Home  About us  Contact
 

Small Grains (small + grain)

Distribution by Scientific Domains
Polymers and Materials Science40%
Physics and Astronomy30%

Terms modified by Small Grains

  • small grain size
    		•

    Selected Abstracts

    Electrochemical deposition of Pt nanoparticles on diamond substrates

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2009
    Jingping Hu
    Abstract Platinum nanoparticles were deposited on polished smooth, as-grown large grain and small grain diamond substrates by a potentiostatic method. The influence of deposition potential and the morphology of BDD substrates were studied. A progressive nucleation along with spherical clusters was observed on smooth BDD electrode, accompanied with a heterogeneous segregation of platinum on diamond facets of higher electrochemical activities and a weak binding to the substrate. In contrast, an instantaneous nucleation was observed on as-grown small grain and large grain BDD electrodes, with a dendritic microstructure and a much larger specific active area. The platinum decorated as-grown smaller grain BDD electrodes show a much better electrochemical stability than the other electrodes investigated. [source]

    Labial Gland and Its Protein Patterns of Hydropsychid Caddisfly (Hydropsyche kozhantschikovi Martynov: Trichoptera)

    ENTOMOLOGICAL RESEARCH, Issue 1 2003
    Sang-Chan PARK
    ABSTRACT There is a pair of labial gland of hydropsychid caddisfly (Hydropsyche kozhantschikovi Martynov) larva. It is in ,Z' formation in the body and the total length is about 20 mm. Hydropsychid caddishfly larvae that were raised under the lab conditions were able to form a nest-spining by connecting the small grains of sand provided. By repeatedly treating the extracted labial gland with methanol/D.W., the cell layer was removed. Accordingly, only the matrix within the labial gland that did not dissolve in water was obtained. The matrix inside the methanol/D.W. treated labial gland was dissolved with 5% acetic acid. Then the results of an acidic electrophoresis with a number of conditions indicated that 5% acetic acid/ 5 M urea/ 8% PAGE was the most effective. Moreover, the result of 2-D PAGE on the labial gland of these hydropsychid caddisfly larva, the number of proteins in the labial gland including the cell layer was about 350 and the number of proteins in the labial gland treated with methanol/D.W. was about 80, showing a substantially small number of proteins. [source]

    Solute Content and the Grain Microstructure of High Pressure Diecast Magnesium,Aluminium Alloys,

    ADVANCED ENGINEERING MATERIALS, Issue 11 2009
    Anumalasetty V. Nagasekhar
    The grain microstructure is strongly bimodal due to the mixture of large dendritic grains that solidify in the shot sleeve and are subsequently injected into the die cavity, and the small grains that nucleate inside the cavity and grow to a size dictated by the solute content and the solidification rate. The large grains form only in concentrated alloys; their size is also partially controlled by the growth restriction factor. [source]

    Strain Hardening Behavior of Ultrafine- Grained Cu by Analyzing the Tensile Stress-Strain Curve,

    ADVANCED ENGINEERING MATERIALS, Issue 5 2008
    C.-X. Huang
    UFG Cu was found to experience two stages of strain hardening processes under uniaxial tensile stress, which was similar to the Stage,IV and V of CG Cu after large plastic deformation. The storage of dislocations in small grains and dynamic recovery caused by annihilation of dislocations and GB-mediated processes were responsible for the different stages of strain hardening behavior. Improvement of strain hardening capability for UFG metals should be based on the mechanisms of strain hardening. [source]

    Pigment study by Raman microscopy of 23 paintings by the Portuguese artist Henrique Pousão (1859,1884)

