Nanoindentation as a strength probe—a study on the hardness dependence of indent size for fine-grained and coarse-grained ferritic steel

A nanoindentation hardness testing system, including an atomic-force microscope (AFM)-based nanoindentation tester and a calibration method using electrolytically polished single-crystal metals as references, was proposed. This was applied to a study of the mechanical properties of fine-grained ferritic steel (grain size of 1.2 μm) and coarse-grained ferritic steel (30 μm). An empirical function giving the macroscopic hardness for all four reference metals from the nanoindentation force curves was established. The converted Vickers hardness (HV^*) of the coarse-grained steel is almost independent of the indent size. The fine-grained steel shows only HV^* 130 with an indent of only 100 nm, compared with a macroscopic hardness of HV 210. The difference, HV 80, is considered to reflect the amount of grain-boundary strengthening. The critical indent size for the hardness transition seems to be around 1 μm, comparable to the grain size of the specimen. This result supports the explanation of grain-boundary strengthening. It is also consistent with Pickering's work on low-carbon steel, as the estimated locking parameter (k of 2.6×10⁵ N/m^3/2) in the Hall-Petch relationship is in good agreement with his value of 2.4×10⁵ N/m^3/2. TOHRU HAYASHI, Senior Researcher, formerly with the Strength and Life Evaluation Research Station, National Research Institute for Metals.     

Dynamic properties of an organic hybrid of chlorinated polyethylene and hindered phenol compound

The dynamic mechanical properties of hybrids of chlorinated polyethylene (CPE) and 3,9‐bis[1,1‐dimethyl‐2{β‐(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl)propionyloxy}ethyl]‐2,4,8,10‐tetraoxaspiro[5,5]‐undecane (AO‐80) were investigated. The CPE/AO‐80 hybrids showed a novel relaxation in addition to the glass transition of CPE. The novel relaxation is attributed to the dissociation of intermolecular hydrogen bonds within the AO‐80–rich domain. The Payne effect, that is, the decrease of the storage modulus E′ with increasing strain amplitude and the appearance of a loss modulus E″ maximum at a strain of 0.6%, was observed for the CPE/AO‐80 hybrids. This result demonstrates that the AO‐80–rich domains within matrix polymer CPE form a network. The Payne effect is considered to be attributed to the mechanical disruption of segment–segment contacts at a sufficiently great strain. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1788–1793, 2001     

Synthesis of Highly Effective CeO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>–MnO<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript>–BaO Catalysts for Direct NO Decomposition

Abstract  

Ce–Mn mixed oxides with a Mn/(Ce + Mn) molar ratio of 0.25 were prepared by solvothermal (ST-1) and co-precipitation (CP) methods, and Ba was loaded on the Ce–Mn oxides. In addition, CeO₂–MnO _x –BaO catalysts with various compositions were directly prepared by the solvothermal (ST-2) method. The NO decomposition activities of these catalysts were examined. Among the catalysts examined, the ST-2 catalyst having a nominal composition of Ce_0.8Mn_0.15Ba_0.05O _x exhibited the highest activity; 77% NO conversion to N₂ was attained at 800 °C. These catalysts were characterized by X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The Raman and XPS results indicate that the CP catalyst had larger amounts of the BaMnO_3-δ and/or Mn₃O₄ phases. The ST-1 and ST-2 catalysts had highly dispersed Ba species on the surface. The ST-2 catalyst had Mn species with the lowest binding energy of Mn 2p and also had a high population of oxygen vacancies in the ceria lattice, suggesting that Mn species with a low oxidation state contributes to the formation of oxygen vacancies, which play an important role in this reaction.     

Surface coating with a high resistance to hydrogen entry under high-pressure hydrogen-gas environment

Development of a surface coating with high resistance to hydrogen entry under a high-pressure hydrogen-gas environment is presented. Two aluminum-based coatings were developed on the basis of preliminary tests: two-layer (alumina/Fe–Al) and three-layer (alumina/aluminum/Fe–Al) coatings, deposited onto cylindrical and pipe (Type 304 austenitic stainless steel) surfaces by immersion into a specially blended molten aluminum alloy. The coated specimens were exposed to hydrogen gas at 10–100 MPa at 270 °C for 200 h. Specimen hydrogen content was measured by thermal desorption analysis; hydrogen distributions were analyzed by secondary ion mass spectroscopy. Both coatings showed high hydrogen-entry resistance at 10 MPa. However, resistance of the two-layer coating clearly decreased with an increase in pressure. In contrast, the three-layer coating showed excellent hydrogen-entry resistance at a wide pressure range (10–100 MPa), achieved by the combined effect of alumina, aluminum, and Fe–Al layers.     

Detection of genistein as an estrogenic contaminant of river water in Osaka

The estrogenic activity in water at various localities on Lake Biwa-Yodo River, a representative watershed in Japan, was measured using a recombinant yeast that expresses the human estrogen receptor. The yeast bioassay revealed that the activities of 13 water samples had an average value of 14 pmol/L (3.8 ng/L) (17beta-estradiol equivalent) with a very wide range from 0 to 72 pmol/L (0-19.6 ng/ L), and two of the samples had prominent levels of activity (72 pmol/L (19.6 ng/L) and 56 pmol/L (15.2 ng/L)). We analyzed these two samples with instrumental approaches. A high-performance liquid chromatogram profile showed that the strong activity in one sample, which was collected just downstream of a sewage-treatment plant, would be due to 17beta-estradiol and estrone, whose source is considered to be human urine contained in the effluent of the plant. The activity in the other sample, which was obtained from a tributary river in a primarily residential area with some industrial development (i.e., Osaka City), however, did not correspond to 17beta-estradiol, estrone, or synthetic chemicals known as estrogenic. Analysis of a fraction with estrogenic activity by liquid chromatography-mass spectrometry (LC-MS) provided evidence that the activity in the water sample resulted from the presence of genistein, an isoflavone compound of plant origin.     

