[en] A method is described of determining the material granulation, which eliminates the mechanical sorting of granular material and simplifies the analysis. The method also permits a continuous process of individual operations required for the determination of material granulation. (V.V.)

[en] This study focuses on characterizing and modeling advanced oxide dispersion strengthened (ODS) NiAl intermetallics with improved high temperature creep strength driven by incorporating a high number density (∼10²⁴ m^-3) of very thermally stable Y-Ti-O nano-clusters, akin to those recently observed to improve creep strength and radiation resistance in nano-structured ferritic alloys. The motivation of the study was; what structure and composition do the nm-scale features/precipitate clusters have and what processing variables control their formation. To answer these questions, advanced experimental characterization techniques, combined with atomic modeling, were used to investigate the material microstructure and strength following processing. In particular, the size, number density and composition of nano-clusters were assessed. There was a clear indication that milling for 5-15 hrs was sufficient to produce good mixing during the mechanical alloying process, as determined by XRD, SEM, and EDS results. Powder consolidation was carried out by spark plasma sintering. Fully dense NiAl alloy materials were produced by SPS. A distribution of 10-20 nm precipitates was found in NiAl-Y₂O₃ and NiAl-Y₂O₃-Ti alloys, and those precipitates were identified as Y-Al-O (garnet) particles in the NiAl-Y₂O₃, while both garnet (Y₂Al₄O₇) and Y₂Al₉Ti₂O₆ phase particles were found at the NiAl-Y₂O₃-Ti alloy. The Al composition of a particle increases as the particle size increases, and Y was dominantly found at the particles size of less than 50 nm while Ti was found at the relatively larger particles with size larger than 100 nm. The Al incorporation believed detrimental to the formation of nanoscale Y-Ti-O precipitates. The effect of Hall-Petch grain size and dispersion strengthening mechanisms in ODS NiAl alloys will be semi-quantatively assessed. The LMC simulations indicate that larger than 10% lattice strain required to form coherent nano-clusters

[en] The effect of the magnetic anisotropy at temperatures above the blocking temperature of a uniaxial, randomly oriented, nanoparticulate magnetic system has been studied. If anisotropy is disregarded in fitting the magnetization curves, apparent particle-size distributions emerge from the calculations, even for monodisperse systems. Apparent mean grain size increases with temperature, with a saturation value corresponding to the actual particle size. This evolution collapses to a master curve for anisotropy energy terms up to the fourth order

[en] The consolidation behavior of tungsten powders with different particle size (ranging from submicron size to several microns) have been investigated by using a novel method combining resistance sintering with ultra-high pressures. The densification effects of the consolidation parameters, including pressure, input power and sintering time, have been investigated. High density is achieved for consolidation of micron sized tungsten powder and the microstructure retained its fine-grain size. The sintered samples achieve higher hardness and bending strength when the finer powder is used. The sintering mechanism of this method was quite different from other sintering techniques

[en] The remanent state of truncated conical particles is investigated as a function of their size, aspect ratio, and anisotropy, using a micromagnetic model based on the Landau - Lifshitz - Gilbert equation. Particles with a base diameter smaller than three times the exchange length show a 'flower' state, while larger particles show a 'vortex' magnetization state. The critical size for this transition increases with increasing anisotropy. Small flower-state particles show abrupt reorientation from out-of-plane to in-plane magnetization at a critical aspect ratio of 0.9. For vortex-state particles, the axial remanence gradually increases as the aspect ratio increases, and high aspect ratio particles have significant remanence even at larger diameters. [copyright] 2001 American Institute of Physics

[en] Keutapang Formation deposited in North Sumatra Basin at the mid to late miocen on regression phase. Air Benakat Formation deposited in South Sumatra Basin, has similar characteristic with Keutapang Formation which deposited in the regression & compressional phase near the same age. The purpose of this study is to know the relationship between Laser Particle Size Analysis (LPSA) and Depositional Environment to include Hydraulic Flow Unit (HFU) in each Formation to help reservoir characterization process and rock type determination. Laser Particle Size Analysis results show that both formations have grain size from 11 to 160 μm in other words is very fine sand (wentworth scale). Sorting ranges from 1.5 to 2.4Ø which is classified as poorly sorted to very poorly sorted. Skewness ranges from -0.091 to 0.658 Ø grouped into near symmetrical, fine, and very fine skewness. Kurtosis ranges from 0.686 to 1.102 Ø grouped into very platykurtic, platykurtic, and mesokurtic. Based on the Linear Discriminate Function (LDF) method, by evaluating the values of Y1, Y2, Y3 and Y4, it describes that both formations are deposited on the Deltaic Environment with Shallow Agitated Water and dominated by traction currents. Difficulties in geomodelling process comes when there is no relationship between log analysis properties (which will be distributed) with HFU (from core data analysis). With LPSA data, we can obtain a linear (indirect) relationship between grain size and the shale volume on the same rock geometry. This relationship can be used to distribute HFU values by using a plot of grain size with HFU or Flow Zone Index. (paper)

[en] An electrostatic field was applied to sintering Ag microwires to achieve a more compact structure and better conductivity. The shrinkage behavior of Ag microwires shows anisotropy, since bigger particle sizes, less micropores and smoother surfaces were observed in the direction of the electrostatic field in comparsion with the direction perpendicular to the electrostatic field, and the shrinkage rate of Ag microwires in the direction of electrostatic field improves about 2.4% with the electrostatic field intensity of 800 V cm⁻¹. The electrostatic field assisted sintering model of Ag microwires is proposed according to thermal diffuse dynamics analysis and experimental research. Moreover, the grain size of Ag microwres sintered with electrostatic field increases with the electrostatic field intensity and reaches 113 nm when the electrostatic field intensity is 800 V cm⁻¹, and the resistivity decreases to 2.07  ×  10⁻⁸ Ω m as well. This method may overcome the restriction of metal wires which fabricated by the pseudoplastic metal nanoparticle fluid and be used as interconnects in nanoimprint lithography. (paper)

[en] The main aim of the present investigation was to study the flow behaviour of two medium carbon microalloyed steels under hot forming conditions, and to analyse their microstructural evolution. the dependence of recrystallized grain size (D_rec) on the Zener-Hollomon parameter Z shows a bimodal behaviour with transition from single to cyclic dynamic recrystallization. We also observed that the variation of D_rec normalized by the Burgers vectors (b) with the steady state stress σ_ss normalized by shear modules (μ) shows the same bimodal behaviour cited above. the Derby's universal equation reported in the literature for recrystallized grain sizes was not followed; it seems that the presence of fine precipitated particles has a clear effect on this disagreement. (Author)

No abstract available

[en] In this work, we try to answer the following question: What is the effective characteristic length of a mixture of Cosserat continua? More generally, homogenization methods for heterogeneous Cosserat media are proposed and applied to the case of linear elasticity. They first application deals with a beam network regarded as a discrete Cosserat medium and the second with a continuous heterogeneous Cosserat continuum. (orig.)