    JOURNAL OF RAMAN SPECTROSCOPY, Issue 11 2007
    Andreia M. Correia
    Abstract Twenty-three paintings by Henrique Pousão,a 19th century Portuguese painter,belonging to the collection of Museu Nacional Soares dos Reis, Porto, Portugal, were analysed by Raman microscopy. The fine focus of a 100× objective allowed the visualisation and individual identification of small grains. As a result, thirty-seven compounds, namely, anatase, barium white, basic lead sulfate, brochantite, cadmium red, cadmium yellow, calcium carbonate, carbon-based black, celadonite, chrome green, chrome orange, chrome yellow, cobalt blue, cochineal lake, copper sulfide, emerald green, iron(III) oxyhydroxide, iron(III) oxide, kaolinite, lead antimonate yellow, lead carbonate, lead white, lead sulfate, madder lake, malachite, Prussian blue, quartz, realgar/pararealgar, red lead, rutile, Scheele's green, strontium yellow, ultramarine blue, vermilion, viridian, zinc white and zinc yellow, were identified. Not all these compounds are pigments; some are extenders, others trace components and others probably products of reactions between pigments. Special attention was given to the Raman characterisation of celadonite, chrome orange, basic lead sulfate and lead antimonate yellow. Complementary techniques were used to confirm the identities of certain pigments and to characterise reference samples. Pousão, whose work has not previously been studied spectroscopically, was found to have used a remarkably wide range of pigments over his painting periods, without showing significant preference for any particular set of pigments. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Microstructure and Piezoelectric Properties of 0.95(Na0.5K0.5)NbO3,0.05SrTiO3 Ceramics

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2007
    Kyung-Hoon Cho
    The 0.95(Na0.5K0.5)NbO3,0.05SrTiO3 (0.95NKN,0.05ST) ceramics formed in this study had a porous microstructure with small grains and low piezoelectric properties due to their low density. However, when a small amount of Na2O was intentionally subtracted from the 0.95NKN,0.05ST ceramics, a liquid phase was formed, which led to increased density and grain size. Piezoelectric properties were also improved for the Na2O-subtracted 0.95NKN,0.05ST ceramics. The increased density and grain size were responsible for the enhancement of the piezoelectric properties. In particular, the 0.95(Na0.49K0.5)NbO2.995,0.05ST ceramics showed high piezoelectric properties of d33=220, kp=0.4, Qm=72, and ,3T/,o=1447, thereby demonstrating their promising potential as a candidate material for application to lead-free piezoelectric ceramics. [source]

    Differential Sintering by Improper Selection of Sintering Parameters during Pulse Electric Current Sintering

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2004
    D. Doni Jayaseelan
    Recently, we reported on the retention of fine-grained micro-structure in Al2O3/3 vol% 3Y-ZrO2 composites using the pulse electric current sintering (PECS) technique. It was demonstrated that a high heating rate is beneficial for the retention of fine grains and homogeneous microstructure. As there are few reports on microstructural inhomogeneity and excessive grain growth in compacts densified by the PECS technique, we carried out a series of experiments on monolithic alumina by varying the sintering parameters and discussed the characteristic results. All specimens that were densified under selective sintering conditions attained high density (,99% of the theoretical density) at 1250°3C in > 5 min. The average fracture strength of monolithic alumina was observed to be 741 ± 25 MPa and the fracture toughness was 2.2 MPa.m <1/2, and these were reasoned out to small grains. However, compacts sintered under very low compaction pressure attained ,92%-93% of the theoretical density, and these specimens had undesirable microstructural inhomogeneity owing to differential sintering. Hence, in the present study, we address the problem of differential sintering. [source]

    Petrography of refractory inclusions in CM2.6 QUE 97990 and the origin of melilite-free spinel inclusions in CM chondrites