Viscoplastic modeling of ABS material under high-strain-rate uniaxial elongational deformation

Uniaxial tensile tests were performed on the newest type of Meissner rheometer with an ABS (acrylonitrile-butadiene-styrene) material. Tests were conducted for constant strain rates varying from 0.01 to 1 (1/s), at the temperatures ranging from 150 to 200 °C. Based on the experimental data, a new model was proposed, in which, strain hardening, strain rate sensitivity, temperature changes and the variation in the hardening index could be taken into consideration. In this new model, a new parameter, w, was introduced, which represents the variation in the hardening index. The proposed model can approximate the experimental data of the uniaxial tensile test quite well. Two existing models were also employed to approximate the material behavior, however, both of them exhibited the poor accuracy. Finally, a simple stretch deformation was simulated employing the three different models, and the differences in the final thickness and shape were confirmed.     

High-performance liquid chromatography-bioassay profiles of endocrine disrupters discharged from point and non-point pollution sources in Lake Biwa basin

Toxic pollution loading from both point and non‐point sources in Lake Biwa should be further reduced. In order to tackle toxicity problems, it is necessary to analyse characteristics of toxic pollution. We have developed a new profiling technique to display toxic distributions of endocrine disrupters in complex mixtures of environmental samples, using high‐performance liquid chromatography in combination with yeast bioassays. We have applied this technique to the major point and non‐point pollution sources in the Lake Biwa basin, that is, to municipal sewage‐treatment water (point) and road dust (non‐point). The dominant oestrogenic chemical in sewage‐treatment water was 17 β‐estradiol. The extracts from screened road dust showed arylhydrocarbon‐receptor binding activity (AhR–ligand activity), with much of this located in smaller particles of sifted dust. There were at least seven major AhR–ligand peaks in the road‐dust sample.     

Optimized synthesis method for K/Co3O4 catalyst towards direct decomposition of N2O

The potassium-doped Co₃O₄ catalysts were prepared by impregnation of potassium sources on commercial cobalt carbonate and on the precursors synthesized by homogeneous precipitation, combustion with glycine, gradual oxidation, and hydrothermal methods. The activities of these catalysts for the direct decomposition of nitrous oxide in the presence of oxygen with or without water vapor were examined. The effects of potassium sources on the catalyst activity were also examined by impregnation of various potassium salts on commercial cobalt carbonate. The catalyst prepared by impregnation of an aqueous solution of KOH on commercial cobalt carbonate showed the highest activity. The catalysts prepared by various methods were analyzed by powder X-ray diffraction, N₂ adsorption, scanning electron microscope, temperature-programmed reduction with H₂, temperature-programmed desorption of O₂, and X-ray photoelectron spectroscopy. These results suggest that crystallite size and reduction property are key factors for the activity of the catalyst for the direct decomposition of nitrous oxide in the presence of oxygen.     

Analysis of estrogen-like compounds in the environment by high performance liquid chromatography bioassay

To identify chemicals with endocrine-disrupting activity easily, we developed a new bioassay system, consisting of bioassay using genetically modified yeast expressing human estrogen receptor and high performance liquid chromatography (HPLC), in which advantages of instrumental analysis and bioassay are combined. The peaks in the mixture of these estrogen-like compounds analyzed using an HPLC bioassay were similar to those obtained by analysis using an HPLC-UV detector. Underground water and sea sediment were analyzed by an HPLC bioassay, and detected a few estrogen-like compounds, respectively. Estrogen-like compounds and yeast-growth inhibitors can be separated by HPLC-bioassay.     

Production of two types of phytase from Aspergillus oryzae during industrial koji making

In our previous study, it was determined that phytase produced by Aspergillus oryzae plays an important role in supplying phosphate to yeast in the process of making sake. During koji making, two types of phytase (Phy-I and Phy-II) are produced. The purified phytases have high thermal and pH stability, in comparison to phytase purified from a submerged culture (ACP-II). In the present study, Phy-I and Phy-II retained their activities for 45 h. The NH2-terminal sequence of Phy-1, which is eight amino acids in length, was identical to that of ACP-II, but the molecular weights of these two forms, as estimated by SDS-PAGE, were quite different from each other (Phy-I, 120 kDa; ACP-II, 58 kDa). From the NH2-terminal amino acid sequence analysis of the predominant phytase (Phy-II), a molecular weight of 116 kDa was expected to reflect a new type of phytase produced only in koji culture. The substrate specificity of Phy-II was sufficiently broad that it hydrolyzed not only phytic acid and p-nitro phenyl phosphate, but also glucose 6-phosphate and glycerol 1-phosphate. In the process of making koji, Phy-I was produced at an early stage, followed by Phy-II; with both phytases being thought to function to hydrolyze phytic acid cooperatively.