized state. Coupling of the NADH or NAD⁺ regenerating system with alcohol dehydrogenase was examined.     

Effect of Impregnation of Iodine Complex on Friction of Anodic Oxide of Aluminum

Polyvinyl pyrrolidone-Iodine complex (PVP-I) molecules were impregnated into the anodic oxide of an aluminum disk specimen. It was rubbed against a silicon nitride ball specimen using a ball-on-disk type friction test rig. Over the limited range of parameters studied (load: 0.2-1.0 N, sliding velocity: 0.6 mm/s, and sliding distance: 1-7 m), the coefficient of friction decreased to a value as low as 0.01 from values of 0.3 to 0.7 for the anodic oxide surface. Single-crystal iodine rubbed against silicon nitride showed a coefficient of friction of 0.1. The low coefficient of friction is attributed to the thin PVP-I film on the relatively hard anodic oxide. The mechanism of coefficient of friction reduction is the same as that of a thin soft film on a hard substrate.