    METEORITICS & PLANETARY SCIENCE, Issue 10 2007
    Alan E. Rubin
    It contains 1.8 vol% refractory inclusions; 40 were studied from a single thin section. Inclusion varieties include simple, banded and nodular structures as well as simple and complex distended objects. The inclusions range in mean size from 30 to 530 ,m and average 130 ± 90 ,m. Many inclusions contain 25 ± 15 vol% phyllosilicate (predominantly Mg-Fe serpentine); several contain small grains of perovskite. In addition to phyllosilicate, the most abundant inclusions in QUE 97990 consist mainly of spinel-pyroxene (35%), followed by spinel (20%), spinel-pyroxene-olivine (18%), pyroxene (12%), pyroxene-olivine (8%) and hibonite ± spinel (8%). Four pyroxene phases occur: diopside, Al-rich diopside (with , 8.0 wt% Al2O3), Al-Ti diopside (i.e., fassaite), and (in two inclusions) enstatite. No inclusions contain melilite. Aqueous alteration of refractory inclusions transforms some phases (particularly melilite) into phyllosilicate; some inclusions broke apart during alteration. Melilite-free, phyllosilicate-bearing, spinel inclusions probably formed from pristine, phyllosilicate-free inclusions containing both melilite and spinel. Sixty-five percent of the refractory inclusions in QUE 97990 appear to be largely intact; the major exception is the group of spinel inclusions, all of which are fragments. Whereas QUE 97990 contains about 50 largely intact refractory inclusions/cm2, estimates from literature data imply that more-altered CM chondrites have lower modal abundances (and lower number densities) of refractory inclusions: Mighei (CM , 2.3) contains roughly 0.3,0.6 vol% inclusions (,10 largely intact inclusions/cm2); Cold Bokkeveld (CM2.2) contains ,0.01 vol% inclusions (on the order of 6 largely intact inclusions/cm2). [source]

    ISO observations of 3,200 ,m emission by three dust populations in an isolated local translucent cloud

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2005
    M. G. Rawlings
    ABSTRACT We present isophot spectrophotometry of three positions within the isolated high-latitude cirrus cloud G 300.2,16.8, spanning from the near- to far-infrared (NIR to FIR). The positions exhibit contrasting emission spectrum contributions from the unidentified infrared bands (UIBs), very small grains (VSGs) and large classical grains, and both semi-empirical and numerical models are presented. At all three positions, the UIB spectrum shapes are found to be similar and the large grain emission may be fitted by an equilibrium temperature of ,17.5 K. The energy requirements of both the observed emission spectrum and optical scattered light are shown to be satisfied by the incident local interstellar radiation field (ISRF). The FIR emissivity of dust in G 300.2,16.8 is found to be lower than in globules or dense clouds and is even lower than model predictions for dust in the diffuse interstellar medium (ISM). The results suggest physical differences in the ISM mixtures between positions within the cloud, possibly arising from grain coagulation processes. [source]

    The effect of oxygen on interface microstructure evolution in CdS/CdTe solar cells

    PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 5 2002
    D.S. Albin
    Microstructural changes at the CdS/CdTe solar cell interface where close-spaced sublimation (CSS) is used as the growth technique to deposit the p -type CdTe absorber layer are studied by systematic layer characterization at various stages during heterojunction growth. CdS layers grown by both chemical bath deposition (CBD) and CSS provide a basis for determining the effects of CdS crystallinity, grain size, and oxygen content on the subsequent CdTe layer. As-grown CBD CdS films exhibit small grains and variations in optical properties attributed to film impurities. In contrast, CSS yields CdS films with good crystallinity, larger grains, and nearly ideal optical properties. The hexagonal nature of CSS-grown CdS is seen to nucleate hexagonal CdTe during the initial stages of CdTe film growth. Cubic CdS deposited by CBD in contrast promotes cubic CdTe nucleation. Oxygen anneals in the latter case can aid hexagonal CdTe nucleation. Auger electron spectroscopy (AES) and transmission electron microscopy (TEM) of the CdS/CdTe interface show CdS-dependent differences in interdiffusion at the interface. This interdiffusion appears to be determined by the oxygen level in the CdS. When low-oxygen-containing CSS CdS films are used, sulfur diffusion is substantial, leading to significant consumption of the CdS layer. When these same films are annealed in oxygen, the consumption is reduced. Te diffusion into the CdS layer is also observed to decrease with oxygen anneals. Optical modeling shows that Te alloying with the CdS layer can greatly reduce the short-circuit current of CdS/CdTe devices. Copyright © 2002 John Wiley & Sons, Ltd. [source]